Browse Prior Art Database

In Situ Multilevel Resist Polysilicon Etch Process

IP.com Disclosure Number: IPCOM000036971D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Smith, KC: AUTHOR

Abstract

By changing etch gas and electrical connections to elements internal to an etching tool, materials in a multilayer stack are etched at controlled relative rates and degree of anisotropy. The technique may be used to create features smaller than normal photo-limited size.

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In Situ Multilevel Resist Polysilicon Etch Process

By changing etch gas and electrical connections to elements internal to an etching tool, materials in a multilayer stack are etched at controlled relative rates and degree of anisotropy. The technique may be used to create features smaller than normal photo-limited size.

Referring to Fig. 1, a gate oxide 12 is grown on silicon (Si) substrate 14. Polysilicon 16 is deposited next. Base resist layer 18 is applied next and overcoated with a silicon dioxide (SiO2) layer 20. A final layer of photoresist 22 is applied and patterned.

Etching is started with the etching tool configured as shown in Fig. 4, with switch S in the position shown. Patterned wafer 24 is placed on dielectric support member 26. Low frequency generator LF is connected through variable impedance 28 to conductive support 30. High frequency generator HF is connected through variable impedance 32 to cylindrical electrode 34 via switch
S.

Referring to Fig. 2, oxide 20 is first etched using a CF4/CHF3/He etch gas. By changing the etch gas to a CF4/O2 mixture, photoresist 22 is removed and resist layer 18 is etched away. Due to isotropic etching that results from the system electrically configured as shown in Fig. 4, resist 18 is undercut as shown in Fig. 2.

Then, by changing switch S to the position shown in Fig. 5, wherein both generators HF and LF are connected through their respective variable impedances 32 and 28 to conductive support 30 and cylindri...