Introduction to the overall process of wafer testing and testing purposes
Wafer inspection is to carry out needle test on each crystal grain body on the chip, in the inspection head mounted on the gold wire made of fine as hair of the...
Wafer inspection is to carry out needle test on each crystal grain body on the chip, in the inspection head mounted on the gold wire made of fine as hair of the probe needle (probe), and the crystal grain body on the contact (pad) touch, test its electrical characteristics,wafer tester failing to pass the crystal grain body will be labeled mark, and then when the chip according to the crystal grain body as a unit to cut into a separate crystal grain body, labeled with a mark of failing to pass the crystal grain body will be Then when the chip is cut into individual die bodies on a die body basis, the marked failed die bodies will be eliminated from the next manufacturing process to minimize the cost of non-comparison manufacturing.
After wafer fabrication is complete, wafer inspection is a critical step. This step is a report card of the wafer production process. In the whole process of testing, each chip's charge working ability and power circuit function are examined. Wafer testing is also known as die sort or wafer sort.
In the inspection, the wafer is fixed immobile in the vacuum pump adsorption force on the chuck, and with as fine as hair-thin probe needle electrodynamometer pointing, and to go at the same time the probe needle and the chip of each soldering pad touch. The electrometer detects power circuits under the drive of the power supply and records the results. The total number, sequence and type of tests are controlled by an electronic computer system. The tester is of automated technology,wafer probe testing so there is no need for operator assistance in the inspection work after the probe pin ECD is aligned with the first wafer (human pointing or application of a fully automated visual recognition system).
Inspection is carried out with the following three general objectives in mind. Firstly, it will be possible to distinguish whether the wafers are qualified or not and send the qualified wafers to the packaging plant. Secondly, the main parameters of the components/circuits are evaluated for characterization expertise. The technical engineers must check the spread of the main parameters to maintain the quality level of the process. Third, the counting of pass and fail chips provides feedback to the wafer fabrication staff on all aspects of performance. The standard chip and defective products in the wafer part of the computer to the wafer map on the way to write down. In the past, the old-fashioned technique was to scribble a dot of ink on the defective chip.
Wafer inspection is one of the main methods for statistical analysis of chip product qualification rate.vibration isolation table Along with the expansion of the total area of the chip and the increase in relative density, the cost of wafer inspection is increasing. As a result, chips must be inspected for longer periods of time and their more sophisticated and complicated power supplies, mechanical equipment, and computer systems must be used to perform the inspection work and monitor the inspection results. Visual inspection systems are also more sophisticated and expensive as chip sizes expand. Chip designers have been asked to introduce test patterns into storage arrays. Inspection designers are exploring ways to simplify and rationalize test procedures, such as applying simplified test codes after the core references have been evaluated for major counts, in addition to inspecting chips on a wafer line by line, or carrying out several chip inspections at the same time.