Instrumentation

Optical Monitor

Model 820

In-Situ Spectroscopic Optical Monitor

Full Spectrum, Real-time Analysis and Control of Reflectance and Transmittance During Thin-Film Deposition

Features

• Full Spectrum Analysis
• Real-time Chamber Characterization
• Offline Stage
• Plasma Diagnostics/Endpoint

Full Spectrum Analysis - Spectrometer monitors from 400-930nm to analyze the true reflectance or transmittance of the test chips being monitored.

Multiple Endpoint Techniques - The Model 820 can be configured to endpoint each layer with Pre-Quarter wave, Post-Quarter wave or Simulation Template Match. The Essential Macleod thin film design and optimization software is integrated into the Model 820 software to enable template matching.

Real-time Chamber Characterization - Because the Model 820 monitors the full spectrum during the deposition process, the system can identify shifts in spectrum due to various changes in material composition and chamber parameters. The spectrum data can then be used to calculate new N&K values which can update the design of the product being produced.

The Model 820 can also characterize the optical constants of the films related to process steps, such as venting, spectral shifts due to temperature, and/or gas flow rates.

Offline Stage(optional) - measurement of transmittance, reflectance or Color for QC of Filters, Prisms, or Beam Splitters.

Plasma Diagnostics/Endpoint - The Model 820 software also includes the capability for control and analysis of plasma processes.

Functional Description

The Model 820 is a multi-wavelengths spectrophotometer, comprised of a low voltage halogen light source, silicon photodiode array detector, embedded computer and software with sophisticated algorithms. State of the art fiber optic components deliver high signal to noise ratio and long-term stability. The photodiode array allows the entire range of individual wavelengths in the spectrum to be detected simultaneously. A curve fitting approach to layer termination further assists in detecting and controlling small signals in a process environment when dispensing materials like SiO on glass substrates.

Transmittance Mode

The light is illuminated from the bottom (or Top) of the chamber by the light source probe. The light will transmit through the test chip and into the transmission probe on the top (or bottom) of the chamber. The light is collected in the probe and focused into a fiber where it is transferred to the spectrometer for analysis. See Figure 1 for illustration.

Reflectance Mode

The light is illuminated from the bottom of the chamber by the light source probe. The light will reflect from the test chip and back down to the bottom of chamber to the reflection probe. The light is collected in the probe and focused into a fiber where it is transferred to the spectrometer for analysis. See Figure 1 for illustration.

Endpoint Techniques

The optical monitor is capable of using several techniques for controlling the thickness of each layer. The techniques are described below.

Quarter Wave

The quarter wave technique is the most common technique used in the deposition industry. It consists of monitoring a single wavelength vs. time during the coating process. During this time, the single wavelength intensity signal will change due to the constructive and destructive wavelength interference, based on the refractive index of the film being deposited. From the wavelength and refractive index of the material, the film thickness can be calculated.

Wavelength/(Refractive Index)

An illustration of multiple quarter wave reflectance is shown in Figure 3.

Template Match

In the Template Match technique the raw collected spectrum is compared to a predicted simulation from a simulation software like Essential Macleod. The algorithm uses a Merit Function to identify the match. A single file of templates are used to control all layers. See figure 4 for illustration.

Full Spectrum

Figure 4

Figure 4 shows the template matching technique. The screens above displays the raw collected value (Blue line) and the template used for matching (Green line). The screen on the left shows the “Root Mean Square” algorithm fit of the data vs. time. When the two spectral displays (bottom left) match, the system will terminate the layer deposition. A simulation package, such as Essential Macleod must be used to generate the templates for matching.

Multi-layer User Interface