JPS6142409B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mark position detection method in a variable shape electron beam exposure method.

In order to draw fine patterns arranged at high density such as in LSIs and VLSIs, the direct exposure method, in which electron beams are used to draw directly onto a semiconductor substrate, is often used because it can form patterns with particularly high precision.

In the above-mentioned direct exposure method, after the position is detected using alignment marks formed on a chip on a semiconductor substrate, exposure processing of a desired pattern is performed. In ultraviolet exposure methods, masks are carefully aligned using alignment marks, but direct exposure using an electron beam requires much more precise alignment. The mark position is detected by scanning and detecting the reflected electron signal.

To do this, as shown in Fig. 1, a square area 2 including a circular alignment mark 1 coated with aluminum (Al) or the like is scanned with a minute square or spot-shaped electron beam 3, and a reflected electron signal is generated at each scanning point. Detect the amount, store it in a matrix in an electronic computer, calculate the sum of the reflected electron signal amounts for each row and column, and find the position where the sum is maximum in the X-axis direction and Y-axis direction. By determining each of these, the coordinates of the center of gravity of the circular alignment mark are detected.

Note that if the alignment mark is a recess formed by etching on the substrate to be processed, the position where the sum of the reflected signal amounts is the minimum is determined.

However, in this mark position detection method,
If the number of scanning points in the axial direction and the Y-axis direction is n, the amount of information handled by a computer is n ² , and n is usually 200.
Since the above is required, the amount of information becomes enormous and the computer processing time is also extremely long.

The present invention aims to solve the above-mentioned problems, and therefore, the mark position detection method of the present invention scans an area including alignment marks in the X-axis direction and the Y-axis direction with a slit-shaped rectangular beam, and The position of the center of gravity of the alignment mark is detected by detecting the amount of reflected electron signal at and determining the coordinates of the position where the amount of reflected electron signal is maximum or minimum in each of the X-axis direction and the Y-axis direction. shall be.

The present invention will be explained below with reference to Examples.

2 and 3 are top views of main parts showing an embodiment of the mark position detection method of the present invention.

In FIG. 1, 1 is a circular alignment mark formed by depositing aluminum (Al) or the like on the surface of the exposed object, 2 is a region containing the alignment mark to be scanned with an electron beam, and 13 is a slit-shaped alignment mark. An elongated rectangular electron beam is shown. The length of one side of this slit-like rectangle in the Y-axis direction is as short as possible, and the length of one side of the X-axis direction is made larger than the diameter of the circular alignment mark 1. Also, X ₁ , X ₂ ,...
..., X _o and Y ₁ , Y ₂ , ..., _Yo represent the coordinates of the scanning position in the X-axis direction and the Y-axis direction, respectively.

Next, a method for detecting the position of the alignment mark will be explained.

Scanning points arranged in a matrix as described above
Conventionally, XiYj (i, j=1, 2, . . . , n) was irradiated one point at a time with an electron beam having a minute area, and the amount of reflected electron signal was detected for each point.

In contrast, in this embodiment, first, the entire row of _Y1 is irradiated with the slit-shaped rectangular beam 13, and the amount of reflected electron signals at that time is detected and stored. The method of detecting and storing the reflected electron signal amount is no different from the conventional method.

Then a slit rectangular beam 1 is applied to the entire row of Y ₂ .
3 is irradiated, the amount of reflected electron signal is detected and stored. Thereafter, the same operation is performed up to the row of Y _o .

In this way, the area 2 is
is scanned in the Y-axis direction, and after detecting and storing the backscattered electron signal amount for each scanning position in the Y-axis direction, that is, for each row, as shown in FIG.
Region 2 is sequentially scanned in the X-axis direction from X ₁ to X _o with the slit-shaped rectangular beam 13' long in the axial direction, and the amount of reflected electron signal at each scanning position in the X-axis direction is detected and stored as before. .

The amount of reflected electron signals obtained for each traveling position is compared in each of the X-axis direction and the Y-axis direction, and the coordinates Xi of the position where the amount is maximum,
and Yj, the coordinates (Xi, Yj) become the coordinates of the center of gravity of the alignment mark 1.

In this embodiment, as described above, the mark position can be detected by scanning area 2 in the X-axis direction and the Y-axis direction n times each, so the amount of information to be processed is 2n, which is reduced to 2/n of the conventional method. , the computer processing time is also significantly reduced in proportion to this.

In the above embodiment, the alignment mark 1 is made of aluminum (Al) on the surface of the object to be processed, such as a silicon substrate.
The coordinates of the position where the amount of reflected electron signal is maximum were detected by forming the alignment mark surface such that the amount of reflected electron signal is larger on the surface of the alignment mark than on the surface of the object to be processed. Alternatively, the alignment mark may be a circular recess formed by selectively removing the surface of the object to be processed using an etching method.
In this case, the coordinates of the position where the amount of reflected electron signal is the minimum are detected.

As explained above, according to the present invention, when detecting the mark position by scanning the alignment mark with an electron beam, the number of scans, amount of information, and computer processing time are increased by using a slit-shaped rectangular beam as the electron beam. can be reduced to width.

[Brief explanation of the drawing]

FIG. 1 is a top view of a main part showing a conventional mark position detection method using electron beam scanning, and FIGS. 2 and 3 are top views of main parts showing a mark position detection method using a slit-shaped rectangular electron beam according to the present invention. be. 1... Alignment mark, 2... Scanning area, 1
3,13'...Slit-shaped rectangular electron beam, X ₁ ,
X ₂ , ..., X _o ... Scanning position coordinate in the X-axis direction,
Y ₁ , Y ₂ , ..., _Yo ... Scanning position coordinates in the Y-axis direction, Xi, Yj, ... Coordinates in the X-axis direction and Y-axis direction of the scanning position where the amount of backscattered electron signal becomes maximum.

Claims (1)

[Claims] 1. In a mark position detection method in which the position of an alignment mark provided on an exposed object is detected by scanning the alignment mark with an electron beam, an area including the alignment mark is scanned with a slit-shaped rectangular beam in the X-axis direction and The positioning is performed by scanning in the Y-axis direction, detecting the amount of backscattered electron signal at each scanning position, and determining the coordinates of the position where the amount of backscattered electron signal is maximum or minimum in each of the X-axis direction and the Y-axis direction. A mark position detection method characterized by detecting the center of gravity position of a mark.