JPS59114818A - Electron beam pattern drawing method - Google Patents

Abstract

PURPOSE:To prevent variation of pattern dimension even if setting shift occurs in a mask substrate or the like, by a method wherein output correction value of an object lens in fine regions by imaginarily dividing a substrate is determined, output correction value of a deflection electrode in the fine regions is determined from above correction value, and the object lens output and the deflection electrode output are corrected and electron beam is projected. CONSTITUTION:Values 1/n, 1/m by equally dividing a mask substrate 13 in direction (x) and direction (y) are outputted from CPU 24 to a rate multiplier 30. Scanning of electron beam is synchronized by a synchronizing circuit 31 and the rate multiplier 30 outputs signals i/n (i=1-n), j/m (j=1-m) corresponding to divided region positions on the mask substrate 13 in one pulse per one scan of the electron beam through a counter 26b of an object lens controller 26 into an arithmetic circuit 26a. The arithmetic circuit 26a estimates object lens correction value DELTALij in each divided region on the mask substrate 13 by proportional allotment. An arithmetic circuit 28a of a deflection electrode controller 28 estimates deflection correction values DELTAXwij and DELTAFij or DELTAYBij in each divided region on the mask substrate 13.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to an electron beam pattern writing method.

[Technical background of the invention and its problems]

When using an electron beam exposure apparatus to form a pattern on a mask substrate, for example, a glass substrate surface coated with a chromium layer or the like to make a mask, the glass substrate is placed on a cassette and electron beam exposure is performed.

At this time, if the mask substrate is properly set on the cassette, the electron beam irradiated from the aperture 1 will be accurately focused on the mask substrate 2, as shown in FIG. The pattern will be the dimensions of the design.

However, when the mask substrate 2 is tilted and set on the cassette 3 as shown in FIGS. 2 and 3, the irradiation position of the electron beam on the mask substrate 2 deviates from the depth of focus, so the relative The dose decreases and the dimensions of the noreen decrease.

Such misalignment when the mask substrate 2 is set on the cassette 3 (indicated by 2 in Fig. 2) occurs, for example, due to abrasion of the bottle of the cassette 3, and may range from several tens of μm to several hundred μm, which may be large in pattern dimensions. influence

For example, Al~3°B on the mask substrate 2 shown in FIG.
~3+C1~3 When the design dimension of the turn is set to 10 μm in both the X direction and the y direction, z
In the case of an inclination of = 500 μm, the dimensions of the pattern actually formed on the mask substrate 2 are as shown in FIG.

In other words, A with the largest deviation from the normal set position
At the position 3 + B3 + c3, the gino and turn dimensions are about 6 μm due to the decrease in the dose amount, which is about 4 μm thinner than the designed dimension.

Further, misalignment of the mask substrate 2 has a large effect on the total pitch (long dimension pitch) of the pattern, as shown in FIG.

However, conventional electron beam exposure equipment does not have a function to adjust the mask substrate so that it does not deviate from the focal depth of the electron beam even if the mask substrate is misaligned as described above. The disadvantage is that it cannot be prevented.

[Purpose of the invention]

The present invention was made in order to eliminate the above-mentioned drawbacks.Even if the mask substrate, etc. is misaligned, it prevents the mask substrate, etc. from deviating from the focal depth of the electron beam, thereby preventing variations in the turn dimension. The purpose of this study is to provide an electron beam pattern drawing method that can be used.

[Summary of the invention]

In the electron beam pattern drawing method of the present invention, first, an electron beam is line-scanned over markers two-dimensionally provided at at least three locations on a substrate surface, and when each marker is focused, the output value of the objective lens is Measure. Next, based on this output value, the correction value of the output of the objective lens in each subdivision area where the substrate is virtually divided during pattern drawing is determined, and from these correction values, the output of the deflection electrode in each corresponding subdivision area is calculated. This method is characterized in that a correction value is determined, the objective lens output and the deflection electrode output are corrected, and the electron beam is irradiated.

The correction value of the output of the objective lens in each subdivision area mentioned above corresponds to the vertical deviation from the normal set state 75) of each subdivision area. The depth of focus of the beam can be tailored to each subregion surface. In addition, the correction value of the output of the deflection electrode in each subdivision area corresponds to the horizontal deviation from the normal set state of each subdivision area, and by correcting the output of the deflection electrode by that correction value valve, the output of the deflection electrode is corrected in the horizontal direction. This can eliminate the misalignment. Therefore, according to the above-described method, it is possible to irradiate the electron beam with the focal depth and focal position always being adjusted in each subdivision area, and it is possible to draw a noreen with little variation from the design dimension.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 7 to 12.

First, as shown in FIG. 7, a Cr layer 1 is placed on a glass substrate 11.
21 and Cr xOy layer 122 are sequentially deposited to fabricate a mask substrate 13, as shown in FIGS.
Layer 121. Markers 141 to 144 are formed on the CrxOy layer 122, and a resist 15 is further applied to the entire surface.

Next, after setting the mask substrate 13 in a cassette on a table, the electron beam is line-scanned over the markers 141 to 144, for example, in the direction of the arrow in FIG. 8, and the state of the focus is evaluated before writing.

I can do that.

At this time, if the electron beam is focused at one marker position and the beam diameter is the minimum, the signal calibration section will produce a reflected electron profile corresponding to the grooves of the markers 141 to 144 as shown in FIG. can be obtained. Here, the marker 141 of the mask substrate 13 that has been set normally
The output value of the objective lens when the profile shown in FIG. 9 is obtained by line scanning through 44 is assumed to be LO. However, if a misalignment occurs in the mask substrate 13, the output value of the objective lens will not be in focus, making it impossible to obtain the profile shown in FIG. 9. Therefore, it is necessary to correct the output value of the objective lens to a different value to focus. In other words, the difference Lo-L'=ΔL (hereinafter referred to as objective lens correction value) between the output value Lo during normal setting and the output value L' when setting deviation occurs is calculated from the normal setting state of the markers 141 to 144. corresponds to the vertical deviation of .

On the other hand, when a set deviation occurs, the focal point position is shifted in the horizontal direction from the normal set state, so it is also necessary to correct the output of the deflection electrode. The correction value of the output of this deflection electrode (
(hereinafter referred to as the deflection correction value) is the objective lens correction value Δ
It has been confirmed by measurements that the curves take values according to L and form curves as shown in FIG. 10 for x direction ΔXw, y forward direction Δy, and y backward direction ΔYB.

As described above, by line-scanning the electron beam over the markers 141 to 144, the objective lens correction values ΔL and deflection correction values ΔXw, ΔY, lΔY of the markers 14° to 144 are determined.
You can know B. From these values, mask substrate I3
To know the objective lens correction value and deflection correction value over the entire surface, first, as shown in FIG. 11, the mask substrate 13 is virtually divided into n equal parts in the Divide into rectangular subregions. Next, markers 141-1
The objective lens correction value ΔL in each subdivision area is calculated by performing calculation processing to proportionally distribute the 44 objective lens correction values ΔL1 to 4.
Find Lij (i-1 to n, j=1 to m). Next, we calculate these values of ΔLB as ΔXw2ΔYF and Δ
Equations ΔXw(ΔL), ΔYF(
By substituting ΔL) and ΔYB(ΔL), the deflection correction values Δx1V, , ΔYFij, ΔYB,j in the subdivision region can be obtained.

For example, when the tops of the markers 141 to 144 are tilted and the markers 141 to 144 are in focus, the correction values are ΔL1 = O + ΔL2 = 01 ΔL3 = LoL
Considering a relatively simple case where 'rΔL4=L, -L', the following results.

First, in the first row, the two objective lens correction value is ΔL11 =
Lg +ΔL1m==Lo L', and in these intermediate subdivision regions, Δ[,1j= LO+'(LOL'
) (j=2~ml). At this time, the deflection correction values ΔX W 1 j and ΔY F 1 j are respectively the first
The value may be set to a value corresponding to ΔL1j in FIG. Next, in the second column, the objective lens correction value is ΔL2 m = LOL
'rΔL21=0, and in these intermediate subdivision regions ΔL2 j=Lo +L(Lo −L) (j
=2~m-1). At this time, the deflection correction value ΔX W
2 j and ΔYn2j are respectively ΔL in FIG.
A value corresponding to 2J may be used. The same applies to each subdivision area in each column.

Therefore, the signal of the objective lens correction value ΔLij is sent to the objective lens, and the signal of the deflection correction value ΔXwij and Δ'F
By outputting the signals ij or ΔYBi· to the deflection electrodes, electron beam exposure can be performed in all sub-regions of the mask substrate 13 with the focal depth and focal position aligned.

A case in which the above method is carried out using an actual electron beam exposure apparatus will be described with reference to FIG. 12.

The main body of the electron beam exposure apparatus includes an objective lens 21 and a deflection electrode 2.
2. The mask substrate 13 is placed in a cassette on a table (not shown), which includes a signal detector 23 and the like. The control system that controls the main body of this electron beam exposure apparatus is a central processing unit (C
PU), IM, detection signal processor 25, arithmetic circuit 26a1
An objective lens controller 26 consisting of a counter z6b, a 7-touch 26c, and an objective lens system DAC (Digital t.

The components include an analog converter (R, M, ) 27, a deflection electrode controller 28 consisting of an arithmetic circuit 28a1, a counter 2&b1 rate 28c, a deflection system DAC 29, a rate multiplier (R, M, ) 3o, and a synchronization circuit 31.

Here, the CPU 24 performs all signal processing for other members (not shown) of the main body of the electron beam exposure apparatus. The detection signal processor 25 is connected to the signal detector 23 and the CPU 24. The objective lens controller 26 sends C to its arithmetic circuit 26a.
A signal from the PU 24 and a signal from the rate multiplier 30 are input via the counter 26b, and the calculated signal is sent to the objective lens system DAC 27 via the latch 26c.
Output to. Furthermore, this objective lens system DAC,? 7 outputs an analog signal to the objective lens 21.

The deflection electrode controller 28 connects the CPU 2 to its arithmetic circuit 28a.
4, a signal from the rate multiplier 30 via the counter 28b, and a signal from the calculation circuit 26a of the objective lens controller 26 are input, and the calculated signal is output to the deflection system DAC 29 via the latch 28c. do.

Furthermore, this deflection system DAC 29 outputs an analog signal to the deflection electrode 22. Also, the rate multiplier 30 is C
It receives signals from the PU 24 and the synchronization circuit 3, and outputs signals to the counter 26b of the objective lens controller 26 and the counter 28b of the deflection electrode controller 28.

First, an electron beam is applied to the marker 14 provided on the mask substrate 13. .about.144 is sequentially scanned, focusing is performed, and the objective lens output values L1 to 4 are obtained when the signal detector 23 and the detection signal device 25 are brought into focus. Next, the CPU 24 outputs the objective lens output values L1 to L4 and the objective lens output value in the normal set state to the arithmetic circuit 26a of the objective lens controller 26. At the same time, a value 1/n, which is obtained by equally dividing the mask substrate 13 in the X direction and the X direction, is sent from the CPU 24 to the rate multiplier 3°.
1/m (thinning rate) is output, and the rate multiplier 3 is synchronized with the scanning of the simulator beam by the synchronization circuit 31.
i/n (i=1
~n).

The signals of j, /m (j=1 to m) are sent to the objective lens controller 26.
It is output to the arithmetic circuit 26a via the counter 26b.

In this arithmetic circuit 26a, the proportion distribution is
The objective lens correction value ΔLij in each of the above subdivision areas is determined. In addition, the calculation circuit 28a of the deflection electrode controller 28
Equations ΔXw (ΔL), ΔYF (ΔL), ΔY corresponding to the deflection correction value curves shown in FIG. 10 from the CPU 24
B(ΔL), the arithmetic circuit 26a of the objective lens controller 26 outputs the objective lens correction value ΔL1j, and the rate multiplier 30 outputs 1 of the electron beam.
A signal of 1/n Hj/m of one pulse per scan is outputted via the counter 28b. This calculation circuit 2
8a, the deflection correction value ΔXwij and ΔYF1j or ΔYBij in each subdivision area on the mask substrate 13 are determined.

The objective lens correction value ΔL1j obtained as described above is sent to the objective lens system DAC 27 via the latch 26c, and the output of the objective lens 21 is corrected.

In addition, the deflection correction value ΔXw1j and ΔYFi or ΔYB
ij is sent to the deflection electrode system DAC 29 via the latch 28c, and the output of the deflection electrode 22 is corrected.

According to the above method, even if the mask substrate 13 is misaligned, the focal depth and focal position of the electron beam can always be adjusted at any position on the mask substrate 13. Therefore, variations in pattern dimensions that conventionally occur due to misalignment of the mask substrate 130 can be reduced.
A pattern with the dimensions of a design can be drawn. Further, the total pitch of the flat turns can also be made consistent with the design.

In the above embodiment, the markers are formed at the four corners of the mask substrate, but the markers may be formed four-dimensionally in at least three corners of the mask substrate other than the formation area.

Further, various arithmetic processing in the above embodiments, as well as signal processing for table movement, etc., are normally performed by the CPU.

〔Effect of the invention〕

As described in detail above, according to the present invention, it is possible to provide an electronic pattern drawing method that can prevent variations in pattern dimensions even if misalignment of a mask substrate or the like occurs.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing the electron beam exposure state when the mask substrate is normally set, Figure 2 is a perspective view showing the state where the mask substrate is misaligned on the cassette, and Figure 3 is the same state. 4 is a plan view of the mask substrate, and FIG. 5 is a diagram showing the variation in i4 turn dimension when the mask substrate is misaligned.
Fig. 6 is a diagram showing the variation in total pitch when the mask substrate is misaligned, Fig. 7 is a cross-sectional view showing the markers on the mask substrate, and Fig. 8 is a plane showing the marker position on the mask substrate. Figure 9 is a backscattered electron profile at the marker, Figure 10 is a line diagram showing the relationship between the objective lens correction value and the deflection correction value, and Figure 11 is a diagram showing the mask substrate virtually divided into sub-regions. The plan view and FIG. 12 are block diagrams showing the control system for carrying out the method of the present invention. 22... Deflection electrode, 23... Signal detector, 24...
・CPU, 25...Detection signal processor, 26...Objective lens controller, 27...Objective lens system DAC, 28...
... Deflection electrode controller, 29... Deflection system DAC, 30.
...Rate multiplier, 31...Synchronization circuit, 26
a, 28a... arithmetic circuit, 26 b, 28 b
counter, 26c. 28c...Latch.

Claims (1)

[Claims] An electron beam is passed through an objective lens, deflected by a deflection electrode, and irradiated onto a substrate. In order to draw a pattern on the substrate surface, an electron beam is passed through an objective lens, deflected by a deflection electrode, and irradiated onto a marker provided two-dimensionally at at least three locations on the substrate surface. The output value of the objective lens is measured when the electron beam is line-scanned and focused at each marker, and based on this output value, the output value of the objective lens is determined in subdivided areas where the substrate is virtually divided during 4-turn writing. The method is characterized in that a correction value for the output is determined, and from these correction values, a correction value for the output of the deflection electrode in each subdivision region corresponding thereto is determined, and the objective lens output and the deflection electrode output are corrected and the electron beam is irradiated. Electron beam pattern drawing method.