Semiconductor device manufacturing: process – Chemical etching – Liquid phase etching
Reexamination Certificate
2000-01-17
2001-06-19
Utech, Benjamin L. (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Liquid phase etching
Reexamination Certificate
active
06248670
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to the field of wet processing of substrates, and in particular, to an apparatus and method for wet processing silicon substrates in a controlled environment to facilitate an improved etch rate, uniformity, contamination reduction, and other performance enhancements.
BACKGROUND OF THE INVENTION
Wet processing of silicon substrates is well known in the art. It is a process where substrates are treated with liquid agents, such as etchant chemicals or water, to etch selective portions of the substrate, remove photoresist, clean, and to perform other functions generally related to the fabrication of semiconductor devices.
Currently, the etchant chemicals are introduced to the substrates in one of two ways. The first way, known as batch processing, is to immerse a batch of substrates in a chemical bath for a specified period of time and removing them from the bath for rinsing. The second way, known as one-to-one processing, is to flood a single substrate with a wet chemical spray and to spin the substrate on a chuck. These two methods can be used in conjunction with each other. A typical wet processing of substrates entails a series of steps where the substrate is exposed to one type of chemical, then rinsed or dried, exposed to a different type of chemical (if needed), and so on, until the desired pattern is formed on the surface of the substrate.
Currently, the wet processing of substrates is not a completely controlled process for two main reasons. First, the substrates being processed are exposed to environmental factors which may cause undesirable effects on the final product. Because the substrate processing is done in an open environment, factors such as humidity, temperature, and contamination levels are not precisely controlled. Control over these factors is important because they affect the processing parameters and consequently the final outcome. For instance, humidity can affect how quickly an etchant evaporates from the surface of the substrate. If the evaporation occurs too quickly, there may not have been enough exposure to sufficiently etch the substrate.
To avoid these environment-related problems, the system must be in a closed environment. However, currently, the closed environment is generally only found in the dry-processing systems such as plasma etching or ion etching systems. And while the dry etching systems generally do not suffer from some of the shortcomings discussed above, they have other shortcomings not present in the wet processing such as lack of selectivity. Hence, dry-processing does not provide a complete solution.
The second reason for failure to achieve a controlled environment aside from the open environment is the inability to precisely control the amount of exposure the substrate has with a particular chemical. Excessive exposure may cause excessive removal of the substrate or photoresist. Under-exposure, on the other hand, may cause not enough removal. Controlling the amount of exposure to the various chemicals has been difficult because it is generally difficult to controllably remove the residual liquid from the surface of the substrate when the exposure is deemed to have been enough. This is particularly true for batch processing since the etchant chemical trickles over the edge of the substrate when the substrate is removed from the chemical bath. Although the one-to-one processing has attempted to solve this problem, the existing systems generally have not been completely successful.
These and other shortcomings have lead to slower processing time and/or performance defects that contribute to the general slow down in the overall manufacturing of semiconductor devices, and the lowering of yield. Although some wet processing systems with closed environment do exist, they have failed to achieve the level of etching uniformity that can be achieved via the present invention. As of this date, there has not been an apparatus or method of utilizing the selectivity of wet processing with the environmental controllability of dry etching while providing superior uniformity. Therefore, it is easy to see the desirability of having an apparatus and method for facilitating a controlled environment for a wet processing of wafer substrates.
OBJECT OF THE INVENTION
It is therefore, an object of the present invention to provide a wet processing apparatus which can control the pertinent so as to achieve a superior result in the wet processing of a substrate.
SUMMARY OF THE INVENTION
The present invention is an apparatus for wet processing of substrates in a controlled environment. It is a single-substrate processing apparatus which is capable of carrying out etching, rinsing, and drying processes all in a single apparatus and in a controlled environment.
The present wet-processing apparatus comprises a processing chamber which is placed inside a container. Inside the chamber is a set of vacuum contacts which support and hold the substrate. The chamber is connected to a shaft which is coupled to a motor. The motor facilitates the spinning of the shaft which in turn rotates the entire chamber and the wafer substrate.
The chamber is sealed by a cover. The cover is attached to a movable shaft which facilitates the opening and the closing of the chamber by raising or lowering the cover from the chamber. The interface between the cover and the chamber side walls should be sufficiently tight so as to preserve a substantially closed environment inside the chamber when the cover is in a closed position. A pin holds the cover to the chamber wall such that the cover rotates with the chamber when the chamber is being rotated.
A dispenser is located above the substrate for dispensing a processing liquid onto the substrate. The processing liquid may be deionized water, chemical etchant or some other liquid depending upon whether the process is washing, etching or some other treatment process. To avoid mixing the liquids, separate nozzles connected to separate pipelines may be provided.
The dispensed chemicals and other processing liquids are removed via an opening in the chamber walls. Air bearing is provided at the interface between the dispenser and the cover so as to allow the cover to rotate around the dispenser while providing a relatively good sealant to prevent gases from entering into and escaping from the chamber.
To prevent an etchant from etching the backside of the substrate and the chemically-sensitive portions of the chamber, a ring of protective wall is provided underneath the substrate to block the etchant from flowing towards the inner portion of the substrate. Furthermore, a backside rinse agent, e.g., deionized water, is continuously supplied through an opening which delivers the agent to the underside of the substrate.
Inside the shaft is a hollow channel for delivering processing gases to the chamber. The gas may be deionized water vapor, N
2
, isopropylalcohol (IPA), or some other gas depending on whether the chamber is being purged, dried, wetted, or processed in some other manner. A heater is provided to control the temperature inside the chamber by heating the processing gas to the necessary temperature. The humidity inside the chamber is controlled by controlling the percentage of water vapor which is mixed in with the other gases.
To remove the gas which is released into the chamber, the chamber wall has small openings. To facilitate the removal of the gas from the chamber and into the container, the container is provided an exhaust pipe which draws out the gas from the container.
REFERENCES:
patent: 5089084 (1992-02-01), Chhabra et al.
patent: 5169408 (1992-12-01), Biggerstaff et al.
Fu Ta-Hsing
Hung Ching-Chang Alex
Baird Andrea M
Chung David
Ho Lawrence Y. D.
Techpoint Pacific Singapore Pte. Ltd.
Utech Benjamin L.
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