JPH10144746A - Pattern for superposition accuracy measurement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pattern for superposition accuracy measurement, which can measure superposition accuracy with high precision. SOLUTION: A pattern for superposition accuracy measurement is constituted of a first insular layer region 20 and a second insular layer region 22. The region 20 has a structure that the region 20 is provided with a slit-shaped reference groove 24 formed into a frame type. The groove width of this slit-shaped reference groove 24 is formed in a width of 1 to 2μm. The region 22 has a structure that the region 22 is provided with a slit-shaped joint groove 28 formed into a frame type. The groove width of this slit-shaped joint groove 28 is formed in a width of 1 to 2μm. These regions 20 and 22 are arranged into such a shape that when the pattern for superposition accuracy measurement is seen from above, the periphery of the frame, which is formed of he slit-shaped reference groove 24, is encircled by the frame, which is formed of the slit-shaped joint groove 28.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a pattern for measuring overlay accuracy for measuring the exposure position accuracy of a reduction projection exposure apparatus (hereinafter, referred to as a stepper) used in a photolithography step in manufacturing a semiconductor device. .

[0002]

2. Description of the Related Art In general, when a pattern on a mask is transferred onto a wafer by using a stepper, the mask is first aligned and a pattern already formed on the wafer (hereinafter, referred to as an existing pattern) is used. Match the positional relationship with the pattern on the mask. Thereafter, the entire mask is irradiated with light to expose the resist.

[0003] The registration accuracy of the resist pattern formed by transferring the pattern on the mask and the existing pattern (ie, the exposure position accuracy of the stepper) is adjusted by using a registration accuracy measurement pattern (overlay) specially prepared on the wafer. (Sometimes referred to as a target) (Reference 1: “Innovation in ULSI lithography technology, Science Forum, p349-355, 199”).
4 "). Usually, the pattern for overlay accuracy measurement is
Each shot (chip) is formed in a region other than a region where a semiconductor device is formed on a so-called base such as a wafer or a structure in which a required film is formed on the wafer. The pattern for measuring overlay accuracy includes a reference box (also referred to as a reference layer box or a lower layer box) and a matching box (also referred to as a matching layer box or an upper layer box).
The reference box is formed before a certain circuit pattern is formed, and thereafter, a registration box is formed simultaneously with the formation of a resist pattern for forming the circuit pattern, thereby forming the pattern for measuring overlay accuracy.

FIG. 8 shows a conventionally used convex reference box 10 (FIG. 8A) and a concave reference box 12.
FIG. 9 is a schematic plan view showing the planar shape of FIG. 8 (B). FIG. 9 shows a conventionally used convex matching box 14 (FIG. 9A) and a concave matching box 16.
It is a schematic plan view which shows the planar shape of (FIG.9 (B)). In FIGS. 8 and 9, hatched portions are the convex portions 10, 12 b, and 14.
b, 16b, and 16c, and the hatching does not indicate a cross section. In addition, the concave portions are 12a, 14a, 1
6a.

FIG. 10 shows the cross-sectional shape of a pattern for measuring overlay accuracy provided on the base 17 by combining the convex and concave reference boxes of FIG. 8 and the convex and concave matching boxes of FIG. FIG. 10A is a schematic cross-sectional view showing a pattern for measuring overlay accuracy composed of a convex reference box 10 and a convex alignment box 14, and FIG. FIG. 10 is a schematic cross-sectional view showing an overlay accuracy measurement pattern composed of a reference box 10 and a concave alignment box 16;
FIG. 10C is a schematic cross-sectional view showing an overlay measurement pattern composed of a concave reference box 12 and a convex alignment box 14, and FIG. 10D is a concave reference box 12 and a concave alignment box. FIG. 4 is a schematic cross-sectional view showing a pattern for measuring overlay accuracy constituted by a matching box 16 of FIG. However, FIGS. 10A to 10D show a case where an intermediate film 18 is interposed between the reference boxes 10 and 12 and the matching boxes 14 and 16.

Generally, when measuring the overlay accuracy,
A light intensity profile of the reflected light from the pattern for measuring overlay accuracy is measured using an overlay measuring device of an optical image processing system. Then, from this light intensity profile, the left and right edge positions of the reference box and the matching box (the boundary positions of the irregularities, that is, the positions of the step portions of the irregularities) are detected. After detecting the edge position, the center position of the reference box and the center position of the matching box are calculated based on the detected edge position. Then, the shift between these center positions is defined as the overlay accuracy.

[0007]

However, when the above-described conventional pattern for measuring overlay accuracy is used,
The light intensity profile at the edge position may not be symmetrical between the right edge and the left edge, for example, due to the unevenness of the shape of the step portion of the unevenness of the reference box and the alignment box. The light intensity profile at the edge position of the box may be different for each shot (chip).

For this reason, the detection accuracy of the edge position detected from the light intensity profile is low, and as a result, the measurement accuracy of the overlay accuracy is low.

Therefore, the appearance of a pattern for measuring overlay accuracy capable of measuring overlay accuracy with high accuracy has been desired.

[0010]

According to the pattern for measuring overlay accuracy of the present invention, a first island-shaped region provided on a base and forming a reference box, and a first island-shaped region formed of the first island-shaped region are formed. In an overlay accuracy measurement pattern including a second island-shaped layer region provided on the upper side with an intermediate film therebetween and forming a matching box, one or both of the first and second island-shaped layer regions is , Two slit-shaped grooves spaced apart from each other, and each of these grooves has a profile in which the light intensity profile of light reflected by these grooves with respect to incident light for overlay accuracy measurement is formed by one edge. It is characterized by having a groove width of a size that can be considered as.

When the pattern for measuring overlay accuracy has such a structure, when light for measurement is scanned and incident on each box, the light intensity profile of the reflected light from the position of the slit-shaped groove is changed. As if it were like a light intensity profile of the reflected light from one edge, the detection accuracy of the edge position, that is, the groove position is improved. as a result,
It is possible to accurately measure the overlay accuracy of the existing circuit pattern formed in the reference box forming step and the resist pattern formed in the matching box forming step. This is because when observing the light intensity distribution of the reflected light from the position of the slit-shaped groove, the groove itself acts as if it were an edge, and this light intensity change becomes steep. The light intensity profile at the position (groove position) and the light intensity profile at the left edge position (groove position) are similar to reduce the asymmetry of the two, and each shot of the light intensity profile at the box edge position (groove position) This is because variation among (chips) is reduced.

According to the present invention, it is preferable that the grooves provided at two places are formed by one rectangular frame-shaped groove. By forming the grooves in this manner, the direction of optical scanning for measuring accuracy can be set in any direction.

In the above-described pattern for measuring overlay accuracy according to the present invention, in order to obtain a steep change in light intensity at which preferable measurement accuracy is obtained, the width of the slit-like groove must be within a range of 1-2 μm. It is preferable to use a value. This is because if the width of the groove is too narrow, the contrast of the reflected light from the position of the slit-like groove becomes small. On the other hand, if the width of the groove is too wide, when the film on which the groove is formed is covered with another film, another film enters the groove and the position of the groove becomes unclear.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. In each of the drawings used in the following description, each component merely schematically shows its shape, size, and positional relationship so that the present invention can be understood. Further, in each of the drawings used for description, the same components are denoted by the same reference numerals. Therefore, it should be understood that the present invention is not limited to the embodiments described below.

FIG. 1 and FIG. 2 are schematic views for explaining a pattern for measuring overlay accuracy according to this embodiment. FIG. 1A is a schematic plan view showing the planar shape of the pattern for measuring overlay accuracy according to this embodiment, and FIG. 1B is a view along the line II in FIG. 1A. Schematic cross-sectional view showing the cross-sectional shape taken (however, a cutaway view)
FIG. 2A is a schematic plan view showing the planar shape of the first island-like layer region constituting the pattern for measuring overlay accuracy of this embodiment, and FIG. FIG. 4 is a schematic plan view showing a planar shape of a second island-like layer region forming a pattern for measuring overlay accuracy according to the embodiment.

As shown in FIGS. 1 (A) and 1 (B), the pattern for measuring overlay accuracy according to this embodiment is a first pattern.
It is composed of an island-shaped layer region 20 and a second island-shaped layer region 22.

FIGS. 1A and 1B and FIG. 2A
As shown in (1), the first island-shaped layer region 20 has a structure including a slit-shaped reference groove 24 formed in a frame shape. The groove width of the slit-shaped reference groove 24 is 1 to 2 μm.
The shape of the frame formed by the reference groove 24 is a square having a side of about 15 μm. First island-shaped layer region 20
Are provided on the base 26.

FIGS. 1A and 1B and FIG. 2B
As shown in FIG. 5, the second island-shaped layer region 22 has a structure including a slit-shaped alignment groove 28 formed in a frame shape. The groove width of the slit-shaped alignment groove 28 is 1-2.
μm, and the shape of the frame formed by the alignment grooves 28 is a square having a side of about 30 μm. The second island-shaped layer region is provided on the intermediate film 30 that covers the first island-shaped layer region 20.

As shown in FIG. 1A, the first island-like region 20 and the second island-like region 22 form slit-like reference grooves 24 when the pattern for measuring overlay accuracy is viewed from above. Are arranged so that the frame formed by the slit-shaped matching groove 28 surrounds the frame formed by the frame.

The pattern for measuring the overlay accuracy shown in FIG. 1A is hatched except for the region where the alignment groove 28 is formed. FIG. 2 (A)
The reference box shown in FIG. 7 is hatched except for a region where the reference groove 24 is formed. FIG.
The matching box shown in (B) is hatched except for the region where the matching groove 28 is formed. These hatchings do not indicate sections.

The pattern for measuring overlay accuracy of this embodiment having such a structure is formed at the same time as processing an insulating film, a metal film, a resist film, and the like in order to manufacture a semiconductor device. You. For example, the first island-shaped region 20
Is formed at the same time when a certain circuit pattern is formed on the base 26 using an etching technique. In addition, the second island-shaped layer region 22 is formed at the same time as forming a resist pattern as a mask used for etching the intermediate film 30 provided on the circuit pattern using the photolithography technique and the etching technique. Is done.

Generally, when measuring the overlay accuracy,
A light intensity profile of the reflected light from the pattern for measuring overlay accuracy is measured using an overlay measuring device of an optical image processing system. Thereafter, the left and right edge positions of the reference box and the matching box (the boundary positions of the unevenness, that is, the positions of the step portions of the unevenness) are detected from the light intensity profile. After detecting the edge position, the center position of the reference box and the center position of the matching box are calculated based on the detected edge position. Then, the shift between these center positions is defined as the overlay accuracy.

When the overlay accuracy is measured by the above-described method using the overlay accuracy measuring pattern of this embodiment, the slit-like reference groove 24 and the alignment groove 28 are used.
When the reference groove 24 is set as the edge of the reference box and the matching groove 28 is set as the edge of the matching box, the change in the light intensity of the reflected light from the position is sharp. The light intensity profile at the left edge position (groove position) is similar to the light intensity profile, reducing the asymmetry of the two, and for each shot (chip) of the light intensity profile at the edge position (groove position) of each box. Is reduced. For this reason, the detection accuracy of the edge position, that is, the groove position is increased, and as a result, the accuracy of the overlay of the existing circuit pattern formed in the reference box forming process with the resist pattern formed in the matching box forming process is improved. It becomes possible to measure well.

Next, a change in the light intensity of the reflected light from the position of the slit-shaped groove and the reflected light from the edge position of the conventionally used concave box (the boundary position of the unevenness, that is, the position of the step portion of the unevenness). This will be described in comparison with the change in light intensity.

FIG. 3A is a schematic plan view showing the planar shape of the pattern for measuring the overlay accuracy used for measuring the change in the light intensity of the reflected light from the position of the slit groove.
FIG. 3B is a schematic cross-sectional view (a cutaway view) showing a cross-sectional shape taken along the line II in FIG. 3A. As shown in FIGS. 3A and 3B, the overlay accuracy measurement pattern used for the measurement includes a convex reference box 32 and two slit-shaped alignment grooves formed in a frame shape. Structure matching box 34
(Hereinafter, one of the mating grooves is referred to as an inner mating groove 36a,
The other alignment groove is referred to as an outer alignment groove 36b. ). Slit-shaped inner matching groove 3
The groove width of 6a and the outer alignment groove 36b is about 1-2 μm. The reference box 32 is provided on a base (not shown), and the matching box 34 is provided on an intermediate film 38 covering the reference box 32. The reference box 32 and the alignment box 34 are surrounded by a frame formed by a slit-shaped inner alignment groove 36a around the reference box 32 when the overlay accuracy measurement pattern is viewed from above, and the outer side is further slit-shaped. Are arranged so as to surround the frame formed by the outer alignment groove 36b. Here, the reference box 32 is formed of a polysilicon film 32x having a thickness of 1500Å and a tungsten (W) -silicon (Si) alloy film 32y having a thickness of 1000Å provided thereon. The matching box 34 is made of a resist film having a thickness of 12000 °. The intermediate film 38 is formed of an insulating film having a thickness of 16000 degrees and formed using BPSG and NSG. Note that FIG.
The pattern for measuring the overlay accuracy shown in (A) is hatched except for the region where the inner alignment groove 36a and the outer alignment groove 36b are formed. This hatching does not indicate a cross section.

FIG. 4 shows a measurement result of a change in the light intensity of the reflected light from the position of the slit-like groove. The light intensity profile at the position surrounded by a rectangular broken line indicated by R in FIG. , L, and the light intensity profile at the position surrounded by the rectangular dashed line are combined and shown at the position C in FIG. The light intensity profile shown on the right side of the position C in FIG. 4 is the light intensity profile at the R position,
The light intensity profile shown on the left side of the position C is the light intensity profile at the position L. In FIG. 4, the vertical axis indicates light intensity, and the horizontal axis indicates position.

FIG. 5A is a schematic plan view showing the planar shape of the pattern for measuring the overlay accuracy used for measuring the change in the light intensity of the reflected light from the edge position of the concave box. 5B is a schematic cross-sectional view (a cutaway view) showing a cross-sectional shape taken along the line II in FIG. 5A. As shown in FIGS. 5A and 5B, the overlay accuracy measurement pattern used for the measurement includes a convex reference box 32 and a concave alignment box. The width of the recess 34a is about 10 μm. The reference box 32 is a base (not shown)
The matching box 34 is provided on an intermediate film 38 that covers the reference box 32. And
The reference box 32 and the alignment box 34 are arranged so that the recess 34a of the alignment box 34 surrounds the reference box 32 when the overlay accuracy measurement pattern is viewed from above. Here, the reference box 32 is composed of a 1500 ° thick polysilicon film 32x and a 1000 ° thick tungsten (W) -silicon (Si) alloy film 32y provided thereon. The matching box 34 is made of a 10000-thick resist film. The intermediate film 38 is made of BPSG and NS.
It is composed of an insulating film having a thickness of 9000 ° formed using G. The pattern for measuring the overlay accuracy shown in FIG. 5A is hatched except for the region where the concave portion 34a is formed. This hatching does not indicate a cross section.

FIG. 6 shows the measurement results of the change in the light intensity of the reflected light from the edge position of the concave box.
(A) shows a light intensity profile at a position surrounded by a rectangular broken line indicated by R and a light intensity profile at a position surrounded by a rectangular broken line indicated by L at a position C in the figure. . The light intensity profile shown on the right side of the position C in FIG. 6 is the light intensity profile at the R position, and the light intensity profile shown on the left side of the position C is L.
It is a light intensity profile in a position. In FIG. 6, the vertical axis indicates light intensity, and the horizontal axis indicates position.

By comparing the result shown in FIG. 4 with the result shown in FIG. 6, the change in the light intensity of the reflected light from the position of the slit-like groove indicates the light intensity of the reflected light from the edge position of the concave box. It can be seen that it is sharper than the change.
In addition, it can be understood that the light intensity profile of the reflected light from the position of the slit-shaped groove looks like the light intensity profile of the reflected light from one edge.

It is clear that the present invention is not limited to the above embodiment. For example, in this embodiment, a case has been described in which both the first and second island-shaped layer regions have a structure having a slit-shaped groove, but a structure having only one of them has a slit-shaped groove. May be used. FIG. 7 shows an overlay accuracy measurement pattern having a structure in which only one of the first and second island-like layer regions has a slit-like groove, that is, an overlay accuracy measurement pattern of this embodiment provided on the base 40. FIG. 7 shows a cross-sectional shape of a modification of the application pattern.
(A) is a conventionally used convex reference box (first type).
FIG. 7B is a schematic cross-sectional view showing a pattern for measuring overlay accuracy composed of an island-shaped layer region 10 and the second island-shaped layer region 22 shown in this embodiment, and FIG. Concave reference box (first island layer region) 12
FIG. 7C is a schematic cross-sectional view showing a pattern for measuring overlay accuracy composed of the second island-like layer region 22 shown in this embodiment, and FIG. FIG. 7 is a schematic cross-sectional view showing a pattern for measuring overlay accuracy, which is composed of a pattern layer region 20 and a conventionally used convex matching box (second island layer region) 14;
(D) shows the first island-shaped region 20 of this embodiment and a concave matching box (second island-shaped region) conventionally used.
16 is a schematic cross-sectional view showing an overlay accuracy measurement pattern composed of No. 16 and FIG. However, FIG.
(D) shows the case where the intermediate film 42 is interposed between the first island-shaped region and the second island-shaped region.

[0031]

As is apparent from the above description, according to the pattern for measuring overlay accuracy of the present invention, one or both of the first and second island-like regions are located at two places separated from each other. Each of the grooves has a size such that a light intensity profile of light reflected by the grooves with respect to incident light for overlay accuracy measurement can be regarded as a profile formed by one edge. The structure has a groove width.

When the pattern for measuring overlay accuracy has such a structure, the use of the slit-like groove as the edge of the box increases the detection accuracy of the edge position and thus the groove position, and as a result, the formation of the reference box It is possible to accurately measure the overlay accuracy of the existing circuit pattern formed in the process and the resist pattern formed in the process of forming the alignment box.

[Brief description of the drawings]

FIG. 1A is a schematic plan view showing a pattern for measuring overlay accuracy according to an embodiment, and FIG. 1B is a schematic view taken along line II in FIG. FIG.

FIG. 2A is a schematic plan view showing a reference box forming a pattern for measuring overlay accuracy according to the embodiment, and FIG. 2B is a diagram illustrating a pattern for measuring overlay accuracy according to the embodiment; It is a schematic plan view which shows an alignment box.

3A is a schematic plan view showing a pattern for measuring overlay accuracy used for measuring a change in light intensity of reflected light from a position of a slit-like groove, and FIG. 3B is a plan view of FIG. It is the schematic sectional drawing cut | disconnected along the II line in the inside.

FIG. 4 is a measurement result of a change in light intensity of reflected light from a position of a slit-shaped groove.

5A is a schematic plan view showing a pattern for measuring overlay accuracy used for measuring a change in light intensity of reflected light from an edge position of a concave box, and FIG. 5B is a schematic plan view of FIG. It is the schematic sectional drawing cut | disconnected along the II line in the inside.

FIG. 6 is a measurement result of a light intensity change of reflected light from an edge position of a concave box.

FIGS. 7A to 7D are schematic cross-sectional views showing modified examples of the pattern for measuring overlay accuracy according to the embodiment.

FIGS. 8A and 8B are schematic plan views showing a reference box conventionally used.

9 (A) and 9 (B) are schematic plan views showing a conventionally used matching box.

10A to 10D are schematic cross-sectional views showing a conventional pattern for measuring overlay accuracy.

[Explanation of symbols]

 20: first island-like region 22: second island-like region 24: reference groove 26: base 28: alignment groove 30: intermediate film

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tokio Shino 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd.

Claims (3)

[Claims] 1. A first island-shaped region provided on a lower ground to form a reference box, and a first island-shaped region provided above the first island-shaped region via an intermediate film to form a matching box. In a pattern for measuring overlay accuracy comprising two island-shaped regions, one or both of the first and second island-shaped regions include slit-shaped grooves at two locations separated from each other, Each of these grooves has a groove width large enough that a light intensity profile of light reflected by these grooves with respect to incident light for overlay accuracy measurement can be regarded as a profile formed by one edge. A pattern for measuring overlay accuracy characterized by the following. 2. The pattern for measuring overlay accuracy according to claim 1, wherein the two grooves are formed by a single rectangular frame-shaped groove. . 3. The pattern for measuring overlay accuracy according to claim 1, wherein the width of the groove is a value within a range of 1 to 2 μm.