JPH0336293B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an electron beam exposure method capable of forming a highly accurate pattern by correcting the so-called proximity effect.

Problems with the Prior Art Generally, when forming a pattern by applying an electron beam exposure method, an electron beam exposure apparatus is controlled based on pattern data created in advance.

FIG. 8 shows a block diagram of the main parts of an electron beam exposure apparatus.

In the figure, 41 is the main body, 42 is an electron gun, and 43
is a convergent electron lens system, 44 is an X/Y deflector, 45
4 shows a workpiece, 46 a processor, 47 a DA converter, and 48 an amplifier, respectively.

In the illustrated device, pattern data is stored in the processor 46, and the pattern data is processed as needed.
Read data, DA converter 47, amplifier 48
The X and Y deflectors are driven through the wafer, thereby advancing the electron beam spot and irradiating the electron beam so as to fill in a predetermined pattern to perform drawing. Furthermore, irradiation and blanking control is applied to the electron beam by a blanking device in accordance with signals from the processor 46. In the case of the apparatus shown in FIG. 8, control of the electron beam irradiation density is achieved by controlling the stepping speed and blanking time of the electron beam spot.

When implementing such an electron beam exposure method, it is of course important to improve pattern accuracy, and for this purpose it is essential to correct the so-called proximity effect.

As is well known, the proximity effect is caused by electron beam scattering (forward scattering) in the resist layer coated on the exposed object and electron beam scattering (backward scattering) from the substrate, which is the exposed object. Therefore, it is a phenomenon in which the resist pattern after drawing expands more than the electron beam irradiation pattern, and especially when the interval between patterns becomes 3 [μm] or less, it results in significant distortion of the pattern shape and reduces accuracy. .

By the way, the electron beam scattering intensity distribution in the resist due to the above-mentioned scattering is expressed as a function of the distance r from the center of the externally irradiated beam: f(r)=e ^-(r/A)2 +B・e ^{-( r/C)2} ...(1) It is known that the first term is given by forward scattering and the second term is given by backward scattering. Note that A, B, and C used in equation (1) are constants determined depending on conditions such as the thickness of the resist and the material of the substrate.

Conventionally, the most common method for correcting the proximity effect is to calculate the optimal irradiation by considering the electron beam scattering intensity distribution expressed by equation (1) for each pattern and the distance between the pattern and the adjacent pattern. The amount of correction is set in advance for each pattern, or the pattern dimensions of the drawn pattern are corrected (reduced), but in both cases, the correction amount is determined in advance at the time of creating the pattern data. It is something to do.

Therefore, as shown in FIG. 1, for example, a sample point SP1 is set on a predetermined side of the pattern P1,
The influence from all other patterns, for example patterns P2 and P3, is calculated using equation (1), and this is done for each pattern.The dimensions and Correction amounts for both irradiation amounts are determined.

However, as shown in equation (1), the electron beam scattering intensity distribution decreases exponentially as the distance increases, resulting in an equation with strong nonlinearity with respect to distance.

For this reason, an integrated circuit pattern having an arbitrary size, especially an exposure pattern after the pattern to be formed is divided into rectangular shapes as shown in FIG. Moreover, if the width is small like the pattern P13, it is often impossible to find a solution to the above-mentioned simultaneous equations, and it is particularly difficult to precisely find the amount of dimensional correction. Incidentally, P14 in FIG. 2 is also a pattern.

Purpose of the Invention The present invention is an approximate method when performing electron beam exposure, but it is relatively simple and allows for a pattern that has a small pattern width and is in contact with other patterns to be This makes it possible to obtain correction amounts for both amounts and to obtain highly accurate patterns.

Structure of the Invention The present invention provides an electron beam exposure method in which a workpiece is irradiated with an electron beam to draw a large number of patterns. If it is in contact with the pattern, the exposure pattern and the polygonal pattern that is within the range that affects the exposure pattern and that is in contact with the exposure pattern are regarded as one rectangular pattern (approximate rectangular pattern and ), consider the influence between patterns due to electron beam scattering and the size of the approximate rectangular pattern, calculate the irradiation dose and dimension correction amount to obtain the target exposure pattern dimensions, and then calculate the electron It performs beam drawing.

Embodiment of the Invention FIG. 3 is a plan view of a main part of a pattern for explaining an embodiment of the present invention.

In the figure, P21, P22, and P23 are the exposure patterns a ₁ , a ₂ , a ₃ , b ₁ , b ₂ ,
_b3 indicates the length of each side in the exposure patterns P21, P22, and P23.

In this case, the exposure pattern P after being divided into rectangles
21 is in contact with the exposure pattern P22, and the exposure pattern P22 is in contact with another exposure pattern P23.

Now, let us consider a case where the exposure pattern P21 is to be corrected and its correction amount (intra-pattern dimensional correction amount and inter-pattern dimensional correction amount) is calculated.

FIG. 4 shows a flow chart for explaining the procedure for determining the amount of correction of an exposure pattern, and the explanation will be given below according to this flow.

Steps seen in FIG. 4 As explained with reference to FIG. 3, the exposure pattern is divided into rectangles as indicated by P21, P22, and P23.

The stage seen in FIG. 4 As seen in FIG. 3, the exposure pattern P21 after being divided into rectangles is in contact with the exposure pattern 22, and the exposure pattern 22 is in contact with another exposure pattern P23. Determine.

Steps seen in FIG. 4 First, the polygonal pattern (here, composed of exposure patterns P22 and P23) that is in contact with the exposure pattern P21 to be corrected is approximated as one rectangular pattern together with the exposure pattern P21. As one side of the approximate rectangular pattern, a portion of the contact side between the exposure pattern to be corrected and the polygonal pattern that touches and shares a line segment is adopted.

The rectangular pattern indicated by the broken line in FIG. 3 is an approximate rectangular pattern, and its sizes a ₀ and b ₀ are calculated as follows.

a ₀ = a ₁ b ₀ = (a ₁ b ₁ + a ₂ b ₂ + a ₃ b ₃ )/a ₁ ...(2) Here, ai, bi (i = 1 to 3) are the exposure pattern P21, These are the lengths of the long and short sides of P22 and P23, and _a1 represents the length of the shared portion of the contacting sides. In addition, when ai and bi are longer than a certain length ε [μm], it is set as ε. still,
In the case of the example, it is 5 [μm].

(This step is the end.) FIG. 5 shows an approximate rectangular pattern obtained by approximating the exposure pattern P21 in FIG. It is a principal part plan view showing the state after setting NP1 together with other approximate rectangular patterns NP2 and NP3.Next, the procedure for calculating the dimension correction amount will be explained with reference to this figure.

Step (a) shown in FIG. 4: For each approximate rectangular pattern, take into consideration the spread of the pattern itself, and determine the intra-pattern dimension correction amount Si and the irradiation amount Qi to obtain the target pattern dimension. Note that the approximate rectangular patterns NP1, NP2, and NP3 shown by solid lines in FIG. 5 represent patterns after the internal pattern dimensions have been corrected.

First, the in-pattern dimension correction amount Si is determined using the relationship that the ratio between the exposure intensity before dimension correction (Si=0) and the exposure intensity after dimension correction is constant.

That is, sample points of each approximate rectangular pattern, for example, point A in pattern NP1, pattern NP
For pattern NP3, point B is set, and for pattern NP3, point C is set. The exposure intensity after dimension correction at each sample point is the integral formula of equation (3), and the exposure intensity before dimension correction is expressed by equation (3). Si is given by Si=0, and since these ratios are constant, Si can be found. Note that the ratio of exposure intensities is determined for each exposure condition and is determined in advance through experiments or the like.

∫ ^(b/2)-Si _-(b/2)+Si ∫ ^(a/2)-Si _-(a/2)+Si f(r)dydx
...(3) Here, r is the distance from the sample point to the integration point, a, b are the pattern length and pattern width of each approximate rectangular pattern, and f(r) is the electron beam scattering in equation (1). This shows the intensity distribution.

Next, the irradiation amount Qi is determined by dividing the development energy intensity E by the exposure intensity at each sample point. That is, the exposure intensity F can be obtained by substituting the already obtained Si into the integral equation of equation (3) and using the following equation.

Qi=E/F Stage (b) seen in Figure 4: For each approximate rectangular pattern, the inter-pattern dimension correction amount SSi takes into account the influence of surrounding patterns.
seek.

At the sample point A of the approximate rectangular pattern NP1 in FIG. 5, the following equation holds true.

Q ₁ F (r ₁ , S ₁ , SS ₁ ) +Q ₂ F (r ₂ , S ₂ , O) +Q ₃ F (r ₃ , S ₃ , O)=E …(4) Already S ₁ , S ₂ , Since S ₃ , Q ₁ , Q ₂ , and Q ₃ have been determined, the inter-pattern dimension correction amount SS ₁ can be determined so as to satisfy the above equation (4). Here, F (ri, Si, SSi) is the exposure intensity of the drawn pattern, and ri (i.e., r ₁ , r ₂ , r _3, etc.) is the distance from the center of the patterns NP1, NM2, NP3 to the sample point A. (known), and SSi is the dimensional correction amount and is unknown. Note that ri remains constant unless the sample point is moved.

F(ri, Si, SSi) is given by the following formula.

F (ri, Si, SSi) =∫ ^(b/2)-Si-SSi _{-(b/2)+Si+SSi} ∫ ^(a/2)-Si _-(a/2)+Si
f(r)dydx...(5) Note that r represents the distance from the sample point to the integration point.

As described above, the dimensional correction amount (intra-pattern dimensional correction amount S ₁ and inter-pattern dimensional correction amount SS ₁ ) of the exposure pattern P21 is determined, and the actual correction amount is the sum of Si and SSi.

(Up to this stage, the steps are over.) FIG.
Symbols used in the drawings indicate the same parts or have the same meaning.

In the figure, S ₁ ′ is the in-pattern dimension correction amount,
SS′ indicates the inter-pattern dimension correction amount.

In this case, an approximate rectangular pattern NP22 is obtained by considering the pattern P23, and an approximate rectangular pattern NP22 is obtained by considering the pattern P23.
The point A of No. 22 is set as a sample point, and the in-pattern dimension correction amount S ₁ ' and the irradiation amount Q for obtaining the target pattern dimension are determined. Next, the surrounding pattern P2
1, P23, P24, and P25 to determine the inter-pattern dimension correction amount SS'.

FIG. 7 is a plan view of essential parts for explaining another embodiment.

In the figure, P31, P32, P33, P34
is the exposure pattern.

As shown in the figure, when a part of the exposure pattern divided into rectangles is in contact with another exposure pattern, the exposure pattern P32 and the contact exposure pattern P that affect the correction target exposure pattern P31
The contact pattern is selected depending on the positional relationship with P33 and P34.

In the case of this embodiment, the exposure pattern P33, which is within the influence range of the exposure pattern P32, is used as a contact pattern, and the exposure pattern P34, which is not under the influence of the exposure pattern P32, is not used as a contact pattern.

Therefore, here, the exposure pattern P31 to be corrected and the exposure pattern P33 in contact with it may be approximated to a rectangular pattern in exactly the same manner as in the embodiment described above.

As described above, the amount of correction for the dimensions and electron beam irradiation density is determined at the time of pattern data creation.

Effects of the Invention According to the present invention, when performing electron beam exposure, an exposure pattern is obtained by dividing the pattern into rectangular shapes among the patterns to be formed, and a predetermined exposure pattern has another polygonal exposure pattern. If the predetermined exposure pattern becomes a correction target, the exposure pattern to be corrected and the polygonal exposure pattern within the range that influences it are approximated to one rectangular exposure pattern, and the electronic Taking into account the influence between patterns due to beam scattering and the size of the approximate rectangular pattern, determine the irradiation amount and dimensional correction amount to obtain the target exposure pattern dimensions, and perform drawing based on the irradiation amount and dimensional correction amount. Because of this, the pattern width is small, and
For patterns that are in contact with other patterns, correction amounts for both dimensions and irradiation amount can be determined relatively easily, and this is effective in obtaining highly accurate patterns.

[Brief explanation of the drawing]

1 and 2 are plan views of main parts showing patterns for explaining the problems of the prior art, and FIGS. 3 and 4 are main parts showing patterns for explaining one embodiment of the present invention. 4 is a flow chart for explaining the procedure for determining the correction amount of an exposure pattern. FIG. 5 is a plan view of the main part showing a pattern for explaining one embodiment of the present invention. 7 and 7 are plan views of essential parts showing patterns for explaining other embodiments, respectively, and FIG. 8 is a block diagram of essential parts showing an example of an electron beam exposure apparatus. In the figure, P21, P22, P23 are the exposure patterns after dividing into rectangles, P24, P25 are the exposure patterns, a ₁ , a ₂ , a ₃ are the long sides of the exposure patterns,
b ₁ , b ₂ , b ₃ are the short sides of the exposure pattern, NP1 is the approximate rectangular pattern, a ₀ is the short side of the approximate rectangular pattern, b ₀
is the long side of the approximate rectangular pattern, A is the sample point,
SS is the inter-pattern dimension correction amount.

Claims (1)

[Scope of Claims] 1. In an electron beam exposure method in which a large number of patterns are drawn by irradiating an electron beam onto a workpiece, an exposure pattern obtained by dividing a polygonal exposure pattern to be formed into rectangular sections. If the predetermined exposure pattern comes into contact with another exposure pattern and the predetermined exposure pattern becomes a correction target, the exposure pattern is within the range that affects the exposure pattern and the exposure pattern that is the correction target, and the exposure pattern Irradiation dose and dimensions to approximate other exposure patterns in contact with one rectangular exposure pattern and obtain the target exposure pattern dimensions by taking into account the influence between patterns due to electron beam scattering and the size of the approximated rectangular exposure pattern. An electron beam exposure method characterized in that a correction amount is determined and drawing is performed based on the irradiation amount and the dimension correction amount.