Reactive plasma etcher with chlorine chemistry (ICP-RIE)

ICP Plasmalab 100 (Oxford Plasma Technology) is a ICP-RIE system (Inductively Coupled Plasma – Reactive-Ion Etching) used mainly for semiconductor dry etches using various soft and hard masks. There is also a separate RIE unit, but the advantage of ICP system is the separation of the plasma generation and the electric field accelerating the ions, allowing more precise control of the etch parameters

Details

Location: Tampere University (TAU), Tampere

Contact person: Jukka Viheriälä (Tampere)

Info:

System Description

ICP Plasmalab 100 (Oxford Plasma Technology) is a ICP-RIE system (Inductively Coupled Plasma – Reactive-Ion Etching) we use mainly for semiconductor dry etches using various soft and hard masks. We also have a separate RIE unit, but the advantage of ICP system is the separation of the plasma generation and the electric field accelerating the ions, allowing more precise control of the etch parameters. The basic division of use between the RIE and ICP systems is that processes requiring fluorine based gasses are done with RIE and processes using chlorine based gasses are to be made with ICP to avoid chamber contamination.

The system has a separate load lock, through which the samples are transported into the process chamber, which allows the chamber to be kept in constant vacuum. The chamber is temperature controlled through a liquid nitrogen supply, though operation without temperature control is also possible. The system also includes a laser interferometry system for in-situ etch depth monitoring. The system is controlled through an intuitive GUI, similar to the ones in RIE and PECVD systems.

Spesifications

The system specifications and allowed materials are stated below.

Before proceeding with a process, consult the equipment responsible on the material compatibility with the system and creation of a new recipe.

The compatibility of the intended process and materials with the system has to check to avoid system contamination or breakdown.
New recipies can be created only by trained personel. Wrong recipe might not be fuctional or could damage the sample or the system.
Any non-standard process needs an approval from the equipment responsible.
- Standard process refers to processes used standardly in our facilities. Processes previously not used in our enviroment fall to the cathegory of non-standard.

Operating parameter ranges

Maximum sample size	3″ wafer
Total gas flow	10 – 200 sccm
Pressure	1 – 60 mTorr (below 5 mTorr and above 20 mTorr plasma striking possibly difficult)
ICP power	200 – 2500 W (minimum power depends on plasma striking with each gas)
RF power	5 – 400 W
Helium backing pressure	0 – 30 Torr
Temperature	-150°C … +300°C
Etch duration	Recipes longer than 20 min should be done in two parts

Compatible materials

If you wish to use materials not listed, consult the equipment responsible.

Process gasses	BCl₃ \| SiCl₄ \| Cl₂ \| Ar \| SF₆ \| O₂ \| N₂
Allowed materials for etching	Compound semiconductors: GaAs, InP and GaSb based III-V compounds Semiconductors: Ge Metals: Al, Ti, Cr
Allowed mask materials	Photoresists (non-silicone): AZxxxx NIL resists: mr NIL 210, PMGI EBL resists: PMMA Ni, Cr SiO₂, SiN, Al₂O₃
Forbidden materials for etching	SiO₂, SiN PDMS, polymers, silicones, BCB Au, Pt, noble metals, Ni Silicon
Allowed processes	Cl-based etching, F-based plasma only for cleaning purposes No O₂ etching of polymers or SF₆ based etching of dielectrics / Si

Training

The training of all new users is conducted by the equipment responsible. Independent training or use of the system is not allowed unless otherwise agreed with the equipment responsible. Training is also required for personel that has used similar systems in other facilities.

Requirements:

For a user to receive training in the use of the ICP-RIE system, they a required to have:

Frequent and present need
- The system should be used regularly and taken into use soon after training in order to maintain the level of competence of the operator
Plan of the intended use: etched materials, mask materials, process gasses and parameters
- Basic help with the process details can be provided to ensure proper operation of the system: https://tuni.sharepoint.com/sites/TG-microandnanofabrication/SitePages/Process-Training.aspx
Understanding of the basic principles of plasma etching processes (be aware of the involved process mechanisms)
Complete training in the safe and proper use of the system will require several days (not necessarily back-to-back) so the need for the training should be carefully considered and suffiecient time alloted in schedule.

Training requests:

Contact the equipment responsible (Heidi Tuorila), email prefered.

Provide the information stated in the requirements.
Make the initial inquiry well in advance.
- Depending on the equipment availability and and the schedule of the equipment responsible there might be some delay in training.

Process and system problems

In case of irregularities in the system operations, stop using the system and contact the equipment responsible.

In case of imminent/catastrophic danger/system failure contact Laboratory Chief (Ilkka Hirvonen).

Standard operating procedure (SOP) for the system can be found at the end of this page. Note that the document is intended to be used as a support and it does not replace face-to-face training.

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