JP2006319144A - Method and apparatus for detecting fault in electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a defect-detecting apparatus for detecting in more detail the defect conditions, such as breakdown or the like in an electronic component. <P>SOLUTION: The defect-detecting apparatus comprises a laser beam radiator 1 for irradiating the femto-second laser to a semiconductor substrate C, an electromagnetic wave detector 6 for detecting the terahertz electromagnetic waves generated by the irradiation of the femto-second laser, and a computer for deciding the existence of a fault such as disconnection or the like in the semiconductor substrate, by inputting a detecting signal detected with this electromagnetic wave detector. The electromagnetic wave detector 6 is constituted with corrosion-proof first and second antennas 23, 24 having detecting directional characteristic for the polarized plane of electromagnetic wave and a movable stage 21 for holding both antennas and sequentially moving these antennas to the electromagnetic wave detecting position. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a defect detection method and a defect detection apparatus capable of detecting defects such as disconnection of an electronic circuit formed on a substrate of an electronic component, for example.

A large number of electronic circuits are formed on a printed circuit board of an electronic component, and non-destructive inspection, for example, inspection using X-rays is performed for disconnection or the like that occurs during the manufacturing process.
However, recently, light pulses have been used due to difficulties in handling such as X-rays. According to this light pulse, it is possible to detect a defect of an electronic component in a non-contact manner without placing the electronic component in a special environment, that is, under normal atmospheric pressure.

Specifically, there is one that inspects for the presence or absence of defects in an electronic component by irradiating an electronic component with a light pulse and detecting a terahertz electromagnetic wave generated by a current induced thereby (see, for example, Patent Document 1). ).
JP 2004-228235 A

  By the way, according to the inspection method described above, there is only one type of electromagnetic wave detection circuit for detecting the electromagnetic wave generated on the electronic component side, and there is a possibility of overlooking the presence or absence of a defect. For this reason, it is desired to detect the defect state in more detail and reflect it in future manufacturing processes.

  Therefore, an object of the present invention is to provide a defect detection method and a defect detection apparatus such as a disconnection in an electronic component that can detect the content of the defect in more detail.

  In order to solve the above-mentioned problems, the defect detection method for disconnection or the like in the electronic component of the present invention is a method for detecting a terahertz electromagnetic wave generated by irradiating the electronic component with a light pulse by the electromagnetic wave detection means and detecting a defect such as disconnection in the electronic circuit When detecting the electromagnetic wave, the electromagnetic wave detecting means is provided with at least two antennas having detection directivity characteristics with respect to the electromagnetic wave deflection surface, and the two antennas are sequentially moved to the electromagnetic wave detection position to generate the terahertz electromagnetic wave. It is a method of detection.

  According to a second aspect of the present invention, there is provided a defect detection method for an electronic component in which the bow tie type antennas are used as the two antennas in the defect detection method according to the first aspect, and the detection directivity characteristics are different from each other. Is the method.

  A defect detection method for an electronic component according to claim 3 is the defect detection method according to claim 1, wherein each of the two antennas having detection directivity has a bowtie type, and each detection directivity has In this method, spiral antennas are arranged so as to be different from each other and the detection directivity is omnidirectional.

  Furthermore, the defect detection apparatus for an electronic component according to claim 4 of the present invention includes an optical pulse irradiation means for irradiating the electronic component with an optical pulse, an electromagnetic wave detection means for detecting a terahertz electromagnetic wave generated by the optical pulse irradiation, An apparatus comprising defect detection means for inputting a detection signal detected by the electromagnetic wave detection means and determining whether or not a defect such as a disconnection exists in the electronic component, wherein the electromagnetic wave detection means It comprises at least two antennas having detection directivity characteristics with respect to the deflection surface, and a movable member that holds these antennas and can be sequentially moved to the electromagnetic wave detection position.

  In addition, the defect detection device for an electronic component according to claim 5 uses a bow-tie type antenna as the two antennas in the defect detection device according to claim 4, and is arranged so that the detection directivity characteristics thereof are different from each other. It is a thing.

  According to a sixth aspect of the present invention, there is provided a defect detection apparatus for an electronic component according to the fourth aspect, wherein each of the two antennas having detection directivity has a bow-tie type, and each detection directivity has The spiral antennas that are arranged so as to be different from each other and that have the detection directivity characteristics in all directions are arranged on the movable member.

  According to the defect detection method and the defect detection apparatus, the electromagnetic wave detection means is provided with at least two antennas having different detection directivity characteristics, and these two antennas are sequentially moved to the electromagnetic wave detection position to generate the terahertz electromagnetic wave. Since the detection is made, it is possible to detect in more detail a defect state such as disconnection in the electronic component.

  In addition to two bow-tie antennas with different detection directivity characteristics, a spiral antenna with detection directivity characteristics in all directions is used as the antenna, and there are defects such as disconnection in the spiral antenna first. If there is no disconnection or the like, it is not necessary to perform detection with a bow-tie antenna, so that the detection work time can be shortened.

[Embodiment]
Hereinafter, a defect detection method and a defect detection apparatus for an electronic component according to an embodiment of the present invention will be described.

  In the present embodiment, the case where the electronic component is a semiconductor substrate on which a large number of electronic circuits are formed, and the case where the defect is a disconnection or the like in the electronic circuit will be described.

Here, the principle that a defect such as disconnection can be detected will be briefly described.
When a semiconductor substrate to be inspected is irradiated with a femtosecond laser that is an optical pulse, a current is induced in the semiconductor substrate by the laser to generate a terahertz electromagnetic wave, and the electric field strength of the generated terahertz electromagnetic wave has a defect such as a disconnection. Therefore, it is different from the case where there is not, and therefore, by comparing a current signal waveform (hereinafter referred to as a detection signal) related to the detection of electromagnetic waves with a current signal waveform (hereinafter also referred to as a reference signal) during normal operation, defects such as disconnection It can be known whether or not exists.

First, the defect detection apparatus will be described with reference to FIG.
As shown in FIG. 1, this defect detection apparatus is arranged in a laser irradiator (light pulse irradiating means) 1 that irradiates a femtosecond laser, and in the middle of an emission optical path of a laser emitted from the laser irradiator 1. A splitter 2 for separating an inspection laser (hereinafter referred to as pump light) A and a trigger laser (hereinafter referred to as probe light) B, and an optical path of the pump light A from the splitter 2 An inspection table (also referred to as a two-dimensional table or an XY table) 3 on which the semiconductor substrate C can be placed and moved in a horizontal plane, and a condensing lens 4 disposed in the optical path of the pump light A And a half mirror [for example, having a transparent conductive film (ITO film) capable of passing the pump light A that has passed through the condenser lens 4 and reflecting the terahertz electromagnetic wave generated in the semiconductor substrate C 5, an electromagnetic wave detector (electromagnetic wave detection means) 6 that can detect terahertz electromagnetic waves (hereinafter simply referred to as electromagnetic waves) from the semiconductor substrate C reflected by the half mirror 5, and the electromagnetic wave detector 6 includes the splitter 2. A reflection mirror 7 for guiding the probe light B from the beam to the electromagnetic wave detector 6 as a trigger, and a time delay unit (time) for sequentially delaying the probe light B disposed between the splitter 2 and the reflection mirror 7. A delay means 8, a lock-in amplifier 9 for amplifying only a detection signal (current signal) of a predetermined frequency detected by the electromagnetic wave detector 6, and a detection signal amplified by the lock-in amplifier 9 A computer device (defect determination means) 10 is provided for input and analysis to determine whether or not a defect such as a disconnection exists. A parabolic mirror 11 for guiding the electromagnetic wave detector 6 is disposed in the middle of the terahertz electromagnetic wave reflected by the half mirror 7 (also referred to as an optical path).

  By the way, as shown in FIG. 2, the electromagnetic wave detector 6 includes, for example, a movable stage (movable member) 21 movably provided in a predetermined direction (indicated by an arrow a), and the movable stage 21 in a predetermined direction. A moving device (not shown, for example, using a linear guide mechanism) to be moved, and first and second antennas 23 and 24 disposed on the movable stage 21 via a holding member 22 are configured. Yes.

  Then, the movable stage 21 is moved in a predetermined direction by the moving device, and the first and second antennas 23 and 24 are sequentially moved to a detection position (A) where electromagnetic waves can be received.

Here, the antennas 23 and 24 will be described with reference to FIG.
Each of these antennas 23 and 24 is also called a photoconductive antenna or an optical switch, and a bow-tie type is used. The bow-tie antennas 23 and 24 have detection directivity characteristics with respect to the electromagnetic wave deflection surface, and are specifically orthogonal to each other so that the respective detection directivity characteristics are different from each other (the directions are 90 ° different from each other). Placed in.

  For example, the first antenna 23 is arranged so as to detect a longitudinal wave whose deflection surface is in the vertical direction, whereas the second antenna 24 is arranged so as to detect a transverse wave whose deflection surface is in the horizontal direction. Is done. Of course, the arrangement may be reversed.

  Since both the antennas 23 and 24 can detect only the electromagnetic wave corresponding to the deflecting surface of the electromagnetic wave, the contents of the broken state generated in the electronic circuit of the semiconductor substrate C can be detected by, for example, the broken circuit wiring. It is possible to know the break position from the direction of.

Here, a bow-tie antenna will be described with reference to FIG.
In this antenna, as shown in FIG. 4, a parallel transmission path 33 including a pair of transmission lines 33a and 33b is formed on a semiconductor substrate 31 such as GaAs that responds at high speed and a photoconductive film 32 such as low-temperature grown GaAs. In addition, a bowtie (bow tie) type circuit 34 is formed at the center thereof, and a minute gap 35 (G) of, for example, about several μm is formed at the center of the circuit 34.

  By the way, the electromagnetic wave detector 6 can receive the terahertz electromagnetic wave only when the probe gap (which is also a femtosecond pulse) B is irradiated to the gap portion G of the antenna, and also receives the terahertz electromagnetic wave itself. Since it is extremely short, the signal waveform cannot be detected at once. Note that a sufficiently narrow time width of 50 femtoseconds or less is used as the pulse width of the femtosecond laser that is a light pulse applied to the electronic component.

  For this reason, the terahertz electromagnetic wave is detected at a plurality of locations in the middle of the current signal waveform, although it is an extremely short interval (also referred to as a sampling interval) Δt, as shown in FIGS. Has been.

  That is, since the same detection location is irradiated with the probe light B a plurality of times, and the probe light of each time is irradiated with a slight delay (Δt) by the time delay device 8, Are detected little by little, and the detection signal waveform is detected (sampling detected) at predetermined intervals. In FIG. 5E, the sampling position in the entire detection signal is indicated by a circle.

  The lock-in amplifier 9 amplifies and extracts a specific frequency signal. As a reference signal, the lock-in amplifier 9 is supplied from an optical chipper (not shown) provided in the middle of a laser emission optical path from the laser irradiator 1. Signal is being input.

The detection signals detected by the antennas 23 and 24 are input to the lock-in amplifier 9, where only the current signal is amplified and input to the computer apparatus 10.
Although not shown in the drawing, the computer 10 receives a signal generation unit that inputs signal values at predetermined intervals amplified by the lock-in amplifier 9 to generate an entire signal waveform (current signal waveform), and this signal. Compare the detection signal created by the creation unit with the reference signal obtained in advance according to the state of the defect such as disconnection (pattern matching of the signal waveform), and which defect the input detection signal corresponds to A defect determination unit for determining whether or not.

Of course, the signal generation unit and the defect determination unit are configured by a program.
In the inspection table 3, as shown in FIG. 6, the inspection area of the semiconductor substrate C, which is the inspection object, is sequentially arranged in, for example, a zigzag shape (indicated by an arrow b) at the irradiation position of the femtosecond laser. It is made to scan by moving to. Of course, the scanning direction can be set arbitrarily.

Next, a method for detecting defects such as disconnection in the semiconductor substrate will be described.
First, the movable stage 21 is moved by the moving device to move the first antenna 23 to the detection position (A), and the semiconductor substrate C as the inspection object is placed on the inspection table 3. .

  Next, a femtosecond laser is emitted from the laser irradiator 1, and the pump light A is irradiated onto the semiconductor substrate C through the splitter 2. When the pump light B is irradiated onto the semiconductor substrate C, a current is induced in the electronic circuit to generate a terahertz electromagnetic wave, and this terahertz electromagnetic wave is transmitted to the electromagnetic wave detector 6 via the reflection mirror 7 and the plane mirror 11. Entered.

  In the electromagnetic wave detector 6, first, terahertz electromagnetic waves are input to the first antenna 23 that is moved to the detection position (A). The probe light B, which is the same femtosecond laser, is input through the reflection mirror 7 to detect terahertz electromagnetic waves.

A detection signal detected by the first antenna 23 is input to the lock-in amplifier 9, and only the detection signal is amplified and then input to the computer device 10 and accumulated.
Of course, the terahertz electromagnetic waves are detected at predetermined intervals as described above, and one detection signal waveform is obtained in the computer device 10.

  When the electromagnetic wave is detected by the first antenna 23 in this way, the movable stage 21 is moved and the second antenna 24 is moved to the detection position (A). Detection is performed.

  In the computer device 10, the detection signals detected by the antennas 23 and 24 are compared with the reference signal corresponding to the input defect in advance to determine whether or not there is a disconnection or the like. A position such as determination and disconnection is detected.

  When the inspection at the first inspection location of the semiconductor substrate C is completed, the inspection location on the semiconductor substrate C is shifted in a predetermined direction by the inspection table 3, and the inspection is performed in the same procedure as described above. This inspection procedure is performed over the entire inspection region of the semiconductor substrate C.

  As described above, the electromagnetic wave detector 6 is provided with two antennas 23 and 24 having different detection directivity characteristics, for example, orthogonal (90 ° different), and the two antennas 23 and 24 are set as electromagnetic wave detection positions. Since the terahertz electromagnetic wave is detected by sequentially moving, the disconnection of the electronic circuit in the semiconductor substrate C can be detected in more detail.

  Further, since the two antennas 23 and 24 are held on the same movable stage 21, both the antennas 23 and 24 can be moved to their detection positions in the same posture and at almost the same time. Terahertz electromagnetic waves can be detected under the same conditions by using antennas having different detection directivity characteristics, so that defects such as disconnection of electronic components can be detected with high accuracy.

  Incidentally, in the above embodiment, two antennas having detection directivity characteristics are arranged in the electromagnetic wave detector 6. However, as shown in FIG. 7, for example, a spiral third antenna 25 may be further arranged. .

In this case, the spiral third antenna 25 can detect the electromagnetic wave without depending on the deflection surface of the electromagnetic wave (so-called directivity is omnidirectional).
That is, by providing the third antenna 25, when detecting electromagnetic waves, the detection directivity characteristics are omnidirectional, so any terahertz electromagnetic waves are generated. In other words, the electronic circuit of the semiconductor substrate C is disconnected. It can be seen that a defect has occurred.

  Therefore, when inspecting defects, detection is first performed using the third antenna 25, and only the presence or absence of defects such as disconnection is examined. Only when there is a defect, detection by the first and second antennas 23 and 24 is performed. By doing so, it is not necessary to perform detection by the first and second antennas when there is no disconnection or the like, so that the detection work time can be shortened.

  Furthermore, in the above embodiment, the antenna having the detection directivity is described as the bow-tie type, but a dipole antenna or a stripline antenna can be used as long as it has the detection directivity.

It is a block diagram which shows schematic structure of the defect detection apparatus which concerns on embodiment of this invention. It is a schematic diagram which shows schematic structure of the electromagnetic wave detector in the defect detection apparatus. It is a figure explaining the detection effect | action with each antenna of the electromagnetic wave detector. It is a figure explaining the bowtie type antenna in the electromagnetic wave detector. It is a figure explaining the detection effect | action with the same electromagnetic wave detector. It is a figure explaining the irradiation position of the femtosecond laser in the same defect detection apparatus. It is a figure explaining the detection effect | action of the antenna which concerns on the modification of the same electromagnetic wave detector.

Explanation of symbols

A Laser (pump light)
B Laser (probe light)
C Semiconductor substrate 1 Laser irradiator 2 Splitter 3 Inspection table 6 Electromagnetic wave detector 8 Time delay device 9 Lock-in amplifier 10 Computer device 21 Movable stage 22 Holding member 23 First antenna 24 Second antenna 25 Third antenna

Claims (6)

When detecting terahertz electromagnetic waves generated by irradiating an electronic component with an optical pulse with an electromagnetic wave detecting means and detecting defects in an electronic circuit,
The electromagnetic wave detecting means is provided with at least two antennas having detection directivity characteristics with respect to the electromagnetic wave deflection surface, and the terahertz electromagnetic waves are detected by sequentially moving these two antennas to the electromagnetic wave detection position. For detecting defects in electronic components.   The defect detection method for an electronic component according to claim 1, wherein the two antennas are arranged so that their detection directivity characteristics are different from each other. Two antennas having detection directivity are arranged so that their detection directivities are different from each other,
The defect detection method for an electronic component according to claim 1, further comprising an antenna whose detection directivity is omnidirectional. A light pulse irradiation means for irradiating an electronic component with a light pulse, an electromagnetic wave detection means for detecting a terahertz electromagnetic wave generated by the irradiation of the light pulse, and a detection signal detected by the electromagnetic wave detection means are input to detect a defect in the electronic component. An apparatus comprising defect determination means for determining whether or not a
An electronic device characterized in that the electromagnetic wave detecting means comprises at least two antennas having detection directivity characteristics with respect to an electromagnetic wave deflection surface, and a movable member that holds each of the antennas and can be sequentially moved to an electromagnetic wave detection position. Defect detection device for parts.   The defect detection apparatus for an electronic component according to claim 4, wherein the two antennas are arranged so that their detection directivity characteristics are different from each other. Two antennas having detection directivity are arranged so that their detection directivities are different from each other,
The defect detection apparatus for an electronic component according to claim 4, further comprising an antenna having a detection directivity characteristic in all directions arranged on a movable member.

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