The completely automated, non-destructive FilmTek™ 4000 optical property and thickness metrology instrument was created to meet the rigorous process control requirements of planar waveguides, silicon photonics, and photonic integrated circuits.
The system offers a best-in-class refraction (n) resolution and repeatability index using patented multi-angle reflectance technology with beams specially designed for 50 nm to 150 μm films. When creating materials like BPSG, Ge-SiO2, P-SiO2, Si3N4, SiON, and LiNbO3, the FilmTek 4000 makes precise real-time in-line monitoring of optical characteristics n and coefficient of extinction (k) possible.
The FilmTek 4000 delivers:
- Refractive index resolution is 100× greater than conventional optical techniques, with superior repeatability
- Control the refractive index and thickness of advanced films, from monolayers to multilayer stacks, with ease and reliability
- Automatically handle wafers, match patterns, optimize beams, and process data efficiently
Uniformity plot of Ge-doped SiO2 (a) refractive index and (b) thickness. Image Credit: Bruker Nano Surfaces and Metrology
Superior Metrology Performance for Optoelectronics
FilmTek 4000 schematic. Image Credit: Bruker Nano Surfaces and Metrology
The FilmTek 4000 accurately measures film thickness and optical characteristics (n and k). The innovative multi-angle reflectometry structure captures reflectance spectra from 400 nm to 920 nm at both normal incidence and 70°.
By modifying the source and detector to extend capabilities to the NIR wavelength range (up to 1700 nm), where certain silicon-based photonics devices function, or by including an optional spectroscopic ellipsometer to support ultrathin film measurements from 0–500 Å, the FilmTek 4000 platform can also be customized to meet particular metrology needs.
Ultimate Non-Contact Refractive Index Resolution
DPSD plot comparing 5 μm SiO2 on Si to 5 μm Si3N4 on Si. Image Credit: Bruker Nano Surfaces and Metrology
The FilmTek 4000 provides prece, refractive index resolution, and repeatability needed to satisfy waveguide manufacturing requirements. It combines a specialized optical design with multi-angle reflectometry and Bruker’s patented multi-angle differential power spectral density (DPSD) analysis capability.
By individually calculating the refractive index from the ratio of the normal and 70° peak positions, the DPSD approach shifts reflectance data to the frequency domain.
The measurement is optimized in every way, yielding separate thickness and refractive index values for the core and cladding layers' transverse magnetic (TM) and transverse electric (TE) modes. The technology offers process and quality engineers a non-destructive way to meet stricter tolerance requirements with a refractive index resolution of up to 2 × 10–5.
The FilmTek 4000 touts a 100-time improvement over contact technologies, like prism couplers, and a hundred-time greater precision in measuring refractive index than any other optical approach.
Enhanced Versatility for Single- and Multi-Layer Stacks
Index of refraction as a function of temperature, showing high accuracy. Image Credit: Bruker Nano Surfaces and Metrology
Film thicknesses ranging from 50 nm to 150 μm can be measured using multi-angle reflectometry, which covers thicker films commonly seen in planar waveguides. Using the same mechanical design, a spectroscopic ellipsometer with an extra polarizer and compensator can be optionally added to increase compatibility with ultrathin films like monolayers or bare substrates.
Combining multi-angle reflectometry and spectroscopic ellipsometry with Bruker’s DPSD technology allows for accurate and consistent thickness measurements by separating the effects of thickness and optical properties variations. The novel dispersion formula, which follows Kramers-Kronig relationships and is based on quantum mechanics, simplifies the impact of refractive index and thickness on multi-thin layer stacks.
FilmTek 4000 provides quick data collection and processing, making it perfect for monitoring product lines, process evolution, and quality control of sophisticated films.
Fully Automated, High-Throughput In-Line Metrology
Multilayer thickness results for Si3N4 on CVD Si3N4, showcasing applications in Si photonics. Image Credit: Bruker Nano Surfaces and Metrology
The FilmTek 4000 allows for the automatic loading and measurement of 300 mm wafers, with the results being sent to the host network for process control in real time. With precise stage location, wafer handling from FOUP or cassette to the stage is rapid. Using Cognex’s PatMax for pattern matching, stage accuracy is improved to within a micron.
The equipment generates consistently accurate results without requiring user input, thanks to fully automated beam alignment, calibration, and focusing. With an average processing time of a few seconds or less per point, data processing is quick and simple. The FilmTek 4000 is designed to be completely integrated into in-line production for film thickness and refractive index metrology.
FilmTek 4000 Specifications
Source: Bruker Nano Surfaces and Metrology
| . |
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| Measurement Function |
Index of refraction n and extinction coefficient k, film thicknesses t, roughness, crystallinity |
| Film Thickness Range |
0 Å to 150 μm |
| Film Thickness Accuracy |
±1.5 Å for NIST traceable standard oxide 5000 Å to 1 μm |
| Film Thickness Precision (1σ) |
5 μm Oxide (t,n): 2 Å / 0.00002 |
| Spectral Range |
400 nm to 1700 nm |
| Spectral Resolution |
Visible: 0.3 nm; NIR: 2 nm |
| Measurement Spot Size |
1 mm (normal incidence); 2 mm (70°) |
| Light Source |
Regulated halogen lamp and optional NIR source |
| Detector Type |
2048-pixel Sony linear CCD array; 512-pixel cooled Hamamatsu InGaAs CCD array (NIR) |
| Wafer Handling |
Brooks or Bruker’s internal handling solutions |
| Automated Stage |
150 mm to 300 mm |
| Measurement Time |
<5 s per site |