Patent Application
20140134852
The present application is based upon and claims the benefit of priority to Japanese Patent Application No. 2012-251106, filed Nov. 15, 2012, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method and an apparatus for forming a low-k film on a substrate and a method for detaching a porogen.
2. Description of Background Art
In a semiconductor device such as a complementary metal oxide semiconductor (CMOS) device, copper (Cu) having a low electric resistance is usually employed as a wiring material for a fast processing. However, unlike aluminum (Al) which is widely employed in the art, it is difficult to apply plasma etching to copper. In this regard, when copper is used as a wiring material, a dual damascene technique is applied, in which a via hole or a trench matching a wiring is formed on an insulation film through etching in advance, and copper is buried in the trench through electroplating.
In a semiconductor device developed in recent years, the wiring is densely arranged to the point that crosstalk is generated between neighboring wirings. For alleviating the crosstalk, a low-dielectric insulation film (hereinafter referred to as a “low-k film”) is employed as an interlayer insulation film for lowering a dielectric constant of the insulation film interposed between the wirings (for example, refer to JP 2005-236285 A). As the low-k film, a porous low-k film is employed. The porous low-k film is formed by forming a SiOCH film containing a porogen, which is a hydrocarbon having a large molecular weight, through a plasma-enhanced chemical vapor deposition (PECVD) technique or a spin-on dielectric (SOD) technique and detaching multiple porogens from the SiOCH film to form pores in the film. The entire contents of this publication are incorporated herein by reference.
According to one aspect of the invention, a method for forming a porous low-k film having an Si—O structure includes irradiating infrared light upon a film including a material having an Si—O structure, and irradiating ultraviolet light upon the film including the material having the Si—O structure such that a porous low-k film including the material having the Si—O structure is formed. The irradiating of the infrared light has an irradiation period of infrared light which is set shorter than an irradiation period of ultraviolet light in the irradiating of the ultraviolet light.
According to another aspect of the invention, an apparatus for forming a low-k film includes a holding device which holds a substrate on which a film including a material having an Si—O structure is formed, an infrared light emitting device which irradiates infrared light upon the film including the material having the Si—O structure formed on the substrate held by the holding device, an ultraviolet light emitting device which irradiates ultraviolet light upon the film including the material having the Si—O structure formed on the substrate held by the holding device, and a control device which controls the infrared light emitting device and the ultraviolet light emitting device such that an irradiation period of infrared light by the infrared light emitting device is shorter than an irradiation period of ultraviolet light by the ultraviolet light emitting device.
According to yet another aspect of the invention, a method for detaching a porogen, includes irradiating infrared light upon a material having a structure which includes CxHy in a bonding structure, and irradiating ultraviolet light upon the material having the structure which includes the CxHy in the bonding structure such that the CxHy in the bond structure is detached from the material having the structure which includes the CxHy in the bonding structure. The irradiating of the infrared light has an irradiation period of infrared light which is set shorter than an irradiation period of ultraviolet light in the irradiating of the ultraviolet light.
A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:
The embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings.
Referring to
A window 15 is fitted to a part of a ceiling portion of the chamber 11 facing the UV lamp 13 so that the ultraviolet light emitted from the UV lamp 13 transmits through the window 15 and arrives at a wafer W placed on the stage 12. The UV lamp 13 may be, for example, a direct current (DC) lamp or a pulse lamp. Specifically, the UV lamp 13 may be, for example, a heavy hydrogen lamp, a mercury lamp, a metal-halide lamp, or a xenon lamp. In the UV lamp 13, the ultraviolet light is generated, for example, from a microwave source, an arc discharge, a dielectric barrier discharge, or electron collision. An output power density of the ultraviolet light is set at approximately 0.1 to 2000 mW/cm2, and a wavelength of the ultraviolet light is set at approximately 100 to 600 nm. Since the UV lamp 13 emits the ultraviolet light across a wide range, the ultraviolet light can be irradiated at the entire surface of the wafer W.
Instead of the UV lamp 13, an ultraviolet light-emitting diode (UVLED) or an ultraviolet laser light emitter may also be employed. The ultraviolet light emitter may include a light emitter capable of emitting a semiconductor laser (diode), a (nitrogen) gas laser, a third harmonic generation Nd:YAG laser, or a copper vapor laser.
A window 16 is also fitted to a part of the ceiling portion of the chamber 11 facing the infrared laser light emitter 14 so that the infrared laser light emitted from the infrared laser light emitter 14 transmits through the window 16 and arrives at the wafer (W) placed on the stage 12. The infrared laser light emitter 14 includes a carbon gas laser oscillator in which a carbon dioxide (CO2) is used as a medium. The output power density of the infrared laser light is set at approximately 5000 W/cm2 at maximum, and a wavelength of the infrared laser light is set at approximately 1 to 25 μm. While the infrared laser light emitter 14 irradiates the infrared laser light condensed by a condensing lens at a part of the wafer (W), an orientation angle can change so that the condensed infrared laser light can be irradiated at the surface of the wafer (W).
It is also an option to use a semiconductor laser (diode), a YAG laser, YVO4 laser or a Yb-fiber laser instead of the carbon laser oscillator.
The curing treatment apparatus 10 applies curing treatment to the SiOCH film formed on the wafer (W) to form a low-k film 20. In the curing treatment, the SiOCH film of the wafer (W) is heated by the infrared laser light, and a porogen is detached. In addition, a Si—O bond inside the SiOCH film is reinforced by the ultraviolet light.
Referring to
The low-k film 20 is formed by applying the curing treatment of
The barrier layer 23 is made of a metal layer, a metal nitride layer, and a combination thereof. In addition, a portion of the barrier layer 23 making contact with the low-k film 20 may be made of a metal nitride film, and a portion of the barrier layer 23 making contact with the copper wire 21 or the copper via 22 may be made of a metal layer.
For example, the metal nitride film making contact with the low-k film 20 is made of a tantalum nitride (TaN) or a titanium nitride (TiN), and the metal layer making contact with the copper wire 21 or the copper via 22 is made of, for example, tantalum (Ta), titanium (Ti), ruthenium (Ru), or rhenium (Re).
In order to obtain a structure related to both a low dielectric constant and film strength of the low-k film 20, minute porogens are detached from the SiOCH film. To detach minute porogens, the SiOCH film is heated for a long time. However, in the semiconductor device 18, films or structures other than the low-k film 20 may be adversely affected by heating for such a long period.
It was determined that each porogen can be detached from the SiOCH film and adverse effects caused by heating films or structures other than the SiOCH film can be prevented by applying the curing treatment to the SiOCH film and heating the SiOCH film to a high temperature of, for example, 500° C. or higher for a short period of, for example, 2 seconds to form the low-k film 20.
It is difficult to clearly describe why porogens can be detached by heating the SiOCH film to a temperature of 500° C. or higher even for a short period. However, as a result of observing a process of forming the low-k film 20 through the curing treatment, the inventors analyzed that, while the SiOCH film is heated to a vicinity of 400° C., it is difficult to detach each porogen because each porogen is not highly active, and a binding such as a Si—O—Si bond of the SiOCH film that binds each porogen has not loosened much, while once the SiOCH film is heated to 500° C. of higher, each porogen becomes highly active, and a binding of the Si—O—Si bond of the SiOCH film that binds each porogen is loosened so that each porogen is easily detached.
In a film formation apparatus separate from the curing treatment apparatus 10, a wafer (W) having a SiOCH film containing multiple minute porogens on the silicon substrate 19 is introduced into the inside of the chamber 11 of the curing treatment apparatus 10 and is placed on the stage 12. The SiOCH film formed by the film formation apparatus has a structure in which multiple silicon atoms (Si) linking to a hydrocarbon group or a hydroxyl group are bonded to each other by interposing an Si—O bond or an Si—CH2 bond, and multiple porogens (CxHy) are interposed between such bond structures as illustrated in
Then, the wafer (W), specifically the SiOCH film, is heated to a high temperature (hereinafter, referred to as a “base temperature”) (first temperature) of, for example, 360° or higher but 430° C. or lower, preferably 360° C. or higher but 380° C. or lower using the heater 17, and ultraviolet light is irradiated at the SiOCH film using the UV lamp 13 (ultraviolet light irradiation step) (step S30). In addition, infrared laser light is irradiated at the SiOCH film from the infrared laser light emitter 14, and the infrared laser light is irradiated at the surface of the SiOCH film (infrared light irradiation step) (step S30).
The heating using the heater 17 and the irradiation of ultraviolet light are continuously performed for a relatively long period, for example, 180 seconds. In addition, in the irradiation of the infrared laser light, an irradiation period of the infrared laser light for each part of the SiOCH film is set for a short period, for example, 2 seconds or shorter, preferably, 0.5 seconds or shorter. However, a vibration is generated in each Si—O bond of the SiOCH film by the infrared laser light to generate instantaneous heating, so that each part of the SiOCH film is heated to a temperature higher than a base temperature (hereinafter, referred to as a “spike temperature”) (second temperature), for example, of 500° C. or higher but 700° C. or lower, preferably 550° C. or higher but 700° C. or lower, and more preferably 600° C. or higher but 700° C. or lower.
The high-temperature and short-period heating based on infrared laser light irradiation described above is called spike annealing, and a temperature profile of the SiOCH film in the spike annealing is illustrated in
The temperature profile of
In step S30, once the SiOCH film is heated to 500° C. or higher even for a short period by irradiating infrared laser light, motions of each porogen are activated and instantaneously detached from the aforementioned bond structure (refer to
In the curing treatment in
In the curing treatment of
While embodiments of the present invention have been described above, the present invention is not limited to the aforementioned embodiments.
The curing treatment in the method for forming the low-k film according to the embodiment is not limited to the processing shown in
Alternatively, as illustrated in
In the curing treatment of either of
In the method for forming the low-k film according to the present embodiment, a pure SiOCH film is employed as a film with an Si—O structure for applying the curing treatment. However, the film for applying the curing treatment is not limited to the pure SiOCH film and may include an SiOCH film containing some additives. In addition, a film having an Si—O structure containing porogens and capable of substituting the Si—OH bond or the Si—CH3 bond with the Si—O bond when irradiated by ultraviolet light may be employed.
Also, by installing a storage medium that stores codes of a software program capable of implementing functionalities of the embodiments described above in a computer provided in the curing treatment apparatus 10 or the film formation apparatus, a CPU of the computer reads the program codes stored in the storage medium and executes the command.
In this case, the program codes read from the storage medium implement functionalities of the aforementioned embodiments, and the program codes and the storage medium that stores the program codes embody an embodiment of the present invention.
A storage medium may take any form, including but not limited to, a random access memory (RAM), a non-volatile (NV) RAM, a floppy disk (registered trademark), a hard disk, an optical-magnetic disk, optical disks such as CD−ROM, CD−R, CD−RW, and DVD (such as DVD−ROM, DVD−RAM, DVD−RW, and DVD+RW), a magnetic tape, a non-volatile memory card, and other ROMs as long as it can store the program codes. Alternatively, the program codes may be downloaded and supplied to the computer from a computer or database connected via the Internet, a commercial network, a local area network or the like.
By executing the program codes read by the computer, functionalities of the embodiments described above are implemented, and an operating system (OS) or the like operated on the CPU may execute a part or all of the processes in practice in response to the commands from the program in order to implement the functionalities of the embodiments described above.
The functionalities of the embodiments described above may also be embodied when the program codes read from the storage medium are written to a functionality expansion board inserted in a computer or a functionality expansion unit connected to a computer, and a CPU or the like provided in the functionality expansion board or the functionality expansion unit then executes a part or all of the processes in practice.
The program codes may have many forms such as an object code, a program code executed by an interpreter, and script data supplied to the OS.
Hereinafter, examples according to the present invention will be described.
Influence on the low-k film caused by heating it for a short period to a spike temperature was examined.
Initially, in Example 1, a wafer (W) obtained by forming an SiOCH film on a silicon substrate 19 was prepared, and pressure inside a chamber 11 of a curing treatment apparatus 10 was set at 15 Torr. Then, the SiOCH film of the wafer (W) was heated to a base temperature of 380° C. for 180 seconds according to the curing treatment in
Next, in Comparative Example 1, a wafer (W) obtained by forming a SiOCH film on a silicon substrate 19 was prepared, and pressure inside a chamber of a curing treatment apparatus was set to 15 Torr. Then, a conventional curing treatment was applied for 300 seconds to form a low-k film. Specifically, the SiOCH film of the wafer (W) was heated to a base temperature of 435° C. using a heater 17, and ultraviolet light was irradiated at the SiOCH film to form the low-k film. Infrared laser light was not irradiated at each part of the SiOCH film.
Then, a component of the low-k film 20 of Example 1 and a component of the low-k film of Comparative Example 1 were analyzed using a Fourier transform infrared spectroscopy (FTIR) analyzer, and the results are illustrated in the graphs in
A porogen absorbs infrared light having a wavenumber of 2850 to 2940 cm−1 in the FTIR. However, as illustrated in
From the aforementioned description, it was found that each porogen can be sufficiently detached when the SiOCH film is heated to the spike temperature (620° C. in Example 1) even through instantaneous heating.
The Si—CH3 bond contributing to a low dielectric constant of the low-k film absorbs infrared light having a wavenumber of 1275 cm−1 in the FTIR. However, as illustrated in the graph of
That is, it was found that a bonding state in the low-k film structure is not damaged if the heating is performed for a short period even at a high spike temperature. In addition, it was also found that the structure of the low-k film relating to the film strength and the dielectric constant are not affected.
Although not illustrated in the graphs of
From the aforementioned description, it was found that the film strength or the dielectric constant of the low-k film between Example 1 and Comparative Example 1 is not different even when the base temperature of Example 1 is set at 380° C. and the base temperature of Comparative Example 1 is set at 435° C. Therefore, it was found that the temperature of the curing treatment of the low-k film is effectively lowered by applying spike annealing at a high temperature for a short duration.
Comparing the curing treatment period between Example 1 and Comparative Example 1, the curing treatment period is set for 180 seconds in Example 1 and 300 seconds in Comparative Example 1. That is, it was found that the curing treatment period can be reduced by applying spike annealing at a high temperature for a short period.
In Example 2, a wafer (W) obtained by forming a SiOCH film on a silicon substrate 19 was prepared, and pressure inside a chamber 11 of a curing treatment apparatus 10 was set at 15 Torr. Then, the SiOCH film of the wafer (W) was heated to a base temperature of 400° C. for 210 seconds according to the curing treatment of
Next, in Comparative Example 2, a wafer (W) obtained by forming an SiOCH film on a silicon substrate 19 was prepared, and pressure inside a chamber of a curing treatment apparatus was set at 3 Torr. Then, a curing treatment was applied for 300 seconds to form a low-k film. Specifically, the SiOCH film of the wafer (W) was heated to a base temperature of 420° C. using a heater 17 and through infrared light irradiation using an IR lamp, and ultraviolet light was irradiated at the SiOCH film to form the low-k film.
Then, a component of the low-k film 20 of Example 1 and a component of the low-k film of Comparative Example 1 were analyzed using a FTIR analyzer, and the results are shown in the graphs of
As shown in
From the aforementioned description, similar to comparison between Example 1 and Comparative Example 1, it was found that each porogen can be sufficiently detached as the SiOCH film is heated to the spike temperature (600° C. in Example 2) even through instantaneous heating.
As illustrated in the graph of
Although not illustrated in the graphs of
Next, influence on the film strength and the dielectric constant caused by applying spike annealing at a high temperature for a short period was examined in detail.
In Example 3, a wafer (W) obtained by forming an SiOCH film on a silicon substrate 19 was prepared, and pressure inside a chamber 11 of a curing treatment apparatus 10 was set at 15 Torr. Then, the SiOCH film of the wafer (W) was heated to a base temperature of 400° C. for 180 seconds, 360 seconds, and 540 seconds according to the curing treatment in
In Example 4, a wafer (W) obtained by forming a SiOCH film on a silicon substrate 19 was prepared, and pressure inside a chamber 11 was set at 15 Torr. Then, the SiOCH film was heated to a base temperature of 400° C. for the same period as that of Example 3 according to the curing treatment of
Next, in Comparative Example 3, a wafer (W) obtained by forming a SiOCH film on a silicon substrate 19 was prepared, and pressure inside a chamber of a curing treatment apparatus having an IR lamp capable of irradiating the entire surface of the wafer W was set at 15 Torr. Then, a curing treatment was applied for 180 seconds, 360 seconds and 540 seconds to form a low-k film. Specifically, by irradiating infrared light at the SiOCH film of the wafer (W) using a heater 17 and the IR lamp, the SiOCH film was heated to a base temperature of 400° C. Then, ultraviolet light was irradiated at the SiOCH film to form the low-k film.
Then, film shrinkage factors (serving as an index of the film strength of the low-k film) and refractive indices (serving as an index of the dielectric constant of the low-k film) of the low-k films 20 of Examples 3 and 4 and Comparative Example 3 were measured. The results are illustrated in the graph in
In general, as the refractive index decreases, porogens are detached better, and the dielectric constant decreases. However, in the graph in
In general, as the film shrinkage factor increases, the Si—O bond is reinforced, and the film strength is improved. However, referring to the graph in
Next, influence on the sheet resistance of the silicon substrate caused by the curing treatment was examined.
In Example 5, a wafer (W) was prepared, and phosphorus (P) was doped on the silicon substrate 19. Then, a silica (SiO2) film was formed on the wafer (W), and an SiOCH film was formed on the silica film. Then, the SiOCH film of the wafer (W) was heated to a base temperature of 400° C., and infrared laser light was irradiated at the surface of the SiOCH film to form a low-k film 20. While the irradiation period of infrared laser light for each part of the SiOCH film was set to be 0.08 seconds, each part of the SiOCH film was heated to 550° C. (spike temperature). That is, spike annealing was applied to the SiOCH film of Example 5 at a high temperature for a short period.
Then, the silica film and the SiOCH film were removed from the wafer (W) and the sheet resistance of the exposed silicon substrate 19 was measured. The result is illustrated in the graph in
Next, in Comparative Examples 4 to 9, a wafer was prepared, and phosphorous was doped on the silicon substrate 19 of the wafer (W). Then, a silica film was formed on the wafer (W), and a SiOCH film was formed on the silica film. Then, the SiOCH film of each wafer (W) was heated for 190 seconds to 350° C. (Comparative Example 4), 400° C. (Comparative Example 5), 450° C. (Comparative Example 6), 500° C. (Comparative Example 7), 550° C. (Comparative Example 8), and 600° C. (Comparative Example 9).
Then, the silica film and the SiOCH film were removed from each wafer (W), and the sheet resistance of the exposed silicon substrate 19 was measured. The results are shown in the graph of
Referring to the graph of
That is, if the spike annealing is applied at a high temperature for a short period, the thermal budget does not increase. Therefore, it is found that adverse effects caused by heating the silicon substrate 19 in the curing treatment are prevented.
If the SiOCH film is heated for a longer period in order to detach multiple porogens from the SiOCH film, the amount of heat (thermal budget) received by the SiOCH film increases. For this reason, there may be an adverse effect caused by heating films or structures other than the low-k film, such as a wiring fracture or a decrease of the sheet resistance of the silicon substrate as an underlying layer.
In the method and apparatus for forming the low-k film and the method for detaching a porogen according to embodiments of the present invention, adverse effects caused by heating films or structures other than the Si—O structure film can be prevented.
In the method for forming a low-k film and the method for detaching a porogen according to an embodiment of the present invention, there is provided a method for forming a porous low-k film having an Si—O structure, including an infrared laser light irradiation step for irradiating infrared light, and an ultraviolet light irradiation step for irradiating ultraviolet light. In such a method, an irradiation period of the infrared light is set shorter than an irradiation period of the ultraviolet light.
According to an embodiment of the present invention, there is provided an apparatus for forming a low-k film, including an infrared light emitting unit structured to irradiate infrared light at an Si—O structure film formed on a substrate for a short period, and an ultraviolet light emitting unit structured to irradiate ultraviolet light at the Si—O structure film. In such an apparatus, an irradiation period of the infrared light emitting unit is set shorter than an irradiation period of the ultraviolet light emitting unit.
Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-251106 | Nov 2012 | JP | national |
