Bill-for what I am about to do, I should get a huge check from UTEK as
a PR consultant. I have gleaned information from their literature to
post on this thread. By no means is this meant to be a hype. This is
a presentation of some facts which will hopefully result in
intelligent questions being asked of the company or people
knowledgeable about the UTEK product line. Pardon the poor formatting
if it comes out bad. I spent 4 hours putting it together under
Microsoft Word. Who knows how it will ciopy over.
I will be glad to answer any questions anyone has, to the best of my
abilities (which are damn good when it comes to UTEK).
Mix-and-Match to Step-and-Scan With the Saturn Wafer Stepper
Mix-and-match lithography has become a key technique in the control of
semiconductor manufacturing costs. Ultratech's Saturn Wafer Stepper
is used in mix-and-match with advanced lithography systems in leading
edge fabs. An important aspect of the Saturn is the ability to
perform mix-and-match to step-and-scan systems. The Saturn differs
from other wide field mix-and-match tools when used in mix-and-match
with step-and-scan.
OVERLAY ADVANTAGE
The Saturn field can match the full field size of any step-and-scan
tool. Exposing a full step-and-scan field in one shot may result in
improved overlay. Other very wide field steppers have been designed
to expose two step-and-scan fields in one shot.
The Saturn approach allows correction of step and-scan field rotation
and other field placement errors . This type of correction is not
possible with very wide field steppers.
GRID MATCHING ISSUES
Another Saturn advantage is the ability to match to staggered grids
of step-and-scan fields on the product wafer. A manufacturer will
sometimes stagger step-and-scan fields by a whole number of chip
widths to ensure that the maximum number of chips can be placed on the
wafer. The Saturn field size is better suited to match to such an
array.
CHARACTERIZATION OF MVS AND THROUGHPUT IN MIX-AND-MATCH LITHOGRAPHY
In a presentation at the SEMICON/Japan Cost-Effective Lithography
seminar, Itsuro Sanomiya of Fujitsu AMD Semiconductor Ltd. (FASL)
discussed the characterization of a mix-and-match lithography strategy
for a new given to the selection of exposure equipment. flash memory
production facility.
.
BACKGROUND
Equipment performance was one of FASL's criteria for selecting
manufacturing equipment for their new production facility. However,
the reduction of manufacturing costs was also considered to be a
major issue. Due to the high cost of reduction steppers, including
annual operating expenses, particular attention was given to the
selection of exposure equipment. As part of their plan to lower device
manufacturing costs, FASL analyzed the introduction of an Ultratech
Stepper 2244i mix-and-match lithography strategy.
2244i SELECTION
During a preliminary evaluation, FASL found that although the
resolution and alignment precision of the 2244i were lower than those
of the newest reduction steppers, the 2244I showed processing
capabilities that would perform well for noncritical layers.
Furthermore, FASL found that the throughput of the 2244i was 1.6 times
that of top-of-the-line reduction steppers. Based on this
information, as well as the comparatively low price of the Ultratech
system, FASL decided to introduce the 2244i into the factory.
MACHINE VISION SYSTEM
The 2244i was first used with the wafer alignment system (WAS) through
the lens darkfield alignment system. However, to accomplish the goal
of using existing re- duction stepper alignment marks without having
to add alignment marks in the scribe line, FASL decided to use
Ultratech's machine vision system (MVS). The MVS allows an existing
reticle pattern to be used as the alignment mark.
Although the MVS aligns to looser specifications than the WAS, it is
extremely useful for very noncritical layers such as pads.
2244i EVALUATION
MVS Recognition
The MVS system recognized the alignment marks from the newest model
reduction steppers without difficulty.
Resist-to-Resist Alignment
Using an Uitratech Stepper test reticle, FASL measured the
resist-to-resist alignment precision over a specified period of time.
The results showed the precision at an average of X = 0.320 nm and Y
= 0.298 pm (mean + 3(F). This performance was very satisfactory for
pad layers,
Production Alignment
A product reticle was made and used to expose an actual device. There
were no optical verniers or overlay metrology marks on this reticle,
so the accuracy could not be confirmed. However, based on the view
through a metallurgical microscope, with marks of 0.5 um, precision
was quite sufficient for pad layers.
Throughput
2244i throughput was very high at 82 wph (200 mm wafers, 24 exposures
per wafer at 100 MJ/CM2).
Conclusion
Currently, FASL is making a reticle for noncritical layers with
optical vernier and overlay measurement marks. Ultratech Stepper is
also planning improvements to the image recognition system and FASL
anticipates using it for layers with tighter tolerances. FASL
recognizes that the success or failure of mix-and-match lithography
strategies will be an important key to survival in the future memory
market.
5 Inch Reticle Loader Capability Added
(2244i, SATURN, AND TITAN IC STEPPERS AND 4700 AND 5700 TFH STEPPERS)
In the continuing effort to supply the most cost-effective lithography
solutions to the IC and TFH industries, Ultratech Stepper has added 5
inch reticle loading capability to its large field steppers. The
2244i, Saturn, and Titan IC steppers and the 4700 and 5700 TFH
steppers can now be configured with either a 5 or 6 inch reticle
handling system.
The 5 inch reticle program was initiated at the request of several
Ultratech semiconductor ASIC customers. This request focused on the
following advantages:
-5 inch reticle manufacturing costs are currently 25 to 35 percent
lower than comparable 6 inch reticle costs
-As with 6 inch reticles, 5 inch reticles can accommodate two 22 x 44
mm fields
-Customers currently using 5 inch reticles do not have to add 6 inch
storage capability
-5 inch reticles can be used for most products, which reduces stepper
cost of ownership.
UltraSteps
July 1996
Advanced Reticle Symposium
The second annual Advanced Reticle Symposium was held on June 4 in San
Jose, California. This year's symposium was even more successful than
last year's with a 30 percent increase in attendance (250 attendees).
The majority of attendees were from leading edge wafer and TFH fabs.
The symposium was presented by Solid State Technology Magazine and
Microlithography World Magazine in association with DuPont Photomask,
Photronics Inc., and Ultratech Stepper Inc. The symposium focused on
technical mask issues that face todays leading edge fabs and practical
solutions from leading edge reticle manufacturers.
Ultratech Receives over $11 Million in Orders for Its Titan Wafer
Stepper'
Ultratech recently announced that it has received over $11 million in
orders for its Titan Wafer Stepper. The systems will be used in the
manufacture of leading-edge memory and logic devices by a major
semiconductor manufacturer in Japan, as well as in the production of
high-volume, lowcost integrated circuits (ICs) by a North American
customer at its new 8 inch wafer fab. Ultratech reports that the
Japanese customer, which currently has an installed base of Titans in
several of its Japanese fabs, is planning to implement the systems at
various manufacturing sites throughout the world.
Ultratech's new U.S. customer will utilize the Titan's large field
size, high illumination intensity, and throughput capability to help
meet the productivity demands of its high-volume 8 inch line.
Ultratech's Senior Vice President of Sales and Service Daniel Berry
noted that using the Titan in semiconductor manufacturing applications
provides high-volume manufacturers moving into the 8 inch realm with a
cost-effective productivity solution. "We believe the Titan is the
only lithography system available that provides high throughput,
g-line processing for 8 inch wafers. In addition to the improved
throughput, this customer chose Titan to benefit from cost savings
associated with using g-line photoresist, as well as the high uptime
afforded by the system," explained Berry.
The Titan Wafer Stepper was designed to reduce cycle time and simplify
the polylmide buffer overcoat processes required in ultrathin chip
package technology such as thin small outline package (TSOP) and lead
on chip (LOC). Its broadband gh-line optics enable exposure of
photosensitive polyimide films with thicknesses up to 40 microns.
This enables manufacturers to eliminate several process steps
previously necessitated by the use of nonphotosensitive polyimide,
thus simplifying their operations.
Ultratech
July 1996
DuPont Polyimide Symposium
The seventh meeting of the DuPont Symposium on Polyimides in
Microelectronics, cosponsored by the Electrochemical Society, will be
held September 16, 17, and 18.. First held in 1988, this symposium
has developed into one of the most comprehensive technical meetings
on the implementation and the processing of polyimides and new
polymeric materials in advanced microelectronic applications.
Other subjects to be discussed may include MCM, high density
interconnects and flat panel displays, and new emerging technologies.
Wide Field Steppers for Cost. Effective ASIC Manufacturing
The 1996 SEMICON/West Cost Effective Lithography seminar, KJaus G.
Weyer of ELMOS GmbH highlighted the cost advantages of introducing
wide field steppers into an ASIC production line. Presenting a paper
coauthored by Dieter Rosenkranz, Dr. Weyer discussed the strategy
used by ELMOS to reduce reticle costs, one of the most significant
cost items in their ASIC production. (ELMOS develops and manufactures
ASICs and also specializes in CMOS mixed-signal system integration.)
Reticle Cost Reduction with 2244i/Saturn Strategy
Step 4 4 field 8 layer fast prototyping
Step 3 4 field 4 layer for low volume production devices
Step 2 4 field 4 layer reticle version for fast prototyping and
R&D devices
Step 1 Conversion from 6 to 5" reticle (two different layers per reticle)
TOOL SELECTION
ELMOS made a study of the available wide field stepper models and
determined that the Ultratech 2244i and Saturn steppers would best
meet ELMOS' needs for the coming years.
RETICLE COST-REDUCTION STEPS
The first cost-reduction step was the conversion from 6 to 5 inch
reticles (see Figure 1). It was determined that this conversion alone
would result in a 29 percent reduction in annual reticle costs for
ELMOS' 6 inch wafer line.
To gain maximum flexibility in reticle costs and throughput, ELMOS
also decided to use two exposure field sizes, 20 x 21 mm for fast
prototyping/R&D and low volume production, and 44 x 22 mm for high
volume production. The two exposure field sizes offered the option of
placing two to four layers on a 5 inch reticle without any redundancy
in layers. ELMOS concluded that the 4 field/4 layer (4F/4L) version
for the fast prototype/R&D and low volume runs would lead to a
significant reduction in the number of reticles used per year. This
approach would also reduce reticle storage capacity requiring fewer
reticle changes.
A 4F/8L version could also be used by dividing the 20 x 21 mm field
into two subfields with a field size of 20 x I0 mm or 20 x 5 mm that
would be sufficient for most prototyping runs in R&D applications.
This multilayer reticle technology has allowed large reductions in
lithography costs because 60 percent of ELMOS' yearly reticle
production is prototyping reticles, but only 6 percent of their
processed wafers are used for the prototyping and R&D runs (see Table
1).
Fast prototyping Production devices Production and R&D devices high volume devices
low volume
Device lifetime A few weeks Years Years
Costs per chip Very high Low Medium
Cycle time Very short Normal Normal Normal
Annual reticle costs 60% 40% 40%
Processed wafers 6% 94% 94%
Table 1: Characterization of ELMOS'Main Product Groups
ISSUES
An issue that arises when using two field sizes is that an automatic
field aperture (to change the field size very quickly) is not yet
available. However, this difficulty can be partially compensated for
by dedicating specific Ultratech tools to a particular field size
using a fixed field aperture.
A challenge in reducing the field size is the corresponding decrease
in throughput. In ELMOS' case, the unusual ratio of processed wafers
(prototyping/R&D to production) resulted in a relatively small loss in
overall throughput. Nevertheless, future activities will concentrate
on the enhancement of over-all 2244i and Saturn effectiveness in an
effort to provide compensation for any throughput loss.
RESULTS
The wide field of the 2244i and Saturn wafer steppers permits a
multifield reticle technique that can dramatically reduce reticle
costs in an ASIC fab. An overall reduction of 30 to 40 percent can be
achieved when the conversion from 6 to 5 inch reticles is taken into
account.
This huge cost reduction, compared with the original 6 inch reticle
layout, is due to the reticle ratio at ELMOS (number ofprototyping
reticles to number ofproduction reticles). According to their cost
distribution, ELMOS is able to reduce total lithography costs by 20
percent with the 4F/4L layout and 25 percent with the 4F/8L option.
A similar reduction in cost is possible with other wide field
steppers, like Niko@s 4425i or Cano@s 30OOiW stepper. However, any
cost savings would be partially offset by the higher initial
investment. The 6 to 5 inch reticle conversion can be done on the
4425i but with a reduction in usable field size from 44 x 44 mm to
approximately 40 x 40 mm. Also the 30OOiW can only use 6 inch
reticles with a 50 x 50 mm field, which is too large for a 6 inch
wafer line. So the use of Ultratech steppers is the best solution for
ELMOS.
CONCLUSION
As ELMOS reviews their lithography roadmap, they recognize
cost-effective solutions possible for CMOS devices down to 0.8 um
using 1X wide field steppers from Ultratech Stepper. In addition to
the low initial investment cost and depreciation advantages, the
reticle set costs can be reduced by using 5 inch instead of 6 inch
reticles and by using multifield/multilayer reticles with different
field sizes. Although decreasing field size is correlated to a loss
in throughput, a compromise between reticle costs and throughput can
be found for the product mix of every ASIC manufacturer.
Ultratech Voted a 10 Best Supplier (Sept 1996)
Ultratech earns the distinction of being the highest ranked optical
stepper supplier represented in thw 1996 survey. In achieving this
ranking, which marks the company's fourth appearance on the 10 BEST
list, Ultratech surpassed all other optical stepper suppliers in the
categories of product performance, technical leadership, process
support, software support, service after sales, uptime, and overall
commitment.
CEO Art Zifiropoulo noted, "As evidenced by the results of the survey,
we are committed to providing our customers with low cost lithography
solutions that emphasize product performance, reliability, and
service. Zafiropoulo added that he was pleased to see this year's
rankings validate the success of the new programs Ultratech
implemented last yea to enhance customer service and support
functions.
Lithography Tools for Micromachining
Micromachining evolved from the technologies developed for
microelectronics, which are now applied to the world of sensors and
actuators. A term often used to describe this device technology is
microelectromechanical systems (MEMS). As the name implies, MEMS
relates to tiny structures capable of physical movement, usually
involving some form of electronic signal for either sensing or
actuation.
By using new micromachining fabrication approaches, devices can be
created that are ideal miniature sensors for products such as
accelerometers for automobile airbags. The accelerometer uses a set
of tiny fingers a few tens-of-microns wide that are suspended over a
cavity to sense changes in motion. The associated electronics then
watch for movement and trigger the deployment of an airbag, for
example, when certain conditions are met.
Just as microelectronics has grown to the point where it has impacted
almost everyone's lifestyle, micromachining has the potential to grow
into a significant economic force. For instance, the revolution in
digital video displays that is being brought to the market today by
Texas Instruments will soon make brighter, sharper, and probably less
expensive entertainment units available to everyone.
Implanted medical devices that monitor patient conditions and alert
medical personnel when necessary, are another example.
Ultratech prides itself in providing low cost solutions to meet the
lithography needs of a wide variety of industries The company
currently has steppers located on three continents being used for
Micromachining applications. By investigating micromachining market
needs and developing lithography tools to meet these needs, Ultratech
will continue to grow with this exciting industry.
UltraSteps September 1996
Model 6700-Ultratech's New i-line TFH Stepper
UItratech Stepper's Model 6700 i-line system is the latest in a family
of new submicron thin film head (TFH) photolithography tools designed
to address the advancing requirements of the hard disk drive industry.
Building on the cornpanys worldwide leadership in TFH lithography,
the Model 6700 leverages Ultratech"s experience with
production-proven i-line lithography tools for the semiconductor
industry. This experience provides hard disk drive manufacturers with
the technology needed to image submicron geometries with
uncompromising productivity,cost of ownership, or reliability.
The Model 6700 is designed specifically for the production of advanced
magnetoresistive (MR) heads. The high precision wafer stage provides
the superior overlay and field stitching capability required for more
advanced TFH processes. Improved CD uniformity and a 0.65 micron
resolution offer TFH manufacturers the ability to achieve the smaller
features needed for critical layers. The system's 18 x 55 mm field
size enables the exposure of an entire width of a 2 inch strip of
magnetic head devices. This wide field capability provides up to a 50
percent reduction in the number of exposures imaged on the wafer.
Moreover, the field size is consistent with Ultratech's Model 4700 and
Model 5700 TFH lithography systems, allowing for mix-and-match with
these products. These factors and the system's high wafer plane
irradiance, enable the throughput, cost, and productivity advantages
for which Ultratech's steppers are known.
Ultratech Steppers for Bump Processing
Packaging technology is presently going through a revolution. This
change is from the use of wire leads to solder balls as the method of
connecting die to a package. The process of depositing the solder
balls on the wafer is called bumping and the process of placing bump
die onto packages is called flipchip.
The process of bumping a wafer requires the use of photolithography to
define the area for the solder deposition and the height of the bump.
Thick photoresist, 25 to 100 @, is used in the bump process to
control the height of the bump and align the deposited material to the
bond bad. Such thick photoresist works best with a stepper with high
wafer plane irradiance and large depth of focus. Both of these
requirements are typical characteristics of Ultratech models.
Presently, several Ultratech customers are using Model 1500 and
Titan Wafer Steppers for bump processing.
IF THIS DOESN"T CURE YOUR INSOMNIA, NOTHING WILL.<gg>
Regards
Andrew Vance |
