Patent Publication Number: US-11383514-B2

Title: Die for a printhead

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. § 371, this application is a United States National Stage Application of PCT Patent Application Serial No. PCT/US2019/016791, filed on Feb. 6, 2019, the contents of which are incorporated by reference as if set forth in their entirety herein. 
     BACKGROUND 
     A printing system, as one example of a fluid ejection system, may include a printhead, an ink supply which supplies liquid ink to the printhead, and an electronic controller which controls the printhead. The printhead ejects drops of print fluid through a plurality of nozzles or orifices onto a print medium. Suitable print fluids may include inks and agents for two-dimensional or three-dimensional printing. The printheads may include thermal or piezo printheads that are fabricated on integrated circuit wafers or dies. Drive electronics and control features are first fabricated, then the columns of heater resistors are added and finally the structural layers, for example, formed from photo-imageable epoxy, are added, and processed to form microfluidic ejectors, or drop generators. In some examples, the microfluidic ejectors are arranged in at least one column or array such that properly sequenced ejection of ink from the orifices causes characters or other images to be printed upon the print medium as the printhead and the print medium are moved relative to each other. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Certain examples are described in the following detailed description and in reference to the drawings, in which: 
         FIG. 1A  is a view of an example of a die used for a printhead; 
         FIG. 1B  is an enlarged view of a portion of the die; 
         FIG. 2A  is a view of an example of a die used for a printhead; 
         FIG. 2B  is an enlarged view of a portion of the die; 
         FIG. 3A  is a drawing of an example of a printhead formed from a black die that is mounted in a potting compound; 
         FIG. 3B  is a drawing of an example of a printhead formed using color dies, which may be used for three colors of ink; 
         FIG. 3C  shows cross-sectional views of the printheads including mounted dies through solid sections and through sections having fluid feed holes; 
         FIG. 4  is a printer cartridge that incorporates the color dies described with respect to  FIG. 3B ; 
         FIG. 5  is a drawing of a portion of an example of a color die showing layers used to form the color die; 
         FIGS. 6A and 6B  are drawings of the color die showing a close-up view of an example of a polysilicon trace connecting logic circuitry of the color die to FETs on the power side of the color die; 
         FIGS. 7A and 7B  are drawings of the color die showing close-up views of the traces between the fluid feed holes; 
         FIGS. 8A and 8B  are drawings of an electron micrograph of the section between two fluid feed holes; 
         FIG. 9  is a process flow diagram of an example of a method for forming a die; 
         FIG. 10  is a process flow diagram of an example of a method for forming components on a die using a plurality of layers; 
         FIG. 11  is a process flow diagram of an example of a method for forming circuitry on a die with traces coupling circuitry on each side of the die; 
         FIG. 12  is a schematic diagram of an example of a set of four primitives, termed a quad primitive; 
         FIG. 13  is a drawing of an example of a layout of the digital circuitry, showing the simplification that can be achieved by a single set of nozzle circuitry; 
         FIG. 14  is a drawing of an example of a black die, showing the impact of cross-slot routing on energy and power routing; 
         FIG. 15  is a drawing of an example of a circuit floorplan for a color die; 
         FIG. 16  is another drawing of an example of a color die; 
         FIG. 17  is a drawing of an example of a color die showing a repeating structure; 
         FIG. 18  is a drawing of an example of a black die showing an overall structure for the die; 
         FIG. 19  is a drawing of an example of a black die showing a repeating structure; 
         FIG. 20  is a drawing of an example of a black die showing a system for crack detection; 
         FIG. 21  is an expanded view of an example of a fluid feed hole from a black die showing the crack detection trace routed around the fluid feed hole; and 
         FIG. 22  is a process flow diagram of an example of a method for forming a crack detection trace. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EXAMPLES 
     Printheads are formed using die having fluidic actuators, such as microfluidic ejectors and microfluidic pumps. The fluidic actuators can be based on thermal or piezoelectric technologies, and are formed using long, narrow pieces of silicon, termed dies herein. As used herein, a fluidic actuator is a device on a die that forces a fluid from a chamber and includes the chamber and associated structures. In examples described herein, one type of fluidic actuator, a microfluidic ejector, is used as a drop ejector, or nozzle in a die used for printing and other applications. For example, printheads can be used as fluid ejection devices in two-dimensional and three-dimensional printing applications and other high precision fluid dispensing systems including pharmaceutical, laboratory, medical, life science and forensic applications. 
     The cost of printheads is often determined by the amount of silicon used in the dies, as the cost of the die and the fabrication process increase with the total amount of silicon used in a die. Accordingly, lower cost printheads may be formed by moving functionality off the die to other integrated circuits, allowing for smaller dies. 
     Many current dies have an ink feed slot in the middle of the die to bring ink to the fluidic actuators. The ink feed slot generally provides a barrier to carrying signals from one side of an die to another side of a die, which often requires duplicating circuitry on each side of the die, further increasing the size of the die. In this arrangement, fluidic actuators on one side of the slot, which may be termed left or west, have independent addressing and power bus circuits from fluidic actuators on the opposite side of the ink feed slot, which may be termed right or east. 
     Examples described herein provide a new approach to providing fluid to the fluidic actuators of the drop ejectors. In this approach, the ink feed slot is replaced with an array of fluid feed holes disposed along the die, proximate to the fluidic actuators. The array of fluid feed holes disposed along the die may be termed a feed zone, herein. As a result, signals can be routed through the feed zone, between the fluid feed holes, for example, from the logic circuitry located on one side of the fluid feed holes to printing power circuits, such as field-effect transistors (FETs), located on the opposite side of the fluid feed holes. This is termed cross-slot routing herein. The circuitry to route the signals includes traces that are provided in layers between adjacent ink or fluid feed holes. 
     As used herein, a first side of the die and a second side of the die denote the long edges of the die that are in alignment with the fluid feed holes, which are placed near or at the center of the die. Further, as used herein, the fluidic actuators are located on a front face of the die, and the ink or fluid is fed to the fluid feed holes from a slot on the back face of the die. Accordingly, the width of the die is measured from the edge of the first side of the die to the edge of the second side of the die. Similarly, the thickness of the die is measured from the front face of the die to the back face of the die. 
     The cross-slot routing allows for the elimination of duplicate circuitry on the die, which can decrease the width of the die, for example, by 150 micrometers (μm) or more. In some examples, this may provide a die with a width of about 450 μm or about 360 μm, or less. In some examples, the elimination of duplicate circuitry by the cross-slot routing may be used to increase the size of the circuitry on the die, for example, to enhance performance in higher value applications. In these examples, the power FETs, the circuit traces, power traces, and the like, may be increased in size. This may provide dies that are capable of higher droplet weights. Accordingly, in some examples, the dies may be less than about 500 μm, or less than about 750 μm, or less than about 1000 μm. 
     The thickness of the die from the front face to the back face is also decreased by the efficiencies gained from the use of the fluid feed holes. Previous dies that use ink feed slots may be greater than about 675 μm, while dies using the fluid feed holes may be less than about 400 μm in thickness. The length of the dies may be about 10 millimeters (mm), about 20 mm, or about 20 mm, depending on the number of fluidic actuators used for the design. The length of the dies includes space at each end of the die for circuitry, accordingly the fluidic actuators occupy a portion of the length of the die. For example, for a black die of about 20 mm in length, the fluidic actuators may occupy about 13 mm, which is the swath length. A swath length is the width of the band of printing, or fluid ejection, formed as a printhead is moved across a print medium. 
     Further, it allows the co-location of similar devices for increased efficiency and layout. The cross-slot routing also optimizes power delivery by allowing left and right columns, or fluidic actuator zones, of multiple fluidic actuators to share power and ground routing circuits. A narrower die may be more fragile than a wider die. Accordingly, the die may be mounted in a polymeric potting compound that has a slot from a reverse side to allow ink to flow to the fluid feed holes. In some examples, the potting compound is an epoxy, although it may be an acrylic, a polycarbonate, a polyphenylene sulfide, and the like. 
     The cross-slot routing also allows for the optimization of circuit layout. For example, the high-voltage and low-voltage domains may be isolated on opposite sides of the fluid feed holes allowing for improvements in reliability and form factor for the dies. The separation of the high-voltage and low-voltage domains may decrease or eliminate parasitic voltages, crosstalk, and other issues that affect the reliability of the die. Further, repeat units that include the logic circuits, fluidic actuators, fluid feed holes, and power circuitry for a set of nozzles may be designed to provide the desired pitch in a very narrow form factor. 
     The fluid feed holes placed in a line parallel to a longitudinal axis of the die may make the die more susceptible to damage from mechanical stresses. For example, the fluid feed holes may act as a series of perforations that increase the chance that a crack will develop through the fluid feed holes along the longitudinal axis of the die. To detect cracks during manufacturing, for example, before mounting in the potting compound, a crack detection circuit may be placed around the fluid feed holes in a serpentine manner. The crack detection circuit may be a resistor that breaks if a crack forms, causing the resistance to go from a first resistance, such as hundreds of kiloohms, to an open circuit. This may lower production costs by identifying broken dies prior to completion of the manufacturing process. 
     The die used for a printhead, as described herein, uses resistors to heat fluids in the fluidic actuator causing droplet ejection by thermal expansion. However, the dies are not limited to thermally driven fluidic actuators and may use piezoelectric fluidic actuators that are fed from fluid feed holes. As described herein, the fluidic actuator includes the driver and associated structures, such as the fluid chamber and a nozzle for a microfluidic ejector. 
     Further, the die may be used in to form fluidic actuators for other applications besides a printhead, such as microfluidic pumps, used in analytical instrumentation. In this example, the fluidic actuators may be fed test solutions, or other fluids, rather than ink, from fluid feed holes. Accordingly, in various examples, the fluid feed holes and inks can be used to provide fluidic materials that may be ejected or pumped by droplet ejection from thermal expansion or piezoelectric activation. 
       FIG. 1A  is a view of an example of a die  100  used for a printhead. The die  100  includes all circuitry to operate fluidic actuators  102  on both sides of a fluid feed slot  104 . Accordingly, all electrical connections are brought out on pads  106  located at each end of the die  100 . As a result, the width  108  of the die is about 1500 μm.  FIG. 1B  is an enlarged view of a portion of the die  100 . As can be seen in this enlarged view, the fluid feed slot  104  occupies a substantial amount of space in the center of the die  100 , increasing the width  108  of the die  100 . 
       FIG. 2A  is a view of an example of a die  200  used for a printhead.  FIG. 2B  is an enlarged cross-section of a portion of the die  200 . In comparison with the die  100  of  FIG. 1A , the design of the die  200  allows a portion of the activation circuitry to a secondary integrated circuit, or application specific integrated circuit (ASIC)  202 . 
     In contrast to the fluid feed slot  104  of the die  100 , the die  200  uses fluid feed holes  204  to provide fluid, such as inks, to the fluidic actuators  206  for ejection by thermal resistors  208 . As described herein, the cross-slot routing allows circuitry to be routed along silicon bridges  210  between the fluid feed holes  204  and across the longitudinal axis  212  of the die  200 . This allows the width  214  of the die  200  to be substantially decreased over previous designs that did not have the fluid feed holes  204 . 
     The decrease in the width  214  of the die  200  decreases costs substantially, for example, by decreasing the amount of silicon in the substrate of the die  200 . Further, the distribution of circuitry and functions between the die and the ASIC  202  allows further decreases in the width  214 . As described herein, the die  200  also includes sensor circuitry for operations and diagnostics. In some examples, the die  200  includes thermal sensors  216 , for example, placed along the longitudinal axis of the die near one end of the die, at the middle of the die, and near the opposite end of the die. 
       FIGS. 3A to 3C  are drawings of the formation of a printhead  300  by the mounting of dies  302  or  304  in a polymeric mount  310  formed from a potting compound. The dies  302  and  304  are too narrow to attach to pen bodies or fluidically route fluid from reservoirs. Accordingly, the dies  302  and  304  are mounted in a polymeric mount  310  formed from a potting compound, such as an epoxy material, among others. The polymeric mount  310  of the printhead  300  has slots  314  which provide an open region to allow fluid to flow from the reservoir to the fluid feed holes  204  in the dies  302  and  304 . 
       FIG. 3A  is a drawing of an example of a printhead  300  formed from a black die  302  that is mounted in a potting compound. In the black die  302  of  FIG. 3A , two lines of nozzles  320  are visible, wherein each group of two alternating nozzles  320  are fed from one of the fluid feed holes  204  along the black die  302 . Each of the nozzles  320  is an opening to a fluid chamber above a thermal resistor. Actuation of the thermal resistor forces fluid out through the nozzles  320 , thus, each combination of thermal resistor fluid chamber and nozzle represents a fluidic actuator, specifically, a microfluidic ejector. It may be noted that the fluid feed holes  204  are not isolated from each other, allowing fluid to flow from fluid feed holes  204  to nearby fluid feed holes  204 , providing a higher flow rate for the active nozzles. 
       FIG. 3B  is a drawing of an example of a printhead  300  formed using color dies  304 , which may be used for three colors of ink. For example, one color die  304  may be used for a cyan ink, another color die  304  may be used for a magenta ink, and a last color die  304  may be used for a yellow ink. Each of the inks will be fed into the associated slot  314  of the color dies  304  from a separate color ink reservoir. Although this drawing shows only three of the color dies  304  in the mount, a fourth die, such as a black die  302 , may be included to form a CMYK die. Similarly, other die configurations may be used. 
       FIG. 3C  shows cross-sectional views of the printheads  300  including mounted dies  302  or  304  through solid sections  322  and through sections  324  having fluid feed holes  318 . This shows that the fluid feed holes  318  are coupled to the slots  314  to allow ink to flow from the slots  314  through the mounted dies  302  and  304 . As described herein, the structures in  FIGS. 3A to 3C  are not limited to inks but may be used to provide other fluids to fluidic actuators in dies. 
       FIG. 4  is an example of a printer cartridge  400  that incorporates the color dies  304  described with respect to  FIG. 3B . The mounted color dies  304  form a pad  402 . As described herein the pad  402  includes the multicolor silicon dies, and the polymeric mounting compound, such as an epoxy potting compound. The housing  404  holds the ink reservoir used to feed the mounted color dies  304  in the pad  402 . A flex connection  406 , such as a flexible circuit, holds the printer contacts, or pads,  408  used to interface with the printer cartridge  400 . The different circuit design, as described herein, allows for fewer pads  408  to be used in the printer cartridge  400  versus previous printer cartridges. 
       FIG. 5  is a drawing of a portion  500  of a color die  304  showing layers  502 ,  504 , and  506  used to form the color die  304 . Like numbered items are described as with respect to  FIG. 2 . The materials used to make the layers include polysilicon, aluminum-copper (AlCu), Tantalum (Ta), Gold (Au), implant doping (Nwell, Pwell, and etc.). In the drawing, layer  502  shows the routing of layers, or polysilicon traces,  508  from logic circuitry  510  of the color die  304  between the fluid feed holes  204  to field-effect transistors (FETs) forming power circuitry  512  of the color die  304  (partially shown in the drawing). This allows the energization of the FETs to drive the thermal inkjet resistors (TIJ)  514  that power the fluidic actuators to force liquid out of the chamber above the thermal resistor. Additional layers  516  and  518 , may include metal 1  504  and metal 2  506 , are used as power ground returns for the current to the TIJ resistors  514 . It may also be noted that the color die  304  shown in  FIG. 5  is the TIJ resistors  514  placed only on one side of the fluid feed holes  204 , which alternates between high weight droplets (HWD) and low weight droplets (LWD) to provide different drop sizes for increasing drop accuracy. To control the drop weights, the TIJ resistors  514 , and associated structures, for the HWD are larger than the TIJ resistors  514  used for the LWD, as discussed further with respect to  FIG. 15 . As described herein, the associated structures in the fluidic actuator include a fluid chamber and nozzle for a microfluidic ejector. In a black die  302 , the TIJ resistors  514 , and associated structures, are the same size, and alternate between each side of the fluid feed holes  204 . 
       FIGS. 6A and 6B  are drawings of the color die  304  showing a close-up view of a trace  602  connecting logic circuitry  510  of the color die  304  to FETs  604  in the power circuitry  512  of the color die  304 . Like numbered items are as described with respect  FIGS. 2, 3, and 5 . The conductors are stacked to allow multiple connections between the left and right sides of the array  608  of the fluid feed holes  204 . In examples, the fabrication is performed using complementary metal-oxide semiconductor technology, wherein conductive layers, such as the polysilicon layer, the first metal layer, the second metal layer, and the like, are separated by a dielectric that allows them to be stacked without electrical interference, such as crosstalk. This is described further with respect to  FIGS. 7 and 8 . 
       FIGS. 7A and 7B  are drawings of the color die  304  showing close-up views of the traces between the fluid feed holes  204 . Like numbered items are as described with respect to  FIGS. 2 and 5 .  FIG. 7A  is a view of two fluid feed holes  204 , while  FIG. 7B  is an expanded view of the section shown by the line  702 . In this view of the different layers between the fluid feed holes  204  can be seen including a tantalum layer  704 . Further the layers described with respect to  FIG. 5  are shown, including the polysilicon layer  508 , the metal 1 layer  516 , and the metal 2 layer  518 . In some examples, as described with respect to  FIGS. 20 and 21 , 1 of the polysilicon traces  508  may be used to provide an embedded crack detector for the color die  304 . The layers  508 ,  516 , and  518  are separated by a dielectric to provide insulation, as discussed further with respect to  FIGS. 8A and 8B . It should be noted that, although  FIGS. 6A, 6B, 7A, and 7B  show the color die  304 , the same design features are used on the black die  302 . 
       FIGS. 8A and 8B  are drawings of an electron micrograph of the section between two fluid feed holes  204  of the color die  304 . Like numbered items are as described with respect to  FIGS. 2, 3, and 5 . The top layer in this structure is a SU-8 primer  802 , which is used to form the final covering over the circuitry, including the nozzles  320  for the color die  304 . However, the same layers may be present between the fluid feed holes  204  in a black die  302 . 
       FIG. 8B  is a cross-section  804  between two fluid feed holes  204  of the color die  304 . As shown in  FIG. 8B , fluid feed holes  204  are etched through a silicon layer  806 , which functions as a substrate, leaving a bridge that connects the two sides of the color die  304 . Several layers are deposited on top of the silicon layer  806 . A thick field oxide, or FOX layer,  808  is deposited on top of the silicon layer  806  to insulate further layers from the silicon layer  806 . A stringer  810 , formed from the same material as metal 1  516  is deposited at each side of the FOX layer  808 . 
     On top of the FOX layer  808 , the polysilicon layers  508  are deposited, for example, to couple logic circuitry on one side of the die  200  to power transistors on an opposite side of the die  200 . Other uses for the polysilicon layers  508  may include crack detection traces deposited between fluid feed holes  204 , as described with respect to  FIGS. 20 and 21 . Polysilicon, or polycrystalline silicon, is a high purity, polycrystalline form of silicon. In examples, it is deposited using low-pressure, chemical-vapor deposition of silane (SiH 4 ). The polysilicon layers  508  may be implanted, or doped, to form n-well and p-well materials. A first dielectric layer  812  is deposited over the polysilicon layers  508  as an insulation barrier. In an example, the first dielectric layer  812  is formed from borophosphosilicate glass/tetraethyl ortho silicate (BPSG/TEOS), although other materials may be used. 
     A layer of metal 1  516  may then be deposited over the first dielectric layer  812 . In various examples, metal 1  516  is formed from titanium nitride (TiN), aluminum copper alloy (AlCu), or titanium nitride/titanium (TiN/Ti), among other materials, such as gold. A second dielectric layer  814  is deposited over the metal 1  516  layer to provide an insulation barrier. In an example, the second dielectric layer  814  is a TEOS/TEOS layer formed by a high-density plasma chemical vapor deposition (HDP-TEOS/TEOS). 
     A layer of metal 2  518  may then be deposited over the second dielectric layer  814 . In various examples, metal 2  518  is formed from a tungsten silicon nitride alloy (WSiN), aluminum copper alloy (AlCu), or titanium nitride/titanium (TiN/Ti), among other materials, such as gold. A passivation layer  816  is then deposited over the top of metal 2  518  to provide an insulation barrier. In an example, the passivation layer  816  is a layer of silicon carbide/silicon nitride (SiC/SiN). 
     A tantalum (Ta) layer  818  is deposited over the top of the passivation layer  816  and the second dielectric layer  814 . The tantalum layer  818  protects the components of the trace from degradation caused by potential exposure to fluids, such as inks. A layer of SU-8  820  is then deposited over the die  200 , and is etched to form the nozzles  320  and flow channels  822  over the die  200 . SU-8 is an epoxy based negative photoresist, in which parts exposed to a UV light are cross-linked, becoming resistant to solvent and plasma etching. Other materials may be used in addition to, or in place of, the SU-8. The flow channels  822  are configured to feed fluid from the fluid feed holes, or fluid feed holes  204 , to the nozzles  320  or fluidic actuators. In each of the flow channels  822 , a button  824  or protrusion is formed in the SU-8  820  to block particulates in the fluid from entering the ejection chambers under the nozzles  320 . One button  826  is shown in the cross section of  FIG. 8B . 
     The stacking of conductors over the silicon layer  806  between the fluid feed holes  204  increases the connections between left and right sides of the array of fluid feed holes  204 . As described herein, the polysilicon layer  508 , metal 1 layer  516 , metal 2 layer  518 , and the like, are all unique conductive layers separated by dielectric, or insulating layers,  812 ,  814 , and  816 , that allow them to be stacked. Depending on the design implementation, such as the color die  304  shown in  FIGS. 8A and 8B , a crack detector, and the like, the various layers are used in different combinations to form the VPP, PGND, and digital control connections to drive the FETs and TIJ Resistors. 
       FIG. 9  is a process flow diagram of an example of a method  900  for forming a die. The method  900  may be used to make the color die  304  used as a die for color printers, as well as the black die  302  used for black inks, and other types of dies that include fluidic actuators. The method  900  begins at block  902  with the etching of the fluid feed holes through a silicon substrate, along a line parallel to a longitudinal axis of the substrate. In some examples, layers are deposited first, then the etching of the fluid feed holes is performed after the layers are formed. 
     In an example, a layer of photoresist polymer, such as SU-8, is formed over a portion of the die to protect areas that are not to be etched. The photoresist may be a negative photoresist, which is cross-linked by light, or a positive photoresist, which is made more soluble by light exposure. In an example, a mask is exposed to a UV light source to fix portions of the protective layer, and portions not exposed to UV light are washed away. In this example, the mask prevents cross-linking of the portions of the protective layer covering the area of the fluid feed holes. 
     At block  904 , a plurality of layers is formed on the substrate to form the die. The layers may include the polysilicon, the dielectric over the polysilicon, metal 1, the dielectric over metal 1, metal 2, the passivation layer over metal 2, and the tantalum layer over the top. As described above, the SU-8 may then be layered over the top of the die, and patterned to implement the flow channels and nozzles. The formation of the layers may be formed by chemical vapor deposition to deposit the layers followed by etching to remove portions that are not needed. The fabrication techniques may be the standard fabrication used in forming complementary metal-oxide-semiconductors (CMOS). The layers that can be formed in block  904  and the location of the components is discussed further with respect to  FIG. 10 . 
       FIG. 10  is a process flow diagram of an example of a method  1000  for forming components on a die using a plurality of layers. In an example, the method  1000  shows details of the layers that may be formed in block  904  of  FIG. 9 . The method begins at block  1002  with forming logic power circuits on the die. At block  1004 , address line circuits, including address lines for primitive groups, as described with respect to  FIGS. 12 and 13 , are formed on the die. At block  1006 , address logic circuits, including decode circuits, as described with respect to  FIGS. 12 and 13 , are formed on the die. At block  1008 , memory circuits are formed on the die. At block  1010  power circuits are formed on the die. At block  1012 , power lines are formed in the die. The blocks shown in  FIG. 10  are not to be considered sequential. As would be to one of skill in the art, the various lines and circuits are formed across the die at the same time as the various layers are formed. Further, the processes described with respect to  FIG. 10  may be used to form components on either a color die or a black-and-white die. 
     As described herein, the use of the fluid feed holes allow circuitry to cross the die in traces formed over silicon between the fluid feed holes. Accordingly, circuits may be shared between each side of the die, decreasing the total amount of circuits needed on the die. 
       FIG. 11  is a process flow diagram of an example of a method  1100  for forming circuitry on a die with traces coupling circuitry on each side of the die. As used herein, a first side of the die and a second side of the die denote the long edges of the die in alignment with the fluid feed holes placed near or at the center of the die. The method  1100  begins at block  1102  with the formation of logic power lines along a first side of the die. The logic power lines are low-voltage lines used to supply power to the logic circuits, for example, at a voltage of about 2 to about 7 V, and associated ground lines for the logic circuits. At block  1104 , address logic circuits are formed along the first side of the die. At block  1106 , address lines are formed along the first side of the die. At block  1108 , memory circuits are formed along the first side of the die. 
     At block  1110 , ejector power circuits are formed along a second side of the die. In some examples, the ejector power circuits include field-effect transistors (FETs) and thermal inkjet (TIJ) resistors used to heat a fluid to force the fluid to be ejected from a nozzle. At block  1112 , power circuit power lines are formed along the second side of the die. The power circuit power lines are high-voltage power lines (Vpp) and return lines (Pgnd) used to supply power to the ejector power circuits, for example, at a voltage of about 25 to about 35 V. 
     At block  1114 , traces coupling the logic circuits to power circuits, between the fluid feed holes, are formed. As described herein, the traces may carry signals from logic circuits located on the first side of the die to power circuits on the second side of the die. Further, traces may be included to perform crack detection between the fluid feed holes, as described herein. 
     In dies in which the nozzle circuitry is separated by a center fluid feed slot, logic circuitry, address lines, and the like are repeated on each side of the center fluid feed slot. In contrast, in dies formed using the methods of  FIGS. 9 to 11  the ability to route circuitry from one side of the die to the other side of the die eliminates the need to duplicate some circuitry on both sides of the die. This is clarified by looking at physical structure circuitry on the die. In some examples described herein, the nozzles are grouped into individually addressed sets, termed primitives, as discussed further with respect to  FIG. 12 . 
       FIG. 12  is a schematic diagram  1200  of an example of a set of four primitives, termed a quad primitive. To facilitate the explanation of the primitives and the shared addressing, primitives to the right of the schematic diagram  1200  are labeled east, e.g., northeast (NE) and southeast (SE). Primitives to the left of the schematic diagram  1200  are labeled west, e.g., northwest (NW) and southwest (SW). In this example, each nozzle  1202  is fired by an FET that is labeled Fx, where x is from 1 to 32. The schematic diagram  1200  also shows the TIJ resistors, labeled Rx, where x is also 1 to 32, which correspond to each nozzle  1202 . Although the nozzles are shown on each side of the fluid feed in the schematic diagram  1200 , this is a virtual arrangement. In a color die  304  formed using the current techniques, the nozzles  1202  would be on the same side of the fluid feed. 
     In each primitive, NE, NW, SE, and SW, eight addresses, labeled 0 to 7, are used to select a nozzle for firing. In other examples, there are 16 addresses per primitive, and 64 nozzles per quad primitive. The addresses are shared, wherein an address selects a nozzle in each group. In this example, if address four is provided, then nozzles  1204 , activated by FETs F9, F10, F25, and F26 are selected for firing. Which, if any, of these nozzles  1204  fire depends on separate primitive selections, which are unique to each primitive. A fire signal is also conveyed to each primitive. A nozzle within a primitive is fired when address data conveyed to that primitive selects a nozzle for firing, data loaded into that primitive indicates firing should occur for that primitive, and a firing signal is sent. 
     In some examples, a packet of nozzle data, referred to herein as a fire pulse group (FPG), includes start bits used to identify the start of an FPG, address bits used to select a nozzle  1202  in each primitive data, fire data for each primitive, data used to configure operational settings, and FPG stop bits used to identify the end of an FPG. Once an FPG has been loaded, a fire signal is sent to all primitive groups which will fire all addressed nozzles. For example, to fire all the nozzles on the printhead, an FPG is sent for each address value, along with an activation of all the primitives in the printhead. Thus, eight FPG&#39;s will be issued each associated with a unique address 0-7. The addressing shown in the schematic diagram  1200  may be modified to address concerns of fluidic crosstalk, image quality, and power delivery constraints. The FPG may also be used to write to a non-volatile memory element associated with each nozzle, for example, instead of firing the nozzle. 
     A central fluid feed region  1206  may include fluid feed holes or a fluid feed slot. However, if the central ink feed region  1206  is a fluid feed slot, the logic circuitry and addressing lines, such as the three address lines in this example that are used provide addresses 0-7 for selecting a nozzle to fire each primitive, are duplicated, as traces cannot cross the central ink feed region  1206 . If, however, the central fluid feed region  1206  is made up of fluid feed holes, each side can share circuitry, simplifying the logic. 
     Although the nozzles  1202  in the primitives described in  FIG. 12  are shown on opposite sides of the die, for example, on each side of the central fluid feed region  1206 , this is a virtual arrangement. The location of the nozzles  1202  in relation to the central ink feed region  1206  depends on the design of the die, as described in the following figures. In an example, a black die  302  has staggered nozzles on each side of the fluid feed hole, wherein the staggered nozzles are of the same size. In another example, a color die  304  has a line of nozzles in a line parallel to a longitudinal axis of the die, wherein the size of the nozzles in the line of nozzles alternates between larger nozzles and smaller nozzles. 
       FIG. 13  is a drawing of an example of a layout  1300  of the digital circuitry, showing the simplification that can be achieved by a single set of nozzle circuitry. The layout  1300  can be used for either the black die  302  of the color die  304 . In the layout  1300 , a digital power bus  1302  provides power and ground to all logic circuits. A digital signal bus  1304  provides address lines, primitive selection lines, and other logic lines to the logic circuits. In this example, a sense bus  1306  is shown. The sense bus  1306  is a shared, or multiplexed, analog bus that carries sensor signals, including, for example, signals from temperature sensors, and the like. The sense bus  1306  may also be used to read the non-volatile memory elements. 
     In this example, logic circuitry  1308  for primitives on both the east and west side of the die share access to the digital power bus  1302 , digital signal bus  1304 , and the sense bus  1306 . Further, the address decoding may be performed in a single logic circuit for a group of primitives  1310 , such as the primitives NW and NE. As a result, the total circuitry required for the die is decreased. 
       FIG. 14  is a drawing of an example of a black die  302 , showing the impact of cross-slot routing on energy and power routing. Like numbered items are as described with respect to  FIGS. 2 and 6 . As a black die  302  is shown in this example, the TIJ resistors are on either side of the fluid feed holes  204 . A similar structure would be used in a color die  304 , although the TIJ resistors would be on a single side of the fluid feed holes  204  and would alternate in size. Connecting power straps  1402  across the silicon ribs  1404  between the fluid feed holes  204  increases the effective width of the power bus for delivering current to the TIJ resistors. In previous solutions that use a slot for ink feed, the right and left column power routing cannot contribute to the other column. Further, using metal 1 and metal 2 layers as a power plane running between fluid feed holes enables the left column (east) and right column (west) of nozzles to share common ground and supply busing. The traces  602  that connect the logic circuitry  510  of the black die  302  to the FETs  604  in the power circuitry  512  of the black die  302  are also visible in the drawing. 
       FIG. 15  is a drawing of an example of a circuit floorplan illustrating a number of die zones for a color die  304 . Like numbered items are as described with respect to  FIGS. 2, 3, and 5 . In the color die  304 , a bus  1502  carries control lines, data lines, address lines, and power lines for the primitive logic circuitry  1504 , including a logic power zone that includes a common logic power line (Vdd) and a common logic ground line (Lgnd) to provide a supply voltage at about 5 V for logic circuitry. The bus  1502  also includes an address line zone including address lines used to indicate an address for a nozzle in each primitive group of nozzles. Accordingly, the primitive group is a group or subset of fluidic actuators of the fluidic actuators on the color die  304 . 
     An address logic zone includes address line circuits, such as primitive logic circuitry  1504  and decode circuitry  1506 . The primitive logic circuitry  1504  couples the address lines to the decode circuitry  1506  for selecting a nozzle in a primitive group. The primitive logic circuitry  1504  also stores data bits loaded into the primitive over the data lines. The data bits include the address values for the address lines, and a bit associated with each primitive that selects whether that primitive fires an addressed nozzle or saves data. 
     The decode circuitry  1506  selects a nozzle for firing or selects a memory element in a memory zone that includes non-volatile memory elements  1508 , to receive the data. When a fire signal is received over the data lines in the bus  1502 , the data is either stored to a memory element in the non-volatile memory elements  1508  or used to activate an FET  1510  or  1512  in a power circuitry zone on the power circuitry  512  of the color die  304 . Activation of an FET  1510  or  1512  provides power to a corresponding TIJ resistor  1516  or  1518  from a shared power (Vpp) bus  1514 . In this example, the traces include power circuitry to power TIJ resistors  1516  or  1518 . Another shared power bus  1520  may be used to provide a ground for the FETs  1510  and  1512 . In some examples, the Vpp bus  1514  and the second shared power bus  1520  may be reversed. 
     A fluid feed zone includes the fluid feed holes  204  and the traces between the fluid feed holes  204 . For the color die  304 , two droplet sizes may be used, which are each ejected by thermal resistors associated with each nozzle. A high weight droplet (HWD) may be ejected using a larger TIJ resistor  1516 . A low weight droplet (LWD) may be ejected using a smaller TIJ resistor  1518 . Electrically, the HWD nozzles are in the first column, for example, west, as described with respect to  FIGS. 12 and 13 . The LWD nozzles are electrically coupled in a second column, for example, east, as described with respect to  FIGS. 12 and 13 . In this example, the physical nozzles of the color die  304  are interdigitated, alternating HWD nozzles with LWD nozzles. 
     The efficiency of the layout may be further improved by changing the size of the corresponding FETs  1510  and  1512  to match the power demand of the TIJ resistors  1516  and  1518 . Accordingly, in this example, the size of the corresponding FETs  1510  and  1512  are based on the TIJ resistor  1516  or  1518  being powered. A larger TIJ resistor  1516  is activated by a larger FET  1512 , while a smaller TIJ resistor  1518  is activated by a smaller FET  1510 . In other examples, the FETs  1510  and  1512  are the same size, although the power drawn through the FETs  1510  used to power smaller TIJ resistors  1518  is lower. 
     A similar circuit floorplan may be used for a black die  302 . However, as described for examples herein, the FETs for a black die are the same size, as the TIJ resistors and nozzles are the same size. 
       FIG. 16  is another drawing of an example of a color die  304 . Like numbered items are as described with respect to  FIGS. 3, 5, and 15 . As can be seen in the drawing, the TIJ resistors  1516  and  1518  are placed in a line parallel to a longitudinal axis of the color die  304 , along one side of the fluid feed holes  204 . The grouping of the TIJ resistors  1516  and  1518  with the fluid feed holes  204  may be termed a micro-electrical mechanical systems (MEMS) area  1604 . Further, in this drawing, the decoding circuitry  1506  and the non-volatile memory elements  1508  are included together in a circuitry section  1602 . The FETs  1510  and  1512  are shown as the same size in the drawing of  FIG. 16 . However, in some examples the FETs  1510 , which activate the smaller TIJ resistors  1518 , are smaller than the FETs  1512 , which activate the larger TIJ resistors  1516 , as described with respect to  FIG. 15 . Thus, the dies, both color and black, have repeating structures that optimize the power delivery capability of the printhead, while minimizing the size of the dies. 
       FIG. 17  is a drawing of an example of a color die  304  showing a repeating structure  1702 . Like numbered items are as described with respect to  FIGS. 5 and 16 . As discussed herein, the use of the fluid feed holes  204  allows the routing of low-voltage control signals from logic circuitry to connect to high-voltage FETs between the fluid feed holes  204 . As a result, the repeating structure  1702  includes two FETs  604 , two nozzles  320 , and one fluid feed hole  204 . For a color die  304  with  1200  dots per inch, this provides a repeating pitch of 42.33 μm. As the FETs  604  and nozzles  320  are only to one side of the fluid feed hole  204 , the circuit area requirements are reduced which allows a smaller size for the color die  304 , versus the black die  302 . 
       FIG. 18  is a drawing of an example of a black die  302  showing an overall structure for the die. Like numbered items are as described with respect to  FIGS. 2, 3, 6, and 16 . In this example, the TIJ resistors  1802  are on either side of the fluid feed holes  204 , allowing the nozzles to be of a similar size, while maintaining the close vertical spacing, or a dot pitch. In this example, the FETs  604  are all the same size to drive the TIJ resistors  1802 . The logic circuitry  510  of the black die  302  is laid out in the same configuration as the logic circuitry  510  of a color die  304 , described with respect to  FIG. 15 . Accordingly, traces  602  couple the logic circuitry  510  to FETs  604  in the power circuitry  512 . 
       FIG. 19  is a drawing of an example of a black die  302  showing a repeating structure  1702 . Like numbered items are as described with respect to  FIGS. 5, 6, 16 , and  17 . As described with respect to the color die  304 , because the low-voltage control signals that connect to high-voltage FETs can be routed between the fluid feed holes  204  a new column circuit architecture and layout is possible. This layout includes a repeating structure  1702  that has two FETs  604 , two nozzles  320 , and one fluid feed hole  204 . This is similar to the repeating structure of the color die  304 . However, in this example, one nozzle  320  is to the left of the fluid feed hole  204  and one nozzle  320  is to the right of the fluid feed hole  204  in repeating structure  1702 . This design accommodates larger firing nozzles, for higher ink drop volumes, while maintaining lower circuit area requirements and optimizing the layout to allow a smaller die. As for the color die  304 , the cross-slot routing is performed in multiple metal layers exit naturally speaking, including poly silicon layers and aluminum copper layers, among others. 
     The black die  302  is wider than the color die  304 , since nozzles  320  are on both sides of the fluid feed holes  204 . In some examples, the black die  302  is about 400 to about 450 μm. In some examples, the color die  304  is about 300 to about 350 μm. 
       FIG. 20  is a drawing of an example of a black die  302  showing a system for crack detection. Like numbered items are as described with respect to  FIGS. 2, 3, 5, 6, and 16 . The introduction of an array of fluid feed holes  204  in a line parallel to the longitudinal axis of the black die  302  increases the fragility of the die. As described herein, the fluid feed holes  204  can act like a perforation line along the longitudinal axis of either the black die  302  or the color die  304 , allowing cracks  2002  to form between these features. To detect these cracks  2002 , a trace  2004  is routed between each fluid feed hole  204  to function as an embedded crack detector. In an example, with a crack forms, the trace  2004  is broken. As a result, the conductivity of the trace  2004  drops to zero. 
     The trace  2004  between the fluid feed holes  204  may be made from a brittle material. While metal traces may be used, the ductility of the metal may allow it to flex across cracks that have formed without detecting them. Accordingly, in some examples the trace  2004  between fluid feed holes  204  are made from polysilicon. If the trace between the fluid feed holes  204  throughout the black die  302 , both alongside and between the fluid feed holes  204 , were made from polysilicon, the resistance may be as high as several megaohms. In some examples, to reduce the overall resistance and improve the detectability of cracks, the portions  2006  of the trace  2004  formed alongside the fluid feed holes  204  and connecting the traces  2004  between the fluid feed holes  204  are made from a metal, such as aluminum-copper, among others. 
       FIG. 21  is an expanded view of a fluid feed hole  204  from a black die  302  showing the trace  2004  routed between adjacent fluid feed holes  204 . In this example, the trace  2004  between the fluid feed holes  204  is formed from polysilicon, while the portion  2006  of the trace  2004  beside the fluid feed holes  204  is formed from a metal. 
       FIG. 22  is a process flow diagram of an example of a method  2200  for forming a crack detection trace. The method begins at block  2202 , with the etching of a number of fluid feed holes in a line parallel to a longitudinal axis of a substrate. 
     At block  2204 , a number of layers are formed on the substrate to form the crack detector trace, wherein the crack detector trace is routed between each of the plurality of fluid feed holes on the substrate. As described herein, the layers are formed to loop from side to side of the die, between each pair of adjacent fluid feed holes, along the outside of a next fluid feed hole, and then between the next pair of adjacent fluid feed holes. In examples, layers are formed to couple the crack detector trace to a sense bus that is shared by other sensors on the die, such as the thermal sensors described with respect to  FIG. 2 . The sense bus is coupled to a pad to allow the sensor signals to be read by an external device, such as the ASIC described with respect to  FIG. 2 . 
     The present examples may be susceptible to various modifications and alternative forms and have been shown only for illustrative purposes. Furthermore, it is to be understood that the present techniques are not intended to be limited to the particular examples disclosed herein. Indeed, the scope of the appended claims is deemed to include all alternatives, modifications, and equivalents that are apparent to persons skilled in the art to which the disclosed subject matter pertains.