JPH03222409A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to inhibit patterns dimensional deviation induced by interference effect and control the dimensions of transfer patterns with high accuracy by forming a resin film having light transmission properties with exposure light on a photo resist film and then exposing by way of the resin film. CONSTITUTION:An insulation separation layer 2 is selectively formed on the surface of a semiconductor substrate 1 and a silicon polycrystal layer 3 is formed on the whole surface of the substrate 1. A resin film 6 which has light transmission properties with a specified exposure light is formed on a photo resist film 4. In this case, the light transparent resin film 6 whose light reflectance is substantially identical to that of the photo resist film 4 is formed so that the sum of the thickness of the photo resist film 4 and the thickness of the light transparent resin film may be uniform all over the active region. Then, when an attempt is made to expose with a specified pattern, it will be possible to inhibit dimensional deviations in terms of the width of patterns of the resist film 4 induced by interference effect, thereby enabling the highly accurate formation of the patterns of the resist film 4 with a specified width.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device in which a photoresist film is used to form a film to be processed into a desired pattern, and particularly to a method for manufacturing a semiconductor device such as an MO8 type integrated circuit. The present invention relates to a method of manufacturing a semiconductor device suitable for forming a gate electrode on a semiconductor device having a step on the surface of a semiconductor substrate.

[Prior Art] In MO8 type integrated circuits, the dimensions of the gate electrode have a great influence on the characteristics and manufacturing yield of the integrated circuit device.

Therefore, in the gate electrode forming process, it is necessary to strictly control dimensional accuracy.

FIG. 3 is a cross-sectional view showing an example of a conventional method for manufacturing a semiconductor device.

First, an insulating isolation layer 22 is formed in an element isolation region of a semiconductor substrate 21.
selectively formed. Then, the entire surface of the substrate 21 is coated with a silicon polycrystalline layer 23 that will become a gate electrode. In this case, a step is formed in the silicon polycrystalline layer 23 at the boundary between the element isolation region where the insulation isolation layer 22 is formed and the active region where the insulation isolation layer 22 is not formed.

Next, a positive photoresist film 24 is formed on this silicon polycrystalline layer 23 to a thickness of about 1.2 μm. Then, a predetermined mask pattern is transferred onto the photoresist film 24 using a reduction projection exposure apparatus that uses G-line having a wavelength of 43 Gnm.

Next, tetramethylammonium hydroxide (
The photoresist film 24 is developed using an organic alkaline developer containing TMAH as a main component. In this way, a resist film with a predetermined pattern is obtained. Thereafter, after a post-baking process is performed, the polycrystalline silicon layer 23 is dry etched using a parallel plate type reactive ion etching apparatus using this resist film as a mask.

Thereby, the silicon polycrystalline layer 23 is formed into a predetermined gate electrode pattern.

Next, the resist film is removed using plasma or acid.

In this way, a semiconductor device having a predetermined gate electrode can be manufactured.

[Problems to be Solved by the Invention] However, in the conventional semiconductor device manufacturing method described above, when trying to form gate electrodes and the like with a predetermined width in multiple active regions having different areas, it is difficult to maintain dimensional accuracy with high precision. The disadvantage is that it cannot be controlled. The reason for this will be explained below.

Figure 4 shows the film thickness of a photoresist film when a pattern in which lines with a width of 1 μm are arranged at 1 μm intervals is transferred onto a photoresist film coated on a semiconductor substrate using a G-line reduction projection exposure device. FIG. 4 is a graph diagram showing the relationship between the line width of the resist pattern and the line width of the resist pattern.

In FIG. 4, the horizontal axis represents the thickness of the photoresist film, and the vertical axis represents the line width of the resist pattern at the interface between the photoresist film and the substrate.

As is clear from FIG. 4, the line width of the transferred pattern changes sinusoidally with respect to the film thickness of the photoresist film. This phenomenon is known as the interference effect. This interference effect occurs when the single-wavelength exposure light incident on the photoresist film coated on the substrate interferes with the reflected light reflected from the substrate, resulting in the amount of light energy absorbed in the thickness direction of the photoresist film. This occurs due to differences in the numbers. Due to this interference effect, variations in the thickness of the photoresist film affect variations in the pattern width of the resist film after development. Therefore, it is preferable that the thickness of the photoresist film is as uniform as possible.

By the way, when a photoresist film is formed by spin footing on a semiconductor substrate which is separated by an insulating separation layer and has various active regions with different areas, as shown in FIG. The thickness d1 of the film is completely different from the thickness d2 of the photoresist film in a wide area, and the thickness of the photoresist film changes depending on the area of the active region.

FIG. 5 is a graph showing the relationship between the logarithm of the area S (μm2) of the active region on the horizontal axis and the thickness of the photoresist film on the vertical axis. As is clear from FIG. 5, as the area of the active region increases, the thickness of the photoresist film becomes thinner.

FIG. 8 shows that three types of active regions with different areas S are covered with a photoresist film formed by a spin code.
FIG. 7 is a graph showing the results of examining the pattern width of the resist film after transferring a gate electrode pattern of the same width to the photoresist film of each active region. As is clear from FIG. 6, due to the difference in the area of the active region, 0.17
Pattern dimensional deviation on the order of μm occurs. Therefore, in the conventional method, it is difficult to control the dimensions of the gate electrode and the like with high precision.

In addition to the interference effect, the thickness of the photoresist film influences the width of the resist pattern due to the bulk effect. That is, the pattern of the resist film obtained by developing the photoresist film after exposure is slightly wider at the bottom than at the top.

For this reason, if the film thickness of the photoresist film differs, variations will occur in the pattern width of the resist film after development processing.

However, in the case of a normal gate electrode pattern, the rate at which the pattern width of the resist film changes due to this bulk effect is extremely small compared to the interference effect.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a method for manufacturing a semiconductor device in which pattern dimension deviation due to interference effects is suppressed and the dimensions of a transferred pattern can be controlled with high precision.

[Means for Solving the Problems] A method for manufacturing a semiconductor device according to the present invention includes a step of forming a film to be processed on a semiconductor substrate, a step of forming a photoresist film on the film to be processed, and a step of forming a photoresist film on the film to be processed. a step of forming a resin film that is transparent to exposure light on the resist film; a step of transferring a predetermined pattern to the photoresist film by exposing through the resin film; a step of removing the resin film; a step of developing the photoresist film to form a resist film with the predetermined pattern; and a step of forming the processed film into the predetermined pattern using the resist film as a mask. It is characterized by having the following.

[Function] In the present invention, a resin film that is transparent to predetermined exposure light is formed on a photoresist film. In this case, even if the thickness of the photoresist film is uneven, for example, a light-transmitting resin film whose refractive index is approximately the same as that of the photoresist film may be compared to the thickness of the photoresist film. is formed on the photoresist film so that the sum of the film thicknesses is the same in all active regions. Then, when exposed in a predetermined pattern, dimensional deviations in the pattern width of the resist film due to interference effects are suppressed. Thereby, a resist film pattern can be formed with a predetermined width and high precision.

In addition, by appropriately selecting the refractive index and film thickness of the light-transmitting resin film, even if the sum of the film thicknesses of the photoresist film and the light-transmitting resin film is different for each active region, all active regions can be The influence of interference effects can be made the same in both cases. This suppresses pattern dimensional deviation of the resist film after development, so that the film to be processed can be formed to a desired width with high precision.

[Embodiments] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIGS. 1(a) to 1(d) are cross-sectional views showing the method of the first embodiment of the present invention in the order of steps.

First, as shown in FIG. 1(a), an insulating separation layer 2 is selectively formed on the surface of a semiconductor substrate 1. Then, a polycrystalline silicon layer 3 to be formed into a predetermined gate electrode pattern is formed over the entire surface of the substrate 1 by vapor phase growth. Thereafter, a normal positive type photoresist film 4 made of novolac resin and naphthoquinonediazide sulfonic acid ester is formed on this silicon polycrystalline layer 3. In this case, the thickness of the photoresist film 4 is thinner in the active region with a larger area than in the active region with a smaller area.

Next, as shown in FIG. 1(b), the photoresist film 4
For example, a PVA (polyvinyl alcohol) film 5 is placed on top.
Formed with a thickness of 0.00 people. Then, a resin with high G-line transmittance and a refractive index close to that of photoresist, such as a novolac resin whose monomer is mt p cresol, is dissolved in a solvent to make an extremely low viscosity solution, and this solution is processed using a spin code. is applied onto the PVA film 5 to form a transparent resin film 6. In this case, the thickness of the resin film 8 is set to about 1.
It is made relatively thick to 0 μm so that its upper surface is flat. Note that polyvinyl alcohol, which is the material of the PvA film 5, is a water-soluble resin. Further, this PVA film 5 is formed to prevent the photoresist film 4 and the resin film 8 from coming into contact with each other and mixing them.

Next, a predetermined gate electrode pattern having a width of, for example, 1.0 μm is transferred onto the photoresist film 4 in the active region using a 115 reduction projection exposure apparatus that uses G-line as exposure light. At this time, since the sum of the film thicknesses of the photoresist film 4 and the resin film 6 in each active region is the same, variations in the dimensions of the transferred pattern in each active region due to interference effects are suppressed.

Next, as shown in FIG. 1(C), the resin film 6 is removed. The resin film θ is removed by supplying, for example, ethyl cell solve acetate (ECA) several times from a nozzle to the semiconductor substrate 1 fixed on the spin chuck of a spinner.
It is preferable to perform this by rotating the substrate 1 at high speed after dissolving the .

Next, as shown in FIG. 1(d), for example, the concentration is 2.3.
The photoresist film 4 is developed using an alkaline developer such as an 8% by weight aqueous solution of tetramethylammonium hydroxide. As a result, unnecessary portions of the photoresist film 4 are removed, and a resist film 4a having a predetermined pattern is obtained.

Note that since the PVA film 5 is water-soluble, it is completely removed by a pre-wet process before the development process. Further, even when the pre-wet process is not performed, when the developer is supplied onto the substrate 1, the PVA film 5 is completely dissolved in the developer and removed in a few seconds.

Next, as in the prior art, the silicon polycrystalline layer 3 is etched using the resist film 4a as a mask.

After that, the resist film 4a is removed. Thereby, the gate electrode can be formed in a predetermined pattern.

In this embodiment, as described above, a resin film 6 having a refractive index substantially the same as that of the photoresist film 4 is coated on the photoresist film 4 in each active region.
Since the photoresist film 4 is exposed after being formed so that the sum of the film thicknesses is approximately the same, variations in pattern width due to interference effects are avoided, and the width of the gate electrode in each active region can be increased. It can be controlled to a predetermined value with precision.

FIGS. 2(a) to 2(C) are cross-sectional views showing the second embodiment of the method of the present invention in order of steps.

First, as shown in FIG. 2(a), an insulating isolation layer 12 is selectively formed on a semiconductor substrate 11 in the same manner as in the first embodiment. Thereafter, a silicon polycrystalline layer 13 and a photoresist film 14 are formed on the entire surface of the substrate 11.

Next, as shown in FIG. 2(b), the photoresist film 1
4, a water-soluble resin film 15 such as PVA is applied. After that, a predetermined pattern is formed on the photoresist film 1 using an exposure device.
Transfer to 4.

At this time, the photoresist film 1 in the active region, which has a small area,
The film thicknesses of the photoresist film 14 and the water-soluble resin film 15 in the large active area are d2 and t2, respectively. If the refractive index is nR1 and the refractive index of the water-soluble resin film 15 is np, then if the following formula (1) holds true, dimensional deviation due to interference effects can be avoided.

dxnR+t+np = (LnI?+t2np ・(1) Therefore, the photoresist film 14 and the resin film 15 are formed so as to satisfy this formula (1). In this case, the thickness dt+d2 and the refractive index nR of the photoresist film 14 are It may be difficult to set t8 to a desired value due to process constraints. However, by selecting the material and coating method of the water-soluble resin film 15, the thickness t8.t2 of the resin film 15 can be set to a desired value.
and the refractive index nP can be adjusted to satisfy the above formula (1). This suppresses variations in the dimensions of the transferred pattern due to interference effects.

Next, as shown in FIG. 2(C), the photoresist film 14 is developed in the same manner as in the first embodiment. In this case, the water-soluble resin film 15 is removed in the pre-wet process, and a resist film 14a having a predetermined pattern can be obtained.

Next, as in the conventional method, the silicon polycrystalline layer 13 is etched using the resist film 14a as a mask. Thereafter, by removing the resist film 14a, a gate electrode with a predetermined pattern can be obtained.

In this embodiment, as described above, by appropriately selecting the thickness and refractive index of the water-soluble resin film 15, the same effects as in the first embodiment can be obtained. Furthermore, in this embodiment, since the resin film 15 formed on the photoresist film 14 is water-soluble, there is also the effect that the number of steps can be reduced compared to the first embodiment.

[Effects of the Invention] As explained above, according to the present invention, after a transparent resin film is formed on a photoresist film, the photoresist film is exposed to light through this resin film, so that transfer due to interference effects is prevented. Dimensional deviation of the pattern can be suppressed. Therefore, in an MO8 type integrated circuit, for example, gate electrodes can be formed with a predetermined width in each of a plurality of active regions having different areas, which has the effect of improving the characteristics and manufacturing yield of the integrated circuit device. play.

[Brief explanation of drawings]

FIGS. 1(a) to (d) are cross-sectional views showing a method according to the first embodiment of the present invention in the order of steps, and FIGS. 2(a) to (c) are sectional views showing the method according to the second embodiment of the present invention in order of steps. 3 is a sectional view showing an example of a conventional semiconductor device manufacturing method, and FIG. 4 shows the film thickness of the photoresist film and the transferred pattern when a pattern with a line width and interval of 1 μm is transferred. A graph showing the relationship between line width, Figure 5 is a graph showing the relationship between the area of the active region and the thickness of the photoresist film, and Figure 6 is a graph showing the relationship between the area of the active region and the pattern dimensions transferred to the photoresist film. It is a graph diagram showing the relationship. 1.11, 21; semiconductor substrate, 2, 12, 22; insulating separation layer, 3.13, 23; silicon polycrystalline layer, 4.14.
24; Photoresist film, 5; PVA film, 6. Translucent resin film,

Claims (1)

[Claims] (1) A process of forming a film to be processed on a semiconductor substrate, a process of forming a photoresist film on the film to be processed, and a process of forming a resin film that is transparent to exposure light on the photoresist film. a step of transferring a predetermined pattern onto the photoresist film by exposing it to light through this resin film; a step of removing the light-transmitting resin film; and a development process on the photoresist film. 1. A method of manufacturing a semiconductor device, comprising: forming a resist film having the predetermined pattern using the resist film; and using the resist film as a mask, forming the film to be processed into the predetermined pattern.