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You are here: Home / Equipment / Dry Etching / Plasmatherm Etchers (pt-dse, pt-ox and pt-mtl) / PlasmaTherm Oxide Etcher (pt-ox) / PT-OX Capabilities, Specifications and Operation

PT-OX Capabilities, Specifications and Operation

PT-OX is an ICP (inductively Coupled Plasma) etch system configured for dielectric etching. Etch chemistry is mainly fluorine based. It has both optical and laser endpoint systems.
 
Contents
  1. Picture and Location
  2. Background
  3. Process Capabilities
    1. Cleanliness Standard
    2. Performance of the Tool
  4. Contact List and How to Become a User
    1. Contact List
    2. Training to Become a Tool User
  5. Operating Procedures
  6. Process Monitoring and Machine Qualification
    1. Tool Qualification Run
    2. Machine Status States
    3. Process Monitoring Results

Picture and Location

 PT-OX - PlasmaTherm Oxide Etcher

PT-OX

The tool is located in the C area next to Pt-MTL.

Equipment Locations (gif)

 

Process Capabilities

 

Cleanliness Standard 

PT-OX is a flexible tool and so can process materials belonging to "Contaminated" group.

Performance of the Tool:

What the Tool CAN do:

 Etch SiO2, SiN and other dielectrics.

Etch high aspect ratio features.

Pattern quartz wafers.

What the Tool CANNOT do

  • Process sticky wafers.  Wafers will stick to the clamp and cause clamping as well as unloading issues.

 

Process Monitoring

 

Contact List and How to Become a User

Contact List

The following people make up the Tool Quality Circle:

  • Process Staff: Nancy Latta, Jim McVittie, Usha Raghuram
  • Maintenance: Elmer Enriquez
  • Super-Users: Jim Kruger (jimkruger@yahoo.com)

 

Training to Become a Tool User

 

Read the training materials.

Consult the training calendar for a training session that is convenient to attend.

Contact the appropriate staff member or Super-user for enrolling to the training session.

** Shadowing a qualified user prior to the training session is highly recommended and will speed up your understanding of the tool.

 

General Information about Plasma Therm Versaline Software

PT-Ox Rules of Engagement- Is this the right tool for you?

Here is information that may be used to determine if PT-Ox is the best tool for you work.

  • No metal etching or sputtering is allowed.  One concern is that sputtered metals may coat and hence short out the chamber.
  • Due to the mechanical clamp and the possibility the wafer sticking to it Edge Bead Removal (EBR) is required.  Please refer to the General Operating Procedure for more details.
  • Many users want to etch oxide which will be used as an etch mask for the PlasmaTherm DRIE system (PT-DSE).  Selectivity for various oxides are; ccp SiO300-1 = 200 : 1, ccp SiO350-1 = 400 : 1 (almost as good as Thermal Oxide).
  • For the standard ox etch recipe (jkPRmask OxSTD) the selectivity of photoresist is 1.5 : 1.  The recipe can be modified to achieve 3.5 : 1 but polymer deposition increases and a post etch polymer clean  (seO2Clean-1) is needed to clean the chamber.  Polymer may need to etched off the sample, too.
  • The software that runs the pt-ox is the same as runs three other systems.  It is described here.
  • Here is a typical process sequence step for the pt-ox system.  It contains ranges and min/max for various parameters.

 

Special Considerations for Use of the Tool (Hints and Tips)

 

Transparent Wafers (quartz, pyrex, sapphire or glass) present unique loading issues.  A procedure for the loading of these substrates can be found here.

Process Parameters/ Limits

Process pressure, Max = 100mT

Backside He cooling pressure, max = 10 Torr

ICP (3-turn coil) power, max = 3500 W; min = 400 W

Bias power, max = 600 W

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 = 201.8 sccm

H2 = 98.4 sccm

Ar = 97.3 sccm

CF4 = 102.1 sccm

O2 = 95.4 sccm

CHF3 = 103.5 sccm

He = 97.8 sccm

N2 = 191.8 sccm

 

Process Monitoring and Machine Qualification

Tool Qualification Run

 

Frequency

Quals are run monthly by SUMO. The SUMO member in charge of the tool is Zach (zclong@stanford.edu).

Quals are also run by labmembers periodically, especially under the following circumstances:

Roughly once a quarter to check system performance. 

After major repairs to the system. 

When a labmember reports a variance from normal results.

Procedure

 

Use 1 blank Si wafer with 1.6um layer of SPR3612 photoresist with EBR and 120sec post bake and 1 wafer with 10000A SiO2, unpatterned. The Si wafer is patterned with the SUMO MASK 2.0.

 

  1. Measure photoresist thickness of the Si wafer and the SiO2 thickness on the oxide wafer .  Be sure to use reference wafer before testing to calibrate the tool.  Take readings for the Center, Top, Bottom, Right and Flat positions of the wafers.  Readings should be taken about 20mm from the edge. For the Si wafer, measure on the Photoresist on silicon. For the SiO2 wafer, measure with program 10000A silicon oxide on silicon.  Record.

  2. Season the chamber for 10 minutes using the O2 Clean Recipe (00:10:00), running with a blank Si wafer.  Be sure to check the program parameters before starting. Use the step editor to edit the etch time if needed.

  3. Condition the chamber with the OX_ER_TEST Recipe for 5 minutes.

  4. Etch one of the qual wafers (Si or SiO2, order does not matter) with OX_ER_TEST for 1 minute (change etch time in step 3).

  5. Repeat the same etch with the other qual wafer.

  6. Measure post-etch thicknesses using the same Nanospec.  Be sure to use reference wafer before testing to calibrate the tool. Again, take readings for the Center, Top, Bottom, Right and Flat positions of the wafers. Readings should be taken in more-or-less identical spots as the pre-etch measurements. Again, for the Si measure, measure on the PR. For the SiO2 wafer, measure on the SiO2 directly. Record in the Log.

  7. Calculate the amount of photoresist etched from the Si measurements. Record

  8. Strip both wafers of photoresist via matrix.

  9. Now measure the depth of the etches into the Si (on the Si wafer) using alphastep. Find a place that has been etched and measure across it. Make sure to LEVEL if the trace is not horizontal.

  10. Take readings in about the same 5 places as you took readings from step 1. Once you get consistent readings in each spot, record the measurement in the Log.

  11. Repeat with the SiO2 wafer.

  12. Record results on the Monitor Log. Record results in data file to get within-a-wafer uniformity.

 

 

Responsibility

 

 

Recommendation to users with critical processes

 

Machine Status States

Red:

Yellow:

Green:

 

Process Monitoring Results 

Recipe Name: Oxide_ER_Test

Etch Conditions: 600W ICP/ 50W BP/ 45 CHF3/ 2 O2/ 5mT/4T BSHe/Electrode 10C/ Lid 90C/ Liner 70C/ Spool 90C/ 60sec

7/30/2014

 Etch rate and selectivity data on 4" wafers

·         Silicon dioxide ER = 2010A/min; Uniformity = 6.0% (NanoSpec; 5 points; Thermal oxide - Patterned wafer)

·         Si ER = 803A/min; Uniformity = 2.7% (Step height; AlphaStep; 5 points; Patterned wafer)

·         Photo resist ER = 1009A/min; Unif = 2.7% (NanoSpec; 5 points; SPR3612; Si wafers pattered with 3612 resist)

·         SiO2:PR Selectivity = 2.0

·         SiO2: Si Selectivity = 2.5

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