PlasmaTherm-DSE (PT-DSE) Capabilities, Specifications and Operation
- Picture and Location
- Process Capabilities
- Contact List and How to Become a User
- Operating Procedures
- Process Monitoring and Machine Qualification
Picture and Location
The tool is located in area B on the Lab Map.
The Deep Silicon Etching (DSE™) Technology has been developed to achieve extremely high aspect ratio features on silicon substrates. The DSE™ Technology is based on the well-known time division multiplex (TDM) etch process. The TDM process (also known as the Bosch process) employs alternating deposition (passivation) and etching cycles as illustrated below.
For enabling faster etch rate, the source power generator (ICP power, 2MHz) has an increased capacity of 3500 W and the max flow for SF6 MFC is 653 sccm. In order to minimize the sidewall roughness, DSE uses a faster gas switching technique. During cycling the reactive gases (C4F8 for dep and SF6 for etch step) are diverted to either the process module or pump depending on whether it is a dep or an etch step. This enables a cycle time smaller than 1 sec if needed. In addition, in order to facilitate faster RF tuning when switching between steps frequency tuning option is utilized in the DSE. Also, in the DSE, bias voltage is controlled as opposed to bias power in the other etchers.
PT-DSE is a flexible tool and belongs to the "Contaminated" group.
Performance of the Tool
What the Tool CAN do
- Deep silicon etching
- Etching SOI wafers
What the Tool CANNOT do
- Resist reticulation with deeper etches restricts the utilization of resist mask.
- Hard clamp and resulting stickiness also restricts the versatility of the resist mask process.
Contact List and How to Become a User
The following people make up the Tool Quality Circle:
- Process Staff: Usha Raghuram, Jim McVittie, Nancy Latta
- Maintenance: Elmer Enriquez
- Super-Users: Jim Kruger, Justin Snapp
General Information About Plasma Therm Verasline Software
The software that runs the pt-dse is the same as runs three other systems. It is described here.
Here is an example of a typical process sequence step. It contains ranges, gases, and min/max for various parameters.
PT-DSE is very similar to other PlasmaTherm etchers and the operating procedure is described here. Recipe set up is slightly different for PT-DSE as "Looping" and "Morphing" options are utilized in DSE and not in other etchers. Procedure to set up looping and morphing parameters can be found here.
Process Parameters/ Limits
Process pressure, Max = 100mT
Backside He cooling pressure, max = 10 Torr
ICP power, max = 3500 W
Bias voltage, max = 1500 V
Electrode temp, max = 40 C; min = -40 C
Lid temp, Max = 180 C
Liner temp, max = 180 C
Spool temp, max = 180 C
Process gases, max flow
C4F8 = 420 sccm
SF6 = 653.4 sccm
Ar = 48.5 sccm
O2 = 48.25 sccm
Process Monitoring and Machine Qualification
Tool Qualification Run
Quals are run periodically:
- Roughly once a quarter to check system performance
- After major repairs to the system
- When a labmember reports s variance from normal results.
A patterned Si wafer (with resolution pattern) was etched using the standard recipe (DSE-FAT) for 15 cycles. Resist loss was measured using NanoSpec and Si loss using AlphaStep.
Recommendation to users with critical processes
Machine Status States
Process Monitoring Results
Etch Recipe: DSE-FAT
Dep Step: 150 C4F8/ 30 Ar/ 25mT/ 2000W ICP/ 10 V BV/ 2.5sec
Etch A Step: 150 SF6/30 Ar/ 40mT/ 2000W ICP/ 250V BV/ 1.5sec
Etch B Step: 300 SF6/ 30 Ar/ 75 mT/3000W ICP/ 10V BV/3.0sec
Electrode temp - 15 C; Liner temp - 70 C; Lid temp - 150 C; Spool temp - 180 C; Backside He = 4 T
Qual Data from 7/30/2014 (No of cycles = 15)
Si Etch rate = 8.55 um/min; Unif = 4.1% (AlphaStep Step height measurement; 5 sites; Patterned Si wafer)
Photoresist (PR) ER = 764 A/min; Unif = 3.7% (NanoSpec measurement; 5 sites; Patterned Si wafer with 3612 resist)
Si: PR Selectivity = 112
Qual Data 10/2/2014 (No of cycles = 20)
Si Etch rate = 8.03um/min; Uniformity = 2.19% (Alpha Step- Step height measurements; 5 sites; patterned Si wafer)
PR Etch rate = 747A/min; Uniformity = 2.95% (Nanospec measurements; 5 sites; patterned Si wafer with 1um 3612 resist)
Si: PR Selectivity = 108