JP2011112361A - Device and method for inspecting bump - Google Patents

Abstract

An object of the present invention is to efficiently and accurately inspect a bump bonding portion.
A bump inspection apparatus for inspecting a bump formed between a substrate and a semiconductor element includes a laser irradiation apparatus for irradiating a laser beam between the substrate and the semiconductor element, and a bump. The workpiece holder 14 holding the substrate 53 on which the semiconductor element 51 is placed via the laser beam, and the incidence of the laser light irradiated toward the bump 52 while moving the laser irradiation device 10 in the direction perpendicular to the substrate surface An XYZ stage 13 that irradiates laser light from the laser irradiation device 10 so that the direction is parallel to the substrate 53, and a light receiving device 11 that receives reflected light reflected in a direction parallel to the substrate 53 from the bump surface. The control unit 17 determines that the bonding state of the bump 52 is good when the intensity distribution of the reflected light received by the light receiving device 11 satisfies a predetermined condition.
[Selection] Figure 1

Description

  The present invention relates to a bump inspection apparatus and a bump inspection method.

  As a method for mounting a semiconductor chip or a semiconductor package on a substrate, a connection method using bumps is known. In this case, the quality of the bumps determines the connection reliability. As a bump inspection apparatus for inspecting the shape of the bump, for example, there is one described in Patent Document 1. This bump inspection apparatus includes a stage, a CCD (Charged Coupled Device) camera, and an image processing apparatus, and inspects whether or not the bumps are correctly formed on the substrate.

  In Patent Document 2, a light beam is incident obliquely between the bump rows along the back surface of the package, and the position of the imaging point of the light reflected by the bump is measured and compared with a predetermined reference position. Thus, a technique for determining whether or not a bump is defective is described.

JP 2006-234667 A JP-A-3-215704

  However, in the technique described in Patent Document 1, the position and shape of a bump are inspected using an image representing a bump included in an object image obtained by imaging from above the substrate. Therefore, it is not suitable as a method for inspecting the bump bonding portion of the substrate after mounting the semiconductor element or the package.

  Further, if an image of the bump bonding portion is taken from the side, the substrate end face portion may be reflected before the bump to be imaged, and a clear image cannot be acquired. In order to solve this problem, if the optical axis of the camera is tilted, the silicon substrate of the semiconductor element gets in the way, and it may not be possible to detect an abnormality at the top of the bump.

  On the other hand, in the method described in Patent Document 2, light is incident in parallel between the bump rows along the back surface of the package or in an oblique direction with respect to each bump row, and the reflected light is detected, thereby joining the bumps. Inspect the part. However, according to such a technique, since the light reflected in a direction different from the incident light is detected, the trajectory of the reflected light varies depending on the shape of the bump. For this reason, it is necessary to align the optical system in accordance with the shape of the bump at every inspection. Therefore, there is a problem that inspection efficiency deteriorates.

  In view of the above, development of a method for inspecting bump joints efficiently and accurately is desired.

According to the present invention,
A bump inspection apparatus for inspecting a bump formed between a substrate and a semiconductor element,
A light irradiation unit for irradiating light between the substrate and the semiconductor element;
A stage for holding the substrate on which the semiconductor element is placed via the bump;
While moving the light irradiation unit in a direction perpendicular to the substrate surface, light is irradiated from the light irradiation unit so that the incident direction of the light irradiated toward the bumps is parallel to the substrate. A moving mechanism
A light receiving unit that receives reflected light reflected in a direction parallel to the substrate from the bump surface;
When the intensity distribution of the reflected light received by the light receiving unit satisfies a predetermined condition, a determination unit that determines that the bonding state of the bump is good,
A bump inspection apparatus is provided.

Moreover, according to the present invention,
A bump inspection method for inspecting a bump formed between a substrate and a semiconductor element,
Holding the substrate on which the semiconductor element is placed via the bumps on a stage;
Scanning the bumps in a direction perpendicular to the substrate surface while irradiating light between the substrate and the semiconductor element so that a light incident direction is parallel to the substrate;
Receiving reflected light reflected from the bump surface in a direction parallel to the substrate;
When the intensity distribution of the received reflected light satisfies a predetermined condition, the step of determining that the bump bonding state is good;
A bump inspection method is provided.

  According to this invention, while moving the light irradiation unit in the direction perpendicular to the substrate surface, the light is irradiated so that the incident direction of light is parallel to the substrate, and from the bump surface in the direction parallel to the substrate. When the intensity distribution of the reflected light reflected satisfies a predetermined condition, the bonding state of the bump is determined to be good. Thereby, since the incident direction of light and the reflection direction to detect become the same track | orbit, it can make the position alignment of light unnecessary. In addition, when the shape of the bump is good, the light is regularly reflected at the center of the bump. Therefore, it is possible to determine whether the bump joint is good or bad by detecting the regularly reflected light. Therefore, it becomes possible to inspect the bump bonding portion efficiently and accurately.

  According to the present invention, it is possible to inspect the bump bonding portion efficiently and accurately.

It is a figure which shows typically the bump test | inspection apparatus of embodiment. It is a figure explaining the bump test | inspection method which concerns on embodiment. It is a figure explaining the bump test | inspection method which concerns on embodiment. It is a figure which shows typically the modification of the bump test | inspection apparatus of embodiment. It is a top view which shows typically the modification of the bump test | inspection apparatus of embodiment. It is a figure explaining the effect of the bump inspection method concerning an embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

  The present embodiment is a bump inspection apparatus that inspects bumps 52 formed between a substrate 53 and a semiconductor element 51. FIG. 1 is a diagram schematically illustrating a bump inspection apparatus according to the present embodiment. As shown in the figure, the bump inspection apparatus of this embodiment includes a laser irradiation apparatus 10 (light irradiation unit) that irradiates a laser beam between a substrate 53 and a semiconductor element 51, and a semiconductor element 51 via a bump 52. The incident direction of the laser beam irradiated toward the bump 52 while moving the laser irradiation device 10 in the direction perpendicular to the workpiece holding unit 14 (stage) holding the placed substrate 53 and the surface of the substrate is determined by the substrate 53. XYZ stage 13 (moving mechanism) that irradiates laser light from laser irradiation device 10 so as to be parallel to the substrate, and light receiving device 11 that receives reflected light reflected in the direction parallel to substrate 53 from the bump surface (light reception). And a control unit 17 (determination unit) that determines that the bonding state of the bump 52 is good when the intensity distribution of the reflected light received by the light receiving device 11 satisfies a predetermined condition, A.

  In the present embodiment, the semiconductor element 51 refers to a semiconductor chip or a semiconductor package. When the semiconductor element 51 is a semiconductor chip, the bottom surface of the semiconductor element 51 refers to the bottom surface of the semiconductor chip. When the semiconductor element 51 is a semiconductor package, the bottom surface of the semiconductor element 51 refers to the bottom surface of the semiconductor package.

  The bump inspection apparatus according to the present embodiment includes a prism 12 that reflects reflected light in a non-parallel direction with respect to the substrate 53. The light receiving device 11 receives the light reflected by the prism 12. Since the prism 12 is disposed on the optical axis to which the laser beam is irradiated, the reflected light from the bump can be reflected in a non-parallel direction with respect to the substrate 53. The “non-parallel direction” may be a direction that does not coincide with the optical axis of laser irradiation, but is preferably a direction of 45 ° to 135 ° with respect to the incident direction of the laser light. By doing so, it is possible to prevent the light reflected by the prism 12 from colliding with the bumps 52 or colliding with other components such as the laser irradiation device 10. Further, from the viewpoint of facilitating installation of the light receiving device 11, it is more preferable that the “non-parallel direction” is defined as a substantially vertical direction (particularly, a direction of 90 °) with respect to the incident direction of the laser light.

  The light receiving device 11 is provided on the optical axis that is split by the prism 12. The D / A converter 16 is connected to the light receiving device 11 and detects a voltage generated by light reception. A predetermined threshold value is set in advance in the D / A converter 16, and when the voltage generated by light reception exceeds the threshold value, the detected voltage value is sent to the control unit 17 as the light intensity. This threshold is the light intensity when the light receiving device 11 receives light via the prism 12 when the object to be irradiated with laser light regularly reflects light. The control unit 17 receives this and performs an inspection process.

  The XYZ stage 13 includes a motor 15, and an encoder 18 is attached to the motor 15. The encoder 18 detects the position of the XYZ stage 13 and sends position information to the control unit 17 for use in inspection processing.

  The work holding unit 14 is positioned in the straight direction of laser irradiation and holds the work 50 to be inspected. The work 50 refers to the substrate 53 on which the semiconductor element 51 is mounted via the bumps 52. The work 50 is, for example, a flip chip using solder bumps. The bumps 52 may be solder bumps or gold bumps. The solder bump is formed on the bottom surface of the semiconductor element 51 by, for example, a screen printing method. Further, the gold bump is formed on the bottom surface of the semiconductor element 51 by, for example, a plating method or a stud bump method. And the workpiece | work 50 can be produced by mounting on the board | substrate 53 which apply | coated underfill resin. Alternatively, bumps 52 may be formed on a silicon wafer and semiconductor element 51 may be mounted, and then substrate 53 may be cut out by dicing to produce workpiece 50.

  Next, a method for inspecting the bump 52 using the bump inspection apparatus of this embodiment will be described. First, the work 50 is held by the work holding unit 14. Next, as shown in FIG. 2, laser light is irradiated between the substrate 53 and the semiconductor element 51 so that the incident direction of light is parallel to the substrate 53, and is perpendicular to the surface of the substrate 53. The bump 52 is scanned. More specifically, the laser irradiation apparatus 10 moves from the surface of the substrate 53 to the bottom surface of the semiconductor element 51 and / or the individual bumps 52 while moving from the bottom surface of the semiconductor element 51 to the surface of the substrate 53 by the XYZ stage 13. Irradiate light. The laser light emitted from the laser irradiation device 10 goes straight and hits the bumps 52.

  As shown in FIG. 3A, when the bumps 52 are well bonded, the shape of the bumps 52 is spherical due to the surface tension at the time of melting. Therefore, at a position having a curvature, the laser light emitted from the laser irradiation apparatus 10 is irregularly reflected without regular reflection. The irregularly reflected light does not reach the prism 12, or even if it reaches, the light intensity is weak. Therefore, when the upper and lower portions of the non-defective bump 52 are irradiated with laser light, the D / A converter 16 does not detect the reflected light received by the light receiving device 11. On the other hand, at the center of the bump, that is, around the position of about half of the bonding height, the curvature of the bump becomes small and the laser beam is regularly reflected. Then, the specularly reflected light is further reflected by the prism 12 and received by the light receiving device 11. Since the light intensity of the received light satisfies a threshold stored in advance, the D / A converter 16 detects it as reflected light and sends the detected light intensity to the control unit 17.

  Here, the control unit 17 records the intensity distribution of the reflected light for each bump 52. While the individual bumps 52 are scanned by the XYZ stage 13, the control unit 17 grasps the position of the XYZ stage 13 via the encoder 18. By doing so, the light intensity (I) equal to or higher than the predetermined threshold detected by the D / A converter 16 is recorded in association with the irradiation position (Z) of the laser light. An example of the intensity distribution is shown in FIG. In this example, the horizontal axis indicates the position in the direction perpendicular to the surface of the substrate 53, and the surface of the substrate 53 is Z = 0. The vertical axis represents the light intensity (I). When the connection state of the bumps 52 is good, a single reflected light peak is detected at an intermediate point between the surface of the bump substrate 53 and the bottom surface of the semiconductor element as shown in the figure. When such a light intensity distribution is obtained, the control unit 17 determines that the bonding state by the bumps is good.

  On the other hand, as shown in FIG. 3B, in the case of the insufficiently melted bump 52, constriction occurs. Therefore, there are a plurality of locations where the laser light is regularly reflected. Therefore, when the XYZ stage 13 irradiates the individual bumps 52 from the surface of the substrate 53 toward the bottom surface of the semiconductor element 51, regular reflection occurs a plurality of times. Then, the D / A converter 16 detects light a plurality of times. Therefore, for example, as shown in FIG. 3E, a light intensity distribution in which a plurality of reflected light peaks are detected is obtained. In such a case, the control unit 17 can determine that the bump 52 to be inspected is defective in bonding.

  Further, as shown in FIG. 3C, in the case of an unmelted (unbonded) bump, the bump becomes a bowl-shaped spherical shape. Therefore, the reflection of the laser light becomes irregular reflection and does not reflect regularly. Therefore, no light is detected by the D / A converter 16, and for example, as shown in FIG. 3F, a light intensity distribution diagram in which no reflected light peak is detected is obtained. In such a case, the control unit 17 can determine that the bump 52 to be inspected is defective in bonding.

  The determination result of the control unit 17 may be displayed on a monitor connected to the control unit 17 or output to a printer or the like. By doing so, the inspector can identify the quality of bump bonding of the workpiece 50 to be inspected.

  It continues and demonstrates the effect of this embodiment. According to the bump inspection apparatus of this embodiment, the laser beam is irradiated so that the incident direction of the laser beam is parallel to the substrate 53 while moving the laser irradiation device 10 in the direction perpendicular to the surface of the substrate 53. When the intensity distribution of the reflected light reflected from the surface of the bump 52 in the direction parallel to the substrate 53 satisfies a predetermined condition, the bonding state of the bump 52 is determined to be good. Thereby, since the incident direction of light and the reflection direction to detect become the same track | orbit, it can make the position alignment of light unnecessary. In addition, when the shape of the bump 52 is good, regular reflection is performed at the center of the bump, so that it is possible to determine whether the bump joint is good or bad. Therefore, it becomes possible to inspect the bump bonding portion efficiently and accurately.

  In the conventional method of inspecting bump bonding by imaging a bump shape using a camera, the camera and illumination must be provided with an angle. As a result, the parts of the semiconductor element 51 and the side surface of the substrate 53 become obstacles, resulting in a portion that cannot be inspected. Even when a good image is obtained, it is difficult to formulate an inspection algorithm from image processing. Furthermore, the entire system becomes complicated and expensive to construct the system.

  On the other hand, since the bump inspection apparatus of this embodiment uses laser light, there is an advantage that a wider range of inspection is possible. For example, as shown in FIG. 6, the first bump 52 a formed at the outermost periphery of the bottom surface of the semiconductor element 51 and the second bump 52 b formed in a staggered manner with respect to the first bump 52 a are formed. If it is, not only the outermost first bump 52a but also the bonding quality of the second bump 52b inside the first bump 52a can be determined.

  In the bump inspection apparatus according to the present embodiment, it is possible to determine whether the bump bonding is good or bad simply by determining whether or not the intensity distribution of the reflected light for each bump 52 has a single peak. Therefore, it is not necessary to create complicated image processing and inspection algorithms, and it is possible to easily and accurately inspect bump bonding.

  Further, in the bump inspection apparatus of this embodiment, the joining state of the bumps having a spherical shape is detected by light having a straight traveling property by laser light and its reflection, so that the constituent elements of the apparatus can be simplified. In addition, an inspection function can be easily provided as compared with expensive and complicated systems such as an illumination camera and image processing.

  As mentioned above, although embodiment of this invention was described with reference to drawings, these are the illustrations of this invention, Various structures other than the above are also employable. For example, in the above embodiment, the example in which the prism 12 is provided has been described. However, the light receiving device 21 may be disposed around the laser irradiation device 20 as shown in FIG. In this example, the XYZ stage 23 moves the light receiving device 21 up, down, left and right using the motor 25. FIG. 5 is a top view of this modification. As shown in FIG. 5, the light receiving device 21 receives the specularly reflected laser light. The light received by the light receiving device 21 is sent to the D / F converter 16 and processed in the same manner as in the embodiment. In addition, according to the apparatus of embodiment, since the light specularly reflected by a bump passes the completely same track | orbit as the laser beam to project, there exists an advantage that a more exact shape detection can be performed.

DESCRIPTION OF SYMBOLS 10 Laser irradiation apparatus 11 Light reception apparatus 12 Prism 13 XYZ stage 14 Work holding part 15 Motor 16 D / A converter 17 Control part 18 Encoder 20 Laser irradiation apparatus 21 Light reception apparatus 23 XYZ stage 25 Motor 50 Work 51 Semiconductor element 52 Bump 52a 1st Bump 52b Second bump 53 Substrate

Claims (7)

A bump inspection apparatus for inspecting a bump formed between a substrate and a semiconductor element,
A light irradiation unit for irradiating light between the substrate and the semiconductor element;
A stage for holding the substrate on which the semiconductor element is placed via the bump;
While moving the light irradiation unit in a direction perpendicular to the substrate surface, light is irradiated from the light irradiation unit so that the incident direction of the light irradiated toward the bumps is parallel to the substrate. A moving mechanism
A light receiving unit that receives reflected light reflected in a direction parallel to the substrate from the bump surface;
When the intensity distribution of the reflected light received by the light receiving unit satisfies a predetermined condition, a determination unit that determines that the bonding state of the bump is good,
A bump inspection apparatus.   The bump inspection apparatus according to claim 1, further comprising a prism that further reflects the reflected light in a non-parallel direction with respect to the substrate, wherein the light receiving unit receives the light reflected by the prism.   When the intensity distribution of the reflected light for each bump detects a single reflected light peak having a light intensity that satisfies a predetermined threshold, the determination unit has a good bonding state by the bump. The bump inspection apparatus according to claim 1, wherein the bump inspection device is determined as follows.   When the intensity distribution of the reflected light for each bump detects a plurality of reflected light peaks having a light intensity that satisfies a predetermined threshold, the determination unit determines that the bonding state by the bump is poor. The bump inspection apparatus according to claim 1, wherein the bump inspection apparatus is determined.   When the intensity distribution of the reflected light for each bump does not detect a reflected light peak having a light intensity that satisfies a predetermined threshold, the determination unit determines that the bonding state by the bump is defective. The bump inspection apparatus according to claim 1 or 2.   The bump includes a first bump formed on the outermost periphery of the bottom surface of the semiconductor element and a second bump formed on the inner side in a staggered manner with respect to the first bump, and the light receiving unit includes the second bump The bump inspection apparatus according to claim 1, wherein the reflected light from the bumps is received, and a bonding state of the first and second bumps is determined based on a determination result of the determination unit. A bump inspection method for inspecting a bump formed between a substrate and a semiconductor element,
Holding the substrate on which the semiconductor element is placed via the bumps on a stage;
Scanning the bumps in a direction perpendicular to the substrate surface while irradiating light between the substrate and the semiconductor element so that a light incident direction is parallel to the substrate;
Receiving reflected light reflected from the bump surface in a direction parallel to the substrate;
When the intensity distribution of the received reflected light satisfies a predetermined condition, the step of determining that the bump bonding state is good;
A bump inspection method.

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