MEMS LAB SESSION 1 Silicon nitride OVERVIEW OF LAB SESSION: This lab session will utilize photolithography and dry etching to transfer a pattern from a mask to a substrate. In Step 1. 1, the thickness and the refractive index of the silicon nitride film are measured. In Step 1. 2, the wafers will be first undergoing a treatment using Hexamethyldisilazane (HMDS)vapor, then be coated by photoresist-containing solvents using a spin-on process. The wafers will then be pre-baked in order to evaporate the solvents and leave the photoresist behind In Step 1.3, the wafers will be aligned to the first mask and the photoresist exposed ultra- violet light. In Step 1. 4, the exposed photoresist will then be removed by development and the unexposed photoresist will be post-baked in order to improve adhesion. In Step 1.5, the wafers will be inspected under the microscope. Then in Step 16, using the photoresist as an etch mask the silicon nitride will be dry-plasma etched. This will selectively remove the silicon nitride that is not masked /protected by photoresist and reveal the underlying silicon. In Step 1. 7, the masking photoresist will be removed by an oxygen plasma by a tool called"asher". After the pattern transfer is completed, the thickness of the remaining silicon nitride film will be measured Step 1.8 LAB OBJECTIVE This lab session has the following primary objectives Introduction to basic photolithographic processes and procedures Complete photoresist patterning and etching of the silicon nitric Instruction on the following major pieces of lab equipment KLA Tencor UV1280 Film Thickness Measurement System EVI Mask Ali Lam 490B Plasma Etcher Matrix 106 System One Stripper(Asher) Before the beginning of this lab, make sure to read the corresponding Standard-Operating Procedures(SOP)for these major pieces of equipment. The SoP for each piece of the equipment can be accessed at the following site http://www-mtl.mitedu/mtlhome/3mfab/sop.html LAB PROCEDURES MEMS Lab Session I has 8 steps 1. I CHARACTERIZE SILICON NITRIDE 1.1.1.Tool:UV1280 1. 1.2. To determine the thickness of the low-stress, silicon-rich, LPCVD silicon nitride 1. 1.3 To measure the refractive index of the low-stress, silicon-rich, LPCVD silicon nitride 1.2 HMDS VAPOR, PHOTORESIST DEPOSITION, PRE-BAKEMEMS LAB SESSION 1 Patterning Silicon Nitride using Photolithography and Dry Etching OVERVIEW OF LAB SESSION: This lab session will utilize photolithography and dry etching to transfer a pattern from a mask to a substrate. In Step 1.1, the thickness and the refractive index of the silicon nitride film are measured. In Step 1.2, the wafers will be first undergoing a treatment using Hexamethyldisilazane (HMDS) vapor, then be coated by photoresist-containing solvents using a spin-on process. The wafers will then be pre-baked in order to evaporate the solvents and leave the photoresist behind. In Step 1.3, the wafers will be aligned to the first mask and the photoresist exposed using ultra￾violet light. In Step 1.4, the exposed photoresist will then be removed by development and the unexposed photoresist will be post-baked in order to improve adhesion. In Step 1.5, the wafers will be inspected under the microscope. Then in Step 1.6, using the photoresist as an etch mask, the silicon nitride will be dry-plasma etched. This will selectively remove the silicon nitride that is not masked / protected by photoresist and reveal the underlying silicon. In Step 1.7, the masking photoresist will be removed by an oxygen plasma by a tool called “asher”. After the pattern transfer is completed, the thickness of the remaining silicon nitride film will be measured in Step 1.8. LAB OBJECTIVES: This lab session has the following primary objectives: ¾ Introduction to basic photolithographic processes and procedures. ¾ Complete photoresist patterning and etching of the silicon nitride. ¾ Instruction on the following major pieces of lab equipment: KLA Tencor UV1280 Film Thickness Measurement System SSI Coater Track EV1 Mask Aligner Lam 490B Plasma Etcher Matrix 106 System One Stripper (Asher) Before the beginning of this lab, make sure to read the corresponding Standard-Operating￾Procedures (SOP) for these major pieces of equipment. The SOP for each piece of the equipment can be accessed at the following site: http://www-mtl.mit.edu/mtlhome/3Mfab/sop.html LAB PROCEDURES: MEMS Lab Session 1 has 8 steps: 1.1 CHARACTERIZE SILICON NITRIDE 1.1.1. Tool: UV 1280 1.1.2. To determine the thickness of the low-stress, silicon-rich, LPCVD silicon nitride. 1.1.3 To measure the refractive index of the low-stress, silicon-rich, LPCVD silicon nitride. 1.2 HMDS VAPOR, PHOTORESIST DEPOSITION, PRE-BAKE Page 1 of 3