Disclosure of Invention
The invention aims to solve the defects of the conventional semiconductor device hard defect fault point positioning device, and provides a novel optical path, so that the semiconductor device hard defect fault point positioning device with three functions of LVP, LVI and OBIRCH can be realized based on the optical path, and the complementation of the dynamic and static semiconductor device hard defect fault point positioning is realized. The basic principle of LVP and LVI in the device is the free carrier absorption effect in the semiconductor device, incoherent focusing is carried out on the active region of the device to be tested, the position of a fault point is positioned by directly detecting the intensity change of reflected light without an interference means, so that the influence of reflected light interference at the silicon substrate and air interface and optical path change caused by external disturbance on signal detection in the existing positioning means is eliminated, and the accuracy of positioning the hard defect fault point is improved.
The invention also introduces a frequency domain analysis technology into the OBIRCH, and extracts the current signal submerged in the noise through frequency domain analysis. The emergent light intensity of the laser light source in the device is periodically modulated, and the modulated laser light can cause the current of the power supply end of the tested device to periodically change when heating the defect point. The series resistance on the power supply line of the device under test converts this periodic current change into a voltage change across the resistance. The voltage signals at two ends of the series resistor are subjected to Fourier transform, and the noise voltage signal and the useful signal voltage are separated in a frequency domain to improve the signal-to-noise ratio, so that the signal submerged in the noise is extracted, and the accuracy of the positioning of the OBIRCH hard defect fault point is improved. In addition, the series resistor can reduce the current in the power supply circuit, so that the current in the circuit is not too large to generate signal distortion. In accordance with the above technical object, the present invention provides a fault point locating apparatus for detecting a hard defect of a semiconductor device, comprising:
a light source module for generating incoherent light;
the optical module is connected with the light source module and used for transmitting incoherent light and receiving incoherent light reflected from the inside of the tested device;
an objective lens disposed between the optical module and the device under test for focusing incoherent light inside the device under test and transmitting the reflected light signal to the optical module;
the signal extraction system is connected with the optical module and used for converting the reflected light signal into an electric signal and extracting a time domain signal or a frequency domain signal of the electric signal;
a three-dimensional moving stage for fixing and moving a device under test;
the mobile station control box is connected with the three-dimensional mobile station and is used for controlling the three-dimensional mobile station;
and the control computer is respectively connected with the light source module, the mobile station control box, the optical module and the signal extraction system and controls the fault point positioning device to work.
Preferably, the light source module includes a light emitting diode,
the incoherent light source is used for obtaining incoherent light with the wavelength of more than 1100 nm;
and the modulation module is respectively connected with the incoherent light source and the control computer and is used for modulating the light intensity of the incoherent light.
Preferably, the signal extraction system comprises,
the photoelectric detector is connected with the optical module and used for converting the reflected light signal into an electric signal;
the amplifier is connected with the photoelectric detector and used for amplifying the electric signal;
the DC isolator is connected with the amplifier and is used for isolating useless large DC background components in the power failure signal and outputting an AC signal;
and the signal extractor is connected with the DC blocking device and is used for extracting a time domain signal or a frequency domain signal of the electric signal, wherein the signal extractor is a spectrum analyzer or an oscilloscope.
Preferably, the optical module comprises an optical isolator, a first polarization beam splitter prism, a spatial filtering system, a second polarization beam splitter prism, a Faraday rotator, a half-transmitting and half-reflecting mirror and a focusing lens;
the optical isolator is connected with the spatial filtering system through a first polarization beam splitter prism;
the spatial filtering system is respectively connected with the Faraday optical rotator and the focusing lens through a second polarization beam splitter prism;
the Faraday optical rotator is connected with the semi-transparent semi-reflecting mirror;
the focusing lens is connected with the photoelectric detector.
Preferably, the optical module further comprises an infrared imaging unit, wherein the infrared imaging unit is used for obtaining an internal infrared layout of the device to be tested;
the infrared imaging unit comprises a beam splitter, an infrared illumination light source, an imaging lens and an infrared camera;
the beam splitter is respectively connected with the infrared illumination light source, the imaging lens and the semi-transparent semi-reflecting mirror;
the imaging lens is connected with the infrared camera.
Preferably, the fault point locating device further comprises,
the tester is used for providing periodic driving signals for the tested device;
the constant voltage source is used for providing constant voltage for the tested device.
Preferably, the photodetector is one of a PIN diode and an avalanche photodiode;
the amplifier is a transimpedance amplifier.
A positioning method for detecting hard defect fault points of a semiconductor device comprises the following steps:
acquiring an infrared microscopic image of a device to be tested at the focus of an objective lens, recording the focus coordinate of the objective lens corresponding to the infrared microscopic image, and generating an integral infrared microscopic image of the device to be tested after the device to be tested is subjected to traversing scanning;
the device to be tested is driven by the driving signal, and the frequency signal intensity of each coordinate point is collected to obtain a frequency intensity distribution graph of the device to be tested;
obtaining a signal intensity distribution diagram of the tested device by superposing the integral infrared microscopic image of the tested device and the frequency intensity distribution diagram of the tested device, wherein the signal intensity distribution diagram is a specific working frequency intensity distribution diagram or a current frequency intensity distribution diagram of the tested device;
based on the signal intensity profile, the location of hard defect failure points on the device under test 5 is obtained.
Preferably, during the acquisition of the drive signal frequency strength of the device under test,
the method comprises the steps of driving a tested device through a periodic driving signal, collecting the intensity of a frequency signal in the tested device, and obtaining a driving signal frequency intensity distribution diagram;
superposing the infrared microscopic image and the driving signal frequency intensity distribution map to obtain a specific working frequency intensity distribution map of the tested device;
and based on the specific working frequency intensity distribution diagram, obtaining the position of the hard defect fault point of the tested device by analyzing the signal intensity of each point in the diagram and extracting a time domain waveform signal.
Preferably, in acquiring the current frequency signal strength of the device under test,
supplying power to the device to be tested through constant voltage, periodically modulating the light intensity of laser, collecting the disturbed current signal intensity of the device to be tested, and obtaining a current disturbance signal frequency intensity distribution diagram;
superposing the infrared microscopic image and the current disturbance signal frequency intensity distribution map to obtain a current frequency intensity distribution map of the tested device;
and obtaining the position of the hard defect fault point of the tested device through the signal intensity of each point in the graph based on the current frequency intensity distribution graph.
The invention discloses the following technical effects:
the technical scheme provided by the invention can be used for positioning the fault point of the Flip-Chip packaged integrated circuit and the full-function fault point of the scan chain circuit in the integrated circuit, is suitable for short circuit, electric leakage and observation of micro failures such as transistor breakdown, aluminum-silicon mutual melting short circuit and dielectric layer crack, is accurate in positioning, and provides a technical thought for fault detection of the integrated circuit.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1 to 4, the present invention provides a positioning apparatus for detecting a hard defect fault point of a semiconductor device, comprising:
a light source module for generating incoherent light;
an optical module 3 connected to the light source module, for transmitting incoherent light and receiving incoherent light reflected from the inside of the device under test;
an objective lens 4 disposed between the optical module 3 and the device under test 5 for focusing incoherent light inside the device under test 5 and transmitting the reflected light signal to the optical module 3;
the signal extraction system is connected with the optical module 3 and used for converting the reflected light signals into electric signals and extracting time domain electric signals or frequency domain electric signals;
a three-dimensional moving stage 6 for fixing and moving the device under test 5;
a mobile station control box 14 connected to the three-dimensional mobile station 6 for controlling the three-dimensional mobile station 6;
and the control computer 13 is respectively connected with the light source module, the mobile station control box 14, the optical module 3 and the signal extraction system and controls the fault point positioning device to work.
The light source module comprises an incoherent light source 1 for obtaining incoherent light with the wavelength of more than 1100 nm; and the modulation module 2 is respectively connected with the incoherent light source 1 and the control computer 13 and is used for modulating the light intensity of the incoherent light.
The signal extraction system comprises a photoelectric detector 9 connected with the optical module 3 and used for converting the reflected light signal into an electric signal; an amplifier 10 connected to the photodetector 9 for amplifying the electrical signal; a dc isolator 11 connected to the amplifier 10 for isolating an unwanted large dc background component in the power-down signal and outputting an ac signal; and the signal extractor 12 is connected with the dc isolator 11 and is configured to extract a time domain electrical signal or a frequency domain electrical signal, where the signal extractor 12 is a spectrum analyzer or an oscilloscope.
The optical module 3 comprises an optical isolator, a first polarization beam splitter prism, a spatial filtering system, a second polarization beam splitter prism, a Faraday rotator, a semi-transparent and semi-reflective mirror and a focusing lens; the optical isolator is connected with the spatial filtering system through a first polarization beam splitter prism; the spatial filtering system is respectively connected with the Faraday optical rotator and the focusing lens through a second polarization beam splitter prism; the Faraday optical rotator is connected with the semi-transparent semi-reflecting mirror; the focusing lens is connected to the photodetector 9.
The optical module 3 further comprises an infrared imaging unit, wherein the infrared imaging unit is used for obtaining an internal infrared layout of the device under test 5; the infrared imaging unit comprises a beam splitter, an infrared illumination light source, an imaging lens and an infrared camera; the beam splitter is respectively connected with the infrared illumination light source, the imaging lens and the semi-transparent semi-reflecting mirror; the imaging lens is connected with the infrared camera.
The fault point locating device further comprises a tester 7 for providing periodic drive signals for the device under test 5; and a constant voltage source 8 for providing a constant voltage to the device under test 5.
The photodetector 9 is one of a PIN diode and an avalanche photodiode; the amplifier 10 is a transimpedance amplifier.
A positioning method for detecting hard defect fault points of a semiconductor device comprises the following steps,
acquiring an infrared microscopic image of a device to be tested 5 at the focus of an objective lens 4, recording the focus coordinate of the objective lens 4 corresponding to the infrared microscopic image, and generating an overall infrared microscopic image of the device to be tested 5 after the device to be tested 5 is subjected to traversal scanning;
the device under test 5 is driven by the driving signal, and the frequency signal intensity of each coordinate point is collected to obtain a frequency intensity distribution graph of the device under test 5; obtaining a signal intensity distribution map of the device under test 5 by superimposing the overall infrared microscopic image of the device under test 5 and the frequency intensity distribution map of the device under test 5, wherein the signal intensity distribution map is a specific operating frequency intensity distribution map or a current frequency intensity distribution map of the device under test; based on the signal intensity distribution map, the location of a hard defect fault point on the device under test 5 is obtained.
In the process of acquiring the frequency intensity of the driving signal of the device under test 5, driving the device under test 5 by a periodic driving signal, acquiring the frequency signal intensity inside the device under test 5, and obtaining a driving signal frequency intensity distribution map; obtaining the specific working frequency intensity distribution diagram of the device under test 5 by superposing the infrared microscopic image and the driving signal frequency intensity distribution diagram; and obtaining the position of the hard defect fault point of the device under test 5 by analyzing the signal intensity of each point in the graph and extracting a time domain waveform signal based on the specific working frequency intensity distribution graph.
In the process of acquiring the current frequency signal intensity of the device under test 5, supplying power to the device under test 5 through a constant voltage, periodically modulating the laser light intensity, acquiring the disturbed current signal intensity of the device under test 5, and obtaining a current disturbance signal frequency intensity distribution diagram; obtaining the current frequency intensity distribution diagram of the device under test 5 by superposing the infrared microscopic image and the current disturbance signal frequency intensity distribution diagram; based on the current frequency intensity distribution diagram, the position of the hard defect fault point of the device under test 5 is obtained through the magnitude of the signal intensity of each point in the diagram.
Example 1: the invention provides a method and a device for positioning hard defect fault points of a semiconductor device, which can realize the complementation of the positioning of dynamic and static hard defect fault points of the semiconductor device and can well cope with most failure modes. When the dynamic fault point is positioned, laser passes through a silicon substrate on the back of a Chip and is focused on an active region of a device to be tested, the intensity change of incident light is caused by a free carrier absorption effect, and fault point positions are respectively positioned from a time domain and a frequency domain by detecting the intensity change of reflected light by the LVP and the LVI, so that the method is particularly suitable for performing fault point positioning on a Flip-Chip packaged integrated circuit and performing full-function fault point positioning on an internal scan chain circuit of the integrated circuit; when a static fault point is positioned, the light energy part at the focus of the OBIRCH is converted into heat energy, if a metal interconnection line has a defect, the temperature of the position of the defect cannot be quickly conducted and dispersed through the metal line, the temperature at the position of the defect is increased accumulatively, the resistance of the metal line is further changed, the static working current of the tested device is changed, the current change is converted into voltage change through the series resistance on the power supply line of the tested device, the position of the fault point is positioned in a frequency domain through Fourier transformation of the collected voltage signal, and the method is suitable for short circuit, electric leakage and observation of micro failures such as transistor breakdown, aluminum silicon mutual melting short circuit and dielectric layer crack.
A dynamic fault point positioning method for semiconductor device hard defect is especially suitable for positioning fault points of Flip-Chip packaged integrated circuits and fully functional fault points of scan chain circuits in the integrated circuits, and comprises the following steps:
LVI determines position and intensity distribution of specific frequency point
Light emitted by an infrared microscopic imaging light source in an infrared imaging unit is focused on an active area of a device to be tested by an objective lens, a three-dimensional mobile station 6 moves the device to be tested to realize traversal scanning of the imaging light to the device to be tested 5, an infrared camera in the infrared imaging unit generates an infrared microscopic image of each focus point in the moving process and sends the infrared microscopic image to a control computer 13 for storage, meanwhile, a mobile station control box 14 also sends coordinate information of each focus point to the control computer 13 for storage, and the stored infrared microscopic images correspond to the coordinate information one by one. After the traversal scanning of the device under test 5 is completed, the control computer 13 generates and stores an infrared microscopic image of the whole device under test according to the internally stored infrared microscopic image and coordinate information of each coordinate point, and simultaneously restores the three-dimensional moving table 6 to the original scanning position. Tester 7 sends periodic drive signals to repeatedly drive device under test 5, and tester 7 does not send clock signals to signal extractor 12 in LVI mode. The signal extractor 12 is directly controlled by the control computer 13, and in LVI mode the signal extractor 12 is a spectrum analyzer, the response frequency of which is set to the same frequency as the device under test 5 drive signal. The control computer 13 controls the three-dimensional mobile station 6 to move the device under test 5 to realize traversal scanning of the focused light on the device under test 5, the frequency spectrum analyzer sends the frequency signal intensity at each focus point to the control computer 13 to be stored, different signal intensities are represented by different colors during storage, meanwhile, the mobile station control box 14 also sends the coordinate information at each focus point to the control computer 13 to be stored, and at the moment, the frequency signal intensity and the coordinate information at each focus point are in one-to-one correspondence. After the scanning is completed, the control computer 13 generates a driving signal frequency intensity distribution map of the device under test 5 based on the frequency signal intensity information and the coordinate information at each coordinate point. The control computer 13 then superimposes the ir microscopic image of the entire device under test 5 with the frequency intensity distribution map to generate a specific operating frequency intensity distribution map for the device under test 5. The specific working frequency intensity distribution diagram obtained by testing comprises layout information of the device, signal intensity of specific working frequency at each position in the layout and coordinate position information.
LVP detection frequency point time domain waveform positioning fault point position
The control computer 13 controls the three-dimensional mobile station 6 to move the device under test 5 to focus light to a signal detection target area, the test machine 7 sends a periodic driving signal to repeatedly drive the device under test 5, and simultaneously sends a clock signal to the signal extractor 12 for synchronizing the signal extractor 12, in the mode, the signal extractor 12 is an oscilloscope, and the oscilloscope performs multiple times of average noise elimination on the acquired waveform to improve the signal-to-noise ratio so as to extract a time domain signal waveform. The waveform signal output by the oscilloscope is sent to the control computer 13, and the operator accurately positions the fault point position in the device under test 5 by analyzing the waveform.
A static positioning method for hard defect fault points of a semiconductor device is suitable for short circuit, electric leakage and observation of micro failures such as transistor breakdown, aluminum-silicon mutual melting short circuit and dielectric layer cracks. The method comprises the following steps:
light emitted by an infrared microscopic imaging light source in an infrared imaging unit is focused inside a device to be tested 5 by an objective lens, a three-dimensional mobile station 6 moves the device to be tested 5 to realize traversal scanning of the imaging light to the device to be tested 5, an infrared camera in an imaging system is converted in the moving process to generate an infrared microscopic image of each focus point and send the infrared microscopic image to a control computer 13 for storage, meanwhile, a mobile station control box 14 also sends coordinate information of each focus point to the control computer 13 for storage, and the stored infrared microscopic images correspond to the coordinate information one by one. After the traversal scanning of the device under test 5 is completed, the control computer 13 generates and stores an infrared microscopic image of the whole device under test 5 according to the internally stored infrared microscopic image and coordinate information of each coordinate point, and simultaneously restores the three-dimensional moving stage 6 to the original scanning position. Light emitted by the light source is modulated by the modulation module 2 into light output with light intensity changing at a certain frequency and a duty ratio of 50%, and the light output is focused on a metal wiring layer of the tested device 5 through an objective lens. The control computer 13 sends a control signal to the polarization beam splitter prism controller to move the second polarization beam splitter prism out of the optical path.
The constant voltage source 8 supplies the device under test 5 with a constant voltage, a series resistor is connected to the power supply line, the voltage signal across the series resistor is transmitted to a signal extractor 12, the signal extractor 12 is directly controlled by a control computer 13, the signal extractor 12 in this mode is a spectrum analyzer, and the response frequency of the spectrum analyzer is set as the modulation frequency of the modulation module 2 for the light source. The three-dimensional mobile station 6 moves the device to be tested 5 to realize traversal scanning of the focused light on the device to be tested 5, the frequency spectrum analyzer sends the frequency signal intensity at each focus to the control computer 13 to be stored in the control computer in the moving process, different signal intensities are represented by different colors, meanwhile, the mobile station control box 14 also sends the coordinate information at each focus to the control computer 13 to be stored, and the frequency signal intensity and the coordinate information at each focus are in one-to-one correspondence. After the scanning is completed, the control computer 13 generates a frequency intensity distribution map of the light modulation frequency from the frequency signal intensity information and the coordinate information at each focal point. The control computer 13 superimposes the infrared microscopic image of the device under test 5 with the frequency intensity distribution map to generate a current frequency intensity distribution map when the device under test 5 is disturbed by the modulated light. The current frequency intensity distribution diagram comprises layout information of the device, and disturbance voltage signal intensity and coordinate position information corresponding to each point in the layout. The defect location is determined by analyzing the frequency intensity profile.
Fig. 1 is a schematic diagram of a semiconductor device hard defect fault point locating device according to an embodiment of the invention. The light source is an incoherent light source 1, such as a superluminescent light emitting diode, providing incoherent light required by the system. The wavelength of the incoherent light source 1 is a non-invasive wavelength > 1100 nm. The light emitted by the incoherent light source 1 is transmitted to the modulation module 2 through a free space optical path/polarization maintaining optical fiber, and the modulation module 2 is controlled by the control computer 13. When using LVP and LVI for dynamic fault point positioning, the modulation module 2 does not work and light directly penetrates the modulation module 2 to reach the optical module 3. When using OBIRCH to locate static fault points, the control computer 13 controls the modulation module 2 to modulate the light input by the incoherent light source 1 into a light output with a light intensity varying at a certain frequency with a duty cycle of 50%. The light output by the modulation module 2 is transmitted to the optical module 3 through a free space optical path/polarization maintaining optical fiber. The optical module 3 comprises a transform imaging system and a polarization beam splitter prism controller. The transform imaging system is used for regulating incident light and focusing the light on an active area of the device under test 5 while infrared imaging is performed on the internal layout of the device under test 5. The focusing of the light in the system is achieved by means of an objective 4, which may be chosen as an air gap lens, a liquid immersion lens or a solid immersion lens. The polarizing beam splitter prism controller is controlled by the control computer 13, and when we use the OBIRCH function of the system, the polarizing beam splitter prism controller moves the polarizing beam splitter prism out of the optical path, at which time no more light will enter the photodetector 9. When we use the LVP and LVI functionality of the system, the polarizing beam splitter prism controller moves the polarizing beam splitter prism into the optical path, and the light reflected back from the device under test 5 is totally reflected by the polarizing beam splitter prism through the free optical path/fiber to the photodetector 9, which can be any conventional photodetector, such as a PIN diode, Avalanche Photodiode (APD), etc. An amplifier 10 (e.g., a transimpedance amplifier) amplifies the input signal from photodetector 9 while sending its output signal to a dc-blocker 11. dc-blocker 11 can isolate unwanted large dc background components in the signal and output only an ac signal to a signal extractor 12. The signal extractor 12 may be a spectrum analyzer or an oscilloscope, the signal extractor 12 is controlled by a control computer 13, and the signal processed by the signal extractor 12 is sent to the control computer 13 for analysis by an operator. The control computer 13 provides a simple programmable operator interface for better operator control of the entire apparatus.
There are two modes of operation in the apparatus of fig. 1: a dynamic hard defect fault location mode and a static hard defect fault location mode. When the dynamic hard defect fault point positioning mode is used, the LVI and LVP functions of the system are used, and the OBIRCH function is not used. When the dynamic hard defect fault point is positioned, the LVI is firstly used for determining the position and the intensity distribution of a specific frequency point. Light emitted by an infrared microscopic imaging light source in the transformation imaging system is focused on an active area of a device to be tested 5 by an objective lens 4, the three-dimensional mobile station 6 moves the device to be tested 5 to realize traversal scanning of the imaging light to the device to be tested 5, an infrared camera in the transformation imaging system generates an infrared microscopic image of each focus point in the moving process and sends the infrared microscopic image to a control computer 13 for storage, meanwhile, a mobile station control box 14 also sends coordinate information of each focus point to the control computer 13 for storage, and the stored infrared microscopic images correspond to the coordinate information one by one. After the traversal scanning of the device under test 5 is completed, the control computer 13 generates and stores an infrared microscopic image of the whole device under test according to the internally stored infrared microscopic image and coordinate information of each coordinate point, and simultaneously restores the three-dimensional moving table 6 to the original scanning position. Tester 7 sends periodic drive signals to repeatedly drive device under test 5, and tester 7 does not send clock signals to signal extractor 12 in LVI mode. The signal extractor 12 is directly controlled by the control computer 13, and a spectrum analyzer is used at the signal extractor 12 in the LVI mode, and the response frequency of the spectrum analyzer is set to the same frequency as the drive signal of the device under test 5. The control computer 13 controls the three-dimensional mobile station 6 to move the device under test 5 to realize traversal scanning of the focused light on the device under test 5, the frequency spectrum analyzer sends the frequency signal intensity at each focus point to the control computer 13 to be stored, different signal intensities are represented by different colors during storage, meanwhile, the mobile station control box 14 also sends the coordinate information at each focus point to the control computer 13 to be stored, and at the moment, the frequency signal intensity and the coordinate information at each focus point are in one-to-one correspondence. After the scanning is completed, the control computer 13 generates a driving signal frequency intensity distribution map of the device under test 5 based on the frequency signal intensity information and the coordinate information at each coordinate point. The control computer 13 then superimposes the ir microscopic image of the entire device under test 5 with the frequency intensity distribution map to generate a specific operating frequency intensity distribution map for the device under test 5. The frequency intensity distribution diagram obtained by testing comprises layout information of the device, and signal intensity and coordinate position information of a specific working frequency corresponding to each point in the layout.
After obtaining the specific operating frequency intensity distribution map of the device under test 5, the LVP function of the system analyzes the time domain waveform of each frequency point to further determine the location of the defect point in the device under test 5. The control computer 13 controls the three-dimensional mobile station 6 to move the device under test 5 so as to focus light to a signal detection target area, the test machine 7 sends a periodic driving signal to repeatedly drive the device under test 5, and simultaneously sends a clock signal to the signal extractor 12 for synchronizing the signal extractor 12, in the mode, the signal extractor 12 uses an oscilloscope, and the oscilloscope performs multiple times of average noise elimination on the acquired waveform to improve the signal-to-noise ratio. The waveform signal output by the oscilloscope is sent to the control computer 13, and the operator accurately positions the fault point position in the device under test 5 by analyzing the waveform.
When using the static hard defect fault location mode, only the OBIRCH function of the system is used. Light emitted by an infrared microscopic imaging light source in the transformation imaging system is focused inside a tested device 5 by an objective lens 4, the three-dimensional mobile station 6 moves the tested device 5 to realize traversal scanning of the imaging light to the tested device 5, an infrared camera in the transformation imaging system generates an infrared microscopic image of each focus point in the moving process and sends the infrared microscopic image to a control computer 13 for storage, meanwhile, a mobile station control box 14 also sends coordinate information of each focus point to the control computer 13 for storage, and the stored infrared microscopic images correspond to the coordinate information one by one. After the traversal scanning of the device under test 5 is completed, the control computer 13 generates and stores an infrared microscopic image of the whole device under test 5 according to the internally stored infrared microscopic image and coordinate information of each coordinate point, and simultaneously restores the three-dimensional moving stage 6 to the original scanning position. The light emitted by the incoherent light source 1 is modulated by the modulation module 2 into light output with light intensity changing at a certain frequency and a duty ratio of 50%, and the light output is focused on a metal wiring layer of a tested device 5 through an objective lens 4. The control computer 13 sends a control signal to the polarization beam splitter prism controller to move the polarization beam splitter prism out of the optical path. The constant voltage source 8 supplies the device under test 5 with a constant voltage, a series resistor is connected to the power supply line, the voltage signal across the series resistor is transmitted to the signal extractor 12, the signal extractor 12 is directly controlled by the control computer 13, in this mode, a spectrum analyzer is used at the signal extractor 12, and the response frequency of the spectrum analyzer is set as the modulation frequency of the modulation module 2 for the incoherent light source 1. The three-dimensional mobile station 6 moves the device to be tested 5 to realize traversal scanning of the focused light on the device to be tested 5, the frequency spectrum analyzer sends the frequency signal intensity at each focus to the control computer 13 to be stored in the control computer in the moving process, different signal intensities are represented by different colors, meanwhile, the mobile station control box 14 also sends the coordinate information at each focus to the control computer 13 to be stored, and the frequency signal intensity and the coordinate information at each focus are in one-to-one correspondence. After the scanning is completed, the control computer 13 generates a frequency intensity distribution map of the light modulation frequency from the frequency signal intensity information and the coordinate information at each focal point. The control computer 13 superimposes the infrared microscopic image of the device under test 5 with the frequency intensity distribution map to generate a current frequency intensity distribution map when the device under test 5 is disturbed by the modulated light. The current frequency intensity distribution diagram comprises layout information of the device, and disturbance voltage signal intensity and coordinate position information corresponding to each point in the layout. And determining the position of the hard defect fault point by analyzing the frequency intensity distribution diagram.
FIG. 2 is a schematic diagram of dynamic hard defect fault location with incoherent light focused on the active area through the silicon substrate on the backside of the device under test 5, in accordance with an embodiment of the present invention. Light from an incoherent light source 1 in fig. 1 is focused on an active area of a device under test 5 through an optical module 3 and an objective lens 4, the free carrier absorption effect of the active area periodically modulates the intensity of incident laser light under the action of a periodic driving signal of the device under test 5, the modulated laser light is reflected by a metal wiring layer on the front surface of a chip and returns, and the reflected light sequentially passes through the objective lens 4 and the optical module 3. The reflected light is totally reflected in the optical module 3 to the photodetector 9, and the photodetector 9 outputs an electric signal whose intensity varies periodically, i.e., an LVP/LVI signal.
FIG. 3 is a view according to the present inventionAccording to the static hard defect fault point positioning schematic diagram of the embodiment of the invention, incoherent light is focused on a metal interconnection layer through a silicon substrate on the back of a tested
device 5. Incoherent light from an incoherent
light source 1 in fig. 1 is modulated into light with light intensity periodically changing at a certain frequency by a
modulation module 2, the light is focused on a metal interconnection layer of a device under
test 5 through an
optical module 3 and an objective lens 4, and partial energy of the light at the focused point is converted into heat. If there are defects or voids in the metal interconnect lines, the heat conduction near these areas will be different from other intact areas, causing local temperature changes and thus resistance value changes Δ R.
Constant voltage source 8 applies constant voltage V to the interconnection line, and current change caused by laser heating
Due to the resistance R
1Connected in series to the supply circuit of the
constant voltage source 8, so that the resistor R
1Voltage change at both ends
By this relationship, the resistance change caused by heat and the resistance R are converted
1The voltage changes at the two ends are linked, and the periodical change of the resistance of the metal interconnection line caused by the photothermal effect is converted into the resistance R
1A periodic variation of the voltage across the terminals. Periodic voltage change signal DeltaV
1Is sent to the
signal extractor 12 where, using a spectrum analyzer at the
signal extractor 12, the voltage signal in the time domain is converted to a voltage signal in the frequency domain to locate the hard defect fault point location.
Fig. 4 is a schematic diagram illustrating an optical path according to an embodiment of the invention. For convenience of introducing the whole optical path principle, we describe the optical path system from two aspects of dynamic hard defect fault point positioning and static hard defect fault point positioning respectively. When the device is in the dynamic hard defect fault point positioning modes, namely LVI and LVP, the incoherent light emitted by the incoherent light source 1 is totally transmitted when passing through the optical chopper (the modulation module 2 in FIG. 1), and the optical chopper does not work. The incoherent light then passes through an optical isolator (eliminating optical feedback, improving signal-to-noise ratio) to a first polarizing beam splitting prism. A portion of the light at the first polarizing beam splitter prism is reflected into an optical power meter for monitoring the output optical power of the incoherent light source 1, and the remaining light passes through a spatial filtering system. The spatial filtering system consists of a lens 1, a pinhole diaphragm and a lens 2, wherein the pinhole diaphragm is positioned at the focus of the lens 1 and the lens 2, and the system can be used for improving the signal-to-noise ratio of a received signal and reducing the size of a light spot. The light emitted from the spatial filter system is transmitted completely when passing through the second polarization beam splitter prism (controlled by the polarization beam splitter prism controller in fig. 1), and the faraday rotator rotates the polarization direction of the linearly polarized light by 45 degrees, passes through the half-transmitting and half-reflecting mirror and the objective lens, and passes through the silicon substrate on the back of the device to be tested to be focused on the active region in the silicon substrate. The modulated light is reflected by a metal wiring reflection original path on the front surface of the tested device, passes through an objective lens, a half-mirror and a Faraday optical rotator, then is changed into linearly polarized light vertical to the polarization state of incident linearly polarized light, is totally reflected at a second polarization beam splitter prism, and reaches a photoelectric detector (namely a photoelectric detector 9 in figure 1) through a focusing lens to detect the phase change of the light reflected from the tested device, so that the frequency signal characteristic and the time domain transmission waveform in the tested device are determined, and the position of a hard defect fault point is positioned.
When the device is in a static hard defect fault point positioning mode, namely OBIRCH, incoherent light emitted by the incoherent light source 1 is modulated into light with light intensity periodically changing at a certain frequency when passing through the optical chopper, and the modulated light passes through the optical isolator (light feedback is eliminated, and stable output of the light power of the incoherent light source 1 is ensured) and reaches the first polarization beam splitter prism. A portion of the light is then reflected to an optical power meter whose output is used to monitor the optical power, with the remainder passing through a spatial filtering system. Because the second polarization beam splitter prism moves out of the optical path when the OBIRCH is operated, light emitted from the spatial filtering system directly reaches the Faraday rotator, then passes through the half-mirror and the objective lens, passes through the silicon substrate on the back of the device to be tested and is focused on the metal interconnection layer, partial energy of laser at the focal point is converted into heat, the resistance change of the defect position is caused, the static working current of the device is changed, and therefore the position of the hard defect fault point is determined.
Fig. 4 also includes an imaging element for performing infrared microscopic imaging on the internal layout of the device under test, including an infrared illumination light source for generating infrared imaging light required for imaging, wherein the light emitted by the infrared illumination light source passes through the beam splitter, the half mirror and the objective lens, and passes through the silicon substrate on the back of the device under test to be focused inside the silicon substrate. The illumination light is reflected by the metal wiring on the front surface of the device to be tested, and reaches the infrared camera through the objective lens, the half-transmitting and half-reflecting mirror, the beam splitter and the imaging lens to form an infrared microscopic image in the device to be tested.
The device integrates the LVP, the LVI and the OBIRCH together to realize the complementation of the positioning of the dynamic and static hard defect fault points of the semiconductor device, and simultaneously improves the positioning precision of the hard defect fault points of the semiconductor device by the optimized design of the LVP, the LVI and the OBIRCH.
The invention is used for fault point positioning of a Flip-Chip packaged integrated circuit and full-function fault point positioning of a scan chain circuit in the integrated circuit, is suitable for short circuit, electric leakage and observation of micro failures such as transistor breakdown, aluminum-silicon mutual melting short circuit and dielectric layer crack, and has accurate positioning.
It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus once an item is defined in one figure, it need not be further defined and explained in subsequent figures, and moreover, the terms "first", "second", "third", etc. are used merely to distinguish one description from another and are not to be construed as indicating or implying relative importance.
Finally, it should be noted that: the above-mentioned embodiments are only specific embodiments of the present invention, which are used for illustrating the technical solutions of the present invention and not for limiting the same, and the protection scope of the present invention is not limited thereto, although the present invention is described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: any person skilled in the art can modify or easily conceive the technical solutions described in the foregoing embodiments or equivalent substitutes for some technical features within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the present invention in its spirit and scope. Are intended to be covered by the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.