JPH08124995A - Measuring method of place of wafer and wafer alignment and method thereof - Google Patents

Abstract

PURPOSE: To obtain the central place of a water from the quantities of light received of photosensors by equally arranging the six sets of light-projecting devices, from which band-shaped light is emitted, and the photosensors at six radial positions in the longitudinal direction on a circumference having the same diameter as the wafer in band-shaped light. CONSTITUTION: Light-projecting devices 1, by which laser beams from a laser source are changed into band-shaped light in width of approximately 10mm by lenses, and photosensors 2 receiving the band-shaped light through lenses are used as one sets in a measuring unit 7, and the measuring unit 7 is composed of a stand 3, on which each set is fixed so that the centers of cut ends 9 by surfaces vertical to the optical axes of band-shaped light are disposed equally at six places on a circumference having the same diameter as a water 6 and the cross directions of the band-shaped light are directed radially, and a control section, into which the quantities of light received of the photosensors 2 are input and in which movement given to the wafer 6 is acquired and by which the movement is indicated to a robot 4 holding and carrying the wafer 6. Accordingly, the central position of the wafer is obtained from the quantities of light received of a plurality of the photosensors of sections not shielded by the wafer in band-shaped light, thus shortening the alignment time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer position measuring unit, alignment unit and method,
In particular, the present invention relates to a centering alignment of a wafer without performing an orientation flat (hereinafter, referred to as an orientation flat) alignment performed during wafer handling.

[0002]

2. Description of the Related Art Usually, a wafer is carried in a state of being stored in a predetermined wafer carrier, and an apparatus for performing a process in a wafer picks up the back surface of the wafer, takes out the wafer from the wafer carrier, and removes the wafer from the process. Center the wafer for processing. As a conventional wafer alignment unit for performing such wafer centering, there is a clean aligner described in the catalog 1991.11P23 of Lhotse Corporation.

FIGS. 5 and 6 are a plan view and a side view, respectively, of a conventional wafer alignment unit showing an example. The wafer alignment unit shown in FIGS. 5 and 6 is provided with a transfer table 11 for transferring the wafer 6 to an external robot hand or the like, and a wafer 6 for the transfer table 11.
An alignment stage 12 having a function of moving in the Z-axis direction for loading / unloading the wafer, and a function of moving the X, Y, and θ axes for centering; Optical sensor group 13 arranged in four
And a control unit (not shown) that controls the alignment stage 12 based on ON / OFF information from the sensor group 13.

In operation, a hand such as a robot places a wafer 6 taken out of a wafer carrier on a transfer table 11 provided in a wafer alignment unit.
The mounting table of the alignment stage 12 moves immediately below the transfer table 11 to receive the wafer 6, and moves in the Z-axis direction to move the wafer 6 to the alignment stage 1.
Transfer to table 2 Next, the alignment stage 12 is moved by a predetermined amount, the wafer 6 is rotated 360 ° by the function of the alignment stage in the θ-axis direction, and the optical sensor 13 is rotated.
After detecting the orientation flat position of the wafer 6 in advance, the orientation of the wafer is determined so that the orientation flat avoids the position of the optical sensor 13, and the alignment stage 12 is arranged so that all four optical sensors 13 are turned on from OFF to barely. In accordance with a predetermined algorithm, the table is moved in the XY directions by cut and try (in small increments), whereby the sensor position of the wafer 6 is determined.
Then, the transfer table 11 is moved to a predetermined position while keeping the center position of the wafer 6 in this way,
The wafer 6 is lowered on the alignment stage 12 in the Z-axis direction and transferred onto the transfer table 11. The wafer 6 on the transfer table 11 is again held by a hand such as a robot, and is handled at a predetermined position to supply the centered wafer to the next process.

[0005]

In the above-described conventional wafer alignment unit, since the alignment operation is a cut-and-try operation using only the ON / OFF information of the optical sensor, it takes a long time to perform the alignment depending on the position of the wafer. The first disadvantage is that the alignment process takes a long time, and the alignment time is long, so that the wafer is held in a unit other than a handling unit for holding and transporting the wafer for the next process, and alignment is performed. In order to supply the wafer to the next process via the wafer carrier, the wafer must be transferred to the alignment unit during that time. Means that the risk of wafer damage increases. Third, the θ-axis must be rotated 360 ° in advance to detect the orientation flat position even if it is not necessary to align the orientation flat in order to center the wafer with four optical sensors. Disadvantages.

[0006]

In a wafer position measuring unit of the present invention, an optical axis is parallel to each other and each width direction is radially arranged, and an intersection of a plane perpendicular to the optical axis and each optical axis is a wafer. A light projecting sensor that emits six strips of light, which are arranged equidistantly at a central angle of 60 degrees on a circumference having the same diameter as the outer shape, and receives the corresponding ones of the six strips of light. Based on the six light receiving sensors and the light receiving amounts of the six light receiving sensors, the center is 6 on a plane perpendicular to the optical axis of the band-shaped light.
Obtain the position of the intersection of the outer periphery of the wafer and the band light, which is placed substantially at the center of the band light of the book, and determine the optical axis of the band light at the intersection of the outer periphery of the wafer and the band light. And a control unit for obtaining a center position of the wafer from an intersection of the belt-like light on the outer periphery of the wafer excluding opposing ones having a significantly different amount of deviation from the wafer.

According to the wafer alignment method of the present invention, the center of the hand of the robot holding the wafer is aligned with the centers of the six strip lights of the measuring unit at the wafer position, and the wafer is the optical axis of the strip light. Position so that the center of the wafer is displaced from the normal position with respect to the center of the hand, and the center of the hand is shifted from the normal position in the direction opposite to the displacement direction. The wafer is positioned so that the center of the wafer is at the regular position.

[0008] The wafer alignment unit of the present invention comprises:
Holds and transports the wafer, and positions the center of the wafer at the normal position by shifting the center of the wafer from its normal position by the amount of shift of the center of the wafer from its own center, and in the direction opposite to the shift direction. A robot hand, the center of which coincides with the center of six strips of light, and the center of the wafer when the wafer held by the hand is perpendicular to the optical axis of the strip of light. A measurement unit for measuring a wafer position for obtaining a shift amount and a shift direction with respect to the center of the hand.

[0009]

The present invention will be described in detail with reference to the drawings.

FIG. 1 is a plan view of an embodiment of the present invention, and FIG. 2 is a side view.

In the wafer alignment unit of the present embodiment, the wafer 6 housed in the wafer carrier 5 is taken out by the robot 4, and the wafer 6 is moved to the measuring unit 7 including the light receiving sensor 2 and the like while being held by the robot 4, Therefore, centering alignment of the wafer 6 is performed. The measurement unit 7 includes a light emitting sensor 1 that converts a laser beam emitted from a laser source such as a semiconductor laser into a band light having a width of about 10 mm by a lens, and a photodetector that receives the band light from the light projecting sensor 1 via a lens. The light receiving sensor 2 and the light projecting sensor 1 and the light receiving sensor 2 are set as one set, and the center of the cut end 9 by a plane perpendicular to the optical axis of the band light is located at six places on the circumference having the same diameter as the wafer 6. A stand 3 (partially not shown) for fixing the light-emitting sensor 1 and the light-receiving sensor 2 so as to be arranged at an equal angle of 60 ° so that the width direction of the band-shaped light is radial; And a control unit (not shown) for instructing the robot 4 that holds and transports the wafer 6 to obtain a movement amount for giving the wafer 6.

The robot 4 sucks the back surface of the wafer 6 accommodated in the wafer carrier 5 by the hand 8 and takes it out. The robot 4 holds the wafer 6 so that the center of the hand 8 coincides with the center of the measurement unit 7. Is moved to hand 8. If the center of the wafer 6 matches the center of the robot hand 8, the center of the wafer 6 matches the center of the measurement unit 7. However, if the hand 8 sucks and holds the wafer 6 in a state where the center of the wafer 6 is deviated from the center of the robot hand 8 due to backlash or the like in the wafer carrier 5, the center of the wafer 6 is deviated from the center of the measurement unit 7. Changes the amount of received light.

As shown in FIG. 3, if the center of the wafer 6 and the center of the measuring unit 7 coincide with each other, the outer periphery of the wafer 6 comes to the center position of the cut end 9 of the strip-shaped light from each light emitting sensor 1. Therefore, half of the projected light amount of the projected sensor 1 is shielded by the wafer 6, and half of the projected light amount is received by the light receiving sensor 2. Since the light emitted from the light emitting sensor 1 is band-shaped light arranged radially in the width direction, a range in which the light is blocked changes according to a positional shift of the outer periphery of the wafer 6, and light is received in proportion to this range. The amount changes. Therefore, the amount of deviation of the center of the wafer 6 from the center of the measuring unit 7 can be measured from the range where the outer periphery of the wafer 6 blocks the band-shaped light. The position shift of the outer periphery of the wafer 6 can be measured at the six positions on the outer periphery of the wafer 6 by the six light emitting sensors 1 and the light receiving sensors 2. When this orientation flat is located at a position where the belt-like light from the light emitting sensor 1 is irradiated,
The amount of light received by the light receiving sensor 2 changes due to the influence of the orientation flat, and it is erroneously recognized that the wafer 6 is displaced.

As shown in FIG. 4, when one of the band lights irradiates the orientation flat, a pair of the band light irradiating the orientation flat and the band light opposing the center of the measuring unit 7 therebetween. The distance between the outer peripheries of the opposing positions of the wafer 6 obtained from the light receiving amounts of the pair of opposing light receiving sensors 2 receiving the band light does not indicate the distance corresponding to the wafer diameter. Even if the center of the wafer 6 is deviated from the center of the measurement unit 7, if the pair of opposing band lights do not irradiate the orientation flat with the center of the measurement unit 7 interposed therebetween, a pair of band light receiving these band lights is received. While the amount of deviation of the outer periphery of the wafer 6 obtained from the amount of light received by the light receiving sensor 2 is substantially the same,
If one of the pair of band-shaped lights irradiates the orientation flat, the amount of deviation of the outer circumference of the wafer 6 obtained from the amount of light received by the pair of light-receiving sensors 2 that receives the band-shaped light will have significantly different values. When the deviation amount of the outer periphery of the wafer 6 obtained from the light reception amounts of the pair of opposing light receiving sensors 2 shows a significantly different value, the result obtained from the pair of opposing light receiving sensors 2 is deleted from the alignment data. In this case, the center of the wafer 6 is calculated based on the shift amount of the outer periphery indicated by the light receiving amounts of the remaining four light receiving sensors 2 to avoid erroneous recognition of the wafer position due to the influence of the orientation flat.

The amount of light received by the four light receiving sensors 2 is the amount of displacement of the four points on the outer periphery of the circular wafer 6 (the amount of deviation of the band-like light from the light emitting sensor 1 from the center of the cut end 9), that is, If the positions of the four points are known, the intersection of the vertical bisector of the line connecting any two of the four points and the vertical bisector of the line connecting the other two points The center of a circle passing through these four points, that is, the center of the wafer 6, can be obtained. The method of finding the center of the wafer 6 is the same as that of the other measured 4
There is also a method of forming two parallel line segments from the points and obtaining the wafer center from the ratio of the line segment lengths or the center position shift amount.

In this way, the amount of deviation of the center of the wafer 6 from the center of the measuring unit 7, that is, the center of the hand 8 is obtained from the positional deviation information of the outer periphery of the wafer 6. This hand 8
After measuring the amount of deviation between the wafer 6 and the wafer 8,
When transported by the robot 4 to the position (regular position) to be positioned in the next step while being adsorbed on the substrate, the direction is opposite to the obtained displacement direction by the displacement amount of the center measured by the measurement unit 7. That is, the hand 8 moves in the direction of canceling the positional deviation.
The hand 8 is positioned by shifting the center of from the normal position. Thereby, the hand 8 of the robot 4 can position the wafer 6 at the regular position.

[0017]

According to the wafer position measuring unit, the wafer alignment unit and the method of the present invention, the outer periphery of the wafer is illuminated with the band light from the plurality of light projection sensors, and the portion of the band light not blocked by the wafer is irradiated. The first effect is that the center position of the wafer is obtained from the light receiving amounts of a plurality of light receiving sensors, so that the cut-and-try operation is not required and the alignment time can be shortened. The second effect is that the wafer is not transferred between the robot hand and the wafer position measuring unit, etc., and the chance of damaging the wafer is small, and the wafer is rotated to detect the orientation flat in advance. There is a third effect that there is no need.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of the present invention.

2 is a side view of the embodiment shown in FIG. 1. FIG.

FIG. 3 shows six light emitting sensors 1 of the measuring unit 7 in FIG.
FIG. 5 is a plan view showing a state where the center of the band-shaped light emitted from the center of the wafer 6 coincides with the center of the wafer 6.

FIG. 4 is a plan view showing a state in which one of band-shaped lights emitted from the light projecting sensor 1 of the measurement unit in FIG. 1 irradiates an orientation flat of a wafer.

FIG. 5 is a plan view of a conventional wafer alignment unit.

FIG. 6 is a side view of a conventional wafer alignment unit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 light emitting sensor 2 light receiving sensor 3 stand 4 robot 5 wafer carrier 6 wafer 7 measuring unit 8 hand 11 transfer table 12 alignment stage 13 optical sensor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B65G 49/07 C G01B 11/00 A

Claims (3)

[Claims] 1. An optical axis is parallel to each other, each width direction is radially arranged, and an intersection of a plane perpendicular to the optical axis and each optical axis is a central angle of 60 degrees on a circumference having the same diameter as the outer shape of the wafer. A light-emitting sensor that emits six strips of light arranged at equal intervals, six light-receiving sensors each receiving a corresponding one of the six strips of light, and a light-receiving sensor of the six light-receiving sensors. From the amount of received light, the center is 6 on a plane perpendicular to the optical axis of the band light.
Obtain the position of the intersection of the outer periphery of the wafer and the band light, which is placed substantially at the center of the band light of the book, and determine the optical axis of the band light at the intersection of the outer periphery of the wafer and the band light. A control unit for obtaining a center position of the wafer from an intersection of the outer periphery of the wafer with the belt-like light excluding opposing ones having a significantly different amount of deviation from the wafer position. 2. The robot hand holding the wafer is aligned such that the center of the hand of the robot holds the center of the six band-shaped lights of the measuring unit at the wafer position according to claim 1, and the wafer is aligned with the optical axis of the band-shaped light. The position of the wafer is set to be vertical, and the shift amount and the shift direction of the center of the wafer with respect to the center of the hand are obtained, and the center of the hand is shifted from the normal position by the shift amount in a direction opposite to the shift direction. A wafer alignment method, characterized in that the wafer is positioned so that the center of the wafer is at the normal position. 3. A wafer is held and transported, and the center of the wafer is shifted from a normal position by an amount of shift of the center of the wafer from its own center and in a direction opposite to the direction of the shift so as to shift the center of the wafer. The robot hand positioned at the regular position, and the hand aligns the center with the center of six strip lights, and when the wafer held by the hand is perpendicular to the optical axis of the strip light. 2. A wafer alignment unit comprising: the wafer position measuring unit according to claim 1, wherein a shift amount and a shift direction of a center of the wafer with respect to a center of the hand are obtained.