JPH0772792B2 - Photo mask - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a photomask used in a photolithography process.

[Prior art]

When manufacturing a semiconductor device such as an integrated circuit, pattern formation is generally performed by a photolithography technique. In recent years, while the degree of integration of this device has increased, pattern accuracy,
The precision of photomask quality, such as overlay accuracy, has improved, and the manufacturing process has become complicated. For this reason, it has begun to be produced by an electron beam exposure apparatus capable of fine processing and capable of high precision and high speed mask making.

A conventional photomask making method will be described with reference to FIGS. In FIG. 1, reference numeral 1 is a substrate made of glass or the like, and a metal thin film 2 of metal chromium or the like is applied on the upper surface thereof to form a photomask plate 10.
3 is a resist applied on the surface of the metal thin film 2. In order to obtain a desired mask pattern, ultraviolet rays P are irradiated from above the substrate 1 as shown in FIG. Development after irradiation,
A resist pattern 4 is obtained as shown in FIG.
Using the obtained resist pattern 4 as a mask, the metal thin film 2 is etched as shown in FIG. 1 (c). After etching, the resist pattern 4 is peeled and removed, and a mask pattern 5 is obtained as shown in FIG. After cleaning the surface of the mask pattern 5 with a brush or the like, the obtained mask pattern 5 is inspected to confirm whether a desired mask pattern is formed. When an excessive pattern exists on the mask pattern 5 due to the inclusion of foreign matter or the like, the laser beam B is irradiated as shown in FIG. 1 (e) to melt and remove the excessive portion. On the other hand, when the pattern is missing with respect to the mask pattern 5, FIG. 1 (f)
As described above, the mask pattern is corrected by the lift-off method or the like.

In the above-described defect repairing method for the mask pattern thus formed, the defect repairing accuracy is not sufficient, and the laser repaired portion is excessively eluted or the substrate 1 is damaged by the laser. The same applies to the lift-off method, and its correction accuracy has been a problem.

Therefore, although the positioning mark of the mask pattern is formed so as to project on the substrate, there is a possibility that the positioning mark may be missing or missing due to the force at the time of cleaning the mask in repairing the mask pattern.

[Outline of Invention]

The photomask according to the present invention has been made in order to eliminate the drawbacks of the above-mentioned conventional method, and includes a mask pattern made of metal deposited on a substrate and a predetermined portion of a substrate region where the mask pattern is not deposited. And a target pattern made of a metal containing a metal element different from that of the mask pattern, and the surface of the target pattern opposite to the substrate deposition surface is the substrate deposition of the mask pattern. It is characterized in that it is formed so as to be substantially flush with the surface opposite to the surface.

Further, in this photomask, the mask pattern is made of chromium, and the target pattern is made of a metal containing tungsten, molybdenum or aluminum.

In such a photomask, by using the target pattern as an alignment mark at the time of mask pattern correction, accurate mask pattern formation is performed, and the surface of the target pattern opposite to the substrate-coated surface is
By making the mask pattern substantially flush with the surface of the mask pattern on the side opposite to the substrate-deposited surface, it is possible to prevent the target pattern from being applied with force when the target pattern projects from the mask pattern due to mask cleaning or the like.

Example of Invention

2 (a) to (g) show an embodiment of the present invention. In FIG. 2, 1 is a substrate made of glass or the like,
A metal thin film 2 such as metal chrome is provided on the upper surface. On the other hand, a metal thin film 21 containing impurities such as tungsten in a metal thin film such as metal chromium is deposited on the end of the substrate 1 in the same thickness as the metal thin film 2. Photomask plate 10A
Is configured.

Next, a procedure for producing a photomask using the photomask plate 10A will be described. First, as shown in FIG. 2 (a), a resist (for example, AZ1350) 3 is deposited on the metal thin films 2 and 21 to a thickness of about 4000Å, and a desired pattern is exposed from the top. After exposure, development (HMK-5) resist pattern 4 is obtained as shown in FIG. 2 (b). The metal thin film 2 is etched as shown in FIG. 2C using the obtained resist pattern 4 as a mask. After etching,
When the resist pattern 4 is peeled and removed, a mask pattern 5 is obtained as shown in FIG. The metal thin film 21 is prepared in advance so that the target pattern 6 having a plane pattern of “+” can be obtained. Further, as shown in FIG. 2 (a), since the metal thin films 2 and 21 are deposited on the substrate with the same film thickness, the surface of the mask pattern 5 and the target pattern 6 opposite to the substrate deposition surface is a flat surface. Make up.

After cleaning the formation surface of the mask pattern 5 with a brush or the like as in the conventional case, the obtained pattern is inspected to confirm whether or not the mask pattern 5 is formed. When the mask pattern 5 has an excessive pattern, it needs to be removed, but the accuracy of removing only that portion has been a problem in the past. Further, accuracy is also a problem when the pattern of the missing portion of the mask pattern 5 is corrected by the lift-off method. However, according to the present invention, first, as shown in FIG. 2 (e), a resist is deposited on the mask pattern 5, and then the obtained target pattern 6 is used as an alignment mark. Is exposed to the electron beam from above the resist 7 deposited on the substrate 1. After the electron beam exposure and development, the obtained resist patterns 8 and 81 are used as a mask to etch the excess portion of the metal thin film 2, and the missing portion of the metal thin film 2 such as the resist pattern 81 is lifted off as shown in FIG. Modify as in g).

As described above, the pattern missing portion and the excessive portion can be corrected very accurately with reference to the target pattern 6 which is the alignment mark. Since metal such as tungsten is used for the target pattern 6, secondary electron detection by the electron beam becomes easy, and the detection accuracy of the target pattern 6 becomes good. In the case of using the conventional photomask plate 10 on which the metal thin film 2 made of metal chrome or the like is deposited on the entire surface in this manner, the above correction method is impossible,
The present invention enables accurate defect correction.

Further, since the mask pattern 5 and the target pattern 6 are coplanar, the force applied by the target pattern 6 protruding from the mask pattern 5, for example, the force applied directly by the brush at the time of cleaning the mask is not received. The target pattern 6 can be prevented from being defective or missing.

Next, another embodiment will be described. The target pattern 6 created in the portion of the metal thin film 21 containing a dissimilar metal is
The mask pattern 5 formed on the substrate 1 can be used as an alignment mark in the case of collective electron beam transfer onto a wafer. In this case, if the metal thin films 2 and 21 are made of only a single metal such as chromium, alignment cannot be performed and batch transfer is impossible. In this case, the dissimilar metal may be aluminum, molybdenum, or the like, and has the same effect. The target pattern 6 may be formed from the beginning, or only the target pattern 6 may be adhered and formed after the mask pattern 5 is formed.

Further, another embodiment will be described. The conventional pattern correction method is the method shown in FIG. 1, but recently, by a metal crystal growth method using a laser beam, a certain kind of metal (for example, aluminum, nitride film) is locally formed.
Have been developed to fix defects. Also in this case, since the laser beam is used, very accurate correction can be performed.

Further, still another embodiment will be described. Recently, the third
As shown in Figure (b), a photomask with a code number 9 or a bar code is beginning to be created at the end of the photomask 10B. However, when detecting by laser beam reflection or transmission, metallic chromium is not always the best choice. If not, it can happen. Therefore, a metal different from the mask pattern 5 having a reflectance or a transmittance suitable for the detection capability is required. Also in this case, the dissimilar metal used for the code number 9 or the like of the photomask 10B of FIG. 3B is the metal thin film 21 formed from the beginning as shown in FIG. 3A.
May be used, or only this portion may be attached later.

In addition, in the above embodiment, the case where the metal thin film 2 is formed by using metal chromium has been described, but other metal may be used, and the metal thin film 2 is not limited to the compound containing tungsten as a different metal, and other metal may be used. Produce the effect of.

Furthermore, in the above-mentioned embodiment, an example of a compound such as metallic chromium tungsten is described, but a combination of two or more different compounds may be used, and the same effect is obtained. Further, in the above embodiment, an example of a dissimilar metal that has been deposited from the beginning is described, but a method of depositing a metal metal after the photomask is formed may be used, and the same effect can be obtained.

〔The invention's effect〕

As described above, according to the present invention, since the target pattern made of a material containing a metal different from the mask pattern is formed on the substrate, this target pattern is used as an alignment mark to perform highly accurate defect correction. In addition, since it can be used as an alignment mark when the electron beam is collectively transferred to the wafer, highly accurate transfer can be performed, and even when this target pattern is used as a bar code or the like, the bar code or the like can be detected with high accuracy. Has the advantage. Further, by making the surface of the target pattern opposite to the substrate deposition surface substantially flush with the surface opposite to the mask pattern substrate deposition surface, the target pattern can be projected from the mask pattern such as in mask cleaning. Since the applied force is not applied, it is possible to prevent defects and omissions in the target pattern.

[Brief description of drawings]

1 (a) to 1 (f) are process diagrams showing a conventional pattern forming method and defect correcting method, and FIGS. 2 (a) to 2 (g) are pattern forming method and defect correcting method according to an embodiment of the present invention. 3A and 3B are explanatory views showing a pattern forming method according to another embodiment of the present invention. In the figure, 1 is a substrate, 2 is a metal thin film, 3 and 7 are resists, 4 and 8 are resist patterns, 5 is a mask pattern, 6 is a target pattern, 10A is a photomask plate, and 10B is a photomask. The same reference numerals in the drawings indicate the same or corresponding parts.

Claims (2)

[Claims] 1. A mask pattern made of a metal formed by depositing on a substrate, and a metal element different from that of the mask pattern, which is formed by depositing on a predetermined portion of a substrate region where the mask pattern is not deposited. A target pattern comprising a gold layer containing the target pattern, and the surface of the target pattern opposite to the substrate deposition surface is formed to be substantially flush with the surface of the mask pattern opposite to the substrate deposition surface. A photo mask that is characterized. 2. The photomask according to claim 1, wherein the mask pattern is made of chromium, and the target pattern is made of a metal containing tungsten, molybdenum or aluminum.