JPH02178927A - Method of polishing plate - Google Patents

Abstract

PURPOSE:To improve throughput and high flatness at the same time by bonding the surfaces of two plates together, and polishing the surfaces which are not bonded at the same time. CONSTITUTION:The surface of a wafer 1 is cleaned very finely through etching. The rear surface of the wafer 1 is bonded to the rear surface of another wafer 1 which is treated by the same way through wax 10. A pair of the bonded wafers 1 and 1 are housed in a housing hole 7 in a carrier 3. Pressure is applied for an upper surface plate and a lower surface plate. The carrier 3 starts planetary rotation in the horizontal direction. The surfaces of the two wafers 1 and 1 whose rear surfaces are bonded are polished with polishing clothes 11 and 11 at the same time. In this way, the processing in the polishing step can be performed efficiently, and the polishing having the high throughput can be performed without decreasing the flatness in polishing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polishing technique that requires highly accurate mirror polishing of plate surfaces, particularly semiconductor wafers, and the like.

[Conventional technology]

An example of this type of technology described is Japanese Patent Application Laid-Open No. 54-5870 by the present applicant.

As described in the above-mentioned publication, in a wafer processing step in a semiconductor device manufacturing process, a wafer that is sliced from an ingot state and processed into a disk shape is subjected to a polishing process.

The polishing process described above is roughly divided into two stages called ramping process and polishing process.

That is, the wafer surface of the sliced wafer is first flattened by the former lapping process. In this lapping process, diamond abrasive grains, GC (clean carborundum) aluminum oxide abrasive grains, etc. are used as the abrasive, and a cast iron surface plate with good flatness is used as a holding material for the abrasive. Although the polished surface of the wafer is still relatively rough due to this lapping process, both surfaces are flattened and variations in thickness throughout the wafer are corrected.

After the above-mentioned ramping process is completed, the surface of the wafer is subjected to an etching process using a predetermined chemical solution to clean the surface, and then the latter polishing process is performed. In the polishing process, a polishing cloth called a cloth is used to repeat several polishing steps, so that the surface of the wafer becomes mirror-like with a predetermined precision.

[Problem to be solved by the invention]

By the way, in the above-mentioned prior art, as described in the above-mentioned publication, only one wafer was mounted in the cross-sectional direction of the polishing disk, so that efficient polishing processing could not be carried out.

There is also a known technique in which polishing disks are placed on both sides of a loaded wafer to polish both sides of the wafer at the same time. Problems include that it is difficult to distinguish between the front and back surfaces of the wafer, and that some inconveniences often occur in subsequent processing steps. This problem was also improved by the inventor.

The present invention has been made with attention to the above-mentioned problems, and its purpose is to provide a technique that can simultaneously improve throughput and obtain high flatness in the polishing process of a plate surface body.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means to solve the problem]

A brief overview of typical inventions disclosed in this application is as follows.

Firstly, when polishing the plate plates, one side of the two plate plates is bonded to each other, and the non-bonded sides are polished at the same time.

Second, the sliced plate is subjected to a lapping process, which is the first polishing process, to flatten at least one surface of the plate, and then the two plate plates are bonded to each other between the flattened surfaces. A polishing device, which is a second polishing process, is simultaneously applied to the two surfaces of the pair of plate surfaces located outwardly from each other.

[Effect]

According to the above-mentioned first means, it is possible to simultaneously polish the two plate surfaces mounted in the cross-sectional direction of the polishing disk, so that the polishing process can be performed efficiently.

According to the second means, the two plate surfaces are bonded together after at least one surface is flattened by the ramping treatment that is the first polishing treatment, and the two surfaces located on the outside are simultaneously bonded together. It is necessary to apply the second polishing process, Polysonk treatment.
Even in polishing equipment, the flatness does not deteriorate.
In addition to the first means described above, a polishing process with high throughput can be realized.

〔Example〕

Fig. 1 is a flowchart showing the processing procedure of a polishing process according to an embodiment of the present invention, Fig. 2 is a perspective view showing a wafer used in this embodiment, and Fig. 3 is a cross-sectional view showing processing by a lapping device. , FIG. 4 is a side view showing two wafers bonded in this example, FIG. 5 is a cross-sectional view showing the two wafers bonded in this way mounted on a polishing device, and FIG. FIG. 7 is a perspective view showing the carrier, FIG. 7 is a plan view showing the rotating state of the carrier, and FIG. 8 is an explanatory diagram for explaining the flatness of the wafer.

The wafer 1 as a plate surface body used in this example has the shape shown in FIG. A part of its periphery has a straight line indicating the crystal direction.
a is formed.

The wafer 1 is processed according to the flowchart shown in FIG. 1 in this embodiment. That is, first, both sides of the sliced wafer l are flattened by the flattening device 2 shown in FIG.

The lapping device 2 has a carrier 3 that accommodates the wafer 1. This carrier 3 has the same structure as the carrier 3 in the polishing device 4, which will be described later.
The structure of the carrier 3 in the polishing device 4 shown in FIG. 5 will be explained.

A gear groove 5 is formed on the entire side surface of the carrier 3, and the carrier 3 is planetarily rotated around a sun gear 6 at the center of the device as shown in FIG.

Each of the carriers 3 has a diameter of, for example, 300 to 600C.
It is configured in a disk shape with a diameter of approximately fTl, and five accommodating holes 7 for wafers 1 are formed in one carrier 3. Therefore, in this embodiment, each carrier 3 can accommodate five wafers 1.

Moreover, such a carrier 3 can carry 5 in a single device.
The structure is such that it can be installed in one piece. Therefore, this lapping apparatus 2 can process 25 wafers 1 at the same time (see FIG. 7).

As shown in FIG. 3, the wafer 1 accommodated in the carrier 3 has its front and back surfaces protruding from the accommodation hole 7 of the carrier 3, and is placed between the upper surface plate 8a and the lower surface plate 8b. each will be contacted.

At least two surfaces of the upper surface plate 8a and the lower surface plate 8b that come in contact with the wafer 1 are made of cast iron or the like, and the carrier 3 moves between the surface plates 3a and 3b which are in a pressurized state. The structure is such that both surfaces of the wafer 1 are polished by planetary rotation in the horizontal direction.

Note that the pressing force applied to both sides of the wafer 1 at this time is, for example, about 100 to 1.30 g/cm2.

Here, to briefly explain the flatness of the wafer 1 using FIG. 8, it is expressed, for example, by the height difference in the uneven state on the surface of the wafer 1, and T T V (Total Th1cknessVar
tion ), or LTV (Local T
This is determined based on a standard called h1ckness Variation.

In the lapping device 2, flattening is performed to bring this difference in height close to zero. To explain this using Fig. 8 as an example, by polishing the part indicated by the line l in the figure, h - Q
becomes.

In the example of the lapping apparatus 2 described above, a case has been described in which both sides of one wafer 1 are polished and both surfaces are flattened, but only one side may be flattened and this may be used as the reference surface.

Next, the surface of the flattened wafer 1 is cleaned by an etching process. Commonly used etching treatments are acid etching using an acidic etching solution and alkali etching using an alkaline etching solution.Although the former can be processed in a short time, the heat of the etching reaction This causes a difference in etching speed within the wafer, which has the disadvantage that the peripheral portion of the wafer 1 is sagged. Therefore, although the present embodiment requires a long time for processing, it is preferable to use alkaline etching, which does not have the above-mentioned drawbacks and causes less deterioration in dimensional accuracy.

The wafer 1 whose surface has been highly cleaned through the above etching process is bonded to another wafer 1 which has undergone the same process using wax 10 on its back sides (the sides on which no circuit is formed). .

The wax 10 must have a predetermined adhesive strength to resist the stress applied by the polishing device 4 in the hardened state, and after the polishing process, the wax 10 must have adhesive strength so that the two wafers 11 can be easily separated. It is desirable that the adhesive be made of a material whose adhesive force can be controlled.

As a specific example of such wax 10, for example, 50
A thermoplastic resin that melts at about 60°C to 60°C, a resin adhesive that melts with an organic solvent, or an adhesive whose adhesive strength decreases when cooled to -10°C or lower may be used.

Next, the pair of wafers 1 bonded as described above are placed in a po'j
It is attached to the monitoring device 4 (Fig. 5).

Also in the polishing device 4, the wafer 1 is placed on the carrier 3.
It is mounted between the upper surface plate 8a and the lower surface plate 8b while being accommodated in the. Note that a polishing cloth 11 is laid on the surfaces of the upper surface plate 8a and the lower surface plate 8b, and this polishing cloth 11 is impregnated with a polishing liquid containing magnetic particles.

Note that the Po'J song process is generally carried out through a multi-step process in which the concentration of the polishing liquid and the rotation speed of the carrier 3 are changed, but in this example, only a typical process will be explained. do.

Since the carrier 3 shown in FIG. 6 has been previously described as a carrier structure in the ramping device 2, repeated explanation will be omitted. This polishing device 4
The difference in the structure of the carrier 3 from that of the lapping device 2 is that a pair of wafers 1,
It is only a point where 1 is accommodated.

The wafers 1, 1 are accommodated in the accommodation hole 7 of the carrier 3, and the weight between the upper surface plate 8a and the lower surface plate 8b is 1.00 to 250 g/cm2.
By applying a certain amount of pressure, the carrier 3 starts planetary rotation in the horizontal direction. As a result, the back sides of the two sheets of Ueno 1.1 are glued together, and the front side of the polishing cloth 11.1 is
1 and simultaneously pollinsynced.

According to this embodiment, two wafers 1, 1 constitute a pair and are mounted in the accommodation hole 7 of the carrier 3. Therefore, when one carrier 3 has five accommodation holes 7, ten carriers 3 are attached to one carrier 3, and the polishing device 4 that can accommodate five carriers 3 is as follows.
It is possible to polish 50 wafers at the same time.

In this way, in this embodiment, the throughput can be doubled by using the double-sided polishing device 4 having the conventional structure.
Efficient polishing processing can be performed.

Also, at this time, we checked the flatness, which is processing accuracy, and found that it was the same value as the conventional technique, in which only one wafer 1 was mounted in the cross-sectional direction and double-sided ponsong processing was performed. It was done. This is thought to be because the processing principles of double-sided bore, such as equal load and planetary motion of the wafer, act as they do when two wafers are combined as a pair, just as when only one wafer is polished. .

In this embodiment, after the above-mentioned polishing device is repeated a predetermined number of times and the surfaces of the two wafers 1, 1 reach a predetermined mirror-like state, the wafers 1, 1 are heated or treated with an organic solvent, etc.
The adhesion state of the wax 10 bonding the wafers to each other is reduced, and the two wafers 11 are separated.

The wafers 1 obtained in this way are mirror-finished only on one side (front side), so that it is extremely easy to identify the front and back sides.

- Although the invention made by the present inventor has been specifically explained based on examples, the present invention is not limited to the above-mentioned examples, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say.

For example, as for the abrasive in the lapping device 2, the case where the upper surface plate 8a and the lower surface plate 8b are made of cast iron or the like has been described, but other abrasives may be used as long as the predetermined flatness processing accuracy can be obtained. Of course it's a good thing. Further, the polishing agent in the polishing device 4 is not limited to the polishing cloth 11 impregnated with a polishing liquid.

In the above explanation, the invention made by the present inventor has been mainly applied to the field of application, which is wafer polishing technology in the manufacture of semiconductor devices, but the invention is not limited to this, for example, in hard disk devices. It is also applicable to polishing techniques for magnetic disks or polishing techniques for quartz glass, etc. in photomask manufacturing.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

That is, since it becomes possible to simultaneously polish two plate face bodies attached in the cross-sectional direction of the polishing disk, it becomes possible to perform processing in the polishing process efficiently.

In addition, two plate face pieces are bonded together after being subjected to wrapping treatment to flatten at least the surfaces, and the two plate faces located outward are bonded together.
Since the polishing process is performed simultaneously on the surface, the flatness does not deteriorate even during the polishing process, and a polishing process with high throughput can be realized.

[Brief explanation of the drawing]

Fig. 1 is a flowchart showing the procedure of a polishing process according to an embodiment of the present invention, Fig. 2 is a perspective view without showing the wafer used in this embodiment, and Fig. 3 shows processing by a runpin device. 4 is a side view showing the two wafers bonded in this example; FIG. 5 is a sectional view showing the two wafers bonded in this way mounted on a linking device; FIG. 6 is a perspective view showing the carrier, FIG. 7 is a plan view showing the rotating state of the carrier, and FIG. 8 is an explanatory diagram showing the flatness of the wafer. 1... Wafer flat, 2. Carrier, 4... Gear groove, 6... a... Upper surface plate, wax, 11. 1a... Oriente... Run pinking device, 3... ・Porin/jig device, 5... Sun gear, 7... Accommodation hole, 8 8b... Lower surface plate, 10... Polishing cloth.

Claims (1)

[Scope of Claims] A method for polishing plate face bodies, which comprises bonding one or two surfaces of one or two plate face bodies to each other, and simultaneously polishing the other surfaces that are not bonded. 2. After applying a lapping process, which is a first polishing process, to the sliced plate face piece and flattening at least one side of the plate face piece, the two plate face pieces are bonded to each other between the flattened surfaces. A method for polishing a plate face body, in which a second polishing process is simultaneously performed on two surfaces of the pair of plate face bodies located outward from each other. 3. The method of polishing a plate surface body according to claim 1 or 2, wherein the plate surface body is a semiconductor wafer. 4. The method of polishing a plate face body according to claim 1 or 2, wherein the plate face body is bonded through a thermoplastic resin.