## Packaging of High Temperature SiC Based Electronics and MEMS Pressure Sensor 

 New Proposal **** Continuing NEPP Work

**Total \$ for FY02**:

**Technology Type:**  Newly Available (COTS) **** Emerging/Advanced

**Project Area:**  Parts **** Packaging  Radiation

**Proposing Center:** NASA GRC

**Participating Center(s):** NASA JPL, NASA MSFC

**([Estimated]{.underline} Center**

**Participation, %\$):** % GRC % JPL % MSFC

**Collaborators:** United Technology Research Center, Case Western
Reserve University

**Point of Contact:** Liangyu Chen, (216) 433-6458,
<Liangyu.Chen@lerc.nasa.gov>

**Investigators:** Dr. Liangyu Chen /AYT/NASA Glenn Research Center
(GRC), Dr. Gary W. Hunter, Dr. Philip G. Neudeck (GRC), Mr. David T.
Mih, Dr. Rajeshuni Ramesham, Dr. David Gerke /Jet Propulsion Laboratory
(JPL), Mr. W. T. Powers/NASA Marshall Space Flight Center (MSFC), Prof.
C. C. Liu/Case Western Reserve University (CWRU), Dr. Shun-Tien (Ted)
Lin/United Technology Research Center (UTRC)

**Objective(s):** Evaluate and validate advanced packaging technology
for Silicon Carbide (SiC) high temperature electronic devices and MEMS
pressure sensors operable up to 500 - 600°C. More specifically, our
Objectives are:

-   Electrically and mechanically evaluate packaging materials and
    components at and beyond 500 ^o^C.

-   Use reliability models to select high temperature packaging
    materials systems for optimal performance and lifetime.

-   Fabricate ceramic prototype packages for various SiC high
    temperature electronic devices and sensors.

-   Analyze the degradation and failure mechanisms of the package
    elements using surface/thin-film analysis tools.

-   Validate the packaging technology at 500 ^o^C for at least 2500
    hours and at 600 ^o^C for at least 50 hours.

-   Validate packaging technology for SiC MEMS pressure sensors in
    engine operation environment with GRC developed SiC high temperature
    pressure sensors.

**Task Description:** We propose to systematically validate thick and
thin film technologies for packaging SiC based high temperature devices.
The materials, metallization technologies, packaging design, and
packaging fabrication process will be validated both mechanically and
electronically. We will evaluate and validate a variety of materials for
use in the sensor/device packaging using both reliability modeling and
experimental characterization. Completely fabricated packages will be
validated and demonstrated with SiC devices and MEMS pressure sensor.

**Task Approach to Meeting NEPP Objectives:** The accomplishment of this
project will be to provide systematically validated baseline technology
for packaging SiC high temperature electronic devices and a specific
packaging system for high temperature SiC pressure sensor, and
therefore, expedite infusion of high temperature electronic devices and
MEMS pressure sensor into space and aeronautic applications.

Technical Background:

Single crystal silicon carbide (SiC) has such excellent physical and
chemical material properties that SiC semiconductor electronics can
operate at temperatures in excess of 600 ^o^C.^1^ Electronic devices and
sensors which can operate in such harsh environment (\~600 ^o^C) are
necessary for many space and aeronautic application such as electronics
and sensors for a space mission to inner solar system and emission
control sensors/electronics located in an aeronautical engine
environment. SiC semiconductor electronics and MEMS pressure sensor
fabricated at NASA GRC have been demonstrated operable at temperatures
as high as 600 ^o^C. However, packaging for high temperature electronics
and MEMS sensors operable over 500 ^o^C have not been completely
validated/evaluated.^2^ Therefore, validating technologies for packaging
SiC based electronic devices/sensors is an immediate need. Ceramic
substrates and thick-film metallization based prototype electronic
packages designed and fabricated at NASA GRC have been electrically
evaluated for operation at 500 ^o^C for \~10^3^ hours recently.^3,\ 4^
However, these materials and technologies need to be more systematically
validated and evaluated (especially mechanically) for long term
operation at higher temperatures.

The SiC MEMS pressure sensor operates not only at high temperature but
high pressure as well. This MEMS high temperature sensor requires
special high temperature electrical contact on the sensor chip and the
sensor is intrinsically sensitive to external forces, such as thermal
stress due to CTE mismatch of the die-attach materials. These additional
and sensor oriented specific packaging requirements generate additional
packaging evaluation/validation task beyond those for basic high
temperature electronics packaging.^5^

### References

1.  P. G. Neudeck, \"Progress Towards High Temperature, High Power SiC
    Devices\", in Institute of Physics Conference Series, Compound
    Semiconductors 1994, edited by H. Goronkin and U. Mishra (IOP
    Publishing, Bristol, United Kingdom, 1995) pp. 1-6.

2.  \"High Temperature Electronics\", edited by F. P. McCluskey, R.
    Grzybowski, and T. Podlesak, CRC Press, Inc., New York, NY, 1997.

3.  Liangyu Chen, Gary W. Hunter, and Philip G. Neudeck, *Silicon
    Carbide Die-attach Scheme for 500 ^o^C Operation*, 2000 MRS Spring
    Meeting Proceedings, San Francisco, CA, April 10-14, 2000.

4.  Liangyu Chen and Philip G. Neudeck, *Thick and Thin Film Materials
    Based Chip Level Packaging for High Temperature SiC Sensors and
    Devices*, Proceedings of 5^th^ International High Temperature
    Electronics Conference, Albuquerque, New Mexico, June 12-16, 2000.

5.  Liangyu Chen *et al*, Validation of Packaging Technology for High
    Temperature Silicon Carbide MEMS Pressure Sensor - NEPP FY02
    proposal submitted by NASA GRC.

**Technical Approach:** This project features an interdisciplinary team
from government, industry, and academia. This work draws upon a
considerable amount of expertise in this field at various institutions.
Activities will include material selection and testing (GRC, UTRC), high
temperature reliability modeling (UTRC), sensor and device fabrication
(GRC, CWRU), fabrication and testing of packages with devices and
sensors (GRC, JPL, UTRC), inspection of configuration of functional and
failed die-attach components (JPL), and testing of complete packaged
devices and sensors in relevant engine test standard environments
(MSFC). In particular, activities performed in this task include:

1.  Electrically and mechanically evaluate materials, especially,
    thick-film metallization materials, for packaging SiC based
    electronics and devices operable at high temperatures. Thick film
    materials will be used for die attach, printed wires, wire-bond
    (pads), lead surface process, and seals. In order to systematically
    validate the performance of each of these packaging elements, both
    the mechanical and electrical properties of these elements will be
    evaluated at and beyond 500 ^o^C. The mechanical properties of die
    attach such as shear and tensile strength will be systematically
    tested/validated and correlated to the processing conditions. The
    \"Wire Loop Test\" will be performed for mechanical validation of
    wire bond. The electrical resistance of thick-film printed wire and
    wire bond, and inter-printed-wire impedance on various substrates
    will be systematically validated at both low and high temperatures.

2.  Use reliability models to optimize candidate material selection. The
    material properties, especially, metal/metal and metal/ceramic
    interfaces, of packaging elements will be modeled to select
    materials for optimized performance/functionality and life time
    under a variety of harsh environmental conditions such as high
    temperature and thermal cycling.

3.  Thick film metallization based ceramic test packages for various SiC
    devices/sensors will be fabricated, assembled, and tested at 500
    ^o^C and 600 ^o^C. Systematic test reports will be generated.

4.  The degradation and failure mechanisms of these packages at high and
    low temperatures will be analyzed using surface analysis
    technologies such as scanning electron microscopy (SEM), and
    scanning Auger electron spectroscopy (SAM), and X-ray photoelectron
    spectroscopy (XPS). The die-attach configuration will also be
    evaluated nondestructively by real-time radiography and scanning
    acoustic microscopy. These results will be used to improve the
    material selection, parts fabrication process, package design, and
    assembly for a better overall package performance.

5.  Validate the packaging technology using operational SiC devices. The
    electronic packages will be finally tested and validated using SiC
    devices/sensors at both low and high temperatures. The
    devices/sensors properties both before and after packaging will be
    tested. The packaging performance will be evaluated by comparing the
    device performance before and after packaging. The final goal of
    this project is a package operable at 500 ^o^C for at least 2500
    hours and 600 ^o^C for at least 50 hours. This project is a part of
    efforts to make high temperature electronics/sensors available to
    NASA.

6.  Pt/Au mixture interconnection system: High temperature MEMS have its
    own preference for various contact metallization. One of the most
    successful high- temperature Ohmic contact scheme uses Pt as cap
    material. Therefore, the Pt/Au electrical interconnection system,
    either a mixture or alloy material system, needs to be validated for
    high temperature and high-pressure operation. This validation task
    includes electrical resistance stability test and interfacial
    chemical and mechanical properties characterization before and after
    long term operation/testing at high temperatures. Wire-bond process
    using various bonding methods including laser welding for this
    interconnection system (with Pt) also needs to be systematically
    validated both electrically and mechanically.

7.  Thermo-mechanical stress reduction: the basic operation principle of
    MEMS pressure sensor is based on mechanical deformation of the
    sensor, therefore, the sensor response is very sensitive to thermal
    stress generated from CTE mismatch of sensor material (SiC) and
    packaging environment. Die-attach material and sealing materials
    with good mechanical properties, especially at high temperatures,
    need to be experimentally validated. Finite Element Analysis (FEA)
    can also be used for long term thermal dynamic modeling and failure
    prediction.

**NASA Customers:** Since high temperature electronic packaging is an
essential part of high temperature electronics which is one of major
needs to improve the safety, efficiency, and low emissions of aero and
space engines. This project will significantly benefit these NASA
programs/projects: Ultra Efficient Engine Technology (UEET), Space
Propulsion Technology and Integration, Higher Operating Temperature
Propulsion Components, Turbo-machinery and Combustion Technology,
Information Technology, Spaceliner 100, and Glennan Microsystems
Initiative (GMI).

**Program Deliverables:**

-   Validated high temperature electronic prototype package operable at
    500 ^o^C for at least 4000 hours and at 600 ^o^C at least for 50
    hours.

-   Final project report of 500 ^o^C operable packaging technology for
    SiC high temperature devices.

-   Electrical and mechanical specs of a validated general high
    temperature electronic package.

-   Evaluated technology of packages/components for operation in variety
    of harsh environment.

-   Reliability models for a range of potential high temperature
    packaging components/materials.

-   Validated high temperature prototype package for SiC pressure sensor
    operable at 500 ^o^C for at least 2000 hours.

Milestones (FY02):

Validate wire and lead bonds operable at 500^o^C for 2500 hours and 25
hours at 600^o^C Q1/02

Validate die attach operable at 500^o^C for at least 1000 hours and 25
hours at 600^o^C Q2/02

Validation of electronic package at 500^o^C for 2500 hours and 600^o^C
for 25 hours

Validation of the electrical interconnection system for SiC pressure
sensor at 500^o^C Q3/02

Evaluation of micro-welded components for SiC pressure sensor packaging

Validate prototype package in standard engine test environments at MSFC
Q4/02

**Top Level Schedule:**

Extend validation of wire and lead bonds at 500^o^C to 3000 hours/50
hours at 600 ^o^C Q1/03

Extend validation of die attach operable at 500^o^C to 1500 hours/50
hours at 600 ^o^C Q2/03

Extend validation of electronic package at 500^o^C to 3000 hours/50
hours at 600 ^o^C Q3/03

Evaluate improved electronic package in standard engine test
environments at MSFC

Evaluation of high temperature high pressure sealing system for SiC
pressure sensor Q4/03

**List of Procurements (FY02 over \$5K):**

CWRU Grant 10K Q1/02

OAI Service Support Contract 70K Q1/02

UTRC Contract 50K Q1/02

High temperature electronic and mechanic testing equipment 5K Q2 /02

High temperature electronic packaging materials (thick-film materials,
ceramic

substrates, and fabrication) 15K Q2-Q4/02

**Manpower Loading:** Average Heads (FTEs)

  ----------------------------- --------- ---------- ---------- ----------
                                Q1        Q2         Q3         Q4

  NASA GRC                      0.2       0.2        0.2        0.2

  NASA MSFC                     0.06      0.06       0.06       0.06

  NASA JPL                                                      .25

  SSC (OAI and AKAMI)           0.85      0.85       0.85       0.85

  Case Western Reserve          0.1       0.1        0.1        0.1
  University (CWRU)                                             
  ----------------------------- --------- ---------- ---------- ----------

**Leveraging:** This validation/evaluation effort will leverage with
High Temperature Electronic Packaging project of Glennan Microsystems
Initiative (GMI) at GRC and a NASA GRC funded SBIR which concentrate on
technology development.