JPH029571A - Two-side polishing method - Google Patents

Abstract

PURPOSE:To enhance the reliability by affixing an abrasive cloth, which forms a flaw capable of catching contaminant on the surface of a wafer, to a surface reference board, forming flaw simply on one surface of the wafer to be two-side ground, allowing this flaw to make gettering of contaminant, and thereby eliminating contaminant from the operating zone for semiconductor element. CONSTITUTION:A wafer 9 is held by a carrier 5 rotated round its own axis and also orbited by a sun gear 3 and an internal gear 4, and an upper and a lower surface reference board 1, 2 fitted with abrasive cloth 6, 7 are rotated oppositely to polish the two sides of the wafer 9, which is held by a carrier 5 between the surface reference boards 1, 2. Therein the abrasive cloth 7 affixed to the upper surface reference board 1 shall have an Asker C hardness as high as 82 deg. or more and be provided with a flaw to catch contaminant (for ex., Ni, Cr) on the oversurface of the wafer 9 during polishing. This flaw will make gettering of the contaminant to cause the operating zone of semiconductor element free of contaminant, which should enhance the reliability of semiconductor element.

Description

[Detailed Description of the Invention] ((Already required)) A double-sided polishing method for forming defects capable of trapping contaminants on the surface of a wafer. With the aim of providing a double-sided polishing method that can be carried out, the wafer is held in a carrier that rotates around its axis using a sun gear and an internal gear, and the upper and lower polishing plates, each with a polishing cloth attached to them, are reversed. A double-sided polishing method in which the surface of the wafer held by the carrier between the surface plates is polished by rotating the wafer in a direction, the surface of the wafer being rotated in the direction of This is done by attaching a polishing cloth that forms defects that can be captured.

[Industrial application field]

The present invention relates to a method for polishing a wafer, and more particularly to a double-sided polishing method for forming defects on the surface of a wafer that can trap contaminants.

In wafers used for manufacturing semiconductor devices, the wafers become contaminated during the process of completing the formation of semiconductor elements on bare wafers.

In order to protect the operating area of the semiconductor element several micrometers thick from the wafer surface from this contamination, defects are introduced into the wafer surface or inside the wafer on the opposite side of the wafer's operating area of the semiconductor element, and the area where the defect is formed is removed. It is designed to capture various contaminants such as iron, nickel, and chromium.

This phenomenon is called gettering, and in order to cause this phenomenon, defects that trap contaminants are introduced on the surface of the wafer or inside the wafer.

Such a gettering effect prevents contaminants from being present in the operating region of the semiconductor element on the wafer, making it possible to prevent deterioration of the characteristics of the semiconductor element.

In order to prevent the deterioration of the characteristics of semiconductor elements from the above-mentioned situation, there is a method that can introduce defects that trap contaminants TIM on the surface of the wafer opposite to the operating area of the semiconductor wafer or inside the wafer. It is requested.

[Conventional technology]

There are two conventional methods for obtaining gettering ability:

One method is to control the oxygen concentration in the crystal during the crystal bowing process for cutting out the wafer, and introduce defects into the bulk during the heat treatment process in the process. , a method of introducing defects into the surface of a wafer by irradiating it with an excimer laser.

[Problem to be solved by the invention]

In the conventional method of introducing defects explained above, in the oxygen concentration control method, the wafer is exposed to a high temperature. Since the wafer is controlled to contain a certain amount of oxygen, there is a problem in that the device characteristics are deteriorated due to the oxygen that is better not present in the wafer, and the excimer laser irradiation method is expensive to process. There was a problem with that.

In view of the above-mentioned circumstances, it is an object of the present invention to provide a double-sided polishing method that allows defects to be introduced into the wafer surface quickly and inexpensively by selecting a polishing cloth in the double-sided wafer polishing method.

[Means to solve the problem]

The above problem is solved by holding the wafer in a carrier that rotates on its own axis using a sun gear and an internal gear, and rotating the upper and lower surface plates, each with a polishing cloth attached to them, in opposite directions to polish the surface of the wafer. According to the double-sided polishing method according to the present invention, the double-sided polishing method according to the present invention is carried out by attaching a polishing cloth that forms defects capable of trapping contaminants on the surface of the wafer to one of the surface plates. resolved.

(Function) That is, in the present invention, a polishing cloth that forms defects that can trap contaminants on the surface of the wafer is attached to either the upper or lower surface plate of the double-sided polisher. Since double-sided polishing is performed, defects capable of trapping contaminants are introduced into the surface of the wafer polished with this polishing cloth, making it possible to obtain a gettering ability to trap contaminants.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to FIG. 1, and another embodiment of the present invention will be explained with reference to FIG.

As shown in FIG. 1, the double-sided polishing machine used in the present invention is configured to place a wafer 9 on a carrier 5 between two surface plates 1.2 of the wafer polishing machine that rotate in opposite directions to which a polishing cloth is attached. The wafer 9 is placed in the hole and held, and both sides of the wafer 9 are simultaneously polished by applying pressure while supplying a polishing agent from the upper surface plate 1.

This carrier 5 is made of epoxy resin reinforced with metal or glass fiber fibers, and has a thickness of 1 to 1 mm.
It is a 00 μm thin disc surrounded by gears, and while it revolves around the rotating sun gear 3 and internal gear 4, it rotates on its own axis depending on the combination of the rotational speeds of the internal gear 4 and the sun gear 3.

In these embodiments shown in FIGS. 1 and 2, the polishing cloths attached to the upper surface plate 1 and the lower surface plate 2 have different properties from the commonly used rlJF fa cloth. ing.

I! 1, in the embodiment shown in FIG.
A hard polishing cloth 7 with an Asker-C hardness of 82 degrees or higher is attached, and a conventional polishing cloth 6 with an Asker-C hardness of 72 degrees or higher is attached to the lower leg 22, so that the wafer is not polished during polishing. A defect is introduced on the top surface of 9.

In the other embodiment shown in FIG. 2, a special polishing cloth 8 is attached to the lower surface plate 2 to which fine powder of #1000 to #2000 of quartz glass is adhered, and a conventional polishing cloth is attached to the upper surface plate 1. 6
is pasted on the wafer 9, defects are introduced on the lower surface of the wafer 9.

In addition, in any of the embodiments, the hard polishing cloth 7! I
! Alternatively, it is also possible to introduce defects by attaching the special polishing cloth 8 to the surface plate on the opposite side and attaching the conventional polishing cloth 6 to the other surface plate to perform double-sided polishing.

In this way, double-sided polishing is performed by attaching an inexpensively available hard polishing cloth 7 or a special polishing cloth 8 that introduces defects into the surface of the wafer 9 to be polished on one of the upper surface plates.
By doing so, it is possible to introduce defects on one surface of the wafer 9, and the defects can trap contaminants, and the gettering effect can prevent contaminants from existing in the operating area of the semiconductor element. , it becomes possible to prevent deterioration of the characteristics of the semi-quadram element.

Note that when comparing the cost of the excimer laser irradiation method and the defect introduction method of the present invention, the method of the present invention can be processed at about 65% of the cost, and the yield of wafers after processing is lower than that between the two. No significant difference was observed.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, by selecting a polishing cloth, it is possible to very easily introduce defects on one side of a wafer to be double-sided polished, and thereby to remove contaminants. This method has the advantage of making it possible to prevent contaminants from being present in the operating region of a semiconductor element, and can be expected to significantly reduce costs and improve reliability, making it extremely useful industrially.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing one embodiment according to the present invention, and FIG. 2 is a side sectional view showing another embodiment according to the present invention. In the figure, ■ is the upper surface plate, 2 is the lower surface plate, 3 is the sun gear, 4 is the internal, l-'a, 5 is the carrier, 6 is the conventional polishing cloth, 7 is the hard polishing cloth, 8 9 indicates a special polishing cloth, and 9 indicates a wafer. FIG. 1 is a side cross-section showing one embodiment of the present invention; FIG. 2 is a side cross-section showing another embodiment of the present invention; FIG.

Claims (1)

[Claims] A wafer (9) is held in a carrier (5) that rotates on its own axis by a sun gear (3) and an internal gear (4), and an upper surface plate (1) and a lower surface plate (2) each having a polishing cloth pasted thereon.
) in the opposite direction to polish the surface of the wafer (9) held by the carrier (5) between the surface plates (1, 2), the surface plate (1, 2
) is a polishing cloth (7, 8) which forms a defect capable of trapping contaminants on the surface of the wafer (9).
) is a double-sided polishing method characterized by pasting.