Semiconductor device manufacturing: process – With measuring or testing
Reexamination Certificate
2000-06-22
2003-02-04
Sherry, Michael (Department: 2829)
Semiconductor device manufacturing: process
With measuring or testing
C073S053010
Reexamination Certificate
active
06514776
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an instrument used for detecting contamination of the surface of a semiconductor wafer and to technology associated therewith, and more particularly, to an instrument suitable for detecting contaminants adhering to a wafer surface by means of the water-extracting technique.
2. Background Art
Contaminants adhering to a wafer surface are responsible for deterioration of the yield, performance, and reliability of a semiconductor device. Processes for manufacturing a semiconductor device include a number of cleaning steps. In spite of those cleaning steps, a wafer surface may be contaminated with particles, metal, various ions, or organic substances. In the event of a wafer surface being contaminated, immediate investigation of the source and cause of contamination is required for maintaining a high degree of cleanliness of semiconductor manufacturing processes. The importance of high-degree cleanliness grows increasingly in association with an increase in the density and integration of a semiconductor device.
Contamination of a wafer surface is usually determined by means of extracting. contaminants adhering to a wafer surface, through use of a specifically-designed solvent. The thus-extracted solution is subjected to qualitative/quantitative analysis by use of an analyzer [for example, ICP-MS (High-Frequency Inductively-Coupled Plasma Mass Analyzing System)].
According to the conventional technique for extracting contaminants to be delivered to analyzing processes, a wafer is put in a film pack for extracting a hot-water bag, and pure water is poured into the film pack. The wafer is left in its present form in a thermostatic chamber while being immersed in pure water within the film pack, to thereby extract the contaminants adhering to the wafer surface.
In the course of processes for manufacturing a semiconductor device, handling of an upper surface (a mirror-surface side) of a wafer completely differs from handling of an underside surface of the wafer. Further, the required cleanliness of an upper surface also greatly differs from that of an underside surface. Naturally, the state of contamination of the upper surface of the wafer greatly differs from that of the underside of the same. For this reason, contamination of the upper surface and contamination of the underside are preferably determined on an individual basis. The conventional extraction method involves a chance of the substances (contaminants) extracted from the upper surface and the substances extracted from the underside being mixed during the course of extraction processes, with the result that determination of contamination of solely the upper surface of a wafer has been infeasible.
To enable determination of contamination of a single side of a wafer, there, is used an extraction system which can extract contaminants from a respective side of a wafer by means of adding pure water to the surface of the wafer situated horizontally and vibrating the wafer. Although the extraction system enables extraction of contaminants from a single side of a wafer, the system can extract contaminants from solely either side of the wafer by way of a single determination operation. In a case where contamination of either side,of a wafer is desired to be determined, there must be prepared two wafers; i.e., one to be used for extracting contaminants from the upper surface of a wafer, and the other one to be used for extracting contaminants from the underside of the wafer.
Further, contaminants cannot be accurately determined unless contaminants are removed from the extraction system. For this reason, the extraction system must be cleaned every extraction operation. Thus, extraction of contaminants from either side of a wafer through use of such a extraction system involves consumption of much time and labor.
In association with a recent tendency toward an increase in the diameter of a wafer, predetermined areas on the same side of a wafer must be controlled in manners which differ from area to area. therefore, demand exists for not only attaining uniform cleanliness of solely either side of a wafer but also for attaining different degrees of cleanliness in a plurality of respective areas on the same surface. Increasing demand exists for a necessity for measuring contamination of a single surface as well as contamination of limited areas within a single surface. Any of the foregoing methods encounters difficulty in measuring contamination of limited areas on a wafer surface.
The present invention has been conceived in consideration of the above-described drawback of the background art and is aimed at providing an instrument capable of immediately and accurately extracting contaminants from solely either side of a wafer surface or from a certain area on the wafer surface.
SUMMARY OF THE INVENTION
As a result of considerable studies conducted by the inventors in order to solve the above-described drawback of the background art, the inventors have conceived an instrument suitable for independently and simultaneously measuring contaminants from the upper surface and underside of a wafer to be inspected, by means of enclosing certain areas on the upper surface and underside of the wafer independently, and feeding extraction solvent to the thus-enclosed areas independently. Thus, the inventors have completed the present invention.
To this end, a wafer to be inspected is held in a disposable film pack, and extraction solvent is fed into and drawn from the film pack, thereby eliminating a necessity for cleaning the extraction instrument every measurement operation. As a result, the clean state of the extraction instrument can be maintained, and an extraction operation can be made simple.
The instrument for measuring contamination of a wafer surface embodying the aforementioned idea is essentially materialized as follows:
(1) An instrument to be used for extracting contaminants from a wafer surface to be inspected, comprising:
a pair of wafer holding members which are provided opposite each other and hold the wafer from respective sides;
a curved protruding member provided on a surface of at least one of the wafer holding members, the surface being faced with the wafer, so as to cover a certain portion of the wafer surface while ensuring a predetermined entrance space; and
solvent to be used for extraction being reserved in a space formed between the wafer holding member and the wafer as a result of presence of the curved protruding member.
(2) Preferably, a support member for supporting the lower edge of the wafer to be inspected is provided on a lower portion of the wafer holding member, to thereby position the wafer.
(3) Preferably, the curved protruding member is a cord-like member.
(4) Preferably, the curve of the curved protruding member assumes a circular geometry.
(5) Preferably, an instrument set for measuring contamination of a wafer comprises the instrument for measuring contamination of a wafer surface, and a disposable bag for holding the wafer. The wafer held in the bag is held from both side thereof.
(6) Preferably, a portion of the disposable bag to be enclosed by the curved protruding member and a portion of the same corresponding to the predetermined entrances bulge particularly.
In a case where such a bag is used, storage of solvent to be used for extracting contaminants becomes comparatively easy. Therefore, a disposable bag is suitable for measurement.
The present invention further includes the following method derived by generalization of use of the instrument according to the present invention.
(7) The present invention provides a method of measuring contaminants adhering to a wafer surface through extraction, the method comprising the steps of:
enclosing a certain area on the upper surface of a wafer to be inspected independently of another certain area on the underside of the wafer; and
feeding and drawing extraction solvent to and from each of the enclosed areas independently, to thereby enable simultaneous and independe
Nagai Kiyoshi
Shibata Harumi
Yanagi Kumiko
Pert Evan
Sherry Michael
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