JP3321838B2 - Electron beam drawing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection distortion correcting method for an electron beam lithography system which employs a method of continuously moving a sample stage of an electron beam lithography system at a variable speed according to the density of a figure pattern to be drawn.

[0002]

2. Description of the Related Art Normally, in a pattern drawing apparatus using an electron beam, a deflector, which exists in the path of the electron beam in advance, is formed in order to form the electron beam with high accuracy over the entire surface of the sample.
The deflection error of the electron lens and the like is measured and calibrated. Factors of the deflection error include deflection sensitivity error, displacement due to rotational distortion, focus error, astigmatism, and the like. In order to correct these factors, the coordinates of a plurality of marks provided on the sample surface are detected in advance by sweeping them with an electron beam, the difference between the input orthogonal coordinates and the difference is obtained, and the deflection error is calculated using the least squares method. Generate the minimum high-order polynomial. When a pattern is drawn, the drawing coordinates are input to a circuit for calculating a polynomial, and correction is performed by performing a correction calculation.

Conventionally, in a step-and-repeat type electron beam lithography apparatus, a circuit for performing a correction calculation has been configured so that the calculation is completed within a calculation allowable time represented by equation (1). Specifically, the correction calculation circuit has been configured using a calculator such as a microcomputer. In Equation 1, the sample settling time was much longer than the beam settling time, and the allowable calculation time greatly depended on the sample settling time.

Calculation allowable time = (beam setting time + average exposure time) × average number of exposures + sample stage setting time
(Equation 1) Here, literatures showing a conventional device related to the present invention include:
"Japan Society for the Promotion of Science: Application of Charged Particle Beams to Industry, 132nd Committee, 83rd Study Group Material: High-Speed, High-Accuracy Electron Beam Drawer HL-600".

[0005]

When writing is performed while continuously moving the sample stage of the electron beam lithography apparatus for the purpose of improving the throughput, the allowable calculation time of Expression 1 does not need to allow for the sample stage settling time. Will be. Generally, when the continuous movement method is adopted, the allowable calculation time of the deflection distortion correction circuit is within the beam settling time. The conventional deflection distortion correction circuit has a problem that it cannot be used because the calculation of the deflection distortion correction takes time. In order to increase the speed of the deflection distortion correction circuit, it is conceivable to adopt a pipeline method and configure the deflection distortion correction calculation by hardware, but the pipeline method has a problem that the circuit scale increases, There is a problem that the calculation formula is fixed and the functions of various correction elements cannot be changed.

SUMMARY OF THE INVENTION It is an object of the present invention to speed up deflection distortion correction of an electron beam lithography apparatus employing a method of continuously moving a sample stage .
Lies in the fact that.

[0007]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
Is as follows. Means for moving sample stage
And the drawing coordinates are used as input to correct the electron beam deflection distortion.
Means for dividing the drawing area into a plurality of fields,
Means for deflecting the electron beam into a field;
Means for drawing a figure pattern in the field.
In the sagittal drawing apparatus, the figure pattern is drawn.
The next field drawing coordinates in advance
Input to the deflection distortion correction means and repeat the deflection distortion correction calculation to calculate
And prepare the setting data before a setting request occurs.
That the drawing of the graphic pattern is completed.
The result of the iterative calculation is transferred to an electron beam driving circuit.
An electron beam lithography device that is set to.

[0008]

The electron beam lithography apparatus of the present invention constructed as described above greatly shortens the deflection distortion correction time of the electron beam lithography apparatus which could not be realized by the conventional correction calculation circuit using a microcomputer. In addition, function changes can be easily realized,
In addition, a deflection distortion correction circuit having a small circuit scale can be configured. Thus, it is possible to realize a deflection distortion correction circuit of an electron beam lithography apparatus employing the sample stage continuous movement method.

[0009]

FIG. 1 is a block diagram of an electron beam lithography apparatus according to the present invention, showing a situation in which a sample 16a such as a semiconductor wafer is irradiated with an electron beam and swept to perform drawing. The electron beam is deflected by the beam deflector 15. 14 is
A drive circuit that deflects the electron beam. 17a is the sample 16a
This is a detector for detecting the backscattered electrons generated from the light.

The electron beam lithography system first detects the distortion of the deflection system. The control computer 10 fetches several mark signals provided on the sample via the backscattered electron detector 17a and the signal processing circuit 17b, obtains input coordinates and a difference,
The least-squares method is used to generate a high-order polynomial that minimizes the deflection error. The coefficient is determined by the detection. This coefficient is calculated for all fields on the sample and stored in the control computer 10. When drawing a pattern, the control calculator 10
Calculates the correction coefficient and the drawing coordinates of the drawing field
Set to When the field deflection amount is determined, the field deflection distortion correction circuit calculates a subfield coordinate correction coefficient based on the deflection amount, and transfers it to the subfield deflection distortion correction circuit.

The calculation circuit 12 receives the difference between the field coordinates and the subfield coordinates and performs a correction calculation based on the coefficients. The calculation circuit 12 is composed of three calculation circuits. Specifically, the calculation circuits 12a and 12b correct the X-axis and Y-axis deflection amounts of the electrostatic deflector 15c represented by the cubic equation. The calculation circuit 12c corrects the astigmatism represented by the quadratic expression, and further performs focus correction. The correction amount of the astigmatism is supplied to the correction electrode 15 via the electron beam driving circuit 13.
Give to a.

The calculation contents of the calculation circuit 12 perform the product-sum operation of Expression 2 shown in FIG. In Expression 2, 42 is a coefficient part calculated by the field, and 41 is a field coordinate and
Input signal obtained from the difference from the subfield coordinates. 43
Is a term calculated based on the input signal. By performing the calculation of 42 externally and exclusively, it is possible to reduce the correction calculation time of the subfield. 40 is 4
It is a correction result obtained by the product-sum calculation of 1, 42, and 43.

Ue calculates the X-axis deflection correction of the electrostatic deflector 15c. Ve calculates the Y axis deflection correction of the electrostatic deflector 15c. Xds is a correction formula for the X-axis astigmatism correction electrode, and Yds is for the Y-axis astigmatism correction. Df
s is a correction formula for the focus correction electrode.

Xds, Yds and Dfs are quadratic expressions, and Uds
e and Ve are cubic expressions. The quadratic expressions are collectively calculated by one calculation circuit 12c. The cubic expression is calculated by the calculation circuit 12a
And 12b. The correction coefficient obtained by the calculation circuit 12 is transferred to the pattern drawing unit 19 and used for correcting the deflection of the figure.

When the equation (2) is calculated using a deflection distortion correction calculation circuit using a conventional microcomputer,
The number of processing steps is about 300 or more. According to the present invention, the calculation circuits 12a and 12b perform a calculation process of 50 steps. 12c is 40 steps. Therefore, when the number of calculation steps is compared, the time required for calculation can be reduced to 1/6 or less of the conventional case. Calculation result is in register 1
3 is set in the electron beam drive circuit 14 by the control circuit 11 which manages and controls the calculation state.

The control circuit 11 activates the calculation circuit after setting the coefficients and drawing coordinates from the control computer 10 to the calculation circuit. Further, the calculation result is set to the electron beam driving circuit. The sequence is programmed and stored in the control circuit 11. The control circuit 11 is configured using a processor.

FIG. 2 is a diagram showing a deflection distortion correction procedure of the step-and-repeat type electron beam lithography apparatus. The correction procedure will be described below. 20 activates the sample stage control unit and moves the sample stage to a target drawing area. The control computer 10 sets a correction coefficient and a field coordinate of the deflection area in the deflection distortion correction circuit. The correction calculation of the field coordinates is performed in a time series at 23a, 23b, 23c, and 23d. 24 sets the calculation result to the beam drive unit and the pattern drawing unit. In step 25, after confirming that the sample stage is settled, the pattern drawing unit is activated to perform drawing. The correction calculation time for 20a, 20b, 20c, and 20d generally took several hundred microseconds or more, but did not pose a problem because the sample stage settling time was longer than that. When the sample stage continuous movement method is adopted, the allowable calculation time is within the electron beam settling time. The settling time of the electron beam in the subfield region is usually within several microseconds, and there is a problem that the conventional deflection distortion correction circuit cannot calculate within the allowable calculation time.

FIG. 3 is a diagram showing a correction calculation of deflection distortion of subfield coordinates according to the present invention. Reference numeral 30 inputs the field coordinates and the drawing coordinates of the subfield, and performs deflection distortion correction calculation, astigmatism correction, focus correction, and correction coefficient calculation for the figure drawing area. Numeral 30 arranges the calculation circuits in parallel and holds the calculation results in registers. 31
Performs pre-reading of the coordinates of the next drawing area while the pattern drawing unit is drawing the figure pattern, and calculates the deflection amount of the next subfield drawing coordinates and the correction coefficient of the figure drawing in combination with 30. . Drawing of the graphic area is completed,
When a request is made to set the next drawing area,
The subfield coordinates prepared in the register and the correction coefficient of the graphic area are collectively set. Therefore, the time from when the request is generated until the data is set can be set within the electron beam settling time by setting the result obtained in advance calculation in advance. This makes it possible to perform the deflection distortion correction calculation within the allowable calculation time.

The deflection correction circuit for the field region receives the difference between the field coordinates and the current coordinates of the sample table as input, and outputs the output as the field deflection amount and the subfield correction coefficient to the electromagnetic deflector 15c and the subfield deflection distortion correction circuit. Forward. Others can be realized by a circuit configuration that operates in the same manner as this description.

[0020]

According to the present invention, the sample stage is continuously moved.
Speedup of deflection distortion correction of electron beam lithography system that adopts
Can be planned.

[Brief description of the drawings]

FIG. 1 is a block diagram of a deflection distortion correction circuit according to the present invention.

FIG. 2 is a flowchart showing the operation of a conventional deflection distortion correction circuit.

FIG. 3 is a flowchart showing the operation of the deflection distortion correction circuit according to the present invention.

FIG. 4 is a diagram showing a subfield deflection distortion correction formula.

[Explanation of symbols]

10: control computer, 11: control circuit, 12: calculation circuit,
13 register, 14 drive circuit, 15 deflector, 16
a: sample, 16b: sample stage, 17a: secondary electron detector,
17b ... Signal processing circuit, 18a ... Laser length gauge, 18b
... sample stage controller, 19 ... pattern drawing unit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-17252 (JP, A) JP-A-57-157027 (JP, A) JP-A-2-183515 (JP, A) JP-A-55-1982 102231 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7/20

Claims (1)

(57) [Claims] 1. A means for moving a sample stage, a means for correcting deflection distortion of an electron beam using drawing coordinates as input, and a means for dividing a drawing area into a plurality of fields and deflecting the electron beam into the fields. Means for drawing a figure pattern in the field, while drawing the figure pattern, inputting the next field drawing coordinates to the deflection distortion correction means in advance. Means for repeatedly performing a deflection distortion correction calculation and preparing setting data before a setting request is generated. When the drawing of the graphic pattern is completed, the result of the repetitive calculation is determined by electron beam driving. An electron beam drawing apparatus designed to be set in a circuit.