JPH03212922A - Forming method of alignment mark of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent roughening of the surface of a film on an alignment mark and to improve precision in detection of the alignment mark by forming a separating film on a substrate and by forming the alignment mark on this film. CONSTITUTION:Before an alignment mark 3 is formed on a substrate 1, a separating film 2 being broader than the mark 3 is formed. Thereby a film 4 around the mark 3 is separated from the substrate 1 and the surface of the film 4 is prevented from roughening due to the reaction of the film 4 with the substrate 1. Accordingly, noise of the intensity of a reflected light on the mark 3 and a part around it is reduced, the mark 3 can be detected with high precision and the yield of a semiconductor device is improved.

Description

[Detailed description of the invention] 〔overview〕 Regarding a method for forming alignment marks for semiconductor devices.

The purpose of this paper is a method for forming alignment marks to improve alignment mark detection accuracy.

The method includes a step of forming a separation film on a semiconductor substrate, a step of forming an alignment mark on a part of the separation film, and a step of forming a connecting film covering the alignment mark and the separation film. The separation film separates the substrate and the coating, and the substrate is formed by a method of forming an alignment mark for a semiconductor device in which the coating does not affect the coating on the alignment mark. The present invention relates to a method for forming an alignment mark.

2. Description of the Related Art In recent years, as semiconductor devices have become highly integrated, highly accurate alignment is required in resist pattern formation using an exposure device.

As semiconductor devices become more highly integrated, alignment marks become smaller, and various methods are being implemented to detect them with high precision.

For example, by arranging multiple alignment marks to form a diffraction grating and observing the reflected light intensity while scanning the laser beam, detection is performed by taking advantage of the fact that the reflected light intensity increases due to interference where alignment marks are formed. A method of capturing alignment mark patterns into an image and detecting them by two-image processing, and a method of detecting using light of multiple wavelengths have been implemented.

These all relate to the shape of the alignment mark, its placement, and its detection method.

If the quality of the alignment mark is poor, the accuracy of alignment mark detection cannot be improved. Therefore, in order to improve alignment accuracy, it is necessary to devise ways to form alignment marks.

[Conventional technology]

FIGS. 3(a) to 3(c) are cross-sectional views showing the conventional process of forming alignment marks for forming wiring patterns.
The following description will be made with reference to these figures.

Referring to FIG. 3(a), alignment marks 3 are formed on the Si substrate 1 at the scribe portions of the substrate 1. As shown in FIG. The alignment mark 3 is formed simultaneously with the formation of the contact hole by etching the PSG, for example.

Referring to FIG. 3(b), an At film 4 for forming a wiring pattern is formed on the entire surface.

See Figure 3(c) A resist film 5 is formed on the coating 4.

In this state, alignment for wiring patterning is performed.

FIG. 4(a) shows an example of alignment mark detection performed by the method using the above-mentioned diffraction grating marks.

Shown in (b).

FIG. 4(a) corresponds to FIG. 3(c) and schematically shows that the coating 4 is in the state of large crystal grains.

FIG. 4(b) shows the reflected light intensity when scanning with a laser beam. Where alignment marks are formed, the intensity of reflected light increases as it interferes with each other.

By processing this waveform, the center of the alignment mark can be found. For example, for 9 reflected light intensity, the peak value is 100, and a point is drawn when 1 reflected light intensity is 50,
The intersection points with the waveform are designated as A and B, and the midpoint of line segment AB can be known as the center of the alignment mark.

However, depending on the film thickness, material, heat treatment, etc., the film 4 reacts with the substrate 1, causing crystal grains to grow large.

When the width of the alignment mark 3 is narrow, the influence extends to the coating 4 on the alignment mark 3, and the surface of the alignment mark 3 and its edges becomes extremely uneven. Figure 4 (b
), the noise increases and the accuracy of detecting the center position of the alignment mark 3 decreases.

[Problem to be solved by the invention]

Therefore, even if various methods are employed to detect the alignment mark 3, the alignment accuracy will not improve unless the surface condition of the coating 4 on and at the ends of the alignment mark 3 is improved.

An object of the present invention is to provide an alignment mark forming method that prevents the surface of the coating 4 of the alignment mark from becoming rough and improves the accuracy of alignment mark detection.

[Means to solve the problem]

The above-mentioned problems include a step of forming a separation film 2 on a substrate l, a step of forming an alignment mark 3 on a part of the separation film 2, and a connecting film 4 covering the alignment mark 3 and the separation film 2. The separation film 2 separates the substrate 1 and the coating 4, and the substrate 1 does not affect the coating 4 on the alignment mark 3. solved by.

[Effect]

In the present invention, before forming the alignment mark 3, the separation film 2, which is wider than the alignment mark 3, is formed on the substrate 1. As a result, the coating 4 around the alignment mark 3 is separated from the substrate 1, and the substrate 1 no longer affects the coating 4. Also.

It is possible to avoid a situation where the surface of the coating 4 becomes rough due to the influence of the substrate 1 and becomes extremely uneven.

As a result, noise in the intensity of reflected light on and around the alignment mark 3 is reduced, and the alignment mark 3 can be detected with high precision.

[Embodiment] FIGS. 1(a) to 1(d) are cross-sectional views showing steps of an embodiment of forming an alignment mark for forming a wiring pattern, and will be described below with reference to these figures.

FIG. 1(a) A Si substrate is used as a reference substrate 1, and a poly-Si film with a thickness of 1000 nm is formed thereon as a separation film 2. FIG.

FIG. 1(b) A diffraction grating is formed on a part of the reference separation membrane 2 by arranging seven square alignment marks 3 having a side of 4 μm at intervals of 4 μm (only negative marks are shown). These alignment marks 3 are
It is formed by etching a PSG film with a thickness of 7,000 yen.

At the same time, a concoction hole is also formed (not shown)
.

Referring to FIG. 1(c), an A1 film having a thickness of 1 μm is formed as a coating 4 on the entire surface. This film is for forming a wiring pattern.

See Figure 1(d) A resist film 5 with a thickness of 2 μm is formed over the entire surface.

In this state, alignment for wiring patterning is performed.

FIG. 2(a) shows an example of alignment mark detection performed by the method using the above-mentioned diffraction grating marks.

Shown in (b).

FIG. 2(a) corresponds to FIG. 1(d) and schematically shows that the coating 4 in contact with the substrate 1 is in the state of large crystal grains. The coating 4 on the separation membrane 2 near the edge of the separation membrane 2 is also in the state of large crystal grains, but this effect does not extend to the vicinity of the alignment mark 3 and the coating 4 on the alignment mark 3, where the surface of the coating 4 is It is smooth.

FIG. 2(b) shows the reflected light intensity when scanning with a laser beam. Where alignment marks are formed, the intensity of reflected light increases as it interferes with each other.

By processing this waveform, the center of the alignment mark can be found.

For example, one reflected light intensity has a peak value of 100, a line is drawn at a point where one reflected light intensity is 50, the intersection points with the waveform are designated as A and B, and the midpoint of the line segment AB can be known as the center of the alignment mark.

As shown in FIG. 2(b), there is very little noise and the center of the alignment mark can be detected with high accuracy.

In addition, in the embodiment, an example was explained in which a poly-Si film was used as the separation film 2 and an AI film was used as the coating 4. However, the separation film 2 prevents the reaction between the substrate 1 and the coating 4, and the substrate 1 is aligned with the alignment mark 3.
Any material may be used as the separation film 2 as long as it does not affect the surface condition of the upper coating 4. For example, a silicon nitride film, a silicon oxide film, etc. can also be effectively used as the separation film 2.

[Effects of the Invention] As explained above, according to the method of the present invention, even though the alignment mark detection method remains the same as the conventional one, - due to the improvement in alignment mark formation, it is possible to perform alignment with higher precision than before, and the semiconductor Contributes to improving device yield.

[Brief explanation of drawings]

FIGS. 1(a) to 1(d) are cross-sectional views for explaining an embodiment of alignment mark formation. FIGS. 2(a) and 2(b) are diagrams for explaining an embodiment of alignment mark detection. FIGS. 3(a) to 3(c) are cross-sectional views for explaining a conventional example of alignment mark formation. FIGS. 4(a) and 4(b) are diagrams for explaining a conventional example of alignment mark detection. In fig. 1 is a substrate, which is a Si substrate. 2 is a separation membrane, which is a poly-Si film. 3 is the alignment mark. 4 is a film, which is an AI film. 5 is an example of the formation of a resist film filament mark (d) (b) A view of the cost of a filament mark 11.

Claims (1)

[Claims] A step of forming a separation film (2) on a substrate (1), a step of forming an alignment mark (3) on a part of the separation film (2), and a step of forming an alignment mark (3) on a part of the separation film (2). ) and a step of forming a connecting film (4) covering the separation membrane (2),
2) separates the substrate (1) and the coating (4), and separates the substrate (1) and the coating (4);
A method for forming an alignment mark for a semiconductor device, characterized in that 1) does not affect the coating (4) on the alignment mark (3).