JP2940250B2 - Method of forming dry development pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a resist pattern used in a process of manufacturing an integrated circuit device by dry development, and more particularly to a method for forming a high resolution dry development pattern.

[0002]

2. Description of the Related Art Conventionally, in the manufacture of integrated circuit devices such as ICs and LSIs, a radiation-sensitive resin such as a positive type photoresist obtained by mixing a quinonediazide compound with a novolak resin is applied onto a substrate to be processed, and then the integrated circuit device is manufactured. In order to form a pattern shape corresponding to the circuit pattern of the above, a photolithography method of exposing using a mercury lamp g-line (wavelength 436 nm) or i-line (wavelength 365 nm) through a pattern mask and developing with a developer is known. Has been used.

However, in recent years, integrated circuit devices have become highly miniaturized, and the size of a circuit pattern to be formed on a substrate has entered a region of 1 μm or less. In such a size region, a conventional photolithography method has been used. Even when used, especially when a substrate having a step structure is used, problems such as the influence of reflection of incident light during exposure and a shallow depth of focus in an optical system occur, making it difficult to achieve sufficient resolution. Occurs.

In order to solve such a problem, Japanese Patent Application Laid-Open No. 61-107346 discloses a method using a g-line or an i-line of a mercury lamp or far ultraviolet light as in the conventional photolithography method. A method has been proposed in which after exposing a circuit pattern, an exposed portion of a resist layer is selectively silylated by treatment with, for example, a silicon compound gas and then anisotropically etched using reactive plasma or the like.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In the method described in Japanese Patent No. 7346, after selectively diffusing a silicon compound gas into exposed portions, a silylated layer is selectively fixed to these exposed portions by reaction with a functional group of a resist. Things. However, the shape of the fixed silylated layer is affected by the intensity distribution of incident light due to exposure. That is, in the exposed portion, the diazoquinone moiety causes a photoreaction to change the silicon compound gas permeability of the resin, and the intensity distribution of the changed ratio is proportional to the energy distribution of the incident light. Therefore, when the exposed portion is selectively silylated, it is understood that the shape of the silylated layer approximates the energy distribution of incident light. On the other hand, in dry plasma etching (dry development), the silylated layer in the exposed portion changes to silicon oxide and remains during the etching process, so that these portions can be efficiently protected. Therefore, the size of the resist pattern formed by etching is affected by the shape of the silylated layer. In addition, the formed resist pattern has a great effect on subsequent steps.

Moreover, when the shape of the formed pattern fluctuates, it is quite complicated to grasp the cause of the fluctuation, and it is difficult to set process parameters required for pattern formation. It is also difficult to confirm whether a change in pattern shape is caused by dry development conditions or a change in other process parameters.

[0007] The object of the present invention is to solve the problem described in the above-mentioned JP-A-61-107.
No. 346, a method for forming a high-resolution dry development pattern by controlling the shape of a selective silylated layer when forming an etching mask layer by selective silylation of an exposed portion with a silicon compound gas in a silicon compound gas. Is to do.

[0008]

According to the present invention, there is provided a method for forming a dry development pattern by partially silylating a dry development resist containing a phenolic polymer bonded to diazoquinone, comprising the steps of: The width of the cross-sectional shape of the silicon-containing region is L,
When the maximum thickness from the surface is d, L and d are formed so as to satisfy the relationship of 0.1 ≦ d / L ≦ 0.7.

If d / L <0.1, the silylated layer is too thin and the silylated layer itself is also etched during dry development, making it impossible to form an accurate pattern.

On the other hand, when d / L> 0.7, it is considered that the silylated layer at the upper end of the silylated layer is relatively thinner than the depth of the silylated layer. It becomes a hang-like pattern shape, and it becomes impossible to form a pattern having vertical walls.

In order for L and d to be in the range of 0.1 ≦ d / L ≦ 0.7, the formation of the silylated layer in the lateral direction (L)
And by controlling the diffusion rate of silicon in the depth direction (d). That is, the diffusion rate of silicon in the lateral direction can be controlled by the pre-bake condition of the resist and the heat treatment condition after exposure. The diffusion rate of silicon in the depth direction can be controlled by the silylation condition. Therefore, by properly selecting these conditions,
The shape of the silylated layer can be controlled so that 0.1 ≦ d / L ≦ 0.7.

The pre-bake conditions are usually a temperature of 50 to 140 ° C. and a time of about 10 seconds to 10 minutes. The heat treatment conditions after exposure are as follows.
The temperature is 200 ° C. and the time is about 10 seconds to 10 minutes. Further, the silylation conditions are usually a temperature of 90 to 200 ° C. and a time of 1 hour.
It is about 0 seconds to 10 minutes.

The resist material used in the present invention includes:
A phenolic polymer bound to diazoquinone, preferably a novolak resin, can be used, and the phenolic polymer is further substituted with an alkyl group, an aryl group or a phenol, naphthol and a derivative thereof optionally substituted by a halogen atom, and a halogen atom. A condensate with an aliphatic or aromatic aldehyde which may be substituted, preferably a condensate of a phenol derivative substituted with a lower alkyl group with an aliphatic aldehyde, wherein the phenol group is substituted with an aryl group or a halogen atom. Poly (vinyl phenol), a copolymer of vinyl phenol and an ethylenically unsaturated compound, or the like may be used in combination.

In the present invention, the above resist material is dissolved in an ester solvent such as ethyl acetate and propylene glycol monoethyl acetate, a ketone solvent such as methyl isobutyl ketone, and an aromatic solvent such as toluene and xylene. After forming the solution, a resist solution is applied on a semiconductor substrate such as a silicon wafer or a metal substrate such as aluminum by a normal method such as a spin coating method, and a resist film is formed by a pre-baking process.

Thereafter, ultraviolet light, far ultraviolet light, electron beam, soft X
By irradiating with radiation such as radiation and then treating with a silylating agent, the silylating agent is diffused in the irradiated portion to immobilize the silylating agent.

Next, a resist pattern is formed by performing dry development using oxygen plasma or the like using the immobilized silylated layer as a mask.

Examples of the silylating agent include tetrachlorosilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, trimethylbromosilane, trimethyliodosilane, triphenylchlorosilane, hexamethyldisilazane, 1,1,3,3-tetra Methyldisilazane, heptamethyldisilazane, hexaphenyldisilazane, 1,3-bis (chloromethyl)-
1,1,3,3-tetramethyldisilazane, N-trimethylsilylimidazole, N-trimethylsilylacetamide, N-trimethylsilyldimethylamine, N-trimethylsilyldiethylamine, hexamethylsilanediamine, N, O-bis (triethylsilyl) acetimide, N, N'-bis (trimethylsilyl) urea, N,
N'-diphenyl-N- (trimethylsilyl) urea and the like can be mentioned. The treatment temperature of the radiation-sensitive resin layer with the silylation agent is determined by the composition of the radiation-sensitive resin layer, the type of the silylation agent used and the treatment time, and is preferably selected from 0 to 250 ° C. And more preferably 90 to 200 ° C.

[0018]

The cross-sectional shape of the resist after dry development (reactive ion etching) is affected by the cross-sectional shape of the silylated layer before development, and by forming the silylated layer into a specific cross-sectional shape, the resist has vertical walls. A resist pattern can be formed. An example of a method for observing the silylated layer will be described. First, the sample subjected to the silylation treatment is cleaved, and the cleaved surface is irradiated with isotropic oxygen plasma to change silicon exposed on the surface into silicon oxide, and observed with an electron microscope. At this time, it was confirmed that the shape of the silylation layer did not change even when the conditions for contacting with oxygen plasma, particularly the high-frequency output value for generating plasma, the flow rate of oxygen used, and the processing time were changed over a wide range. . Therefore, it was found that the shape of the silylated layer can be confirmed by the above method.

FIG. 1 shows an example of the cross-sectional shape of the silylated layer obtained by observation with an electron microscope. Assuming that the width of the silylated layer 3 on the surface of the resist 2 formed on the substrate 1 is L and the maximum depth (the depth at the center) is d, a cross section in which the value of d / L is within a specific range Only when a silylation layer having a shape is formed, the resist pattern after dry development shows a shape having vertical walls. Here, a method for measuring the d / L value will be described. First, the sample on which the silylated layer was formed was cleaved to expose a vertical section, and a high frequency output of 100 to 500 w and an oxygen flow rate of 300 to 500 SC were used using a barrel-type etching apparatus.
CM, the exposed cross section in the processing time of 1 to 10 minutes is exposed to oxygen plasma to oxidize silicon. There is no change in the shape of the silylated layer within the above range. The width L of the silylated layer is the length between both ends of the silylated layer, where the ends where the thickness of the silylated layer is 0.01 μm or less are defined as the ends of the silylated layer.

[0020]

The present invention will be described in detail with reference to the following examples.

Example 1 6-diazo-5,6-dihydro-5 as a resist material
A resin consisting of a partial condensation product of -oxo-1-naphthalenesulfonic acid chloride and a novolak resin (condensate of pt-butylphenol and formaldehyde) was used. This resin was dissolved in propylene glycol monoethyl acetate to prepare a 30% by weight solution. This solution was spin-coated on a silicon wafer at a spin speed of 4000 rpm using a spin coater. Further, prebaking was performed on a hot plate at 120 ° C. for 90 seconds to obtain a resist film having a thickness of 1.5 μm. Next, the wavelength 43
A predetermined pattern was exposed with an exposure amount of 750 mJ / cm ² using an ultraviolet exposure apparatus having a wavelength of 5 nm and a lens numerical aperture (NA) of 0.54. Next, heat treatment after exposure is performed at 150 ° C. for 3 hours.
For 30 minutes under a reduced pressure of 300 mmHg, and then subjected to a silylation treatment in a vapor of hexamethyldisilazane at 150 ° C. for 1 minute. Next, using a magnetron type etching apparatus, high-frequency output 1.0 kw, oxygen flow rate 70 s
Dry development processing by reactive ion etching was performed under the conditions of ccm and a substrate cooling temperature of −20 ° C. The resist pattern formed by development is transferred to an electron microscope (SE
As a result of observation in M), a line and space pattern having a minimum resolution of 0.4 μm was accurately formed. 0.6 μm cross-sectional shape from the formed pattern
When the pattern was measured, it was found that the dimensional ratio between the upper and lower parts of the pattern was 1.0, and that the pattern had a vertical wall with no dimensional difference between the upper and lower parts of the pattern. Next, a sample formed under the same conditions as the sample before the dry development was prepared, and an etching process was performed for 6 minutes using a barrel-type etching apparatus under the conditions of a high frequency output of 500 w and an oxygen flow rate of 500 sccm. Was partially changed to silicon oxide so that SEM observation was possible. Figure 1 is an SEM
It is the figure which copied the shape of the silylation layer by a photograph. The ratio of the maximum depth d at the center of the silylated layer to the length L of both ends of the silylated layer was d / L = 0.19. In FIG. 1, the width of the silylated portion 3 is larger than 0.6 μm, but after dry development, the line and space pattern is 0.6 μm.

Example 2 The same resist material as in Example 1 was used, and the pre-bake was 9
Perform at 0 ° C for 1 minute, and set the exposure amount of the UV exposure device to 350 m
J / cm ² and heat treatment after exposure at 160 ° C. for 1
A resist pattern was formed under the same conditions as in Example 1 except that the reaction was performed for 20 seconds and the silylation was performed at 160 ° C. for 2 minutes.
The pattern formed by dry development was accurately resolved down to 0.4 μm. Further, when the 0.6 μm pattern was observed, the pattern had vertical walls with no dimensional difference between the upper and lower parts of the pattern. Further, when the shape of the silylated layer before dry development was observed by the same method as in Example 1, it was found that d / L
= 0.66.

Examples 3 to 6 Using the same resist material as in Example 1, the pre-bake conditions and
An experiment was performed in the same manner as in Example 1 except that the heat treatment temperature after the exposure, the treatment time, the silylation temperature, and the silylation time were changed as shown in Table 1. Table 1 shows the results.

Example 7 As a resist, a portion of cresol, formaldehyde novolak resin, 6-diazo-5,6-dihydro-5-oxo-1-naphthalenesulfonic acid chloride and novolak resin (condensate of cresol and formaldehyde) A resin consisting of a condensation product was used. This resin is dissolved in propylene glycol monoethyl acetate and
A weight percent solution was prepared. The resist film formed under the same conditions as in Example 1 had a thickness of 1.6 μm. Since then
An experiment was carried out in the same manner as in Example 1 except that the prebake conditions, the heat treatment temperature and the treatment time after exposure, the silylation temperature, and the silylation time were changed as shown in Table 1. Table 1 shows the results.

Example 8 The same resist material as in Example 1 was used, and the pre-bake was performed 9 times.
Performed at 0 ° C for 1 minute, and the exposure amount of the ultraviolet exposure device was 175 m
J / cm ² and heat treatment after exposure at 110 ° C. for 2 hours.
For 1 minute, and the silylation was performed in the same manner as in Example 1 except that the silylation was performed at 110 ° C. for 4 minutes in the vapor of 1,1,3,3-tetramethyldisilazane. The pattern formed by dry development was accurately resolved down to 0.4 μm. Further, when the 0.6 μm pattern was observed, the pattern had vertical walls with no dimensional difference between the upper and lower parts of the pattern. Further, the shape of the silylated layer before the dry development was observed by the same method as in Example 1. As a result, d / L = 0.2
It was 0. Table 1 shows the results.

Example 9 As a resist material, 6-diazo-5,6-dihydro-
A resin consisting of a partial condensation product of 5-oxo-1-naphthalenesulfonic acid chloride and a novolak resin (a condensate of m-cresol and p-cresol with formaldehyde) was used. This resin was dissolved in propylene glycol monoethyl acetate to prepare a 30% by weight solution. Next, pre-baking is performed at 120 ° C. for 90 seconds, and the exposure amount of the ultraviolet exposure apparatus is set to 150 mJ / cm ² ,
The heat treatment after the exposure was performed at 170 ° C. for 3 minutes and the silylation was performed at 170 ° C. for 4 minutes in the same manner as in Example 1. 0.4 μm pattern formed by dry development
Resolved accurately up to. Further, when the 0.6 μm pattern was observed, the pattern had vertical walls with no dimensional difference between the upper and lower parts of the pattern. Further, the shape of the silylated layer before the dry development was observed by the same method as in Example 1.
L = 0.38. Table 1 shows the results.

Comparative Examples 1 to 3 The same resist material as in Example 1 was used,
Heat treatment temperature and treatment time after exposure, silylation temperature,
An experiment was performed in the same manner as in Example 1 except that the silylation time was changed as shown in Table 1. Table 1 shows the results. FIG. 2 shows the shape of the silylated portion of Comparative Example 1.

[0028]

[Table 1]

As shown in Table 1, in Examples 1 to 7 in which the value of d / L is 0.1 or more and 0.7 or less, the resist pattern after dry development has vertical side walls. In contrast, d
In Comparative Examples 1 to 3 in which the value of / L is larger than 0.7, the resist pattern after dry development has an overhang shape.

[0030]

According to the present invention, a resist pattern can be formed with high resolution and a resist pattern having a vertical cross-sectional shape can be formed, which is effective for manufacturing ultra-fine and high-density LSI.

[Brief description of the drawings]

FIG. 1 is a diagram showing a silylated portion in an example of the present invention.

FIG. 2 is a diagram showing a silylated portion in a comparative example.

[Description of Signs] 1 silicon wafer 2 resist 3 silylated portion

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yukari Ishibashi 2--11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (56) References JP-A-2-20869 (JP, A) JP-A JP-A-1-186934 (JP, A) JP-A-2-93463 (JP, A) JP-A-2-213850 (JP, A) JP-A-2-127645 (JP, A) JP-A-2-1857 (JP, A A) JP-A-2-52357 (JP, A) JP-A-61-107346 (JP, A) JP-A-3-19310 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name ) G03F 7 / 38,7 / 022

Claims (1)

(57) [Claims] 1. A method for forming a dry development pattern by partially silylating a dry development resist containing a phenolic polymer bonded to diazoquinone, wherein a cross-sectional shape of a silicon-containing region of the silylated resist is When the width at the surface is L and the maximum thickness from the surface is d, the L and d are formed so as to satisfy the relationship of 0.1 ≦ d / L ≦ 0.7. A method for forming a dry development pattern.