At Glew Engineering Consulting, our team has expertise in computer aided design (CAD), electronic design automation (EDA), and finite element analysis (FEA) modeling. Our FEA capability includes elite abilities in stress analysis, radiation, and multiphysics modeling.
Among our specialties are Semiconductor technology, process tools and chambers, and hold extensive knowledge in the design, manufacturing, and implementation of these machineries. Requiring extreme conditions, high precision, and advanced materials, semiconductor process chambers must be built to specifications sufficient to function safely for the people working around the chamber, as well as for the protection of the equipment itself.
FEA allows for comprehensive modeling of the chamber’s integrity during testing conditions. The FEA model serves as a virtual experiment that allows reduction in prototype cost and testing. An accurate model can reduce the costly repercussions of an incorrectly designed system. Not only does the FEA model provide a useful tool in validating a design, but it can also provide a platform for motivating design improvements and innovations once the product has graduated from beta phase and even after the product is released to market. FEA can help with continuous improvement, as well as the next generation or innovation.
Specifically in the design of a semiconductor chamber, FEA can be done to test the structural stability of the quartz dome cover, and test the conduction, convection, and radiation of heat throughout the chamber when operating temperatures are reached. Cooling channels inserted in the stainless steel body and clamp ring can be iteratively designed to optimize the cooling of the system to safe conditions for all materials. One particular point of failure that can occur is at the interface with o-rings securing the quartz dome within its stainless steel frame. With a steady-state temperature analysis, the conditions at the points along the o-ring can be investigated precisely, and recommendations can be made for modification of the design.
In addition to normal operation, emergency situations must be accounted for in the safe design of a semiconductor chamber. Transient temperature analysis can be performed to understand how the system behaves in case of an emergency power shutdown, when chamber cooling may be significantly reduced, increasing the risk of heat damage to the system.
Our main software tools include Autodesk Simulation (Algor)(TM), Inventor(TM), and Mathematica(TM).
The chamber analysis below is for a chamber in excess of 700 C. The dominant heat transfer mechanism is radiation. There are channels with cooling water, and o-rings to seal the vacuum chamber. The cooling fluid must be kept from excessing heat, otherwise it will over pressurize the chamber and other problems will occur in the cooling loop. The o-rings are elastomer, and can't be subjected to excessive heat. The analysis must show how hot certain parts of the chamber become.
The chamber
Figure 1: Chamber blow out.
Figure 2: Chamber section view.
FEA as virtual laboratory
FEA analysis results of a semiconductor chamber before cooling channel revision. The analysis showed temperatures are too high for the material to withstand the conditions. A redesign and subsequent FEA analysis showed that the thermal objectives could be achieved.
Figure 3: Chamber Thermal Results
Finite Element Analysis (FEA)
A finite element analysis of a pipe as the pipe restraint is tightened shows how the stresses develop in a pipe. This was a mechanical event simulation (MES), in which we were able to watch the stresses grow as the clamp tightened. The uni-strut is shown, but the pipe hangers are hidden for ease of viewing. This analysis was performed without heating. Other analysis were performed with heating, and the results compared.
The first figure shows the distance that the clamp was tightened to induce the stresses, represented by the motion of a node in the matrix. The second figure shows the stresses that are induced after the clamp was tightened.
An important aspect in stress analysis is to understand when a part is under compressive or tensile stress. Some materials have different properties or strength in compression or tension. Most know that concrete has reinforcing bars, re-bar. The reason is that concrete is strong in compression, but not tension. The Romans understood the strength of a dome which keeps most of itself in compression. Materials that are isotropic have the same properties in all directions, and those that do not are anisotropic. Another example of this phenomenon are the class of materials known as polymers.
Below is an example of a semiconductor process chamber, shown in general form so as to avoid confidentiality concerns.
Figure 1: Exploded view of chamber.
Figure 2: A partial sectional view with some components hidden: