Correcting Problems Caused by Misaligned Semiconductor Equipment

An often overlooked variable during preventive maintenance, accurate semiconductor equipment alignment is critical to optimum machinery performance and output.  Misaligned wafer processing equipment can negatively impact wafer production as wafers transferred between two stations of different inclinations increase the chance of particle generation though wafer scratching, slipping, misplacement or even breakage.  Even a slight process variance during a transfer step can accumulate over the wafer manufacturing process, ultimately impact wafer uniformity. 

The example below shows leveling data for a number of consecutive Diffusion Furnace stations and how the effects of the variance in inclination for a number of transfer stations can compound over the path of travel through equipment.  The goal is to have each wafer process and transfer location within tolerance.

In another scenario, a slight deviation in the inclination of a wafer boat could result in a significant deviation at the top.  Even slight wafer placement deviation between the bottom and the top of a wafer carrier can result in both wafer damage and wafer process non-uniformity.

To avoid these problems, very precise leveling standards must be followed during semiconductor equipment preventative maintenance.  However, many fabs do not have leveling standards or are limited to traditional methods such as eyeballing and bubble levels that do not provide the accuracy and form factor needed to correctly characterize and service equipment, making it impossible to determine and resolve magnified inclination errors.  Establishing level standards is also impossible with traditional devices as they were not developed with semiconductor equipment needs in mind.

WaferSense® precision wireless leveling systems make inclination adjustments quick and accurate so fab equipment can get back online faster. And because they output real data, fab engineers don't have to rely upon eyeballing or estimation. WaferSense data ensures consistent results to optimize equipment's setup to limit scrap, improve uptime, and harness better yields.

WaferSense Automatic Leveling Systems (ALS) allow engineers to easily take level measurements. Levels can be set to any reference plane within the sensor's operating range (± 4 degrees from absolute). Users can even define Go/No Go regions and log data and notes for future reference. Parametric readouts for battery life, sensor temperature and connection status are visually represented within the control panel for correct and effective use of the devices.

For more about WaferSense Automatic Leveling Systems, please refer to http://www.cyberopticssemi.com/products/wafersense/als_alsr or contact us at or contact CyberOptics at CSsupport@cyberoptics.com or 800.366.9131