JPS59165421A - Mark for positioning of semiconductor device - Google Patents

Abstract

PURPOSE:To realize highly accurate positioning in all stages of manufacturing process by providing a plurality of marks in different sizes on a semiconductor substrate and protecting marks with an oxide film formed after formation of the epitaxial layer. CONSTITUTION:Two square marks M1, M2 having different pattern widths are simultaneously formed on a semiconductor substrate pattern 1. The mark M1 is used before growth of epitaxial layer, while the mark M2 after growth of epitaxial layer. The mark M1 after growth of epitaxial layer 3 has an enlarged size and can no longer be used. The mark M2 is enlarged and can be used. The epitaxial layer 3 is protected by a thin oxide film 4 formed by thermal oxidation and accordingly an error caused by scattered reflection of laser beam is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of an alignment mark for a semiconductor chip, which is used when working with a stepper or an EB exposure apparatus.

In the manufacturing process of semiconductor devices, patterns for the next process are formed by alignment with patterns formed in the previous process, but as semiconductor devices become more highly integrated, requirements for alignment accuracy are becoming increasingly strict. As a high-precision alignment method, a set of 2 to 4 alignment marks (hereinafter referred to as marks b) is formed in advance on a semiconductor chip, and a laser beam is irradiated and the reflected light is reflected by an exposure device. Then, the specific heat is used to align the position with the position of the reference mark stored in the exposure device. Note that the shape of the mark varies depending on the model of the exposure device, such as a square or a cross. In the conventional semiconductor device manufacturing process, as shown in FIG. 1, a rectangular mark, for example, is formed on a semiconductor substrate 1, then the semiconductor substrate is oxidized and aligned using the mark, as shown in FIG. 2, and then exposed. to form a pattern. In FIGS. 1 and 2, (a) is a fc view of the mark as seen from the top surface of the chip, and Φ) is a front sectional view of the chip. As shown in Figure 2, the mark on the oxide film 2 formation edge is reduced by the amount of oxidation, but since this reduction rate is constant depending on the oxidation conditions, it is corrected when forming the mark on the i-plate. It's better to just make it bigger. However, in the manufacturing process of semiconductor devices, after a buried layer is formed, a surface etching process is performed to remove dirt, scratches, etc. on the semiconductor substrate surface, and then an epitaxial layer is formed, which causes alignment problems. . Figure 3 shows the mark at this time. (a) is a view of the mark seen from the top of the chip, (b)
is a front sectional view of the chip. As shown in the figure, when the oxide film 2 of FIG. 2 is etched, the peripheral edge of the mark is etched, so that the mark is greatly enlarged by the growth of the epitaxial layer 3 compared to the size originally formed on the substrate. It is not possible to take this enlargement into consideration when forming a mark on the substrate and correct the mark accordingly to make it smaller. The specific heat due to the reference mark of the exposure equipment is possible when the mark of the semiconductor device falls within a certain range of the reference mark of the exposure equipment, in the case of oxidation of the semiconductor substrate, in the case of after epitaxial layer growth, and the size of the mark. This is because the change in size cannot be corrected for all of the above cases because the direction of change is reduction on one side and expansion on the other. It is conceivable to add a step of forming a new mark after the growth of the epitaxial layer and then perform alignment with the mark, but this has the disadvantage of complicating the process. In addition to the above-mentioned problem of irregularly sized marks, after the epitaxial layer is grown, the surface is rough due to post-processes such as etching or diffusion, and the reflection of laser light becomes diffused, making alignment difficult. There is a drawback.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide an alignment mark that can be aligned with high precision even after the formation of an epitaxial layer or even after a subsequent process.

In a semiconductor device in which an epitaxial layer is formed on a semiconductor substrate, the alignment mark according to the present invention is provided on the semiconductor substrate and has a portion similar to a reference mark of an exposure device, and has a plurality of portions having different sizes. Depending on the structure of the individual, the percentage indicates that the epitaxial layer is covered with an oxide film after the formation of the epitaxial layer.

The present invention will be described in detail below with reference to the drawings. FIG. 4 is a diagram in which two rectangular marks M1 and M2 having different pattern widths are simultaneously formed on the semiconductor substrate 1 in one embodiment of the present invention. Ml shown in (a) is a mark used before epitaxial layer growth, and M2 is a mark used after epitaxial layer growth.

(I)) is a front sectional view of the chip. Next, FIG. 5 shows the thermally oxidized state after the growth of the epitaxial layer 3.

On the semiconductor substrate 1, the epitaxial layer 3 forms enlarged marks at the positions of the marks shown in FIG. 4, respectively.

The epitaxial layer 3 is protected from thermal oxidation by a thin oxide film 4. The oxide film 4 is thin, and the reduction of the mark due to this does not affect alignment.

In FIG. 4, the M1 mark has a size that can be used as a mark in an exposure device, and in FIG. 5, it cannot be used in an enlarged size. The mark M2 is too small in FIG. 4 to be used as a mark in the exposure device, but in FIG. 5 it is enlarged and can be used.

In addition, by always protecting the oxide film 4, which is resistant to thermal oxidation after the epitaxial layer 3 is formed, in a subsequent process and maintaining the coating in a state where the coating is preserved, errors caused by diffused reflection of laser light can be prevented.

In the above description, the shape of the mark is described as being rectangular, but it is not limited to the rectangular shape. As long as the reference mark of the exposure device has a similar portion, the pattern may be different in other portions, and it is sufficient to prepare a plurality of sets of marks having different sizes for similar portions.

As explained above, according to the present invention, a plurality of sets of marks are provided on a semiconductor substrate, and an oxide film is formed after the epitaxial layer is formed to protect the marks. Marks can be obtained that allow precise alignment.

[Brief explanation of drawings]

FIGS. 1 to 3 are diagrams for explaining how alignment marks on a semiconductor device are reduced and enlarged during the process, and FIG. 4 is an embodiment of the present invention, in which marks provided on a semiconductor board are shown. FIG. 5 is a diagram showing that the mark in FIG. 4 has a different shape after the epitaxial layer is formed. l... Semiconductor substrate, 2,4... Oxide film, 3... Group epitaxial layer, M, Ml, M2...
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Claims (1)

[Claims] In a semiconductor device in which an epitaxial layer is formed on a semiconductor substrate, a plurality of assembled patterns are provided on the semiconductor substrate and have a portion similar to a reference mark of an exposure device, and the portions have different sizes. . An alignment mark for a semiconductor device, characterized in that it is covered with an oxide film after the epitaxial layer is formed.