JP2874795B2 - Orientation flat detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting an orientation flat of a wafer, and more particularly to an apparatus suitable for detecting an orientation flat of a glass wafer or the like having a light transmitting property. .

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

As a method for detecting the orientation flat, the following detection devices have been conventionally proposed.

As for the contact type, the probe is brought into contact with the outer peripheral edge of the wafer, and the wafer is rotated around the center axis to determine the displacement of the probe, and the maximum value of the displacement is set as the orientation flat position. There is.

The non-contact type is a detection device as shown in FIG. 5 which is used for detecting the position of an orientation flat of a silicon wafer. The configuration will be described with reference to FIG.

Reference numeral 21 denotes a wafer having an orientation flat (OF), and reference numeral 22 denotes a rotary stage for rotating the wafer 21 around a central axis. Reference numeral 23 denotes a light source for projecting the vicinity of the outer peripheral end of the wafer 21 from a direction perpendicular to the wafer 21, and reference numeral 24 denotes a lens for converting the projection light into a parallel light flux. Reference numeral 25 denotes a light receiving unit that receives projection light from a light source such as an image sensor. Reference numeral 26 denotes a processing unit that receives information from the light receiving unit and detects the position of the orientation flat.

With the device having the above-described configuration, the position of the orientation flat is detected by detecting the light amount of the light receiving unit 25 with respect to the rotation angle or sampling the distance to the rotation center with respect to the rotation angle.

[Problems to be Solved by the Invention] However, in the case of the contact type, which is the former, since the wafer comes into contact with the probe, there is a serious disadvantage that dust on the wafer or the probe is generated and adheres to the wafer.

Further, since the non-contact type device such as the latter utilizes the property that the wafer 21 does not transmit light from the light source 23, the light source such as a glass wafer used as a mask for semiconductor manufacturing is used. It cannot be used for detecting the position of the orientation flat of a wafer having light transmittance with respect to the wavelength of the emitted light beam. That is,
The wafer has no difference in light amount between the orientation flat portion and the other outer peripheral portion, and cannot detect the distance from the rotation angle to the rotation center by an image sensor or the like.

The present invention has been devised in view of the above-described reason, and has as its technical object to provide an apparatus capable of detecting the position of an orientation flat of a light-transmitting wafer such as a glass wafer.

[Means for Solving the Problems] In order to achieve the above object, an orientation flat detection device of the present invention includes: a rotation unit configured to rotate a wafer having an orientation flat around a rotation axis;
A measurement projection optical system for projecting a parallel light beam arranged so as to have a portion which is irradiated to the wafer end face when the orientation flat and the optical axis cannot be parallel and does not travel straight, and when the orientation flat is parallel, has a portion which travels straight; and It is characterized by comprising a light receiving element arranged at a position for receiving a light beam traveling straight in the system, and a processing unit for deriving the position of the orientation flat based on information from the light receiving element.

Further, the orientation flat detection device is characterized in that a display means for calculating a distance from a rotation center based on a signal of the light receiving element and displaying an error when the calculated distance is out of a predetermined range is provided. .

Further, the light receiving element from which the distance is calculated is a linear image sensor.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

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

Reference numeral 1 denotes a glass wafer as an object, and OF in FIG.
Has an orientation flat as shown by.

Reference numeral 2 denotes a rotary stage for holding the glass wafer 1 horizontally and rotatably by vacuum suction.
Is set on the rotation axis of the rotary stage 2.

Reference numeral 3 denotes a light-emitting diode that emits measurement light, and may use He-Ne laser light. Reference numeral 4 denotes a collimating lens for converting the light emitted from the light emitting diode 3 into a parallel light beam, and reference numeral 5 denotes an aperture for narrowing the measurement light beam. The light emitting diode 3, the collimating lens 4, and the aperture 5 form a measurement projection system. The measurement projection system is shielded when the orientation flat (OF) and the optical axis of the measurement projection system are not parallel,
When they are parallel, they are arranged so as to have a portion that goes straight without being shielded from light (see FIGS. 1 and 2).

The optical path of the measurement light when the orientation flat and the optical axis of the measurement projection system are not parallel will be described with reference to FIG. When A is a measurement projection optical axis, when both are not parallel, a part of the measurement light applied to the end face of the glass wafer 1 is reflected and becomes an optical path R, and a part of the transmitted light is refracted and an optical path T
Thus, there is no longer a component that travels straight along the optical path A.

Reference numeral 6 denotes a light receiving element that uses a photodiode or a line image sensor that detects the amount of incident light. The light receiving element 6 is not shielded by the wafer 1 and is placed at a position where a measurement light beam that goes straight ahead enters.

The arrangement of the measurement projection system and the light receiving unit is not in principle inconvenient as long as the incident amount changes depending on the position of the orientation flat.

The light emitting diode 3, the collimating lens 4, the aperture 5, and the image sensor 6 are configured to be able to move integrally according to 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 the A / D converter 8 and is temporarily recorded in the latch 9. The recorded data is stored in the memory 9.
Written to 10.

A microcomputer 11 controls and processes the entire apparatus.

Reference numeral 12 denotes a motor for driving the rotary stage 2. Reference numeral 13 denotes a motor drive driver, and reference numeral 14 denotes a motor drive control circuit that drives the rotary stage 2 to rotate at a constant angle.

Reference numeral 15 denotes an address counter for adding a rotation angle every time the rotary stage 2 is driven at a constant angle to obtain a rotation angle.

Note that a rotary encoder or the like can be used for detecting the angle of the rotary stage 2.

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

Glass wafer 1 transported by equipment not shown
The center of the circle is made to coincide with the center of rotation of the rotary stage 2 by a device not shown, and the rotary stage 2 is vacuum-adsorbed and held horizontally and rotatably.

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

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

The above operation is repeated until the glass wafer 1 makes one rotation, 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 unit 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 the maximum specifies the position of the orientation flat. Further, the position can be represented by 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 surely set so as to be on the rotation axis of the rotary stage 2, but there is a possibility that the measurement may be erroneously performed due to eccentricity for some reason. Therefore, it is possible to detect the light shielding position (or the light receiving position) with the linear image sensor, determine the erroneous measurement by obtaining the distance from the rotation center, and display the result. Even in the case of a photodiode, the light shielding position (or light receiving position) can be detected almost accurately, for example, by dividing the measuring light by a beam splitter before entering the wafer and obtaining the respective light amount ratios at the light receiving position.

[Effect] According to the configuration of the present invention, it is possible to easily detect the position of the orientation flat of the wafer having the property of transmitting the wavelength of the measurement light source.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of an orientation flat detecting device of the present embodiment, and FIG. 2 is an explanatory diagram showing an arrangement relationship between a measurement projection system, a light receiving element, and an orientation flat. FIG. 3 is an explanatory diagram showing an optical path when measurement light is applied to the end face of the wafer, FIG. 4 is a graph showing a relationship between the rotation angle of the orientation flat and the amount of received light,
FIG. 5 is an explanatory view showing a conventional detection device. DESCRIPTION OF SYMBOLS 1 ... Glass wafer 2 ... Rotation stage 3 ... Light emitting diode 4 ... Collimating lens 5 ... Aperture 6 ... Light receiving element 12 ... Motor

Claims (3)

(57) [Claims] A rotating means for rotating a wafer having an orientation flat around a rotation axis; and a portion which is irradiated on the wafer end face when the orientation flat and the optical axis are not parallel and does not go straight, and when the optical axis is parallel, a portion which goes straight. A measuring projection optical system for projecting a parallel light beam arranged so as to have a light receiving element disposed at a position for receiving a straight light beam of the measuring projection optical system; and the orientation flat based on information from the light receiving element. And a processing unit for deriving the position of the orientation flat. 2. An orientation flat detecting apparatus according to claim 1, further comprising a display means for calculating a distance from a rotation center based on a signal from said light receiving element, and displaying an error when the calculated distance is out of a predetermined range. An orientation flat detection device. 3. An orientation flat detecting device according to claim 2, wherein said light receiving element is a linear image sensor.