JPH05243136A - Pattern registration evaluating method using electron beam exposure system - Google Patents

Abstract

PURPOSE:To easily evaluate the registration of a multilayer pattern with high precision using the title electron beam exposure system. CONSTITUTION:The evaluation patterns P1, P2 on the first and second layers are formed on a material. A stage 6 is shifted to make the intermediate position of the two kinds of pattern P1 and P2 and an optical axis in alignment with one another. At this time, the shifting amount of the stage 6 is computed by a stage measuring instrument 13 using a laser interferometer. The electron beam is deflected to respective pattern parts P1, P2 by a large deflector 11 furthermore, respective pattern parts are scanned by small deflector 12 so as to locate the positions a, b, of respective patterns P1, P2. Finally, a computer 8 computes the misregistration DELTAepsilon by the formula as follows DELTAepsilon=(b-a)-D where a, b, and D respectively represent the positions of both patterns P1, P2 and the theoretical distance D.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating the superposition of patterns formed in multiple layers by using an electron beam drawing apparatus.

[0002]

2. Description of the Related Art When making a device such as an LSI,
The pattern is formed in multiple layers on the substrate. For example, a specific substance is vapor-deposited on a silicon wafer, a resist is applied thereon, and then a predetermined pattern is drawn by an electron beam. After drawing, processing such as development and etching is performed to form a first pattern of a specific substance. Next, a second specific substance is vapor-deposited on the wafer on which the first pattern is formed, a resist is applied thereon, and then a predetermined pattern is drawn by an electron beam. After drawing, processing such as development and etching is performed to form a second pattern of the second specific substance. In this way, the pattern is formed in multiple layers, and the first pattern and the second pattern are formed.
The positional relationship of the pattern must be within a certain allowable value. For this reason, a vernier pattern is drawn and formed at the time of drawing the first pattern and at the time of drawing the second pattern, and the formed vernier pattern is observed using an optical microscope, The overlay error with the second pattern is read and the overlay of the multilayer pattern is evaluated.

[0003]

However, since the above-described evaluation of overlay has an optical inspection machine, there is a limit in accuracy depending on the wavelength of light, and the evaluation can be performed with sufficient accuracy. Can not. Also, the vernier pattern must be formed in chip units together with the predetermined pattern, which limits the range of use of the wafer for forming the vernier pattern. Furthermore, reading the overlay accuracy with a vernier pattern is inconvenient.

The present invention has been made in view of the above circumstances, and an object thereof is to perform pattern superposition using an electron beam drawing apparatus capable of easily evaluating superposition of multilayer patterns with high accuracy. To realize the evaluation method.

[0005]

A pattern superposition evaluation method using an electron beam drawing apparatus according to the present invention has a first predetermined distance from a reference position when drawing various patterns of a first layer on a material. A first evaluation pattern is drawn by an electron beam at a distant position to form a first evaluation pattern, and when drawing various patterns of the second layer on the material, a second predetermined distance from the reference position. A second evaluation pattern is drawn by an electron beam at a distant position to form a second evaluation pattern, and then the first layer and the second evaluation pattern are moved from the first and second evaluation pattern positions.
In a method for evaluating the accuracy of layer superposition, the material is set in an electron beam drawing apparatus having first and second deflectors, and the electron beam is directed by the first deflector to a first evaluation pattern portion. Then, the electron beam is scanned by the second deflector in the first evaluation pattern portion in this state. Based on the signal obtained by this scanning and the deflection amount by the first deflector, The position of the evaluation pattern is measured, and then the electron beam is deflected by the first deflector to the second evaluation pattern portion. In this state, the electron beam is deflected by the second deflector at the second evaluation pattern portion. Scanning is performed, the position of the second evaluation pattern is measured based on the signal obtained by this scanning, and the deflection amount of the first deflector, and the measured first evaluation pattern position and the second evaluation pattern position are measured. Pattern position and both From the theoretical value between valence pattern position it is characterized in that so as to measure the pattern overlay accuracy of drawing between the first and second layers.

[0006]

According to the pattern superposition evaluation method using the electron beam drawing apparatus according to the present invention, when drawing various patterns of the first layer on the material, the electron beam is placed at a position a first predetermined distance away from the reference position. The first evaluation pattern is drawn with to form the first evaluation pattern, and when the various patterns of the second layer are drawn on the material, the electron beam is placed at a position a second predetermined distance away from the reference position. The second evaluation pattern is drawn with to form the second evaluation pattern, and after the two kinds of evaluation patterns are formed, the electron beam is deflected by the first deflector to the first and second evaluation pattern portions. Then, the electron beam is scanned by the second deflector at each evaluation pattern portion, and each evaluation pattern position is measured by the deflection amount by the first deflector and the signal based on the electron beam scanning, and is obtained from this position. Rated rating putter The measured value of the distance between the evaluation of the superposition of the pattern formed on the multi-layered from the design value (theoretical value) between the evaluation pattern performed.

[0007]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows an example of an electron beam drawing apparatus for carrying out the overlay evaluation method according to the present invention, and 1 is an electron gun. The electron beam generated from the electron gun 1 is focused on the drawing material 3 by the electron lens portion 2 and is deflected by the first deflector 4 and the second deflector 5. The first deflector 4 is a deflector capable of large deflection and operates as a large deflector, and the second deflector 5 is a small deflector capable of deflecting an electron beam in a small area at high speed and with high accuracy. It works as a container. The drawing material 3 is placed on a moving stage 6, and the stage 6 is two-dimensionally moved by a drive system 7. The drive system 7 is controlled by a computer 8, which controls a blanking control system 9, a lens control system 10, and deflector control systems 11 and 12. Reference numeral 13 is a stage length measuring system using a laser interferometer for measuring the amount of movement of the stage 6.
Next, the operation using such a device will be described.

First, a first specific substance is vapor-deposited on a silicon wafer as the material 3, and a resist is further applied thereon, and the stage 6 is mounted. Then, the stage 6 is moved under the control of the computer 8, the blanking control system 9 is controlled for each field to perform the blanking of the electron beam, and the deflector control systems 11 and 12 are controlled to control the electron beam. Deflection is performed to draw a desired pattern.
At this time, together with the drawing of various patterns, as shown in FIG. 2, the evaluation pattern P1 is drawn at a position apart from the mark M provided in advance by a predetermined distance. After the drawing of the predetermined first layer is completed, the material 3 is taken out from the electron beam drawing apparatus and subjected to a developing process and an etching process to form a pattern of the first layer. Then, the second specific substance is vapor-deposited on the material 3 on which the first layer pattern is formed, and a resist is further applied thereon, and the stage 3 is placed. Then, the stage is moved under the control of the computer 8, the electron beam is deflected for each field, and a desired pattern is drawn. At this time, together with the drawing of the various patterns of the second layer, as shown in FIG. 2, the evaluation pattern P2 is drawn at a position away from the mark M by a predetermined distance. After the drawing of the predetermined second layer is completed, the material 3 is taken out from the electron beam drawing apparatus and subjected to a developing process or an etching process to form the pattern of the second layer.

As a result of such processing, as shown in FIG. 2, the evaluation pattern P1 of the first layer and the evaluation pattern P2 of the second layer are formed on the same material in an overlapping manner. Ideally, the positional relationship between the patterns P1 and P2 is the distance D.
(Design value) They are formed apart from each other, and the difference between the actually measured distance d and the ideal distance D is the overlay error,
The overlay can be evaluated by the difference.
Now, in measuring the actual distance d, the stage 6 is moved under the control of the computer 8, and generally, the first evaluation pattern P1 and the second evaluation pattern P2.
The optical axis is made to coincide with the intermediate part between and. At this time, the stage length measuring system 13 measures the amount of movement of the stage from the reference position. After the stage stops, the large deflector 11
The electron beam is deflected to the first evaluation pattern P1 portion by the small deflector 12, and the electron beam scans the first area S1 portion shown by the dotted line in FIG. By scanning the electron beam in the S1 portion, secondary electrons generated from the material 3 are detected, and based on this detection signal and the deflection amount of the electron beam by the two kinds of deflectors 11 and 12,
The computer 8 obtains the position a of the first evaluation pattern P1. Next, the electron beam is deflected by the large deflector 11 to the second evaluation pattern P2 portion, and the small deflector 1
2, the electron beam scans the second area S2 shown by the dotted line in FIG. By scanning the electron beam in this S2 portion, secondary electrons generated from the material 3 are detected,
The computer 8 determines the position b of the second evaluation pattern P2 based on this detection signal and the deflection amount of the electron beam by the two types of deflectors 11 and 12. After that, the computer 7 obtains the overlap error Δε from the positions a and b of both patterns and the theoretical distance D by the following calculation.

[Delta] [epsilon] = (ba) -D This overlapping error [Delta] [epsilon] is equal to the first error formed when drawing the first layer.
Amount between the theoretical distance between the evaluation pattern P1 of No. 2 and the second evaluation pattern P2 formed at the time of drawing the second layer and the measured value between the evaluation patterns actually drawn and formed Therefore, this shift amount corresponds to the error amount of the overlay of the drawing of the first layer and the second layer. Therefore, overlay evaluation is performed based on this error amount Δε.

As described above, in the above-described embodiment, the stage is moved to the two types of pattern portions formed for evaluation of superposition, and then the electron beam is deflected for each evaluation pattern so that the evaluation pattern Since the position is measured, this position can be measured accurately at high speed.

Further, in this embodiment, the electron beam is deflected to each evaluation pattern portion by the first deflector capable of large deflection, and each evaluation pattern portion can be deflected in a small area at high speed and with high precision. Since the second deflector is used to scan with the electron beam, each evaluation pattern is deflected by only one type of deflector capable of deflecting the evaluation pattern with the same accuracy as the second deflector, and the pattern of the electron beam is deflected. Pattern overlay evaluation can be performed significantly faster than when overlay evaluation is performed. Further, since the deflection range of the second deflector in this embodiment is much smaller than the deflection range of the latter deflector, distortion due to deflection is significantly small, and therefore the accuracy of pattern overlay evaluation is high.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to this embodiment. For example, the center position of each evaluation pattern is measured, but one end position of the evaluation pattern may be measured to obtain the overlay error.

[0014]

As described above, the pattern overlay evaluation method using the electron beam drawing apparatus according to the present invention based on the present invention is a reference position when drawing various patterns of the first layer on a material. A first evaluation pattern is formed by an electron beam at a position away from the first predetermined pattern by the electron beam to form a first evaluation pattern, and when the various patterns of the second layer are drawn on the material, the reference position The second evaluation pattern is formed by the electron beam at a position separated by the second predetermined distance from to form the second evaluation pattern, and after the two types of evaluation patterns are formed, the first deflector deflects the electron beam. Are deflected to the first and second evaluation pattern portions, the electron beam is scanned by the second deflector at each evaluation pattern portion, and the deflection amount by the first deflector and the signal based on the electron beam scanning are used to determine the Of evaluation pattern position Since the measured value of the distance between the evaluation patterns obtained from this position and the design value (theoretical value) between the evaluation patterns are used to evaluate the superposition of the patterns formed in multiple layers, Highly accurate overlay evaluation can be performed. Furthermore, since visual observation such as the vernier pattern is not performed, the evaluation can be easily performed.

[Brief description of drawings]

1 shows an example of an electron beam writing apparatus for carrying out the method according to the invention.

FIG. 2 is a diagram showing an evaluation pattern formed on a material.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electron gun 2 ... Electron lens part 3 ... Material 4,5 ... Deflector 6 ... Stage 7 ... Drive system 8 ... Computer 9 ... Blanking control system 10 ... Lens control system 11, 12 ... Deflector control system 13 ... Stage Length measurement system

Claims (1)

[Claims] 1. When drawing various patterns of a first layer on a material, a first evaluation pattern is drawn by an electron beam at a position that is away from a reference position by a first predetermined distance to form the first evaluation pattern. When the various patterns of the second layer are formed on the material, the second evaluation pattern is formed by drawing the second evaluation pattern with an electron beam at a position apart from the reference position by a second predetermined distance. In the method of forming and then evaluating the overlay accuracy of the first layer and the second layer from the positions of the first and second evaluation patterns, an electron beam having the first and second deflectors The electron beam is set on the drawing device, the electron beam is deflected to the first evaluation pattern portion by the first deflector, and in this state, the electron beam is scanned by the second deflector on the first evaluation pattern portion, and this scanning is performed. The signal obtained by
The position of the first evaluation pattern is measured based on the amount of deflection by the first deflector, and then the electron beam is deflected by the first deflector to the second evaluation pattern portion. The electron beam is scanned by the second deflector in the evaluation pattern part of, and the signal obtained by this scanning,
The position of the second evaluation pattern is measured based on the amount of deflection by the first deflector, and the measured first evaluation pattern position and the second evaluation pattern position, and a theoretical value between both evaluation pattern positions. From the above, a pattern superposition evaluation method using an electron beam drawing apparatus for measuring the accuracy of superposition drawing of patterns between the first layer and the second layer.