Frequently Asked Questions
Dynamic Temperature Control Systems are capable of rapid changes in temperature to correspond to changes in wafer processing temperatures. With dynamic systems, the temperature of the fluid supplied to the chamber is managed to compensate for changing processing conditions, so the temperature of the wafer chuck can be maintained in a narrow range.
These systems have the ability to sense chamber temperature drifts and compensate faster and more precisely than a conventional (remotely located) static compressor-based systems.
A typical compressor-based or static cooling system receives a temperature set-point from the host tool. The system maintains this temperature set-point in its reservoir by cycling the compressor and heater on and off. The fluid is pumped to the chamber at the set-point temperature from its remote location. Heat losses between the unit and chamber are substantial and vary from installation to installation. As a result, wafer chuck temperatures will fluctuate because the static system is only capable of maintaining a constant temperature in its reservoir.
True Dynamic Temperature Control can only be achieved when all five (5) of the following system design and installation requirements are met:
- fluid set-point temperature is controlled at the return loop
- very small fluid reservoir and process fluid-loop volume (< 1 US GA.)
- heating / cooling elements with rapid ramp rates
- short hose lengths from the POU module to the chamber
- maximized process fluid flow rate
(Therefore, installing a static unit next to a chamber will not enable it to provide dynamic temperature control)
Dynamic Temperature Control maintains temperature set-point in real time. This allows our customers the opportunity to optimize each process step with tailored temperature set-points.
The ability to manipulate temperature for various stages of the process enables process flexibility and eliminates temperature-induced CD variability.
There is also evidence of increases in yield due to temperature stability.
Etch is a chemical process and temperature is a catalyst that impacts the etch process. With stable temperature on the wafer, we have stable etch profiles and better control of polymer build-up. As temperature changes, the rate of etch can change outside the desired process specifications.
Both main etch temperature drift and wafer to wafer temperature drift are not desirable and can result in an unacceptable temperature-induced profile. Temperature drift within a batch of 1, 10 or 30 "boats" describes wafer-to-wafer drift.
Delta temperature change on the wafer is a characteristic of the chuck. Every chuck has an inherent temperature distribution across the surface that is unique to its design.
The temperature distribution across the wafer reflects the temperature distribution of the chuck. For example, the edge temperature may differ from the center temperature. POU will not eliminate this problem but will maintain temperature within the design parameters of the chuck.
The LAUDA-Noah POU has one moving part: a magnetically-coupled pump. This seal-less pump minimizes the risk of leaks, and is designed for continuous operation for the service life of the POU module, which is more than 4 years.
POU also incorporates solid-state Peltier devices, which provide both heating and cooling capacity to the system. These devices have no moving parts and temperature control is achieved electrically without the use of greenhouse gases. Consequently, LAUDA-Noah POU products are highly reliable, environmentally desirable, costing the end-user less to own and operate.
Compressor-based systems have large internal volumes, frequent leaks and oversized unreliable pumps, all of which require substantial routine maintenance.
Etch applications using LAUDA-Noah POU systems generally operate at <20% of total system capacity, and under these circumstances consumes much less power when compared to a conventional compressor-based system. The LAUDA-Noah POU utilizes Peltier devices, which both heat and cool. Since the heat pump capacity is directly controlled by the applied power, energy consumption is based on cooling or heating demand. By applying power on demand, the POU system can also minimize the load of the facility water system, and saves the energy going into a cooling tower. Oxide etch typically releases heat, and metal etch consumes heat. Therefore, the LAUDA-Noah POU is uniquely capable of active energy recycling by heating and cooling with Peltier devices.
Conventional chillers have oversized pumps designed to manage ~6X more process fluid than a LAUDA-Noah POU while being installed in the sub-fab. These systems also incorporate compressors that are always running regardless of the load. This combination equates to an average power consumption of >2.2kW, which is more than 50% higher than a LAUDA-Noah POU system.
The initial purchase price of a LAUDA-Noah POU system can be higher than a compressor system, however the overall Cost-of-Ownership is always lower. The LAUDA-Noah POU does not require costly PM's, requires fewer spares since it is more reliable, consumes much less power, all while occupying less space with the smallest footprint in the industry.
Upon installation, conventional compressor-based systems require 6-10 gallons of process fluid per loop. The LAUDA-Noah POU system only requires less than 1 gallon of process fluid, thus reducing the overall (fluid) installation cost.
Our customers demand lower Cost-of-Ownership. They have a critical need to solve conventional chiller reliability problems. These problems include frequent leaks that lead to excessive fluid consumption, frequent compressor maintenance, large footprint, short-lived deteriorating pumps, and poor support by their chiller suppliers. The mere size of a conventional chiller can prohibit on-site service, support, and repair without adversely affecting chamber up-time.
Recently, a survey was conducted at several leading IDM's concerning the most important attributes of a chiller/supplier. The top five (5) results of that survey are:
- Proven track record
- Refurbish capability
- Redesign capability
- Energy Efficiency
The standard warranty is one (1) year and the current MTBF is approximately 4 years.
LAUDA-Noah offers start-up and/or turn-key installation service with each system shipped. These services also include ad-hoc system operational training during the installation. However, the LAUDA-Noah POU system is user-friendly and within the capability of most users. Customers can also receive formal training on-site, or at any LAUDA-Noah facility.