Tpir apparatus for monitoring tungsten hexafluoride processing to detect gas phase nucleation, and method and system utilizing same

Abstract

Apparatus and method for monitoring a vapor deposition installation in which a gas mixture can undergo gas phase nucleation (GPN) and/or chemically attack the product device, under process conditions supportive of such behavior. The apparatus includes a radiation source arranged to transmit source radiation through a sample of the gas mixture, and a thermopile detector assembly arranged to receive output radiation resulting from interaction of the source radiation with the gas mixture sample, and to responsively generate an output indicative of onset of the gas phase nucleation and/or chemical attack when such onset occurs. Such monitoring apparatus and methodology is useful in tungsten CVD processing to achieve high rate tungsten film growth without GPN or chemical attack.

What is claimed is: 
     
         1 . A method of carrying out vapor deposition, comprising contacting a substrate with a gas mixture containing gas species that can cause gas phase nucleation and/or chemical attack under process conditions supportive of such behavior, said process comprising:
 impinging radiation on a sample of said gas mixture for interaction of the radiation with one or more gas species in the gas mixture to produce output radiation from said interaction having a characteristic that is indicative of onset of said gas phase nucleation and/or chemical attack when said onset occurs; and   processing said output radiation to responsively generate an output indicative of onset of said gas phase nucleation and/or chemical attack when said onset occurs.   
     
     
         2 . The method of  claim 1 , wherein said processing includes analyzing a spectral portion of said output radiation for a gas species of interest to determine presence or absence of said characteristic. 
     
     
         3 . The method of  claim 2 , wherein said analyzing includes at least one of the following:
 (i) determination of peak heights of one or more gas species of the gas mixture;   (ii) determination of differences in peak heights between two or more of the gas species of the gas mixture;   (iii) determination of ratios of peak heights of two or more of the gas species of the gas mixture;   (iv) determination of AUC of said spectral portion for one or more gas species of the gas mixture;   (v) determination of differences of AUC for spectral portions for two or more gas species of the gas mixture;   (vi) determination of ratios of AUC for spectral portions for two or more gas species of the gas mixture;   (vii) determination of slope of a spectral curve in a spectral portion of one or more gas species of the gas mixture;   (viii) determination of differences of slopes of spectral curves in spectral portions of two or more gas species of the gas mixture;   (ix) determination of ratios of slopes of spectral curves in spectral portions of two or more gas species of the gas mixture;   (x) determination of peak heights of one or more gas species of the gas mixture at a predetermined point in time;   (xi) determination of differences in peak heights between two or more of the gas species of the gas mixture at a predetermined point in time;   (xii) determination of ratios of peak heights of two or more of the gas species of the gas mixture at a predetermined point in time; and   (xiii) monitoring of a gas species reactant that is consumed during vapor deposition, as an indicator of onset of gas phase nucleation and/or chemical attack.   
     
     
         4 . The method of  claim 1 , wherein said processing includes analyzing a spectral portion of said output radiation for a gas species of interest to determine presence or absence of said characteristic, wherein said vapor deposition comprises tungsten chemical vapor deposition, and the gas mixture includes silane and tungsten hexafluoride, wherein said analyzing includes querying a database of spectra or spectral characteristics of the gas species of interest, and correlating said spectral portion of the output radiation with the database to generate said output indicative of onset of said gas phase nucleation and/or chemical attack when said onset occurs, and wherein said method further comprises controlling the vapor deposition in response to said output, so as to avoid gas phase nucleation and chemical attack. 
     
     
         5 . The method of  claim 1 , wherein the one or more gas species comprise WF 6 , SiF 4  and SiH 4 . 
     
     
         6 . The method of  claim 1 , comprising carrying out tungsten chemical vapor deposition to avoid incidence of gas phase nucleation and chemical attack in said deposition, wherein said chemical vapor deposition comprises contacting a gas mixture comprising WF 6  and SiH 4 , with a Ti:TiN layer on a microelectronic device substrate, monitoring at least one of WF 6 , SiF 4  and SiH 4  in an effluent from the chemical vapor deposition by TPIR monitoring to detect said onset of gas phase nucleation and/or chemical attack, and responsively controlling the chemical vapor deposition to avoid incidence or continuation of gas phase nucleation and/or chemical attack. 
     
     
         7 . The method of  claim 6 , wherein said responsively controlling comprises at least one of: (i) adjusting the relative concentrations of WF 6  and SiH 4  in the gas mixture, and (ii) change of a process condition of the chemical vapor deposition. 
     
     
         8 . The method of  claim 6 , wherein the monitoring comprises one or more of:
 (i) determining peak heights, H WF6  and H SiF4 , in IR spectra of WF 6 , and SiF 4 ;   (ii) determining a peak height difference (H WF6 −H SiF4 ), in IR spectra of WF 6 , and SiF 4 ;   (iii) determining a peak height ratio (H WF6 /H SiF4 ) of SiF 4  and WF 6 , in IR spectra of WF 6 , and SiF 4 ;   (iv) determining peak area under curve (AUC) in IR spectra of WF 6 , and SiF 4 ;   (v) determining an AUC difference (AUC SiF4 −AUC WF6 ) in IR spectra of WF 6 , and SiF 4 ;   (vi) determining an AUC ratio (AUC SiF4 /AUC WF6 ) in IR spectra of WF 6 , and SiF 4 ;   (vii) determining slope, S, of spectral curves of IR spectra of WF 6 , and SiF 4 ;   (viii) determining a difference in slopes (S SiF4 −S WF6 ) of spectral curves of IR spectra of WF 6 , and SiF 4 ;   (ix) determining a slope ratio (S SiF4 /S WF6 ) of spectral curves of IR spectra of WF 6 , and SiF 4 ;   (x) determining peak heights, H WF6  and H SiF4 , in IR spectra of WF 6 , and SiF 4  at a predetermined time of operation;   (xi) determining a peak height difference (H WF6 −H SiF4 ), in IR spectra of WF 6 , and SiF 4  at a predetermined time of operation;   (xii) determining a peak height ratio (H WF6 /H SiF4 ) of SiF 4  and WF 6 , in IR spectra of WF 6 , and SiF 4  at a predetermined time of operation; and   (xiii) monitoring silane concentration.   
     
     
         9 . The method of  claim 1 , comprising determining occurrence of gas phase nucleation in a chemical vapor deposition chamber having one or more windows, comprising energizing an infrared radiation diode laser to transmit IR radiation through a window into the chamber for said impinging and interaction with vapor therein as said sample during chemical vapor deposition in the chamber and generating said output radiation from said interaction, detecting with a photodiode detector the output radiation transmitted through a same or different window of the chamber, and responsively generating said output, indicative of occurrence or non-occurrence of gas phase nucleation in the chemical vapor deposition chamber. 
     
     
         10 . The method of  claim 9 , wherein the chemical vapor deposition chamber is arranged in an arrangement in which:
 (A) the chemical vapor deposition chamber comprises a single window, and the photodiode detector is arranged for detecting back-scatter IR radiation indicative of occurrence of gas phase nucleation in the chamber, or   (B) the chemical vapor deposition chamber comprises two windows in opposing registration with one another, with the infrared radiation diode laser being arranged for transmitting IR radiation through a first one of said windows, and the photodiode detector being arranged for detecting output radiation transmitted through a second one of said windows and indicative of occurrence of gas phase nucleation in the chamber.   
     
     
         11 . A process for controllably maintaining a process within a predetermined operating regime, using a TPIR monitoring and control system including a monitoring cell adapted to receive material from the process, wherein the material in the monitoring cell interacts with infrared radiation generated by the monitoring system and infrared radiation resulting from such interaction is detected by a TPIR detector of the TPIR monitoring and control system as a TPIR monitoring output from the monitoring cell, said process comprising:
 generating a TPIR monitoring output from the monitoring cell;   removing ambient radio frequency noise spikes from TPIR monitoring output to produce a first refined data output;   smoothing the first refined data output using a binomial smoothing algorithm to produce a second refined data output;   calculating slope and offset values for signals of material components monitored in the monitoring cell;   utilizing the slopes and offsets for the monitored material components to temperature correct the second refined output and produce a third refined output;   conducting a peak search algorithm of the third refined output and calculating peak heights of the monitored material components, to generate peak heights of such monitored material components, and determining from peak height differences of such monitored material components whether processing associated with the monitoring is within a predetermined operating regime; and   correspondingly modulating the process by adjustment of one or more operating parameters thereof, to maintain the process within the predetermined operating regime.   
     
     
         12 . The process of  claim 11 , wherein the TPIR monitoring and control system comprises a memory unit in which a data analysis algorithm and associated monitoring and control operational instructions for said process are stored, and from which said instructions are able to be accessed and executed by a monitoring and control system processor. 
     
     
         13 . The process of  claim 11 , wherein: (A) the process comprises a tungsten CVD process, and the predetermined operating regime comprises a process operating regime that is free of GPN and/or Ti attack; or (b) the process comprises a chemical process producing an effluent, wherein said material from the process comprises effluent material, and the predetermined operating regime comprises effluent concentration below a predetermined value.