Process Guidelines rev. 1 (1063229), страница 2
Текст из файла (страница 2)
Make appropriate arrangements if alarge block of time is needed.3.2 Vacuum Hotplates:- Cleanliness of the hotplates requires cooperation from all users. The hotplatesbecome dirty and sticky with photoresist from users who do not follow properspinning, handling, or edge-bead removal processes.- Allowing photoresist to collect on the surface of the hotplate will result in unevencontact with the hotplate, and consequently, uneven baking on the surface ofyour wafers as well as everyone else’s.- Many CNTech processes involve a hard-contact bake, thus, all three hotplates-have vacuum and nitrogen supply. A hard contact bake allows the substrate tobe held in intimate thermal contact by vacuum ports in the chuck.
Thus ensuringbake uniformity.There are three vacuum hotplates in the CNTech cleanroom. Two are locatedwithin the fume hood (the orange manual hotplate and the silver programmable8Basic Photoresist Processing Techniqueshotplate) and the third (silver manual hotplate) is on a stainless steel table next tothe SVG wafer track system.- The temperature reading on the hotplate controller differs slightly from thetemperature on the surface of your wafer.
For the most accurate temperaturesetting on the wafer surface, please consult the Appendix. The chart is alsoposted above the fume hood.3.2.1 The Orange Hotplate:Figure 2: Orange Manual Hotplate located inside the Fume Hood- The orange hotplate contains a microprocessor-driven three-mode (PID),temperature controller that has a range from 30° to 300°C.
The maximumsubstrate size is 6” round. Do not set temperatures over 200°C unless youconsult with CNTech staff.- The panel displays the current temperature of the chuck at all times, exceptwhen changing the set point as detailed below.- Vacuum adjustments can also be made for different wafer sizes. It is locatedbetween the orange housing panel and the hotplate surface. The square dialturns and the number of die marks indicates different settings.9Basic Photoresist Processing Techniques- Keyboard Functions:o SP1/NEXT Used in conjunction with the UP ARROW and DOWN ARROWkeys to alter the set point of the controller.o UP ARROW Use this key in conjunction with the SP1/NEXT key to alter the setpoint (desired temperature setting) of the controller. Depressingthis key while holding down the SP1/NEXT key raises the set point.o DOWN ARROW This key is the inverse function of the UP ARROW key.Depressing this key while holding down the SP1/NEXT key lowersthe set point.o SP2/RETURN Used for calibration and tuning the temperature controller duringmanufacturing.
Will not be used by the operator; do not touchthis button.- Control Switches:o The front panel contains two toggle switches for controlling the nitrogenand vacuum flow.o Each switch has two “ON” positions. In the up direction, the switches aremomentary (they automatically return to the center “OFF” position whenreleased). In the down direction, the switches remain “ON” until turnedoff.3.2.1.1 Setting Bake Temperature:1. Press and hold the SP1/NEXT key.
This will display the current set point.2. While holding the SP1/NEXT key, use the arrow keys to increase or decreasethe set point. After holding an arrow key for several seconds, the display willswitch to a high-speed change mode to minimize the time needed to makelarge adjustments in the set point.3. When the display nears the desired set point, release the arrow key, andpress it again to return to the normal-speed change mode. Make any fine setpoint adjustments.4. Allow the hotplate to equilibrate.5. Adjust the vacuum setting for you wafer size on the side of the hotplate.10Basic Photoresist Processing Techniques3.2.2 The Silver Manual Hotplate:Figure 3: The Silver Manual Hotplate located against the back wall of the Process Cleanroom- The Silver Manual Hotplate’s control setting slightly differs from the OrangeHotplate.
To change the set point temperature, press the INDEX key until thelower display panel reads SP1. Use the up and down arrows to adjust thetemperature. Press the ENTER key to store your temperature.- The Silver Manual Hotplate has a Wafer Size Setting (silver knob in Fig. 4) forvacuum flow located on the front of the control panel. You can select 75, 100,125, 150 mm (3, 4, 5, and 6 in.) wafer sizes.11Basic Photoresist Processing Techniques3.2.3 The Silver Programmable Hotplate (CEE 1100):Figure 4: The Silver Programmable Hotplate is found inside the fume hood.- The CEE 1100 is also PID microprocessor controlled with a maximumtemperature of 300°C with a 1.0°C resolution. Maximum substrate size is a 6”round wafer (150mm).- The hotplate is capable of storing up to 10 user programs containing presetvalues for bake temperature, bake time, and bake method (proximity, softcontact, and hard-contact).- Several programs have already been set up for commonly used resist PAB andPEB.
Consult the list posted on the hotplate for program numbers.- To use in simple vacuum/nitrogen toggle mode (like the other two hotplates),press the DIAG key. Press 0 or 1 for proximity (nitrogen purge) or vacuum. Tochange from vacuum to proximity (or vice versa) you must hit the DIAG keyagain to return to the option menu.- To set the vacuum diameter for you wafer size, press the OPT key and enteryour wafer size in millimeters (mm).- If you wish to set up your own user program, please contact Janice Eddington formore information.12Basic Photoresist Processing TechniquesPart 4: Coating SamplesGeneral Comments:Understand your process parameters before beginning. Some common recipes areavailable, located in the process cleanroom, but are to be used as a starting point for yourexperiment.
Ask yourself: Is my resist chemically amplified? How will varying bake timesand temperatures affect my resist’s contrast, clearing dose, and film thickness? If you areunsure, ask Quinn Leonard prior to beginning your experiment.The quality of your coated wafer depends largely on your process controls. Have you kepteverything as clean as possible? Have you changed the hotplate set point and allowedtime for it to equilibrate? Have you allowed the PR to come to room temperature? Haveyou primed your wafers? These factors, and others, will affect the response of ChemicallyAmplified Resists (CARS), and the film quality of all PRs.4.1 Mounting and Centering your Sample:-Before mounting your sample, make sure you have turned on the nitrogen supplyon the Solitec 5110-CT Resist Spinner before you begin.
Failure to do this willresult in an error message from the spinner (MOTOR PURGE button will light).-Always use the wafer centering handler to center your wafer. Do not try to centerthe wafer yourself or you will sacrifice the uniformity of your resist. There are 3”,4”, and 6” handlers as well as corresponding vacuum chucks for the SolitecResist Spinner. All are located in the plastic bin above the spinner.-There are also chucks for quartz masks and small wafer pieces.-If you have an oddly-shaped or heavy work piece, see Quinn or Janice beforeyou try to spin it.4.1.2 Mounting a Wafer:-Find the appropriate wafer centering handler for you wafer size.
Using wafertweezers, select a clean wafer for photoresist coating. Mount on recessed edgeof the centering handler. See Fig. 1.-The inner diameter of the wafer centering handler is the same as the outerdiameter of the vacuum chuck. Therefore, to center your wafer, slide the handlerand wafer over the vacuum chuck and align them vertically.13Basic Photoresist Processing TechniquesFigure 5: Centering a wafer on the Solitec Resist Spinner-Once you are satisfied with the alignment, press VACUUM on the Solitec controlpanel.-To set the SPREAD and/or SPIN speed, press START, and adjust the knobsunder SPREAD and SPIN until you reach your desired speed. If you do not wanta SPREAD cycle, simply depress the SPREAD button at the top of the controlpanel.
See Fig. 2 below. Use this dry spin to check the centering of your wafer.-To adjust the time, use controls on the lower right side of the control panel. Liftthe small ‘+’ and ‘-‘ tabs and push in to increase or decrease the SPREAD/SPINtime. Flip the tabs down, when you are done. See Fig. 2.14Basic Photoresist Processing TechniquesSpread ButtonRPM AdjustmentKnobsTimeSettingsFigure 6: Solitec Control Panel-Once you have set your spin speed and time, press STOP. You are now readyto apply you photoresist.-If you have not read Part 1: Preparing Photoresist, do it now.-Use the plastic pipettes supplied in the cleanroom.
Use the high pressurenitrogen gun to blow out any flashing within the pipette before use.-Carefully insert the pipette into your bottle of photoresist. Cleanliness isessential to the outcome of your spun surface. Do not ‘burp’ the pipette in thebottle. This creates bubbles within the resist, which often translates to bubbleson your wafer surface. Do not drip resist onto the bottle rim or threads.
If resistdoes get on these surfaces, clean with a wipe and acetone. Replace the cap toyour photoresist bottle when you are done. Remember, the cleanliness of yourbottle will influence future spins.-Apply photoresist to the center of your wafer. Squeeze slowly. Avoid bubbles.Do not touch the wafer with your pipette. See Fig. 3.15Basic Photoresist Processing TechniquesFigure 7: Applying photoresist-The size of your photoresist pool will depend on the speed at which you spin.You might need to adjust the amount of photoresist applied if the photoresistdoes not cover the entire wafer surface after the spin is complete.-Press START. If the vacuum button is not depressed, the spinner will not start.Do not let your pool of PR sit for more than a few seconds before you startspinning.-As your wafer spins, you will see diffraction lines spread throughout the surfaceof the wafer as the resist changes thicknesses. As the rate of the changinginterference lines decrease, prepare a bottle of Acetone for edge bead removal(EBR).
![](https://s.studizba.com/z.php?f=/templates/si/i/noavatar.png&w=100&h=100&t=1"){kind=avatar}
