WAFER POLISHING HEAD
A wafer polishing head according to the invention is disclosed. In the wafer polishing head, an automatic control device is additionally installed outside the wafer polishing head for automatically adjusting a pressure applied on a retaining ring. This ensures the bottom of the retaining ring always lower than that of a carrier, thereby preventing a semiconductor wafer from slip during polishing. Furthermore, a liquid pressure generated to press the carrier can efficiently alleviate wabble during polishing. Therefore, the wafer polishing head of the invention can greatly improve a polishing uniformity.
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This application is a continuation of a prior application Ser. No. 09/741,072, filed Dec. 21, 2000. The prior application Ser. No. 09/741,072 claims the priority benefit of U.S. Pat. No. 6,220,930 B1, issued on Apr. 24, 2001. The U.S. Pat. No. 6,220,930 B1 is a continuation-in-part of a prior application Ser. No. 09/185,098, filed Nov. 3, 1998. All disclosure of the prior patent and applications are incorporated herein by references.
BACKGROUND OF THE INVENTION1. Field of the Invention
The invention relates to a chemical mechanical polishing (CMP) device, and in particular to a wafer polishing head controlled by gas and liquid pressures.
2. Description of the Related Art
Chemical mechanical polishing (CMP) is a global planarization technique. In chemical mechanical polishing, the rear surface of a semiconductor wafer is fixed by a wafer polishing head. Then, the front surface of the semiconductor wafer is pressed against a polishing pad which is installed on a removable platen. When polishing, a chemical agent conducive to CMP is continuously supplied to the platen. By the chemical reaction between the chemical agent and the front surface of the semiconductor wafer and mechanical polishing, the front surface of the semiconductor wafer can be completely planarized.
The wafer polishing head is used to safely and firmly hold the semiconductor wafer without any damage or contamination on the semiconductor wafer. In an early phase, a semiconductor wafer was adhered on a carrier with a material like wax. After polishing, the wax must be completely removed or the semiconductor wafer is contaminated. Currently, a wafer adhering layer is additionally disposed on the bottom of the carrier. Since the wafer adhering layer is made of a porous material, a semiconductor wafer can be firmly held on the carrier by creating a vacuum environment. However, a high-speed rotation could cause the semiconductor wafer slipping during polishing. Therefore, a retaining ring is additionally installed to surround the semiconductor wafer, thereby preventing the semiconductor wafer from slip. The retaining ring must be rigid and uneasily react with any chemical agent. Typically, Delrin and Tecktron are used to make the retaining ring.
During polishing, the retaining ring 26 always contacts the diaphragm 22, resulting in an abrasion therebetween. Under this condition, it is easy to cause the semiconductor wafer 16 slipping if the bottom of the carrier 12 is lower than that of the retaining ring 18. To resolve this problem, it is necessary to regularly adjust the retaining ring 18 thereby to maintain the bottom of the retaining ring 16 at a lower position than that of the carrier 10.
As can be obviously seen from the above, the prior wafer polishing head uses a gas pressure to provide a vertical force to the semiconductor wafer and the polishing pad, thereby alleviating wabble during polishing. However, the gas pressure depends on the stability of the gas source. As a result, it is easy to cause wabble on the semiconductor wafer and the polishing pad, resulting in a poor polishing uniformity. Moreover, the retaining ring always contacts the polishing pad, causing an abrasion therebetween. In this case, it is easily to make the semiconductor wafer slip if the bottom of the carrier is lower than that of the retaining ring. To overcome this problem, the retaining ring must be regularly and manually adjusted to an appropriate position, and pressures generated by a gas to press the carrier and the retaining ring are also manually adjusted to different proper pressure values even though the gas comes from the same gas source.
SUMMARY OF THE INVENTIONIn view of the above, an object of the invention is to provide a wafer polishing head which uses a liquid pressure to press a carrier thereby to obtain a better polishing uniformity. Furthermore, a pressure applied on a retaining ring is automatically adjusted by an automatic control device, thereby allowing the retaining ring to efficiently prevent a semiconductor wafer from slip during polishing.
As to the wafer polishing head according to the invention, an automatic control pressure device, which is additionally installed outside the wafer polishing head, can automatically adjust a pressure applied on a retaining ring, thereby ensuring a polished semiconductor wafer does not slip away. In addition, the wafer polishing head can greatly alleviate wabble on the carrier by using a liquid pressure to press the carrier. Accordingly, the wafer polishing head of the invention can greatly improve a polishing uniformity.
BRIEF DESCRIPTION OF THE DRAWINGSThe invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only, and thus do not limit the present invention, and wherein:
Referring to
In summary, the advantages of the wafer polishing head according to the invention are as follows:
(1) A polishing uniformity is greatly improved since the liquid pressure generated to press the carrier can efficiently alleviate wabble, and make the carrier and the semiconductor wafer parallel to each other.
(2) The retaining ring is adjusted by the automatic control pressure device without manual adjustments. This ensures that the bottom of the retaining ring is always lower than that of the carrier. Therefore, the semiconductor wafer can be well protected during polishing and the lifetime of the retaining ring is extended.
While the invention has been described by way of example and in terms of the preferred embodiment, it is to be understood that the invention is not limited to the disclosed embodiment. To the contrary, it is intended to cover various modifications and similar arrangements as would be apparent to those skilled in the art. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
Claims
1. A wafer polishing head for planarizing a wafer comprising a carrier for loading the wafer, a wafer adhering layer disposed beneath the carrier, a retaining ring surrounding the carrier and the wafer adhering layer, the wafer polishing comprising:
- a first pressure chamber having a first inner pressure disposed above the retaining ring;
- a second pressure chamber having a second inner pressure disposed on the carrier; and
- an automatic control system respectively coupled to the first pressure chamber and the second pressure chamber for adjusting a relative height between the carrier and the retaining ring.
2. A wafer polishing head for planarizing a wafer comprising a carrier for loading the wafer, a wafer adhering layer disposed beneath the carrier, a retaining ring surrounding the carrier and the wafer adhering layer, the wafer polishing comprising:
- a first pressure chamber having a first inner pressure disposed above the retaining ring; and
- a second pressure chamber having a second inner pressure disposed on the carrier, wherein a relative height between the retaining ring and the carrier can be adjusted by changing the first and second inner pressure.
3. A wafer polishing head for planarizing a wafer comprising a carrier for loading the wafer, a wafer adhering layer disposed beneath the carrier, a retaining ring surrounding the carrier, the wafer adhering layer, a first pressure chamber having a first inner pressure disposed above the retaining ring, and a second pressure chamber having a second inner pressure disposed on the carrier, the wafer polishing comprising:
- an automatic control system respectively coupled to the first pressure chamber and the second pressure chamber for adjusting a relative height between the carrier and the retaining ring.
Type: Application
Filed: Sep 5, 2007
Publication Date: Dec 27, 2007
Applicant: UNITED MICROELECTRONICS CORP. (Hsinchu)
Inventors: Chin-Kun Lin (Kaohsiung City), Jian-Shing Lai (Kaohsiung Hsien), Peng-Yih Peng (Hsinchu Hsien), Chia-Jui Chang (Keelung)
Application Number: 11/850,453
International Classification: B24B 37/04 (20060101);