Indium phosphate, or InP, is a binary semiconductor with outstanding electron velocity. This makes it more suitable for such applications compared to other semiconductors, like GaAs and silicon, particularly in high-power and high-frequency applications. However, prime-grade wafers can be expensive, making InP reclaim wafers an attractive alternative.
The reclamation process allows a former semiconductor to be used again by preserving its surface and crystallographic integrity, producing a new wafer with characteristics that satisfy the majority of requirements.
Indium Phosphide (InP) wafer reclamation is a delicate and technical process mostly used to lower material costs in semiconducting. Wafers can be reclaimed or repolished up to three times, depending on the removal rate. Because InP is more brittle and delicate than silicon, extra caution is used during reclamation to prevent breakage.
The key steps of this process involve:
While reclaimed InP wafers offer cost-effective and environmentally sustainable alternatives to virgin substrates, their physical, electrical, and structural properties can differ depending on the reclaim process used and the number of reclaim cycles.
One of the advantages of indium phosphide is its carrier mobility, which enables faster switching speeds and higher yield rates. On average, InP wafers exhibit high electron mobility (~5400 cm²/V·s) and low defect-related trap density. InP wafers also have high dielectric strength.
Reclaimed wafers also possess high carrier mobility but may show slightly degraded mobility and increased background doping due to surface contamination or damage.
When it comes to their performance, this can lead to a slight decline in device speed and noise performance. If this happens, requalification can be performed to improve results.
InP wafers possess a high thermal conductivity of 0.68 W/cm·K (at room temperature). This data is similar for properly reclaimed InP semiconductors, that is, as long as they are not severely damaged or contain residual contaminants.
Both virgin and reclaimed InP are stable mechanically, offering predictable responses to etching and cleaning chemicals. This is because InP reclaimed wafers are tested thoughtfully to ensure these capabilities.
Wafers exposed to several reclaim cycles may be more susceptible to chipping or warping. Additionally, they are more prone to possible chemical non-uniformity due to prior film residues or chemical stress.
This reduces handling yield and possible challenges in downstream lithography or CMP steps. To prevent it, make sure to inquire how many reclaim cycles an InP wafer has gone through before purchase.
Virgin InP wafers are incredibly smooth, with an RMS surface roughness of typically < 0.3 nm. These atomically flat surfaces make them ideal for epitaxial growth.
On the other hand, reclaimed InP wafers tend to have slightly higher roughness (~0.5–1.0 nm RMS), especially depending on the polishing quality. In sensitive applications, such as photonics or HEMTs, this may result in reduced epitaxial layer quality, which can lead to a potential yield loss in advanced device fabrication.
Brand-new indium phosphide offers a perfect lattice structure with minimal dislocations. For that reason, they’re ideal for lattice-matched epitaxy.
Reclaimed InP may exhibit increased dislocation density, stacking faults, or crystal strain due to mechanical or thermal stress during processing.
Brand new InP wafers and reclaimed ones have several points in common—but in certain applications, reclaimed wafers performance is slightly lower. For that reason, the secret to taking advantage of the reclaimed process lies in understanding what properties your project really needs.
While reclaimed InP wafers are suitable for many R&D and low-risk manufacturing applications, they typically exhibit slightly degraded surface quality and crystallographic perfection compared to virgin wafers.
These differences may not be critical in some use cases, such as backend test wafers, monitor wafers, or non-critical epitaxy, but high-performance optoelectronic and RF devices often demand the pristine quality of virgin substrates. For applications with strict performance requirements, thorough incoming inspection and qualification of reclaimed wafers is essential.
It’s important to analyze each case in detail, assessing the downsides and advantages, to reach a satisfying and efficient outcome.
The InP reclaim process allows us to recycle wafers without sacrificing their efficiency and quality. By removing old layers and preparing the substrate for reuse, you can create a new wafer with properties that satisfy most requirements. In addition to saving money, this benefits the environment by reducing waste.
However, InP reclaim wafers do have some limitations. It’s important to understand their properties in detail to know whether or not they can be a solution to reducing costs for your next project. If you’re still unsure, Wafer World can help. Reach out for more information!
