JPH0247655A - Photomask - Google Patents

Abstract

PURPOSE:To decrease the number of photomasks used for a manufacture process and to facilitate mask control by forming two kinds of patterns of materials which differ in light absorption characteristics on one photomask. CONSTITUTION:The photomask 1 which has the two kinds of patterns is formed on a transparent glass substrate 2 and a 1st pattern 3 is made of a material which absorbs all wavelength components of ultraviolet light. A 2nd pattern 4, on the other hand, includes the 1st pattern 3 as part of its constitution area and its pattern area 5 which does not coincide with at least the 1st pattern is formed of a material which increases light transmissivity in the ultraviolet- light wavelength range with the wavelength. Therefore, when resist which has high sensitivity on the long-wavelength side is used, the 1st pattern 3 is obtained and when resist which has low sensitivity on the long-wavelength side is used, the 2nd pattern 4 consisting of the patterns 3 and 5 in combination is obtained. Consequently, the number of photomasks can be decreased, the quality is maintained, and the control is facilitated.

Description

[Detailed Description of the Invention] [Summary] Regarding the structure of a photomask used for manufacturing semiconductor ICs, LSIs, etc., two types of patterns made of materials with different light absorption characteristics are formed on one photomask, and the photomask is The purpose of this method is to reduce the number of photomasks used in the manufacturing process of ICs, LSIs, etc. by using masks for two types of pattern transfer processes, thereby facilitating mask management. Among them, the first pattern is formed of a material that absorbs all wavelength components of ultraviolet light, and the second pattern has the first pattern as a part of its constituent area and matches at least the first pattern. The pattern area is formed of a material whose light transmittance increases as the wavelength increases in the ultraviolet wavelength region.

[Industrial application field]

The present invention relates to the structure of a photomask used for manufacturing semiconductor ICs, LSis, etc.

In recent years, with the demand for higher quality and diversification of semiconductor ICs, LSIs, etc., the number of photomasks used has also increased in accordance with the increase in the number of types and the number of patterns per type.

[Conventional technology]

Semiconductor ICs, LSIs, etc. are manufactured by overlapping and forming many different types of patterns on a semiconductor substrate. Specifically, the above pattern formation involves overlapping a photomask having the necessary pattern on a semiconductor substrate coated with resist, either closely or with a small gap.
Thereafter, the method includes a step of irradiating ultraviolet light (including a far ultraviolet wavelength range) from the photomask side to transfer the pattern of the photomask onto the resist. A photomask usually has one type of pattern on each mask substrate, and this pattern is made of a material that absorbs ultraviolet light in the sensitive wavelength range of the resist used.

Therefore, when the photomask is irradiated with ultraviolet light, the resist coated on the semiconductor substrate is not exposed to light in areas corresponding to the pattern of the photomask, but is exposed to light in other areas, thereby changing its chemical properties. As a result, the pattern of the photomask is transferred onto the resist by the subsequent development process.

[Problem to be solved by the invention]

As mentioned above, conventional photomasks have patterns formed from materials that absorb all wavelength components of ultraviolet light, so when UV light is irradiated, all the patterns on the photomask are transferred onto the resist. . Therefore, one photomask could only be used for transferring one type of pattern.

The present invention forms two types of patterns made of materials with different light absorption characteristics on one photomask, and uses the photomask in two types of pattern transfer processes to create an IC,
The purpose is to reduce the number of photomasks used in the manufacturing process of LSIs, etc., and thereby facilitate mask management.

[Means to solve the problem]

FIG. 1 shows a plan view of a photomask l according to the present invention. The above problem is a photomask having two types of patterns on a transparent glass substrate 2. The first pattern 3 is made of a material that absorbs all wavelength components of ultraviolet light, and the second pattern 4 is made of a material that absorbs all wavelength components of ultraviolet light. The pattern region 5 that has the first pattern 3 as a part of its constituent region and that does not match at least the first pattern 3 is formed of a material whose light transmittance increases as the wavelength increases in the ultraviolet wavelength region. This problem is solved by a photomask characterized by the following.

[For production]

FIG. 2 is a schematic sectional view for explaining the function of the photomask according to the present invention, and the numbers in the figure correspond to the numbers shown in FIG. 1. 7 is a semiconductor substrate; 6 is a resist coated thereon; as shown in the figure, it is in close contact with the photomask 1 or overlapped with it with a minute gap, and is used to expose the photomask 1; Pattern 3 or pattern 4 is transferred thereon.

Which pattern to transfer, pattern 3 or pattern 4, is determined by selecting the resist as follows. That is, after the ultraviolet light irradiated onto the photomask 1 passes through the pattern 5, the light intensity of the long wavelength component is relatively stronger than that of the short wavelength component. Therefore, the area corresponding to pattern 5 is exposed when a resist with high sensitivity on the long wavelength side is used, but is not substantially exposed when a resist with low sensitivity on the long wavelength side is used. On the other hand, the area corresponding to pattern 3 is not exposed to light no matter which resist is used. Therefore, in the subsequent development process, if a resist with high sensitivity on the long wavelength side is used, the first pattern 3 will be obtained, and if a resist with low sensitivity on the long wavelength side is used, pattern 3 and pattern 5 will be obtained. A combined second pattern 4 is obtained.

Pattern 3 or pattern 4 can be selected by changing the type of resist as described above, but it can also be done by changing the type of exposure light source.

That is, when using ultraviolet light having a maximum light intensity in the long wavelength region, pattern 5 only blocks the short wavelength component with low light intensity and transmits the long wavelength component with high light intensity, so that the ultraviolet light is substantially Most of the light is transmitted. Furthermore, when using ultraviolet light that has a maximum light intensity in the short wavelength range, the short wavelength component with high light intensity is blocked, and only the long wavelength component with low light intensity is transmitted. Parts will be occluded. On the other hand, in pattern 3, any ultraviolet light is blocked. Therefore, when ultraviolet light having maximum light intensity in a long wavelength region is used, only the area corresponding to pattern 3 is not exposed, and the first pattern 3 is obtained by subsequent development processing. Furthermore, when ultraviolet light having a maximum light intensity in a short wavelength region is used, the combined area of patterns 3 and 5 is not exposed, and a second pattern 4 is obtained by subsequent development processing.

As is clear from the above explanation, when transferring the second pattern using any of the above methods,
Inevitably, the first pattern will also be transferred at the same time. Therefore, it is necessary that the second pattern has the first pattern as part of its constituent area.

〔Example〕

Examples of the present invention will be described below.

First, a pattern corresponding to one conventional photomask is used as a unit layer pattern, and all design patterns such as [C, LSI, etc.] are decomposed into layer patterns. Any two layer patterns among these layer patterns are sequentially compared, and a set of layer patterns in which one layer pattern has the other layer pattern as part of its constituent area is selected. Of the two selected layer patterns, the smaller layer pattern is used as the first pattern, and the larger layer pattern is used as the second pattern.These patterns are formed on one glass substrate, and used as a photomask. use

An embodiment of the photomask and its usage method according to the present invention will be explained with reference to FIG.

A first pattern 3 made of a chromium (Cr) film is formed on a glass substrate 2 by a normal photoetching method,
Next, the pattern 4 including the pattern 3 is selectively irradiated with ultraviolet light in a vacuum to alter the surface of the glass substrate, thereby forming a second pattern 4. The above ultraviolet light is, for example, an excimer laser with a wavelength of 248 nm.
500 pulses are irradiated under a pressure of ITorr. Note that, at this time, the pattern 3 on the glass substrate 2 is not altered in quality because it is covered with a Cr film, and therefore only the area 5 excluding the pattern 3 from the pattern 4 is altered in quality. FIG. 4 shows data regarding the ultraviolet light wavelength dependence of the light transmittance of patterns 3 and 5 on the photomask 1 prepared as described above. The same figure also shows the light transmittance of the glass part. Note that the data regarding region 5 in the same figure naturally changes when the conditions of the reactive ion etching are changed, and the conditions can be set to the optimum conditions according to the properties of the resist and the ultraviolet light source, which will be described later. can.

Prepare the photomask 1 as described above, and proceed as follows (
al, (b1) The photomask was used in two ways.

(It is known that when an ultra-high-pressure mercury lamp is used as the exposure light source for the photomask 1 shown in Fig. 2, the light intensity of the irradiated ultraviolet light is approximately equal over the entire ultraviolet light wavelength range shown in Fig. 4. Therefore, resists with high sensitivity in the long wavelength range of ultraviolet light, such as ultraviolet light with a wavelength of 436 nm (
Registration l-0 with maximum sensitivity to g-line (hereinafter referred to as g-line)
When FPR-800 (Tokyo Ohka) is used, as is clear from FIG. 4, the g-line is blocked by pattern 3 and passes through the A region other than that. Therefore, the first pattern 3 is transferred by performing normal development processing thereafter.

In addition, resists with maximum sensitivity in the short wavelength region of ultraviolet light,
For example, when using AZ-5200 (manufactured by Hoechst) (a resist having maximum sensitivity to ultraviolet light with a wavelength of 365 nm (hereinafter referred to as i-line)), the area corresponding to region 5 on the resist 6 has an i-line intensity. Since it is lowered, it is not exposed to light, and of course, the area corresponding to pattern 3 is not exposed to light either. Therefore, by performing normal development processing thereafter, a second pattern 4 consisting of areas corresponding to patterns 3 and 5 is transferred.

('b) When the photomask is irradiated with g-rays (for example, Nikon N5R-1505G can be used as a light source), the g-rays are blocked only by pattern 3. Therefore, the first pattern 3 is obtained by subsequent development processing.

Further, when the photomask is irradiated with i-rays (for example, Nikon N5R-1010i3 can be used as a light source), the i-rays are blocked by patterns 3 and 5.

Therefore, pattern 3 and pattern 5 are created by the subsequent development process.
A second pattern 4 consisting of regions corresponding to is obtained.

In the above method (bl), for example, 0FPR-800 (Tokyo Ohka) can be commonly used as the resist 6.

In addition to the above-mentioned photo master having the configuration shown in Fig. 2, as shown in the first figure (^),
A second pattern 4 is formed in advance on a glass substrate 2, and a first pattern 3 made of a Cr film is formed on this.
can also be formed by a normal photoetching method.

Furthermore, when decomposing the design pattern of IC, LSI, etc. into layer patterns, if pattern 3 and pattern 4 partially match as shown in the first diagram (B), the pattern as shown in the first diagram (C) There may be cases where pattern 3 and pattern 4 are separated, and the present invention can be applied to such cases as well.

Furthermore, as a method for forming the second pattern, in addition to the method shown in this embodiment, reactive ion etching, ion implantation, plasma etching, etc. can also be applied.

〔Effect of the invention〕

As described above, according to the present invention, a photomask having two types of patterns made of materials with different light absorption characteristics is prepared, and by selecting a light source or resist according to the material forming the pattern, one photomask can be printed. It is now possible to provide the functions of two photomasks, and the number of photomasks can be reduced by 20 to 30% on average compared to the conventional method.

Therefore, the present invention is effective in preventing the complication of quality maintenance and management such as mask cleaning that occurs with an increase in the number of photomasks used, and in preventing accidents such as mistakes in the use of photomasks.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a photomask according to the present invention, FIG. 2 is a schematic cross-sectional view showing one embodiment of the present invention, and FIG. 3 is a schematic cross-sectional view showing another example of the photomask according to the present invention. FIG. 4 is a diagram showing the light transmission characteristics of the material forming the photomask. In the figure, ■ is a photomask, 2 is a glass substrate, 3 is a first pattern, 4 is a second pattern, 5 is a region forming a part of the second pattern, 6 is a resist, 7 is a semiconductor substrate, and be.

Claims (1)

[Claims] A photomask having two types of patterns on a transparent mask substrate (2), the first pattern (3) being formed of a material that absorbs all wavelength components of ultraviolet light; The second pattern (4) has the first pattern (3) as a part of its constituent area, and at least the pattern area (5) that does not match the first pattern (3) has a wavelength in the ultraviolet wavelength range. A photomask characterized in that it is formed of a material whose light transmittance increases as the light transmittance increases.