The disclosure of Japanese Patent Application No. 2010-220294, filed on Sep. 30, 2010 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Technical Field
The present invention relates to a semiconductor device and a method of manufacturing the same.
2. Related Art
In silicon semiconductor integrated circuits (hereinafter, referred to as LSIs), formerly aluminum (Al) or an Al alloy has been widely used as a conductive material. With the progress of miniaturization of LSIs, copper (Cu) has been used as a conductive material in order to achieve the reduction in the interconnect resistance and the high reliability of the interconnect. Since Cu is easily diffused into a silicon oxide film, a technique is known in which a barrier insulating film is formed on the upper surface of a Cu interconnect, to thereby prevent Cu from being diffused (see, for example, Japanese Unexamined Patent Publication No. 2007-88495, Japanese Unexamined Patent Publication No. 2009-170872, and Japanese Unexamined Patent Publication No. 2009-182000).
For example, Japanese Unexamined Patent Publication No. 2007-88495 discloses a technique for forming a barrier insulating film having a thickness of 30 to 150 nm so as to cover the upper portion of the Cu interconnect, and forming a SiOCH film having a thickness of 200 to 500 nm as an insulating interlayer on the barrier insulating film.
In addition, Japanese Unexamined Patent Publication No. 2009-170872 discloses a technique for forming a silicon carbide-based barrier layer including a silicon-carbon bond or a carbon-carbon bond such as a carbon-carbon single bond (C—C), a carbon-carbon double bond (C═C), and a carbon-carbon triple bond (C≡C), or a combination thereof. Thereby, it is possible to provide a method of forming a dielectric barrier having a low dielectric constant, an improved etching resistance, and an excellent barrier performance.
Further, Japanese Unexamined Patent Publication No. 2009-182000 discloses a technique for making the density of at least a portion of a second insulating barrier film higher by performing high-density treatment. In this way, even when the second insulating barrier film becomes thin, it is possible to prevent water from infiltrating from a low-dielectric-constant insulating film provided on the second insulating barrier film, and to obtain an interconnect structure having a low effective relative dielectric constant while preventing surface oxidation of a copper film provided below the second insulating barrier film, and sufficiently securing the electro migration (EM) resistance of an interconnect and the time dependent dielectric breakdown (TDDB) lifetime between interconnects.
The present inventors have now discovered a problem in the related art disclosed in Japanese Unexamined Patent Publication No. 2009-182000, which the higher density of the barrier insulating film cause the higher dielectric constant of that. For this reason, there has been a problem that the effective dielectric constant can be decreased only if a high-density layer makes very thin. However, in the technique disclosed in Japanese Unexamined Patent Publication No. 2009-182000, since a high-density layer is formed by high-density treatment on a SiCO film formed on a Cu film through helium plasma treatment, it has been very difficult to control the thickness of the high-density layer.
The present inventors also have discovered a problem water permeability of the barrier insulating film formed by 4MS (tetramethylsilane) is high. Therefore, we have recognized that problems such as EM and TDDB cannot be sufficiently solved by the barrier insulating film formed by 4MS.
Accordingly, it has been discovered that the techniques mentioned above has made it impossible to sufficiently improve the reliability of a semiconductor device having a fine interconnect.
In one embodiment, there is provided a semiconductor device including:
a metal interconnect; and
a barrier insulating film provided over the metal interconnect, which prevents a metal from being diffused from the metal interconnect,
wherein the barrier insulating film is made of a silicon-based insulating film having a branched alkyl group and a carbon-carbon double bond.
In another embodiment, there is provided a method of manufacturing a semiconductor device, including:
forming a metal interconnect; and
forming a barrier insulating film on the metal interconnect, which prevents a metal from being diffused from the metal interconnect,
wherein forming the barrier insulating film includes forming a silicon-based insulating film having a branched alkyl group and a carbon-carbon double bond.
According to the invention, since the barrier insulating film is made of a silicon-based insulating film having a branched alkyl group and a carbon-carbon double bond, it is possible to secure the EM resistance and the TDDB lifetime between interconnects by suppressing the water permeability while reducing the effective relative dielectric constant. Therefore, it is possible to improve the reliability of a semiconductor device having a fine interconnect.
According to the invention, it is possible to improve the reliability of a semiconductor device having a fine interconnect.
The above and other objects, advantages and features of the present invention will be more apparent from the following description of certain preferred embodiments taken in conjunction with the accompanying drawings, in which:
The invention will be now described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teachings of the present invention and that the invention is not limited to the embodiments illustrated for explanatory purposes.
Hereinafter, the embodiment of the invention will be described with reference to the accompanying drawings. In all the drawings, like elements are referenced by like reference numerals and signs and descriptions thereof will not be repeated.
Hereinafter, the semiconductor device of the embodiment will be described in detail. The semiconductor device of the embodiment includes a lower-layer film in which transistors are formed on a semiconductor substrate (not shown), and a first insulating interlayer 101 is formed on the lower-layer film. In addition, the first barrier insulating film 103, a second insulating interlayer 104, and the second barrier insulating film 106 are laminated on the first insulating interlayer 101 in this order.
The first and second insulating interlayers 101 and 104 are all low dielectric constant films having a relative dielectric constant lower than the relative dielectric constant (k=3.9 to 4.5) of a silicon oxide film. The thicknesses of the first and second insulating interlayers 101 and 104 are larger than that of the first barrier insulating film 103, and can be set to, for example, 200 to 500 nm. The first and second insulating interlayers 101 and 104 can be formed as, for example, a SiCH film, a SiCNH film, a SiCOH and a SiCONH film.
Trenches are formed in each of the first insulating interlayers 101 and the second insulating interlayer 104. A first barrier metal film 102a and a first Cu film 102b are formed in the inside of the trench formed in the first insulating interlayer 101, which constitute the first Cu interconnect 102. In addition, a second barrier metal film 105a and a second Cu film 105b are formed in the inside of the trench formed in the second insulating interlayer 104, which constitute the second Cu interconnect 105. Further, via 107 is formed in the second insulating interlayer 104. Via 107 passes through the first barrier insulating film 103, and is connected to the first Cu interconnect 102 formed in the first insulating interlayer 101. A via hole is formed in the second insulating interlayer, and a third barrier metal film 107a and a third Cu film 107b are formed in the inside thereof to give the via 107.
The first, second, and third barrier metal films 102a, 105a, and 107a are respectively films containing tantalum (Ta) or titanium (Ti) as a main metal, and can be formed of, for example, Ta, TaN, TiN or the like. The first, second, and third barrier metal films 102a, 105a, and 107a may be a single layer, and may be a layer in which two or more different types of layers are laminated. Thereby, it is possible to prevent Cu in the first Cu interconnect 102 from being diffused to the first insulating interlayer 101. In addition, it is possible to prevent Cu in the second Cu interconnect 105 and the via 107 from being diffused to the second insulating interlayer 104.
The first, second, and third Cu films 102b, 105a, and 107a may be a film containing Cu as a main component, may be a film made of only Cu, and may be a Cu alloy containing Cu and other metals (Al, Mn, Mg and the like).
The first Cu film 102b exposed to the surface of the first insulating interlayer 101, and the second and third Cu films 105b and 107b exposed to the surface of the second insulating interlayer 104 may be covered with a cap metal film (not shown). The cap metal film can be formed of a film containing, for example, cobalt (Co), tungsten (W) or the like as a main component.
The first and second barrier insulating films 103 and 106 may be a silicon-based insulating film having a branched alkyl group and a carbon-carbon double bond, and can be set to be 1 to 100 nm in thickness. The branched alkyl group is preferably a substituent having a C—CH3 bond. The branched alkyl group and the carbon-carbon double bond can be confirmed by examining infrared absorption with infrared spectroscopy.
The relative dielectric constant k of the first and second barrier insulating films 103 and 106 can be set to 4.0 or less, more preferably 3.5 or less, and much more preferably 3.0 or less. In addition, the first and second barrier insulating films 103 and 106 make possible to decrease the water permeability while maintaining such a low dielectric constant. For example, it is possible to maintain the low water permeability even under the conditions of the temperature of 105 to 143° C., the humidity of 75 to 100%, the pressure of 0.02 to 0.2 MPa, and 100 hours.
The first and second barrier insulating films 103 and 106 may be a silicon-based insulating film containing silicon (Si), and can be formed of any of a SiCH film, a SiCNH film, a SiCOH film, a SiCONH film or the like. Nitrogen atom (N) or oxygen atom (O) is contained in the first and second barrier insulating films 103 and 106 like the SiCNH film, the SiCOH film and the SiCONH film, thereby allowing the leakage current to be reduced. In addition, nitrogen atom (N) is contained in the first and second barrier insulating films 103 and 106 like the SiCNH film and the SiCONH film, thereby allowing the ratio of the dry etching selectivity to the upper-layer insulating interlayer such as the second insulating interlayer 104 to be increased. In addition, oxygen atoms (O) are added to the first and second barrier insulating films 103 and 106 like the SiCOH film and the SiCONH film, thereby allowing the adhesion to the upper-layer insulating interlayer such as the second insulating interlayer 104 to be improved.
An insulating film (for example, SiCN film or the like) made of a material different from that of the first insulating interlayer 101 and the first barrier insulating film 103 may be provided between the first insulating interlayer 101 and the first barrier insulating film 103. In addition, similarly, an insulating film made of a material different from that of the second insulating interlayer 104 and the second barrier insulating film 106 can also be provided between the second insulating interlayer 104 and the second barrier insulating film 106. In this way, it is possible to improve the adhesion between the first insulating interlayer 101 and the first barrier insulating film 103, or between the second insulating interlayer 104 and the second barrier insulating film 106.
Subsequently, an example of a method of manufacturing the semiconductor device of the embodiment will be described with reference to
Subsequently, the first barrier metal film 102a is formed in the trench 102c by a sputtering method or a CVD method, and then first Cu film 102b is buried by a sputtering method, a CVD method or a plating method. The first barrier metal film 102a and the first Cu film 102b is removed on the first insulating interlayer 101 by a chemical mechanical polishing (CMP) method (
Subsequently, the first barrier insulating film 103 is formed so as to cover the first insulating interlayer 101 and the first interconnect 102 exposed from the first insulating interlayer 101 (
In general formula (1), R1 is a branched-chain alkyl group having a carbon number of 3 to 6, R2 and R3 are an unsaturated hydrocarbon group or a saturated hydrocarbon group, and X is any one of a silicon atom to which an unsaturated hydrocarbon group or a saturated hydrocarbon group is bonded; a hydrogen atom; a nitrogen atom to which any one of an unsaturated hydrocarbon group and a saturated hydrocarbon group is bonded; an unsaturated hydrocarbon group; or a saturated hydrocarbon group, wherein each of the unsaturated hydrocarbon group and the saturated hydrocarbon group is any one of a vinyl group, an allyl group, and an alkyl group having a carbon number of 1 to 6, and R1, R2, R3 and X may be equal to or different from each other.
Specifically, in general formula (1), R1 is preferably a substituent having a C—CH3 bond, more preferably any one of an isobutyl group, a sec-butyl group, a tert-butyl group, an isopentyl group and an isohexyl group, and particularly preferable an isobutyl group. In addition, X is more preferably a chain-like or branched alkyl group having a carbon number of 1 to 6.
R2 is also preferably a branched-chain alkyl group having a carbon number of 3 to 6. The lower water permeability can be obtained by increasing the number of isobutyl groups bonded to one Si atom. Therefore, any two or more of X, R1, R2 and R3 preferably have an isobutyl group. Further, in general formula (1), X is preferably an unsaturated hydrocarbon group or a saturated hydrocarbon group. In this way, it is possible to form the barrier insulating film made of a SiCH film. For example, butyl silane such as diisobutyl dimethyl silane, isobutyl trimethoxy silane, triisobutyl methyl silane, and tetramethyl isobutyl silane can be used as raw material gas. It is preferable that substituent groups bonding to one Si atom include more branched-chain alkyl groups (particularly, isobutyl groups).
Ammonia gas may be added to a compound of general formula (1) in which X is an unsaturated hydrocarbon group or a saturated hydrocarbon group. In this way, the barrier insulating film made of a SiCNH film can be formed. CO2, CO or O2 gas may be added to the compound in which X is an unsaturated hydrocarbon group or a saturated hydrocarbon group to form a SiCOH film, and N2O or NO gas or the like may be added thereto to form a SiCONH film.
Subsequently, the second insulating interlayer 104 is formed on the first barrier insulating film 103 by a plasma CVD method, and then an trench 105c and a via hole 107c are formed in the second insulating interlayer 104 with a photolithography technique (
Thereafter, the second and third barrier metal films 105a and 107a are simultaneously formed in the trench 105c and the via hole 107c by a sputtering method or a CVD method, and then the second and third Cu films 105b and 107b are simultaneously buried by a sputtering method, a CVD method or a plating method. The second Cu film 105b, the third Cu film 107b, the second barrier metal film 105a and the third barrier metal film 107a on the second insulating interlayer 104 are removed by a chemical mechanical polishing (CMP) method (
Next, the second barrier insulating film 106 is formed by the similar method as that in the first barrier insulating film 103, and the structure of
Subsequently, the operations and effects of the embodiment will be described. According to the semiconductor device of the embodiment, the first and second barrier insulating films 103 and 106 are made of a silicon-based insulating film having a branched alkyl group and a carbon-carbon double bond, and thus water permeability is suppressed while reducing the effective relative dielectric constant, thereby allowing the EM resistance and the TDDB lifetime between interconnects to be secured. Therefore, it is possible to improve reliability of the semiconductor device having a fine interconnect.
It is considered that carbon of a carbon-carbon double bond and a branched alkyl group in the barrier insulating film made of a silicon-based insulating film having a branched alkyl group and a carbon-carbon double bond react with water, and are oxidized to form a C═O bond or the like, thereby trapping water molecules (H2O). In this way, it is assumed that water does not permeate to the lower-layer Cu interconnects, and copper oxide is not generated. Therefore, if the barrier insulating film has a carbon-carbon double bond and a branched alkyl group (particularly, a C—CH3 bond), it is considered to be capable of suppressing (blocking moisture absorption) the water permeability even in the case where the density of the barrier insulating film is not very high.
For example, the barrier insulating film is formed using diisobutyl dimethylsilane (DiBDMS) as the first and second barrier insulating films 103 and 106, thereby allowing the water permeability of the film to be decreased. For this reason, oxidation of the first, second, and third Cu films 102b, 105b, and 107b is suppressed, thereby allowing the Cu oxide film not to be generated.
In the structure of the embodiment, it is preferable to form a SiC(H) film or a SiCN(H) film including a carbon-carbon double bond and a branched alkyl group (particularly, C—CH3 bond) as the barrier insulating film, and to form a SiCOH or SiCONH film or the like thereon as an insulating interlayer. In this way, since the diffusion of water (oxygen) can be reliably blocked, it is possible to more effectively reduce both the relative dielectric constant and the water permeability of the barrier insulating film.
As described above, although the embodiment of the invention has been set forth with reference to the drawings, it is merely illustrative of the invention, and various configurations other than those stated above can be adopted.
For example, in the embodiment, although the Cu interconnect has been described as a metal interconnect by way of example, the embodiment is not limited to the Cu interconnect, and it is possible to obtain the effect of the invention even in the semiconductor device having an aluminum (Al) interconnect or the like.
The structure of
Meanwhile, the CVD growth conditions of the first and second barrier insulating films 103 and 106 were as follows.
<Film Formation Conditions of DiBDMS>
Temperature: 350° C.
Flow rate of DiBDMS: 15 sccm
N2 gas=0 sccm
He gas=0 sccm
RF frequency: 13.56 MHz
RF power: 700 W
Pressure: 0.47 kPa (3.5 Torr)
As shown in
In Evaluation Example 1-1, when nitrogen gas or helium gas of approximately 5,000 sccm was added to the DiBDMS and the plasma CVD method was performed, or when the DiBDMS was formed by taking a margin of approximately 10% in the range of the pressure of 0.2 to 0.67 kPa (1.6 to 5 Torr) and the power of 400 to 650 W, it was possible to confirm the Si—H bond of the HSQ film 601 after the moisture absorption test. Therefore, it was confirmed that the SiCH film formed by the DiBDMS had a low water permeability.
The same conditions with those in evaluation 1-1 were set except that isobutyl trimethoxy silane (iBTMS) was used as raw material gas instead of the DiBDMS, and the plasma conditions were changed to the range of the flow rate of 15 to 30 sccm, the pressure of 0.30 to 0.67 kPa (2.2 to 5 Torr), and the power of 450 to 700 W, to thereby form the SiCH film using a parallel plate type plasma CVD method. The SiCH film having a relative dielectric constant of 3.0, 3.5, and 4.0 was formed. A result of FT-IR is shown in
In Evaluation Example 1-2, when nitrogen gas or helium gas of approximately 5,000 sccm was added to the iBTMS and the plasma CVD method was performed, or when the iBTMS was formed by taking a margin of approximately 10% in the range of the pressure of 0.2 to 0.67 kPa (1.6 to 5 Torr) and the power of 400 to 650 W, it was possible to confirm the Si—H bond of the HSQ film 601 after the moisture absorption test. Therefore, it was confirmed that the SiCH film formed by the iBTMS had a low water permeability.
The same conditions with those in Evaluation Example 1-1 were set except that 4MS (tetramethylsilane: Si(CH3)4) was used as raw material gas instead of the DiBDMS, and the plasma conditions was changed as follows, to thereby form the SiCH film by performing a parallel plate type plasma CVD method. The plasma conditions are shown below. The SiCH film having a relative dielectric constant of 3.6 was obtained.
<Film Formation Conditions of 4MS>
Temperature: 350° C.
Gas flow rate: 30 sccm
N2 gas: 0 sccm
He gas: 0 sccm
RF frequency: 13.56 MHz
RF power: 600 W
Pressure: 0.4 kPa (3 Torr)
A result of FT-IR is shown in
According to the formation conditions of the barrier insulating film of manufacturing example 1, a single-layer SiCH film having a thickness of 100 nm was formed by the DiBDMS, and the moisture absorption test was performed in the PCT conditions of Evaluation Example 1-1.
According to the film formation conditions of Evaluation Example 1-3, a single-layer SiCH film having a thickness of 100 nm was formed by the 4MS, and the moisture absorption test was performed in the PCT conditions of Evaluation Example 1-1.
The result of the SiCH film obtained by Evaluation Examples 2-1 and 2-2 before the PCT with FT-IR is shown in
The result of the SiCH film obtained by Evaluation Examples 2-1 and 2-2 before and after the PCT with FT-IR is shown in
Quantification of the results of FT-IR obtained in Evaluation Example 2-1 and Evaluation Example 2-2 is shown in
Each of the profiles of the SiCH film formed in Evaluation Examples 2-1 and 2-2 before and after the PCT was confirmed in the depth direction by X-ray photoelectron spectroscopy (XPS). The variation of the oxygen concentration in the film before and after the PCT is shown in
It is apparent that the present invention is not limited to the above embodiment, and may be modified and changed without departing from the scope and spirit of the invention.
Number | Date | Country | Kind |
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2010-220294 | Sep 2010 | JP | national |