Trench etch endpoint detection by LIF
First Claim
1. A reactive ion etching apparatus capable of automatically changing the etching when a given layer of one or more integrated circuit wafers is etched through to a second layer therebelow, wherein said given layer and said second layer have different concentrations of a minor species to be monitored, with the layer concentration thereof being less than or equal to 10% of the wafer layer by weight, comprising:
- a plasma reactor housing containing a chamber and means for placing said wafer therein;
means for generating an etching ion plasma in said chamber suitable for etching said given layer through to said second layer and for causing said minor species to enter said plasma, wherein when said given layer is etched through to said second layer, the concentration of said minor species in said plasma changes;
means for directing a laser beam through said plasma in said chamber, with said laser beam having a first frequency suitable for pumping said minor species in its plasma to an excited energy state thereof, with said pumped minor species in said excited energy state then emitting a second frequency of radiation as said pumped minor species decays to a lower energy state;
means for detecting only said second frequency of radiation in said chamber and for generating a control signal when a change in a parameter of said second radiation frequency is detected; and
means for controlling said etching ion plasma generating means to change the plasma generation in accordance with said control signal from said detecting means.
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Accused Products
Abstract
Laser induced fluorescence is utilized to detect and control the reactive ion etch-through of a given layer in a wafer by detecting a large change in the concentration of a selected minor species from the wafer in the etching plasma. This selected minor species must be present in a significantly different concentration in the etched given layer compared to adjacent layers in the wafer in order to provide a proper endpoint detection. In one embodiment, when the large change in the selected minor species concentration is detected, then the RF electrodes for the reactor are automatically de-energized.
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Citations
43 Claims
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1. A reactive ion etching apparatus capable of automatically changing the etching when a given layer of one or more integrated circuit wafers is etched through to a second layer therebelow, wherein said given layer and said second layer have different concentrations of a minor species to be monitored, with the layer concentration thereof being less than or equal to 10% of the wafer layer by weight, comprising:
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a plasma reactor housing containing a chamber and means for placing said wafer therein; means for generating an etching ion plasma in said chamber suitable for etching said given layer through to said second layer and for causing said minor species to enter said plasma, wherein when said given layer is etched through to said second layer, the concentration of said minor species in said plasma changes; means for directing a laser beam through said plasma in said chamber, with said laser beam having a first frequency suitable for pumping said minor species in its plasma to an excited energy state thereof, with said pumped minor species in said excited energy state then emitting a second frequency of radiation as said pumped minor species decays to a lower energy state; means for detecting only said second frequency of radiation in said chamber and for generating a control signal when a change in a parameter of said second radiation frequency is detected; and means for controlling said etching ion plasma generating means to change the plasma generation in accordance with said control signal from said detecting means. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method for automatically controlling the etching of an integrated circuit wafer in the chamber of a reactive ion etching reactor when a given layer of radiation as said pumped minor species decays to a said wafer is etched through to a second layer therebelow, wherein said given layer and said second layer have different concentrations of a minor species, with the larger concentration thereof being less than or equal to 10% of either of the wafer layers by weight, comprising the steps of:
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etching said wafer in said etching reactor with an etching ion plasma suitable for etching said given layer through to said second layer and for causing said minor species to enter said plasma, wherein when said given layer is etched through to said second layer, the concentration or said minor species changes; directing a laser beam through said plasma in said chamber, with said laser beam having a first frequency suitable for pumping said minor species in said plasma to an excited energy state thereof, with said pumped minor species in said excited energy state then emitting a second frequency of radiation as said pumped minor species decays to a lower energy state; detecting said second frequency of radiation in said chamber; generating a control signal when a change in a parameter of said second frequency of radiation is detected, thereby indicating that said given layer has been etched through to said second layer; and changing the plasma generation in said chamber in accordance with said control signal. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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Specification