Thermal Processing Module Research Articles

Equipment Design and Control of Advanced Thermal-Processing Module in Lithography

A programmable multizone thermal-processing module is developed to achieve wafer-temperature uniformity during the thermal-cycling process in lithography. The bake and chill steps are conducted sequentially within the same module without any substrate movement. An array of thermoelectric devices (TEDs) is used to provide a distributed heating to the substrate for uniformity and transient temperature control. The TEDs also provide active cooling for chilling the substrate to a temperature suitable for subsequent processing steps. This design is an improvement of a previous work, eliminating the need of a mica heater. The system is designed via detailed modeling and simulations based on first-principle heat-transfer analysis. Experimental results on the prototype demonstrate about ±0.4°C spatial uniformity during the entire thermal cycle.

Integrated bake/chill system for across-wafer temperature uniformity control in photoresist processing

An integrated bake/chill thermal processing module is developed and experimentally evaluated to achieve spatial temperature uniformity of a silicon wafer throughout the entire processing temperature cycle of ramp, hold, and quench in lithography. The module uses a set of thermoelectric devices which are used to provide distributed heating and cooling to the substrate for uniformity and transient temperature control. The experimental results demonstrate that the wafer spatial temperature uniformity is within ±0.3 and ±0.1°C during transient and steady-state thermal processing, respectively.

A heater plate assisted bake/chill system for photoresist processing in photolithography

A thermal processing module, which consists of a dense distribution of multivariate controlled heat/chill elements, is developed to achieve temperature uniformity of a silicon wafer throughout the processing temperature cycle of ramp, hold and quench in microlithography. In the proposed unit, the bake and chill steps are conducted sequentially within the same module without any substrate movement. The unit includes two heating sources. The first is a mica heater which serves as the dominant means for heat transfer. The second is a set of thermoelectric devices (TEDs) which are used to provide a distributed amount of heat to the substrate for uniformity and transient temperature control. The TEDs also provide active cooling for chilling the substrate to a temperature suitable for subsequent processing steps. The feasibility of a practical system is demonstrated via detailed modeling and simulations based on first principle heat transfer analysis.

Temperature Cycling for Photoresist Processing

A programmable multizone thermal processing module together with a model-based feedback control method are developed to achieve temperature uniformity of a silicon wafer throughout the processing temperature cycle of ramp, hold and quench in post-exposure bake (PEB) step of lithography. The module comprises of numerous small thermoelectric devices (TEDs) capable of precise substrate spatial temperature control. The detailed thermal modeling of the module is presented and the simulation results are compared with the experimental results to verify its feasibility. A model-based PID feedback control method is employed to minimize temperature nonuniformity across the wafer. With the method, temperature nonuniformity could be controlled less than 0.1°C throughout the entire thermal cycle. Advanced applications are enabled due to the proposed system.

Programmable Thermal Processing Module for Semiconductor Substrates

This paper proposes the use of multivariable control methods to design a thermal platform for processing semiconductor substrates (semiconductor wafers and/or quartz reticles for photomasks) that far exceeds conventional methods in performance and flexibility. A thermal processing module for lithography applications is presented and demonstrated. The module comprises numerous (49) small, disjoint, and independently controlled heating elements capable of precise substrate spatial temperature control. The module also has a low thermal mass that allows for rapid element temperature variation, and hence transient control of substrate temperature. In addition, the module integrates active baking and chilling in a single unit, eliminating the need for substrate transfer between separate baking and chilling units and the temperature control limitations associated with it. The module is compared to a current state-of-the-art commercial system and shown to provide a factor of two improvement in transient temperature uniformity control on a six in quartz reticle using "hand-tuned" control techniques. A linear-quadratic regulator (LQR) feedback controller is also demonstrated and shown to provide peak-to-peak reticle temperature uniformity that does not exceed 1.6/spl deg/C throughout the transient bake.