Structural devices
Structural devices

This free course is available to start right now. Review the full course description and key learning outcomes and create an account and enrol if you want a free statement of participation.

Free course

Structural devices

8.3.5 Alternative plasma chamber designs: MERIE and ICP

There are several variants of the parallel-plate RIE chamber. For example:

  • The ‘magnetically enhanced’ MERIE, where magnetic fields are used to slow the leakage of plasma to the chamber walls, reducing the operating voltage and improving the power efficiency.

  • ‘Plasma mode’ operation, where the RF voltage is applied to the chamber ceiling and the platen is grounded. This reduces the ion energy at the wafer from hundreds of volts to tens of volts, giving a physically much gentler etch for low-damage processing.

Parallel-plate chambers, however, have two significant limitations

  • It is not possible to control the current (ion flux), voltage (ion energy) and power (chemical dissociation) independently of one another.

  • They will operate only over a limited range of pressure, from ~20 Pa to ~200 Pa.

To achieve independent ion flux and energy control requires two power sources – one to create the plasma and a second to accelerate the ions to the wafer. Plasma creation in this case uses a very different technology, in the form of an inductively coupled plasma (ICP) chamber – see Figure 39. The chamber has an insulating wall (or sometimes ceiling), with an antenna coil wrapped around the outside (or occasionally inside) through which an RF current flows. The oscillating magnetic field induces currents in the plasma, heating its electrons and driving the electron-molecule collisions that sustain it.

The choice of RIE (high pressure, low ion flux, high ion energy, and low radical density) against ICP (low pressure, high ion flux, controllable ion energy and high radical density) depends on the process result required – each has its advantages and there is not always agreement on the best choice.

Figure 39
Figure 39 (a) ICP chamber and (b) its operating principle. RF current around an antenna (red) generates an oscillating magnetic field that passes through the insulating chamber wall (green) to induce an opposing current in the plasma (blue)
T356_1

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has over 40 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to university level study, find out more about the types of qualifications we offer, including our entry level Access courses and Certificates.

Not ready for University study then browse over 900 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus