From Particle Control to Yield Improvement in Epitaxy Processes

Particles as small as tiny microscopic pieces can ruin the wafers in Epitaxy growth production and therefore ruin your yield. Even an invisible particle inside the reactor can make the defects on the wafer such that it doesn't pass. Therefore controlling particles is a crucial step to a stable and good quality product.

Many of the particle problem solutions are based on broken parts, bad cleaning process or improper handling of the parts. It can make an amazing difference to the yield if the problem is solved by fixing these trivial things.

How Surface Roughness Causes Particle Issues in Epitaxy Production

The problem that you have at the moment is a rough surface is actually emitting particles due to high temperature processing.

The small scratches that can exist on parts for example when subjected to repetitive temperature cycles, can eventually develop in to microscopic cracks, and small chunks of the material begin to travel around the inside of the vacuum chamber. It is these particles that fall onto the wafers and causes defects.

The most commonly seen problem like this in Graphite parts is where the graphite is no longer effectively coated due to wear, when the protective coating wears off, it can exposes the rough graphite below and that will then shed particles more readily.

Rough surfaces will affect the gas flow within the reactor, which will easily cause stray particles to make their way into the processing area.

Routine checks will find surfaces in this state before they become so bad, if components were re-coated or polished this will help maintain the components lifespan. Care taken when handling components at this stage would also minimize scratching that might become particle sources later on.

Gradual and careful heating and cooling cycles will place less stress on the coatings and in turn, the surface below.

Ensuring that all surfaces stay smooth, has in the past, improved many wafer processing fabs in their battle with particles, and therefore increased their wafer yield.

Advanced CVD SiC Coating Technologies for Cleaner Reactor Chambers

The Cvd sic coating , as a chemical resistant, hard and smooth layer, prevent particle generated during the reactor operation and thus to prevent particles from polluting wafers.

In old process, the thickness of the coating was non-uniform and the corners and complicated shaped areas tended to be wear off easily after heating, generating particles and contaminating the wafers.

Modern CVD SiC process and Epitaxial growth semiconductor try to get a uniformity film on the surface by controlling the temperature and gas flow carefully, producing a more stable and durable film with less possibility to be wear off and particles. Some factories found fewer particles in the reactor after upgrading the coating system. Their coating life is longer and the particles were reduced during the whole process.

Smoothness of the film is also one of the parameters which are critical for preventing particles and contaminations. Fine polish the film surface. This will reduce small pit on surface where the particle or residue will collect. Furthermore, the smooth surface of the coating can also prevent the accumulation of particle around the feature of the reactor which may also affect the gas flow and can help particles away from wafers.

Monitor the coating color, surface structure and thickness is necessary. If you find a color change, the film will lose its property, the surface is getting coarser, and if the coating thickness are getting thinner, maybe it is time to replace the spare parts.

Surface Treatment Techniques for High-Performance Epitaxial Parts

This is very important in increasing component life and reducing particle formation. If the surface is not prepared correctly the coating will have a weak bond and be liable to flake off when used in service.

This involves removing dust, oil and machining marks, before application of the coating and Epitaxial growth in ic fabrication . There are other additional surface preparations as well. Activation will result in a more effective coating, increasing it's resistance to temperature and cycling.

Surface texture is important; if the surface is too rough the coating can not adequately 'hold on', or too smooth and it has a weak bond. When parts are removed from manufacturing they must be handled very carefully as dust or oil will stick to the surface from hands or tools.

Some production lines have fixed their particle problems by only focusing on their surface preparation, and others treat the surface using plasma to reduce micro contamination.

Improving Yield Stability in AIXTRON and Veeco EPIK Platforms

Wafer yield stability is maintained with cleanliness of the reactor and its components. The most prevalent problem is the post-cleaning scenario. Even the smallest bit of leftover residual can break off within the chamber during processing to generate particles, ultimately forming wafer defects.

A second problem is with wear and age on coated graphite components. Even though there is no visible problem on the coated graphite after many cycles, micro cracks can be forming under the coating which will produce particles at the time of operation. Gas flow can become erratic as surfaces age and rough over time which will cause uneven deposition or entrain particles into the wafer stream.

In an effort to improve stability many factories use a component life tracker. They can identify how long parts have been operating, estimate when the part needs to be replaced, and take preventative measures to improve yield. While clean is good, overly aggressive cleaning can degrade protective coatings and result in surface roughening. In general, diligent preventative maintenance and proper replacement schedules can improve wafer yield.

Failure Analysis of Contaminated High-Purity Graphite Components

Pure graphite parts are made to withstand high temperatures, but a contamination can still lead to failure in the long run.

Contamination can happen through contact contamination when working with the material. If the tool that works with graphite, the glove or the area where graphite is kept are dirty, the dust might appear on the surface and then during the high temperature process will react with graphite. Also, during the high temperature treatment inside the small pores of the graphite chemical traces will remain inside. Those compounds are later expanded and/or reacting and release the particles.

As an example: During one production run the defects rate on the wafer had been steadily increasing in time during weeks. When checking it appeared the contamination inside the graphite liners that corresponded to location of the particle on the wafer.Thermal cycling makes the problem worse. Each heat-up and cool-down puts stress on contaminated areas. Clean graphite usually handles this well, but contaminated zones expand at different rates, which slowly creates micro-cracks.

There are a few practical steps to reduce this risk. Careful storage in clean, sealed containers helps prevent early contamination. Handling tools should stay dedicated for high-purity parts only. During maintenance, gentle cleaning methods work better than strong chemical or abrasive steps, since rough treatment can open new pores on the surface.

Tracking part history also helps. When a component has gone through many cycles or multiple cleaning steps, it is useful to inspect it more closely before reuse. Small changes in surface color or texture can give early signs of deeper contamination.

Over time, controlling these small details helps keep graphite parts stable and reduces unexpected particle events inside epitaxy systems.