JPH05182884A - Alignment mark - Google Patents

Abstract

PURPOSE:To accurately perform a mark alignment operation by a method wherein a fine dislocation between two marks is made sensitively clear. CONSTITUTION:A first alignment mark 10 is composed of eight squares 11 to 18 which are composed of four transverse rows in two longitudinal columns; three longitudinal straight-line gaps 19a to 19c and one transverse straight-line gap 19d are formed. In a second alignment mark 20, three longitudinal straight- line belt-shaped parts 21 to 23 are crossed at three parts in the lengthwise direction of one transverse straight-line belt-shaped part 24. The corresponding straight-line belt-shaped part 24 is situated in the center at the straight gap 19b in the center of the first alignment mark 10; the corresponding straight-line belt-shaped parts 21, 23 are situated so as to be displaced to one side in the straight-line gaps 19a, 19c on both sides. When the degree of a dislocation is compared in the center and on both sides, a fine dislocation in the straight- line belt-shaped part at the straight-line gap in the center can be made sensitively clear.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alignment mark used for mask alignment in the process of forming a circuit pattern on the surface of a semiconductor substrate by a photolithography technique using a plurality of masks.

[0002]

2. Description of the Related Art As conventional alignment marks of this type, there are those shown in FIGS. 3 and 4, for example. In the figure, A is a first alignment mark, B is a second alignment mark, and the first alignment mark A is provided on, for example, a mask used in the first pattern transfer,
The second alignment mark B is provided on the mask used during the second and subsequent pattern transfer.

Specifically, the first alignment mark A
Is a square in the case of FIG. 3 and “+” in the case of FIG.
The second alignment mark B is formed in a "b" shape in FIG. 3 and in a shape in which four squares are arranged vertically and horizontally in FIG. 4, respectively.

At the time of the first pattern transfer, the pattern provided on the first mask and the first alignment mark A are transferred and formed on the surface of the semiconductor wafer, and the first alignment mark A formed on the semiconductor wafer is transferred. Then, the second alignment marks B provided on the second and subsequent masks are vertically overlapped. In this state,
First alignment mark A and second alignment mark B
Visually match through a microscope so that the linear gaps between and are equal.

[0005]

By the way, in the above-mentioned conventional example, since the vertical and horizontal linear gaps formed between both marks are set to the same size, even if the respective linear gaps are slightly deviated, It is pointed out that it is difficult to accurately perform mark alignment, such as it is difficult to visually perceive slight deviations.

The present invention has been devised to solve such a problem, and aims to make it possible to accurately perform mark alignment by making it possible to intuitively understand a slight deviation between two marks. To aim.

[0007]

In order to achieve the above object, the present invention provides a pair used for mask alignment in the process of forming a circuit pattern on the surface of a semiconductor substrate by a photolithography technique using a plurality of masks. The alignment mark has the following configuration.

The alignment mark of the present invention includes a first alignment mark provided on the first mask and transferred onto the surface of the semiconductor substrate by using the first mask, and an alignment mark provided on the second mask and on the semiconductor substrate. A combination of a first alignment mark and a second alignment mark that is vertically overlapped with each other. The one alignment mark is arranged in a line so that vertical and horizontal sides are parallel to each other and a linear gap is formed between them. Consists of at least four rectangular portions, the other alignment mark consists of at least three linear strips arranged so as to be parallel to each other, and in the state where both alignment marks are superposed, the four rectangles The above three linear strips are located in the three linear gaps formed by the Only strip portion is disposed in the center of the linear gap in the middle, straight strip portions on both sides are arranged offset to one side of the straight line gap corresponds.

[0009]

According to the present invention, by aligning the three linear strip portions, which are the other alignment marks, with the three linear gaps formed by the four rectangular portions, which are the one alignment mark, the alignment is performed. I do.

The proper arrangement of the linear strips in each linear gap means that the corresponding linear strips are located at the center in the middle linear gap, and the corresponding linear strips are located in the linear gaps on both sides. Refers to a form in which is biased to one side. Positioning is performed so as to approach this proper arrangement state.

As described above, in the case where only one of the middle of the three linear strips is located at the center of the linear gap in the middle, the degree of misalignment between the middle and both sides can be compared. Since it is possible, even if there is a slight positional deviation between the linear gap in the center and the linear strip, it becomes easy to visually understand.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

1 and 2 show an embodiment of the present invention. In the figure, 10 is a first alignment mark, and 20 is a second alignment mark.

The first alignment mark 10 is composed of eight squares 11 to 18 which are arranged in two rows and four columns so that the vertical and horizontal sides thereof are parallel to each other, and between the eight squares 11 to 18, respectively. Is a vertical linear gap 19a-
19c and a horizontal linear gap 19d are formed.
The intervals of these linear gaps 19a to 19d are all set to the same size.

The second alignment mark 20 is composed of three vertical linear strip portions 21 to 23 and one horizontal linear strip portion 24. The vertical linear strip portions 21 to 23 are horizontal linear strip portions. 24 intersect at three points in the longitudinal direction. The widths of these linear strip portions 21 to 24 are all set to the same dimension.

In the three linear gaps 19a to 19c of the first alignment mark 10, the second alignment mark 2 is formed.
When the three linear strip portions 21 to 23, which are 0, are positioned in association with each other, the corresponding linear strip portion 22 is located in the center in the middle linear gap 19b, and the linear gaps 19 on both sides are located.
In a and 19c, the corresponding linear strip portions 21 and 23 are set to be biased to one side. In the linear gap 19a on the left side of the figure, the linear strip portion 21 is biased to the right side of the figure, and in the linear groove 19c on the right side of the figure, the linear strip portion 23 is biased to the left side of the figure. This arrangement state is defined as an appropriate state.

Next, a mask alignment operation for transferring and forming a circuit pattern on the surface of a semiconductor wafer by the photolithography technique will be described.

First, at a predetermined position above a semiconductor wafer coated with a photoresist, a first mask having the above-described first alignment marks 10 at its four corners is arranged together with a circuit pattern (not shown). The photoresist on the semiconductor wafer is exposed to light from above the first mask and then developed to pattern the photoresist. By performing etching using this photoresist as a mask, the circuit pattern of the first mask and the first alignment mark 10 are transferred and formed on the surface of the semiconductor wafer.

The above-mentioned second alignment mark 20 is drawn on the mask used in the pattern transfer after the first-step pattern transfer. Therefore, after the second time, the front and rear circuit patterns are relatively aligned by aligning the second alignment mark 20 on the mask side with the first alignment mark 10 transferred and formed on the semiconductor wafer first. Of.

By the way, when the arrangement of the linear strip portions 21 to 23 of the second alignment mark 20 in the three linear gaps 19a to 19c of the first alignment mark 10 is not proper, the degree of misalignment between the center and both sides is determined. By comparison, the positional deviation between the marks 10 and 20 is easier to see visually than in the conventional example, so that the positioning can be performed easily and accurately.

The present invention is not limited to the above embodiment. For example, it is assumed that the first alignment mark 10 is composed of sixteen squares arranged in four horizontal and four vertical, and the second alignment mark 20 is composed of a total of six linear strips of three vertical and three horizontal. Good. Further, other forms of these combinations will not be specifically described, but it goes without saying that various forms can be considered.

[0022]

As described above, according to the present invention, when the linear strip portion corresponding to the straight linear gap is located at the center of the middle linear gap among the three linear gaps, the linear strips corresponding to the linear gaps on both sides are formed. Since the parts are located eccentrically, by comparing the degree of misalignment between the middle and both sides, a slight misalignment between the straight line gap in the middle and the corresponding linear strip can be visually recognized. It becomes easy to understand.

Therefore, according to the present invention, a pair of alignment marks can be easily and accurately aligned, and the reproducibility of transferring a circuit pattern onto a semiconductor wafer can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing first and second alignment marks according to an embodiment of the present invention.

FIG. 2 is a plan view showing first and second alignment marks that are vertically stacked.

FIG. 3 is a diagram corresponding to FIG. 2 according to a first conventional example.

FIG. 4 is a diagram corresponding to FIG. 2 according to a second conventional example.

[Explanation of symbols]

 10 1st alignment mark 11-18 Square part 19a-19c Linear gap 20 2nd alignment mark 21-23 Linear strip part

Claims (1)

[Claims] 1. A pair of alignment marks used for mask alignment in the process of forming a circuit pattern on the surface of a semiconductor substrate by a photolithography technique using a plurality of masks, the alignment marks being provided on the first mask and A first alignment mark transferred onto the surface of the semiconductor substrate using one mask;
A combination of a second alignment mark provided on a second mask and vertically overlapped with a first alignment mark on the semiconductor substrate, wherein the one alignment mark has vertical and horizontal sides parallel to each other. Between at least four rectangular portions arranged in a line so as to form a linear gap between them, and the other alignment mark consists of at least three linear strip portions arranged so as to be parallel to each other. In the state where the marks are overlapped, the three linear strips are located in the three linear gaps formed by the four rectangular portions, and only the middle straight strip is located in the center of the straight gap in the middle. Are arranged, and the linear strip portions on both sides are arranged so as to be biased to one side of the corresponding linear gaps. Instrument mark.