| AVS 61st International Symposium & Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS-MoM |
| Session: | Current Challenges of Plasma Etching Technologies |
| Presenter: | Chih-Chien Wang, United Microelectronics Co., Taiwan, Republic of China |
| Authors: | C.-C.. Wang, United Microelectronics Co., Taiwan, Republic of China F.Y. Chang, United Microelectronics Co., Taiwan, Republic of China C. Li-Chiang, United Microelectronics Co., Taiwan, Republic of China S.-Y. Lu, United Microelectronics Co., Taiwan, Republic of China P.-W. Huang, Lam Research Corporation Y.-C. Kao, Lam Research Corporation S.-Y. Cheng, Lam Research Corporation T.-T. Su, Lam Research Corporation |
| Correspondent: | Click to Email |
Dummy Poly Removal (DPR) is one of the critical processes of hi-K metal gate formation of gate last integration scheme of semiconductor wafer fabrication. A typical DPR process flow includes plasma etching a wafer to open hardmask and to remove dummy poly, then wet etch the wafer with Tetra-Methyl Ammonium Hydroxide (TMAH) to remove any residue that is remained inside the dummy gate trench.
Amorphous silicon is commonly used as the dummy poly materials. A plasma composed of Cl2, HBr, NF3, or combination of above is used to dry etch the dummy poly; however, poly residue defect is observed after DPR process flow. Experimental data indicates that after plasma etch, a Si-O layer is formed on the surface of amorphous silicon which suppress the dummy poly removal capability of the subsequent wet etch. Therefore, dummy poly material is left behind and forms the poly residue defects.
If extended plasma is used to remove the poly residue, the barrier layer (TiN) will be etched and thus damage the hi-K.
To resolve the poly residue defect issue, a post etch treatment (PET) is added after dummy poly is etched by plasma. The purpose of PET is three-folded: it converts the Si-O layer to a layer of which wet etch rate is significantly improved; PET activates the residual F, Cl or Br inside the gate trench and enhance the poly removal; PET has high selectivity to the barrier layer (TiN) and thus TiN film is preserved. The result is no poly residue defects and no hi-K damage.