JPH11160059A - Measuring apparatus for film thickness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a measuring apparatus by which the deviation of a wafer is corrected mechanically before the wafer which is taken out from a cassette is delivered to a stage. SOLUTION: A measuring apparatus for a film thickness is constituted so as to be provided with mounting stages 1 on which wafer cassettes 11, 12 are mounted, with an indexer part 2 by which a semiconductor wafer is taken in and out with reference to the wafer cassettes 11, 12 and with a measuring part 3 which measures the film thickness of the semiconductor wafer. An indexer robot 21 and a center adjusting device 22 are installed at the indexer part 2. The deviation of the semiconductor wafer which is taken out by the indexer robot 21 is corrected by the center adjusting device 22. A pair of chucks 221 are installed at the center adjusting device 22. The semiconductor wafer which is taken out is sandwiched between, and held by, the chucks 221. Thereby, the deviation of the semiconductor wafer with reference to a hand 211 is corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film thickness measuring method for measuring the thickness of a transparent thin film formed on a substrate such as a photomask substrate for producing a semiconductor integrated circuit, a semiconductor wafer or a glass substrate for a liquid crystal display device. It concerns the device.

[0002]

2. Description of the Related Art As a film thickness measuring apparatus for measuring the thickness of a transparent thin film formed on a substrate such as a semiconductor wafer, the present applicant has proposed an apparatus disclosed in Japanese Patent Application Laid-Open No. 8-320389. And filed.

This apparatus measures the thickness of a thin film formed on a semiconductor wafer (hereinafter abbreviated as "wafer"). The apparatus includes a mounting portion for mounting a wafer cassette, a loader as a transfer means, and a wafer loading device. A pre-alignment unit for detecting eccentricity,
The measuring head includes an optical system for measuring a film thickness, and a measuring stage for holding a wafer to be measured by the measuring head.

According to this apparatus, a wafer taken out of a cassette by a loader is first transferred to a pre-alignment unit by the loader, and eccentricity detection (pre-alignment) is performed. It is arranged at a position and the film thickness is measured. When the film thickness measurement is completed, the film is picked up from the measurement stage by the loader and stored in a wafer cassette.

[0005]

In the above-described apparatus, the wafer may move in the cassette during transportation or the like. When the wafer is taken out of the cassette, the wafer is shifted, that is, the loader is moved. May be taken out with the center position of the wafer with respect to the theoretical position deviated from the theoretical position. However, such a wafer shift is, for example, one of the factors that hinders proper delivery of the wafer,
It is preferable to make corrections as early as possible.

In general, wafer pre-alignment is performed by detecting the displacement of the peripheral edge of a wafer held on a dedicated stage by a sensor while rotating the wafer integrally with the stage. If such a deviation is large, the amount of displacement of the peripheral edge of the wafer naturally becomes large.
Therefore, when the displacement amount of the wafer peripheral edge exceeds the detection width of the sensor, a disadvantage that the pre-alignment becomes impossible is caused. On the other hand, it is conceivable to use a sensor having a relatively wide detection width in consideration of such a wafer shift, but in this case, the size of the pre-alignment unit is increased and the cost is increased. is not. Therefore, it is more convenient to be able to correct the above-mentioned misalignment of the wafer to some extent before performing the pre-alignment.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and a film thickness measuring apparatus capable of mechanically correcting a displacement of a substrate before transferring a substrate taken out of a cassette to a stage. It is intended to provide.

[0008]

According to the present invention, there is provided a film thickness measuring apparatus for transferring a substrate taken out of a cassette to a stage, positioning the substrate at a predetermined measuring position, and measuring a film thickness. Take out the substrate from the cassette,
Transfer means for transferring the substrate to the stage, and a substrate taken out of the cassette by the transfer means prior to transfer of the substrate to the stage and further conveyed to the correction position. And a position correcting means for correcting the position of (1).

According to this apparatus, the substrate taken out of the cassette is transported to a correction position, where the substrate is clamped from the periphery thereof by the position correction means to correct the position.
Delivered to the stage. Therefore, when the taken-out substrate is displaced from the theoretical position of the transfer means, such a displacement is corrected and transferred to the stage.

In such a configuration, a plurality of chuck members capable of moving back and forth toward a specific position and moving means for uniformly moving each chuck member are provided in the position correcting means, and a predetermined substrate center position is set. If the substrate taken out of the cassette is conveyed to the correction position so as to coincide with the specific position (claim 2), it is possible to correct the displacement of the substrate center with respect to the transfer means.

In this case, the moving means is configured to advance and retreat each chuck member by a predetermined distance, and each chuck member is provided with a vertical contact portion with respect to a substrate end surface corresponding to a plurality of types of substrates having different sizes. It is preferable that the chuck member is provided in a plurality of stages, and the chuck member is configured to be vertically movable relative to the substrate supported by the transfer means. In this manner, the position of a plurality of types of substrates having different sizes can be corrected with a single mechanism by holding the substrate between the chuck members in a state where the substrate corresponds to the contact portion corresponding to the size. Becomes possible.

Further, in the apparatus according to any one of claims 1 to 3, if a detecting means capable of detecting the amount of protrusion of the substrate stored in the cassette is provided (claim 4), the apparatus is inappropriate. This makes it possible to prevent an inappropriate position correction from being performed.

[0013]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a film thickness measuring apparatus according to the present invention. The film thickness measuring device shown in FIG. 1 is a device for measuring the film thickness of a thin film formed on a semiconductor wafer, and includes a mounting stage 1 for mounting a wafer cassette, and an indexer section for moving a wafer into and out of the wafer cassette. 2 and a measuring unit 3 for measuring the film thickness of the wafer. The film thickness measuring apparatus according to this embodiment has a layout configuration in which the above-described placement stage 1 and the measuring unit 3 are arranged around the indexer unit 2.

In the illustrated example, two mounting stages 1 are provided. Each stage 1 has wafer cassettes 11 and 12 storing a plurality of wafers in multiple stages, each of which has a storage opening in an indexer section 2. It is placed in a state of facing. Each mounting stage 1 has a wafer cassette 11, 12
Irradiating part 131 and light receiving part 132
Is provided above and below, and a predetermined amount or more of wafers are ejected from the storage openings of the wafer cassettes 11 and 12, and irradiation light from the irradiation unit 131 is blocked by the wafers. In such a case, such an abnormal wafer jumping out state is detected, and the operator is notified of the fact through a monitor described later. In other words, if the wafer is protruding beyond a certain amount,
Since the correction of the position of the wafer by the later-described center adjustment device 22 may not be performed properly, abnormal jumping out of the wafer is detected to prevent such a situation from occurring.

The indexer section 2 has an indexer robot 21 (transfer means) as a means for transferring wafers, and the wafer cassette 11 and the wafer cassette 11 by the indexer robot 21.
A center adjusting device 22 (position correcting means) for correcting (centering) the center position of the wafer taken out of the wafer 12 is provided.

The indexer robot 21 is a horizontally articulated robot that can move up and down, and a thin plate-like hand 211 for holding a wafer is mounted at the end of the arm. A suction hole 212 is opened on the surface of the hand 211, and a negative pressure is supplied through the suction hole 212 so that the hand 211 sucks and holds the wafer. In the present embodiment, one suction hole 212 is provided at the distal end of the hand 211, and theoretically, the wafers are loaded into the wafer cassettes 11 and 12 with the center of the suction hole 212 at the center of the wafer. The indexer robot 21 is controlled so that the robot moves in and out of the robot.

The center adjusting device 22 includes a pair of chucks 221 that can be separated from each other, and the wafer cassette 11,
The position of the wafer with respect to the hand 211 is mechanically corrected by clamping the wafer taken out from the chuck 12 in the radial direction by the chuck 221.
The specific configuration of the center adjusting device 22 will be described later in detail.

The measuring section 3 has a measuring stage 4 serving as a holding portion for a wafer to be measured, and a measuring head 5 arranged on the measuring stage 4 for measuring a film thickness.

The measurement stage 4 includes a six-axis table 41 for movably holding a wafer, a pre-alignment sensor 47, and an auxiliary stage 48 for holding the wafer on standby.
Are provided.

The six-axis table 41 has a disk-shaped holding plate 411 for holding a wafer by suction, and holds the disk in a six-axis direction, ie, an X-axis, a Y-axis, a Z-axis, and around these axes (θY direction, θX direction). The holding plate 41 includes a supporting mechanism 412 that supports the holding plate 41 so as to be displaceable in the
The wafer is transferred to and from the auxiliary stage 48 while the wafer 1 is moved in each of the above directions.
In addition, the wafer is arranged at a predetermined measurement position of the pre-alignment sensor 47.

The pre-alignment sensor 47 has a light irradiation section 471 and a light receiving section 472 arranged vertically above and below a predetermined inspection space. The pre-alignment sensor 47 has a wafer edge in the inspection space. Is rotated, the pre-alignment, that is, the eccentricity of the center of the wafer with respect to the center of the holding plate 411 is detected.

The auxiliary stage 48 is disposed between the indexer unit 20 and the six-axis table 41. In the illustrated example, the auxiliary stage 48 is the same as the supply side stage 481 in which the wafer before measurement is placed on standby. And a discharge-side stage 482 that waits for the wafer after measurement.
Each of the stages 481 and 482 is formed in a substantially U-shape having a cutout for interposing the holding plate 411 as shown in FIG. The delivery of the wafer is performed under the holding plate 41 below the notch of the supply side stage 481.
1, the supply side stage 481 and the holding plate 4
11 is moved up and down relatively. On the other hand, the transfer of the wafer from the six-axis table 41 to the discharge side stage 482 is performed based on the reverse operation.

In FIG. 1, reference numeral 31 denotes an operation section provided at the front of the apparatus for inputting various data and commands to the film thickness measuring apparatus by an operator. A monitor (not shown) for displaying various messages, information, and the like to the worker is provided above the monitor.

FIGS. 2 to 4 show a specific configuration of the center adjusting device 22. FIG. The center adjusting device 22 is provided with the pair of chucks 221 as described above, and each chuck can be moved in and out of the X-axis direction to hold the wafer.

That is, the base 2 of the center adjusting device 22
A rail 222 extending in the X-axis direction is fixed on 2a, and each chuck 221 is slidably mounted on the rail 222 via a movable member 223. Also, two pulleys 224 are provided at the center of the side of the rail.
And an endless timing belt 227 is mounted over each of the pulleys 224 and the pulleys 225 which are respectively supported at both ends of the rail, and each movable member 223 is connected to each of the timing belts 227. Have been. The shaft of one pulley 225 (right pulley 225 in FIG. 2) located at the end of the rail is connected to the output shaft of the motor 230, and a gear 228 is attached to the shaft of each pulley 224 located at the center of the rail. , 2
The gears 228 and 229 are meshed with each other.

Thus, when the motor 230 is driven forward and reverse, the timing belts 227 rotate in the opposite directions to each other, and the chucks 221 move to the retracted position (the position shown by the solid line in FIG. 11). , Each chuck 22
1 are evenly moved along the rail 222 over an operating position approaching each other (a position indicated by a dashed line in the drawing). That is, the rail 222, the movable member 223, the timing belt 227, the motor 230, and the like constitute the moving means of the present application.

Each of the chucks 221 is formed in a fan shape in a plan view as shown in the figure, and its surface has arc-shaped contacts 221a to 221d corresponding to a plurality of types of wafers having different diameters (sizes). The (contact portion) is formed in multiple steps in the upper and lower directions, and is formed in a stepwise manner so that the lower the contact corresponding to a wafer having a smaller diameter, the lower the contact. 221a to 221 for each
The shape of d is the contour of the wafer when the center of the wafer is located at the center (referred to as a specific position) in the movement direction of each chuck 221. Therefore, when the center of the wafer is displaced from the specific position, By holding the wafer by the chucks 221, the position on the hand 211 is corrected so that the center of the wafer coincides with the specific position.

The rail 2 is located within the movable range of the one movable member 223 (the left movable member 223 in FIG. 2).
22, sensors 231 and 231 for detecting a detection piece 234 attached to one of the movable members 223 are provided.
32 are arranged at predetermined intervals in the X-axis direction, and the detection of the detection piece 234 by the sensors 231 and 232 detects that each chuck 221 is at the retracted position or the operating position. ing.

Next, a film thickness measuring operation by the above film thickness measuring apparatus will be described with reference to a timing chart of FIG. 5 showing a flow of a wafer.

In the film thickness measuring apparatus, for example, the wafer cassettes 11 and 12 are carried onto the mounting stage 1 by a transfer means (not shown), and the wafer is taken out from the wafer cassette 11 or 12 by the indexer robot 21. However, if a wafer is detected by the pop-out detection sensor 13, that is, the loaded wafer cassette 1
If any one of the wafers 1 and 12 has protruded by a certain amount or more, the removal of the wafer is not performed and the fact is displayed on the monitor. For example, when the operator remounts the wafer cassettes 11 and 12, When the wafer is no longer protruded, for example, the wafer is taken out.

The wafer (first wafer) taken out of the wafer cassette 11 or 12 by the indexer robot 21 is first centered by the center adjusting device 22 as shown by the solid line in FIG.

In this centering operation, first, with each chuck 221 of the center adjusting device 22 set at the retracted position, the hand 211 of the indexer robot 21 is adjusted so that the center of the suction hole 212 coincides with the specific position. Activated, whereby the wafer is placed between the chucks 221 (the state shown in FIG. 2). At this time, the wafers 221a to 221a contact the chucks 221 corresponding to the wafers.
The position of the indexer robot 21 in the vertical direction is adjusted so that 1d (the contact portion) matches.

When the chuck 221 moves to the operating position, the position of the wafer is corrected so that the center of the wafer coincides with the specific position. As a result, the center of the wafer coincides with the center of the suction hole 212. Hand 2
The position of the wafer on 11 will be corrected. Note that the chuck 221 is reset to the retracted position immediately after moving to the operating position.

In such a centering operation of the wafer, for example, the supply of the negative pressure to the hand 211 is interrupted at a predetermined timing until the chuck 221 reaches the operating position, and immediately after reaching the operating position. The supply of the negative pressure is resumed. By doing so, the resistance of the wafer to the hand 211 during the centering operation is reduced, and the centering by the chuck 221 is performed smoothly.

The wafer thus centered is then transferred from the indexer robot 21 to the supply stage 481, and further transferred from the supply stage 481 to the holding plate 411 of the six-axis table 41. After the wafer is detected (pre-aligned) by the pre-alignment sensor 47, the wafer is placed at a predetermined measurement position immediately below the measurement head 5 and the film thickness is measured.

While the pre-alignment and the film thickness measurement of the first wafer are being performed, the indexer robot 21 moves the next wafer from the wafer cassette 11 or 12 by the indexer robot 21 as shown by the dashed line in FIG. The second wafer is taken out, centered by the center adjustment device 22, and mounted on the supply stage 481.

When the measurement of the film thickness of the first wafer is completed,
The wafer is moved from the six-axis table 41 to the discharge-side stage 482.
The wafer cassette 1 is then picked up from the discharge side stage 482 by the indexer robot 21 and transferred to the wafer cassette 1.
1 or 12. Thus, all the steps of measuring the film thickness of the first wafer are completed.

When the first wafer is transferred to the discharge-side stage 482 as described above, the holding plate 411
Is moved to the discharge side stage 482 side, and the waiting wafer is transferred from the discharge side stage 482 to the six-axis table 41. Then, in the same manner as the first wafer, pre-alignment and film thickness measurement of the second wafer are sequentially performed, and during that, the next wafer is moved by the indexer robot 21 as shown by a broken line in the figure. (The third wafer) is taken out of the wafer cassette 11 or 12.

In the same manner, the pre-alignment of the wafer and the measurement of the film thickness and the transfer of the wafer into and out of the wafer cassette 11 or 12 are performed in parallel, and the film thickness of the wafer stored in each of the wafer cassettes 11 and 12 is measured. Will be performed.

As described above, in the above-described film thickness measuring apparatus, the center adjusting device 22 is provided in the indexer section 2 to correct the displacement of the wafer taken out of the wafer cassette 11 or 12 (ie, the displacement of the wafer with respect to the hand 211). Then, the wafer is transferred to the measurement unit 3, so that the wafer can be appropriately transferred, for example, by effectively preventing the wafer from dropping due to such misalignment of the wafer.

Further, by transferring the wafer to the measuring section 3 after correcting the displacement, the displacement of the wafer periphery due to the rotation of the wafer during the pre-alignment can be reduced, so that the detection width is relatively narrow. Pre-alignment sensor 47
Can be used to perform pre-alignment. Therefore, there is an advantage that pre-alignment can be appropriately performed while suppressing an increase in size and cost of the apparatus due to an increase in the size of the pre-alignment sensor 47.

Further, in the above-described apparatus, the jump-out detection sensor 13 detects the jump-out of the wafer from the wafer cassettes 11 and 12, and if the wafer has jumped out by a predetermined amount or more, the hand 211 does not take out the wafer. Therefore, there is also an advantage that the shift of the wafer by the center adjusting device 22 can be corrected more appropriately. That is, if the wafer is taken out from the wafer cassettes 11 and 12 with a certain amount of protrusion from the wafer cassettes 11 and 12, for example, in FIG. 2, the center of the wafer is largely shifted in the Y-axis direction from the center of the suction hole 212. In this state, for example, when the chucks 221 hold the wafer, an appropriate force does not act on the wafer, and as a result, there is a possibility that an appropriate position correction may not be performed. However, by detecting an abnormal protrusion of the wafer by the protrusion detection sensor 13 as described above, such a situation can be prevented from occurring beforehand, and the displacement of the wafer can be appropriately corrected.

The center adjusting device 22 of the above embodiment is used.
Then, the timing belt 227 is rotated by a motor drive, and the chuck 22 is attached to the timing belt 227.
Although each chuck 221 is moved by attaching the chuck 1, for example, each chuck 221 may be moved forward and backward by an air cylinder, or each chuck 221 may be moved forward and backward by using a ball screw mechanism.

In the center adjusting device 22, since the chuck 221 is displaced between the operating position and the retracted position, hits 221a to 221d corresponding to a plurality of kinds of wafers having different diameters are formed in multiple stages. Chuck 2
Although the centering of a plurality of types of wafers having different diameters is possible by using the
If the position of the chuck 221 is displaced in multiple stages by using a stepping motor, it is possible to center a plurality of types of wafers having different diameters in a single contact. You may make it. In this case, as the chuck 221, for example, a chuck having a contact that can partially contact the peripheral portion of the wafer, such as a V-shape in plan view, may be used.

The chuck 2 of the center adjusting device 22
In the step 21, the steps 221a to 221d are provided. However, for example, pin members or the like having different heights may be erected on the surface of the chuck formed in a flat plate shape so as to hit various wafers. Absent. That is, chuck 2
The specific shape and the like of the contact 21 and the contacts 221a to 221d may be appropriately selected so that the wafer can be sandwiched by the chucks 221 and the centering can be appropriately performed.

[0046]

As described above, according to the present invention, in a film thickness measuring apparatus for measuring a film thickness by transferring a substrate taken out of a cassette to a stage, the substrate taken out of the cassette by a transfer means is transported to a correction position. Here, since the position of the substrate relative to the transfer means is mechanically corrected by being pinched from the periphery thereof by the position correcting means and then the substrate is transferred to the stage, the dropping of the substrate and the like can be reliably avoided. The substrate can be properly delivered. Further, it is possible to appropriately perform the pre-alignment of the substrate without increasing the size of the pre-alignment unit and increasing the cost.

In particular, in this configuration, a plurality of chuck members capable of moving back and forth toward a specific position and moving means for uniformly moving each chuck member are provided in the position correcting means, and a predetermined substrate center position is set. If the substrate taken out of the cassette is transported to the correction position so as to coincide with the specific position, it is possible to correct the displacement of the substrate center with respect to the transfer means.

In this case, the moving means is configured to move each chuck member back and forth by a predetermined distance.
Each chuck member is provided with a plurality of upper and lower contact portions for the substrate end surface corresponding to a plurality of types of substrates having different sizes, and furthermore, the chuck member is configured to be movable up and down relative to the substrate supported by the transport means. By doing so, the position of a plurality of types of substrates having different sizes can be corrected by a single mechanism.

Further, by providing a detecting means capable of detecting the amount of protrusion of the substrate stored in the cassette, a state in which the position of the substrate cannot be properly corrected is detected in advance, and an inappropriate state is detected. Such a position correction can be prevented beforehand.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a film thickness measuring apparatus according to the present invention.

FIG. 2 is a schematic plan view showing a configuration of an indexer unit.

FIG. 3 is a sectional view taken along line AA in FIG. 2, showing a mechanism for moving a chuck.

FIG. 4 is a sectional view taken along line BB of FIG. 2 showing a configuration of the chuck.

FIG. 5 is a timing chart illustrating a flow of a semiconductor wafer in the film thickness measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mounting stage 11, 12 Wafer cassette 2 Indexer part 21 Indexer robot (transfer means) 22 Center adjustment device (positioning means) 221 Chuck 222 Rail 223 Movable member 224, 225 Pulley 227 Timing belt 228, 229 Gear 230 Motor 3 Measurement part 4 Measuring Stage 5 Measuring Head 41 6-Axis Table 411 Holding Plate 412 Support Mechanism 47 Pre-Alignment Sensor 48 Auxiliary Stage

Claims (4)

[Claims] 1. A film thickness measuring device for transferring a substrate taken out of a cassette to a stage and positioning the substrate at a predetermined measurement position to measure a film thickness, taking out the substrate from the cassette,
Transfer means for transferring the substrate to the stage, and a substrate taken out of the cassette by the transfer means prior to transfer of the substrate to the stage and further conveyed to the correction position. And a position correcting means for correcting the position of the film. 2. The apparatus according to claim 1, wherein the position correcting means includes a plurality of chuck members capable of moving back and forth toward a specific position, and moving means for uniformly moving each of the chuck members.
2. The film thickness measuring apparatus according to claim 1, wherein the substrate taken out of the cassette is transported to the correction position so that a preset substrate center position coincides with the specific position. 3. The moving means moves the chuck members back and forth by a fixed distance, and each of the chuck members has a plurality of upper and lower stages of contact portions on the substrate end surface corresponding to a plurality of types of substrates having different sizes. 3. The film thickness measuring device according to claim 2, wherein the film thickness measuring device is configured to be vertically movable relative to a substrate supported by the transporting means. 4. A film thickness measuring apparatus according to claim 1, further comprising a detecting means capable of detecting an amount of protrusion of the substrate stored in said cassette.