Clean Room Robots Sweep Up Big Savings In Semiconductor Applications

Among the most compelling benefits of the use of Class 1 and Class 100 Clean Room Robots in semiconductor manufacturing are the reduction in scrap from broken wafers and chips, which translate into major cost savings in wafer handling.

'When you consider that each wafer is worth over $100,000, the avoidance of contamination and the savings in scrap from dropped wafers in machine loading and unloading can exceed millions of dollars,' explains Joe Portelli, electronics industry program manager, FANUC Robotics North America Inc., Rochester Hills, MI.

The most significant advancement in Clean Room robots for the semiconductor industry is the move from the 200 mm to 300 mm standard in wafer handling. To place matters in their proper context, Clean Room robots are used predominantly in machine loading, unloading, and parts transfer in the semiconductor industry. There are two main divisions of robotic labor in this context-front-end processing which is machine loading in a clean room environment by a clean room robot in a Class 1 semiconductor application to a Class 100 video tape manufacturing facility. And the back-end processing that is concerned with assembly, packaging, and testing, again handled by clean room robots.

The type of equipment used in such applications as photolithography, ion implantation, and Chemical Mechanical Planarization (CMP) of wafers and chips is in general very expensive, with each machine ranging from 1 to several million dollars. In the 200 mm world, such machines are being rapidly obsoleted, with the result being that more robots are being used in CMP machine processing. CMP is used not only in the semiconductor industry, but also in data storage for hard drive disks, flat panel displays, and others, according to Portelli.

CMP machines are specifically used to polish wafers to a near-perfect flat finish. Here, robots pick up unprocessed wafers or disks out of a cassette commonly called a Front Opening Unified Pod (FOUP), and place them onto the bottom platform of the CMP machine. The robot then signals the machine that loading is complete, whereupon the top platen of the machine comes down onto the wafers, and the polishing process begins. When the polishing process is complete, the robot picks up the polished wafers and places them onto a cassette on an outbound conveyor, and then the cycle repeats itself. CMP machine loading and unloading is usually done by Class 100 Clean Room Robots, primarily because human handling introduces contamination into the process and increases the chance of dragging wafers on the bottom platen of the CMP machine, which results in scrap and loss of several thousands of dollars in case of careless human handling. In addition, robots are used because of their repeatability, accuracy, and lack of fatigue in a repetitive motion that keeps million-dollar CMP machines utilized to their fullest extent-that is, continuous operation and maximum utilization of capital equipment that costs several million dollars.

'A typical standard cassette holds 25 wafers and these wafers are as brittle as glass,' explains Portelli. 'If a cassette is dropped through human handling, the cost in scrap is gigantic. Also, robots are used because people are the number one source of contamination. And contamination can be anything from dust to bacteria. Robots reduce the cost associated with people in terms of consumables.'

One example of a Class 100 cleanroom robot is in the case of SpeedFam-IPEC, a large supplier of CMP equipment to the semiconductor and data storage industries. One of SpeedFam-IPEC's customers, a leading manufacturer of hard disk media, challenged the company to automate the loading/unloading of disks in its CMP machines.

Automation was a priority for the following reasons:

• Product damage-Improper manual handling damaged expensive hard disks. In addition, the cleanroom environment required that the hard disk manufacturer follow Class 100 protocols. Particle contamination or dragging of the disks on the polishing platen damaged the sensitive disk surface.
• Inefficient machine utilization-Production was seriously hampered due to downtime of expensive CMP machines waiting to be tended. Downtime frequently exceeded 30%.
• Employee availability-Turnover and absenteeism in a tight labor market made manpower scheduling imprecise.
• Floorspace constraints-Proximity to other machines restricted access and aisleways.

SpeedFam-IPEC considered both hard automation and robotics, but decided on the latter due to the technology's flexibility and price. The company selected FANUC Robotics' FANUC LR Mate 100i Class 100 cleanroom robot-a compact five-axis articulated arm. Two robots were installed on the CMP machine: one primarily as loader and the other as unloader.

The user company reaped the following process advantages:

• Elimination of product damage-Disk damage was eliminated because the robots follow a perfectly vertical path to pick and place the disks in the CMP machine. In addition, the robots' Class 100 capability greatly reduced contamination due to dust particles and also eliminated organic adulterants.
• Increased machine utilization-CMP machine uptime increased to near 100%. The machine never stood idly while waiting to be loaded/unloaded. Upon receiving the signal from the machine, the robots would remove the processed disks and replace them with unprocessed ones. The robots would then signal to the machine to begin a new cycle.
• Employee availability-The robots allowed the scarce manpower to be deployed more efficiently elsewhere.
• Eliminated floorspace constraints-The manufacturer realized space savings since the robots were mounted into the CMP machine itself.

Floor space around the machine was minimized.

Another industry leader in the Clean Room robot genre is Adept Technology Inc., San Jose, CA. The company recently showcased its 200/300mm Flexible Front End Systems at the SEMICON West '00 Exposition held recently in San Francisco, CA. The Adept Flexible Front End Systems, including the FFE 200 and FFE 300, combine wafer sorting and Standard Mechanical InterFace (SMIF) load functions into one compact tool integrated front-end system to reduce cycle times, process complexity, and cost. The FFE 200/300 combine wafer value-added operations such as wafer orientation, OCR, Sort and Merge into a front-end system, thereby eliminating the need for wafer sorters in the factory. The systems are said to be the only wafer handling systems that use motion and vision control.

'We've integrated discrete operations into one flexible front end system, reducing cost and time to market for our process tool customers,' says Joe Campbell, vice president of marketing for Adept Technology.

The FFE 200 is designed to be a replacement for adaptive 'bolt-on' SMIF solutions; it fits within the same depth as current SMIF solutions and provide up to four SMIF load ports for optimizing tool utilization. This unit enables the use of dedicated tool cassettes, reducing the risk of cross-contamination and tool robot mis-picks. The FFE 300, which is designed to be the factory interface for 300mm tools, is configurable with respect to both layout and finish so that it looks like an integrated part of the process tool. The FFE 300 is also 200mm configurable so that it can perform as a 'bridge tool,' capable of handling 200mm wafers now and 300mm wafers in the future.

Adept Technology also has a user for its FFE 200/300 system and for the Adept MV controls. Solid State Measurements Inc., Pittsburgh, PA, is working with the Adept systems for its new SSM 6000 series of semiconductor fabrication metrology systems. This Adept customer is an industry leader in the design and manufacture of equipment for semiconductor materials characterization. The company produces an array of C-V and I-V systems as well as the automatic Spreading Resistance Probe. The company uses contacting and non-contacting techniques for electrical measurement of semiconductor films and materials.

'The combination of Adept's automation and SSM's FastGate Elastic Probe technology represents a breakthrough that will enable fabs to produce next-generation silicon devices more efficiently,' comments Adept's Joe Campbell.

The Adept FFE 200/300 systems at use at SSM will include a Vicron 300D dual arm wafer handling robot, along with an integrated motion and vision controller, vibration isolation, wafer inspection system, precision stage, and microenvironment packaged in an ISO 2 cleanliness enclosure. In addition to the Vicron 300D, the Adept controller will control the precise movement of the metrology probes and it will oversee all other motion, vision, and environmental elements of the platform.

James F. Manji is a free-lance writer specializing in manufacturing automation topics. He is based in Brunswick, OH.