Photolithography

The manufacture of integrated circuits requires various physical and chemical processes performed on semiconductor substrates (for example, silicon wafers). By creating the structure of various integrated circuit components, millions of transistors can be built and wired together to form the complex circuits of modern microelectronic devices.

Lithography is defined as "a method of printing from a prepared plane so that the ink only adheres to the design to be printed." In the manufacture of semiconductor devices, the combined effects of photolithography and etching processes can produce desired features. Since photolithography for device manufacturing involves the use of optical exposure to create patterns, semiconductor photolithography is often referred to as "lithography." Lithography is the preferred technique for patterning, which can achieve small size and high wafer yield.

Photolithography is a photographic process by which a photosensitive polymer called a photoresist is exposed and developed to form a three-dimensional relief image on a substrate. The general processing steps of a typical photolithography process are as follows: substrate preparation, photoresist spin coating, pre-baking, exposure, post-exposure baking, development and post-baking. After the resist pattern is transferred to the underlying layer, the resist strip is the final operation in the photolithography process.

Fig 1. Conventional nanofabrication methods. (a) Standard photolithography produces a masking layer for etching to fabricate nanoslit structures; (b) A nanochannel array was milled using an FIB on the silicon surface; (c) Nanochannels were fabricated by nanoimprinting. SEM pictures of a 2D silicon nano-mold and its replicated nanochannels; (d) A periodic nanopattern array is fabricated by interference lithography in which two split beams make both constructive and destructive interferences sequentially, producing a periodic nanopattern array. (Ha D, et al. 2016)

The importance of lithography can be understood in two ways. First of all, since a large number of photolithography steps are required in the manufacture of integrated circuits, photolithography usually accounts for about 30% of the manufacturing cost. Second, photolithography tends to become a technical limitation, which limits the shrinking of feature sizes, thereby further increasing the speed of transistors and silicon area. Although lithography is not the only technologically important and challenging process in the IC manufacturing process, advances in lithography technology have made progress in controlling IC cost and performance.

Alfa Chemistry provides a variety of products to support your research. These products have a wide range of applications, including but not limited to lithography monomers, photoresists, as well as stamps for nanoprint lithography and microcontact printing.

Reference

1. Ha D, et al. (2016). "Unconventional Micro-/Nanofabrication Technologies for Hybrid-scale Lab-on-a-chip." Lab Chip. 16: 4296-4312.