Magnesium (Mg) Pellets Evaporation Materials

Magnesium (Mg) Pellets 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 .

Magnesium (Mg) General Information

Magnesium is a grey-white, alkaline earth metal with a melting point of 649°C, a density of 1.74 g/cc, and a vapor pressure of 10^-4 Torr at 327°C. It is extremely flammable, especially in powder form, and fires are difficult to extinguish. Magnesium is also an essential element to life. Magnesium is responsible for regulating nerve function, blood pressure, and the levels of nutrients in the human body. It is extensively used in the production of aircraft, engine casings, laptops, cell phones, and cameras. Magnesium and its alloys are evaporated under vacuum for the development of magnetic storage media, optical storage media, and semiconductors.

Magnesium (Mg) Specifications

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 Magnesium (Mg)

We recommend using a dimple-style, tungsten boat such as our EVS8B005W to thermally evaporate magnesium. At about 430°C, we expect good deposition rates by thermal evaporation.

Cleaning material overspray is a concern for many users depositing magnesium films. Proper cleaning procedures are essential to preventing film contamination. Magnesium has a relatively high vapor pressure versus temperature curve. If a process chamber contains a substrate heater, subsequent films run the risk of contamination from residual magnesium when working at temperatures above 250°C. The vapor pressure of magnesium at this temperature is around 2 X 10^-6 Torr. Generally, systems that are used to deposit magnesium are dedicated for magnesium film work alone because of this high vapor pressure versus temperature curve.

Another concern is the pyrophoric nature of magnesium overspray. The overspray is invariably highly granular and, depending on the surface area to volume ratio, can spontaneously combust in air. Water presents another problem as its presence can help ignite the magnesium flakes. Users should consult their lab safety manager for more information about avoiding and extinguishing magnesium fires.

E-beam Evaporation of Magnesium (Mg)

We recommend a FABMATE^®, graphite, or tungsten crucible liner when e-beam evaporating magnesium. High rates of deposition are possible under this method.

A key process note is to consider the fill volume in the e-beam application because we 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 fill the crucible between 2/3 and 3/4 full to prevent these difficulties. Crucible liners should be stored in a cool, dry place and always handled with gloves or forceps.

Cleaning material overspray is a concern for many users depositing magnesium films. Proper cleaning procedures are essential to preventing film contamination. Magnesium has a relatively high vapor pressure versus temperature curve. If a process chamber contains a substrate heater, subsequent films run the risk of contamination from residual magnesium when working at temperatures above 250°C. The vapor pressure of magnesium at this temperature is around 2 X 10^-6 Torr. Generally, systems that are used to deposit magnesium are dedicated for magnesium film work alone because of this high vapor pressure versus temperature curve.

Another concern is the pyrophoric nature of magnesium overspray. The overspray is invariably highly granular and, depending on the surface area to volume ratio, can spontaneously combust in air. Water presents another problem as its presence can help ignite the magnesium flakes. Users should consult their lab safety manager for more information about avoiding and extinguishing magnesium fires.