JPS60126827A - Electron beam exposing method - Google Patents

Abstract

PURPOSE:To obtain the primary conversion coefficient for beam deflection by a method wherein a mark is provided at the prescribed point of a sample using a main deflector, said mark is measured by a sub-deflector, and the amount of correction of the electron beam is calculated based on the difference between the computed value and the measured value. CONSTITUTION:The electron beam 9 is deflected to the position of point 9 by outputting position-designating signals of (X-a) and (Y-a) to the main deflector 35. Then, the mark G(X, Y) is detected by deflecting the electron beam using the sub-deflector 34. The distance between X-direction and Y-direction of the point F1 and the mark G when the above-mentioned detection is performed is indicated by (a+DELTAx1) and (a+DELTAy1). Besides, the measurement of said distance is repeated a plurality of times, the average value of the measurements is found, and it is used as the above-mentioned distance. The same procedures are performed on the points F2-F4, and the distance between said points and the mark G is calculated. The error to be corrected is calculated using DELTAx1-DELTAx4 and DELTAy1-DELTAy4.

Description

[Detailed Description of the Invention] ta> Technical Field of the Invention The present invention relates to an electron beam exposure method, and in particular, to an electron beam exposure method, in which beam deflection-order conversion coefficients of sub-deflectors can be matched between deflectors for large deflection and deflectors for small deflection. Regarding how to decide.

(bl) Prior art and problems When performing electron beam exposure, Figure 1 (al, (bl)
As shown in FIG. 1, a drawing area 1 is divided into a plurality of main fields 2, which are further divided into a plurality of sub-fields 3. A predetermined pattern 4 is then drawn within the sub-field 3.

In this drawing step, the exposure position is selected as shown in FIG. The selection of the sub-field 3 within the sub-field 3 is performed by operating the main deflector 7, and the selection of the exposure position within the sub-field 3 is performed by deflecting the electron beam 9 by operating the sub-deflector 8.

That is, as shown in FIG. 3, the sample stage 6 is moved to select a predetermined main field 2, and the main deflector 7 is
is activated to deflect the electron beam 9 in the direction of and select a predetermined sub-field 3 within the main field 2. Next, the selected sub-field 3 (between points B and C in the figure) is scanned with the electron beam 9 by operating the sub-deflector 8. When the drawing in one sub-field 3 is finished in this way,
The main deflector 7 is operated again to deflect the electron beam 9 in the direction E in the figure, and the subfield 3 to be exposed next is selected. And this subfield 3 (C
The sub-deflector 8 scans and draws the area between point E and point E.

After completing the exposure of all subfields 3 in one main field 2 in this way, move the sample stage 6 to select the next main field 2, and perform the same operation as above to select the next main field 2.・Exposure within field 2. By repeating this operation, drawing can be performed over the entire surface of the exposed substrate 5.

However, since there are generally various errors in electron beam exposure, the sub-field 3'' formed by the series of exposure operations described above is different from the intended sub-field 3, as shown in Figure 3. Therefore, the pattern 4 drawn therein also becomes discontinuous.

As is well known, the above-mentioned errors include the gain of the sub-deflector 8, rotation, trapezoidal distortion, and offset.
It is expressed by the following formula.

Δx=gXx×rxy+hXxy+dx −■Δy=r
yy+gyy+hyxy dy... ■In the above equation, ΔX and Δy on the left side are the coordinates in main field 2 where the position coordinates in the X and Y directions are X and Y, respectively, (
gx on the right side represents the error in the X and Y directions at the position (x, y).

gy is the gain of the sub-deflector in the X and Y directions,
rX+ TV rotates, hX, h.

is a trapezoidal distortion, and dX and d are beam deflection-order conversion coefficients (hereinafter simply abbreviated as conversion coefficients) of the sub-deflector 8 indicating offset (or distortion).

The following method is usually used to calculate each conversion coefficient in the above equation. That is, as shown in FIG. 4(al), a mark 11 consisting of a concave portion formed by selectively removing the surface of the sample substrate 10 is placed on the surface of the sample substrate 10 with an X and a mark as shown in FIG. 4(b). A plurality of marks are formed in the Y direction with a predetermined pinch.In other words, the above mark 11 is located at the intersection of the meshes.Then, as shown in the figure, the main mark is placed at the center point F of one mesh (its coordinates are X and Y).・The electron beam 9 is deflected by the deflector 7, and from this position as a starting point, the electron beam 9 is deflected by the sub-deflector 8 in the above 4.
The marks 11 were scanned, and each conversion coefficient at the coordinates X and Y was determined from the difference between the design value and the actual measurement value.

However, in this method, the value of the conversion coefficient is influenced by the quality of the mesh formed by each mark 11. For example, if the shoulder of the mark 11 is sagging, there will be an error in the actual measurement value of the mark 11 even if the device is accurate, and there will also be an error in the distance between the mark 11 and the center point F. However, the true value is unknown and the design value must be regarded as the correct value. Therefore, even if the actual measured value is accurate, it is not possible to determine an appropriate conversion coefficient.For this reason, conventionally, adjacent It is difficult to say that the patterns could be connected with high accuracy at the boundary between the two areas.As described above, the conventional electron beam exposure method still had problems in terms of accuracy.

(C1 Purpose of the Invention The purpose of the present invention is to provide an adjustment method for an electron beam exposure apparatus that can solve the above problems and easily determine the conversion coefficient with high precision.

fdl Structure of the Invention The characteristics of the present invention are that deflection information is given to the main deflector to deflect the electron beam from a mark provided on the sample to a predetermined point based on the deflection information, and then the electron beam is deflected by a sub-deflector. Scan the mark by deflecting from the acid point, measure the distance between the acid point and the mark, calculate the difference between the distance between the acid point and the mark based on the deflection information, and the measured value, and based on the difference. The purpose is to perform exposure by correcting the amount of deflection of the electron beam.

(8) Examples of the invention An embodiment of the present invention will be described below with reference to the drawings.

FIG. 5 is a diagram for explaining the method of determining conversion coefficients in this embodiment.

In the same figure, G is a mark formed at the coordinate (X, Y) position, F1 to F4 are all points in four areas adjacent to the mark G, and the main deflector is located in the X direction and Y direction. Both direction and coordinate (X.

Δx1 to Δx4 respectively indicate the deflection position of the electron beam when a position separated by a from Y) is specified, and the error in the distance between F1 to F4 and the mark G, respectively. The mark G is scanned by deflecting the electron beam from the above four points F1 to F4 using a sub-deflector.

That is, signals specifying the positions (X-a) and (Y-a) are applied to the main deflector to deflect the electron beam to the position of point F1. Next, the electron beam is deflected by a sub-deflector to scan the mark G, and the mark G is detected. The distances between the point F°1 and the mark G at this time in the X and Y directions are expressed as (a+Δxl) and (a+Δy+). Note that this distance measurement is repeated multiple times, and the average value is calculated and used as the above-mentioned distance.

A similar operation is performed for points F2 to F4, and the distance between each point and the mark G is determined. Δx1 to ΔX4 obtained in this way. and Δy1 to Δy4. Substituting and a into the above formulas ① and ②, 8Xl = gx a+r) <
a+h×a2+d×Δx2 =-gx a+rXa-
hXa2+a×ΔX3 Child-gx a-rxa+hxa
2+aXΔX4 = gx a-rx a-hxa2+
a×...■ and ΔV1=gy a+r, a+h, a2+a.

hy2 = gy a-ry a-hy a2+dyΔ
y3 =-gy a"ry a+h, a2+dyΔ)'
a =-gy a+ry a-hy a2+dy...
... ■ The formula is obtained. Therefore, from the above 0.0 formula, dx=(ΔX,
+Δx2+Δx3+ΔXa)/4gx””(ΔXl−Δ
x2-Δx3+Δx4)/4r8=(Δx1+Δx2-
Δx3-ΔX4)/4hX=(Δx1-Δx2+Δx3
-Δx4)/4... ■ d, = (hy1 +Δy2 +Δy3 +Δya')/
4gy-(Δy, +Δy2-Δy3-Δya)/4ry
=(Δy, -Δy2-Δy3 +Δya)/4h, =(
Δy, -Δy2 +Δy3-Δya)/4...
■ All conversion coefficients can be determined.

In this way, in this embodiment, the combinations of coordinates given to the main deflector and sub-deflector are made different at each sample point in the main field, and the same mark is scanned using multiple combinations to determine the gain of the sub-field. , rotation, keystone distortion, and offset 4
Determine the conversion coefficients.

Furthermore, this operation is executed at all sample points, the conversion coefficients at each sample point are found, and the conversion coefficients between each sample point are determined by interpolation.

As described above, in this embodiment, when determining each conversion coefficient, unlike the conventional method, it does not depend on the quality of the mesh formed by each sample point.

That is, in this embodiment, the main deflector first deflects the electron beam to the position of each sample point, and the main deflector deflects the electron beam by a predetermined amount in the X and Y directions based on the coordinates (X, Y) at that time. (±a in the above embodiment) is deflected. Next, at this position (F in Figure 5)
The sample point is detected by deflecting the electron beam from points 1 to F4) using a sub-deflector, the distance to the sample point is actually measured in the X direction and the Y direction, and the difference from a is calculated. After this, conversion coefficients such as gain and rotation are determined in the same manner as in the conventional method.

In this way, in this embodiment, it is not assumed that the sample point is at the intersection of the meshes, so it is not affected by the quality of the mesh, and moreover, the same sample point can be connected to four adjacent points at the sample point. Since the transform coefficients are determined by scanning from the area, the transform coefficients in adjacent sub-fields are not discontinuous, and therefore the drawn patterns are smoothly connected.

FIG. 6 is a block diagram of a main part showing the system configuration of an electron beam exposure apparatus that performs writing using the conversion coefficients determined as described above.

In the figure, 20 is a central processing unit (CPU), 21.
Reference numeral 22 represents an external storage device that stores the conversion coefficients corresponding to the drawing data and position coordinates, 23 represents a pattern data buffer memory that stores the pattern data transferred from the external storage device 21, and 24 represents the pattern data. A register 25 temporarily stores pattern data sequentially transferred from the buffer memory 23, a correction memory 25 stores conversion coefficients corresponding to position coordinates transferred from the external storage device 22, a correction calculation circuit 26, and a correction calculation circuit 27. Addition circuit (ADD), 28, 30.31 is digital-to-analog converter (DAC), 29.32.33 is amplifier, 34
is a sub-deflector, and 35 is a main deflector.

The conversion coefficients requested as described above are stored in the external storage device 22 together with the position coordinates, and are transferred to the correction memory 25 via the CRU 20 prior to drawing. On the other hand, the pattern data is transferred from the external storage device 21 to the pattern data buffer memory 23. After doing this, the pattern data is sequentially sent from the pattern data buffer memory 23 to the register 24 based on commands from the CPLI, and the coordinate data X, Y for the main deflector 35 is sent to the correction memory 25 and the adder 27.
Further, the coordinate data x, y for the sub-deflector 34 is sent to the correction calculation circuit 26. Upon receiving these data, among the conversion coefficients corresponding to the position coordinates from the correction memory 25, gain gx + gy; rotation rX + r
y and trapezoidal distortion hx, h are sent to the correction calculation circuit 26, and offset) dX, d is sent to the adder 27.

The adder 27 adds the two input values and outputs the result as DA.
The DAC 28 converts it into a corresponding analog value, which is further amplified by an amplifier 29 and applied to the main deflector 35 as a deflection current. As a result, the electron beam is deflected to the reference position of the sub-field to be drawn, that is, to a predetermined coordinate within the main field.

On the other hand, the correction calculation circuit 26 performs a correction calculation using the input conversion coefficient and the coordinates x and y in the main field, and sends out data indicating the corrected position coordinates in the sub-field. Then, it is converted into corresponding analog data by the DACs 30 and 31, and then the amplifier 32
．． 33 and input to the sub-deflector 34,
The electron beam is deflected to a predetermined position within the sub-field.

In this embodiment, since appropriately determined conversion coefficients are used, patterns can be drawn with good accuracy.

In the explanation of FIG. 6 above, among the 4 (11) conversion coefficients, the offsets dx and d become constants that uniquely correspond to the coordinates once the coordinates within the sub-field are determined, so this value It is sufficient to directly shift the electron beam, and there is no need to perform correction calculations.Therefore, among the four conversion coefficients, only the offset is not sent to the correction calculation circuit 26, and the coordinate data X, which is used to control the main deflector, is Y is added to correct the deflection position by the main deflector 35. Therefore, instead of this, the coordinate data of the sub-deflector 34 may be shifted.

ffl As described in detail, according to the present invention, the beam deflection-order conversion coefficient of the sub-deflector can be determined with high accuracy and appropriately, so that the electron beam exposure position can be adjusted appropriately.

[Brief explanation of drawings]

Figures 1 to 4 are diagrams for explaining the problems of the adjustment method in the conventional electron beam exposure method. Figure 1 is a plan view, and Figure 2 is a diagram schematically showing the electron beam deflection method. Fig. 3 is a plan view showing the drawing result, Fig. 4(a),
(b) is a cross-sectional view and a plan view of the main part showing how to calculate the beam deflection-order conversion coefficient of the sub-deflector, respectively, and FIG. FIG. 6 is a plan view showing the determination method, and a block diagram of main parts showing the configuration of an electron beam control section of an electron beam exposure apparatus used in an embodiment of the present invention. In the figure, 1 is the drawing area, 2 is the main field,
3 is a sub-field, 4 is a double turn, 5 is a substrate to be processed, 6 is a sample stage, 7 and 35 are main deflectors, 8 and 34 are sub-deflectors, 9 is an electron beam, 1
1 indicates a mark, and G & Ma sample ~ F4 indicates a point displaced from the above point G by a predetermined amount. Figure 1 Figure 2

Claims (1)

[Claims] Deflection information is given to the main deflector to deflect the electron beam from a mark provided on the sample to a predetermined point based on the deflection information, and then the sub-deflector deflects the electron beam from the acid point to scan the mark. Then, the distance between the acid point and the mark is measured, the difference between the distance between the acid point and the mark based on the deflection information and the measured value is calculated, and the amount of deflection of the electron beam is corrected based on the difference. An electron beam exposure method characterized by performing exposure.