Semiconductor device manufacturing: process – Including control responsive to sensed condition – Optical characteristic sensed
Reexamination Certificate
2000-08-03
2001-10-02
Powell, William A. (Department: 1765)
Semiconductor device manufacturing: process
Including control responsive to sensed condition
Optical characteristic sensed
C156S345420, C216S060000, C438S710000
Reexamination Certificate
active
06297064
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of detecting the end point of a semiconductor plasma process in performing the process for a target object and, more particularly, to an end point detection method in dry etching. The semiconductor plasma process refers to various types of plasma processes performed to form a semiconductor layer, insulating layer, conductive layer, and the like on a target object such as a semiconductor wafer or LCD substrate with a predetermined pattern, so that a semiconductor device or a structure including an interconnection, electrode, and the like to be connected to the semiconductor device is manufactured on the target object.
BACKGROUND ART
In the semiconductor device manufacturing process, dry etching is an indispensable technique to form micropatterns. Dry etching is a method of generating a plasma in vacuum by using a reactive gas, and removing an etching target by using ions, neutral radicals, atoms, molecules, and the like in the plasma. If etching is continued after the etching target is completely removed, the underlying material may be unnecessarily etched, or the etching shape may be changed. Therefore, to obtain a structure as designed, it is very important to detect the end point of the etching process accurately.
Jpn. Pat. Appln. KOKAI Publication No. 5-102086 discloses a prior art of the end point detection method in etching, which was filed by the present inventor. According to this method, the end point of a dry etching process is determined on the basis of the intensity ratio of the emission intensity of an active species to the emission intensity of the reaction product, in the etching gas. More specifically, first, a conversion coefficient, which causes the average gradients of characteristic curves respectively representing the changes over time of the emission intensities of the active species and reaction product to coincide with each other in a predetermined specified period, is obtained. After the specified period elapses, the ratio of the emission intensity of the active species to that of the reaction product is detected while correcting the characteristic curves by using this conversion coefficient, and the end point of the dry etching process is determined on the basis of this ratio.
As described above, according to the method disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-102086, the two characteristic curves representing the emission intensities of the active species and reaction product after the lapse of the specified period are corrected by using the conversion coefficient that causes the average gradients of the two characteristic curves representing the emission intensities of the active species and reaction product to coincide with each other within the specified period. Since the average gradients of the characteristic curves are expressed by straight lines, i.e., linear functions, it is difficult to ideally overlay the non-linear two characteristic curves after the lapse of a specified period, as shown in
FIG. 2
of this reference. Since the average gradients of the characteristic curves largely differ depending on the width of the specified period, the reliability of end point determination largely depends on the width of the specified period.
Furthermore, the method described above aims at correcting the fluctuations in emission intensities of the active species and reaction product, which are caused by a slight variation in output from the power supply, the influence of a mass-flow controller, a variation in process pressure, an increase in temperature of the target object due to the plasma, and the like, by canceling each other. However, the fluctuation components of the emission intensities of two different materials differ regardless of whether they are active species or reaction products. Accordingly, this method cannot sufficiently correct these different fluctuation components.
DISCLOSURE OF INVENTION
The present invention has been made to solve the conventional problems as described above, and has as its object to provide a method which, when a target object such as a semiconductor wafer or LCD substrate is subjected to a semiconductor plasma process, can accurately detect the end point of the process.
According to the first aspect of the present invention, there is provided an end point detection method in a semiconductor plasma process, comprising the steps of:
determining a specified period set before an ideal end point of the plasma process is reached;
subjecting a target object to the plasma process;
obtaining, during the plasma process, an approximate expression which approximates a characteristic curve representing a change over time in emission intensity of a gas in the plasma within the specified period;
obtaining, during the plasma process, a criterion expression representing a ratio or difference between the emission intensity of the gas in the plasma and a value of the approximate expression after the specified period elapses; and
determining an end point of the plasma process on the basis of the criterion expression.
According to the second aspect of the present invention, there is provided an end point detection method in a semiconductor plasma process, comprising the steps of:
determining first and second specified periods set before an ideal end point of the plasma process is reached;
subjecting a target object to the plasma process;
obtaining, during the plasma process, a first approximate expression which approximates a characteristic curve representing a change over time in emission intensity of a first gas in the plasma within the first specified period, and a second approximate expression which approximates a characteristic curve representing a change over time in emission intensity of a second gas in the plasma within the second specified period;
obtaining, during the plasma process, first and second intermediate expressions representing ratios or differences between the emission intensities of the first and second gases in the plasma and values of the first and second approximate expressions after the first and second specified periods elapse;
obtaining a criterion expression representing a ratio of the first intermediate expression to the second intermediate expression; and
determining an end point of the plasma process on the basis of the criterion expression.
According to the third aspect of the present invention, there is provided an end point detection method in a semiconductor plasma process, comprising the steps of:
determining first to fourth specified periods set before an ideal end point of the plasma process is reached;
subjecting a target object to the plasma process;
obtaining, during the plasma process, a first approximate expression which approximates a characteristic curve representing a change over time in emission intensity of a first gas in the plasma within the first specified period, and a second approximate expression which approximates a characteristic curve representing a change over time in emission intensity of a second gas in the plasma within the second specified period;
obtaining, during the plasma process, a first deviation corresponding to a deviation of the emission intensity of the first gas in the plasma with respect to a value of the first approximate expression within the third specified period, and a second deviation corresponding to a deviation of the emission intensity of the second gas in the plasma with respect to a value of the second approximate expression within the fourth specified period;
obtaining, during the plasma process, first and second intermediate expressions representing ratios or differences between the emission intensities of the first and second gases in the plasma and the values of the first and second approximate expressions after the first to fourth specified periods elapse;
correcting the first and second intermediate expressions with the first and second deviations, and obtaining a criterion expression representing a ratio of the first intermediate expression to the second intermediate exp
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Powell William A.
Tokyo Electron Yamanashi Limited
LandOfFree
End point detecting method for semiconductor plasma processing does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with End point detecting method for semiconductor plasma processing, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and End point detecting method for semiconductor plasma processing will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2578947