JP2786662B2 - Charged beam drawing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a charged beam writing apparatus for writing a fine pattern such as an LSI on a sample, and particularly to a method for setting a shape of a variable shaped beam. The present invention relates to an improved charged beam writing method.

2. Description of the Related Art Conventionally, as a device for drawing a desired pattern on a sample such as a semiconductor wafer, an electron beam drawing device of a variable shaped beam system has been used. To draw a diagonal pattern with such an electron beam drawing apparatus, the diagonal pattern was approximated by a fine rectangle. For this reason, in the hatched portions, the throughput is reduced, and the pattern formation accuracy is deteriorated due to the edge roughness.

In order to solve the above-mentioned problem, a method of generating a beam having a non-rectangular shape, for example, a triangular shape, in an electron beam writing apparatus using a variable shaped beam method has been attempted. By using these beams, it is possible to improve the formation accuracy of the oblique line pattern and improve the throughput. In such an apparatus, the irradiation position of the beam having a different shape on the sample usually differs depending on the shape, and therefore a correction technique for accurately adjusting the position is required. However, as the types of beam shapes increase, the correction technique (including the beam position and beam size) becomes extremely complicated, and a simple and high-precision correction technique is required to obtain pattern accuracy.

In particular, when a rectangular beam and other beams, such as a triangular beam, are formed, it is difficult to form these beams with high dimensional accuracy due to the rotational displacement between the two apertures and the shaping deflection system. In addition, when a non-rectangular triangular beam is generated, a displacement of the triangular beam with respect to the rectangular beam occurs on the sample surface. To correct this displacement, a dedicated position correction deflector was required, and it was necessary to calibrate the deflector specially, and a high-speed deflection amplifier and a deflection control circuit were required, complicating the hardware. .

(Problems to be Solved by the Invention) As described above, conventionally, by using a rectangular or non-rectangular shaped beam, it is possible to improve the formation accuracy and throughput of a diagonal pattern, but to obtain a high-precision pattern formation accuracy. At present, there is no beam correction technology. In particular, it has been difficult to accurately set the shapes and dimensions of the rectangular and other shaped beams.

The present invention has been made in view of the above circumstances, and an object thereof is to be able to generate rectangular and non-rectangular shaped beams, and to accurately set the shape and dimensions of the beams. Another object of the present invention is to provide a charged beam writing method capable of improving the pattern writing accuracy.

[Structure of the Invention] (Means for Solving the Problems) The gist of the present invention is to determine the positional relationship between the first aperture image and the second aperture in the shaping deflection coordinates,
An object of the present invention is to correct a rotational deviation or the like of a forming deflector by calibrating the sensitivity of a forming deflection system.

That is, in the present invention, a shaping deflection system for beam shaping is arranged between the first and second shaping apertures, and the size and shape of the rectangular and non-rectangular charged beams are variably controlled to draw a desired pattern on the sample. A charged beam writing method for generating a rectangular beam and a shaped beam other than a rectangular beam.
In determining the reference position of the shaping aperture, the shaping deflection system scans the first shaping aperture image on the second shaping aperture to determine the relationship between the beam current passing or reflecting through the second shaping aperture and the shaping deflection coordinates. In this method, the edge position of the second shaping aperture in the shaping deflection coordinates is obtained from the relationship (1).

According to the present invention, a shaping deflection system for beam shaping is arranged between the first and second shaping apertures, and a desired pattern is drawn on a sample by variably controlling the size and shape of a rectangular or non-rectangular charged beam. In the charged beam writing method, the first shaping aperture image is scanned on the second shaping aperture by the shaping deflection system, and the first shaping aperture is determined based on the relationship between the beam current passing or reflecting through the second shaping aperture and shaping deflection coordinates. 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 and the actual size match on the sample surface.

(Action) According to the present invention, the first shaping aperture image is scanned on the second shaping aperture by the shaping deflection system, and the relationship between the beam current passing or reflecting through the second shaping aperture and the shaping deflection coordinates is obtained. In addition, the edge position of the second shaping aperture in the shaping deflection coordinates can be obtained, whereby the reference position on the second shaping aperture necessary for generating a shaping beam other than a rectangle can be accurately obtained. Further, the positional relationship between the first aperture image and the second aperture is obtained, and the sensitivity coefficient of the shaping deflection system is calibrated so that the dimension setting value of the rectangular beam matches the actual beam dimension, so that the rectangular beam and the Other shapes and dimensions of the shaping beam can be accurately set.

(Examples) Hereinafter, details of the present invention will be described with reference to the illustrated examples.

FIG. 1 is a schematic structural view showing an electron beam drawing apparatus used in the method of one embodiment of the present invention. In the figure, reference numeral 10 denotes a sample chamber, in which a sample table 12 on which a sample 11 such as a semiconductor wafer is placed is accommodated. The sample stage 12 is a computer 30
Are moved in the X direction (left and right directions on the paper) and the Y direction (front and back directions on the paper) by the sample stage drive circuit 31 which receives the command from. Then, the movement position of the sample table 12 is measured by the laser length measurement system 32, and the measurement information is transmitted to the computer 30 and the deflection control circuit.
33.

On the other hand, above the sample chamber 10, an electron gun 21, various lenses 22
There is provided an electron optical barrel 20 comprising a,..., 22e, various deflectors 23,..., and beam shaping aperture masks 27a, 27b. Here, the deflector 23 is a blanking deflector for turning on and off the beam, and a blanking signal from a blanking control circuit 34 is applied to the deflector 23. The deflector 24 is a beam size changing deflector that variably controls the beam size by utilizing the optical aperture overlap of the aperture masks 27a and 27b. A signal is applied. The deflectors 25 and 26 are beam scanning deflectors for scanning the beam on the sample 11, and a deflection signal is applied to the deflectors 25 and 26 from a deflection control circuit 33.

In the sample chamber 10, an electron detector 37 for detecting reflected electrons and the like from the sample 11 is provided. This electronic detector
Reference numeral 37 is used to detect reflected electrons and the like when scanning the alignment mark formed on the sample 11 with an electron beam and measure the mark position. The detection signal of the electronic detector 37 is sent to the computer 30.

Next, a method for controlling a shaped beam using the above apparatus will be described.

First, as shown in FIG. 2, the first shaping aperture image 41
a is uniformly scanned on the second shaping aperture 42, and the beam current is measured by a Faraday cup provided on the sample surface. Thus, a rough positional relationship between the first shaping aperture image 41a and the second shaping aperture 42 can be obtained from the relationship between the coordinates of the shaping deflection system and the beam current passing through the second shaping aperture 42. Further, instead of the beam current, electrons reflected by the second shaping aperture 42 may be detected. Note that the first formed aperture image 41a is the first shaped aperture image 41a.
The aperture (first shaping aperture) 41 of the aperture mask 27a shown in FIG.
It is an image obtained by projecting on 7b. Further, the second shaping aperture 42 is provided with an aperture mask 27b shown in FIG.
Aperture.

Next, calibration is performed so that the dimension setting value of the rectangular beam matches the actual beam dimension on the sample surface. In the case of the present embodiment, after calibrating the main / sub two-stage deflectors 25 and 26 with respect to the laser coordinates, the waveform of the reflected electron signal obtained by scanning the fine particles of gold with the edge of the forming beam becomes horizontal. As the first
And the directions of the second forming apertures 41 and 42 are aligned.
With this method, the sides of each of the apertures 41 and 42 can be accurately adjusted to the laser coordinates. Further, a zero-point beam is calibrated so that a rectangular beam is generated and the beam current changes linearly with respect to the X and Y beam dimensions, and the beam current becomes zero when the dimension is zero. The beam size is measured, and the sensitivity coefficient of the shaping deflection system is calibrated so that the rate of change of the set value of the beam size and the rate of change after measurement match. The deflection sensitivity coefficient of the molding deflection system obtained from this is shown in the equation, and the sensitivity correction equation of the molding deflection system based on this deflection sensitivity coefficient is shown in the equation.

However, in the above formula, X and Y are shaping deflection coordinates, x and y are beam dimensions,
i indicates a beam shape.

Here, when the beam current is measured while changing the beam size in the directions shown in FIGS. 3 (a) and 3 (b), FIG. 4 (a)
The relationship shown in (b) is obtained. From these results, the dimensions L ₁ and L _{2 of} the first shaping aperture image 41a and the second shaping aperture 42
The length L of one side AB can be obtained as a dimension on the sample surface. For example, this dimension is 2 μm, and the actual dimension of side AB is 80 μm
Then, the reduction ratio (1/40) of the shaped beam can be obtained. Therefore, in order to move the first shaping aperture image 41a to the position shown in FIG. 5, the positional relationship converted into dimensions on the sample surface is substituted into the second equation, and a value converted into shaping deflection coordinates is obtained. Then, if the first shaping aperture image 41a is deflected, it can be positioned at the point shown in FIG. This makes it possible to determine the reference position P ₁ to P ₄ for triangular beam generates a rectangular beam as a reference (reference position P ₀₎ with high accuracy.

As a method for improving the accuracy of the reference position,
The following method is effective. The reference position P ₁ to
The beam current is measured while changing the dimensions of the four types of triangular beams with P ₄ as the zero point, and the relationship between the beam size and the beam current is applied to a quadratic function to set the zero point (actually when the beam size setting data is zero (The point at which the beam size of zero becomes zero) is adjusted. Here, as shown in FIG. 6, the first shaping aperture image 41a is moved so as to obtain one fixed point 61 and two fixed sides 62 sandwiching the fixed point 61 on the sample surface. The deflection sensitivity coefficients and the correction equations for the four triangular beams are shown in the following equations.

This zero point adjustment means that the parameters of Si, Ti (i = 1, 2, 3, 4) in the equation have been adjusted. With the above method, the calibration of the shaping deflection system is completed, and a triangular beam having the set value and the actual size matched can be generated on the sample surface.

Note that the above calibration can be performed only by measuring the beam current without calculating the beam size on the sample surface.
If the mechanical assembly accuracy of the shaping deflector 24 is high, the beam dimensional accuracy does not deteriorate even if a, b, c, and d in the equations are set as follows.

As shown in FIGS. 3 (a) and 3 (b), the beam current is measured while changing the size of the rectangular beam, and the relationship between the two is applied to a quadratic function to obtain θ in the equation from the coefficient of the quadratic function obtained. be able to. When the shaping deflection system is corrected with the obtained θ, the beam current changes linearly with the change in the X and Y beam dimensions. The same effect can be obtained by mechanically rotating the forming deflector by θ. After that, when the beam current becomes zero when the beam size is zero,
When the relationships shown in FIGS. 4 (a) and 4 (b) are obtained, the value of K in the expression converted by the dimension on the second aperture can be obtained. That is, assuming that the length of the side AB of the second aperture is 80 μm, the value of K is determined so that the first formed aperture image moves from the side AA ′ to the side BB ′ when 80 μm is input to x in the equation. At the same time, the size of the first shaping aperture image on the second shaping aperture can be obtained. Finally, as shown in FIG. 5, triangle beams first shaped beam at the reference position four points P ₁ to P ₄ of the second aperture for generating dimensions and a second shaping zeros P ₀ of the rectangular beam as a reference By calculating from the dimensions of the aperture and substituting it into the equation, it is possible to obtain a reference position for generating four triangular beams at the shaping deflection coordinates.

Next, the position of each beam is corrected by the sub deflector in order to smoothly connect the five types of beams including the rectangle and the triangle on the sample surface. When the drawing data is configured with the fixed point 61 of the five types of beams (the end point of the beam that does not move on the sample surface even when the beam size is changed) as the origin of the graphic data, all the five types of beams have one fixed point. Since there are a point 61 and two immovable sides 62 (sides of the beam that do not move on the sample surface even when the beam size is changed), the positional relationship of each beam is only a parallel movement component depending on the beam shape.

In order to calibrate this, in the present embodiment, as shown in FIG. 7, the gold fine particles 71 provided on the sample surface are scanned with each beam, and the fixed point 61 of each beam is measured. In the case of the triangular beam 72, scanning in a direction of 45 degrees is also required as shown in FIG. At this time, it is necessary to correct the position shift amount of the backscattered electron detector and its amplifier due to signal delay. The deviation amount (parallel movement amount) of the fixed point coordinates of each beam with respect to the rectangular beam is obtained and stored in a memory or the like of the correction circuit. At the time of actual drawing, when the beam shape and the size are determined, the shaping deflector deflects the first shaping aperture image to generate a beam having the specified shape and size, and performs a triangular swingback operation corresponding to the shape ( (Parallel movement correction) is executed by the sub deflection control circuit to correct the position of the rectangular and triangular beams.

FIG. 9 shows the positional relationship between the first shaping aperture image 41a and the second shaping aperture 42 in this embodiment. When the rectangular and four types of triangular beams are generated in this way, as shown in FIG. 10, the beams are irradiated on the sample surface at positions deviated from the respective beams. These displacements can be corrected by the sub deflector. For this reason, in the present embodiment, these positional deviation correction (triangular swingback calculation) circuits are added to the deflection correction calculation circuit of the sub deflector to correct the position of each beam. The correction equation is expressed by a first-order polynomial using the beam size as a variable for each beam shape, as shown in the following equation.

However, X, Y position correction amount, x, y is the beam size, M ₀ ~M _3, N
₀ to N ₃ represents the coefficient for each beam shape.

In the present embodiment, the beam size and the irradiation position are corrected as follows. First, a 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 the zero point is adjusted. As a result, if the dimensions of the rectangular beam and the triangular beam are specified using the deflection sensitivity and the zero point data, a beam having the specified size can be generated on the sample surface.

Here, the beam size is further changed for each beam shape, and from the intensity distribution of the reflected electron signal obtained by scanning the fine gold particles provided on the sample surface, the fixed side of the rectangular beam (beam size The position of the edge of the right-angled triangular beam with respect to the edge of the beam that does not move on the sample surface when changed is measured at several points. Using these data, the relationship with the size of the triangular beam is substituted into the equation, and the correction coefficients M _{0 to} M ₃ and N _{0 to} N ₃ are determined. This is performed for each shape of the beam, and a correction coefficient is determined for each beam. At the time of actual writing by using the correction coefficients determined as described above, when the shape and size of the beam are determined, the shaping deflector 24 deflects the first shaping aperture image 41a so that the beam having the specified shape and size is formed. A triangular swing-back operation that can be generated and corresponds to the shape can be executed with high accuracy by the sub deflection control circuit, and highly accurate pattern drawing using rectangular and triangular beams can be performed.

The correction amount of the beam position by the sub deflector (the correction amount of the return of the triangle) can be measured by the following method. As shown in FIG. 11, this method measures the edge positions of the moving side 63 and the immovable side 62 of each triangle. In this method, the setting accuracy of the beam size is included as a measurement error.However, the signal delay correction of the backscattered electron detector and its amplifier is not required, and not only the fine particles of gold but also the step mark are measured at the edge position measurement. Can also be used.

When measuring the positional relationship between a rectangular beam and a triangular beam in order to increase the accuracy of measuring the edge position of the beam, which further affects the joining accuracy of the triangular beam, both beams having the same area are measured on the sample surface. It is effective to fix the gain and level of the backscattered electron detector amplifier and measure the edge positions of the two with the same threshold level for edge detection.

The present invention is not limited to the above-described embodiment, and can be implemented with various modifications without departing from the spirit of the invention. For example, as a method of measuring the edge position of a right-angled triangular beam, not only gold particles but also protrusions and holes may be used. Further, the device configuration is not limited to what is shown in FIG. 1 and can be appropriately changed according to the specifications. Furthermore, the present invention is not limited to electron beam lithography, and can be applied to ion beam lithography.

[Effects of the Invention] As described in detail above, according to the present invention, the positional relationship between the first aperture image and the second aperture in the shaping deflection coordinates is obtained, and the rotational deviation is corrected for the sensitivity of the shaping deflection system. Therefore, a rectangular or non-rectangular shaped beam can be generated, and the shape and size of the beam can be accurately set. Therefore, it is possible to improve the pattern writing accuracy in the charged beam writing apparatus.

[Brief description of the drawings]

FIG. 1 is a schematic structural view showing an electron beam writing apparatus used in the method of one embodiment of the present invention, FIGS. 2 to 5 are schematic views for explaining a zero point adjusting method, and FIGS. 6 to 8. FIG. 9 is a schematic diagram for explaining a beam shape correction method, and FIGS.
FIG. 11 is a schematic diagram for explaining a beam position correction method for a sample. 10 ... Sample chamber, 11 ... Sample, 12 ... Sample table, 20 ... Electronic optical column, 21 ... Electron gun, 22a-22e ... Lens, 23-26
…… Deflector, 27a, 27b …… Aperture for beam shaping, 30
... Computer, 31 ... Sample stage drive circuit, 32 ... Laser measurement system, 33 ... Deflection control circuit, 34 ... Blanking control circuit, 35 ... Variable shaped beam size control circuit, 41 ... First Forming aperture, 41a ... First forming aperture image, 42 ...
Second forming aperture, 61: fixed point, 62: fixed side, 63
... fixed side, 71 ... fine gold particles, 72 ... triangular beam.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) H01L 21/027 G03F 7/20

Claims (5)

(57) [Claims] 1. A shaping deflection system for shaping a beam is arranged between a first shaping aperture and a second shaping aperture, and a desired pattern is drawn on a sample by variably controlling the size and shape of a rectangular or non-rectangular charged beam. In obtaining the reference position of the second shaping aperture for generating the rectangular beam and the non-rectangular shaping beam, the shaping deflection system scans the first shaping aperture image on the second shaping aperture. A charged beam drawing method comprising: obtaining a relationship between a beam current passing or reflecting through a second shaping aperture and shaping deflection coordinates, and obtaining an edge position of the second shaping aperture in the shaping deflection coordinates from the relationship. 2. A reference edge position of the second shaping aperture is determined by shaping deflection coordinates from a relationship between a position of the first shaping aperture image at shaping deflection coordinates and a beam current passing through the second shaping aperture. Actual dimensions and first
From the relationship between the size obtained by converting the size of the shaping aperture image into shaping deflection coordinates and the beam current passing through the second shaping aperture, the edge position of the second shaping aperture necessary to generate a beam other than a rectangular beam is determined by shaping deflection coordinates. The charged beam writing method according to claim 1, wherein 3. A shaping deflection system for beam shaping is disposed between the first and second shaping apertures, and a desired pattern is drawn on a sample by variably controlling the size and shape of a rectangular or non-rectangular charged beam. In the charged beam writing method, the first shaping aperture image is scanned on the second shaping aperture by the shaping / deflecting system, and the first shaping aperture image is formed based on the relationship between the beam current passing or reflecting through the second shaping aperture and shaping deflection coordinates.
The positional relationship between the shaping aperture 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 and the actual size match on the sample surface. Charged beam drawing method. 4. A means for calibrating the sensitivity coefficient of the shaping deflection system, wherein the sides of the first and second shaping apertures are adjusted to laser coordinates, and then a rectangular beam is generated so that both X and Y correspond to the beam size. After the beam zero point is calibrated so that the beam current changes linearly and the beam current becomes zero when the dimension is zero, the rate of change of the dimension setting value of the rectangular beam and the rate of change of the measured value on the sample are 4. The charged beam drawing method according to claim 3, wherein the sensitivity coefficient of the shaping deflection system is calibrated so as to match. 5. A charged beam drawing apparatus according to claim 1, wherein said first shaping aperture is rectangular, and said second shaping aperture is formed by connecting two rectangles at an angle of 45 degrees to each other. Method.