Measuring Thermal Conductivity and Resistance for Dielectric Films as Thin as 1 Nanometer

SSTR can measure the thermal conductivity of films as thin as 1 nm, shown here for thin dielectric films (TiO2, Al2O3 and HfO2) on silicon substrates.

The Challenge

The need for increased control of layer thickness and uniformity as device dimensions shrink has spurred increased use of atomic layer deposition (ALD) for thin film growth. The ability to deposit high dielectric constant (high-k) films via ALD has allowed for their widespread use in a swath of optical, optoelectronic, and electronic devices, including integration into CMOS compatible platforms. However, as characteristic length scales of device nodes decrease to nanometers scales, temperature and power dissipation become a critical concern. The need to understand the thermal properties of these thin high k layers is paramount.

The Solution

SSTR offers all the flexibility, capabilities and sensitivities as lab-based, open-table optical pump-probe systems such as TDTR and FDTR to make these measurements. The TDTR-measured thermal conductivities were reported in our prior work (APL Materials 6, 058302 (2018)) agree perfectly with our SSTR-measurements.

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Nanoscale to bulk

Thermal conductivity of nanoscale thin films

SSTR is ideal for your thin film thermal conductivity testing needs.
In addition to measurements of bulk wafers and substrates (source 1, source 2), SSTR has the unprecedented spatial resolution to measure the thermal conductivity of thin films.
For example, SSTR can measure the thermal conductivity of single nanometer thick ALD grown thin films or micron thick AlN films (source).

SSTR measurements on ALD grown ultrathin film amorphous gate dielectrics (compared to TDTR) (source).

SSTR measurements of AlN crystalline thin films.2 SSTR data (temperature rise vs. power) on right for AlN film and silicon wafer control.

Validated results

SSTR-F measures the thermal conductivity of Corning Pyroceram 9606 and Corning high purity fused silica (HPFS) 7980 to within 5% of their published values.
Additional validation was provided by measuring samples from the same piece of material using the Transient Plane Source technique.
Pyroceram is no longer available from NIST but was measured on similar material to the material that was validated as a Certified Reference Material.
Corning HPFS was procured from a distributor of HPFS 7980 wafers.

	Literature Value	TPS Measurement	SSTR-F Measurement
Pyroceram 9606	4.07 +/- .26	3.95	3.95 +/- 0.2
HPFS 7980	1.38	1.39	1.39 +/- 0.09

Unparalleled reliability

Thermal conductivity measurements: Accuracy +/- 10%, Repeatability +/- 0.5%, Reproducibility +/- 1%
Accurate thermal conductivity measurements of materials in agreement with literature values
With exceptional instrumentation reliability and repeatability, SSTR-F offers unprecedented measurement stability on a daily basis for any user, exemplified by the SSTR-F data shown below. Spread in randomly sampled spots are sample related, not measurement driven.

Source

20 SSTR-F measurements at same spot

20 SSTR-F measurements at random spots

Turnkey testing

Our patented fiber-optic design enables turnkey, automated testing of thermal conductivity.
High-throughput SSTR-F testing of multiple samples facilitates, for example, screening the thermal conductivity of different thin films processed under different conditions
Defects, stresses, compositional differences, and changes in density and microstructure that occur up during film growth result in changes in thermal conductivity, easily and rapidly identified vis SSTR-F

SSTR-F data on 4 different 200 nm dielectric films on silicon with thermal conductivity ranging from ~0.35 W/m/K up to 1.8 W/m/K. SSTR-F allows for easy, rapid and automated identification of different temperature rises based on the thermal conductivity of the different films.