TEOS assisted oxide CMP process
View Patent ↗CMP of integrated circuits containing DRAM arrays with trench capacitors fill the trenches with oxide, resulting in a an array of oxide structures that is dense compared with the concentration in the surrounding support structures and therefore has a higher loading. A conformal layer is deposited over the wafer, increasing the loading in the array, but filling in spaces between active areas. A blanket etch removes material in both the array and the supports. A block etch balances the amount of material in the array and the supports. A supplementary oxide deposition in the array fills spaces between the structures to a nearly uniform density.
1. A method of planarizing an integrated circuit wafer containing at least two areas of different structure density comprising the steps of:
etching trenches in two areas of said wafer of different density, a first area of higher density and a second area of lower density;
filling trenches in both of said areas with a filler material, whereby said first area has a concentration of structures having a first height above a surface of said wafer and said first density and said second area has a concentration of structures having a second height above said surface of said wafer higher than said first height and a second density lower than said first density;
depositing a blanket conformal film on said wafer, thereby filling and planarizing said first area;
performing a blanket etch on said wafer;
performing a block etch on said first area while said second area is protected; and
performing a CMP step on said wafer.
2. A method according to claim 1 , in which said first area is an array of memory cells containing trenches and active areas between trenches.
3. A method according to claim 1 , in which said blanket conformal film has a conformal film thickness substantially less than said first height.
4. A method according to claim 1 , in which said conformal film has a thickness such that the space between said structures in said first area is filled and there is a continuous layer of said conformal film above said structures.
5. A method according to claim 3 , in which said conformal film has a thickness such that the space between said structures in said first area is filled and there is a continuous layer of said conformal film above said structures.
6. A method according to claim 1 , in which said blanket etch removes said conformal film back to said first height.
7. A method according to claim 5 , in which said blanket etch removes said conformal film back to said first height.
8. A method according to claim 1 , further comprising a blanket deposition of material after said step of depositing said conformal layer.
9. A method according to claim 5 , further comprising a blanket deposition of material after said step of depositing said conformal layer.
10. A method according to claim 7 , further comprising a blanket deposition of material after said step of depositing said conformal layer.
11. A method according to claim 1 , in which said block etch removes material in said first area to a height below a corresponding thickness in said second area.
12. A method according to claim 5 , in which said block etch removes material in said first area to a height below a corresponding thickness in said second area.
13. A method according to claim 2 , in which said blanket conformal film has a conformal film thickness substantially less than said first height.
14. A method according to claim 13 , in which said conformal film has a thickness such that the space between said structures in said first area is filled and there is a continuous layer of said conformal film above said structures.
15. A method according to claim 14 , in which said blanket etch removes said conformal film back to said first height.
16. A method according to claim 15 , further comprising a blanket deposition of material after said step of depositing said conformal layer.