JP2697028B2 - Charged particle beam drawing method and apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam drawing method and apparatus using a variable shaped beam capable of changing the cross-sectional shape of the beam.

[Conventional technology]

Conventionally, a charged particle beam drawing method apparatus using a variable shaped beam has been known. That is, to describe a simple example of this, for example, a source of an electron beam, which is a kind of charged particle beam, a focusing lens for forming a crossover image of the source of the electron beam (electron gun), and a crossover by a focusing lens A first mask placed at a position where an image is generated, a second mask disposed at a predetermined distance from the first mask, a focusing lens forming a conjugate between the first mask and the second mask, A first deflecting device provided between the first mask and the second mask for deflecting the electron beam passing through the first mask on the second mask, and an electron beam passing through the second mask. A projection lens that focuses on the target, and a second deflecting device that deflects the electron beam on the target;
The deflection device deflects (moves) the electron beam that has passed through the first mask on the second mask, and changes the cross-sectional shape of the beam generated on the target.

[Problems to be solved by the invention]

An electron beam lithography system using such a variable shaped beam has a problem that the dimensional accuracy is not good due to a physical phenomenon called resist heating instead of having the advantage of high throughput. That is, the pattern size is different between the case where the same pattern is drawn with a beam in a small area and the case where the same pattern is drawn with a beam in a large area. In some cases, development did not proceed to the substrate and pattern formation was not possible.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method and an apparatus for finishing a pattern drawn with a small-area beam and a pattern drawn with a large-area beam into a pattern of a correct size under the same developing conditions.

[Means to solve the problem]

The development of a pattern drawn with a set of small-area beams is slower than the development of a pattern drawn with a set of large-area beams, and thus the pattern size after development is reduced. Therefore, in order to correct this effect, when writing with a beam having a small area, the dose is relatively increased, conditions for forming a pattern with the same dimensions under the same developing conditions are found, and writing is performed under those conditions.

That is, the present invention is characterized in that in a charged particle beam writing method using a variable shaped beam, the dose per unit address area is made variable depending on the beam area to be shot, and development is performed under the same development conditions. A charged particle beam writing method, wherein in a charged particle beam writing apparatus using a variable shaped beam, output means (16) for outputting a signal corresponding to the size of the shaped beam; Beam irradiation time control means (2, 12, 14, 17) for changing the irradiation time of the beam to the target so as to enable development under the same development conditions regardless of the beam area. Is a charged particle beam drawing apparatus.

[Action]

According to the method of the present invention, the influence of resist heating is corrected by changing the dose, and as a result, development can be performed under the same development conditions regardless of the beam area, and accurate pattern formation can be performed.

Further, according to the apparatus of the present invention, since the dose is adjusted by changing the irradiation time of the shaped beam to the target, not only can the image be developed under the same developing conditions regardless of the beam area, but the dose can be controlled. Stable and easy to do.

〔Example〕

FIG. 1 is an apparatus block diagram of one embodiment of the present invention,
The electron beam from the electron gun 1 passes through the position of the shutter 2, and forms a crossover image at the position of the opening 4 a of the first mask 4 by the focusing lens 3. The crossover image at the position of the opening 4a is again returned to the second mask 7 by the focusing lenses 5, 6.
Formed in the opening 7a. That is, the first mask 4 and the second mask 7 are conjugated by the focusing lenses 5 and 6. A deflection coil 8 is provided between the focusing lenses 5 and 6 so that the position of the electron beam passing through the opening 4a of the first mask 4 on the second mask 7 can be changed two-dimensionally. Has become. That is, the image formation position of the opening 4 a of the first mask 4 on the second mask 7 by the electron beam changes according to the value of the current flowing through the coil 8. Therefore, the opening 4a of the mask 4
Opening 7a of the second mask 7 of the electron beam forming the
The electron beam at the position overlapping with the opening of the second mask 7
Go through 7a. The second mask 7 is conjugated with the target 10 by the objective lens 9. Accordingly, an electron beam pattern having a shape corresponding to the superimposed image of the opening 4a of the first mask 4 and the opening 7a of the second mask 7 is formed on the target 10. The deflection coil 11 between the objective lens 9 and the target 10 changes the position where the pattern of the electron beam occurs on the target 10 two-dimensionally.

The shutter 2 moves in the Y direction orthogonal to the axis of the electron optical system, and operates in response to a control command from the CPU 14 so as to select a position shown in FIG. It is controlled by the control device 12.

The value of the current flowing through the coil 8 is controlled by the coil current control device 13 in accordance with a command from the CPU 14. Further, the deflection coil 11 is also controlled by the coil current control device 15 according to a command from the CPU. The CPU 14 controls the shutter control device according to the contents of the first memory 16 and the second memory 17.
12. Control the coil current controllers 13 and 15.

The first memory 16 stores a circuit pattern designed by CAD or the like (not shown). Specifically, the circuit pattern is divided into fine rectangular patterns (divided patterns), and the X-Y coordinate position of the center of these divided patterns on the target 10 and the size of the divided pattern are determined. It is as if it is made to correspond. Therefore, the CPU 14 can determine the value of the current flowing through the deflection coils 8 and 11 by sequentially reading the contents of the first memory 16.

The second memory 17 stores correction data created as described below.

That is, first, the beam variable range is, for example, 0.01 μm square to
In a drawing apparatus of 2 μm square, a pattern of 2 μm square was drawn with a dose and a beam size in Table 1 below, and development was performed under a developing condition in which the No. 1 pattern was almost 2 μm square.

FIG. 3 shows the result of measuring the pattern dimensions in each pattern No.

As can be seen from FIG. 3, pattern No. 1 was measured to have a pattern size of 1.95 μm square. Accordingly, considering this 1.95 μm as a reference, the position of the 1.95 μm square pattern dimension in the curve 3-1 connecting the actually measured values of Pattern Nos. 2, 3, and 4 has a dose of 1.2, and the pattern Nos. , 7. The position of the pattern dimension 1.95 μm square in the curve 3-2 connecting the measured values is 1.6, and the pattern dimension 1.95 μm in the curve 3-3 connecting the measured values of the patterns No. 8, 9, and 10 is 1.95 μm. At the corner positions, the dose is 2.05, and pattern Nos. 11, 12, and 13
1.95 pattern size in curve 3-4 connecting actual measured values
The position of μm square is 2.25, and pattern No.14, 1
The dose at the position of the pattern dimension 1.95 μm square in the curve 3-5 connecting the actually measured values of 5 and 16 is 2.95.

Therefore, from these data, the pattern size was 1.95μ.
In order to obtain the m-square, the relationship between the beam area and the relative dose for obtaining the same pattern size under the same developing condition is obtained as shown in FIG.

The relationship between the beam area (the size of the shaped beam) and the relative dose shown in FIG.
Is stored in

With such a configuration, when the power is turned on, the CPU controls the shutter control device 1 so that the shutter 2 is closed.
2 to give control commands to various control devices (not shown), that is, exhaust devices, control devices for the focusing lenses 3, 5, and 6 so that predetermined initial currents flow into the deflection coils 8 and 11. A control command is issued to the coil current controllers 13 and 15 (step 200 in FIG. 2). When one of the circuit patterns (tick patterns) stored in the first memory 16 is specified from a keyboard or the like (not shown), the specified chip pattern data is called and stored in the RAM (not shown). Then, the total number of shots of the chip pattern (the number of divided patterns constituting the chip pattern) N is searched (step 201 in FIG. 2). After storing the total number N of shots in the RAM (not shown), n = 1 (step 2 in FIG. 2).
02), the coordinate data of the number of shots n = 1 and the shape data of the divided pattern are called out from the RAM (step 203 in FIG. 2), and the two-dimensional coordinate data of the number of shots n = 1 A control command is issued (step 204 in FIG. 2), and a two-dimensional control command is issued to the coil current control device 13 according to the shape data of the number of shots n = 1 (step 205 in FIG. 2). Next, from the 21st memory, as the correction data of the number of shots 1, the dose (expressed in coulombs per unit area) corresponding to the shape data (corresponding to the pattern dimension) is controlled by either the current value or the time. It is only necessary to change one or both of them, but it is not preferable to change the electron beam from the electron gun 1. Therefore, in this example, the irradiation time is controlled. May be stored), and the irradiation time for the shot number n = 1 is calculated (step 206 in FIG. 2). Thereafter, a control command is issued to the shutter control device 12 to open the shutter 2 (step 207 in FIG. 2), and after a time corresponding to the correction data (the irradiation time calculated in step 206), the shutter 2 is closed. Thus, the control command is issued to the shutter control device 12 (step 208 in FIG. 2).

If the number of shots n is not equal to the total number of shots N (step 209 in FIG. 2), the current n (now n =
The number obtained by adding 1 to 1) is set as a new n (n = 2 because n = 1 now) (step 210 in FIG. 2), and the process returns to step 203.

It is apparent that the relationship between the beam area and the dose in FIG. 4 used in the above-described embodiment can be used as it is even when a pattern having a pattern size other than 1.95 μm is formed.

The relationship between the beam area and the dose in FIG. 4 is obtained by obtaining the dose for the reference beam area. However, all the doses corresponding to the usable beam areas are measured. The beam area and the dose may be associated with each other and stored in a memory.

〔The invention's effect〕

As described above, according to the present invention, irrespective of the beam area for performing the shot (the size of the shaping beam), that is, both the pattern drawn with the small-area beam and the pattern drawn with the large-area under the same developing conditions. The pattern can be finished to the correct dimensions.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a flowchart of a CPU 14 used in FIG. 1, and FIG. 3 is a diagram showing measured values of dose and pattern size when beam size is changed as a parameter. FIG. 4 is a diagram showing the relationship between the dose and the beam area. [Description of Signs of Main Parts] 2... Shutter 4... First mask 5, 6... Focusing lens 7... Second mask 8. Device 14 CPU 16 First memory 17 Second memory

Continuation of front page (56) References Vac. Sci, Technol. B5 (1) Jan / Feb 1987. P. 105-109. Vac. Sci, Technol. B15 (2), Mar / Apr 1997, p. P. 311-315J. Vac. Sci, Technol. B6 (3) May / Jun 1988 P. 853-857

Claims (4)

(57) [Claims] 1. A charged particle beam lithography system for forming a pattern of a predetermined shape on a target using a variable shaped beam, comprising: a beam variable unit for changing an area of the beam; And a dose control means for changing a dose to the target according to an area of the beam. 2. The charged particle beam writing apparatus according to claim 1, wherein the amount of change of the dose is calculated in accordance with a relationship between a previously determined beam area where the same pattern size is formed and the dose. . 3. The charged particle beam lithography apparatus according to claim 2, wherein the relationship between the beam area and the dose is a relationship experimentally obtained by using a pattern having a size of 1.95 μm or more. . 4. The charged particle beam writing apparatus according to claim 1, wherein said dose control means changes the irradiation time of said beam on said target.