The Semion SystemProduct Overview

Overview

Semion System

• The Semion System is a precision plasma measurement instrument used in a large number of plasma laboratory applications. The Semion is the key instrument used by scientists to measure the ion energy and flux arriving at a surface in a plasma process chamber.

• The Semion System can be placed on a biased or grounded surface. Among the key parameters measured are Ion Energy, Ion Flux, Electron Energy, Plasma Potential and Floating Potential and the Semion provides plasma parameter measurement in DC, RF, Microwave, Continuous and Pulsed plasma.

Overview

Semion System

• The Semion System is the most advanced and trusted, fully automated retarding field energy analyser on the market. It helps the user to understand ion surface interactions and the ions impact on surface treatment.

• The Semion System is an essential plasma process diagnostic to understand the correlation between plasma inputs and the plasma state. The Semion System reduces process and tool development time, as well as the time to market for new plasma products.

Motivation

Customers Requirements

• As substrates become larger, and feature sizes smaller, there is an increasing demand for ion flux and ion energy measurement to aid process development.

• Direct measurement of the ion energy distribution (IED) and total ion flux can be performed using our advanced retarding field energy analyser (RFEA) technology, the Semion System. The RFEA is constructed from process compatible materials and the sensor’s miniature size allows it to be mounted on the substrate or any other surface inside the reactor.

Design

Specifications

• The Semion System incorporates a miniature design to avoid the need for differential pumping. Operating pressures of up to 300 mTorr can be achieved in Argon discharges.

• The Semion System also uses high impedance low-pass filters to allow the RFEA to float at the substrate bias potential. The system supports bias frequencies in the range 1kHz to 100MHz and bias potentials up to 1kV peak-to-peak maximum.

Design

Features

• High temperature cabling connects the RFEA to the external data acquisition unit through a vacuum feed-through, which is mounted at the reactor wall, and enables the senor to operate to 200o Celcius.

• Replaceable Button ProbeTM sensing elements is a convenient feature for the user, especially when operating in deposition systems. The standard system uses three grids, there is also a four grid option where the fourth grid is configured to prevent secondary electron emission from the collector plate.

Theory of Operation

The Grid Structure

• Figure 1(a) show Ions enter the RFEA through an array of sampling apertures exposed to the plasma.

Theory of Operation

The Grid Structure

• A grid G0, covers the internal side of the apertures and reduces the open area ‘seen’ by the plasma to a scale less the Debye length to prevent plasma entering the analyser.

• A second grid G1, is biased with a negative potential relative to G0 to repel any electrons that may enter the device.

• A third grid G2, is biased with a positive potential sweep, creating a potential barrier for the positive ions.

• A collector plate C, oriented in the same plane as the grids, collects the current of ions which cross the potential barrier set by G2.

Theory of Operation

Grid Potential Configuration

• The data acquisition unit records the ion current at each potential applied to G2 and the graphical user interface GUI displays the resultant current-voltage characteristic.

• The IED is also displayed - obtained by differentiation of the current-voltage characteristic. The potential configuration is depicted in figure 1(b).

Theory of Operation

Grid Potential Configuration

• The analyser (including G0, G1, G2, and C), floats at the AC/RF component of the substrate bias potential. This is achieved by means of high impedance low-pass filters. These high impedance filters prevent disturbance of the applied bias signal and provide sufficient attenuation at the output to protect the measurement electronics.

• The RFEA chassis also floats at the dc bias component of the powered electrode potential. The required dc electric fields between adjacent grids are produced by setting the grid potentials relative to (not relative to ground).

• The Semion System feed-through interface provides a filtered connection to the RFEA chassis to enable a direct measurement of . The acceptance angle of a sampling orifice is approximately 450 allowing detection of ions arriving at the surface within this angle. The calculated IED is the energy distribution of the ions perpendicular to the electrode surface.

Typical Results

Semion System on a Lam Research Chamber

• A typical Semion System installation is shown in figure 2. The RFEA was mounted at the biased substrate holder in a Lam Research capacitively coupled plasma reactor. The substrate holder was driven with 13.56MHz RF power to ignite the discharge. The working gas was pure Argon at a pressure of 10 mTorr. IEDs were measured for a range of RF power levels applied to the substrate holder.

Figure 2: Semion System installation in an Lam Research CCP reactor.

Typical Results

Current – Voltage Characteristic

• A typical current-voltage characteristic and IED are shown in figure 3. The RF power was set at 50W and the argon gas pressure was 10 mTorr. The well know bi-modal saddle shaped IED structure associated with sinusoidal biasing is clearly visible.

Figure 3: Current-Voltage characteristic (dashed) and IED measured at 50W and 10 mTorr.

Typical Results

Ion Energy Varies as a Function of RF Power

Figure 4: shows how the ion energy distribution varies as a function of RF power applied to the substrate holder

while the pressure is maintained at 10 mTorr throughout.

Products

The Semion 800

Products

The Semion HV-2500

Products

The Semion Pulsed DC

Products

The Semion Spatial

Questions

Our Systems Measure Plasma

Helping You to Understand Your Processes

Allowing You to Control

Thank You for Your Time