JPH0231443A - Wafer aligner - Google Patents

Abstract

PURPOSE:To accurately determine the quantity of eccentricity by a method wherein a value most frequently detected in diameter distribution is presumed to be a wafer diameter before an accurate wafer diameter is determined, a four-point position detection free of noise, etc., is accomplished, and the quantity of eccentricity is determined using the result of the four-point position detection. CONSTITUTION:Outer circumference position data along the entire wafer circumference are determined by a wafer outer circumference position data detecting means, distances rhofrom the center of rotation of a theta-stage 2 to the wafer edge is detected at every point, a distance rho1 involving a point (i) and a distance rho1+180 deg. involving a point i+180 deg. which is 180 deg. degrees apart from said point (i) are summed up, for the approximation of a wafer diameter r1 involving said point (i). The same is repeatedly accomplished to cover half the wafer circumference for the preparation of a wafer diameter frequency distribution, wherein the most frequently observed value is presumed to be a diameter (r). Distances from the center of rotation of the theta-stage 2 to four points, free of noise and 90 deg. apart from each other, are measured for the determination of the quantity of eccentricity from the center of rotation. When four points are not available, three points separated by 90 deg. may be used to determine the quantity of eccentricity, when the most frequently appearing value in the frequency distribution is determined to be the quantity of eccentricity.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a wafer alignment device, and particularly to a wafer alignment device for aligning the direction of an orientation flat to a sea urchin and the wafer center position in a predetermined direction and position in a semiconductor manufacturing device. The present invention relates to a suitable wafer alignment apparatus.

[Conventional technology]

In an electron beam drawing apparatus, when drawing circuit patterns in an overlapping manner on a wafer, it is necessary to align the circuit patterns accurately and at high speed.

In order to perform circuit pattern alignment at high speed, first,
It is necessary to accurately match the wafer outline to the reference position. The wafer alignment device is a device that performs this wafer outer alignment. Wafer alignment is performed by aligning an orientation flat (hereinafter referred to as an orientation flat) provided to indicate the wafer center position and crystal direction with a reference position.

Wafer center alignment is performed by calculating the amount of deviation (eccentricity) between the wafer center and the rotation reference axis center from the wafer outer edge position data. The amount of eccentricity is according to JP-A-60-8161.
As disclosed in Publication No. 3, data on the outer edge position of the wafer other than the orientation flat portion is calculated from the results of detecting three or four points.

First, a method using three-point detection will be explained.

The wafer is rotated by 90' from the angle at which the center of the orientation flat is located at the wafer outer edge position detection part, and the distance ρ from the rotation center to the wafer edge is detected, and this is set as a. Next, rotate the wafer by 90@, detect the same distance ρ,
Let it be c. Using these a, b, and c, the amount of eccentricity is determined by calculation.

Next, a method using four-point detection will be explained.

First, the wafer is rotated by 45'' from the angle at which the orientation flat center is located at the wafer outer edge position detection part, and the distance ρ from the rotation center to the wafer edge is detected, and this is set as a.Then, the wafer is rotated 90 degrees at a time. , similar distances ρ are detected and set as S, c, and d. Using these a, b, Q, and d, the amount of eccentricity is determined by calculation.

The amount of eccentricity can be determined using any of the above methods.

[Problem to be solved by the invention]

In the above conventional technology, it is difficult to determine whether the outer edge position data of the three or four points necessary to determine the amount of eccentricity is correct (whether the data contains noise components due to wafer chipping, resist peeling, sub-orientation flats, etc.). ) without judging
Since the eccentricity was calculated assuming that the three or four outer edge position data detection positions are on the wafer circumference, if there is a sub-orientation flat or chip at the outer edge position data detection position, there may be an error factor in the outer edge position data. This causes a problem in that matching accuracy is significantly impaired.

An object of the present invention is to provide a wafer alignment device that can accurately determine eccentricity even if a wafer has a chip or a sub-orientation flat.

[Means to solve the problem]

The above purpose is to provide a wafer outer edge position data detection means using transmitted light, which detects wafer outer edge position data around the entire wafer, and further detects the distance ρ from the rotation center of the θ stage to the wafer edge at each point. Then, the distance ρ1 at a certain point i and the distance ρ1 at a point i+180m 180° apart
+1110, the wafer diameter r1 at point i
can be approximated, so this is done over half the wafer,
The frequency distribution of the wafer diameter is determined, and the mode in this frequency distribution is set as the wafer diameter r, and the frequency distribution is 90, which does not contain noise components.
``The distance from the rotation center of the θ stage to four points separated by 4 points is calculated, and the eccentricity of the center of the wafer from the rotation center of the θ stage is calculated, and if four points that satisfy the conditions cannot be detected. is a patent that detects eccentricity using data from three points around the entire circumference of the wafer, calculates the amount of eccentricity using data from three points separated by 90' from each other, and calculates the mode of the frequency distribution of the amount of eccentricity. I decided to achieve this by.

[Effect]

Since the mode value from the diameter distribution is taken as the wafer diameter, the accurate wafer diameter can be determined.The 4-point position detection, which does not include noise components, is performed, and the eccentricity is calculated from this 4-point position data. , it is possible to obtain an accurate amount of eccentricity.

Also, even if 4-point position data cannot be detected,
Since the amount of eccentricity is determined from the distribution of the amount of eccentricity based on the three-point position data over the entire circumference of the wafer, the amount of eccentricity can be determined accurately.

〔Example〕

An embodiment of the present invention will be described in detail below using FIGS. 1 to 6.

FIG. 1 is an overall configuration diagram showing an embodiment of the wafer alignment apparatus of the present invention. In Fig. 1, 1 is an X-Y stage;
2 is a θ stage that vacuum-chucks and rotates the wafer 3;
The X-Y stage 1 has an X-axis control system 4. The position of the 0 stage 2 is controlled by a Y-axis control system 5, rotated by a drive motor 6 and a timing belt 7, and includes a rotation angle detector 8 for detecting the rotation angle of the rotation axis. Reference numeral 11 denotes a light source, and light from the light source 11 is condensed by a condensing lens 12.

A computer that illuminates the outer edge of the wafer 3, forms an image of the outer edge position of the wafer 3 on a one-dimensional image sensor (CCD) 14 through an imaging lens 13, and inputs information on the outer edge position at each fixed angle into a computer 15. In step 15, when data for one rotation is completed, the amount of correction necessary for wafer alignment operation is calculated from the wafer outer edge position information according to the flowchart shown in Figure 2, and the X-axis control system is adjusted based on the amount of correction. 4
, the Y-axis control system 5, and the θ stage 2 to align the direction of the orientation flat of the wafer 3 and the position of the wafer center to a predetermined direction and position.

FIG. 3 is a diagram showing the relationship between the wafer 3 and the CCD 14.
(a) shows the relationship between the two, and (b) shows the waveform of outer edge position data for one rotation of the wafer 3.

Here, in FIG. 3(a), 0 indicates the rotation center of the θ stage 2, and W indicates the center of the wafer 3. In FIG. 3(a), Ao, Al, Az, -An are the rotation angles of the XY stage 2, and the distance between the corresponding outer edge position of the wafer 3 and the rotation center ○ of the θ stage 2 is the distance from the CCD 14. This is the outer edge position data of the wafer 3. An example of the relationship between these rotation angles and outer edge position data is shown in FIG. 3(b).

Next, we will discuss the calculation of the amount of eccentricity required to align the center of the wafer 3 (the amount of deviation between the wafer center and the rotation center of the θ stage).
This will be explained in detail using the flowchart shown in the figure and FIGS. 4 to 6. The amount of eccentricity can be determined from the outer edge position information of three or four points.

First, a method for determining the amount of eccentricity from the outer edge position information of four points will be explained. In this example, in order to avoid noise components (wafer chipping, resist peeling, sub-orientation flats, etc.) from affecting the data at the four points, we used the method of determining the wafer diameter explained using FIG. , by the data compression method explained using FIG. First, a method for determining the diameter of the wafer 3 will be explained using FIG. First, as shown in FIG. 4(a), the distance from the rotation center O of the θ stage 2 corresponding to the rotation angle Ao of the XY stage 2 to the outer edge position of the wafer 3 is set to ρ0. Similarly, if the data corresponding to the rotation angle A1 is ρ1 (i=o=n),
The diameter r1 of the wafer 3 can be approximated by the following equation.

r direct = ρkura + ρt + n/z...
(1) An example of the results of detecting r for i=0 to n/2 is shown in FIG. 4(b). In order to obtain the diameter r of the wafer 3 from this result, the mode (value with a large data frequency) is obtained from the frequency distribution of the diameter, as shown in FIG. 4 CQ).

If only the data included within the effective range ±α (α is an arbitrary constant that determines the permissible range of the wafer diameter) from the mode value are taken out and averaged, the diameter r of the wafer 3 can be approximated by the following equation.

Here, rJ; data m included within the effective range from the mode; number of the data. Next, use this diameter r together with the compressed data shown below to obtain data at four points that do not contain noise components. Figure 5(a)
Detect as shown in . FIG. 5(b) shows the waveform of the compressed data value of the outer edge position data. The compressed data is -Lx/N, Lz/N (N
, LL, L2. is determined by multiplying by a weighting function (an arbitrary constant that can distinguish noise components from outer edge position data) and adding the results. The result of the operation is an integer, and the decimal places are rounded down.

A method for selecting four points based on the obtained diameter r and compression data will be described below. First, the distance between the rotation center 0 of the θ stage 2 and the outer edge position of the wafer 3 corresponding to the rotation angle θ is defined as a. Below, θ+π/2. θ+π, θ+3/
Let the data corresponding to 2π be s, c, and d, respectively. a
, b, c, and d.

r-β≦a+c≦r+β...(3)
r-β≦b+d≦r+β...(4) cd
(θ) = cd (θ + π/2) = cd (θ + π) = cd (θ + 3 / 2 π) = O - (5) Here,
β: An arbitrary constant cd(θ) that determines the allowable range of the diameter; θ=A is the rotation angle that satisfies all conditions greater than or equal to the compressed data value corresponding to the rotation angle θ.

- An is detected from the range. 4 detected by the above
The X-axis component e of the eccentricity is determined by point data a, b, c, and d.
, the Y-axis component is determined by the following equation.

However, u and v are shown by the following formula.

Next, the eccentricity detection (3
Detection of eccentricity using point data) will be explained with reference to FIG. The data corresponding to the rotation angle θ=A is set as al, and hereinafter, θ+π/2. The data corresponding to θ+3/2π are respectively 1) 1. dt, equation (7) can be transformed as shown in the following equation (Fig. 6, where r is the diameter of Ueno 1 detected by the method described above. By applying equation (8) to equation (6), 3 Eccentricity can be detected from point data.This can be expressed as θ= A o ~ A,
The most frequent frequencies of the X-axis component and Y-axis component are detected from the frequency distribution (Fig. 5(b)). Effective range ±
γ1. If only data included in γ2 (γ1 and γ2 are arbitrary constants allowable as the eccentricity of the X-axis component and Y-axis component, respectively) is extracted, the eccentricity can be determined by the following equation.

Kj=1 Q j=1 Here, e4; data included in the valid range ±γ1 from the mode; data Q included in the valid range ±γ2 from the mode; the number of data Q; The direction detection is performed by recognizing both ends of the orientation flat based on the characteristics of the orientation flat portion (data width, change in polarity) using the waveform of the compressed data value described above, and determining the center as the orientation flat center.

〔Effect of the invention〕

According to the present invention described above, even if there is a chip on the wafer outer periphery, resist peeling, sub-orientation flat, etc., the direction of the orientation flat and the position of the center of the wafer can be aligned in a predetermined direction and position.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram showing one embodiment of the wafer alignment apparatus of the present invention, FIG. 2 is a flowchart showing an embodiment of the program in the computer of FIG. 1, and FIG. 4 is an explanatory diagram of the wafer diameter detection method, FIG. 5 is an explanatory diagram of the eccentricity detection method using 4-point data, and FIG. 6 is an explanatory diagram of the eccentricity detection method using 3-point data. . 1...X-Y stage, 2...θ stage, 3...
・Wafer, 4...X-axis control system, 5...Y-axis control system,
6... Drive motor, 7... Timing belt, 8...
...Rotation angle detector, 1.1...Light source, 12...Condensing lens, 13...Imaging lens, 14...-dimensional image sensor (CCD), Pavilion 3 Figure A1 Illustration 5 of Menko

Claims (1)

[Claims] 1. In a wafer aligning device for semiconductor manufacturing equipment,
An X-Y stage that is movable in two axes, a θ stage that vacuum-chucks and rotates the wafer, a rotation angle detector that detects the rotation angle of the θ stage, and a transmitted light that detects the position of the outer edge of the wafer. wafer outer edge position data detection means, and the wafer outer edge position data detected by the detection means is processed and distributed. A wafer alignment apparatus comprising: a correction means for determining an amount of eccentricity of the center of the θ stage with respect to a rotation center of the θ stage, and correcting the amount of eccentricity with the XY stage. 2. The diameter of the wafer is determined by the rotation angle A_ of the θ stage.
Let the distance from the rotation center of the θ stage corresponding to i to the outer edge position of the wafer be ρ_1, and the distance from the rotation center on the opposite side to the rotation center to the outer edge position of the wafer be p_1+n/2. Then, since the diameter r_i of the wafer can be approximated by r_i=ρ+ρ_i+n/2, a frequency distribution of the diameter of the wafer is created from the results obtained for r_i from i=0 to n/2, and the mode is 2. The wafer alignment apparatus according to claim 1, wherein the diameter of the wafer is determined from an average value of data included within an effective range of the diameter of the mode. 3. The eccentricity is the θ that does not include noise components.
The distance from the rotation center of the θ stage to the outer edge position of the wafer corresponding to the rotation angle θ of the stage is a, and the data corresponding to θ+π/2, 0+π, and θ+3/2π are b, c, and d, respectively, Data of the above four points a, b, c
, d to calculate the X-axis component and Y-axis component of the eccentricity, or if the data for the four points cannot be obtained, the data corresponding to the rotation angle θ is set as a_i, and hereinafter θ
Data corresponding to +π/2 and θ+3/2π are respectively b
_1, d_1, calculate the X-axis component and Y-axis component of the eccentricity amount using the three-point detection method, create a frequency distribution of the X-axis component and Y-axis component, find the mode, and remove the wafer. The wafer alignment apparatus according to claim 1, wherein the eccentricity is set to .