JP2000260694A - Mask for transferring pattern and charged particle beam transfer exposure method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stencilled electron beam transfer mask for which various patterns can be housed in a mask. SOLUTION: This mask is provided with a bridge 63 having a width narrower than the resolution of transfer exposure between two non-exposure patterns 61, 61' without opened holes, which are provided adjacent to each other separated by an exposure pattern 62 with open holes. Since this bridge 63 is in a shape narrower than the resolution, it is not left in the transferred pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a pattern transfer mask for forming a semiconductor device pattern or the like by lithography. In particular, a so-called stencil mask having a perforated pattern, which can effectively hold normally non-perforated or difficult non-perforated portions,
The present invention relates to a pattern transfer mask having improved applicability to various patterns. The present invention also relates to a charged particle beam transfer exposure method using such a pattern transfer mask.

[0002]

2. Description of the Related Art A split transfer system is under development aiming at applying an exposure apparatus using an electron beam, which is a kind of charged particle beam, to mass production of semiconductor devices. The method is 1
In this method, a mask having a pattern of individual semiconductor devices as a whole is manufactured, and the pattern is transferred part by part onto a wafer (sensitive substrate) to join the entire pattern on the wafer.

In the division transfer method, use of a scattering stencil mask and a scattering membrane mask has been studied. The scattering stencil mask has a perforated pattern opened in the mask substrate, similar to a conventional absorbing stencil mask. However, in a scattering stencil mask, a beam that hits a non-perforated portion passes through the mask without being absorbed, but only scattered. In the projection optical system, a contrast aperture is provided on or near the beam converging surface of the projection lens, which is the Fourier surface of the mask surface, for capturing the electron beam scattered by the mask and preventing passage of the electron beam toward the wafer. Then, a beam that is not scattered on the wafer is imaged to obtain a pattern contrast.

In a stencil mask, an island-shaped non-perforated portion cannot be provided at the center of a perforated portion.
This is because the portion of the film constituting the island-shaped non-perforated portion cannot support gravity. Such inconvenience is called a stencil problem or a donut pattern problem. In order to address this problem, a perforated portion surrounding the non-perforated portion in the form of an island is separately formed in two separate pattern regions, and the two pattern regions are separately projected and exposed on a wafer. . Then, by connecting the two perforated portions on the wafer, an exposed portion for one round and an island-shaped non-exposed portion at the center thereof are formed.
Such a method is called a complementary division of a pattern. However, with this complementary split,
Exposure must be performed twice to form one pattern, which is not preferable since the exposure throughput is reduced accordingly.

Therefore, a scattering membrane mask having a pattern film (a high scatterer film) through which an illumination beam is transmitted with relatively high scattering is formed on a thin base film through which the illumination beam is transmitted without being relatively scattered. was suggested. In this scattering membrane mask, the above-mentioned island pattern can be formed by one exposure using one mask, so that the throughput can be improved.

[0006]

However, in the case of the membrane type mask, the electron beam passing through the membrane has an energy spread of about 20 eV, so that the chromatic aberration increases, and a large current cannot be obtained or a high resolution cannot be obtained. May not be possible. On the other hand, the complementary 2
In the method of dividing into two masks, the mask area is doubled, so the mask stage becomes huge, the throughput is reduced by half,
Alternatively, there is a problem that the mask cannot be accommodated in one Si wafer.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and an object of the present invention is to provide a stencil-type mask capable of accommodating various patterns on a single mask. Aim.

[0008]

Means for Solving the Problems and Embodiments of the Invention In order to solve the above problems, a pattern transfer mask of the present invention is a pattern transfer mask having an exposure pattern with holes; A bridge having a width smaller than the resolution of the transfer exposure is provided between two non-exposed patterns having no holes formed therebetween. Alternatively, the width of the bridge may be greater than the resolution of the transfer exposure and so narrow that no pattern is formed due to proximity effects of the exposure.

Further, in the charged particle beam transfer exposure method of the present invention, a mask having a pattern to be transferred onto a sensitive substrate is illuminated with the charged particle beam, and the charged particle beam passing through the mask is imaged on the sensitive substrate. A pattern transfer mask having a hole-exposed exposure pattern, wherein the resolution is smaller than the transfer exposure resolution between two non-hole-exposed patterns adjacent to each other across the exposure pattern. A bridge having a width is provided, and transfer exposure is performed using the mask.

In the present invention, since a bridge is provided to communicate between non-exposure patterns, it is not necessary to divide a complex pattern into two complementary masks even when a complicated pattern is exposed using a stencil mask. Therefore, enlargement of the mask stage and reduction in throughput can be avoided. Further, since the bridge has a thin shape smaller than the resolution, the bridge does not remain in the transferred pattern. If the width of the bridge is less than half the resolution limit, the bridge can be prevented from remaining even if the process becomes somewhat unstable. In addition, a width of 20 to 50 nm (80 to 20 nm on the mask)
Even a bridge of 0 nm) can sufficiently support an unexposed portion.

A description will be given below with reference to the drawings. First,
An outline (example) of an exposure technique using an electron beam, which is a kind of charged particle beam, will be described. FIG. 3 is a diagram showing an outline of an image forming relationship and a control system in the entire optical system of the electron beam projection exposure apparatus of the division transfer system. The electron gun 1 arranged at the uppermost stream of the optical system emits an electron beam downward. Below the electron gun 1, two stages of condenser lenses 2, 3 are provided.
Through the blanking aperture 7 to image the crossover CO.

A rectangular opening 4 is provided below the condenser lens 3.
Is provided. The rectangular aperture (illumination beam shaping aperture) 4 allows only an illumination beam that illuminates one subfield (unit exposure pattern area) of the mask (reticle) 10 to pass. Specifically, the opening 4 forms the illumination beam into a square having a size of slightly more than 1 mm square (example) in mask size conversion. The image of the opening 4 is formed on the mask 10 by the lens 9.

Below the beam shaping aperture 4, a blanking deflector 5 is arranged. The deflector 5 deflects the illumination beam to hit the non-opening of the blanking opening 7,
The beam does not hit the mask 10. An illumination beam deflector 8 is arranged below the blanking opening 7. The deflector 8 mainly scans the illumination beam sequentially in the horizontal direction (X direction) in FIG. 3 to illuminate each subfield of the mask 10 within the field of view of the illumination optical system. An illumination lens 9 is disposed below the deflector 8. The illumination lens 9 converts the electron beam into a parallel beam, impinges the beam on the mask 10, and forms an image of the beam shaping aperture 4 on the mask 10.

Although only one subfield on the optical axis is shown in FIG. 3, the mask 10 actually extends in the plane perpendicular to the optical axis (XY plane) (described later with reference to FIG. 2). And has a number of subfields. On the mask 10, a pattern (device pattern) forming one semiconductor device chip as a whole is formed. Mask 10
Is mounted on a mask stage 11 that can move in the X and Y directions, and can mechanically move the mask 10 to illuminate each subfield beyond the field of view of the illumination optical system.

Below the mask 10, projection lenses 12 and 14 and a deflector 13 are provided. Then, an illumination beam is applied to a certain subfield of the mask 10,
The electron beam that has passed through the pattern portion of the mask 10 is reduced and deflected by the projection lenses 12 and 14 and deflected by the deflector 13 to form an image at a predetermined position on the wafer 15. An appropriate resist is applied on the wafer 15, and the resist is given a dose of an electron beam.
The pattern on the mask is reduced and transferred onto the wafer 15.

A crossover CO is formed at a point at which the space between the mask 10 and the wafer 15 is internally divided at a reduction ratio, and a contrast opening 18 is provided at the crossover position. The opening 18 blocks the electron beam scattered by the non-pattern portion of the mask 10 from reaching the wafer 15.

The wafer 15 is placed on a wafer stage 17 that can move in the X and Y directions via an electrostatic chuck 16. By synchronously scanning the mask stage 11 and the wafer stage 17 in directions opposite to each other,
A large number of subfield bands (deflection bands, which will be described in detail later) arranged in the device pattern can be sequentially exposed.
Note that both stages 11 and 17 are equipped with an accurate position measurement system using a laser interferometer, and the position of the stage is accurately controlled.

Each of the lenses 2, 3, 9, 12, 14 and each of the deflectors 5, 8, 13 are provided with a coil power supply 2a, 3c,
a, 9a, 12a, 14a and 5a, 8a, 13a. The mask stage 11 and the wafer stage 17 are also controlled by the control unit 21 via the stage drive motor control units 11a and 17a. The electrostatic chuck 16 is connected to the main controller 21 via the electrostatic chuck controller 16a.
Is controlled by By controlling the accurate stage position and the optical system, the reduced images of the subfields on the mask 10 are accurately joined on the wafer 15, and the entire device pattern on the mask is transferred onto the wafer.

Next, a detailed example of a mask used for the electron beam transfer exposure of the division transfer system will be described with reference to FIG. FIG. 2 is a diagram schematically illustrating a configuration example of a mask for electron beam transfer exposure. (A) is an overall plan view,
(B) is a partial perspective view, and (C) is a plan view of one small membrane region.

In FIG. 2, an area indicated by a large number of squares 41 is a small membrane area (having a thickness of 0.1 μm to several μm) including a pattern area corresponding to one subfield.
It is. As shown in FIG. 2C, the small membrane area 41 is a central pattern area (subfield) 42.
And a frame-shaped non-pattern area (skirt 4
3). The subfield 42 is a portion where a pattern to be transferred is formed. The skirt 43 is a portion where no pattern is formed, and corresponds to an edge portion of the illumination beam.

One sub-field 42 has a size of about 0.5 to 5 mm square on a mask as it is currently being studied. The size of the area (image field) of the projected image in which this subfield is reduced and projected on the wafer is 0.1 to 1 mm square as the reduction rate is 1/5. A portion 45 called a grid-like grid in the vicinity of the small membrane region 41 is a beam having a thickness of about 0.5 to 1 mm to maintain the mechanical strength of the membrane. The width of the grenage 45 is about 0.1 mm.

As shown in FIG. 2A, a number of small membrane regions 41 are arranged side by side in the X direction to form a group (deflection band 44), and a large number of such deflection bands 44 are arranged in the Y direction. Form one stripe 49. The width of the stripe 49 corresponds to the width of the deflectable visual field of the electron beam optical system. A plurality of stripes 49 exist in parallel in the X direction. Struts 47 between adjacent stripes 49
The thick beams shown as are for keeping the deflection of the entire mask small. The strut 47 is integral with the grenage, has a thickness of about 0.5 to 1 mm, and has a width of several
mm. In addition, a method in which a non-pattern area such as a skirt or a grenage is not provided between adjacent subfields in one deflection band is also being studied.

According to a system which is currently considered to be influential,
At the time of projection exposure, the rows (deflection bands) of the X-direction subfields in one stripe 49 are sequentially exposed by electron beam deflection. On the other hand, the columns in the Y direction in the stripe 49 are sequentially exposed by continuous stage scanning. Next stripe 4
When going to 9, the stage is sent intermittently.

At the time of projection exposure, non-pattern areas such as a skirt and a grenage are removed on the wafer, and the patterns of the respective subfields are joined together over the entire chip. A transfer reduction ratio of 1/4 or 1/5 has been studied, and the size of one chip on a wafer is 4GDR.
Since AM is assumed to be 27 mm × 44 mm, the overall size of the mask including the non-pattern portion of the chip pattern is:
It is about 120 to 230 mm x 150 to 350 mm.

Next, the structure of a pattern transfer mask according to one embodiment of the present invention will be described with reference to FIG. FIG.
1 is a plan view of a pattern transfer mask according to one embodiment of the present invention. (A) is an embodiment in which a bridge is provided between long linear patterns, and (B) and (C) are embodiments in which a donut pattern is supported by a bridge.

FIG. 1A shows an elongated exposure pattern 62.
Two non-exposure patterns 61 and 61 '(hatched portions) are arranged across (for example, 0.4 μm in width and 300 μm in length). These non-exposure patterns 61 and 61 'are elongated patterns, and are portions where the base of the mask remains. In the case of such an elongated line and space pattern, the non-exposed pattern 61 (non-perforated portion) has an extremely elongated string form supported only at both ends, and the supporting state is extremely insufficient. Therefore, the positions of the patterns 61 and 61 'are shifted, and the patterns 61 and 61' are easily cut.

Therefore, a bridge 63 is provided between the non-exposure patterns 61 and 61 'to connect them. The bridge 63 has a width of, for example, 80 to 100 nm. The bridge 63 in this example has a zigzag shape. That is, the bridge 63 projects substantially perpendicularly from the side of the contact portion 64 of the non-exposed pattern 61 (portion 63a),
Next, it extends horizontally parallel to the non-exposure pattern 61 (parallel portion 6).
3b), it bends again at a right angle (portion 63c) and is connected to the non-exposed pattern 61 'at the contact portion 64'. Parallel part 63b
Is provided substantially at the center of the exposure pattern 62, and its length is, for example, 4 to 10 μm.

Since the bridge 63 is thinner than half the resolution (200 nm in terms of mask size, 50 nm in terms of wafer size) of the electron beam exposure apparatus used for transfer, no pattern is formed on the wafer. However, the contact portion 6 between the bridge 63 and the non-exposed patterns 61, 61 '
At 4,64 ', a portion of the bridge may remain unexposed. Therefore, the bridge 63 is bent as shown in the figure, and the positions of both contact portions 64 and 64 'are shifted in the longitudinal direction of the patterns 61 and 61'. Therefore, even if a little non-exposed portion remains in the contact portions 64 and 64 ', they are not connected because the distance between them is large. Therefore, there is no possibility that the wiring is disconnected. The wiring is generally formed of a negative resist.

In the pattern of FIG. 1B, there is a non-exposed portion (portion with a base) 69 surrounded by an exposed portion (perforated portion). Normally, the central non-exposed portion 69
Cannot exist as a normal stencil mask because it can exist only in a form floating in the air. However, in this example, bridges 67 are provided at the four corners of the non-exposed portion 69 to support the non-exposed portion 69. This bridge 67 also has a width smaller than the exposure resolution (for example, 20
μm).

In this example, the corner 66 of the non-exposed portion (singular point)
A bridge is provided to pass through. Since the inner angle of the exposed portion is 270 °, the dose is given extra by the proximity effect, so that the bridge 67 does not remain. Further, in this example, since the bridge 67 is bent, the contact 68 where the bridge 67 is likely to remain is located at the point 6.
Since the position is far from 6, there is no possibility that a non-exposed portion is connected.

FIG. 1C shows an embodiment of a donut pattern similar to that of FIG. 1B. In this example, the non-exposed portion 8
The exposed portion 83 around the portion 5 includes a wide portion 83b on the left and right sides of the non-exposed portion 85 and a narrow portion 8 on the upper and lower portions of the non-exposed portion 85.
3a. In this case, the bridge 89 is connected to the wide part 8.
3b. On the side where the exposed portion is wide, the amount of backscattered electrons applied to the bridge portion is large, so that a bridge pattern is not formed due to the proximity effect, and a desired pattern without a bridge is formed. Even if the width of the bridge is larger than the resolution of the transfer exposure, no pattern is formed if the width is too small to form a pattern due to the proximity effect of exposure. For example, when the resolution is 50 nm (on the wafer), the width of the bridge may be about 60 nm (on the wafer) in some cases.

[0032]

As is apparent from the above description, according to the present invention, it is possible to provide a stencil type mask capable of accommodating various patterns on one mask.

[Brief description of the drawings]

FIG. 1 is a plan view of a pattern transfer mask according to one embodiment of the present invention. (A) is an embodiment in which a bridge is provided between long linear patterns, and (B) and (C) are embodiments in which a donut pattern is supported by a bridge.

FIG. 2 is a view schematically showing a configuration example of a mask for electron beam transfer exposure according to the present invention. (A) is an overall plan view,
(B) is a partial perspective view, and (C) is a plan view of one small membrane region.

FIG. 3 is a diagram showing an outline of an image forming relationship and a control system in the entire optical system of the electron beam projection exposure apparatus of the division transfer type according to the present invention.

[Explanation of symbols]

Reference Signs List 1 electron gun 2, 3 condenser lens 4 illumination beam shaping aperture 5 blanking deflector 7 blanking aperture 8 deflector 9 illumination lens 10 mask 11 mask stage 12 projection lens 13 deflector 14 projection lens 15 wafer 16 electrostatic chuck 17 wafer Stage 18 Contrast opening 41 Membrane area 42 Subfield 43 Skirt 44 Deflection band 45 Grid stripe 47 Strut 49 Mask stripe 61 Non-exposure pattern 62 Exposure pattern 63 Bridge 64 Contact portion 67 Bridge 69 Non-exposure pattern 70 Exposure pattern 71 Non-exposure pattern 81, 85 , 87 Non-exposure pattern 83 Exposure pattern 89 Bridge

Claims (6)

[Claims] 1. A pattern transfer mask having an exposure pattern with holes; a bridge having a width smaller than the resolution of transfer exposure between two non-hole exposure patterns adjacent to each other across the exposure pattern. A pattern transfer mask, comprising: 2. A pattern transfer mask having a perforated exposure pattern, wherein a narrow bridge is provided between two non-perforated non-perforated patterns adjacent to each other across the exposure pattern. A pattern transfer mask characterized in that the width of the bridge is greater than the resolution of the transfer exposure and is so thin that no pattern is formed due to the proximity effect of the exposure. 3. The pattern transfer mask according to claim 1, wherein the non-exposure pattern is an elongated linear shape. 4. The pattern transfer mask according to claim 1, wherein the bridge is provided at a singular point such as a corner or a step of the pattern. 5. The bridge according to claim 1, wherein the bridge is provided in a bent shape or a staggered shape between opposing non-exposure patterns. Pattern transfer mask. 6. A method of illuminating a mask having a pattern to be transferred onto a sensitive substrate with a charged particle beam, and imaging the charged particle beam passing through the mask onto the sensitive substrate to transfer the pattern; A bridge having a width smaller than the resolution of the transfer exposure is provided between two non-exposure patterns in which a hole is not formed between adjacent non-exposure patterns of a pattern transfer mask having an open exposure pattern. A charged particle beam transfer exposure method, comprising performing transfer exposure.