Plasma for Backend

Plasma is used to etch, clean, activate, or modify surfaces to improve the adhesion, reliability and quality of components such as chips and sensors, or during wafer level packaging.

The surface of an object can assume various energy states. One way of describing them relates to how resistant they are to water. Highly resistant surfaces are called hydrophobic. This state can be determined by a simple test in which a small drop of liquid is applied to the surface. The extent to which the drop spreads or forms a sphere is observed here. The related measurement is known as the contact angle. In the case of hydrophobic surfaces, this angle is very large.

The surface energy can be transferred from the hydrophobic to the hydrophilic state in a very simple activation process. A short process with oxygen, possibly mixed with argon, changes the surface to a very low contact angle, with the result that a subsequent wet-chemical process takes place much more quickly and uniformly than without this pretreatment.

Another application of plasma processes is conversion with various contact angles of different surfaces of the same substrate. This is used, for example, as pretreatment of glasses for OLED flat screens that are manufactured with the inkjet method.

Edge isolation is an important step in the manufacture of solar cells. Here, the doping on the edges is removed, as this layer acts as a short circuit for the P-N junction. For this process step, we have devised a special plasma-etching process in the cell stack that works with a process mixture of a a fluorine-containing gas, and with an oxidant.

The cell stack is only exposed to the etching process at the edges; the adjacent cells protect the surfaces. Rotation of the cell stack during processing ensures uniformity. The throughput for this process is around 800 cells per hour.

The cell stack is held together in a cell clamp, which is available as an optional extra. With the loading aid, it is very easy to load a stack into the cell clamp or remove it. The cell clamp and loading aid are designed for cells of 4″, 5″ or 6″ and for different stack heights.

The process requires a relatively high proportion of gas containing fluorine in combination with an oxidant in order to attain the desired removal rate.

The products can be treated by plasma as a batch (in magazines) or as strip type. 

The systems are available as manual and automated versions. You can choose the ideal system based on your application. We offer a variety of sizes to ensure the perfect fit for your specific requirements.