NTS Optel usecase - optics experience center

Opto-mechanical tooling that helps the world’s leading wafer stepper manufacturer leveling silicon wafers

Application | Custom designed tooling for optical alignment – level sensor tooling.
Market segment | Semiconductor
Business activities | Specification and concept design, engineering and prototyping, performance validation, small series production.

 

The trend in doubling transistor density of computer processors and memory cell density every two years (Moore’s law) requires projecting ever smaller structures onto the photo-lithography resin layers used on the silicon wafers. The projection lens used for this purpose has a depth of focus in the range of tens of nanometers. This is far shallower than the flatness of the wafer. Mapping the wafer height variations before projecting the pattern is essential in order to have the wafer surface in focus. This mapping is done using the a so-called level sensor.

 

Application context

To enable creating ever smaller details for higher resolution camera sensors, faster processors and denser memory chips the silicon wafer needs to be leveled with nanometer precision. For this purpose a large and complex device, called the UV-level sensor maps the exact location of the wafer surface. The opto-mechanical tools, that we have developed, enable our customer to accurately align this UV-level sensor for optimal performance.

 

Business benefits

Our custom designed tools, allow the customer to align their opto-mechanical equipment more accurately , faster and easier. The key success factor in this project was bringing together a unique combination of optics, mechanics, electronics, software, ergonomics knowledge and use of superior materials and components. The solution lived up to the world’s highest standards with the required accuracy and repeatability performance.

 

Used techniques

Unique to this particular example of tooling are its custom designed telecentric, low distortion imaging optics in Scheimpflug configuration and its ability to withstand airplane transport conditions, i.e. 30g shock and -25°C to +70°C temperature range. For the latter we designed centrally mounted CMOS sensors, flexure mountings and applied non-outgassing glue to keep lenses centered in the optical path. Furthermore the tool features a built-in custom DSP (Digital Signal Processing)-board performing the image processing to provide basic information and feedback to the engineer performing the alignment. The tool complies with our customer’s highest cleanliness grades so as to provide extremely low particle and outgassing contamination.

 

 

 

 

 

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