Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
1998-05-26
2001-03-06
Gordon, Paul P. (Department: 2786)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C356S237300, C716S030000
Reexamination Certificate
active
06198982
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to semiconductor exposure equipment which irradiates a wafer with light passed through a design pattern in order to expose a photoresist on the wafer to the design pattern. More particularly, the present invention relates to a method of and apparatus for detecting the presence of particles on a wafer holder of the semiconductor equipment which supports the wafer, and to a method of determining whether the presence of such particles is significant enough to constitute a defect.
2. Description of the Related Art
Generally, when manufacturing semiconductor devices, photomasking is used to transfer a semiconductor design pattern onto a wafer. This is achieved by first depositing photoresist on a wafer. Then the wafer/resist combination is inserted into a mask aligner, which contains the optics, ultraviolet (UV) light source, and the circuit layer image contained on a mask or reticle, which is to be transferred to the resist film. The mask or reticle pattern image can be transferred to the wafer on a scale of one-to-one, or at a reduced scale using projection optics to focus and reduce the image.
The exposure equipment (mask aligner) also contains a wafer holder for mounting the wafer thereon. The wafer holder itself is disposed on a stage, with the stage being driven by a motor or other driving device. After the wafer is mounted on the wafer holder, the reticle and wafer are aligned by driving the stage. Then, the design pattern is transferred onto the photoresist of the wafer using a light source which irradiates the reticle, and a reduction projection lens through which the light is passed to the wafer.
It is common for registration tolerances in high density chips to be on the order of ±2000 Å. The total exposure energy is the combination of light intensity and exposure time, which must be tightly controlled to assure proper image reproduction.
However, this exposure process is often carried out while particles inadvertently remain on the wafer holder beneath the wafer, which can not be detected by conventional methods. Because the exposure process is carried out repeatedly, an accumulation of particles on the stage often results in some malfunction of the exposure equipment. Accordingly, the particles may also cause a mass of defects in the final semiconductor devices or, at the every least, may adversely affect the production yield.
SUMMARY OF THE INVENTION
An object of the invention, therefore, is to substantially overcome the problems, limitations and disadvantages in the prior art by providing a method of and apparatus for detecting the presence of particles beneath a wafer on the wafer holder of semiconductor exposure equipment.
To achieve this and other objects, the present invention provides a method of detecting the presence of particles on the wafer holder of semiconductor exposure equipment characterized by a step of analyzing any up-and-down movement of the stage supporting the wafer holder during the wafer alignment step(s) to determine whether particles are present on the wafer holder beneath the wafer.
The analysis of the up-and-down movement of the stage is conducted based on signals from a motor which moves the stage in the vertical (Z-axis) direction, or based on signals from a sensor indicative of the distance that the stage deviates vertically from a reference position. Preferably, the signals are voltage signals generated at the time a shutter of the exposure equipment has opened.
The present invention also provides a method of determining a defect caused by the presence of particles on the wafer holder during the exposure of a wafer in the manufacture of a semiconductor device. In this case, as respective portions of the wafer are aligned for exposure, each portion is checked for the presence of particles therebelow according to the method outlined above. The number of respective portions of the wafer which are determined to have a particle(s) therebelow is tracked. When this number reaches a predetermined value, it is judged that the presence of the particles is so serious as to constitute a fatal defect.
The present invention also provides an apparatus for detecting the presence of particles on the wafer holder of semiconductor exposure equipment, the apparatus including feedback means for producing signals representative of the up-and-down movement of the stage, and processing means for processing the signals in a manner that produces data indicative of whether particles are present on the wafer holder beneath the wafer.
The feedback means can be either a feedback loop (of a type well known to those of ordinary skill in the art) from the control of the motor which moves the stage in the direction of the Z axis, or a sensor which senses the position of the surface of the wafer at a fixed location where specific portions of the wafer are brought for alignment in preparation of their exposure. The processing means includes an input device for inputting the signals as analog signals, a computer processor which processes the analog signals to generate data indicative of whether particles are present on the stage, and an output device for outputting the data as digital signals.
The feedback means may be provided for each of several sets of exposure equipment. In this case, the input device of the processing means is connected to each feedback means. That is, the processing means may be connected to at least two sets of exposure equipment so that the processor can simultaneously monitor the exposure of several wafers at a time for the presence of potentially harmful particles.
REFERENCES:
patent: Re. 33991 (1992-07-01), Shiba et al.
patent: 4641967 (1987-02-01), Pecen
patent: 4849901 (1989-07-01), Shimizu
patent: 5291239 (1994-03-01), Jackson
patent: 5311275 (1994-05-01), Taniguchi et al.
patent: 5361122 (1994-11-01), Kataoka et al.
patent: 5365051 (1994-11-01), Suzuki et al.
patent: 5422724 (1995-06-01), Kinney et al.
patent: 5483056 (1996-01-01), Imai
patent: 5673208 (1997-09-01), Meier et al.
patent: 5913105 (1999-06-01), McIntyre et al.
patent: 5940175 (1999-08-01), Sun
patent: 5963315 (1999-10-01), Hiatt et al.
patent: 6011619 (2000-01-01), Steffan et al.
Park Soon-jong
Yun Jong-soon
Gain, Jr. Edward F.
Gordon Paul P.
Jones Volentine, LLC
Samsung Electronics Co,. Ltd.
LandOfFree
Method and apparatus for detecting the presence of particles... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for detecting the presence of particles..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for detecting the presence of particles... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2451763