Browse Prior Art Database

Process for Etching Multilayer Polycide Films

IP.com Disclosure Number: IPCOM000060147D
Original Publication Date: 1986-Mar-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Bergendahl, A: AUTHOR [+4]

Abstract

This article describes a two-step etch process (with a clean step in between) to achieve a highly directional and selective etch of an unannealed multilayer polycide film structure in a field-effect transistor fabrication process. The etch requirements are: 1) A near vertical sidewall of the etched silicide to allow for a lightly doped drain (LDD) structure. 2) No shorting of silicide lines. Fig. 1 shows a cross-section of an unannealed multilayered polycide film stack to be etched. It should be noted that the vertical film thickness at B and C is not equal. Because etch end point is critical, the difference in vertical film thickness is one of the problems this etch technique overcomes. A parallel plate center pump reactive ion etch (RIE) tool is utilized for both etch steps.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 61% of the total text.

Page 1 of 2

Process for Etching Multilayer Polycide Films

This article describes a two-step etch process (with a clean step in between) to achieve a highly directional and selective etch of an unannealed multilayer polycide film structure in a field-effect transistor fabrication process. The etch requirements are: 1) A near vertical sidewall of the etched silicide to allow for a lightly doped drain (LDD) structure. 2) No shorting of silicide lines. Fig. 1 shows a cross-section of an unannealed multilayered polycide film stack to be etched. It should be noted that the vertical film thickness at B and C is not equal. Because etch end point is critical, the difference in vertical film thickness is one of the problems this etch technique overcomes. A parallel plate center pump reactive ion etch (RIE) tool is utilized for both etch steps. The first etch step is less selective (poly to oxide) than the second etch step. Selectivity is controlled by the flow rates of the active etch gasses (i.e., sulfur hexafluoride and chloroform) as well as the flow rate of an inert gas, such as helium. The patterned pyro/oxide cap acts as a mask for the RIE process. Etch step one is a low pressure, high power anisotropic etch carried out using an 8:1 ratio of sulfur hexafluoride to chloroform with a comparatively large amount of inert gas. A large positive DC bias (e.g., + 375 volts) is provided. After the first etch step, the wafer is subjected to a dry strip acid dip combination, which removes...