Gemini Series

Ultra-High Resolution & Ultra-High Sensitivity
Scatterometer and Thin Film Measurement System
for Photomask or Semiconductor Wafer Applications

The n&k Gemini series are automated metrology systems used to fully characterize and monitor Thin Film and OCD applications for both current and next generation IC processes. Capable of simultaneous Reflectance and Transmittance measurements the Gemini series is ideal for applications with transparent substrates (i.e., Photomasks, SiC Wafers, Quartz Wafers, Flat Panels, etc.).

Utilizing patented all-reflective optics, a broadband wavelength range (190 – 1000nm), proprietary optical formulation, and an industry leading signal-to-noise ratio, each system provides the accurate and reproducible data required to monitor subtle changes in critical device parameters (thin film thickness, optical properties, critical dimensions (CD), poly recess profile, sidewall angle) across various key applications.

High Throughput, Fully Automated Optical Metrology System for Higher Yields for either Opaque or Transparent Substrates.

Gemini Series General Specifications

  • Wide Wavelength Range which allows for an extensive variety of applications
  • Film Thickness and Optical Properties
  • Trench/OCD Metrology Capabilities
  • Micro-Spot Technology
  • Configurable for all Wafer types and sizes
  • Full Automation that meets all Industry Fab and Foundry Standards
  • Easy to Maintain and Service
  • SEMI Standards and Third-Party Certifications
  • GEM/SECS Communication Interface

Thin Film & OCD Scatterometry Applications

Photomask Application Examples

Photoresist CrOx (ARC) Cr MoSi Back sideR T Front sideR Qz
MoSi Uniformity
+5 Å Mean -5 Å
Cr Uniformity
+4 Å Mean -4 Å
CrOx (ARC) Uniformity
+5 Å Mean -5 Å
Photoresist Uniformity
+13 Å Mean -13 Å
n and k Spectra of Cr:
Layer Mean (Å) Range (Å) StandardDev. (Å) MoSi Cr CrO x (ARC) Photoresist 940 Å 365 Å 240 Å 3075 Å 9 Å 7 Å 6 Å 25 Å 1.5 Å 1.6 Å 1.1 Å 4.5 Å

In this example application, the desired measurement output is the degree of rounding of contact holes in MoSi on quartz.

The figure on the right shows the sensitivity of the raw reflectance and transmittance data to corner rounding. The high sensitivity of the transmittance data allows for accurate measurements of this quantity. Also note the high level of the transmittance (65% at 800 nm) compared to the reflectance (15% at 800 nm). This high level improves the signal-to-noise and hence the repeatability of the measurement.

This example illustrates the importance of the n&k Gemini’s unique transmittance capability in achieving accurate and repeatable results.

Measurements of Corner Rounding: Sensitivity of Rp & Tp
ΔTp = 2.16% Rp Tp CORNER ROUNDING MEASUREMENT Contact Hole Shape Perfect Square Perfect Circle Rounded Square ΔRp = 0.82% Wavelength (nm) Rp & Tp (%) 200 300 400 500 600 700 800 900 1000 0 20 40 60 80

As critical dimensions (CD) become smaller, mask manufacturers increasingly use phase shift technologies to enhance the resolution of the resist image that is formed on the wafer

Frontside Measurement
Incident Beam Reflected Beam Transmitted Beam
Backside Measurement
Incident Beam Reflected Beam Transmitted Beam

The n&k Gemini determines phase shift from 190-1000 nm through R and T measurements and through the analysis of film optical properties, film thickness and quartz etch depth.


The n&k Gemini can measure structures used in EUV lithography, as well as the thickness and n and k spectra of the associated materials.

Using measurements on blanket areas, the thicknesses and n and k spectra can be found for:

Si Mo Si Si Mo ARC Buffer Cap Mo/Si Multi-layer Absorber LTEM Substrate 80Layers
Example: Depth Uniformity Map
+ 1.5 nm Mean - 1.5 nm + 1.5 nm Mean - 1.5 nm
Example: CD Uniformity Map
+ 18 nm Mean - 18 nm
Mo/Si Multi-layer ARC Buffer Cap Depth CD Absorber LTEM Substrate

Semiconductor Wafer Application Examples

Poly Recess in SiC
Trenches in SiC
Media Processing
Media Final Product
Typical top views for the above profiles:

n&k Technology Gemini Series Markets

Our products will be your eyes on the Nano scale, to ensure your IC’s and products have the highest yields.

Flat Panel Display

Displays continue to play a part of everyday life by way of smartphones, tablets, TV’s and monitors. Our products continue to enable the display manufacturers to produce high quality displays at the highest yield possible. 


Optical metrology for Conventional, Phase Shift, or EUV photomasks remains key for Photomask shops worldwide. Our unique combination offering to measure both Reflectance and Transmittance has proven to be very beneficial to Photomask makers throughout the years.

Power Device

Foundational in our technological eco-system in respect to electrical voltage and current flow, these devices are everywhere from the smallest consumer goods to the largest aircraft.

Specialty IC

Bridging the digital and physical worlds, Specialty IC’s supplement Logic technology, creating a new wave of technological innovation.