JPS63288654A - Method and device for grinding semiconductor wafer - Google Patents

Abstract

PURPOSE:To uniformize surface coarseness in a position in the vicinity of the center of a wafer with that in a position in the vicinity of the outer periphery of a wafer, by a method wherein a grinding stone is cut in the wafer with specified pressurization and the grinding streak in the wafer is formed in a concentric shape or approximately in a concentric shape by increasing the number of revolutions of the wafer over that of a grinding stone. CONSTITUTION:Since grinding resistance is normally specified by constant pressurization cutting, saddleform warp is prevented from occurring and grinding precision is excellent, and damage on a wafer 26 is low. By increasing the number of revolutions of the wafer 26 over that or the grinding stone 5 right before return backward movement of a grinding cycle, the grinding streak in the wafer 26 is formed in a concentric shape or approximately in a concentric shape. This method uniformizes surface coarseness of the wafer 26, resulting in prevention of the occurrence of unevenness in bending strength when the water produces chips, and improvement of bending strength.

Description

[Detailed description of the invention] The present invention is applicable to microcircuits such as transistors and diodes,
The present invention relates to a method and apparatus for grinding a semiconductor wafer, which is a substrate for manufacturing C.

The above semiconductor wafer has a diameter of 5 mm corresponding to the wafer.
It is made by slicing six single silicon rods made to a thickness of 0 to 150 square meters to a thickness of 625 to 725 μm using a diamond cutter. The thickness of the sliced wafer is then finished by grinding.

By the way, there are usually two methods for grinding a wafer: through-feed and wafer drive. In the former through-feed grinding method, a plurality of chuck tables are arranged around the circumference of a rotary table that rotates continuously, and a grindstone is placed on the rotation orbit of this chuck table. The wafer is chucked onto a chuck table using, for example, Baquième suction, and then ground using a grindstone.The latter wafer drive grinding method uses multiple chuck tables on an index table that rotates at a fixed angle intermittently. are arranged at the same circumference, and a grindstone is arranged at the index position of this chuck table, and as the index table rotates intermittently, the wafer chucked on the chuck table by, for example, a vacuum 't> is conveyed to the index position, At this index position, the wafer is rotated by a chuck table while being ground by a grindstone.

However, in the case of the above-mentioned through-feed grinding method, the grinding marks are unidirectional as shown in Figure 8, and the length of the grinding marks gradually changes as the wafer is transported. , the grinding resistance was not constant, and therefore the damage to the wafer was not constant, resulting in saddle-shaped warping, and the warping was large.In addition, in the case of the above wafer drive grinding method, the grinding streaks were as shown in Figure W49. As shown in the figure, the grinding resistance is constant from beginning to end, the warpage is small, and the grinding accuracy is good. There was a problem that the surface roughness was different between the center and the outer periphery of the wafer.In other words, when comparing the surface roughness near the center and the outer periphery of the wafer, there is a tendency for the outer periphery to be rougher. When cutting and dividing into 10s* IC or LSI chips, there was a drawback that there was a difference in the bending strength of the chips near the center of the wafer and near the outer periphery.Furthermore, since both grinding methods are mechanically forced cuts, The cutting operation is performed regardless of the sharpness of the whetstone, causing significant damage to the wafer and resulting in low bending strength when made into chips.

Therefore, an object of the present invention is to make the surface roughness near the center and the outer periphery of the wafer uniform, and to reduce damage to the wafer.

To achieve the above object, the present invention provides a method for grinding a wafer in a predetermined grinding cycle by rotating a wafer and a grindstone to make cuts on the grindstone. The semiconductor wafer is characterized in that the number of rotations of the wafer is made higher than the number of rotations of the grinding wheel immediately before the return and retreat of the grinding wheel, so that the grinding marks on the wafer are made into a concentric circular shape or a substantially concentric circular shape. Grinding method: A constant pressure cylinder set so that the thrust of the piston is constant is attached and fixed to the column, and a grindstone rotation shaft rotated by a grindstone drive motor is provided on the constant pressure cylinder, and the grindstone rotation main shaft is rotated by a grindstone drive motor. A grinding device for semiconductor wafers is provided, which is characterized by comprising a grindstone rad provided with a grindstone at its end, and a chuck table for rotating a wafer held on its upper surface by a wafer drive motor.

According to Tachigai's method, since the wafer is ground under constant pressure, damage to the wafer is small, and, moreover, the rotation speed of the wafer is set higher than that of the grinding wheel just before the grinding wheel returns to make the grinding marks on the wafer concentric. Since the wafers are circular or substantially concentric, the surface roughness of the wafer becomes uniform.

1.A An embodiment of the present invention will be described below with reference to FIGS. 1 to 7.

In Fig. 1, (1) is a grinding wheel head supported by a column (2) so that its tilt can be adjusted forward, backward, left, and right, and includes a constant pressure cylinder (3), a grinding wheel rotation main shaft (4), a grinding wheel (5), It consists of a grindstone drive motor (6).

The constant pressure cylinder (3) has a piston (8) slidably inserted through a cylinder tube (7) that is attached to the column (2) so as to be tiltable back and forth and left and right, and a pressure sensor is installed in the piston (8). (9) is installed nearby, and the pressure generating device (
10) to the fluid circuit consisting of piping and electromagnetic switching valves (
11) to the cylinder tube (7) to raise and lower the piston (8), and the thrust of the piston (8) is detected and fed back by the pressure sensor (9) so that the pressurizing force always becomes the set pressure. is being done.

The grindstone rotating main shaft (4) is rotatably supported through a piston (8) of a constant pressure cylinder (3) through a piston (8) of a constant pressure cylinder (3) at the top and bottom through a rolling bearing or a static pressure bearing (not shown). A grinding fluid supply channel (12) is bored.

A diamond grindstone is used as the grindstone (5), and is detachably attached to the lower end of the grindstone rotation main shaft (4). This grindstone (5) has a circular hole (13) in its center that connects with the grinding fluid supply path (12) of the grindstone rotating main shaft (4), and the grindstone grinds at equidistant positions on the circumference of this circular hole (13). A nozzle hole (14) is formed that opens slightly inside the inner diameter of the surface.

The above-mentioned grindstone drive motor (6) is integrally attached and fixed to the constant pressure cylinder (3), and the boo 9 (16) fixed to the output inner shaft (15) and the grindstone rotation main shaft (4) are splined. The fitted and fixed pulley (17) is connected to the bell l-(1
B) is connected to rotate the grindstone (5).

(19) is an index table disposed facing below the grinding wheel head (1), and includes a plurality of chuck tables (
20) are installed at equal positions on the circumference, and the drive v1a structure [
(not shown) intermittently rotates by a constant angle.

The rotating shaft (21) of the chuck table (20) is rotatably supported by the index table (19) via a rolling bearing or a static pressure bearing (not shown), and is driven by a pulley by a wafer rotation drive motor (22). (23),
(24) and pulley (25).

(26) is a wafer whose thickness is to be finished by grinding, and is held on the upper surface of the chuck table (20) by appropriate means, such as vacuum suction.

(27) is a sizing device that measures the thickness of the wafer (26), and includes two in-process gauges (28) (2
9), the probe is brought into contact with the ground surface of the wafer (26) and the chuck surface of the chuck table (20) to measure the surface position, and from the subtracted value of the measured values. The thickness of the wafer (26) is continuously measured during grinding, and the constant pressure cylinder (3)
, the rotation speed of the grindstone (5), and the rotation speed of the wafer (26).

Next, a semiconductor wafer grinding method according to the present invention in the above configuration will be explained.

First, the index table (19) is intermittently rotated by a certain angle, and the wafer (26) is held on the chuck table (20) by vacuum suction. The wafer (26) held on the chuck table (20) with the intermittent rotation of the index table (19)
When the grinding wheel (5) of the grinding wheel head (1) is conveyed directly below the grinding wheel head (1), the grinding wheel drive motor (6) moves the grinding wheel (5) of the grinding wheel head (1) to the pulley (16), belt (17), pulley (18), and grinding wheel rotation main shaft. (4), and the wafer (26) of the Chichak table (20) is rotated by the wafer rotation drive motor (22) through the pulley, (23), belt (24), pulley (25) and rotating shaft (21). ), and then the grinding fluid supply path (
12) and the nozzle hole (
Discharge the grinding fluid from 14). In this state, the constant pressure cylinder (3) of the grinding wheel head (1) moves the grinding wheel (5) up and down via the grinding wheel rotation main shaft (4), and the wafer (26) is moved by the grinding wheel (5), for example, as shown in FIG. Grinding is performed using the grinding cycle shown in A) of rough grinding → fine grinding → spark out → return and retreat, or the grinding cycle of rough grinding → fine grinding → return and retreat. During the grinding process, the pressure force of the constant pressure cylinder (3) is feedback-controlled by the pressure sensor (9) in order to keep the grinding resistance constant. At this time, the pressurizing force of the constant pressurizing cylinder (3) is variably controlled according to rough grinding, fine grinding, spark-out, and return retreat as shown in FIG. Further, as shown in FIG. 3, the rotational speed of the grindstone (5) and the wafer (26) is variably controlled according to rough grinding, fine grinding, spark-out, and return retreat. The characteristics of the grinding method of the present invention are, for example, in the case of the grinding cycle shown in FIG. 3(A), at the time of spark-out, and in the case of the grinding cycle shown in FIG. ) than the wafer (
By increasing the rotation speed of wafer (26),
6) The grinding marks are made concentric or approximately concentric as shown in FIG. When the grinding of the wafer (26) is completed, the index table (19) rotates by a certain angle, and as the index table (19) rotates intermittently, the wafer (26) in the grinding method is transported toward the unloading position. At the same time, an unground wafer (26) is transported directly below the grindstone head (1). after that,
The wafer (26) is continuously ground by repeating the above grinding cycle.

According to the above grinding method, the grinding resistance is constant from beginning to end due to constant pressure grinding, so saddle-shaped warping does not occur and the grinding accuracy is good.Moreover, damage to the wafer (26) is small, and the grinding cycle is Just before returning and retracting, grindstone (5)
The rotation speed of the wafer (26) is increased to increase the rotation speed of the wafer (26).
Since the grinding marks of 26) are made concentrically or approximately concentrically, the surface roughness of the wafer (26) becomes even and negative, and as a result, there is no variation in bending strength when it is made into chips.
Moreover, the bending strength was increased.

Figures 5 and 6 show the experimental results of the surface roughness near the center and around the outer periphery of wafers ground by the conventional wafer drive grinding method and the grinding method of the present invention. It can be seen that there is a difference in surface roughness near the center and near the outer periphery of a wafer ground by the grinding method of the present invention, whereas there is no difference in surface roughness near the center and near the outer periphery of a wafer ground by the grinding method of the present invention.

Figure 7 shows the experimental results of the chip bending strength of wafers ground by the conventional wafer drive grinding method and the grinding method of the present invention. It can be seen that there is no variation in the chip bending strength of wafers ground by the grinding method of the present invention, and the bending strength is significantly increased, compared to the case where the bending strength is low.

In the above embodiment, the grinding wheel (5) and the grinding wheel rotating main shaft (4) are arranged concentrically, but the grinding wheel head (1) can be oscillated by using an eccentric grinding wheel or without using an eccentric grinding wheel. If you let
Even if the grinding wheel (5) wears unevenly due to aging, the wafer (3)
6) The center part can be reliably ground. Further, although the above embodiments describe only the finish-ground portion, it goes without saying that the present invention can also be applied to the rough-ground portion.

Furthermore, it is applicable not only to the vertical type but also to the horizontal type.

Further, as explained above, according to the grinding method and apparatus of the present invention, it is possible to grind the wafer with uniform surface roughness and with less damage, thereby improving chip bending strength. Can be done.

In addition, the grindstone rotating main shaft, which has a grindstone attached to the shaft end, passes through the piston of the constant pressure cylinder and rotatably supports a rolling bearing or a static pressure bearing, so the grindstone head becomes smaller.
This allows the entire device to be manufactured compactly. Furthermore, since the grindstone head is tiltably supported by the column, it is possible to grind convex and concave surfaces. In addition, the grinding fluid nozzle holes are provided on the grinding wheel at several locations on the circumference slightly inside the inner diameter of the grinding surface of the grinding wheel, so that the grinding fluid can be efficiently supplied to the grinding part and good grinding can be performed.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a schematic configuration diagram showing a semiconductor wafer grinding apparatus of the present invention that implements the semiconductor wafer grinding method according to the present invention, and FIG. 2 is a sectional view of a grindstone used in the present invention. , FIG. 3 is a diagram showing the relationship between the grinding cycle, the pressure of the constant pressure cylinder, the rotation speed of the grindstone, and the rotation speed of the wafer, and FIG. 5 and 6 are diagrams showing the experimental results of surface roughness near the center and around the outer periphery of wafers ground by the conventional wafer drive grinding method and the grinding method of the present invention, and FIG. 7 is a diagram showing the marks. is a diagram showing the experimental results of the chip bending strength of wafers ground by the conventional wafer drive grinding method and the grinding method of the present invention, and FIGS. 2 is a drawing showing grinding marks on a wafer. (1) - Grinding wheel head, (2) - Column, (3) - Constant pressure cylinder, (4) - Grinding wheel rotation spindle, (5L - Grinding wheel, (6) -... - Grinding wheel drive motor, (7) - Cylinder tube, (8) - Piston, (9) - Pressure sensor, (14) - Nozzle hole, (19) - Index table, (20) -・Chuck table, (22)・−・−・Wafer rotation drive motor, (26)
・−・Wafer, (27) −・Sizing device. [Figure 1

Claims (7)

[Claims] (1) In the method of grinding the wafer in a predetermined grinding cycle by rotating the wafer and the grinding wheel and making cuts on the grinding wheel, the grinding wheel is made to cut with constant pressure, and the wafer is cut just before the grinding wheel returns and retreats. A method for grinding a semiconductor wafer, the method comprising making grinding marks on the wafer concentric or substantially circular by making the rotation speed higher than that of a grindstone. (2) A constant pressure cylinder set so that the thrust of the piston is constant is attached and fixed to the column, and a grindstone rotating shaft rotated by a grindstone drive motor is provided on the constant pressure cylinder,
A semiconductor wafer grinding device comprising: a grindstone head having a grindstone provided at the end of the grindstone rotating main shaft; and a chuck table on which a wafer held on the upper surface is rotated by a wafer drive motor. (3) A semiconductor wafer grinding apparatus according to claim 2, wherein the pressing force of the constant pressure cylinder, the rotation speed of the grindstone, and the rotation speed of the wafer are variably controlled according to the grinding cycle. . (4) The semiconductor wafer grinding apparatus as set forth in Claims 2 and 3, wherein the constant pressure cylinder is mounted and fixed to a column so that it can be tilted back and forth and left and right. (5) The semiconductor wafer according to claims 2 to 4, wherein the grindstone rotating main shaft is rotatably supported in a constant pressure cylinder via a rolling bearing or a static pressure bearing. Grinding equipment. (6) The semiconductor wafer grinding apparatus according to any one of claims 2 to 5, characterized in that a grinding fluid supply path is provided in the axial center of the grindstone rotating main shaft. (7) The semiconductor wafer according to claims 2 to 6, wherein the grindstone is provided with nozzle holes for the grinding fluid at several locations on the circumference slightly inside the inner diameter of the grinding surface of the grindstone. Grinding equipment.