JPH11135417A - Pattern transfer method and for the method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pattern transfer method with less affect on device manufacture, even if the joint precision of an aligner is relatively worse. SOLUTION: Related to a pattern transfer method, a pattern bent-back part is taken as a division border, as possible, when a transfer pattern is divided. When an angle a formed between pattern sides L1 and L2 at a bent-back part of an exposure part is acute, a double exposure part 1 is provided at a division part while a non-exposure part 2 is provided if an angle β formed between pattern sides L3 and L4 is obtuse.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for forming a very fine pattern of 4G DRAM or later at a high throughput. In particular, the present invention relates to a pattern transfer method for transferring a pattern on a mask onto a sensitive substrate (such as a resist-coated wafer) using an energy beam such as an electron beam, and a pattern transfer mask used therefor. More specifically, the present invention relates to a method involving pattern division on a mask, and more particularly to a pattern transfer method and the like that can reduce the problem of poor pattern joining at division boundaries on a sensitive substrate.

[0002]

2. Description of the Related Art An electron beam exposure technique will be described as an example.
The drawback of electron beam exposure is high accuracy but low throughput, and various techniques have been developed to overcome the drawback. At present, cell projection,
A figure part batch exposure method called character projection or block exposure has been put to practical use. In the pattern part batch exposure method, a small pattern of a repeatable circuit (about 5 μm square on a wafer) is repeated using a mask in which a plurality of types of similar small patterns are formed, with one small pattern as one unit. Perform transfer exposure. But,
Even in the graphic part batch exposure method, the throughput is lower by about one order of magnitude when applied to wafer exposure in actual production of a full-scale semiconductor integrated circuit device (DRAM or the like).

On the other hand, as an electron beam transfer exposure system aiming at a much higher throughput than the graphic partial batch exposure system,
2. Description of the Related Art An electron beam reduction transfer apparatus has been proposed in which an electron beam is irradiated onto a mask having a circuit pattern of an entire semiconductor chip, and an image of a pattern in the irradiation range is reduced and transferred by a two-stage projection lens (for example, Japanese Patent Application Laid-Open (JP-A) No) 5-160012). In this type of apparatus, when a pattern is transferred at once by irradiating the entire area of the mask with an electron beam at once,
Since the pattern cannot be transferred accurately, the field of view of the mask and optical system is divided into a number of small areas (main field and subfield), and the pattern is sequentially transferred while changing the conditions of the electron beam optical system for each subfield. Then, on the wafer, the entire circuit pattern is transferred by connecting and arranging the images of the respective sub-fields of view (split transfer method, for example, see US Pat. No. 5,260,151).

In a mask for electron beam exposure, another mask division may be required. The stencil mask for electron beam transfer exposure is a thin electron scatterer (Si or the like) in which patterned holes are formed. The electron beam passing through the through hole is imaged on a wafer via a projection optical system to transfer a pattern. The electron beam hitting other than the through hole is greatly scattered, and most of the electron beam is captured by the stop in the projection optical system and does not reach the wafer. In this stencil mask, a pattern (island-like pattern) in which the entire periphery of the region that blocks the electron beam is surrounded by the through-hole cannot hold the mask portion of the region, so that the pattern is complementary. 2
It is necessary to divide the pattern into two patterns and transfer the pattern twice. Also, it is difficult to hold a peninsula-shaped pattern held at only one end, so that it is necessary to compliment a long and slender pattern.

[0005] In the above-described pattern division in the division transfer method or the complementary division, once the dimensions of the main visual field and the sub-visual field are determined, the pattern is mechanically divided from the end according to the dimensions. The dividing line at that time was a straight line as a matter of course. In the partial batch exposure method, the size of the unit transfer area (field of view) is determined to be an integral multiple of the memory cell size of a normal memory device, and a dividing line passes between cells.

[0006]

In such a transfer method of dividing a pattern on a mask and joining pattern images on a wafer, if the joining of patterns at the division boundary is not performed correctly, Failures such as poor connection of the pattern and short circuit occur. On the other hand, if the positioning, rotation, and magnification setting of the transferred image are to be made extremely high in order to avoid such problems, excessive demands must be made on the accuracy of the device and the accuracy of the alignment adjustment. As a result, the throughput increases and the throughput decreases.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and an object of the present invention is to provide a pattern transfer method which does not hinder device fabrication even if the accuracy of connecting an exposure apparatus is somewhat poor, and a mask used therefor. I do.

[0008]

According to a first aspect of the present invention, there is provided a pattern transfer method comprising: forming an image of a pattern divided on a mask on a sensitive substrate; A pattern transfer method for transferring a pattern onto a sensitive substrate; transferring the divided pattern for each unit area, and connecting the divided patterns on the sensitive substrate to transfer the entire pattern; In dividing the pattern, a bent portion of the pattern is preferentially set as a division boundary. In such a bent portion, even if the connection accuracy is slightly poor, it does not lead to a noticeable defect. This is because, in the case of an electron beam transfer apparatus, such corners are rounded due to the proximity effect and are not formed according to the pattern data, so that a pattern design with a margin is originally provided.

In this aspect, when the angle formed by the two pattern sides in the bent portion of the pattern (measured in the exposed portion) is relatively acute, it is preferable to provide a double-exposed portion in the divided portion of the pattern. . When the corner is relatively obtuse, it is preferable to provide a non-exposed portion at the division of the pattern. With such a correction, the rounding of the corner due to the proximity effect in the acute angle portion is mitigated by adding a dose to the double exposure portion, and the rounding of the corner in the obtuse angle portion due to the proximity effect of the corner is caused by insufficient dose in the non-exposed portion. The pattern is relaxed and a pattern close to the pattern data can be formed. Therefore, it is possible to suppress pattern deterioration due to poor connection of the visual field.

[0010] The pattern transfer method according to the second aspect of the present invention comprises:
A pattern transfer method for forming an image of a pattern divided on a mask on a sensitive substrate and transferring the pattern on the sensitive substrate; transferring the divided pattern for each unit area Then, on the sensitive substrate, transfer the whole pattern by joining the divided patterns,
When a pattern is divided across a parallel line or a parallel space, two adjacent points where the pattern division line and the edge of the line pattern intersect each other are defined as one line width of the line pattern.
The dividing line is set at a distance of at least / 2 in the longitudinal direction of the line pattern. That is, when several lines or linear spaces are arranged in parallel, the joining positions (division positions) are shifted from each other between adjacent pattern edges. As a result, the positions of thick and thin lines are dispersed, so that the risk of disconnection or short circuit is reduced even if the joining accuracy is somewhat poor.

According to a first aspect of the present invention, there is provided a pattern transfer mask for forming an image of a pattern divided on a mask on a sensitive substrate and transferring the pattern onto the sensitive substrate. A bent portion of the pattern is preferentially used as a division boundary.

According to a second aspect of the present invention, there is provided a pattern transfer mask for forming an image of a pattern divided on a mask on a sensitive substrate and transferring the pattern onto the sensitive substrate. Two adjacent points where the pattern dividing line and the edge of the line pattern intersect each other at a portion where the pattern is divided across the parallel line or the parallel space, and which is one of the line widths of the line pattern. / 2
As described above, the dividing line is set in a state of being separated in the longitudinal direction of the line pattern.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. First, an outline of an electron beam reduction transfer apparatus to which the present invention is applied will be described with reference to FIG. FIG. 4 is a diagram showing an image forming relationship in the entire optical system of the electron beam exposure apparatus of the division transfer system. The electron gun 11 emits an electron beam downward. A two-stage condenser lens 13, 15 is provided below the electron gun 11, and the electron beam forms a crossover image on the blanking aperture 17 through the condenser lens 13, 15. These two condenser lenses 13 and 15 act as zoom lenses,
The current density for irradiating the reticle 20 can be made variable.

Above and below the condenser lenses 13 and 15,
Two stages of rectangular openings 12, 16 are provided. The rectangular apertures (sub-field limiting apertures) 12 and 16 allow passage of only the electron beam illumination light in an area corresponding to one sub-field. Specifically, the first opening 12 shapes the illumination light into a square having a dimension of slightly more than 1 mm square in mask size conversion. This opening 12
Is formed on the second aperture 16 by the lenses 13 and 15.

Below the second opening 16, the above-mentioned blanking opening 1 is located at the position where the crossover is formed.
A sub-field-of-view selection deflector 18 is arranged alongside 7. This sub-field-of-view selection deflector sequentially scans the illumination light in the X direction in the drawing to expose all the sub-fields in one main field. A condenser lens 19 is provided below the sub-field selection deflector 18.
Is arranged. The condenser lens 19 converts the electron beam into a parallel beam, impinges on the mask 20, and forms an image of the second opening 16 on the mask 20.

Although only one sub-field of view on the optical axis of the mask 20 is shown in FIG.
(Y direction), and has many sub-fields and main fields (rows of sub-fields). When illuminating and exposing each sub-field within one main field, the electron beam is deflected by the sub-field selection deflector 18. The mask 20 is placed on a mask stage 21 that can move in the X and Y directions. The wafer stage 2 is also capable of moving the wafer 24 as a sample in the XY directions.
5. By scanning the mask stage 21 and the wafer stage 25 in directions opposite to each other in the Y direction, each main view in the stripe of the chip pattern (row of the main view) is continuously exposed. Further, each stage is exposed intermittently by scanning both stages 21 and 25 in the X direction. In addition, both stages 2
1 and 25 are equipped with an accurate position measuring system using a laser interferometer, and the sub-fields and the main field are accurately connected on the wafer 24 by separate alignment means and adjustment of each deflector. Are combined.

Below the mask 20, a two-stage projection lens 2 is provided.
2 and 23 (objective lens) and a deflector (not shown) are provided. Then, one sub-field of the mask 20 is irradiated with an electron beam, and the electron beam patterned by the mask 20 is reduced and deflected by the two-stage projection lenses 22 and 23, and is deflected to a predetermined position on the wafer 24. It is imaged. An appropriate resist is applied on the wafer 24, and a dose of an electron beam is given to the resist, so that a reduced pattern of a mask image is transferred onto the wafer 24. Wafer 24
Is mounted on the wafer stage 25 movable in the direction perpendicular to the optical axis as described above.

FIG. 1 is a diagram showing an example of pattern division by a pattern transfer method according to an embodiment of the first aspect of the present invention.
(A) is a plan view showing the entire square line pattern, (B) is a plan view showing a divided upper mask region, and (C) is a plan view showing a lower mask region.
FIG. 2A is a plan view showing details of a corner portion of the pattern. FIGS. 2B and 2C are plan views showing the divided upper and lower mask regions, respectively. Pattern C in this example
Consists of square lines (exposed portions). The square region surrounded by the line and the outside of the line are non-exposed portions.

In this example, the division boundaries 6 indicated by broken lines are arranged at the upper left and upper right corners (bent portions) of the pattern C. In other words, the division boundary 6 extends from the right to the left in the figure from the right to the left in a substantially middle position in the vertical direction of the pattern C (6a), rises from it, and intersects the upper right corner of the pattern C (6b), From there, it descends along the diagonal line in the pattern C in the lower left direction at 45 ° (6c), enters the non-exposed portion of the pattern C, further descends (6d), and advances laterally at the position of the middle part of the pattern C (6e). Rises again and intersects the upper left corner of pattern C (6f),
It rises obliquely at 45 ° along a diagonal line (6g), advances a little laterally (6h) after exiting the pattern C, sharply falls (6i), and again advances leftward on the same line as the first (6a).

By the dividing boundary 6, the pattern C becomes
It is divided into an upper trapezoidal pattern C1 and a lower U-shaped pattern C2. That is, as shown in FIG. 1B, a through-hole a1 in the shape of the pattern C1 is opened at the lower corner of the upper region M1 on the mask, and as shown in FIG. A through hole a2 in the shape of the pattern C2 is opened in the upper corner of the lower region M2. Then, after either C1 or C2 is transferred and exposed on the wafer, the other is aligned and transferred and exposed on the wafer.

By arranging the dividing line at the bent portion of the pattern as described above, it is possible to reduce defects caused by the connection accuracy even if the connecting accuracy is slightly poor. Because
In the case of an electron beam transfer device, such a corner portion is rounded due to the proximity effect and is not formed according to the pattern data, so that a pattern design with a margin is originally made. In addition, the division boundary 6 may be formed not through the upper right corner of the pattern C but through the lower right corner, and each of the divided patterns may be L-shaped.

Next, the detailed processing of the corner will be described with reference to FIG. First, in a portion outside the corner, the angle formed by the pattern edges L1 and L2 is set to the exposed portion side (pattern C).
The angle α is 90 °, which is smaller than the reference angle (eg, 160 °). Therefore, a small square double-exposure portion 1 is provided at the end of the corner. The double-exposure portion 1 is formed as a hole in both the mask region having the hole C1 and the mask region having the hole C2. Therefore, the double exposure portion 1 is exposed both at the time of the exposure at C1 and at the time of the exposure at C2. This is done for the following reason. In an acute-angled exposed part, the proximity effect causes the electron dose to be scattered to the surrounding non-exposed parts, and the dose is likely to be insufficient,
Therefore, the corner is easily rounded. Therefore, the dose is raised by double-exposure of the tip of the acute angle to reduce the rounding of the corner.

On the other hand, when the angle between the pattern edges L3 and L4 is measured on the exposed portion side (within the pattern C), the angle β is 270 °, which is a reference angle (for example, 200). °) greater than. Therefore, a small square non-exposed portion 2 is provided at the base of the corner. The non-exposed portion 2 is not formed as a hole in any of the mask region having the C1 hole and the mask region having the C2 hole. Therefore, the non-exposed portion 2 is not exposed at the time of the exposure of C1 and the exposure of C2. However, the non-exposed portion 2 is substantially surrounded by the exposed portion, and a scattering dose due to the proximity effect is given to the portion from the periphery, so that a dose equal to or larger than the threshold is usually given without direct exposure. On the contrary, by not directly exposing the same portion, rounded corners can be prevented. The dimensions of the double-exposed portion 1 and the non-exposed portion 2 are, for example, C1,
0.01 to 0.03 μm when the line width of C2 is 0.1 μm
m.

That is, by such correction, the rounding of the corner due to the proximity effect at the acute angle portion is mitigated by adding a dose to the double exposure portion 1, and the rounding of the corner at the obtuse angle portion due to the proximity effect is reduced. A pattern close to the pattern data can be formed by being alleviated by insufficient dose in the exposed portion 2. Therefore, it is possible to suppress pattern deterioration due to poor connection of the visual field.

FIG. 3 is a plan view showing an example of pattern division by the pattern transfer method according to one embodiment of the second aspect of the present invention. FIG. 3A shows an example of setting a division boundary, and FIGS. )
9 schematically shows the effect of this embodiment. In this embodiment, two line patterns 3 and 5 are arranged in parallel with a space 4 therebetween. Since the line extends beyond the movable length of the division boundary, an appropriate bent portion cannot be used as the division boundary.

When such a pattern is divided into upper and lower parts, the dividing boundary is usually determined in a horizontal straight line. However, in the present embodiment, the dividing boundaries are bent in the lines 3 and 5 and the space 4. That is, the dividing boundary is line 3,
In 5, the vehicle enters from intersections 7 and 9 from left to right, proceeds halfway along the line, rises to a height h, and further proceeds to the right to exit the line at intersections 8 and 10. Similarly, in the space 4, it falls by h at the center in the left-right direction. The height h is required to be at least １ ／ or more of the line width of the line or space, and is preferably equal to or more than the line width. Note that a line that diagonally connects the intersections in a line or space may be used as the division boundary.

Next, the effect of this embodiment will be described with reference to FIGS. 3 (B) and 3 (C). Typical pattern deformations at the joining portion include thick and thin lines.
Thickness occurs when two transferred images overlap and an excessive dose seeps around. Thinning occurs when the two transferred images are separated and the dose is insufficient.

However, in the present embodiment, when the body becomes fat,
As shown in (B), the fatness 3a on the right side of the lines 3 and 5,
5a occurs around the intersections 8 and 10, and the thickenings 3c and 5c on the left side of the line occur around the intersections 7 and 9 and the positions where the thickening occurs are staggered up and down. By the way, assuming that the division boundary passes through the lines 3 and 5 right beside, as shown by the broken lines, the thickenings 3b and 5b on the left side of the line are also replaced with the thickenings 3 on the right side.
a and 5a appear at the same vertical position. In this case, the thick portion 3a on the right side of the line 3 and the thick portion 5b on the left side of the line 5 approach each other, and a short circuit may occur. However, in the present embodiment, as described above, the thickening occurs on both sides of the lines 3 and 5 so as to be staggered up and down.

On the other hand, the same can be said for a lean case as shown in FIG. That is, if the thinning of the lines 3 and 5 occurs at the same position (3d and 3e, 5d and 5e), the lines 3 and 5 may be disconnected. However, if the leanness is vertically different (3d and 3f, 5d and 5f), it is difficult for the left and right leanness to be connected, and the risk of disconnection is reduced.

Although the above description has been given of pattern division by the division transfer method, division of a complementary pattern can be handled in the same manner.

[0031]

As is clear from the above description, in the pattern transfer method of the first embodiment of the present invention, when dividing a pattern, a bent portion of the pattern is preferentially used as a dividing boundary, so that the joining accuracy is slightly poor. But it does not lead to noticeable defects. In addition, in the case where a double exposure portion is provided at an acute angle portion in a bent portion of a pattern, or a non-exposure portion is provided at an obtuse angle portion, rounding of a corner due to a proximity effect is reduced, and a pattern close to pattern data can be formed. . Therefore, it is possible to suppress pattern deterioration due to poor connection of the visual field. In the pattern transfer method according to the second aspect of the present invention, when dividing across a parallel pattern, the pattern dividing lines are staggered, so that the positions of thickening and thinning of the lines are dispersed, and even if the joining accuracy is somewhat poor, the disconnection is performed. And the risk of short circuits is reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of pattern division in a pattern transfer method according to an example of a first aspect of the present invention. (A) is a plan view showing the entire square line pattern, (B) is a plan view showing an upper mask area (field of view), and (C) is a plan view showing a lower mask area.

FIG. 2A is a plan view showing details of a corner of the pattern. (B) and (C) are plan views showing upper and lower mask regions, respectively.

FIG. 3 is a plan view showing an example of pattern division in a pattern transfer method according to an example of the second aspect of the present invention. (A) shows an example of setting a division boundary, and (B) and (C) schematically show the effect of the present embodiment.

FIG. 4 is a diagram showing an image forming relationship in the entire optical system of the electron beam exposure apparatus of the division transfer system.

[Explanation of symbols]

1 double exposure part, 2 non-exposure part, 3, 5 line pattern, 4 space, 6 division boundary, 7, 8, 9, 1
0 ... intersection, 11 ... electron gun, 12, 16 ... rectangular aperture, 1
3, 15, 19: condenser lens, 17: blanking aperture, 18: deflector, 20: mask, 21: mask stage, 22, 23: projection lens, 24: wafer, 25
... wafer stage, C, C1, C2 ... pattern, a1,
a2: Through-hole, M1, M2: View, L1, L2, L3, L
4 ... Pattern edge

Claims (10)

[Claims] 1. A pattern transfer method for forming an image of a pattern divided and formed on a mask on a sensitive substrate and transferring the pattern on the sensitive substrate; The pattern is transferred for each unit area, and on the sensitive substrate, the divided pattern is joined to transfer the entire pattern. In dividing the pattern, a bent portion of the pattern is preferentially used as a division boundary. Pattern transfer method. 2. A method according to claim 1, wherein said pattern has a bent portion.
2. The pattern transfer method according to claim 1, wherein a double-exposed portion is provided in a divided portion of the pattern when an angle between the two pattern sides (measured in the exposed portion) is relatively acute. 3. An angle between the two pattern sides is 160.
3. The pattern transfer method according to claim 2, wherein the double-exposed portion is provided when the angle is equal to or less than .degree. 4. A method according to claim 1, wherein said pattern has a bent portion.
2. The pattern transfer method according to claim 1, wherein when the angle formed by the two pattern sides is relatively obtuse, a non-exposed portion is provided in a divided portion of the pattern. 5. An angle between the two pattern sides is 200.
5. The pattern transfer method according to claim 4, wherein the non-exposed portion is provided when the angle is equal to or more than .degree. 6. A pattern transfer method for forming an image of a pattern divided and formed on a mask on a sensitive substrate and transferring the pattern onto the sensitive substrate; When the pattern is transferred for each unit area and the divided pattern is joined on the sensitive substrate to transfer the entire pattern, and when the pattern is divided across a parallel line or a parallel space, the pattern dividing line and the line are used. A pattern transfer method, wherein a dividing line is set by separating two adjacent points crossing an edge of a pattern in a longitudinal direction of the line pattern by half or more of a line width of the line pattern. 7. A pattern transfer mask for forming an image of a pattern divided and formed on a mask on a sensitive substrate and transferring the pattern onto the sensitive substrate; wherein a bent portion of the pattern is formed. A pattern transfer mask, which is preferentially a division boundary. 8. The method according to claim 8, wherein the bent portion of the pattern has
8. The pattern transfer mask according to claim 7, wherein a double-exposed portion is provided at a portion where an angle (measured in the exposed portion) between two pattern sides is relatively acute. 9. The method according to claim 9, wherein the bent portion of the pattern has
8. The pattern transfer mask according to claim 7, wherein a non-exposed portion is provided at a portion where the angle between the two pattern sides is relatively obtuse. 10. A pattern transfer mask for forming an image of a pattern divided and formed on a mask on a sensitive substrate and transferring the pattern onto the sensitive substrate;
In a part where a pattern is divided across a parallel line or a parallel space, two adjacent points where the pattern division line and the edge of the line pattern cross each other are １ ／ or more of the line width of the line pattern. In the longitudinal direction of the
A pattern transfer mask, wherein a dividing line is set.