New Etch Gases Could Replace PFCs
Peter Singer, Editor-in-Chief -- Semiconductor International, 2/1/1999
Alcatel Vacuum Technology's Thin Film Systems unit
(Annecy, France) entered into a licensing agreement with Robert Bosch
GmbH of Germany to use the patented 'Bosch process' on Alcatel's ICP deep
etching systems. The process helps produce vertical anisotropic etching of
silicon at room temperature.
Allied Signal Electronic Materials announced the
construction of a multi-million dollar low-k dielectric integration
facility at its Sunnyvale, Calif., location. The facility will be equipped
with low-k spin coaters, curing equipment and film characterization tools
as well as CMP, etch, CVD and strip modules.
Applied Materials (Santa Clara, Calif.) said
SEMATECH (Austin, Texas) will characterize and qualify its Endura
Barrier/Seed Cu system for production of copper interconnects. Applied
Materials also announced that the Defense Evaluation and Research Agency
of the United Kingdom (DERA) has purchased an Epi Centura system for its
facility in Malvern, England, to be used for SiGe applications.
Lam Research Corp. (Fremont, Calif.) announced a
joint development program with National Semiconductor Corp. to
develop aluminum plasma etch processes (for 0.18-0.13 mm devices) on its
TCP 9600PTX metal etch cluster system.
Novellus Systems (San Jose, Calif.) shipped its
SABRE copper 'electrofill' tool to SEMATECH's Advanced Tool
Development Facility in Austin, Texas. SEMATECH will use the tool, along
with Novellus' INOVA PVD system, to characterize Novellus' Damascus copper
dual damascene deposition solution.
Silicon Genesis Corp. (Campbell, Calif.) received
an order for its SiGen PIII (Plasma Immersion Ion Implantation) system
from Komatsu Electronic Materials Co., Ltd., a wafer manufacturer
in Japan. SiGen and Komatsu also signed a joint research agreement for the
study of SPIMOX (Separation by Plasma Implantation of Oxygen).
An important mission in the
semiconductor industry is to reduce emissions of perfluorocompounds (PFCs),
presently used to clean PECVD chambers and for etching. PFCs such as
CF4, C2F6 and C3F8 are
believed to contribute to global warming. Several approaches are being
considered, including abatement, capture/recovery, process optimization and the
development of alternative chemistries as substitutes.
Company News
Researchers at MIT and Motorola have addressed the latter approach and have come up with novel hydrofluorocarbon and iodofluorocarbon chemistries that they have shown to be suitable replacements to PFCs now used, or, at least, good enough to warrant further evaluation.
The most promising results came from two isomers of iodoheptafluoropropane:
1-iodoheptafluoropropane (CF2I-CF2-CF3) and
2-iodoheptafluoropropane (CF3-CFI-CF3). 'It is
particularly encouraging that, in the case of 1-iodoheptafluoropropane, it was
possible to simultaneously improve both emissions and process performance,'
noted the researchers in a recent paper in the Journal of the Electrochemical
Society (December 1998). 2H-heptafluoropropane (CF3
-CFH-CF3), another gas studied, was found to be capable of process
performance that was roughly equivalent to that of C3F8,
while yielding a reduction in global warming gas emission on the order of 60%.
A New Equation for CMP
Throw out Preston's equation; researchers at Rockwell Semiconductor (Newport Beach, Calif.) and the University of California (Irvine, Calif.) have shown that there is a critical threshold pressure in chemical mechanical polishing (CMP). If the pressure applied to the wafer during CMP is less than this threshold pressure, CMP removal is negligible.
Preston's equation, which states that the polishing rate or removal rate (RR) depends linearly (or is proportional to) the pressure (P) applied to the polished wafer, RR } P, has been widely used to understand the CMP process but does not take into account a threshold pressure.
In work presented at the International Electron Devices Meeting, Bin Zhao of Rockwell and Frank Shi of the University of California showed that abrasive particles used during the CMP process are almost completely embedded in the polishing pad, because the pad is much softer than the wafer and abrasive particles. The polishing rate does not depend on the pressure applied to the abrasive particles as much as how many abrasive particles there are. Also, they showed that below a certain pressure it is possible for the abrasive particle to simply roll in place and not contribute to the CMP action.
A new polishing rate equation that takes into account these factors is as follows:
RR = K(V)(P2/3 - P2/3th) (P > Pth,
where K(V) is a function of the relative velocity between the
polishing pad and the polished wafer surface (V) and other CMP variables,
and Pth is the threshold pressure.
DUMIC and CMP-MIC: Feb 8-12
Two
separate conferences will be held later this month at the Santa Clara Marriott.
The fifth international Dielectrics for ULSI Multilevel Interconnect Conference
(DUMIC) will be held Feb. 8-9. The fourth international CMP Planarization for
ULSI Multilevel Interconnection Conference (CMP-MIC) will be held Feb. 11-12.
For more information, see www.eng.usf.edu/vmic.
