Leaders of the chip making industry at this year's ISMI Symposium on Manufacturing
Effectiveness examined how engineers used a wireless method to measure the gap
between a plasma-enhanced chemical vapor deposition (PECVD) heater and showerhead
and improved first pass film checks by 24 percent during a session on equipment
productivity with the CTO of CyberOptics
Semiconductor, Craig C. Ramsey, Ph.D.
 | | Engineers increased the first pass film-check rate from 80 percent to over 99 percent, as well as chamber availability by four percent using a wireless gap-measurement method that employs the WaferSense(R) Auto Gapping System (AGS). |
At the 6th annual symposium, which offered attendees information to reduce
manufacturing expenses and increase productivity, Ramsey addressed how engineers
control gap uniformity and magnitude with high stability over time. He contrasted
a legacy gap-measurement method used by engineers that employs a wired leveling
device and crush blocks with a method that employs a wireless gapping device
and NIST traceable gap field standard.
Ramsey detailed how the legacy method led to lower first pass film checks --
with 20 percent of chambers failing film checks -- and lower chamber availability,
as well as increased maintenance cycle time and expenses. Ramsey added that
the legacy method isn't a repeatable process and doesn't yield reproducible
data. Measurements obtained by the wired leveling device and crush blocks are
susceptible to instrument and operator variances.
Engineers often repeat the legacy gapping process multiple times before a chamber
comes within the gap tolerances required to deposit quality films, according
to Ramsey. The films are then deposited onto monitor wafers and the average
thickness and thickness uniformity are measured to ensure that films are within
specification.
"And when films fail the parametric check with the legacy method, the
gapping process must be repeated and six hours of chamber production time is
lost," Ramsey said. "When you walk through the steps of the legacy
gapping method, you really see the extra work and challenges the instruments
present."
Ramsey's presentation, titled "Improved Film Production in a High-Volume
Fab," detailed how engineers increased the first pass film-check rate from
80 percent to over 99 percent, as well as chamber availability by four percent
using the wireless gap-measurement method. The wireless method is repeatable
and gives engineers data to optimize their preventive maintenance (PM) schedules
and process controls, according to Ramsey.
The wireless device used by engineers contains three non-contact distance sensors
that return gap measurements in real time to a laptop or PC in numerical and
graphical form. Engineers used the device to ensure gaps were accurate and uniform
to allow for enough film at the proper thickness. The vacuum-compatible device
also minimized the possibility of chamber contamination and shortened the total
tool maintenance cycle.
"Average film-thickness variation was maintained within specification
with the wireless gap-measurement method," Ramsey said. "And the fab
experienced improved film production."
Ramsey said the wireless gap-measurement device is the WaferSense® Auto
Gapping System (AGS).
The AGS' parallelism accuracy is 0.025 mm (+/-0.001"), and its gap accuracy
is 0.025 mm (+/-0.001") with a gap of 15 mm (0.600"). The AGS is available
in 200 and 300 mm form factors, with the AGS300 being the best-known method
(BKM) -- for 40 percent improvement in film uniformity -- for gapping Novellus
VECTOR® tool chambers.
CyberOptics Semiconductor is a maker of wireless metrology devices for wafer
processing equipment. The company's WaferSense family of devices includes the
Airborne Particle Sensor (APS), Auto Leveling System (ALS2 Vertical), Auto Vibration
System (AVS) and Auto Teaching System (ATS). Each device follows the processing
life of a wafer and reports real-time metrology data.
Posted November 2nd, 2009
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