JP3031303B2 - Method for manufacturing semiconductor device - 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 of manufacturing a semiconductor device, and more particularly, to a method of forming a photoresist pattern at that time. Specifically, a photoresist film formed on a semiconductor substrate is exposed through a reticle or a mask on which a desired semiconductor integrated circuit pattern is drawn, and after exposure, heat treatment, and development using a developer to form a photoresist pattern On how to do it.

[0002]

2. Description of the Related Art The degree of integration of semiconductor integrated circuits typified by DRAMs keeps increasing, and accordingly, high resolution is required in an optical lithography process for forming a circuit pattern on a semiconductor substrate. For this reason, the wavelength of the exposure light has been shortened, and in photolithography having a design rule of 0.3 μm or less, far ultraviolet light (wavelength 0.248 μm) has been used.
m, 0.193 μm, etc.). As the resist, a novolak resin-based resist which has been used in the conventional g-line (0.436 μm) or i-line (0.365 μm) lithography has a considerably large light absorption coefficient of the novolak resin and has a large resist shape. Because of poor verticality, it cannot be used. Therefore, a chemically amplified resist is newly devised and put to practical use.

A chemically amplified resist generates an acid from a photosensitizer upon exposure to light, and the acid is diffused by heat treatment to act as a catalyst to decompose or remove a base resin which is a main component of the resist material. It is a resist that increases its solubility in a developer by changing its molecular structure, that is, a resist that solubilizes the resist.It has a base resin, a photo-acid generator that generates an acid upon exposure, and a solubility in the developer due to an acid-catalyzed reaction. It consists of a compound having a variable reactive group in its molecule. Since this resist utilizes the catalytic reaction of acid, basic impurities contained in the air,
For example, a small amount of ammonia in the air or basic substances such as ethylenediamine used for wall coating and amines generated from hexamethyldisilazane used for hydrophobic treatment come into contact with acids near the surface of the resist to lose the acid. Active, the acid concentration near the resist surface layer is reduced, so that the catalytic reaction of the acid is suppressed, the sufficient solubilization reaction of the resist does not proceed, and the surface becomes insoluble, so-called T-type resist shape is generated.
There is a problem that the resolution, depth of focus, and dimensional accuracy of optical lithography are impaired.

Several methods have been proposed for preventing acid deactivation due to basic impurities, such as post-exposure bake (PEB).
A method in which the atmosphere of the treatment is replaced with an inert gas to prevent acid deactivation (JP-A-4-369221), and a method in which the process from pattern exposure to development is performed in an atmosphere free from gas impurities (JP-A-6-36961)
140299), or a method in which a chemical filter is attached to a coating and developing machine to perform PEB treatment and development at an ammonia concentration of 1 ppb or less to prevent acid deactivation (Japanese Patent Application Laid-Open No. 7-14312).

[0005]

However, the shape of the T-type resist is caused by reasons other than the deactivation of acid by the above-mentioned basic impurities. FIG. 3 is a schematic sectional view showing a procedure and a result when a pattern is formed on a certain chemically amplified resist according to a conventional pattern forming method while controlling the environment without a basic impurity using a chemical filter. A chemically amplified resist film 302 was formed on a wafer 301 (FIG. 3A), and pattern exposure was performed with a laser beam 304 using a reticle pattern 303 (FIG. 3B).
Reference numeral 305 schematically shows the acid generated in the resist at that time. Thereafter, PEB processing was performed (FIG. 3C). Subsequently, when a developing process was performed, as shown in FIG.
The resulting resist pattern 306 had a T-shape.

As a result of measuring the acid concentration in the resist film before and after the PEB treatment by an absorptiometric method using an indicator, it was found that the amount of the acid was reduced by about 40% by the PEB treatment. It was found that it was caused by acid transpiration due to the treatment. 307 shown in FIG.
Indicates schematically the evaporated acid resulting from the PEB treatment.

That is, the conventional method of preventing the deactivation of an acid by a basic impurity alone cannot completely prevent the formation of a surface insoluble layer. This is because even when the acid concentration near the surface layer is reduced due to the evaporation of the acid during the PEB treatment, the surface hardly soluble layer is formed. In particular, for the formation of a fine pattern, deterioration in the shape and resolution of the resist pattern caused by such a surface insoluble layer is fatal. Therefore, it is essential to prevent or reduce acid transpiration.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a resist which suppresses formation of a hardly-solubilized layer due to evaporation of an acid on a resist surface peculiar to a chemically amplified resist and prevents a resist pattern after development from becoming a T-shaped resist. It is to provide a pattern forming method. As a result, a rectangular resist pattern can be obtained, resolution, depth of focus, and dimensional accuracy can be improved, and high integration of a semiconductor device can be achieved.

Another object of the present invention is to provide a method of manufacturing a semiconductor device in which a resist pattern is formed by such a method of forming a chemically amplified resist pattern.

[0010]

According to the present invention, there is provided a method for forming a chemically amplified resist pattern, comprising the steps of: exposing a chemically amplified resist film formed on a substrate; heating the resist film; In a resist pattern forming method in which a step of developing a film to form a resist pattern is performed in this order, the heat treatment of the resist film is performed under a pressure higher than a normal atmospheric pressure. It is a forming method.

[0011] A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device, wherein a resist pattern used in the manufacture is formed by the above-described method of forming a chemically amplified resist pattern.

According to the present invention, the transpiration of the acid generated during the PEB process is reduced by performing the PEB process, that is, the post-exposure bake treatment of the chemically amplified resist film formed on the substrate at a higher pressure than usual. Thus, it is possible to prevent the formation of a hardly-soluble surface layer due to a decrease in the acid concentration near the resist surface, and to obtain a good resist shape without a T-shaped shape.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment of the method of the present invention, the pressure at the time of PEB treatment of a resist film is such that the amount of acid evaporated by heating is 10% or less of the amount of acid before heat treatment. It is preferable that the pressure is such that the pressure during the PEB treatment is at least 10 times the vapor pressure of the acid used.

The absolute value of the above-mentioned preferable atmospheric pressure during the PEB processing cannot be specified because the vapor pressure varies depending on the kind of the acid generated at the time of exposure and the amount of the acid before the PEB processing changes. P under pressure of 2 atmospheres or more in absolute pressure
It is generally preferred to perform EB processing.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. In the examples, the resist is a t-butoxycarbonyl (tBOC) protected polyhydroxystyrene resin, and the resist is exposed to the following formula (1):

[0016]

Embedded image Acid generator for producing aromatic sulfonic acid, and propylene glycol monomethyl ether acetate (PG
(MEA) An experiment was performed using a chemically amplified resist composed of a solvent.

Embodiment 1 In this embodiment, a resist pattern forming step of the present invention will be described. As shown in FIG. 1A, a resist film 102 was formed on a wafer 101, and pattern exposure was performed using KrF excimer laser light using a reticle pattern 103 as shown in FIG. 1B. Thereafter, as shown in FIG. 1 (c), PEB was
Processing was performed. Subsequently, development processing is performed, and FIG.
Was obtained.

In this embodiment, when the pressure at the time of PEB treatment was performed at 2 atm using the above-mentioned chemically amplified resist, the T-shaped shape was reduced by half. From this, it was found that the degree of the T-shape can be reduced by performing the PEB treatment under high pressure.

Example 2 In this example, a description will be given of the atmospheric pressure during PEB processing of a resist film in a preferred embodiment of the present invention. In this embodiment, the pressure at the time of PEB treatment was changed to 1, 2, and 4 atm in absolute pressure in the case where the above-mentioned chemically amplified resist was used, and the amount of acid transpiration at each pressure was measured by an absorptiometric method using an indicator. I asked. The result is shown in FIG. It was found from FIG. 2 that the higher the pressure, the more the evaporation of the acid was suppressed. Along with this, the pattern shape also changed from a T-shaped shape to a rectangular shape. When the PEB treatment was performed at 4 atm, the amount of acid transpiration could not be completely suppressed to about 10%, but a good non-T-shaped pattern shape could be obtained.

The PEB temperature of this aromatic sulfonic acid (10
As a result of measuring the vapor pressure at 0 ° C), it was found to be about 300 mmHg. Since 4 atm is 3040 mmHg, in the case of this acid, if the PEB treatment is performed under a pressure of about 10 times or more of the vapor pressure of the acid, the amount of evaporation of the acid can be suppressed to 10% or less, and a good pattern having no T-shaped shape can be obtained. It was found that the shape was obtained.

As described above, in Examples 1 and 2, a chemically amplified resist comprising t-butoxycarbonyl (tBOC) protected polyhydroxystyrene as a resin, aromatic sulfonic acid as an acid, and propylene glycol monomethyl ether acetate (PGMEA) as a solvent. However, the constituent components of the chemically amplified resist to which the present invention is applied are not limited to these components.
And if the target chemically amplified resist is different,
In some cases, the type of acid generated by the exposure is different, and the vapor pressure of the acid at the PEB temperature is also different. In this case, the amount of the acid evaporated by the PEB treatment is reduced to 10% of the amount of the acid before the PEB treatment. %, Or the numerical value of the pressure at the time of PEB treatment required to be less than 10%, or the numerical value of the pressure at the time of PEB treatment necessary to make the vapor pressure of the acid 10 times or more, also depends on each case. Therefore, the specific numerical values of the pressure in the above-described Examples 1 and 2 and the numerical value of the external pressure on the horizontal axis in FIG. 2 related thereto are all the specific values used in these two Examples. It should be understood as the specific numerical value of the chemically amplified resist of, if the type of chemically amplified resist targeted by the present invention is different,
It is noted here that the specific values of the pressure are also different.

[0022]

As described above, the method for forming a pattern of a chemically amplified resist according to the present invention can reduce the evaporation of acid during PEB treatment, and can obtain a good pattern shape without a T-shaped shape. As a result, the resolution performance of the chemically amplified resist can be improved. In addition, this leads to the manufacture of a stable semiconductor device with a good industrial yield.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic cross-sectional views for explaining a resist pattern forming process according to a first embodiment of the present invention. FIG. 1A shows a case where a resist is formed on a wafer, and FIG. (C) shows the resist pattern obtained when the pressure PEB treatment was performed, and (d) shows the obtained resist pattern.

FIG. 2 is a graph showing the relationship between the external pressure and the amount of acid transpiration during PEB processing in Example 2 of the present invention.

3A and 3B are schematic cross-sectional views showing steps and results of a conventional resist pattern forming method. FIG. 3A shows a case where a resist is formed on a wafer, FIG. 3B shows a case where pattern exposure is performed, and FIG. When the PEB treatment was performed, (d) shows the obtained resist pattern.

[Explanation of symbols]

 101, 301 wafer 102, 302 resist 103, 303 reticle pattern 104, 304 exposure light 105, 305 acid generated by exposure 106, 306 resist pattern 307 acid evaporated by PEB process

Claims (6)

(57) [Claims] A step of exposing a chemically amplified resist film formed on a substrate, a step of heating the resist film, and a step of developing the resist film to form a resist pattern. In the method for forming a resist pattern, when heat treatment of the resist film,
A method for forming a chemically amplified resist pattern, wherein the heat treatment of the resist film is performed at a pressure higher than the normal pressure by pressurizing the heat treatment chamber to a pressure higher than the normal pressure. 2. The method for forming a chemically amplified resist pattern according to claim 1, wherein the pressure during the heat treatment is such that the amount of the acid evaporated by the heat treatment is 10% or less of the amount of the acid before the heat treatment. A method for forming a chemically amplified resist pattern, wherein the method is pressure. 3. The method for forming a chemically amplified resist pattern according to claim 1, wherein the pressure during the heat treatment is at least 10 times the vapor pressure of the acid used. . 4. A method for manufacturing a semiconductor device, wherein a resist pattern used in manufacturing a semiconductor device is formed by the method for forming a chemically amplified resist pattern according to claim 1. 5. A method of manufacturing a semiconductor device, wherein a resist pattern used for manufacturing a semiconductor device is formed by the method of forming a chemically amplified resist pattern according to claim 2. 6. A method of manufacturing a semiconductor device, wherein a resist pattern used in manufacturing a semiconductor device is formed by the method of forming a chemically amplified resist pattern according to claim 3.