Patent Application
20090058450
1. Technical Field
The present invention relates generally to the field of semiconductor test and quality assurance methodologies, and more particularly to a method of and system for functionally testing multiple semiconductor devices in parallel in a burn-in environment.
2. Description of the Related Art
An important part of the semiconductor device manufacturing process is testing. Before devices can be shipped to customers, the devices must be tested to determine if the devices perform their intended and advertised functions. Such testing is referred to as functional testing.
Experience is shown that an electronic device will most likely fail in the early part of its operating life if it is prone to failure. The failure rate than levels off throughout the devices normal life and again increases when the device becomes old. Failure during the device's early life is referred to as early life failure, or infant mortality.
Burn-in is an electrical stress test that employs voltage and temperature to accelerate the electrical failure of a device. Burn-in essentially simulates the operating the operating life of the device. Burn-in is usually done at 125° Celsius, with electrical excitation applied to the devices. The burn-in process is facilitated by using burn-in boards upon which devices are loaded. The burn-in boards are then inserted into a burn-in oven, which supplies the necessary voltages to the devices while maintaining the devices at the burn-in temperature. The electrical bias applied may be either static or dynamic, depending upon the failure mechanism being accelerated. Devices are typically maintained at the burn-in temperature from 48 to 168 hours. Devices that survive burn-in should, if they are operated within the rated limits, have low and predictable failure rates.
Currently, burn-in and functional testing are performed separately. Separate burn-in and functional testing increases device manufacture and shipping time.
The present invention provides a method of and a system for testing semiconductor devices. Embodiments of the method and system of the present invention simultaneously heat a plurality of devices to a burn-in temperature, and simultaneously perform functional tests on the plurality of devices at the burn-in temperature. Embodiments of the systems according to the present invention include a burn-in oven and a test multiplexer. The burn-in oven is adapted to receive and heat the devices to the burn-in temperature. The test multiplexer is adapted to apply signals to and receive signals from the devices in the burn-in oven.
The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further purposes and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, where:
Referring now to the drawings, and first to
System 100 includes a joint test action group (JTAG) system 105 and a flexible service processor 125. JTAG system 105 is designed to multiplex JTAG test signals from flexible service processor 125 to devices 103 in burn-in oven 101. JTAG system 105 includes a JTAG multiplexer 107. JTAG multiplexer 107 is coupled to receive test, select, and control signals from flexible service processor 125. JTAG multiplexer 107, under control of flexible service processor, provides the ability to select an individual target device 103, all target devices 103, or any subset of target devices 103.
JTAG multiplexer 107 is coupled to provide test signals in parallel to a serializer 109. Serializer 109 converts parallel signals to a serial bit stream. Serializer 109 is coupled to a de-serializer 111, which converts the serial bit stream back to parallel signals. De-serializer 111 is coupled to provide parallel test signals to devices 103 contained within burn-in oven 101. JTAG multiplexer 107 is coupled to receive test data signals in parallel from a de-serializer 113. Deserializer 113 is coupled to receive a parallel bit stream from a serializer 115. Serializer 115 is coupled to receive test data signals from devices 103 housed in burn-in oven 101. JTAG multiplexer 107 is configured to demultiplex signals received from de-serializer 113 under control of flexible service processor 125.
JTAG system 105 includes a programmable read-only memory (PROM) 117 and an oscillator 119. PROM 117 stores configuration and programming information for JTAG system 105. Oscillator 119 controls scan speed for JTAG system 105. JTAG system 105 also includes reference voltage circuitry 121 and regulator circuitry 123, which provide selectable voltage levels for signals multiplexed to target devices 103 under control of flexible service processor 125.
Flexible service processor 125 cooperates with JTAG system 105 to test devices 103 and burn-in oven 101. Flexible service processor 125 is coupled to provide test clock (TCK), test data in (TDI), and test mode select (TMS) signals to, and receive test data out (TDL) signals from, JTAG multiplexer 107. Flexible service processor 125 provides TMS selects signals to JTAG multiplexer 107 to apply test signals to selected ones of devices 103 housed in burn-in oven 101. In the preferred embodiment, TMS select signals are provided through a seven-line bus, thereby allowing 128 selections. Flexible service processor 125 receives reference voltage signals from reference voltage circuitry 121 of JTAG system 105 and provides control signals to regulator 123 of JTAG system 105, monitoring and controlling the voltage of signals supplied to devices 103.
Functional tests may include tests of memory coherency, bus interactions, interprocessor communication, I/O functionality, and the like. Test cases may be built using random instruction streams. Random operations are selected and test code stream is built and saved. Then, the random test code stream is run on selected devices. Certain devices may fail as a result of the functional tests performed under burning conditions. The system detects the fail devices, at step 209. At the completion of burn-in testing, the devices are allowed to cool and are removed from the burn-in oven, at step 211. Additional functional tests may be performed during the cooling period. After the devices have been removed from the burn-in oven, the failed devices are discarded, as indicated at step 213.
From the foregoing, it will be apparent to those skilled in the art that systems and methods according to the present invention are well adapted to overcome the shortcomings of the prior art. While the present invention has been described with reference to presently preferred embodiments, those skilled in the art, given the benefit of the foregoing description, will recognize alternative embodiments. Accordingly, the foregoing description is intended for purposes of illustration and not of limitation.
