JPS62141548A - Formation of pattern - Google Patents

Abstract

PURPOSE:To obtain the sectional shape of a resist pattern having high contrast by making double exposure at the adequate irradiation quantity consisting of the exposure by the prescribed irradiation quantity corresponding to the prescribed pattern shape and the exposure by the prescribed irradiation quantity to the central part of the pattern shape. CONSTITUTION:The irradiation quantity to the prescribed pattern forming region is set at n-times the quantity required for the pattern formation on the upper and lower layer resists to be applied and the irradiation quantity to the region which includes said region and has the width of 2-3 times the size of the prescribed pattern is set at k-times the quantity necessary for the pattern formation. The values n and k are so determined that the irradiation quantity to the prescribed pattern part attains the necessary for the pattern formation. The adequate irradiation quantity as a whole is eventually applied to each of the two layers of the upper and lower layers when the most adequate irradiation quantity to take the sensitivity of the upper and lower two layers into consideration is applied to the pattern having the line width of 2-3 times the pattern width of the actually designed pattern and when the pattern of the line width corresponding to the actually designed pattern is irradiated and exposed double at the adequate irradiation quantity. As a result, the resist pattern having a T-shaped section is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a pattern forming method, and more specifically,
Forming a resist pattern using a two-layer resist structure using two different types of positive resists -Island--ax-+L-
,,am1. +tA, 4-@-54-^m, da*qp
It1-Table 11-1, --11.

[Conventional technology]

A conventional two-layer pattern forming method of this kind is shown in FIGS. 3 and 4(a) and (b).

That is, FIG. 3 shows two different types of positive resists,
For example, positive resists 1 and 2 having different sensitivities are sequentially coated and formed on a semiconductor substrate 3 such as Si.
This is a sample with a layered resist structure.

Therefore, when the sample shown in FIG. If the sensitivity is lower than that of Fig. 4(a)
As seen in , the opening of the upper resist 1 is narrower than the opening of the lower resist 2, creating a so-called undercut shape, and conversely, the sensitivity of the upper resist 1 is lower than the sensitivity of the lower resist 2. If it is higher than that, the opening of the upper resist 1 becomes wider than the opening of the lower resist 2, as shown in FIG. 2B, resulting in a so-called overcut shape.

However, in any of these cases, the cross-sectional shape of the resist formed depends on the sensitivity of the resist.

It is uniquely determined by the amount of light or electron beam irradiation, development conditions, etc. In this case, the pattern width is determined by the width of the opening in the upper resist l in the case of FIG. The pattern size is determined by the width of this opening, and on the other hand, in the case of FIG. 4(b), the pattern size is determined by the width of the opening in the lower resist 2.
When an etching pattern is formed thereon, the width of the pattern is determined by the width of the opening in the lower resist 2.

[Problem that the invention seeks to solve]

However, in the conventional method, from the standpoint of pattern refinement, in the case of FIG. 4(a), the upper layer resist l
In the case of (b) in the same figure, the openings in the lower resist 2 must be made finer, and at this time, as in the conventional method described earlier, In the 1fRa method for a two-layer resist structure, each opening size is determined by the sensitivity of the two types of resists applied, and it is necessary to increase the difference in opening size between the upper and lower layers. The problem was that it was difficult.

The method of this invention was developed to improve the problems of the conventional method, and its purpose is to reduce the difference in opening size between the upper and lower layers in a two-layer resist structure by improving pattern fineness. It is an object of the present invention to provide a pattern forming method for obtaining a cross-sectional shape of a resist pattern which can be made large without hindering the resist pattern formation and has a strong contrast.

[Means for solving problems]

In order to achieve the above object, in the method of this invention, 2
It has a two-layer resist structure using different types of positive resists, and by exposing the two-layer resist to light or electron beams from the surface side and developing the parentheses, the cross section is overcut or overcut between each resist layer. When forming a pattern with an undercut shape, double exposure is performed: exposure with a predetermined dose corresponding to the predetermined pattern shape and exposure with a predetermined dose to the center of the pattern shape. .

[For production]

That is, in the method of the present invention, double exposure is performed: exposure to a two-layer resist with a predetermined dose corresponding to a predetermined pattern shape, and exposure to a predetermined dose to the center of the same pattern shape. As a result, it is possible to form a resist pattern having a cross-sectional shape with a strong contrast and an overcut or undercut shape between each resist layer.

〔Example〕

Hereinafter, one embodiment of the pattern forming method according to the present invention will be described in detail with reference to FIGS. 1(a) to 1(f).

First, in the method of this invention, a two-ball exposure method is used for a two-layer resist structure. Namely.

In the double exposure method according to this embodiment, the amount of irradiation to a predetermined pattern forming area is set to n times the amount required for pattern formation in the applied upper and lower resist layers, and the predetermined pattern size including the same area is set. The amount of irradiation to a region with a width 2 to 3 times larger than the amount required for pattern formation is set to 1 times the amount necessary for pattern formation. The value is determined to be the value required for formation.

In other words, in this case, when the dose of radiation required for pattern formation is N, the predetermined pattern formation area has nN+ &
nN= (S+k)nN, and from (1+1)nN=N, (1+t)n=1 is obtained, and &nN is the irradiation amount to the surrounding area including the same area, but the value of kn is divided into two types. When determined in consideration of the sensitivity of the resist, the values of length and n can be set simultaneously using the above equations. For example, the sensitivity of the upper layer resist is about I - In the case of about C/cj,
N = lXl0-4 (1+4)n = l, 1n
From N= txto-5, t= '/g= 0.11
, n = 0.9, tn = 0.1, and by giving the periphery of the pattern 0.1 times the irradiation dose as the center of the pattern, the upper and lower resist layers can be properly exposed to each other. It is possible to perform irradiation exposure.

Next, FIGS. 1(a), (b) and 2 show a specific embodiment of the present invention, and among these embodiments, FIGS. 3 and 4(a), (b) The same reference numerals as in the conventional example represent the same or equivalent parts, and in the case of this embodiment, it is assumed that the sensitivity of the upper resist 1 is higher than the sensitivity of the lower resist 2.

Therefore, in this embodiment, in FIG. 1(a).

The pattern has a line width that is two to three times the line width of the actual design pattern, and provides the optimal dose taking into consideration the sensitivity of the upper and lower layers, as shown in FIG. 2(b).

If a pattern with a line width corresponding to the actual design pattern is exposed twice at an appropriate dose, an appropriate dose will be applied to each of the upper and lower resist layers as a whole, and as a result, this will occur. - As seen in FIG. 2, a resist pattern with a T-shaped cross section is obtained.Moreover, in the case of the double exposure method according to this embodiment, the opening width of the upper resist l can be freely set, and the lower resist 2
This allows the opening width to be kept constant at all times.

Therefore, in this case 1, for example, using a resist pattern with a T-shaped cross section as shown in FIG. A T-shaped pattern can be easily obtained, and this cross-sectional T-shaped metal pattern is
- For example, when used as a submicron gate electrode in a GaAs device, increase in gate resistance can be suppressed and device characteristics can be improved.

Also, here is what happens when the method of this embodiment is applied.

More specific numbers are listed below.

That is, the sensitivity is I
0EBR-1030 with a sensitivity of about 10'c/c+J is used as the lower resist 2, and PM with a sensitivity of about 10'c/cd is used.
When forming the metal pattern having the T-shaped cross section using each MA, as described above, the width is 0.8 to 1. Q
The pattern of ILta is exposed with IX 1O-5C/c irradiation noise, and on the other hand, a pattern with a width of 0.1 to 0.2 mm is exposed at the center of this irradiation pattern.
By exposing with a dose of C/c♂, the 'PMMA of the lower resist 2 has lXl0-'C/c♂.
0EBR-1 on the upper resist l.
For the center of 030, lXl0 C/c7
Overexposure occurs when the irradiation amount is
A has a width of 0.1 to 0.2 JLI.

0EBR-1030 has a width of 0.8 to 1. A resist pattern of OILta can be formed, and an overcut shape with extremely strong contrast can be obtained.

Although this embodiment has been described on the assumption that the sensitivity of the upper resist pattern □ is higher than the sensitivity of the lower resist layer 2, it is of course applicable to the opposite case. For example, a two-layer resist l has a sensitivity of about 1x to-5c/cJ.

When the lower resist 2 has a sensitivity of about l x 10-4C/c♂, 0.9 x 10-'C is applied to the center of the pattern.
Irradiation amount of /cj, IX 1O-5 on the 6 sides of the pattern
By applying the C/C♂ dose to each □, an undercut pattern suitable for lift-off can be obtained, and in this case, the line width of the upper resist 1 is set independently of the line width of the lower resist 2. As a result, an undercut shape with extremely strong contrast can be obtained.

〔Effect of the invention〕

As detailed above, according to the method of this invention.

For a two-position resist structure made of two different types of positive resists, exposure with a predetermined dose corresponding to a predetermined pattern shape and exposure with a predetermined dose to the center of the same pattern shape are performed at an appropriate dose. Since double exposure is performed, there is a cross-sectional overcut shape between each resist layer.
Alternatively, an undercut-shaped resist pattern can be formed satisfactorily and effectively with a strong contrast, and the forming means itself is relatively simple and can be easily implemented.

[Brief explanation of drawings]

FIGS. 1(a) and (b) are cross-sectional views showing the irradiation exposure state of a two-layer resist structure to which an embodiment of the method of the present invention is applied, and FIG. 2 is a cross-sectional view showing the formation state of the same resist pattern. FIG. 3 is a cross-sectional view showing a state of irradiation and exposure to a two-layer resist structure by the conventional method same as above, and FIG. 4(a). (b) is a sectional view showing the formation state of the same resist pattern as above. 1.2... Two different types of positive resist, 3...
...Semiconductor substrate, 4...Light or electron beam. Agent Masuo Oiwa Figure 1 (a) Figure 1 (b) Figure 2 A (Q) ] (b) Moshi・

Claims (1)

[Claims] It has a two-layer resist structure using two different types of positive resists, and by exposing the two-layer resist to light or electron beams from the front side and developing it, the cross-section of the two-layer resist layer is overcut, Or, in a method of forming a pattern having an undercut shape, double exposure is performed: exposure with a predetermined dose corresponding to a predetermined pattern shape and exposure with a predetermined dose to the center of the pattern shape. A pattern forming method characterized by: