JP2536558B2 - Method of manufacturing mask for X-ray exposure - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask manufacturing method, and particularly for X-ray exposure used when manufacturing a T-type control electrode in a field effect semiconductor device having a T-type control electrode. The present invention relates to a mask manufacturing method.

[Conventional technology]

(1) It is necessary for a semiconductor device that operates at an ultrahigh speed to employ an element structure that minimizes the electron migration distance inside the semiconductor. As a typical example thereof, there is a field effect semiconductor device using a T-type control electrode, and FIG. 1 is a diagram showing a cross section of the example.

In the figure, an n-type substrate 2 is diffused and formed on a substrate 1, and an ohmic junction source electrode 3, a T-type Schottky control electrode 5 and an ohmic junction drain electrode 4 are formed thereon. Although the operation is similar to that of the conventional field effect semiconductor device, the T-type control electrode has a T-shaped cross-sectional shape, so that the cross-sectional area does not decrease as compared with the conventional short-shaped one, and n The contact width with the mold substrate 2 can be reduced. That is, the gate length can be shortened without increasing the resistance value. Therefore, the operation can be performed at a higher speed, and the internal noise is reduced due to the effect of improving the gain. In recent years, methods for forming such T-type control electrodes have been studied in various places, and one example thereof will be described here. (See Figure 2). For example, a 1 μm thick RE-5000P X-ray sensitive positive resist 7 is formed on a substrate 8 made of gallium arsenide (GaAs),
The X-ray 11 is passed through the X-ray exposure mask for forming the T-type control electrode formed by the X-ray absorber 10 and the X-ray transmission substrate 9 having the shape shown in FIG. To irradiate. At this time, since the X-ray transmission amount differs depending on the film thickness of the absorber 10 of the X-ray exposure mask, the X-ray irradiation amount passing through the A ₁ portion, the A ₂ portion and the A ₃ portion in FIG. 2A. However, the positive resist 7 having a T-shaped opening cross section as shown in FIG. 2 (b) is formed by developing with a developing solution of NMD-3 for an appropriate time. Further, a T-type control electrode film 6 such as Au is formed on the positive resist 7 by a vacuum deposition method (see FIG. 2 (c)), and the film is immersed in a solution of the positive resist 7 to form a positive film. By removing the control electrode film 6 on the resist 7 and the positive resist 7, the T-type control electrode 5 is completed. (Refer to FIG. 2) This T-type control electrode forming method is characterized in that a T-type control electrode forming X-ray exposure mask (FIG. 2A) is used to form a single layer of resist on a semiconductor substrate once. Since the T-type control electrode can be formed by patterning using direct drawing exposure, there is an effect that the forming process is simplified and the processing capacity is further improved.

(2) Next, FIG. 3 is a sectional view showing an embodiment of a conventional method of manufacturing an X-ray exposure mask for forming a T-type control electrode according to the present invention.

In the figure, for example, an X-ray absorber 10 such as an Au film that functions as an Au-plated electrode is provided on an X-ray transparent film substrate 9 such as SiN.
a is formed to a thickness of about 500 Å, and the lower layer is a polyimide 12a with a thickness of 0.5 μm, and the intermediate layer is a molybdenum 13 with a thickness of 0.1 μm, and the electron beam resist with an upper layer of 0.3 μm.
A three-layer resist No. 4 is formed (see FIG. 3 (a)).

Next, using the electron beam exposure technique, the electron beam resist 14 is exposed to a desired width corresponding to the lower width of the T-type control electrode to obtain a desired pattern of the electron beam resist 14 (FIG. 3 (b)).
reference).

After the molybdenum 13 and the polyimide 12a are removed by reactive ion etching (RIE) using the pattern of the electron beam resist 14 as a mask, the remaining electron beam resist 14 is removed (see FIG. 3 (c)).

After removing the remaining molybdenum 13, an X-ray absorber 10b such as Au is electroplated as a mold for polyimide 12b plating to form an X-ray absorber 10b having a thickness of about 0.2 μm (see FIG. )reference).

Next, as in FIG. 3A, a three-layer resist consisting of a polyimide 12b having a thickness of 1.0 μm, molybdenum 15 having a thickness of 0.3 μm, and an electron beam resist 16 having a thickness of 0.3 μm is attached to the X-ray absorber 10b.
And formed on the polyimide 12b (see FIG. 3 (e)).

Here again, the electron beam resist 16 is exposed to a desired width corresponding to the upper width of the T-type control electrode by using the electron beam exposure technique as in FIG. 3B, and the pattern of the desired electron beam resist 16 is exposed. Is obtained (see FIG. 3 (f)).

Similar to FIG. 3 (c), after removing the molybdenum 15 and the polyimide 12b by reactive ion etching (RIE) using the pattern of the electron beam resist 16 as a mask, the remaining electron beam resist 16 is removed (FIG. 3). (G)
reference).

After removing the remaining molybdenum 15, the X-ray absorber 10c such as Au is electroplated using the polyimide 12b as a plating mold to obtain an X-ray absorber 10c having a thickness of about 0.8 μm (see FIG. 3 (h )reference).

Finally, the polyimide 12 and the exposed X-ray absorber 10a serving as the plating electrode are removed to complete an X-ray exposure mask for forming a T-type control electrode having a desired cross-sectional shape (FIG. 3 (i)). reference).

[Problems to be solved by the invention]

In the conventional method of manufacturing the X-ray exposure mask for forming the T-type control electrode as described above, the direct writing exposure is required twice to obtain the T-shape, which complicates the forming process. Further, there is a problem that the accuracy of the alignment during the second direct writing exposure affects the accuracy of the T-shaped pattern.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a method for manufacturing an X-ray exposure mask capable of forming a T-shaped pattern by a single direct drawing exposure. .

[Means for solving problems]

A method of manufacturing an X-ray exposure mask for forming a T-type control electrode according to the present invention is direct drawing exposure for a two-layer resist (electron beam resist / UV resist) on a plating base formed on an X-ray transparent film substrate. Electron beam exposure and development are performed once, and the entire surface is exposed to UV light for an appropriate time, and this is developed to form a T-shaped resist pattern. Electroplating process,
An X-ray absorber having a desired cross-sectional shape is obtained by performing an etching process.

[Action]

In the method of manufacturing an X-ray exposure mask for forming a T-type control electrode of the present invention, when performing UV light exposure using an electron beam resist having a width corresponding to the width corresponding to the upper width of the T-type control electrode as a mask, Light wraps around the electron beam resist pattern, and by appropriately selecting the exposure time, the UV sensitive resist is exposed while leaving the T-shaped pattern. Next, a development and an electrolytic plating process and an etching process are performed to obtain a desired X-ray exposure mask for forming a T-type control electrode.

Example of Invention

FIG. 4 is a process sectional view of a method for manufacturing an X-ray exposure mask for forming a T-type control electrode according to the present invention.

In the figure, an X-ray absorber, for example, a plating base of about Au500Å is formed on an X-ray transparent film substrate, and a UV sensitive resist 17 is formed thereon with a film thickness of about 5000Å. Absorbing electron beam resist 16
Is formed with a film thickness of about 5000Å. Next, using the electron beam exposure technique, the electron beam resist 16 is exposed by the width of the opening cross section corresponding to the upper width of the desired T-type control electrode to obtain the desired pattern of the electron beam resist 16 (see FIG. 4). (See (a)).

Using the pattern of the electron beam resist 16 as a mask, the UV sensitive resist 17 is exposed with UV light 19 so that it is exposed while leaving a T-shape.
Then, the exposure is performed for an appropriate time in consideration of the wraparound of light due to the diffraction phenomenon (see FIG. 4 (b)).

The UV sensitive resist 17 is developed to obtain a T-type resist composed of the electron beam resist 16 and the UV sensitive resist 17 (see FIG. 4 (c)).

Next, an X-ray absorber is electrolytically plated on the X-ray transparent film substrate 9 to a thickness such that the upper surface of the UV sensitive resist is not exposed (see FIG. 4 (d)).

The electron beam resist 16 and the UV sensitive resist 17 are etched, and then the entire surface is subjected to plasma etching to remove the plating base 19 corresponding to the lower width of the T-type control electrode to obtain a desired X-ray absorber shape (fourth). (See FIG. (E)).

Although the thickness of the electron beam resist or the UV sensitive resist is limited in the above embodiment, the X-ray transmission amount when the T-type control electrode is formed, the output of the X-ray source, the shape of the T-type control electrode, the electron beam The film thickness may be changed depending on the types of the resist and the UV sensitive resist. Further, instead of Au which is an X-ray absorber, any metal that has a large X-ray absorption coefficient and can be plated can be used.

Further, instead of the electron beam resist, an ion focused beam (FIB) resist having a good UV light absorption property may be used to perform the FIB exposure, or the exposure is limited to the UV light. If a V-shaped resist pattern is obtained, light having another wavelength may be used to expose the resist to which the light is exposed.

Although a thin film of silicon nitride (SiN) is used for the X-ray transparent film substrate, another substance may be used as long as it has a good X-ray transparency.

Further, although the T-shape is limited to the opening cross section of the control electrode, the lower width may be shorter than the upper width even if it is not T-shaped as long as a desired effect can be obtained.

〔The invention's effect〕

As described above, the method for manufacturing the X-ray exposure mask for forming the T-type control electrode of the present invention is, in the UV exposure, an exposure due to the wraparound of light caused by the diffraction phenomenon under the electron beam resist which is the UV absorber. By using, it is possible to form an X-ray absorber having a desired cross-sectional shape with a single direct drawing exposure without the need for alignment, so that it is possible to reduce the number of manufacturing steps and improve the accuracy of the T-shaped pattern. is there.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a field effect semiconductor device having a T-type control electrode, and FIG. 2 is an X for forming a T-type control electrode.
4 is a process sectional view showing an embodiment of a method for forming a T-type control electrode using a line exposure mask, FIG. 3 is a process sectional view showing an embodiment of another invention of the present invention, and FIG. 4A to 4C are process cross-sectional views showing an embodiment of the present invention. In the figure, 1 is a semiconductor substrate, 2 is an n-type substrate, 3 is a P-type source electrode, 4 is a P-type drain electrode, 5 is a T-type control electrode,
6 is a control electrode film, 7 is an X-ray sensitive positive resist, 8 is a substrate, 9 is an X-ray transparent film substrate, 10 is an X-ray absorber, 11 is an X-ray,
12 is a polyimide, 13 and 15 is molybdenum, 14 and 16 are electron beam resists, 17 is a UV sensitive resist (before exposure), 18 is a UV sensitive resist (after exposure), 19 is a plating base, and 20 is UV light. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (10)

(57) [Claims] 1. A first step of forming an entire surface of a plating base that is an X-ray absorber on a substrate that transmits X-rays, and a second step of forming a whole surface of a photoresist on the plating base, A third step of forming a light absorber having an opening cross section of a desired width on the photoresist, and a fourth step of forming a desired resist shape of the photoresist by using an exposure technique with the light absorber as a mask. A fifth step of forming an X-ray absorber on the plating base to a height such that the upper surface of the photoresist is not exposed, and a sixth step of removing the photoresist and the light absorber And a seventh step of removing a plating base corresponding to the lower width of the control electrode in the field effect semiconductor device, the method for manufacturing an X-ray exposure mask. 2. The third step is a step of forming a light absorber on the photoresist, and exposing and developing the light absorber by a direct writing exposure technique to form an upper width of the control electrode. The method for manufacturing an X-ray exposure mask according to claim 1, further comprising the step of forming a corresponding pattern of the light absorber. 3. The fourth step is suitable for using the light absorber as a mask so that the lower width of the unexposed portion of the photoresist after exposure is shorter than the upper width thereof and has a desired width. The method for producing an X-ray exposure mask according to claim 1, further comprising: a step of exposing the photoresist for a certain period of time; and a step of developing the photoresist with a developer thereof. 4. The method for manufacturing an X-ray exposure mask according to claim 1, wherein the substrate is silicon nitride (SiN). 5. The method of manufacturing an X-ray exposure mask according to claim 1 or 4, wherein the substrate is boron nitride (BN). 6. The method for manufacturing an X-ray exposure mask according to claim 1, 2, or 3, wherein said light absorber is an electron beam resist having a good absorption property for light to be used. . 7. The light absorber according to claim 1, wherein the light absorber is an ion beam resist having good absorptivity for light used.
Item 7. A method for manufacturing an X-ray exposure mask according to items 2, 3, and 6. 8. The method of manufacturing an X-ray exposure mask according to claim 1, wherein the X-ray absorber is gold (Au). 9. The method of manufacturing an X-ray exposure mask according to claim 1 or 8, wherein the X-ray absorber is platinum (Pt). 10. The method of manufacturing an X-ray exposure mask according to claim 1, wherein the X-ray absorber is formed by electrolytic plating.