Plasma Etching

Plasma EtchingUsed in integrated circuits, plasma etching shoots an appropriate gas mixture at high speed at a chosen sample. The plasma, or etch species, can be either charged ions or neutral atoms and radicals. The physical properties of the target will be modified as the atoms of the shot element will embed themselves at or just underneath the surface of the target.

There is a need to measure ion and neutral flux, energy, and angle arriving at the etch surface. In addition, for pulsed shots, these parameters need to be time-resolved.


Semion Sensors

The Semion measures the ion energy and flux to a biased surface. This is a key diagnostic tool for monitoring etch processes. The ions have a crucial role in anisotropic etch applications. Variations in ion flux will affect uniformity of etch and variations in the ion energy will affect the charging on the substrate as well as the etch rate.

SE02: Ion flux and ion distribution function measurements in synchronously pulsed inductively coupled plasmas
Study showing a Semion retarding field energy analyser demonstrating the impact of the duty cycle on time variations of ion flux and time-averaged ion distribution function measured at the wafer surface in an ICP-processing chamber.


Vertex Sensors

Vertex allows the user to measure the energy of ions in both the vertical and angular directions. Ion energy distributions over a range of elevation angles is measured. Measuring and understanding the angular distribution of ions arriving at a surface is a key parameter in determining the wall profile of etch particularly near the edges of the wafer.


Quantum Sensors

The Quantum Sensor can be used in etch applications to measure the polymer deposition rate and its dependence on ion energy and flux at a biased surface. The ratio of deposition rate to ion energy is an important parameter in controlling the etch profile.


Species Sensors

The Species measures the ion energy and flux of different species arriving at a biased substrate. The ability to seperate ions into their different mass species is very important in understanding the chemistry of etch processes. The etch chemistry is in a highly non-equilibrium environment and requires a knowledge of both the type of species and its energy arriving at the surface.



Langmuir Probes

The Langmuir Probe is one of the most common and widely used plasma diagnostics and measures plasma parameters in the bulk of the plasma. Key parameters in etch applications are the ion density, the plasma potential and the electron temperature. These parameters control etch rate, uniformity and plasma damage. The Langmuir Probe is routinely used to measure and understand these key parameters in the design and development of plasma etchers.

LP03: End-point detection of polymer etching using Langmuir Probes
This study uses a Langmuir probe in order to determine the end point of a polymer etching, by measuring the floating potential Vf which changes at the end of an etching process.

LP10: Langmuir Probe used in experimental and numerical investigations of the phase-shift effect in capacitively coupled plasma discharges
In this study, the authors have used a Langmuir Probe to measure the electron density and the electron energy distribution function in phase-shift controlled capacitively coupled plasmas.


Plato Probes

In some plasma etch applications process gasses are used which deposit polymers on the exposed surfaces. These films are insulating and need to be removed when using a standard langmuir probe. The Plato Probe has been designed to operate with immunity to deposited layers on the probe surface. This makes the Plato Probe a useful diagnostic of plasma density and uniformity in etch plasma. In many etch plasma the plasma chamber walls are insulating and the Plato Probe draws no DC current and is not affected by a poor chamber ground return path. The Plato Probe can be synchronised with pulsed power supplies to measure time resolved plasma parameters in pulsed etch applications.


Bdot Probes

The Bdot Probe measures the time varying rate of change in the magnetic field in the bulk of the plasma. The bdot probe is particularly useful in etch plasmas where the source of the plasma is an ICP. Power is coupled into the plasma by means of the changing magnetic field generated by the RF in the ICP coil. Measuring Bdot as a function of position across the substrate holder is very sensitive to the uniformity of the plasma and the nature of the ICP coupling.

BD01: B-Dot probe measurements in an ICP discharge
This study focuses on alternating magnetic field measurements in an RF ICP discharge using a B-Dot probe. B-Dot probes can be used to determine the plasma current, electric field and the complex conductivity for the alternating magnetic field measurements.



Octiv Range

The Octiv is an in-line RF voltage, current and phase measurement system. It can measure fundamental frequencies simultaneously and harmonics with frequency agility at 1% accuracy and 1 micro second time resolution. The Octiv allows real time monitoring of the etch plasma and can be used to diagnose or control a specific application. the Octiv is particularly useful in pulsed etch applications which give greater control in advanced plasma etch applications. With a time resolution of 1 microsecond the time dependence of both source and bias RF waveforms can be monitored.


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