JPH09283404A - Electron beam exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for realizing improvement in overlay accuracy and significant reduction in mark detection time, in detection of an alignment mark for performing overlay on a pattern on a wafer by electron beam exposure. SOLUTION: In the case where overlay is performed on chips A, B, C,... n on a wafer 10 by electron beam exposure, alignment marks A1-A4 arranged on the chip A at one position on the wafer 10 are first detected, and chip distortion is corrected. Then, with respect to arbitrary m chips of the total n chips A, B, C,... n on the wafer 10 (where 1<m<=n), an alignment mark at one position within each chip is detected, and an array error of the chips on the wafer 10 (that is, wafer distortion) is corrected by a correction formula. Subsequently, electron beam exposure is performed while the array error and the chip distortion are corrected in accordance with the chip distortion correction formula and the wafer distortion correction formula.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron beam exposure method and, more particularly, to an electron beam direct writing technique in a lithography technique in LSI manufacturing, and more particularly, to a technique for writing a pattern on a sample by electron beam exposure. The present invention relates to an electron beam exposure method related to a method for aligning a sample.

[0002]

2. Description of the Related Art Conventionally, when a pattern is accurately drawn by using an electron beam at a desired position on a sample, the position of a "reference positioning mark" previously arranged on the sample is detected. ,
The pattern is drawn by an electron beam based on the position.

FIG. 2 is a view for explaining an example of the prior art, and is a view showing an arrangement of chips on a wafer. FIG. In FIG. 2, reference numeral 10 denotes a wafer;
B, C, n are chips on the wafer, A ', B', C '
n 'indicates an electron beam exposure chip, and A1, B1, C1, and n1 indicate alignment marks.

In the conventional global alignment method (hereinafter referred to as “conventional method 1”), an arbitrary m (1) among n chips (A, B, C... N) arranged on a wafer 10 is used. <M
.Ltoreq.n) For one chip (i, j, k... M), one alignment mark (il, jl, kl.
In this method, the position of l) is detected in advance, and exposure is performed by correcting only the arrangement error of the chips on the wafer 10 (see FIG. 2).

As an alignment method generally used together with the above-mentioned conventional method 1 (global alignment method), a “die-by-die (Die-by-Die) alignment method” (hereinafter referred to as “conventional method”) 2 ") is known. In this conventional method 2, as shown in FIG. 3 (a diagram for explaining another example of the related art and showing a chip arrangement on a wafer), n individual chips (A , B, C
... N), a plurality of “positioning marks (A1 to A4, B)
1 to B4, C1 to C4... N1 to n4), and detects a plurality of alignment marks for each individual chip. This is an alignment method that performs exposure while correcting the like.

[0006]

In the above-mentioned conventional method 1 (global alignment method: see FIG. 2), when each chip is rotating or when the magnification of the chip is different, it is necessary to deal with them. Since the correction cannot be performed, there is a problem that the overlay accuracy is deteriorated.

On the other hand, the conventional method 2 (die-by-die alignment method) can solve the above-mentioned problems of the conventional method 1. However, in the alignment method according to the conventional method 2 (see FIG. 3), generally, alignment marks are arranged at four corners of a rectangular chip, and the chip is detected by detecting the four alignment marks. This is a method for correcting rotation, magnification, etc. Therefore, for all the chips on the wafer, it is necessary to detect the alignment mark four times for each chip, and the alignment time is lengthened.
There is a problem that the throughput is reduced.

The present invention has been made in view of the above-mentioned problems of the conventional methods 1 and 2, and an object of the present invention is to provide a conventional method 1 (global) when performing superposition by electron beam exposure. Higher overlay accuracy than alignment method) and conventional method 2 (die-by-die alignment method)
An object of the present invention is to provide an electron beam exposure method related to an alignment method that does not cause a decrease in throughput as described above.

[0009]

According to the present invention, as a means for detecting an alignment mark for superimposing a figure on a wafer by electron beam exposure, any representative chip can be used to detect all the marks on the wafer. It is characterized in that the chip distortion of the chip is corrected collectively, thereby achieving the above object.

That is, according to the present invention, "an alignment marker for overlaying a pattern on a wafer by electron beam exposure is used.
The step of detecting the alignment marks of a plurality of chips on the wafer to correct the alignment error of the chips on the wafer, and at least one of the chips within the chip And a step of correcting the chip distortion by detecting the positions of at least two or more alignment marks. (Claim 1).

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION As a preferred embodiment of the present invention, in the "step of correcting chip distortion" in the above-mentioned gist of the present invention, an alignment mark is provided for two or more non-overlapping chips. A means for detecting the position and individually correcting the chip distortion is employed (claim 2).

[0012]

EXAMPLE An example of the present invention will be described with reference to FIG. FIG. 1 is a view for explaining an embodiment of the present invention, showing a chip arrangement on a wafer.

In this embodiment, alignment marks (A1 to A4, B1 to B4, B1 to B4, B1 to B4, N1) are formed at the four corners of n chips (A, B, C... N) formed on the wafer 10. C1 ~ C4 ... n1 ~
n4) is formed in advance. When positioning the wafer 10 and performing electron beam exposure, first, the alignment marks (A1, A2, A3, A4) arranged on at least one chip on the wafer 10, for example, the chip (A). Is detected, and the chip distortion is corrected. In this case, the primary distortion (magnification, rotation) and trapezoidal distortion of the chip are corrected from the positions of the four alignment marks by the chip distortion correction formula.

Next, of the n chips (A, B, C... N) arranged on the wafer 10, any m (1 <m ≦ m)
With respect to the n) chips (i, j, k... m), the position of one alignment mark (il, jl, kl... Correct the alignment error (wafer distortion). In this case, in this embodiment, the wafer 1
Alignment marks are detected for 9 chips on 0 and the primary distortion (magnification, rotation) of the chip array on the wafer 10 is detected.
And the trapezoidal distortion was corrected by the correction equation of the wafer distortion.

Thereafter, the electron beam is corrected while correcting the chip arrangement error on the wafer by the wafer distortion correction formula obtained by the detection of the alignment mark, and correcting each chip distortion by the chip distortion correction formula. Perform exposure. In this case, the overlay accuracy was as high as that obtained by using the conventional method 2 (die-by-die alignment method) and detecting the alignment marks at four locations for each chip. . Also, at this time, the number of chips arranged on the wafer was 100 chips. Therefore, when the conventional method 2 (die-by-die alignment method) was used, 400 alignment mark detections were required. However, according to the method of the present embodiment, only 13 detections were required, and the alignment time could be reduced to 1/30 or less.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.
Various changes can be made without departing from the gist of the present invention. For example, the order of the detection of the alignment mark for correcting the chip distortion and the detection of the alignment mark for correcting the wafer distortion described in the above embodiment may be performed in any order.

Further, the number of alignment marks to be arranged or detected for each of the chip distortion correction and the wafer distortion correction may be any number as long as it is at two or more places, and the order of correction is also arbitrary according to the number. The order can be appropriately changed.
Further, when correcting the chip distortion, it is also possible to perform the alignment mark detection for two or more chips and to perform the chip distortion correction using statistical processing.

In the above-described embodiment, the alignment mark of one chip is detected, and the chip distortion of all the chips on the wafer is corrected by the same correction formula. When exposing using-, etc., because a plurality of chips are formed on the mask,
There are cases where chips with different chip distortions are mixedly mounted on the wafer. In such a case, an alignment mark position is detected in advance for a plurality of chips having different chip distortions, and a chip distortion correction formula is obtained for each of them. Exposure can also be performed using a chip distortion correction formula specified for a chip.

[0019]

As described above in detail, the present invention relates to a method for detecting an alignment mark for superimposing a figure on a wafer by electron beam exposure, by using an arbitrary representative chip to detect all of the positions on the wafer. It is characterized in that the chip distortion of the chip is corrected in a lump, and as a result, a high overlay accuracy equivalent to the conventional die-by-die alignment method can be obtained, and the alignment time can be greatly reduced. A possible effect occurs.

[Brief description of drawings]

FIG. 1 is a view for explaining an embodiment of the present invention, showing a chip arrangement on a wafer.

FIG. 2 shows a conventional example (conventional global alignment method)
FIG. 3 is a diagram illustrating chip arrangement on a wafer.

FIG. 3 is a diagram illustrating another example of the related art (conventional die-by-die alignment method), and is a diagram illustrating a chip arrangement on a wafer.

[Explanation of symbols]

10 Wafers A, B, C, n Chips on wafer A ', B', C'n 'Electron beam exposure chips A1-A4, B1-B4, C1-C4, n1-n4 Positioning mark

Claims (2)

[Claims] 1. As a positioning mark detecting means for superimposing a pattern on a wafer by electron beam exposure, the positions of the positioning marks of a plurality of chips on the wafer are detected, Comprising a step of correcting the array error of the upper chip and a step of correcting the chip distortion by detecting the positions of at least two or more alignment marks in the chip for at least one of the chips. An electron beam exposure method comprising: 2. In the step of correcting the chip distortion,
Alignment marker for two or more chips that do not overlap
2. The electron beam exposure method according to claim 1, wherein the position of the mask is detected, and the chip distortion is individually corrected.