Semiconductor device inspection apparatus and method

Abstract

To provide an inspection device which realizes more accurate inspection more quickly. The system includes a planar imaging device HR for imaging the chip top surface 10c of a semiconductor chip, end surface imaging devices SLa, SLb for imaging the chip end surfaces 10a, 10b, and an operation control device CTL which positions the end surface imaging devices SLa, SLb at a first reference position P0, evaluates the images captured during movement, stops the end surface imaging devices SLa, SLb at a second reference position Ps, and then tilts and moves the end surface imaging devices SLa, SLb toward the semiconductor chip 10 while repeatedly capturing the chip end surfaces 10a, 10b. The multiple captured images are evaluated from the viewpoint of whether the portion connecting the chip top surface 10c and the chip end surfaces 10a, 10b can be clearly detected, and an optimal image is determined.

Description

[Technical field]

[0001] The present invention relates to an inspection method and an apparatus for quickly and reliably inspecting chip end faces during the manufacturing process of semiconductor chips such as semiconductor lasers LDs (Laser Diodes). [Background technology]

[0002] LD chips generally have a double heterostructure in which an active layer that emits light at the laser emission wavelength is sandwiched between a P-type cladding layer and an N-type cladding layer. When a forward voltage is applied between the P-type and N-type layers, both end faces of the active layer function as reflecting mirrors, causing the laser light to travel back and forth within the active layer while being amplified, resulting in stimulated emission.

[0003] Here, edge-emitting lasers can be broadly classified according to their reflection structure into Fabry-Perot lasers, which use a semiconductor cleavage surface as a reflection mirror, distributed feedback lasers (DFB lasers) in which a diffraction grating is formed in the waveguide, and distributed Bragg reflector lasers (DBR lasers) in which diffraction gratings are formed before and after the active region.

[0004] For semiconductor chips with such a configuration, it is necessary to inspect the induced emission apertures formed on the chip end faces for scratches or dust, for example, at the final manufacturing stage. Therefore, the applicant has proposed an invention that can quickly and reliably inspect the quality of the induced emission apertures (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2023012966 (filed August 5, 2021) Summary of the Invention

[0006] In the above invention, the imaging device is tilted away from the semiconductor chip from a start position of the tilt movement, which is somewhat forcibly defined, and multiple images are taken during this movement, from which the best focused image is selected.The quality of the stimulated emission port is then judged based on the selected best image. [Problem to be solved by the invention]

[0007] However, in an inspection environment in which a large number of semiconductor chips are placed on a mounting surface that is not necessarily perfectly flat, the above configuration makes it impossible to move the imaging device to an optimal position that differs for each semiconductor chip when the tilt movement begins.

[0008] In other words, since there is some thickness error in the thickness of each semiconductor chip, and furthermore, some unevenness (e.g., on the order of several hundred microns) is unavoidable in the mounting surface on which the semiconductor chip is attached, the optimal starting point for the tilt movement actually differs for each semiconductor chip to be inspected.

[0009] Therefore, the inclined movement of the imaging device may start from an inaccurate movement start position, and in such a case, the end face of the semiconductor chip cannot be determined accurately.

[0010] In particular, even if the imaging device captures a large image of the semiconductor chip when it is closest to the semiconductor chip as in the cited document 1, there is a risk that the imaging device may miss the semiconductor chip as it ascends in the inclined direction. Also, there are cases where it is necessary to determine the quality of both end faces of the semiconductor chip, and there is a demand for accurate and rapid quality inspection in such cases.

[0011] The present invention has been made in consideration of the above problems, and an object of the present invention is to provide an inspection method and an inspection apparatus that realize more accurate inspection more quickly. [Means for solving the problem]

[0012] The semiconductor element inspection apparatus according to the present invention includes a planar imaging device capable of imaging the upper surface of a semiconductor chip to be imaged that is placed on a light-reflective or light-transmitting mounting surface, an end surface imaging device capable of imaging the chip end surface of the semiconductor chip while moving back and forth in an oblique direction between a diagonally upward position of the semiconductor chip and the semiconductor chip, and an operation control device which positions the end surface imaging device at a first reference position based on an image captured by the planar imaging device, moves the end surface imaging device in a horizontal direction from the first reference position, evaluates the captured image of the semiconductor chip during movement, stops the end surface imaging device at a second reference position, and then moves the end surface imaging device at an oblique angle toward the semiconductor chip. An inspection device, wherein a first reference position is a position including a second reference position, beyond or within the first reference position in a planar positional relationship with the semiconductor chip, and the second reference position is a position at which an entire image of the semiconductor chip is captured within an imaging screen of the end face imaging device, and the operation control device is configured to include an imaging means for imaging a plurality of images while illuminating the chip end face while tilting the end face imaging device from the second reference position, and an identification means for extracting data on an evaluation line extending from the top surface of the chip to the chip end face from the plurality of images captured by the imaging means, evaluating the manner in which the data on the evaluation line changes, and identifying an optimal image.

[0013] Furthermore, a method for inspecting a semiconductor element according to the present invention includes a planar imaging device capable of imaging an upper surface of a semiconductor chip to be imaged that is placed on a light-reflective or light-transmitting mounting surface; an end surface imaging device capable of imaging a chip end surface of the semiconductor chip while moving back and forth in an oblique direction between a position diagonally above the semiconductor chip and the semiconductor chip; and an operation control device that executes a first step of positioning the end surface imaging device at a first reference position based on an image captured by the planar imaging device, a second step of moving the end surface imaging device in a horizontal direction from the first reference position, evaluating the image captured of the semiconductor chip during the movement, and stopping the end surface imaging device at a second reference position, and a third step of moving the end surface imaging device at an oblique angle toward the semiconductor chip. a first reference position is a position including a second reference position, beyond or within the first reference position, in a planar positional relationship with the semiconductor chip; the second reference position is a position at which an entire image of the semiconductor chip is captured within an imaging screen of the end face imaging device; and the operation control device is configured to include an imaging means for imaging a plurality of images while illuminating the chip end face, while tilting the end face imaging device from the second reference position; and an identification means for extracting data on an evaluation line continuing from the top surface of the chip to the chip end face from the plurality of images captured by the imaging means, evaluating the manner in which the data on the evaluation line changes, and identifying an optimal image. Effect of the Invention

[0014] According to the present invention, the second reference position where the end surface photographing device starts to move inclinedly toward the semiconductor chip is defined for each semiconductor chip of the inspection target, so that the photographing means functions properly and the identifying means can be accurately determined. Also, by adopting the configurations of claims 2 and 3, both side surfaces of the semiconductor chip can be inspected efficiently, quickly and accurately. [Brief description of the drawings]

[0015] [Figure 1] 4 is a diagram for explaining a procedure for determining a first reference position Po and a second reference position Ps. [Diagram 2]1 is a diagram for explaining the arrangement state of semiconductor chips and the operation of an end surface imaging device. [Diagram 3] 1 is a diagram illustrating the configuration of an end surface imaging device and the depth of field. [Figure 4] 1 is a diagram for explaining a maximum value of a shooting pitch Pi. [Diagram 5] 11 is a flowchart illustrating an interrupt process that is started every time a motor that realizes tilt movement rotates by a predetermined angle Φ. [Figure 6] 11 is a flowchart illustrating an entire inspection operation. [Figure 7] 13 is a diagram for explaining an embodiment in which the mounting surface is a light-transmitting sheet. [Figure 8] 8 is a photographed image in the embodiment of FIG. 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will be described in detail below based on the embodiments shown in Figures 1 to 3. In the following embodiments, a semiconductor laser LD (hereinafter referred to as a semiconductor chip 10) is exemplified as a semiconductor element, and the stimulated emission apertures at the chip end faces 10a, 10b of a large number of semiconductor chips 10, 10 aligned vertically and horizontally as shown in Figure 2 are inspected.

[0017] As shown in FIG. 1, the inspection equipment EQU of the embodiment is configured to include a movable holding device BS that holds semiconductor chips 10, 10; a planar imaging device HR that images the chip top surface 10c of the semiconductor chip 10 that is the inspection target from directly above; an end surface imaging device SL that moves horizontally from the holding device BS along a horizontal movement line L0 of height VR from a first reference position Po to a second reference position Ps, and, when the second reference position Ps is reached, moves at an inclination along an inclined movement line LN toward the semiconductor chip 10 at a predetermined inclination angle θ, thereby imaging the semiconductor chip 10; and a central control device CTL that controls the operation of the planar imaging device HR, the end surface imaging device SL, etc., and determines whether the semiconductor chip 10 is good or bad based on the image captured by the end surface imaging device SL.

[0018] Here, a large number of semiconductor chips 10 are attached to the mounting surface 40 of the holding device BS in an aligned arrangement as shown in Fig. 2(b) or in a staggered aligned position as shown in Fig. 2(c). The holding device BS is configured to be movable so that the semiconductor chip to be inspected is positioned directly below the planar imaging device HR by appropriately moving on a horizontal plane based on the control of the central control device CTL.

[0019] Although not particularly limited, in this embodiment, both end faces 10a, 10b in the longitudinal direction of each semiconductor chip 10 are inspection surfaces. Therefore, in this embodiment, in addition to the first end face imaging device SLa, a second imaging device SLb is arranged. Also, the mounting surface 40 is configured to have light reflectivity, and the inspection light 20 is reflected by the mounting surface 40, and the reflected light 30 reflected again by the chip end faces 10a, 10b returns to the end face imaging devices SLa, SLb (see FIG. 2(d)).

[0020] These end surface imaging devices SLa, SLb are configured to include an illumination unit that irradiates inspection light 20 toward the semiconductor chip 10 that is the inspection target, an incident-light microscope that receives reflected light 30, a tilt movement unit that tilts and moves the illumination unit and the microscope, and a horizontal movement unit that moves the illumination unit and the microscope horizontally.

[0021] Fig. 3(c) is a diagram for explaining in outline the inclined movement unit which realizes reciprocating movement in the inclined direction (Z direction) and the horizontal movement unit which realizes horizontal movement in the horizontal direction (X direction). Here, the illumination unit is provided with a mechanical shutter, and based on the ON / OFF operation of the shutter, it is controlled whether or not the inspection light is actually irradiated from the illumination unit in the operating state toward the inspection target. Note that, instead of the ON / OFF operation of the shutter, the operation of the illumination unit may be turned ON / OFF, but this is inferior in response speed and is not suitable for high-speed blinking operation.

[0022] As shown in Fig. 1 and Fig. 3(c), the Z direction of the present invention forms an inclination angle θ with respect to the X direction. The inclination angle θ is determined in consideration of the arrangement pitch of the semiconductor chips 10 in the illumination direction (W1, W2 shown in Fig. 2) and the height difference of the inspection range on the chip end faces 10a, 10b, and is preferably determined in the range of 20° to 40°. In other words, this inclination angle θ is an angle at which the chip end faces 10a, 10b of the inspection target can be photographed without being obstructed by the adjacent semiconductor chips 10, and the staggered arrangement in Fig. 2(c) has the advantage that the inclination angle θ can be set smaller than the aligned arrangement in Fig. 2(b).

[0023] As shown in FIG. 3(c), the end surface imaging devices SLa, SLb are configured to include a stepping motor Mx that realizes reciprocating movement in the X direction, a horizontal slide table 45 that can move back and forth in the X direction based on the rotation of the stepping motor Mx and a first ball screw mechanism, a slide unit 44 that incorporates a stepping motor Mz and a second ball screw mechanism, a slide table 43 that can move back and forth in an inclined direction along the slide unit 44, and an imaging main body portion 42.

[0024] In this configuration, the stepping motor Mx and the horizontal slide table 45 form a horizontal moving part, and the ride unit 44 and the slide table 43 form an inclined moving part. Note that Fig. 3(c) merely shows a simplified schematic configuration of the horizontal moving part and the inclined moving part, and the actual end surface imaging device SL does not precisely correspond to the configuration of Fig. 3(c).

[0025] Continuing the explanation based on the above, the central control unit CTL monitors the shooting screen of the planar imaging device HR while moving the holding device BS on the horizontal plane, thereby positioning the semiconductor chip 10, which is the inspection target on the mounting surface 40, directly below the planar imaging device HR.

[0026] Next, the end face imaging device SL is positioned at a first reference position Po on the horizontal movement line L0 in correspondence with the coordinate position of the planar imaging device HR (see FIG. 1). Note that the first end face imaging device SLa is positioned at the first reference position Po in correspondence with the chip end face 10a, and the second end face imaging device SLb is positioned at another first reference position Po in correspondence with the chip end face 10b.

[0027] Here, the first reference position Po is uniformly defined based on the coordinate position of the planar imaging device HR (position O directly above the inspection target), and the relative separation distance DST between the planar imaging device HR and the inspection target is determined as, for example, DST={VR / tan(θ)}+Δ. Here, VR is the height difference between the placement surface 40 and the horizontal movement line L0, and θ is the inclination angle formed by the inclined movement line LN and the horizontal movement line L0. Also, Δ is an appropriate correction value determined according to the plate thickness and length dimension of the semiconductor chip 10.

[0028] In this embodiment, the correction value Δ is a positive value, and is set so that the first reference position Po is located in the outer region of the second reference position Ps, which is the final stop position on the horizontal movement line L0, with respect to the position O directly above the inspection target. However, the present invention is not limited to this configuration, and the correction value Δ may be a negative value, and the first reference position Po may be set to be located in the inner region of the second reference position Ps.

[0029] In either case, the end surface imaging devices SLa, SLb, which have been moved to the first reference position Po on the horizontal movement line L0 under the control of the central control device CTL, will capture an image of the semiconductor chip 10 at the top of the camera screen or outside it based on the above-mentioned positive correction value Δ. Note that Fig. 1(b) shows a state in which the bottom edge of the semiconductor chip 10 is captured at the top of the camera screen. However, since the focus is not achieved at all, the reflected light from the semiconductor chip 10 is actually captured dimly as a "bright capture portion."

[0030] Next, the central control device CTL starts the photographing operation of the end surface photographing devices SLa and SLb, and while photographing the semiconductor chip 10 that is the inspection target, moves the end surface photographing devices SLa and SLb further forward on the horizontal movement line L0 toward the planar photographing device HR. Then, the "bright capture portion" in the photographed image descends from the state shown in FIG. 1(b) toward the state shown in FIG. 1(b) in response to the forward movement of the end surface photographing device SL.

[0031] Therefore, the central control device CTL stops the forward movement on the horizontal movement line L0 when the "bright capture part" reaches the center of the captured image, and sets the stop position as the second reference position Ps. Here, the state where the "bright capture part" reaches the center of the captured image means a state where the "bright capture part" is surrounded by a "dark background" that is clearly inferior in brightness, as shown in Figure 1(c), and the chip end face 10 is not an issue as in Prior Art 1.

[0032] This is because, since the horizontal movement line L0 is set as an out-of-focus line, it is practically impossible in terms of computer processing to accurately recognize the chip end face 10 on the horizontal movement line L0.

[0033] In addition, in this embodiment, the end surface photographing devices SLa and SLb are then lowered on the inclined movement line LN, in contrast to the operation of Prior Art Document 1, so that the image captured at the second reference position Ps will not be missed in the subsequent downward movement as long as the line of sight of the camera coincides with the inclined movement line LN. Therefore, in this embodiment, the condition for stopping the horizontal movement of the end surface photographing devices SLa and SLb is that a "dark area (dark background)" of at least 15% or more of the vertical and horizontal size of the camera screen exists around the "bright capture portion."

[0034] Thereafter, the tilt movement unit functions under the control of the central control device CTL, and the illumination unit and microscope, which are essential parts of the end face imaging device SL, move downward on the tilt movement line LN. Note that the tilt movement on the tilt movement line LN descending from the second reference position Ps and the photographing operation on the tilt movement line LN will be described in detail later with reference to Figs. 5 to 6.

[0035] Based on the above, first, in relation to the photographing operation, the incident-light microscope, the focal depth, and the depth of field δ will be described with reference to Figures 3(a) and 3(b). As shown in Figure 3(a), the incident-light microscope is configured to include an objective lens 1 facing a sample 6, an imaging lens 2 that forms an image of the photographing light 30 on an image sensor 7, an illumination lens 3 that receives the illumination light 20, a splitter 5 that guides the illumination light 20 that has passed through the illumination lens 3 to the sample 6, and a light source 4 that generates the illumination light 20.

[0036] The imaging light 30, which is a wave reflected from the chip end faces 10a, 10b (sample 6), passes through the splitter 5 and is guided to the image sensor 7. Furthermore, illumination light 20 is introduced into the imaging main body 42, and passes through the objective lens 1 to illuminate the end face 10a of the semiconductor chip 10. The reflected waves from the chip end faces 10a, 10b are imaged on the image sensor 7 of the imaging camera 41 as imaging light.

[0037] Next, the depth of field δ (see FIG. 3(b)) means the allowable range of the distance between the sample surface 6 and the lens, in other words, the depth of field δ means the range in which the image is in focus. This depth of field depends on the focal length of the lens and the aperture, but the image of an object that exists within the depth of field will be within the imaging range (depth of focus) of the image sensor 7 such as a CCD (Charge Coupled Device).

[0038] In this embodiment, in order to evaluate the quality of the chip end faces 10a and 10b of the semiconductor chip 10, a total magnification of 10 to 20 times is suitable, and correspondingly, the depth of field δ is about δ=10 μm to 2 μm.

[0039] Moreover, the multiple images to be acquired during the inclined movement of the end face imaging device SL are preferably acquired intermittently every time the end face imaging device SL moves a specified distance (imaging pitch) Pi, and the imaging pitch Pi is determined in consideration of the height dimension H of the inspection range including the judgment area to be judged for pass / fail judgment. In detail, as described in Prior Art 1, the imaging pitch Pi on the inclined movement line LN is appropriately set under the condition of Pi≦δ-H*SIN(θ).

[0040] Fig. 4 is a diagram explaining this relationship, with the top surface of the semiconductor chip 10 being the origin line ORG (see Fig. 2(a)), and the range H downward from the origin line ORG being the inspection range H. Fig. 4(b) shows the case where the focal position F1 is located at -X1 on the front side of the origin line ORG, and Fig. 4(c) shows the case where the focal position F2 is located at +X2 on the rear side of the origin line ORG.

[0041] Next, the inclined movement and imaging operation on the inclined movement line LN will be described with reference to Fig. 5. Although not particularly limited, in this embodiment, the inclined movement of the end surface imaging device SLa and the end surface imaging device SLb is managed by the rotation angle of each stepping motor Mz that drives each inclined movement part (slide table 43). Specifically, each time the stepping motor Mz of the end surface imaging device SLa and the stepping motor Mz of the end surface imaging device SLb rotate by a predetermined angle Φ, a pulse signal is output from the rotary encoder, and this pulse signal is transmitted to the central control device CTL as an interrupt signal (encoder interrupt) (see Figs. 5(c) and (d)).

[0042] The photographing pitches Pia, Pib of the end surface photographing devices SLa and SLb are set to the same value determined appropriately under the condition of Pi≦δ-H*SIN(θ), and this photographing pitch Pi (Pia, Pib) is managed by the number of interrupts N of the encoder interrupt. Here, the number of interrupts N means that the stepping motor Mz rotates by a rotation angle N*Φ and the end surface photographing devices SLa, SLb move by the photographing pitch Pi. Therefore, each time the number of interrupts N corresponding to the photographing pitch Pi is reached, the end surface photographing devices SLa and SLb photograph the end surfaces 10a, 10b of the semiconductor chip 10.

[0043] 5(c) and 5(d) illustrate this relationship, showing the imaging timings Pia1, Pia2,... Pian and the imaging timings Pib1, Pib2,... Pibn, which are defined by the number of interrupts N. Note that, as shown in the figure, the rotation start timings of each stepping motor Mz, Mz are appropriately shifted by about the number of interrupts N / 2, which corresponds to about 1 / 2 the imaging pitch Pi when converted into distance, so that the imaging timings Pia, Pib of the end surface imaging device SLa and the end surface imaging device SLb do not overlap.

[0044] 1(b) to 1(d), in order to improve the accuracy of judgment by a computer, the imaging screen of the end face imaging device SL needs to capture a bright image of the semiconductor chip 10 against a dark background with clearly poor brightness. Therefore, in this embodiment, while one of the end face imaging devices SLa and SLb is performing imaging, the other end face imaging device has its illumination unit turned off based on its respective mechanical shutter, that is, does not emit inspection light.

[0045] 5(c) and 5(d), the irradiation of the inspection light starts at the encoder interruption one timing before the imaging timings Pia and Pib, and ends at the encoder interruption one timing after the imaging timings Pia and Pib. As described above, the rotation start timings of the stepping motors Mz of the end surface imaging devices SLa and SLb are appropriately shifted by about 1 / 2 the imaging pitch Pi, so that while one end surface imaging device is irradiated with the inspection light, the other end surface imaging device does not perform an imaging operation.

[0046] As described above, in this embodiment, for any end face imaging device SL, the imaging screen shows the semiconductor chip 10 brightly against a dark background with clearly poor brightness, optimizing the computer-based process of determining the semiconductor chip end face.

[0047] Incidentally, the need to photograph the semiconductor chip 10 brightly against a clearly poorly lit dark background does not depend on whether or not the end face of the semiconductor chip 10 is in focus. Therefore, the positioning operation for detecting the second reference position Ps (start position of the tilt movement) on the horizontal movement line L0 is not performed simultaneously by the two end face photographing devices SLa, SLb but is performed sequentially.

[0048] Next, the inclined movement and photographing operation on the inclined movement line LN will be explained based on a flowchart. Fig. 5(a) shows the encoder interrupt process (SLa interrupt) of the end surface photographing device SLa, and Fig. 5(b) shows the encoder interrupt process (SLb interrupt) of the end surface photographing device SLa, and both processes are started at the timing when the stepping motors Mz, Mz rotate by a predetermined angle Φ.

[0049] When any of the encoder interrupt processes is started, it is determined whether or not the irradiation timing has arrived (ST1), and if it has arrived, the irradiation of the inspection light is started (ST2). Next, it is determined whether or not the photographing timing (Piaj / Pibj) has arrived (ST3) for j=1 to n, and if it has not arrived, the interrupt process is terminated.

[0050] On the other hand, if it is the photographing timing (Piaj / Pibj), the chip end face 10a / 10b is photographed, the image is stored (ST4), and the irradiation of the inspection light is stopped (ST5). Next, it is determined whether the end face photographing device SL has reached the limit position where the photographing process should be ended (ST6), and if it has not reached the limit position, the interrupt process is ended as it is.

[0051] On the other hand, when the end surface photographing device SL reaches the limit position where the photographing process should end, a final process is executed to judge the quality of the end surface of the inspection target based on the acquired series of image data (ST7), and the control flags Ia and Ib are cleared to 0 to prohibit any further encoder interrupts.

[0052] Here, the control flags Ia and Ib are flags corresponding to whether or not an encoder interrupt is permitted, and when the positioning operation for detecting the second reference position Ps (the start position of the tilt movement) is completed and the tilt movement on the tilt movement line LN is started, the control flags Ia and Ib are set to 1 in response to the encoder interrupt being permitted (see ST13 in Figure 6).

[0053] 6(a) is a flow chart explaining the whole inspection operation realized by the positioning movement on the horizontal movement line L0 and the inclined movement on the inclined movement line LN. First, the interrupt number N corresponding to the photographing timing Pi is determined, and characteristic parameters are specified for the reference image of the reference chip, which is a typical non-defective product of the semiconductor chip 10 (ST11). In addition, for the reference range, which is the pass / fail judgment area of ​​the reference chip, the horizontal range H1 / HMAX to H2 / HMAX from the left end of the reference chip and the vertical range V1 / VMAX to V2 / VMAX from the top end are specified.

[0054] Next, the central control unit CTL moves the holding device BS horizontally to position the semiconductor chip 10, which is the inspection target on the mounting surface 40, directly below the planar imaging device HR, and then positions the end surface imaging devices SLa and SLb at their respective inclined movement start positions (second reference position Ps) on the horizontal movement line L0 (ST12).

[0055] The positioning operation is performed, for example, in the order of the end surface photographing device SLa and the end surface photographing device SLb, and on the horizontal movement line L0, the end surface photographing device SLa is first moved to the first reference position Po, and then moved to the second reference position Ps. Next, the same positioning movement is performed for the end surface photographing device SLb. Note that, as shown in FIG. 1, the end surface photographing device SLa is positioned at the second reference position Ps corresponding to the chip end surface 10a, and the end surface photographing device SLb is positioned at another second reference position Ps corresponding to the chip end surface 10b.

[0056] As explained above, when the end surface photographing device SLa moves horizontally while photographing the semiconductor chip 10, inspection light is not emitted from the end surface photographing device SLb, and conversely, when the end surface photographing device SLb moves horizontally while photographing the semiconductor chip 10, inspection light is not emitted from the end surface photographing device SLa.

[0057] When the above positioning operation is completed, the central control device CTL enables the SLa encoder interrupt and the SLb encoder interrupt, sets both control flags Ia and Ib to 1 (ST13), and starts the rotation of the stepping motors Mz, Mz of the end surface imaging device SLa and the end surface imaging device SLb. As shown in Figures 5(c) and (d), first, the stepping motor Mz of the end surface imaging device SLa starts to rotate, and after this stepping motor Mz has rotated about 1 / 2 the imaging pitch Pi, the stepping motor Mz of the end surface imaging device SLb starts to rotate.

[0058] By the process of step ST13, every time the stepping motor Mz rotates by a predetermined angle Φ, an encoder interrupt is started and the operation of Fig. 6(b) or Fig. 6(c) is executed. Note that the process contents of the SLa encoder interrupt and the SLb encoder interrupt are as shown in Fig. 5(a) and Fig. 5(b) described above.

[0059] Fig. 6(d) is a diagram for explaining the operation of the image acquisition timing of step ST4 in Fig. 5. When the image acquisition timing Pia / Pib is reached, first, the end faces 10a, 10b of the semiconductor chip 10 are photographed and stored (ST41). Next, the area of ​​the semiconductor chip 10 is determined, and an evaluation line from the top face 10c of the semiconductor chip 10 to the end faces 10a, 10b of the semiconductor chip 10 is specified (ST42).

[0060] As shown in Fig. 1(d), when the image is in focus, the top surface 10c and the end surfaces 10a / 10b of the semiconductor chip are photographed brightly, and a brighter band portion indicated by a double line is detected between them. Note that for convenience of drawing, the band portion is indicated by a double line, but this band portion is the connecting curved portion between the top surface 10c and the end surfaces 10a / 10b, and in reality, it shines brighter than the flat surfaces 10a / 10b.

[0061] The evaluation line is then defined to detect this bright band. Note that, although the band cannot be clearly detected when the image is not in focus, even in this case, as shown in Figure 1(c), the "bright capture portion" appears in the "dark background," so the line that includes the "dark background" and vertically crosses the "bright capture portion" is defined as the evaluation line.

[0062] Following the process of step ST42, the brightness data on the evaluation line is averaged, such as by calculating a moving average value, to remove noise (ST43), and the noise-processed data is differentiated to extract positive and negative edges (ST44).Furthermore, focusing on the positive edge or negative edge, the positive edge is binarized based on a predetermined threshold value TH, and the pulse width PL of the binarized pulse wave is calculated as a first evaluation value (ST45).

[0063] If the calculated first evaluation value (pulse width PL) is narrower than the specified value, the brightness data on the evaluation line is evaluated from the viewpoint of whether the portion shown by the double line in Fig. 1(d) (i.e., the band portion brighter than the flat surface 10a / 10b) is clearly detected or not, and a second evaluation value is calculated (ST45). This second evaluation value is a parameter indicating whether the band portion shown by the double line in Fig. 1(d) is clear or not.

[0064] Next, this second evaluation value is compared with the previous evaluation value ANS, and if it is better than the previous evaluation value, the evaluation value ANS is rewritten to the current second evaluation value and the image number i corresponding to this second evaluation value is stored (ST47).

[0065] As described above, for each image acquisition timing Pia / Pib, the pulse width PL that has the potential to clearly identify the band portion that is the boundary between the chip top surface and the chip end surface is calculated, and the best second evaluation value is sequentially updated to the variable ANS.

[0066] Based on the above, the final process (ST7) shown in Figures 5(a) and 5(b) will be described. As shown in Figure 6(d), in the final process, an optimal image is identified based on the image number i corresponding to the second evaluation value ANS stored at that time (ST71). Then, for the identified optimal image i, the background is removed and the necessary feature parameters are calculated.

[0067] Next, the similarity is calculated based on a comparison with the characteristic parameters of the reference image, and the chip end faces 10a, 10b corresponding to the optimal image i are judged to be good or bad (ST72). For semiconductor chips 10 that are judged to be defective, their placement positions on the mounting surface, etc. are stored and the chips are then subjected to the necessary subsequent processing (ST13).

[0068] Incidentally, in the above embodiments, a reflected light microscope has been used, but there is no limitation thereto, and a transmission microscope is also suitable. Fig. 7 shows an embodiment utilizing a transmission microscope, and shows a holding device BS in which a transparent glass table TL and a transparent film material 40 that serves as a mounting surface 40 are laminated. A large number of semiconductor chips 10...10 are attached to the transparent film material 40 in an orderly manner with a predetermined arrangement gap W therebetween.

[0069] In this embodiment, an illumination unit LH is disposed below a transparent glass table TL, and illumination light 20 from the illumination unit LH illuminates the entire back surface of the transparent film material 40. This illumination light 20 is blocked by the back surfaces of the semiconductor chips 10...10, but passes through the gaps between the semiconductor chips 10...10 to reach both left and right end faces 10a, 10b of the semiconductor chip 10. Then, reflected light 30 from both left and right end faces 10a, 10b of the semiconductor chip 10 reaches end surface imaging devices SLa, SLb equipped with a transmission microscope.

[0070] 8(a) and 8(b) show images captured by the end face imaging device SLa. The blue to purple bands indicate the semiconductor chip end face 10a, which is a reflecting surface of the illumination light 20, and above that, the semiconductor chip top face 10c, which blocks the illumination light 20, appears black. The white parts are due to the illumination light that has passed through the gap between the semiconductor chips 10, 10.

[0071] Fig. 8(b) is a captured image in the case where the arrangement gap W of the semiconductor chips is narrow in the left-right direction of Fig. 7. Therefore, the upper surface 10c of the semiconductor chip 10 on the left side of the semiconductor chip 10 that is the inspection target in Fig. 7 appears black at the bottom of Fig. 8(b). Note that not only the arrangement gap W but also the inclination angle θ and the microscope magnification are not the same between Fig. 8(a) and Fig. 8(b), and the thickness of the semiconductor chip end surface 10a is not the same.

[0072] According to this embodiment, not only can the arrangement gap W be set narrow, but also the boundary line between the chip top surface 10c and the chip end surfaces 10a / 10b can be clearly grasped, so that the pass / fail judgment area can be easily determined and a high-precision pass / fail judgment can be made. In addition, there is no need to operate the end surface photographing device SLa and the end surface photographing device SLb in a time-sequential manner, and no ON / OFF control of the illumination light is required, and there is an advantage that it is sufficient to keep the illumination light on all the time. Note that the end surfaces 10a, 10b of the semiconductor chip 10 are photographed at each image acquisition timing Pia / Pib, and the optimal image is selected based on the data on the evaluation line, and the rest are the same as in the other embodiments.

[0073] Although the embodiment has been specifically described above, the specific configuration can be appropriately changed without departing from the spirit of the present invention. For example, in the embodiment, the chip end face is photographed while the end face photographing device SLa and the end face photographing device SLb are moving, but the chip end face may be photographed in a stopped state. In addition, the method of detecting the minimum pulse width PL is not limited to the sequential operation shown in FIG. 6. For example, after acquiring and saving all the required number of images, a batch process in which edge extraction is performed on each image and the optimal image is selected is also suitable.

[0074] In the embodiment of Fig. 5, for convenience of explanation, the rotation angle and the number of rotations of the stepping motor Mz are grasped based on the output pulses of the rotary encoder, but this configuration is not essential. For example, it is of course possible to grasp the rotation angle and the number of rotations of the stepping motor Mz by counting the drive pulses that rotate the stepping motor Mz without using a rotary encoder. In addition, for convenience of explanation, the interrupt processing shown in Fig. 5 is adopted in the above embodiment, but it is not limited thereto, and the same processing can be realized without using the interrupt processing if the central control device CTL samples the drive pulses of the stepping motors Mz, Mz of the end surface imaging devices SLa, SLb.

[0075] In the embodiment of Figure 8, it goes without saying that the two end surface imaging devices SLa, SLb may start horizontal or inclined movement at any timing, including simultaneous timing, and each may perform an imaging operation at any timing. [Explanation of symbols]

[0076] HR Planar Imaging Device SLa,SLb End surface imaging device Po 1st reference position Ps 2nd reference position CTL Motion control device (Central control device)

Claims

1. a plane imaging device capable of imaging an upper surface of a semiconductor chip to be imaged that is placed on a light-reflective or light-transmissive mounting surface; an end surface photographing device capable of photographing an end surface of the semiconductor chip while moving back and forth in an inclined direction between a position obliquely above the semiconductor chip and the semiconductor chip; an operation control device which positions the end surface imaging device at a first reference position based on an image captured by the planar imaging device, moves the end surface imaging device in a horizontal direction from the first reference position, evaluates an image captured of the semiconductor chip during the movement, stops the end surface imaging device at a second reference position, and then tilts and moves the end surface imaging device toward the semiconductor chip, the first reference position is a position including a second reference position, beyond or within the first reference position, in a planar positional relationship with the semiconductor chip, and the second reference position is a position at which an entire image of the semiconductor chip is captured within an imaging screen of the end face imaging device; The motion control device includes: an imaging means for imaging a plurality of images of the chip end face while illuminating the chip end face and tilting the end face imaging device from a second reference position; a determination means for extracting data on an evaluation line extending from the top surface of the chip to the end surface of the chip from a plurality of images captured by the photographing means, evaluating the manner in which the data on the evaluation line changes, and determining an optimal image.

2. 2. The inspection device according to claim 1, further comprising an illumination unit for illuminating a lower surface of the semiconductor chip placed on a light-transmitting mounting surface.

3. a first end surface imaging device capable of capturing a first image including a first chip end surface and a top surface of the semiconductor chip, and a second end surface imaging device capable of capturing a second image including a second chip end surface and a top surface of the semiconductor chip, The inspection device according to claim 1 , wherein the first end surface imaging device and the second end surface imaging device are configured to perform imaging operations in a time-sequential manner or at an arbitrary timing.

4. The first end surface imaging device and the second end surface imaging device perform imaging operations in a time-sequential manner, 4. The inspection device according to claim 3, further comprising an illumination unit that illuminates the first chip end face when illumination of the second chip end face is stopped, and illuminates the first chip end face when illumination of the second chip end face is stopped.

5. The first end surface photographing device and the second end surface photographing device perform photographing operations at any timing, 4. The inspection device according to claim 3, further comprising an illumination unit for illuminating a lower surface of the semiconductor chip placed on a light-transmitting mounting surface.

6. a plane imaging device capable of imaging an upper surface of a semiconductor chip to be imaged that is placed on a light-reflective or light-transmissive mounting surface; an end surface photographing device capable of photographing an end surface of the semiconductor chip while moving back and forth in an inclined direction between a position obliquely above the semiconductor chip and the semiconductor chip; a first step of positioning the end surface imaging device at a first reference position based on an image captured by the planar imaging device; a second step of moving the end surface photographing device in a horizontal direction from a first reference position, evaluating a photographed image of the semiconductor chip during the movement, and stopping the end surface photographing device at a second reference position; and then, a motion control device that executes a third step of tilting the end surface imaging device toward the semiconductor chip, the first reference position is a position including a second reference position, beyond or within the first reference position, in a planar positional relationship with the semiconductor chip, and the second reference position is a position at which an entire image of the semiconductor chip is captured within an imaging screen of the end face imaging device; The motion control device includes: an imaging means for imaging a plurality of images of the chip end face while illuminating the chip end face and tilting the end face imaging device from a second reference position; A method for inspecting a semiconductor element, comprising: a determination means for extracting data on an evaluation line extending from the top surface of the chip to the end surface of the chip from a plurality of images captured by the photographing means, evaluating the manner in which the data on the evaluation line changes, and determining an optimal image.

Images