Filling high aspect ratio isolation structures with polysilazane based material

Abstract

Isolation trenches and capacitor trenches containing vertical FETs (or any prior levels p-n junctions or dissimilar material interfaces) having an aspect ratio up to 60 are filled with a process comprising: applying a spin-on material based on silazane and having a low molecular weight; pre-baking the applied material in an oxygen ambient at a temperature below about 450 deg C.; converting the stress in the material by heating at an intermediate temperature between 450 deg C. and 800 deg C. in an H20 ambient; and heating again at an elevated temperature in an O2 ambient, resulting in a material that is stable up to 1000 deg C., has a compressive stress that may be tuned by variation of the process parameters, has an etch rate comparable to oxide dielectric formed by HDP techniques, and is durable enough to withstand CMP polishing.

1 . A method of forming an integrated circuit containing a set of thermally sensitive circuit elements having a thermal budget associated therewith and a set of isolation trenches comprising the steps of: 
 providing a silicon substrate;    forming at least one circuit element having a thermal budget prior to forming the isolation structure;    etching said set of trenches in said silicon substrate;    filling said set of trenches with a spin on trench dielectric material containing silazane;    heating said substrate at a temperature of less than about 450 deg C.;    converting the stress in said trench dielectric material from tensile stress to compressive stress by heating in an ambient containing H2O at a temperature between about 450 deg C. and about 900 deg C.;    annealing said substrate by heating in an ambient containing O2 at a temperature above 800 deg C.; and    completing said integrated circuit.    
   
   
       2 . A method according to  claim 1 , in which the time of the stress conversion step and the time of the anneal step are related such that the thermal budget of the thermally sensitive component is not exceeded.  
   
   
       3 . A method according to  claim 1 , in which: said step of stress conversion and said step of annealing are related such that the resulting material has compressive stress in the range of 0.1 to 2 Gdynes/cm2 and has a WERR of less than about 2.  
   
   
       4 . A method according to  claim 2 , in which: 
 said step of stress conversion and said step of annealing are related such that the resulting material has compressive stress in the range of 0.1 to 2 Gdynes/cm2 and has a WERR of less than about 2.    
   
   
       5 . A method according to  claim 2 , in which: 
 the step of heating said substrate in an ambient containing ) O2 is performed for an adjustment time such that the WERR of the final material is made substantially equal to a design value.    
   
   
       6 . A method according to  claim 3 , in which: 
 the step of heating said substrate in an ambient containing O2 is performed for an adjustment time such that the WERR of the final material is made substantially equal to a design value.    
   
   
       7 . A method according to  claim 4 , in which: 
 the step of heating said substrate in an ambient containing O2 is performed for an adjustment time such that the WERR of the final material is made substantially equal to a design value.    
   
   
       8 . A method according to  claim 1 , in which: the trench has an aspect ratio of greater than 6; 
 the trench dielectric material is planarized by CMP after the step of annealing in an O2 ambient; and    an anneal in an ambient containing water vapor is performed after the step of planarizing for a time sufficient to convert Si—N bonds to Si—O bonds in trench dielectric material at the bottom of the trench.    
   
   
       9 . A method according to  claim 8 , in which the time of the stress conversion step and the time of the anneal step are related such that the thermal budget of the thermally sensitive component is not exceeded.  
   
   
       10 . A method according to  claim 8 , in which: 
 said step of stress conversion and said step of annealing are related such that the resulting material has compressive stress in the range of 0.1 to 2 Gdynes/cm2 and has a WERR of less than about 2.    
   
   
       11 . A method according to  claim 9 , in which: 
 said step of stress conversion and said step of annealing are related such that the resulting material has compressive stress in the range of 0.1 to 2 Gdynes/cm2 and has a WERR of less than about 2.    
   
   
       12 . A method according to  claim 9 , in which: 
 the step of heating said substrate in an ambient containing O2 is performed for an adjustment time such that the WERR of the final material is made substantially equal to a design value.    
   
   
       13 . A method according to  claim 10 , in which: 
 the step of heating said substrate in an ambient containing O2 is performed for an adjustment time such that the WERR of the final material is made substantially equal to a design value.    
   
   
       14 . A method according to  claim 11 , in which: 
 the step of heating said substrate in an ambient containing O2 is performed for an adjustment time such that the WERR of the final material is made substantially equal to a design value.    
   
   
       15 . A method of forming an integrated circuit containing a set of circuit elements and a set of isolation trenches comprising the steps of: 
 providing a silicon substrate;    etching said set of trenches in said silicon substrate;    filling said set of trenches with a spin on trench dielectric material containing silazane; heating said substrate at a temperature of less than about 450 deg C.;    converting the stress in said trench dielectric material from tensile stress to compressive stress by heating in an ambient containing H2O at a temperature between about 450 deg C. and about 900 deg C.;    annealing said substrate by heating in an ambient containing O2 at a temperature above 800 deg C.; and    completing said integrated circuit.    
   
   
       16 . A method according to  claim 15 , in which: 
 said step of stress conversion and said step of annealing are related such that the resulting material has compressive stress in the range of 0.1+2 Gdynes/cm2 and has a WERR of less than about 2.    
   
   
       17 . A method according to  claim 16 , in which: 
 the step of heating said substrate in an ambient containing O2 is performed for an adjustment time such that the WERR of the final material is no greater than a design value.    
   
   
       18 . A method according to  claim 17 , in which: 
 the step of heating said substrate in an ambient containing O2 is performed for an adjustment time such that the WERR of the final material is made substantially equal to a design value.    
   
   
       19 . A method of forming an integrated circuit containing a set of thermally sensitive vertical transistor DRAM cells having a thermal budget associated therewith and a set of isolation trenches, comprising the steps of: 
 providing a silicon substrate;    forming at least one vertical transistor DRAM cell having a thermal budget prior to forming the isolation structure;    etching said set of trenches in said silicon substrate;    filling said set of trenches with a spin on trench dielectric material containing silazane; heating said substrate at a temperature of less than about 450 deg C.;    converting the stress in said trench dielectric material from tensile stress to compressive stress by heating in an ambient containing H2O at a temperature between about 450 deg C. and about 900 deg C.;    annealing said substrate by heating in an ambient containing O2 at a temperature above 800 deg C.; and    completing said integrated circuit.    
   
   
       20 . A method according to  claim 19 , in which the time of the stress conversion step and the time of the anneal step are related such that the thermal budget of the vertical transistor DRAM cell is not exceeded.  
   
   
       21 . A method according to  claim 19 , in which: 
 said step of stress conversion and said step of annealing are related such that the resulting material has compressive stress in the range of 0.1 to 2 Gdynes/cm2 and has a WERR of less than about 2.    
   
   
       22 . A method according to  claim 20 , in which: 
 said step of stress conversion and said step of annealing are related such that the resulting material has compressive stress in the range of 0.1 to 2 Gdynes/cm2 and has a WERR of less than about 2.    
   
   
       23 . A method according to  claim 20 , in which: 
 the step of heating said substrate in an ambient containing O2 is performed for an adjustment time such that the WERR of the final material is made substantially equal to a design value.    
   
   
       24 . A method according to  claim 21 , in which: the step of heating said substrate in an ambient containing O2 is performed for an adjustment time such that the WERR of the final material is made substantially equal to a design value.  
   
   
       25 . A method according to  claim 22 , in which: 
 the step of heating said substrate in an ambient containing O2 is performed for an adjustment time such that the WERR of the final material is made substantially equal to a design value.    
   
   
       26 . An integrated circuit containing a set of thermally sensitive circuit elements having a thermal budget associated therewith and a set of isolation trenches in a silicon substrate, in which: 
 said set of trenches have an aspect ratio of at least four and have been filled with a spin on trench dielectric material containing silazane;    said substrate has been heated at a temperature of less than about 450 deg C.; the stress in said trench dielectric material is compressive stress that was converted from tensile stress to compressive stress by heating in an ambient containing H2O at a temperature between about 450 deg C. and about 900 deg C.; and    said substrate has been annealed by heating in an ambient containing O2 at a temperature above 800 deg C. until Si—N bonds at the bottom of said trench are substantially converted to Si—O bonds, in which the time of the stress conversion step and the time of the anneal step are related such that the thermal budget of the thermally sensitive component is not exceeded; and    said step of stress conversion and said step of annealing are related such that the resulting material has compressive stress in the range of 0.1 to 2 Gdynes/cm2, whereby the operation of transistors adjacent to said set of trenches is not affected and has a WERR of less than about 2.    
   
   
       27 . A circuit according to  claim 26 , in which the time of the stress conversion step and the time of the anneal step were related such that the thermal budget of the thermally sensitive component was not exceeded.  
   
   
       28 . A circuit according to  claim 26 , in which: 
 said step of stress conversion and said step of annealing were related such that the resulting material has compressive stress in the range of 0.1 to 2 Gdynes/cm2 and has a WERR of less than about 2.    
   
   
       29 . A circuit according to  claim 26 , in which: 
 a subset of isolation trenches surround transistor areas containing a transistor; and    the time and temperature of the stress conversion step is such that the stress in the dielectric trench material is not greater than a design limit value.    
   
   
       30 . A circuit according to  claim 29 , in which: 
 the time and temperature of the stress conversion step is such that the stress in the dielectric trench material is substantially equal to a design value.    
   
   
       31 . A circuit according to  claim 26 , in which: 
 the time and temperature of the stress conversion step and the annealing steps are such that the stress in the dielectric trench material is substantially equal to that of oxide deposited by the HDP technique.    
   
   
       32 . A circuit according to  claim 29 , in which: 
 the time and temperature of the stress conversion step and the annealing steps are such that the stress in the dielectric trench material is substantially equal to that of oxide deposited by the HDP technique.