JPH02262328A - Charged beam pattern drawing method - Google Patents

Abstract

PURPOSE:To generate forming beams of rectangle and other shapes, and precisely set form and size of the beam, by scanning a first forming aperture image on a second forming aperture by a forming deflection system, and obtaining the relation between the beam current which passes the second forming aperture or is reflected and forming deflection coordinates. CONSTITUTION:Between a first and a second forming apertures 41, 42, a forming deflection system 24 for beam forming is arranged; sizes and shapes of charged beams of rectangle and of the other forms are controlled, thereby drawing a desired pattern on a sample 11. In this charged beam pattern drawing method, when the reference position of the second forming aperture 42 for generating forming beams of rectangle and other shapes is obtained, a first forming aperture image 41a is scanned on the second forming aperture 42 by the forming deflection system 24. The relation between the beam current which passes the second forming aperture 42 or is reflected and forming deflection coordinates is obtained, and from said relation, the edge position of the second forming aperture 42 in the forming deflection coordinates is obtained. For example, the second forming aperture 42 is formed by connecting two rectangles so as to be mutually inclined at 45 deg..

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a charged beam drawing device for drawing fine patterns of LSI etc. on a sample, and particularly relates to a method for setting the shape of a variable shaped beam. This paper relates to an improved charged beam writing method.

(Prior Art) Conventionally, a variable shaped beam type electron beam drawing apparatus has been used to draw a desired pattern on a sample such as a semiconductor urchin. In order to draw a diagonal line pattern using such an electron beam drawing apparatus, the diagonal line pattern is approximated by a fine rectangle. For this reason, in the shaded area, the throughput was reduced and the pattern formation accuracy was degraded due to edge roughness.

In order to solve the above-mentioned problems, attempts have been made to generate a beam having a shape other than a rectangle, for example, a triangular shape, in an electron beam lithography apparatus using a modified beam method. By using these beams, it is possible to improve the accuracy of forming the diagonal line pattern and to improve the throughput. In such an apparatus, the irradiation position of beams of different shapes on the sample usually differs depending on the shape, so a correction technique is required to accurately match the positions. However, as the number of types of beam shapes increases, the correction techniques (including beam positions and beam dimensions) become extremely complex, and simple and highly accurate correction techniques are required to obtain pattern accuracy.

In particular, when forming rectangular beams and other beams, such as triangular beams, it is difficult to form these beams with high dimensional accuracy due to rotational misalignment between the two apertures and the shaping deflection system. Furthermore, when a triangular beam other than a rectangular beam is generated, a positional shift of the triangular beam with respect to the rectangular beam occurs on the sample surface. Correcting this positional deviation requires a dedicated position correction deflector, which requires special calibration, and requires a high-speed deflection amplifier and deflection control circuit, making the hardware complex. .

(Problems to be Solved by the Invention) As described above, conventionally, by using rectangular and non-rectangular shaped beams, it is possible to improve the formation accuracy and throughput of diagonal line patterns, but it is difficult to obtain high pattern formation accuracy. At present, there is no beam correction technology available. In particular, rectangular and other shaped beam shapes and -
・It was difficult to set the accuracy of the method.

The present invention has been made in consideration of the above circumstances, and its purpose is to be able to generate rectangular and non-rectangular shaped beams, and to set the shape and dimensions of the beam with high precision. Another object of the present invention is to provide a charged beam drawing method that can improve pattern drawing accuracy.

[Configuration of the Invention (Means for Solving the Problems) The gist of the present invention is to obtain the positional relationship between the first aperture image and the second aperture in the shaping deflection coordinates, and to correct rotational deviation of the shaping deflector, etc. The purpose is to correct the sensitivity of the system by calibrating it.

That is, the present invention arranges a shaping deflection system for beam shaping between the first and second shaping apertures, variably controls the dimensions and shapes of a rectangular and non-rectangular charged beam, and draws a desired pattern on a sample. In the charged beam drawing method, when determining the reference position of the second shaping aperture for generating a rectangular beam and a non-rectangular shaped beam, scanning the first shaping aperture image over the second shaping aperture by a shaping deflection system, In this method, the relationship between the beam current passing through or reflecting from the second shaping aperture and the shaping deflection coordinates is determined, and the edge position of the second shaping aperture in the shaping deflection coordinates is obtained from these relationships.

Furthermore, the present invention arranges a shaping deflection system for beam shaping between the first and second shaping apertures, variably controls the dimensions and shapes of the rectangular and non-rectangular charged beams, and draws a desired pattern on the sample. In a charged beam writing method, a first shaping aperture image is scanned over a second shaping aperture by a shaping deflection system, and from the relationship between the beam current passing through or reflecting the second shaping aperture and the shaping deflection coordinates, the first shaping aperture image is scanned by a shaping deflection system. In this method, the positional relationship between the image and the second shaping aperture is determined, and then the sensitivity coefficient of the shaping deflection system is calibrated so that the dimension setting value of the rectangular beam matches the actual dimension on the sample surface.

(Function) According to the present invention, by scanning the first shaping aperture image over the second shaping aperture using the shaping deflection system and determining the relationship between the beam current passing through or reflecting through the second shaping aperture and the shaping deflection coordinates. , the edge position of the TS2 shaping aperture in the shaping deflection coordinates can be obtained, and thereby the reference position on the second shaping aperture required when generating a shaped beam other than rectangular can be determined with high accuracy. In addition, by determining the positional relationship between the first aperture image and the second aperture, and calibrating the sensitivity coefficient of the shaping deflection system so that the dimension setting value of the rectangular beam matches the actual beam dimension, the rectangular beam and It becomes possible to accurately set the shape and dimensions of the other shaped beams.

(Example) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic configuration diagram showing an electron beam lithography apparatus used in an embodiment of the method of the present invention. In the figure, 10 is a sample chamber, and within this sample chamber 10 is accommodated a sample stage 12 on which a sample 11 such as a semiconductor wafer is placed. The sample stage 12 is
The sample stage drive circuit 31 receives commands from the computer 30 in the X direction (left and right directions on the page) and Y direction (front and back directions on the page).
will be moved to The moving position of the sample stage 12 is measured by the laser beam length system 32, and the measurement information is sent to the computer 3.
0 and the deflection control circuit 33.

On the other hand, above the sample chamber 10, there are an electron gun 21, various lenses 22a, various deflectors 23, 2
6 and an electron optical mirror t? consisting of beam shaping aperture masks 27a, 27b, etc. i20 is provided. Here, the deflector 23 is a blanking deflection plate for turning the beam ON-OFF, and a blanking signal from a blanking control circuit 34 is applied to this deflector 23.

1- The inner device 24 is a deflection plate for variable beam size that variably controls the beam size using the optical aperture overlap of the aperture masks 27a and 27b;
4 is applied with a deflection signal from a variable beam size control circuit 35. Further, the deflectors 25 and 26 are beam scanning deflection plates that scan the beam on the sample 11, and a deflection signal is applied from the deflection control circuit 33 to these deflectors 25 and 26.

Furthermore, an electron detector 37 for detecting reflected electrons from the sample 11 is provided in the sample chamber 10 . This electron detector 37 detects reflected electrons and the like when the alignment mark formed on the test sample 111 is scanned with an electron beam.
It is used to determine the mark position aPI. Note that the detection signal from the electronic detector 37 is sent to the computer 30.

Next, a method of controlling a shaped beam using the above device will be explained.

First, as shown in Figure 2, the first molding aperture is 1 m4.
1a is uniformly scanned on the second shaping aperture 42, and the beam current is set to 1l with a Faraday cup provided on the sample surface.
l11 is determined. As a result, from the relationship between the coordinates of the shaping deflection system and the beam current passing through the second shaping aperture 42,
First molding aperture a41a and second molding aperture 42
You can get a rough positional relationship with Further, instead of this beam current, electrons reflected by the second shaping aperture 42 may be detected. Note that the first shaped aperture image 41a is the same as the aperture mask 27a shown in FIG.
The aperture (first molded aperture) 41 of the lens 2
2c is an image obtained by projecting onto the aperture mask 17b. Further, the second shaping aperture 42 is the aperture of the aperture mask 27b shown in FIG. 1 above.

Next, calibration is performed so that the dimension settings of the rectangular beam and the actual beam dimensions match on the sample surface. In the case of this example, after calibrating the main and sub-stage deflectors 25 and 26 with respect to the laser coordinates, the waveform of the reflected electron signal obtained by scanning the gold particles with the edge of the shaped beam becomes horizontal. The directions of the first and second shaping apertures 41, 42 are aligned in this manner. By this method, the sides of each aperture 41, 42 can be aligned with the laser coordinates with high precision. moreover,
After calibrating the beam zero point so that a rectangular beam is generated and the beam current changes linearly with respect to both X and Y beam dimensions, and the beam current becomes zero when the dimensions are zero, the beam dimensions are adjusted on the sample. -P1 is set, and the sensitivity coefficient of the shaping deflection system is calibrated so that the rate of change in the beam dimension setting value matches the rate of change after measurement. The deflection sensitivity coefficient of the shaping deflection system obtained from this is shown in equation 0, and the sensitivity correction equation of the shaping deflection system based on this deflection sensitivity coefficient is shown in equation (2).

[type O] However, in the above formula, X and Y are shaping deflection coordinates, x and y are beam dimensions, and i is a beam shape.

Here, the beam is directed in the directions shown in Figures 3(a) and (b).
If the beam current is determined by A11l while changing the modulus, the fourth
The relationships shown in Figures (a) and (b) are obtained. From this result, the dimensions L1L2 of the first forming aperture image 41a and the second
The length of one side AB of the molding aperture 42 can be determined from the dimension on the sample surface.

For example, this dimension is 2μm, and the actual size of one side AB is 80μ [
If n, the reduction ratio (+/40) of the shaped beam can be found. Therefore, in order to move the first forming aperture B41a to the position shown in FIG. , first forming aperture 1m41a
By deflecting the object, it is possible to position the object at the point shown in FIG. This allows the rectangular beam to be set as a reference position (reference position P
. ), the reference positions P1 to P4 for generating triangular beams can be determined with high precision.

Also, this 2! As a way to improve quasi-position accuracy,
The following methods are effective. Reference position P1 obtained using the above method
~ Set the beam current to 71111 while changing the dimensions of the four types of triangular beams by closing P4 as the zero point, and apply the relationship between the beam justice and the beam current to a quadratic function to find the zero point (beam dimension setting data is zero) Adjust the point at which the actual beam justice becomes zero when . Here, as shown in Figure 6,
The first forming aperture image 41a is moved so that one fixed point 61 and two fixed sides 62 sandwiching this point are obtained on the sample surface. Note that the deflection sensitivity coefficients and correction formulas for the four triangular beams are shown in formulas (1) to (2).

[Lypel] [type 2] [: type 3] [type 4] This zero point adjustment is performed using Si, Ti (i-1,
This means that parameters 2, 3, and 4) have been adjusted. By the above method, the calibration of the shaping deflection system is completed, and a triangular beam whose set value matches the actual size can be generated on the sample surface.

Note that the above-mentioned calibration can be performed only by measuring the beam current without determining the beam dimensions on the sample surface. If the mechanical assembly accuracy of the shaping deflector 24 is high, the beam dimensional accuracy will not deteriorate even if a, b, c, and d of equation (2) are set as follows.

As shown in Figure 3 (a) and (b), the beam current is measured while changing the dimensions of the rectangular beam, and the relationship between the two is applied to a quadratic function. From the coefficients of the quadratic function obtained, θ in equation (■) can be calculated. You can ask for it. When the shaping deflection system is corrected using the obtained θ, the beam current changes linearly with respect to changes in both the X and Y beam dimensions. In addition, the molded deflector can be mechanically adjusted to θ
A similar effect can be obtained by rotating it. Then, after calibrating so that the beam current is zero when the beam size is zero, and finding the relationships shown in Figures 4(a) and (b), the K of formula (■) converted by the size on the second aperture is You can find the value. In other words, the length of the side AB of the second aperture is 80
Assuming μm, when 80μm is manually added to X in the formula ■, the first
The value of K is determined so that the shaped aperture image moves from side AA' to side BB'. Moreover, at the same time, the dimensions of the first shaping aperture image on the m2 shaping aperture can be determined. Finally, as shown in FIG. 5, the zero point P of the rectangular beam. Using this as a reference, four reference positions P1 to P4 for generating a triangular beam are determined from the .j' method of the T51 shaped beam on the second aperture and the .1 method of the second shaping aperture,
By substituting into equation (2), the base positions for generating four triangular beams in the shaping deflection coordinates can be found.

Next, in order to connect the five types of beams consisting of rectangular and triangular shapes smoothly on the sample surface, the position of each beam is corrected using a sub-deflector. Fixed point 61 of five types of beams (
If the writing data is created using the origin of the graphic data as the point at the edge of the beam that does not move on the sample surface even if the beam dimensions are changed, all five types of beams will be at one fixed point 61 and 2.
Since the beam has an immovable side 62 (a side of the beam that does not move on the sample surface even if the beam size is changed), the positional relationship between the respective beams is only a parallel movement component that depends on the beam shape.

In order to calibrate this, in this embodiment, as shown in FIG. 1 set. In the case of a triangular beam 72, scanning in a 45 degree direction is also required, as shown in FIG. At this time,
The amount of positional deviation due to signal delay of the backscattered electron detector and its amplifier must be corrected. The amount of deviation (parallel movement amount) of the fixed point coordinates of each beam with respect to the rectangular beam is determined and stored in the memory of the correction circuit or the like. During actual writing, once the beam shape and dimensions are determined, a shaping deflector deflects the first shaping aperture image to generate a beam with the specified shape and dimensions, and a triangular deflection operation corresponding to the shape ( (parallel movement correction) is executed by the sub-deflection control circuit to correct the positions of the rectangular and triangular beams.

FIG. 9 shows the first forming aperture lf&41 in this example.
The positional relationship between a and the second molding aperture 42 is shown. Like this, rectangle and 4FI! When such triangular beams are generated, each beam is irradiated at different positions on the sample surface, as shown in FIG. These positional deviation amounts can be corrected by the sub-deflector. Therefore, in this embodiment, these positional deviation correction (triangular swing back calculation) circuits are added to the deflection correction calculation circuit of the sub-deflector to correct the position of each beam.

The correction formula is expressed by a first-order polynomial with the beam size as a variable for each beam shape, as shown in the following formula.

However, X, Y are position correction amounts, x+Y is beam dimension, M
o = M 3 and N o -N 3 indicate coefficients for each beam shape.

In this embodiment, the beam size and its irradiation position are corrected as follows. First, the rough positional relationship between the first shaping aperture image 41a and the second shaping aperture 42 is obtained from the relationship between the coordinates of the shaping deflection system and the beam current measured earlier, and zero point adjustment is performed. As a result, by specifying the dimensions of the rectangular beam and triangular beam using the deflection sensitivity and zero point data, it is possible to generate a beam with the specified dimensions on the sample surface.

Here, the beam dimensions are changed for each beam shape, and the fixed side of the rectangular beam (beam dimension is The amount of positional deviation of the right triangular beam edge with respect to the edge of the beam that does not move on the sample surface when the beam is changed is measured at several points. Using these data, substitute the relationship between the triangular beam and the J method into equation (2) and calculate the correction coefficient M. -M,,N,-N.

Determine. This is performed for each shape of beam, and the correction coefficients are determined for each beam. When the shape and dimensions of the beam are determined during actual drawing by using the correction coefficients determined above, the first shaping aperture image 41a is deflected by the shaping deflector 24 to produce a beam having the specified shape and dimensions. In addition, the sub-deflection control circuit can perform triangular reversal calculations corresponding to the shape with high precision.
Highly accurate pattern drawing using rectangular and triangular beams is possible.

Further, the amount of correction of the beam position by the sub-deflector (the amount of correction of triangular downward movement) can also be determined Apj by the following method. As shown in FIG. 11, this method measures the edge positions of the moving sides 63 and fixed sides 62 of each triangle.

In this method, the beam size setting accuracy is included in the aP1 constant error, but it does not require correction of the signal delay of the backscattered electron detection and its amplifier, and when measuring the edge position, it is possible to detect not only fine gold particles but also step marks. You can also use

In addition, in order to further improve the accuracy of the beam edge position ap'r determination, which affects the joint viscosity of the triangular beam, when determining the positional relationship between the rectangular beam and the triangular beam in 4-1,
Both generate beams with the same area on the sample surface, fix the gain and level of the backscattered electron detector amplifier, and
It is effective to measure both edge positions with the same threshold level for edge detection.

Note that the present invention is not limited to the embodiments described above, and can be implemented with various modifications without departing from the gist thereof. For example, as a method for determining the 4p1 edge position of a right triangular beam, not only gold particles but also protrusions and holes may be used. Further, the device configuration is not limited to the same as shown in FIG. 1, and can be changed as appropriate according to specifications ↑1. Furthermore, it is possible to apply not only to electron beam lithography but also to ion beam lithography.

[Effects of the Invention] As detailed above, according to the present invention, the positional relationship between the first aperture image and the second aperture in the shaping deflection coordinates is determined, and these rotational deviations are used to calibrate the sensitivity of the shaping deflection system. Since the correction is performed by I-cutting, rectangular and non-rectangular shaped beams can be generated, and the shape and dimensions of the beam can be set with high accuracy.

Therefore, it is possible to improve the pattern drawing accuracy in the 6:I electronic drawing apparatus.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the configuration of an electron beam lithography system used in a method according to an embodiment of the present invention, FIGS. 2 to 5 are schematic diagrams for explaining the zero point adjustment method, and FIGS. 6 to 8 9 is a schematic diagram for explaining a beam shape correction method, and FIGS. 9 to 11 are schematic diagrams for explaining a beam position correction method on a sample. DESCRIPTION OF SYMBOLS 10... Sample chamber, 11... Sample, 12... Sample stand, 20... Electron optical V1 tube, 21... Electron gun, 22
a to 22e... Lens, 23 to 26... Deflector, 2
7a. 27b... Beam shaping aperture, 30... Computer, 31... Sample stage drive circuit, 32... Laser length measurement system, 33... Deflection control circuit, 34... Blanking control circuit, 35...Variable shaping beam size control circuit, 4
1... First shaping aperture, 41a... First shaping aperture image, 42... Second shaping aperture, 61...
・Fixed point, 62...Fixed edge, 63...Fixed edge, 71
...Gold particles, 72...triangular beam. Applicant's agent Patent attorney Takeshi Suzue Hikogayu (a) Congee diagram

Claims (5)

[Claims] (1) A shaping deflection system for beam shaping is arranged between the first and second shaping apertures, and the dimensions and shapes of the rectangular and non-rectangular charged beams are variably controlled to draw a desired pattern on the sample. In the beam writing method, when determining the reference position of the second shaping aperture for generating a rectangular beam and a non-rectangular shaped beam, the shaping deflection system scans an image of the first shaping aperture over the second shaping aperture; 1. A charged beam drawing method, characterized in that a relationship between a beam current passing through or reflected through a second shaping aperture and a shaping deflection coordinate is determined, and an edge position of the second shaping aperture in the shaping deflection coordinate is obtained from these relationships. (2) Find the reference edge position of the second shaping aperture in the shaping deflection coordinates from the relationship between the position of the first shaping aperture image in the shaping deflection coordinates and the beam current passing through the second shaping aperture, and determine the actual size of the second shaping aperture. and the dimensions obtained by converting the dimensions of the first shaping aperture image into shaping deflection coordinates and the dimensions of the second shaping aperture image.
The charged beam drawing method according to claim 1, characterized in that the edge position of the second shaping aperture necessary for generating a non-rectangular beam is determined by shaping deflection coordinates from the relationship with the beam current passing through the shaping aperture. . (3) A shaping deflection system for beam shaping is arranged between the first and second shaping apertures, and the dimensions and shapes of the rectangular and non-rectangular charged beams are variably controlled, and the charging is performed to draw a desired pattern on the sample. In the beam writing method, the first shaping aperture image is scanned over the second shaping aperture by the shaping deflection system, and the first shaping aperture image is determined from the relationship between the beam current passing through or reflecting from the second shaping aperture and the shaping deflection coordinates.
The method is characterized by determining the positional relationship between the shaping aperture image and the second shaping aperture, and then calibrating the sensitivity coefficient of the shaping deflection system so that the dimension setting value of the rectangular beam matches the actual dimension on the sample surface. Charged beam drawing method. (4) As a means of calibrating the sensitivity coefficient of the shaping deflection system, after aligning the sides of the first and second shaping apertures with the laser coordinates, a rectangular beam is generated and the beam is After calibrating the beam zero point so that the current changes linearly and the beam current becomes zero when the dimension is zero, the rate of change of the set value of the rectangular beam dimension on the sample matches the rate of change of the measured value. 4. The charged beam drawing method according to claim 3, wherein the sensitivity coefficient of the shaping deflection system is calibrated as follows. (5) The charged beam drawing method according to claim 1 or 3, wherein the first shaping aperture is rectangular, and the second shaping aperture is two rectangles connected at an angle of 45 degrees.