Issued Date：2025/10/14
Issued By：iST
Silicon Photonics
Silicon Photonics
When it comes to “leakage”, most engineers immediately think of electrical leakage. But in the photonics world, there’s another kind of leakage — light leakage.
In the realm of Electrical Integrated Circuits (EICs), issues such as short circuits, opens, and metal migration are part of daily life for engineers. However, once “light” is integrated into the chip, the game changes completely.
In the world of Photonic Integrated Circuits (PICs), engineers no longer deal with electrons but with photons. Coupling loss, waveguide cracks, scattering, and absorption can all become invisible killers. Instead of only checking whether current flows smoothly, engineers must now measure attenuation at different wavelengths (Insertion Loss, IL), Polarization Dependent Loss (PDL), and even trace light leakage points hidden inside the waveguide.
On the path toward Co-Packaged Optics (CPO), nearly every R&D team faces the same dilemma: just as they overcome design barriers, they soon get stuck in testing or packaging. From optical loss and reliability to yield, each phase in the CPO process can become a hidden obstacle that drags the entire project behind.
Five Common Roadblocks in Silicon Photonics (SiPh) Development
Based on iST’s extensive project experience, the main pain points along the process flow can be summarized as follows:
1. Insufficient PIC Pre-test:
Without proper pre-test interfaces and precise die-to-die alignment, the post-integration yield often drops significantly.
2. Difficulty in Quantifying Optical Component Reliability:
Two challenges remain unsolved for many PIC developers:
(1) The lack of a programmable, multi-channel PD (Photodiode) aging platform, making it hard to quantify lifetime characteristics under high-power or long-duration operation.
(2) Insufficient IL variation data during temperature cycling, humidity, vibration, or dust exposure, leaving long-term reliability evaluation uncertain.
3. High Die Sawing Risk for Low-k PIC Materials:
During dicing, edge chipping and structural damage can easily occur, compromising both yield and reliability.
4. Challenges in Defect Analysis and CP Testing:
It remains difficult to quickly localize optical loss hotspots or light leakage, and to analyze structural defects within waveguides, couplers, and modulators with sufficient precision.
5. Severe CPO Packaging Challenges:
During PIC + EIC + FAU (Fiber Array Unit) assembly, warpage often leads to yield degradation — a recurring challenge that engineers urgently need to overcome.
iST’s One-Stop Silicon Photonics (SiPh) Verification Solutions
iST offers complete, standardized, and scalable verification platforms that cover the entire CPO development process — from substrate/socket design, optical and electrical testing, reliability verification, to structural analysis.
Q1: How to test a PIC before packaging? What if there’s no interface?
A1: Many teams face high risk by waiting until final packaging to test results. iST designs custom substrates and chip bonding solutions that enable high-speed optical pre-testing before packaging. With precise die-to-die alignment, engineers can secure yield early in the validation phase.
Q2: How to simulate high-power and long-term operation for Photodiodes (PD)?
A2: Most customers lack multi-channel programmable systems for long-term aging tests. iST provides constant-current/constant-voltage test modules capable of testing multiple PDs simultaneously, with programmable laser sources to emulate high-power conditions. Comprehensive optical aging and PD stress solutions ensure long-term PD stability and reliability.
Q3: How to quantify optical component reliability when IL variation has no standard reference?
A3: IL changes during temperature cycling, humidity, vibration, or dust tests are often undefined. iST establishes a complete reliability qualification framework (TCT, TH, vibration, dust, etc.), using Insertion Loss variation as a pass/fail criterion, enabling data-driven risk control and design optimization.
Q4: How to rapidly identify optical loss hotspots or waveguide defects?
A4: Traditional methods often act like a “black box,” lacking precise localization. Through collaboration with Enlitech, iST integrates the NightJar optical inspection platform for wafer-level optical loss mapping, capable of locating leakage points and quantifying optical attenuation with high precision. Combined with deep structural analysis for couplers, waveguides, modulators, and PDs, iST fully exposes hidden defects.
Q5: How to prevent yield loss during CPO packaging and die sawing?
A5: Packaging warpage in PIC + EIC + FAU assemblies is a major yield killer. iST provides pre-assembly warpage metrology to detect risks before integration. For Low-k PICs, iST’s Laser Grooving and Blade Dicing (BD) technologies effectively minimize edge chipping, improving both yield and long-term reliability.
Eliminate Detours to Accelerate Your Leap from Electrical to Optical
As demand for AI servers and high-speed switches surges, the industry is accelerating the adoption of Co-Packaged Optics (CPO) and Electro-Optical Integration (EIC+PIC) applications.
iST’s one-stop solution for Silicon Photonics verification covers the entire process—from design and electro-optical testing to reliability verification and packaging challenges. Not only help you shorten your R&D cycles but also ensure every step is data-driven, enabling you to navigate the development path efficiently and minimize costly detours.
Interested in receiving the iST Silicon Photonics Solutions Overview? Connect with us now! We will send you a detailed chart for your reference, helping you break through CPO R&D bottlenecks together!
For inquiries, please contact Ms. Skylar Chen at +886-3-5799909 ext. 8926 │ Email: IST_GS_SPSDD@istgroup.com；marketing_tw@istgroup.com