Waferless clean process of a dry etcher

Details Waferless clean process of a dry etcher Waferless clean process of a dry etcher

1999-09-20

2001-12-04

Powell, William A. (Department: 1765)

Etching a substrate: processes

Gas phase etching of substrate

Application of energy to the gaseous etchant or to the...

C134S031000, C134S001100, C216S079000, C438S710000

Reexamination Certificate

active

06325948

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a waferless clean process and, more particularly to a waferless automatic clean process for cleaning a reaction chamber of dry etchers in semiconductor manufacturing processes.
2. Description of the Related Art
Many conventional etching machines cause byproducts to deposit on the surfaces of the reaction chamber to form particles. The particles will contaminate a wafer being produced and thus a defection wafer is produced. Thus, after a period of production, wet cleaning the chamber by a chemical solution is necessary. However, wet cleaning the chamber is time-consuming. To overcome this problem, a periodic plasma cleaning is usually used for cleaning the chamber and may extend MTBC (Mean Time Between Wet Clean).
The conventional plasma cleaning method includes: after a wafer produced in a reaction chamber, transporting the wafer from the reaction chamber to a loading dock; unloading the wafer from the loading dock by an operator; loading a plasma cleaning and seasoning dummy wafer to the loading dock by the operator and then to the chamber; plasma cleaning and seasoning the chamber, unloading the plasma cleaning and seasoning wafer from the chamber to the loading dock; unloading the plasma cleaning and seasoning wafer from the loading dock by the operator; and loading a monitoring wafer to the loading dock by the operator and then to the chamber.
The shortcomings of the conventional plasma cleaning method are:
a) The production of wafers is interrupted by an operator in order to perform the plasma cleaning, and thus downtime of the etcher is increased and the throughput is decreased.
b) Oxide wafers are used for cleaning, and blanket Si or poly dummy wafers are used for seasoning. The silicon of the dummy wafer will react with the fluoride to produce a gaseous silicon fluoride (SiFx) to be dissipated and driven off by a pump, so that the reaction chamber is restored to the initial process conditions. Therefore, extra loading of providing oxide wafers, silicon wafers and poly wafers is imposed on a thin film module. Consequently, the cost is increased.
c) The MTBC is increased from 2000 RF minutes to 8000 RF minutes only (RF minutes stand for the time spent by a radio coil or the operation time of plasma cleaning).
The present invention provides a plasma cleaning method for a dry etcher without dummy wafers so as to overcome the above-mentioned disadvantages.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a waferless cleaning process for a dry etcher, which is an automatic process and does not need operators.
A further object of the present invention is to provide a waferless cleaning process for a dry etcher, which does not require any seasoning wafers, can reduce dummy wafer usage, and the wafer cost and loading on a thin film module can be reduced.
Another object of the present invention is to provide a practical waferless cleaning process for a dry etcher, which can increase the MTBC from 8000 RF minutes to 20000 RF minutes.
Still another object of the present invention is to provide a waferless cleaning process for a dry etcher which can overcome the above-mentioned disadvantages and can reduce the downtime of the etcher and increase the throughput.
In order to achieve the above objects, the present invention discloses a waferless cleaning process for a dry etcher, comprising: removing a first batch of wafers out of a reaction chamber of a dry etcher; automatically starting waferless plasma cleaning to clean the reaction chamber when at least a process factor reaches a preset condition; loading a second batch of wafers into the chamber after the cleaning procedure is finished; and performing normal production procedures. The process factor could be a lot number or the number of wafers processed in the chamber.
In one of preferred embodiments, the waferless cleaning process of the present invention further includes a waferless recovery step in which at least a reactive gas is input and plasma cleaning at a power ranging from 400 watts to 900 watts is performed before the step of loading next batch of wafers into the chamber. The reactive gas used in the waferless recovery step could be halide gas or oxygen. In one of the preferred embodiments, the reactive gas is a gaseous fluoride. In another preferred embodiment, the waferless cleaning process of the present invention further includes an inert gas purge step between the steps of loading next batch of wafers into the chamber and the waferless recovery step.
The operation procedures are simplified as follows:
After production of a batch of wafers is finished, the wafers are removed out of the chamber to the loading dock. Meanwhile the etcher automatically starts waferless plasma cleaning. The operator unloads the wafers and then loads monitoring wafers to the loading dock. After cleaning, the monitoring wafers are loaded into the chamber immediately.


REFERENCES:
patent: 5294262 (1994-03-01), Nishimura
patent: 5679214 (1997-10-01), Kuo
patent: 5679215 (1997-10-01), Barnes et al.
patent: 5756400 (1998-05-01), Ye et al.

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