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MiRC >> Training >> Text Instructions

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Lindberg Furnaces

The Lindberg furnaces are used for curing polymers, sintering, and growing oxides and nitrides on silicon wafers.

Overview of Controls

Gas Flow Timers These timers stop the flow to the flow meters. The maximum time is 12 hours. The orientation of the timers match the orientation of the tubes (ie tube 1 is the top right tube and the top right timer). Note: the timer must be turned to a minimum of 2 hours to function correctly and gas will NOT FLOW if the timer is at 0.
	Flow meters The flow meter valves are located at the bottom of the flow meters. Each flow meter has two valves. The cutoff valve is the valve closest to the flow meter. The handle at a 90 degree angle from the flow meter is closed and the handle parallel with the flow meter is open. The lower valve is the needle valve (round handle) which controls the flow into the flow meter. Turning the round handle clockwise is opening the valve. The needle valve should never be turned all the way open or closed. Over tightening of the valve could damage it. If you want to turn off the gas flow temporarily, turn off the the cutoff valve. The far left flow meter is for tube 4, the middle one is for tube 2 and the right meter is for tube 1. Tube 3 is controlled by the mass flow controller located on the wall.
3-Way valve The 3-way valve controls which gas flows to tube 2. The narrow pointed end of the handle points to the gas being used. In the picture to the left, nitrogen is the selected gas. When you are finished please return the valve to off.
	Temperature Controls The furnace temperature is controlled by a programmable temperature controller. There is one controller for each furnace zone.
Temperature Controller Each furnace zone heater is controller by a programmable temperature controller. The controller allows the programming of several process steps.

Operating Instructions

To operate the furnaces, you must basically perform the following steps:

1. Set appropriate atmosphere
2. Load furnace
3. Set temperature program
4. Run
5. End run

Setting atmosphere

1. Flow rates for the three furnaces are set by the flow controllers mounted between the tubes. The round, black knob sets the flow. The narrow black lever is a shutoff valve for the gas line.
2. Tube #1 has a flow timer installed. Set the timer to the length of your run. This will prevent the waste of gas in the system when the tube sits idle at the end of the run.
3. Ensure the gas line is connected to the furnace and that gas is flowing either by sound, feel, or bubbling water (when using the wet oxidation bubbler).

Load Furnace

1. Place samples in quartz boat. Full wafers can be loaded vertically. Partial pieces may need to be placed on horizontal slides in the boat. Use only the special oxidation boats (located in the N₂ boxes) for wafer oxidation to avoid contamination.
2. Remove the cap from the end of the tube and place the boat just inside the opening.
3. Use the quartz rod to carefully push the boat to the middle of the furnace tube.
4. Put the cap back on the end of the tube. Do not force it.

Set Temperature Program

(Note that two of the temperature controllers on furnace 3 are different from the one described here. See the instructions for the 847 controllers below for instructions for programming these controllers.)

Programming is done using three settings for each part of the program. "Pr1" is the first ramp rate in °C/min, "PL1" is the first set temperature you wish to achieve in °C, and "Pd1" is the delay time at that set temperature in hours. The "1" will increase incrementally as you continue through. Controller boxes correspond to the furnace tubes in the same relative position. To program the controller:

1. Open the black cover below the white arrow keys on the front panel (see diagram) of the central controller to display the "Run/Hold," "REM," and "P" keys.
2. To initiate programming procedure, press the "P" key and hold until "Pr1" is displayed in the program display. The "P" key must be pressed and held for a small time to enter programming mode. You may see "Pnr1" displayed; depress and press the "P" key once to advance to "Pr1." Programming is done using the three elements: "Prn," "PLn," and "Pdn" for each step n.
3. With "Pr1" displayed, press the white arrow keys to set the first desired ramp rate in °C/min. Holding the arrow keys will increase the speed with which numbers change. Both the up and down arrow keys can be used. Ramp rate is sign-independent. Direction will be automatically set by the difference between previous set temperature and current set temperature.
4. Now press the "P" key again to display "PL1." Select the desired set temperature in °C using the arrow keys.
5. Press "P" key again to display "Pd1" and set the delay time in hours at the set temperature using the arrow keys.
6. Press "P" again to display "Pr2." Repeat the steps above for the next process step.
7. To ramp down to room temperature, set "Pln" to 25°C. Set "Pdn" to "END" by pushing the down arrow key until "END" is displayed. You must have "END" to end all programs. You must have an option to set "Prn" to a set ramp rate which the furnace will attempt to keep, or to the setting "SLEEP." "SLEEP" shows when toggling the ramp rate below zero, and tells the controller to allow the furnace to cool by natural convection, however long it takes to the set ending temperature. A sample temperature profile is shown below.
8. Check your program by not touching anything, allowing the controller to return to rest, and pressing "P" as before to check your settings. If you mess up at some point in programming, you can stop, allow controller to return to rest, and hit "P" to begin programming again. You cannot go backwards. Momentarily hitting an arrow key will allow you to check a value without changing it.

Sample Temperature Profile

Run

• To run the program, hit the "Run/Hold" key.
• To hold a program, allowing correction settings, hit "Run/Hold" key, and hit again to return to run.
• To abort the program that is running press the up and down arrows at the same time.

End Run

1. Make sure temperature is about room temperature and program is done. "E" will show, signifying end.
2. Remove boat by reversing loading procedure.
3. If you turned gas on, turn it off now.
4. Leave the furnace as you found it.

Eurotherm 847 Controller Operating Instructions

For use with zone 1 and zone 3 controllers for furnace tube 3.

Programming is done using three settings for each part of the program. "r1" is the first ramp rate in °C/min, "L1" is the first set temperature you wish to achieve in °C, and "d1" is the delay time at that set temperature in minutes. Note that the other controllers use hours.

• To initiate programming procedure, press the "PAR" key and hold until "Prog" is displayed in the program display. The "PAR" key must be pressed and held for a small time to enter programming mode.
• The name of the parameter being changed is displayed on the top of the display. The current setting is displayed on the bottom.
• Pressing "PAR" while in programming mode will cause the controller to display the next parameter. A table showing all of the parameters and their meaning is shown below.
• To change the value of a parameter use the up and down arrow buttons.
• If you do not press any button for about five seconds, or if you press "PAR" repeatedly to cycle past the last variable the controller will exit programming mode.
• If you press "PAR" too many times and accidently go past the variable you want to set you must cycle through all of the variables or wait five seconds to exit programming mode. Then press and hold "PAR" again to reenter programming mode.
• All processes on the 847 controller must have exactly two ramp periods and two dwell periods. At the completion of the second dwell step the controller will return to room temperature. To run a process that looks something like the one below look at the sample values in the table below. If the process needs only one ramp and one dwell step set the second ramp rate (r2) to a high value and the second temperature level (L2) to 22°C.

PAR menu parameters

Parameter	Sample Value	Meaning
Prog		Set to "run" to run program, "hold" to pause program, "idle" to stop program
r1	1	first ramp rate in °C/minute
L1	100	first temperature level in °C
d1	30	first dwell time in minutes
r2	1	second ramp rate in °C/minute
L2	200	second temperature level in °C
d2	60	second dwell time in minutes

Run

• To run the program, set the "Prog" parameter to "run" using the procedure above.
• To hold a program, allowing correction settings, set the "Prog" parameter to "hold" and set it back to "run" to return to run.
• To stop the running program, set the "Prog" parameter to "idle". You may need to manually return the setpoint to room temperature using the arrow buttons.

Revision 4 - 31 March 2000