JPH0685039A - Centering method for wafer - Google Patents

Abstract

PURPOSE:To perform centering only by shifting a circular wafer in one direction. CONSTITUTION:Position detecting sensors 11 and 12 are assigned along radius R of wafer with setting origin C as a center, and the wafer F is shifted in parallel along either X or Y direction. The first right triangle Ta having the wafer chord, as an oblique line, formed by connecting the second sensor position q with a point (a) where a wafer shifting direction extension line Lp of the first sensor's, conducted firstly, position p crosses with the wafer circumference at the second sensor conduction position, with the other two sides in X and Y direction, is formed. And further, the second right triangle Tb having the first distance between a middle point e and a wafer center f at the second sensor conduction point as an oblique line, and the other two sides in X and Y directions is formed. Then using the sine and cosine of the second right triangle Tb of the angle theta formed between the chord and the Y direction, the length of its the other two sides is calculated, and using them and XY coordinate of the middle point e, the displacement of the wafer center f against the origin C at the position of the second sensor conduction is calculated for compensation of wafer position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for centering a circular substrate such as a semiconductor wafer.

[0002]

2. Description of the Related Art When manufacturing a semiconductor wafer (hereinafter, simply referred to as a wafer), there are cases where a circular wafer needs to be centered on the basis of its outer shape and positioned. For example, when a large number of wafers with different product numbers that are randomly stored in the first cassette are automatically sorted into the plurality of second cassettes having the same product number,
After centering the wafer taken out from the first cassette by the robot etc. and aligning it so that the product number is located directly under the CCD camera, the CCD camera character-recognizes the number and the robot etc. moves it to the corresponding second cassette. Sequentially store by type. Alternatively, the wafer is centered and positioned when the wafer is centered during a visual check, or when the wafer is automatically stored by a robot or the like in a cassette that has a guide with a small clearance allowed for the outer diameter of the wafer. Then store it.

When centering the above wafer,
For example, there is known a means for mechanically positioning a wafer by storing it in a vertically movable cup-shaped concave portion having an inclined inner wall surface whose diameter increases toward the opening. There is a problem that it becomes a dust source.

Therefore, as shown in FIG. 2A, the position detecting light transmission type first, second, third and fourth sensors (1) are provided.
Means for centering the wafer (F) in a non-contact manner using (2), (3) and (4) are also known. According to the centering means, first, the virtual XY axes and the origin (C) are set, and the origin (C) is the center and the wafer radius (R) and the same distance (wafer circumference) are spaced at predetermined positions. 1st, 2nd, 3rd, 4th sensors (1) (2) (3)
(4) is arranged, and at the same time, the wafer (F) is randomly held on the XY suction stage (not shown). Therefore,
The wafer (F) is separated from the first, second, third, and fourth sensors (1), (2), (3), and (4) in advance, for example, Y
When the wafer (F) is translated in the direction, the edge of the wafer (F) shields the first sensor (1) (sensor conduction).
Then, the position of the wafer (F) is detected. Next, when the wafer (F) is translated from that position along the X direction and the wafer (F) shields the fourth sensor (4),
The movement distance (La) is a wafer eccentric distance, and the distance (La) is measured by a pulse encoder or the like. Therefore, when the wafer (F) is translated from that position to a half (La / 2) of the distance (La) in the direction opposite to the X direction, the center of the wafer (F) is located on the Y axis (X axis center). . Next, when the wafer (F) is moved in parallel along the Y direction as it is, the second and third sensors (2) and (3) are shielded at the same time, and the first and fourth sensors (1) and (4) are simultaneously shielded. With the light shielded, the center of the wafer (F) coincides with the origin (C) and is centered.

Next, when the wafer (F) has an OF (orientation flat) or a notch, the radius becomes short at the OF or notch. Then, for example, in FIG.
As shown in (b), each sensor position is set so that OF (Fa) does not interfere with two or more sensors at the same time. Then, it is assumed that the first sensor (1) detects OF (Fa), and the fourth sensor (4) moves in parallel from that position in the X direction to detect the wafer position. At this time, even if the wafer is moved parallel to the half (Lb / 2) of the moving distance (Lb) in the direction opposite to the X direction, the OF position is insufficient in radius, so the center of the wafer (F) is located on the Y axis. Without moving the wafer, the wafer (F) does not shield the second and third sensors (2) and (3) at the same time. In this case, for example, when the third sensor (3) first conducts, the wafer (F) is translated in the direction opposite to the X-axis direction until the second sensor (2) conducts, and half of the movement amount is the correction amount. As a result, the wafer (F) is position-corrected and positioned on the Y axis (centered on the X axis) by the second and third sensors (2) and (3). At this time, the second sensor (2), the third sensor (3), and the fourth sensor (4) are simultaneously shielded from light (the first sensor (1) cannot be shielded by OF (Fa)) Wafer (F) centering Is completed.
In addition, OF (F) is applied to the first sensor (1) and the fourth sensor (4).
If a) is not applied, the first sensor (1) is shielded from light, and then the wafer (F) is moved in the X direction to move the fourth sensor (4).
Read the distance that the light is shielded and move half the distance in the opposite direction to the X direction to move the wafer (F) on the Y axis (X axis center)
Position to. Then, the wafer (F) is moved again in the Y direction. At this time, if there is no OF (Fa), the second
The sensor (2) and the third sensor (3) are shielded simultaneously, and the four sensors are shielded simultaneously, and the centering is completed.
Even when either the second sensor (2) or the third sensor (3) is not shielded from light (when OF (Fa) is located at either the second sensor (2) or the third sensor (3)) (First sensor (1), second sensor (2), fourth sensor (4) or first sensor (1), third sensor (3), fourth sensor (4)) Simultaneous three sensors Is shaded and the centering is completed. Generally OF
When (Fa) is present, it is determined that centering is completed when three or more sensors are simultaneously conducted (at the same position).

Further, as shown in FIG. 3, position detecting light transmission type fifth, sixth, seventh, eighth, ninth and tenth sensors (5).
Means for centering the wafer (F) in a non-contact manner using (6), (7), (8), (9) and (10) are also known. According to this, first, the virtual XY axes and the origin (C) are set, and the fifth, sixth, and seventh sensors (5), (6), (7) are arranged in parallel with the origin (C) in parallel with the X-axis. And the eighth, ninth, and tenth sensors (8), (9), and (10) are arranged at regular intervals, and the sixth sensor (6) and the ninth sensor (9) at the center are arranged on the Y axis. Deploy. Therefore, first, the 5th and 7th
The sensor (5) (7) positions the wafer (F) in the Y-axis direction (center of the X-axis), and the sixth sensor (6)
And the ninth sensor (9) positions in the X-axis direction (Y-axis center). Here, when OF (Fa) shields the fifth sensor (5) from light, further, the eighth and tenth sensors (8) (1
0) may be additionally used.

[0007]

The problem to be solved is that when the wafer (F) is centered using the first to tenth sensors (1) to (10), the wafer (F) is moved to the X direction.
Since it has to move in two different Y-axis directions,
The point is that the time required for centering increases and the index decreases.

[0008]

According to the present invention, when centering a circular substrate whose radius dimension is known, two position detecting devices are arranged at predetermined positions on the same distance as the substrate radius with a set origin as a center and at predetermined positions. The sensor is arranged and the above substrate is randomly held on the suction stage so that the X direction or Y
XY with the substrate chord that connects the second sensor position and the point where the extension line of the first sensor position, which is translated first, which is parallel to the first sensor position and which intersects the substrate circumference at the second sensor conduction position as the hypotenuse. Forming a first right triangle having two other sides in each direction, calculating the XY coordinates of the midpoint of the chord, and calculating the first distance between the coordinate position and the substrate center at the second sensor conducting position, A second right triangle which is similar to one right triangle and has two other sides in the XY direction with the first distance as the hypotenuse is formed, and the sine of the second right triangle at the angle between the chord and the X or Y direction is formed. The length of the other two sides of the second right triangle is calculated by the cosine, and the XY coordinate of the midpoint of the chord and the length of the other two sides of the second right triangle are used to set the origin of the substrate center at the second sensor conduction position. Calculate the amount of deviation from It is characterized in that the substrate position is corrected and centered based on the amount of deviation, and at the time of centering a circular substrate whose radius dimension is known, which partly has a deformed portion, at least four or more position detecting sensors are provided. 2. At least 6 or more of the sensors according to claim 1, wherein two or more of the sensors are arranged so as not to interfere with the deformed portion at the same time, the substrate is translated in one axis direction, and the predetermined sensors are used as references at different substrate positions. Forming a first right triangle, each first
For each right triangle, find the center of the board,
When at least three or more substrate centers coincide with each other, the position is determined to be the proper substrate center to center the substrates, and the circular substrate is a semiconductor wafer.

[0009]

According to the above-mentioned technical means, the two light-transmitting position detecting sensors are arranged at a predetermined distance on the same distance as the substrate radius with the set origin as the center, and at the same time, on the suction stage. The substrate is randomly held and moved in parallel along the X direction or the Y direction to form first and second right triangles, the displacement amount of the substrate is calculated, and the substrate is centered based on the displacement amount.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a substrate centering method according to the present invention will be described below with reference to FIG. First, as shown in FIG. 1A, a known position (p) on the same distance as the wafer radius (R) centering on the set origin (C) as in the conventional case.
Two light transmission type sensors (11) and (12) for position detection are arranged at a constant interval in (q), and the wafer (F) is randomly held on an XY adsorption stage (not shown) to be X-ray-disposed. Translate along the direction. Therefore, the first conducting sensor (11) is the first sensor, the position of the wafer (F) at the conducting position is the substrate B position, and the further conducting sensor (12) in the same direction is the second sensor. The position of the wafer (F) at the conduction position is the substrate D position. Therefore, the XY coordinates (Xf) (Y about the origin (C) of the wafer center (f) at the substrate D position.
Wafer center (f) with respect to origin (C) by calculating f)
Of the wafer (F) based on the calculated amount of deviation
Center.

Therefore, first, the point where the extension line (Lp) in the wafer movement direction at the first sensor position (p) intersects the wafer circumference at the substrate D position is defined as (a), and the intersection point (a) and the second sensor position (q). The first right triangle (Ta) having the other two sides in the XY directions is formed with the chord of the wafer (F) that is connected to each other as a hypotenuse. When the midpoint of the hypotenuse in the first right triangle (Ta) is (e) and the intersection of the other two sides is (d), the vertical bisector of the hypotenuse (chord) passing through the midpoint (e) is the wafer center. Go through (f). At this time, the XY coordinates (Xe) (Ye) of the midpoint (e) are (Xe) = (Xa + Xq) / 2,
(Ye) = (Ya + Yq) / 2. However, (Xa,
Ya): XY coordinate of position (a) {Xa = [wafer movement distance measured by pulse encoder (length of Lp)] +
[X coordinate (Xp) of position (p)], Ya = Y coordinate (Yp) of position (p)}, (Xq, Yq): XY of position (q)
Coordinates. In addition, [distance between ef (first distance)] =
{[(Distance between af) ² − (distance between ae) ² ] square root}. Here, (distance between af) = wafer radius (R), and (distance between ae) = (distance between aq) / 2 =
^{{[(Xa-Xq) 2} + (Ya-Yq) 2] square root of} /
It becomes 2. Therefore, similar to the first right triangle (Ta), the distance between ef is the hypotenuse, and the other 2
If a second right-angled triangle (Tb) having a side is formed and the intersection of the other two sides is (g), the XY coordinate (Xf) of the center (f)
(Yf), that is, the amount of deviation of the center (f) with respect to the origin (C) is (Xf) = (Xe) − (distance between fg) = (Xe) − (distance between ef) · cos (θ) (Yf) = (Ye)-(distance between eggs) = (Ye)-(distance between ef) .sin (?). However, θ is equal to the angle formed by the hypotenuse of the first right triangle (Ta) and the Y-axis direction, and is calculated by θ = arctan [(distance between qd) / (distance between ad)]. That is, the displacement amount (Xf) (Yf) is calculated only by moving the wafer (F) in one direction along the X or Y direction, and the displacement amount (Xf) (Yf) is used as a correction amount to determine the center (f) of the wafer (F). ) Is corrected to the origin (C) and centered.

When centering an OF (Fa) or a wafer (F) having a notch, as shown in FIG. 1B, four sensors (11) (12) (13) (14) are used.
Are arranged on the same distance as the wafer radius (R) and so that two or more sensors do not simultaneously interfere with the OF (Fa) of the wafer (F). Then, the wafer (F) is randomly held on the XY adsorption stage and moved in parallel along the X direction, and after the first sensor (11) is brought into conduction at the position of the substrate B, it is further moved in parallel and moved to the second sensor ( The first right triangle (Ta) is formed at the position of the substrate D where 12) is conducted. Next, a right-angled triangle (Tc) is further formed with the first sensor (11) as a reference at the position of the substrate E where the third sensor (13) is electrically connected in parallel with the fourth sensor (1).
4) A right triangle (Td) is formed with the first sensor (11) as a reference at the position of the substrate G where it is conducted. In addition to this, a right triangle (Te) (not shown in the hypotenuse) can be formed at the position of the substrate E with the second sensor (12) as a reference, and similarly the second and fourth sensors (12) (14). ) Using a right-angled triangle (Tf) at the position of the substrate G (the hypotenuse is partially omitted),
In addition, the fourth sensor is placed at the position of the substrate G with the third sensor (13) as a reference.
A sensor (14) can be used to form a right triangle (Tg). As described above, the wafer (F) is moved in the uniaxial direction, and six patterns of right triangles having two points radially contacting each other at the positions of the substrates B, D, E, and G are formed while the four sensors are conducting. It can be confirmed that the center of each substrate position is obtained by using these right triangles while correcting and confirming the movement amount for each substrate position. Therefore, OF (F) and notch are 1
If 6 sensors are shielded from light, 3 out of 6 right triangles
Although the normal center position is not calculated for each of the three formed by using that sensor as a reference, the center position calculated from the other three right triangles is the normal position, and therefore, among the six calculated center positions, 3 When the center positions of the individual pieces match, that position is determined to be the normal position. And the center position is the origin (C)
The wafer (F) may be centered accordingly.

The wafer (F) is set on the suction stage and centered automatically by a robot and a computer.

[0014]

According to the present invention, when a circular substrate such as a semiconductor wafer is centered, the centering can be performed only by moving it in one axis direction. Therefore, the time required for the centering is reduced to about half that of the conventional method, and the index is greatly reduced. Is improved.

[Brief description of drawings]

FIG. 1A is an operation explanatory diagram of a substrate showing an embodiment of a substrate centering method according to the present invention. FIG. 7B is an operation explanatory view of the substrate showing the embodiment of the method of centering the substrate having the deformed portion according to the present invention.

FIG. 2A is an operation diagram of a substrate showing an example of a conventional substrate centering method. FIG. 9B is an operation explanatory view of the substrate showing another example of the conventional centering method for a substrate having a deformed portion.

FIG. 3 is an operation explanatory diagram of a substrate showing another example of a conventional substrate centering method.

[Explanation of reference numerals] 11 sensor 12 sensor F substrate Ta first right triangle Tb second right triangle

Claims (3)

[Claims] 1. When centering a circular substrate having a known radius, two position detecting sensors are arranged at predetermined positions on the same distance as the substrate radius centering on a set origin, and a suction stage is provided. Hold the above substrate randomly and move in parallel along the X or Y direction,
The point at which the extension line of the first sensor position, which is first conducted, in the substrate movement direction intersects with the circumference of the substrate at the second sensor conduction position;
A first right triangle having two other sides in the XY direction is formed with the board chord connecting the sensor position as the hypotenuse, and the XY coordinate of the midpoint of the chord is calculated to determine the coordinate position and the second sensor conduction position. A first distance from the center of the substrate is calculated, and a second right triangle is formed that is similar to the first right triangle and that has the first distance as the hypotenuse and has two other sides in the XY directions.
The lengths of the other two sides of the second right triangle are calculated from the sine or cosine of the second right triangle at the angle between the chord and the X or Y direction, and the XY coordinates of the midpoint of the chord and the second right triangle are calculated. A method of centering a substrate, wherein a displacement amount of a substrate center at a second sensor conduction position with respect to a set origin is calculated based on the other two sides, and the substrate position is corrected and centered based on the displacement amount. 2. When centering a circular substrate having a known radius dimension partially having a deformed portion, at least four or more position detecting sensors, two or more of which do not interfere with the deformed portion at the same time. Are arranged in such a manner that the substrates are translated in one axis direction, and at least six or more first right triangles according to claim 1 are formed with reference to predetermined sensors at different substrate positions, and each first right triangle is formed. A substrate centering method, wherein the substrate center is obtained, and when at least three or more substrate centers are coincident with each other, the position is judged to be a normal substrate center and the substrates are centered. 3. The method for centering a substrate according to claim 2, wherein the circular substrate is a semiconductor wafer.