Improving Wafer Circuit Pattern Quality In Semiconductor Manufacturing

Why Choose Dpstar

Types Of Semiconductor Environments

Whether you are working in design or quality in a Semiconductor application, you need a partner who understands your challenges and knows how to help you achieve your goals. Dpstar supports customers within a variety of Semiconductor environments and applications. Our customers in the semiconductor industry are usually looking for environmental control in one of these areas:

Temperature

Semiconductors have a negative temperature coefficient for resistance—this means that conductance increases and resistance decreases when heated. Heat applied to semiconductor material causes the separation of the outermost electrons from the atomic nucleus of the material compounds due to an increase in energy. These free electrons become conductive. As the number of free electrons increases, there will be an associated drop in resistance. Maintaining temperatures within a specific range is necessary to facilitate the proper function of electronic devices that operate using semiconductors. Tightly regulated temperature control is even more critical in semiconductor manufacturing.

Humidity

The presence of excessive humidity/moisture causes corrosion of ‘circuit points’, condensation on a microchip’s circuit surface and improper adhesion of photoresists, causing operational failure of the semiconductor assembly process. What can happen when RH is too high? As an example, in the photolithographic area, there is a risk of degradation, as photoresist processes have very tight parameters and are highly sensitivity to humidity. When RH is too high, the risk of particle adhesion to substances such as silicon increases. The ability to manage resist stability, adhesion and dimensional precision can be more challenging. Photoresist viscosity can quickly decrease with higher RH, affecting the thickness of the resist film using a fixed coating recipe. Metals can corrode, including equipment, and condensation and water absorption issues can arise when RH is too high. It can intensify water absorption, increasing resist swelling after a bake cycle. When developer solvents are sprayed onto a wafer surface, the solvents evaporate quickly, cooling the wafer enough to condense moisture from the air, potentially causing a change in the developer characteristics and absorption onto the semiconductor wafers. Higher RH levels can foster the growth of various biological contaminants. Bacteria, viruses, mold can spread and multiply when relative humidity is greater than 60 percent. When RH is too low, the build-up of static electrical charge and the consequent discharges can be detrimental to semiconductor environments.

Pressure

When considering dewpoint measurement, a change in pressure also changes the dewpoint. The increase in overall pressure also increases water vapor pressure. As a result, since water vapor pressure is directly related to dewpoint, the dewpoint increases (becomes wetter) as the overall pressure increases. Similarly, the dewpoint decreases as the overall pressure declines (becomes drier). Given a gas mixture that is composed of several pure gas components, the pressure of the gas is the sum of the partial pressures of the component gases. At any given temperature there is an upper limit as to how much water vapor a gas can contain, called the saturation vapor pressure (SVP).