Cleaning and liquid contact with solids – Processes – Including application of electrical radiant or wave energy...
Reexamination Certificate
1999-03-13
2001-02-27
Markoff, Alexander (Department: 1746)
Cleaning and liquid contact with solids
Processes
Including application of electrical radiant or wave energy...
C134S018000
Reexamination Certificate
active
06192898
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for cleaning a vacuum chamber used in fabricating integrated circuits, such as a chemical vapor deposition (CVD) chamber or physical vapor deposition (PVD) chamber.
2. Background of the Prior Art
In a typical CVD process adopted for manufacturing semiconductor devices, chemical reactions for depositing a desired material takes place in an enclosed processing chamber. The substrate receiving the material is typically supported on a susceptor or other substrate support member located inside the processing chamber. While the material is being deposited on the substrate, the material may also deposit as a film on the wall of the processing chamber. A residue of the material builds up corresponding to the number of substrates processed in the chamber, leading perhaps to an unstable process and typically to the generation of contaminants or particles in the chamber. Consequently, it is necessary to clean the interior of the processing chamber on a regular basis, for example by plasma discharge.
When the chamber cleaning operation is performed, the production of semiconductor devices can not continue. As a result, the effective productivity of the chamber, as measured by substrate throughput, decreases significantly. In order to increase the chamber productivity, it is necessary to quickly finish the cleaning operation and restart the production promptly after the end of the cleaning operation. Conventional plasma cleaning operations are complete, or reach an end point, when the residue is fully eliminated from the chamber as indicated by monitoring a variation in a prescribed light wavelength emitted by the plasma. However, it is difficult to correctly detect the end point of the cleaning operation using this method, because light emitted from lamps used to heat the substrate also heats, reacts with or otherwise affects the wavelength monitor.
Japanese Kokai Patent Application No. Hei 6[1994]-224163 (“the '163 patent”) discloses a process that attempts to solve this problem by detecting the end point of the cleaning operation using a mass spectrometer, or by monitoring the chamber pressure using a pressure meter. According to the method disclosed, the pressure variations within the chamber during the self-cleaning operation are measured directly. For example, when a pressure meter is used, the variation in the pressure in the vacuum chamber caused by generation of the reaction product is measured using a dial gauge to detect the end point of the self-cleaning operation.
However, when a mass spectrometer is used in accordance with the '163 patent, the system for detecting the end point of the cleaning operation becomes too large for practical use in a manufacturing process. Furthermore, when the pressure measurement is performed in the vacuum chamber according to the '163 patent, only the pressure drop inside the vacuum chamber is measured. This method of detecting the end point of a cleaning reaction is impractical and can easily provide false endpoints due to normal fluctuations in the chamber pressure.
Therefore, there is a need for a device and method for practical use in semiconductor manufacturing processes that can detect the end point of a process chamber cleaning operation without the problems described above.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for determining the endpoint of a chemical reaction in real time in a processing environment. Specifically, the present invention provides a method and apparatus for determining the endpoint of a cleaning process in a processing chamber by detecting a pressure change using a pressure detector positioned in an exhaust line downstream from the processing chamber. An advantage of detecting the endpoint using a pressure detector located outside of the chamber is that the endpoint detector is not subjected to the processing environment and will not be adversely affected by the sensitivities of the chamber or the real time regulation of the processing environment.
In one aspect of the invention, a self-cleaning chemical vapor deposition device is described and comprises a pressure-adjustable processing chamber having a pair of electrodes for generating a plasma therebetween; a source of electric power that is electrically connected to the electrodes; a cleaning gas supply line connected to the chamber, wherein the cleaning gas reacts with deposits in the chamber; an exhaust line having a first end connected to the processing chamber, a second end connected to an exhaust means, and an adjustable valve located between the first and second ends for controlling the pressure in the processing chamber, a first pressure detector connected to the exhaust line in a position between the exhaust means and the adjustable valve; and a controller that monitors the pressure detected by the first pressure detector to determine the end point of the cleaning gas reaction.
In another aspect of the invention, a method of cleaning deposits in a chemical vapor deposition chamber is provided comprising the steps of supplying a cleaning gas to the chamber; forming a plasma within the chamber; reacting the cleaning gas with deposits within the chamber until the deposits are consumed; exhausting gases from the chamber through an exhaust line communicating with an exhaust means; controlling an adjustable valve in the exhaust line to maintain a setpoint pressure within the chamber, detecting the pressure in the exhaust line between the adjustable valve and the exhaust means; and determining the end point of the reaction according to a change in the exhaust line pressure.
In still another aspect of the invention, a reaction chamber is provided comprising an enclosure for containing a solid or liquid material, the enclosure having a first pressure detector for detecting the pressure therein; a gas supply in communication with the enclosure for reacting with the material; and an exhaust line extending from the chamber and having an exhaust valve and a second pressure detector positioned in the exhaust line downstream from the exhaust valve, wherein the exhaust valve receives a signal from the first pressure detector and is controlled to maintain a substantially constant pressure in the enclosure.
In still another aspect of the invention, a method for determining the endpoint of a reaction between a first material in a processing chamber and a continuous flow of gas passing through the chamber to an exhaust line having an exhaust valve is provided, comprising the steps of detecting an operating pressure within the chamber; operating the exhaust valve to maintain the operating pressure; and detecting a pressure change in the exhaust line between the exhaust valve and the exhaust means to determine the endpoint of the reaction.
REFERENCES:
patent: 5311452 (1994-05-01), Yokota et al.
patent: 5423936 (1995-06-01), Tomita et al.
patent: 5914051 (1999-06-01), Kanai et al.
patent: 58-140126 (1983-08-01), None
patent: 6-224163 (1994-12-01), None
Aitani Terukazu
Yamamoto Takaaki
Applied Materials Inc.
Markoff Alexander
Thomason Moser & Patterson
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