Systems and methods for controlling temperatures of process tools

• US 6,783,080 B2
• Filed: 05/16/2003
• Issued: 08/31/2004
• Est. Priority Date: 05/16/2002
• Status: Expired due to Term

• Current Assignee: B/E Aerospace, Inc. (Rtx Corporation)
• Original Assignee: Advanced Thermal Sciences Corporation (Rtx Corporation)
• Inventors: Antoniou, Matthew, Christofferson, Bryan
• Primary Examiner(s): NORMAN, MARC E
• Application Number:
  US10/439,299
• Publication Number:
  US 20040035851A1
• Time in Patent Office: 473 Days
• Field of Search: 236/78.D, 236/47, 236/91.R, 236/91.D, 236/93.R, 236/97, 236/12.12, 165/61, 165/263, 165/264, 700/29, 700/42, 340/606
• US Class Current: 236/78.00D
• CPC Class Codes: G05D 23/1917 using digital means

Abstract

A system and method for controlling a critical process variable, such as the temperature of one or more temperature control units for cluster tools in a semiconductor fabrication facility, uses dual interrelated PID) algorithms for interrelated but at times separate control of heating capabilities. The temperature control units operate with high power efficiency, because no heating energy is expended during cooling and non-transition modes. When approaching a temperature threshold, however, the heating algorithm is reinstated just long enough to provide minimum undershoot and enabling precise, low per consuming, steady state control at ±0.1° C., minimizing undershoot and enabling precise steady state control at ±0.1° C.

Claims

1. A method for adaptively controlling the operation of a temperature control system having both heating and cooling capabilities and different operational modes to adjust the temperature of a thermal transfer fluid supplied to a process tool, the system receiving a cooling medium of inconstant temperatures and monitoring the adjusted temperature, the method comprising the steps of:

establishing separate but dual proportional, integral and derivative (PID) control algorithms for the heating and cooling capabilities;

loading in initial PID values for the operational mode that is chosen;

operating the system in accordance with the algorithm to adjust the temperature toward a target value;

monitoring the adjusted temperatures and its variations with time;

increasing the integral values of both PID algorithms if the adjusted temperature oscillates and

loading different bias values into the PID calculation in response to temperature variations in the cooling medium.

2. The method as set forth in claim 1 above, further including the steps of resetting/suspending the use of the heating capability by resetting the heating PID during cooling and non-transitional periods when the adjusted process temperature is more than a selected amount above the bias offset setpoint level selected for the operational mode.

3. The method as set forth in claim 2 above, the heating PID is reinstated by loading in a variable bias-value when the adjusted bias offset setpoint is more than about 2°

C. less than the setpoint level.

4. The method as set forth in claim 3 above, wherein the temperature control system circulates the thermal transfer mass with minimal fluid storage in the loops, and maintains the fluid and the process tool within ±

1°

C. of selected levels in steady state operation while transitioning to a different level with minimal delay.

5. The method of claim 1 above, wherein the temperature control system comprises at least two temperature control units operating independently in individual operation modes, and wherein the method further comprises establishing PID algorithms for each of the temperature control units.

6. The method of claim 1 above, wherein the temperature control units include at least two of different types and wherein the method further comprises establishing independent dual PID algorithms for each different temperature control unit.

7. A control system for operating from one to a number of temperature control units each having both heating and cooling capability to regulate the temperature of a thermal transfer fluid circulating through an associated process tool, comprising:

a data processor unit having interior EEPROM circuits storing invariant portions of control algorithms for the temperature control units;

a selectively variable external EEPROM associated with the internal EEPROM to provide therewith adaptive dual PID algorithm for enabling the data processor to command the heating and cooling capabilities of the temperature control units;

a data input device including a display, coupled to the data processor, for providing thereto initial perspective, integral and derivative setpoint values for the dual control algorithms for each of the temperature control units;

temperature sensing devices providing thermal transfer fluid temperature readings for each of the circulating fluids to the data processor;

circuits for detachably coupling the data processor to the individual temperature control units to enable removal and replacement of individual control units without affecting operation of other individual control units, and

the data processor including progress means for displaying a range of status indications as to system operations.

8. The control system as set forth in claim 7 above, wherein the data processor is configured with modular inputs and outputs, such that input units can be changed as changes are made to the temperature control units, and wherein the system includes low voltage switching circuits interconnected between the data processor and the power connections to the individual temperature control units for allowing safe removal of power connections.

9. The control system as set forth in claim 8 above, wherein the data processor unit includes performance monitoring software generating data for the display of the input device, including temperature set points, actual temperatures, and percentage of heating and cooling, flow rate, reservoir pressure and pump pressure.

10. A control system as set forth in claim 9 above, wherein the data processor includes software for indicating alarm conditions, software for providing safety commands in the event of non-normal conditions, and instructional commands to enable an operator to set up and check the system.

11. A control system as set forth in claim 7 above wherein the process tool system has command capability for signaling desired operating levels for some or more process tools, and the data process includes communication circuits for alternatively selecting commands from the process tool system.

12. The method of controlling the temperature of a thermal transfer fluid passing through a thermal control unit having both heating and cooling capabilities so as to provide, with relatively low power consumption, precisely controlled steady state operation at a target temperature and rapid transitions between temperature levels, comprising the steps of:

1) employing systematic PID loop control sequences for the heating and cooling capabilities;

2) choosing initial set point values for approaching a target temperature value using the PID loop control sequences;

3) monitoring actual fluid temperatures to accumulate historical changes in approaching the target value;

4) changing set point values for the integral term in accordance with the historical performance;

5) terminating usage of the heating capability during those times when the temperature of the thermal transfer fluid is higher than a first predetermined amount relative to the target value or the operational mode is transitioning to a lower temperature,

6) Resuming dual PID control for temperatures below the bias offset setpoint, and

7) Suspending heating PID control for temperatures above the bias offset setpoint.

13. A method as set forth in claim 12 above, wherein the method further includes the step of measuring the amount of error between the set point and the target value over predetermined time intervals, and resetting the integral bias term in accordance with the magnitude of the error over such intervals.

14. The method as set forth in claim 13 above, wherein the proportional term in the PID system comprises the product of error amplitude times gain, wherein the integral term comprises the summation of error signals over a period of time multiplied by gain and wherein the derivative term comprises the rate of change of the error signal with time multiplied by gain.

15. The method as set forth in claim 14 above, wherein the first predetermined amount is greater than about 1°

C. than the target value and wherein the second predetermined amount is about 0.2°

C. or less than the target value, and wherein the method operates to provide a steady state operation with a temperature variation of ±

0.1°

C.

16. An expandable system for controlling the temperature of operation of more than one process tool, with independent flows of thermal transfer fluid comprising:

at least two temperature control units, each circulating thermal transfer fluid through a different process tool in response command signals, the temperature control units having heating and cooling capabilities that are separately controllable;

a central processor providing command signals to control the separate heating and cooling capabilities of all the temperature control units;

instrumentation providing inputs to the central processor indicative of the temperature levels of thermal transfer fluid flows at the process tools;

programmable logic circuits at the central processor and functioning with the processor to provide at least two concurrent program sequences, one for heating and one for cooling, for each thermal control unit, and

and software operable with the central processor for varying the program sequences in accordance with real time variations in the thermal transfer fluid temperatures.

17. A system as set forth in claim 16 above, wherein the system operates to maintain each process tool at selected temperatures at different levels, with minimum transition times between temperature levels and with steady state levels being maintained with high precision, comprising in addition sensors associated with the circulating thermal transfer fluid for providing signals representing the temperature levels thereof to the central processor, with the programmable logic circuits and central processor providing separate heating and cooling commands in accordance with proportional, integral and derivative terms.

18. The system as set forth in claim 17 above, wherein the control processor includes a modular expandable array of transducer devices responsive separately to operative conditions in the associated thermal control units.

19. The system as set forth in claim 18 above, including in addition a touch screen display and interface coupled to the central processor, and the central processor includes a data storage system retaining initial set point values for the control loops, selectable by use of the touch screen and display.

20. A system as set forth in claim 19 above, wherein said system programming detects marginal conditions by comparing sensed values to preset limits.