JPH0332017A - Method and apparatus for electron beam lithography - Google Patents

Abstract

PURPOSE:To improve accuracy in lithography by computing the error component of the area of a cross section which is proportional to the area of the cross section of an electron beam, and correcting the cross sectional shape of the electron beam by the error component. CONSTITUTION:An electron beam 61 from an electron beam source 6 is made to sweep, and a pattern is drawn on a wafer 7. The parts corresponding to the two sides of the quadrangle of the beam are cut out with a shaping aperture 82. Then, the parts corresponding to the other two sides of the quadrangle are cut out with a shaping aperture 82. Thus, the beam is shaped into the quadrangle. Therefore, when the two sides of the beam 61 are shaped with the aperture 81 and thereafter the beam is deflected to the side of the aperture 82, the size of the square shape can be changed. The deflection is performed by applying deflecting signals on deflecting plates 33, 34 and 35 through a data control device 11 and a deflection control device 13 based on the signals from an operating device 10. The accuracy in lithography can be improved by correcting the error in a cross sectional area which is proportional to the area of the cross section of the electron beam.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electron beam lithography method and apparatus for manufacturing masks and the like for semiconductor integrated circuits, and particularly to a method and apparatus for improving the lithography accuracy.

[Prior Art] A conventional electron beam lithography system used for manufacturing masks for semiconductor integrated circuits is as described in Japanese Patent Application Laid-Open No. 62-44850.
For example, the area of the electron beam was changed in proportion to the area of the figure to be drawn, so that a figure with a large area could be filled in quickly. In addition, if the cross-sectional shape of the electron beam is circular, the corners of a square figure will be sagging, so this is made into a square, and the cross-sectional shape of the electron beam is determined according to the area, shape, etc. of the figure to be drawn. I was trying to change the size of the rectangle.

In reality, since there is an error in the cross-sectional shape of the rectangular electron beam, the error is measured in advance and corrected. As shown in Fig. 5, this correction method is to sweep the cross-sectional shape 1 of the electron beam whose two side lengths are specified as xo and yo at a constant speed in the The length of the electron beam is detected by detecting the change in the area of the area where the electron beam does not exist, and the length is similarly determined by rotating the shielding plate 2 by 90 degrees and sweeping the electron beam in the y-axis direction. Ta.

The error component included in the length of each side above, that is, the difference ΔX and ΔY between the input values XO and YO specifying the length of each side of the quadrilateral and the measured value above, is a linear approximation as shown in equation (1). is expressed in

ΔX=a 1+b 1 ・XO+c 1
・YOΔY=a 2+b 2'・XO+c 2 ・
The three coefficients al, bl, and cl of YO(1)ΔX are the fifth
It can be determined from three sets of simultaneous equations obtained by repeating the measurements shown in the figure three times by changing the values of xo, yo, etc. a2. b2 and c2 can also be found in the same manner. Furthermore, by further increasing the number of measurements described above and calculating each of the coefficients using the least squares method, the accuracy of each coefficient can be improved.

FIG. 6 is a block diagram showing an example of a conventional correction device that performs correction using the six coefficients described above.

The signal actually applied to the deflection plates 31, 32, etc. is the input signal x
It is obtained by adding the above ΔX and ΔY to O and YO, respectively. Therefore, the memory device 4 has (XO+AX) and (Y
Each component constituting ΔY) is stored in the form of a table in correspondence with the values of XO and YO. When xO and YO are input, these are used as address signals, for example, as the X-axis output.

[aL+ (b1+1)XO], cl-Yo, etc. are read out, and addition I! 51 and temporarily stored in a register 52, the signals are applied to the deflection plate 31 via a DA converter (digital/analog converter) 53 and a deflection amplifier S4. The same applies to the Y-axis signal.

[Problems to be Solved by the Invention] In the conventional correction method described above, the correction amounts ΔX, ΔY, etc. corresponding to various X01YO are obtained using the six coefficients a1 to c2 obtained as described above. However, no consideration was given to the fact that the size of the beam spot changes depending on the beam current value, that is, the influence of the Coulomb effect, and it was difficult to further improve the precision of electron beam lithography.

The Coulomb effect becomes particularly noticeable when the current density of the electron beam is high, and thus degrades the accuracy in high-speed writing performed at high current density.

Note that the Coulomb effect is an effect in which an electron beam tends to spread due to a repulsive force acting between electrons constituting the electron beam.

An object of the present invention is to provide an electron beam lithography method and an apparatus thereof, in which electron beam dimensions are corrected by adding correction for the Coulomb effect to the above-described conventional correction method.

[Means for Solving the Problems] In order to achieve the above object, the present invention adds a new correction term proportional to the area (xo-yo) of the beam spot to equation (1). This is because the beam current value increases in proportion to the cross-sectional area of the electron beam, and errors due to the Coulomb effect increase. Therefore, formula (2) is used as the formula for calculating the correction amount.

ΔX=al+bl-XO+C1・YO+dl・XO-Y
OA X=C2+b2・XO+C2・YO+d240・
YO(2) In equation (2), the number of coefficients has increased from 6 to 8. For this reason, the measurements shown in FIG.
, yo, etc. and repeating the four sets of equations four times as simultaneous equations to find 81 to dl, and similarly rotate the shielding plate 2 by 90 degrees to find a1 to d2. In the invention, the correction term dl・xO・YO proportional to the cross-sectional area of the electron beam is calculated using the coefficients dl and dl
and dl, xO, YO, etc., and further correct the cross-sectional shape of the electron beam to achieve highly accurate drawing.

[Operations] The electron beam lithography method and apparatus of the present invention configured as described above corrects the error in the cross-sectional area that is proportional to the area of the cross-section of the electron beam, thereby eliminating the error in the spread of the electron beam due to the Coulomb effect. This effect can be obtained.

[Example] Hereinafter, an example of the present invention will be described using the drawings. 1st
The figure is a block diagram of a correction device that performs the correction according to the present invention shown in equation (2) above. The signals actually applied to the deflection plates 31, 32, etc. are the input signals XO and YO plus ΔX and ΔY shown in equation (2). Therefore, each component constituting (XO+ΔX) and (YO+ΔY) is stored in the memory device 41 in the form of a table corresponding to the values of XO and YO. When Xo and YO are input, they are used as address signals, for example, as the X-axis output, [al+(bl+
1) XOl, CI-YO and di-XO・'1
0 etc. are read out and added by adders 51 and 61,
After being temporarily stored in the register 52, the DA converter (
The signal is applied to the deflection plate 31 via a digital/analog converter (digital/analog converter) 53 and a deflection amplifier 54. The above dl・Xo-YO
is a newly generated term according to the present invention, and an adder 61 is newly added to add this term.

The same applies to the Y-axis signal.

FIG. 2 is a diagram illustrating the outline of an electron beam lithography apparatus that implements the present invention. Electron beam 6 emitted from electron beam source 6
1 is swept and drawn on the wafer (substrate) 7. As shown in FIG. 3, the electron beam 61 emitted from the electron beam source 6 is shaved off by a shaping aperture 81 at a portion corresponding to two sides of a quadrilateral, and then by a shaping aperture 82 as shown in FIG. The other two sides of the quadrilateral are shaved off to form a quadrilateral.

Therefore, the bottom-shaped aperture 81 allows the electron beam 61 to
After shaping the two sides of the quadrangle, the size of the quadrangle can be changed by deflecting the electron beam 61 toward the shaping aperture 82. This deflection is performed by applying a deflection signal to the deflection plates 33, 34, 35, etc. via the data controller 11 and the deflection controller 113 in response to a signal from the calculation bag [10]. Memory device 41 shown in
．． Adders 51, 55, 61, 62, registers 52, 56, etc. are included, and the deflection control device 13 includes DA converters 53, 57, deflection amplifiers 54, 58, etc.

In addition to the deflection control described above, the calculation device 10 measures the length of each side of the rectangular electron beam plate explained in FIG. 3, and uses the obtained data and equation (2) to perform eight corrections. A control operation is also performed in which the coefficients are calculated and required data is written into the memory device [41 of FIG. 1] based on the coefficients.

Reference numeral 9 denotes a shaping lens for electron beam convergence, which is controlled by the arithmetic unit 0 via the lens control device 12, but since it has no direct relation to the present invention, a detailed explanation of its operation will be omitted.

Note that in the embodiment of the present invention shown in FIG.
41, each term on the right side of equation (2) was calculated and stored in advance in correspondence with the values of ,c
l, dl, b2, C2, dl, etc., and store the above xo, y
It is also possible to calculate and correct each error component by multiplying them by the proportional coefficient using a multiplier every time o, etc. are input.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to correct the spread error of the electron beam due to the Coulomb effect, so that the drawing accuracy of the electron beam drawing apparatus can be improved.

In particular, errors due to the Coulomb effect, which have conventionally become apparent when increasing the current density of the electron beam to speed up the writing speed, can be quickly and accurately corrected, so it is possible to achieve the effect of significantly increasing the writing speed.

[Brief explanation of drawings]

Fig. 1 is a block diagram explaining the operating principle of the present invention;
The figure is a configuration diagram of an electron beam lithography apparatus that implements the method of the present invention.
3 and 4 are diagrams explaining the action of the shaping aperture that shapes the cross-sectional shape of the electron beam into a square, and Figure 5 is a diagram explaining the method of measuring the length of each side of the square electron beam cross-section. FIG. 6 is a block diagram illustrating the operating principle of the conventional device. 1... Electron beam cross section, 2... Shielding plate, 31 to 35
- Deflection plate, 4 and 41... Memory device, 51... Adder, 52... Register, S3... Digital-to-analog converter, 54... Deflection amplifier, 6... Electron beam Source, 7... Substrate, 81... Molding aperture, 9...
Molded lens, 1O... Arithmetic device, 11... Data control device, 12... Lens control device, 13... Deflection control device.

Claims (1)

[Scope of Claims] 1. In an electron beam drawing method in which the cross-sectional shape of an electron beam emitted by an electron beam source is shaped into a predetermined shape and irradiated onto a substrate, the electron beam is at least proportional to the area of the cross-sectional shape. An electron beam lithography method characterized in that an error component of the cross-sectional shape of the electron beam is calculated, and the cross-sectional shape of the electron beam is corrected using the error component. 2. Shape the cross-sectional shape of the electron beam emitted by the electron beam source into a quadrilateral, measure the length of each side of the quadrilateral, calculate their error components, and calculate the cross-section of the electron beam using the error components. In an electron beam drawing method that corrects the shape and irradiates the substrate, an error component proportional to the area of the quadrangular electron beam cross section is calculated, and the cross-sectional shape of the electron beam is further corrected based on this. An electron beam drawing method characterized by: 3. The electron beam lithography method according to claim 2, wherein the length of each side of the quadrangle is measured at least eight times. 4. In an electron beam drawing apparatus in which the cross-sectional shape of an electron beam emitted by an electron beam source is shaped into a predetermined shape and irradiated onto a substrate, an error component in the cross-sectional shape of the electron beam is at least proportional to the area of the cross-sectional shape. What is claimed is: 1. An electron beam lithography apparatus comprising: a storage device for storing the error component; and an addition device for adding the error component to other error components. 5. In an electron beam drawing apparatus in which the cross-sectional shape of an electron beam emitted by an electron beam source is shaped into a predetermined shape and irradiated onto a substrate, an error component in the cross-sectional shape of the electron beam is at least proportional to the area of the cross-sectional shape. 1. An electron beam lithography apparatus comprising: a storage device that stores a proportionality coefficient; and a multiplier that multiplies the proportionality coefficient by the area of the cross-sectional shape.