Silicon Thermal Properties

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Thermal Conductivity of Silicon Nitride

A Ph.D student in Middle East University requested the following quote:

I need PECVD silicon nitride to use for membranes and cantilevers. Thermal conductivity of this film is important in my project. Would you please send me Thermal Conductivity of your low stress PECVD silicon nitride, I wonder if I could ask how you can control it.

UniversityWafer, Inc. Quoted:
Item   Qty.  Description
FA46. 10   Silicon wafers, per SEMI Prime, NP/E 4"Ø×525±25µm, SEMI Flat (one), p-type Si:B[100]±0.5°, Ro=(5-10)Ohmcm, TTV<4µm, Bow<12µm, Warp<30µm, with 1.0µm thick Low Stress (<200 MPa) PECVD Silicon Nitride on polished side, Sealed in Empak or equivalent cassette.

Reference #225415 for specs and pricing.

Key Terms Associated with Silicon Thermal Conductivity

Below are just some of the keywords that are important to research.

  • thermal conductivity
  • thermal expansion silicon
  • thermal properties
  • specific heat thermal
  • diffusivity temperature range
  • thermal resistance
  • heat thermophysical properties
  • latent heat
  • heat capacity
  • expansion coefficient
  • average value cm crystalline silicon
  • silicon wafer heat conduction
  • polysilicon layers
  • silicon carbide
  • phonon density type
  • silicon nanocrystalline
  • silicon films
  • thermal shock
  • thin films
  • physical properties
  • electrical properties
  • nanoscale structure
  • temperature single crystals coefficient
  • semiconductor



Understanding the Thermal Conductivity of Silicon

Having a good understanding of thermal properties of silicon is important for many silicon thermal properties chartengineers and scientists, especially in the field of semiconductors. It is also important to know that the composition of the phase and the microstructure of the material can affect its heat transfer and thermal conductivity.

Temperature dependence of thermal conductivity

Using an ab initio equilibrium molecular dynamics simulation of phosphorus doped silicon, researchers have calculated the temperature dependent thermal conductivity of silicon. These calculations are in good qualitative agreement with the reference data.

As temperature increases, the thermal conductivity of silicon decreases by ten to twenty percent. These findings are important for applications that involve solving different materials problems. The calculated value of k(nP) was found to be 57 W*m-1*K-1. This figure reflects the deviation of the crystal structure from a perfect atomic distribution. It also is not in contradiction with the heat conductivity studies of less heavily phosphorus doped silicon.

To calculate the temperature dependent thermal conductivity of silicon, the mean phonon scattering time ts(T) is used. This time is related to the thermal conductivity coefficient k. In this study, researchers have used an ab initio equilibrium molecular dynamics method to calculate the ts(T). They have also calculated the k(nP) value.

The ts(T) calculation is made using a two-laser Raman thermometry system designed by J.S.R. This method is useful for transient thermal simulations. In addition, it has been used to estimate the temperature profile of an IC. The calculated thermal conductivity value is less than three percent error for a range of temperatures.

The Power Blurring method is another tool to compute the temperature profile of an IC. This method is hundreds of times faster than a finite element method. It can be extended to 3D chips. For high temperature changes, the Power Blurring method has a maximum error of seven to twelve percent.

The Power Blurring method ignores the temperature dependence of the thermal conductivity of silicon. It is also limited to very low temperature changes. Nevertheless, the Power Blurring method provides an accurate calculation of the temperature profile of an IC.

Chemical/phase composition

Several studies have been carried out on the chemical/phase composition of silicon for thermal properties. These studies have shown that the solid solutions form a bcc structure at ambient temperature and pressure. This is different from the B2 structure that appears in a range of Fe-Si alloys. Similarly, the elastic properties of bcc-type alloys are different from those of B2 alloys.

The present study is aimed at determining the compositional constraints of the two-phase field of bcc-type Fe-Si alloys. The present studies also investigated the volume of the fcc and bcc structures. Moreover, the thermal stability of the alloys was studied at selected pressures.

The bulk phase diagram of the Fe-Si system is complex at pertinent compositions. This is likely due to the strong interatomic interactions that are responsible for the DO3 structure. The phase order is observed at Si concentrations of 5 to 17 wt% Si. This ordering is attributed to the long-range forces that result from competing interatomic interactions. Moreover, the elasticity of the B2 and DO3 phases is similar.

The fcc + B2 miscibility gap extends to both the solidus and the liquidus temperatures. This can explain the decreasing Si solubility at higher pressures. This is consistent with the eutectic over solid solution. However, previous studies suggested that the Si solubility in the fcc phase is lower than in the hcp phase.

The phase rule states that any gas phase can be either condensed to a liquid or converted into a solid. Similarly, if a less dense solid is formed, it would rise upwards. In the case of a bcc-type alloy, a core can be formed in higher Si concentrations. This could lead to the formation of a liquid Fe-Si core. In this case, the core will be less dense than the liquid and will have a melting temperature equivalent to pure iron. This phenomenon is known as the FeSi snow regime.


Several studies have been conducted to characterize the microstructure of silicon thermal properties. The results suggest that a large dip in the thermal conductivity curve indicates an exothermic reaction. This study investigates the effects of microstructural evolution on the thermal properties of an additively manufactured AlSi10Mg part.

Generally, solution treatable metallic parts have a unique nonequilibrium microstructure. However, the microstructure of RB-SiC preforms is closely related to C/SiC preforms. Therefore, this study focuses on the effect of microstructural evolution on the thermal properties and mechanical behavior of an AlSi10Mg part.

As shown in Figure 2, the microstructure of the produced ceramics had two kinds of homophase boundaries. The larger features were separated by tens to hundreds of microns. The smaller features, on the other hand, were not aligned. This could result in scattering events. The efficacy of the scattering events depends on the microstructure.

To observe the effect of microstructural evolution on the microstructural properties, a series of samples was annealed at various temperatures. The selected annealing temperatures were determined based on the DSC measurements. The results showed that the microstructure ripened at the higher temperatures. The grain sizes of the equiaxed grains were from 300 to 800 nm. This is a sign of the first stage of ripening.

At the higher temperature range, the number of particles per area decreased dramatically. This is attributed to the increase in the distance between particles. The number of interfaces also decreases. Consequently, the amount of the solute concentration decreases. The overall scattering event is also affected.

This study demonstrates that the microstructural evolution has an important effect on the thermal and electrical properties of an AM fabricated part. The result of the study is that the rapid solidification of an AM part develops a unique cellular microstructure.


Using the Youngs modulus, silicon has a coefficient of thermal expansion (CTE) of 2.5 x 10 -6 K-1. The ductility of silicon is the property of the material to resist deformation under pressure. The silicon conductivity is 156 W m -1 K -1.

Thermal conductivity is one of the key properties of semiconductors. It is important to design the thermal properties of an IC in a way that minimizes stress. During operation, silicon chips produce a lot of heat. It is important to move this heat out of the system. This is accomplished by using a strong binder.

In addition to electrical and thermal properties, the ductility of silicon is also a significant parameter to consider. As power levels increase, the thermal properties of ICs become even more important.

The thermal properties of a polymer composite are greatly dependent on the shape of the fillers. A silicone composite with large aspect ratio fillers is better than a polymer composite with small aspect ratio fillers. The temperature distribution in the simulated material is a good measure of the thermal conductivity of the polymer composite.

The best way to improve the thermal conductivity of a polymer composite is to use GNPs with a high aspect ratio. Using this technique, the thermal conductivity of the polymer composite can be increased by up to 30%. Typical tricks include lowering the equipment temperature after the Si has been inserted into the device.

Another interesting study was performed by Unkic et al. They investigated the effect of increasing the number of graphite particles on the UTS of a ductile iron alloy with a 2.5-2.8 wt% Si content. Their results showed that the UTS increases by up to 40 MPa, but it decreases by up to a third when the particle count is increased by a factor of three.

Silicon Carbon (SiC) vs Glassy Carbon

During the past century, silicon carbide (SiC) has been used for a variety of applications including cutting tools, sandpapers, and refractory linings in industrial furnaces. SiC has also been used as a substrate in semiconductor light-emitter diodes and in rocket engines. However, it has a lot of disadvantages when used as a structural material. One of the problems is cracking.

Another disadvantage is oxidation resistance. In order to overcome this problem, we developed an oxidation resistant coating. It consists of a dense CMAS glass outer layer and an inner layer of SiC. The thickness of the outer layer is 40 mm, while that of the inner layer is 50 mm. The oxidation resistance of the coating is good due to the high temperature stability of SiC and the good adhesion between the two layers.

We prepared the composite coating by using the slurry method. The slurry was mixed with carrier gas and a concentration of trichloromethylsilane. The carrier gas flow rate was adjusted to adjust the rate of trichloromethylsilane flow. The surface conditions of the graphite substrate were also taken into account to improve the quality of the coating. The coating was tested for oxidation and thermal shock resistance. X-ray diffraction was performed to determine the SiC crystals.

The diffraction peak intensity of the SiC film-covered glassy carbon material was 80% of the crystal plane. Its surface roughness Ra was 0.4-15 mm. In the thermal shock test, the film was peeling. The film is thicker than 30 mm and may cause cracks. This may result in part of the part being not covered with the SiC film.

When the SiC film-covered glassy carbon materials were enlarged in size, the thermal expansion coefficient caused a problem of cracking. This is more likely to occur in the enlarged material.

Video: Thermal Properties of Silicon (Si)