A method of manufacturing wafers of semiconductor material incorporates the steps of: providing an elongated ingot of semiconductor material having a curved surface along the direction of elongation; mounting a structure for ingot mounting on each of the end surfaces of the ingot; positioning the ingot mounting structures on fixture structures to mount the ingot; and rotating the mounted ingot. The positioned ingot mounting structures are released and the ingot is removed from the fixture structures; however, during the course of the process the mounting structures are again positioned on fixture structures to mount the ingot and the ingot is rotated a second time. The method is adapted for accurate centering of the ingot during processing involving the sawing of the ingot to provide opposed elongated planes therealong (including rotation of the ingot in accomplishing such) and involving further rotation of the ingot during grinding. The ingot mounting structures are centered on the basis of crystallographic node lines that appear on the grown ingot. The mounting structures have spherical surface portions for accuracy in centering the ingot in fixtures having conical surface portions to abut the spherical surfaces in mounting the ingot.
A drum-shaped workpiece (37) is machined according to a method whereby the workpiece (37) is fastened to a rotatable holder (1) of a machine tool (3) by means of an adhesive (45), for example a mixture including rosin and beeswax, such that a centerline (51) of the workpiece (37) coincides substantially with an axis of rotation (19) of the holder (1). This adhesive (45) is exclusively provided between the holder (1) and support surfaces (47, 49) of the workpiece (37) directed substantially parallel to the centerline (51), the workpiece (37) being brought into connection with the holder (1) exclusively via the adhesive (45). It is achieved thereby that mechanical stresses in the workpiece (37) caused by the fastening of the workpiece (37) to the holder (1) are as small as possible. A dimensional accuracy which the workpiece (37) has after being machined by the machine tool (3) and before being removed from the holder (1) thus remains intact when the workpiece (37) is removed from the holder (1). A drum-shaped carrier (83) manufactured by the method is used as a carrier of a selenium layer (101) in an X-ray diagnosis apparatus (85). A further drum-shaped carrier (107) manufactured by the method is used as a carrier for a selenium layer (129) in a photocopier (109).
The diameter, the orientation flat width/notch depth and the length of the block 10p are measured by the measuring devices 71a, 71b and 71c respectively and then the machining errors .DELTA.Dp, .DELTA.Wp and .DELTA.Lp in the measured values against the set values are calculated at the error calculation unit 833. Then .DELTA.Dp, .DELTA.Wp and .DELTA.Lp are stored in memory at the memory unit 834 in correspondence with the identification codes IDi and IDj of the grinding device 5i (i=1-N) and the cutting device 6j (j=1-M) that performed the machining. Then at the average value calculation unit 835, the average values of .DELTA.Dp and .DELTA.Wp for each of the grinding devices 51-5N and the average value of the .DELTA.Lp for each of the cutting devices 61-6M are calculated. The average values of .DELTA.Dp and .DELTA.Wp are supplied to the corresponding grinding device 5i as the diameter correction value and the width/depth correction value respectively and the average value of .DELTA.Lp is sent to the corresponding cutting device 6j as the length correction value from the transmission unit 836.
The cutting process is executed after the grinding process and for one semiconductor ingot, one grinding device and one inner diameter saw slicing machine are used to perform grinding process and cutting process respectively. During the grinding process, the entirety of the cylindrical body portion of the semiconductor ingot is cylindrically ground, a portion of the tail end is cylindrically ground, the orientation flat position is determined and an orientation flat is formed by surface grinding. During the cutting process the tail portion is cut off and a sample for lifetime measurement is taken and a wafer sample is cut off from the end of the cylindrical body portion on the tail side. The semiconductor ingot is reversed in the direction of the axis and the head portion of the semiconductor ingot is cut off and a wafer sample is cut off from the cylindrical body portion on the head side. Wafer samples are cut off from the end of the cylindrical body portion on the head side and from the middle portion of cylindrical body portion to divide the cylindrical body portion into two blocks.
Silicon wafers oriented in the (100) crystal planes are sawed from a silicon ingot using the (111) faces on the as drawn silicon ingot as reference planes. The reference planes permit determination of the ingot orientation during the sawing process.
A method and apparatus for controlling a mounting pressure for semiconductor ingots provide appropriate mounting pressure so that a high quality bond is formed between a semiconductor ingot and a mounting beam. The pressure between the semiconductor ingot and the mounting beam can be directly determined, but other indications representative of the pressure can be also used to control the mounting pressure.
