CN102359758B - Method for detecting appearance of semiconductor chip - Google Patents

Abstract

The invention discloses a method for detecting appearance of a semiconductor chip. The device comprises a sucking mechanism, a U-shaped reflecting plate, two light sources, plane reflecting mirrors, a lens, a camera and an adjusting mechanism, wherein the sucking mechanism is used for sucking a chip to be detected to a position to be detected; the U-shaped reflecting plate is arranged on the sucking mechanism; the two light sources are symmetrically arranged on the side of the chip; one part of light emitted by the two light sources irradiates the U-shaped reflecting plate and performs backlight illumination on the bottom surface and one group of opposite sides of the chip, and the other part of light performs backlight illumination on the other group of opposite sides of the chip; a plurality of plane reflecting mirrors are obliquely and symmetrically arranged at the periphery below the chip, so that light rays reflected by the plane reflecting mirrors are vertically transmitted to the front end face of the lens; the lens is arranged on the camera and positioned below the chip; the camera is arranged on the adjusting mechanism; and the adjusting mechanism is used for adjusting the working distance of the camera. By a backlight illumination technology, a device is clearly imaged, contrast is high, lighting uniformity is achieved, detection time is shortened, and efficiency is improved.

Description

Appearance inspection device for a semiconductor chip

technical field

The present invention relates to the field of optical detection devices, in particular to a detection device for semiconductor integrated circuit chips, which is mainly applied to (but not limited to) semiconductor chips of square flat packaging technology, and can detect missing or damaged pins of the chip. , pin width, pin spacing, pin length deviation, pin stack height, pin coplanarity, pin bending, pin span, pin row bending, pin tilt and other indicators are tested.

Background technique

In the semiconductor industry, before the packaged integrated circuit device is used as a patch component, it needs to go through an effective pin appearance inspection. The inspection items generally include pin spacing, width, span, and stack height. In large-scale production, the following methods are traditionally used to inspect the appearance of device tube legs: make limit samples of various appearance items in advance, compare the actual devices that need to be inspected with the limit samples, and use them to judge the appearance of the device. pass and fail. However, in the case of borderline or blurred and difficult to judge after comparison, it is necessary to measure the difficult-to-judge items one by one with a factory microscope, and compare the differences between the measurement results and the standard values one by one.

With the rapid development of microelectronics technology, the integration of various semiconductor chips is getting higher and higher. At the same time, the volume of chips tends to be miniaturized and miniaturized, all of which put forward higher requirements for the detection of chips. The large-scale production on site makes it difficult for traditional manual visual inspection to meet actual needs.

There are two main detection methods in the field of semiconductor chip appearance inspection today: the appearance inspection system based on laser measurement technology and the appearance inspection system based on machine vision. Laser detection technology has high requirements on software and hardware, so the cost will increase significantly, and the maintenance complexity and cost will be relatively expensive. With the continuous deepening of research in the field of machine vision, the application of machine vision in the field of device appearance inspection is becoming more and more mature. More and more equipment manufacturers are beginning to use machine vision technology to inspect the appearance of semiconductor chips, such as Belgium's ICOS company and Singapore's STI company. Many inspection items that were previously regarded as unrealizable by non-laser measurement can already be completed using vision systems.

Compared with laser measurement, the application of machine vision to semiconductor inspection is mainly through the analysis and processing of real-time captured images, so as to obtain various parameters of the image, and compare and calculate with the preset detection standards to judge whether the device is qualified or not. no. In industrial production, it is necessary to conduct appearance inspection on the pins of IC devices in QFP, TQFP, SOP and SSOP packages. The inspection indicators include missing pins, broken pins, pin spacing, pin width, and pin length. Deviation, height of pin stack and coplanarity of pipes, etc. The detected indicators include two-dimensional indicators and three-dimensional indicators (including height information), and the detection of two-dimensional indicators only needs to collect an image of the bottom surface of the device through the image acquisition device, and then It can be obtained through software processing; the detection of three-dimensional indicators needs to take pictures of the device in at least two directions at the same time, and then reconstruct the three-dimensional information of the device pins through software.

At present, the structure of the appearance inspection system based on machine vision is relatively complicated, and the cost of the inspection device is high.

Contents of the invention

The present invention aims to provide an appearance inspection device for a semiconductor chip, which uses a single camera and a plane mirror to simultaneously image the bottom surface and four sides of the device to be inspected, and the images of the five sides of the device are all concentrated in one picture, which is convenient At the same time, the ingenious U-shaped reflector design can make the suction mechanism absorb the device and fly into the detection position in parallel without falling action, which reduces the detection time and improves the efficiency.

The specific technical scheme adopted to realize the object of the present invention is as follows:

An appearance inspection device for a semiconductor chip, comprising a suction mechanism, a U-shaped reflector, a light source, a plane mirror, a lens, a camera and an adjustment mechanism, wherein,

The suction mechanism is used to suck the chip to be detected to the position to be detected. The U-shaped reflector is installed on the suction mechanism. There are two light sources, which are symmetrically arranged on the side of the chip to be detected, and part of the light emitted by the two light sources illuminates On the U-shaped reflector, backlighting is performed on the bottom surface of the chip to be detected and a group of opposite sides thereof, and a part is backlit on the other group of opposite sides of the chip to be detected. There are four plane reflectors, It is arranged symmetrically and evenly around the bottom of the chip to be detected at a certain angle, so that the light reflected by the plane mirror is vertically incident on the front end of the lens. The lens is installed on the camera and is located below the chip to be detected. The camera is installed On the adjustment mechanism, the adjustment mechanism is used to adjust the working distance of the camera.

An important feature of the present invention is to use a single camera plus four plane mirrors to simultaneously image the bottom surface and four sides of the device, and the five sides are imaged in one picture, which is convenient for software processing, and compared with the multi-camera imaging method , the structure is more compact, and the cost of the device is reduced.

An important feature of the present invention is that the lens with a large depth of field can eliminate the negative influence of the optical path difference between the bottom surface imaging and the side imaging, so that the bottom surface and the four sides can be clearly imaged.

An important feature of the present invention is that a large-diameter lens can be used to reliably image IC devices with a size ranging from 5mm*5mm to 40mm*40mm.

An important feature of the present invention is that it adopts parallel optical paths and a special installation angle of the plane mirror. It only needs to calibrate the camera once, and the same IC device placed in different positions can also be used for reliable calibration of different IC devices placed in different positions. of imaging.

An important feature of the invention is that the imaging of the bottom surface and four sides adopts backlight illumination, the imaging contrast is high, and the software is easy to process.

An important feature of the present invention is that the U-shaped reflector can image and light the bottom surface and both sides of the device at the same time, so that the suction mechanism can absorb the device and fly into the detection position in parallel without falling action, which reduces the detection time and improves the efficiency.

The present invention uses a single camera plus a plane mirror to image the bottom surface and four sides of the device from two directions at the same time. There are five images of the device in one picture, and the bottom surface of the device is imaged to calculate the two-dimensional index, combined with the bottom surface The three-dimensional index of the pin is calculated from the image and the four-side image. The invention adopts the backlight lighting technology, the imaging of the device is clear, the contrast is high, and the lighting is uniform; by using a special lighting method, the invention can reliably image various specifications of devices within the range of 5mm*5mm～40mm*40mm, and only It needs to be calibrated once, and there is no need to re-calibrate when changing the device model, and there is no need to replace any parts, which greatly improves the adaptability of the detection device.

Description of drawings

FIG. 1 is a schematic diagram of the front view optical path of an appearance inspection device for a semiconductor chip according to the present invention, expressing the principle of the optical path for imaging the bottom surface of the device to be inspected.

Fig. 2 is a schematic view of the right-view optical path of the present invention (with the light source removed), expressing the principle of the optical path for imaging the side 1 and side 3 of the device to be inspected.

Fig. 3 is a schematic diagram of the optical path of the main view of the present invention, expressing the principle of the optical path for imaging the side 2 and side 4 of the device to be inspected.

Fig. 4 is a schematic diagram of the optical path of the main view of the imaging of a larger type device in the present invention, expressing the principle of the optical path of imaging the bottom surface of the device to be inspected.

FIG. 5 is a schematic view of the right-view optical path (with the light source removed) for imaging a larger device in the present invention, expressing the principle of the optical path for imaging side 1 and side 3 of the device to be inspected.

FIG. 6 is a schematic diagram of the optical path of the main view of the imaging of a larger type device in the present invention, expressing the optical path principle of the imaging of the side 2 and the side 4 of the device to be inspected.

Fig. 7 is a schematic diagram of the optical path of the main view of the imaging of a smaller type device in the present invention, expressing the principle of the optical path of imaging the bottom surface of the device to be inspected.

Fig. 8 is a schematic diagram of the right-view optical path of the present invention for imaging a smaller device (light source is removed), expressing the optical path principle of the imaging of the side 1 and side 3 of the device to be inspected.

Fig. 9 is a schematic diagram of the optical path of the main view of the imaging of a smaller type device in the present invention, expressing the optical path principle of the imaging of the side 2 and the side 4 of the device to be inspected.

Fig. 10 is a schematic structural view of the reflective plate of the present invention, wherein (a) is a schematic front view, and (b) is a schematic right view.

Fig. 11 is a physical diagram of a certain type of device to be tested in the present invention.

Fig. 12 is an effect diagram of the imaging of the device to be detected according to the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Fig. 1, the appearance inspection device of the semiconductor chip of the present invention includes a suction mechanism 1, a U-shaped reflector 2, two light sources 3, four plane mirrors 5, a lens 6, a camera 7 and a working distance adjustment mechanism 8.

The suction mechanism 1 is responsible for sucking the device 4 to be tested to the detection position. After the detection is completed, the suction device 1 leaves the detection position; the U-shaped reflector 2 is installed on the suction mechanism 1 to reflect light. The specific principle is that the light emitted by the light source 3 is irradiated on the U-shaped reflector 2, reflected by the U-shaped reflector 2, and simultaneously the bottom surface of the device 4 to be detected and a group of opposite side sides thereof (such as the device side 1 and the device side 1 among Fig. 11 ). The side 3 or the side 2 and the side 4) carry out backlighting, and move together with the suction mechanism 1 during work; two light sources 3 are installed between the U-shaped reflector 2 and the plane reflector 5, and part of the light emitted during work is irradiated on the U On the shaped reflector 2, another group of opposite sides of the device 4 to be detected (such as the device side 2 and side 4 or side 1 and side 3 in Figure 11) are backlit; The angle is installed on four sides (to calculate the appropriate angle, so that the light is reflected by the plane reflector and then incident on the front of the lens vertically, such as 50°, 53°), which plays a role in changing the optical path, as shown in Figure 1 and Figure 2.

Lens 6 is a large diameter, large depth of field (depth of field greater than 20mm) lens (such as diameter is φ 100mm, depth of field is 60mm), installed on the camera 7; camera 7 is installed on the working distance adjustment mechanism 8, device 4 is collected during work Fig.; If gather clear image, the distance (hereinafter referred to as working distance) between lens front face and device must be suitable, and working distance adjustment mechanism 8 is exactly to camera and lens be adjusted up and down, and camera and lens are adjusted to a suitable Working distance (such as 182mm).

The lighting principle of this solution is shown in Fig. 1, Fig. 2 and Fig. 3. The collected images mainly have two parts, the image of the bottom surface of the device 4 and the images of the four sides of the device 4 (as shown in Fig. 12), as shown in Fig. 4 . The imaging principle of the bottom surface of the device 4 is shown in Figure 1. The light emitted by the light source shines on the U-shaped reflector 2, illuminates the entire area inside the U-shaped reflector 2, and is reflected by the U-shaped reflector 2. Imaging in the camera, the imaging optical path is shown in the thin solid line in Figure 1, and the effect of an imaging example is shown in the bottom view in Figure 12. The imaging of the four sides of the device 4 is divided into two groups according to different lighting methods, side 1 and side 3 are grouped as group A, side 2 and side 4 are grouped as group B. The imaging principle of Group A is shown in Figure 2. The light emitted by the light source is irradiated on the U-shaped reflector 2, illuminating the entire area inside the U-shaped reflector 2, and the light reflected from the side of the U-shaped reflector 2 passes through the side 1 and side 3 of the device. The pins are reflected by the plane mirror and then incident on the lens vertically, forming an image on the camera. The imaging optical path is shown in the thin solid line in Figure 2. The effect of an imaging example is shown in Side View 1 and Side View 3 in Figure 12. The imaging principle of Group B is shown in Figure 3. The light emitted by the light source directly penetrates the pins on the side 2 and side 4 of the device, and is reflected by the plane mirror and then enters the lens vertically to form an image on the camera. The imaging optical path is shown in the thin solid line in Figure 3. The effect of an imaging example is shown in side view 2 and side view 4 in Figure 12 .

When changing the device model, if the size of the device becomes larger, the imaging optical path of the bottom surface and four sides of the device will move in parallel from the position of the thin solid line to the position of the dotted line, as shown in Figure 4, Figure 5 and Figure 6; when the size of the device becomes smaller, the bottom surface of the device will and the four side imaging light paths move parallel to the position of the thin solid line to the position of the dotted line, as shown in FIG. 7 , FIG. 8 and FIG. 9 . When the device size changes from small to large in the range of 5mm*5mm to 40mm*40mm, the imaging optical path of the bottom surface and four sides of the device will move in parallel from the dotted line position shown in Fig. 7, Fig. 8 and Fig. 9 to Fig. 4, Fig. 5 and The dotted line position shown in Figure 6. Since the light rays move in parallel, and the incident light rays of the bottom surface and side imaging are perpendicular to the lens, the optical path only needs to be calibrated once. When changing the device specification, there is no need to re-calibrate, and there is no need to replace parts.

Claims (5)

1. An appearance inspection device for a semiconductor chip, comprising a suction mechanism (1), a U-shaped reflector (2), a light source (3), a flat mirror (5), a lens (6), a camera (7) and an adjustment mechanism (8), where, The suction mechanism (1) is used to suck the chip to be detected to the position to be detected, the U-shaped reflector (2) is installed on the suction mechanism (1), and the light sources (3) are two, symmetrically arranged on the On the side of the detection chip, part of the light emitted by the two light sources (3) is irradiated on the U-shaped reflector (2), backlighting the bottom surface of the chip to be detected and a set of opposite sides thereof, and a part of the light is illuminated to the other side of the chip to be detected. A group of opposite sides are directly transmitted for backlighting. The plane reflectors (5) are four, which are arranged symmetrically and evenly around the bottom of the chip to be detected at a certain angle, so that the light reflected by the plane reflectors (5) The light is vertically incident on the front surface of the lens (6), the lens (6) is installed on the camera, located below the chip to be detected, the camera (7) is installed on the adjustment mechanism (8), and the adjustment mechanism (8) uses for adjusting the working distance of the camera (7). 2. The appearance inspection device according to claim 1, characterized in that, the plane mirror (5) is coated with a film, and the coating material is gold, silver, aluminum or PVC. 3. The appearance inspection device according to claim 1 or 2, characterized in that, the plane mirror (5) can be replaced by a prism. 4. The appearance inspection device according to claim 1 or 2, characterized in that the U-shaped reflective plate (2) is coated with reflective material inside. 5. The appearance inspection device according to claim 1 or 2, characterized in that the lens (6) has a diameter larger than

50mm lens with a depth of field greater than 20mm.

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