Semiconductor Photolithography

The fundamental process of creating integrated circuits (ICs) is dependent on pattern transfer techniques encompassed in photolithography. The IC industry relies on three main processes: metal deposition, patterning, and selective doping. 

This allows memory chips, microchips, PCBs, and microprocessors to be created onto a semiconductor surface. Within a semiconductor, conductors and insulators are used to create either connections or areas of isolation. Patterned electrode designs within an electronic device create non-uniform electric fields. As electric fields dissipate, this in turn allows a lower voltage to be applied, thus lowering the necessary power consumption.  

Metal Deposition 

Metal film deposition is used for creating electrical components and sensor coatings. Structural, sacrificial, conductive, and insulating layers can be created through metal deposition. For instance, silicon dioxide is used as both a sacrificial layer and masking material. A resulting film thickness during metal deposition is given by the amount of material that reacts and grows onto a substrate material. Key parameters that affect film growth include temperature and deposition time. Thermal oxidation is used to grow a uniform layer of silicon dioxide onto an Si substrate. The length of oxygen (O₂) exposure determines oxide layer thickness, where a longer duration results in a thicker layer. High temperatures cause a higher reaction rate. It is important to note that during the formation of an oxide layer, part of the underlying silicon is consumed. About 45% of Si is consumed during oxidation. Oxide thickness is also directly correlated to Si wafer color. A color chart is commonly used to indicate oxide thickness.  

Patterning 

Attaining mico-features onto a substrate requires a shorter wavelength of light which is currently being explored in next-generation photolithography. Microchips consist of minute circuit components patterned onto a semiconductor, like silicon. Transistors are patterned onto a substrate to serve as a switch and amplifier. The most common types of microchips include logic and memory chips. Chips are often grouped according to their corresponding functions. Logic chips process information, while memory chips store information. Creating these microchips involves photolithography. During photolithography, a substrate surface is cleaned, spin coated with a photoresist, covered with a photomask, exposed to UV light, and developed in a solvent to create a pattern.

Selective Doping 

Semiconductor doping involves modifying a materials conductivity. This can be achieved through diffusion or ion implantation. The amount of valence, or outer electrons, is used to identify the type of doping. In p-type doping there are three valance electrons, whereas in n-type there are five valance electrons. Both types of doping are used to increase semiconductor conductivity either through an increase in free electrons (n-type) or number of holes (p-type). When combined, a p-n junction is formed and is used to control the flow of charges. Silicon is a common substrate material due to its ability to be manipulated by mixing it with other conductive metals.  

Platypus Technologies is proud to accommodate companies and projects in the semiconductor industry. We offer custom photolithography services and a range of patterned electrodes to enable scientists and researchers working with ICs. Contact us today!