JPH03268316A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable detection even when the shape of an alignment mark is deformed to some extent, by performing alignment after the surface of the alignment mark is subjected to surface roughening treatment. CONSTITUTION:At the time of alignment of a photomask and a wafer in an exposing process, the surface of an alignment mark 2 formed on the wafer is subjected to a surface roughening treatment, and then alignment is performed. By roughening the surface of the alignment mark 2, the form of a detected signal is disordered, but the signal level is increased. That is, when an epitaxial layer 4 is grown on a substrate so as to cover the alignment mark 2, the bottom part surface of the alignment mark 2 is roughened and made to reflect on the epitaxial layer, thereby increasing the intensity of scattering light of the mark part of the epitaxial layer 4. Hence the alignment mark 2 can be detected even when the mark shape is deformed to some extent.

Description

[Detailed Description of the Invention] [Summary] This invention relates to an alignment method in an exposure step of a wafer process.

The purpose is to enable detection even if the shape of the alignment mark is slightly distorted.

1) When aligning a photomask and a wafer in an exposure process, the alignment is performed after roughening the surface of an alignment mark formed on the wafer.

2) The surface roughening treatment is performed by bombarding the surface of the alignment mark with ions.

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device, and particularly to an alignment method in an exposure step of a wafer process.

[Conventional technology]

As semiconductor factories have moved online in recent years, it has become necessary to avoid stopping processing due to the occurrence of errors.

However, as the types of exposure equipment have increased, the wafer process has become more complex, and the number of patterns formed on one wafer has increased, it has become difficult to form alignment marks, and it has become necessary to create alignment marks in several layers. It is also forced to be used for both purposes.

Therefore, during alignment in the exposure process.

This has caused a problem in that the alignment signal cannot be detected and processing stops.

[Problem to be solved by the invention]

An object of the present invention is to enable detection even if the shape of an alignment mark is slightly distorted.

[Means to solve the problem]

What is the solution to the above problem?

1) A method for manufacturing a semiconductor device in which alignment is performed after roughening the surface of an alignment mark formed on a wafer during alignment of a photomask and a wafer in an exposure process, or 2) The roughening process. The processing is achieved by a semiconductor device manufacturing method in which ions are bombarded onto the surface of the alignment mark.

[Effect]

In the present invention, by roughening the surface of the alignment mark, the shape of the detection signal becomes irregular, but the level of the signal is increased and detection is made possible.

Next, the reason will be explained using FIG.

FIGS. 1(a) to 1(p) are diagrams explaining the principle of the present invention.

In the figure, a convex alignment 2 is formed on a silicon substrate 1, and a silicon dioxide (SiO□) film 3 is coated thereon.

(1) Normal mark alignment (conventional) Figure 1 (a)
, (b) are a plan view and a cross-sectional view of a normal alignment mark.

FIG. 1(C) shows the distribution of signal intensity with respect to position, which is the intensity of scattered light when the laser beam is scanned over the alignment mark.

FIG. 1(d) also shows the distribution of signal intensity with respect to position, and represents the signal intensity when laser step alignment (LSA) l) is used.

In this case, a diffraction grating is formed on the wafer by arranging multiple concave or convex alignment marks in a row at intervals, and the laser beam covering each mark is scanned perpendicular to the direction of the row. It detects scattered and diffracted light.
The output signal becomes stronger as the laser overlaps the alignment mark.

The center position of the alignment mark is determined from the signal.

1) N, Magome and N, 5hirais
hi.

La5er Alignment Signal Si
Mulation for Analysis of A
I Layers.

Proc, 5PIF (Soc, Photo-optic
al Instrumentation Eng.),
Vol108B, p23B (1983).

(2) Alignment of normal marks (present invention) Fig. 1 (e
) and (f) are a plan view and a sectional view of an alignment mark with a roughened surface according to the present invention.

FIG. 1 (The top shows the distribution of signal intensity with respect to position, and is the intensity of scattered light when the laser beam is scanned over the alignment mark.

In this case, since there is scattered light at a position corresponding to the surface of the mark, a detection signal is also obtained at the center of the mark.

FIG. 1(b) also shows the distribution of signal intensity with respect to position, and represents the signal intensity when laser step alignment is used.

In this case, since scattered light on the mark surface is detected, many irregularly shaped peaks appear.

Therefore, although the center position of the mark cannot be determined accurately, the detection sensitivity is the same as in the case of FIG. 1(d) because the signal strength level is high.

(3) Alignment of abnormal marks (conventional) Figure 1 (i)
, (j) is a plan view and a cross-sectional view of an alignment mark with an extremely low height.

FIG. 1 shows the distribution of signal intensity with respect to position, which is the intensity of scattered light when the laser beam is scanned over an alignment mark.

In this case, the signal strength is small and detection becomes difficult.

FIG. 1 (1) also shows the distribution of signal intensity with respect to position, and represents the signal intensity when laser step alignment is used.

The signal strength in this case is also low, making detection difficult.

(4) Alignment of abnormal marks (present invention) FIGS. 1(b) and 1(n) are a plan view and a sectional view of an extremely low-height alignment mark with a roughened surface according to the present invention.

FIG. 1(0) shows the distribution of signal intensity with respect to position, which is the intensity of scattered light when the laser beam is scanned over the alignment mark.

In this case, since there is scattered light at a position corresponding to the surface of the mark, a detection signal can be obtained over the entire mark.

FIG. 1 CP) is also a distribution of signal intensity with respect to position, and represents the signal intensity when laser step alignment is used.

〔Example〕

FIGS. 2(a) to 2(d) are diagrams illustrating an embodiment of the present invention.

FIG. 2(a) is a plan view of a rectangular alignment mark formed on the surface of a silicon substrate.

FIG. 2(b) is a cross-sectional view of the same, and 1 is a silicon substrate.

2 is a concave alignment mark formed, for example, 48 m x 4 μm x 0.7 μm.

FIG. 2(C) is a cross-sectional view of a coating layer 3, such as a shrimp layer 4, grown on the substrate to cover the alignment mark 2.

In this case, the alignment mark cannot be detected from above the shrimp layer 4.

Therefore, the present invention is applied as shown in FIG. 2(d).

When the bottom surface of the alignment mark is roughened and reflected on the shrimp layer 4, the intensity of the scattered light at the mark portion of the shrimp layer 4 becomes thicker and detection becomes possible.

As a method for roughening the mark surface, the substrate is covered with a mask that exposes the mark surface, and the substrate is bombarded with ions using, for example, an ion milling device.

The ion species and acceleration energy at this time are determined by observing the degree of scattering on the mark surface.

[Effects of the Invention] As described above, according to the present invention, even if the shape of the alignment mark is slightly distorted, it can be detected, and when used for rough alignment, there will be no trouble that cannot be processed.

[Brief explanation of drawings]

FIGS. 1(a) to 1(P) are diagrams explaining the principle of the present invention. FIGS. 2(a) to 2(d) are diagrams illustrating an embodiment of the present invention. In fig. 1 is a silicon substrate. 2 is the alignment mark. 3 is a SiO□ film. 4 is a diagram explaining the principle of the shrimp layer of the present invention Male Figure 1 (Part 1) (k) (o) (fl) (p) -7~-1 Figure 1 (Part 2) of the principle explanatory diagram of the present invention Figure 1

Claims (1)

[Claims] 1) A semiconductor device characterized in that when aligning a photomask and a wafer in an exposure process, the alignment is performed after roughening the surface of an alignment mark formed on the wafer. manufacturing method. 2) The method of manufacturing a semiconductor device according to claim 1, wherein the surface roughening treatment is performed by bombarding the surface of the alignment mark with ions.