Semiconductor devices such as ICs and LSIs are used in various kinds of electronic equipment and have been developed for improved density, performance, and miniaturization. Preprocessing in semiconductor manufacturing includes several processing steps for wafers, which are sliced from a single-crystal block (ingot) of silicon. Coating is used in many situations in the manufacturing process for surface processing, functionalization, and adhesion for processing.

Coating in Semiconductor Manufacturing

Adhesion in semiconductor manufacturing

Adhesion of semiconductor wafers and supporting glass plates
During ultra-thin polishing of wafers, the wafer is bonded to a supporting glass plate with UV-curing liquid adhesive. The adhesive turns into a UV resin layer and comes off together with the glass plate after the process ends. (In addition to liquid adhesive, solid adhesives in tape form or sheet form are also used.)

Wafer adhesion/bonding requires a uniform coating of the adhesive.

Functionalization and surface processing in semiconductor manufacturing (preprocessing)

Coating plays an important role in various processing situations, including surface processing and resist coating or film-forming on wafers, which form the base for integrated circuits.

Example of semiconductor wafer processing steps
The following is a summary of the steps involved in processing single-crystal silicon wafers. Note that this is merely an example, and the actual steps may vary depending on the chips being manufactured.
• A wafer is cleaned with a solution and undergoes surface processing such as drying and polishing.
• The wafer is baked in a high-heat furnace, and a film of silicon dioxide (SiO₂) is formed on the surface.
• Photoresist (light-sensitive solution) is coated and formed into a film over the SiO₂ film. (A spin coater is generally used to form a uniform film.)
• A photo mask with a printed wiring pattern is aligned on the wafer and irradiated with far ultraviolet (FUV) light. The photoresist film reacts only in the areas illuminated by the light, and the pattern is transferred (exposure). The resist in the unmasked areas is removed by developer solution.
• Unneeded thin film is corroded and removed by acid such as hydrofluoric acid or phosphoric acid (wet etching), or removed by ions (dry etching), and the pattern is formed.
• Phosphorous or boron ions are implanted. Ions enter the areas without the SiO₂ film, providing semiconductor properties to the wafer.
• The wafer is rapidly heated in an annealer for dopant activation.
• The resist is peeled off with solution or gas, and the wafer is coated with insulation film.

This process is repeated before post-processing, where the chips are cut out from the wafer (dicing), connected to metal frames (lead frames) with gold wire (wire bonding), and encapsulated with resin sealant (molding).

Topic: Checking and maintaining the accuracy of processing equipment

In order to maintain processing accuracy and quality in the mass-production of semiconductors, it is necessary to maintain the accuracy of automatic processing equipment. Any inclination or improper hieght from placement or positioning of the wafer will greatly affect the processing quality. The compact Confocal Displacement Sensor can be placed inside wafer processing equipment to monitor for abnormal heights and inclinations of the wafers and improve processing quality.

Checking and maintaining the accuracy of processing equipment

Introduction example: Wafer position check inside processing equipment