Good Repeatability Harmless Vacuum Coating Machine

In semiconductor (chip/integrated circuit) manufacturing processes, photolithography is a crucial step in integrated circuit pattern transfer. The quality of the photoresist coating directly affects the quality of photolithography, making the coating process particularly important. Most photoresists used in photolithography are hydrophobic, while the hydroxyl groups and residual water molecules on the silicon wafer surface are hydrophilic. This results in poor adhesion between the photoresist and the silicon wafer, especially with positive photoresists. During development, the developer solution can penetrate the interface between the photoresist and the silicon wafer, easily causing phenomena such as peeling and floating of the photoresist, leading to failure in photolithographic pattern transfer. Simultaneously, wet etching is prone to lateral etching.  After pretreatment with an HMDS pretreatment system, a siloxane-based compound is coated onto the substrate surface. The wafer surface changes from hydrophilic to hydrophobic, reducing the contact angle, decreasing the amount of photoresist required, and enhancing adhesion to the photoresist. This inhibits lateral etching and pattern drift during the development process, improves photoresist adhesion, and enhances the corrosion resistance of the material in harsh environments, thereby significantly improving product quality and reducing the defect rate.

Process Objective:
The equipment operates fully automatically using PLC control.  The process involves high-temperature baking of the substrate to remove surface moisture, combined with vacuum drying and nitrogen protection technology to remove moisture and contaminants from the wafer surface, preventing oxidation and impurity diffusion, and ensuring cleanliness before coating. HMDS (hexamethyldisilazane C6H19NSi2) gas is then introduced. Under high temperature, the substrate surface and HMDS fully react, forming a compound primarily composed of siloxane. This changes the substrate surface from hydrophilic to hydrophobic, allowing the hydrophobic group to bond well with the photoresist, acting as a coupling agent.

Process Flow:
First, the vacuum pump is turned on to begin vacuuming. Once the vacuum level in the chamber reaches the set value (this value can be set by changing the P2 value on the vacuum gauge, see the vacuum gauge manual), nitrogen is introduced. After reaching the set vacuum level (this value can be set by changing the P1 value on the vacuum gauge), the vacuuming and nitrogen introduction process is repeated. After reaching the set number of nitrogen introductions, vacuuming begins again, followed by the introduction of the chemical solution. After the set time, the introduction of the chemical solution stops, and the holding phase begins. After the set holding time, vacuuming and nitrogen introduction begin again, for the set number of cycles. Once the system automatically completes the process, an audible and visual alarm is given, indicating that the wafers are ready for removal.