JPH01228773A - Surface processing method - Google Patents

Abstract

PURPOSE:To uniformalize the distribution of load added on a processed matter and restrain tapering occurring at the processed matter after processing, by conducting abrasion by making the center of pressurization eccentric against the circular arc center of the processed matter according to the shape of the processed matter. CONSTITUTION:A sheet like processed matter 4 having an approximately uniform thickness is processed in abrasion while it is being retained in pressurization by means of a pressurization plate 3 on a lower fixed tray 1. In this instance, processing in abrasion is done by making eccentric the center p of pressurization against the center o of the circular arc of the processed matter 4 according to the plane shape of the processed matter 4. As a result, the distribution of the surface internal pressure of the processed matter 4 can be uniformalized, and the occurrence of tapering occurring at the processed matter 4 can be drastically restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a surface treatment method for polishing the surface of a thin plate-shaped workpiece such as a semiconductor wafer with high precision.

(Prior Art) Conventionally, as a surface treatment method for polishing a thin plate-shaped workpiece, a method has been used in which polishing is performed by rotating the surface plate and pressure plate while holding the workpiece under pressure with a pressure plate on a surface plate. There is.

Moreover, in this conventional method, FIG. 4(a).

As shown in (b), the polishing process was performed while applying pressure so that the center of pressure P by the pressure plate was located on the center O of the circular arc of the workpiece.

(Problems to be Solved by the Invention) However, according to the above conventional surface treatment method, for example,
As shown in FIG. 4(a), even if the workpiece is not completely circular, polishing is performed while applying pressure so that the pressure center P is on the edge center 0 of the workpiece. The load distribution on the workpiece becomes uneven as shown in Figure 4(b),
As a result, the shape of the workpiece after the polishing process becomes a shape having an inclination (Taber), which poses a problem in that highly accurate polishing becomes difficult.

Therefore, in the method of the present invention, it is an object of the present invention to provide a surface treatment method that can suppress the inclination (Taber) that occurs in a workpiece by polishing while applying pressure so that the load distribution on the workpiece is uniform. The purpose is

(Means for Solving the Problems and Their Effects) The surface treatment method according to the present invention is a surface treatment method in which a thin plate-shaped workpiece having a substantially uniform thickness is polished while being held under pressure by a pressure plate on a surface plate. According to the planar shape of the workpiece, the center of pressure applied to the workpiece is eccentrically set to perform polishing.

Therefore, by making the pressure center eccentric according to the shape of the workpiece, the in-plane pressure distribution of the workpiece can be made uniform, and the occurrence of taper on the workpiece can be suppressed.

(Example) An example of the present invention will be described below based on the drawings.

FIG. 1 shows the main parts of a surface treatment apparatus for carrying out the method of the present invention.

In both figures, l denotes a lower surface plate, and the lower surface plate 1 is rotated in the direction of the arrow in the figures by a drive device. An upper surface plate 2 is disposed above the lower surface plate 1 so as to be rotatable in the direction of the arrow in the figure and movable up and down by a drive device, and a pressure plate 3 is provided on the lower plane of the upper surface plate 2. Each driving device for the upper surface plate 2 and the lower surface plate 1 is driven by a control device, and the control device performs surface treatment on a workpiece 4 such as a semiconductor silicon wafer. During surface treatment, the workpiece 4 is supported on the lower surface of the pressure plate 3 by adhesion or suction, a predetermined load is applied to the workpiece 4, and the workpiece 4 is polished on the lower surface plate 1 (on which a polishing cloth or the like may be attached). After flowing the liquid, surface treatment is performed while the workpiece 4 is rotated and oscillated.

At this time, if the workpiece 4 is not completely circular, the surface treatment is performed by eccentrically (shifting) the load center P from the arc center 0 of the workpiece 4 using the pressure plate 3.

Figure 2 (a) shows data obtained when surface-treating a silicon wafer with a diameter of 5" that is not perfectly circular. It shows the amount of load eccentricity (mm) at the center of the wafer's circular arc (0) and the amount of eccentricity generated on the wafer after processing. It shows the relationship with Taber (μm).In other words, when the eccentricity is b in Fig. 2(a), that is, when the arc center 0 and the load center P overlap as shown in Fig. 2(C). The taper generated in the workpiece is B, and it can be seen that when the load center P is eccentric to the left side of the figure from the arc center O as shown in FIG. 2(b), the amount of taper after machining increases.

On the other hand, if the center of the wafer is eccentric to the right side in the figure from point b at the center of Fig. 2 (Ca'), the taper amount will be reduced at three points where the center of gravity G of the wafer and the load center P overlap, as shown in Fig. 2 (d). It can be seen that is the minimum.

Therefore, in this example, as shown in FIG. 2(d), polishing was performed with the eccentricity of the load and the distance from the calculated center of gravity position to the arc center O of the workpiece being 1t (am).

As a result, the inclination (Taber) that occurs in the workpiece and the amount of polishing are approximately proportional to each other, so as the amount of polishing increases as shown by However, in this example, as shown by Y in the figure, by making the load eccentric, the inclination (Taber) could be significantly suppressed and reduced to less than half compared to the conventional method. .

(Effects of the Invention) As explained above, according to the present invention, the load applied to the workpiece is polished by making the load center eccentric to the arc center of the workpiece according to the shape of the workpiece. The distribution becomes uniform, and as a result, it is possible to significantly suppress the inclination (Taber) that occurs in the workpiece after processing, and it can be used very effectively, especially for the ultra-high precision that will be required in the future for silicon wafers for semiconductors. It has advantages such as being able to

[Brief explanation of the drawing]

1 to 3 relate to embodiments of the present invention, in which FIG. 1 is an enlarged sectional view of the main part of the surface treatment apparatus, FIG. 2(a) is a relationship between eccentricity and Taber, and FIG. b). (C) and (d) are schematic plan views showing each amount of eccentricity, Figure 3 is a diagram of the relationship between polishing amount and Taber, Figure 4 Ca)
, (b) relates to a conventional example, FIG. 4(a) is a schematic plan view showing a workpiece, and FIG. 4(b) is a side view thereof. 1... Lower surface plate 3... Pressure plate 4... Workpiece P... Pressure center 0... Arc center Patent applicant Kyushu Electronic Metals Co., Ltd. Patent applicant Osaka Titanium Manufacturing Co., Ltd. Agent Man
Patent Attorney Sumi Mori Figure 1

Claims (1)

[Scope of Claims] A surface treatment method in which a thin plate-like workpiece having a substantially uniform thickness is polished while being held under pressure by a pressure plate on a surface plate, the workpiece being polished according to the planar shape of the workpiece. A surface treatment method characterized by polishing an object by eccentrically centering the center of pressure on the object.