Photoresist

The semiconductor process begins with photolithography. Forming semiconductor circuits in the photolithography step requires the use of a special material: Photoresist. Just what is photoresist, and how does the semiconductor process make use of it? All about photoresist: a critical element of the semiconductor process

Photoresist is a type of photosensitive material which undergoes a chemical change in reaction to light. Photosensitivity is a blanket term for the tendency of materials to undergo a physical and chemical change when exposed to light. When a photosensitive material is exposed to light, the parts exposed undergo change, and the parts not exposed to light remain unchanged. This allows for certain patterns to be created. The process of developing photos makes use of photosensitivity. But photoresist is quite different from the runny photosensitive liquid used for developing photos. Instead of exposure to light simply causing color contrast, photoresist hardens or melts when exposed to light. This makes it possible to expose photoresist to light selectively, creating prominences and depressions like those in a printing block. Depending on how it reacts to light, photoresist is categorized as ‘positive’, where parts not exposed to light are left behind, or ‘negative’, where parts exposed to light remain. Printing circuits onto wafers: Photoresist in the semiconductor process

In the photolithography step, a thin and uniform layer of photoresist is applied onto a wafer. This is like turning the wafer into a sheet of photographic paper. A mask, which is a plate with transparencies or holes formed in the pattern of the desired semiconductor circuit, is placed above the photoresist with a light-gathering lens under it. Light is then emitted toward the wafer, transferring the circuit pattern on the mask to the wafer. The blueprint for the microcircuits can be drawn onto the wafer because of the photoresist. Once the circuit pattern has been transferred onto the wafer, the dissolved portion and the non-dissolved portion of the photoresist are removed selectively. This completes the photolithography process. The circuits on the wafer pass through an etching process to more clearly define them, and the semiconductor passes through a number of subsequent processes until completion. As we have learned today, ‘photoresist’ is crucial for forming circuit patterns onto wafers. This makes photoresist irreplaceable in the semiconductor process. Clearly, materials play many important roles in the semiconductor industry. Samsung is committed to materials R&D to ensure we continue to introduce state-of-the-art semiconductors to the market.