JP2004273940A - Method and device for pattern formation - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pattern formation method and a pattern formation device which can form a desired pattern in a processing substrate by using F<SB>2</SB>laser beam. <P>SOLUTION: The method has a process for forming a reflection preventing film on a processing substrate, a process for forming a resist film on the reflection preventing film, a process for forming a resist pattern latent image by irradiating the resist film with exposure light via a prescribed mask, a process for forming a resist pattern by developing the resist film, a process for forming a reflection preventing film pattern by etching the reflection preventing film by using the resist pattern as a mask, a process for hardening the reflection preventing film pattern and a process for etching the processing substrate by using the reflection preventing film pattern as a mask after hardening treatment. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pattern forming method and a pattern forming apparatus. ₂ The present invention relates to a pattern forming method and a pattern forming apparatus using an exposure machine using a laser as a light source.
[0002]
[Prior art]
In recent years, as the degree of integration of semiconductor devices has increased, the dimensions of individual elements have been miniaturized, and the widths of wirings, gates, etc. constituting each element have also been miniaturized.
[0003]
The photolithography technology that supports this miniaturization includes a process of applying a resist composition to the surface of a substrate to be processed to form a resist film, and irradiating light to expose a predetermined resist pattern to form a resist pattern latent image. Forming, a heat treatment if necessary, a step of developing this to form a desired resist pattern, and a step of performing processing such as etching on a substrate to be processed using the resist pattern as a mask. included.
[0004]
When a semiconductor device having a fine design rule is manufactured using such a photolithography technique, it is necessary to form a fine resist pattern.
[0005]
As one of means for miniaturizing a resist pattern, shortening of the wavelength of exposure light used for forming the above-described resist pattern latent image has been promoted.
[0006]
Conventionally, in the manufacture of a DRAM (Dynamic Random Access Memory) having a degree of integration of, for example, up to 64 Mbits, an i-line (wavelength: 365 nm) of a high-pressure mercury lamp has been used as a light source. In recent years, a technology using a KrF (krypton fluoride) excimer laser (wavelength: 248 nm) as an exposure light source has been put to practical use in a mass production process of a 256 megabit DRAM. For the manufacture of a DRAM having a degree of integration of 1 gigabit or more, practical use of an ArF (argon fluoride) excimer laser (wavelength: 193 nm) is being studied. Further, as a technique for realizing a fine pattern corresponding to a design rule of 100 nm or less, F has a shorter wavelength. ₂ It has been considered to use a (fluorine) laser (wavelength: 157 nm) as an exposure light source.
[0007]
However, in the step of forming the resist pattern latent image, there have been the following problems conventionally.
[0008]
One is that when exposure light is applied to the resist film, a standing wave is generated inside the resist film due to multiple interference of light, thereby causing exposure unevenness in the thickness direction of the resist film. Such exposure unevenness causes a deterioration in the shape of the resist pattern, leading to a reduction in pattern resolution.
[0009]
The second is a problem of reflection of exposure light when the substrate to be processed has a step. When the resist film is irradiated with exposure light, the exposure light travels through the resist film and is reflected at the interface with the underlying unprocessed substrate. At this time, when the surface of the substrate to be processed is horizontal, light is reflected in a direction opposite to the incident direction. On the other hand, when there is a step on the surface of the substrate to be processed and the exposure light is reflected at this step, the light is reflected in various directions corresponding to the inclination angle of the step. As a result, the reflected light also enters a region that is not originally exposed (a region shielded by the mask) and exposes the resist film in that portion, making it impossible to form a desired resist pattern.
[0010]
In order to solve such a problem, a method of interposing an anti-reflection film between a substrate to be processed and a resist film (Bottom Anti Reflective Coating Method, hereinafter referred to as a BARC method) has been used. According to this method, the exposure light transmitted through the resist film is absorbed by the antireflection film and is not reflected at the interface.
[0011]
A photolithography process using the BARC method will be described with reference to FIGS.
[0012]
First, an antireflection film 62 is formed on a film to be processed 61 formed on a semiconductor substrate 60 (FIG. 11A). Next, a resist film 63 is formed on the antireflection film 62 (FIG. 11B), and is irradiated with exposure light 65 via a mask 64 (FIG. 11C). Subsequently, a developing process is performed to form a resist pattern 66 (FIG. 12A). Thereafter, using the resist pattern 66 as a mask, the antireflection film 62 is dry-etched to form an antireflection film pattern 67 (FIG. 12B). Further, the processing target film 61 is dry-etched using the resist pattern 66 as a mask to form a desired processing target film pattern 68 (FIG. 12C). Finally, the resist pattern 66 and the antireflection film pattern 67 are removed to obtain a structure shown in FIG.
[0013]
[Problems to be solved by the invention]
By the way, according to the BARC method, F ₂ When exposing a resist film using a laser as an exposure light source, there are the following problems.
[0014]
F ₂ Since the laser oscillation wavelength is as short as 157 nm, the resist film is required to have high transparency for transmitting such short-wavelength light. However, conventionally, F ₂ There was no resist film corresponding to the laser. Therefore, a resist film corresponding to a KrF excimer laser or an ArF excimer laser is used, ₂ Irradiation with laser light has a problem that the exposure light does not sufficiently reach the bottom of the resist film because the transmittance of the resist film to light having a wavelength of 157 nm is low, and a desired resist pattern cannot be formed.
[0015]
In this case, if the thickness of the resist film is reduced, the exposure light can reach the bottom of the resist film. However, when the anti-reflection film and the substrate to be processed are etched using such a thin resist pattern as a mask, there is a problem that the resist pattern is lost by etching before the patterning is completed. Further, when the thickness of the antireflection film is reduced to prevent the resist pattern from disappearing, there is a problem that the reflection of the exposure light increases and the function as the antireflection film cannot be performed.
[0016]
The present invention has been made in view of such a problem. That is, an object of the present invention is to use a resist which has been conventionally used, and ₂ An object of the present invention is to provide a pattern forming method and a pattern forming apparatus capable of forming a desired pattern on a substrate to be processed by an exposure machine using a laser as a light source.
[0017]
Other objects and advantages of the present invention will become apparent from the following description.
[0018]
[Means for Solving the Problems]
The pattern forming method of the present invention includes a step of forming an anti-reflection film on a substrate to be processed, a step of forming a resist film on the anti-reflection film, and a step of exposing light to the resist film through a predetermined mask. Forming a resist pattern latent image by irradiating the resist film, developing the resist film to form a resist pattern, and etching the anti-reflection film using the resist pattern as a mask to form the anti-reflection film pattern. The method includes a step of forming, a step of performing a hardening treatment on the antireflection film pattern, and a step of etching the substrate to be processed using the hardened antireflection film pattern as a mask. The curing treatment can be a heat treatment or an ultraviolet irradiation treatment. In addition, a process in which heating and irradiation with ultraviolet light are performed in the same manner may be employed. Further, the curing treatment may be an electron beam irradiation treatment.
[0019]
Further, in the pattern forming method of the present invention, a step of forming an anti-reflection film on the substrate to be processed, and introducing any one atom selected from the group consisting of boron, arsenic and germanium into the surface of the anti-reflection film And a step of forming a resist film on the antireflection film in which the atoms are introduced, and a step of forming a resist pattern latent image by irradiating the resist film with exposure light through a predetermined mask, Forming a resist pattern by developing the resist film, forming an antireflection film pattern by etching the antireflection film using the resist pattern as a mask, and processing using the antireflection film pattern as a mask Etching the substrate. The introduction of atoms into the antireflection film can be performed using an ion implantation method. Further, it can also be performed by exposing the antireflection film to the plasma of the atoms to be introduced.
[0020]
In the pattern forming method of the present invention, the antireflection film can be formed from a novolak-based resin composition. Exposure light is F-wave having a wavelength of 157 nm. ₂ Laser light can be used. Further, the resist film can be a KrF resist film or an ArF resist film.
[0021]
In the pattern forming method of the present invention, the substrate to be processed has a tungsten film, and an antireflection film is formed on the tungsten film, and the tungsten film can be etched using the antireflection film pattern as a mask.
[0022]
Further, in the pattern forming method of the present invention, the substrate to be processed has a tungsten film and an inorganic film formed on the tungsten film, and an antireflection film is formed on the inorganic film. The inorganic film can be etched using the film pattern as a mask.
[0023]
The pattern forming apparatus of the present invention is a dry etching unit that forms an antireflection film pattern by etching an antireflection film formed on a substrate to be processed, an ultraviolet irradiation unit that irradiates the antireflection film pattern with ultraviolet light, It has a transport means for transporting the substrate to be processed between the dry etching section and the ultraviolet irradiation section. The UV irradiator may further generate heat. Further, the dry etching section and the ultraviolet irradiation section can be arranged in the same vacuum chamber.
[0024]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
A pattern forming method and a pattern forming apparatus according to the present embodiment will be described with reference to FIGS.
[0025]
First, a semiconductor substrate on which a tungsten film is formed is prepared as a substrate to be processed. For example, as shown in FIG. 1A, a tungsten (W) film 2 is formed on a semiconductor substrate 1 by a chemical vapor deposition (hereinafter, referred to as CVD) or the like. The tungsten film 2 is used, for example, as a gate electrode material of a transistor corresponding to a design rule of 70 nm.
[0026]
As the semiconductor substrate 1, for example, silicon dioxide (SiO 2) is formed on a silicon substrate on which an element isolation region and a diffusion layer serving as a source or a drain are formed. ₂ ) A film on which a gate insulating film such as a film is formed can be used.
[0027]
The film formed on the semiconductor substrate 1 is not limited to a tungsten film. For example, another conductive film such as molybdenum (Mo), tantalum (Ta), or titanium (Ti) may be formed. Further, the film is not limited to the gate electrode material, and another film may be formed as long as the film is used in a semiconductor device manufacturing process and requires patterning.
[0028]
Next, as shown in FIG. 1B, an antireflection film 3 is formed on the tungsten film 2. In this embodiment, the antireflection film preferably has a refractive index n of 1.60 ≦ n ≦ 1.90 and an extinction coefficient k of 0.12 ≦ k. Further, the thickness is preferably 10 nm or more and 200 nm or less.
[0029]
Further, as the antireflection film 3 in the present embodiment, a film mainly containing an organic material is preferably used. The organic material may be any of a thermosetting resin, a photocurable resin, and an electron beam curable resin. Further, the photo-curable resin composition may be one that cures by utilizing radical polymerization or one that is cured by an acid generated by light.
[0030]
Next, as shown in FIG. 1C, a resist film 4 is formed on the antireflection film 3. The formation of the resist film 4 can be performed using, for example, a spin coating method. Further, the thickness of the resist film 4 can be set to a predetermined thickness according to the manufacturing process of the semiconductor device. It becomes possible.
[0031]
The resist film used in the present invention may be a positive resist film or a negative resist film. Further, a resist film which reacts by light or a resist film which reacts by an electron beam may be used. For example, a polyvinyl phenol-based resist such as polyhydroxystyrene used as a resist for a KrF excimer laser (also referred to as a KrF resist, the same applies hereinafter), or a resist for an ArF excimer laser (also referred to as an ArF resist. The same applies hereinafter.) ), A polyacrylic acid-based resist such as polymethyl methacrylic acid can be used.
[0032]
Next, as shown in FIG. 2A, the resist film 4 is irradiated with exposure light 6 via a predetermined mask 5. As an exposure apparatus, for example, F ₂ An exposure apparatus using a laser as a light source can be used. Further, as the mask 5, a mask corresponding to a resist pattern having a desired line width can be used.
[0033]
This exposure is performed for the purpose of forming a predetermined resist pattern latent image on the resist film 4. That is, by irradiating the resist film 4 with exposure light, a resist pattern latent image including an exposed portion 41 and an unexposed portion 42 is formed in the resist film 4 as shown in FIG.
[0034]
Next, a heat treatment is performed on the exposed semiconductor substrate. The heat treatment can be performed using a closed heating furnace, a hot plate, or the like.
[0035]
After the heat treatment process, the resist film is subjected to a development process. The development can be performed, for example, by alkali development using an aqueous solution of tetramethylammonium hydroxide.
[0036]
For example, when a positive resist film is used, the exposed portion 41 has an alkali-soluble polymer structure, while the unexposed portion 42 has an alkali-insoluble polymer structure. Therefore, by performing the alkali developing treatment, only the exposed portion 41 is dissolved and removed in the developing solution, so that the resist pattern 7 as shown in FIG. 2B is formed.
[0037]
Next, the developing solution attached to the semiconductor substrate and the resist dissolved in the developing solution are washed away with a rinsing solution. Specifically, the rinsing liquid can be washed away by discharging the rinsing liquid onto the semiconductor substrate in a shower state or a spray state. When an alkaline aqueous solution is used as the developing solution, pure water can be used as the rinsing solution, for example.
[0038]
After washing away the developing solution and the resist dissolved in the developing solution with the rinsing solution, the rinsing solution is removed by drying. For example, drying can be performed by rotating the semiconductor substrate at a high speed.
[0039]
Next, the antireflection film 3 is dry-etched using the resist pattern 7 as a mask to form an antireflection film pattern 8 as shown in FIG. At this time, it is preferable to set the etching conditions so that the etching of the anti-reflection film 3 proceeds and the tungsten film 2 is exposed almost simultaneously with the etching of the resist pattern 7.
[0040]
In the present embodiment, as shown in FIG. 3A, after the etching of the antireflection film is completed, the formed antireflection film pattern 8 is irradiated with ultraviolet rays 9. Depending on the type of antireflection film, electron beam irradiation may be performed instead of ultraviolet irradiation, or heat treatment may be performed. Further, these may be performed in combination.
[0041]
By performing such a treatment, the curing of the resin forming the antireflection film can be advanced, and the resistance to dry etching in a later step can be improved. Specifically, the etching rate of the antireflection film is set to be higher than the etching rate of the underlying tungsten film.
[0042]
For example, when a thermosetting resin composition is used as a material for forming the anti-reflection film, heat treatment is performed on the anti-reflection film pattern. The conditions of the heat treatment are set to a temperature and a time at which a curing reaction of the resin occurs.
[0043]
When a photocurable resin composition is used as a material for forming the antireflection film, the antireflection film pattern is irradiated with ultraviolet rays. The wavelength and irradiation amount of the light to be irradiated are set so as to cause the resin to be cured.
[0044]
Further, when an electron beam-curable resin composition is used as a material for forming the antireflection film, the antireflection film is irradiated with an electron beam having an appropriate energy.
[0045]
By performing the above treatment on the anti-reflection film, the cross-linking density of the resin forming the anti-reflection film is increased, and the dry etching resistance can be improved. Note that, depending on the type of the antireflection film, for example, heating and ultraviolet irradiation may be performed simultaneously.
[0046]
In the present embodiment, an antireflection film formed using a material having a large volume shrinkage due to curing is not preferable because variation in pattern dimensions after heating or irradiation with ultraviolet rays or electron beams becomes large. Therefore, it is preferable to use an antireflection film formed of a resin composition having a small volume shrinkage due to curing.
[0047]
For example, in the case of an antireflection film formed using a heat-curable novolak resin composition, the pattern size after exposure can be maintained because there is almost no shrinkage (dimension reduction) of the pattern after heat treatment. It is.
[0048]
Next, the tungsten film 2 is dry-etched using the antireflection film pattern 8 as a mask to form a tungsten film pattern 10 as shown in FIG.
[0049]
As described above, in the present embodiment, the tungsten film is etched using the antireflection film pattern as a mask instead of the resist pattern. This corresponds to the fact that the hardening reaction of the anti-reflection film pattern was promoted to improve the etching resistance, so that the anti-reflection film pattern could be sufficiently used as a mask when etching the tungsten film. Is what you do. This allows the resist pattern to be used only as a mask when etching the antireflection film, so that the thickness of the resist film can be made smaller than before. Therefore, using a resist corresponding to a KrF excimer laser or an ArF excimer laser, ₂ Even when exposure is performed using a laser as a light source, it is possible to sufficiently expose the bottom of the resist.
[0050]
After the formation of the tungsten film pattern, the unnecessary anti-reflection film pattern is removed to obtain a structure shown in FIG.
[0051]
As one example, a 50-nm-thick tungsten film was formed on a substrate to be processed. Next, a thermosetting novolak resin composition was applied on the tungsten film and heated at 205 ° C. for 60 seconds to form an antireflection film having a thickness of 120 nm. Subsequently, a polyvinylphenol-based resist composition was applied and heated at 130 ° C. for 60 seconds to form a resist film having a thickness of 80 nm.
[0052]
Next, F ₂ The resist film was exposed through a mask using an exposure machine using a laser as a light source. After the exposure, heating was performed at 130 ° C. for 90 seconds. Subsequently, development was performed using a 2.38% concentration tetramethylammonium hydroxide solution to form a resist pattern.
[0053]
Next, dry etching of the antireflection film was performed using the resist pattern as a mask. A mixed gas of nitrogen and oxygen was used as an etching gas. At this time, the resist pattern was completely etched almost at the same time when the underlying tungsten film was exposed.
[0054]
Next, the antireflection film pattern was irradiated with ultraviolet rays for 60 seconds using a lamp that generates ultraviolet rays having a wavelength of 365 nm. Thereafter, dry etching of the tungsten film was performed using the antireflection film pattern as a mask. As an etching gas, a mixed gas of sulfur hexafluoride and nitrogen was used.
[0055]
Finally, the gate electrode structure having a good fine pattern was obtained by removing the antireflection film pattern with oxygen plasma.
[0056]
According to the pattern forming method of the present embodiment, by performing the curing treatment of the antireflection film pattern, the tungsten film can be etched using the antireflection film pattern as a mask. Therefore, the resist pattern may be used only as a mask when etching the antireflection film, and the thickness of the resist film can be reduced. Thus, using a resist corresponding to a KrF excimer laser or an ArF excimer laser, ₂ Even when exposure is performed by an exposure machine using a laser as a light source, the exposure light can sufficiently reach the bottom of the resist film. In addition, since it is not necessary to reduce the thickness of the antireflection film, it is possible to prevent reflection of exposure light and form a good resist pattern.
[0057]
4A to 4C show an example of a pattern forming apparatus according to the present embodiment. The pattern forming apparatus includes a dry etching section for etching an antireflection film formed on a substrate to be processed to form an antireflection film pattern, an ultraviolet irradiation section for irradiating the antireflection film pattern with ultraviolet light, and a dry etching section. And a transport means for transporting the substrate to be processed between the substrate and the ultraviolet irradiation unit.
[0058]
As shown in the figure, the pattern forming apparatus 100 according to the present embodiment has a dry etching unit 12 and an ultraviolet irradiation unit 13 in a vacuum chamber 11. Further, the vacuum chamber 11 is provided with an inlet 14 for introducing an etching gas into the vacuum chamber 11 and an exhaust port 15 for exhausting gas generated in the vacuum chamber 11.
[0059]
The dry etching unit 12 has an upper electrode 16 that is grounded, and a lower electrode 17 that is disposed at a position facing the upper electrode 16 with a predetermined interval. The lower electrode 17 is connected to a radio frequency (RF) power supply 18. In addition, the lower electrode 17 is provided on a stage 19 which also serves as a substrate mounting table and is movable in a lateral direction. That is, the stage 19 has a role as a transport unit that transports the substrate placed on the lower electrode 17 between the dry etching unit 12 and the ultraviolet irradiation unit 13.
[0060]
On the other hand, the ultraviolet irradiation unit 13 has a lamp unit 20 that generates ultraviolet light.
[0061]
First, the step of etching the antireflection film will be described with reference to FIG.
[0062]
The substrate 21 to be processed is placed on the lower electrode 17. The substrate to be processed 21 has a tungsten film (not shown) formed according to the present embodiment. An anti-reflection film and a resist pattern (not shown) are formed on the substrate 21 to be processed, and the resist pattern is placed so as to face the upper electrode 16.
[0063]
Next, the etching gas G is introduced through the inlet 14. ₁ At a predetermined flow rate. When a high frequency is applied to the lower electrode 17, the etching gas reaching the plasma discharge region 22 is turned into plasma. Using this plasma gas, anisotropic etching of the antireflection film is performed using the resist pattern as a mask. Gas generated by etching or surplus etching gas G ₂ Is discharged from the exhaust port 15 to the outside of the vacuum chamber 11.
[0064]
After the etching of the anti-reflection film is completed, a curing treatment of the anti-reflection film pattern is performed. The curing treatment of the antireflection film pattern will be described with reference to FIG.
[0065]
The lower electrode 17 is moved leftward in the figure by the stage 19 so that the substrate 21 to be processed is located below the lamp unit 20 provided in the ultraviolet irradiation unit 13 (FIG. 4B). The lamp section 20 is provided with a lamp for irradiating ultraviolet rays suitable for curing the resin forming the anti-reflection film. Here, it is preferable that the ultraviolet irradiation unit 13 can irradiate the processing target substrate with ultraviolet light and can heat the processing target substrate 21 by radiant heat from the lamp unit 20. For example, the lamp unit can be configured using a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a low-pressure mercury lamp, a metal halide lamp, or the like. In order to prevent the decomposition reaction from occurring, a short wavelength light (for example, a wavelength of 200 nm or less) may be cut by using a filter in the lamp unit.
[0066]
The gas G generated by the curing process ₃ Is discharged from the exhaust port 15 to the outside of the vacuum chamber 11.
[0067]
According to the pattern forming apparatus of the present embodiment, curing of the photocurable resin forming the antireflection film can be advanced by irradiating the antireflection film pattern with ultraviolet light in the ultraviolet irradiation section. Further, even when the antireflection film is formed of a thermosetting resin, the resin can be cured by radiant heat generated in the ultraviolet irradiation unit.
[0068]
The curing treatment performed in the present embodiment is performed on a resin that has already been cured to some extent, and its purpose is to increase dry etching resistance. Therefore, the curing conditions do not need to be so strict as compared with the case where the resin composition is cured to form the antireflection film. Therefore, even with an antireflection film formed from a thermosetting novolak resin composition, curing can be promoted by heat generated upon irradiation with ultraviolet light, and the object of the present invention can be achieved.
[0069]
As described above, according to the pattern forming apparatus of the present embodiment, by providing the ultraviolet irradiation unit using a lamp that generates radiant heat, for both the photocurable resin and the thermosetting resin, The curing can be advanced to improve the etching resistance.
[0070]
However, when it is not preferable that heat is applied to the substrate to be processed when the antireflection film is formed of a photocurable resin, it is preferable to provide a cooling unit in the lamp unit. For example, by cooling the lamp unit, it is possible to suppress a rise in temperature on the substrate to be processed.
[0071]
In the case where the anti-reflection film is formed of a thermosetting resin and it is not preferable that the substrate to be processed is irradiated with ultraviolet rays, a pattern forming apparatus having a heat treatment section instead of the ultraviolet irradiation section And For example, a heater unit is provided instead of the lamp unit in FIGS. Thereby, only the heat treatment can be performed on the antireflection film.
[0072]
Further, a pattern forming apparatus having both an ultraviolet irradiation unit and a heat treatment unit may be used. For example, in the apparatus shown in FIGS. 4A to 4C, a heater (not shown) is arranged below the lower electrode 17. When the anti-reflection film is formed of a photocurable resin, the ultraviolet irradiation is performed in the ultraviolet irradiation unit 13 with the power supply of the heater turned off. At this time, if the generation of radiant heat from the lamp section 20 is suppressed by a cooling means (not shown), the substrate to be processed can be prevented from being heated. On the other hand, when the anti-reflection film is formed of a thermosetting resin, the power of the heater is turned on to perform the heat treatment. In this case, it is not necessary to move the lower electrode 17 from the dry etching section 12 to the ultraviolet irradiation section 13 by the stage 19 after the dry etching processing.
[0073]
4A to 4C, an electron beam irradiation unit (not shown) may be provided instead of the ultraviolet irradiation unit 13. This makes it possible to perform a curing treatment on the antireflection film formed from the electron beam curable resin.
[0074]
After the curing treatment of the anti-reflection film pattern is completed, an etching process of the substrate to be processed is subsequently performed. Specifically, an etching process is performed on the tungsten film formed according to the present embodiment. This etching process will be described with reference to FIG.
[0075]
First, in FIG. 4B, the lower electrode 17 in the ultraviolet irradiation section 13 is moved rightward in the figure by the stage 19 to obtain the arrangement shown in FIG. 4C. Thereby, the substrate 21 to be processed can be positioned again in the dry etching section 12.
[0076]
Next, the etching gas G is introduced through the inlet 14. ₄ At a predetermined flow rate. When a high frequency is applied to the lower electrode 17, the etching gas reaching the plasma discharge region 22 is turned into plasma. Using this plasma gas, anisotropic etching of the tungsten film is performed using the antireflection film pattern as a mask. Gas generated by etching or surplus etching gas G ₅ Is discharged from the exhaust port 15 to the outside of the vacuum chamber 11.
[0077]
As described above, according to the pattern forming apparatus of the present embodiment, the etching treatment, the curing treatment, and the tungsten film etching treatment of the antireflection film can be performed in the same chamber. As a result, the throughput can be improved, and the yield can be improved by preventing the attachment of foreign substances and the like.
[0078]
Note that the dry etching section and the ultraviolet irradiation section need not always be arranged in the same chamber. As long as there is a transport means for transporting the substrate to be processed between the two, they may be provided in different chambers.
[0079]
Embodiment 2 FIG.
The pattern forming method according to the present embodiment will be described with reference to FIGS. Unlike the first embodiment, the present embodiment is characterized in that a silicon nitride film is formed between a tungsten film and an antireflection film.
[0080]
First, a semiconductor substrate on which a tungsten film is formed is prepared as a substrate to be processed. For example, as shown in FIG. 5A, a tungsten (W) film 26 is formed on the semiconductor substrate 25 by a CVD method or the like. The tungsten film 26 is used, for example, as a gate electrode material of a transistor corresponding to a design rule of 70 nm.
[0081]
As the semiconductor base material 25, for example, silicon dioxide (SiO 2) is formed on a silicon substrate on which an element isolation region and a diffusion layer serving as a source or a drain are formed. ₂ ) A film on which a gate insulating film such as a film is formed can be used.
[0082]
The film formed on the semiconductor substrate 25 is not limited to a tungsten film. For example, another conductive film such as molybdenum (Mo), tantalum (Ta), or titanium (Ti) may be formed. Further, the film is not limited to the gate electrode material, and another film may be formed as long as the film is used in a semiconductor device manufacturing process and requires patterning.
[0083]
Next, as shown in FIG. 5B, a silicon nitride film 27 is formed on the tungsten film 26. The silicon nitride film 27 is used as a mask when etching the tungsten film, and can be formed by, for example, a CVD method. Note that the film formed on the tungsten film may be an inorganic film other than the silicon nitride film (for example, a silicon oxide film).
[0084]
Next, as shown in FIG. 5C, an antireflection film 28 is formed on the silicon nitride film 27, and then a resist film 29 is formed.
[0085]
In this embodiment, the antireflection film preferably has a refractive index n of 1.60 ≦ n ≦ 1.90 and an extinction coefficient k of 0.12 ≦ k. Further, the thickness is preferably 10 nm or more and 200 nm or less. As the resin composition for forming the antireflection film, the same resin composition as in Embodiment 1 can be used, but it is particularly preferable to use a novolak-based resin composition.
[0086]
The same resist film 29 as that in Embodiment 1 can be used. For example, a resist corresponding to an exposure machine using a KrF excimer laser or an ArF excimer laser as a light source can be used.
[0087]
The formation of the resist film 29 can be performed by using, for example, a spin coating method or the like. Further, the thickness of the resist film 29 can be set to a predetermined thickness according to the manufacturing process of the semiconductor device. However, according to the pattern forming method of the present embodiment, the thickness can be made smaller than the conventional thickness. It becomes possible.
[0088]
Next, as shown in FIG. 6A, the resist film 29 is irradiated with exposure light 31 via a predetermined mask 30. As an exposure apparatus, for example, F ₂ An exposure apparatus using a laser as a light source can be used. Further, a mask corresponding to a resist pattern having a desired line width can be used.
[0089]
This exposure is performed for the purpose of forming a predetermined resist pattern latent image on the resist film 29. That is, by irradiating the resist film 29 with exposure light, a resist pattern latent image including an exposed portion 291 and an unexposed portion 292 is formed in the resist film 29 as shown in FIG.
[0090]
Next, a heat treatment is performed on the exposed semiconductor substrate. The heat treatment can be performed using a closed heating furnace, a hot plate, or the like.
[0091]
After the heat treatment process, the resist film is subjected to a development process. The development can be performed, for example, by alkali development using an aqueous solution of tetramethylammonium hydroxide.
[0092]
For example, when a positive resist film is used, the exposed portion 291 has an alkali-soluble polymer structure, while the unexposed portion 292 has an alkali-insoluble polymer structure. Therefore, by performing the alkali developing treatment, only the exposed portions 292 are dissolved and removed in the developing solution, and as a result, a resist pattern 32 as shown in FIG. 6B is formed.
[0093]
Next, the developing solution attached to the semiconductor substrate and the resist dissolved in the developing solution are washed away with a rinsing solution. Specifically, the rinsing liquid can be washed away by discharging the rinsing liquid onto the semiconductor substrate in a shower state or a spray state. When an alkaline aqueous solution is used as the developing solution, pure water can be used as the rinsing solution, for example.
[0094]
After washing away the developing solution and the resist dissolved in the developing solution with the rinsing solution, the rinsing solution is removed by drying. For example, drying can be performed by rotating the semiconductor substrate at a high speed.
[0095]
Next, the anti-reflection film 28 is dry-etched using the resist pattern 32 as a mask to form an anti-reflection film pattern 33 as shown in FIG. At this time, it is preferable to set the etching conditions so that the etching of the antireflection film 28 progresses and the silicon nitride film 27 is exposed almost at the same time as the resist pattern 32 disappears by the etching. In this case, when the anti-reflection film is formed of a novolak type epoxy resin, nitrogen (N ₂ ) And oxygen (O ₂ ) Mixed gas or tetrafluoromethane (CF ₄ ) And oxygen can be used as an etching gas.
[0096]
Next, in the same manner as in Embodiment 1, after the etching of the anti-reflection film is completed, the formed anti-reflection film pattern 33 is irradiated with ultraviolet rays 34 (FIG. 7A). Note that, depending on the type of the antireflection film, electron beam irradiation may be performed instead of ultraviolet irradiation, or heat treatment may be performed. Further, these may be performed in combination.
[0097]
By performing such a treatment, the curing of the resin forming the antireflection film can be advanced, and the resistance to dry etching in a later step can be improved. Specifically, the etching rate of the antireflection film is set to be higher than the etching rate of the underlying silicon nitride film.
[0098]
The material for forming the anti-reflection film is preferably a resin composition having a small volume shrinkage due to curing, as in the first embodiment. For example, a heat-curable novolak resin composition hardly shrinks (reduces dimensions) of the pattern after the heat treatment, so that the pattern size after exposure can be maintained.
[0099]
Next, the silicon nitride film 27 is dry-etched using the antireflection film pattern 33 as a mask to form a silicon nitride film pattern 35 as shown in FIG. In this case, as an etching gas, for example, tetrafluoromethane (CF ₄ ), Oxygen (O ₂ ) And difluoromethane (CH ₂ F ₂ )) Or a mixed gas of tetrafluoromethane and oxygen can be used.
[0100]
When a mixed gas of tetrafluoromethane and oxygen is used, the etching of the antireflection film and the etching of the silicon nitride film can be used as a common etching gas.
[0101]
Next, the tungsten film 26 is etched using the silicon nitride film pattern 35 as a mask to form a tungsten film pattern 36 (FIG. 7C). As an etching gas, for example, sulfur hexafluoride (SF ₆ ) And nitrogen (N ₂ ) Can be used.
[0102]
As one example, a 50-nm-thick tungsten film was formed on a substrate to be processed. Next, a 70-nm-thick silicon nitride film was formed over the tungsten film by a CVD method.
[0103]
Next, a thermosetting novolak resin composition was applied on the silicon nitride film, and heated at 205 ° C. for 60 seconds to form an antireflection film having a thickness of 100 nm. Subsequently, a polyvinylphenol-based resist composition was applied and heated at 130 ° C. for 60 seconds to form a resist film having a thickness of 60 nm.
[0104]
Next, F ₂ The resist film was exposed through a mask using an exposure machine using a laser as a light source. After the exposure, heating was performed at 130 ° C. for 90 seconds. Subsequently, development was performed using a 2.38% concentration tetramethylammonium hydroxide solution to form a resist pattern.
[0105]
Next, dry etching of the antireflection film was performed using the resist pattern as a mask. A mixed gas of nitrogen and oxygen was used as an etching gas. At this time, the resist pattern was completely etched almost simultaneously with the exposure of the underlying silicon nitride film.
[0106]
Next, the antireflection film pattern was irradiated with ultraviolet rays for 60 seconds using a lamp that generates ultraviolet rays having a wavelength of 365 nm. Thereafter, dry etching of the silicon nitride film was performed using the antireflection film pattern as a mask. As an etching gas, a mixed gas of tetrafluoromethane, oxygen and difluoromethane was used.
[0107]
Next, dry etching of the tungsten film was performed using the silicon nitride film as a mask. As an etching gas, a mixed gas of sulfur hexafluoride and nitrogen was used. Through the above steps, a gate electrode structure having a good fine pattern was obtained.
[0108]
According to the pattern forming method of the present embodiment, by performing the hardening treatment of the antireflection film pattern, the silicon nitride film can be etched using the antireflection film pattern as a mask. The tungsten film is etched using the silicon nitride film pattern as a mask. Therefore, the resist pattern may be used only as a mask when etching the antireflection film, and the thickness of the resist film can be reduced. Thus, using a resist corresponding to a KrF excimer laser or an ArF excimer laser, ₂ Even when exposure is performed by an exposure machine using a laser as a light source, the exposure light can sufficiently reach the bottom of the resist film. In addition, since it is not necessary to reduce the thickness of the antireflection film, it is possible to prevent reflection of exposure light and form a good resist pattern.
[0109]
Further, the etching treatment of the antireflection film, the curing treatment of the antireflection film pattern, the etching treatment of the silicon nitride film, and the etching treatment of the tungsten film in this embodiment are performed using the pattern forming apparatus 100 described in the first embodiment. It can be done preferably.
[0110]
Hereinafter, a case where the pattern forming apparatus 100 of FIG. 4 is applied to the present embodiment will be described. It is assumed that the substrate 21 to be processed in FIGS. 4A to 4C has been subjected to a resist pattern forming step according to the method of the present embodiment.
[0111]
First, the substrate 21 to be processed is placed on the dry etching section 12 (FIG. 4A). Then, the etching gas G is introduced through the inlet 14. ₁ Is introduced to etch the antireflection film. Next, the stage 19 is moved to the ultraviolet irradiation unit 13 to perform a hardening process on the substrate 21 (FIG. 4B). After that, the stage 19 is moved to the dry etching section 12, and the silicon nitride film is etched (FIG. 4C). Subsequently, the etching gas is replaced (if necessary), and the tungsten film is etched.
[0112]
As described above, by performing the processes from the etching treatment of the anti-reflection film to the etching treatment of the tungsten film in the same chamber, the throughput can be improved, and the yield can be improved by preventing the attachment of foreign substances and the like. It becomes.
[0113]
Embodiment 3 FIG.
The pattern forming method according to the present embodiment will be described with reference to FIGS. The present embodiment is characterized in that atoms for lowering the etching rate are introduced into the surface of the antireflection film.
[0114]
First, a semiconductor substrate on which a tungsten film is formed is prepared as a substrate to be processed. For example, as shown in FIG. 8A, a tungsten (W) film 41 is formed on a semiconductor substrate 40 by a CVD method or the like. The tungsten film 41 is used, for example, as a gate electrode material of a transistor corresponding to a design rule of 70 nm.
[0115]
As the semiconductor substrate 40, for example, silicon dioxide (SiO 2) is formed on a silicon substrate on which an element isolation region and a diffusion layer serving as a source or a drain are formed. ₂ ) A film on which a gate insulating film such as a film is formed can be used.
[0116]
The film formed on the semiconductor substrate 40 is not limited to the tungsten film. For example, another conductive film such as molybdenum (Mo), tantalum (Ta), or titanium (Ti) may be formed. Further, the film is not limited to the gate electrode material, and another film may be formed as long as the film is used in a semiconductor device manufacturing process and requires patterning.
[0117]
Next, as shown in FIG. 8B, an antireflection film 42 is formed on the tungsten film 41. In this embodiment, the antireflection film preferably has a refractive index n of 1.60 ≦ n ≦ 1.90 and an extinction coefficient k of 0.12 ≦ k. Further, the thickness is preferably 10 nm or more and 200 nm or less. As the resin composition for forming the antireflection film, the same resin composition as in Embodiment 1 can be used, but it is particularly preferable to use a novolak-based resin composition.
[0118]
The present embodiment is characterized in that after forming the anti-reflection film 42, atoms that slow down the etching rate of the anti-reflection film 42 are introduced into the surface thereof. Specifically, the etching rate of the antireflection film 42 is set to be higher than the etching rate of the underlying tungsten film 41.
[0119]
Examples of atoms that lower the etching rate of the antireflection film include boron (B), arsenic (As), and germanium (Ge). By introducing such atoms into the anti-reflection film, the structure of the anti-reflection film at the introduced portion can be changed, and the dry etching resistance can be improved.
[0120]
The introduction of atoms into the antireflection film 42 can be performed by using, for example, an ion implantation method as shown in FIG. The purpose of this embodiment is to improve the dry etching resistance of the surface of the antireflection film, and preferably does not affect the electrical characteristics of the semiconductor device. Therefore, in ion implantation, the implantation energy is reduced so that the implantation layer 43 is formed only on the surface of the antireflection film 42. It is preferable that the specific thickness of the injection layer 43 be appropriately set according to the conditions of dry etching.
[0121]
The introduction of atoms into the antireflection film can also be performed by subjecting the antireflection film to a plasma treatment. For example, by exposing the antireflection film to boron plasma, boron can be introduced to the surface of the antireflection film. According to this method, atoms can be introduced only in the vicinity of the surface, and there is no possibility that the electrical characteristics of the semiconductor device will be affected.
[0122]
Next, as shown in FIG. 9A, a resist film 45 is formed on the anti-reflection film 44 after the surface modification processing. As the resist film 45, the same one as in Embodiment 1 can be used. For example, there is a resist corresponding to an exposure machine using a KrF excimer laser or an ArF excimer laser as a light source.
[0123]
The formation of the resist film 45 can be performed by, for example, a spin coating method or the like. In addition, the thickness of the resist film 45 can be a predetermined thickness according to the manufacturing process of the semiconductor device. However, according to the pattern forming method of the present embodiment, the thickness can be smaller than the conventional thickness. It becomes possible.
[0124]
Next, as shown in FIG. 9B, the resist film 45 is irradiated with exposure light 47 via a predetermined mask 46. As an exposure apparatus, for example, F ₂ An exposure apparatus using a laser as a light source can be used. Further, the mask 46 can be a mask corresponding to a resist pattern having a desired line width.
[0125]
This exposure is performed for the purpose of forming a predetermined resist pattern latent image on the resist film 45. That is, by irradiating the resist film 45 with exposure light, a resist pattern latent image including an exposed portion 451 and an unexposed portion 452 is formed in the resist film 45 as shown in FIG. 9B.
[0126]
Next, a heat treatment is performed on the exposed semiconductor substrate. The heat treatment can be performed using a closed heating furnace, a hot plate, or the like.
[0127]
After the heat treatment process, the resist film is subjected to a development process. The development can be performed, for example, by alkali development using an aqueous solution of tetramethylammonium hydroxide.
[0128]
For example, when a positive resist is used, the exposed portion 451 has an alkali-soluble polymer structure, while the unexposed portion 452 has an alkali-insoluble polymer structure. Therefore, by performing the alkali developing treatment, only the exposed portions 451 are dissolved and removed in the developing solution, so that a resist pattern 48 as shown in FIG. 9C is formed.
[0129]
Next, the developing solution attached to the semiconductor substrate and the resist dissolved in the developing solution are washed away with a rinsing solution. Specifically, the rinsing liquid can be washed away by discharging the rinsing liquid onto the semiconductor substrate in a shower state or a spray state. When an alkaline aqueous solution is used as the developing solution, pure water can be used as the rinsing solution, for example.
[0130]
After washing away the developing solution and the resist dissolved in the developing solution with the rinsing solution, the rinsing solution is removed by drying. For example, drying can be performed by rotating the semiconductor substrate at a high speed.
[0131]
Next, the antireflection film 44 is dry-etched using the resist pattern 48 as a mask to form an antireflection film pattern 49 as shown in FIG. At this time, it is preferable to set the etching conditions so that the etching of the antireflection film 44 proceeds and the tungsten film 41 is exposed almost simultaneously with the etching of the resist pattern 48. When the anti-reflection film is formed of a novolak type epoxy resin, nitrogen (N ₂ ) And oxygen (O ₂ ) Mixed gas or tetrafluoromethane (CF ₄ ) And oxygen can be used as an etching gas.
[0132]
Next, the tungsten film 41 is etched using the antireflection film pattern 49 as a mask. According to the present embodiment, since atoms for lowering the etching rate are introduced into the surface of the antireflection film 44, an antireflection film pattern 49 having high dry etching resistance can be obtained. Therefore, the tungsten film 41 can be etched using the antireflection film pattern 49 as a mask instead of the resist pattern 48.
[0133]
Through the above steps, a tungsten film pattern 50 as shown in FIG. 10B can be obtained.
[0134]
According to the pattern forming method of the present embodiment, the dry etching resistance of the antireflection film can be improved by performing the modification treatment of the antireflection film. Thus, the tungsten film can be etched using the antireflection film pattern as a mask. Since the resist pattern may be used only as a mask when etching the antireflection film, the thickness of the resist film can be reduced. Therefore, using a resist corresponding to a KrF excimer laser or an ArF excimer laser, ₂ Even when exposure is performed by an exposure machine using a laser as a light source, the exposure light can sufficiently reach the bottom of the resist film. In addition, since it is not necessary to reduce the thickness of the antireflection film, it is possible to prevent reflection of exposure light and form a good resist pattern.
[0135]
In the present embodiment, the anti-reflection film is formed on the tungsten film, but the present embodiment is not limited to this. As in Embodiment 2, an inorganic film such as a silicon nitride film is provided between the tungsten film and the antireflection film, the inorganic film is etched using the antireflection film pattern as a mask, and tungsten is formed using the formed inorganic film pattern as a mask. The film may be etched. In this case, the etching rate of the antireflection film is set to be higher than the etching rate of the underlying inorganic film.
[0136]
When the inorganic film is a silicon nitride film and the antireflection film is formed of a novolak resin composition, tetrafluoromethane (CF ₄ ) And oxygen (O ₂ By using the mixed gas of (2) as an etching gas, etching of the antireflection film and etching of the silicon nitride film can be performed continuously. In this case, according to the first method, these films can be etched using the resist pattern as a mask. According to another method, first, the antireflection film is etched using the resist pattern as a mask, and when the resist pattern has disappeared by etching, the silicon nitride film can be etched using the antireflection film as a mask. .
[0137]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the hardening process of an antireflection film pattern can improve the dry etching resistance. Accordingly, the base film can be etched using the anti-reflection film pattern as a mask, and the resist pattern can be used only as a mask when etching the anti-reflection film. it can. Further, since it is not necessary to reduce the thickness of the antireflection film, reflection of exposure light at the interface can be effectively suppressed.
[0138]
Further, according to the present invention, a pattern forming apparatus is used in which an etching treatment, a curing treatment, and an etching treatment of a substrate to be processed are performed in the same chamber. Therefore, the throughput can be improved, and the yield can be improved by preventing the attachment of foreign substances and the like.
[0139]
Further, according to the present invention, the dry etching resistance of the antireflection film can be improved by performing the modification treatment of the antireflection film. Accordingly, the base film can be etched using the anti-reflection film pattern as a mask, and the resist pattern can be used only as a mask when etching the anti-reflection film. it can.
[Brief description of the drawings]
FIGS. 1A to 1C are cross-sectional views illustrating steps of a pattern forming method according to a first embodiment;
FIGS. 2A to 2C are cross-sectional views illustrating steps of a pattern forming method according to the first embodiment.
FIGS. 3A to 3C are cross-sectional views illustrating steps of a pattern forming method according to the first embodiment;
FIGS. 4A to 4C are cross-sectional views illustrating an example of a pattern forming apparatus according to the present invention.
FIGS. 5A to 5C are cross-sectional views illustrating steps of a pattern forming method according to a second embodiment;
FIGS. 6A to 6C are cross-sectional views illustrating steps of a pattern forming method according to a second embodiment;
FIGS. 7A to 7C are cross-sectional views illustrating steps of a pattern forming method according to a second embodiment;
FIGS. 8A to 8C are cross-sectional views illustrating steps of a pattern forming method according to a third embodiment;
FIGS. 9A to 9C are cross-sectional views illustrating steps of a pattern forming method according to a third embodiment;
FIGS. 10A and 10B are cross-sectional views illustrating steps of a pattern forming method according to a third embodiment;
FIGS. 11A to 11C are cross-sectional views showing steps of a conventional pattern forming method.
12A to 12D are cross-sectional views illustrating steps of a conventional pattern forming method.
[Explanation of symbols]
1,25,40 semiconductor substrate, 2,26,41 tungsten film, 3,28,42 antireflection film, 4,29,45 resist film, 5,30,46 mask, 6,31,47 exposure light, 7 , 32, 48 resist pattern, 8, 33, 49 anti-reflection film pattern, 9, 34 ultraviolet ray, 10, 36, 50 tungsten film pattern, 12 dry etching part, 13 ultraviolet irradiation part, 21 substrate to be processed, 27 silicon nitride film , 35 silicon nitride film pattern, 43 injection layer, 100 pattern forming apparatus.

Claims (14)

Forming an anti-reflection film on the substrate to be processed;
Forming a resist film on the antireflection film,
Forming a resist pattern latent image by irradiating the resist film with exposure light through a predetermined mask,
Forming a resist pattern by performing a development process on the resist film;
Forming an anti-reflection film pattern by etching the anti-reflection film using the resist pattern as a mask,
Performing a curing treatment on the antireflection film pattern,
Etching the substrate using the antireflection film pattern after the curing treatment as a mask. The pattern forming method according to claim 1, wherein the curing treatment is a heat treatment and / or an ultraviolet irradiation treatment. The pattern forming method according to claim 1, wherein the curing treatment is an electron beam irradiation treatment. Forming an anti-reflection film on the substrate to be processed;
A step of introducing any one atom selected from the group consisting of boron, arsenic, and germanium to the surface of the antireflection film,
Forming a resist film on the antireflection film in which the atoms have been introduced,
Forming a resist pattern latent image by irradiating the resist film with exposure light through a predetermined mask,
Forming a resist pattern by performing a development process on the resist film;
Forming an anti-reflection film pattern by etching the anti-reflection film using the resist pattern as a mask,
Etching the substrate to be processed using the antireflection film pattern as a mask. The pattern forming method according to claim 4, wherein the atoms are introduced using an ion implantation method. 5. The pattern forming method according to claim 4, wherein the atoms are introduced by exposing the antireflection film to the plasma of the atoms. The pattern forming method according to claim 1, wherein the antireflection film is formed from a novolak-based resin composition. The pattern forming method according to any one of claims 1 to 7 wherein the exposure light is the _{F 2} laser beam having a wavelength of 157 nm. The pattern forming method according to any one of claims 1 to 8, wherein the resist film is a KrF resist film or an ArF resist film. The substrate to be processed has a tungsten film, and the antireflection film is formed on the tungsten film,
The pattern forming method according to claim 1, wherein the tungsten film is etched using the antireflection film pattern as a mask. The substrate to be processed has a tungsten film and an inorganic film formed on the tungsten film, and the antireflection film is formed on the inorganic film,
The pattern forming method according to claim 1, wherein the inorganic film is etched using the antireflection film pattern as a mask. A dry etching portion for etching the antireflection film formed on the substrate to be processed to form an antireflection film pattern,
An ultraviolet irradiation unit that performs ultraviolet irradiation on the antireflection film pattern,
A pattern forming apparatus comprising: transport means for transporting the substrate to be processed between the dry etching unit and the ultraviolet irradiation unit. The pattern forming apparatus according to claim 12, wherein the ultraviolet irradiation unit further generates heat. 14. The pattern forming apparatus according to claim 12, wherein the dry etching section and the ultraviolet irradiation section are arranged in the same vacuum chamber.

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