Etching Semiconductor Wafers Relies On Tight Temperature Control

kapton flexible heater

The Challenge
All semi-conductor wafers, as part of their micro-fabrication, must undergo an etching process which chemically removes layers from the surface of a wafer during manufacturing. Since the depth of these etched cavities are extremely critical, the etch rate must be precisely controlled through chemistry, time, and tight temperature control. Our customer, a manufacturer of semi-conductor wafers, had a new etchant which relied on a higher than normal temperature control profile. In addition, this had to be done to the top layer of a multilayer structure while preserving the other masked layers. It was critical for this manufacturer to have superior control in this new temperature sensitive etching chemistry.

The Solution
The Chromalox team evaluated the equipment and pumping systems for the customer's etching process to determine load characteristics, and thermal characteristics, equipment insulation, exposed surface area, etc. We then designed Kapton® controlled heat profile heaters complete with sensors to strategic places on the equipment based on FEA analysis, process/equipment monitoring, optimization, and thermal sub-assemblies controls. Their controller was updated (with software programming) for closed loop sensing/control based on the thermal behavior in particular points of the etching process equipment.

The Benefits
Due to the enhanced temperature control of their new etching process they customer realized a 68% decrease in rejects due to a reduction in temperature related undercut. Before, this undercut manifest itself as isotropic (sloping walls) as opposed to the current desirable anisotopic profile (straight wall). The customer now has unparalleled wet-etching capability in both the horizontal and vertical direction to precisely chemically mill the cavities down to 2 mils. Pre-bonding to the substrate was also a convenience and cost savings to the customer. This is a typical example of how Chromalox offers new innovative world class cost saving solutions to exceed customer needs