Silicon (Si (P-type)) Pieces Evaporation Materials

Silicon (Si (P-type)) Pieces Overview

We sell these pellets and pieces by unit weight for evaporation use in deposition processes. These approximate materials prices are published to provide budgetary guidelines. Actual prices can vary and may be higher or lower, as determined by availability and market fluctuations. To speak to someone directly about current pricing, please click here .

Silicon (Si (P-type)) General Information

Silicon is one of the most extensively used elements in the world. It is dark gray and semi-metallic with a bluish tinge. It has a melting point of 1,410°C, a density of 2.32 g/cc, and a vapor pressure of 10^-4 Torr at 1,337°C. It is a brittle metalloid which can chip easily. Silicon is a semiconductor which is heavily utilized in the electronics and computer industries. It is often doped with arsenic, phosphorus, or boron depending on the application. It is evaporated under vacuum for circuit device, data storage device, and battery fabrication.

Silicon (Si (P-type)) Specifications

‡ One run only.

Z-Factors

Empirical Determination of Z-Factor

Unfortunately, Z Factor and Shear Modulus are not readily available for many materials. In this case, the Z-Factor can also be determined empirically using the following method:

• Deposit material until Crystal Life is near 50%, or near the end of life, whichever is sooner.
• Place a new substrate adjacent to the used quartz sensor.
• Set QCM Density to the calibrated value; Tooling to 100%
• Zero thickness
• Deposit approximately 1000 to 5000 A of material on the substrate.
• Use a profilometer or interferometer to measure the actual substrate film thickness.
• Adjust the Z Factor of the instrument until the correct thickness reading is shown.

Another alternative is to change crystals frequently and ignore the error. The graph below shows the % Error in Rate/Thickness from using the wrong Z Factor. For a crystal with 90% life, the error is negligible for even large errors in the programmed versus actual Z Factor.

Thermal Evaporation of Silicon (Si (P-type))

Thermally evaporating silicon is difficult, if not, impossible.

We refer to a material's evaporation temperature as the temperature required to achieve a vapor pressure of 10^-2 Torr. At this vapor pressure, a high deposition rate is possible in a system that has a normal source-to-substrate geometry. In order to reach this vapor pressure, silicon must be heated to ~1,600°C. Because this temperature is higher than its melting point (1,410°C), silicon will evaporate from liquid form.

However, liquid silicon reacts with refractory metals. We have attempted to thermally evaporate silicon from a thick-gauged tungsten boat (0.025" thickness) with little success. The liquid silicon wet and alloyed with the boat, causing it to fail before a reasonable layer could be deposited. We also attempted to use a shielded crucible heater with a graphite crucible. This approach failed as well because the liquid silicon reacted with the crucible.

As it stands, we do not have a good source recommendation for thermally evaporating silicon and generally recommend e-beam evaporation or sputtering for depositing silicon films. However, the e-beam evaporation process can be complicated as well.

E-beam Evaporation of Silicon (Si (P-type))

Silicon is rated as fair for e-beam evaporation.

We refer to a material's evaporation temperature as the temperature required to achieve a vapor pressure of 10^-2 Torr. At this vapor pressure, a high deposition rate is possible in a system that has a normal source-to-substrate geometry. In order to reach this vapor pressure, silicon must be heated to ~1,600°C. Because this temperature is higher than its melting point (1,410°C), silicon will evaporate from liquid form.

We recommend using either a FABMATE^® or tantalum crucible liner for e-beam evaporating silicon. Crucible liners will need to be replaced fairly often because liquid silicon has the tendency to damage liners. When silicon melts, it will mechanically bond to the inner walls of the crucible liner. Upon cooling or re-heating, the difference in thermal expansion/contraction of the silicon in contact with the liner can produce enough stress to break the liner. We also find that the melt level of a material in the crucible directly affects the success of the crucible liner. Overfilling the crucible will cause the material to spill over and create an electrical short between the liner and the hearth. The outcome is cracking in the crucible. This is the most common cause of crucible liner failure. Placing too little material in the crucible or evaporating too much material before refilling can be detrimental to the process as well. When the melt level is below 30%, the e-beam is likely to strike the bottom or walls of the crucible which immediately results in breakage. Our recommendation is to maintain a melt level between 30-80% and slowly ramp power up and down to prevent these complications. However, even when following these guidelines, the liners will still need to be replaced frequently.

It is important to note that the FABMATE^® liners will likely survive only one evaporation run. It is possible to get multiple runs from tantalum liners. However, tantalum liners are generally more expensive than the FABMATE^® ones. Users will need to consider the extra life of the tantalum liner versus the extra cost to determine if it is more economical to purchase additional FABMATE^® liners and replace after each run.