This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2005-050939, filed Feb. 25, 2005, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a film forming technique which stacks an insulating film around an interconnect or the like, and more particularly, to a method of manufacturing a semiconductor device in which strength near an interface between an interlayer insulating film which is constituted by a so-called low-relative-dielectric-constant film (low-k film) and in which an interconnect or the like is buried and another insulating film which is stacked on the interlayer insulating film and in which an interconnect or the like is buried.
2. Description of the Related Art
In recent years, with micropatterning, high integration density, speeding up, or the like of a semiconductor device, micropatterning or multi-layering of an interconnect structure in the semiconductor device is advanced, and the main stream of the internal interconnect structure has shifted from a single-layer structure to a multi-layer structure. Some semiconductor having a multi-layer interconnect structure constituted by five or more layers is also developed and produced. However, as micropatterning of an internal interconnect structure progresses, signal transmission delay based on a so-called interconnection parasitic capacitance and an interconnect resistance is posed as a problem. With multi-layering of the internal interconnect structure, signal transmission delay caused by the multi-layer interconnect structure frequently prevents a high-speed operation of the semiconductor device. At the present, various countermeasures are studied against these signal transmission delays.
In general, the signal transmission delay can be expressed by a product of an interconnection parasitic capacitance and an interconnection resistance. Therefore, in order to reduce the signal transmission delay, at least one of the interconnection parasitic capacitance and the interconnection resistance may be reduced. More specifically, in order to reduce the interconnection resistance, a technique that changes the material of an interconnect from aluminum to copper having a lower resistance is examined. However, unlike formation of an aluminum interconnect, it is very difficult for a current techniques that a copper interconnect is formed by a dry etching method. For this reason, when a copper interconnect is used as an internal interconnect, a so-called buried interconnect (Damascene interconnect) structure is generally employed.
In order to reduce an interconnection parasitic capacitance, a technique that applies a so-called low-relative-dielectric-constant film to an interlayer insulating film in place of a general insulating film is tried. Such a technique is described in, for example, Japanese Patent No. 3436221. The technique is also described in H. Kudo et al., “Copper Dual Damascene Interconnects with Very Low-k Dielectrics Targeting for 130 nm Node”, Proceeding of the IEEE 2000 International Interconnect Technology Conference, pp. 270 to 272, 2000, (San Francisco, Calif., USA) or the like. More specifically, a technique is examined that applies an SiOF film formed by a CVD method, a so-called SOG (Spin on Glass) film formed by a spin coat method, an organic resin film made of a polymer, etc., or the like to an interlayer insulating film in place of a silicon oxide film made of an SiO2 or the like and formed by a CVD method.
For example, although the relative dielectric constant of a general SiO2 film is 3.9, the relative dielectric constant of an SiOF film can be lowered to about 3.4. However, from a viewpoint of stability of the film, it is very difficult for practical use that the relative dielectric constant of the SiOF film is lowered to about 3.4. In contrast to this, the relative dielectric constant of a low-relative-dielectric-constant coating film formed by a coating method such as a spin coat method can be lowered to about 2.0. For this reason, a study to apply the low-relative-dielectric-constant coating film to an interlayer insulating film is powerfully advanced at the present.
In this case, as a typical method of forming a buried interconnect, an example in which an upper-layer interconnect is formed as a buried interconnect on an underlying film in which a buried interconnect serving as a lower-layer interconnect is formed in advance will be briefly described below. It is assumed that a low-relative-dielectric-constant film is used as an interlayer insulating film.
First, an etching stopper film is formed on an underlying film in which a buried interconnect serving as a lower-layer interconnect is formed in advance. Then, an interlayer insulating film composed of a low-relative-dielectric-constant film is formed on the etching stopper film. Subsequently, a cap film is formed on the interlayer insulating film. A resist mask film for forming a via hole is formed on the cap film. Subsequently, a via hole is formed in the inside of the resist mask film for forming a via hole, the cap film and the interlayer insulating film by etching. Thereafter, the resist mask film for forming a via hole is removed.
Next, a resist mask film for forming an interconnect groove is formed on the cap film having the via hole formed therein. Then, an interconnect groove is formed in the inside of the resist mask film for forming an interconnect groove. An interconnect groove is formed in the inside of the cap film and the interlayer insulating film by etching. Subsequently, the via hole is further dug down by etching to open the etching stopper film, so as to expose the surface of the lower-layer interconnect. Thereafter, the resist mask film for forming an interconnect groove is removed.
Next, a barrier metal film and a seed Cu film serving as the underlying film of the upper-layer interconnect are continuously formed in the via hole and the interconnect groove. Subsequently, a Cu film serving as a main body of the upper-layer interconnect is formed on the seed Cu film by a plating method to bury the via hole and the interconnect groove with the barrier metal film and the Cu film. Finally, the surface of the cap film is polished by a CMP method to flatten the surface. In this manner, the buried Cu interconnect serving as an upper-layer interconnect is formed on an the underlying film in which the buried interconnect serving as the lower-layer interconnect is formed in advance.
In the step of forming the upper-layer interconnect described above, a low-relative-dielectric-constant film containing a methyl radical (—CH3) in SiO2 is generally used as the low-relative-dielectric-constant film serving as the interlayer insulating film. Accordingly, as the cap film, an SiO2 film is generally used. The cap film is generally formed by a plasma CVD method using TEOS/O2 or SiH4/N2O as a source gas. In such a case, a plasma containing oxygen (O) generated when the cap film is formed oxidizes the surface part of the low-relative-dielectric-constant interlayer insulating film serving as the underlying film. At this time, an organic component is removed from the inside of the interlayer insulating film to form a damage layer in the surface part of the interlayer insulating film. The damage layer is brittler than the other parts of the interlayer insulating film. After the cap film is formed, the damage layer serves as a brittle layer near the interface between the cap film and the low-relative-dielectric-constant interlayer insulating film. As a result, when a CMP method is performed on the surface of the cap film (SiO2), the possibility of peeling a film near the interface between the cap film and the low-relative-dielectric-constant interlayer insulating film becomes very high.
According to an aspect of the invention, there is provided a manufacturing method of a semiconductor device, comprising: providing a low-relative-dielectric-constant film above a substrate, the low-relative-dielectric-constant film containing at least oxygen (O) and having a relative dielectric constant of 3.3 or more, a conductor being to be buried in the low-relative-dielectric-constant film; performing a plasma processing by discharging a gas containing a noble gas as a main component to the low-relative-dielectric-constant film, the plasma processing being executed while the substrate above which the low-relative-dielectric-constant film is provided is storing in a processing chamber having an inside covered with a material composed of an element except for oxygen and substantially set under an oxygen-free atmosphere; and providing a first insulating film above the low-relative-dielectric-constant film by a plasma CVD method, the first insulating film being made of a material containing at least one of a material containing oxygen and a material containing an element reacting with oxygen, a conductor being to be buried in the first insulating film.
According to another aspect of the invention, there is provided a manufacturing method of a semiconductor device, comprising: providing a first low-relative-dielectric-constant film above a substrate, the first low-relative-dielectric-constant film containing at least oxygen (O), and having a relative dielectric constant of 3.3 or less, a conductor being to be buried in the first low-relative-dielectric-constant film; providing a second low-relative-dielectric-constant film on the first low-relative-dielectric-constant film, the second low-relative-dielectric-constant film containing at least oxygen (O), having a relative dielectric constant of 3.3 or less and having a film density higher than that of the first low-relative-dielectric-constant film, a conductor being to be buried in the second low-relative-dielectric-constant film; and irradiating an electron beam on at least the first and second low-relative-dielectric-constant films.
Embodiments according to the present invention will be described below with reference to the accompanying drawings.
A first embodiment according to the present invention will be described below in detail with reference to
As shown in
First, as shown in
Next, as shown in
In the embodiment, the SiCN:H film 7 is formed by a plasma process like the SiCN:H film 5 or the SiCO:H film 6. However, the SiCN:H film 7 is formed by a film forming method (processing method) different from that of the SiCN:H film 5 or the SiCO:H film 6 in a processing chamber different from a processing chamber (reaction vessel) (not shown) in which the SiCN:H film 5 or the SiCO:H film 6 is formed. The semiconductor substrate 1 having the SiCO:H film 6 arranged thereon is held under an oxygen-free atmosphere until the formation of the SiCN:H film 7 is finished such that the surface part of the SiCO:H film 6 is prevented from being oxidized by oxygen (O) and deteriorated in film quality. More specifically, the semiconductor substrate 1 having the SiCO:H film 6 arranged thereon is held under an atmosphere which is not in contact with atmospheric air or the like until the formation of the SiCN:H film 7 is finished such that a brittle layer is prevented from being formed on the surface part of the SiCO:H film 6. The step of forming the SiCN:H film 7 will be described below in detail.
First, with reference to
As shown in
In the processing chamber 20, an upper electrode 21 serving as a first electrode and a lower electrode 22 serving as a second electrode, both the upper electrode 21 and the lower electrode 22 having planar shapes, are arranged such that the facing surfaces are parallel to each other. Therefore, the plasma CVD apparatus 18 is also called a parallel-plate plasma CVD apparatus. The upper electrode 21 is electrically connected to a high-frequency power supply (AC power supply) 23 through a rectifier (not shown). In contrast to this, the lower electrode 22 is grounded. In this manner, a high-frequency high electric field is generated between the upper electrode 21 and the lower electrode 22 to make it possible to realize high-frequency discharge in the processing chamber 20. In the lower electrode 22, a heater 24 serving as a temperature adjuster is arranged. As will be described below, when a film-forming process is performed, the semiconductor substrate 1 placed on the lower electrode 22 is heated by the heater 24 such that the substrate temperature becomes an appropriate film forming temperature and is kept.
As shown in
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Next, with reference to
First, as described above, in order to prevent the SiCO:H film 6 from being in contact with oxygen until the film-forming process of the SiCN:H film 7 is finished, as indicated by a bold-line arrow in
Subsequently, as indicated by an outline arrow in
Subsequently, a high-frequency voltage of about 13.56 MHz is applied to the upper electrode 21 by using the high-frequency power supply 23. In this manner, a high-frequency high electric field is generated between the upper electrode 21 and the lower electrode 22 to realize high-frequency discharge in the processing chamber 20. The gas mixture of the trimethyl silane gas and the ammonia gas in the processing chamber 20 is set in a plasma state by the high-frequency discharge to cause various plasma ions contained in the plasma gas to react each other. In this manner, SiCN:H molecules are generated in the processing chamber 20, and the generated SiCN:H molecules begin to adhere to the inner side of the processing chamber 20. More specifically, the SiCN:H film 27 serving as a precoat film begins to be formed in the processing chamber 20.
When SiCN:H film 27 almost entirely adheres to the inner side of the processing chamber 20, and when the film thickness of the adhered SiCN:H film 27 reaches a predetermined desired thickness, application of a high-frequency voltage to the upper electrode 21 is stopped. In this manner, the gas mixture (atmosphere) of the trimethyl silane gas and the ammonia gas in the processing chamber 20 is released from the plasma state to end the film-forming process of the SiCN:H film 27. More specifically, the precoating in the processing chamber 20 is ended. Thereafter, as indicated by a bold-line arrow in
With the steps up to now, the inside of the processing chamber 20, including the surfaces or the like of the upper and lower electrodes 21 and 22, is almost entirely coated with the SiCN:H film 27. Thereafter, the semiconductor substrate 1 having the SiCO:H film 6 formed thereon is conveyed (arranged) into the processing chamber 20 to start film formation of the second insulating film 7 serving as the second insulating film.
Next, a method of forming the second insulating film 7 will be described below. The semiconductor substrate 1 having the SiCO:H film 6 formed thereon is conveyed into the processing chamber 20 of the plasma CVD apparatus 18 coated with the precoat film (SiCN:H film) 27 while keeping the SiCO:H film 6 free from oxygen. More specifically, the semiconductor substrate 1 having the SiCO:H film 6 formed thereon is conveyed out of a CVD apparatus (CVD film-forming processing chamber) (not shown) in which the film-forming process of the SiCO:H film 6 is performed without being exposed to the air (atmosphere), and the semiconductor substrate 1 is conveyed into the processing chamber 20 coated with the precoat film 27. At this time, the inside of the processing chamber 20 is held in a high-vacuum state by the pressure-regulating valve 26, the vacuum pump, and the like. More specifically, the inside of the processing chamber 20 is set under an oxygen-free atmosphere in which oxygen atoms, oxygen molecules, consequently, materials containing oxygen atoms, and the like are substantially rarely present.
As shown in
First, as indicated by an outline arrow in
When a high-frequency high electric field is generated between the upper electrode 21 and the lower electrode 22 by a high-frequency voltage applied to the upper electrode 21 to cause high-frequency discharge in the processing chamber 20, a negative potential (voltage) called a self bias is applied to the upper electrode 21. In this case, argon atoms (argon ions: Ar+) 29 plasma-ionized are attracted by the upper electrode 21 while being accelerated at high speed. As a solid arrow in
As shown in
The SiCN:H film 7 on the SiCO:H film 6 serves as a so-called sacrifice film (barrier film) to suppress the SiCO:H film 6 from being oxidized when the SiO2 film 8 serving as the first insulating film (to be described later) is formed on the SiCN:H film 7. According to an experiment executed by the present inventors, it has been found that the probability of eliminating the SiCN:H film 7 is high when the SiO2 film 8 is formed because the SiCN:H film 7 is very thin, i.e., about 2 nm. As shown in
In the SiCN:H film 7, the barrier function that suppresses the SiCO:H film 6 from being oxidized is improved as the thickness of the SiCN:H film 7 increases. Therefore, the SiCN:H film 7 easily achieves its object when the thickness of the SiCN:H film 7 increases. However, the SiCN:H film 7 is a general insulating film having a low relative dielectric constant unlike the SiCO:H film 6 which is a low-relative-dielectric-constant interlayer insulating film. As the thickness of the SiCN:H film 7 increases, it is difficult to achieve a high-speed operation of a semiconductor device by employing the SiCO:H film 6 as a member occupying a large part of the interlayer insulating film. With respect to both the effects having the trade-off relation, the present inventors have further executed an experiment to find a thickness of the SiCN:H film 7 at which the effects are compatible at a high level in a balanced manner. As a result, it has been understood that the thickness of the SiCN:H film 7 is preferably about 5 nm or less. More specifically, according to the experiment executed by the present inventors, it has been understood that, when the thickness of the SiCN:H film 7 is about 5 nm or less, the oxidization suppressing function of the SiCO:H film 6 and the high-speed operation of the semiconductor device can be compatible at a high level in a balanced manner.
The SiCO:H film 6 which is a low-relative-dielectric-constant insulating film is a porous insulating film and has a film density lower than that of the SiCN:H film 7 which is a normal insulating film. For this reason, the SiCO:H film 6 also has a mechanical strength (physical strength) lower than that of the SiCN:H film 7. However, as described above, in the embodiment, a plasma processing by the argon ions 29 is performed to the surface part of the SiCO:H film 6 under an atmosphere from which oxygen ions an d the like are substantially excluded, in the step of forming the SiCN:H film 7 on the SiCO:H film 6. In this manner, the surface part of the SiCO:H film 6 is densified (density-grown) in comparison with a part except for the surface part. More specifically, as shown in
Next, as shown in
Next, as shown in
In the first recessed part 10, a plug (via plug or contact plug) 16 serving as a first conductor which is electrically connected to the lower-layer interconnect 3 as will be described later is arranged. Therefore, more specifically, the first recessed part 10 is a plug recessed part (plug groove, via hole, or contact hole) 10. Similarly, the first-recessed-part-forming resist film 9 is a plug-recessed-part-forming resist film (plug-groove-forming resist film, via-hole-forming resist film, or a contact-hole-forming resist film) 9. In the following explanation, it is assumed that the first-recessed-part-forming resist film 9, the first recessed part 10, and the first conductor 16 are called a via-hole-forming resist film 9, a via hole 10, and a via plug 16, respectively.
Next, as shown in
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As shown in
In the second recessed part 12, an interconnect (upper-layer interconnect) 15 serving as a second conductor which is electrically connected to the lower-layer interconnect 3 through the via plug 16 as will be described later is arranged. Therefore, the second recessed part 12 is specifically an interconnect recessed part (interconnect groove, upper-layer interconnect recessed part, or upper-layer interconnect groove) 12. Similarly, the second-recessed-part-forming resist film 11 is specifically an interconnect-recessed-part-forming resist film (interconnect-groove-forming resist film, upper-layer-interconnect-recessed-part-forming resist film, or upper-layer-interconnect-groove-forming resist film) 11. In the following explanation, it is assumed that the second-recessed-part-forming resist film 11, the second recessed part 12, and the second conductor 15 are simply called an upper-layer-interconnect-recessed-part-forming resist film 11, an upper-layer interconnect recessed part 12, and an upper-layer interconnect 15, respectively.
Next, as shown in
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Next, as shown in
As described above, according to the first embodiment, the SiCO:H film 6 having a film density and a mechanical strength which are lower than those of a normal insulating film, as shown in
In this case, as a comparative example for the embodiment, a semiconductor device and a method of manufacturing the semiconductor device will be briefly described below with reference to
As shown in
Subsequently, the SiO2 film 107 and the SiCO:H film 106 are processed by a normal photolithograhy method or a reactive ion etching (RIE) method to form a via hole 108 in the SiO2 film 107 and the SiCO:H film 106 above the lower-layer interconnect 103. Subsequently, the SiO2 film 107 and the SiCO:H film 106 are processed by the normal photolithography method or the RIE method to form an interconnect groove 109 communicating with the via hole 108 in the films 106 and 107. Then, the SiCN:H film 105 is processed by an RIE method until the via hole 108 penetrates the SiCN:H film 105 forming the bottom of the via hole 108 to expose the surface of the lower-layer interconnect 103.
Subsequently, a barrier metal film 110 is formed in the via hole 108 and the interconnect groove 109 and on the SiO2 film 107. A Cu film 111 is formed on the barrier metal film 110 until the via hole 108 and the interconnect groove 109 are buried. Subsequently, the barrier metal film 110 and the Cu film 111 on the SiO2 film 107 are removed by a chemical mechanical polishing (CMP) method, and the barrier metal film 110 and the Cu film 111 are buried in the via hole 108 and the interconnect groove 109. As a result, an upper-layer interconnect 112 and a via plug 113 integrally formed by the Cu film 111 are electrically connected to the lower-layer interconnect 103 through the barrier metal film 110 and formed in the via hole 108 and the interconnect groove 109. More specifically, a semiconductor device 114 is obtained which has a buried interconnect structure in which the Cu upper-layer interconnect 112 constituted by a so-called dual damascene structure is buried in the SiO2 film 107, the SiCO:H film 106, and the SiCN:H film 105.
However, according to an experiment executed by the present inventors, it has been found that peeling occurs at a very high ratio on the interface between the SiO2 film 107 and the SiCO:H film 106 in a CMP method to manufacture the semiconductor device 114 by the manufacturing method as shown in
According to the manufacturing method, the SiO2 film 107 is formed on the SiCO:H film 106 by a plasma CVD method. In this case, it has been found that the surface part of the SiCO:H film 106 serving as an underlying film of the SiO2 film 107 is oxidized by O2 gas (oxygen plasma ions) to cause a chemical reaction expressed by the following chemical equation:
≡S1—CH3+2O2→≡Si—OH+CO2+H2O (1)
In this chemical equation (1), ≡S1—CH3 denotes a methyl radical contained in the SiCO:H film 106. The ≡Si—OH radical generated by the chemical reaction functions as a so-called moisture-absorption site which adsorbs moisture (H2O). By the ≡Si—OH radical, a brittle layer 106a which adsorbs moisture (H2O) is formed on the surface part of the SiCO:H film 106 serving as the interface between the SiCO:H film 106 of the lower-layer film and the SiO2 film 107 of the upper layer film as shown in
When the peeling occurs between the brittle layer 106a and the SiO2 film 107, the subsequent CMP step cannot be actually continued. More specifically, the buried interconnect structure constituted by the Cu upper-layer interconnect 112 and the Cu via plug 113 cannot be actually realized. Consequently, the semiconductor device 114 cannot be actually manufactured. Even though the CMP step is continued to make it possible to realize the buried interconnect structure constituted by the upper-layer interconnect 112 and the Cu via plug 113, deterioration of the SiCO:H film 106, the SiO2 film 107, the barrier metal film 110, the Cu upper-layer interconnect 112, the Cu via plug 113, and the like is easily started from a position where peeling occurs. Such a phenomenon is especially conspicuous when Cu which is easily oxidized (corroded) is used as the material of the interconnect or the via plug.
In this manner, when peeling occurs near the interlayer insulating film 106, the buried interconnect structure is deteriorated in quality and reliability. Consequently, the semiconductor device 114 is deteriorated in quality, reliability, performance, and the like as a whole. The semiconductor device 114 is hard to sufficiently and appropriately exert the desired functions. Therefore, the semiconductor device 114 in which peeling occurs near the interlayer insulating film 106 is regarded as a defective product, so that the semiconductor device 114 cannot be shipped to the market. More specifically, the yield and productive efficiency of the semiconductor device 114 are down.
In comparison with the semiconductor device 114 and the method of manufacturing the semiconductor device which are described as the comparative example, the semiconductor device 17 according to the first embodiment of the present invention and the method of manufacturing the same have the many advantages described below. The advantages will be described below in detail.
First, in the embodiment, as described above, the SiCO:H film 6 which is a low-relative-dielectric-constant interlayer insulating film, and the SiCN:H film 7 and the SiO2 film 8 which are normal insulating films formed on the SiCO:H film 6 are not continuously formed in the same reaction vessel (film-forming device). And, the semiconductor substrate 1 having the SiCO:H film 6 formed thereon is kept from being in contact with oxygen until the formation of the SiCN:H film 7 on the SiCO:H film 6 is finished. Prior to the formation of the SiCN:H film 7 on the SiCO:H film 6, the inside of the reaction vessel 19 for forming the SiCN:H film 7 is almost entirely coated with the oxygen-free precoat film (SiCN:H film) 27. In this manner, the risk that oxygen is inserted from the outside of the reaction vessel 19 into the reaction vessel 19 (processing chamber 20) through a gap or the like (not shown) can be very low.
In this manner, under an oxygen-free atmosphere in which oxygen molecules (O2) or the like are substantially absent, an oxygen-free gas containing an argon gas as a main component is plasma-discharged, and a plasma processing is performed to the SiCO:H film 6 by using the plasma argon gas. While the plasma processing using the plasma argon gas (argon ion 29) is performed to the SiCO:H film 6, the SiCN:H film 7 constituted by an element except for oxygen is formed on the SiCO:H film 6. According to the film-forming method, the risk that plasma ions (plasma O2 gas) are generated by plasma discharge in the processing chamber 20 can be eliminated in the formation of the SiCN:H film 7. Consequently, the risk that oxygen ions produced by mixing oxygen in the plasma argon gas chemically react with the surface part of the SiCO:H film 6 can be eliminated.
The SiCN:H film 7 contains carbon atoms (C) and nitrogen atoms (N) which easily react with oxygen atoms (O). In general, when the film containing the elements which easily react with oxygen is arranged on the SiCO:H film 6 in direct contact with the SiCO:H film 6, the oxygen atoms in the SiCO:H film 6 are coupled to the carbon atoms or the nitrogen atoms to form a film which easily adsorbs moisture (H2O) in an SiO2 film, an SiON film, or the like on the surface part of the SiCO:H film 6. As a result, as in the semiconductor device 114 explained as the comparative example, the surface part of the SiCO:H film 6 is oxidized to form a brittle layer on the surface part of the SiCO:H film 6, and peeling or the like very easily occurs on the interface between the SiCO:H film 6 and the upper-layer film thereon. However, as described above, in the embodiment, plasma processing is performed to the SiCO:H film 6 under the atmosphere in which oxygen is substantially absent when the SiCN:H film 7 is formed on the SiCO:H film 6. In this manner, since the dense layer 6a is formed on the surface part of the SiCO:H film 6, the risk that not only the oxygen atoms in the surface part of the SiCO:H film 6 but also the oxygen atoms in the porous layer 6b are coupled to the carbon atoms or nitrogen atoms in the SiCN:H film 7 can be very low.
A low-relative-dielectric-constant insulating film is generally a porous insulating film, and has a film density lower than that of a normal insulating film. The low-relative-dielectric-constant insulating film has a mechanical strength (physical strength) lower than that of a conventional insulating film. However, in the embodiment, the dense layer 6a is, as described above, formed on the surface part of the SiCO:H film 6 serving as the low-relative-dielectric-constant insulating film. In this manner, the dense layer 6a of the SiCO:H film 6 is hard to be coupled to oxygen molecules, oxygen ions, or the like under an atmosphere around the SiCO:H film 6. More specifically, the dense layer 6a of the SiCO:H film 6 is not easily oxidized. According to an experiment executed by the present inventors, it has been found that the dense layer 6a having a thickness of about 10 nm can sufficiently suppress the porous layer 6b from being oxidized and made brittle. More specifically, it has been found that the dense layer 6a having a thickness of about 50 nm is ideal because the relative dielectric constant of the entire SiCO:H film 6 can be preferably suppressed by increasing.
According to these result, in the embodiment, the risk can be very low that, in the formation of the SiCN:H film 7, the surface part of the SiCO:H film 6 adsorbs moisture (H2O) and is oxidized to form a brittle layer on the dense layer 6a of the SiCO:H film 6 serving as an underlying film of the SiCN:H film 7. Therefore, according to the film-forming method of the embodiment, the SiCN:H film 7 can be formed on the SiCO:H film 6 without deteriorating the film quality of the SiCO:H film 6 while performing a plasma processing to the SiCO:H film 6 having appropriate film quality. In this manner, the risk that the adhesiveness of the interface between the SiCO:H film 6 and the SiCN:H film 7 is lowered is very low.
As the material of the precoat film (SiCN:H film) 27 coating the inside of the processing chamber 20, SiCN:H which is the same as that of the SiCN:H film 7 formed inside the processing chamber 20 is used. In this manner, the risk that a material which prevents the SiCN:H film 7 having appropriate quality from being formed is generated in the processing chamber 20 can be suppressed. That is, the risk can be very low that a material which deforms or deteriorates the film quality of the SiCO:H film 6 serving as the underlying film of the SiCN:H film 7 is generated in the processing chamber 20. More specifically, the risk can be very low that various contaminants including metal particles which cause metal pollution, dust or particles which cause particulate pollution, or an organic or inorganic material which does not contribute to formation of the SiCN:H film 7 are generated by plasma discharge from the apparatus main body (reaction vessel) 19 or the like surrounding the processing chamber 20.
According to the embodiment, not only the inner wall surface of the processing chamber 20 but also the surfaces or the like of the upper and lower electrodes 21 and 22 are almost entirely coated with the SiCN:H film 27. As described above, the SiCN:H molecules 30 sputtered by collision of the argon ions 29 from the SiCN:H film 27 deposited on the major surface of the upper electrode 21 facing the lower electrode 22 are deposited on the surface of the SiCO:H film 6 again. In this manner, the SiCN:H film 7 is formed on the SiCO:H film 6. Such a phenomenon is the same as the phenomenon occurring in a general sputtering device (not shown). According to a normal plasma CVD method, the SiCN:H film is formed by performing electrical discharge using a gas mixture of an organic silane gas and an NH3 gas. In this method, however, the SiCO:H film serving as the underlying film is damaged by the electrical discharge of the NH3 gas. In this manner, the surface part of the SiCO:H film is made brittle, and defective peeling may be caused near the interlayer insulating film in a post-process of the step of forming the SiCN:H film. In contrast to this, according to the method of manufacturing a semiconductor device in the embodiment using a sputtering phenomenon with the argon ions 29, electrical discharge of the NH3 gas or the like does not occur at all. For this reason, when the SiCN:H film 7 is formed on the SiCO:H film 6, the risk that the SiCO:H film 6 is damaged can be very low.
In this manner, according to the embodiment, the risk that the brittle film is formed on the surface part of the SiCO:H film 6 serving as the underlying film of the SiCN:H film 7 or that the film quality of the SiCO:H film 6 is deteriorated is very low to make it possible to form the SiCN:H film 7 having appropriate film quality. Consequently, the risk that the mechanical strength of the interface between the SiCO:H film 6 and the SiCN:H film 7 is lowered is very low to make it possible to improve the adhesiveness of the interface between the SiCO:H film 6 and the SiCN:H film 7.
In the embodiment, the film density of the surface part (dense layer) 6a of the SiCO:H film 6 is increased enough to be resistant to external force (stress) applied on the surface part 6a in the CMP step by a plasma processing. As a result, the mechanical strength of the dense layer 6a is improved enough to be resistant to stress applied on the dense layer 6a in the CMP step. Consequently, the adhesiveness of the interface between the dense layer 6a of the SiCO:H film 6 and the SiCN:H film 7 is improved such that peeling between the dense layer 6a and the SiCN:H film 7 is not caused by stress applied on the dense layer 6a in the CMP step. The mechanical strength of the surface part (dense layer) 6a of the SiCO:H film 6 is improved to be higher than the mechanical strength of the porous part (porous layer) 6b except for the surface part 6a of the SiCO:H film 6 having a follow film structure more than that of the surface part 6a as a matter of course.
As described above, since the dense layer 6a is formed on the surface part of the SiCO:H film 6, oxygen molecules, oxygen ions, and the like under the atmosphere around the SiCO:H film 6 can rarely reach the porous layer 6b of the SiCO:H film 6. That is, the dense layer 6a serves as a barrier layer which prevents oxygen molecules, oxygen ions, and the like from reaching the porous layer 6b. In this manner, the porous layer 6b is hard to be oxidized at the same level as that of the dense layer 6a, and the film quality of the porous layer 6b is not easily deteriorated. Consequently, the risk that the mechanical strength of the dense layer 6a and the adhesiveness of the interface between the dense layer 6a and the SiCN:H film 5 serving as the underlying film are lowered is very low.
The SiO2 film 8 and the SiCN:H film 7 immediately below the SiO2 film 8 are general insulating films each having a relative dielectric constant higher than that of the low-relative-dielectric-constant film unlike the SiCO:H film 6 which is the low-relative-dielectric-constant film (low-k film). Therefore, the SiO2 film 8 and the SiCN:H film 7 have film densities and mechanical strengths higher than those of the SiCO:H film 6. Accordingly, the adhesiveness of the interface between the SiO2 film 8 and the SiCN:H film 7 is higher than the adhesiveness of the interface between the SiO2 film 107 and the SiCO:H film 106 according to the background art described above. For this reason, unlike in the semiconductor device 114 which is the comparative example in which peeling occurs on the interface between the SiO2 film 107 and the SiCO:H film 106 in the CMP step, the risk that peeling occurs on the interface between the SiO2 film 8 and the SiCN:H film 7 even in the CMP step is very low.
As described above, the SiCN:H film 7 serving as a sacrifice film is formed between the SiCO:H film 6 and the SiO2 film 8. When the SiO2 film 8 made of a material containing oxygen is formed above the SiCO:H film 6, the SiCN:H film 7 serves as a barrier film (layer) which blocks plasma oxygen ions generated from an N2O gas which is one of the source gases of the SiO2 film 8 from reaching the surface part 6a of the SiCO:H film 6. For this reason, even though plasma oxygen ions are generated from the N2O gas in formation of the SiO2 film 8, the risk that the oxygen ions reach the surface part 6a of the SiCO:H film 6 is very low. More specifically, in the formation of the SiO2 film 8, the risk that the plasma oxygen ions react with the SiCO:H film 6 to cause the surface part 6a of the SiCO:H film 6 to adsorb moisture (H2O) is very low.
Therefore, unlike in the semiconductor device 114 which is the comparative example, the risk is very low that, when the SiO2 film 8 is formed above the SiCO:H film 6, the surface part 6a of the SiCO:H film 6 is oxidized by plasma oxygen ions to form a brittle layer (damage layer) on the surface part 6a of the SiCO:H film 6. As a result, even though the SiO2 film 8 is formed above the SiCO:H film 6, the mechanical strength of the dense layer 6a formed on the surface part of the SiCO:H film 6 is kept increased enough to be resistant to stress applied in the CMP step, and the risk that the mechanical strength is lowered is very low. Similarly, the adhesiveness of the interface between the surface part (dense layer) 6a of the SiCO:H film 6 and the SiCN:H film 7 is also kept improved enough to be resistant to stress applied in the CMP, and the risk that the adhesiveness is lowered is very low.
In the embodiment, as the first insulating film arranged above the SiCO:H film 6, the SiO2 film 8 made of a material containing oxygen is formed as described above. However, as in the embodiment, the first insulating film is not limited to the SiO2 film according to the step of forming the SiCN:H film 7 between the SiCO:H film 6 and the first insulating film while performing a plasma processing to the SiCO:H film 6 under an oxygen-free atmosphere in which oxygen is substantially absent. For example, as the first insulating film, a film made of a material which does not contain oxygen atoms themselves and contains an element which reacts with oxygen like the SiCN:H film 7 is formed above the SiCO:H film 6, the same effect as that in the embodiment can be obtained. This will be briefly, concretely described below.
Although not shown, it is assumed that, for example, an SiC film, an SiN film, or the like is formed above the SiCO:H film 6 as the first insulating film made of a material containing an element reacting oxygen. At this time, as in the semiconductor device 114 which is the comparative example, it is assumed that a plasma processing is not performed to the SiCO:H film 6 under an atmosphere in which oxygen is substantially absent. Alternatively, it is assumed that the SiCN:H film 7 serving as a barrier film is formed between the SiCO:H film 6 and the SiC film or the SiN film. In this case, oxygen atoms (O) in the SiCO:H film 6 are coupled to carbon atoms (C) in the SiC film or nitrogen atoms (N) in the SiN film to form a film which easily adsorbs moisture (H2O) of the SiO2 film or the SiON film on the surface part of the SiCO:H film 6. As a result, as in the semiconductor device 114, a brittle layer is formed on the surface part of the SiCO:H film 6, and peeling or the like very easily occurs on the interface between the SiCO:H film 6 and the SiC film or the SiN film.
As described above, in the embodiment, a plasma processing is performed to the SiCO:H film 6 under the atmosphere in which oxygen is substantially absent to form the dense layer 6a on the surface part of the SiCO:H film 6. Accordingly, the SiCN:H film 7 serving as a barrier film is formed on the SiCO:H film 6 such that the SiCN:H film 7 is in direct contact with the SiCO:H film 6. In this manner, not only oxygen atoms in the surface part of the SiCO:H film 6 but also oxygen atoms in the porous layer 6b can be rarely coupled to carbon atoms in the SiC film on the SiCN:H film 7 or nitrogen atoms in the SiN film. Therefore, according to the embodiment, even though any one of the SiC film, the SiN film, and the like made of a material containing an element reacting with oxygen is employed as the first insulating film formed above the SiCO:H film 6, the risk that a brittle layer is formed on the surface part of the SiCO:H film 6 can be very low. Consequently, the risk that peeling occurs between the SiCO:H film 6 and another insulating film formed thereon can be very low.
In this manner, according to the embodiment, the adhesiveness and the mechanical strength near the interface between the SiCO:H film 6 which is a low-relative-dielectric-constant interlayer insulating film and the SiCN:H film 7 which is a general insulating film formed in direct contact with the SiCO:H film 6 are improved enough to be sufficiently resistant to stress generated in the CMP step. Accordingly, the adhesiveness between the SiCO:H film 6 and the SiO2 film 8 which is another general insulating film indirectly stacked on the SiCO:H film 6 through the SiCN:H film 7 and the mechanical strength of the laminate film constituted by the three insulating film, i.e., the SiCO:H film 6, the SiCN:H film 7, and the SiO2 film 8 are also improved enough to sufficiently resistant to stress generated in the CMP step. More specifically, the SiCO:H film 6, the SiCN:H film 7, and the SiO2 film 8 are improved in resistance to stress (external force) applied by the CMP method or the like. For this reason, when the upper-layer interconnect 15 and the Cu via plug 16 are buried in the SiO2 film 8, the SiCN:H film 7, the SiCO:H film 6, and the SiCN:H film 5, the risk that peeling occurs on interfaces among the films 6, 7, and 8, i.e., the SiCO:H film 6 to the SiO2 film 8 is very low.
According to an experiment executed by the present inventors, unlike in the semiconductor device 114 which is the comparative example, peeling did not occur on the interfaces among the SiCO:H film 6, the SiCN:H film 7, and the SiO2 film 8 according to the embodiment in the CMP step serving as a post-process of the film forming step. More specifically, according to the method of manufacturing a semiconductor device (film-forming method) of the embodiment, it has been found that defective peeling can be avoided which easily occurs near the interface between the SiCO:H film 6 and the SiCN:H film 7 when the conductor 14 is buried in the SiCO:H film 6 constituted by a low-relative-dielectric-constant insulating film and the SiCN:H film 7 formed in contact with the SiCO:H film 6. In the semiconductor device 17 according to the embodiment, peeling does not occur on the interface between the SiCO:H film 6 which is a low-relative-dielectric-constant interlayer insulating film and the SiCN:H film 5 which is a general insulating film serving as an underlying film of the SiCO:H film 6 in the CMP step as a matter of course. Also when the n-th interlayer insulating film 2 in which the Cu lower-layer interconnect 3 is buried is constituted by a low-relative-dielectric-constant film (SiCO:H film) like the (n+1)th interlayer insulating film 6, peeling does not occur on the interface between the SiCN:H film 5 and the n-th interlayer insulating film 2 in the CMP step as a matter of course.
According to an experiment executed by the present inventors, after the SiCO:H film 6 is deposited on the SiCN:H film 5, a plasma processing using an argon gas (argon ions) to the SiCO:H film 6 is continuously performed in the reaction vessel of the plasma CVD apparatus which forms the SiCO:H film 6. In this case, the same effect as that in the embodiment cannot be obtained. As a matter of fact, the defective peeling on the interfaces among the SiO2 film 8, the SiCN:H film 7, and the SiCO:H film 6 is degraded, or the probability of occurrence of defective peeling increases. As a result of study committedly executed by the present inventors, it has been found that the cause is occurrence of the following phenomenon.
When the SiCO:H film 6 is formed by the plasma CVD method, the SiCO:H film 6 is deposited not only on the semiconductor substrate 1 but also in the reaction vessel. When a sputtering process is performed in the reaction vessel, SiCO:H molecules in the SiCO:H film 6 deposited in the reaction vessel, especially on a target electrode which is a counter electrode of a wafer electrode are sputtered by plasma ions. The sputtered SiCO:H molecules are excited in a plasma atmosphere to generate oxygen ions. In this case, it has been found that the generated oxygen ions react with the SiCO:H film 6 on the semiconductor substrate 1 to cause a chemical reaction expressed by the chemical equation (1) described in the comparative example. As a result obtained by the chemical reaction, it has been found that moisture (H2O) is adsorbed on the surface part of the SiCO:H film 6 on the semiconductor substrate 1 to oxidize the surface part of the SiCO:H film 6.
Since the phenomenon occurs, the plasma processing is continuously performed to the SiCO:H film 6 in the reaction vessel in which the SiCO:H film 6 has been formed, in contrast, the defective peeling on the interfaces among the SiO2 film 8, the SiCN:H film 7, and the SiCO:H film 6 may be degraded, or the probability that the defective peeling occurs may increase. Therefore, in order to obtain the effect of the embodiment, the plasma processing to the SiCO:H film 6 should not be continuously performed after the film-forming process of the SiCO:H film 6 in the reaction vessel in which the SiCO:H film 6 has been deposited.
Furthermore, according to an experiment executed by the present inventors, it has been found that, also when a precoat film made of a material free from oxygen is coated in the reaction vessel for depositing the SiO2 film 8 as a pre-process of the step of forming the SiO2 film 8 before the SiO2 film 8 is formed by a plasma CVD method, the same effect as that in the embodiment can be obtained. For example, it has been found that, also when the SiO2 film 8 is continuously formed by a plasma CVD method in the reaction vessel for depositing the SiO2 film 8 after a precoat film except for an SiO2 film is coated in the reaction vessel, the same effect as that in the embodiment can be obtained.
As described above, according to the first embodiment, as shown in
Since peeling does not occur on the interfaces among the SiO2 film 8, the SiCN:H film 7, the SiCO:H film 6, and the SiCN:H film 5 in the semiconductor device 17 according to the embodiment, the risk that the upper-layer interconnect 15 and the Cu via plug 16 buried in the films 5, 6, 7 and 8 are deteriorated is very low. More specifically, the risk that the buried interconnect (Cu upper-layer interconnect) 15 held by the semiconductor device 17 is deteriorated in quality, reliability, and the like is very low. Consequently, the risk that the semiconductor device 17 is deteriorated in quality, reliability, performance, and the like as a whole is very low. Therefore, the semiconductor device 17 can sufficiently and appropriately exert the desired functions for a long period of time. In other words, the semiconductor device 17 has a long life. Furthermore, as described above, a rate of occurrence of defective peeling is reduced in the semiconductor device 17, and thus, a production yield or productive efficiency is high.
A second embodiment of the present invention will be described below with reference to
In the second embodiment, unlike in the first embodiment, there is not employed the step of, in order to prevent peeling on an interface (between films) between a low-relative-dielectric-constant interlayer insulating film and another general insulating film formed thereon, forming the another general insulating film on the low-relative-dielectric-constant interlayer insulating film while performing a plasma processing to a surface part of the low-relative-dielectric-constant interlayer insulating film. In the embodiment, before the another general insulating film is formed on the low-relative-dielectric-constant interlayer insulating film, the low-relative-dielectric-constant interlayer insulating film is formed to have a two-layer structure constituted by a first low-relative-dielectric-constant film and a second low-relative-dielectric-constant film. In this case, as the second low-relative-dielectric-constant film formed on the first low-relative-dielectric-constant film, a low-relative-dielectric-constant film which has a more dense film structure having a film density higher than that of the first low-relative-dielectric-constant film and which has a relative dielectric constant higher than that of the first low-relative-dielectric-constant film. After an electron beam is irradiated on the first and second low-relative-dielectric-constant films, the another general insulating film is formed on the second low-relative-dielectric-constant film. In this manner, peeling on the interface (between films) between the low-relative-dielectric-constant interlayer insulating film and the another general insulating film formed thereon is prevented. This will be described below in detail.
First, as shown in
The relative dielectric constant of the SiCO:H film 31 is reduced to about 2.9, although the relative dielectric constant of a silicon dioxide (SiO2) serving as a general interlayer insulating film is about 4.0. As described in the first embodiment, the SiCO:H film 6 has a relative dielectric constant of about 2.5. Therefore, the SiCO:H film 31 has a relative dielectric constant higher than that of the SiCO:H film 6. In relation to this, the film density of the SiCO:H film 31 is made higher than the film density of the SiCO:H film 6 and has a film structure denser than that of the SiCO:H film 6. More specifically, although the film density of the SiCO:H film 6 is about 1.1 g/cc, the film density of the SiCO:H film 31 is about 1.2 g/cc which is slightly higher than the film density of the SiCO:H film 6.
In formation of the SiCO:H film 31, a gas which is different from a source gas used in the formation of the SiCO:H film 6 and which contains organic silane having a cyclic structure is not used. More specifically, the SiCO:H film 31 is formed by using a gas containing an organic material such as trimethyl silane having a relatively low molecular weight. A film forming temperature (substrate temperature) at which the SiCO:H film 31 is formed is set at about 350° C. which is equal to the film forming temperature used when the SiCO:H film 6 is formed. The SiCO:H film 31 is deposited on the SiCO:H film 6 until the thickness of the SiCO:H film 31 is about 5 nm. In this manner, as shown in
The film-forming process of the upper-layer SiCO:H film 31 may be continuously performed in a reaction vessel 19 (film forming apparatus 18) used in formation of the lower-layer SiCO:H film 6 after the lower-layer SiCO:H film 6 is formed. Alternatively, the film-forming process of the upper-layer SiCO:H film 31 may be performed such that the semiconductor substrate 1 having the lower-layer SiCO:H film 6 formed thereon is moved from the reaction vessel 19 into another reaction vessel (film forming apparatus) (not shown) after the lower-layer SiCO:H film 6 is formed in the reaction vessel 19. In the formation of the upper-layer SiCO:H film 31, an atmosphere around the semiconductor substrate 1 may be set in a state in which a film-forming gas of the upper-layer SiCO:H film 31 and a film-forming gas of the lower-layer SiCO:H film 6 are not substantially mixed with each other. The semiconductor substrate 1 having the lower-layer SiCO:H film 6 formed thereon is preferably kept in a state in which the semiconductor substrate 1 is not exposed to the air or the like until the film-forming process of at least the upper-layer SiCO:H film 31 is finished. Furthermore, the semiconductor substrate 1 having the lower-layer SiCO:H film 6 and the upper-layer SiCO:H film 31 formed thereon is more preferably kept in a state in which the semiconductor substrate 1 is not exposed to the air or the like until at least electron beam irradiation (to be described later).
Next, as shown in
The electron beam irradiation densities (increases a density) the film structure of a brittle layer formed on the surface part 6a of the lower-layer SiCO:H film 6 to substantially eliminate the brittle layer. As a result, the surface part 6a of the lower-layer SiCO:H film 6 on which the upper-layer SiCO:H film 31 has been formed has a dense film structure the film density of which is equal to that of the upper-layer SiCO:H film 31. In other words, the surface part 6a of the lower-layer SiCO:H film 6 is deformed by irradiation of the electron beam into a dense layer having a film density of about 1.2 g/cc. Therefore, the electron-beam-irradiated lower-layer SiCO:H film 6 according to the embodiment, as shown in
The surface part 6a of the lower-layer SiCO:H film 6 is substantially integrated with the upper-layer SiCO:H film 31 in the step (process) of increasing the film density of the surface part 6a to a film density almost equal to that of the upper-layer SiCO:H film 31. That is, the dense layer 6a is formed while being integrated with the upper-layer SiCO:H film 31. In this manner, upon completion of the step of forming the dense layer 6a, the dense layer 6a and the upper-layer SiCO:H film 31 substantially constitute a single-layer structure. As a result, the (n+1)th low-relative-dielectric-constant interlayer insulating film 32 on which the electron beam irradiation is finished is formed as a low-relative-dielectric-constant interlayer insulating film having a two-layer structure obtained by stacking two low-relative-dielectric-constant films of two types substantially having different film qualities. More specifically, the (n+1)th low-relative-dielectric-constant interlayer insulating film 32 on which the electron beam irradiation is finished, as shown in
Next, as shown in
Next, as shown in
As described above, in the second embodiment, the upper-layer SiCO:H film 31 which has a film structure denser than that of the lower-layer SiCO:H film 6 and a film density higher than that of the lower-layer SiCO:H film 6 is formed by using the low-film-density porous lower-layer SiCO:H film 6 as an underlying film. Both the upper and lower SiCO:H films 6 and 31 are formed by a plasma CVD method. After the upper-layer SiCO:H film 31 is formed on the lower-layer SiCO:H film 6, an electron beam is irradiated on the SiCO:H films 6 and 31. Thereafter, the SiO2 film 8 is formed above the upper-layer SiCO:H film 31 by a plasma CVD method.
According to the film-forming method, when the SiO2 film 8 serving as an upper-layer oxide film is formed by a plasma CVD method above the low-relative-dielectric-constant interlayer insulating film 32 (upper and lower SiCO:H films 6 and 31) serving as an underlying film, the surface part of the low-relative-dielectric-constant interlayer insulating film 32 can be easily suppressed from being oxidized by plasma oxygen ions and being made brittle, as in the first embodiment. Consequently, the mechanical strength of surface part of the low-relative-dielectric-constant interlayer insulating film 32 can be easily improved, and it is possible to easily secure the high adhesiveness of the interfaces among the low-relative-dielectric-constant interlayer insulating film 32, the SiCN:H film 7, and the SiO2 film 8. Therefore, in the CMP step which is a post process of the step of forming the SiO2 film 8, the risk that peeling occurs on the interfaces among the low-relative-dielectric-constant interlayer insulating film 32, the SiCN:H film 7, and the SiO2 film 8 can be easily suppressed.
As a result, as shown in
As described above, in the embodiment, the upper-layer SiCO:H film 31 which has a film structure denser than that of the lower-layer SiCO:H film 6 and a film density higher than that of the lower-layer SiCO:H film 6 is formed on the lower-layer SiCO:H film 6 by a plasma CVD method. Therefore, in formation of the upper-layer SiCO:H film 31, plasma discharge of an oxygen gas is performed, and oxygen ions are generated as plasma-ionized oxygen. At this time, in general, as described in the first embodiment, the surface part 6a of the lower-layer SiCO:H film 6 serving as the underlying film of the upper-layer SiCO:H film 31 is oxidized by oxygen ions, and the risk that a brittle layer (not shown) is formed on the surface part 6a of the lower-layer SiCO:H film 6 is very high. Consequently, when an interconnect or the like is buried in the upper-layer SiCO:H film 31 and the lower-layer SiCO:H film 6 by a CMP method in the subsequent step, peeling very easily occurs on the interface between the upper-layer SiCO:H film 31 and the lower-layer SiCO:H film 6.
However, in the embodiment, as described above, an electron beam is irradiated on the upper-layer SiCO:H film 31 and the lower-layer SiCO:H film 6 after the upper-layer SiCO:H film 31 is formed on the lower-layer SiCO:H film 6. In this manner, the lower-layer SiCO:H film 6 becomes a low-relative-dielectric-constant interlayer insulating film substantially having a two-layer structure constituted by the dense layer 6a of the surface part and the porous layer 6b of a part except for the surface part, the dense layer 6a and the porous layer 6b having different film qualities. The lower-layer SiCO:H film 6 and the upper-layer SiCO:H film 31 integrated by the electron beam irradiation serve as a barrier layer (sacrifice film) which prevents oxygen ions or the like from reaching the porous layer 6b like the dense layer 6a formed on the surface part of the lower-layer SiCO:H film 6 by the plasma processing in the first embodiment. In this manner, the porous layer 6b can be suppressed from being oxidized by an oxygen plasma gas (oxygen ions) generated when the SiO2 film 8 is deposited when the SiO2 film 8 is deposited above the upper-layer SiCO:H film 31 by a plasma CVD method in a post-process. As described above, since the upper-layer SiCO:H film 31 has a film structure denser than that of the lower-layer SiCO:H film 6 and a film density higher than that of the lower-layer SiCO:H film 6, the upper-layer SiCO:H film 31 is not influenced by oxidization easily more than the lower-layer SiCO:H film 6. For this reason, the upper-layer SiCO:H film 31 is rarely deteriorated in film quality in the film-forming step. More specifically, the risk that the mechanical strength of the upper-layer SiCO:H film 31 and the adhesiveness between the upper-layer SiCO:H film 31 and the surface part 6a of the lower-layer SiCO:H film 6 are deteriorated is very low.
According to an experiment executed by the present inventors, it has been found that, when the low-relative-dielectric-constant interlayer insulating film 32 is formed by the film-forming method described above, defective peeling can be prevented from occurring on the interface between the upper-layer SiCO:H film 31 and the lower-layer SiCO:H film 6 in the CMP step which is a post-process, as in the first embodiment. Accordingly, it has been found that defective peeling can be prevented from occurring on the interface between the low-relative-dielectric-constant interlayer insulating film 32 and the SiCN:H film 5 serving as the underlying film of the low-relative-dielectric-constant interlayer insulating film 32 and the interface between the low-relative-dielectric-constant interlayer insulating film 32 and the SiCN:H film 7 serving as the upper-layer film of the low-relative-dielectric-constant interlayer insulating film 32 in the CMP step.
A third embodiment of the present invention will be described below with reference to
In the third embodiment, unlike in the first embodiment, there is not employed the step of, in order to prevent peeling on an interface (between films) between a low-relative-dielectric-constant interlayer insulating film and another general insulating film formed thereon, forming the another general insulating film on the low-relative-dielectric-constant interlayer insulating film while performing a plasma processing to a surface part of the low-relative-dielectric-constant interlayer insulating film. In the embodiment, as in the second embodiment, a two-layer structure constituted by a first low-relative-dielectric-constant film and a second low-relative-dielectric-constant film is formed. In addition, as the second low-relative-dielectric-constant film formed on the first low-relative-dielectric-constant film, a low-relative-dielectric-constant film is used which has a more dense film structure having a film density higher than that of the first low-relative-dielectric-constant film and which has a relative dielectric constant higher than that of the first low-relative-dielectric-constant film.
However, unlike in the second embodiment, a third low-relative-dielectric-constant film having a relative dielectric constant of 3.3 or less is formed on the second low-relative-dielectric-constant film before an electron beam is irradiated on the first and second low-relative-dielectric-constant films in the third embodiment. Thereafter, an electron beam is irradiated to the first, second, and third low-relative-dielectric-constant films. After the electron beam is irradiated on the first, second, and third low-relative-dielectric-constant films, another general insulating film is formed on the third low-relative-dielectric-constant film. In this manner, peeling on the interface (between films) between the low-relative-dielectric-constant interlayer insulating film and the other general insulating film formed thereon can be prevented. This will be described below.
First, as shown in
Next, as shown in
In formation of the PAr film 41, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
Next, as shown in
As described above, the same effects as those in the first and second embodiments can be obtained according to the third embodiment. In the embodiment, the upper-layer SiCO:H film 31 serving as a dense layer is formed between the porous lower-layer SiCO:H film 6 and the PAr film 41 made of a polymer. In this manner, the upper-layer SiCO:H film 31 can function as a barrier film which suppresses the lower-layer SiCO:H film 6 from being deteriorated when the PAr film 41 is formed. The adhesiveness between the PAr film 41 and the lower-layer SiCO:H film 6 can be improved through the upper-layer SiCO:H film 31. Furthermore, since the PAr film 41 serving as a polymer coated film is formed on the surface of the upper-layer SiCO:H film 31 by using as an underlying film the upper-layer SiCO:H film 31 serving as a dense layer, the wettability of the PAr film 41 can be improved. Consequently, the mechanical strength of the (n+1)th low-relative-dielectric-constant interlayer insulating film 42 constituted by the PAr film 41, the upper-layer SiCO:H film 31, and the lower-layer SiCO:H film 6 can be easily improved. That is, the risk that peeling occurs in the low-relative-dielectric-constant interlayer insulating film 42 can be easily suppressed.
As a result, as shown in
According to an experiment executed by the present inventors, peeling occurs on the interface between the PAr film 41 and the lower-layer SiCO:H film 6 in a CMP step when the upper-layer SiCO:H film 31 is not formed between the PAr film 41 and the lower-layer SiCO:H film 6. In contrast to this, according to the film-forming method of the embodiment, peeling does not occur on the interfaces among the PAr film 41, the upper-layer SiCO:H film 31, and the lower-layer SiCO:H film 6 which constitute the (n+1)th low-relative-dielectric-constant interlayer insulating film 42 in the CMP step. Consequently, peeling does not occur on the interface between the (n+1)th low-relative-dielectric-constant interlayer insulating film 42 and the SiO2 film 8 serving as the upper-layer film of the (n+1)th low-relative-dielectric-constant interlayer insulating film 42 and the interface between the (n+1)th low-relative-dielectric-constant interlayer insulating film 42 and the SiCN:H film 5 serving as the underlying film of the (n+1)th low-relative-dielectric-constant interlayer insulating film 42 in the CMP step. In addition, peeling does not occurs on the interface between the SiCN:H film 5 and the n-th interlayer insulating film 2 serving as the underlying film of the SiCN:H film 5 as a matter of course.
According to another experiment executed by the present inventors, it has been found that, in formation of the PAr film 41, an electron beam is irradiated on the PAr film 41 or the like to make it possible to reduce heat load on the PAr film 41. It has been also found that the adhesivenesses of the interfaces between at least the PAr film 41 and the upper-layer SiCO:H film 31, between the upper-layer SiCO:H film 31 and the lower-layer SiCO:H film 6, and between the lower-layer SiCO:H film 6 and the SiCN:H film 5 can be improved. As in the first and second embodiments, it has been found that the mechanical strength of the lower-layer SiCO:H film 6 can be improved. Furthermore, it has been found that, due to the presence of the upper-layer SiCO:H film 31 serving as a dense layer immediately under the PAr film 41, the adhesive strength between the PAr film 41 and the upper-layer SiCO:H film 31 is increased from about 0.2 MPa·m1/2 to about 0.4 MPa·m1/2, i.e., approximately doubled.
More specifically, it has been found that the mechanical strength and the adhesiveness of the (n+1)th low-relative-dielectric-constant interlayer insulating film 42 having the three-layer structure can be resistant to stress generated in the CMP step and are improved enough to prevent peeling from occurring on the interfaces among the low-relative-dielectric-constant films 6, 31, and 41. Consequently, it has been found that the adhesiveness between the low-relative-dielectric-constant interlayer insulating film 42 and the SiCN:H film 5 serving as the underlying film of the low-relative-dielectric-constant interlayer insulating film 42 and the adhesiveness between the low-relative-dielectric-constant interlayer insulating film 42 and the SiO2 film 8 serving as the upper-layer film of the low-relative-dielectric-constant interlayer insulating film 42 are improved enough to be resistant to stress generated in the CMP step and to prevent peeling from occurring on the interfaces among the insulating films 5, 42, and 8.
As described above, in the embodiment, an NH3 gas is used as an etching gas when the PAr film 41 is etched by an RIE method to dig down the upper layer interconnect recessed part 45. In this case, the film quality of the lower-layer SiCO:H film 6 serving as the underlying film of the PAr film 41 may be deteriorated by the NH3 gas. This phenomenon may be caused by occurrence of the following chemical reaction between the lower-layer SiCO:H film 6 and the NH3 gas. The deterioration phenomenon of the film quality of the lower-layer SiCO:H film 6 caused by the NH3 gas will be described below with reference to typical chemical reactions.
Since the lower-layer SiCO:H film 6 is an almost porous film having weak bonding force, the lower-layer SiCO:H film 6 easily reacts with the NH3 gas. More specifically, when the NH3 gas adheres to the surface of the lower-layer SiCO:H film 6, methyl radicals of the surface part of the lower-layer SiCO:H film 6 react with hydrogen (H) in the NH3 gas to cause a chemical reaction expressed by the following chemical equation (2).
≡Si—CH3+H→≡Si—+CH4 (2)
Subsequently, the surface part of the lower-layer SiCO:H film 6 further reacts moisture (H2O) in the atmosphere to cause a chemical reaction expressed by the following chemical equation (3).
2≡Si—+H2O→≡Si—OH+≡Si—H (3)
In the chemical equation (2), ≡Si—CH3 denotes a methyl radical contained in the lower-layer SiCO:H film 6. A hydroxyl function (≡Si—OH) generated by the chemical reaction expressed by the chemical equation (3) functions as a so-called moisture-absorption site which adsorbs moisture (H2O). For this reason, when the NH3 gas is used as an etching gas in formation of the upper layer interconnect recessed part 45, moisture easily adheres to the surface of the lower-layer SiCO:H film 6. When the Cu upper-layer interconnect 15 is formed in the upper layer interconnect recessed part 45, the Cu upper-layer interconnect 15 is easily oxidized (corroded) and deteriorated. As a result, the interconnect easily decreases in reliability and performance.
However, in the third embodiment, the upper-layer SiCO:H film 31 having a film structure which is denser than that of the lower-layer SiCO:H film 6 is formed on the lower-layer SiCO:H film 6 as in the second embodiment. As described in the first and second embodiments, the upper-layer SiCO:H film 31 which is a dense layer is not easily oxidized. For this reason, an influence (oxidization) of the NH3 gas to the lower-layer SiCO:H film 6 is reduced by the presence of the upper-layer SiCO:H film 31 which is a dense layer. In other words, when the PAr film 41 is etched to dig down the upper layer interconnect recessed part 45, damage of the NH3 gas to the lower-layer SiCO:H film 6 is reduced by the upper-layer SiCO:H film 31. As a result, in the semiconductor device 47 according to the embodiment and the method of manufacturing the same, the risk that the Cu upper-layer interconnect 15 is considerably deteriorated in reliability and performance is very low. This is true in the TaN film (barrier metal film) 13 formed to cover the Cu upper-layer interconnect 15. As a result, the interconnect structure of the embodiment is improved in reliability and performance.
The chemical reactions expressed by the chemical equations (2) and (3) are only several typical chemical reactions of various chemical reactions caused between the lower-layer SiCO:H film 6 and the NH3 gas. Actually, various chemical reactions except for the chemical reactions expressed by the chemical equations (2) and (3) occur between the lower-layer SiCO:H film 6 and the NH3 gas.
The method of manufacturing a semiconductor device according to the present invention is not limited to the first to third embodiments. The method can be executed by changing some configurations, some manufacturing steps, or the like of the first to third embodiments into various settings or using appropriate combinations of the various settings without departing from the spirit and scope of the invention.
For example, although the plasma processing to the lower-layer SiCO:H film 6 and the film-forming process of the SiCN:H film 7 are performed in the same step in the first embodiment, this configuration does not limit the invention. The plasma processing to the lower-layer SiCO:H film 6 and the film-forming process of the SiCN:H film 7 may be performed in different steps, respectively.
Although the SiCN:H film 27 is employed as a precoat film formed in the reaction vessel 19 in the first and second embodiments, the SiCN:H film 27 does not limit the invention. The precoat film 27 may be formed by a material including at least an element except for oxygen (O). More preferably, the precoat film 27 may be formed by a material which is free from oxygen and contains at least one element of silicon (Si), carbon (C), and nitrogen (N). For example, an SiCN:H film may be formed as the precoat film 27 by using a gas mixture of monosilane (SiH4) and ammonia (NH3). Alternatively, an SiC:H film is employed in place of the SiCN:H film 27, the same antioxidant effect as that of the SiCN:H film 27 can be obtained when a film-forming process is performed in the reaction vessel 19.
Similarly, although an argon gas is used as a gas for plasma processing to the lower-layer SiCO:H film 6 or the upper-layer SiCO:H film 31 in the first and second embodiments, the gas for plasma processing is not limited to the argon gas. A gas containing a noble gas as a main component may be used as the gas for plasma processing. For example, also when a gas containing at least one element of helium (He), neon (Ne), krypton (Kr), xenon (Xe), and radon (Rn) as a main component in place of argon (Ar), the same effects as those in the first and second embodiments can be obtained. Alternatively, a plasma processing to the lower-layer SiCO:H film 6 or the upper-layer SiCO:H film 31 may be performed more than once by using noble gases of different types. For example, after a plasma processing is performed to the lower-layer SiCO:H film 6 or the upper-layer SiCO:H film 31 by using a plasma argon gas, a plasma processing may be continuously performed by using a plasma helium gas. According to an experiment executed by the present inventors, it has been confirmed that the same effects as those in the first and second embodiments can be obtained by using the plasma processing described above.
The plasma process to the SiCO:H film or the like in the first embodiment and the electron beam irradiation in the second and third embodiments are performed at about 350° C. which is equal to the film-forming temperatures of the SiCO:H films in the first to the third embodiments. However, the set temperatures are not limited to 350° C. According to an experiment executed by the present inventors, it has been confirmed that, when a temperature at which a plasma processing or electron beam irradiation is performed to the SiCO:H film or the like is about 450° C. or less, the same effects as those in the first to third embodiments can be obtained.
In the second and third embodiments, organic silane which is not contained in the film-forming material of the porous lower-layer SiCO:H film 6 is used as one of film-forming materials of the upper-layer SiCO:H film 31 serving as a dense layer, but different materials are not always used. According to an experiment executed by the present inventors, it has been confirmed that, even though the same source gas as the film-forming material of the lower-layer SiCO:H film 6 is used as the film-forming material of the upper-layer SiCO:H film 31, the same effect as described above can be obtained by optimizing discharging conditions.
The effects obtained by the first to third embodiments are not limited to the same interconnect structures as those in the semiconductor devices 17, 33, and 47 in the first to third embodiments. According to an experiment executed by the present inventors, it has been confirmed that, when an interconnect structure of at least one type of the interconnect structures shown in
Although the SiCO:H films 6 and 31 are used as main low-relative-dielectric-constant interlayer insulating films in the first to third embodiments, the low-relative-dielectric-constant interlayer insulating films are not limited to the SiCO:H films. As the low-relative-dielectric-constant interlayer insulating film, a low-relative-dielectric-constant film containing at least oxygen and having a relative dielectric constant of 3.3 or less may be used. Preferably, a low-relative-dielectric-constant interlayer insulating film made of a material containing oxygen and at least one element of silicon (Si), carbon (C), and hydrogen (H) is used, the same effects as those in the first to third embodiments can be obtained. Similarly, although the SiO2 films 8 and 44 are used as the upper-layer oxide films of the low-relative-dielectric-constant interlayer insulating films in the first to third embodiments, the upper-layer oxide film is not limited to the SiO2 film. The upper-layer oxide film may be formed by a material containing oxygen. Preferably, when an upper-layer oxide film made of a material containing oxygen and at least silicon (Si) is used, the same effects as those in the first to third embodiments can be obtained.
In the first embodiment, a high-frequency voltage of about 13.56 MHz is applied to the upper electrode 21 when the SiCN:H film 27 is precoated on the inside (processing chamber 20) of the reaction vessel 19. However, the high-frequency voltage is not limited to about 13.56 MHz. The value of the high-frequency voltage applied to the upper electrode 21 may be appropriately set depending on the film quality, the film thickness, and the like of the precoat film 27 such that the precoat film 27 is appropriately formed.
Furthermore, the plasma CVD apparatus 18 used in the first and second embodiments is not used to form only the SiCN:H film 27. By using the plasma CVD apparatus 18, films of different types may be formed on the semiconductor substrate 1 in the reaction vessel 19. In this case, for example, after a film of one type is formed in the reaction vessel 19, an etching gas (cleaning gas) which etches and decomposes the film adhering to the inside of the reaction vessel 19 into a gas is supplied into the reaction vessel 19 through the air-supply holes 21a of the air-supply nozzle (upper electrode) 21. After the film adhering to the inside of the reaction vessel 19 is decomposed into a gas not to influence the next film-forming process, the gas and the gas in the reaction vessel 19 may be exhausted out of the reaction vessel 19 through the exhaust pipe 25 and the vacuum pump 26. Thereafter, a gas serving as a material of a precoat film suitable for the next film-forming process is supplied into the reaction vessel 19 through the air-supply holes 21a of the air-supply nozzle (upper electrode) 21, and a new precoat film may be coated on the inside of the reaction vessel 19. When these steps are repeated to make it possible to form high-quality insulating films of different types such that the insulating films are rarely deteriorated in film quality by oxidization to the low-relative-dielectric-constant films by using one plasma CVD apparatus 18.
Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
Number | Date | Country | Kind |
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2005-050939 | Feb 2005 | JP | national |