JPS63231348A - Photomask - Google Patents

Abstract

PURPOSE:To increase the service life of a photomask by forming a 1st pattern having a normal shape on one main plane of a transparent substrate and drawing a 2nd pattern on the rear face of the transparent substrate so as to correspond to the 1st pattern. CONSTITUTION:A 2nd black ground part 16 is formed by reducing said part to the size smaller than the size of a 1st black ground part, by which the exact transfer of the 1st pattern 12, i.e., the normal pattern is permitted in an exposing stage. The 1st pattern 12 and the 2nd pattern 15 are simultaneously drawn on the image plane of the transparent substrate 11 and, therefore, even if a fresh pinhole is generated in either of the patterns, the other pattern shuts off the exposing light. The exact pattern transfer to prevent exposing of the pinhole is thus permitted. Since there is substantially no probability of generating the pinhole in exactly the same position of the 1st pattern 12 and the 2nd pattern 15, the lifetime of the photomask is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to improvements in photomasks used in the manufacture of semiconductor integrated circuits.

(b) Conventional technology In recent years, semiconductor integrated circuits have become smaller and more highly integrated.
In particular, positive resists are used in the photo-etching process to open contact holes in semiconductor integrated circuits, which is advantageous for miniaturization, and the photomasks used in this process have mostly black areas that correspond to the contact holes inside. The area of the white background portion is only a few percent of the total area.

FIG. 3 shows such a photomask as described, for example, in Japanese Patent Publication No. 61-54213. In the figure, (1) is a transparent substrate such as quartz glass, (2) is a black background part made of a metal chromium film, and (3) is a white background area where the transparent substrate (1) is exposed. If a pinhole exists in the black background part (2) of a photomask for a contact hole, a hole will be made in the oxide film covering the surface of the semiconductor integrated circuit.
It is desirable that there be no pinholes at all during the photomask manufacturing stage, as they can lead to fatal defects.

(c) Problems to be Solved by the Invention However, with conventional photomasks, even if defect-free is achieved at the manufacturing stage, metal chrome cannot be removed due to the handling of the photomask or the cleaning process of the photomask during the semiconductor device manufacturing process. The drawback was that the membrane was chipped and new pinholes were created, resulting in a limited service life.

(2) Means for Solving the Problems The present invention has been made in view of the above-mentioned drawbacks, and is based on a transparent substrate (11
) - the first pattern (trap) with a regular shape on the main surface
is formed, and a second pattern (1?) is drawn on the back surface of the transparent substrate (11) so as to correspond to the first pattern (1?).

(*) Effect According to the present invention, the first . Even if a pinhole occurs in one of the second patterns (12) and (15), the other pattern acts as a light-shielding film, so the service life of the photomask can be extended.

(F) Example Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing a photomask according to the present invention.
11) is a transparent substrate such as quartz glass, (tsubo) is a transparent substrate (
11)--The first black background part (13) made of the metal chromium film formed on the main surface and the first white background part (14) where the transparent substrate (11) is exposed are drawn in a desired regular shape. The pattern (long) is the first black background part (13) on the back side of the transparent substrate (11) corresponding to the first black background part (13>).
) A second black background area (16) made of a metal chromium film formed in a smaller size than the first white area (14) is formed on the back surface of the transparent substrate (11) corresponding to the first white area (14). This is the second pattern drawn by the second white background part (17) formed by the process.The second black background part (16) is drawn so as not to violate the first pattern (Akira) which is the regular pattern. It is formed in the above relationship so that its end portion is inside the end portion of the first black background portion (13).

According to the photomask of the present invention configured as described above, since the second black background portion (16) is formed smaller than the first black background portion (13), the first black background portion which is a regular pattern is formed in the exposure process. The pattern can be transferred accurately, and at the same time, the first pattern can be transferred onto both sides of the transparent substrate (11).
Since we have drawn the second pattern (su) and the second pattern (su), even if a new pinhole occurs in one of the patterns, the other pattern will block the exposure light and the pinhole will not be exposed. It is possible to perform pattern transfer. Since there is little probability that a pinhole will be formed at the exact same position in the first pattern (super) and the second pattern (su), the service life of the photomask can be extended. The pattern (trap) is used as a regular pattern, whereas the second pattern (1st base) is used for the so-called protection purpose, so it is created with higher precision than the first pattern (tsubo). There is no need for it, and some flaws can be tolerated.

Hereinafter, a method for manufacturing the above photomask will be explained.

The photomask according to the present invention can be manufactured extremely easily by the following steps.

First, as shown in FIG. 2A, a first pattern (tool) is drawn on the main surface of the transparent substrate (11) by a normal manufacturing process. In that case, it is desirable that the first pattern (L8) be free of defects or nearly defect-free by some correction method or the like.

Next, as shown in FIG. 2B, a negative type resist (18) such as AZ5200 (Hoechst Co., Ltd., product name) is applied to the entire surface of the back surface of the transparent substrate (11). - 2 of the normal exposure from the main surface side
Approximately twice as much exposure light is applied to expose the resist (18) to the same pattern as the first pattern (trap).
0 resist usually exhibits positive properties, but
It is a resist that can be changed into a negative type during the process depending on the processing method, and even when used as the negative type, it has the characteristic of exhibiting high resolution similar to that of a positive type. Therefore, it is possible to handle extremely fine patterns such as empty holes.

Furthermore, as shown in FIG. 2C, the exposed resist (1
8) is developed, and the resist (18) in the portions not irradiated with light due to the first black background portion (13) is removed. At this time, since the exposure light that has passed through the first white background part (14) is accompanied by a light diffraction phenomenon, the remaining resist (18) is formed slightly enlarged with respect to the first white background part (14). .

Then, as shown in the second diagram, a metal chromium film (
19) is deposited and formed.

Finally, as shown in FIG. 2E, the remaining resist (18) is removed by the chrome paste lift-off method, and a second black background part (13) is added to the area corresponding to the first black background part (13).
6> in the area corresponding to the first white background part (14).
By forming the white background portion (17) of the transparent substrate (
11) Draw a second pattern (scale) on the back side.

According to this manufacturing method, since the regular first pattern (Tsubo) is used as a mask to form the second pattern (Tsubo), the photomask of the present application can be fabricated without any difficulties such as positioning. It is extremely easy to manufacture. Furthermore, since the second pattern (Takumi) is accompanied by a light diffraction phenomenon, the pattern accuracy of the second pattern (Takumi) is worse than that of the first pattern (Takumi), but since the first pattern (Takumi) is normally used as a transfer pattern, There is no problem.

Furthermore, it is possible to equivalently correct the pinholes in the first pattern (pattern) using the above-described manufacturing method. In other words, if the pinhole is extremely small, the resist (18) remains due to the light diffraction phenomenon, so a second black background part (16) is formed in the corresponding area, and this second black background part (16) is formed in the corresponding area. Since the portion blocks the exposure light, it is equivalent to correcting the pinhole that occurred in the first pattern (L8).
Even if there is a pinhole that leaves a resist (18), after completing the process shown in FIG.
) is irradiated with laser light using a general laser repair device to completely remove the remaining resist (18), thereby completing a photomask with pinholes repaired in the same way.

(G) As described in detail, the present invention has the advantage that it is possible to provide a photomask that does not require discarding the photomask even if new pinholes are generated during handling or cleaning process of the photomask. In addition, it has the advantage of providing a photomask with a significantly increased service life.

The manufacturing method described above has the advantage that the photomask of the present invention can be produced extremely easily, and furthermore, the pinholes in the first pattern (tsubo) can be equivalently corrected. It also has the advantage of being possible.

[Brief Description of the Drawings] Figure 1 is a sectional view for explaining the present invention, Figures 2A to 2E are sectional views for explaining the manufacturing method of the present invention, and Figure 3 is a sectional view for explaining the manufacturing method of the present invention.
The figure is a sectional view for explaining a conventional example. (11) is a transparent substrate, (shell) is a first pattern, (su) is a second pattern, and (18) is a resist.

Claims (1)

[Claims] (1) In a photomask in which a first pattern is drawn on one main surface of a transparent substrate by a first black background portion made of a metal thin film and a first white background portion where the transparent substrate is exposed, the first black background portion A second black background portion is formed on the back surface of the transparent substrate corresponding to the first black background portion and is smaller than the first black background portion, and a second black background portion is formed on the back surface of the transparent substrate corresponding to the white background portion and is larger than the white background portion. A photomask characterized by drawing a second pattern with a white background part.