Monitoring etching of a substrate in an etch chamber

Abstract

A substrate etching apparatus comprises a chamber having a wall with a window, substrate support pedestal, energy source, and monitoring assembly with signal sensor capable of detecting reflected radiation from the substrate from directly above the substrate after the radiation propagates through the window in the wall. An etching method comprises the steps of: providing a substrate in a chamber, etching a channel or trench in the substrate by coupling energy through the wall of the chamber to energize an etch gas in the chamber, detecting radiation reflected from the substrate from directly above the substrate after the radiation propagates through the wall and evaluating the detected radiation to monitor the depth of etching of the channel or trench being etched on the substrate.

1 . A method of etching a substrate in a chamber having a wall and detecting an endpoint of the etching process, the method comprising:
 (a) providing a substrate in the chamber;   (b) etching a channel or trench in the substrate by coupling energy through the wall of the chamber to energize an etch gas in the chamber;   (c) detecting radiation reflected from the substrate from directly above the substrate after the radiation propagates through the wall; and   (d) evaluating the detected radiation to monitor the depth of etching of the channel or trench being etched on the substrate.   
   
   
       2 . A method according to  claim 1  comprising coupling energy to the etch gas by inductive coupling. 
   
   
       3 . A method according to  claim 2  comprising inductively coupling energy through a substantial portion of a ceiling of the process chamber. 
   
   
       4 . A method according to  claim 3  comprising coupling energy by powering a multi-turn antenna that is non-vertical. 
   
   
       5 . A method according to  claim 1  comprising detecting radiation comprising an optical beam. 
   
   
       6 . A method according to  claim 1  comprising detecting radiation passing through a window in the wall. 
   
   
       7 . A method according to  claim 1  wherein (d) comprises detecting radiation propagating through the wall in a line-of-sight view of the substrate in the process chamber. 
   
   
       8 . A method according to  claim 1  further comprising directing radiation onto the substrate surface from directly above the surface of the substrate. 
   
   
       9 . A method according to  claim 1  comprising collimating the detected radiation and evaluating the detected collimated radiation to monitor a depth of the trench being etched on the substrate. 
   
   
       10 . An etching apparatus for etching a substrate, the apparatus comprising:
 (a) an etch chamber comprising a wall having a window;   (b) substrate support pedestal in the etch chamber, upon which a substrate can be retained;   (c) an energy source to couple energy to an etch gas in the chamber to form a plasma to etch a channel or trench in the substrate; and   (b) a process monitoring assembly to monitor a depth of the channel or trench being etched in the etch chamber, the process monitoring assembly comprising a signal sensor capable of detecting radiation reflected from the substrate from directly above the substrate after the radiation propagates through the window in the wall.   
   
   
       11 . An apparatus according to  claim 10  wherein the signal sensor monitors an optical emission intensity of the plasma. 
   
   
       12 . An apparatus according to  claim 10  wherein the signal sensor generates a plurality of signals indicative of the spectral intensity of the plasma. 
   
   
       13 . An apparatus according to  claim 10  wherein the signal sensor detects an optical beam that is reflected from the surface of the substrate. 
   
   
       14 . An apparatus according to  claim 10  wherein the energy source comprises an antenna proximate to the etch chamber. 
   
   
       15 . An apparatus according to  claim 14  wherein the antenna covers a ceiling of the etch chamber. 
   
   
       16 . An apparatus according to  claim 14  wherein the antenna is a multi-turn, non-vertical antenna. 
   
   
       17 . An apparatus according to  claim 10  wherein the process monitoring assembly comprises a collimating assembly. 
   
   
       18 . An apparatus according to  claim 17  wherein a signal source and signal sensor are connected to the collimating assembly via a transmission cable. 
   
   
       19 . An apparatus according to  claim 10  wherein the energy source comprises (i) a multi-turn antenna covering the wall of the etch chamber, and (ii) a cathode within the chamber. 
   
   
       20 . An apparatus according to  claim 19  wherein the wall of the process chamber is flat and the multi-turn antenna at least partially covers the flat wall. 
   
   
       21 . An apparatus according to  claim 10  wherein the wall of the process chamber comprises a ceiling. 
   
   
       22 . An apparatus according to  claim 21  wherein the ceiling comprises a ceramic. 
   
   
       23 . An apparatus according to  claim 10  wherein the ceramic comprises alumina or silica. 
   
   
       24 . An apparatus according to  claim 10  wherein the signal sensor monitors radiation reflected from two spaced apart surfaces on the substrate. 
   
   
       25 . An apparatus according to  claim 10  wherein the signal sensor monitors radiation reflected from two spaced apart surfaces on the substrate which include a surface of a mask pattern and a channel or trench being etched of the substrate. 
   
   
       26 . An apparatus according to  claim 10  wherein the source of the radiation comprises the plasma, and wherein the process monitoring assembly monitors an optical emission intensity of the plasma in a wide band to generate a plurality of signals indicative of the spectral intensity of the plasma. 
   
   
       27 . An apparatus according to  claim 10  wherein the process monitoring assembly generates a termination signal to terminate an etch process being conducted in the chamber when the signals diverge. 
   
   
       28 . An apparatus according to  claim 10  wherein the source of radiation comprises a signal source. 
   
   
       29 . An apparatus according to  claim 28  wherein the signal source comprises an optical source capable of emitting an optical beam. 
   
   
       30 . An apparatus according to  claim 28  wherein the signal source is connected to the signal sensor via one end of a fiber-optic cable that is bifurcated into first and second branches, the first branch comprising an end that is attached to the signal source, and the second branch comprising an end that is attached to the signal sensor. 
   
   
       31 . An apparatus according to  claim 28  wherein the signal source comprises at least one of the following:
 (i) a plasma lamp operating in the nm range;   (ii) a plasma lamp operating in the 185-700 nm range;   
   
   
       32 . An apparatus according to  claim 10  wherein the process monitoring assembly comprises at least one of:
 (i) a narrow band monochromator;   (ii) a CCD system;   (iii) a spectroscopy system; or   (iv) a laser interferometer.   
   
   
       33 . An apparatus according to  claim 10  wherein the window comprises quartz or fused silica. 
   
   
       34 . An apparatus according to  claim 10  comprising a plurality of separate windows in the walls of the process chamber, each window provided to receive a radiation reflected from the substrate. 
   
   
       35 . An apparatus according to  claim 34  comprising a plurality of sensors.