Solved Servo Applications

Front End Semiconductor Manufacturing

Front end semiconductorSemiconductor processing can be divided into two parts - "front-end" and "back-end". Front end semiconductor manufacturing refers to the fabrication from a blank wafer to a completed wafer (i.e. the microchips are created but they are still on the wafer). Many front-end processes involve spinning the wafer. This sounds easy at first until you realize that the inertial mismatch between the wafer fixture and motor can easily be upwards of 2000:1 for a direct drive system. This presents a tuning problem if trying to maintain excellent velocity and position response. ADVANCED Motion Controls servo drives have the tools and controls to get this application tuned to your specification.

The semiconductor industry has some of the most demanding applications in motion control. A combination of extreme accuracy and precision combined with high throughput, makes for exciting technology.

Wafer Handling / Transfer

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.  ADVANCED Motion Controls servo drives offer a wide selection of power capabilities to control any axis with coordinated motion.

A FOUP transports silcon wafers to the chemical vapor deposition process

FOUP Handling / Transport

The box that holds the wafers is called a "FOUP" (Front Opening Unified Pod). A FOUP full of wafers is an expensive payload so it must be handled with the greatest care. AMC servo drives are relied upon to transport these important packages. In transport applications using high performance servo drives reduces weight and increases efficiency.

Chamber Open / Close

Chamber doors need to be opened and closed to seal in process materials for various steps throughout the front end semiconductor manufacturing processes. Servo drives provide the power and precision needed to create reliable seals as well as provide feedback to allow the system to monitor the position throughout the operation.

A lady operates a semiconductor fab in a clean room environment
Deionized water cleans a 100mm wafer during a spin-rinse-dry step

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.

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 front end semiconductor manufacturing processes. AMC servo drives are up to the task.

Etched silicon features under heavy magnification showing before and after the cleaning process
Layout of a chemical vapor deposition chamber used in semiconductor manufacturing

Chemical Vapor Deposition (CVD)

CVD is used for coating everything from tinted glasses to potato-chip bags.  In semiconductor fabrication, this process is used to apply thin layers of material to act as conductors, semi-conductors, or insulators to the wafer.  Low Pressure Chemical Vapor Deposition or (LPCVD) is more commonly used because it produces a more uniform thickness and prevents undesirable reactions. Servo drives can be used to insert and extract the wafer boat from the chamber, open and close the chamber door, and add or remove wafers from the boat.

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. CMP creates the flat, smooth surface necessary to prepare the wafer for successive steps in the fabrication process. CMP is required multiple times during the front end semiconductor manufacturing process.

This process requires vibration free and exact velocity and force control with no velocity ripple. AMC servo drives have the right tuning tools and control algorithms to get the tuning done quickly so you can move on with your design.

Chemical mechanical planarization polishes a wafer surface flat to prepare for the next step in a semiconductor fab
stepper machine moves the silicon wafer into position


During photolithography, laser light is passed through the reticle containing the image of one or more dies. 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 dies at a time, then steps to the next die or set of dies until it has exposed the entire wafer.

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