#3D DRAM manufacturing
## Process flow for 3D devices on DRAM

Xiao((Xiao, H. (2016). 3D IC Devices, Technologies, and Manufacturing. SPIE press.)) provides the most detailed description of the processes used to manufacture 3D DRAM and NAND devices. Such a detailed public explanation is rare to find and applies only to two types of devices for advanced technology nodes. Nevertheless, it provides a detailed understanding of the various process loops for each mask. 

#### AA Module
  * Wafer clean
  * Pad oxidation 
  * SiN hard mask deposition 
  * Amorphous silicon hard mask deposition
  * *AA mask 1* 
  * Etch top hard mask 
  * PR strip/clean
  * *AA mask 2* 
  * Etch bottom hard mask 
  * PR strip and clean
  * Etch pad oxide
  * Etch silicon trench
  * Wafer clean
  * Oxidation
  * STI oxide CVD to fill the trench 
  * STI oxide CMP, stop on nitride 
  * Wet strip nitride and pad oxide
  * Wafer clean

#### Well formation
  * Sacrificial oxide growth
  * *Cell p-well mask*
  * P-well implantation
  * N + S/D implantation
  * PR removal and clean
  * *Peripheral n-well mask* 
  * N-well implantation
  * PMOS VT adjust implantation
  * PR removal and clean 
  * *Peripheral p-well mask*
  * P-well implantation
  * NMOS VT adjust implantation
  * Photoresist removal and clean
  * Sacrificial oxide removal and clean
  * Rapid thermal anneal

#### BWL module
  * Wafer clean
  * Oxidation
  * Hard-mask deposition
  * BWL mask
  * Etch hard mask
  * BWL trench etch
  * PR strip & clean
  * Oxidation
  * W and TiN etch back 
  * Wafer clean
  * Oxide deposition
  * Oxide CMP
  * Strip hard-mask
  * Oxide deposition
  * TiN gate electrode deposition
  * W deposition

#### BLC module
  * Wafer clean
  * Peripheral mask 
  * Etch oxide
  * PR strip/clean 
  * Gate oxidation and nitridation
  * Polysilicon deposition
  * Wafer clean
  * PMOS poly-dope mask
  * PMOS poly implantation
  * PR strip/clean
  * Array area mask
  * Etch polysilicon
  * PR strip/clean 
  * BLC mask 
  * Etch oxide
  * PR strip clean 
  * Polysilicon deposition
  * TiN and W deposition
  * SiN deposition 

#### BL and peripheral transistor module
  * Wafer clean
  * BL mask
  * BL and peripheral gate etch
  * PR strip/clean/ACI 
  * Re-oxidation
  * Peripheral NMOS SDE mask
  * Peripheral NMOS SDE implantation
  * PR strip/clean
  * Peripheral PMOS SDE mask
  * Peripheral PMOS SDE implantation
  * PR strip/clean
  * Spacer dielectric film deposition
  * Spacer film etch back 
  * Peripheral NMOS SD mask
  * Peripheral NMOS SD implantation
  * PR strip/clean
  * Peripheral PMOS SD mask
  * Peripheral PMOS SD implantation
  * PR strip/clean
  * RTA


#### SNC, peripheral contact, and M1 process steps
  * ILD1 deposition
  * LD1 CMP
  * HM deposition 
  * SNC mask 1
  * Etch HM
  * PR strip/clean
  * SNC mask 2 
  * Etch HM
  * PR strip/clean
  * Etch ILD1
  * Wafer clean
  * Ti/TiN/W deposition
  * W/TiN/Ti CMP
  * Etch stop layer deposition
  * ILD2 deposition
  * M1 mask
  * Etch ILD2
  * PR strip/clean
  * Ti/TiN/W deposition
  * W/TiN/Ti CMP 

#### SN module
  * Wafer clean
  * Each stop layer (ESL) deposition 
  * ILD deposition 
  * SiN deposition
  * SN mask 1
  * Etch nitride 
  * PR strip/clean 
  * SN mask 2 
  * Etch nitride
  * PR strip/clean
  * Etch oxide
  * TiN deposition
  * PR coating
  * RP etch back
  * TiN etch
  * SiN slot mask
  * Nitride etch
  * PR strip/clean
  * ILD removal
  * Wafer clean
  * High-k film deposition
  * TiN and conducting filler deposition 


#### V1 and M2 process steps
  * Peripheral area mask
  * Etch SiGe/TiN/ZAZ
  * PR strip/clean
  * ILD3 deposition
  * ILD3 CMP
  * V1 mask 
  * V1 etch
  * PR strip and clean
  * Ti/TiN deposition
  * W deposition 
  * W/TiN/Ti CMP 
  * ESL deposition
  * ILD4 deposition 
  * M2 mask
  * M2 etch
  * PR strip and clean
  * Barrier and seed-layer deposition
  * Bulk copper plating
  * Cu anneal
  * Cu CMP

#### V2 and M3 process steps
  * ESL, ILD5, and dielectric cap deposition
  * Metal HM deposition 
  * M3 mask
  * HM etch
  * PR strip and clean
  * V2 mask 
  * Dielectric cap and ILD5 etch
  * PR strip and clean
  * ILD 5 etch
  * ESL removal 
  * Clean
  * Barrier and seed-layer deposition
  * Bulk copper plating
  * Cu anneal
  * Cu CMP

#### V3-M4 and passivation process steps
  * ESL and ILD6 deposition
  * V3 mask
  * ILD6 and ESL etch
  * Pr strip and clean
  * Ti/TiN/W deposition
  * W/TiN/Ti CMP
  * Wafer clean
  * Ti/Al-Cu/TiN deposition
  * M4 mask
  * Etch TiN/Al-Cu/Ti stack
  * PR strip and clean
  * Passivation oxide and nitride deposition
  * Bond pad mask
  * Etch nitride and oxide
  * PR strip and clean