JPH04124667A - Manufacture of semiconductor - Google Patents

Abstract

PURPOSE:To improve the selectivity of silylizing of a resist film and to reduce variance in the line width of a resist pattern after dry development by bringing an alkali solution into contact with the resist film prior to an exposing process. CONSTITUTION:The resist film 2 is exposed selectively, silylizing agent is brought into contact with the exposed resist film for the selective silylizing 4 of the surface of the exposed resist film corresponding to an exposed and an unexposed area, and oxygen plasma is brought into contact with the resist film, which is developed. Prior to the exposing process, the alkali solution is brought into contact with the resist film to attain the diazo-bonding of resin in the resist with a sensitizer, thereby improving the selectivity of the silylizing corresponding to the exposed and unexposed areas. Consequently, the dry development is performed by using only oxygen and the variance in the line with of the formed resist pattern is reducible.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for manufacturing a semiconductor device, in particular, a method for patterning a resist mask used in the manufacturing process of a semiconductor device, the present invention improves the selectivity of silylation of a resist film, and improves the selectivity of silylation of a resist film after dry development. The purpose of the present invention is to provide a patterning method for a resist mask that can reduce the variation in line width of a resist pattern. A method for manufacturing a semiconductor device comprising the steps of selectively silylating the surface of the exposed resist film corresponding to exposed and unexposed areas, and developing the resist film by bringing it into contact with oxygen plasma. Prior to the process, the resist film is configured to be brought into contact with an alkaline solution.

[Industrial application field]

The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for patterning a resist mask used in the manufacturing process of a semiconductor device.

[Prior Art] In order to increase the degree of integration of semiconductor integrated circuits, miniaturization of circuit patterns is essential.In order to miniaturize a single circuit pattern, it is first necessary to increase the resolution of an exposure device. Resolution is λ/N
A (where λ is the wavelength of the exposure light and NA is the numerical aperture of the lens), so if the wavelength of the exposure light is shortened (
However, the numerical aperture of the lens is increased to improve resolution.

On the other hand, since the depth of focus of an exposure device is proportional to λ/(NA), increasing the resolution inevitably results in a shallower depth of focus.When forming a resist film on a base layer with steps,
Since the thickness of the resist film is non-uniform, for example, when focusing on a thin resist film, if the depth of focus is shallow, the resolution in the thick resist film will decrease. A multilayer resist method was developed to overcome this drawback. This method prevents a decrease in resolution by having separate films for mapping and smoothing, but it has the disadvantage of increasing the number of steps and increasing the economic burden.
Therefore, a patterning method for resists and masks using a selective silylation method that can obtain the effects of a single-layer resist and a two-layer resist method has attracted attention.

Silylation refers to contacting a resin having an OH group as shown in the structural formula (1) with hexamethyldisilazane having the structural formula shown in (2) as a silylating agent (3).
This refers to bonding a silyl group consisting of silicon and an alkyl group to a resin by reacting as shown in the figure below.

(Ctrs ).

5t-N-3j (CH.

).

S r (CHs ) s ・ ・ ・ (3) A photosensitizer containing a 5-position naphthoquinonediazide group having the structural formula shown in (4) or a 4-position naphthoquinonediazide group having the structural formula shown in (5) in the resin. When mixed, the unexposed area has a selectivity that is difficult to be silylated and the one-light area is easily silylated, although the reason is not necessarily clear.

A conventional resist mask patterning method that utilizes the above-mentioned silylation selectivity will be described below.

A resist in which a photosensitive agent containing a naphthoquinone diazide group shown in (4) or (5) as shown in (4) or (5) is mixed into a resin having an OH group is applied to the workpiece, and after exposure using a mask,
The exposed areas are selectively silylated by contacting with hexamethyldisilazane shown in (2), and then dry development is performed using a plasma etching device to remove the non-silylated resist film in the unexposed areas. to form a resist mask.

[Problem to be solved by the invention]

However, when contacting hexamethyldisilazane after exposure, the selectivity of silylation between the exposed and unexposed areas is insufficient, so the unexposed areas are also shallowly silylated as shown in Figure 2. .

In FIG. 2, 1 is a substrate, 2 is a resist film coated on the substrate, and 3 is an exposure mask. 4 indicates a silylated region, and the unexposed region is also shallowly silylated. Therefore, dry development using only oxygen plasma can also etch the silicon dioxide layer because the silicon in the silylated areas reacts with oxygen and forms a silicon dioxide layer over the entire surface, making development impossible. In this way, dry development must be performed by mixing carbon tetrafluoride or the like with oxygen, which causes the line width of the resist pattern after development to become unstable and cause variations.

The purpose of the present invention is to eliminate this drawback, and to improve the selectivity of silylation of a resist film, and to reduce variations in the line width of a resist pattern after dry development, it is possible to pattern a resist mask. The purpose is to provide a method.

(Means for Solving the Problems) The above object is to selectively expose a resist film, bring a silylation agent into contact with the exposed resist film, and then change the exposed/unexposed surface of the exposed resist film. In a method for manufacturing a semiconductor ITF, which includes a step of selectively silylating the resist film corresponding to the exposed area and then developing the resist film by bringing it into contact with oxygen plasma, the resist film is exposed to an alkali prior to the exposure step. This is achieved by a method for manufacturing a semiconductor device that includes a step of contacting a solution.The resist is preferably a mixture of a phenol-novolac resin and a photosensitizer containing a naphthoquinone diazide group, and Preferably, the curing agent is selected from the group of chlorosilanes and silazane, and said alkaline solution is selected from the group of tetramethylammonium hydroxide, choline, caustic soda and caustic potash.

In addition, typical rolosilane and silazane are described below.

Table 1 Chlorosilane trimethylchlorosilane (CHs >25iCfDimethyldichlorosilane (CHz) t S i Clx Methyltrichlorosilane CHsSjCIlz Methyldichlorosilane CHs HS i C1tDimethylchlorosilane (CH,) l HS i Cm!Dimethylvinylchlorosilane CCHs ) z V f S i Cl Methylvinyldichlorosilane CHs V j S i C1m Methylchlorodisilane (CHI ) a S i! C
a6-s(n-2-3) Methyldiphenylchlorosilane CHs (Ca Hs )i 5iCj! Diphenyldichlorosilane (Ca Ha ) t SiCff1g Methylphenyldichlorosilane CHs Ca Ha S r Cl1z Phenyltrichlorosilane Ch Hs Si Cj! 3Chloromethyldimethylchlorosilane Cj! CH* (CHs) z S i C
j! Table 2 Silazane hexamethyldisilazane (CHg) s S 1NH3i (CHs)
s cyclic silazane mixture ((CHs)mS1Nu)-(n=3-4)N,
N'-bis(trimethylsilyl) trifluoroacetamide dimethyltrimethylsilylamine CCHs) m NS 1 diethyltrimethylsilylamine (Cm Hs) * NS 1 (CI(s)s (CHs)* trimethylsilylimidazole [action] Contacting the resist film with an alkaline solution As a result, a diazo bond is generated between the resin and the photosensitizer as shown in (6), and the number of OH groups in the resin is reduced.

Since the silyl group has a property of being easily attached to the OH group of the resin, it is difficult to be silylated even if a silylating agent is brought into contact with a resist film having a reduced number of OH groups as described above.

However, when the resist film in this state is exposed, (6)
The bonds shown in are broken and decomposed into , and the OH groups in the resin return to their original amount, making them more likely to be silylated.

In this way, by contacting the alkaline solution,
The selectivity of silylation between exposed and unexposed areas is improved,
Since the silylated region in the resist film is formed only in the exposed region as shown by 4 in FIG. 1, dry development can be performed using only oxygen plasma.
The variation in line width of the formed resist pattern is reduced.

In FIG. 1, 1 is a substrate, 2 is a resist film, and 3 is an exposure mask.

〔Example〕

A resist mask patterning method according to an embodiment of the present invention will be described below.

A resist prepared by mixing a phenol-novolak resin and a photosensitizer containing a naphthoquinone diazide group in a solvent is applied to a thickness of 1 to 2 mm on a wafer, and baked on a hot plate at a temperature of 90° C. for 90 seconds.

Next, an alkaline solution in which 1.5 to 2.5% of tetramethylammonium hydroxide having the structural formula shown in (7) is dissolved in water is placed on the surface of the resist film.
After standing still for about 30 seconds to 2 minutes, spin dry or place the wafer in the alkaline solution for about 3 minutes.
After soaking for 0 seconds to 2 minutes, air dry.

Next, the IC pattern is exposed using a reduction projection exposure device or the like (exposure amount is 50 to 500 m, J/d), and then exposed on a hot plate at a temperature of about 130 to 150°C for 1 to 20 minutes. While baking, hexamethyldisilazane, which is a silylating agent, is brought into contact with the surface of the resist film.

The above wafer was placed in a vacuum chamber of a plasma etching apparatus, oxygen was supplied at 60 SCCM to maintain the pressure inside the vacuum chamber at 30 mTorr, and high frequency power was applied so that the power density was 1.57 W/d. to turn oxygen into plasma, bring this oxygen plasma into contact with the resist film, and remove the unsilylated resist film in the unexposed area,
Form a resist mask.

In addition, as the silylating agent, in addition to hexamethyldisilazane, the chlorosilane shown in Table 1 and the silazane shown in Table 2 can be used.As the alkaline solution, tetramethyldisilazane can be used. In addition to ammonium hydroxide, choline, caustic soda, caustic potash, etc. having the structural formula (8) can be used.

〔Effect of the invention〕

As explained above, in the method for manufacturing a semiconductor device according to the present invention, the resist film is brought into contact with an alkaline solution to form a diazo bond between the resin contained in the resist and the photosensitizer, thereby forming an exposed region and an unexposed region. The selectivity of the corresponding silylation has been improved, making it possible to perform dry development using only oxygen, reducing the variation in line width of the formed resist pattern, and enabling higher integration of semiconductor integrated circuits. This is a major contribution.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the state of formation of a silylated layer in a resist pattern forming method according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the state of formation of a silylated layer in a resist pattern forming method according to the prior art.・Substrate, ・Resist film, ・Mask, ・Silylated layer.

Claims (1)

[Scope of Claims] [1] Selectively exposing a resist film, bringing a silylating agent into contact with the exposed resist film, and changing the surface of the exposed resist film corresponding to exposed and unexposed areas. A method for manufacturing a semiconductor device comprising a step of selectively silylating and developing the resist film by contacting the resist film with oxygen plasma, the method further comprising the step of contacting the resist film with an alkaline solution prior to the exposure step. A method for manufacturing a semiconductor device. [2] The method for manufacturing a semiconductor device according to claim [1], wherein the resist is a mixture of a phenol-novolac resin and a photosensitizer containing a naphthoquinone diazide group. [3] The method for manufacturing a semiconductor device according to claim 1 or 2, wherein the silylation agent is selected from the group consisting of chlorosilane and silazane. [4] Claim [1] characterized in that the alkaline solution is selected from the group consisting of tetramethylammonium hydroxide, choline, caustic soda, and caustic potash.
, [2] or [3].