Duocel® Foam for Semiconductor Applications

 

Duocel Foam in Fluid Flow Devices

 

The semiconductor industry is driving the state of the art in many manufacturing fields and is using new and creative methods to do so. One of the new technologies being used is open-celled metal or ceramic foam materials. Duocel is one such foam which has recently been introduced after being used extensively in the defense industry for years before going public. Duocel is being used to perform a number of critical functions in the manufacturing of integrated circuit chips. A few of these functions are described below:

  • Foam diffuser disks designed for fluid flow control allow sub-micron circuit paths and higher wafer yields through improved etching gas flow and plasma field control.
  • Stiff, lightweight, and stabile structures for precise alignment and rapid motion mechanical processes, especially step and repeat systems.
  • Modulus matching interfaces for ceramic and metallic structures.
  • Compact condensation of by-products and process chemicals for disposal or cycling.
  • Compact and highly efficient heat transfer.

Our technical staff would be pleased to discuss these and any other possible semiconductor applications with you. The description of the first item that follows is provided to illustrate some of the general principles involved.

 

Duocel Foam in Fluid Flow Devices

The processes of dry etching and Chemical Vapor Deposition (CVD) require precise control of gas flows and the ionized plasma field to enable the uniform deposition and removal of materials. Through such precise control, the yield of sub-micron path width chips can be improved greatly. One of our products designed specifically to address these issues is an input gas diffuser disk. The diffuser disk consists of 40 PPI foam which has been compressed to provide an even greater specific surface area. The disk is generally mounted in contact with the upstream of a shower head. In this position, the disk performs four primary functions:

1. Uniform Gas Distribution: Using the high specific area and constant viscosity (flow friction) of gases at low pressures, the disk provides uniform pressure drop and distribution of gasses to all areas of the shower head regardless of turbulence or flow asymmetry in the diffusion chamber.

2. Orifice Flow Stabilization: By acting as a fluid flow straightener, gasses enter all shower head ports in a uniaxial direction with uniform velocity. This uniformity minimizes the chugging, or flutter, which occurs in such orifices as a result of upstream cross flow and turbulence.

3. Plasma Stabilizer: The diffuser disk acts as a grounding plate and flame arrestor, preventing backfiring or arcing of the plasma back up through the shower head and into the diffusion chamber. This arcing can occur as a result of plasma instability and manufacturing irregularities in the shower head. Unfortunately, the arcing not only disrupts the current process, but also damages the shower head, thus increasing the likelihood of further arcing and process disruption. The diffuser disk can inhibit this behavior and stabilize the plasma process.

4. Contamination Filtration and Condensation: While not normally needed in a properly operating system, there have been cases where the disk has served to accumulate particulate and vaporous contamination entering the diffusion chamber due to some type of upstream problem. By providing a fluid flow disruption and a large surface area available for attachment, the contaminants often preferentially attach to the disk. The resulting symptom is a clogged disk and reduced fluid flow, which is usually preferable to the contaminants passing freely into the plasma zone.

 

Depending on the equipment and process details, these functions assume various degrees of importance. The disks are custom designed accordingly to provide appropriate diameter, thickness, pressure drop, and surface area for your specific application. Most diffusers are currently made out of 6101 aluminum alloy, a very pure material which is used regularly in the nuclear power industry because of its lack of high atomic number alloying agents and low residual alloying content. As the concept of foam materials becomes more familiar in the semiconductor industry, vitreous carbon and silicon carbide foams are being introduced to address applications which involve higher temperatures or chemicals incompatible with aluminum as well.

 

While diffusers disks often perform a variety of functions, some applications are targeted just for one or two functions. Large pore, uncompressed foams which are electrically conductive and have low gas flow pressure drops can be used to contain plasma fields while permitting a relatively unimpeded flow of gases. Finer pore foams are occasionally used in process chambers, as they are are in laser chambers as acoustic damping baffles. In this role, the foam attenuates sympathetic sound pulses that can develop depending on chamber characteristics. While more commonly used in gas lasers to stabilize output frequence and yield, high surface area foams doped with catalytic materials are also being examined as a means of artificially biasing the chemical population distribution in process chambers.

 

These are only a few of the applications for open celled foam materials in the semiconductor industry. Our engineers would be pleased to discuss these and any other applications with you and to put our 30 years of experience at your service to solve the most demanding challenges.

Assortment of Duocel Aluminum Foam

 

 

On the left, you can see a variety of Duocel foam applications in the semiconductor industry.

 

From left to right:

CVD/Etch Condensation (2 Items)

Gas Diffuser Disks (5 Items)

Compact Heat Exchangers (3 Items)

Composite Structures (3 Items)

 

If you have any other questions or would like more information, please contact us.

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