JPS6157837A - Inspecting device for outer appearance - Google Patents

Abstract

PURPOSE:To perform precise defect detection with high efficiency by lighting vertically and slantingly above a pellet and detecting defects of end parts and the surface. CONSTITUTION:The semiconductor pellet 3 is set on an XY table 2 at a specific position and a lighting device 6 is driven to light the pellet 3 vertically. In this state, an ITV camera 54 is driven and an image pickup signal is converted by a circuit 81 into a binary signal, which is stored in an image memory 82. Then, a control circuit 83 decides on the signal level to detect an end part defect, deciding whether there is the defect or not. Then, the operation of the device 6 is stopped and slanting lighting by a lighting device 7 is started; and the camera 54 is driven to pick up an image of the object surface of the pellet 3; and the obtained image pickup signal is converted by the circuit 81 into a binary signal, which is stored in the memory 82. Then, the circuit 83 detects a surface defect of the pellet 3 from the binary-coded pattern image to decide whether there is the defect or not.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a visual inspection apparatus for inspecting defects in semiconductor pellets, for example.

[Technical front of the invention and its problems]

Generally, on an integrated circuit production line, a mask pattern is formed on a wafer, and then it is diced and divided into semiconductor pellets, which are then subjected to subsequent processes such as bonding, but this process affects the quality of the integrated circuit. This is the most important step in making a decision, and visual inspection for scratches, dirt, etc. is essential. For this reason, in the past, for example, with a mask pattern formed on a wafer, visual observation was performed using a microscope, or images of the pattern-formed surface of the wafer were taken and adjacent patterns of one note were compared with each other. inspected for defects. However, the semiconductor P1 knot is
When dicing and dividing the wafer, the edges may be cracked or chipped (
The wafer was determined to be free of defects because it is easy to cause J, and when each semiconductor pellet knot is housed in a 1.1 no, the surface of the pellet may be contaminated, chipped, scratched, etc. 1) It is not always possible to predict that semiconductor pellets 1 to 1 are good products.

Therefore, recently, defect inspection has been carried out in the state of semiconductor pellets. However, if you try to perform an inspection on this semiconductor pellet, the pellet 1~
Since each pattern is divided, a method of inspecting the wafer by comparing captured images of adjacent patterns used in wafer inspection cannot be applied. For this reason, conventionally, an inspector performs inspection by visual observation using a microscope. However, such inspection by visual observation has low inspection efficiency and inspection accuracy, making it impossible to improve productivity.

On the other hand, it is also being considered to image semiconductor pellets individually and automatically detect defects from the binarized image, but the imaging means conventionally used for wafer inspection uses illumination from perpendicularly above the surface to be inspected. Then, the reflected image was viewed vertically upward and each wiring pattern was inspected one by one. For this reason, defects such as cracks and chips that occur at the edges of semiconductor pellets 1~ can be detected with high accuracy, but surface defects such as dirt and crushing, which are common on semiconductor pellets 1~, can be detected at high speed. It was possible to detect it at low cost.

[Purpose of the invention]

The present invention provides a visual inspection device that can detect defects with high efficiency and accuracy without relying on an inspector, and can detect any type of defects with high precision and a simple configuration. The purpose is to provide

[Summary of the invention]

In order to achieve the above object, the present invention provides a first illumination means that performs vertical epi-illumination and a second illumination means that performs illumination from diagonally above, and uses these illumination means to respectively illuminate the object to be inspected. Illumination is performed, and edge defects such as cracks and chips of the object to be inspected are detected from the captured image obtained during the above-mentioned vertical epi-illumination. This system detects surface defects such as stains and crushing of the object to be inspected from the image.

[Embodiments of the invention]

FIG. 1 shows the configuration of a visual inspection apparatus according to an embodiment of the present invention, where 1 indicates a base and 2 indicates an XY table. This XY table 2 is powered by a step motor 21.2.
A semiconductor pellet 3 as an object to be inspected is taken out from a stocker (not shown) by a collet and placed on a table 2a. On the other hand, an imaging device 5 is disposed vertically above the semiconductor pellet 3 while being supported by a support shaft 51 . This imaging device 5 has a fixed arm 52 attached to the support shaft 51 so as to be movable up and down, and a microscope 53 for enlarging the surface to be inspected of the semiconductor pellet 3 and an image enlarged by the microscope 53 on the fixed arm 52. An industrial television (ITV) camera 54 for taking images is fixed.

By the way, this imaging device 5 is provided with two different illumination devices 6.7. Among them, the first illumination device 6 is installed perpendicularly to the semiconductor pellet 3 placed on the XY table 2 by reflecting the output light of the light source 61 with a semi-transparent mirror 62 as shown in FIG. 2(a). It provides epi-illumination. - The second illumination device 7 consists of a light source 71 and a light projecting section 72 fixed to the tip of the microscope 53, and the output light of the light source 71 is transmitted from the light projecting section 72 to the direction shown in FIG. 2(b). As shown, the semiconductor pellet 3 is irradiated obliquely from above, thereby obliquely illuminating the surface of the semiconductor pellet 3 to be inspected. Note that the angle of this oblique illumination is 20 degrees to 30 degrees (150 degrees to 160 degrees) with respect to the surface of the semiconductor pellet 3.
degree) is optimal.

Now, the captured image obtained by the ITV camera 54 is first binarized by a binarization circuit 81 according to a predetermined binarization level, then temporarily stored in an image memory 82, and then introduced into a control circuit 83. It is now possible to do so. This control circuit 83 has a microprocessor as a main control section, and as shown in FIG.
Visual field control means 32, position control means 33, edge defect detection means 34, surface defect inspection means 35, and illumination switching means 36
It has various control functions consisting of: Imaging control -〇- The control means 31 drives the ITV camera 54, and
It sets a binarization level in the binarization circuit 81 and controls writing and reading operations of the image memory 82. The visual field control unit 32 variably controls the imaging visual field of the ITV camera 54 with respect to the semiconductor pellet 3 by driving the XY table 2 via the motor drive circuit 84 .

The position detection means 33 detects the position of the semiconductor pellet 3 from an image obtained by vertical epi-illumination. Further, the edge defect detection means 34 detects edge defects such as cracks and chips (J) by determining the signal level of the binarized pattern image obtained after the vertical epi-illumination. The means 35 is configured to:
By determining the signal level of the binarized pattern image 3J, surface defects such as dirt, crushing, and surface scratches on the semiconductor pellet 1 are detected. Finally, the first stage of lighting switching 36 is
The light source 61 of the first illumination device 6 and the light source 71 of the second illumination device 7 are separately driven, I), to inspect the semiconductor pellets 1 to 3. 3=11 on the surface
．． ! The ri mO·1 illumination and the oblique illumination are performed separately.

Next, a control circuit 8 controls the operation of the device configured as described above.
The explanation will be given according to the control procedure of No. 3. Figure 4 (a), (b)
are flowcharts 1 to 3 showing the control procedure.

Place the semiconductor pellets i~3 into the cellar 1~ at a predetermined position on the ×Y table 2, and in this state turn on the inspection start switch (not shown).
When the control circuit 83 first operates the first
A driving signal is emitted to the light [61 of the illumination device 6], thereby vertically epi-illuminating the semiconductor pellet 3.

In this state, the ITV camera 54 is
A drive signal is output to start the imaging operation, and the captured image signal 1q is thereby binarized by the binarization circuit 81 and then stored in the image memory 82. At this time, the control circuit 83 sets a relatively high binarization level to the lowering circuit 81 (2 constant, this = 1 The straightening level is the image IM t' of the bonding butt part.
It is set to an intermediate value between the U level (approximately 0.8 V) and the image signal level of the portion excluding the bonding pad (approximately 0.4 V). FIG. 5(a) shows an example of a binarized pattern image obtained as a result, and shows an example of the bonding pad portion 3b.
When the binary pattern image for position detection is obtained, the control circuit 83 subsequently detects the bonding pad 3b from the binary pattern image in step 4C. The position of the semiconductor pellet 3 is detected by pattern recognition and the position of the semiconductor pellet 3 is detected from that position.Then, in step 4d, the XY table 2 is driven via the motor drive circuit 84 to adjust the position of the semiconductor pellet 3, thereby adjusting the imaging field of view. Set the initial position.

After completing the positioning of the imaging position, the control circuit 83 first drives the ITV camera 54 in step 4e to image the surface to be inspected of the semiconductor pellet 3, and converts the obtained image signal into a binary image signal. After being binarized by the conversion circuit 81, it is stored in the image memory 82. By the way, at this time, the control circuit 83 sets the binarization circuit 81 to a binarization level lower than the detection level of the bonding parameters 1 to 1 in order to detect the portion excluding the bonding parameter portion.
For example, the image signal level of the part excluding the bonding pad part (0.71V) and the image signal level of the stocker 4 (
0.2V).

Therefore, as a result of this binarization, the image memory 82 has a portion 3a excluding the bonding pad portion as shown in FIGS. 5(b) and 5(C). A binarized pattern image is stored. Furthermore, Fig. 5(b) shows an example of a binarized pattern image when there are no edge defects such as cracks or chips, and Fig. 5(C) shows an example of a binarized pattern image when the same defects exist. It shows. Then, in step 4f, the control circuit 83 detects an edge defect by determining the signal level at the end of the portion 3a excluding the bonding pad portion in the binarized pattern image, and then in step 4q, the edge defect is detected. Determine the presence or absence of defects. This determination means is performed, for example, by detecting the presence or absence of a signal corresponding to a defect from a signal obtained by digitizing the output of the TV camera 54 for each scanning line. If it is determined that there is no defect, the XY table 2 is driven in step 4i to move the field of view of the ITV camera 54 relative to the semiconductor pellet 3, and then the process returns to step 4e to repeat the defect detection operation. . And semiconductor pellet 1~
The above-mentioned end defect inspection is repeatedly performed on the entire circumference of the end of pellet No. 3, and when it is determined in step 4h that the end defect inspection for one pellet has been completed, step 4j of FIG. 4(b) is performed.
to move to. On the other hand, during the inspection of each of these end defects, if it is determined in step 4Q that there is an end defect, the control circuit 8
3 finishes the inspection of the semiconductor pellet at that point and moves to step 4S of FIG. Transition.

Now, after completing the inspection for the edge defects, proceed to step 4,+
When it moves to the control circuit 83 (J, then the
v) Stop the operation of the first lighting device 6 which has been in a state of failure, and switch on the light source 71 of the second lighting device 7 instead.
A drive signal is output to cause the second illumination device 7 to start diagonal illumination. In other words, the form of illumination for the semiconductor pellets 1 to 3 is switched. In this state, first, in step 4k, the initial position of the imaging field of view is set according to the position of the semiconductor pellet 3 detected in step 4G during the vertical epi-illumination, and then, in step 4a, the ITV camera 54 is driven. The surface to be inspected of the semiconductor pellet 3 is imaged, and the obtained image signal is binarized by a binarization circuit 81 according to a predetermined binarization level, and then stored in the image memory 82. At this time, the above binarization level is
The image signal level of the portion 3a excluding the bonding pad portion is set to an intermediate value between the image signal level of the surface defect, so if there is no surface defect, the entire area is “L” as shown in FIG. 6(a). On the other hand, if there is a surface defect, the defective portion 3G becomes ``H'' level as shown in FIG. 6(b), for example.
This is because by performing oblique illumination, the illumination light is totally reflected in the part 3a excluding the normal bonding pad part and is not introduced into the ITV camera 54, whereas the surface defect part 3C This is because the illumination light from diagonally above is diffusely reflected and guided to the TTV camera 54.

Then, the control circuit 83 detects surface defects such as stains and crushing on the surface of the semiconductor pellet 3 from the thus obtained binary pattern image by counting the number of pixels at the '1-4'' level in step 4m. Thereafter, in step 4n, the presence or absence of surface defects is determined.

If it is determined that there is no defect, the surface defect inspection operation is repeated every time the position of the imaging field of view is moved by the XY table 2 in step 4p in the same way as when detecting the edge defect, and the entire area of one pellet is inspected. When it is determined in step 40 that the process has been completed, the process moves to step 4r and outputs a signal indicating that there is no defect, that is, a non-defective signal, and then the next semiconductor pellet]・3 is detected for this semiconductor pellet 3. Move on to inspection. On the other hand, during the above-mentioned inspection operation for each surface defect, if it is determined that there is a defect in step 4n described in -, the process moves to step 4S at that point, where an exclusion command is output, and the next semiconductor chip is inspected. - Move on to inspection for 3.

In this way, with this embodiment, defects can be automatically inspected for each semiconductor pellet 3, and by performing vertical epi-illumination and oblique illumination, each of these illuminations can detect edge defects such as cracks and chips, and dirt. By detecting surface defects such as cracks and cracks separately, all defects can be detected easily, quickly, and accurately without performing complicated image processing. Therefore, the configuration can be simplified and productivity can be improved.

Note that the present invention is not limited to the above embodiments. For example, in the above embodiment, vertical epi-illumination was first used to detect edge defects, and then diagonal illumination was used to detect surface defects, but this order can also be reversed. good. However, in this case, it is necessary to once perform vertical epi-illumination to detect the position of the semiconductor pellet 3 before performing oblique illumination. Further, in the above embodiment, a case was described in which a semiconductor pellet was inspected for defects, but the present invention can be similarly applied to any product as long as it has edge defects and surface defects.

In addition, the configuration of each illumination device, control procedure, control content, defect detection means, image conveyance means, field of view control means, etc. can be modified in various ways without departing from the gist of the present invention. .

(Effects of the Invention) As detailed above, according to the present invention, the first illumination means performs vertical epi-illumination, and the second illumination means performs illumination from diagonally above.
illumination means, and these illumination means illuminate the object to be inspected to detect edge defects such as cracks and chips from the captured image obtained during the vertical epi-illumination. By detecting surface defects such as dirt and crushing of the object to be inspected from the image obtained when illumination is performed from diagonally above, it is possible to detect surface defects with high efficiency and accuracy without relying on inspectors. It is possible to provide a visual inspection device that can detect defects and can detect any type of defects with high precision and with a simple configuration.

[Brief explanation of the drawing]

The drawings are for explaining a visual inspection device according to an embodiment of the present invention, and FIG. 1 is a diagram showing the overall configuration of the device;
Figures 2 (a) and (b) are diagrams schematically showing the configuration of a lighting device that performs vertical epi-illumination and oblique illumination, respectively, Figure 3 is a block diagram showing the functions of the control circuit, and Figure 4 ( a)
, (b) is a flowchart showing the control procedure of the control circuit,
FIGS. 5(a) to 5(C) and FIGS. 6(a) and 6(b) are schematic diagrams showing binarized pattern images for use in explaining the operation, respectively. 1... Base, 2... XY table, 3... Semiconductor pellet! 〜, 3a...Bon A7 portion excluding deging pad part, 3b...Bonding para 1~ portion, 3
G...Surface defect portion, 5...Illumination device, 53...
Microscope, 54... ITV camera, 6... First illumination device, 7... Second illumination device, 81... Binarization circuit, 82... Image memory, 83... Control circuit, 84・
...Motor drive circuit.

Claims (3)

[Claims] (1) A first illumination means that vertically illuminates the object to be inspected, and a second illumination means that illuminates the object obliquely from above.
an illumination means, an imaging means for taking an image vertically above the inspection surface of the object to be inspected that is separately illuminated by these illumination means, and image information obtained by the imaging means when illuminated by the first illumination means. and means for detecting surface defects of the object to be inspected from image information obtained by the imaging means during illumination by the second illumination means. Appearance inspection equipment. (2) The visual inspection apparatus according to claim (1), wherein the illumination by the first illumination means and the illumination by the second illumination means are switched during the visual inspection. (3) The appearance inspection apparatus according to claim (1), wherein the object to be inspected is a semiconductor pellet.