OFC 2026: A Deep Dive into VCSEL Mass Production and Process Control at WIN Semiconductors

In 2026, with AI compute demand and 3D sensing both surging, the vertical-cavity surface-emitting laser (VCSEL) has become a core component for short-reach (SR) data center links and consumer sensing. As the world's largest III-V compound semiconductor foundry, WIN Semiconductors used OFC 2026 to show how precise process control and advanced process development support a VCSEL business producing millions of wafers a year.

WIN Semiconductors' Foundry Footprint and the Strategic Role of VCSELs

WIN currently runs 3 fabs, with 6-inch GaAs capacity of 43K wafers per month and roughly 800 wafers for 4-inch InP. Revenue reached $530M in 2024, and the company keeps investing about 11% of revenue in R&D. It operates as a pure-play foundry, offering a one-stop service from epitaxial growth and wafer fabrication through optical inspection and test.

In VCSELs, WIN has been doing MOCVD epitaxial growth since 2006 and has produced more than 2 million epi wafers to date. That huge data base gives it very high process stability and yield control.

Core Technology Breakdown: Three Key Process Controls for VCSEL Mass Production

WIN Vice President Hung-Pin Xiao pointed out that the biggest challenge in VCSEL manufacturing is maintaining tight uniformity at high volume. Here are the three core metrics of its production process:

1. Trench Etching: ±0.2 μm Accuracy

Trench etching exposes the high-aluminum-content layers for oxidation. To improve thermal behavior at high temperature, some designs add a 100% aluminum layer in the N-side DBR, which makes etch-depth control extremely demanding.

• Metric: using endpoint detection mode, WIN keeps trench etch depth variation within ±0.2 μm.

  
  

• Process upgrade: WIN developed a new POR recipe that reduces sidewall footing from about 3 DBR pairs to under 1 pair, sharply improving within-wafer uniformity (<3%).

  
  

2. Oxidation: Defining the Optical Aperture

The oxidation process sets the VCSEL's optical aperture (OA) size, which directly affects electro-optical performance.

• Pilot strategy: in each EPI run, WIN first oxidizes one wafer, then fine-tunes the oxidation time for the rest of the lot based on the result.

  
  

• Control precision: this strategy keeps wafer-to-wafer OA size variation at the same tight ±0.2 μm level.

  
  

3. Silicon Nitride (SiNx) Thickness Control: ±0.2 μm Variation

Silicon nitride thickness affects mirror loss, photon lifetime and the device's high-speed modulation performance.

• Metric: using a feed-forward recipe system, WIN keeps thickness variation within ±0.2 μm.

  
  

Advanced Technology Development: Positioning from 100G to 1.6T

For next-generation data center and autonomous driving needs, WIN showed several forward-looking processes:

• High-reliability oxidation recipe: in an overstress test at 150°C and a current density of 21 kA/cm², the optimized recipe showed almost no performance degradation after 500 hours of aging, meeting automotive sensing requirements.

  
  

• Advanced microfabrication:

  • LOCAP process: a thicker PBO layer lowers pad capacitance to raise data rates.

    
    

  • DUV grating: used for polarization control.

    
    

  • Micro lens: developed on the back side of the substrate for light collimation.

    
    

Epitaxy Research: N-type vs. SI Substrates

WIN's research confirms that VCSELs grown with a thick N-buffer layer on semi-insulating (SI) substrates perform on par with those grown on conventional N-type substrates, in both LIV characteristics and 500-hour reliability. This lays the technical groundwork for more flexible circuit integration in the future.

The Simple Tech Trend View: Process Control Is the Core Barrier

In 2026's optical communications market, while everyone is talking about 1.6T and faster system architectures, WIN's talk is a reminder to the industry: extreme control of the underlying materials and processes is the last line of defense for volume cost and reliability.

1. Leadership in production data: experience with more than 2 million epi wafers gives WIN an SPC (statistical process control) moat that competitors will find hard to cross.

   
   

2. Built for AI compute clusters: as AI clusters drive surging demand for 400G/800G short-reach fiber links, VCSEL high-temperature stability becomes critical. WIN's oxidation recipe optimized for 150°C is aimed squarely at the hot environment inside AI servers.

   
   

3. Technology migration from sensing to transmission: WIN is leveraging the volume experience it built in consumer electronics (Face ID) and quickly bringing it to datacom. This cross-market scale gives it a strong cost advantage on 6-inch GaAs.

   
   

Over the next 18 months, as CPO and multi-chip packaging mature, we expect VCSELs to integrate more tightly with micro-lens and grating processes, and WIN's investment in advanced back-end processes to become a new engine of profit growth.