Patent Description:
This disclosure relates to defect detection in workpieces.

Evolution of the semiconductor manufacturing industry is placing greater demands on yield management and, in particular, on metrology and inspection systems. Critical dimensions continue to shrink, yet the industry needs to decrease time for achieving high-yield, high-value production. Minimizing the total time from detecting a yield problem to fixing it determines the return-on-investment for a semiconductor manufacturer.

Defect detection at the sides of a workpiece, such as a semiconductor wafer or part of a semiconductor wafer, is increasing in importance as semiconductor devices become more advanced. <FIG> illustrate a previous system for finding side defects in a workpiece. The system <NUM> of <FIG> detects superficial defects or interior defects that extend to a workpiece surface by looking at the sides of a workpiece. <FIG> is a schematic representation of an image obtained using the system <NUM> of <FIG>. The system <NUM> has four mirrors, such as mirrors <NUM>, that face each other in a square arrangement. The workpiece <NUM> (or other object under inspection) is positioned in a cavity between the mirrors <NUM>. The workpiece <NUM> has a side defect <NUM>.

A camera <NUM> with lens <NUM> looks at the bottom face of the workpiece <NUM>. The mirrors <NUM> are arranged at a <NUM>° angle with each of the four side faces (two of which are illustrated in the cross-section of <FIG>). Deviation angles of ± <NUM>° are possible due to non-telecentric optics. The system <NUM> of <FIG> is used to obtain an image <NUM>, as shown in <FIG>, of the bottom surface of the workpiece <NUM> and images 107a-107d of each of the four side surfaces of the workpiece <NUM> (see <FIG>). Coaxial illumination can be positioned between the camera <NUM> and lens <NUM> and the workpiece <NUM>. Only reflected light images of the four sides of the workpiece <NUM> are imaged using the four mirrors <NUM>.

The design of system <NUM> has drawbacks. The system <NUM> can only use reflected light. Thus, the system must be larger to support both reflected and transmitted light. Equipment with a smaller footprint is preferred in semiconductor manufacturing facilities. For transmitted light images, the system has low inspection speed. For reflected light images, the system <NUM> tends to suffer from large inspection overkill caused by rough, superficial dicing marks on the workpiece. These dicing marks are resolved, visualized, and/or highlighted by the imaging setup, but are typically not a reason to reject a workpiece <NUM> under inspection.

Both underkill and overkill are expensive and should be minimized if possible. Overkill is the risk of falsely rejecting a good workpiece. Underkil1 is the risk of failing to reject an actual bad workpiece.

An additional drawback of the system <NUM> is that reflected and transmitted light image acquisitions for the same workpiece are spread over multiple inspection apparatuses and are spread over time. This makes it more difficult to combine images for processing and post-processing purposes.

Therefore, improved systems and methods are needed. <CIT> discloses an apparatus for inspecting a micro-structured sample, such as a wafer, comprising a sample support for supporting the sample, an incident-light illumination for illuminating the sample in the incident-light mode and a transmitted-light illumination for illuminating the sample in the transmitted-light mode. A combined incident and transmitted-light IR image and a visual incident-light image can be imaged via a wavelength selective video double output simultaneously onto an IR special camera and onto a normal visual colour or monochromatic CCD camera and displayed on a monitor via a computer.

A system is provided in a first embodiment. The system includes a vacuum pump, a nozzle in fluid communication with the vacuum pump, a nozzle actuator configured to move the nozzle, and an inspection module. The nozzle is configured to hold a workpiece. The inspection nozzle includes: a first light source, a second light source, a first mirror, a second mirror, a first semi-mirror, a second semi-mirror, a camera, a third mirror, and a fourth mirror. The first mirror is disposed to receive light from the first light source. The first mirror directs the light from the first light source at an outer surface of the workpiece. The second mirror is disposed to receive light from the second light source. The second mirror directs the light from the second light source at the outer surface of the workpiece. The first semi-mirror is disposed between the first light source and the first mirror. The first semi-mirror receives the light from the first light source that is reflected from the outer surface of the workpiece and the light from the second light source that is transmitted through the workpiece. The second semi-mirror is disposed between the second light source and the second mirror. The second semi-mirror receives the light from the second light source that is reflected from the outer surface of the workpiece and the light from the first light source that is transmitted through the workpiece. The camera receives the light from the first light source and the second light source. The third mirror is disposed to direct the light from the first semi-mirror to the camera. The fourth mirror is disposed to direct the light from the second semi-mirror to the camera.

The first light source and the second light source can be LEDs.

The system can further include at least one optical lens disposed between the camera and the third mirror and the fourth mirror.

The system can further include a camera actuator configured to move the camera relative to the third mirror and the fourth mirror.

The first mirror and the second mirror can be disposed on opposite sides of the outer surface of the workpiece.

The system can further include a second of the inspection module. The first mirror and the second mirror of the second of the inspection module are disposed at a <NUM>° angle relative to the first mirror and the second mirror of the inspection module, respectively. The nozzle actuator can be configured to move the workpiece between the inspection module and the second of the inspection module.

A method is provided in a second embodiment. The method includes directing light from a first light source at an outer surface of a workpiece in a first inspection module. The light from the first light source reflected from the outer surface of the workpiece is received at a camera. The light from the first light source that is reflected from the outer surface of the workpiece is directed to the camera via a first mirror and a first semi-mirror. The light from the first light source transmitted through the workpiece is received at the camera. The light from the first light source that is transmitted through the workpiece is directed to the camera via a second mirror and a second semi-mirror.

The method can further include, using the camera, taking an image of the light from the first light source that is reflected from the outer surface of the workpiece and an image of the light from the first light source transmitted through the workpiece in a single exposure of a sensor in the camera.

The method can further include directing light in the first inspection module from a second light source at a point on the outer surface of a workpiece <NUM>° from that of the first light source. The directing light from the second light source is simultaneous with the directing light from the first light source. The light from the second light source is at a lower intensity than that of the first light source.

In an instance, the method can further include directing light from a second light source at a point on the outer surface of a workpiece <NUM>° from that of the first light source in the first inspection module. The light from the second light source reflected from the outer surface of the workpiece can be received at the camera. The light from the second light source that is reflected from the outer surface of the workpiece is directed to the camera via the second mirror and the second semi-mirror. The light from the second light source transmitted through the workpiece can be received at the camera. The light from the second light source that is transmitted through the workpiece is directed to the camera via the first mirror and the first semi-mirror.

In this instance, the method can further include, using the camera, taking an image of the light from the second light source that is reflected from the outer surface of the workpiece and an image of the light from the second light source transmitted through the workpiece in a single exposure of a sensor in the camera.

In this instance, the method can further include directing light from the first light source at a point on the outer surface of a workpiece <NUM>° from that of the second light source in the first inspection module. The directing light from the first light source is simultaneous with the directing light from the second light source. The light from the first light source is at a lower intensity than that of the second light source.

The method can further include positioning a focal plane inside the workpiece by adjusting a position of the camera and/or the first mirror, the first semi-mirror, and the first light source.

The method can further include tuning a wavelength of the light from the first light source thereby adjusting a penetration depth of the light from the first light source in the workpiece.

In an instance, the method can further includes positioning the workpiece on a nozzle in fluid communication with a vacuum pump and moving the workpiece on the nozzle relative to the first mirror using a nozzle actuator.

In this instance, the method can further include moving the workpiece from the first inspection module to a second inspection module.

In this instance, the method can further include directing light from a first light source at the outer surface of a workpiece in the second inspection module. The light from the first light source reflected from the outer surface of the workpiece is received at a camera in the second inspection module. The light from the first light source that is reflected from the outer surface of the workpiece is directed to the camera in the second inspection module via a first mirror and a first semi-mirror in the second inspection module. The light from the first light source transmitted through the workpiece is received at the camera in the second inspection module. The light from the first light source that is transmitted through the workpiece is directed to the camera in the second inspection module via a second mirror and a second semi-mirror in the second inspection module. The first mirror and the second mirror of the second inspection module are disposed at a <NUM>° angle relative to the first mirror and the second mirror of the first inspection module, respectively.

In this instance, the method can further include directing light from a second light source at a point on the outer surface of a workpiece <NUM>° from that of the first light source in the second inspection module. The light from the second light source reflected from the outer surface of the workpiece is received at the camera in the second inspection module. The light from the second light source that is reflected from the outer surface of the workpiece is directed to the camera in the second inspection module via the second mirror and the second semi-mirror in the second inspection module. The light from the second light source transmitted through the workpiece is received at the camera in the second inspection module. The light from the second light source that is transmitted through the workpiece is directed to the camera in the second inspection module via the first mirror and the first semi-mirror in the second inspection module.

The workpiece can be fabricated of one of silicon, gallium nitride, or gallium arsenide.

Although claimed subject matter will be described in terms of certain embodiments, other embodiments, including embodiments that do not provide all of the benefits and features set forth herein, are also within the scope of this disclosure. Various structural, logical, process step, and electronic changes may be made without departing from the scope of the disclosure. Accordingly, the scope of the disclosure is defined only by reference to the appended claims.

Embodiments of the inspection apparatus disclosed herein can enable the simultaneous acquisition (i.e., in a single camera sensor exposure) of a reflected light image of one side and a transmitted light image of the opposite side of a workpiece that is at least partially transparent to the light wavelengths of a light source that is illuminating the one side of the workpiece. The workpiece can be a semiconductor wafer, part of a semiconductor wafer, or other object. For example, the workpiece can be a singulated die, such as a silicon die from <NUM> by <NUM> to <NUM> by <NUM>. Larger dies, such as dies with a size of <NUM> by <NUM>, are possible. The dies can be formed from a <NUM> wafer, which is in a preceding step is diced with blades and or lasers in one or multiple steps to singulate the individual dies.

The transmitted light image can visualize internal defects inside the workpiece, while the reflected light image can find superficial defects occurring only at the surface of the workpiece under inspection. Combining the results of the inspection of both images improves overkill and underkill rate of the overall inspection of the workpiece. Distinction can be made between superficial defects of the workpiece that are visible in reflected light image only, which are still considered as part of a good workpiece by a semiconductor manufacturer, and internal defects inside the workpiece that are visible in the transmitted image only, which are considered as part of a bad workpiece by a semiconductor manufacturer. The bad workpiece should be scrapped or further inspected. Thus, if the algorithm detects the defect in the reflected image and not in the transmitted image, it is considered a good workpiece, which reduces overkill. Likewise, the recipe for the transmitted light image can be set up to be sensitive enough to detect the smallest/lowest contrast potential defects and then classify as a bad workpiece in case the potential defect is not detected in the reflected light image, which reduces underkill.

Using embodiments disclosed herein, the transmitted and reflected light images of a side of the workpiece can be acquired one after the other (i.e., in two consecutive camera sensor exposures) by illuminating one side for the first image acquisition and then illuminating the opposite side for the second image acquisition. Based on the nature of the workpiece under inspection, the transmitted and reflected light images of opposite sides of the workpiece, one after the other, can be acquired using embodiments disclosed herein. This may use four consecutive camera sensor exposures for all sides of a workpiece.

Embodiments disclosed herein can be implemented and used in two optical path orientations. One implementation images two opposite sides of the workpiece. Another implementation images the two adjacent opposite sides of a workpiece. The latter is obtained by rotating the optical path <NUM>° with respect to the first optical path. In an embodiment of a system, both orientations can be integrated to inspect all four sides of the workpiece. In another embodiment, both <NUM>° and <NUM>° rotated optical paths can be included in one system such that all four workpiece sides can be imaged with a single camera sensor.

Embodiments disclosed herein can enable acquisition of images of workpieces of different sizes by changing camera position and/or positions of the mirrors. For example, actuators can be used to change their positions to accommodate workpieces of different sizes.

Embodiments of this inspection apparatus can be implemented with a line sensor camera or an area sensor camera and can be implemented with LED, superluminescent diode (SLD), laser, or halogen light source. Wide band or small band wavelength illuminations of different wavelength ranges, with or without bandpass, cut-on, or cut-off filters, can be used to select certain wavelengths.

Transmitted and reflected light images of the same or opposite sides of the workpiece under inspection can be combined using image processing or post-processing algorithms to discriminate superficial workpiece defects from defects protruding internally in the workpiece under inspection.

<FIG> is a diagram of an embodiment of a system <NUM>. The system <NUM> includes a nozzle <NUM> in fluid communication with a vacuum pump <NUM>. The nozzle <NUM> is configured to hold a workpiece <NUM>. While a semiconductor die is specifically disclosed as workpiece <NUM>, other workpieces also can be used as workpiece <NUM>. A nozzle <NUM> that uses vacuum to hold the workpiece <NUM> is illustrated, but magnetic or mechanical clamping also can be used.

A nozzle actuator <NUM> can move the nozzle <NUM> and, consequently, the workpiece <NUM>, in a Z direction indicated by the arrows. Thus, the workpiece <NUM> can be positioned between the first mirror <NUM> and second mirror <NUM> using the nozzle actuator <NUM>. The nozzle actuator <NUM> also can move the nozzle <NUM> and workpiece <NUM> in the X direction or Y direction. The nozzle actuator <NUM> also can move the nozzle <NUM> and workpiece <NUM> in three perpendicular directions (i.e., X, Y, and Z directions).

The workpiece <NUM> can be made of silicon, gallium nitride, gallium arsenide, or other materials. The workpiece <NUM> also can be made of glass. Advanced semiconductor devices can be inspected using embodiments disclosed herein. Thus, workpieces with transparent, translucent, or non-transparent materials can be inspected using the system <NUM>. However, the workpiece may be transparent to at least some wavelengths of light to use the design of the system <NUM>. Cracks, chipping, contamination (e.g., internal contamination), foreign materials (e.g., dust or dirt), or other defects can be detected.

The workpiece <NUM> can be positioned in an inspection module <NUM>. The inspection module <NUM> includes a first light source <NUM> and a second light source <NUM>. The first light source <NUM> and/or second light source <NUM> can be LEDs, SLDs, lasers, or halogen light sources.

In an instance, the first light source <NUM> and second light source <NUM> are LEDs that have a narrow bandwidth around <NUM>. Other wavelengths are possible and this value is merely one example.

In another instance, the first light source <NUM> and second light source <NUM> are halogen light sources with a filter.

A first mirror <NUM> can be positioned to receive light from the first light source <NUM>. The first mirror <NUM> can direct the light from the first light source at an outer surface of the workpiece <NUM>. The workpiece <NUM> can be square, rectangular, polygonal, round, or other shapes. The first mirror <NUM> can deflect the light.

A second mirror <NUM> can be positioned to receive light from the second light source <NUM>. The second mirror can direct the light from the second light source <NUM> at the outer surface of the workpiece <NUM>. The second mirror <NUM> can deflect the light.

The first mirror <NUM> and the second mirror <NUM> can be positioned on opposite sides of the outer surface of the workpiece <NUM>. Thus, the first mirror <NUM> and the second mirror <NUM> can be <NUM>° opposite each other relative to a center of the workpiece <NUM>.

A first semi-mirror <NUM> can be positioned in the path of light between the first light source <NUM> and the first mirror <NUM>. In an instance, the first semi-mirror <NUM> receives the light from the first light source <NUM> that is reflected from the outer surface of the workpiece <NUM> and/or the light from the second light source <NUM> that is transmitted through the workpiece <NUM>. The first semi-mirror <NUM> directs light to the third minor <NUM>.

A second semi-mirror <NUM> can be positioned in the path of light between the second light source <NUM> and the second mirror <NUM>. In an instance, the second semi-mirror <NUM> receives the light from the second light source <NUM> that is reflected from the outer surface of the workpiece <NUM> and/or the light from the first light source <NUM> that is transmitted through the workpiece <NUM>. The second semi-mirror <NUM> directs light to the fourth mirror <NUM>.

A semi-mirror can be partially transparent and partially reflective to the beam of light. For example, the reflective portion of the semi-mirror may only be positioned partially in a beam of light, which reflects only some of the light. The semi-mirror also can be a half mirror that reflects some of the light and is penetrated by the rest. Other semi-mirror configurations are possible. The first semi-mirror <NUM> and second semi-mirror <NUM> can instead be beam splitters or other optical components.

A camera <NUM>, which can be coupled with one or more lenses <NUM>, receives the light from the first light source <NUM> and/or the second light source <NUM>. The camera <NUM> can be a line sensor camera or an area sensor camera. The light from the first light source <NUM> and/or the second light source <NUM> can be imaged at the same point on the sensor of the camera <NUM> or different points on the sensor of the camera <NUM>.

The one or more lenses <NUM> can be positioned in the path of light between the camera <NUM> and a third mirror <NUM> and fourth mirror <NUM>. The third mirror <NUM> can be positioned to direct the light from the first semi-mirror <NUM> to the camera <NUM> using deflection. The fourth mirror can be positioned to direct the light from the second semi-mirror <NUM> to the camera <NUM> using deflection.

A camera actuator <NUM> can be configured to move the camera <NUM> (with or without the one or more lenses <NUM>) relative to the third mirror <NUM> and fourth mirror <NUM> in a direction perpendicular to the camera plane and/or in the camera sensor plane (e.g., in the X, Y, or Z directions). The camera actuator <NUM> also can move the camera <NUM> and the lenses <NUM> relative to each other in an embodiment.

The camera <NUM> can be connected to a framegrabber (not illustrated). The framegrabber can apply image processing to the acquired images to capture defects in the workpiece under inspection, such as the workpiece <NUM>.

A processor (not illustrated) in electronic communication with the camera, can concatenate transmitted and reflected images of both opposite sides into a single image instance for further image processing. The processor may be coupled to the components of the system <NUM> in any suitable manner (e.g., via one or more transmission media, which may include wired and/or wireless transmission media) such that the processor can receive output. The processor may be configured to perform a number of functions using the output. The system <NUM> can receive instructions or other information from the processor.

The processor, other system(s), or other subsystem(s) described herein may be part of various systems, including a personal computer system, image computer, mainframe computer system, workstation, network appliance, internet appliance, or other device. The subsystem(s) or system(s) may also include any suitable processor known in the art, such as a parallel processor. In addition, the subsystem(s) or system(s) may include a platform with high-speed processing and software, either as a standalone or a networked tool.

The processor may be implemented in practice by any combination of hardware, software, and firmware. Also, its functions as described herein may be performed by one unit, or divided up among different components, each of which may be implemented in turn by any combination of hardware, software, and firmware. Program code or instructions for the processor to implement various methods and functions may be stored in readable storage media, such as a memory in the electronic data storage unit.

The first light source <NUM>, first mirror <NUM>, and first semi-mirror <NUM> can be moved in a horizontal direction (e.g., X direction or Y direction) using the first horizontal actuator <NUM>. The second light source <NUM>, second minor <NUM>, and second semi-mirror <NUM> can be moved in a horizontal direction (e.g., X direction or Y direction) using the second horizontal actuator <NUM>. The first horizontal actuator <NUM> and the second horizontal actuator <NUM> can be used to adjust focus or to accommodate a wider workpiece <NUM>. While a first horizontal actuator <NUM> and second horizontal actuator <NUM> are disclosed, a single actuator can be used with a transmission to reposition these components.

For example, the first light source <NUM>, first mirror <NUM>, and first semi-mirror <NUM> can be positioned on a first bracket <NUM> that ensures that spacing between these three components in the Z direction does not change. The second light source <NUM>, second mirror <NUM>, and second semi-mirror <NUM> can be fixed to a second bracket <NUM> at ensures that spacing between these three components in the Z direction does not change. The first bracket <NUM> can be moved using the first actuator <NUM>. The second bracket <NUM> can be moved using the second actuator <NUM>. The first bracket <NUM> and second bracket <NUM> can be moved horizontally (e.g., X direction or Y direction), simultaneously inwards and outwards, and symmetrically with respect to an optical axis of the camera <NUM>. Thus, the system <NUM> can acquire images of workpieces with different sizes. Asymmetric movement of the first bracket <NUM> and second bracket <NUM> also is possible. Alternatively or additionally, the camera <NUM> and optionally lens <NUM> can be moved in the Z direction.

The first mirror <NUM>, second mirror <NUM>, third mirror <NUM>, and fourth mirror <NUM> are illustrated as <NUM>° mirrors, but other designs are possible.

Using the system <NUM>, functionality is combined to acquire transmitted light images and reflected light images of sides of the workpieces in one system. The system <NUM> can accommodate different workpiece sizes. The optical path has a focal plane at both opposite sides of the workpiece <NUM> or other object under inspection. This is for both transmitted and reflected light imaging. Images of the opposite sides of the workpiece are imaged side-by-side on the camera <NUM>. This allows higher speed inspection in a compact apparatus, which has a smaller footprint, and provides additional possibilities for processing or post-processing because reflected and transmitted light images of the workpiece <NUM> are combined.

The reflected light image using system <NUM> contains two light response parts: one part is the direct reflection from the illuminated side of the workpiece <NUM> and a second part is the light that transmits back through the illuminated side after transmission through the workpiece <NUM> and reflection at the opposite side of the illuminated side. This second part also contains the light transmitted back through the illuminated side after multiple internal reflections between these opposite sides. This second light response part can be referred to as "secondary reflection. " The direct reflected part is dominant and can be referred to as "primary reflection. " The secondary reflection can suppress the primary reflection (undesired) signal from the (rough) superficial dicing marks at the illuminated side of the workpiece in the overall reflected light imaging, which reduces the overkill linked to these dicing marks. Light scattered by the superficial dicing marks at primary reflection is compensated by the secondary reflected light. Both add up in the image acquisition and, hence, the signal of the superficial dicing marks is suppressed. This overkill is a serious drawback of previous techniques that used only reflected imaging.

While the light collected by the camera <NUM> is illustrated in the Z direction, one or more additional mirrors can be added (not illustrated) so that the light collected by the camera <NUM> goes into or out of the page (i.e., in the Y direction). The camera <NUM> can be positioned appropriately to acquire images with this redirected light.

The wavelength used in the embodiments disclosed herein should allow for light transmission and integration. Thus, the workpiece can be transparent or translucent for the applied wavelengths of the light source, and the camera can be sensitive to some extent to these applied wavelengths. The camera <NUM> can be a VIS (visual light) or NIR (near-infrared, such as below <NUM>) sensitivity-enhanced silicon sensor-based camera, which can operate with or without combination with infrared-to visible wavelength conversion optical parts. In a particular instance, the camera <NUM> is uses a colloidal quantum dot-based sensor.

During operation, the workpiece <NUM> is placed between the first mirror <NUM> and second mirror <NUM>. The first mirror <NUM> and second mirror <NUM> and/or camera <NUM> are positioned such that the two opposite sides of the workpiece <NUM> are in the focal plane of the camera <NUM>. Then the first light source <NUM> is turned on to create the primary and secondary reflected light image of the left side and the transmitted light image of the right side of the workpiece <NUM>.

The emitted light travels through the first semi-mirror <NUM>, is deflected by the first mirror <NUM>, is primary and secondary reflected back by the left side of the workpiece <NUM>, is deflected by the first mirror <NUM>, by the semi-mirror <NUM>, by the third mirror <NUM>, and then is imaged by the lens <NUM> on the camera <NUM>. Simultaneously, the emitted light travels through the first semi-mirror <NUM>, is deflected by the first mirror <NUM>, is transmitted through the workpiece <NUM>, is deflected by the second mirror <NUM>, by the second semi-mirror <NUM>, by the fourth mirror <NUM>, and then is imaged by the lens <NUM> on the camera <NUM>.

Then the first light source <NUM> is turned off and the second light source <NUM> is turned on to create the primary and secondary reflected light image of the right side of the workpiece <NUM> and the transmitted light image of the left side of the workpiece <NUM>.

The sensor of camera <NUM> can be sensitive for the wavelengths of the transmitted light path. For example, silicon workpieces may need infrared wavelength for transparency and the sensor of the camera <NUM> can be sensitive to infrared wavelengths.

One or both of the two opposing flat surfaces of the workpiece <NUM>, which can be contacted by the nozzle <NUM>, also can be imaged using the system. In an instance, the system can image the two opposing points on the outer surface of the workpiece <NUM> and a device side (e.g., a flat side) of the workpiece <NUM>.

<FIG> shows a first example of operation of the system <NUM> of <FIG>. As shown in <FIG>, light from the first light source <NUM> is directed at an outer surface of the workpiece <NUM> in the inspection module <NUM>. The second light source <NUM> is not operating. Light reflected from the outer surface of the workpiece <NUM> (shown with the solid line) is received by the camera <NUM>. This reflected light includes light from secondary and primary reflection. This light from the first light source <NUM> reflected from the workpiece <NUM> is directed to the camera <NUM> via the first mirror <NUM> and the first semi-mirror <NUM>. Light transmitted through the workpiece <NUM> (shown with the dashed line) is also received by the camera <NUM>. The light from the first light source <NUM> transmitted through the workpiece <NUM> is directed to the camera <NUM> via the second mirror <NUM> and the second semi-mirror <NUM>. The camera <NUM> can take an image of the light from the first light source <NUM> reflected from the outer surface of the workpiece <NUM> and an image of the light from the first light source <NUM> transmitted through the workpiece <NUM> in a single exposure of a sensor in the camera <NUM>.

<FIG> shows a second example of operation of the system <NUM> of <FIG>. As shown in <FIG>, light from the second light source <NUM> is directed at an outer surface of the workpiece <NUM> in the inspection module <NUM>. The second light source <NUM> directs light at a point on the outer surface of the workpiece <NUM><NUM>° from a point on the outer surface of the workpiece <NUM> that the first light source <NUM> directs light at. The first light source <NUM> is not operating. Light reflected from the outer surface of the workpiece <NUM> (shown with the solid line) is received by the camera <NUM>. This reflected light includes light from secondary and primary reflection. This light from the second light source <NUM> reflected from the workpiece <NUM> is directed to the camera <NUM> via the second mirror <NUM> and the second semi-mirror <NUM>. Light transmitted through the workpiece <NUM> (shown with the dashed line) is also received by the camera <NUM>. The light from the second light source <NUM> transmitted through the workpiece <NUM> is directed to the camera <NUM> via the first mirror <NUM> and the first semi-mirror <NUM>. The camera <NUM> can take an image of the light from the second light source <NUM> reflected from the outer surface of the workpiece <NUM> and an image of the light from the second light source <NUM> transmitted through the workpiece <NUM> in a single exposure of a sensor in the camera <NUM>.

<FIG> shows a third example of operation of the system <NUM> of <FIG>. The operation in <FIG> is similar to that of <FIG>, but light from the second light source <NUM> is directed to a point on an outer surface of the workpiece <NUM><NUM>° from the light directed by the first light source <NUM>. This light from the second light source <NUM> is shown with a dotted line and is positioned adjacent the light transmitted through the workpiece <NUM> in <FIG> merely for ease of illustration. The pathway of the light from the second light source <NUM> may be the same as that transmitted through the workpiece <NUM> by the first light source <NUM>. Operation of the first light source <NUM> and second light source <NUM> may be simultaneous. Light from the second light source <NUM> is at a lower intensity than that of the first light source <NUM>. For example, light from the second light source <NUM> may be from greater than <NUM>% to approximately <NUM>% of the intensity of the first light source <NUM>. Transmitted light imaging can suffer from dark areas in the region of interest on the workpiece side view due to different surface angles slants in a dual dicing process (e.g., using two different dicing blades). By also operating the second light source <NUM> this phenomenon disappears or is at least largely attenuated. Hence, overall signal-to-noise ratio on real defects increases, which enables less overkill and less underkill.

<FIG> shows a fourth example of operation of the system of <FIG>. The operation in <FIG> is similar to that of <FIG>, but light from the first light source <NUM> is directed to a point on an outer surface of the workpiece <NUM><NUM>° from the light directed by the second light source <NUM>. This light from the first light source <NUM> is shown with a dotted line and is positioned adjacent the light transmitted through the workpiece <NUM> in <FIG> merely for ease of illustration. The pathway of the light from the first light source <NUM> may be the same as that transmitted through the workpiece <NUM> by the second light source <NUM>. Operation of the first light source <NUM> and second light source <NUM> may be simultaneous. Light from the first light source <NUM> is at a lower intensity than that of the second light source <NUM>. For example, light from the first light source <NUM> may be from greater than <NUM>% to approximately <NUM>% of the intensity of the second light source <NUM>.

In the embodiments of <FIG> or <FIG>, a focal plane can be positioned inside the workpiece <NUM> by adjusting a position of the camera <NUM>, the first mirror <NUM>, the first semi-mirror <NUM>, and/or the first light source <NUM>. A wavelength of the light from the first light source <NUM> also can be tuned, which can adjust a penetration depth of the light in the workpiece <NUM>.

In the embodiments of <FIG> or <FIG>, a focal plane can be positioned inside the workpiece <NUM> by adjusting a position of the camera <NUM>, the second mirror <NUM>, the second semi-mirror <NUM>, and/or the second light source <NUM>. A wavelength of the light from the second light source <NUM> also can be tuned, which can adjust a penetration depth of the light in the workpiece <NUM>.

A focal plane can be positioned inside the workpiece in any of the embodiments disclosed herein. The mirrors and semi-mirrors setup splits the focal plane to a left and a right focal plane, respectively on the left and right sides of the workpiece. By moving the camera <NUM> closer to the workpiece <NUM>, both focal planes can be moved simultaneously and symmetrically (i.e., over the same distance) inwards (i.e., inside the workpiece <NUM>). If only the first mirror <NUM>, the first semi-mirror <NUM>, and the first light source <NUM> are moved closer to the workpiece, only the left focal plane moves inwards (i.e., inside the workpiece <NUM>). The right focal plane position stays unaltered. Similarly, moving only the second mirror <NUM>, the second semi-mirror <NUM>, and the second light source <NUM> closer to the workpiece <NUM>, only the right focal plane moves inwards (i.e., inside the workpiece <NUM>).

The focal plane also can be a point on the outer surface of the workpiece <NUM>.

In an instance, images are taken sequentially. For example, the imaging schemes of <FIG> and <FIG> can be performed sequentially. The imaging schemes of <FIG> and <FIG> can be performed sequentially. A combination of the imaging schemes of <FIG> and <FIG> or <FIG> and <FIG> also can be performed.

<FIG> shows a diagram of another embodiment of the system <NUM> of <FIG>. The system <NUM> can include a second inspection module <NUM> substantially the same as the inspection module <NUM>, which can be referred to as a first inspection module. The system <NUM> also includes a second inspection module <NUM>. The first mirror <NUM> and second mirror <NUM> in the first inspection module <NUM> and the second inspection module <NUM> are positioned at a <NUM>° degree relative to each other, respectively. Thus, the mirrors, semi-mirrors, and light sources in the first inspection module <NUM> are rotated <NUM>° degree relative to these components in the second inspection module <NUM>. The first inspection module <NUM> can image outer surfaces <NUM> and <NUM> of the workpiece <NUM>. The second inspection module <NUM> can image outer surfaces <NUM> and <NUM> of the workpiece <NUM>. The outer surfaces <NUM>-<NUM> are shown in dashed straight lights to show the surface that can be imaged.

In the embodiment of <FIG>, the nozzle actuator <NUM> can move the workpiece <NUM> and nozzle <NUM> between the first inspection module <NUM> and second inspection module <NUM>. Thus, the nozzle actuator <NUM> can move the workpiece <NUM> and nozzle <NUM> in two or three perpendicular directions (e.g., X, Y, and/or Z directions). The workpiece <NUM> can be held by the nozzle <NUM> during this movement.

The second inspection module <NUM> can operate as shown in the embodiments of <FIG>. The images of the workpiece <NUM> using the second inspection module <NUM> is at different parts of the outer surface of the workpiece <NUM> than the first inspection module <NUM>.

In another embodiment to acquire reflected and transmitted light images of the two sets of outer surfaces <NUM> and <NUM> and outer surfaces <NUM> and <NUM>, the system <NUM> can include only the first inspection module <NUM>. The first inspection module <NUM> can spin the workpiece <NUM><NUM>° on the nozzle <NUM>. The first inspection module <NUM> also can rotate the various mirrors, light sources, semi-mirrors, and optionally the camera in the first inspection module <NUM>, such as by <NUM>°. An actuator can be used to rotate the various mirrors, light sources, semi-mirrors, camera, or other components in this embodiment.

Using embodiments disclosed herein, transmitted and reflected light images can be acquired in one system with the ability to simultaneously acquire a transmitted light image of one workpiece side (and optionally its adjacent side) of a workpiece and a reflected light image of the opposite workpiece side (and optionally its adjacent side) in one single image acquisition step (e.g., in one single camera sensor exposure). The transmitted and reflected light images of both opposite sides of the workpiece can be acquired one after the other (e.g., in two consecutive camera sensor exposures) on the same camera sensor by illuminating the first side for the first image acquisition and then illuminating the second side for the second image acquisition. These operations can be performed with or without moving parts or lens refocusing during or between consecutive image acquisitions.

Furthermore, the creation and use of secondary reflection in the reflected light imaging method can suppress rough superficial dicing marks and, hence, reduce overkill on workpieces that are inspected.

The focal planes can be positioned at different locations inside the workpiece under inspection to determine the internal defect location by changing camera and/or light sources and mirror positions.

Different penetration depth of the light at different wavelengths can be performed by tuning the wavelengths while acquiring a plurality of images. The different images can be used to provide better discrimination between defects at the surface of the workpiece under inspection and defects that are more internal in the workpiece under inspection. This can improve the defect capture rate and inspection performance.

Claim 1:
A system comprising:
a vacuum pump(<NUM>);
a nozzle (<NUM>)
in fluid communication with the vacuum pump, wherein the nozzle is configured to hold a workpiece (<NUM>);
a nozzle actuator (<NUM>) configured to move the nozzle; and
an inspection module (<NUM>) that includes:
a first light source (<NUM>);
a second light source (<NUM>);
a first mirror (<NUM>) that is disposed to receive light from the first light source, wherein the first mirror directs the light from the first light source at an outer surface of the workpiece;
a second mirror (<NUM>) that is disposed to receive light from the second light source, wherein the
second mirror directs the light from the second light source at the outer surface of the workpiece;
a first semi-mirror (<NUM>) disposed between the first light source and the first mirror, wherein the
first semi-mirror receives the light from the first light source that is reflected from the outer surface of the workpiece and the light from the second light source that is transmitted through the workpiece;
a second semi-mirror (<NUM>) disposed between the second light source and the second mirror,
wherein the second semi-mirror receives the light from the second light source that is reflected from the outer surface of the workpiece and the light from the first light source that is transmitted through the workpiece;
a camera (<NUM>) that receives the light from the first light source and the second light source;
a third mirror (<NUM>) that is disposed to direct the light from the first semi-mirror to the camera; and
a fourth mirror (<NUM>) that is disposed to direct the light from the second semi-mirror to the camera.