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Solutions for Photonics Integrated Circuits for Quantum

Discover the leading solutions for the fabrication of integrated quantum photonics.

Plasma-enhanced Deposition and Etching Solutions for Quantum

We offer three key applications for photonic integrated circuits for quantum:

  • Atomic layer deposition of superconducting nitrides for SNSPDs
  • High temperature, SiH4 and NH3-free PE (ICP) CVD of Si3N4 for low-loss waveguides
  • Plasma etching for optical components (e.g. gratings, waveguides)

ALD of Superconducting NbN for Single Photon Detectors

Thin films of superconducting NbN deposited by plasma ALD using bias for applications as superconducting nanowire single photon detectors (SNSPDs)

  • Thicknesses required: <30 nm
  • ALD allows for deposition of superconducting thin films with thickness precision, high Tc, good thickness uniformity, and great control of stoichiometry
  • Table bias enables stress control to achieve minimal room temperature resistivity 
  • Low room temperature resistivity correlates to higher Tc
  • 12.9 K Tc measured at Oxford Instruments
    • For ~30 nm NbN film deposited at 250°C
    • Room temperature ρ = 139 µΩcm, Tc = 12.9 K
Bias RF power chart Tc = 12.9K diagram

Silicon/SiNx Etch for Low-loss Optical Components

Cryogenic etch to overcome sidewall roughness issues in Bosch etch

We propose a range of cryogenic etch processes to fabricate optical components such as gratings, ring resonators, optical filters, delay lines and waveguides, made from Si/Si3N4. These are key building blocks of a Quantum Computer, enabling light coupling into the chip, photon manipulation and transport down to single photon detectors.

Our cryogenic etch processes are characterized by:

  • Smooth sidewalls, leading to low optical signal loss
  • Low etch rate, allowing for good etch depth accuracy & reproducibility
  • High selectivity, limited by mask thickness
  • Notch control
Bosh etched structures SEM

Bosh etched structures

SiNx cryo etch SEM

SiNx cryo etch

Grating coupler on SOI SEM

Grating coupler on SOI

Cryo etched SOI waveguide SEM

Cryo etched SOI waveguide

Flexible Solutions Tailored for Photonic Components

Bosch process SEM

Bosch process targeting smooth sidewalls

Minimal scallop size
Etch rate > 3 μm/min
Profile 90 ±0.5°
Selectivity > 45:1
Scallops < 35 nm
Depth 22 μm
AR ≈ 11
Cryo process SEM

Cryo process targeting smooth sidewalls

Smooth sidewalls
Etch rate > 2 μm/min
Profile 91°
Selectivity > 65:1 Si:SiO<sub>2</sub>
Sidewall roughness < 5 nm
Depth 22 μm
AR ≈ 6
Mixed gas process SEM

Mixed gas process targeting shaped profile

Curved profile
Etch rate > 190 nm/min
Profile Shaped
Selectivity > 12:1
Sidewall roughness < 5 nm
Depth 485 nmm
Pillar width ≈ 105 nm 

Wide Range of III-V Optical Components Processing

GaAs / AlGaAs Heterostructures

GaAs / AlGaAs Heterostructures

InP Ridge Waveguide

InP Ridge Waveguide

GaN Photonics Crystal

GaN Photonics Crystal

GaAs / AlGaAs Photonic Crystal

GaAs / AlGaAs Photonic Crystal

InP Photonic Crystal

InP Photonic Crystal

InSb / InSbAs

InSb / InSbAs

PE/ICPCVD of Si3N4 for Low-loss Optical Components

Silicon Nitride (Si3N4) is a very promising candidate for low-loss optical components

One of the greatest challenges with Si3N4 deposition for applications in waveguides is the in-film hydrogen content, typically coming from the precursors and leading to optical losses.

Therefore, we've developed a high-temperature PECVD process which shows a low concentration of hydrogen and enables enhanced stress control as well as a higher deposition rate, These make high-temperature PECVD of Si3N4 particularly suited for the fabrication of low-loss optical components.

Other approaches include ICP CVD using SiCl4 or low-temperature ICP CVD followed by in-situ anneal at temperatures above 1000°C in our PlasmaPro 100 Nano system (maximum temperature: 1200°C).

  • High temperature and NH3-free PECVD of Si3N4 (800°C) allowing for good control of the refractive index, stress and enhanced deposition rate
  • SiH4-free ICP CVD of Si3N4 using a SiCl4 process
  • Low-temperature ICP CVD of SiN
PECVD film stress control graph

PECVD film stress control

High temp PECVD with low BHF etch rate graph

High temp PECVD with low BHF etch rate

Systems for Superconducting Qubit & Quantum Circuit Applications

Enabling these solutions are the FlexAL and PlasmaPro 100 deposition and etch systems, capable of producing small coupons through to 200 mm wafers, clusterable to increase throughput and avoid vacuum breaks. Our PlasmaPro 100 platform enables high precision deposition and etching of a wide range of materials for quantum devices.

We offer key processing solutions for various device fabrication challenges for the various approaches in today’s quantum technology R&D and device development.

Oxford Instruments have a strong history in providing state of the art solutions in this rapidly developing applications are a key enabler of quantum technologies beyond device fabrication solutions.


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