Red Avenue New Materials increases investment in photoresist

The domestic semiconductor industry has always been relatively weak in some upstream materials and equipment fields. Many domestic listed companies have entered the field of photolithography machines and photoresists to help the development of domestic semiconductors. Tongcheng New Materials recently invested 698 million yuan in ArF high-end photoresists.

In the manufacturing process of semiconductor chips, photoresist back etching and planarization is an important process technology, which mainly uses the photoresist coated on the dielectric layer to etch it, so as to achieve the purpose of planarizing the dielectric layer. However, in the above process, if there are small gaps on the surface of the dielectric layer, the air in the small gaps is prone to expansion during the photoresist coating and baking process, which will cause a bubble to form on the surface of the small gap. Due to the presence of bubbles, the thickness of the photoresist here will be very small and it is easy to be etched through, which will cause the dielectric layer in the area where the bubbles are located to be easily over-etched, and even damage other film layers under the dielectric layer, resulting in poor planarization effect.

To this end, Tongcheng New Materials applied for an invention patent entitled "A method for photoresist back-etching and planarization" on July 12, 2017 (application number: 201710564645.1), and the applicant was Shanghai Tongcheng Electronic Materials Co., Ltd.

Figure 1 Schematic diagram of the photoresist back-etching planarization method

FIG1 is a schematic flow chart of the photoresist back-etching planarization method proposed in the present invention, which mainly includes the following steps: first, a dielectric layer is formed on the surface of a silicon wafer having a circuit structure (S1), and then the silicon wafer is subjected to a first baking treatment to remove water vapor on the surface of the silicon wafer (S2). Specifically, after the dielectric layer is formed on the silicon wafer, the silicon wafer is further placed in a baking device for a first baking treatment, the main purpose of which is to remove water vapor on the surface of the silicon wafer. The baking temperature and baking time can be determined according to actual needs.

Then, the surface of the silicon wafer is covered with a tackifier (S3), and the coverage area of ​​the tackifier is specifically the surface of the dielectric layer, mainly to increase the adhesion between the photoresist and the silicon wafer during the subsequent photoresist coating process. Then, photoresist is coated on the surface of the silicon wafer, wherein the photoresist covers the dielectric layer (S4). Since the silicon wafer is not cooled before the photoresist coating in S4, the silicon wafer itself still has a certain temperature after the first baking. The photoresist coating process is actually a natural cooling process of the silicon wafer. Therefore, the air temperature inside the small gap in the dielectric layer gradually decreases, further causing the air to shrink. Therefore, the photoresist with a certain viscosity will be sucked into the small gap and filled to the bottom of the small gap. Ideally, the small gap can be completely filled with photoresist.

After the photoresist coating is completed, the silicon wafer is baked for a second time to remove the solvent of the photoresist (S5). Specifically, after the photoresist coating is completed, the silicon wafer can be baked for a second time to quickly remove the solvent in the photoresist by heating. Finally, the photoresist and the dielectric layer are etched back to flatten the surface of the silicon wafer (S6).

In short, Tongcheng New Materials' photoresist patent, by baking the silicon wafer twice and etching back the photoresist and dielectric layers, avoids excessive etching or even damage to other film layers during the photoresist planarization etching process, and can effectively ensure the flatness of the photoresist etching back.

Tongcheng New Materials is one of the world's important suppliers and service providers of chemical materials for tire rubber. It insists on technological innovation and management innovation and is committed to becoming a global chemical materials manufacturer and service provider with competitive advantages in the entire industry chain. In the future, the company will further deepen its business layout in the field of electronic materials to make up for the gap between domestic photoresist technology and the global advanced level.