About Us

           Angstrom Sun Technologies Inc. is a privately held company, headquartered in Boston, USA. The focus of company is to provide a series of cost-effective optical solutions for characterizing thin film thickness, thick coating thickness, their optical properties (refractive index N and extinction coefficient K), surface and interface behavior, alloy concentrations and their uniformities across surface.

          Affordable, low cost, but advanced and high performance tools, including Spectroscopic Reflectometers, Microspectrophotometers, Microreflectometers, film thickness mapping system, simple desktop film thickness station and automatic variable angle spectroscopic ellipsometers, offer a way to  probe film stacks nondestructively and precisely. In addition, Angstrom Sun Technologies Inc also delivers advanced analytical services for characterizing thin films, thick coatings and complicated layer stacks.

          Angstrom Sun Technologies Inc is NOT a distributor or representative to other manufacturers for their ellipsometers, Reflectometers or Microspectrophotometers. Angstrom Sun Technologies Inc. designs and manufactures all TFProbe tools in a facility located in Boston, USA. TFProbe tools are sold and distributed by international sales networks

          With performance and professional support as our mission, Angstrom has established a worldwide customer base since 2002,  including well-known education institutions, government agencies and Fortune 500 companies, such as NASA Marshall Space Flight Center, Massachusetts Institute of Technology (MIT), Seoul National University, NanoTech Center (CESTM) at SUNY, Columbia University,  Hewlett-Packard Co., Lockheed Martin Co., General Electric (GE), Corning Inc., Bell Laboratories, Johnson-Johnson, Mylan Technologies,  EPV Solar, AVA Solar/Colorado State University, Sierra Solar Systems,  just mentioning a few here. 

Technology Development

1. Thin film (optical, semiconductor, metal and other type) materials development
2. Thin film processing technique development
3. Thin film and materials characterization technique development
4. Optical monitoring system design and implementation to various processing systems including but not limited to CVD, PECVD, PVD, CMP, e-beam deposition or ion beam sputtering system
5. Fiber optics based sensor development and instrumentation
6. Optical passive and active component design and development

About Ellipsometry, Reflectometry and Microspectrophotometry

        There are many techniques for characterizing materials, each having its own advantages and disadvantages and each being uniquely able to reveal material properties that other techniques can't access. Spectroscopic ellipsometry (SE) and spectroscopic reflectometry (SR) are optical techniques that are particularly flexible in that they can be used to determine the optical and physical properties of a wide variety of thin-film materials such as silicon oxide, nitride, silicon, even metal films. Their ability to do this without contact or damage to the material of interest has seen it become routinely used in R&D laboratories and within manufacturing facilities for monitoring thin film growth and deposition processes.

         In general, reflectometer is used to acquire reflection spectrum over a wavelength range. If there is film or coating on some kind of substrate, the film or coating thickness can also be figured out from the measured  reflection  spectrum. Ellipsometry measurement is performed at non normal incident angles. The two ellipsometry parameters, Psi and Del, give more information than reflectance itself. Therefore, more information can be accessible through ellipsometry technique, such as multiple layer analysis, dielectric constants calculation, surface or interface roughness, inhomogeneity behavior etc. Of course, those information is always derived from an optical model, which leads to some difficulties  to use this technique although it is much more powerful than reflectometry technique.

       Angstrom Sun Technologies Inc manufactures both ellipsometer and reflectometer tools. Besides ellipsometer and reflectometer hardware systems, the advanced analysis software is essential to extract the desired information as above-mentioned, such as thickness, roughness, alloy concentration and dielectric constants. TFProbe 3.0 and TFProbe 2.0 software from us offer powerful analysis functions for ellipsometry and photometry with simulation and data regression. Unique but configurable mode allows different users to access different level and suitable for both R&D and production quality control purpose.

Thickness Measurement Tools

        For thickness measurement, both techniques rely on modeling. In general, ellipsometry gives better accuracy than reflectometry in thin thickness range such as below micron level. For a typical ellipsometer configuration, the maximum thickness measurable is below 10 microns. However, reflectometer can measure up to hundreds microns of non absorbing thick coatings.

Measurable Thickness range for Thin Films or Thick Coatings in general

       These optical methods need to have light to penetrate through film and reflect back from film/substrate interface. Without meeting such condition, the film thickness can not be figured out because of lacking necessary phase information. One example is a sample with thick metal films on it. Because metal has high absorption in visible and Near infrared range, light only can penetrate metal film with a depth of less than 1000 Angstroms. For such film with a thickness above 1000 Angstroms, it is impossible to measure its thickness by reflectometry or ellipsometry although reflection spectrum can be obtained with reflectometer and optical properties for metal film can be obtained with ellipsometry. Roughly, the measurable thickness for various films can be estimated from penetration depth if knowing its extinction coefficient or absorption coefficients.

Some application examples with spectroscopic ellipsometer or reflectometer measurements

• Optical constants (refractive index n and extinction coefficient k) for thin films, coatings and bulk substrate

• Accurate nondestructive thickness determination for thin films

• Alloy concentration determination for various thin films such as Ge in SiGe alloy, Al in AlGaN films

• Band gap determination for GaN, SiC, AlN, AlGaN, etc.

• Porosity measurement in low-K films

• Relative volume fraction determination for each component in nano-composite

• Physical thickness and optical properties for each layer in a multiple layer stack or periodic structure such as quantum well structure

• Thickness and optical properties uniformity information

• Inhomogeneous film analysis in physical density or alloy concentration

• Optical properties for high-k films

• Nondestructive measurement for electrical conductivity of metal films, metallic compounds (such as WN, TiN, TaN, etc.), doped semiconductor epi layers (thickness can be also determined at the same time), other compound oxides such as ITO films

• Nondestructive measurement for doping concentration in doped semiconductors (active dopant! not total concentration as given by destructive SIMS analysis)

Microspectrophotometer is used to characterizing optical properties of thin films, thick coatings over a micron region area, which is typically found useful in patterned device or tiny medical device fabrications such as measuring silicone lubricant thickness on needles etc.