JPH0982603A - Misalignment evaluation in electron beam lithography equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately evaluate an inherent misalignment by coating a resist liquid on a treatment substrate having an alignment mark, aligning and drawing on the basis of positional information on the alignment mark detected through scanning of an electron beam, and developing the resist liquid. SOLUTION: First, an alignment mark is formed on a treatment substrate (step F2). A negative resist is then applied on the substrate (step F4). Next, the alignment mark is detected through scanning with an electron beam (step F6) to obtain such information as position, size and rotational amount on the substrate. The substrate is subjected to a pattern drawing process and then to a developing process (step F8). Subsequently the substrate is subjected to a misalignment measurement (step F10). From the measured misalignment data, a shift, rotation and expansion or contraction of the electron beam pattern are calculated (step F12). From the calculated shift, rotation and expansion or contraction, an electron beam lithography equipment is adjusted to improve an alignment wiring accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a misalignment evaluation method for an electron beam drawing apparatus.

[0002]

2. Description of the Related Art In general, when writing with an underlying pattern using an electron beam drawing apparatus, the position of an alignment mark formed on a sample is detected by scanning an electron beam and based on this position information. Then, the desired pattern is drawn.

In this alignment drawing, it is important to measure the alignment deviation (positional deviation) between the base pattern and the drawing pattern. Conventionally, when obtaining this alignment deviation, when forming the alignment mark on the base, a pattern for alignment deviation measurement is formed separately at the same time, and after performing alignment drawing, the alignment deviation measurement pattern and the drawing pattern. This is done by measuring the position of and measuring the displacement between the two.

For example, as shown in FIG.
After forming a film 62 to be processed on 0, a resist (not shown) is applied, and a base pattern, a positioning mark, and a pattern for measuring misalignment are drawn (first drawing) using a drawing device. , A resist pattern is formed by development, and the film to be processed (base) 62 is patterned using the resist pattern as a mask to form a base pattern 62a, alignment marks 62b,
And the misalignment measurement pattern 62c is formed (see FIG. 10A).

Subsequently, after forming an interlayer insulating film 65 and the like on the entire surface, a film to be processed 66 is formed, and then the resist 6 is again formed.
8 is applied, and the alignment mark 62b is detected. After that, draw a drawing pattern on the resist 68 (second drawing)
Then, the drawing pattern 68a is formed by developing (see FIG. 10B). Then, the misalignment is obtained by measuring the misalignment between the misalignment measurement pattern 62c and the drawing pattern 68a. At this time, if the first exposure and the second exposure are performed using the same exposure apparatus (drawing apparatus), it is possible to measure the unique alignment accuracy of the writing apparatus alone.

In the manufacturing process of a semiconductor device, the misalignment of a wafer after drawing is measured, and this misalignment data is fed back to the drawing device to perform the subsequent wafer alignment drawing. Parameters to be fed back at this time include expansion / contraction, rotation, and shift amount of the drawing pattern.

[0007]

In general, electron beam writing has a slow writing throughput, and thus may be used in combination with an optical exposure apparatus. In the case of obtaining the above-mentioned misalignment, when the light exposure apparatus is used for the first drawing, the pattern including the misalignment measurement pattern is affected by the lens projection distortion. In this case, the position of the misalignment measurement pattern formed by light exposure is also distorted, so the misalignment data measured includes misalignment due to lens projection distortion.

Therefore, the expansion / contraction of
In order to feed back the rotation, shift amount, etc. to the electron beam writing apparatus and utilize them for subsequent wafer writing, it is necessary to separate the influence of lens projection distortion from the measured misalignment data.

However, in the conventional misalignment evaluation method, no attempt has been made to separate the influence of lens projection distortion from the measured misalignment data.

Further, electron beam exposure is generally used for drawing a photomask used for light exposure. In recent years, in light exposure, a phase shift mask is required to increase the resolution. In the production of this phase shift mask, matching writing is required by the electron beam writing apparatus. In this case, the alignment mark is formed by the first drawing using the electron beam, and the second alignment mark is formed by using the electron beam.
In the drawing, the alignment mark created in the first drawing is detected, and the matching drawing is performed. In the case of obtaining the above-described misalignment, even when the electron beam drawing apparatus is used for both the first drawing and the second drawing, the pattern including the misalignment measurement pattern is affected by the bending of the mask itself and thus the drawing position accuracy is increased. May deteriorate. That is, the first
When the photomask substrate is processed after drawing, the mask is deflected due to the stress change of the film to be processed on the substrate, and the misalignment measurement pattern formed in the first drawing is displaced by the mask deflection. Will be included.

Therefore, it is necessary to separate the influence of the mask deflection from the measured misalignment data, but in the conventional misalignment evaluation method, the influence of the mask deflection is separated from the measured misalignment data. Had not been tried.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an evaluation method capable of accurately evaluating a misalignment peculiar to an electron beam drawing apparatus.

[0013]

A method of evaluating misalignment in an electron beam drawing apparatus according to the present invention comprises a step of applying a resist film on a substrate to be processed on which alignment marks are formed, and an electron beam on the resist film. Detecting the position of the alignment mark by scanning, performing alignment drawing based on the detected position information, forming a resist pattern by developing the resist film, the alignment mark and A step of measuring a misalignment based on the resist pattern, and the step of performing the misalignment drawing,
A step of drawing a mark area surrounding the alignment mark at the time of pattern drawing, and the step of measuring the alignment deviation includes measuring the alignment deviation based on the alignment mark and the drawing pattern of the mark area. Characterize.

[0014]

According to the misalignment evaluation method of the electron beam drawing apparatus according to the present invention having the above-described structure, the alignment drawing is performed based on the position of the alignment mark, so that the vernier and the alignment which have been conventionally required. Displacement measurement mark is unnecessary. This makes it possible to remove the effects of light projection distortion, mask deflection, etc., and accurately evaluate the misalignment peculiar to the electron beam drawing apparatus.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a misalignment evaluation method for an electron beam drawing apparatus according to the present invention will be described with reference to FIGS. In the misalignment evaluation method of the first embodiment, an accelerating voltage of 50 kV, a vector scanning method, and a continuously moving stage variable shaping electron beam drawing apparatus were used.

FIG. 1 shows the processing procedure of the misalignment evaluation method according to the first embodiment. First, as shown in step F2 of FIG. 1, alignment marks are formed on a substrate to be processed (eg, a silicon substrate). At this time, unlike the conventional case,
No other misalignment measurement pattern is formed. The alignment marks 4 are formed at the four corners of the electron beam drawing pattern formation planned area 2 as shown in FIG. The alignment mark 4 has a cross shape, and has a size of 20 μm, a mark groove width of 5 μm, and a mark groove depth of 0.5 μm as shown in FIG.

Next, a negative resist is applied to the substrate to be processed (see step F4 in FIG. 1). Then, the above-mentioned processed substrate is set in an electron beam drawing apparatus and alignment drawing is performed.
In this alignment writing, first, the electron beam is scanned to detect the alignment marks 4 in all the electron beam writing pattern formation planned regions 2 (see step F6). At this time, information such as the position, size, and rotation amount of each drawing pattern formation scheduled area 2 on the substrate is obtained. Then, the deflection parameters of the electron beam writing apparatus are corrected based on these pieces of information, and a desired pattern is written in each drawing pattern formation scheduled area 2.

When the alignment mark 4 is detected, the electron beam is scanned in the direction shown by the arrow 12 in FIG. 4, so that the resist 14 around the alignment mark 4 is detected.
Is exposed. Therefore, when the pattern is drawn after the alignment mark 4 is detected, the alignment mark 4
A range 10 of 30 μm is drawn so as to surround (see FIGS. 3 and 4).

After the pattern drawing, the substrate is taken out from the electron beam drawing apparatus and developed (see step F8 in FIG. 1). At this time, since the resist is a negative type, a 30 μm range (mark region) 10 surrounding the alignment mark 4 remains.

Subsequently, misalignment measurement is performed (see step F10 in FIG. 1). This misalignment measurement is first shown in FIG.
As shown in (a), the intensity of light at the positions of AA ′ line 21 and BB ′ line 22 of the mark image captured by the optical microscope is captured by the optical sensor, and the alignment mark 4 and the mark area 10 are detected. The edge position is obtained from the detection output 25 of the optical sensor shown in FIG. Then, the center position 26 of the alignment mark 4 and the center position 27 of the mark region 10 are obtained from these edge positions, and the misalignment 28 is deviated from these center positions in the X direction (direction along the line AA ') and Measurement is performed in the Y direction (direction along the line BB ').

Next, the shift amount, rotation amount, and expansion / contraction amount of the electron beam drawing pattern are calculated based on the measured misalignment data (see step F12 in FIG. 1). Then, the electron beam drawing apparatus is adjusted based on the calculated shift amount, rotation amount, and expansion / contraction amount to improve the accuracy of alignment drawing. An example of the misalignment data (X misalignment data) calculated by the misalignment evaluation method of the present embodiment is shown in FIG. Reference numerals 4a, 4b, 4c and 4d in FIG. 6A indicate alignment marks formed at the four corners of the drawing pattern area 2 shown in FIG. 6C.

From the result shown in FIG. 6 (a), in the X direction,
It can be seen that the average misalignment is reduced by drawing with a shift of 0.02 μm. This result is fed back to the electron beam drawing apparatus, and the position of the drawing pattern area 2 obtained by the detection of the alignment mark is −0.
FIG. 6B shows the measurement result of the misalignment amount in the case where the drawing is performed by shifting by 02 μm. This figure 6
As can be seen from (b), the average misalignment amount is small, and it can be seen that the alignment drawing accuracy is improved.

As described above, according to the misalignment evaluation method of the present embodiment, since the alignment mark itself is used as the misalignment measurement pattern, the electron beam drawing in which the misalignment component due to the light projection exposure is removed. The inherent misalignment of the device can be measured. Further, since the misalignment measurement pattern is unnecessary, the semiconductor chip area can be effectively utilized.

Next, a second embodiment of a misalignment evaluation method for an electron beam drawing apparatus according to the present invention will be described with reference to FIGS.
This will be described with reference to FIG. The misalignment evaluation method of the second embodiment uses a positive resist in place of the negative resist in the misalignment evaluation method of the first embodiment. Since the positive type resist is used, the resist in the region 30 scanned by the electron beam upon detection of the alignment mark 4 becomes negative as shown in FIG. 7, but the region 31 outside the region 30 is developed. It has the property of dissolving in liquid. Therefore, in the second embodiment, when the pattern is drawn, the alignment mark 4
A range 35 (see FIG. 8) of 30 μm surrounding the area 35 is drawn to make it negative, and an area 38 outside thereof is drawn with a lower irradiation amount than the area 35. By drawing in this way, a resist groove 38 is formed outside the negative region 35 when the pattern is developed.

The misalignment is measured in the same manner as in the first embodiment, but at this time, the center position of each figure is obtained from the boundary of the resist groove 38 and the edge of the alignment mark 4, and the misalignment is determined. Measure.

It goes without saying that the misalignment evaluation method of the second embodiment also has the same effects as the misalignment evaluation method of the first embodiment.

Next, a third embodiment of a method for evaluating misalignment of an electron beam drawing apparatus according to the present invention will be described with reference to FIG. The evaluation method of the third embodiment is for misalignment of alignment drawing on a chrome mask.

First, a resist 42 is applied on the chrome layer 41 formed on the chrome mask 40 (see FIG. 9A). Next, the alignment mark 44 and the pattern 43 are drawn on the resist 42 and developed to form a resist pattern (see FIG. 9B). The chrome layer 41 is etched by using this resist pattern as a mask to form a chrome layer pattern 45 and an alignment mark 46, and the resist is removed (see FIG. 9C). At this time, the alignment mark 46 has a cross shape as in the first and second embodiments.

Next, a shift film 47 made of a shift material for shifting (reversing) the phase of exposure is formed on the patterned chromium layer, and then a resist 48 is applied again on this shift film 47 (see FIG. 9 ( See d)). Then, matching drawing is performed. In this alignment drawing, after the mark area 49 (see FIG. 9E) on the alignment mark 46 is drawn and development is performed, the alignment mark is formed in the same manner as in the first and second embodiments. The misalignment with 46 is measured.

In the misalignment evaluation method of the third embodiment, it is not necessary to provide a vernier for measuring misalignment on the mask 40, and the chip area can be effectively utilized. Further, it becomes possible to remove the misalignment component due to the bending of the chrome mask, and it is possible to accurately evaluate the misalignment accuracy of the drawing device.

In the misalignment evaluation methods of the first to third embodiments, the optical microscope is used to measure the misalignment, but an electron beam drawing device may be used.

In the first to third embodiments described above, the variable shaped beam system is used as the electron beam drawing system, but a round beam system electron beam drawing system may be used.

[0033]

As described above, according to the present invention, since it is not necessary to provide a pattern for measuring misalignment, it is possible to remove misalignment components due to light projection distortion, mask deflection, etc. Can be accurately evaluated.

[Brief description of drawings]

FIG. 1 is a flowchart showing a processing procedure of a first embodiment of a misalignment evaluation method for an electron beam drawing apparatus according to the present invention.

FIG. 2 is a view showing the arrangement of alignment marks used in the alignment deviation evaluation method according to the present invention.

FIG. 3 is a schematic view of alignment marks according to the alignment deviation evaluation method of the present invention.

FIG. 4 is an explanatory view when detecting the position of an alignment mark.

FIG. 5 is an explanatory diagram illustrating a method for measuring misalignment.

FIG. 6 is an explanatory diagram illustrating an effect of the present invention.

FIG. 7 is an explanatory diagram illustrating a second embodiment of a misalignment evaluation method according to the present invention.

FIG. 8 is a diagram showing a mark area drawn by a second embodiment of a misalignment evaluation method according to the present invention.

FIG. 9 is a cross-sectional view showing a processing procedure of a third embodiment of a misalignment evaluation method according to the present invention.

FIG. 10 is an explanatory diagram illustrating a conventional misalignment evaluation method.

[Explanation of symbols]

 2 drawing pattern region 4 alignment mark 10 mark region 12 electron beam scanning direction 14 exposed resist region 25 edge detection signal 26 center position between alignment mark edges 27 center position of mark region 28 misalignment amount

Claims (1)

[Claims] 1. A step of applying a resist film to a substrate to be processed on which an alignment mark is formed, the position of the alignment mark being detected by scanning an electron beam on the resist film, and the detected position A step of performing alignment drawing based on the information of, a step of forming a resist pattern by developing the resist film, a step of measuring a misalignment based on the alignment mark and the resist pattern, The step of performing the alignment drawing includes a step of drawing a mark area surrounding the alignment mark at the time of pattern drawing, and the step of measuring the alignment deviation is based on the alignment mark and the drawing pattern of the mark area. Electron beam drawing apparatus characterized by measuring misalignment Misalignment evaluation method.