JPH03280447A - Detection of substrate - Google Patents

Abstract

PURPOSE:To detect correctly a substrate and to make it possible to reduce the generation of the erroneous operation of a device by a method wherein a substrate is irradiated with a light beam in such a way that the light beam intersect obliquely the substrate to detect the substrate, and when the result of the detection of the substrate is unclear, the incident angle of the light beam is modified and the substrate is again detected. CONSTITUTION:A cassette placing stage 13 is moved in such a way as to pass through between a light-emitting element 15 and a photodetector 16 and a scanning for detecting semiconductor wafers 11 is performed. Information obtained by the above scanning is stored in a memory or the like and a carrying-in and a carrying-out of the wafers 11 are carried out according to this information. for example, in the case of a semiconductor wafer 11a of a small diameter, as the wafer 11a can not be detected between the positions (a) and (b) of a light beam 14 in the state as the angle of the light beam is (theta), a support member 17 is rotated at a prescribed angle and the angle which is made by the beam 14 with the surface of the wafer 11a is modified from the (theta) to (theta1) according to the diameter of the wafer 11a. When the incident angle of the beam 14 is modified according to a wafer diameter, the wafers 11 can be detected at the optimum beam angle to the wafers 11 of all diameters.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a method for detecting the presence or absence of a substrate.

(Prior Art) As is well known, in semiconductor manufacturing processes, substrates such as semiconductor substrates (semiconductor wafers) have traditionally been transported using cassettes made of resin or the like and configured to accommodate a plurality of semiconductor wafers, for example, about 25 semiconductor wafers. (wafer cassette). In addition, in such semiconductor manufacturing processes, unmanned systems are being attempted for the sake of cleanliness, etc., and various processes are being automated.

Therefore, in semiconductor manufacturing equipment, such as ion implantation equipment, probe equipment, etching equipment, and film deposition equipment,
Many devices are equipped with a substrate loading and unloading device for loading and unloading semiconductor wafers into the wafer 1 cassette, and are configured to automatically load and unload the semiconductor wafers and execute processing without human intervention.

Generally, in such a substrate loading/unloading device, the wafer cassette is placed vertically so that the semiconductor wafer is almost horizontal, and the lower surface (the surface on which no elements are formed) of the semiconductor wafer is supported by a wafer handling arm or the like. It is configured to carry out removal.

Further, the substrate loading/unloading device is provided with a substrate presence/absence detection mechanism that detects the presence or absence of a semiconductor wafer in the wafer cassette.

Conventionally, such a substrate presence/absence detection mechanism generally consists of a light emitting element that irradiates a light beam and a light receiving element that is provided to face the light emitting element with the wafer cassette in between. is fixed so that the light beam forms a predetermined angle with the semiconductor wafer surface. The device is configured to recognize that a semiconductor wafer exists if the light beam is not detected by the light receiving element, and to recognize that the semiconductor wafer does not exist if the light beam is detected.

In addition, a mechanism for moving the wafer cassette, light emitting element and light receiving element up and down relative to each other, such as a mechanism for vertically moving the light emitting element and the light receiving element or a mechanism for vertically moving the wafer cassette, is provided. With this mechanism, before starting loading/unloading of semiconductor wafers, scanning is performed to recognize in advance where the semiconductor wafer is located in the wafer cassette, and then the wafer handling arm etc. It is configured to start loading/unloading.

Note that the substrate loading/unloading device is generally configured to be able to handle semiconductor wafers of different diameters, such as 4 inches, 6 inches, and 8 inches, for example.

(Problem to be solved by the invention! fi) However, in the above-mentioned substrate loading/unloading device, when a semiconductor wafer is ejected from a wafer cassette due to vibration or the like and is displaced from a predetermined position, reflections from the upper and lower semiconductor wafers Due to the influence of light (semiconductor wafer surfaces are considered to be mirror surfaces), erroneous detections may occur and normal loading and unloading may not be possible.

The present invention has been made in response to such conventional circumstances, and is a method for detecting the presence or absence of a board, which can accurately detect the presence or absence of a board, and can significantly reduce the possibility of malfunctions compared to the conventional method. This is what we are trying to provide.

[Structure of the Invention] (Means for Solving the Problems) That is, the present invention detects the presence or absence of a plurality of substrates housed at predetermined intervals by irradiating the substrates with a light beam in an oblique manner. However, when detecting from the transmitted light or reflected light, at least means for detecting by changing the incident angle of the light beam on the substrate surface when the presence or absence of the substrate is unknown. It is characterized by

(Function) In the substrate presence/absence detection method of the present invention, the angle between the light beam and the substrate surface is optimally set. Therefore, the presence or absence of a board can be accurately detected, and the possibility of malfunctions occurring can be significantly reduced compared to the prior art.

(Example) Hereinafter, an example in which the method of the present invention is applied to a substrate loading/unloading device for loading/unloading semiconductor wafers will be described with reference to the drawings.

As shown in FIGS. 1 and 2, the substrate loading/unloading device of this embodiment is provided with a cassette mounting table 13 on which a wafer cassette 12 configured to accommodate a plurality of semiconductor wafers 11 is placed. It is being

Although the cassette mounting table 13 is configured to be movable up and down by a drive mechanism (not shown), the cassette mounting table 13 is fixed and a light emitting element 15 and a light receiving element 1 which will be described later
6 may be moved up and down. However, if the cassette mounting table 13 is fixed, it is necessary to configure the wafer handling arm and the like for loading and unloading the semiconductor wafers 11 into and out of the wafer cassette 12 to move up and down.

Further, as a mechanism for detecting the presence or absence of the semiconductor wafer 11 in the wafer cassette 12, the following substrate detection mechanism is provided.

That is, a light emitting element 15 that emits the light beam 14 and a light receiving element 16 are provided, sandwiching the wafer cassette 12 therebetween. The light-emitting element 15 and the light-receiving element 16 are provided at opposite ends of a support member 17 formed in the shape of a trowel so as to face each other with the light-emitting element 15 facing inward.
The light beam 14 emitted from the light receiving element 16 is fixed with its optical axis aligned so that it enters the light receiving element 16.

Further, the support member 17 is supported by a frame (not shown) by a rotating shaft 18 provided at an intermediate portion thereof, and is rotated at a predetermined angle by a motor (not shown) about this rotating shaft 18 as shown by an arrow in FIG. , for example, is configured to be rotatable by several degrees to several degrees. That is, by rotating the support member 17 about the rotation axis 18, an angle adjustment mechanism is constructed that can adjust the angle θ between the surface of the semiconductor wafer 11 and the front beam 14.

Note that, similar to the conventional substrate loading/unloading device, a wafer handling arm (not shown) or the like is provided on the side of the cassette mounting table 13 for loading/unloading the semiconductor wafer 11 into/out of the wafer cassette 12.

The substrate loading/unloading device of this embodiment having the above configuration is installed in a semiconductor manufacturing device such as an ion implantation device, a probe device, an etching device, a film forming device, etc. It is used as a mechanism to automatically load and unload files. At this time, the semiconductor wafer 11 is handled by a wafer handling arm, etc.
Before starting loading/unloading, the cassette mounting table 13 moves between the light emitting element 15 and the light receiving element 16 by raising or lowering the cassette mounting table 13 while the light beam 14 is irradiated from the light emitting element 15. The semiconductor wafer 111 is moved to pass, and scanning is performed to detect the presence or absence of the semiconductor wafer 111. That is, the semiconductor wafer is placed inside the cassette mounting table 13.
11 exists, the light beam 14 emitted from the light emitting element 15 is blocked by this semiconductor urchin /\11,
Since the light beam 14 is no longer incident on the light receiving element 16, the presence or absence of the semiconductor wafer 11 is detected depending on whether the light beam 14 is detected by the light receiving element 16.

The information obtained by the scanning is stored in a memory or the like, and the semiconductor wafer 11 is loaded or unloaded by a wafer handling arm or the like according to this information. For example, when unloading the semiconductor wafer \11 from the wafer cassette 12, the unloading operation of the semiconductor wafer \11 is performed using the wafer \no\ holding arm or the like only from the portion where the semiconductor wafer \11 is recognized as being present.

Further, as shown in FIG. 3, when handling a semiconductor wafer lla with a small diameter, for example, the support member 17 is rotated by a predetermined angle, and the surface of the semiconductor wafer lla and the light beam 14 are rotated according to the diameter of the semiconductor wafer 11a. θ to θ
Change to 1.

In this way, by changing the incident angle of the light beam 14 depending on the diameter of the semiconductor wafer, it is possible to detect the presence or absence of the semiconductor wafer 11 of any diameter at the optimum beam angle. That is, for example, as shown in FIG. 4, if detection is performed on a semiconductor wafer 11a with a small diameter while the angle of the light beam 14 remains θ, the position a of the first beam 14 will be
The semiconductor wafer lla cannot be detected between -b, and the semiconductor wafer lla is detected only between the positions b and c of the light beam 14. For this reason, the detection accuracy becomes worse than when the angle of the light beam 14 is set to 01, and if the position of the semiconductor wafer 11a is shifted, for example, there is a possibility that erroneous detection will occur.

In addition, in order to increase detection accuracy, when performing detection scanning, the scanning speed (cassette mounting table
It becomes necessary to slow down the lifting speed (elevating speed (elevating speed (elevating and lowering speed) in step 3), resulting in a decrease in throughput.

The optimal beam angle is determined by the positional relationship such as the semiconductor wafer diameter and wafer pitch (the distance between semiconductor wafers), so if you input the semiconductor wafer diameter, the optimal beam angle will be automatically set. In this way, it is also possible to control a motor or the like that rotates the support member 17. Further, the support member 17 may be rotated manually instead of using a motor or the like.

In other words, the substrate loading/unloading device of this embodiment can accurately detect the presence or absence of semiconductor wafers with a valley diameter at the optimal beam angle, and the possibility of malfunctions is significantly reduced compared to the conventional method. can do. Particularly when it is difficult to detect the presence or absence of a semiconductor wafer that has been moved during transport of a wafer cassette, changing the incident angle of the light beam described above has the effect of enabling accurate detection.

[Effects of the Invention] As explained above, according to the method for detecting the presence or absence of a board of the present invention, the presence or absence of a board can be detected more accurately than before, and the possibility of malfunctions can be significantly reduced compared to the past. can be reduced.

[Brief explanation of the drawing]

1 and 2 are diagrams showing the configuration of a substrate detection mechanism of a substrate loading/unloading device according to an embodiment of the present invention, FIG. 3 is a diagram for explaining a method of setting the light beam angle, and FIG. FIG. 6 is a diagram for explaining a detection state when the light beam angle is fixed. 11... Semiconductor wafer, 12... Wafer cassette, 13... Cassette mounting stand, 14...
... Light beam, 15 ... Light emitting element, 16
...... Light receiving element, 17... Supporting member, 1
8...Rotation axis.

Claims (1)

[Claims] (1) When detecting the presence or absence of a plurality of substrates housed at predetermined intervals by irradiating the substrates with a light beam obliquely and using the transmitted light or reflected light, at least the above-mentioned A method for detecting the presence or absence of a substrate, comprising means for detecting the presence or absence of a substrate by changing an incident angle of the light beam onto the substrate surface when the judgment of the presence or absence of the substrate is unclear.