JP3120051B2 - Proximity effect corrector for charged particle beam writing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged beam drawing apparatus which draws a figure on a surface to be irradiated by a charged particle beam, and corrects the effect of charged particle scattering on the surface to be irradiated so as to obtain an appropriate dose. The present invention relates to a required dose correction device, and more particularly to a proximity effect correction device for drawing a charged particle beam suitable for drawing a circuit pattern of a fine semiconductor integrated circuit.

[0002]

2. Description of the Related Art Conventionally, when a circuit pattern of a fine semiconductor integrated circuit is drawn on a mask, an electron beam drawing apparatus has been used. When drawing a mask with a charged particle beam such as an electron beam, the proximity effect caused by the scattering of the electron beam in the resist causes inadequate exposure of narrow patterns and corners of the pattern, resulting in poor dimensional accuracy and rounded rectangular patterns. Is generated. In addition, when the patterns are disposed close to each other, there is a problem that a portion other than the patterns is exposed by charged particles scattered from both patterns, and the drawing pattern on the resist is distorted.

In recent years, integrated circuit patterns on a mask to be drawn have been miniaturized, and high-precision correction of the proximity effect has become indispensable. When the acceleration voltage of the charged particle beam is increased in order to improve the contrast of writing a fine pattern, the influence of the proximity effect becomes even greater.

[0004] In order to reduce the pattern dimensional error due to the scattering of the electron beam, various proximity effect corrections have been conventionally attempted. One is a method of weakly exposing a part without a pattern with a diffused beam while writing a pattern part. Although this method does not require correction calculation, it takes a long time to draw a non-pattern portion in addition to pattern drawing. In addition, since exposure is performed to a portion where there is no pattern, the resist contrast is reduced and the pattern dimensional accuracy is reduced. For this reason, the higher the precision and the higher the precision of drawing, the more unusable it becomes.

The other is a method of calculating the influence from an adjacent pattern and writing while changing the irradiation amount for each electron beam writing unit. This method is advantageous for high-precision drawing with little deterioration in resist contrast. However, as semiconductors become more highly integrated, the amount of data,
The processing time of the correction calculation is enormous.

Therefore, recently, as a method of performing the calculation processing at high speed, a method of performing a correction calculation using the area density of a fine and complicated pattern has been proposed.

Japanese Unexamined Patent Publication No. Hei 3-225816 "Charged particle beam drawing apparatus" is a charged particle beam drawing apparatus incorporating a proximity effect correction circuit based on an irradiation area density. There are provided means for correcting the numerical value of the nearby partial area, and means for correcting the exposure time set in advance by the numerical value.

In Japanese Patent Application Laid-Open No. 4-258111, "Method of Correcting Proximity Effect in Electron Beam Lithography", a convolution is calculated from a proximity matrix and a sub-density matrix using a square cell mesh.
A method for obtaining a dose correction matrix is proposed.

[0009] Further, a document (T. Abe, et all, "Representati
ve Fegure Method fer Proximity Effect Correction ",
Japanese Journal of Applied Physics.Vol.30.No.3B, p
p.L528-531, 1991) shows a method for speeding up the calculation process using a representative figure of a pattern.

In Japanese Patent Application No. 8-36441, "charged beam drawing method and drawing apparatus", recalculation of backscattering using a corrected irradiation amount is repeated as a method for increasing the accuracy of proximity effect correction. Instead, a method of reducing the number of repetitive calculations by expressing the correction formula of the irradiation dose by a certain perturbation expansion is shown.

However, in any of the apparatuses and methods, a great deal of time is required for calculation for the proximity effect correction, and the amount of calculation for the proximity effect correction increases as more accurate drawing is required. However, there is a problem that the calculation time becomes enormous. In other words, the calculation time is enormous when trying to increase the drawing accuracy, and its practical use has been extremely difficult.

[0012]

In order to correct the proximity effect of a high-precision electron beam lithography system for producing fine semiconductors, it is necessary to find an optimum electron beam irradiation amount for a fine partial region. There is. As more accurate drawing is required, it is necessary to find the optimum electron beam irradiation amount for a fine partial region. However, as this partial area is made smaller, the amount of calculation for correcting the proximity effect increases, the calculation time becomes enormous, and the practicality at the production site decreases. In addition, if the acceleration voltage of the electron beam is increased for high-definition writing, the width of backscattering of the electron beam is widened, the area where the calculation of the scattering effect on the irradiation needs to be widened, and the calculation time increases. .

In the prior art, the backscattering in a range in which the influence of the proximity effect is considered for a certain point on the drawing surface is calculated by convolution calculation of all the irradiation doses in the range and is proportional to the area of the range. The number of product-sum operations is required. If detailed calculation is required, the method of dividing the range into grid regions is made finer, and the calculation amount is further increased. That is, for proximity effect correction of a charged particle beam writing apparatus with high precision, a proximity effect correction apparatus capable of executing correction calculation suitable for accuracy requirements in a short time is required.

The present invention has been made in view of the above circumstances, and an object of the present invention is to enable a high-precision charged particle beam writing apparatus to perform high-accuracy proximity effect correction at high speed. An object of the present invention is to provide a proximity effect correction device.

[0015]

[Means for Solving the Problems]

(Configuration) In order to solve the above problem, the present invention employs the following configuration.

That is, the present invention (claim 1) provides a charged particle beam for correcting the irradiation amount by evaluating the proximity effect due to the scattering of the irradiation beam when drawing by irradiating the surface of the drawing object with the charged particle beam. In the proximity effect correction device for drawing, from the irradiation area and irradiation intensity of the charged particle beam irradiating the irradiation target surface, the irradiation amount calculation means for obtaining the irradiation amount of a minute grid region divided in the vertical and horizontal directions on the target surface and A scattering effect evaluating means for evaluating, for each lattice area, an irradiation effect due to scattering of the irradiation amount obtained by the irradiation amount calculating means on a plurality of peripheral lattice areas surrounded by a rectangle around the lattice area; A correction irradiation intensity deriving unit for calculating a correction irradiation intensity of a charged particle beam appropriate for drawing a target drawing graphic pattern for each grid region from a result of the evaluation unit. The scattering effect evaluation unit performs convolution calculation by the product of the dose and the Gaussian distribution function at each peripheral grid area which has been determined by the dose calculating means, and the I different parameter values spread of the distribution function convolution calculation
The proximity effect is evaluated by obtaining as a sum of results calculated by weighting two or more Gaussian distributions with the scattering rate.

Further, according to the present invention (claim 2 ), when performing drawing by irradiating a charged particle beam to a surface to be drawn, a charged particle beam for correcting a dose by evaluating a proximity effect due to scattering of the irradiated beam. In the proximity effect correction device for drawing, from the irradiation area and irradiation intensity of the charged particle beam irradiating the irradiation target surface, the irradiation amount calculation means for obtaining the irradiation amount of a minute grid region divided in the vertical and horizontal directions on the target surface and A scattering effect evaluating means for evaluating, for each lattice area, an irradiation effect due to scattering of the irradiation amount obtained by the irradiation amount calculating means on a plurality of peripheral lattice areas surrounded by a rectangle around the lattice area; A correction irradiation intensity deriving unit for calculating a correction irradiation intensity of a charged particle beam appropriate for drawing a target drawing graphic pattern for each grid region from a result of the evaluation unit. The scattering effect evaluation means, the convolution calculation by the product of the dose and the Gaussian distribution function at each peripheral grid area which has been determined by the dose calculating means, wide distribution function
Are those determined as the sum of the results rising parameter value is calculated by weighting the scattering rate for two or more different Gaussian distribution, and in each of the convolution calculation, a one-dimensional Gaussian distribution function in one direction along said grating Is performed, and the convolution calculation is performed using the product of the convolution calculation result and the same one-dimensional Gaussian distribution function as the Gaussian distribution function in other orthogonal directions.

Further, as a desirable third aspect of the present invention,
3. The charged particle beam drawing apparatus according to claim 1 , wherein the irradiation amount calculation means irradiates a single irradiation of the charged particle beam from the position of the irradiation figure and the projection shape. Divided into irradiation patterns in each of the single or plural lattice regions to be obtained, an irradiation pattern area in each of the lattice regions is obtained, and the irradiation amount obtained by multiplying the pattern area by the intensity of the charged particle beam irradiation is calculated. The irradiation amount of each lattice region is obtained by accumulating the irradiation amount already obtained inside each lattice region.

Further, as a desirable claim 4 of the present invention,
In any one of claims 1 to 3 , the correction irradiation intensity is obtained again by each of the means based on the correction irradiation intensity obtained by each of the means.

Further, as a desirable claim 5 of the present invention,
According to a fourth aspect of the present invention, in the second and subsequent irradiation dose calculating means, the product of the already calculated irradiation area for each grid region and the corrected irradiation intensity is calculated as each grid region irradiation dose.

Further, as a desirable claim 6 of the present invention,
6. The correction irradiation intensity deriving means of the second and subsequent stages according to claim 4 or 5, wherein the correction irradiation intensity obtained up to the previous stage and an appropriate irradiation amount for drawing a target drawing graphic pattern are used instead of the new correction irradiation intensity. And an approximate value of the difference between the two.

(Operation) FIG. 1 shows the structure of the first aspect of the present invention, and its operation will be described. In the figure, 11 is an irradiation amount calculating means for calculating an irradiation amount for each lattice region, 21 is a convolution calculation based on the irradiation amount of the lattice region and a two-dimensional Gaussian distribution weighted by two or more Gaussian distributions with a scattering rate, Scattering effect evaluation means for calculating the sum of the output results for each grid area, and 31 is a corrected irradiation intensity deriving means for calculating a corrected irradiation intensity for each grid area.

The scattering effect evaluation means of the proximity effect correction device of the present invention evaluates the scattering effect based on the following principle.

Irradiation intensity D (X, Y) at position (X, Y)
Is the product of the rate of backscattering to the location (x, y) with the Gaussian density function using the scattering width σ and the overall backscattering rate η,

[0025]

(Equation 1)

Now, evaluation will be made. However, backscattering may not exactly follow the Gaussian density function, and instead of the above equation, a weighted sum of the scattering rates of multiple Gaussian density functions,

[0027]

(Equation 2)

## EQU2 ## eta _b is the ratio forward scattering amount of backscattering amount of width sigma _b of the scattering of the respective Gaussian distributions.

By integrating all (X, Y) in the region E where the irradiation figure exists, the exposure effect U (x, y) at the position (x, y) due to the backscattering of the charged particle beam is obtained.
y) is evaluated.

[0030]

(Equation 3)

Assuming that the value of the irradiation intensity D (X, Y) at a point that is not irradiated, that is, at a point that does not belong to the region E, is 0, this integration is a convolution calculation. Convolution using a two-dimensional Gaussian distribution density function can be expressed by multiplying the result of integration with the one-dimensional Gaussian distribution density function in the X direction by the same one-dimensional Gaussian distribution density function and integrating in the Y direction. it can.

The proximity effect correction device according to the first aspect performs the processing in the scattering effect evaluation means 21 by the following method.

As an approximation of (Equation 3), the influence of charged particle beam scattering is evaluated by the following procedure. Instead of multiplying and integrating the dose and the Gaussian density function, the influence of scattering can be obtained by using the product of the dose and the Gaussian density function, which is obtained from the area irradiated at a uniform irradiation intensity within the micro-grating area. The sum of the products within the range is obtained, and the convolution is approximated.

A two-dimensional lattice area with an interval M on the irradiation target surface is set. The irradiation amount calculated by the irradiation amount calculating means 11 in the grid region [i, j] on the i-th row and the j-th column is defined as S _ij . S
_ij is obtained by accumulating the product of the irradiation intensity of all irradiations applied to the lattice area [i, j] and the area of each irradiation. The irradiation intensity of the irradiation G applied to the lattice area [i, j] is D _G , and the area of the irradiation in the lattice area [i, j] is A
_{Given Gij} ,

[0035]

(Equation 4)

## EQU1 ## The plurality of Gaussian density functions used have different widths of scattering. Let σ _{b be} the scattering width of 1 / e of the b-th Gaussian distribution density function. From the value of σ _b , in terms of error evaluation, the distance from the most distant lattice region to be considered in evaluating the scattering effect on one lattice region is defined as the width expressed by the number of lattices, and the one-dimensional lattice region Select the number _Kb . For each direction of the coordinate axes X and Y, a discrete approximation U _{b, ij} of convolution by the following Gaussian distribution density function is calculated.

[0037]

(Equation 5)

The integral calculation of the above equation can be calculated in advance, given the width M of the lattice region, the width σ _{b of the} backscatter, and the range k _{b of the} convolution approximation. That is, for all combinations of integers x and y in the range from -k _b to + k _b, can be pre-calculated P _{x, y,} and _b as follows.

[0039]

(Equation 6)

As described above, the amount of scattering U _{b, ij} due to σ _b on the grid area [i, j] is evaluated.

From the convolution by the b-th Gaussian distribution density function, to evaluate the total backscattering quantity,

[0042]

(Equation 7)

Is calculated, and the scattering amount U _ij is calculated. These U _ij are the outputs of the scattering influence evaluation means 21.

In the correction irradiation intensity deriving means 31, the scattering amount U
_{From ij} , an appropriate dose in consideration of the scattering effect of the figure to be finally drawn is obtained for each grid region.

Generally, it is called Pavkovich's equation.

[0046]

(Equation 8)

Are often used. Here, D ₀ is a standard irradiation intensity, and D ⁽⁰⁾ _ij is an appropriate irradiation intensity.

As a reference example, a convolution meter in the X direction is used.
FIG. 2 shows the configuration and operation of the proximity effect correction device for evaluating the scattering effect by the product of the calculation and the convolution calculation in the Y direction . Only the scattering effect evaluation means 22 in the figure is different,
31 is the same as FIG.

The proximity effect correction device of the reference example performs the processing in the scattering effect evaluation means 22 by the following method.

In Equation (3), σ _b is simply σ, and η _b is η
And without taking the sum by b,

[0051]

(Equation 9)

Assume that: The lower part of the above equation indicates that the convolution in the X direction and the convolution in the Y direction can be performed separately. The scattering effect evaluation means can be realized by the following discrete approximation by convolving the X-direction convolution result in the Y-direction with the number k of lattice regions up to a lattice region sufficiently distant from the error evaluation.

[0053]

(Equation 10)

An integral calculation common to both directions of the coordinate axes X and Y can be calculated in advance. If M and σ are determined, P _L can be calculated in advance for all the integers L in the range from −k to + k as follows.

[0055]

[Equation 11]

Is rewritten as follows.

[0057] Figure 3 shows the structure and operation of the proximity effect correction apparatus according to claim 2. The other configurations 11 and 31 are the same as those in FIG. 1 except for the scattering influence evaluation means 23 in the figure.

The proximity effect correction device according to the second aspect performs the processing in the scattering effect evaluation means 23 by the following method.

By applying (Equation 13) of the reference example to a plurality of Gaussian distribution density functions having different scattering widths, the b-th scattering width is σ _b , and the scattering rate is η _b ,

[0060]

(Equation 12)

As an approximation of the discrete convolution calculation, the scattering amount U _ij is calculated from U _{b, ij by} the sum of b, that is, (Equation 8).

FIG. 4 shows the structure and operation of the proximity effect correction device according to the third embodiment. 3. The method according to claim 1, wherein the irradiation amount calculation unit is configured to output the irradiation amount.
Different from the above, the other configuration is the same as that of claim 1 or 2 .
The scatter influence evaluation means 21, 22, 23 is the first or second aspect.
May be selected.

The irradiation amount calculating means 12 of the proximity effect correction device according to the third aspect obtains the irradiation amount of the lattice area as follows.

The width and height of one lattice region are M, and the maximum length in the vertical and horizontal directions of a figure by one charged particle beam irradiation is N.
And C is a minimum integer equal to or greater than N / M. If M is smaller than N, the effect according to claim 3 of the present invention is large.

One irradiation of the charged particle beam is performed around the center of the circumscribed circle of the irradiation pattern as a center (C + 1) × (C + 1)
One or more lattice areas included in each square are always included.

For each charged particle beam irradiation, the area of the charged particle beam irradiation figure divided into each of the (C + 1) × (C + 1) lattice regions is calculated and multiplied by the irradiation intensity. The irradiation amount in all the lattice regions is obtained by adding the calculated irradiation amount to the already calculated irradiation amount of the charged particle beam in each lattice region and performing accumulation.

FIG. 5 shows the configuration of the proximity effect correction apparatus according to the fourth aspect .
Shown in In the figure, reference numeral 10 denotes an irradiation amount calculating means, 20 denotes a scattering influence evaluating means, 30 denotes a corrected irradiation intensity deriving means, and each means may select any one of claims 1 and 2 .

In the proximity effect correction apparatus according to the fourth aspect , the irradiation amount calculation means uses the correction means intensity calculated in the preceding stage to obtain the irradiation amount of each irradiation in the next stage.

FIG. 6 shows the structure and operation of the proximity effect correction device according to the fifth embodiment. The basic configuration is the same as FIG.

In the proximity effect correction apparatus according to a fifth aspect , the irradiation amount calculating means 10 calculates the corrected irradiation intensity calculated in the preceding stage by:
By multiplying the irradiation area for each lattice area calculated in the previous stage, the irradiation amount of each lattice area is obtained.

FIG. 7 shows the structure and operation of the proximity effect correction device according to claim 6 . The basic configuration is the same as FIG.

In the proximity effect correction device according to the sixth aspect , in order to asymptotically correct the corrected irradiation intensity calculated up to the previous stage to a more appropriate irradiation intensity, the next stage uses not the corrected irradiation intensity but the increment of the corrected irradiation intensity. Ask. The final corrected irradiation intensity is the sum of the output results of the corrected irradiation intensity deriving means 30 of each stage.

The calculation of the correction irradiation intensity deriving means 30 of each stage can be calculated by, for example, the following method. The output result of the scattering influence evaluation means of the n-th stage is U ⁽ⁿ⁾ _ij , the output of the corrected irradiation intensity deriving means is D ⁽ⁿ⁾ _ij , the optimum irradiation intensity is D ⁽⁰⁾ _ij , and the standard irradiation amount is D _0. Can be expressed as

[0074]

(Equation 13)

Then, the output of the corrected irradiation intensity deriving means is obtained.
When n = 1, as in the upper part of the above equation, it corresponds to (Equation 9).

[0076]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments.

(First Embodiment) FIG. 8 is a diagram for explaining a proximity effect correction device according to a first embodiment of the present invention.

This embodiment is an embodiment of the second and third aspects of the present invention, in which a proximity effect correction device is implemented by combining arithmetic circuits, and is realized by pipeline processing, thereby realizing the proximity effect correction device in real time. Make corrections. The effect of backscattering is evaluated up to a position 25 μm or more away from the irradiation position.

The size of the lattice area is 1 μm in length and 1 μm in width.
Then, the correction irradiation intensity is derived for each area of 1000 μm in length and 1000 μm in width. 1000μm × 1000μm
For the calculation of the corrected irradiation intensity for the area
1050μm × 1050μ including the area of 5μm each
The calculation of the corrected irradiation intensity is applied using the region of m, and the central region of 1000 μm × 1000 μm is output as a result.

[0080] This embodiment, according to claim 3 and the irradiation amount calculating circuit 112 for implementing the action of dose calculating means 12 according scattered impact assessment circuit 123 to carry out the operation of claim 2, wherein the scattering impact assessment means 23 And a corrected irradiation intensity deriving circuit 131 for performing the operation of the corrected irradiation intensity deriving means 31.

In this embodiment, one irradiation is 1 μm on one side.
It is assumed that the figure is limited to a figure that can be surrounded by a square having sides parallel to the X and Y axes.

The dose calculation circuit 112 according to this embodiment will be described below. FIG. 9 shows the dose calculation circuit 112 according to the present embodiment.
The action of

First, the irradiation amount calculation circuit 112 sequentially inputs each irradiation figure to the irradiation figure input section for inputting the irradiation figure. Here, 1050 μm × 10 to be calculated
Extraction of all the irradiation figures irradiated to 50 μm is a target to be input from the input unit.

Next, the irradiation figure conversion unit converts each irradiation figure into a rectangle having the same area and the same center of gravity as each input irradiation figure and having a side of 1 μm or less. Since the size of the grid area is 1 μm and the size of one irradiation pattern is 1 μm or less, the converted rectangle can be selected to be placed in two adjacent grid areas of 2 × 2.

The converted rectangle is sent to the irradiation figure division unit. The lower left coordinate of the k-th input irradiation is (x ^(k) , y ^(k) ), and its width and height are w ^(k) , h
^(k) . (X ^(k) , y ^(k) ) is assumed to be in a grid area [i, j] of i rows and j columns (0 ≦ i ≦ 104
9,0 ≦ j ≦ 1049). This irradiation pattern is divided into four rectangles included in the four grid regions. Each of the divided rectangles is output to four parallelized dose accumulation units.

The irradiation amount accumulating unit first obtains the area of the input figure. The width w of the side of the lower left rectangle divided by the grid area
0 ^(k) and height h0 ^(k), and the area of each rectangle in each of the four divided areas is A ^(k) _{i, j} , A ^(k) _{ij + 1} , A ^(k)
_{i + 1, j} , A ^(k) _{i + 1, j + 1} .

A ^(k) _{i, j} = w0 ^(k) × h0 ^(k) A ^(k) _{ij + 1} = w0 ^(k) × (h ^(k) −h0 ^(k) ) A ^(k) _{i + 1, j} = (W ^(k) −w0 ^(k) ) × h0 ^(k) A ^(k) _{i + 1, j + 1} = (W ^(k) −w0 ^(k) ) × (h ^(k) − h0 ^(k) ) By the four parallel circuits corresponding to these four figures and their areas, the product of these areas and the k-th irradiation intensity D _k of the irradiation is calculated by the lattice areas [i, j], [ i, j + 1], i
+1, j] and [i + 1, j + 1] are cumulatively added to the irradiation amount of the (k−1) th irradiation.

For all the irradiations relating to the area of 1050 μm × 1050 μm, after the processing in the above-mentioned four parallelized irradiation amount accumulating units is completed, the irradiation amount of each grid region accumulated in each of the four parallels is calculated as The irradiation amount adding unit performs addition for all four parallels to determine the irradiation amount _Sij of each grid region [i, j].

The scatter influence evaluation circuit 123 of this embodiment will be described below. FIG. 10 shows the operation of the horizontal convolution unit and the vertical convolution unit corresponding to one of the three scattering widths of the scattering influence evaluation circuit 123 of the present embodiment.

It is assumed that convolution calculation is performed with three scattering widths of σ ₁ , σ ₂ and σ ₃ . Since there is a calculation area margin of 25 μm at the top, bottom, left and right, if the maximum of σ ₁ , σ ₂ , σ ₃ is, for example, about 10 μm, it is necessary to calculate about 99.96% or more of the influence of the maximum backscattering width. Can be. Let the respective scattering rates be η ₁ , η ₂ , η ₃ . The scattering effect evaluation means performs the scattering effect evaluation with three parallel scattering effect evaluation circuits corresponding to these three scattering widths. One of each parallel will now be described.

For each grid region of the 1050 μm × 1050 μm region obtained by the dose adding unit of the dose calculation circuit 112, the horizontal row convolution calculation is performed by the horizontal convolution unit. The horizontal convolution unit is implemented using a product-sum operation unit. As the sum-of-products arithmetic unit, a commercially available arithmetic unit as an FIR filter is cascade-connected as necessary according to the width of scattering. With a grid area width of 1 μm,
Since the input area is set to be larger by 25 μm on one side than the calculation output, it is possible to perform calculation including a grid area distant to 25 grid areas for the widest scattering width. Assuming that the width of the product-sum operation is 51, for the grid area [i, j],
Applying the above (Equation 14),

[0092]

[Equation 14]

Is calculated. R _L (L is -250 ≦ L ≦ 2
The value of (an integer of 5) is calculated in advance and stored as a system value of the product-sum operation unit.

The result obtained in the horizontal convolution unit is subjected to a vertical convolution operation in the vertical convolution unit. The vertical convolution unit has the same configuration as the horizontal convolution unit, and differs only in that it is input to the product-sum operation unit in the vertical direction of the lattice area. The vertical convolution unit applies the above (Equation 14),

[0095]

(Equation 15)

Is output.

The output of the scattering effect evaluation circuit 123 is obtained by adding the outputs of three parallels of the vertical convolution unit for each lattice area by the convolution addition unit.

U _ij = U _{1, ij} + U _{2, ij} + U _{3, ij} The corrected irradiation intensity deriving circuit 131 of this embodiment will be described below.

The input of the correction irradiation intensity derivation circuit is the U _ij . The correction irradiation intensity deriving circuit 131 calculates the appropriate irradiation amount D
⁽⁰⁾ _ij is calculated by the above (Equation 9) and output.

D ^(O) _ij = D ₀ / (1/2 + U _ij ) At this time, the range of the output area is the grid area [i, j]
25 ≦ i ≦ 1024, 25 ≦ j ≦ 1024.

(Second Embodiment) A second embodiment of the present invention will be described below. FIG. 11 shows the configuration of the second embodiment of the present invention. In the present embodiment, the dose calculation circuit 212 that performs the operation of the dose calculation unit 12, the scatter effect evaluation circuit 223 that performs the operation of the scatter effect evaluation unit 23, and the operation of the corrected irradiation intensity derivation unit 31 are described. And a correction irradiation intensity deriving circuit 231 for performing the above.

This embodiment is an embodiment of the first and third aspects of the present invention, in which a proximity effect correction device is implemented by combining arithmetic circuits. 223 is the same as the first embodiment except that it is implemented as follows.

The scatter effect evaluation circuit 223 of this embodiment will be described below.

The scattering effect evaluation circuit 223 of this embodiment is configured by an FFT unit, a multiplication unit, and an inverse FFT unit instead of the horizontal convolution unit and the vertical convolution unit of the first embodiment.

The convolution calculation of (Equation 7) is performed as follows using a fast Fourier transform (FFT) digital signal processor.

A two-dimensional fast Fourier transform (FFT) is performed on the output S _ij of the irradiation amount calculation circuit 212 by the FFT unit of the scattering influence evaluation circuit 223. The result is FF
It is represented by T (S _ij ). Since P _{xy in} (Equation 7) is represented by an exponential function as shown in (Equation 6), when the fast Fourier transform (FFT) is performed with the constant omitted, FFT [exp {− (x ² + y) represented by ^{_{(V x 2 + V y 2}} ) / σ vb2} - 2) / σ b}] = exp {. Here, V _x and V _y are the spatial frequencies for the coordinates (x, y).

By simply multiplying the Fourier transform, the convolution operation can be replaced by multiplication in the frequency domain.
The multiplication section performs this multiplication.

U _{b, ij} is the inverse fast Fourier transform of FFT ⁻¹
U _{b, ij} = (η _b / πσ _b ² ) · FFT ⁻¹ [FFT (S _ij ) · exp {− (V _x ² + V _y ² ) /
σ _vb2 ｝]. This inverse Fourier transform is performed by the FFT unit.

Third Embodiment A third embodiment of the present invention will be described below. FIG. 12 shows the configuration of the third embodiment.

This embodiment is a sixth embodiment of the present invention, in which the proximity effect correction device of the first embodiment is connected in three stages,
The difference between the corrected irradiation intensity and an appropriate irradiation intensity is calculated by a perturbation expansion at a later stage.

In this embodiment, as shown in FIG. 12, an irradiation amount calculation circuit 310-
1, 2, 3 are provided, and a scattering influence evaluation circuit 320-1, 2, 3 is provided for the scattering influence evaluating means 20,
The corrected irradiation intensity deriving means 30 is provided with corrected irradiation intensity deriving circuits 330-1, 2, and 3.

The differences from the first embodiment will be described below. In the first embodiment, the height is 1000 μm and the width is 1000
In order to obtain an output in the area of μm,
The region of 50 μm was set as a calculation target. In the present embodiment, 3
In order to use the irradiation intensity of the output result of the previous stage in the second and subsequent stages of the stage connection, a three-fold margin width is taken, and
μm, 1150 μm in width, and 100
An output in an area of 0 μm and a width of 1000 μm is obtained.

The first stage of this embodiment is the same as the first embodiment except that the irradiation area is calculated for each lattice region by the irradiation amount calculation circuit 310-1.

In the second stage of the present embodiment, instead of inputting each charged particle beam irradiation figure in the irradiation amount calculation circuit 310-2, the irradiation area for each lattice region obtained in the first stage is calculated.
The irradiation amount obtained by multiplying the corrected irradiation intensity of the first stage is obtained. The corrected irradiation intensity deriving circuit 330-2 performs the calculation when n = 2 in the middle stage of (Equation 15).

In the third stage of the present embodiment, instead of inputting each charged particle beam irradiation figure in the irradiation amount calculation circuit 310-3, the irradiation area for each lattice region obtained in the first stage is calculated.
The irradiation amount is determined by multiplying the corrected irradiation intensity in the second stage. The corrected irradiation intensity deriving circuit 330-3 calculates the corrected irradiation intensity by the sum of the lower stage of (Equation 15) after performing the calculation when the middle stage of (Equation 15) is set to n = 3, The output of the effect correction device.

[0116]

According to the proximity effect correction device of the present invention, when the distribution of the influence of the charged particle beam cannot be approximated by the double Gaussian, the influence of the back scattering of the charged particle beam by the sum of a plurality of Gaussian distributions. Can be evaluated,
Accurate proximity effect correction can be performed at high speed. Also, in order to evaluate the effect of backscattering of the charged particle beam by the sum of a plurality of Gaussian distributions, it is easy to realize the calculation of the amount of backscattering by parallelizing the same processing mechanism, and it is possible to reduce the actual processing time. Provides a means to avoid increase.

The proximity effect correction apparatus of the reference example utilizes the fact that a two-dimensional Gaussian distribution can be expressed by a product of a one-dimensional Gaussian distribution, instead of performing a two-dimensional convolution calculation, and is performed once each in the vertical and horizontal directions. By performing convolution calculations twice in total, the number of product-sum operations can be reduced, and high-speed proximity effect correction processing can be realized. As in the first embodiment,
For example, when the product-sum operation is required for the surrounding 51 grid area, the calculation can be performed by 102 product-sum operations per grid area instead of 2601 product-sum operations. Therefore, the effect is large particularly when the backscattering is wide and convolution calculation of a wide area is required as in the case of drawing with a charged particle beam having a high accelerating voltage.

[0118] Proximity effect correction apparatus according to claim 2 is a combination of reference example of claims 1 and above, has the effect of both. When the backscattering cannot be approximated by the Gaussian distribution, the proximity effect correction device of the reference example can be prevented from being ineffective, and the processing speed can be prevented from decreasing due to an increase in the amount of calculation. That is, by evaluating the influence of backscattering by the sum of Gaussian distributions, two-dimensional convolution can be performed by one-dimensional convolution calculation twice, and high-speed proximity effect correction with high accuracy is provided.

The proximity effect correction device according to a third aspect of the present invention is a device in which the proximity effect correction device according to the first and second aspects is provided with means for calculating the dose of the grid region at a high speed. It is possible to realize the calculation of the dose of the grid region at the same speed as that of the above.

The proximity effect correction device according to claim 4 can correct the proximity effect when the proximity effect correction device according to claims 1 to 3 uniformly performs charged particle beam irradiation at an assumed irradiation intensity. By repeating recalculation with the corrected irradiation intensity, the proximity effect correction accuracy is improved.

The proximity effect correction device according to the fifth aspect is different from the proximity effect correction device according to the fourth aspect in that the corrected irradiation intensity is applied to each irradiation at the time of recalculation. By applying the irradiation intensity, the processing can be speeded up and the configuration of the irradiation amount calculation means can be realized.

In the proximity effect correction device according to the sixth aspect, the proximity effect correction device according to the fourth and fifth aspects improves the proximity effect correction accuracy by recalculating by applying the corrected irradiation intensity. The effect of improving the proximity effect correction accuracy with a smaller number of repetitions than the proximity effect correction device according to claims 4 and 5 , wherein the difference from the optimum irradiation intensity is obtained by applying the corrected irradiation intensity by perturbation expansion. have.

[Brief description of the drawings]

FIG. 1 is a view for explaining the configuration and operation of the invention of claim 1;

FIG. 2 is a diagram illustrating the configuration and operation of a reference example .

FIG. 3 is a diagram for explaining the configuration and operation of the invention according to claim 2 ;

FIG. 4 is a diagram for explaining the configuration and operation of the invention according to claim 3 ;

FIG. 5 is a diagram for explaining the configuration and operation of the invention according to claim 4 ;

FIG. 6 is a diagram for explaining the configuration and operation of the invention according to claim 5 ;

FIG. 7 is a diagram for explaining the configuration and operation of the invention according to claim 6 ;

FIG. 8 is a view for explaining the first embodiment.

FIG. 9 is a diagram for explaining the operation of the dose calculation circuit according to the first embodiment.

FIG. 10 is a diagram for explaining the operation of a horizontal convolution unit and a vertical convolution unit corresponding to one of three scattering widths of the scattering influence evaluation circuit according to the first embodiment.

FIG. 11 is a diagram illustrating a second embodiment.

FIG. 12 is a diagram illustrating a third embodiment.

[Explanation of symbols]

 10, 11, 12 ... dose calculation means 20, 21, 22, 23 ... scattering effect evaluation means 30, 31 ... correction irradiation intensity derivation means 112, 212, 310 ... dose calculation circuit 123, 223, 320 ... scattering effect evaluation Circuits 131, 231, 330 ... Correction irradiation intensity derivation circuit

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideyuki Tsurumaki 1 Toshiba-cho, Komukai-shi, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba R & D Center (72) Inventor Takayuki Abe Toshiba-cho, Koyuki-ku, Kawasaki-shi, Kanagawa No. 1 Toshiba R & D Center Co., Ltd. (72) Inventor Susumu Oki 1 Toshiba R & D Center Co., Ltd. (72) Inventor Mitsuko Shimizu Komukai Koyuki, Kawasaki City, Kanagawa Prefecture 1 Toshiba Town R & D Center Toshiba Corporation (72) Inventor Takashi Uekubo 1 Tokoba Toshiba Town Koyuki Mukai-ku, Kawasaki City, Kanagawa Prefecture 72 R & D Center Toshiba Corporation (72) Tohru Tojo Ginza 4 Chuo-ku, Tokyo Ryoichi Yoshikawa 4-2-1 Ginza, Chuo-ku, Tokyo Higashi 2-11, Toshiba Machine Co., Ltd. Inside Machinery Co., Ltd. (72) Inventor Mitsunori Katayama 4-2-1, Ginza, Chuo-ku, Tokyo Toshiba Machinery Co., Ltd. (56) References JP-A-55-83234 (JP, A) JP, A) JP-A-7-78737 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7/20 504

Claims (7)

(57) [Claims] 1. A proximity effect correction device for drawing a charged particle beam for correcting a dose by evaluating a proximity effect due to scattering of an irradiation beam when performing drawing by irradiating a charged particle beam on a surface to be drawn. From the irradiation area and the irradiation intensity of the charged particle beam irradiating the irradiation target surface, the irradiation amount calculation means for obtaining the irradiation amount of a small grid region divided in the vertical and horizontal directions on the target surface, and for each grid region, A scattering effect evaluation means for evaluating an irradiation effect due to the scattering of the irradiation amount obtained by the irradiation amount calculation means on a plurality of peripheral grid regions surrounded by a rectangle, and a target drawing based on a result of the scattering effect evaluation means. it comprises a correction irradiation intensity deriving means for calculating a corrective irradiation intensity of suitable charged particle beam for drawing a graphic pattern for each grid area, the scattering effect evaluation means, In one direction along the grating relative to the grating area, performs convolution calculation using a one-dimensional Gaussian distribution function, all grid territory on the basis of the convolution calculation result
A proximity effect correction device for drawing a charged particle beam , wherein a convolution calculation is performed using a one-dimensional Gaussian distribution function that is the same as the Gaussian distribution function in another direction orthogonal to a region . 2. A proximity effect correction device for drawing a charged particle beam for correcting a dose by evaluating a proximity effect due to scattering of an irradiation beam when performing drawing by irradiating a charged particle beam on a surface to be drawn. From the irradiation area and the irradiation intensity of the charged particle beam irradiating the irradiation target surface, the irradiation amount calculation means for obtaining the irradiation amount of a small grid region divided in the vertical and horizontal directions on the target surface, and for each grid region, A scattering effect evaluation means for evaluating an irradiation effect due to the scattering of the irradiation amount obtained by the irradiation amount calculation means on a plurality of peripheral grid regions surrounded by a rectangle, and a target drawing based on a result of the scattering effect evaluation means. Correction irradiation intensity deriving means for calculating a correction irradiation intensity of a charged particle beam appropriate for drawing a graphic pattern for each grid region, and the scattering influence evaluation means, The convolution calculation based on the product of the dose and the Gaussian distribution function in each peripheral grid area obtained by the dose calculation means is weighted by the scattering rate for two or more Gaussian distributions having different parameter values for the spread of the distribution function. It is obtained as the sum of the calculated results, and in each convolution calculation, the convolution calculation is performed using a one-dimensional Gaussian distribution function in one direction along the grid for the entire grid area , and based on this convolution calculation result Whole grid area
A proximity effect correction device for drawing a charged particle beam , wherein a convolution calculation is performed using a one-dimensional Gaussian distribution function that is the same as the Gaussian distribution function in another direction orthogonal to a region . 3. A convolution calculation using a one-dimensional Gaussian distribution function in the X direction along the lattice. And the convolution calculation in the X direction in the Y direction orthogonal to the X direction is performed by multiplying the result of the convolution calculation in the X direction by the same one-dimensional Gaussian distribution function as the Gaussian distribution function. The proximity effect correction apparatus for drawing a charged beam according to claim 1 or 2, wherein the correction is performed. Here, S is the dose in the grid area obtained by the dose calculation means, P is an integral calculation common to both coordinate axes X and Y, η is the backscattering ratio, i is the grid coordinate in the X direction, and j is the grid coordinate in the Y direction. The grid coordinates are shown. 4. A charged particle beam writing apparatus having a variable projection shape, wherein the irradiation amount calculation means performs one irradiation of the charged particle beam based on the position of the irradiation figure and the projection shape. Is divided into irradiation patterns in each of the lattice regions, the irradiation pattern area in each of the lattice regions is obtained, and the irradiation amount obtained by multiplying the pattern area by the intensity of the charged particle beam irradiation is calculated for each of the lattice regions. The proximity effect correction apparatus for drawing a charged particle beam according to claim 1 or 2, wherein the irradiation amount of each lattice region is obtained by accumulating the irradiation amount already obtained inside. 5. The charged particle beam drawing apparatus according to claim 1, wherein the corrected irradiation intensity is obtained again by each of the means based on the corrected irradiation intensity obtained by each of the means. Proximity effect correction device. 6. The irradiation amount calculation means of the second and subsequent stages calculates a product of the already calculated irradiation area for each grid region and the corrected irradiation intensity as each grid region irradiation amount. Item 6. A proximity effect correction device for drawing a charged particle beam according to Item 5. 7. The correction irradiation intensity deriving means of the second and subsequent stages is not a new correction irradiation intensity but a correction irradiation intensity obtained up to the previous stage and an appropriate irradiation amount for drawing a target drawing graphic pattern. 7. The proximity effect correction apparatus for drawing a charged particle beam according to claim 5, wherein the apparatus is configured to obtain an approximate value of the difference.