What Industry Would Use Langmuir Probes and Why?

The use of plasma in the scientific industry has increased over the last several decades and is continuing to do so. Plasma are the new cutting tool for the nanotechnology (the manipulation of matter on an atomic and molecular scale) age which is coming more and more to the fore in modern science. They are electrical gases and can be directed towards a work piece by biasing the work piece, usually with a radio frequency bias. The electrons in them are extremely hot, often at temperatures of up to a million degrees centigrade. The chemistry in such a hot electron bearing gas is really reactive making it an ideal cutting tool to etch away material and create features. In a plasma the cutting edge is in reality, just the reactive ion then the size of any feature that can be etched is very small. In semiconductor applications thousands of lines can be etched on the width of a human hair. In order to control such a sophisticated process it is necessary to better understand the physics of the plasma used in etch. In order to measure the density of it, the R&D scientist will use a Langmuir probe. This is a small wire less than a millimeter in diameter, and typical a few mm long that draws current from it and determines the density of the plasma as well as the temperature of the electrons which determines the reactivity of the plasma. In etch applications the probe tip can be scanned across the wafer holder to determine the uniformity. This is important when the plasma needs to etch large area wafers. In plasma etch systems the plasma is cutting fine lines in large wafers and it is very important that it is uniform so that the etch rate is uniform. The lines are also being etched in what will become very high speed circuits of silicon. These structures can easily be damaged by even small voltages across the area of the wafer. If the plasma potential at one point on the wafer exceeds the plasma potentials at a nearby point then the electrical field can be large enough to cause a small arc across the silicon surface which will damage the delicate circuit. It is thus very important to ensure that the plasma potential is uniform in etch systems. Again, a Langmuir probe can be used to measure the local potentials and determine if the plasma potential variation poses a threat to the wafer during processing that is ongoing. These are important parameters to measure during the design phase of a plasma etch reactor. To conclude, in the design and verification of a plasma reactor for industrial applications the Langmuir probe is a key diagnostic. It helps to determine it’s uniformity, the reactivity of the chemistry and the likely hood of damaging potential variations that will determine the quality and performance of the tool design. Hopefully this will clear up any issues you have trying to clarify what a Langmuir probes use is. If you need more information please follow the link below to help you understand more