Semiconductor Processing
Where millisecond moves and sub-micrometer accuracy is the norm. Semiconductor processing can be divided into two sections - "front-end" and "back-end". Front-end refers to the fabrication of the chips, where all of the transistors and components have been formed on the chip (but all the chips are still on the wafer). Back-end refers to dicing the wafer into individual chips and all the processes thereafter; such as test, assembly and packaging. AMC controls the motion in both front-end and back-end processes. An excellent introduction to semiconductor manufacturing is available from Infrastructure.
Front End
Many front-end processes involve spinning the wafer. This sounds easy at first until you realize the inertial mismatch between the wafer fixture and motor can easily be upwards of 2000 to 1 (for a direct drive system). This presents a tuning problem if trying to maintain excellent velocity and position response. AMC drives have the tools to get this application tuned in short order.
Wafer Handling / Tranfer
 Wafers need to be quickly and gently transferred from process to process. Wafer handling robots powered with servos are the standard method. Robots are typically in a SCARA configuration (Selective Compliant Articulated Robot Arm) where servos can control all axes including shoulder, elbow and wrist.
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Foup Handling / Transport
 The box that holds the wafers is called a "foup". A foup full of wafers is an expensive payload so it must be handled with the greatest care. AMC drives are relied upon to transport these important packages.
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Chamber Open/Close
 Chamber doors need to be opened and closed to seal in process materials for various steps during wafer fabrication. Servos provide excellent control for this application.
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Spin Rinse Dry
 Just like it sounds. The wafer is brought up to speed in a very controlled fashion. Once spinning, de-ionized water is evenly sprayed onto the wafer to rinse off the chemicals used in the previous process. Then centrifugal drying and heated nitrogen combine to remove water and latent moisture.
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Surface Preparation
 Including removal of photoresist, Post-CMP clean, Pre-Photo Lithography clean, Polymer Removal, Pre-Epi clean, Pre-Deposition, Photoresist Strip and other similar processes. AMC servo drives are up to the task.
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Chemical Vapor Deposition (CVD)
This process applies thin layers of material to act as conductors or insulators during the wafer fabrication process.
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Chemical Mechanical Planarization (CMP)
 An abrasive process used for polishing the surface of the wafer flat. It involves the use of chemical slurries and a circular (sanding) action to polish the surface of the wafer smooth. A smooth surface is necessary to maintain correct focus during the photolithography process. CMP is required multiple times during wafer fabrication.
This process requires vibration free and exact velocity control with no velocity ripple. AMC servo drives have the right tuning tools to get the tuning done quickly so you can move on with your design.
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Stepper
 During photolithography, laser light is passed through the reticle containing the image of one or more die. The image is then projected onto the wafer. Since the whole wafer isn't treated at the same time, the wafer needs to be moved so the next die can receive the image. The machine used to do all of this is called a "stepper" because it does one die or a few die at a time, then steps to the next die or set of die until it has exposed the entire wafer.
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Back End
Wafer Inspection
 This is an optical inspection of the wafer to look for physical abnormalities that will indicate damage in the fabricated wafer. For this process, the wafers must be correctly positioned in front of the viewing lens for accurate optical inspection.
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Wafer Probe / Wafer Test
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Dice
  This process takes the completed wafer and slices it into individual chips. A circular dicing blade is used to slice the chips. This is an ideal application for servo motion on both the blade control and positioning.
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Die Bond
 Each die is bonded or attached to the frame of a package. The classic chip package is the familiar black oblong rectangle with silver pins sticking out like bug legs, known as a dual in-line package, or DIP.
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Wire Bond
  After Die Bonding each pad on the die is connected to a corresponding pin on the package frame via a thin gold wire. This is one of our highest bandwidth applications because throughput increases with any bit of extra speed.
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Ball Bump / Flip Chip
  A newer alternative to wire bonding, flip chips are mounted "upside-down". Hence the name "flip chip". Instead of wires connected around the periphery of the chip as in wire bonding, an array of "bumps" are formed on the surface of the chip. These bumps are then used as connection points from the chip to the outer package. The advantages of flip chip technology include:
- Better connections to the chip as opposed to wire bonding where the wires add extra length, capacitance and inductance that limit signal speed.
- More attachment points available since the whole area of the chip is available instead of just the edges
- Faster production
- Smaller overall package size
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Encapsulation
 The bonded die and frame are sealed - either by a molded plastic compound, or by the attachment of a sealed lid.
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This is the first time in the fabrication process that the chips are tested to see if they work as designed. The chips are still on the wafer and are functionally tested using a test fixture with hundreds needles that contact tiny metal pads on the surface of each chip. The probes send and measure signal responses from the chips. Chips that fail can sometimes be repaired, otherwise they are marked as failed and discarded after the dicing process.
