News Column

Researchers Submit Patent Application, "Polishing Pad", for Approval

August 20, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventor Kimura, Tsuyoshi (Osaka-shi, JP), filed on August 24, 2012, was made available online on August 7, 2014.

The patent's assignee is Toyo Tire & Rubber Co., Ltd.

News editors obtained the following quote from the background information supplied by the inventors: "Production of a semiconductor device involves a step of forming an electroconductive film on a surface of a semiconductor wafer (hereinafter also referred to as a wafer) to form a wiring layer by photolithography, etching or the like; a step of forming an interlaminar insulating film on the wiring layer; and the like; and an uneven surface made of an electroconductive material such as metal and an insulating material is formed on the surface of a wafer by these steps. In recent years, processing for fine wiring and multilayer wiring have been advancing for the purpose of higher integration of semiconductor integrated circuits, and accordingly techniques of planarizing an uneven surface of a wafer have become important.

"As the method of planarizing an uneven surface of a wafer, a CMP method is generally used. CMP is a technique in which while the surface of a wafer to be polished is pressed against a polishing surface of a polishing pad, the surface of the wafer is polished with an abrasive in the form of slurry having abrasive grains dispersed therein (hereinafter, referred to as slurry).

"As shown in FIG. 1, a polishing apparatus used generally in CMP is provided, for example, with a polishing platen 2 for supporting a polishing pad 1; a supporting stand (polishing head) 5 for supporting a polished material (wafer) 4; a backing material for uniformly pressurizing a wafer; and a mechanism of feeding an abrasive 3. The polishing pad 1 is fitted with the polishing platen 2, for example, by sticking with a double-sided tape. The polishing platen 2 and the supporting stand 5 are provided with rotating shafts 6 and 7, respectively, and are arranged such that the polishing pad 1 and the polished material 4, both of which are supported by them, are opposed to each other. The supporting stand 5 is provided with a pressurizing mechanism for pressing the polished material 4 against the polishing pad 1.

"When such CMP is conducted, there is a problem of judging the planarity of wafer surface. That is, the point in time when desired surface properties or planar state are reached is required to be detected. With respect to the thickness of an oxide film, polishing speed and the like, the following has been conventionally conducted that a test wafer is periodically treated, the results are confirmed, and thereafter a wafer to be a product is subjected to a polishing treatment.

"In this method, however, the treatment time of a test wafer and the cost for the treatment are wasteful, and the test wafer not subjected to processing at all in advance and a product wafer are different in polishing results due to a loading effect unique to CMP, and accurate prediction of processing results is difficult without actual processing of the product wafer.

"Accordingly, there has been a need in recent years for a method capable of in situ detection of the point in time when desired surface properties and thickness are attained at the time of CMP processing, in order to solve the problem described above. In such detection, various methods are used. From the viewpoints of measurement accuracy and spatial resolution in non-contract measurement, optical detection means comes to be used mainly.

"The optical detection means is specifically a method of detecting the end-point of polishing by irradiating a wafer via a polishing pad through a window (light-transmitting region) with light beam, and monitoring interference signal generated by reflection of the light beam.

"In such method, the endpoint is determined by knowing an approximate depth of surface unevenness by monitoring a change in the thickness of a surface layer of a wafer. When such change in thickness becomes equal to the thickness of unevenness, the CMP process is finished. As a method of detecting the endpoint of polishing by such optical means and a polishing pad used in the method, various methods and polishing pads have been proposed.

"Besides, a proposal is also offered for preventing a slurry from leaking out an interface (joint line) between a polishing region and a light-transmitting region (Patent Document 1 and 2).

"Further, in order to prevent slurry leakage, there is disclosed a method for interposing, between an upper-layer pad and a lower-layer pad, a transparent film with an adhesive agent applied to upper and lower surfaces thereof (Patent Document 3). However, if an adhesive layer is interposed between a light-transmitting region and the transparent film, there is fear that the optical detection accuracy also decreases because of a reduction in light transmittance.

"In addition, in order to prevent slurry leakage, there is disclosed a polishing pad, wherein a polishing layer and a porous subpad layer are laminated; a light transmissive window is disposed within the internal opening part between the polishing layer and the porous subpad layer; and a pressure-sensitive adhesive layer is attached to the bottom surface of the porous subpad layer and the light transmissive window (Patent Document 4). However, if there is a pressure-sensitive adhesive layer on the bottom surface of the light transmissive window, the same problem as above occurs.

"Moreover, in order to prevent slurry leakage and improve optical detection accuracy, there is disclosed a lengthy polishing pad which is provided with a space between a light-transmitting region and a transparent support film (Patent Document 5). However, if there is a transparent support film on the bottom surface of the light-transmitting region, the same problem as above occurs."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventor's summary information for this patent application: "Problems to be Solved by the Invention

"An object of the invention is to provide a polishing pad that is prevented from slurry leaks and has high optical detection accuracy.

"Means for Solving the Problems

"As a result of investigations to solve the above problems, the inventors have made the invention based on the finding that the object can be achieved using the polishing pad described below.

"That is, the present invention relates to a polishing pad comprising a polishing region, a cushion layer, and a support film layered in this order, wherein

"a light-transmitting region is provided on the support film and in an opening part that passes through the polishing region and the cushion layer;

"the light-transmitting region has a peripheral part and a recessed part on the surface of a polishing platen-side;

"the support film is layered on the peripheral part; and

"the support film is not layered on the recessed part, which remains open.

"It is preferable to provide a covering member on the side surface of the recessed part. Further, the covering member is preferably formed by bending an end part of the support film laminated in the peripheral part. This makes it possible to certainly prevent slurry leakage.

"The present invention also relates to a method for producing a semiconductor device, the method including the step of polishing a surface of a semiconductor wafer using the polishing pad.

"Effect of the Invention

"Because the polishing pad of the present invention has a structure such that the peripheral part is provided in the surface of the polishing platen-side of the light-transmitting region and the support film is laminated in the surface of the polishing platen-side of the cushion layer, slurry leakage can be prevented by the support film even if a slurry leaks from the boundary between the polishing region and the light-transmitting region and from the boundary between the cushion layer and the light-transmitting region. Further, a recessed part is provided on the surface of the polishing platen-side of the light-transmitting region, and the recessed part is open because a member such as an adhesive layer or a film is not layered thereon. Accordingly, it is possible to prevent a reduction in light transmittance so that optical detection accuracy can be improved. Moreover, it is possible to protrude an optical detection device from the surface of the polishing platen so that the device can be closer to the recessed part in the light-transmitting region. As a result, optical detection accuracy can be more improved because the distance between the material (wafer) to be polished and the optical detection device can be shortened.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a schematic view showing one example of a polishing apparatus used in CMP polishing.

"FIG. 2 is a schematic sectional view showing one example of a structure of the polishing pad of the present invention.

"FIG. 3 is a schematic sectional view showing another example of a structure of the polishing pad of the present invention."

For additional information on this patent application, see: Kimura, Tsuyoshi. Polishing Pad. Filed August 24, 2012 and posted August 7, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=2522&p=51&f=G&l=50&d=PG01&S1=20140731.PD.&OS=PD/20140731&RS=PD/20140731

Keywords for this news article include: Electronics, Semiconductor, Toyo Tire & Rubber Co. Ltd.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Electronics Newsweekly


Story Tools






HispanicBusiness.com Facebook Linkedin Twitter RSS Feed Email Alerts & Newsletters