Plasma Etching Seminar -- Thursday afternoon

Jim McVittie mcvittie at snf.stanford.edu
Wed Jun 8 10:02:12 PDT 2005


June Plasma Etch Users Group Meeting on Conductor Etching

Cost: Free
Sponsor: American Vacuum Society
Chair: Jim McVittie, SNF
Time: 2:15 to 4:30, Thursday, June 9
Location:  National Semiconductor Auditorium,  955 Kifer Rd., Sunnyvale,

CA
Directions:

>From 101: Go south on Lawrence Expressway. Turn right on Kifer Rd. Turn

right into the driveway of the National Semiconductor Auditorium (955
Kifer Rd.) and find parking in the rear parking lot. The auditorium is
on
the West Side of the building and can be entered from the door in the
rear next to the company park.

*** Metal Etch:  Challenges and Opportunities***
Jeff Stokes, Applied Materials, Conductor Etch Division

Metal etch has been an industry standard for decads of generations of IC

devices.  Even now, advanced memory customers use metal etch systems for

the patterning of the interconnect lines on the latest set of chips.
Although the focus of extremely high etch control often is with the
advanced front end, such as logic gate, there are still significant
requirements for etching Al metal lines.  Given the advanced design
rules even for Al etch, it is important to have a robust, production
proven processes which give good profiles and good across wafer
uniformity. These requirements present challenges especially in the
context of providing reliable etch with good thruput and low operating
costs. Although, metal etch has often been associated with the standard
of Al interconnect lines, there is increasing interest and development
work on other applications.  Some of these uses for metal etch are
gaining in interest and in capability.  One application is the case of
TiN for use as a hard mask to avoid resist poisoning for the low-k
dielectric in  damascene processes.  Part of the capability is to use
integrated metrology at the step of TiN etch to control the CD's which
can impact the device performance.  As a more complex application, the
use of metal etch for front end metal gates is being actively explored.
In addition, there are other uses such as MRAM's and FeRAM's which
require advanced metal etch hardware and processing.  This talk will
cover the challenges of providing the capabilities for the highly
demanding Al connect process, as well as provide a brief overview of
other metal etch applications, current capabilities, and future
directions.

***Uniformity Control Knobs for the Dual Frequency Poly Etcher***
Lee Chen, TEL

 The experimental results of a capacitively coupled (ccp) dual-frequency

poly etcher are presented. The etcher has a 60MHz plasma source (the top

electrode) and a 13.56MHz biased wafer-electrode. 3 additional control
knobs are implemented to further expand its control over CD-uniformity
while maintaining its overall simplicity and reliability. The 1st knob
is a 2-zone temperature wafer-electrode (2-zone ESC) and it is a strong
knob for CD-uniformity since the wafer temperature affects
feature-side-wall reactivity strongly. The 2nd knob is the 2-zone gas
whose primary effect is on the neutral species' radial distribution. Its

second-order effect is on the plasma density's radial uniformity. The
3rd knob is a device called IC-Unit which is a wafer-electrode VHF
Impedance Control Unit. Its primary function is to adjust the plasma's
uniformity. The wafer-electrode's VHF impedance can move the plasma
radially and has a strong effect on the radial uniformity of the etch
rate.  As an example, 35nm poly-width (85nm gate-litho) with 3s=2.5nm
can be achieved with the optimized 2-zone ESC and IC-Unit settings.

***Unraveling the complex processes in a Fluorocarbon plasma***
M.J. Goeckner, University of Texas at Dallas

The chemistry of fluorocarbon plasmas are perhaps one of the most
complex processes known. In general it can be thought of as the
interactions between three main scientific subsystem, plasma physics,
gas phase chemistry/physics and surface phase chemistry/physics. To
understand this complexity one simply needs to consider how a given
reactive gas-phase specie might interact with a surface. Does it stick
to the surface? Does it chemically react with the surface? Does it
promote film growth? How does this interaction change the gas
composition? Does an altered gas-phase chemistry alter the plasma?
Understanding these interactions is key to producing better models of
plasmas, allowing the optimization of complete process systems and hence

improved product yield. This talk will review how various groups,
including our group at UTD, are attacking this complex problem and a
small sample of the results observed to date. Based on this knowledge,
we discuss possible future studies.



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