JPH05259021A - Method for formation of wafer alignment mark - Google Patents

Abstract

PURPOSE:To obtain a wafer, having an alignment mark, with which an alignment operation can be conducted easily and accurately. CONSTITUTION:An interlayer insulating film 4 is formed on the base film 3, and a patter, which becomes an alignment mark 2, is formed on the base film 3 by conducting an etching treatment on the interlayer insulating film 4. At the same time, the surface of the above-mentioned pattern is fused by heat treatment, and the pattern is formed into an almost globular cross-sectional shape. Then, a wiring material 5 is coated almost uniformly in a film-like form from upper side of the pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an alignment mark on a wafer for use in aligning the wafer in a photolithography (resist processing) step of a semiconductor device manufacturing process. ..

[0002]

2. Description of the Related Art In a photolithography process in a semiconductor device manufacturing process, a laser beam is directed toward a wafer surface while scanning, and an alignment mark formed on the wafer surface is detected by a difference in intensity of the reflected laser beam. A method of performing automatic alignment based on this alignment mark is used.

The alignment mark is, for example, a square alignment mark 101 as shown in FIG.
It is formed on the wafer 100. Further, the structure of the wafer 100 in the portion where the alignment mark 101 is provided has a structure as shown in FIG. 5, for example. That is, FIG. 5 is a schematic vertical sectional side view taken along the line BB of FIG. 4, in which the alignment mark-shaped field oxide film 103 is formed on the silicon wafer substrate 102, and thereafter, the film to be etched 104 and the resist film 105 are formed. Is applied to each.

When detecting the alignment mark 101, the wafer surface is scanned while shining a laser beam, and the light reflected at this time is received by a detector (not shown).
Due to the difference in the intensity of the reflected light, the alignment mark 101
It is designed to detect the edge of.

[0005]

However, in the alignment mark detecting method using the above-mentioned conventional alignment mark 101, interference of the multilayer thin films becomes a problem. That is, when the film thicknesses of the field oxide film 103, the film to be etched 104, and the resist film 105 are each minutely changed, the reflectance from the portion of the alignment mark 101 becomes extremely small accordingly. Then, it becomes difficult to detect the edge of the alignment mark 101, and it is often the case that the accurate alignment work cannot be performed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a wafer alignment mark capable of easily and accurately performing alignment work on a wafer. It is to provide a method of forming.

[0007]

In order to achieve the above object, the present invention is a method of forming a wafer alignment mark on a wafer substrate, which is detected by the reflection intensity of laser light applied toward the surface of the wafer. Then, an interlayer insulating film is formed on the base film, and then the interlayer insulating film is etched to form a pattern serving as an alignment mark on the base film, and the surface of the pattern is heat-treated and melted. The pattern is formed into a substantially spherical cross-sectional shape, and then a wiring material is applied on the underlying film from above the pattern in a substantially uniform film shape, and a resist film is further formed on the wiring material. It is a thing.

[0008]

In the wafer having the alignment mark formed by this method, the alignment mark formed on the base film by the interlayer insulating film is formed into a small spherical shape, and then the alignment mark is covered and the wiring material is formed on the base film. Therefore, the surface of the wiring material is also formed in a wavy state. Therefore, when the laser light is applied from the surface side and hits the wiring material portion on the alignment mark, the laser light is scattered outward on the undulating and raised surface, and the reflection intensity returning to the detector etc. Get smaller. On the other hand, except the portion on the alignment mark, the light is reflected as it is in the incident direction and the reflection intensity is increased. Therefore, in this wafer structure, a large difference in reflectance between the portion where the alignment mark exists and the portion where the alignment mark does not exist can be obtained,
An alignment mark with high contrast can be obtained.

[0009]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a top view showing an example of a wafer manufactured by applying the wafer alignment mark forming method according to the embodiment of the present invention. In FIG. 2, the wafer 1 is in a state in which a plurality of square alignment marks 2 (16 in this embodiment) are formed on the front surface side of the wafer. The alignment mark 2 may have a shape other than a square, for example, a rectangular shape, and the size thereof is about 0.3 to 1.0 μm (“micro millimeter”, the same applies hereinafter).

FIG. 1 is a process diagram showing a procedure for forming an alignment mark on a wafer by the wafer alignment mark forming method according to the present invention. Therefore, a method of forming the wafer 1 described with reference to FIG. 2 will be described below in the order of steps 1 to 5 using the process chart shown in FIG.

First, in the "process 1", for example, boron (B) -doped phosphorus glass (B) for forming the alignment mark 2 is formed on the base film 3 to be a silicon wafer substrate.
The interlayer insulating film 4 made of a PSG film or the like is applied and formed. Next, in "step 2", the interlayer insulating film 4 on the base film 3 is subjected to well-known photolithography and etching treatment to form a pattern (2) to be the alignment mark 2.
The pattern (2) here is 0.3 to 1.0 μm.
Formed as a square or a rectangle. "Process 3"
Then, heat treatment at 850 to 950 ° C. is performed on the interlayer insulating film 4 formed as the pattern (2) in step 2,
The surface of the pattern (2) is melted, the heat-treated interlayer insulating film 4 is used as an alignment mark 2, and the alignment mark 2 is formed into a nearly spherical cross-sectional shape by the above-mentioned melting. In the "process 4", the wiring material 5 is applied in a film shape with a substantially uniform thickness on the base film 3 so as to cover the alignment marks 2. Then, only the portion 5A corresponding to the alignment mark 2 is raised on the surface of the wiring material 5, and the other portion becomes a concave portion, which is formed in a wavy state as a whole. In the “process 5”, the resist film 6 is coated on the wiring material 5 to make the surface smooth, whereby the formation of the alignment mark 2 on the wafer 1 is completed.

FIG. 3 shows the cross-sectional structure of the wafer 1 thus formed, and when laser light 7 is applied to the wafer 1, the light hits the surface of the wiring material 5 in the wafer 1 and is reflected. It shows the state.

That is, in this structure, when the laser beam 7 is applied to the surface of the wafer 1 while scanning and is incident on the portion of the wiring material 5 on the alignment mark 2, the wiring material 5 swells and rises. Part of surface 5A
In this case, the intensity of the reflected light scattered toward the outside and returning to a detector (not shown) or the like becomes small. On the other hand, in the portion 5B other than the portion of the alignment mark 2, the intensity of the reflected light increases as it is reflected in the incident direction. In this way, the difference in reflectance between the incident laser beam 7 and the portion 5A on the alignment mark 2 and the portion 5B other than the alignment mark 2 becomes large. Further, even if there is a variation in the thickness of the resist film 6 on the wafer 1, the reflectance on the portion above the alignment mark 2 is increased due to the reduction in reflectance due to the scattering of the wiring material 5. Since it does not exist, the portion 5A of the alignment mark 2 is not affected by the film thickness.
Thus, a large difference in reflectance with the other portion 5B can always be obtained, and an alignment mark with high contrast can be obtained.

[0014]

As described above, the wafer having the alignment mark formed by the method for forming a wafer alignment mark according to the present invention does not exist in the portion where the alignment mark exists and when the laser beam is applied to the surface. Since a large difference in reflectance with the portion is always obtained, it is possible to expect an effect that the alignment mark can be easily detected, and the alignment work can be performed easily and accurately.

[Brief description of drawings]

FIG. 1 is a process drawing showing a procedure of a wafer alignment mark forming method according to the present invention.

FIG. 2 is a top view showing an example of a wafer formed by applying a wafer alignment mark forming method according to an embodiment of the present invention.

FIG. 3 is an enlarged vertical cross-sectional side view taken along the line AA of FIG. 2 showing a state where light is reflected and returned when a laser beam is applied to a wafer formed by applying the wafer alignment mark forming method of the present invention. is there.

FIG. 4 is a top view showing an example of a conventional wafer with alignment marks.

5 is a schematic vertical sectional side view taken along the line BB of FIG.

[Explanation of symbols]

 1 wafer 2 alignment mark 3 base film (silicon wafer substrate) 4 interlayer insulating film 5 wiring material 6 resist film 7 laser light

Claims (1)

[Claims] 1. A method for forming a wafer alignment mark on a wafer substrate, which is detected by a reflection intensity of a laser beam applied toward a surface of a wafer, wherein an interlayer insulating film is formed on a base film, and the interlayer insulating film is formed. The film is subjected to an etching treatment to form a pattern serving as an alignment mark on the base film, and the surface of the pattern is subjected to a heat treatment to be melted to form the pattern into a substantially spherical cross-sectional shape, and then on the base film. A method for forming a wafer alignment mark, comprising: applying a wiring material from above the pattern to a substantially uniform film shape, and further forming a resist film on the wiring material.