JPS59165432A - Device for aligning direction of wafers - Google Patents

Abstract

PURPOSE:To improve the yield by preventing generation of minute damages on the circumferential end portion of a wafer by keeping the wafer from touching something but a holding means during the alignment operation. CONSTITUTION:A wafer 10 is attracted by an attracting plate 9 and an elevating device 3 raises a base plate 4 to keep it away from a conveyer 15. A pulse generating circuit 14-1 of a rotation controlling part 14 sends the pulses to a pulse motor 5 to rotate the wafer 10 together with the attracting plate 9 in clockwise direction. When a front end (a) of orientation flat (OF) of the wafer 10 comes on (O) just right above a light-conducting tube 11-1 of a photosensor 11, the reflected light from the wafer surface ceases and the output of the senser 11 also ceases. A pulse counter 14-3 counts number of the pulse while there is no output from the senser 11, namely the pulse for the angle theta1. OF is rotated from the position PO only by the number of pulses corresponding to the angle of theta2-1/2theta1 in clockwise direction by the pulse motor 5, thereby aligning OF in a predetermined direction Q.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic transfer device used for wafer processing in a semiconductor manufacturing process, and relates to a wafer direction alignment device for aligning the crystal orientation of a wafer in an arbitrary direction at a specific position within a transfer path. be. Silicon single crystal wafers used as element substrates for semiconductor integrated circuits, etc.
In order to identify the crystal direction, a part of the outer periphery of the disk in a direction having a certain relationship with the crystal direction is notched in a straight line to form an orientation 7 laser. This orientation flat is used to align the crystal directions during multi-step wafer processing.

Conventionally, when performing such an alignment operation, a method using a plurality of rollers arranged along the outer circumference of the wafer has been common. In this method, the outer peripheral end surface of the wafer is brought into contact with a plurality of freely rotatable rollers using spring pressure or the like, and among the plurality of rollers, only one roller provided at a position where the orientation flats are aligned is used as a driving roller. Rotate. When the outer periphery of the wafer comes into contact with such a group of rollers and a constant contact pressure is applied by spring pressure or the like, the wafer is rotated by the one drive roller. At this time, when the orientation flat portion of the wafer rotates near the drive roller, the orientation flat portion of the wafer separates from the drive roller, and the rotation of the wafer stops. In this way, all the wafer orientations 7 can be aligned at the position of only one drive roller.

However, in this conventional method, the outer peripheral end surface of the wafer is in pressure contact with each roller, and the wafer is rotated using the frictional force between the drive roller and the wafer. Problems include damage and contamination caused by dust. This problem occurs when the next process for the wafer is an epitaxial film production process, and the above-mentioned microscopic damage and contamination may cause crystal defects in the produced film, or trace impurities in the dust may vaporize due to high-temperature heating. It diffuses into the produced film, making it difficult to control the resistivity, and becomes a major cause of a decrease in yield. Further, in this method, the accuracy of the stop position is poor, and furthermore, since the stop position is determined by the position of the drive roller, it is difficult to align the rollers in any direction.

The present invention has been developed to solve these problems, and provides a wafer direction alignment device that allows wafers to be aligned in any direction without making movable contact with other objects during the alignment operation. It is.

This will be explained in detail below with reference to the drawings. 1 shows the configuration of the main parts of the wafer direction alignment apparatus of the present invention. This alignment device is fixed on the base 1 of the automatic conveyance device in which it is installed. Lifting devices 3 are provided on three or four legs 2 on a base 1, and a moving plate 4 is fixed on top of these lifting devices 3. Furthermore, this leg 2
The order of the and lifting device 3 is reversed, and the base 1, lifting device 3,
The legs 2 and the board 4 may also be used. A pulse motor 5 is provided on the lower surface of the substrate 4, and a shaft 6 of this motor passes through the substrate 4 and extends vertically upward. A bearing portion 7 through which the shaft 6 passes is provided on the upper surface of the substrate 4, and a portion of the shaft 6 above the bearing portion 7, 6', is hollow. Furthermore, the bearing part 7 is provided with an exhaust pipe 8 so that the pressure in the hollow part of the shaft 6' inside the bearing part 7 can be reduced. At the upper end of the shaft 6' is a suction plate 9 that performs vacuum suction as a wafer holding means.
is provided perpendicularly to the axis 6' so that the top surface is horizontal.

Reference numeral 10 indicates a wafer adsorbed on the adsorption plate 9, and an oto sensor 1 7 is placed at a position that emits light on the inner side of the outer peripheral edge.
1 is provided on the substrate 4. Light is guided to this photosensor 11 up to the vicinity of the wafer 10 by a light guide tube 11-1 to prevent malfunction. These 2 to 9 and 11 constitute a rotation stage. Reference numeral 12 denotes a control unit, which includes a stop position setting unit 13 that specifies the direction in which the orientation flats are aligned, and a rotation control unit 14. a generation circuit 14-1 and a dart circuit 14-2 that supplies this output pulse to the pulse motor 5.
and a pulse counter circuit 14-3 that measures the number of pulses required to rotate the wafer by the orientation flat width from the detection outputs of the start and end ends of the orientation flat of the rotating wafer detected by the photosensor 11; Instructing the dirt circuit 14-2 the number of pulses necessary to rotate the way to the alignment direction specified by the stop position setting unit 13.
and a virus control circuit 14-4.

Note that 15 is Ueno 10 up to just above the rotation stage.
The belt conveyor -116 that conveys the is a stopper.

FIG. 2 shows a suction plate 9, a wafer 10, a photosensor 11,
FIG. 3 is a plan view of a portion of the alignment device showing the mutual positions of the belt conveyor 15 and the stopper f-16.

Next, the operation of the wafer direction alignment apparatus of the present invention will be explained. When the wafer 10 is carried by the belt conveyor 15, the wafer 10 comes into contact with the stopper 16 and stops. At this stop position, the inner surface forms a part of a cone so that the center of the wafer 10 is on the center line of the suction plate 9, and the aperture is set at an opening angle (inclined ) The position of the stopper 16 is adjusted. The surface that the stopper 16 comes into contact with has an upward slope, so when the wafer 10 is lifted as will be described later, the wafer 1
0 is set to move away from the ST2 F-16. When the wafer 10 comes into contact with the stopper or -16, the pressure is reduced in the hollow part of the shaft 6' through the exhaust pipe 8 and the bearing part 7 according to instructions from a control device (not shown), and the wafer 10 is moved to the suction plate 9.
At the same time, hydraulic or pneumatic pressure is applied to the lifting device 3 to attach the suction plates 9, A? of the alignment device. A substrate 4 on which a pulse motor 5 and a photosensor 11 are provided is placed on a wafer 1.
0 is raised by a distance away from the belt conveyor 15, and an operation command is issued to the rotation control unit 14.

The orientation flat of the wafer 10 when it is transferred onto the wafer direction alignment device faces an unspecified direction. In the operation explanatory diagram shown in Fig. 6, this direction is a
It is indicated by b. Therefore, at this time, since the periphery of the wafer 10 exists above the light guide tube 11-1 of the photosensor 11, the light from the light projector provided inside the photosensor 11 is reflected by the wafer 10. The photo sensor 11 enters a light receiver also provided inside and provides an output to the rotation control section 14.

On the other hand, the rotation control unit 14 applies a pulse to the pulse motor 5 from the pulse generation circuit 14-1 through the gate circuit 14-2, and rotates the wafer 10 attracted to the attraction plate 9 in a clockwise direction. When the front end a of the orientation flat of the wafer 10 comes to the position 0 directly above the light guide tube 11-1 of the seven photosensor 11, there is no reflected light from the wafer surface, and the output of the photosensor 11 disappears. The wafer 10 is further rotated and the front end a of the orientation flat is
When the rear end reaches the position P and the rear end reaches the position O, the reflected light appears again and the output of the photosensor 11 appears. During this time, the pulses from the pulse generating circuit 14-1 are input to the pulse counter circuit 14-3 as well as to the pulse motor 5, so the number of pulses is counted while the photosensor 11 is not outputting. That is, the number of pulses is counted for the angle θ1 connecting both ends of orientation flat ab and the center of way 10.

On the other hand, if the alignment direction Q of the orientation flat is set in advance from the stop position setting unit 13, the pulse motor 5 adjusts the central angle θ2 from the point O of the light guide tube 11-1 of the photosensor 11 to the specified position Q. Since the angle of rotation required for rotation is determined, the point at which the rear end of the orientation flat passes the 0 point, that is, the orientation flat is at an angle θ2 - %θ1 from the PO position.
Rotate the pulse motor 5 clockwise by the number of pulses corresponding to When rotated clockwise, the orientation plate can be aligned in the set direction Q. The pulse control circuit 14-4 controls the number of these pulses.

Also, when Ueno 10 is transferred onto the alignment device, the orientation flat happens to be the photo sensor 11.
If it is on the top, the orientation flat can be aligned in the setting direction Q by the above operation after being rotated in a groove where the orientation flat part is no longer on the photosensor 11.

Furthermore, as shown in Fig. 4, for a way in which there is a sub-orientation flat 18 (which is always shorter than the main orientation flat 17), rotate the Wayno 10 in the position setting operation box and set the orientation flat. Locate the primary or secondary orientation flat 18 by counting the length;
Thereafter, by performing the position setting operation described above, the orientation flat of the wafer 10 can be aligned in the setting direction Q.

The waeno 10 with the orientation flats aligned in the setting direction Q in this manner is transported to the next process with the orientation flats kept in the same direction by another transport means (not shown). Although the photosensor 11 is of a reflective type in this embodiment, it may be of a transmissive type with a light projecting section and a light receiving section arranged on both sides of the sensor. Further, although a vacuum suction plate 9 is used as a holding means for the Waeno 10 in this embodiment, other means such as an electrostatic chuck may be used.

As described above, in the wafer direction alignment apparatus of the present invention, during the alignment operation, the wafer 10 is not in contact with any other object other than being held by the holding means, which is a major cause of a decrease in wafer yield. Crystal defects such as 'slip' caused by minute damage to the outer peripheral end face of the wafer 10, contamination by dust contained as a result, or micro damage to the outer peripheral end face do not occur. In addition, the accuracy of the stop position is high due to the optical passage detection of the orientation flat and the determination of the rotation angle by the number of pulses, and the stop position can be easily specified, so the practical effect is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of the wafer direction alignment apparatus of the present invention. FIG. 2 is a plan view of a portion of the wafer direction alignment device when the wafer 10 is attracted. FIG. 6 is an explanatory diagram of the alignment operation. FIG. 4 is a plan view of a wafer with major and minor orientation flats. In the figure, 3 is a lifting device, 5 is a pulse motor, 9 is a suction plate, 10 is a wafer, 11 is a photosensor, 13 is a stop position setting section, and 14 is a rotation control section, among which 14-1
is a pulse generation circuit, 14-2 is a gate circuit, 14-3
14-4 is a pulse control circuit, and 14-4 is a pulse control circuit. Figure 2 10

Claims (1)

[Claims] 1. A wafer having a notched orientation flat on its outer periphery is transported along a horizontal plane with the orientation flat facing in an unspecified direction, on the transport path of an automatic transport device. Wafer Orientation A wafer that aligns the direction of the flat in a certain direction.
The direction alignment device includes a rotation stage provided directly below the end point of the conveyance path, and a control unit that controls the operation of the rotation stage, and the rotation stage
holding means for holding the wafer in a horizontal state on its upper surface; rotating means provided below the holding means for rotating the holding means for the wafer on a vertical axis; A non-contact detection means is provided at a peripheral position to detect an orientation flat that the wafer passes through as it rotates, and a wafer is rotated from above the transfer surface of the automatic transfer device to hold and rotate the wafer. The control section may be a lifting device that raises the holding means, the rotation means and the non-contact detection means as a unit by a possible distance, and the control section controls the stopping position of the rotating wafer in order to determine the direction in which the orientation flats are aligned. The number of pulses applied to the rotation means during the time period during which the designated stop position setting unit and the cutout circumferential portion corresponding to the length of the orientation flat passed by the rotation of the wafer pass the non-contact detection means. is calculated using the presence or absence of a detection signal of the non-contact detection means, and from this calculation result and the number of pulses given to the rotation means to rotate the orientation flat from the position of the non-contact detection means to the specified stop position. , the wafer direction alignment is similar to a rotation control unit that rotates the rotation means by calculating the number of lugs required for the central portion of the orientation flat to stop at the designated stop position; Device. 2. The wafer direction alignment apparatus according to claim 1, wherein the wafer holding means is a vacuum suction plate. 3. The wafer direction alignment apparatus according to claim 1, wherein the wafer holding means is an electrostatic chuck. 4. The wafer direction alignment device according to claim 1, wherein the non-contact detection means for detecting passage of the orientation flat is a photosensor that uses reflected light. 5. The wafer direction alignment apparatus according to claim 1, wherein the non-contact detection means for detecting passage of the orientation 7 laser is a photosensor that uses transmitted light. 6. In the wafer direction alignment apparatus according to claim 1, the rotation control section generates a /F pulse with a constant frequency. The number of pulses required to rotate the wafer by the orientation flat width is determined from the detection outputs of the starting and ending ends of the orientation flat of the rotating wafer detected by the gate circuit that supplies the pulse motor and the non-contact detection means. a pulse counter circuit for the eaves side, and a pulse control circuit that calculates the number of pulses necessary to rotate the wafer to the alignment direction specified by the stop position setting section and instructs the gate circuit. The wafer direction alignment apparatus.