Method for cmp uniformity control

Abstract

A method for injecting slurry between the wafer and the pad in chemical mechanical polishing of semiconductor wafers comprising a solid crescent shaped injector the concave trailing edge of which is fitted to the size and shape of leading edge of the polishing head with a gap of between 0 and 3 inches, the bottom surface facing the pad, which rests on the pad with a light load, and through which CMP slurry or components thereof are introduced through one or more openings in the top of the injector and travel through a channel or reservoir the length of the device to the bottom where it or they exit multiple openings in the bottom of the injector, are spread into a thin film, and are introduced at the junction of the surface of the polishing pad and the wafer along the leading edge of the wafer in quantities small enough that all or most of the slurry is introduced between the wafer and the polishing pad, wherein multiple inlets for the introduction of fluids to different points in the channel or directly to the bottom surface of the injector are utilized and some or all of which inlets are fitted with means for controlling the flow of fluid and adjustment is made to the said flow control means during or after polishing to adjust slurry delivery to the wafer surface to improve uniformity of removal rate at the wafer surface.

1 . A method for injecting slurry between the wafer and the pad in chemical mechanical polishing of semiconductor wafers comprising a solid crescent shaped injector the concave trailing edge of which is fitted to the size and shape of leading edge of the polishing head with a gap of between 0 and 3 inches, the bottom surface facing the pad, which rests on the pad with a light load, and through which CMP slurry or components thereof are introduced through one or more openings in the top of the injector and travel through a channel or reservoir the length of the device to the bottom where it or they exit multiple openings in the bottom of the injector, are spread into a thin film, and are introduced at the junction of the surface of the polishing pad and the wafer along the leading edge of the wafer in quantities small enough that all or most of the slurry is introduced between the wafer and the polishing pad, wherein multiple inlets for the introduction of fluids to different points in the channel and directly through the bottom surface of the injector to the polishing pad are utilized and some or all of which inlets are fitted with means for controlling the flow of fluid and adjustment is made to the said flow control means during or after polishing to adjust slurry delivery to the wafer surface to improve uniformity of removal rate at the wafer surface. 
   
   
       2 . A method according to  claim 1  wherein the said number of multiple openings is between 2 and 10. 
   
   
       3 . A method according to  claim 1  wherein the at least one of the inlets is for the introduction of slurry to the channel. 
   
   
       4 . A method according to  claim 1  wherein all of the inlets introduce slurry, diluted slurry or diluent to the channel. 
   
   
       5 . A method according to  claim 1  wherein some inlets introduce slurry, diluted slurry or diluent to the channel and the remaining inlets introduce slurry, diluted slurry or diluent directly to the polishing pad through the bottom surface of the injector. 
   
   
       6 . A method according to  claim 1  wherein one or more inlets introduce slurry to the channel and the remainder introduce diluted slurry or other diluent to the polishing pad through the bottom surface of the injector. 
   
   
       7 . A method according to  claim 1  wherein said means of controlling the flow of slurry of various concentrations or of diluent is a valve. 
   
   
       8 . A method according to  claim 1  wherein the said valve is a needle valve. 
   
   
       9 . A method according to  claim 1  wherein all of the inlets are for the introduction of slurry. 
   
   
       10 . A method according to  claim 1  wherein the slurry introduced through all of the inlets is of uniform concentration and composition. 
   
   
       11 . A method according to  claim 1  wherein different slurries are introduced through different inlets. 
   
   
       12 . A method according to  claim 1  wherein the slurry introduced through different inlets is the same slurry but of a different concentration or level of dilution depending upon the inlet. 
   
   
       13 . A method according to  claim 11  wherein the slurries introduced through different inlets are of different concentrations or levels of dilution depending upon the inlet. 
   
   
       14 . A method according to  claim 12  wherein the slurry is diluted with water. 
   
   
       15 . A method according to  claim 13  wherein the slurry is diluted with water. 
   
   
       16 . A method according to  claim 1  wherein at least one inlet for slurry is not fitted with a means for controlling flow. 
   
   
       17 . A method according to  claim 16  wherein between one and all but one of the inlets, that one inlet being the said slurry inlet, introduce diluent to the said channel. 
   
   
       18 . A method according to  claim 16  wherein all of the diluent inlets and all but one of the slurry inlets are fitted with a flow control means. 
   
   
       19 . A method according to  claims 11  and  12  wherein the concentration and of slurry or slurries may be varied generally or inlet by inlet over time. 
   
   
       20 . A method according to  claim 12  wherein the composition of the slurries may be varied over time. 
   
   
       21 . A method according to  claim 1  wherein adjustment of the means of flow control is accomplished mechanically. 
   
   
       22 . A method according to  claim 1  wherein adjustment of the means of flow control is accomplished manually. 
   
   
       23 . A method according to  claim 1  wherein adjustment of the means of flow control is made during CMP operation according to the results of analysis of data obtained by a sensor or a sensor array indicating the amount or temperature of slurry on the pad surface or removal rate from the wafer surface. 
   
   
       24 . A method according to  claim 23  wherein the said sensor or sensor array is an infrared sensor or sensor array to measure the temperature of injected slurry in the gap between the wafer and the injector. 
   
   
       25 . A method according to  claim 23  wherein the results are obtained from the sensor or sensor array by visual or audio output. 
   
   
       26 . A method according to  claim 23  wherein the sensor data are obtained from the sensor or sensor array by means of an electronic signal. 
   
   
       27 . A method according to  claim 23  wherein sensor data are analyzed and indicate that increase or decrease of the flow rate in a particular inlet or inlets will optimize distribution of slurry and consequently the magnitude and uniformity of removal rate. 
   
   
       28 . A method according to  claim 23  wherein sensor data analysis feedback is applied manually. 
   
   
       29 . A method according to  claim 23  wherein sensor data analysis feedback is mechanical and automatic. 
   
   
       30 . A method according to  claim 23  wherein the said means of flow control is a valve and adjustment of the valve is accomplished mechanically in accordance with data processing feedback output based on sensor data. 
   
   
       31 . A method according to  claim 23  wherein the said means of flow control is a needle valve and adjustment of the needle valve is accomplished mechanically in accordance with data processing feedback output based on sensor data. 
   
   
       32 . A method according to  claim 23  wherein the adjustment of the needle valve is accomplished mechanically by a microstepdown motor. 
   
   
       33 . A method according to  claim 22  wherein adjustment of the means of flow control is made for subsequent wafers after determination of the uniformity of removal rate on a wafer or wafers. 
   
   
       34 . A method according to  claim 33  wherein uniformity of removal rate is determined by a reflectometer. 
   
   
       35 . A method according to  claim 34  wherein the means of flow control is a valve. 
   
   
       36 . The method according to  claim 35  wherein the valves are needle valves. 
   
   
       37 . The method according to  claim 35  wherein one or more of the inlets are not fitted with needle valves, the inlet or inlets not fitted with a needle valve is for the introduction of slurry and the remainder of the inlets fitted with needle valves are for the introduction of diluent or diluted slurry 
   
   
       38 . The method according to  claim 37  wherein one wafer is polished under conditions of the needle valves all being closed except the first needle valve through which diluent or diluted slurry is introduced at a fixed rate, and for each successive wafer polished the needle valve previously used is closed and the next valve opened fully until all needle valves have been run following which, based upon uniformity of removal results of the earlier needle valve configurations subsequent polishing runs involving combinations of completely opened needle valves at suitably adjusted total flow rates followed finally, if necessary, by configurations involving entirely closed, partially open and fully open needle valves to achieve optimum removal rate. 
   
   
       39 . The method according to  claim 1  wherein the results of adjustment are measured between polishing runs by reflectometer, there is one slurry inlet set at 90 ml/cm flow rate and 7 water inlets evenly spaced, ⅛ inch from the edge of the leading edge of the channel, in the direction opposite the channel from the wafer, opened all the way through the injector to the bottom surface of the injector, equipped with needle valves, adjustment of the needle valves is manual, and a wafer is polished under conditions of the needle valves all completely closed except for the first needle valve, closest to the center of the polishing pad, through which water is introduced at a 30 ml/min, and for each successive wafer polished, the needle valve previously used is closed and the next valve out from the center of the polishing pad opened fully at the same flow rate until all 7 needle valves have been tested, following which, based upon uniformity of removal rate results of the earlier needle valve configurations, subsequent polishing runs subject to configurations of multiple completely opened needle valve at suitably adjusted total flow rates followed are carried out and, finally, polishing runs subject to needle valve configurations utilizing entirely closed. Partially open and fully open needle valves to achieve optimum removal rate. 
   
   
       40 . The method of  claim 1  wherein all of the inlets are evenly spaced. 
   
   
       41 . The method of  claim 13  wherein the inlets fitted with flow control means are evenly spaced.