JPS6116517A - Manufacture of photomask - Google Patents

Abstract

PURPOSE:To enable to display the effect of an electron beam exposure when a mask pattern is microscopically formed by a method wherein a mask layer is formed using a material of good heat conductivity. CONSTITUTION:A resist film 3 is formed on the blank mask whereon a mask layer 2a is provided on a glass substrate 1, and after an electron beam is exposed on an irradiation region 4, the removal region 5 corresponding to the irradiation region 4 on the resist layer 3 is removed by developing. Subsequently, a mask pattern is formed by removing the removal region 6 of the mask layer 2a by performing an etching using the resist layer 3 as a mask. The mask 2a consists of the Al of approximately 0.01mum in thickness and the Cu of approximately 0.1mum in thickness, for example, and the Al is faced to the substrate 1 to increase the adhesiveness with the substrate 1. When an electrode beam is made to irradiate, the temperature rise on the circumference of the irradiation region 4 is lowered than before, and the patterns of the removal regions 5 and 6 are coincided with each other. The mask 2a may be formed with the alloy of Al and AlCu, and the desirable thickness of the mask 2a is 0.1-0.4mum.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a photomask, and in particular, in response to the miniaturization of mask patterns of photomasks used for manufacturing semiconductor devices, etc. The aim is to improve the manufacturing method of photomasks that perform exposure.

Photolithography technology is one of the microfabrication methods used in the manufacture of various devices including semiconductor devices used in a wide range of fields. We request that the mask patterns of photomasks used in

Photomasks are generally manufactured by the process sequence shown in side cross-sectional views in FIGS. 3(a) to 3(f).

That is, a resist is applied to a blank mask (as shown in FIG. 1a) on which a mask layer 2 for forming a mask pattern is provided on a glass substrate 1 to form a resist layer 3 (as shown in FIG. 1b), and the irradiation area is 4 is exposed to light or an electron beam (as shown by the arrow C1 in the figure), the removed region 5 corresponding to the irradiated region 4 in the resist layer 3 is removed by development (as shown in FIG. 4(d)).

Subsequently, the removed region 6 of the mask layer 2 is removed by etching using the resist layer 3 as a mask (as shown in (e) in the same figure) to form a mask pattern, and the resist layer 3 is further removed (as shown in (f1) in the same figure). Manufacture is completed.

The above explanation is for the case where the resist is a positive type, but in the case of a negative type, the removed area and the remaining area of the resist layer 3 are simply reversed, so the following description will be made for the case of a positive type resist.

In the mask pattern miniaturization, the irradiation area 4 is made smaller, so an electron beam is used for irradiation in the exposure, but at this time, the irradiation area 4 pattern and the removal area 6 pattern forming the mask pattern are separated. It is important to match.

In addition, when mass producing the above-mentioned device, a reticle may be manufactured during the photomask manufacturing process, but the reticle is
The present invention also includes the case of a reticle, since it is manufactured by a method similar to that of a photomask.

[Conventional technology and its problems]

When a mask pattern of a photomask is formed by electron beam exposure, a typical conventional method is to make the mask layer 2 shown in FIG. 3 from chromium (Cr) and to have a thickness of about 0.1 μm. .

FIG. 4 is a side sectional view f showing the relationship between the irradiation area pattern and the mask layer removal area pattern in an example of this case.
al top view).

The resist layer 3 is made of PMMA (a typical positive resist for electron beams) with a thickness of approximately 1 μm, the irradiation area 4 is approximately 3 μm square, and the irradiation conditions are set to a current density of 2.0 μm.
0A/, ffl, irradiation dose 3.5 x 10-5 C/c
J, when the irradiation time is 17.5 μs, the 5 patterns of removed areas of the resist layer 3 and the 5 patterns of removed areas of the mask layer 2 accompanying this are larger than the 4 patterns of irradiated areas, and the difference between them is the excessive area 7. The width is about 0.1 μm.

The above-mentioned width of the excessive area 7 is larger than the accuracy with which the exposure area IIJ can be controlled in electron beam exposure, and inhibits the effectiveness of electron beam exposure in miniaturizing mask patterns. This is a problem.

[Means for solving problems]

The problem is that the mask layer, which is provided on a glass substrate and is patterned by electron beam exposure to form a mask pattern, is made of aluminum (Al), 1iJ (Cu).
This problem is solved by the method of manufacturing a photomask of the present invention, which is formed of one or more materials from the group consisting of aluminum-copper alloys (AICu-containing Cu).

According to the present invention, the thickness of the mask layer is 0.1 to 0.
It is desirable that the thickness be 4 μm.

[Effect]

The excessive area occurs because the temperature around the electron beam irradiation area in the resist layer increases due to heat generation and heat conduction of the irradiation area due to the energy of the electron beam.
This is thought to be due to a chemical reaction that occurs during development, where the irradiated area is removed together with the irradiated area.

In the present invention, among the substrate, mask layer, and resist layer, the material of the mask layer that has good thermal conductivity is
-λ/Cρ, λ: thermal conductivity, c2 specific heat, ρ: change the mode of heat conduction by using the material with a large density, that is, speed up the dissipation of heat in the irradiation area, thereby increasing the temperature of the surrounding area. This reduces the rise in temperature compared to the conventional method, suppresses the occurrence of the chemical reaction in the surrounding area, and makes the width of the problematic excessive region smaller than the conventional method.

The above change in the mask layer material reduces the hardness of the mask layer, but if the proximity contact method or projecticon method, which has been widely used in recent years, is used for exposure using the photomask, the photomask can be used to It does not come into contact with the wafer, so there is no problem in using it.

Regarding the thickness of the mask layer, from the point of view of heat conduction mentioned above,
．． The thickness is preferably 1 .mu.m or more, and is preferably 0.4 .mu.m or less in order to limit the size of side etching when the mask layer is etched by a conventional method.

Thus, the method of the present invention makes it possible to manufacture a photomask that can exhibit the effect of employing electron beam exposure in miniaturizing a mask pattern.

〔Example〕

FIG. 1 is a side sectional view (al plan view (BL) showing the relationship between the irradiation area pattern and the removal area pattern of the mask layer in one embodiment of the photomask manufacturing method of the present invention; FIG. A side sectional view (al (bl)) showing an example of calculated temperature distribution during exposure due to differences in .

Figure 1 (a) (bl), Figure 4 (al (b), respectively)
The difference between the method shown in FIG. 1 and the conventional method shown in FIG. Approximately 0.1
The point is that the mask layer 2a is replaced with a two-layer structure with Cu of μm.

The mask layer 2a is deposited by a conventional method such as vapor deposition, and Al is placed on the substrate 1 side to improve adhesion to the substrate 1.

Etching of the mask layer 2a is performed by a normal method in view of the thickness of the mask layer 2a, so that the size of side etching does not become a problem, and the pattern of the 6 removed regions matches the pattern of the 5 removed regions.

By doing this, the temperature rise around the irradiation area 4 in the resist layer 3 when irradiated with the electron beam becomes lower than before, and the removal area 5.6 becomes smaller than before, and in the case shown in FIG. The width of the overextended region 7, which was 1 μm, could be brought close to 0 under the same irradiation conditions.

By the way, in the cases shown in Figures 1 and 4, the temperature distribution trial values of the cross section shown in Figure 2 (a) are shown in both figures immediately after irradiation (a1).
, 0)), the above results can also be understood from this figure. Note that the zero point on the horizontal axis in the figure is the center point of the irradiation area 4, and the zero point on the vertical axis is the surface of the resist layer 3.

The mask layer 2a in the above embodiment has a thermal propagation coefficient α of Cr.
The main layer is made of Cu, which is about 4 times the thickness of Cu, to a thickness of about 0.1 μm, but it may also be formed of Al or AlCu alloy, which is also about 3 times the thickness, and the thicker the layer, the more the oversized region 7 It can be easily inferred that the width of is reduced.

〔Effect of the invention〕

As explained above, according to the structure of the present invention, it is possible to provide a photomask manufacturing method in which the formed mask pattern approaches the irradiation f112 pattern of electron beam exposure, and the effect of adopting electron beam exposure in miniaturizing the mask pattern. This has the effect of making it possible to manufacture a photomask that can exhibit the following properties.

[Brief explanation of drawings]

In the drawings, FIG. 1 is a side cross-sectional view + al plan view (BL) showing the relationship between the irradiation area pattern and the mask layer removal area pattern in one embodiment of the photomask manufacturing method of the present invention, and FIG. Figure 3 is a side cross-sectional view (a) showing an example of the temperature distribution during exposure due to differences in materials, and Figure 3 is a side cross-sectional view (a
1-(f), FIG. 4 is a side cross-sectional view (fa) and a plan view (b) showing the relationship between the irradiation area pattern and the mask layer removal area pattern in an example according to a typical conventional method of manufacturing a photomask. In the figure, 1 is a substrate, 2.2a is a mask layer, 3 is a resist layer, 4 is an irradiation area, 5.6 is a removal area,
7 indicates an excessive area, respectively.

Claims (2)

[Claims] (1) A mask layer provided on a glass substrate and patterned by electron beam exposure to form a mask pattern is formed of one or more materials among aluminum, copper, and aluminum-copper alloy. A method for manufacturing a photomask. (2) The method for manufacturing a photomask according to claim 1, wherein the thickness of the mask layer is set to 0.1 to 0.4 μm.