JPH1187209A - Method for projecting and exposing charged particle beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To project and expose a high density circuit pattern without lowering the throughput. SOLUTION: A low density repetition pattern consisting of rectangular patterns B1 is extracted from a high density repetition pattern for a substrate pattern consisting of rectangular patterns B1 and B2, so that the pattern density on a mask 5 is settled at a value which is sufficient for maintaining the strength of the mask 5. A repetition pattern consisting of rectangular patterns 510M, having the same density as that of the low density repetition pattern, is formed on the mask 5. Exposure is performed by superposing the mask 5 on a wafer 11, so that projection positions of the repetition of patterns 510M are shifted relative to a same exposure region 210 as that of the wafer 11. In this way, a high density substrate pattern can be formed with only a single mask 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam projection exposure method suitable when a pattern to be formed on a sensitive substrate has a high density. More specifically, the present invention relates to a charged particle beam projection exposure method for forming a pattern having a density so high that it is impossible to form a pattern on one mask on a mask strength, on a sensitive substrate.

[0002]

2. Description of the Related Art There is known an exposure method for forming a repetitive pattern such as a circuit pattern of a DRAM on a wafer coated with a resist using a charged particle beam. In this exposure method, a repetitive pattern corresponding to a DRAM circuit pattern is formed on a stencil mask, and the mask is irradiated with a charged particle beam to repeatedly project and expose an image of the repetitive pattern onto a wafer. When the density of the repetitive pattern on the wafer increases, the density of the repetitive pattern on the mask also increases, and the distance between the holes that form the pattern on the mask becomes extremely fine. There is a risk that it will.

For example, assuming that a repetitive pattern having a density as shown in FIG. 5A is formed on a wafer W, a pattern is formed on a mask M at a density as shown in FIG. There is a need. Here, when a boron-doped Si thin film having a thickness of 5 μm is used as a stencil mask, the internal stress generated in the Si thin film before the hole is formed is several hundred MPa, but as shown in FIG. When a hole is formed to form a simple pattern, the internal stress reaches several thousand MPa, and the thin film is broken with a Si thin film whose strength against breakage is several hundred MPa.

Therefore, conventionally, a mask in which a repetitive pattern is formed by white holes A1 in FIG.
A mask having a repetitive pattern formed by hatched holes A2 must be manufactured as a so-called complementary mask. That is, as shown in FIG. 5A, an island-shaped pattern B1 is formed on the wafer W using a mask having holes A1.
Is replaced with a mask having holes A2, and the wafer W is exposed to the island pattern B2 with the mask. Therefore, in the pattern exposure step, there is a problem that the throughput is reduced due to the mask replacement work time.

An object of the present invention is to provide a charged particle beam projection exposure method suitable for a case where a pattern to be formed on a sensitive substrate has a high density.

[0006]

An embodiment of the present invention will be described with reference to FIG. (1) The invention according to claim 1 is a method of projecting and exposing a pattern on a mask 5 on a sensitive substrate 11 at a predetermined reduction rate, wherein the density is equivalent to the density of a substrate pattern to be formed on the sensitive substrate 11. The method is applied to the charged particle beam projection exposure method in the case where the substrate pattern is so dense that the formation of a pattern on the mask 5 is unacceptable in terms of strength. Then, a low-density repetition pattern B1 is extracted from the high-density repetition patterns B1 and B2 of the substrate pattern so that the density of the pattern on the mask 5 becomes an acceptable value in terms of the mask strength. A high-density substrate is formed by forming a repetitive pattern on the mask 5 at a density equivalent to the repetitive pattern B1 and overlappingly exposing the same exposure region 210 of the sensitive substrate 11 while shifting the projection position of the repetitive pattern of the mask 5. A pattern is formed, thereby achieving the above object. (2) According to a second aspect of the invention, in the projection exposure method of the first aspect, at the time of overlapping exposure, the position of the mask 5 with respect to the same exposure region is shifted to shift the projection position of a low-density repetitive pattern with respect to the same exposure region. Things. (3) In the projection exposure method according to the first aspect of the present invention, at the time of the overlay exposure, the amount of deflection of the charged beam transmitted by irradiating the mask 5 is changed at a low density for the same exposure area. This shifts the projection position of the pattern. (4) The invention according to claim 4 is a method for projecting and exposing a pattern on the mask 5 on the sensitive substrate 11 at a predetermined reduction ratio, wherein the density is equivalent to the density of the substrate pattern to be formed on the sensitive substrate 11. The method is applied to the charged particle beam projection exposure method in the case where the substrate pattern is so dense that the formation of a pattern on the mask 5 is unacceptable in terms of strength. Then, at least the first and second low-density repetitive patterns are extracted from the high-density repetitive patterns of the substrate pattern so that the density of the pattern on the mask 5 becomes an acceptable value for the strength of the mask 5. A different repeating pattern is formed on at least the first and second masks 5 at a density equivalent to the first and second low-density repeating patterns, respectively. The above-described object is achieved by forming a high-density substrate pattern by performing overlapping exposure while shifting the projection position of the repeated pattern of the second mask 5.

[0007] In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments of the present invention are used to make the present invention easy to understand. However, the present invention is not limited to the embodiment.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. An outline of the whole charged particle beam projection apparatus used in the projection method according to the present invention will be described with reference to FIG. The charged beam B emitted from the charged particle beam source 1 is turned on / off by a beam blanker 3. Control amplifier 3a
When the beam blanker 3 is turned on based on the above signal, the charged beam B is focused by the condenser lens 2 and irradiated on the mask 5. The charged beam B that has passed through the condenser lens 2 is deflected by the field selection deflector 4 and guided to one of a plurality of subfields 510 (described later) formed on the mask 5. The mask 5 is a mask stage 6
And horizontally moved in the x-axis and y-axis directions. The mask stage 6 is driven by a driving device 7.

The charged beam B that has passed through the mask 5 is deflected in the x-axis and y-axis directions by a deflector 8, and is irradiated on a predetermined projection area of a wafer 11 via a projection lens 9 and a deflector 10. At this time, the position of the charged beam B on the wafer 11 is corrected by the deflector 10. Note that the deflector 10 can be constituted by an electrostatic deflector or an electromagnetic deflector. The wafer 11 is held on the wafer stage 12 and x
It is moved horizontally in the axis and y-axis directions. The wafer stage 12 is driven by a driving device 13.

[0010] Mask stage 6 and wafer stage 1
The positions in the x-axis and y-axis directions of 2 are detected by position detectors 14 and 15 such as a laser interferometer, respectively, and the detection results are sent to a control device 16. Data related to the mask 5 is input to the control device 16 in advance, and based on the data and the detection results by the position detectors 14 and 15 described above, the deflectors 4, 8 and 10, the beam blanker 3, the stage 6 and the 12 and the like are controlled. The control signal of the control device 16 is output to the deflector setting devices 17, 18, 19 provided in the deflectors 4, 8, 10 and the drivers 20, 21 of the driving devices 7, 13, respectively. Note that the following description is based on the assumption that the reduction ratio of the exposure apparatus is 1/5.

As shown in FIG. 2A, a plurality of chip areas 21 are set on the wafer 11 shown in FIG. In the chip area 21, for example, a DRAM is formed. These chip areas 21 are divided into main fields 21a and 21b, and each of the main fields 21a and 21b is 1 μm.
It is divided into a plurality of subfields 210 of m × 1 μm. As shown in FIG. 3A, rectangular sub-patterns 210M having a size of 0.05 μm × 0.1 μm are arranged in this sub-field at a pitch of 0.1 μm vertically and horizontally (distance between centers of adjacent micro-patterns 210M). Have been. This pattern is a pattern used as a gate in a DRAM.

The mask 5 shown in FIG. 1 is a stencil mask formed by patterning holes through which a charged beam passes through a membrane made of silicon. As shown in FIG. 2B, a rectangular pattern area 51 having a similar shape to the chip area 21 on the wafer 11 is set in the stencil mask 5. For example, if the size of the chip area 21 on the wafer 11 is Mmm × Lmm, the size of the pattern area 51 on the mask 5 is 5 Mmm × 5Lmm. The pattern area 51 has two rectangular main fields 51a, 5a.
1b, and further divided into main fields 51a, 51
Each of b is divided into rectangular subfields 510 of 5 μm × 5 μm. This subfield contains
As shown in (b), rectangular micropatterns 510M having a size of 0.25 μm × 0.5 μm are arranged at a pitch of 1.0 μm vertically and horizontally (distance between centers of adjacent micropatterns 510M).

Each main field 51a, 5 of the mask 5
1b is applied to each chip 2 of the wafer 11
When projecting onto one corresponding main field 21a, 21b, the island-like pattern included in one subfield 510 is collectively reduced to the corresponding subfield 210 by one exposure (one shot). In step 5, the projection is reduced.

FIG. 4 shows the mask 5 and the wafer 11 during exposure.
FIG. When the pattern of the pattern area 51 is projected and exposed on the chip 21, the main field 51 is exposed.
Projection exposure is performed in the order of a and 51b. At this time, when the pattern of the main field 51a is projected and exposed on the main field 21a of the chip 21, the mask 5 is moved in the direction of the arrow R1, which is the longitudinal direction of the main fields 51a and 51b, and the wafer 11 is moved in the direction opposite to the R1 direction. While continuously moving each in the R2 direction, the charged beam B is moved to R as shown by the arrow R5.
The projection exposure is performed while being deflected in a direction orthogonal to the R1 and R2 directions. When the pattern of the main field 51b is projected and exposed on the main field 21b of the chip 21, FIG.
In the direction opposite to the direction shown in FIG.
1 while continuously moving each in the R1 direction.
Is deflected in the R5 direction to perform pattern projection exposure.

That is, the beam blanker 3 is turned on / off at a timing when the charged beam B deflected in the R5 direction (strictly, deflected in consideration of the direction in which the mask 5 moves) faces the subfield 510. Subfield 5
The pattern 10 is projected on the subfield 210 of the wafer 11, and then the beam blanker 3 is turned on / off at a timing when the charged beam B opposes the subfield 510 adjacent in the R5 direction, and the pattern of the subfield 510 is projected on the wafer. Projection is performed on eleven subfields 210. The pattern of the main fields 51a and 51b is projected and exposed on the main fields 21a and 21b of the chip 21 by turning on and off the charged beam B for each subfield 510.

FIG. 3 (a)
Are projected onto the wafer 11 as shown in FIG. Next, after the relative positional relationship between the mask 5 and the wafer 11 is shifted by 0.5 μm on the mask in the X and Y directions, the hatching pattern B2 of FIG. 3A is projected onto the wafer 11 by the above-described exposure procedure. As a result, FIG.
A high-density pattern of the patterns B1 and B2 as shown in FIG.

To shift the relative positional relationship between the mask 5 and the wafer 11 by 0.5 μm on the mask in the X and Y directions, the position of the mask 5 at the start of exposure may be shifted. That is, the initial position of the mask 5 at the start of the exposure of the subsequent pattern B2 is shifted by 0.5 μm in the X and Y directions with respect to the initial position of the mask 5 at the start of the exposure of the preceding pattern B1. Can be. Alternatively, the position of the charged beam B may be corrected by the deflectors 8 and 10 without changing the initial position of the mask 5. That is, the deflectors 8 and 10 may be controlled so that the projection position of the charged beam on the wafer 11 when projecting the first pattern is deflected by 0.5 μm in the X and Y directions.

In the above, the main fields 51a and 51a
b, a plurality of subfields 510 are arranged on a matrix, and a pattern 510M is arranged in the subfield 510.
Was used at a low density. However, only one subfield is formed on the mask,
The charged beam may always illuminate the subfield. In this case, a pattern is projected while one subfield on the mask faces each of the subfields on the wafer.

In the above description, as shown in FIG. 3A, the patterns B1 and B2 on the wafer 11 are both the same rectangular pattern, and the same pattern 51 is formed on one mask.
The mask 5 was formed by scattered 0M at a low density. However, the present invention can also be applied to a case where different patterns are formed on the wafer 11 at a high density, such as a rectangular pattern for the pattern B1 and an L-shaped pattern for the pattern B2. That is, although the patterns between the patterns B1 and between the patterns B2 are not dense, the patterns B1 and B2
The pattern including 2 has a high density. In this case, one mask for the rectangular pattern and one mask for the L-shaped pattern are prepared, and the rectangular pattern is projected and exposed by the rectangular pattern mask. Then, the mask is replaced, and the L-shaped pattern mask is used for the L-shaped pattern mask. The pattern is projected onto the same exposure area so as to overlap.

In the correspondence between the above-described embodiment and the structure of the claims, the wafer 11 forms the sensitive substrate, and the subfield 210 forms the same region. Also,
The repeating pattern formed by the rectangular patterns B1 and B2 on the wafer 11 is a high-density substrate pattern, and the repeating pattern formed by the rectangular pattern 510M on the mask 5 is a low-density pattern.

[0021]

As described above, according to the first to third aspects of the present invention, a high-density repetition pattern of a substrate pattern is selected so that the density of the pattern on the mask becomes an acceptable value in terms of the mask strength. A low-density repetitive pattern from the pattern, forms a repetitive pattern on the mask with a density equivalent to the low-density repetitive pattern, and shifts the projected position of the repetitive pattern on the mask to the same exposure area on the sensitive substrate. In this case, high-density substrate patterns are formed by overlapping exposure, so that high-density circuit patterns can be projected and exposed with a single mask at high throughput. According to the fourth aspect of the present invention, even when the density of a substrate pattern including at least two different patterns is high, only a plurality of masks each of which is formed at a low density are prepared, and the high density is obtained. A simple substrate pattern can be formed on the sensitive substrate.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the overall configuration of a charged particle beam projection apparatus that performs a projection exposure method according to the present invention.

FIGS. 2A and 2B illustrate a wafer 11 and a mask 5 shown in FIG. 1, wherein FIG.
Is a plan view showing an example of the mask 5.

FIG. 3 is a diagram illustrating a projection method according to the present invention;
FIG. 2A is a diagram illustrating a part of a repeated circuit pattern formed on a wafer 11, and FIG. 2B is a diagram illustrating a portion of a repeated circuit pattern formed on a mask 5.

FIG. 4 is a diagram showing a relationship between a mask 5 and a wafer 11 during exposure.

5A and 5B are diagrams illustrating a high-density pattern that cannot be exposed by a conventional projection method, wherein FIG. 5A illustrates a part of a high-density circuit pattern on a wafer, and FIG. Diagram showing part of

[Explanation of symbols]

 Reference Signs List 5 mask 6 mask stage 11 wafer 12 wafer stage 21 chip area 51 pattern area 21a, 21b, 51a, 51b main field 210, 510 subfield B charged beam

Claims (4)

[Claims] 1. A method of projecting and exposing a pattern on a mask onto a sensitive substrate at a predetermined reduction ratio, wherein the pattern is formed on the mask at a density equivalent to the density of a substrate pattern to be formed on the sensitive substrate. In the charged particle beam projection exposure method when the substrate pattern is so dense that it is unacceptable in terms of mask strength, the substrate pattern is so formed that the density of the pattern on the mask becomes an acceptable value in terms of mask strength. A low-density repetition pattern is extracted from the high-density repetition pattern, and a repetition pattern is formed on the mask at a density equivalent to the low-density repetition pattern. Forming a high-density substrate pattern by shifting the projected position of the repetitive pattern of the mask and performing overlapping exposure. Particle beam projection exposure method electricity. 2. The charged particle beam projection exposure method according to claim 1, wherein, in the overlapping exposure, the position of the mask with respect to the same exposure area is shifted to project the low-density repetitive pattern onto the same exposure area. And a charged particle beam projection exposure method. 3. The charged particle beam projection exposure method according to claim 1, wherein, during the overlap exposure, a deflection amount of a charged beam transmitted through the mask is changed to form the low-density repetitive pattern for the same exposure area. A charged particle beam projection exposure method characterized by shifting a projection position. 4. A method of projecting and exposing a pattern on a mask onto a sensitive substrate at a predetermined reduction ratio, wherein the pattern is formed on the mask at a density equivalent to the density of a substrate pattern to be formed on the sensitive substrate. In the case of a charged particle beam projection exposure method in which the substrate pattern is so dense that it is unacceptable in terms of strength, the density of the substrate pattern is so high that the density of the pattern on the mask is an acceptable value in terms of mask strength. At least a first and a second low-density repeating pattern are extracted from the first and second low-density repeating patterns, and at least the first and second low-density repeating patterns are extracted at a density equivalent to the first and the second low-density repeating patterns.
And forming different repetitive patterns on the second mask, respectively, and overlappingly exposing the same exposure region of the sensitive substrate while shifting the projection positions of the repetitive patterns of the first and second masks. A charged particle beam projection exposure method comprising forming a dense substrate pattern.