JPH03296245A - Method of recognizing wafer shape - Google Patents

Abstract

PURPOSE:To enable a shape of a wafer to be recognized accurately and positioned even if the wafer is slightly eccentric by projecting a line-shaped light beam to a certain region of an outer-periphery part of the rotating wafer and by monitoring current amount of received light by the outer-periphery part of the wafer. CONSTITUTION:An optical sensor A consists of a light source 20 and a photoelectric element 21 which are fixed below and above a supporting plate 19 and has a thin line-shaped light beam 22 with a constant length in radius direction of a wafer 6. The light beam 22 which is emitted from the light source 20 is emitted to an arbitrary range at the outer-periphery part of the wafer 6 and rays correspond to a length L from a peripheral edge 23 to an outer edge of the light flux 22 hits against a photoelectric element 21. Then, voltage corresponding to the amount of light is transmitted to a detection circuit. Thus, by monitoring a voltage level which changes and comparing it with a rotary data of a stepping motor 13, position and size of the orientation flat and notch can be determined and positioned or detective wafers are found.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a semiconductor wafer that serves as a substrate for forming an integrated circuit, in which a portion thereof has a linear notch, that is, an orientation flat (hereinafter referred to as an orientation flat). Alternatively, the present invention relates to a method for recognizing the outer shape of a disc-shaped wafer having a detection portion such as a notch.

[Prior Art] An example of a conventional wafer alignment method is shown in FIGS. 5 and 6. In Fig. 5, reference numerals 1, 2, and 3 denote rotating rollers of the same diameter, and each of these rotating rollers is rotatably mounted on a mounting base (not shown), and driven by a motor installed on the mounting base. The driven pulley 4 and each rotating roller 1, 2, 3 are rotated at a constant speed in the direction of the arrow by applying an endless heald 5 as shown in FIG.

Further, each rotating roller 1.2.3 has the same diameter and is arranged along the circumference of the wafer 6. Reference numeral 7 denotes a pair of left and right conveyor belts, which are attached to a lifting frame (not shown).

Now, under the condition that the transfer heald 7 is in the lower position, when the wafer 6 is transferred from the left side of FIG. 5 by the heald 7, the wafer 6 protrudes above the heald 1-7 as shown in FIG. It stops when it hits the three rotating rollers 1.2.3.

At this time, as shown in FIGS. 5 and 6, the rotating roller 1
．． 2.3 is in contact with the arcuate periphery of the wafer 6, all the rollers 1.2.3 are in contact with the periphery of the wafer 6, so the wafer 6 is rotated in the direction of the two rollers 2.3.

In this way, the wafer 6 rotates, and the orientation flat 10 is moved to the roller 1.
．． When reaching the section 2.3, the roller 2 separates from the orientation flat 10 and comes into contact with the two rollers 1.3 having opposite rotational directions, as shown in FIG.

In addition to the above method, it is also possible to detect the circumference of the wafer with a single optical sensor installed at a fixed position, measure the circumference between two points of an arbitrary radius of the orientation flat with this optical sensor, and There is also a method of calculating positioning.

[Problem to be solved by the invention]

In the case of the conventional method using a rotating roller as described above, if there is variation in the outer diameter of the wafer, the center position of the wafer will be deviated. Therefore, if it is desired to match the orientation flat to some standard, it is difficult to do so using the above method.

In addition, in the method using an optical sensor, r of the luminous flux of the optical sensor is
Since the JJ is wide, if the detection part of the wafer has a minute notch, detection will be unstable.

In this case, even if a sensor with a narrow optical axis is used, if the center of the wafer is eccentric with respect to the center of rotation, there is a problem that it is difficult to distinguish between the notch portion and the eccentricity.

An object of the present invention is to solve the problems of the conventional methods as described above, and to provide a method that can accurately recognize the outer shape of a wafer and perform positioning even if the wafer is slightly eccentric.

[Failure to solve the problem]

In order to solve the above problems, the present invention includes a turning means for turning a wafer, and an optical sensor for detecting the position of a detection part on the outer periphery of the wafer rotated by the turning means,
This optical sensor has a thin linear light beam with a constant length in the radial direction of the wafer, and a certain area on the outer periphery of the rotating wafer is irradiated with the above light beam to measure the amount of light received momentarily by the outer periphery of the wafer. A method is provided in which the shape of the outer periphery is recognized by changes in line segments while monitoring the wafer, and the outer shape of the wafer is recognized using the data.

〔Example〕

1 to 3 show an example of an apparatus for carrying out the method of the present invention, and 11 in FIG. 2 is a turning means.

This turning means is a suction table 1 rotatably attached to a bearing 12.
4, and a stamping motor 13 that rotates this table 14.
and a fixed frame 18 to which the bearing 12 is fixed together with the motor 13.

As shown in FIG. 1, the suction table 14 has a suction groove 16 on its upper surface, and this groove 16 communicates with a communication hole 17 in FIG. 2 that leads to a vacuum suction device (not shown).

Reference numeral 9 denotes a bracket fixed to the upper end of the bearing 12. On this bracket S, a vertical support plate 1 is fixed as shown in FIG. 2, and an optical sensor +IA is attached to this support plate 19.

The optical sensor A is composed of a light projector 20 and a photoelectric element 21 fixed on the upper and lower sides of a support plate 19, respectively, and as shown in FIG. 22.

Then, a certain area on the outer periphery of the wafer 6 is provided at a position to be irradiated with the light beam.

25 in Figures 1 and 2 is a centering device, and the mounting base 2
A guide rail 27 is provided on 6, and this guide rail 27
A centering plate 31 is removably attached to a pair of upwardly facing arms 30 with screws or the like, and the centering plate 31 has opposing circles as shown in FIG. An arcuate recess 32 is formed.

The four parts 32 correspond to the circumference of the wafer 6, and each arm 30 is opened and closed by a link mechanism (not shown).
When closed, both the recesses 32 form a circle that coincides with the outer circumference of the wafer 6 and are spaced apart from the suction table 14.

Now, the wafer 6, which has been attracted by a suction plate 33 of an arbitrary transport means (not shown), moves onto the centering device 25 as shown by the chain line in FIG.

At this time, since the centering plate 31 is wide open as shown by the solid line in FIG. 1, the wafer 6 moves to the suction table 14'' without contacting the plate 31.

When some kind of detection means detects that the center of the wafer 6 supplied above the suction table 14 almost coincides with the rotation center of the suction table 14 as described above, the suction plate 33 is slightly lowered.
The wafer 6 is placed on the suction table 14 and suction is released.

Next, each centering plate 31 begins to close, and when the recesses 32 of both plates 31 coincide with the outer periphery of the wafer 6, the center of the wafer 6 and the center of rotation of the suction table 14 coincide.

At the same time as this state is reached, the vacuum suction of the suction table 14 starts, and at the same time the wafer 6 is fixed on the suction table 14, both arms 3
0 is opened and both centering plates 31 are separated from the wafer 6.

Next, a light beam is sent from the light projector 20 toward the photoelectric element 21 . At the same time, the stepping motor 13 is activated by a pulse signal from a pulse generator for motor control, and starts rotating the suction table 14 in the direction of the arrow in FIG.

The light beam 22 emitted from the projector 20 irradiates an arbitrary range of the outer periphery of the wafer 6, and the light beam 22 is emitted from the periphery 23 in FIG.
A light beam corresponding to the length L to the outer end of the light beam hits the photoelectric element 21, and a voltage corresponding to the amount of light is sent to the detection circuit.

Therefore, if the circumference 8!23 through which the light beam 22 passes is a part of the same circumference as the rotation center as shown in I in Fig. 4, the level of the voltage monitored by the detection circuit will be a constant horizontal line as shown in Fig. 4. becomes.

When the portion of the orientation flat 10 passes through the portion of the light beam 22 as shown in Figure 4, a gentle symmetrical chevron-shaped waveform becomes maximum when the center of the orientation flat 10 passes through the beam 22 as shown in Figure 4. becomes.

When the non-cut portion 15 as shown in FIG. 4 V passes through the light beam 22, it becomes a sharp protruding waveform as shown in FIG. If it passes through, an abnormal waveform as shown in Figure 4 (■) will result.

Therefore, by monitoring the voltage level that changes as shown in - and comparing it with the rotation data of the stepping motor 13, the position and size of the orientation flat 10, notch, etc. can be determined, and the positioning or ill-defective product can be detected. will be done.

Although the above embodiment uses a stepping motor, the same effect can be obtained by using a DC servo motor instead of the stepping motor and using an encoder that transmits the rotation angle of this motor as a pulse signal.

〔Effect of the invention〕

In this invention, while rotating the wafer as described above, the optical sensor is used to detect detection parts such as orientation flats and notches provided at the periphery of the wafer. It has a linear luminous flux, and a certain area on the outer periphery of the rotating wafer is irradiated with the luminous flux, so by monitoring the voltage output from the photoelectric element while rotating the wafer, the wafer can be measured. The shape of the outer peripheral edge of the wafer can be accurately recognized without touching the peripheral edge at all.

Therefore, 11. The wafer can be positioned by recognizing the orientation flat and notch of the wafer, but at this time, no error occurs even if the center of the circle around the wafer's outer periphery is slightly eccentric with respect to the center of rotation of the wafer.

Furthermore, since the shape of the outer periphery of the wafer can be recognized, it can be applied to the purpose of finding wafers with defects in the outer periphery and monitoring wafers that are not disc-shaped.

[Brief explanation of drawings]

Fig. 1 is a plan view of an apparatus for carrying out the present invention, Fig. 2 is a longitudinal sectional front view of the same as above, Fig. 3 is an enlarged plan view of the main parts, and Fig. 4 is a plan view showing the functions of I to ■. FIG. 5 is a plan view schematically showing an apparatus for carrying out the conventional method, and FIG. 6 is a plan view showing the same operation. 6... Elevator, 10... Orientation flat, 11... Turning means, 13... Stepping motor, 14...
・Suction table, 20... Floodlight, 21...
...Photoelectric element, 22... Luminous flux, 23...
...periphery. A... Light sensor.

Claims (1)

[Claims] (1) A turning means for turning a disk-shaped wafer that has a detecting part due to a shape change such as an orientation flat or a notch, and detecting the position of the detecting part on the outer periphery of the wafer being turned by this turning means. This optical sensor has a thin linear light beam with a constant length in the radial direction of the wafer, and a certain area on the outer periphery of the rotating wafer is irradiated with the light beam to detect the outer periphery of the wafer. A method for recognizing the outer shape of a wafer, which is characterized in that the shape of the outer periphery is recognized by changes in line segments while monitoring the amount of light received from moment to moment by the wafer, and the outer shape of the wafer is recognized using this data.