A mask aligner is the machine which transfers a pattern onto a wafer. It is most commonly associated with photolithography. A mask, with the desired pattern, is placed above the wafer and the mask aligner utilizes a high-intensity ultraviolet light to burn the pattern into the photoresist on the wafer. At first glance, all of these machines appear to be fairly similar, however upon closer inspection there are a handful of critical features which should be compared when deciding which mask aligner will be the best fit.
The first feature to consider is the resolution the mask aligner can operate at. This will not only define how precise the results will be, but also play a significant role in the acceptable margin of error. A resolution of 1 micrometer is often considered as a satisfactory resolution.
The second feature to compare is the precision alignment system. The more precise the alignment system is, the more precise the end result will be. It is important to look at the level of precision on X, Y, Z, and Theta. A key indicator of how precise a machine will be is by looking at the resolution. Using motorized controls, precise truck motion can be achieved with incredible alignment accuracy.
The third feature to consider is how easy the aligner is to use. The shorter the learning curve is, the more likely it will be easily adopted in the workplace. The best options offer multiple different ways to interact with the machine including MEMs, touchscreen panel, flat-panel display, RF microwave, electronics and LED.
The fourth feature to consider that is often overlooked is UV intensity and beam uniformity. These characteristics are capabilities which define capabilities relating to resolution, control, precision, and versatility. The UV intensity is typically defined by the maximum intensity. The beam uniformity is defined by a variance percentage.
The fifth and final set of variables to consider is based entirely on personal preferences. For example, some people prefer to choose a mask with a large number of native program recipes. This allows them to get started with the machine without uploading a significant amount of additional data. If the mask aligner is often used in conjunction with a computer, then the ability to operate the machine directly from the computer will provide a significant time savings and should be considered an important feature to include in the decision calculus. Tact time is important to consider as well. Tact time is the sum of several elements including handling time, mask alignment time, and coating time.
While every mask aligner does essentially the same thing, the actual machines and their functionality can vary greatly. The key is to consider the most important features first to ensure the final decision meets the necessary minimum standards to ensure long-term satisfaction.
