JPS599655A - Formation of resin pattern - Google Patents

Abstract

PURPOSE:To obtain a resist pattern mark good in precision of pattern transfer, by forming a resin layer on a substrate having a relief, and on this layer a layer of a resin having higher mol.wt. than that of the resin of said layer, and then, forming a pattern of the resin layer. CONSTITUTION:A silicon substrate 11 provided with about 500nm vertical level difference is coated as the first layer with a UV sensitive negative resist 12 controlled to 100-10,000 average mol.wt. in a condition of forming 100-1,000nm thickness on a flat base, and baked. The first layer is coated with a UV sensitive positive type resist 13 having 1,000-100,000 average mol.wt. in a condition of forming about 1,000nm thickness on a flat base, and selectively exposed to UV rays to form patterns 13a and 13b. The disclosed part of the undercoat negative resist film 12 is perfectly removed by using the resist 13 as a mask and the RIE method, and for example, the conditions of 10-100Torr, 200W, and several SCCM oxygen.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a resin pattern, and in particular to a method for transferring a pattern that has a steep cross-sectional shape and is not affected by steps on the substrate surface onto a film to be etched formed on the surface of a semiconductor substrate having an uneven shape. The present invention provides a method for forming a highly accurate resist mask pattern.

In manufacturing semiconductor integrated circuits, the surface of a substrate becomes uneven due to repeated deposition and etching of thin films. For example, MO
Taking the manufacturing of an 8-inch integrated circuit as an example, as shown in Figure i1,
p-type diffusion regions 5 and 6 for the source and drain of a p-channel MO8) transistor have been formed on an in-type silicon substrate 1, and the field oxide film 2 is approximately 7000 m thick.
(approximately 3,500 people are raised from the surface of the silicon substrate), approximately 500 people for the gate oxide film 3, and approximately 5,000 people for the polysilicon film 4. In the steps up to this point, the maximum height difference on the substrate surface is about 8,000 between the surface of the polysilicon film 4 on the field oxide film 3 and the surface of the gate oxide film 3.

Next, as a step, a contact window opening step is performed to remove each electrode of the transistor. As shown in figure b, this is the final step in figure a (formation of source/drain diffusion regions).
After that, a silicon oxide film 7 is formed on the entire surface of the substrate to a thickness of 5000 mm.
is formed by CVD method. Next, by one photolithography process, a photosensitive resin such as a positive type photosensitive resin 8 (hereinafter, the photosensitive resin is referred to as a resist) is applied to the entire surface of the silicon oxide film 7 at a density of approximately 100% when the silicon substrate surface τm is flat.
If the resist is coated under the conditions of 0.00 (relevant rotational coating using a spinner), the resist is viscous, so even if there is a step on the substrate surface as shown in Figure 8, a thin field oxide film is formed on the convex parts (q′!f). The resist film thickness is approximately 5,000 to 8,000, although the difference in resist film thickness varies depending on the underlying pattern arrangement and cross-sectional shape. .

Next, when the positive resist 8 is irradiated with ultraviolet rays using a glass mask for contact window openings and, for example, a 1-magnification reflection projection exposure device, the contact window openings 9 and 10 are opened as shown in Figure 0. Differences occur in dimensions, with the aperture 9 of the convex portion being larger and the apertures 10 of the four portions being smaller. In this case, if a 3 μm mask is used, the dimensional difference between the convex portion and the concave portion will be approximately 0.5 μm.

This is because the dimensional deformation of a positive resist is affected by the amount of ultraviolet irradiation and the film thickness; if the film thickness is constant, the diameter of the opening increases as the irradiation meter becomes thicker. As long as the irradiation dose is constant, the thinner the Lennost film is, the larger the size of the opening becomes. This is particularly noticeable in the same magnification reflection projection exposure method. In reality, the thickness of the film varies depending on the underlying substrate, and it is impossible to control the dimensions by partially adjusting the UV irradiation point. When proceeding to step 6 by repeating the film deposition and etching, steps will occur on the substrate surface, and when a resin such as resist is applied, a difference in film thickness will occur between the convex and concave areas. It becomes impossible to control.

In consideration of the above problems, the present invention uses a method of providing a plurality of unique resin layers on the film to be etched in order to form a resin pattern with the same dimensions on the four parts and the convex parts of the substrate surface. A detailed explanation of the present invention will be given below along with examples.

In FIG. 2, for example, in a substrate in which 5,000 vertical steps are provided on the silicon substrate 11, as the first embodiment, the average molecular weight of the negative resist 12 for ultraviolet rays in the first layer is several hundred. ~Controlling thousands of VCs on a flat board
yx conditions (for example, 60 cp and 5000 rprl [[
Coat the coating and bake at approximately 80°C to 140'C for several minutes to several tens of minutes. Next, as a second layer l=I, a UV-sensitive positive resist 13 having an average molecular weight of several thousand to several tens of thousands is coated on a flat substrate with approximately 1
oOoO Conditions for becoming a person (for example, 27cp and 5o○Orp)
1[11] transfer coating is performed in step m) (FIG. 2a) Next, patterns 13a and 13b are formed on the positive resist 13 by selectively irradiating ultraviolet rays. In this case, during the development of the positive resist 13, the underlying negative resist 12 is not dissolved. Further, the surface of the negative resist 120 is substantially flat, and the film thickness of the positive resist 13 is also substantially uniform. Therefore, when forming the positive resist patterns 13a and 13b, there is no influence of the uneven parts of the base substrate, and the dimensions of the positive resist patterns 13a and 13b on the convex parts and the concave parts, respectively, are almost the same, and the dimensions on the four parts of the substrate and the convex parts are almost the same. The dimensional difference in the upper positive resist pattern becomes almost zero. By adjusting the exposure amount at this time (the pattern printing is performed using a contact exposure method), the cross-sectional shape of the remaining blurred mask 13 can be made steep.

Next, using the positive resist 13 as a mask, as shown in FIG.

The exposed portion of the base negative resist film 12 is completely removed under the conditions of 200 W and 0.2 gas SCCM. In this case, since the cross section of the positive resist mask 13 is steep, there is almost no spreading in the lateral direction, and the average molecular weight of the mask 13 is one order of magnitude higher than that of the underlying negative resist 12.
Positive resist mask 13 and negative resist 1 for oxygen
Etching speed ratio d: several times faster for negative resist 12. Therefore, even if the total overetching time of the negative resist 12 is slightly longer, the masking effect of the positive resist mask 13 is sufficiently good (the broken line in the figure shows the change in the positive resist), and there is almost no lateral change in dimensions. Finally, a pattern with good uniformity can be formed on the four parts and the convex parts of the substrate. There is a method using a photosensitive resin for ultraviolet rays or a photosensitive resin for electron beams. Since these have an average molecular weight several orders of magnitude higher than those of the UV-sensitive resins, the same results can be obtained if they are formed in the same manner as described in the first embodiment. In this case, the base first layer resin is not limited to Kyogalesyst, but may also be a positive resist (low molecular resin for ultraviolet ray exposure).

Other non-photosensitive resins such as polymide resins may also be used. If a photosensitive resin for far ultraviolet rays, electron beams, or X-rays is used for the second layer, it will be sensitive to short wavelengths (200 nm or less), so 0.6
A resolution of ~1 .mu.m can be obtained, which enables further miniaturization, which is advantageous for miniaturization.

In order to inject a resin pattern of uniform dimensions on a single uneven substrate as described in 2 below, in the present invention, a resin having the smallest average molecular weight is first formed in the bottom layer to increase the etching rate against oxygen, for example. do. The resin formed in the upper layer has a lower average molecular weight than the lower layer to reduce the etching rate against oxygen, and the photosensitive resin with high resolution is used in the top layer. It is possible to set and form a plurality of combinations on a substrate. Note that the etching gas is not limited to oxygen, but may also be one that does not etch the underlying substrate and can completely etch the resist, such as CF, C04, etc.
Other gases such as No. 4 may also be used.

As described above, according to the present invention, the pattern dimensions are the same for the convex portion and the four portions of the film to be etched which have a high step difference, which greatly contributes to improving the dimensional accuracy and manufacturing of semiconductor technology.

[Brief explanation of the drawing]

Figures 1 (a) to (C) are enlarged cross-sectional views of the main parts of a conventional MO8 type transistor/star manufacturing process, and Figures 2 (a) to (c) are steps of a silicon substrate according to an embodiment of the present invention. - Fig. 5 is a cross-sectional view of the process of forming a pattern using a plurality of resins. 11... Silicon substrate, 12... First
layer negative resist, 13...second layer positive resist)
, 13a. 13b...pattern. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 1.3

Claims (2)

[Claims] (1) A first resin layer having a first average molecular weight is formed on a substrate having irregularities, and the first resin layer has a second average molecular weight larger than the first average molecular weight. forming a sensitive second resin layer, selectively removing the second resin layer to form the second resin layer pattern, and removing the first resin layer using the pattern as a mask; A method for forming a resin pattern, the method comprising: exposing the substrate through a step of exposing the substrate. (2) Removal of the first resin layer using oxygen gas f:
A method for forming a resin pattern according to claim 1.