tekHPoynt

A
utomatic Test Equipment(a.k.a. ATE) is a consequence of computers being interface with digitally-controlled stimulus and measurement instrumentation. ATE replaced the benchtop set-ups of instrumentation that were manually controlled to make measurements. Once started, ATE can continue its operation with no outside intervention and can test thousands of parameters in seconds.

ATE dramatically improves throuhgput and measurement accuracy. It can correct its own errors by comparing its measurements results to a known standard and compensating for the difference. It relieves workers of monotonous tasks by routinely repeating complex tests over and over again. It has inherent data processing capability. ATE doesn't make mistakes when recording test data, usually doesn't compromise a test, doesn't forget tests, and doesn't get tired. ATE has revolutionized the semiconductor industry.

History of ATE
Semiconductor ATE had its beginning, as one might expect, in the same place that semiconductors were first produced in quality. Fairchild Semiconductor recognized the need to automate the test process. Tests on transistors were performed with a separate bench set-up of instrumentation for each type of test. This was a long and tedious process. Each test required that the device be inserted into a different test set-up. It was soon realized tha if the device could be tested with a single insertion, the cost of testing could be reduced.

Fairchild's first ATE, the Model 300, was built by the newly formed Instrumentation Division. It considered of a set of different force and measuring units that were constant voltage and current sources. Plug-in cards were used to connect the various instrumentation to the relevant device-under-test(DUT) terminals. An automatic sequencer selected the proper plug-in cards in the sequence in which they were inserted into the tester. All programming was done by resistor selection on the plug-in cards. To make effective use of the Model 300, the test engineer literally had to make resistors. A plug board was used for direct classification of the devices into various pass and fail bins, depending on the test result. Although primitive, it worked. That was 1960. Not long after, a company was formed in Boston with a charter to develop semiconductor ATE. The company was called Teradyne, and with its inception the ATE industry was born.

With the advent of integrated circuits, Fairchild developed the first automatic IC tester - Model 4000. It too consisted of various constant current and voltage sources and measuring units. It was programmed from a magnetic disc with a a fixed word format in machine language, and it had the ability to "burst" a series of digital pulses to test the IC functionality. This was the first commercially available IC tester. That was in 1965.

The next commercial tester on the market was the model 553, manufactured by Texas Instruments. Similar in concept to the Fairchild Model 4000, it was programmed with continuous paper tape. But it was the introduction of Model J259 by Teradyne that radically changed the ATE industry. Teradyne coupled a digital computer with the test instrumentation and opened new era of semiconductor ATE in 1967.

Fairchild developed their version of a computer-controlled IC tester; and many other manufacturers of ATE emerged. But it was Teradyne that dominated the ATE marketplace for many years.

As faster devices were designed and as LSI began to emerge, the emphasis shifted from parametric tests to functional tests. This required a high degree of parallelism in the tester design. Teradyne tried to fill the need with their SLOT machine. However, although it was adequate for complex MSI and bipolar LSI, it lacked the sophistication for the emerging MOS-LSI.

Until this time, all ATE was designed with the DUT drive and compare circuits in the tester mainframe. Cables were brought to multiplexers from multiple test tables or stations and multiplexed to the tester mainframe. As testing speeds increased due to higher device data rates, this design became unworkable. The first attempt to solve the problem was again made by Teradyne. The drivers in the test head were mulitplexed to test stations with an independent set of comparators. This transmission-line approach was employed in Model J277, but unfortunately it was a failure as a general purpose logic tester. To achieve this, complex performance boards with more general load switching and parametric switching requirements in the test head were needed.

In 1970 the general purpose test system was pioneered by Fairchild and was called the Sentry Series. It was designed with a full set of drivers and receivers in the testhead. Forcing and measuring took place adjacent to the device, as did the GO/NO-GO voltage decision. The time-related pass/fail decision was still made in the mainframe. An advantage of this design was the accomodation of fast data rates. The Sentry was capable of 10Mhz data rates. Tektronix developed a similar test system, called the Model 3260, which had a 20Mhz data rate. Takeda-Riken's Model T320/60Z was the Japanese answer to a general-purpose test system.

Today the general-purpose test system is characterized by pin electronics(PE) in the testhead, while the dedicated test system usually has a less versatile testhead with specific testhead pins that perform specific test functions.

System architecture also developed over the years. The 1st generation systems were self conatined, with local controller that programmed and sequenced the tests. Later, the 2nd generation systems were developed utilizing a minicomputerto program and control the test instrumentation. This greatly enhanced the capability of testing and data handling. The 3rd generation systems of the 1980's employ distributed architecture. In these systems the local controllers operate the tester, while the powerful central host attends to all data manipulations activities. The host computer may interface with many different testers with local microcomputers. Typical 3rd-generation test systems include the Sentry/Integrator, Xincom, Accutest, Adar/MX-17, Lomac, and Megatest Q2/60. The complex designs of ATE systems continue to handle more complex IC designs.