JPS5968744A - Manufacture of photomask - Google Patents

Abstract

PURPOSE:To obtains a highly accurate mask by etching only exposed glass substrate sections to a uniform depth after performing a desired windowing on the glass substrate by using a photo resist and forming a metallic layer on the whole surface of the substrate, and then, removing the resist layer and the metallic layer on the resist layer. CONSTITUTION:A desired windowing 3 is performed on a glass substrate 1 by using photo resist 2. Then etching is performed on the glass substrate 1 to a uniform depth by using a plasma 4 prepared by mixing Freon gas with a little amount of O2 gas. A metallic layer 5 of Cr, etc., is then formed on the whole surface of the substrate 1 by vacuum deposition, etc. Thereafter, the resist layer 2 and metallic layer 5 on the resist layer are removed by rubbing the substrate with raw cotton, etc., after the substrate 1 is soaked in a ketone solvent. Thus a mask which has metallic layers 5' (light blocking sections) which are not projected from the surface of the substrate, suppresses irregular reflection of ultraviolet rays, and can transfer a highly accurate fine pattern of integrated circuit, etc., onto a semiconductor substrate in accordance with the pattern dimension, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a photomask used mainly in the manufacturing process of semiconductors, integrated circuits, etc.

Conventionally, photomasks have been made by forming, for example, a gold coating layer on a glass substrate, and then selectively opening windows in a photoresist process or the like to form a desired pattern on the glass substrate. In such a method, the metal layer protrudes from the glass substrate, and for example, when transferring a minute pattern onto a semiconductor substrate, ultraviolet rays are irradiated while the photomask and the semi-conductor are closely viewed. At this time, the peripheral area of the protruding metal layer formed on the glass substrate is not parallel to the photoresist surface, and due to diffuse reflection of the ultraviolet rays, the ultraviolet rays go around other than the desired area, causing distortion of the pattern. In addition, if the metal layer of the protruding portion is thick, there is a drawback that cracks may occur in the photoresist.

In order to eliminate this drawback, holes were selectively formed in the photoresist in all desired areas of the glass substrate, and then the glass substrate was selectively etched to a desired depth to form a metal layer.

Therefore, according to this method, the metal layer is formed only on the etched region of the glass substrate, so that there are no protrusions and the patterned photomask becomes flat.

However, even with this method, distortion of the pattern and cracks in the photoresist could not be completely resolved. The reason for this is that the glass substrate was not etched uniformly.The purpose of the present invention is to solve the above-mentioned drawbacks, and to provide a method for forming a desired pattern with high precision. There is a particular thing.

An embodiment of the present invention will be described in detail below with reference to the drawings. 1 to 4 show cross-sectional views of one embodiment of the present invention.

First, as shown in FIG. 1, in this embodiment, a desired window opening 3 is made on the glass substrate 1 using a photoresist 82 to selectively expose the glass substrate.
P FL 5ooc (manufactured by Tokyo Ohka Kogyo ■) 30
A photoresist process was performed by spin coating C1) at 500 rpm. The glass substrate on which the desired pattern has been formed is heat treated (in this example, at 120° C. for 30 minutes).

Then, in this example, dry etching is performed using Freon gas as the main component.
Using a mixture of ~4% and etching for about 4 minutes at a power of 400W, the glass substrate can be etched at 200o±1.
It was possible to selectively and uniformly remove the particles with an accuracy of 00A (Fig. 2).

Thereafter, a metal layer 5 was formed on the glass substrate 1 and the photoresist 2 with an accuracy of 2000±100 A using vacuum evaporation in this embodiment (FIG. 3).

FIG. 4 shows a state in which only the 7-otoresist 2 on the glass substrate 1 is removed after the metal layer 5 has been formed. By doing so, only the desired area can be removed.

By the above method, the metal layer region (dark region) 5' can be formed without producing a protrusion on the glass substrate of the photomask. By employing this method, it is possible to suppress the diffused reflection of ultraviolet rays as much as possible, and it is possible to irradiate sufficient ultraviolet rays and transfer the remaining film onto the semiconductor substrate in the same size as the photomask pattern.

In this embodiment, a case has been described in which a positive type 7 photoresist 0FPEL8ooo is used for patterning a glass substrate, but the present invention is not limited to this, and other positive type photoresists or negative type photoresists can also be used. Furthermore, the metal layer 'C' is chromium, but is not limited to titanium or tungsten.

All metals and alloys thereof or multilayer formations may be used.

Furthermore, these metal layers may be formed not only by vacuum evaporation but also by sputtering. Note that it is also possible to use a substance that does not transmit ultraviolet rays, such as an emulsion, in addition to the metal layer.

[Brief explanation of drawings]

1 to 4 are cross-sectional views of each process for explaining an embodiment of the present invention. ■...Glass substrate, 2...Photoresist (OFP"5ooc) s 3...Opening (photoresist 5-degrees), 4... Plasma by dry etching, 5.5/... Metal layer (chromium). 6-

Claims (1)

[Claims] A step of selectively opening a window on the glass substrate through seven photoresist etching steps, a step of etching away the window opening selectively and to a uniform depth only in a region of the glass substrate, and then removing the window by, for example, a vacuum evaporation method, etc. A photoresist comprising the steps of forming a metal layer on a glass substrate including a selective aperture region and the photoresist region, and then selectively removing only the photoresist and the metal layer on the photoresist. How to make a mask.