Methods and systems for imaging and cutting semiconductor wafers and other semiconductor workpieces

Methods and systems for imaging and cutting semiconductor wafers and other microelectronic device substrates are disclosed herein. In one embodiment, a system for singulating microelectronic devices from a substrate includes an X-ray imaging system having an X-ray source spaced apart from an X-ray detector. The X-ray source can emit a beam of X-rays through the substrate and onto the X-ray detector, and X-ray detector can generate an X-ray image of at least a portion of the substrate. A method in accordance with another embodiment includes detecting spacing information for irregularly spaced dies of a semiconductor workpiece. The method can further include automatically controlling a process for singulating the dies of the semiconductor workpiece, based at least in part on the spacing information. For example, individual dies can be singulated from a workpiece via non-straight line cuts and/or multiple cutter passes.

TECHNICAL FIELD

The following disclosure relates generally to the manufacture of microelectronic devices and, more particularly, to methods and systems for imaging and cutting semiconductor workpieces.

BACKGROUND

Packaged microelectronic devices are used in cellular phones, pagers, personal digital assistants, computers, and many other electronic products. Die-level packaged microelectronic devices typically include a die, an interposer substrate or leadframe attached to the die, and a molded casing around the die. The die generally has an integrated circuit and a plurality of bond-pads coupled to the integrated circuit. The bond-pads can be coupled to terminals on the interposer substrate or leadframe. The interposer substrate can also include ball-pads coupled to the terminals by conductive traces in a dielectric material. A plurality of solder balls can be attached to corresponding ball-pads to construct a “ball-grid” array. The steps for making die-level packaged microelectronic devices typically include (a) forming a plurality of dies on a semiconductor wafer, (b) cutting the wafer to singulate the dies, (c) attaching individual dies to corresponding interposer substrates, (d) wire-bonding the bond-pads to the terminals of the interposer substrate, and (e) encapsulating the dies with a molding compound.

Another process for packaging microelectronic devices is wafer-level packaging. In wafer-level packaging, a plurality of microelectronic dies are formed on a wafer and a redistribution layer is formed over the dies. The redistribution layer includes a dielectric layer, a plurality of ball-pad arrays on the dielectric layer, and a plurality of traces coupled to individual ball-pads of the ball-pad arrays. Each ball-pad array is arranged over a corresponding microelectronic die, and the traces couple the ball-pads in each array to corresponding bond-pads on the die. After forming the redistribution layer on the wafer, a stenciling machine can deposit discrete blocks of solder paste onto the ball-pads of the redistribution layer. The solder paste is then reflowed to form solder balls or solder bumps on the ball-pads. After forming the solder balls on the ball-pads, the wafer is cut to singulate the dies.

Another type of packaged microelectronic device is a build-up package (“BUP”) microelectronic device. BUP devices are formed by placing multiple singulated microelectronic dies active side down on a temporary carrier. A fill material is then used to cover the dies and the carrier. Once the fill material cures, the temporary carrier is removed. The active sides of the dies are cleaned, and then a redistribution layer is applied to the active sides. Solder balls can be connected to the redistribution layer, and a dielectric layer can be applied over portions of the redistribution layer so that the solder balls extend through the dielectric layer. The fill material between the dies is then cut to separate the dies from one another and form multiple BUP devices. The solder balls and redistribution layer can then be used to connect the BUP device to a printed circuit board.

BUP devices can also be formed by placing multiple singulated dies active side down on a temporary carrier, and placing fill material between the dies. Once the fill material hardens, the temporary carrier is removed and the BUP devices are separated by cutting the fill material between the dies. It may be difficult to place a redistribution layer on the active sides of the dies with this process, however, because the active sides and the fill material may not form a sufficiently planar surface for effective application of a redistribution layer, and the dies may be skewed such that precise wafer level processes cannot be used.

Whether the dies are encapsulated before or after dicing, the dies are generally organized in a rectilinear array of rows and columns that are separated by streets. The rows and columns are spaced apart from each other in a repeated pattern, generally with a fixed row spacing between neighboring rows, and a fixed column spacing between neighboring columns. The pattern is generally fixed for a given type of wafer and die configuration. Accordingly, even if a particular type of wafer has dies of different sizes, the dies are arranged in a predictable pattern that is repeated from one wafer to the next.

Prior to dicing, a camera or other type of imaging system is used to detect the rotational orientation of the array and the starting point at which the dicing process begins. A dicing blade is then brought into contact with the wafer and either the blade or the wafer is translated to make the first cut (e.g., along a column). The blade or the wafer is then stepped over to the next column by a known distance corresponding to the spacing between columns, and the next cut is made. This process is repeated until all the necessary column cuts are completed. At that point, the wafer (or the blade) is rotated 90° and the same process is repeated until all the row cuts are complete.

While the foregoing process has proven effective for many applications, in certain applications, the spacing between dies may not be consistent from one wafer to the next, or within a given wafer. In such a case, the rotating blade typically cannot account for spacing variations and as a result, may cut through dies that would otherwise be suitable for installation in an end product. Accordingly, there is a desire to improve the versatility of current singulation processes.

FIG. 1is a schematic diagram of a prior art system100for imaging a semiconductor wafer102(“wafer102”) and cutting the wafer102into individual dies. The system100includes an infrared camera110having an infrared detector array (not shown). The infrared camera110is operably coupled to a dicing machine114via a computer112. The dicing machine114can include a saw having, for example, a diamond-tipped blade116that rotates about a spindle to cut through the wafer102. The wafer102is supported by a chuck104that is operably coupled to a heat source106. To facilitate cutting and/or imaging, the chuck104is able to move laterally in an X direction and rotate about its axis in a θ direction. Similarly, the dicing machine114is able to move up and down in a Y direction as well as back and forth in a Z direction.

In operation, the heat source106heats the wafer102to a predetermined temperature, causing the wafer102to generate infrared photons or “flux.” The detector array in the infrared camera110creates a map of the wafer102based on the flux intensity received by each of the individual detectors in the array. The computer112converts the flux detected by each of the detectors into a temperature reading corresponding to a feature on the wafer102. This enables the computer112to determine the location of scribe lines and/or other alignment features (i.e., fiducials) on the wafer102. The computer112provides this information to the dicing machine114, which then cuts the wafer102along the scribe lines to singulate the individual dies.

Another type of infrared imaging system commonly used to align semiconductor wafers does not use a heat source to heat the wafer. This type of system is a reflective system that directs infrared radiation down onto the wafer, and then captures the infrared radiation that reflects off of the wafer with a camera that generates an image of the wafer.

Many semiconductor wafers include layers of material that can inhibit infrared imaging. For example, various types of memory and imaging semiconductor devices include metallized layers on the back side to enhance protection from electromagnetic interference (EMI). These metallized layers can obscure infrared radiation, making accurate infrared imaging difficult, if not impossible. In addition, when cutting BUP devices, the mold material can also obscure infrared imaging, again making it difficult to accurately detect the location of scribe lines and other alignment features. To overcome these problems, semiconductor wafers can be manufactured so that the metallized layer or mold compound is prevented from covering the alignment features. Alternatively, the infrared inhibiting material can be removed from around the alignment features prior to wafer imaging. Both of these approaches, however, are time consuming and can reduce the amount of space on a wafer available for producing dies. Therefore, it would be desirable to have a system for imaging and cutting semiconductor wafers that have infrared inhibiting layers obscuring alignment features.

DETAILED DESCRIPTION

The following disclosure describes methods and systems for imaging and dicing semiconductor wafers and other microelectronic device substrates. Specific details of several embodiments of the disclosure are described below with reference to semiconductor workpieces (“workpieces”) and systems for processing the workpieces. The workpieces can include micromechanical components, data storage elements, optics, read/write components and/or other features. For example, the workpieces can include wafers having dies, including SRAM, DRAM (e.g., DDR-SDRAM), flash-memory (e.g., NAND flash-memory), processor, imager, and/or other dies. Substrates can be semiconductive pieces (e.g., doped silicon wafers, gallium arsenide wafers, or other semiconductor wafers), non-conductive pieces (e.g., various ceramic substrates), or conductive pieces. Several other embodiments of the invention can have configurations, components, or procedures different than those described in this section. A person of ordinary skill in the art, therefore, will accordingly understand that the invention may have other embodiments with additional elements, or the invention may have other embodiments without several of the elements shown and described below with reference toFIGS. 2-15.

Many specific details of certain embodiments of the invention are set forth in the following description and inFIGS. 2-15to provide a thorough understanding of these embodiments. A person skilled in the art, however, will understand that the invention may be practiced without several of the details described below, or with additional details which can be added to the invention. Well-known structures and functions often associated with semiconductor wafers, associated imaging and cutting systems, and microelectronic devices in general have not been shown or described in detail to avoid unnecessarily obscuring the description of the various embodiments of the invention. Where the context permits, singular or plural terms may also include plural or singular terms, respectively. Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list means including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Additionally, the term “comprising” is used throughout the following disclosure to mean including at least the recited feature(s) such that any greater number of the same feature and/or additional types of features or components is not precluded.

While various aspects of the invention are described below in the context of semiconductor wafers, those of ordinary skill in the art will understand that the methods and systems described herein can also be used to singulate dies and/or other microelectronic devices from other types of substrates. For example, the various methods and systems described herein can also be used to separate individual dies from a BUP substrate.

A particular method for singulating semiconductor dies includes detecting spacing information for irregularly spaced dies of an individual semiconductor workpiece, and, based at least in part on the spacing information, automatically controlling a process for singulating the dies of the individual semiconductor workpiece. In further particular arrangements, the method can include directing a cutter (e.g., a laser beam or water jet) to deviate from a single straight line path as it traverses a semiconductor workpiece. Further details of these and other methods and associated systems are discussed below.

FIG. 2is a schematic illustration of a semiconductor wafer imaging and cutting system200(“cutting system200”) in accordance with an embodiment of the invention. As described in greater detail below, the cutting system200includes an X-ray imaging system (e.g., a fluoroscopic X-ray imaging system) for aligning a semiconductor wafer202(“wafer202”) for dicing. The wafer202can include various types of microelectronic devices (e.g., DRAM, SRAM, Flash, Imagers, PCRAM, MRAM, etc.) which are not shown inFIG. 2. The wafer202can also include an infrared inhibiting layer203applied to a backside218. The infrared inhibiting layer203extends over all or a portion of the backside218such that it covers all, or at least a substantial portion, of the wafer alignment features (not shown inFIG. 2). The infrared inhibiting layer203can include a metal layer (e.g., an aluminum, copper, tungsten, nickel layer, etc.) to reduce electromagnetic interference (EMI), shield against infrared radiation and/or for other purposes. The infrared inhibiting layer203can also include quartz, mold compound, and/or other compounds and materials known in the art that obscure infrared imaging of wafer alignment features.

The wafer202is carried by a wafer holder204(e.g., a chuck, such as a vacuum chuck). To facilitate imaging and/or cutting, the wafer holder204can rotate in a θ direction and move laterally in an X direction. In other embodiments, the wafer holder204can also move up and down in a Y direction or back and forth in a Z direction.

The cutting system200further includes a low intensity X-ray emitter or source222operably mounted to a dicing machine214. The X-ray source222projects an X-ray beam226through the wafer202and onto a detector224a(e.g., a detector screen, such as a flat panel detector screen, a fluorescent screen, a Cesium iodide (CsL) screen, etc.). Although the detector224ais positioned proximate to a lower portion of the wafer holder204in the illustrated embodiment, in other embodiments, the cutting system200can include other detector screens in other positions beneath the wafer202. For example, the cutting system200can include a second detector screen224bon an opposite side of the wafer holder204, and/or a third detector screen224cwhich is incorporated into the wafer holder204. The cutting system200can be positioned within a shielded enclosure230to contain the X-ray radiation from the X-ray source222.

The detector224aprovides wafer image information to a signal processor or computer212. The detector224acan optionally be coupled to an image intensifier228that intensifies the wafer image before transmitting the image information to the computer212. As described in greater detail below, the wafer image information is processed by the computer212to determine the relative locations of alignment features on the wafer202. This information is then converted into instructions for controlling the dicing machine214during cutting of the semiconductor wafer202.

The dicing machine214can include a cutter device216for cutting the semiconductor wafer202and/or singulating the dies and/or other microelectronic devices on the wafer. In the illustrated embodiment, the cutter device216can include a saw having, for example, a diamond-tipped blade. In other embodiments, the cutter device216can include a water-jet cutting device, a laser cutting device, and/or other suitable wafer cutting devices known in the art.

FIG. 3is a flow diagram illustrating a method300of imaging and dicing a semiconductor wafer or other microelectronic device substrate in accordance with an embodiment of the invention. For purposes of illustration, the method300is described below with reference to the cutting system200ofFIG. 2. In block302, the wafer202is positioned on the wafer holder204between the X-ray source222and the detector224a. In block304, the X-ray source222emits the X-ray beam226through the wafer202and the infrared inhibiting layer203. The X-ray source222and/or the wafer holder204can be moved as necessary to at least generally align the X-ray beam226with an alignment feature (not shown inFIG. 2, but described in detail below with reference toFIG. 5) in the wafer202. In block306, the detector224adetects at least a portion of the X-rays passing through the wafer202. X-ray image information is then transmitted from the detector224ato the computer212. In block308, the computer212generates wafer alignment information based at least in part on the X-ray image information received from the detector224a. In block310, the computer212transmits the wafer alignment information (in, e.g., the form of cutting instructions) to the dicing machine214. In block312, the dicing machine214operates the cutter device216to singulate the dies on the wafer202. After block312, the routine ends.

FIG. 4is a schematic illustration of a semiconductor imaging and cutting system400(“cutting system400”) in accordance with another embodiment of the invention. Many features of the cutting system400are at least generally similar in structure and function to the corresponding features of the cutting system200described above with reference toFIGS. 2 and 3. For example, the cutting system400includes a movable wafer holder404that supports a semiconductor wafer402. In this particular embodiment, however, the cutting system400further includes an X-ray source422that is spaced apart from a dicing machine414.

To use the cutting system400, the wafer holder404starts in a first position431so that a detector screen424can obtain an X-ray image of the wafer402. In the illustrated embodiment, the detector screen424is mounted independently of the wafer holder404in alignment with the X-ray source422. In other embodiments, the detector screen424can be attached or otherwise incorporated into the wafer holder404as described above with reference toFIG. 2. After the wafer402has been suitably imaged in the first position431, the wafer holder404moves to a second position432proximate to the dicing machine414. The dicing machine414then cuts the wafer402based at least in part on the X-ray image information received from the detector screen424.

FIG. 5is a schematic diagram illustrating an X-ray image540of the semiconductor wafer202captured by the detector224ain accordance with an embodiment of the invention. In this embodiment, the semiconductor wafer202includes a plurality of fiducials or alignment features542(identified individually as a first alignment feature542a, a second alignment feature542b, and a third alignment feature542c). The alignment features542can include metals and/or other materials that are X-ray opaque, and thus can be identified by X-ray imaging.

To align the semiconductor wafer202for cutting, the X-ray image540is taken of a portion of the semiconductor wafer202that includes, for example, the second alignment feature542b. X-ray image data from the detector224ais then transmitted to the computer212(FIG. 2) so that any offset of the second alignment feature542b(shown by a first distance D1and a second distance D2) relative to a known datum544can be determined. In one embodiment, the known datum544can represent the position the second alignment feature542bwould be in if the semiconductor wafer202was properly aligned with the dicing machine214. Once the extent of any offset is known, the computer212can adjust the position of the dicing machine214as necessary to account for any misalignment of the semiconductor wafer202. In certain embodiments, it may be desirable to determine the position of two or more of the alignment features542in the foregoing manner to enhance the level of wafer alignment prior to dicing.

FIG. 6is a schematic diagram of a microelectronic device substrate602having a plurality of variable-pitch microelectronic devices650(identified individually as microelectronic devices650a-i) in accordance with another embodiment of the invention. The microelectronic devices650can include, for example, BUP devices held together in the substrate602by a fill material (e.g., mold compound)652. As is often the case with BUP device substrates, the spacing between the devices650can vary. As a result, cutter street widths (or “kerfs”) can vary from a relatively narrow street width661to a relatively wide street width662. Furthermore, one or more of the individual devices650may also be skewed relative to the other microelectronic devices, as illustrated by the microelectronic device650e. When singulating the microelectronic devices650from the substrate602, however, it is desirable to have the same amount of mold compound surrounding each of the individual devices650following the singulation process, as illustrated by the phantom lines extending around the microelectronic devices650e-650h.

Because some of the microelectronic devices650(e.g., the microelectronic device650e) may be skewed, a rotary saw blade may not be able to negotiate the cutting path between two or more of the devices. To address this problem, various embodiments of the invention can include a laser-based or high pressure water-based cutting device to cut around the individual microelectronic devices650and separate them from the substrate602. (If a water jet cutting device is used to cut around the individual microelectronic devices650, then each of the devices650may need to be individually supported in a manner known in the art.) Some cutting devices (e.g., saws) have to make two or more passes on a given street to achieve the desired street width and/or provide the desired package size. However, if a laser cutting device is used, the spot size of the laser could be dynamically adjusted to vary the thickness of the cutting path. Similarly, if a water jet cutting device is used, the jet stream diameter could be dynamically adjusted to provide the desired cutting path width.

In one embodiment, the X-ray imaging and cutting system200described above with reference toFIGS. 2-5can be used to singulate the individual microelectronic devices650from the substrate602and leave a relatively even amount of mold material or “edge distance” around each of the devices. In this embodiment, the cutting device216can include either a laser cutting device or a water jet cutting device that is able to cut around the periphery of each of the individual devices650. To singulate, for example, the microelectronic device650i, the cutting system200takes a real-time X-ray image of alignment features644a-dto determine the actual location of the device650ibefore instructing the dicing machine214to cut around the device. In another embodiment, the cutting system200can take an X-ray image that locates the edges of the device650i, and then instruct the dicing machine214to cut around the device. In a further embodiment, the cutting system200can use X-ray information relating to the location of one or more contacts654(e.g., bond-pads, solder balls, etc.) on the device650i.

While the use of an X-ray imaging system may be necessary in those cases where the semiconductor wafer or other microelectronic device substrate includes a metal layer, the method disclosed herein of using laser-based or water jet-based cutting devices to cut around variable pitch microelectronic devices is not limited to use with X-ray imaging systems. Indeed, the cutting techniques disclosed herein can be employed with many other types of alignment systems (e.g., visual, infrared, etc.) as long as the particular alignment system is able to locate the periphery of the individual microelectronic devices.

FIG. 7is a schematic block diagram of an apparatus700for singulating a semiconductor workpiece710in accordance with several embodiments of the invention. The apparatus700can include a support701that carries the semiconductor workpiece710during one or more operations, a detection device702that detects characteristics of the semiconductor workpiece710, a singulation device703that singulates dies from the semiconductor workpiece710, and a controller705that directs the operation of the foregoing components. The detection device702, the singulation device703, and/or the support701can translate relative to each other along x, y, and/or z axes, and can also rotate (e.g., about the z axis) to position any of the components relative to the other. Characteristics of these components are described generally below, and associated methods and techniques are then described in further detail with reference toFIGS. 8-15.

The detection device702can be configured and positioned to detect selected characteristics of the semiconductor workpiece710, including but not limited to information corresponding to the spacings between individual dies or groups of dies of the semiconductor workpiece710. Accordingly, the detection device702can include a vision system, for example, a still camera or a motion camera. In a particular embodiment, the detection device702includes a camera that detects radiation in the visible spectrum, and in other embodiments, the detection device702can detect radiation at other wavelengths, for example, infrared radiation or X-ray radiation. Representative embodiments of such detection devices were described above with reference toFIGS. 2-4. In any of these embodiments, the apparatus700can include an appropriate illumination system which may or may not be incorporated into the detection device702. For example, if the detection device702includes a visible wavelength camera, the apparatus700can include a visible wavelength illumination device. If the detection device702includes an X-ray camera, the apparatus700can include an appropriately positioned X-ray radiation source. In other embodiments, the detection device702can obtain information using other types of energy, for example, ultrasonic energy.

In any of the foregoing embodiments, the controller705controls the activation of the detection device702, and optionally, the relative motion between the detection device702and the support701. The detection device702and the support701may move relative to each other to allow the detection device702to obtain information over the entirety of the semiconductor workpiece710, and/or to allow the detection device702to provide detailed information for particular portions of the workpiece710. This function can also be provided by equipping the detection device702with a zoom feature. The support701can also move relative to the detection device702during the singulation process, which is described below.

Based at least in part on the information received from the detection device702, the controller705controls the operation of the singulation device703so as to singulate dies from the semiconductor workpiece710in a manner that accounts for spacing (and/or other) information specific to the particular semiconductor workpiece710presently at the apparatus700. Accordingly, the controller705can include a computer readable medium containing instructions (e.g., programmed instructions) that reduce or otherwise handle the data obtained from the detection device702, and direct the singulation device703accordingly. The singulation device703can include a cutter704positioned proximate to the workpiece support701for singulating dies from the semiconductor workpiece710. In particular embodiments, the cutter704can include a laser (e.g., a hot laser or another type of laser), a liquid or gaseous jet (e.g., an abrasive or non-abrasive water jet) and/or other devices. In many arrangements, the cutter704does not include a rotary blade, so as to enable the cutter704to readily and precisely adjust the cutting path to account for irregular spacings between dies of the semiconductor workpiece710. However, in at least some arrangements, the cutter704can include a rotary blade, for example, in situations in which the straight line cuts made by such blades may be oriented to account for the irregularities in die spacing. Further details of such arrangements will be described later with reference toFIGS. 11-15.

The apparatus700shown inFIG. 7illustrates a detection device702and a singulation device703that operate on the semiconductor workpiece710while it is at a single station. This arrangement can reduce the need for repositioning the workpiece710after the characteristics of the workpiece710have been detected and before the workpiece710is singulated in accordance with the detected characteristics. Such an arrangement can reduce the likelihood that the workpiece710will become misaligned between the detection operation and the singulation operation. However, in other embodiments, for example, when the alignment of the workpiece710can be precisely controlled or accounted for when the workpiece710is moved, the detection device702and the singulation device703can be located at different stations.

FIG. 8illustrates a representative process750for singulating dies from a semiconductor workpiece710in accordance with several embodiments of the invention. The process750can include detecting spacing information for irregularly spaced dies of an individual semiconductor workpiece (process portion752). Based at least in part on the spacing information, the process750can further include automatically controlling a process for singulating the dies of the individual semiconductor workpiece (process portion754). The dies can be singulated using one or more of several techniques to account for the irregular spacing of the dies. For purposes of illustration, several different techniques are shown together inFIG. 8, but it will be understood by one of ordinary skill in the relevant art that any one technique or any combination of techniques may be used for a given workpiece. These techniques include, but are not limited to, directing a cutter along a path that deviates from a straight line (process portion756). Process portion758includes making multiple passes along a single street positioned between rows or columns of dies. In process portion760, the width of a kerf made by the cutter can be changed. In other processes, individual dies can be separated from the workpiece (process portion762), and in still further processes, individual dies can be avoided, for example, if such dies are inoperable or defective (process portion764). Specific locations of the workpiece (e.g., vacancies of the workpiece where no die exists) can also be avoided with this technique.

In process portion770, it is determined whether or not to update the spacing information obtained in process portion752. For example, in some instances, making a cut between dies of the workpiece can cause the dies to shift, changing the relative spacing between such dies. In such cases, it may be desirable to update the spacing information, and so process portion752is repeated. If the information need not be updated, then in process portion772it is determined whether all the dies targeted for singulation have been singulated. If they have not, the process returns to process portion754. If they have, the process ends.

FIG. 9is a schematic plan view of the workpiece710prior to undergoing a singulation operation in accordance with an embodiment of the invention. The workpiece710can include a wafer or other collection of dies711that are to be singulated. For example, the workpiece710can include a collection of dies that have already been singulated from a wafer, then repositioned or repopulated on a substrate, and then encapsulated. The workpiece710is generally supported on a film frame730. The film frame730includes a frame732carrying a film731, which in turn is adhesively attached to the semiconductor workpiece710to support the workpiece710during the singulation operation. Typically, the same film frame730also supports the semiconductor workpiece710during the detection operation so that the semiconductor workpiece710retains the same orientation relative to the film frame730during both the detection operation and the singulation operation. In other embodiments, this need not be the case, and in still further embodiments, the workpiece710can be supported by devices other than the film frame730, or the workpiece710can be unsupported.

FIG. 10is a plan view of a portion of a representative workpiece710having spaced apart dies711. The illustrated workpiece710is covered with an encapsulant714, though in other cases, the workpiece710is not encapsulated. Each of the dies711includes die edges713which are shown in dashed lines inFIG. 10as result of the overlying encapsulant714. The dies711can also include conductive couplers715, for example, solder balls that project through the encapsulant714. In other embodiments, the conductive couplers715can include other structures (e.g., solder bumps, bumps made from other conductive materials, or wire bonds). In many cases, the conductive couplers715and/or the die edges713can be detected by the detector702(FIG. 7) and can provide enough information to enable the dies711to be accurately singulated, despite being irregularly spaced. For example, if the workpiece710is encapsulated, the detection device702can detect the location and orientation of individual dies711by detecting the conductive couplers715using visible light. Alternatively, the detection device702can detect the die edges713using X-ray radiation or another radiation to which the encapsulant714is transparent. If the workpiece710has no encapsulant714, then the detection device702can use visible light to detect the die edges713.

In some cases, the dies711may have other features which are specifically included to provide spacing information. For example, the dies711can include fiducials716that extend through the encapsulant714. For purposes of illustration, two fiducials716are shown for each die inFIG. 10, but it will be understood that in other embodiments, a single fiducial716or more than two fiducials716may be used to provide a basis for the detected spacing information. The fiducials716(or other features) may be used in addition to or in lieu of the conductive couplers715and/or the die edges713to provide spacing information.

In any of the foregoing embodiments, neighboring dies711and neighboring groups of dies711are separated by streets712. Each street has a street width W. In general, the streets W are of uniform width and spacing, or otherwise follow a uniform pattern. However, as will be discussed in greater detail below with reference toFIGS. 11-15, in some cases the spacings are not uniform. Aspects of the present invention are directed to accurately singulating the dies even when the spacings between dies711are not uniform. For purposes of illustration, the workpieces shown inFIGS. 11-15are shown without an encapsulant; however, it will be understood that some or all of the operations described in connection with these Figures may be performed on workpieces with or without an encapsulant.

FIG. 11illustrates a portion of a workpiece710having dies711that are irregularly spaced. At least some of the features of the workpiece710may be generally similar to corresponding features of the substrate602described above with reference toFIG. 6, though the workpiece710has additional features as well. For purposes of completeness, the relevant portions of the workpiece710(including some described above with reference toFIG. 6) are described with reference toFIG. 11. For purposes of illustration, several different types of spacing irregularities are shown together on the same workpiece710inFIG. 11. It will be understood that in many cases, the same workpiece710will not have all these irregularities, while in other cases, the workpieces710may have more and/or different irregularities than are shown inFIG. 11.

The dies711are arranged in rows722and columns717, including first, second, third, fourth and fifth columns717a,717b,717c,717d, and717erespectively. The first and second columns717a,717bare separated by a first street712a, and the second and third columns717b,717care separated by a second street712b. In the illustrated embodiment, the first street712ahas the “correct” (e.g., specified) street width W1, while the second street712bhas an incorrect (e.g., too large) street width W2. Accordingly, the pitch between the dies can vary from one part of the workpiece to another. When the first column717ais singulated from the second column717b, the cutter creates a first kerf718a. The offset O between the dies711in the first column717aand the edge of the first kerf718a, and the dies711of the second column717band the edge of the first kerf718aare the same and have the correct (e.g., specified) value. However, if the same kerf were to be made between the second and third columns717b,717c, the offset between the kerf and the dies711of one or both of the columns717b,717cwould be too large. Accordingly, the dies711of the second and third columns717b,717care specifically singulated to account for this irregularity. In a particular embodiment, two kerfs (shown as a second kerf718band a third kerf718c) are made in the same street (e.g., the second street712b). As a result, the offset O between the dies711of the second column717band the second kerf718bis the same as the offset O between dies711of the third column717cand the third kerf718c.

In another arrangement, a single kerf can be made between the second column717band the third column717c, but it can have a greater width than that of the first kerf718a. For example, if the kerf is made with a water jet or a laser beam, the diameter of the water jet or the laser beam can be increased to ablate or otherwise remove additional material from between the second and third columns717b,717c.FIG. 11illustrates a fourth (wider) kerf718d, identified by a circle that represents the diameter of a jet or beam. When traversed along the second street712b, the jet or beam ablates material to form a single wide kerf718d. Accordingly, the fourth kerf718dproduces the same desired offset between its edges and the edges of dies711in both the second column717band the third column717c. If the fourth kerf718dis made with a rotating blade, the blade can have a different width than that of the blade used to make the first kerf718a, so as to account for the increased spacing between the second and third columns717b,717c, relative to the spacing between the first and second columns717a,717b.

In other embodiments, the spacing irregularity can produce an angular offset. For example, as shown inFIG. 11, the third row717cincludes a single misaligned die711cthat is angularly offset relative to its neighbors. If the workpiece710were cut using standard methods, it is quite likely that the misaligned die711cwould be cut into and therefore not usable. However in a particular embodiment, the individual die711ccan be singulated from the workpiece710separately from the other dies711, as indicated by a fifth kerf718e. In this particular arrangement, the fifth kerf718eincludes a cut or series of cuts that completely encircle the misaligned die711cso it can be removed from the workpiece710. The remaining dies711on the workpiece710can then be singulated using a succession of vertical cuts followed by horizontal cuts, without cutting into or through the misaligned die711c.

In still another embodiment, an entire column or portion of a column of dies can be angularly offset from its neighbors. For example, the fourth column717dof dies711is rotated relative to the y axis by a non-zero, non-orthogonal angle θ so that a corresponding third street712cbetween the third column717cand the fourth column717dhas a variable width. Two representative widths are indicated as W3and W4. One approach to accounting for the variable street width is to provide two kerfs, e.g., a sixth kerf718faligned along the third column717cand a seventh kerf718galigned along the fourth column717d, in a manner generally similar to that described above with reference to the second and third kerfs718b,718c, but with the sixth and seventh kerfs718f,718gbeing nonparallel. Another approach is to change the width of a single kerf718h(represented by circles) as the kerf718hextends in the y direction. For example, if the kerf718his made with a laser beam or water jet, the diameter of the laser beam or water jet can be increased as the kerf718hprogresses in the y direction to account for the increasing width of the third street712c.

In yet another embodiment, a given row or column of dies may have an irregularity along the length of the row or column. For example, the fifth column717eof dies711can include an offset or “joggle” part-way along the column. Accordingly, an associated process can include cutting a kerf718ithat follows a path deviating from a single straight line along the length of the fifth column717e. In one aspect of this embodiment, the kerf718ican be formed from a series of straight line kerfs that account for the offset in the dies711. In another embodiment, the fifth column717ecan be singulated with a curved kerf718jto account for the offset in the dies711.

FIG. 12is a partially schematic, top plan view of a workpiece710having dies711that are irregularly spaced as a result of vacancies719positioned between at least some of the dies711. In some cases, it may be desirable to account for the vacancies719by cutting them out (as indicated by first kerfs1218a) and then proceeding with singulating the remaining dies711with a series of cuts parallel to the y axis, followed by a series of cuts parallel to the x axis. In other embodiments, it may be desirable to separate individual dies711from the workpiece710, without singulating the vacancies719. Such an arrangement is illustrated by second kerfs1218bpositioned around individual dies711. In other still further embodiments, the two foregoing techniques may both be used on a single workpiece, for example a workpiece that has a preponderance of vacancies719in one area and a preponderance of dies711in another area.

FIG. 13illustrates a technique used to singulate first dies711a(e.g., non-defective dies or “known good dies”), that are irregularly spaced from each other by virtue of second dies711b(e.g., defective, inoperative, or “bad” dies). Depending on the relative number of first dies711aand second dies711b, individual first dies711amay be singulated from the workpiece710and the rest of the workpiece710discarded, or individual second dies711bmay be singulated from the workpiece710, and the remaining first dies711acan be singulated using a series of cuts parallel to the y axis followed by a series of cuts parallel to the x axis. The spacing information on which the singulation process is conducted can in this case include the locations of the first dies711aand/or the second dies711b.

FIG. 14Aillustrates a portion of a workpiece710having dies711that are initially uniformly spaced from each other in both the x and y directions. Accordingly, the columns of dies711are separated by first streets712agenerally parallel to the y axis and having a width W1, and the rows of dies711are separated by series of second streets712bgenerally parallel to the x axis and having a width W2. The workpiece710can include build-up packages (BUPs) or other arrangements of singulated dies711that are then encapsulated. Because the workpiece710is carried by a film721that can be flexible, resilient, and/or stretchable, the relative positions of neighboring dies711may change during the course of a singulation process. For example, as shown inFIG. 14Ba first kerf1418ahas been cut along the first street712aand has caused the two neighboring columns of dies711to move apart from each other in the x direction, as indicated by arrow S1. After a second kerf1418bhas been made along one of the second streets712b, the dies711can again move apart, this time in the y direction, as indicated by arrow S2. As a result, the relative spacing between neighboring dies711may change during the dicing process. If this change is not accounted for, it can result in subsequent kerfs being misaligned or mispositioned. To account for this shift, the detection device702(FIG. 7) can be operated at one or more times during the course of a singulation operation. For example, the detection device702can be operated on a continuous basis, or after each street is cut. In a particular embodiment, the information obtained via the detection device702can be used real time or nearly real time to update the spacing information for each die711before it is cut and/or while it is being cut. In this way, misalignments that may result from individual dies711or groups of dies711being separated from the workpiece may be accounted for and corrected as the singulation process continues.

FIG. 15schematically illustrates still another instance in which dies711may be irregularly spaced from each other. In one aspect of this arrangement, the workpiece710has a crack721that causes a first column717aof dies711to be misaligned angularly relative to a second column717b. As is also shown inFIG. 15, one of the dies711astraddles the crack721and is itself cracked. One or more of any of the foregoing techniques may be used to account for this irregularity. For example, the cracked die711amay be removed from the rest of the workpiece710as single die, and the rest of the dies711then singulated. The rest of the dies711may be singulated by providing a first kerf1518athat is parallel to the first column717a, and a second kerf1518bthat is parallel to the second column717b. Alternatively, a single kerf having a varying kerf width can be made between the two rows to account for the angular offset between the two rows.

Features of several of the foregoing embodiments can improve the process in accordance with which semiconductor workpieces are singulated. For example, aspects of the foregoing processes allow greater utilization of workpieces having irregularly spaced dies, which otherwise may become damaged and/or may be discarded during the course of processing. This arrangement can improve the efficiency with which the foregoing processes are conducted by improving the yield of dies produced by the processes.

Another feature of at least some of the foregoing embodiments is that they can be used to produce dies having more uniform dimensions because each cut can be made based on information specific to the region that is being cut, rather than being based on information generic to semiconductor workpieces of a particular type. The more uniform dies are more likely to meet quality control specifications, and again result in a greater yield for a given workpiece. This arrangement can also allow the dies to be made smaller because the manufacturer need not account for likely misalignments by oversizing the offset O around the edges of packaged dies.

In many cases, the cutter used to make the foregoing kerfs includes a laser, water jet, or other device that can be programmed to follow any path, including straight line or curved paths. In other embodiments, at least some of the techniques described above can be performed by blades. For example, making multiple kerfs along a single street can be performed with a blade, when the cuts are straight. Making multiple cuts having different kerf widths can be made by changing the thickness of the blade from one cut to another. Making cuts at a non-zero angle θ relative to the x or y axis can be made by rotating the cutter or the workpiece by the proper amount.

Yet a further feature of at least some of the foregoing embodiments is that the workpiece can be singulated without rotating either the cutter or the workpiece. For example, when the cutter includes a water jet or a laser beam, the water jet or laser beam can be moved over the surface of the workpiece to singulate dies having any of a wide variety of orientations by simply positioning the jet or beam, without rotating the workpiece or the cutter. This is unlike existing arrangements in which the workpiece has one orientation while singulating cuts are made between columns of dies, and is then rotated by 90° for cuts made between neighboring rows. By eliminating the need to rotate the cutter or the workpiece, the overall apparatus can be made simpler, as it requires fewer moving parts.

From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the invention. For example, the workpieces and dies may have configurations and/or irregularities other than those shown in the Figures. The workpieces may be supported by devices other than film frames, and may be encapsulated, partially encapsulated, or not encapsulated at all. Certain aspects of the invention described in the context of particular embodiments may be combined or eliminated in other embodiments. For example, any given workpiece may have any one of the irregularities described above, or any combination of such irregularities. Further, while advantages of associated with certain embodiments of the invention have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the invention. Accordingly, the invention is not limited except as by the appended claims.