TW201926451A - Semiconductor wafer carrier and method for double-sided polishing of semiconductor wafers - Google Patents

Abstract

Carrier for guiding semiconductor wafers during double-sided material-removing processing of the wafers, where the carrier is coated with a layer of diamond-like carbon and the layer comprises hydrogen with a fraction of not less than 10 at% and not more than 30 at% and comprises at least one further extraneous element, the further extraneous element being oxygen, nitrogen, chromium or titanium, and a surface of the layer exhibits a roughness Ra of not less than 5 nm and not more than 40 nm and has a degree of hydrophilicity such that the contact angle of a water drop is less than 25 DEG. Method for double-sided polishing of semiconductor wafers that uses such a carrier.

Description

Semiconductor wafer carrier and method for double-sided polishing semiconductor wafer

The present invention relates to a coated carrier for guiding a semiconductor wafer during a double-sided material removal process on a semiconductor wafer, and a method of double-sided polishing a semiconductor wafer using the carrier.

It is known from US 2008/0166952 A1 that a carrier made of titanium, optionally coated with a titanium nitride layer or a diamond-like carbon (DLC) layer, is used as compared to a carrier made of, for example, stainless steel. It is more suitable for use in double-sided polishing (DSP) of semiconductor wafers.

It is proposed in DE 102 47 200 A1 that the carrier is coated with a DLC layer comprising from 1% by weight to 50% by weight of one or more metals of Groups IV to VI of the Periodic Table of the Elements.

In order to improve the efficiency of polishing, it is proposed in JP 2010 030 013 A2 to roughen the carrier with an abrasive material before application of the carrier and to coat a DLC layer containing metal oxide fine particles. The presence of the metal oxide makes the surface of the carrier more hydrophilic and improves the wettability of the carrier and the aqueous suspension (slurry) of the polishing medium. The water droplet contact angle is 25° to 30°. The disadvantage of this solution is in particular that due to the wear of the DLC layer, metal oxide fine particles are released upon polishing the semiconductor wafer, and the metal oxide fine particles cause scratches on the polished surface.

Moreover, these carriers described in the prior art are still unable to satisfactorily disperse the polishing medium suspension due to their surface characteristics, and may be a cause of large noise at the time of DSP. If the wettability can be brought close to the wettability of an uncoated steel carrier, and the service life of the carrier provided is longer than the service life of a known DLC coated carrier, It would be ideal. Uncoated steel carriers have a relatively high surface energy with a significant polar component and a contact angle that is wetted by water droplets is less than 10°.

The resulting problem addressed by the present invention is addressed by a carrier that directs a semiconductor wafer during a double-sided material removal process on a semiconductor wafer, wherein the carrier is coated with a diamond-like carbon layer, such The diamond carbon layer contains hydrogen in a ratio of not less than 10 atom% and not more than 30 atom% and contains at least one other foreign element, wherein the other foreign element is oxygen, nitrogen, chromium or titanium, and the surface of the diamond-like carbon layer has no A roughness Ra of less than 5 nm and not more than 40 nm and having a hydrophilicity of a water droplet contact angle of less than 25°.

In addition, the problem is solved by a method of double-sided polishing a semiconductor wafer in the presence of an aqueous suspension of polishing medium by means of one or more carriers between two polishing pads. Moving upward, wherein the carrier is coated with a diamond-like carbon layer, and the diamond-like carbon layer comprises hydrogen in a proportion of not less than 10 atom% and not more than 30 atomic % and contains at least one other foreign element, wherein the other foreign element Oxygen, nitrogen, chromium or titanium, the surface of the diamond-like carbon layer having a roughness Ra of not less than 5 nm and not more than 40 nm and having a hydrophilicity of a water droplet contact angle of less than 25°.

The effect of the presence of hydrogen in the diamond-like carbon layer (DLC layer) is to improve the wear resistance of the layer. The proportion of hydrogen is not less than 10 atom% and not more than 30 atom%. Further, if the average roughness Ra of the surface of the DLC layer is not less than 5 nm and not more than 40 nm, preferably not more than 30 nm, the service life of the carrier can be improved. The surface of the carrier can be polished prior to coating the carrier with the DLC layer to achieve a roughness within the range. The roughness of the DLC layer generally falls within the same range as the uncoated carrier. Selecting a smaller average roughness Ra for the carrier will improve its service life because not only is it accompanied by less sliding friction, but also less friction, which causes loss of the DLC layer and reduces the thickness of the carrier. .

The uncoated carrier is preferably composed of a metal, for example composed of titanium, preferably composed of steel, more preferably composed of chrome steel. The DLC layer covers the upper and lower sides of the carrier. It is preferably completely covered, but does not exclude partial coverage. The thickness of the DLC layer on one side is preferably not less than 0.1 μm and not more than 20 μm.

The foreign elements and their proportions contained in the DLC layer can be specifically selected to be uniformly distributed in the DLC layer due to the doping of the foreign elements, thereby producing less than 25°, preferably not more than 20°, and more preferably The contact angle of the water droplets in the range of not more than 10°. According to the invention, these foreign elements are oxygen, nitrogen, chromium, or titanium, or a combination of two or more of the aforementioned foreign elements. It is particularly preferable to have a nitrogen ratio of preferably not less than 1 atom% and not more than 10 atom%. The proportion of oxygen is preferably not less than 5 atom% and not more than 20 atom%. The proportion of chromium is preferably not less than 1 atom% and not more than 20 atom%, and the proportion of titanium is preferably not less than 0.5 atom% and not more than 2.5 atom%. In the case of one of the combinations of the above foreign elements, the ratio of the relevant combination is preferably not more than 20 atom%.

The surface characteristics of the DLC layer containing hydrogen and at least one foreign element of the present invention are important for the effective wettability of the aqueous slurry. The DLC layer has a surface energy of at least 70 millinewtons per meter (mN/m) and a polar component of at least 50%.

The carrier according to the present invention is preferably used for double-sided polishing of germanium semiconductor wafers, particularly germanium semiconductor wafers having a diameter of at least 200 mm, preferably 300 mm or more.

The improved wettability allows a completely cohesive film of polishing medium to be formed upon polishing of the semiconductor wafer, so that a fresh polishing medium can be permanently supplied to the surface to be polished. This wettability is also manifested by the fact that the water film does not break when the carrier is lifted from the water-filled tank. The cohesive polishing dielectric film has the effect of suppressing noise and reducing whistling noise, thereby reducing the cost of protection measures for offsetting the noise. Furthermore, the provision of the polishing medium in this way ensures a high level of material removal from the semiconductor wafer per unit time, which is advantageous for productivity. However, it is particularly advantageous to have an effect on the geometry of the polished semiconductor wafer, in particular on the polishing results of its edge geometry. This can meet more challenging customer requirements. The following table shows the commonly defined geometric parameters. In the column A, the use of a carrier in which the DLC layer does not contain specially added foreign elements is typically performed by double-sided polishing of a 300 mm diameter germanium semiconductor wafer. And the value achieved. For comparison purposes, the values in the column B are typically not exceeded when the vehicle according to the invention is used instead.

table

The parameters are defined in accordance with the SEMI standard. Edge geometry data is considered for edge exclusion of 2 mm (ZDD) or 1 mm (ESFQR). ZDD-FS refers to the ZDD of the front side of a semiconductor wafer, that is, the ZDD of the face on which the electronic component is to be accommodated.

The DLC layer is deposited on the polished uncoated carrier or deposited on an adhesion-promoting interlayer that is pre-applied to the polished uncoated carrier as needed. A source of at least one foreign element is also provided in conjunction with the carbon source and hydrogen source provided to form the DLC layer. The deposition method is preferably CVD (Chemical Vapor Deposition), PVD (Physical Vapor Deposition) or sputtering, in particular plasma-assisted CVD.

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Claims (4)

A carrier for guiding a semiconductor wafer during a double-sided material removal process on a semiconductor wafer, wherein the carrier is coated with a diamond-like carbon layer having a ratio of not less than 10 Hydrogen of at least 30 atomic % and containing at least one other foreign element, wherein the other foreign element is oxygen, nitrogen, chromium or titanium, the surface of the diamond-like carbon layer having not less than 5 nm and not more than 40 nm The roughness Ra of the rice and the degree of hydrophilicity of the water droplet contact angle of less than 25°. The carrier of claim 1, wherein the water droplet contact angle is no more than 20°. The carrier of claim 1 or 2, wherein the diamond-like carbon layer has a surface energy of at least 70 millinewtons per meter (mN/m), and a polar component of the diamond-like carbon layer is Not less than 50%. A method of double-sided polishing a semiconductor wafer, wherein the semiconductor wafer is moved in orbit between two polishing pads by one or more carriers in the presence of a polishing medium aqueous suspension, wherein the carrier is The carrier of any one of claims 1 to 3.