Descriptions
Full List
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Main equipments discriptions
Four Point Bend (4-pt bend)
The 4 point bend test is an experimental method
for measuring adhesion of thin films to substrates. The interface of
interest is sandwiched between two elastic substrates (silicon wafers,
the top piece being called the support piece and the bottom piece being
called the real piece). Load is applied to the beams at 4 points
causing the beam to bend. The force applied to the beams provides the
sample the strain energy release rate, Gc which is the
energy needed to separate the thin film from the substrate. While the
beam bends, this energy is stored and upon debonding, it is released
which enables the crack to propagate along the interface.
Once the crack length (a)3
thickness of the sample
(2h), then the strain energy release rate is constant with crack length
and can be calculated as follows:
where G is the strain energy release rate (J/m2),
E and v are the Young’s
modulus and the poisson’s ratio of the
substrate, b and h are the width and the half-height of strips (mm),
and M = PL/2, where P is the load applied to the strip (N), and L is
the distance between inner and outer pins (mm).
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Double Cantilever Beam (DCB)
The Double Cantilever Beam
test is also an experimental method for both adhesive and cohesive strength measurements.
Different from 4-pt bend test, which has a mode angle about 440, DCB
has the pure mode I configuration, which has the least plasticity involved. The
interface of interest is sandwiched between two elastic substrates (top and
bottom pieces) and a precrack is prepared at one end
so that the crack can further propagate along the interface when load is
applied on the Al end block.
The strain energy release rate G can
be extracted according to the experimental load-displacement curve. The
calculation procedure is relatively complicated compared with the case
of 4-pt bend.
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Electromigration (EM) Test
When current is
applied to the integrated circuit, the momentum of electrons can be
transferred to the atoms of the conductor (Al or Cu), which is so
called eletromigration (EM) behavior. EM
can induce void formation in the conduction line and finally cause open
circuit. Our EM system is to monitor the resistance traces of
package-level Cu lines in a high vacuum chamber at different
temperature range (0~4000C). The constant current source can
provide a very stable current for the test devices. Failure analysis
can be performed by using FIB/SEM and TEM to investigate the failure
mechanism.
EM system configuration:
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Stress Measurement (Bending beam test)
The stress of thin films can be measured by the bending beam technique. Thin film coated silicon beams are placed in a vacuum chamber with desired ambient gas and temperature control. The curvature difference of silicon beams is measured as shown in the following figure:
The stress of thin films can be deduced by Stoney’s equation as shown below:
Where Es is the Young’s modulus of the beam,us s is the poisson ratio of the beam, ts is the thickness of the beam and tf is the thickness of the film.
Following is an example of thermal stress measurement. The stress of one micron film on top of 300 micron of silicon beam was measured from room temperature to 200oC.
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Nanoindentation Measurement (Modulus and hardness test):
Indentation technique is widely used to obtain elastic modulus and hardness of thin films. Based on the method proposed by Oliver and Pharr[3], the elastic modulus E and hardness H can be derived directly from the analysis of unloading force vs. displacement curve. The process is shown schematically in Figure 1. As the indenter is driven into the thin film, both elastic and plastic deformation occurs. The assumption for this analysis is that after the indenter is withdrawn, only the elastic displacements are recovered. The reduced modulus E and hardness can be calculated: 
 (1)
Where S is the contact stiffness, P is the applied load and Pmax is the maxium load, h is the displacement, Er is the reduced modulus of the contact, which is directly related to elastic modulus film. A is the contact area which is deduced by the geometry of the indenter and the displacement h.
 
(a) Standard indentation of the film (b) load vs. displacement
curve
Figure 1. Schematic of nanoindentation technique for modulus and
hardness measurement.
Figure 2 shows some indentation force vs. displacement curves of
different materials. It is obvious that the mechanical responses of
different materials are quite different due to different mechanical
properties of films.
Figure 2. Some indentation force vs. displacement curves of different materials.
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Angle Resolved X-ray Photoelectron Spectroscopy (ARXPS)
XPS is a powerful surface characterization tool capable of monitoring the change of chemical states as well as stoichiometric analysis to determine the chemical composition of a material. Our XPS chamber is currently connected with a plasma chamber via a loadlock. Samples can be transferred to the XPS analysis chamber at any desired process point of interest without breaking the vacuum, which is called in-situ XPS analysis. The plasma ion energy ranges from 0 to 2200 eV and the substrate temperature can be controlled between room temperature and 2500C. XPS sampling depth is ~ 3λ sin θ (λ ~ 2 - 4 nm). Samples in the XPS chamber can be rotated to change the electron exit angle θ.
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3ω Technique for Thermal Conductivity Measurement
3ω technique makes use of the temperature response of metal resistance heater to catch the small temperature gradient. In our experiment, a metal (Al) line, 30 mm wide and 3 mm long, was patterned on the sample film, which had been capped with 90 nm PECVD SiO2. Due to the out-of-plane thermal conduction, resistance of metal line heater varies with the temperature gradient between the heater and the heat sink at the bottom side of the silicon substrate. This generates a small triple frequency (3ω) component in the voltage drop across the heater. The 3w component can be shown to be linearly proportional to the thermal resistance of the whole testing structure. The thermal resistance of the film itself was obtained by subtracting the contribution of the oxide cap and the silicon substrate from the total thermal resistance.
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Thermogravimetry Analysis (TGA)
The technique involves monitoring the weight loss of the sample in a chosen atmosphere (usually nitrogen or argon) as a function of temperature. A derivative weight loss curve can also be derived to tell the point at which weight loss is the most apparent. The furnace can heat samples from room temperature to 9000C. The balance is sensitive to 0.1 microgram.
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Dynamic Mechanical Analysis (DMA)
The Dynamic Mechanical Analysis is a high precision technique for measuring the viscoelastic properties of materials. It consists in applying a sinusoidal deformation to a specimen of material and measuring the resulting force transmitted through the specimen. The samples are loaded in an insulated high temperature oven in which the mechanical properties of the materials are measured as a function of time, temperature, and frequency. The Q800 Dynamic Mechanical Analysis DMA instrument operates over a wide temperature range (-150 to 600°C) and provides multiple modes of deformation including dual/single cantilever and 3-point bending, tension, compression, and shear. The following diagrams shows the typical results, in which glass transition temperature and temperature dependent storage and loss moduli can be derived.
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Dielectric Constant Measurement
The dielectric constant of a thin insulating film is derived by high frequency C-V (capacitance-voltage) measurement on MIS (metal-insulator-semiconductor) capacitors. The dielectric film is deposited on a Si substrate. TiW or Al electrodes are subsequently sputter deposited on the film through a shadow mask. During the measurement, the samples are placed on a vacuum chuck which also serves as the bottom electrode. The top electrodes are connected using a tungsten probe tip and a micromanipulator. Fig 1 shows the test connection and MIS structure on the sample. Keithley 590 analyzer is used for high frequency (100kHz and 1MHz) CV mapping, with a built-in 20V DC bias source or a external 100V DC bias source. Fig 2 shows the typical result of the CV mapping with distinctive accumulation, depletion and inversion regions on the plot. The dielectric constant of the insulating film can be derived from the accumulation capacitance, film thickness and electrode size.
Fig 1 Tungsten probe connection to top electrode and the MIS structure.
Fig 2 Typical CV plots of a high frequency AC measurement
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FTIR
 The above Michelson Interferometer is the basic design of FTIR system with broad band infrared source. The laser is incident on the collimating mirror and is directed to the beam splitter. Then the beam is split to fixed mirror and movable mirror. By adjusting the displacement of movable mirror, optical path difference between fixed mirror and movable mirror is introduced. After bouncing back from fixed mirror and movable mirror, two split beams recombine at the beam splitter and are directed toward the sample. Then the transmitted light is measured by detector. If the movable mirror is displaced a distance x, the optical path difference between the two split beams will cause interference:
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List of Equipments, Testers, and Instruments
Processing & Sample Prep Equipment:
Spin Coater
Atomic Layer Deposition (ALD) system integrated with remote plasma,
Residual Gas Analyzer (GRA), and In-situ X-ray Photoelectron Spectra (XPS)
system
Perkin Elmer three-gun magnetron sputtering system: 8-inches target.
(Plasma-Therm) Batchtop RIE plasma processing system.
Wire bonding, K&S 4123 wedge bonder
K&S wafer Dicing Systems
Heraeus high vacumn oven (up to 500 degree C)
Wafer Silylation system (under construction)
(Blue M Electronic) pro-tronix II electric oven.
Blue-M Oven
Testers:
Micro-tensile systems: for 4- & 3-point bending, DCB: 0.1 um resolution,
10kg load capability
High temperature (up to 200C)/High humidity (up to 80%RH under 80C)
chamber, in which 4-point & 3-point bend test, and DCB test can be
performed for critical adhesion & subcritical crack growth study.
Mixed-mode double cantilever beam (DCB) with humidity control for
adhesion at various mode mixity
Modified Edge Liftoff test (m-ELT), RT to -1800C (liquid N2 cooling), for
adhesion testing
TMC optical table.
Bending beam system, 20~500oC, for stress-induced curvature measurement
Micromanipulator Probe System
(Hysitron) Triboscope nano-mechanical test instrument (nanoindention).
Capacitance measurement + thermal cycling system
Wheatstone Bridge set up for solder EM and IMC study equipped with Two
Sigma M42 temperature chambers, constant-current controlling boards,
Package level EM test system with high vacuum chamber (up to 450 degree
C)
EM and BTS system for BEOL interconnects, High vacuum chamber ~5 mtorr,
up to ~3000C
Stress migration test system setup in atmospheric chamber, Temperature
140~3500C
Analytical Instruments:
Nicolet Magna 560 FTIR system integrated with Harrick ATR setup
Perkin Elmer, Thermo Gravimetric Analysis (TGA)
TA Instruments, Dynamic Mechanical Analysis (DMA) Q800
TA Instruments, Thermal Mechanical Analysis (TMA)
Perkin Elmer DSC
(Digital Instrument) NanoScope III AFM system
J.A. Woollam M-2000 DITM Spectroscopic Ellipsometer
(JEOL) JSM-840 Scanning Electron Microscopes (SEM).
Optical Microscopes
High resolution phase-shift Moire interferometry: 26nm per fringe
capability, for x-y displacement mapping.
(Metricon) Prism coupler model 2010: for reflective indices,
birefringence and thickness.
Tencor alpha-step 200 profilometer.
Keithley CV analyzers, multimeters, and Switch systems
Micro balances.
ABAQUS Software
Gaussian 03 Quantum Chemistry Software
Available within the Research Center:FEI Strata DB235 dual beam FIB/SEM,
TEM Jeol 2010F
STEM
Others:
Revco Freezer (-48 deg C)
QCM system: no one using and falling apart.
(Buehler) Ecomet 4 variable speed grinder-polisher.
(Buehler) Ecomet 3 variable speed grinder-polisher.
(Buehler) Ultramet II Sonic cleanser.
(Buehler) Isomet low speed diamond saw.
(Allied) Techprep 8 polisher.
(Buchi) oilbath B-485.
(Corning) hot plate stirrer PC-351-RC.
(Thermolyne) 47900 furnace.
(Thermolyne) 1900 hot plate.
numerous power supplies and multimeters (ex: Keithley 2000, HP 34401A
multimeter).
heat resistance solder
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