JP2893693B2 - Misalignment measurement method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a misalignment for divided exposure, in which a surface of a substrate is divided into a plurality of regions and exposed separately.

[Summary of the Invention]

The present invention provides a method for measuring misalignment as described above, in which a pair of misalignment measurement marks each having a rectangular shape having four sides equal to each other is formed by forming a straight line passing through two opposing vertices into a plurality of regions. Are formed on both sides of the boundary line so that straight lines that are parallel to and at a predetermined distance from this boundary line and pass through the remaining vertices are straight, and are opposed to each other in these misalignment measurement marks. By determining the interval between straight lines passing through the vertices, it is possible to extremely easily measure the misalignment in the direction perpendicular and parallel to the boundary line.

[Conventional technology]

2. Description of the Related Art In order to satisfy the demand for fine processing by increasing the degree of integration of semiconductor devices, a reduced projection exposure apparatus is often used as an exposure apparatus for a semiconductor wafer.

On the other hand, the chip size has been increased with the increase in the degree of integration of the semiconductor device, and it has become impossible to expose the entirety of one chip by one exposure using the reduced projection exposure apparatus.

For this reason, it is necessary to divide the surface of one chip into a plurality of regions and separately expose them, for example, by forming the pattern of the photosensitive section and the pattern of the accumulation section of the CCD by separate exposure.

However, if the pattern of the photosensitive section formed by the separate exposure and the pattern of the storage section are not accurately connected at the boundary between them, transfer of signal charges and the like will be hindered. Therefore,
It is necessary to measure misalignment between patterns formed by separate exposures.

FIG. 2 and FIG. 3 show a conventional example of a misalignment measuring method for performing such a measurement. FIG.
A mark for measuring misalignment in the X direction, which is a direction perpendicular to the boundary between the divided areas, is shown.

In the first exposure, marks 11 and 12 are formed on the photoresist of the chip separately from the pattern (not shown) of the photosensitive portion of the CCD, and in the second exposure, the pattern (not shown) of the accumulation portion of the CCD and the like. Marks 13 and 14 are separately formed in the photoresist of the chip.

However, the width of the first exposure and the second exposure is 1 μm.
There is an overlapping zone 15 designed as described above, and a positive resist having high resolution and high contrast is used as a photoresist. Therefore, of the marks 11 and 13, the mark portions 11a and 13a included in the overlap zone 15 disappear by development.

The marks 11 to 14 are formed as a group at a plurality of locations along the overlapping zone 15 as shown in FIG.

The actually formed marks 11 to 14 are slightly smaller than the design values due to halation and the like. Thus, for the marks 11 and 13, for example, the actual values obtained by the length measurement SEM and the like are A ', B' and C 'with respect to the design values A, B and C.

To measure the misalignment in the X direction from the marks 11 and 13 thus formed, Is calculated.

To measure the misalignment in the X direction, originally,
The difference between the design value and the measured value of the marks 11 and 13 in the X direction should be used. However, as described above, the mark portions 11a and 13a have disappeared, and this difference cannot be obtained. For this reason, it is considered that the above difference is equal in the X direction and the Y direction, and the expression uses the difference in the Y direction.

FIG. 3 shows marks for measuring misalignment in the Y direction, which is a direction parallel to the boundary between the two divided areas. These marks 21 to 24 also overlap zone 15
Are formed at a plurality of locations along the line and at positions different from the marks 11 to 14.

The lengths A and B in the Y direction of the larger mark 21 and the smaller mark 23 are designed to be 3 μm and 2 μm, respectively, and the marks 23 and 24 are located at the center of the marks 21 and 22 in the Y direction. It is designed to be located. Therefore, the design value D is
0.5 μm.

To measure the misalignment in the Y direction from the marks 21 and 23 formed in this way, the difference between the design value D and the measured value D 'is obtained.

In this case as well, the difference between the actually formed marks 21 and 24 is smaller than the design value, but this difference does not appear in the measured value D ', as is apparent from FIG.

[Problems to be solved by the invention]

However, in the above-described conventional example, it is necessary to actually measure four values A ′ to D ′, and the calculation of the expression is somewhat complicated. Therefore, in the above-described conventional example, the misalignment cannot be easily measured.

[Means for solving the problem]

The method for measuring misregistration according to the present invention includes a method for measuring a pair of misregistration measurement marks 31 and 33 each having a rectangular shape having four sides equal to each other by forming straight lines 35a and 36a passing through two opposing vertices into a plurality of areas. Forming straight lines on both sides of the boundary line 15 so that straight lines 35b and 36b that are parallel to the boundary line 15 between each other and at a predetermined distance from the boundary line 15 and pass through the remaining vertices are straight, Straight lines 35a, 36a passing through the two vertexes of the pair of misalignment measurement marks 31, 33
A step of determining the difference between the measured value and the design value of the interval between the straight lines 35b passing through the remaining vertices of the pair of misalignment measurement marks 31 and 33, in a direction parallel to the boundary line 15 between the straight lines 35b and 36b. Obtaining an actual measured value of the interval.

[Action]

In the misalignment measuring method according to the present invention, a pair of misalignment measuring marks 31 and 33 each having a rectangular shape having four sides equal to each other are formed by forming straight lines 35a and 36a passing through two opposing vertices into a plurality of areas. Since it is formed on both sides of the boundary line 15 so as to be parallel to the boundary line 15 and at a predetermined distance from the boundary line 15, straight lines 35a and 36a passing through two vertices in each of the divided and exposed adjacent regions are formed. By calculating the difference between the measured value and the design value of the distance between the two, the misalignment in the direction (X) perpendicular to the boundary 15 can be measured.

In addition, the pair of misalignment measurement marks 31, 33 are formed on both sides of the boundary line 15 so that the straight lines 35b, 36b passing through the remaining vertices of the pair of misalignment measurement marks 31, 33 are aligned. Therefore, by determining the measured value of the interval in the direction parallel to the boundary 15 between the straight lines 35b and 36b passing through the remaining vertices in each of the divided and exposed adjacent regions, the direction parallel to the boundary 15 (Y) Can be measured.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to FIG.

Also in this embodiment, as shown in FIG. 1, in the first exposure, marks 31 and 32 for measuring misalignment are formed on the photoresist of the chip separately from a pattern (not shown) such as a photosensitive portion of a CCD. In the second exposure, marks 33 and 34 for measuring the misalignment different from the pattern (not shown) of the CCD storage portion and the like are formed in the photoresist of the chip.

Also in the present embodiment, the marks 31 to 34 are formed in a group as shown in FIG.

However, the marks 31 and 33 are square, and are designed such that lines 35a, 35b, 36a and 36b passing diagonally are in the X direction or the Y direction. Each of the patterns 31 to 34 is designed to have the dimensions shown in FIG.

In order to measure the misalignment in the X direction in this embodiment, the line selectors of the length measurement SEM are made to coincide with the lines 35a and 36a, and the distance between the two is actually measured. The difference from 3 μm is determined.

In the Y direction, if the distance between the lines 35b and 36b is measured by matching the line selector of the length measuring SEM to the lines 35b and 36b, the measured value is the actual misalignment in the Y direction.

Therefore, in the present embodiment, only two values of the distance between the lines 35a and 36a and the distance between the lines 35b and 36b need to be obtained as actual measurement for the formed marks 31 to 34, and the calculation for these values is very easy. . Therefore, in the present embodiment, the misalignment can be easily measured.

In this embodiment, the marks 31 to 34 actually formed are smaller than the design values. However, as is clear from FIG. 1, regardless of the size of the marks 31 to 34, the lines 35a, 35b, 36a, The position of 36b is unchanged.

Also, the marks 31 and 33 are symmetrical about the lines 35a and 36a, and when the photosensitive portion and the accumulation portion of the CCD are exposed too close in the X direction, the overlap zone of the marks 31 and 33 is formed.
The 15 side disappears as it is included in this overlapping zone 15.

Therefore, in this case, the marks around the lines 35a and 36a
By comparing the left and right dimensions of 31, 33, the misalignment in the X direction can also be measured.

In the present embodiment, the marks 31 and 33 are square,
Generally, these marks 31 and 33 may be rhombic.

〔The invention's effect〕

In the misalignment measurement mark according to the present invention, in each of the divided and exposed adjacent regions, an actual measurement value of a distance between straight lines passing through opposing vertices is obtained and a comparison with a design value is performed so that the boundary line is perpendicular and parallel to the boundary line. Since misalignment in any direction can be measured, the misalignment can be measured very easily.

[Brief description of the drawings]

FIG. 1 is a plan view of an embodiment of the present invention, and FIGS. 2 and 3 are plan views of a conventional example of the present invention. In the reference numerals used in the plan views, 15 are overlapping zones 31, 33 are marks 35a, 35b are lines 36a, 36b are lines.

Claims (1)

(57) [Claims] 1. A method for measuring misregistration for divided exposure in which a surface of a substrate is divided into a plurality of areas and separately exposed, wherein a pair of misalignment measuring marks having a quadrangular shape with four sides equal in length are formed. A straight line passing through the two vertices facing each other is parallel to the boundary between the plurality of regions and at a predetermined distance from this boundary, and the straight line passing through each of the remaining vertices is straight, Forming on both sides of the boundary line; obtaining a difference between a measured value and a design value of a distance between straight lines passing through the two vertexes in the pair of misalignment measurement marks; Obtaining an actual measured value of an interval in a direction parallel to the boundary line between straight lines passing through the remaining vertices in the measurement mark.