JPH04128605A - Orientation flat detecting apparatus - Google Patents

Abstract

PURPOSE:To detect the position of an orientation flat of a wafer easily by rotating the wafer having the orientation flat on a rotary axis. CONSTITUTION:While the circle center of a glass wafer 1 which is conveyed is agreed with the rotary center of a rotary stage 2 by an apparatus not shown in the figure, the glass wafer is vacuum-adsorbed to the rotary stage 2 and kept horizontally and in freely rotatable condition. A microcomputer 11 rotates and drives a motor 12 by a constant angle through a motor driving drive 13. Consequently, the glass wafer 1 held by the rotary stage 2 is also rotated by a constant angle. Address counter 15 is added with every rotation by a constant angle. Signals from a photoreceptor device 6 with this timing are amplified by a pre-amplifier 7, converted into digital signals by an A/D converter 8, and recorded on a latch 9. The recorded data is written down in a memory 10 and processed by the microcomputer 11. In this case, at the time the quantity of the photoreception is the maximum, the rotary angle determines the position of the orientation flat.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a wafer orientation flat detection device, and particularly to a device suitable for detecting orientation flats of optically transparent glass wafers and the like. .

[Prior Art] A wafer is provided with a flat portion called an orientation flat used for alignment.

As a method for detecting this orientation flat, conventional detection devices have been proposed.

The contact type is one in which the probe is brought into contact with the outer edge of the wafer and the wafer is rotated around the central axis to determine the displacement of the probe and the maximum value of the displacement is determined as the orientation flat position. There is.

Also, a non-contact type detection device is used, as shown in FIG. 5, which is used for detecting the position of the orientation flat of a silicon wafer.

The configuration will be explained based on FIG.

21 is a wafer having an orientation flat (OF), and 22 is a wafer having an orientation flat (OF). This is a rotation stage that rotates the center axis. 23 is a light source that projects the vicinity of the outer peripheral edge of the wafer 21 from a direction perpendicular to the wafer 21, and 24 is a lens for converting this projected light into a parallel light beam. 25 is a light receiving section that receives projection light from a light source such as an image sensor, and 26 is a processing section that takes in information from the light receiving section and detects the position of the orientation flat.

With the device configured as described above, the position of the orientation flat has been detected by detecting the amount of light from the light receiving section 25 with respect to the rotation angle or sampling the distance to the rotation center with respect to the rotation angle.

[Problem to be solved by the invention] However, in the case of the former contact type, since the wafer 71 and the probe come into contact, dust from the wafer or the probe is generated and adheres to the wafer, which is a serious drawback. .

Furthermore, the latter type of non-contact type device utilizes the property that the wafer 21 does not transmit light from the light source 23, so it can be used with a light source such as a glass wafer used as a mask for semiconductor manufacturing. This method cannot be used to detect the position of a wafer orientation flat that is transparent to the wavelength of the emitted light beam. That is, there is no difference in the amount of light between the orientation flat portion and other peripheral portions of the wafer, and the distance to the rotation center relative to the rotation angle cannot be detected by an image sensor or the like.

The present invention was devised in view of the above reasons, and an object of the present invention is to provide an apparatus capable of detecting the position of the orientation flat of a wafer having optical transparency such as a glass wafer.

[Means for Solving the Problems] In order to achieve the above object, the orientation flat detection apparatus of the present invention includes a rotation means for rotating a wafer having an orientation flat around a rotation axis, and a rotation means for rotating a wafer having an orientation flat around a rotation axis, and an optical axis parallel to the orientation flat. a measurement projection optical system that projects a parallel light beam that is arranged so that it has a portion that is irradiated onto the wafer end face and does not travel straight when it is not parallel, and that travels straight when it is parallel; and a measurement projection optical system that receives the light beam that travels straight from the measurement projection optical system. It is characterized by comprising a light-receiving element arranged at a certain position, and a processing section that derives the position of the orientation flat based on information from the light-receiving element.

Further, the orientation flat detection device is characterized by being provided with a display means that calculates the distance from the center of rotation based on the signal of the light receiving element and displays an error when the calculated distance is outside a predetermined range. .

Furthermore, the orientation flat detection device is characterized in that the light-receiving element serving as a basis for calculating the distance is a linear image sensor.

[Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic diagram showing the configuration of one embodiment of the present invention.

1 is a glass wafer which is the object to be inspected, and OF
It has an orientation flat as shown in .

A rotation stage 2 holds the glass wafer 1 horizontally and rotatably by vacuum suction, and is set so that the center of the glass wafer 1 is on the rotation axis of the rotation stage 2.

3 is a light emitting diode that emits measurement light;
A laser light may also be used. 4 is a collimating lens that converts the light emitted from the light emitting diode 3 into a parallel light beam, and 5 is an aperture that narrows down the measurement light beam. The light emitting diode 3, collimating lens 4, and aperture 5 constitute a measurement projection system.

The measurement projection system is arranged so that when the orientation flat (OF) and the optical axis of the measurement projection system are not parallel, light is blocked, and when they are parallel, there is a part that is not blocked and moves straight (
(See Figures 1 and 2).

The optical path of the measurement light when the optical axes of the orientation flat and the measurement projection system are not parallel will be explained using FIG. Assuming that A is the measurement projection optical axis, when the two are not parallel, part of the measurement light irradiated on the end face of the glass wafer 1 is reflected and becomes the optical path R, and a part of the transmitted light is refracted and becomes the optical path T. The component that goes straight on optical path A disappears.

6 uses a photodiode or line image sensor that detects the amount of incident light with a light receiving element. The light receiving element 6 is not blocked by the wafer 1 and is placed at a position where the measurement light beam traveling straight is incident.

Note that there is no problem in principle in arranging the measurement projection system and the light receiving section as long as the amount of incidence changes depending on the position of the orientation flat.

The light emitting diode 3, collimating lens 4, aperture 5, and image sensor 6 are configured to be able to move integrally depending on the size of the wafer 1.

A preamplifier 7 amplifies the signal from the light receiving element 6. The amplified signal is converted into a digital signal by an A/D converter 8, temporarily recorded in a latch 9, and the recorded data is written into a memory 10.

11 is a microcomputer that controls and processes the entire device.

12 is a motor that drives the rotation stage 2.

13 is a motor drive driver, and 14 is a motor drive control circuit, which rotates the rotary stage 2 by a constant angle.

Reference numeral 15 denotes an address counter that adds up each time the rotation stage 2 is driven by a certain angle to obtain the rotation angle.

Note that a rotary encoder or the like can also be used to detect the angle of the rotation stage 2.

Next, the operation of the embodiment having the above configuration will be explained.

A glass wafer 1 is conveyed by a device not shown, and its circular center is aligned with the center of rotation of a rotary stage 2 by a device not shown, and the glass wafer 1 is vacuum suctioned to the rotary stage 2 and held horizontally and rotatably.

Next, the light emitting diode 3 emits light and measurement is started.

The microcomputer 11 issues an activation signal for the motor drive control circuit 14 and drives the motor 12 to rotate by a constant angle via the motor drive 13. As a result, the glass wafer 1 held on the rotation stage 2 is also rotated by a constant angle. The address counter 15 is incremented every time it rotates by a certain angle. The signal from the light receiving element 6 at this timing is amplified by the preamplifier 7, and the A/D converter 8
The signal is converted into a digital signal and recorded in the latch 9. The recorded data is written to memory 10.

The above operation is repeated until the glass wafer 1 rotates once, and data for one rotation is recorded in the memory 10 and processed by the microcomputer 11.

FIG. 3 shows an example of the change in the amount of light received by the light receiving section with respect to the rotation angle of the glass wafer 1 obtained in this manner. The rotation angle when the amount of received light is maximum specifies the position of the orientation flat. Further, the position can also be expressed as an intermediate position between the starting point and the ending point of the light amount change.

In this embodiment, it is assumed that the center of the glass wafer 1 is set reliably on the rotation axis of the rotary stage 2, but there is a possibility that an erroneous measurement is made due to eccentricity for some reason. Therefore, the linear image sensor has a light shielding level of 1! (or the light receiving position) and obtain the distance to the center of rotation, it is possible to determine whether the measurement is incorrect or not, and display the result. Even in the case of a photodiode, the detection of the light-blocking position (or light-receiving position) can be done by splitting the measurement light with a beam splitter before it enters the wafer, for example.
It can be detected almost accurately by taking the ratio of the amounts of light at each light receiving position.

[Effects] According to the configuration of the present invention, the position of the orientation flat of the wafer that is transparent to the wavelength of the measurement light source can be easily detected.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration of the orientation flat detection device of this embodiment, and FIG. 2 is an explanatory diagram showing the arrangement relationship between the measurement projection system, the light receiving element, and the orientation flat. Fig. 3 is an explanatory diagram showing the optical path when the measurement light is irradiated onto the end face of the wafer, Fig. 4 is a graph showing the relationship between the rotation angle of the orientation flat and the amount of received light;
FIG. 5 is an explanatory diagram showing a conventional detection device. ]... Glass wafer 2... Rotating stage 3... Light emitting diode 4... Collimating lens 5... Aperture 6... Light receiving element 2... Motor

Claims (3)

[Claims] (1) A rotating means for rotating a wafer having an orientation flat around a rotation axis, and a portion having a portion that irradiates the end face of the wafer and does not travel straight when the orientation flat and the optical axis are not parallel, but travels straight when the orientation flat and the optical axis are parallel. a measurement projection optical system for projecting a parallel light beam, which is disposed at a position of the measurement projection optical system, a light receiving element disposed at a position to receive the straight light beam of the measurement projection optical system, and a position of the orientation flat based on information from the light receiving element. An orientation flat detection device comprising: a processing unit for deriving the orientation flat detection device; (2) In the orientation flat detection device set forth in item 1, a display means is provided that calculates the distance from the center of rotation based on the signal of the light receiving element and displays an error when the calculated distance is outside a predetermined range. An orientation flat detection device featuring: (3) An orientation flat detection device, characterized in that the light receiving element in item 2 is a linear image sensor.