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EpiScan 1000

 

Product Highlights:

ADE's EpiScan is the first high speed film thickness measurement and mapping tool designed specifically for leading edge characterization of advanced, thin epi.

Model-based, Fourier Transform spectral domain metrology assures accurate data (even in the difficult 2.0 mirco;m - 0.3 µm range). First-principles analysis results in fundamentally accurate measurement of epi thickness, as well as transition layer thickness and substrate carrier concentration.

Elimination of bias adjustment provides excellent inter-machine reproducibility and prevents expensive supplier/customer misunderstandings. It also allows the integration of EpiScan compatible metrology modules with fabrication and metrology cluster tools.

The EpiScan maps 25 points on 200 mm production wafers in less than 1 minute reducing wafer monitoring requirements. Eliminating the effects of drift, vibration and gravitational forces previously associated with epi measurement facilitates precise uniformity verification on a full production basis.

Description

The EpiScan brings an entirely new and improved optical, mechanical, electronics, detector, and data analysis architecture to bear on the problem of fast, accurate epitaxial film thickness measurement. A state-of-the-art WindowsNT based control environment supports inherent networking and automatic integration of standard data analysis and reporting tools such as spreadsheets, databases, and scientific analysis packages.

The ADE standard two cassette AutoLoader provides complete wafer handling flexibility, including sorting operations.

Measurement Principle

The EpiScan model-based analysis, developed by On-Line Technologies, Inc., uses well known principles of infrared spectral reflectometry applied in a new way.

Conventional FT-IR systems generally obtain the thickness information directly from the "interferogram" (time domain) by measuring the distance between the "sideburst" and the "centerburst". This traditional method works satisfactory for thicker epi layers (greater than 3 mm) but encounters difficulties for thin epi layers where sideburst and centerburst begin to merge. Results obtained with this method are completely unreliable at a layer thickness of less than 2 µm.

ADE's EpiScan 1000, on the other hand, employs a fundamentally different, model-based approach. A reflectance spectrum is calculated from first-principles and compared with the measured spectrum (Fourier Transform of the Interferogram). The physical quantities describing the epi-layer, transition region, and substrate model are varied in a systematic iterative manner to yield the optimum fit between the observed and the calculated spectra. This new analytical approach results in substantially higher precision for thin and ultrathin layers combined with greatly reduced measurement times. In addition to epitaxial thickness, this procedure yields precise and accurate information about the thickness of the transition region and the substrate carrier concentration.

Applications

Both manufacturers and users of epi wafers benefit from fundamentally correct measurements that are consistent with other production metrology. Process development schedules can be accelerated. Ramp-up phases are compressed and yields maximized using this fast, non-destructive and easy to use metrology system.