JPH0573579U - Dynamic test equipment for intermediates during integrated circuit manufacturing - Google Patents

Abstract

(57) [Abstract] [Purpose] To perform intermediate-stage testing of integrated circuits such as wafers, dice or chips (test chips) at various stages of manufacturing by non-destructive dynamic test techniques. [Structure] The energy of photons is increased by modification (multiplication) of laser light, and the light is converted into light having a short wavelength. The high energy laser light excites the electron beam as a composite function of the energy of the incident light and the dynamic behavior of the circuit and passes it through the detector. The energy of photoelectrons emitted from the test pads on the test chip is detected as a function of the instantaneous input voltage of the test chip during dynamic operation, including improper operation due to defects. The pulses from the laser are modified by optical modification, bias voltage and tip-grid-detector distance to provide high temporal resolution on the test chip under dynamic conditions simulating real or stressed operation. Radiation is provided to detect the resulting circuit voltage and its changes.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

The present invention relates to integrated circuit testers, and more specifically to the use of pulsed lasers to excite an electron beam as a function of the dynamic behavior of an integrated circuit, with adjacent detectors. The present invention relates to a non-contact type dynamic test device which detects these electron beams and does not require ohmic contacts or a specific circuit on an integrated circuit chip or wafer.

[0003]

[Prior Art]

 The usual way to test electronic circuits is to visually view the current and voltage of the circuit being operated by the oscilloscope. The engineer, for example, applies a point on the test probe to a landing pad for good contact, observes the resulting electrical conditions by analog trajectories on the oscilloscope, and at various test probe locations. Are inspecting. As circuits become smaller and more complex, non-destructive test probe points without destroying the circuit, or at least by making relatively large changes due to the physical mass of the probe, doubtful about the test results. Achieving positioning has become increasingly difficult. A completely non-destructive, non-contacting oscilloscope is generally desired. One way to reach a non-contact type oscilloscope is an electron beam tester. However, due to the high energy of the incident electron beam (greater than 100 eV), the electron beam is somewhat invasive in that it causes a permanent loss of material to the test surface upon which the electron is incident.

Next, a typical device of the prior art will be shown.

US Pat. No. 4,266,138 discloses a technique for exposing X-ray sensitive resist to carbon KX radiation using 2B type diamond. This target consumes significantly more power and produces more intense x-rays than the graphite target. This technology is a manufacturing technology, not a test technology.

US Pat. No. 4,417,948 discloses a technique for photoetching polyester by applying ultraviolet light in an oxygen atmosphere. This technology is also a manufacturing technology, not a test technology.

US Pat. No. 4,380,864 discloses a technique for positioning a surface acoustic wave device adjacent to an annealed semiconductor. An electrical contact is fixed on the top surface of the semiconductor and a combination of surface acoustic waves of the transverse wave and charge carriers of the semiconductor is used to generate the transverse acoustic voltage, which is the function of the conduction plane of the semiconductor. This technology is a contact technology, not a non-contact technology.

US Pat. No. 4,332,833 discloses a technique which utilizes the volumetric rate sensitivity of the dielectric function of crystalline materials to crystalline materials. This technique has been found to vary the volume fraction as a function of the measured dielectric function over a range of approximately 1.5 ev to 6 ev, and provides dynamic monitoring of deposition within the rectifier. This technique is a non-contact optical technique that monitors the material being processed in thin films, not a current-voltage tester.

US Pat. No. 4,440,883 discloses an apparatus for determining the average size of a basic pattern by comparing the Fourier transforms of the pattern images in a processor. The pattern is provided by applying coherent light that is focused onto the target under test, monitors the reflected images, and Fourier transforms them to produce an image pattern with a known Fourier transform. Be compared. This is a non-contact optical technique for image recognition, but it is not a current-voltage tester.

August 1982, IBM Technical Disclosure Bulletin (TDB) Vol. 25, No. 3A, pp. 1171 to 1172, "Non-contact measurement of voltage levels using optical radiation" (Rubloff). , “Contactless Measurement of Voltage Levels Using Photoemission,” IBM Technical Disclosure Bulletin, Vol. 25, No. 3A, August 1982, pp.1171-1172) is an ultraviolet excitation method of light emission for non-contact measurement of voltage level. However, this test method is neither a dynamic test nor a laser (continuous wave or pulsed wave).

A paper entitled "Logic Failure Analysis of CMOS Using Laser Probes" by Henry, Spectrum Science, Inc., 3050 Oakville Village Drive, Zip Code 95051, Santa Clara, Calif. (Henley, “Logic Failure Analysis of CMOS Using a Laser Probe,” Spectrum Sciences, 3050 Oakmead Village Drive, Santa Clara, California, 95051) is a laser for passing through a computer to analyze the current-voltage signal generated by excitation. Discloses a non-contact probe. This technique does not use adjacent detectors to carry the test signal, but uses an area of dedicated circuitry (outside the integrated circuit under test). There is no light emission from the circuit. The logic state of an integrated circuit interrupts its dynamic behavior and measures the current transient response induced in the power supply by laser light absorption in the active semiconductor region (light is incident on metal wires and circuit nodes). Not). During the dynamic operation of this result circuit, neither logic states nor AC switching waveforms are determined.

The prior art conceives, ie, without using actual contacts, a modified pulsed laser beam is focused onto a portion of the integrated circuit in dynamic operation of the signal and emitted as an electron beam. Neither discloses nor proposes a technique for inducing an electron emission signal from an integrated circuit, which determines, with accurate time resolution, whether the circuit is operating properly by comparing C.

[0013]

[Problems to be solved by the device]

 It is an object of the present invention to provide a device for testing an integrated circuit that does not require operator dexterity and is extremely accurate without damaging the integrated circuit.

According to the present invention, a non-probe type oscilloscope test apparatus having a time resolution of about 5 picoseconds is provided.

According to the present invention, it is possible to measure the transient state of AC switching during the period when the logic state changes, and thus to measure the logic state itself of the most advanced high speed circuit.

[0016]

[Means for Solving the Problems]

 The present invention conceptually emits secondary electrons by irradiating a test position of a test chip placed in a dynamic operating state with a specific laser beam pulse, and the secondary electrons are emitted to an input voltage. And a parameter of the laser pulse and a parameter of a bias to the detection device.

Specifically, the device includes the following constituent features. (A) a mounting device including a vacuum chamber having a test tip position for electrically connecting and mounting a test chip in a form accessible by light; and (b) a test mounted at the test tip position. A pulsed laser device that sharply converges to a selected location on the chip, has a pulse width with a very short connection time, and provides a beam of controlled wavelength that is short enough to generate photoelectrons and secondary electrons. And (c) a detection device that is juxtaposed to the mounting device adjacent to the test chip position and that includes bias means for selectively detecting the radiated photoelectrons having an energy of a predetermined level or higher or a predetermined range. And (d) applying a dynamic operation signal to the test chip under normal operating conditions or simulated severe operating conditions, and Equipped with a signal generation and test calculator for comparing the output from the output device with the test standard,

The above-mentioned detection device converts the photoelectron energy emitted from a test pad on the test chip into an instantaneous input voltage on the test chip that is performing improper operation due to proper operation or failure. Detecting a circuit voltage generated on a test chip under an operating condition characterized by detecting as a combined function of a parameter of a pulse from the pulse laser device and a parameter of a bias voltage to the bias means. Semiconductor chip dynamic test equipment.

Next, the main operations and effects will be briefly described.

The test device of the present invention is a contactless test device that monitors the instantaneous voltage generated by inducing electrons from a node selected by a laser in an integrated circuit. The electron emission varies as a function of the instantaneous voltage at the node where the laser is selected. The modified pulsed laser is focused onto the node of the dynamic operating concentrator circuit under test and the emitted electrons are compared to the appropriate criteria for testing.

The feature of the present invention resides in a non-probe type oscilloscope test apparatus having a time resolution of about 5 picoseconds. According to the test apparatus of the present invention, it is possible to measure the transient state of AC switching while the logic state changes, and thus to measure the logic state itself of the most advanced high speed circuit.

[0022]

【Example】

 FIG. 1 is a schematic diagram of a contactless tester for an integrated circuit processing intermediate including wafers, dice or chips at various stages of manufacture. Although these processing intermediates are simple or complex, they have complex semiconductor-doped regions buried in a silicon substrate, with some insulating or passivation layers intervening in some places. , Usually covered with several metallization layers. For ease of presentation, the intermediary of processing all such integrated circuits is simply called a test chip. The test tip 1 is mounted on a suitable mounting device 2. The mounting device 2 provides a connection for the dynamic signal simulation operation and does not obscure light through a contact pad such as the pad 3. The entire operation is carried out in an environmental chamber 4 which provides a vacuum of suitable operating environment for testing integrated circuits. The test chip 1 is supplied with an appropriate bias voltage from the bias source 5, and is supplied with an appropriate dynamic operation signal from the signal generation / test computer 6. Bias source 5 is shown in FIG. 1 as a variable battery, but may in fact be a computer controlled variable voltage source, such as many different power supplies that are separately gated by computer 6. Therefore, the bias source 5 under the control of the computer gives a bias voltage or a non-standard bias voltage to simulate the stress operation. The signal generation and test computer 6 is programmed to provide the test chip 1 with the proper dynamic training so that the circuit can be tested at operating speeds when in normal operation. The test chip 1 is also dynamically stressed by high speed or non-standard voltage, current or timing. Once the test chip 1 has been brought to the operating temperature and to the point where it is expected that the pad 3 will be provided with a signal of known characteristics, it is desirable to determine whether a suitable signal is present or not. Be done. A laser 8 having a laser light modulation mechanism 8 and a focusing mechanism (lens) 9 gives a focused laser beam having appropriate characteristics onto the pad 3. The pad 3 provides an electron emission 10 which is modulated by the signal as a composite function of the applied laser light at the moment of test and the signal applied to the pad 3 of the integrated circuit. The electron emission 10 reaches the detector bias arrangement (grid 11 and bias source 12 are shown) and only those having the appropriate signal characteristics pass through the detector bias arrangement and then to the detector 13. The bias source 12 shown in FIG. 1 is a variable battery similar to the bias source 5, but the bias source 12 is similar to the bias source 5 in that the bias of the detector is appropriate for the detector and the test being performed. As long as it can take various forms. The detection device gives a deceleration electric field to the electrons, and only the electrons having energy above the critical value (1ev when the deceleration voltage difference between the detection device and the test point of the chip is 1ev) reach the detection device and are measured. It is supposed to be done.

A preferred detection device comprises a detector 13, a collector 14 and a counter 15. The detector 13 is a channel electron multiplier or other electronic signal measuring detector that supplies electrons through a collector 14 to an electronic counter 15. Suitable electron multipliers are, for example, Galileo Electrooptics 4219 or 4730. The electron collector and the electron multiplier associated with the pulse discrimination counter or amperometric amplifier together form the detector. A suitable electron collector is simply a plate of stainless steel sheet or a last dynode or electrode connected to an amperometer. The electronic counts are fed back to the test signal generator of the calculator 6 and compared with the appropriate test criteria. This test result is further used to determine whether the test chip should pass or fail.

FIG. 2 shows a schematic diagram of a laser modification technique used to provide focused light for inducing signal modulated electron emission as a function of a dynamic signal in an integrated circuit under test. Laser 7 in FIG. 1 is preferably a compound laser having a first stage which is a CW (continuous wave) pumped laser (argon ion or YAG) and a second stage 17 which is a mode-locked dye laser. . This composite laser provides 6600 (1.88 ev) output focused light with a nominal pulse width of 5 psec and a nominal repetition rate of 1 Mhz. In order to shift the laser energy of 1.88 ev from the compound lasers 16, 17 to the energy above the threshold (4.2 ev) required to produce photoelectron emission in vacuum, the crystal undergoes intense laser irradiation. The optical non-linearity of is used for harmonic generation to add the energy of the photons of the two lasers to produce a single, higher energy laser photon. The second harmonic generating crystal 22 has two 1. The combination of 88 ev photons produces 3.76 ev (3300) photons. For these 3.76 ev photons, an additional 1.88 ev photons (using mirror system 18, 19, 20 but mirror 18 is semi-transparent) third harmonic generating crystal 23. Which are coupled in, the photon of 5.64 ev (2200) is generated by the combination of photons of 3.76 ev and 1.88 ev. The resulting high-energy laser photons (5.64 ev in this case) have sufficient energy to excite the photoemission during the nominal 5 psec pulse width of the pulsed laser. In this way the electron emission carries direct information about the voltage state of pad 3 (FIG. 1) during the duration of the very short laser pulse. By varying the arrival time of the laser pulse with respect to the integrated circuit clock, the voltage and switching behavior of the pad 3 during circuit operation is determined. Using this laser example, a nominal 1 Mhz repetition rate and measurement rate is obtained. Typically, the laser photon flux from such a device is 2 × 10 ⁶ photons / pulse. This optical signal is suitable for providing the signal modulated radiation 10 as a composite function of the dynamic signal during the operation of the integration circuit 1 represented by the signals of the focused laser beam and the pad 3.

Next, appropriate operational characteristics and elements will be shown as long as these items are applicable to FIG. 1 or FIG. The composite laser 7 of FIG. 1 and lasers 16 and 17 of FIG. 2 are composites of mode-locked dye lasers pumped by CW argon ion lasers or YAG lasers. Lens 9 = Compound UV lens (quartz, sapphire) Grid 11 = Stainless steel fine mesh grating, transmittance 80% Detector 13 = Channel electronic amplifier Collector 14 = Stainless steel cup counter 15 = High-speed electronic pulse counter Signal generator The characteristics of the test computer 6 are those of a high-speed logic test system, the characteristics of any type of system common to the technique of testing an integrated circuit by placing the integrated circuit under a dynamic condition that simulates actual or stress operation. Is the same. The operating environment in chamber 4 is a vacuum at about 10 ^-5 to 10 ^-6 (or less) torr-base pressure.

The electron emission signal 10 produced by the laser pulse exhibits a characteristic distribution of electron energy. If the voltage on the pad 3 is more positive with respect to the grid 11, the electrons in the electron emission 10 are correspondingly passed through the grid 11 and are later measured by the detection devices 13, 14, 15. Therefore, the electron emission 10 measured by the detection system consisting of the grid devices 11, 12 and the detection devices 13, 14, 15 reflects the voltage of the pad 3 in the laser pulse. The duration of this laser pulse is short enough, for nominally 5 picoseconds in the case of ultra-fast circuits, to resolve AC switching transients associated with changes in the logic state of pad 3 as well as the logic state itself. it can.

Other embodiments of the bias and detection device can be used. The grid 11 can be eliminated in some cases. When the grid is not used, the front surface of the detection device 13 functions as a bias device. This is because it determines the number of electrons that reach the pad 3 and the detector 13. Such detection systems are sensitive to primary (direct emission) photoelectrons and the resulting secondary electrons. The energy distribution of these electrons is shown in the optical emission graph in the Labrov paper, 1982, IBM TDB, Vol. 25, p. If the signal consists of all electrons with energies above the critical value for detection (similar to a high-pass filter), the sensitivity enhancement is due to laser photons on the material chosen for the test pad, typically aluminum. It is obtained by choosing the energy close to the photoemission threshold. Another compatible detection system is a bandpass electron energy analyzer that only detects electrons that arrive at the analyzer with a specific energy. In this case, the sensitivity advantage is obtained by choosing the photon energy of the laser to be significantly above the photoemission threshold (eg 1 to 2 ev above). In both cases, the sensitivity is enhanced by selectively measuring the electrons at the transition (threshold) of the energy distribution spectra of the secondary and primary electrons.

Other composite pulse laser device embodiments may also be used. These devices include, for example, Raman shift lasers (which use stimulated Raman scattering to change the photon energy), frequency mixing laser devices (more common than harmonic generators), excimer lasers. Device, dye laser device, second harmonic generator (not including third harmonic generator), and the like.

According to the present invention, the energy of the light focused on the pads of the test chip is above a threshold (ev) known as stimulated emission and an intermediate in the manufacturing stage of the integrated circuit or integrated circuit under test. It will be apparent that various light sources or various detection mechanisms other than the preferred or compatible embodiments described above may be used, so long as they are below the value that would hurt.

[0030]

[Effect of the device]

 In accordance with the present invention, there is provided an apparatus for testing an integrated circuit that does not require operator dexterity and is extremely accurate and without damaging the integrated circuit.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a contactless tester for an integrated circuit.

FIG. 2 is a schematic diagram of a laser modification technique used to provide focused light to an integrated circuit and to induce signal modulated radiation as a function of the dynamic signal of the integrated circuit under test.

[Explanation of symbols]

 1 ... test chip, 2 ... mounting device, 3 ... pad, 4 ... environment room, 5 ... bias source, 6 ... calculator, 7 ... laser, 8 ... laser light modulation mechanism, 9 ... ... lens, 10 ... electron emission, 11 ... grid, 12 ... bias source, 13 ... detector, 14 ... collector, 15 ... counter.

Front Page Continuation (72) Inventor Russell Warren Dreyfus, 70, Barker Street, Mount Kisco, New York, USA (72) Inventor, Gary Wayne-Lubrov, 16 Nightingale Road, Katnot, NY, USA

Claims (1)

[Scope of utility model registration request] 1. A mounting apparatus comprising: (a) a vacuum chamber having a test tip position for electrically connecting and mounting a test chip in a form accessible by light; and (b) mounting at said test tip position. A pulse that provides a beam of controlled wavelength that sharply converges to a selected location on a given test chip, has a very short duration pulse width, and is short enough to generate photoelectrons and secondary electrons. A laser device, and (c) a detection device juxtaposed to the mounting device adjacent to the test chip position and including bias means for selectively detecting the radiated photoelectrons having an energy above a predetermined level or within a predetermined range. And (d) applying a dynamic operation signal to the test chip in a normal operating state or a simulated severe operating state. A signal generation and test calculator for comparing the output from the detection device with the test preparation, wherein the detection device detects the photoelectron energy emitted from the test pad on the test chip by proper operation or failure. It is detected as a composite function of the instantaneous input voltage on the test chip performing the improper operation, the parameter of the pulse from the pulse laser device, and the parameter of the bias voltage to the bias means. A semiconductor chip dynamic test device for detecting a circuit voltage generated on a test chip under a characteristic operating condition.