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Mechanical Polish Clean Up After M2 CVD W Blanket Etch for CMOS Dram

IP.com Disclosure Number: IPCOM000034955D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Cote, WJ: AUTHOR [+4]

Abstract

A process sequence is disclosed for achieving planarity after a chemical vapor deposition (CVD) tungsten (W) process step used in a CMOS process to form second level (M2) via studs. Because a non-uniform film thickness of tungsten is created when chemical vapor deposition processes are utilized, current planarization techniques do not achieve their desired effect. A description of the process sequence which creates the problem is shown in Figs. 1-3. Fig. 1 shows a structure of patterned oxide, nitride with CVD W on top. (Note the non-uniform thickness (T1, T2 and T3) of the CVD W.) Fig. 2 shows the structure after a blanket reactive ion etchback process. (Note the undesirable combination of results possible, i.e., over etched studs, over etched nitride and residual W left on the surface.) Fig.

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Mechanical Polish Clean Up After M2 CVD W Blanket Etch for CMOS Dram

A process sequence is disclosed for achieving planarity after a chemical vapor deposition (CVD) tungsten (W) process step used in a CMOS process to form second level (M2) via studs. Because a non-uniform film thickness of tungsten is created when chemical vapor deposition processes are utilized, current planarization techniques do not achieve their desired effect. A description of the process sequence which creates the problem is shown in Figs. 1-3. Fig. 1 shows a structure of patterned oxide, nitride with CVD W on top. (Note the non-uniform thickness (T1, T2 and T3) of the CVD

W.) Fig. 2 shows the structure after a blanket reactive ion etchback

process. (Note the undesirable combination of results possible,

i.e., over etched studs, over etched nitride and residual W left

on the surface.) Fig. 3 shows the structure after a plasma clean up is used to remove the residual metal. (Note the roughened surface of the tungsten

studs and additional nitride removed. The structure shown in Fig. 3 is not planar and as such causes difficulty in the next level of alignment. Simply polishing the tungsten back cannot be done after W deposition because the polishing rate is slow and chemicals added to the slurry attack the sidewall W adhesion layer (not shown). By utilizing a totally mechanical slurry (SiO2) polish after Fig. 2, a truly planar surface is achieved. No attack on the sidewall occurs. Care must be t...