JPS6293932A - Correction of irradiating positions ans size of beam in charged beam exposure device - Google Patents

Abstract

PURPOSE:To reduce the number of multipliers by a method wherein, when beam irradiating positions X, Y and beam size w, h are specified for correction, higher dimensional function terms such as XY, X<2>... wh, w<2>, etc., in addition to said linear terms are stored to digitally multiply each term for correction. CONSTITUTION:The beam irradiating positions (X, Y) and beam size w, h are specified to picture-draw an electrooptical system after correcting an asymmetrical deflection. A digital circuit to calculate the corrected values X', Y' of main and sub asymmetrical deflections respectively require nine each of multipliers; the data inputted in each multiplier 21-29 are stored in a front stage memory of a digital processing circuit comprising nine each of multipliers and an addition circuit; and correction coefficients A, B, a, b are previously measured to be stored. In such a constitution, the number of multipliers to calculate the correction coordinates (X', Y') amounting to 18 each is a reduced number down to 9/16 of the conventional system cutting down the cost inversely proportionally to the increase in the memory capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for correcting the beam irradiation position and beam size in a charged beam exposure apparatus that forms fine patterns necessary for manufacturing semiconductor integrated circuits and the like.

[Conventional technology]

Exposure apparatuses using charged beams include ion beam exposure apparatuses and electron beam exposure apparatuses. Here, '+'j
The conventional technology will be explained by taking an i-son beam exposure apparatus as an example.

When exposing a pattern on a sample surface using an electron beam exposure device, it is required to position the beam irradiation position with high precision at the position where the pattern is to be exposed. 'Since deflection distortion exists in the electron optical system, which is a component of an electron beam exposure apparatus, it is necessary to correct this deflection distortion. Next, a conventional deflection distortion correction method will be explained. The deflection distortion correction method will be explained below.

Takagi et al., “High-precision electron beam exposure system - EB55J.

Research Practical Report Vol. 30 No. 7, p, 1833.198
1 ; is described in.

High-precision electron beam exposure equipment-EB55 adopts a variable shaping beam to deflect the electron beam.

A deflector consisting of two main and sub stages is used. The dimensions of the main deflection field are 2.6 mm x 2.6 mm, and the dimensions of the secondary deflection field are 80IIm x 80-. When drawing a pattern, first, the main deflector is used to align the beam irradiation position with the center coordinates of the sub-deflection field.

Next, a pattern is drawn within that sub-deflection field.

By repeating this process, a pattern is drawn in each sub-deflection field. Here, FIG. 5 shows the structure of drawing data for drawing a pattern within one main deflection field. The data for drawing a pattern in one sub-deflection field is the center coordinates (X, Y) of the sub-deflection field expressed in the main deflection field coordinate system, and the pattern data (X+:/ +w
, h). However, (X.

y) is the position of the drawing pattern expressed in the sub-deflection field coordinate system, W is the width of the drawing pattern, and h is the height of the drawing pattern.

Since deflection distortion exists in the electron optical system of an electron beam exposure apparatus, it is necessary to correct this deflection distortion when drawing a pattern. By correcting the deflection distortion, the beam irradiation position 11' can be determined with high precision. An electron optical system using a two-stage deflector has a main deflection distortion in the main deflection field and a sub deflection distortion in the sub deflection field. The main deflection distortion is the center coordinates (X, Y) of the sub-deflection field expressed in the main deflection field coordinate system, and the sub-deflection distortion is the drawing pattern position (x+
y) to appropriate values.

The main deflection distortion correction formula for correcting the main deflection distortion is shown in equation (L). The corrected data is (x', y'). Cocote, coefficient A1. Bi (i20-9) is a deflection distortion correction coefficient, which is obtained from the results of measuring the main deflection distortion.

A sub-deflection distortion correction formula for correcting the sub-deflection distortion is shown in equation (2). The corrected data is (x'+y'). Here, the coefficient air bi (i=o~3) is a sub-deflection distortion correction coefficient, and is obtained from the result of measuring the sub-deflection distortion.

In the case of a variable shaped beam, it is difficult to adjust the input data w, h regarding the beam dimensions so that they exactly match the actually obtained beam dimensions. , : by correcting the input data.

Ensure that the input data matches the actual beam dimensions. The beam size correction formula is shown in equation (3). The corrected data is defined as W'l h'. Here, the coefficient ei
+f; (i=o~3) is a beam size correction coefficient, which is obtained from the difference between the input data and the actual 8111 value.

In an electron beam exposure apparatus, the calculations of equations (1), (2), and (3) are performed by a digital circuit in order to draw a pattern at high speed. FIG. 6 shows the configuration of a digital circuit for determining X' in equation (1). The configuration of the digital circuit for determining Y' is also similar. 1 to obtain X'
Six multipliers are used. Including the circuit for calculating Y', 32 multipliers are used to calculate equation (1). FIG. 7 shows a digital circuit for determining X' in equation (2). The configuration of the digital circuit for determining y' is also similar. Four multipliers are used to obtain X'. Including the circuit for calculating y', eight multipliers are used to calculate Equation 9 (2). The calculation of equation (3) is performed by a digital circuit having the same configuration as that of equation (2). By the way, type 1 (
A high-bit multiplier is used for the operation in 1). For the multiplier used to calculate equations (2) and (3).

A method with low bits but high calculation speed is used.

[Problem 3 to be Solved by the Invention The digital circuit for calculating deflection distortion correction described above is applied to an electron beam exposure apparatus that uses a single electron beam. By the way, in an electron beam exposure apparatus that simultaneously generates and controls a plurality of electron beams, each electron beam has a different deflection distortion, so it is necessary to correct the deflection distortion of each electron beam individually. For this reason, when a conventional digital circuit for calculating deflection distortion correction is applied to a device that uses multiple electron beams, the number of squaring multipliers becomes enormous, the cost to manufacture this circuit becomes enormous, and the scale of two circuits increases. As the size increases, the total exposure time also increases. Therefore, especially in electron beam exposure systems that use several electron beams, it is important to reduce the scale of the digital circuit in order to reduce manufacturing costs and shorten the total exposure time. Become.

The present invention can reduce the scale of a digital circuit for correcting deflection distortion. The present invention aims to provide a method for correcting the beam irradiation position and beam size in a charged beam exposure bag "t".

[Means for solving problems]

In the present invention, in order to achieve the above object, in addition to the linear function term of X, Y or w, h, the correction formula for correcting the specified beam irradiation position X, Y and beam dimensions w, h is added. Higher order function terms, X, Y.

x2. . . . or when using a correction formula including wh, w”, etc., these higher-order function terms are also stored in advance in the memory device as human data.

The method is to receive this input data, calculate each term of the correction equation using a digital multiplication circuit, and add the calculation results to obtain the corrected beam irradiation position and beam size.

[Effect]

Higher-order function terms xy, x”, ... or wh, w2...
- etc. are stored in the memory device as input data, thereby reducing the number of digital multipliers compared to conventional devices that calculate these higher-order function terms by multiplying them using digital multipliers. This makes it possible to reduce device costs and shorten the total exposure time.

〔Example〕

An electron beam exposure apparatus is an embodiment of the present invention.

Similar to the devices described in the prior art, it uses a variable shaped beam and has two sub-stages of deflectors.

A first embodiment of the present invention will be described.

FIG. 1 shows the structure of pattern drawing data in this embodiment. As input data for correcting the sub-deflection field center coordinates (x, y), not only X, Y but also X2 . XY
,Y”,X3.X2Y,X,Y2゜Yl.

Correction of the main deflection distortion and correction of the sub-deflector are performed using equations (1), 6, and (2) shown in the prior art. FIG. 2 shows the configuration of a digital circuit according to two embodiments for calculating Xr in main deflection distortion correction. The number of multipliers is nine.

The configuration of the digital circuit for calculating Y' is also similar. In FIG. 2, the human data input to each of the multipliers 21 to 2!3 is input to each of the nine multipliers 21 to 29.
The data is stored in a memory device in a data input device provided at the front stage of a digital arithmetic circuit composed of an adder circuit 30 and one adder circuit 30. Among these input data, X, Y are values determined by the set center coordinates, x2 . Data expressed in higher order than second order, such as xy, . The items to be stored, A, ~A, are coefficients determined by measurements as described above, and are stored in the memory device in the data input device according to settings. According to this embodiment, the number of multipliers in the digital circuit for calculating equation 2 (1) is 1.
8 pieces, which is 9/16 of the case using the conventional technology.

The configuration of the digital circuit for sub-deflector correction and beam size correction is the same as that described in the prior art.

Here, the main deflection distortion correction coefficients A0 to Ag1B of Equation 9 (1),
, ~Bq are shown in Table 1. A3~A.

and B3~B, are of the order of 10-1, AG-A, and B, ~B, l:i, lo"" (7) O4'? '9
The maximum value of 6°*f:, X, and Y is approximately 1250 IM. From this.

Find the magnitude of the influence of each term on the right side of equation (1) on the calculation accuracy of X' and Y', X2. XY, Y", X'
.

Recognize. Therefore, in the pattern drawing data used in this embodiment shown in FIG.
Y, XY'', number of bits representing Y3: j, ,X.

It is assumed that the number of bits representing Y is the same.

Table 1 - Deflection distortion correction coefficient In this embodiment, the number of 9 multipliers is reduced to 9/16 of the conventional case, but it is necessary to increase the memory capacity of the memory device that stores input data. Incidentally, in the case of the electron beam exposure apparatus EB-55 described in the prior art section, the memory capacity for input data is 512 kW x 2 (W: word=16 bits). For this example, x
”, xy, y′, x′.

X"Y, XY", and Y' will also be stored in the memory device, but the memory capacity required for this increase is about 10 kW, so the increase in device manufacturing cost due to increased memory capacity is small and the number of 9 multipliers is small. The effect of cost reduction through reduction is significant. In addition, when comparing the time required for pattern exposure, it was found that while the conventional data correction calculation circuit was a series system,
Since this embodiment uses a parallel method, the total pattern exposure time is also significantly shortened according to this embodiment.

Next, as a second embodiment of the present invention, a case will be described in which the first embodiment is applied to an electron beam exposure apparatus that uses a plurality of electron beams and simultaneously controls each beam to draw the same pattern. In this case, the pattern drawing data
The memory is common to each electron beam, and may be a set of -. On the other hand, in order to correct main deflection distortion, it is necessary to separately prepare a main deflection distortion correction circuit for each beam. Assuming that the number of electron beams is 20, the number of multipliers according to the prior art in the main deflection distortion correction digital circuit is 32 x
While there are 20 = 640 electrodes, in the case of the nine embodiments, the number is 18 x 20 == 360. Therefore, even if the memory capacity increases, the effect of reducing the manufacturing cost of the entire device becomes significant. Furthermore, in a circuit including a large number of 9 multipliers, the size of the circuit would be extremely large if two circuits were manufactured, but by adopting this embodiment, the size of one circuit can be reduced.

This has the effect of shortening the total exposure time.

Next, a third example will be described. The electron beam exposure apparatus of this embodiment uses a variable shaped beam like the apparatus described in the prior art.

It has two main and sub-stage deflectors. FIG. 3 shows the structure of pattern drawing data in this embodiment. As in the case of the first embodiment, data regarding the center coordinates of the sub-deflection field includes, in addition to X and Y, x2°XY, Y2 . X3. X2
In this example, instead of +X+yyw, h, the pattern data includes
, w, h, wh.

Correction of the main deflection distortion and correction of the sub-deflection distortion are performed using equations (1) and 9 (2) shown in the prior art. The configuration of the main deflection distortion correction digital circuit is the same as in the first embodiment. FIG. 4 shows the configuration of a digital circuit according to two embodiments for calculating x' in the sub-deflection distortion correction. The number of multipliers is three.

The configuration of the digital circuit for calculating y' is also similar. According to this embodiment, the number of multipliers in the digital circuit for calculating Equation 1 (2) is 6, which is 3/4 of that in the case of the conventional technique.

The digital circuit for calculating equation (3) is 2 equations (2)
It has the same configuration as a digital circuit that calculates , and the number of square multipliers is 6, which is 3/4 of that in the case of the conventional technology.

Here, as in the first embodiment, X'', XY.

Y", X3. X"Y, XY2. The number of bits representing each of Y3 may be approximately the same as the number of bits representing X or Y. For the same reason, the number of bits representing +X"! and wh can be the same as the number of bits representing + Case 2
If we compare the sum of the number of multipliers.

In the conventional technique, the number is 48, but in this embodiment, the number is 30. In this embodiment, the data for pattern drawing is larger than that in the conventional technique. Accordingly, it is necessary to increase the memory capacity of the memory device in the data input device compared to conventional devices. In this embodiment, the memory capacity is approximately 1.5 times that of the prior art. When considering the cost of an electron beam exposure apparatus, the cost required for increasing the memory capacity is compared with the cost reduction due to the reduction in the number of multipliers.

As a fourth embodiment, a case where the third embodiment is applied to an electron beam exposure apparatus using a plurality of electron beams will be described. In this case, the pattern drawing data is common to each electron beam, and may be a - set.

On the other hand, for main deflection distortion correction, sub deflection distortion correction, and beam size correction, it is necessary to prepare individual correction circuits for each electron beam. The number of electron beams is 2
0, the number of multipliers according to the conventional technology is 48×2
Whereas 0=960 pieces.

In the case of this embodiment, the number is 30×20=600. Therefore, even if the memory capacity increases, the manufacturing cost of the entire device is significantly reduced. Further, for the same reason as the second embodiment, by applying this embodiment, the size of the two circuits can be reduced, and the total exposure time can be shortened.

In the above explanation, x is used as pattern drawing data.

In addition to Y, X, ", X, Y, Y", X3. X2Y, XY
”.

Y3, but x'', xy, y2 or x
-2, Y 2 or x 3, y 3 or XY
It may be possible to have In this way, in addition to x and y, various data can be considered to be included in the pattern drawing data.

In addition, although equation (1) was used as the main deflection distortion correction equation,
A correction formula including a term of the fourth or higher order of Y is also conceivable. In this case, by giving the pattern drawing data a value corresponding to this fourth or higher order term.

The scale of the digital circuit for correction calculation can be reduced.

In the third embodiment, the pattern data is
+xy+ w, h, wh, but r X21 y2. W', h
'Or when using an expression that includes these higher-order terms, data corresponding to these terms can also be included in the pattern data. Furthermore, X2°XY, Y2. X′
, X2Y, XY', and Yl are the same as that of X or Y, but it is not necessarily necessary that these bit numbers match. This is +X! Y! The same applies to Xylw, h, and wh. Furthermore, although the explanation above has been made regarding an electron beam exposure apparatus having a main and sub-stage deflector in two stages, the present invention can also be applied to an electron beam exposure apparatus in which a beam is controlled using only one stage of deflector. In this case, +X as the pattern position data
In addition to +y, x'', xy, y'', etc. may be included. Although the above description has been made with reference to an electron beam exposure apparatus, it is obvious that the present invention can also be applied to an exposure apparatus that uses an ion beam.

In the second embodiment, the main deflection distortion expressed by Equation 2 (1) was taken up as correction using the center coordinates (X, Y) of the sub-deflection field. In dynamic focus correction, the input signal to the focus correction lens is X.

When calculating the correction coefficient of the sub-deflection distortion correction formula such as Equation 9 (2) as a function of Y, calculations of these functions are performed using digital circuits. Ruga.

The present invention can also be applied to such cases.

〔Effect of the invention〕

As explained above, according to the second aspect of the present invention, in a charged beam exposure apparatus, when drawing a pattern by specifying the coordinate values X and Y of the beam irradiation position and the width W and height h of the beam dimensions, the deflector optical The correction formula for correcting the beam irradiation positions X, Y and beam dimensions w, h against deflection distortion caused by the system includes X,
, linear function terms A, X, A2Y, B, X, B,
In addition to Y, higher-order function terms of second order or higher A, X'', A, XY,
A, Y2. A correction formula containing at least one of the following, or a linear function term a, w, a regarding w, h
,h.

In addition to blw, b, and h, higher-order function terms a, wh
, a4W'', a5h'', etc., the correction coefficient A z g A 2
1...I all a2+...and specified position rocking values X, Y, specified beam dimensions w, h as well as X.

Higher-order term X 2+ XY, −, w2 regarding Y, w, h
゜Wh,..., etc. can also be input using data manually! Store it in the memory device in A.

By calculating each term in the correction formula using a digital multiplier and adding the calculation results, beam irradiation can be improved compared to the conventional method in which calculations for these higher-order terms were also performed using digital circuits. The number of digital multipliers for position correction or P15 size correction can be reduced. the result.

This has the advantage that the cost of the digital circuit can be reduced, the size of the two circuits can be reduced, and the total exposure time can be shortened. In particular, when the present invention is applied to a charged beam exposure apparatus using a plurality of beams, each of the above effects is significant.

[Brief explanation of drawings]

FIG. 1 shows pattern drawing data in a first embodiment of the present invention, and FIG. 2 shows an example of a digital circuit for beam irradiation position correction in the first embodiment of the present invention. FIG. 3 shows pattern drawing data in the third embodiment of the present invention, FIG. 4 shows the configuration of a sub-deflection distortion correction digital circuit in the third embodiment of the present invention, and FIG. 5 shows a conventional main-sub two-stage structure. Pattern drawing data in a variable shaped beam exposure device having a deflector, FIG. 6 shows the configuration of the main deflection distortion correction digital circuit in the conventional device, and FIG. 7 shows the configuration of the auxiliary deflection distortion correction digital circuit in the conventional device. . Patent Applicant Nippon Telegraph and Telephone Corporation Representative Patent Attorney Junnosuke Nakamura Illustrator 2g! '3 figure 5 members 1P6 figure

Claims (6)

[Claims] (1) In a method of correcting the beam irradiation position in a charged beam exposure apparatus that performs pattern exposure by controlling the deflection of a charged beam and irradiating it onto a designated position on a sample surface for deflection distortion caused by a deflection optical system, ( b) As a deflection distortion correction formula, in addition to the linear function term obtained by multiplying the specified beam irradiation position coordinates X and Y by respective distortion correction coefficients, k and l are integers of 2 or more, and m and n are 1 The above integers are X^k, Y^l,
Using a deflection distortion correction formula that adds at least one of the higher-order function terms obtained by multiplying X^mY^n by distortion correction coefficients, (b) the above distortion correction coefficients and the above designated coordinate values; X, Y, and the above-mentioned X^k, Y^l, X^mY^n calculated in advance based on these X, Y are stored in the memory device as input data, and (c) this input data is In response to the input, each term of the deflection distortion correction formula is calculated and determined by a digital multiplication circuit, and (d) these multiplication results are added to obtain correction values X', Y for the designated coordinate values X, Y.
A method for correcting a beam irradiation position in a charged beam exposure apparatus, characterized in that: (e) the correction value is given to a deflector to correct the beam irradiation position. (2) In a method for correcting a specified beam dimension when a charged beam exposure apparatus that deflects and controls a charged beam to irradiate a specified position on a sample surface to expose a pattern is an exposure apparatus that uses a variable shaped beam, (b) As a beam size correction formula, in addition to the linear function terms obtained by multiplying the specified beam width w and height h by correction coefficients, k and l are
Integers greater than or equal to 1, m and n are integers greater than or equal to 1 w^k, h^
Using a correction formula that adds at least one of the higher-order function terms obtained by multiplying l and w^mh^n by correction coefficients, (b) each of the above correction coefficients and the specified beam width w , beam height h, and the above w^k, h^l, w^mh^n calculated in advance based on w and h are stored in the memory device as input data, and (c) this input Receiving the data as input, calculate each term of the above correction formula using a digital multiplier, and (d) add these multiplication results to obtain correction values w' and h' for the specified dimensions w and h.
and (e) applying this correction value to a deflector to correct the beam size in a charged beam exposure apparatus. (3) In claim 1, the input data X^k, Y^l, X^mY^n and input designated coordinate data X, Y are all digital data and have approximately the same number of bits. A method for correcting a beam irradiation position in a charged beam exposure apparatus, characterized in that: (4) In claim 2, the input data w^k, h^l, w^mh^n and the input specified dimension data w, h are all digital data and have approximately the same number of bits. A method for correcting beam dimensions in a charged beam exposure apparatus, characterized in that: (5) In claim 1, the charged beam exposure apparatus is a charged beam exposure apparatus having a main and sub two-stage deflector, and data X and Y specified as the beam irradiation position are of the sub-deflection field. A method for correcting a beam irradiation position in a charged beam exposure apparatus, characterized in that the data represents center coordinates. (6) In claim 1, the charged beam exposure apparatus is a charged beam exposure apparatus having a main and sub two-stage deflector, and data X and Y specified as the beam irradiation position are within the sub-deflection field. A method for correcting a beam irradiation position in a charged beam exposure apparatus, characterized in that the data is position data of a pattern in a charged beam exposure apparatus.