JPS639655B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photographic etching technique that uses both electron beam exposure and ultraviolet ray exposure, and in particular, a technique that combines the microfabricability of electron beam exposure and the arbitrary shape of ultraviolet ray exposure. It is related to.

In recent years, by using electron beams as a sensitive source for resists instead of ultraviolet rays, finer processing has become possible in response to the difference in wavelength, and even submicron patterns have come to be formed.

The most common method of electron beam exposure involves controlling the irradiation position of the electron beam using a digital computer to selectively sensitize necessary areas. In this method, it is necessary to represent the exposed area with a certain mesh according to the memory capacity of the computer.
In order to reduce the amount of graphic data to be stored, it becomes necessary to represent the pattern using several basic figures using mesh points. In many cases, the basic figure is only a rectangle, and even if the device is said to be able to process figures with arbitrary angles, the reality is that it can only display fixed angles on a mesh, or there are discontinuous shapes between mesh points. The reality is that it becomes a pattern.

On the other hand, with a mask for ultraviolet exposure, circular arc-shaped patterns can be easily created at the original plastic film pattern stage, so it has the advantage of being more arbitrary than electron beam exposure. There are limits to the formation of fine patterns.

An object of the present invention is to put into practical use a unique photographic etching technique that has never existed before by combining electron beam exposure and ultraviolet exposure so as to take advantage of their respective advantages. Therefore, we decided to use a positive resist for ultraviolet exposure that is also sensitive to electron beams, and after first exposing a fine pattern to a wider area than the final area required by electron beam exposure, we created an optimal pattern for electron beam exposure and ultraviolet exposure. By developing the resist by the difference in time, a step is created in the resist so that the position of the fine pattern can be approximately confirmed, and the UV exposure mask is aligned with the resist pattern to irradiate the UV all at once, and further development is performed for the optimum development time for UV exposure. The resist outside the ultraviolet mask pattern is removed, including the part exposed to electron beam.
This is a completely new photo-etching technology that leaves a fine resist pattern formed by electron beam exposure inside the mask pattern.

Hereinafter, the present invention will be specifically explained based on an example of its implementation.

First, a positive ultraviolet exposure resist, such as AZ-2400, which is also sensitive to electron beams, is coated and dried on the workpiece, and then an electron beam with an acceleration voltage of 20 KeV, for example, is irradiated with approximately 3×10 ^-5 C/ ^cm2. After forming a latent image corresponding to the fine pattern, for example, using a 1% aqueous solution of caustic potassium as a developer, the difference between the normal optimum development time of 60 seconds for electron beam exposure and the normal optimum development time of 40 seconds for ultraviolet exposure is used. Develop for just 20 seconds. This process is unique to the present invention,
This allows the resist layer to have a certain degree of electron beam exposure.
A predetermined fine pattern is formed with steps corresponding to the irradiation area. Next, an ultraviolet exposure mask is aligned with the resist layer having this pattern, and ultraviolet exposure is repeated, and additional development is performed for 40 seconds, which is the normal optimum development time for ultraviolet exposure. Then, the part exposed to the electron beam that entered the inside of the UV exposure mask pattern is completely developed, and at the same time, the resist outside the pattern is removed, including the part exposed to the electron beam, and the fine pattern created by the electron beam exposure is cut out into the shape of the UV mask pattern. It is possible to form a unique resist pattern that looks like a double photograph.

Such a uniquely shaped pattern has never been seen before, and has been put into practical use for the first time by the present invention.

By using the technique of the present invention, the microprocessability of electron beam exposure and the arbitrary shape of optical exposure are used in combination, resulting in the advantage that fine patterns can be formed into complex shapes with a simple electron beam exposure program. Another advantage is that only one resist operation is required, and there are also advantages that the defect rate is low and processing can be performed with a high yield.

Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings.

A positive resist Az-2400 is applied to the material to be processed, for example, a silicon substrate 101 to a thickness of approximately 0.5 to 2 μm.
02 (Figure 1).

Next, an electron beam with an accelerating voltage of about 10 to 30 KV is selectively irradiated at a dose of about 1 to 5 × 10 ^-5 C/cm ² , for example, as in the pattern shown in Figure 6, to form a corresponding latent image. , the latent image is developed with about 1% KOH for about 5 to 20 seconds, and the latent image becomes visible as a step of about 0.05 to 0.3 μm, which is 103 (FIG. 2).

A 0.05 μm step difference is sufficient for pattern recognition using a microscope with a magnification of about 100 times that is attached to a normal alignment device, so the step difference that becomes apparent at this stage only needs to be set to that extent.

Next, a mask having a pattern such as that shown in FIG. 7 as an ultraviolet opaque layer 105 on the ultraviolet transparent substrate 104 is aligned as shown in FIG. 8 by dotted lines, and ultraviolet light 106 is irradiated all at once. (Figure 3).

It is convenient to draw the pattern shown in Figure 6, which is formed in advance by electron beam exposure, to be approximately twice the alignment accuracy and wider than the mask pattern, but this margin of approximately 10 μm is generally sufficient. be.

When the resist layer double-exposed to electron beams and ultraviolet rays is developed in a 1% KOH aqueous solution for about 40 to 60 seconds, the resist in the ultraviolet-exposed areas is completely removed, and at the same time, the electron-beam-exposed areas, which take longer to develop, are also removed. Because shallow development is performed in advance, development is completed almost simultaneously as shown in Fig. 9, which takes advantage of the microprocessability of electron beam exposure and the variable shape of optical exposure. A special shaped pattern as shown in FIG. 4 is formed. Thereafter, using the resist layer thus obtained as a mask, the silicon substrate 1
By etching 01 and removing the resist, a silicon substrate with the desired silicon pattern 108 embossed was obtained (FIG. 5).

In this example, the pattern shown in Fig. 6, which is formed by repeating the letter E with a width of 0.5 μm, is formed only in the area shown in Fig. 7, overlapping as shown in Fig. 8, as shown in Fig. 9. We were able to form unique shapes using an extremely simple electron beam exposure program. If you try to form this using only normal electron beam exposure technology,
This is simply impossible.

[Brief explanation of the drawing]

The five figures from FIG. 1 to FIG. 5 are conceptual diagrams sequentially shown to outline the steps of an embodiment of the present invention. Figures 6 and 7 are examples of patterns used in the process, Figure 8 shows the two patterns combined with masks, and Figure 9 shows the pattern unique to the present invention obtained in this way. It is a figure showing a pattern. 101: silicon substrate, 102: resist, 1
03: Shallowly developed resist pattern, 104:
UV exposure mask substrate, 105: Ultraviolet opaque portion, 106: Ultraviolet light, 107: Resist pattern after development, 108: Formed desired silicon pattern.

Claims (1)

[Claims] 1. A step of applying a positive resist that is sensitive to both electron beam exposure and ultraviolet light exposure to a substrate to be processed, a step of selectively sensitizing the positive resist with electron beam exposure, and a step of selectively sensitizing the positive resist that is sensitive to both electron beam exposure and ultraviolet light exposure. a step of shallowly developing the self-developed pattern to the extent that it becomes clear; a step of aligning and exposing the shallowly developed resist pattern with an ultraviolet exposure mask; and developing the resist that has been exposed to the electron beam and ultraviolet light. A photoetching technique characterized by performing the following steps: and a step of processing a substrate using the developed pattern as a mask.