JPS5834254B2 - Kenmasouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polishing apparatus, and is primarily directed to a wafer mirror polishing apparatus for polishing the surface of a semiconductor wafer.

Mirror polishing of a wafer is carried out by, for example, as described in Japanese Utility Model Publication No. 48-5956, in which the whole surface of the wafer is closely supported on a support with a flat surface, and a polishing liquid is supplied onto a polishing plate facing the support. At the same time, the polishing plate is rotated so that the opposite main surfaces of the wafer are rubbed together.

However, when a wafer is polished by the above method, there is a problem in that minute defects are generated on the wafer surface.

However, in the past, there was no effective means for suppressing minute defects, and minute defects were unavoidable.

The inventors investigated the cause of the above-mentioned microdefects and found that the main cause is that the polishing liquid is heated by frictional heat and air flow during polishing, and the water in the polishing liquid evaporates, resulting in a lack of water. I found out something.

That is, when the moisture between the wafer and the polishing cloth evaporates due to frictional heat, the amount of moisture in the iron part becomes extremely small compared to the amount of abrasive grains, resulting in a state where the abrasive grains remain.

If you continue polishing in this state, frictional heat will cause
It was found that the temperature of the iron part increases rapidly, causing a type of burning phenomenon between the remaining abrasive grains, forming coarse particles, which scratch the wafer surface and generate micro defects. .

Particularly in the mirror polishing of semiconductor wafers, a polishing solution consisting of an alkaline solution mixed with abrasive grains such as fine powder of silicon dioxide is generally used, and a chemical reaction caused by the alkali and mechanical polishing using the abrasive grains are combined. Often used.

In this case, silicon is eluted into the solution due to the reaction between the alkaline solution and the semiconductor wafer.

However, when a large amount of moisture in the polishing solution evaporates due to the frictional heat described above, the silicon eluted into the polishing solution becomes more likely to combine with the oxygen in the polishing solution and the abrasive, and polishing is continued in this state. The temperature of the iron part rises rapidly due to frictional heat, promoting bonding between the remaining abrasive grains and making it easier to generate coarse particles.

As is clear from the above explanation, the present inventors have clarified that in order to prevent minute defects on the wafer surface during mirror polishing, it is important to prevent moisture evaporation between the wafer and the polishing cloth. It was done.

Therefore, an object of the present invention is to prevent the formation of minute defects on the wafer surface by preventing moisture from evaporating between the wafer and the polishing cloth.

The gist of the present invention for achieving the above object is to provide a polishing device that sandwiches a workpiece between a holding plate and a polishing plate and polishes the workpiece by rotating the polishing plate and the holding plate. , a cover that covers the workpiece, a holding plate that holds the workpiece, and the top surface of the polishing machine; a first supply mechanism that supplies a polishing liquid containing abrasive grains between the workpiece and the polishing machine; a second supply mechanism that supplies mist-like water particles or water vapor into the cover for keeping the inside of the cover at high humidity.

An embodiment of the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows an embodiment of a polishing apparatus for polishing semiconductor wafers according to the present invention.

In the figure, 1 is an outer main body of a wafer polishing apparatus, and 2 is a rotary polishing machine attached to the center of the main body so as to rotate at a low speed in the direction of the arrow.

A polishing cloth (puff) 3 is attached to the upper surface of the polishing machine 2.

4 is a semiconductor wafer to be polished; 5 is a holder having a disc-shaped holding plate portion 6 for holding the semiconductor wafer on one side (lower surface); when the wafer is held on this plate portion 6, it itself moves as shown by the arrow; Rotate at low speed in the direction.

This is a cover that covers the entire upper side of the holding plate part 6 of the rotary holding body and the rotary polishing machine 2, and thereby keeps the inside of the cover shielded from the outside or in a state close to this.

Reference numeral 8 denotes a polishing liquid supply pipe for pouring an appropriate amount of polishing liquid 9 onto the surface of the polishing machine 2, and is attached to the upper part of the cover.

10 is a mist water particle supply pipe attached to the upper part of the cover;
A large amount of atomized water particles 11 are supplied into the cover to keep the inside of the cover constantly at high humidity.

That is, if a large amount of atomized water particles 11 are supplied, their surface area is large and they are easily evaporated and vaporized, making it easy to maintain high humidity inside the cover.

The semiconductor wafer 4 held in close contact with the lower surface of the holding plate part 6 is kept at high humidity, and the other main surface is polished by the rotation of the polishing machine 2 and the mutual low-speed rotation of the holder 5 in the atmosphere. The wafer is rubbed against the polishing cloth 3 and simultaneously polished by the polishing liquid 9 supplied between the wafer and the polishing cloth, resulting in a good polished surface with almost no micro defects.

According to the present invention as described in the embodiments above, the above object can be achieved for the following reasons.

In other words, the wafer that is the workpiece and the entire top surface of the polishing machine are covered with a cover so as to block the flow of air.
The interior is sealed from the outside, or a state close to this is sealed, and at the same time, atomized water particles are supplied into the cover using the atomized water particle supply pipe, so that the inside of the cover is always kept in a state of high humidity, that is, close to the saturated vapor pressure of water. .

Since polishing is carried out under these conditions,
There are no residual abrasive grains and no bonding between abrasive grains occurs.

In addition, this method also reduces the generation of frictional heat and prevents the polishing fluid from being heated.
It is possible to prevent minute defects from occurring on the wafer surface without causing the conventional problems as described above.

Furthermore, according to such a device, the supply of atomized water particles from the atomized water particle supply pipe suppresses moisture evaporation, so there is no need to increase the supply amount of polishing liquid, and micro defects on the polished surface can be avoided. At the same time, polishing fluid can be used effectively, and an increase in polishing costs can be suppressed.

FIG. 2 shows another embodiment of the invention.

In this case, a protruding edge 12 is provided along the outer periphery of the polishing machine,
The polishing liquid 9 can be stored on the polishing disk 2.

In this configuration, the semiconductor wafer 4 is always processed in a polishing liquid, and the used polishing liquid overflows over the protruding edge 12, and new polishing liquid is constantly supplied from the central portion.

In such a case, since the polished surface is constantly immersed in the polishing liquid, the generation of frictional heat can be reduced more than in the above embodiments, and the effects of the present invention can be further enhanced.

The present invention is not limited to the above-mentioned embodiments. For example, a large amount of water vapor can be directly supplied into the cover from the atomized water particle supply pipe to keep the inside of the cover at high humidity.

The present invention can be applied to a polishing apparatus for mirror polishing wafers made of semiconductor materials, hard brittle materials such as glass and crystal, metal materials, magnetic materials, ferrite, etc. as workpieces.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of one embodiment of the invention, and FIG. 2 is a longitudinal sectional view of another embodiment of the invention. 1...Outer main body, 2...Rotary polishing machine,
3... Polishing cloth, 4... Semiconductor wafer (
Workpiece), 5... Curved holding body, 6... Holding plate portion, 7... Cover, 8... Polishing liquid supply pipe, 9... - Polishing liquid, 10...Atomized water particle supply pipe, 11...Steam, 12...Protrusion.

Claims (1)

[Claims] 1 In a polishing device that holds a workpiece between a holding plate and a polishing plate and polishes the workpiece by rotating the polishing plate and the holding plate, the workpiece and the workpiece are held. a cover that covers the holding plate and the top surface of the polishing machine; a first supplying a polishing liquid containing abrasive grains between the workpiece and the polishing machine;
A polishing device comprising: a supply mechanism; and a second supply mechanism that supplies mist water particles or water vapor into the cover to keep the inside of the cover at high humidity.