JPS636862B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a photomask with high precision by direct scanning exposure using an electron beam.

In recent years, as ICs, LSIs, etc. have become more highly integrated and miniaturized, mask manufacturing using electron beam exposure is becoming an indispensable technology that allows high-quality photomasks used for these to be manufactured accurately, quickly, and at low cost. .

Generally, in order to manufacture a photomask for manufacturing integrated circuits etc. by electron beam exposure, a thin metal film such as Cr is formed in advance on the substrate holder of the XY movement stage of the electron beam exposure device, and then the upper surface of the photomask is formed. A mask substrate on which a resist film is to be applied is fixedly arranged, and an electron beam is scanned perpendicular to the direction of stage movement while continuously moving the moving stage whose movement position is constantly measured and controlled by a laser length measuring machine. A method is adopted in which a desired photomask is manufactured by drawing and exposing a predetermined microcircuit pattern on a mask substrate while deflecting an electron beam based on pattern design data designed in advance.

In this way, by electron beam exposure, prior to forming a large number of fine circuits or fine chip patterns adjacently and accurately in a matrix on a mask substrate, the electron beam is focused on the exposure surface and exposed. It is important to position the position accurately, and for this purpose, for example, a focusing mark for focusing the electron beam may be formed by depositing a different metal at a predetermined position on the substrate holder to allow scanning of the electron beam; The chip pattern is formed by mechanically making notches, and before each of the chip patterns is exposed to an electron beam, the electron beam is irradiated and scanned over the mark, and secondary electrons emitted from that part are scanned. I was trying to focus on or check the signal. In addition, regarding the positioning of electron beam exposure, orthogonality, etc. when each chip pattern is sequentially drawn and exposed on a mask substrate, the pattern drawing signal based on pattern design data is It was decided based on the positional accuracy of the moving stage.

However, the focusing mark disposed on the substrate holder must be placed at the same level as the focal position of the mask substrate set in the substrate holder, which has the disadvantage that adjustment of these levels is complicated. There is also a problem in that the surface of the mask substrate expands and contracts when the temperature of the mask substrate changes due to external temperature or electron beam irradiation, resulting in dimensional errors, positional deviations, etc. in the drawn exposure pattern.

Therefore, electron beam focusing marks can be easily provided, and changes in mask substrate temperature can be easily established.
There has been a need for a method of manufacturing a photomask with good pattern drawing accuracy that allows for easy correction of the electron beam exposure position and expansion/contraction dimension.

In view of the above-mentioned conventional circumstances, the present invention aims to solve these problems and provide a new manufacturing method capable of obtaining a photomask with high pattern drawing accuracy. In this method, a photomask with a predetermined pattern is manufactured by exposing a resist film made of a resist film with an electron beam, in which a plurality of concave reference marks are formed at predetermined positions on a metal film on the mask substrate by etching away the thin film in advance. , detect the position of the fiducial marks, measure the length between the fiducial marks, find the amount of expansion and contraction of the length between the fiducial marks due to temperature changes, etc., and correct the position to be exposed to the electron beam based on the amount of expansion and contraction. The method is characterized in that a predetermined pattern with a size corrected for expansion and contraction is formed by using the same method.

An embodiment of the present invention will be described in detail below with reference to the drawings.

1A to 1D are schematic cross-sectional views showing one embodiment of the photomask manufacturing process of the present invention.

First, as shown in FIG. 1a, a resist film 3 is applied and formed on the upper surface of a glass substrate 1 on which a metal thin film 2 such as chromium Cr is deposited, and the resist film 3 is formed at predetermined positions, that is, at the four corners of the substrate 1. predetermined position A,
For example, a cross pattern 4 is patterned on B, C, and D by ordinary light exposure as shown in FIG. The fiducial marks 5A, 5 are removed with a solvent and have cross-shaped minute openings on the two surfaces of the metal thin film as shown in FIG. 1c.
B, 5C, 5D (in this case only 5A, 5B are shown).

However, in the present invention, a resist film 6 for electron beam exposure is formed on the upper surface of the mask substrate 7 prepared with reference marks provided in advance, as shown in the top views of the mask substrate in FIGS. 1D and 2. Form by applying. Thereafter, the mask substrate 7 is fixedly placed on a substrate holder on an XY moving stage of an electron beam exposure apparatus, and a reference mark, for example 5, is placed on the substrate.
An electron beam is irradiated and scanned from above the resist film 6 at points A and 5B. In this case, it is generally known that the radiation coefficient of the secondary electrons emitted by electron beam irradiation differs depending on various metals, glasses, etc., and this property can be used to irradiate the reference mark with the electron beam. By scanning, the glass of substrate 1 and
Mark positions such as reference marks 5A and 5B can be detected using a signal based on the difference in the secondary electron emission coefficient of the Cr film.
For example, measure the length L between the reference marks 5A and 5B and compare it with the length of the pattern design data value,
For example, even if the mask substrate surface expands or contracts due to temperature changes, by correcting the error, it is possible to accurately determine the beam exposure position for sequentially exposing and drawing a predetermined chip pattern on the mask substrate 7, for example. Can be done. Further, as described above, since the positions of several reference marks can be easily detected, it becomes possible to correct and control the positional deviation, orthogonality deviation, etc. of the exposure mask pattern to be formed based on the reference marks. Furthermore, since the reference mark is formed on the same mask substrate on which the pattern is exposed and drawn, the reference mark is irradiated and scanned with an electron beam to generate a signal due to the difference in secondary electron emission coefficients mentioned in the detection of the mark position. Therefore, the focusing of the electron beam can be easily adjusted.

In this embodiment, an example was explained in which the shape of the reference mark used a cross pattern, but in addition to this, as shown in FIG. 22,
23 may have a mark structure formed by partially etching away the Cr film, but when such a mark on an insulating substrate made of a glass substrate is irradiated with an electron beam, the island-like Cr film 22 is filled with charge. This electric charge makes it difficult to accurately detect the mark position.The present invention does not limit the reference mark provided on the mask substrate to the above-mentioned cross pattern, but the above-mentioned island-shaped conductive As long as the pattern structure does not have a pattern, various shapes can be used.

As is clear from the above description, according to the photomask manufacturing method of the present invention, focusing of the electron beam, determination of the electron beam exposure position, and Since the correction of the positional deviation, orthogonality deviation, etc. of the drawn pattern can be easily controlled, it is extremely advantageous that the pattern drawing accuracy of the photomask can be improved and the degree of integration can be increased.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view showing an embodiment of the photomask manufacturing process according to the present invention, Fig. 2 is a top view illustrating an embodiment of the photomask according to the invention, and Fig. 3 is a schematic cross-sectional view showing an embodiment of the photomask manufacturing process according to the present invention. It is a partial schematic diagram for explanation. 1: Glass substrate, 2: Chromium metal thin film, 3: Resist film, 4: Cross pattern, 5A, 5B, 5
C, 5D: reference mark, 6: resist film, 7: mask substrate.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a photomask with a predetermined pattern by exposing a resist film formed on a mask substrate on which a metal thin film is to be deposited with an electron beam, comprising: A plurality of concave reference marks are formed by etching and removing the thin film in advance, and the positions of the reference marks are detected and the lengths between the reference marks are measured. 1. A method of manufacturing a photomask, which comprises determining an amount of expansion and contraction, correcting a position to be exposed with an electron beam based on the amount of expansion and contraction, and forming a predetermined pattern with a dimension corrected for expansion and contraction.