Method and Apparatus for Measuring Process Parameters of a Plasma Etch Process

• US 20100216263A1
• Filed: 01/31/2008
• Published: 08/26/2010
• Est. Priority Date: 02/02/2007
• Status: Abandoned Application

• Current Assignee: Verity Instruments Incorporated
• Original Assignee: Lexas Research, Ltd. (Verity Instruments Incorporated)
• Inventors: Soberon, Felipe, Tipaka, Maria, Glynn, Shane, Daniels, Stephen
• Application Number:
  US12/524,855
• Publication Number:
  US 20100216263A1
• Time in Patent Office: Days
• US Class Current: 438/16
• CPC Class Codes: H01J 37/32935 Monitoring and controlling tubes by information coming from the object and/or discharge
• CPC Class Codes: H01J 37/32963 End-point detection
• CPC Class Codes: H01J 37/32972 Spectral analysis

Abstract

Method and apparatus for measuring process parameters of a plasma etch process. A method for detecting at least one process parameter of a plasma etch process being performed on a semiconductor wafer. The method comprises the steps of detecting light being generated from the plasma during the etch process, filtering the detected light to extract modulated light; and processing the detected modulated light to determine at least one process parameter of the etch process.

Claims

1-80. -80. (canceled)

81. A method for detecting at least one process parameter of a plasma etch process being performed on a semiconductor wafer, the method comprising the steps of:

detecting light being generated from the plasma during the etch process;

filtering the detected light to extract modulated light; and

processing the detected modulated light to determine at least one process parameter of the etch process.

82. The method of claim 81 wherein the process parameter is the endpoint or the etch rate of the etch process.

98. A data storage medium having a set of machine-executable instructions that describes the method for detecting at least one process parameter of a plasma etch process being performed on a semiconductor wafer according to claim 81.

83. A method for detecting the etch rate of a plasma etch process being performed on a semiconductor wafer, the method comprising the steps of:

detecting light being generated from the plasma during the etch process;

filtering the detected light to extract modulated light; and

processing the detected modulated light to determine the etch rate of the etch process.

84. The method of claim 83, wherein the detecting further comprises the step of filtering the light to detect selected wavelength bands.

85. The method of claim 83, wherein the processing comprises the steps of:

converting the detected light into a digital signal;

transforming the digital signal into a frequency domain signal;

extracting one or more pre-selected frequencies from the frequency domain signal for use as process monitor signals;

generating a plot proportional to the intensity of the process monitor signals over the elapsed time of the etch process; and

determining the etch rate from the plot.

86. The method of claim 85, wherein the step of generating a plot proportional to the intensity of the process monitor signals over the elapsed time of the etch process comprises:

calibrating the values of the process monitor signals so as to generate converted signal values; and

generating a plot of the converted signal values over the elapsed time of the etch process.

87. The method of claim 86 wherein the step of calibrating comprises the multiplication of a conversion constant to the values of the process monitor signals.

88. The method of claim 86, further comprising the step of integrating the plot so as to generate a second plot of etch area over elapsed time of the etch process, and determining the etch depth from the second plot.

89. The method of claim 88, further comprising the step of generating an indicator when a signal level transition in the second plot matches a stored value representing a target etch depth.

90. The method as claimed in any of claim 85, wherein the process monitor signals are determined during a test wafer analysis of wafers of the same batch as the wafer.

91. The method as claimed in any of claim 87, wherein the conversion constant is determined during a test wafer analysis of wafers of the same batch as the wafer.

92. The method of claim 90, wherein the test wafer analysis of the batch comprises the steps of:

detecting modulated light being generated from the plasma of a test wafer being etched over the duration of an etch process;

converting the detected modulated light into digital signals;

transforming the digital signals into frequency domain signals;

determining the main frequencies of the frequency domain signals; and

selecting those main frequencies which are sensitive to changes in the etch rate as the process monitor signals.

93. The method of claim 92, wherein the step of selecting those main frequencies which are sensitive to changes in the etch rate as the process monitor signals comprises the step of:

generating electron microscopy images of a set of test wafers over the etching process, measuring the etch rate and etch depth of the etch process as a function of time from the generated images; and

selecting those main frequencies which have values over time which correlate to the measured etch rate and etch depth as the process monitor signals.

94. The method of claim 93, further comprising the step of establishing the linear relationship between the values of the selected process monitor signals over time and the actual etch rate.

95. The method of claim 94, wherein the established linear relationship is stored as the conversion constant.

99. A data storage medium having a set of machine-executable instructions that describes the method for detecting the etch rate of a plasma etch process being performed on a semiconductor wafer being performed on a semiconductor wafer according to claim 83.

96. A method to determine the process monitor signals and conversion constant for use in a method of detecting the etch rate of a plasma etch process to be performed on a semiconductor wafer from a particular wafer batch, the method comprising the steps of:

placing a test wafer of the wafer batch in a plasma etching tool and initiating the etch process;

detecting modulated light being generated from the plasma of the test wafer over the duration of the etch process;

converting the detected modulated light into digital signals;

transforming the digital signals into frequency domain signals;

determining the main frequencies of the frequency domain signals;

selecting those main frequencies which are sensitive to changes in the etch rate as the process monitor signals;

establishing the linear relationship between the values of the selected process monitor signals over time and the actual etch rate; and

storing the established linear relationship as the conversion constant.

100. A data storage medium having a set of machine-executable instructions that describes the method to determine the process monitor signals and conversion constant for use in a method of detecting the etch rate of a plasma etch process to be performed on a semiconductor wafer from a particular wafer batch according to claim 96.

97. An apparatus for determining the process monitor signals and conversion constant for use in detecting the etch rate of a plasma etch process to be performed on a semiconductor wafer from a particular wafer batch, comprising:

a plasma etching tool;

a means for detecting modulated light being generated from the plasma of the test wafer over the duration of the etch process;

a means for converting the detected modulated light into digital signals;

a means for transforming the digital signals into frequency domain signals;

a means for determining the main frequencies of the frequency domain signals;

a means for selecting those main frequencies which are sensitive to changes in the etch rate as the process monitor signals;

a means for establishing the linear relationship between the values of the selected process monitor signals over time and the actual etch rate; and

a means for storing the established linear relationship as the conversion constant.

101. A method for detecting the endpoint of a plasma etch process being performed on a semiconductor wafer, the method comprising the steps of:

detecting light being generated from the plasma;

filtering the detected light to extract modulated light;

processing the detected modulated light to determine when the endpoint of the etch process has been reached; and

generating an indicator when the endpoint has been determined.

102. The method as claimed in claim 101, wherein the detecting further comprises the step of filtering the light to detect selected wavelength bands.

103. The method as claimed in claim 101, wherein the processing comprises performing an endpoint detection algorithm on the detected modulated light.

104. The method as claimed in claim 103, wherein the endpoint detection algorithm comprises the steps of:

converting the detected light into a digital signal;

transforming the digital signal into a frequency domain signal;

determining whether a signal level transition of one or more pre-selected frequencies matches a stored signal level transition value which corresponds to when the endpoint in the etch process is reached.

105. The method as claimed in claim 104, wherein the step of determining whether a signal level transition of one or more pre-selected frequencies matches a stored signal level transition value comprises the steps of:

extracting the one or more pre-selected frequencies from the frequency domain signal for use as process monitor signals;

generating a plot of the intensity of the process monitor signals over the elapsed time of the etch process; and

determining whether a signal level transition in the plot matches a stored signal level transition value.

106. The method as claimed in any of claim 104, wherein the stored signal level transition value and the process monitor signals are determined during a test wafer analysis of wafers of the same batch as the wafer.

107. The method of claim 106, wherein the test wafer analysis of the batch comprises the steps of:

detecting modulated light being generated from the plasma of a test wafer being etched over the duration of the etch process;

converting the detected modulated light signals into digital signals;

transforming the digital signals into frequency domain signals;

determining the main frequencies of the frequency domain signals;

selecting those main frequencies which exhibit a signal level transition when the endpoint of the etch process is reached as the process monitor signals; and

storing the value of this signal level transition for use as the stored signal level transition value.

108. The method of claim 107 wherein the step of selecting those main frequencies which exhibit a signal level transition when the endpoint of the etch process is reached as the process monitor signals comprises the step of generating a plot of the intensity of the main frequencies over the duration of the time of the etch process;

and selecting those main frequencies which exhibit in the plot a signal level transition when the endpoint of the etch process is reached as the process monitor signals.

109. The method of any of claim 107, further comprising the step of:

generating electron microscopy images of the test wafer; and

wherein the step of selecting further comprises selecting those main frequencies which exhibit in the plot a signal level transition when the test wafer images show that the endpoint of the etch process is reached as the process monitor signals.

114. A data storage medium having a set of machine-executable instructions that describes the method of detecting the endpoint of a plasma etch process being performed on a semiconductor wafer according to claim 101.

110. A method to determine the process monitor signals and a signal level transition value for use in a method of detecting the endpoint of a plasma etch process to be performed on a semiconductor wafer from a particular wafer batch, the method comprising the steps of:

placing a test wafer of the wafer batch in a plasma etching tool and initiating the etch process;

detecting modulated light being generated from the plasma of the test wafer over the duration of the etch process;

converting the detected modulated light signals into digital signals;

transforming the digital signals into frequency domain signals;

determining the main frequencies of the frequency domain signals;

generating a plot of the intensity of the main frequencies over the duration of the time of the etch process;

selecting those main frequencies which exhibit in the plot a signal level transition when the endpoint of the etch process is reached as the process monitor signals; and

selecting the value of this signal level transition as the signal level transition value to be stored.

111. The method of any of claim 110, further comprising the step of:

generating electron microscopy images of the test wafer; and

wherein the step of selecting further comprises selecting those main frequencies which exhibit in the plot a signal level transition when the test wafer images show that the endpoint of the etch process is reached as the process monitor signals.

115. A data storage medium having a set of machine-executable instructions that describes the method to determine the process monitor signals and a signal level transition value for use in a method of detecting the endpoint of a plasma etch process to be performed on a semiconductor wafer from a particular wafer batch according to claim 110.

112. An apparatus for detecting the endpoint of a plasma etch process to be performed on a semiconductor wafer, comprising:

a plasma etching tool;

means for detecting light to be generated from the plasma during an etch process;

means for filtering the detected light to extract modulated light;

means for processing the detected modulated light to determine when the endpoint of the etch process has been reached; and

means for generating an indicator when the endpoint has been determined.

113. An apparatus for determining the process monitor signals and the signal level transition value to be stored for use in detecting the endpoint of a plasma etch process to be performed on a semiconductor wafer from a particular wafer batch, comprising:

a plasma etching tool;

a means for detecting modulated light to be generated from the plasma of a test wafer of the wafer batch over the duration of an etch process;

a means for converting the detected modulated light signals into digital signals;

a means for transforming the digital signals into frequency domain signals;

a means for determining the main frequencies of the frequency domain signals;

a means for selecting those main frequencies which exhibit a signal level transition when the endpoint of the etch process is reached as the process monitor signals; and

a means for selecting the value of this signal level transition as the signal level transition value.