JP3359468B2 - Semiconductor wafer grinding method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for grinding a semiconductor wafer, and more particularly to a semiconductor wafer grinding technique for grinding one side of a semiconductor wafer.

[0002]

2. Description of the Related Art Grinding the front and back surfaces of a semiconductor wafer is effective in increasing its flatness. Therefore, it has been considered to improve the flatness of the semiconductor wafer by grinding. Conventionally, the grinding method of a semiconductor wafer is
One side of the wrapped semiconductor wafer was ground. This is because if grinding is performed after slicing without wrapping, the saw mark cannot be removed. Omitting the lapping step leads to a reduction in the manufacturing cost of the semiconductor wafer.

[0003] A grinding method that does not require the wrap is known. This grinding method, as shown in FIG.
The semiconductor wafer is fixed on a grinding table using a freezing chuck, and one side of the fixed semiconductor wafer is ground. According to this method, the saw mark can be removed by slicing without wrapping.

[0004]

However, even in such a grinding method using a frozen chuck, the following two methods are required.
Had two disadvantages. First, as shown in FIG. 6, when water W is dropped on the grinding table T and the semiconductor wafer WF is placed thereon, the surface of the water is gently curved at a predetermined curvature due to the surface tension, or The frozen wafer WF tilts. As a result, the wafer itself is fixed in a warped state or an inclined state due to the curved surface, and is ground. Second, as shown in FIG. 7, when air or the like is contained in water, the bubbles B expand due to freezing and curve a part of the fixed wafer. As a result, dimples D are formed on a part of the ground wafer.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for fixing a whole and a part of a semiconductor wafer without curving or tilting. It is another object of the present invention to provide a fixing method that does not cause dimples on a ground wafer.

[0006]

According to a first aspect of the present invention, there is provided a semiconductor wafer grinding method for fixing a sliced semiconductor wafer to a grinding table with a freezing chuck and grinding the surface of the semiconductor wafer. The fixing with the chuck is a method of grinding a semiconductor wafer by freezing water containing a surfactant in an amount of 20 to 60% by volume. As the surfactant, those containing potassium stearate / sodium stearate / ammonium stearate / potassium octylate / sodium octylate / ammonium octylate / potassium laurate / sodium laurate / ammonium laurate are suitable.

According to a second aspect of the present invention, the fixing is performed by
The method for grinding a semiconductor wafer according to claim 1, wherein the water is deaerated and then frozen .

[0008] The invention according to claim 3 is characterized in that the sliced
The semiconductor wafer is fixed to the grinding table with a freezing chuck, and this
Grinding the surface of a semiconductor wafer
In the method, fixing with the above-mentioned freezing chuck degass water
This is a method of grinding a semiconductor wafer, which is performed by freezing after processing .

According to a fourth aspect of the present invention, there is provided a wafer fixing table on which a semiconductor wafer is mounted, and water interposed between the mounted semiconductor wafer and the wafer fixing table to freeze the semiconductor and freeze the semiconductor. A freezing chuck for fixing the wafer;
A semiconductor wafer grinding apparatus comprising: a grinding means for grinding one side of a fixed semiconductor wafer; and a degassing means for degassing the water when the water is frozen.

[0010]

According to the first aspect of the invention, the sliced semiconductor wafer is fixed to the grinding table with a freezing chuck. That is, water containing only 20 to 60% by volume of a surfactant is dropped and supplied onto a grinding table, and a semiconductor wafer is mounted thereon. And freeze this water. As a result, the semiconductor wafer is fixed on the grinding table in a flat state. In particular, when the content of the surfactant is 40% by volume, it is more effective in reducing the surface tension. Further, one side of the fixed semiconductor wafer is ground using a grinding blade.

According to the second aspect of the present invention, the water containing only 20 to 60% by volume of the surfactant is subjected to degassing, and thereafter, it is frozen. As a result, the semiconductor wafer is fixed in a flat state. Then, the surface of the semiconductor wafer is ground. As the deaeration treatment, various methods such as boiling water can be employed.

According to the third aspect of the present invention, the sliced semiconductor wafer is fixed to a grinding table with a freezing chuck. Fixing with this freezer chuck degassed water
Freeze later . As a result, the semiconductor wafer is fixed in a flat state. Then, one side of the fixed wafer is ground. Therefore, the surface of the semiconductor wafer can be flattened, and the saw mark can be removed.

According to the invention described in claim 4, water is supplied onto the wafer fixing table, and the semiconductor wafer is mounted thereon. This water has been degassed. In this state, the semiconductor wafer is fixed on the wafer fixing table by freezing the water. As a result, the semiconductor wafer is fixed in a flat state (parallel to the surface of the wafer fixing table).
Then, one side of the fixed wafer is ground. Therefore, the surface of the semiconductor wafer can be flattened, and the saw mark can be removed.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of the grinding machine used in this embodiment. FIG. 2 schematically shows a grinding process according to this embodiment. FIG. 3 shows the relationship between the volume ratio of the surfactant in the frozen liquid and the inclination of the wafer. FIG. 4 shows the relationship between the volume ratio of the surfactant in the frozen liquid and the flatness.

First, the configuration of the grinding machine will be described. In FIG. 1, reference numeral 11 denotes a rotatable work table, on which a freezing chuck 12 is mounted. The freezing chuck 12 is a rectangular body as a whole, and can supply a freezing liquid therein. Wafer 13
Is placed on the surface of this frozen liquid. Further, a coolant is supplied from the outside to the inside of the freezing chuck 12 through a pipe 12A, and the coolant and the wafer 13 are frozen by the coolant.

The grinding head 14 is disposed above the work table 11, and has a grinding blade 14A on its lower surface. The grinding blade 14A is configured to be driven and rotated by a spindle. The grinding head 14 is supported by a support 16 by an arm 15 so as to be swingable in a horizontal plane. Further, the grinding head 14 is configured to be movable also in the vertical direction.

In a method of controlling a grinding allowance using this grinding machine, after the wafer 13 is chucked on the freezing chuck 12, only the spindle is rotated, and the grinding head 14 is moved in the direction of the arrow X. Then, the position of the grinding head 14 (spindle) is lowered in predetermined scale units, and the grinding blade 14
Confirm that A hits the upper surface of the wafer 13.
After confirmation, the grinding head 14 is lowered from this state to the specified cutting amount. When grinding, the grinding head (spindle)
The work table 11 is rotated in the direction of the arrow Y while the wafer 14 is kept cold using, for example, a cold storage material while the work 14 is fixed, and the work (wafer 13) is sent to the grinding head 14.

An embodiment of the grinding method according to the present invention will be described below with reference to FIG. First, the frozen liquid is topped (dropped) by about 10 ml on the frozen chuck 12, and the wafer 13 is placed on the liquid surface. In this case, the solution to be dropped has a surfactant (for example, NCW) mixed with pure water for the purpose of removing the surface tension. Then, before the chuck is fixed, the mixed solution for the ice film is subjected to a degassing process. For example, 6
The mixture will boil when pulled to 00-700 Torr.

Next, the temperature of the chuck 12 is lowered and the wafer 13 is frozen. Here, the parallelism of the ice film (wafer surface) changes depending on the dilution ratio (volume ratio) of the surfactant. Therefore, the parallelism was measured.
For example, the chuck 12 is placed on the work table 11 of the above-mentioned surface grinding machine, the micro gauge is fixed to the grindstone fixing portion, and the work table 11 is moved. Thereby, a partial difference in the height of the chuck, that is, the flatness was measured. As a result, as shown in FIG. 3, when the volume ratio is less than 20%, a remarkable inclination is observed in the wafer. Volume ratio 20% to 6
A solution mixed with a surfactant (NCW) at 0% results in a wafer surface parallel to the chuck surface. If the surfactant exceeds 60% by volume, it freezes at, for example, a freezing temperature of −15 ° C., but its fixing strength is remarkably weak and its flatness deteriorates. Therefore, a dilution of about 25% by volume ratio is appropriate. FIG.
Shows the relationship between the ratio of the surfactant in the mixed solution and the flatness. The broken line in the figure indicates grinding at a low load.

Then, grinding was performed with a # 1000 resin bond grindstone. In this case, management of the stock removal is important. The allowance is 5 to 10 μm. Alternatively, the entire surface is ground with a # 400 metal bond grindstone. The grinding bite amount was set such that the grinding allowance with this low-counter grinding wheel was 40 to 50 μm.

At this time, the rotation speed of the work table 11 also needs to be controlled. If the number of rotations of the worktable 11 is too large, the grindstone (grinding blade) will not bite. The rotation speed of the work table 11 of the grinding machine used is N
C control is performed. However, if an attempt is made to achieve an extremely low rotation speed, the rotation will be discontinuous (that is, the rotation and stop will be repeated periodically). Therefore, the rotation speed of the work table 11 was set to a critical rotation speed of 108 sec / rot for discontinuous driving.

Thereafter, the wafer is once thawed and frozen and fixed to the freezing chuck 12 again with the wafer ground surface down. Then, grinding is performed under the same conditions as above. As a result, wafer 1
The front and back surfaces of No. 3 could be ground flat. Further, a double-sided mirror wafer or a single-sided mirror wafer can be manufactured through a double-side polishing (each having a thickness of about 2 to 3 μm) or the like. Confirmation of saw mark transfer after grinding
For example, it can be performed by magic mirror observation.

[0023]

According to the present invention, the wafer can be fixed parallel to the grinding table, and a flat wafer can be obtained. Also, the saw mark can be reliably removed. Also, no dimples or the like occur on the ground wafer. Further, a mirror wafer can be manufactured without the lapping step.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a grinding machine according to one embodiment of the present invention.

FIG. 2 is a process chart showing a grinding method according to an embodiment of the present invention.

FIG. 3 is a graph showing a relationship between a volume ratio of a surfactant and a tilt of a wafer in a grinding method according to an embodiment of the present invention.

FIG. 4 is a graph showing a relationship between a surfactant volume ratio and a wafer flatness in a grinding method according to an embodiment of the present invention.

FIG. 5 is a process chart showing a conventional grinding method.

FIG. 6 is a schematic diagram for explaining a problem relating to a conventional grinding method.

FIG. 7 is a schematic diagram for explaining another problem relating to a conventional grinding method.

[Explanation of symbols]

 Reference Signs List 11 work table 12 freezing chuck 13 wafer 14 grinding head 14A grinding blade (grinding stone)

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toru Hatanaka 1-5-1, Otemachi, Chiyoda-ku, Tokyo Mitsubishi Materials Silicon Corporation (56) References JP-A-7-78796 (JP, A) JP Hei 6-246567 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/304 B23Q 3/08

Claims (4)

(57) [Claims] 1. A semiconductor wafer grinding method for fixing a sliced semiconductor wafer to a grinding table with a freezing chuck and grinding the surface of the semiconductor wafer, wherein the fixing with the freezing chuck uses a surfactant of 20 to 60.
A semiconductor wafer grinding method performed by freezing water containing only volume% . 2. The method according to claim 1 , wherein the water is deaerated and then frozen.
2. The method for grinding a semiconductor wafer according to claim 1, wherein the grinding is performed. 3. A frozen semiconductor wafer
And fix the surface of this semiconductor wafer to the grinding table.
In the method of grinding a semiconductor wafer to be ground , fixing with the freezing chuck is performed after deaeration of water.
A method of grinding semiconductor wafers frozen. 4. A wafer fixing table on which a semiconductor wafer is mounted, a refrigeration chuck for interposing water between the mounted semiconductor wafer and the wafer fixing table, and freezing the water to fix the semiconductor wafer. An apparatus for grinding a semiconductor wafer, comprising: grinding means for grinding one surface of a fixed wafer; and degassing means for degassing the water when the water is frozen.