Patent Publication Number: US-2006009136-A1

Title: Fixed-abrasive chemical-mechanical planarization of titanium nitride

Description:
RELATED APPLICATIONS  
      This application is a Divisional of U.S. Ser. No. 10/116,585 filed Apr. 4, 2002, which is a Divisional of U.S. Ser. No. 09/339,735 filed Jun. 24, 1999 and issued as U.S. Pat. No. 6,419,554 on Jul. 16, 2002, which applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD  
      The present invention relates generally to methods for planarizing semiconductor substrates, and in particular to planarizing solutions and methods of use for removing titanium nitride from the surface of semiconductor substrates using fixed-abrasive pads, and apparatus produced therefrom.  
     BACKGROUND  
      Chemical-Mechanical Planarizing (CMP) processes are often used for forming a flat surface on a semiconductor substrate in the manufacture of electronic devices. CMP processes generally remove material from a substrate surface to create a highly planar surface. A variety of planarizing machines have been developed to carry out such CMP processes.  
      Planarizing machines for use in CMP processing generally fall into two categories: web-format and fixed-pad format. In each case, a planarizing pad and a planarizing solution are combined to define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of a substrate. The planarizing pad may be of a fixed-abrasive or non-abrasive type. With a fixed-abrasive pad type, abrasive particles are fixedly bonded to a suspension material. Furthermore, the planarizing solution used with a fixed-abrasive pad type is typically a “clean” solution, i.e., substantially devoid of abrasive particles as such abrasive particles are fixedly distributed across a planarizing surface of the planarizing pad. With a non-abrasive planarizing pad, no abrasive particles are associated with the pad, so the abrasive particles are introduced in the planarizing solution. Such planarizing solutions for use with non-abrasive pad types are often slurries of both abrasive particles as well as chemicals to aid removal of material from a substrate.  
      To planarize the substrate with the planarizing machine, the surface of the substrate is first contacted against the planarizing pad in the presence of the planarizing solution, i.e., a planarizing surface of the planarizing medium. While in contact, the substrate is then moved relative to the planarizing surface of the planarizing medium, generally through lateral, rotational, revolving or orbital movement of the substrate, the planarizing pad or both. Lateral movement is defined as movement in one direction. Rotational movement is defined as rotation about an axis located at the center point of the object in motion. Revolving movement is defined as rotation about some axis located at other than the center point of the object in motion. Orbital movement is defined as rotational or revolving movement combined with oscillation. Different types of movement may be combined, e.g., rotational movement of the substrate and rotational movement of the planarizing pad or revolving and rotational movement of the substrate against a stationary planarizing pad. As is well understood in the art, such relative movement is in a plane substantially parallel to the surface of substrate. As a result, the abrasive particles and/or the chemicals in the planarizing medium remove material from the surface of the substrate.  
      Fixed abrasive pad types are well known in the art of semiconductor wafer processing. See, e.g., U.S. Pat. No. 5,692,950 issued Dec. 2, 1997 to Rutherford et al.; U.S. Pat. No. 5,624,303 issued Apr. 29, 1997 to Robinson; and U.S. Pat. No. 5,335,453 issued Aug. 9, 1994 to Baldy et al. Despite widespread recognition and acceptance of fixed abrasive pads in the processing of semiconductor wafers, effective planarizing solutions for use in the fixed-abrasive planarization of an advantageous barrier material and conductor, i.e., titanium nitride (TiN), are lacking. As a result, the customary processing for planarizing titanium nitride utilizes abrasive slurries with non-abrasive pad types.  
      One problem with CMP processing is that the planarized surface of the wafer may not be sufficiently uniform across the whole surface of the wafer. In the competitive semiconductor industry, it is also desirable to maximize the throughput of finished wafers. The uniformity of the planarized surface and maximization of throughput is a function of the effectiveness and repeatability of the planarizing solution utilized with the planarizing pad, as well as a wide array of other CMP operating parameters. While a wide variety of planarizing solutions are available, these solutions are generally specific to the composition of the material to be removed as well as the type of planarizing pad used. For obvious reasons, planarizing solutions developed for non-abrasive pad types are ill suited for use with fixed-abrasive pad types. Therefore, it would be desirable to develop effective planarizing solutions for planarization of titanium nitride on the surface of a semiconductor wafer for use in conjunction with fixed-abrasive planarizing pads.  
      For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for methods of planarizing titanium nitride using fixed-abrasive planarizing pads.  
     SUMMARY  
      Embodiments of titanium nitride layers planarized in accordance with the invention may be utilized in the production of integrated circuits, and various apparatus utilizing such integrated circuits. Planarizing solutions may be used for removing titanium nitride from the surface of a substrate using a fixed-abrasive planarizing pad. The planarizing solutions take the form of an etchant solution or an oxidizing solution. The etchant solutions are aqueous solutions containing an etchant and a buffer. The etchant contains one or more etching agents selective to titanium nitride. The oxidizing solutions are aqueous solutions containing an oxidizer and a buffer. The oxidizer contains one or more oxidizing agents selective to titanium nitride. In either solution, i.e., etchant or oxidizing solution, the buffer contains one or more buffering agents.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIGS. 1A-1B  are a cross-sectional views of a substrate with a titanium nitride layer at sequential processing stages in accordance with an embodiment of the invention.  
       FIG. 2A  is a schematic of a web-format planarizing machine as used in accordance with an embodiment of the invention.  
       FIG. 2B  is a schematic of a fixed-pad format planarizing machine as used in accordance with an embodiment of the invention.  
       FIG. 3  is a block diagram of an integrated circuit memory device in accordance with an embodiment of the invention.  
       FIG. 4  is an elevation view of a wafer containing semiconductor dies in accordance with an embodiment of the invention.  
       FIG. 5  is a block diagram of an exemplary circuit module in accordance with an embodiment of the invention.  
       FIG. 6  is a block diagram of an exemplary memory module in accordance with an embodiment of the invention.  
       FIG. 7  is a block diagram of an exemplary electronic system in accordance with an embodiment of the invention.  
       FIG. 8  is a block diagram of an exemplary memory system in accordance with an embodiment of the invention.  
       FIG. 9  is a block diagram of an exemplary computer system in accordance with an embodiment of the invention. 
    
    
     DESCRIPTION OF THE EMBODIMENTS  
      In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the inventions may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that process or mechanical changes may be made without departing from the scope of the present invention. The terms wafer and substrate used previously and in the following description include any base semiconductor structure. Both are to be understood as including silicon-on-sapphire (SOS) technology, silicon-on-insulator (SOI) technology, thin film transistor (TFT) technology, doped and undoped semiconductors, epitaxial layers of silicon supported by a base semiconductor, as well as other semiconductor structures well known to one skilled in the art. Furthermore, when reference is made to a wafer or substrate in the following description, previous process steps may have been utilized to form regions/junctions in the base semiconductor structure. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims.  
      In one embodiment, the invention provides a method of planarizing titanium nitride on a surface of a substrate. The method includes contacting the surface of the substrate with a planarizing surface of a planarizing medium, the planarizing medium comprising a fixed-abrasive planarizing pad and a clean planarizing solution. The method further includes moving the surface of the substrate relative to the planarizing surface of the planarizing medium, thereby abrading the titanium nitride on the surface of the substrate. In another embodiment, moving the surface of the substrate relative to the planarizing surface of the planarizing medium comprises moving at least one of the substrate and the planarizing surface of the planarizing medium in a manner selected from the group consisting of lateral, rotational, revolving and orbital. In a further embodiment, the planarizing solution is an etchant solution. In a still further embodiment, the planarizing solution is an oxidizing solution.  
      In another embodiment, a method of planarizing titanium nitride on a surface of a substrate includes use of an etchant solution as the planarizing solution, wherein the etchant solution contains an etchant and a buffer in aqueous solution. In one embodiment, the etchant comprises at least one etching agent selected from the group consisting of oxalic acid, ascorbic acid and phosphoric acid. In a further embodiment, the buffer comprises at least one buffering agent selected from the group consisting of ammonium acetate, ammonium oxalate, ammonium phosphate and diammonium phosphate. In a still further embodiment, the etchant solution has a pH of approximately 1 to 5. In yet another embodiment, the etchant solution has a pH of approximately 1.5 to 3.  
      In a further embodiment, a method of planarizing titanium nitride on a surface of a substrate includes use of an oxidizing solution as the planarizing solution, wherein the oxidizing solution contains an oxidizer and a buffer in aqueous solution. In one embodiment, the oxidizer comprises at least one oxidizing agent selected from the group consisting of ammonium persulfate, ammonium heptamolybdate, ceric ammonium nitrate, ceric ammonium sulfate and hydrogen peroxide. In another embodiment, the buffer comprises at least one buffering agent selected from the group consisting of phosphoric acid, ammonium acetate, ammonium oxalate, ammonium phosphate and diammonium phosphate. In yet another embodiment, the oxidizing solution has a pH of approximately 1 to 6. In a further embodiment, the oxidizing solution has a pH of approximately 1.5 to 4.  
      In one embodiment, the invention provides a method of planarizing titanium nitride on a surface of a substrate. The method includes contacting the surface of the substrate with a planarizing surface of a planarizing medium, the planarizing medium comprising a fixed-abrasive planarizing pad and a clean planarizing solution, wherein the planarizing solution is an aqueous solution comprising approximately 1% to 5% by weight of oxalic acid and approximately 2% to 10% by weight of ammonium acetate. The method further includes moving the surface of the substrate relative to the planarizing surface of the planarizing medium, thereby abrading the titanium nitride on the surface of the substrate.  
      In another embodiment, the invention provides a clean aqueous planarizing solution. The clean aqueous planarizing solution includes an etchant having at least one etching agent selected from the group consisting of oxalic acid, ascorbic acid and phosphoric acid, and a buffer. In one embodiment, the buffer comprises at least one buffering agent selected from the group consisting of ammonium acetate, ammonium oxalate, ammonium phosphate and diammonium phosphate. In a further embodiment, the planarizing solution has a pH of approximately 1 to 5. In a still further embodiment, the planarizing solution has a pH of approximately 1.5 to 3. In another embodiment, the planarizing solution has approximately 1% to 10% by weight of the etchant and approximately 0% to 10% by weight of the buffer. In yet another embodiment, the planarizing solution has approximately 1% to 5% by weight of the etchant and approximately 0% to 10% by weight of the buffer. In another embodiment, the planarizing solution has approximately 1% to 5% by weight of oxalic acid and approximately 2% to 10% by weight of ammonium acetate.  
      In a further embodiment, the invention provides a clean aqueous planarizing solution. The clean aqueous planarizing solution includes an oxidizer having at least one oxidizing agent selected from the group consisting of ammonium persulfate, ammonium heptamolybdate, ceric ammonium nitrate, ceric ammonium sulfate and hydrogen peroxide, and a buffer. In one embodiment, the buffer comprises at least one buffering agent selected from the group consisting of phosphoric acid, ammonium acetate, ammonium oxalate, ammonium phosphate and diammonium phosphate. In another embodiment, the planarizing solution has a pH of approximately 1 to 6. In yet another embodiment, the planarizing solution has a pH of approximately 1.5 to 4. In a further embodiment, the planarizing solution has approximately 1% to 10% by weight of the oxidizer and approximately 0% to 10% by weight of the buffer. In a still further embodiment, the planarizing solution has approximately 1% to 5% by weight of the oxidizer and approximately 0.5% to 3% by weight of the buffer.  
      Further embodiments of the invention provide planarizing solutions and methods of removing titanium nitride of varying scope. Still further embodiments of the invention provide apparatus of varying scope produced in accordance with methods and planarizing solutions of the invention.  
       FIG. 1A  illustrates a typical substrate  12  having a first layer  1  and a patterned second layer  2 . In typical semiconductor processing, first layer  1  may represent a wafer of single-crystal silicon or other base semiconductor layer, an insulating layer separating second patterned layer  2  from other layers, or a combination of multiple layers formed in prior processing steps. The composition and structure of first layer  1  and patterned second layer  2  are trivial.  
      A titanium nitride layer  3  is formed on a portion of first layer  1  exposed by patterned second layer  2 . Titanium nitride layer  3  may be formed by chemical vapor deposition (CVD) or other processes well known in the art. In  FIG. 1B , a CMP process in accordance with an embodiment of the invention is used to remove a portion of titanium nitride layer  3  and to planarize the surface of substrate  12 . Titanium nitride layer  3  may be utilized as a contact in an integrated circuit, e.g., where the portion of first layer  1  exposed by patterned second layer  1  forms an active area of a semiconductor device. The integrated circuit may be utilized in the formation of various electronic devices.  
       FIG. 2A  illustrates a web-format planarizing machine  10  for planarizing a substrate  12  in accordance with an embodiment of the invention. The substrate  12  has titanium nitride on its surface as illustrated in  FIG. 1A . Planarizing machine  10  is used to remove at least a portion of the titanium nitride and to planarize the surface of substrate  12 .  
      The planarizing machine  10  has a support table  14  with a top-panel  16  at a workstation where an operative portion (A) of a planarizing pad  40  is positioned. The top-panel  16  is generally a rigid plate to provide a flat, solid surface to which a particular section of the planarizing pad  40  may be secured during planarization.  
      The planarizing machine  10  also has a plurality of rollers to guide, position and hold the planarizing pad  40  over the top-panel  16 . The rollers include a supply roller  20 , first and second idler rollers  21   a  and  21   b,  first and second guide rollers  22   a  and  22   b,  and a take-up roller  23 . The supply roller  20  carries an unused or pre-operative portion of the planarizing pad  40 , and the take-up roller  23  carries a used or post-operative portion of the planarizing pad  40 . Additionally, the first idler roller  21   a  and the first guide roller  22   a  stretch the planarizing pad  40  over the top-panel  16  to hold the planarizing pad  40  stationary during operation. A motor (not shown) drives at least one of the supply roller  20  and the take-up roller  23  to sequentially advance the planarizing pad  40  across the top-panel  16 . As such, clean pre-operative sections of the planarizing pad  40  may be quickly substituted for used sections to provide a consistent surface for planarizing and/or cleaning the substrate  12 .  
      The web-format planarizing machine  10  also has a carrier assembly  30  that controls and protects the substrate  12  during planarization. The carrier assembly  30  generally has a substrate holder  32  to pick up, hold and release the substrate  12  at appropriate stages of the planarizing cycle. A plurality of nozzles  33  attached to the substrate holder  32  dispense a planarizing solution  44  onto a planarizing surface  42  of the planarizing pad  40 . The carrier assembly  30  also generally has a support gantry  34  carrying a drive assembly  35  that translates along the gantry  34 . The drive assembly  35  generally has a actuator  36 , a drive shaft  37  coupled to the actuator  36 , and an arm  38  projecting from the drive shaft  37 . The arm  38  carries the substrate holder  32  via another shaft  39  such that the drive assembly  35  revolves the substrate holder  32  about an axis B-B offset from a center point C-C of the substrate  12 .  
      The planarizing pad  40  and the planarizing solution  44  define a planarizing medium, having the planarizing surface  42 , that chemically-mechanically removes material from the surface of the substrate  12 . The planarizing pad  40  is of a fixed-abrasive type.  
      In one embodiment, the planarizing solution  44  is an etchant solution and contains an etchant of at least one etching agent and a buffer of at least one buffering agent in aqueous solution. Etchant chemistries differ significantly from oxidizer chemistries commonly used in conventional abrasive slurries, i.e., those used with non-abrasive pad types. In etchant chemistries, the etchants are reducing agents which complex the titanium to facilitate removal. Preferred etching agents include oxalic acid (HOOCCOOH.2H 2 O), ascorbic acid (C 6 H 8 O 6 ), and phosphoric acid (H 3 PO 4 ). Preferred buffering agents include ammonium acetate (NH 4 (C 2 H 3 O 2 )), ammonium oxalate ((NH 4 ) 2 C 2 O 4 H 2 O), ammonium phosphate (NH 4 H 2 PO 4 ), and diammonium phosphate ((NH 4 ) 2 HPO 4 ).  
      The etchant solution has a pH of approximately 1 to 5, preferably less than approximately 3, and more preferably in the range of approximately 1.5 to 3. Etchant concentration in the etchant solution is preferably in the range of approximately 1% to 10% by weight and more preferably in the range of approximately 1% to 5% by weight.  
      Suitable buffer concentrations are expected to be in the range of approximately 0% to 10% by weight. Concentrations of etchant and buffer may fall outside the preferred ranges depending upon the combination of etching agents and buffering agents selected. However, it is within the skill in the art to determine appropriate concentrations without undue experimentation to achieve the desired pH ranges. The pH is defined by the equation pH=log 10 [H+] −1 , the logarithm of the reciprocal of the hydrogen-ion concentration of the solution.  
      In one embodiment, more than one etching agent is used as the etchant in the etchant solution. In another embodiment, the etchant in the etchant solution consists essentially of one etching agent. In one embodiment, more than one buffering agent is used as the buffer in the etchant solution. In another embodiment, the buffer in the etchant solution consists essentially of one buffering agent. In still another embodiment, planarizing solution  44  comprises an aqueous solution having approximately 1% to 5% by weight of oxalic acid, approximately 2% to 10% by weight of ammonium acetate, and a pH of approximately 1.5 to 3.  
      The etchant solution may contain additional chemical components that do not materially affect the basic and novel characteristic of the solutions disclosed herein. Some examples include dyes, lubricants, stabilizers, surfactants, thickening agents, preservatives and antimicrobial agents to name a few. Where more than one etching agent is utilized in the etchant solution, the weight % of the etchant is based on the combined weight of all such etching agents in relation to the total weight of the solution. Where more than one buffering agent is utilized in the etchant solution, the weight % of the buffer is based on the combined weight of all such buffering agents in relation to the total weight of the solution.  
      In a further embodiment, the planarizing solution  44  is an oxidizing solution and contains an oxidizer of at least one oxidizing agent and a buffer of at least one buffering agent in aqueous solution. Preferred oxidizing agents include ammonium persulfate ((NH 4 ) 2 S 2 O 8 ), ammonium heptamolybdate ((NH 4 ) 6 Mo 7 O 24 .4H 2 O), ceric ammonium nitrate (Ce(NO 3 ) 4 .2NH 4 NO 3 ), ceric ammonium sulfate (Ce(SO 4 ) 2 .2(NH 4 ) 2 SO 4 ), and hydrogen peroxide (H 2 O 2 ). Preferred buffering agents include phosphoric acid (H 3 PO 4 ), ammonium acetate (NH 4 (C 2 H 3 O 2 )), ammonium oxalate ((NH 4 ) 2 C 2 O 4 .H 2 O), ammonium phosphate (NH 4 H 2 PO 4 ), and diammonium phosphate ((NH 4 ) 2 HPO 4 ).  
      The oxidizing solution has a pH of approximately 1 to 6, preferably less than approximately 4, and more preferably in the range of approximately 1.5 to 4. Oxidizer concentration in the oxidizing solution is preferably in the range of approximately 1% to 10% by weight and more preferably in the range of approximately 1% to 5% by weight. An oxidizer concentration of approximately 2% by weight is further preferred.  
      Suitable buffer concentrations are expected to be in the range of approximately 0% to 10% by weight. Such concentration of buffer is generally expected to be approximately 0.5% to 3% by weight at the preferred oxidizer concentrations. Concentrations of oxidizer and buffer may fall outside the preferred ranges depending upon the combination of oxidizing agents and buffering agents selected. However, it is within the skill in the art to determine appropriate concentrations without undue experimentation to achieve the desired pH ranges.  
      In one embodiment, more than one oxidizing agent is used as the oxidizer in the oxidizing solution. In another embodiment, the oxidizer in the oxidizing solution consists essentially of one oxidizing agent. In one embodiment, more than one buffering agent is used as the buffer in the oxidizing solution. In another embodiment, the buffer in the oxidizing solution consists essentially of one buffering agent.  
      The oxidizing solution may contain additional chemical components that do not materially affect the basic and novel characteristic of the solutions disclosed herein. Some examples include dyes, lubricants, stabilizers, surfactants, thickening agents, preservatives and antimicrobial agents to name a few. Where more than one oxidizing agent is utilized in the oxidizing solution, the weight % of the oxidizer is based on the combined weight of all such oxidizing agents in relation to the total weight of the solution. Where more than one buffering agent is utilized in the oxidizing solution, the weight % of the buffer is based on the combined weight of all such buffering agents in relation to the total weight of the solution.  
      To planarize the substrate  12  with the planarizing machine  10 , the carrier assembly  30  presses the substrate  12  against the planarizing surface  42  of the planarizing pad  40  in the presence of the planarizing solution  44 . The drive assembly  35  then moves the substrate holder  32  relative to the planarizing surface  42  to move the substrate  12  across the planarizing surface  42 . Movement of the substrate holder  32  is in a plane substantially parallel to the surface of substrate  12 . As the surface of the substrate  12  moves across the planarizing surface  42 , material is continuously removed from the surface of the substrate  12  through abrasion.  
      Alternatively, the planarizing machine may utilize fixed pads instead of webs as the planarization pad.  FIG. 2B  illustrates a fixed-pad format planarizing machine  100  for use in accordance with an embodiment of the invention. The planarizing machine  100  has a platen  120 , an underpad  125  attached to the platen  120 , a polishing pad  140  attached to the underpad  125 , and a carrier assembly  130  positioned over the polishing pad  140 . A drive assembly  126  rotates the platen  120  (as indicated by arrow A), or it reciprocates the platen  120  back and forth (as indicated by arrow B). Other planarizing machines may revolve the platen  120  about a point. Since the polishing pad  140  is attached to the underpad  125 , the polishing pad  140  moves with the platen  120 .  
      The carrier assembly  130  has a substrate holder  131  and resilient pad  134  to which a substrate  12  may be attached. The carrier assembly  130  may be a weighted, free-floating substrate holder, or an actuator assembly  136  may be attached to the carrier assembly  130  to impart axial and/or rotational motion (as indicated by arrows C and D, respectively).  
      To planarize the substrate  12  with the planarizing machine  100 , the carrier assembly  130  presses the substrate  12  surface-downward against the polishing pad  140 . While the surface of the substrate  12  presses against the polishing pad  140 , at least one of the platen  120 , and therefore the planarizing surface  142 , or the substrate holder  131  moves relative to the other to move the substrate  12  across the planarizing surface  142 . Movement of the platen  120  and/or the substrate holder  131  are in planes substantially parallel to the surface of substrate  12 . As the surface of the substrate  12  moves across the planarizing surface  142 , material is continuously removed from the surface of the substrate  12  through abrasion.  
      The planarizing pad  140  and the planarizing solution  44  define a planarizing medium that chemically-mechanically removes material from the surface of the substrate  12 . The planarizing pad  140  is of a fixed-abrasive type. The planarizing machine  100  has a planarizing solution dispenser  150  for application of the planarizing solution  44  to the planarizing surface  142  of the planarizing medium. Planarizing solution  44  may be an oxidizing solution or an etchant solution of the invention.  
      It is recognized that the planarizing machines described above are typical of the major formats, i.e., web format or fixed-pad format, but that other mechanical variations and adaptations are well known in the art. However, planarizing solutions of the invention are not dependent upon the planarizing machine format.  
      The various embodiments of the invention permit CMP removal of titanium nitride using fixed-abrasive planarizing pads, regardless of the format of the planarizing machine. In conjunction with the various embodiments of the invention, the CMP process may be a conditionless planarizing process, i.e., conditioning of the planarizing pad prior to use may be eliminated.  
      It will be apparent that semiconductor wafers processed in accordance with the invention may be utilized to produce a variety of integrated circuit devices. It is believed that integrated circuit devices produced in accordance with the invention exhibit less performance variability than devices produced using non-abrasive pad types with abrasive slurry planarizing solutions due to reduced process variability. The reduced process variability arises from the ability to eliminate conditioning of the planarizing pad prior to use as well as elimination of variability associated with the propensity of the abrasive particles in abrasive slurry planarizing solutions to settle or agglomerate during storage and use.  
      Consequently, integrated circuit devices produced in accordance with the invention are expected to exhibit physical characteristics different from the physical characteristics inherent in planarizing titanium nitride using non-abrasive planarizing pads in conjunction with abrasive slurry planarizing solutions due to more uniform abrasion of the titanium nitride on the surface of the substrate. In addition, reactive characteristics inherent in the planarizing solutions of the invention are expected to produce physical characteristics different from the physical characteristics produced by planarizing solutions of alternate chemistries, given the differing reactive characteristics inherent in such alternate chemistries. One typical integrated circuit device for use with the invention is a memory device.  
      Memory Devices  
       FIG. 3  is a simplified block diagram of a memory device according to one embodiment of the invention. The memory device  300  includes an array of memory cells  302 , address decoder  304 , row access circuitry  306 , column access circuitry  308 , control circuitry  310 , and Input/Output circuit  312 . The memory can be coupled to an external microprocessor  314 , or memory controller for memory accessing. The memory receives control signals from the processor  314 , such as WE*, RAS* and CAS* signals. The memory is used to store data which is accessed via I/O lines. It will be appreciated by those skilled in the art that additional circuitry and control signals can be provided, and that the memory device of  FIG. 3  has been simplified to help focus on the invention. The memory device  300  has at least one titanium nitride layer planarized in accordance with the invention.  
      It will be understood that the above description of a DRAM (Dynamic Random Access Memory) is intended to provide a general understanding of the memory and is not a complete description of all the elements and features of a DRAM. Further, the invention is equally applicable to any size and type of memory circuit and is not intended to be limited to the DRAM described above. Other alternative types of devices include SRAM (Static Random Access Memory) or Flash memories. Additionally, the DRAM could be a synchronous DRAM commonly referred to as SGRAM (Synchronous Graphics Random Access Memory), SDRAM (Synchronous Dynamic Random Access Memory), SDRAM II, and DDR SDRAM (Double Data Rate SDRAM), as well as Synchlink or Rambus DRAMs.  
      As recognized by those skilled in the art, memory devices of the type described herein are generally fabricated as an integrated circuit containing a variety of semiconductor devices. The integrated circuit is supported by a substrate. Integrated circuits are typically repeated multiple times on each substrate. The substrate is further processed to separate the integrated circuits into dies as is well known in the art.  
      Semiconductor Dies  
      With reference to  FIG. 4 , in one embodiment, a semiconductor die  710  is produced from a silicon wafer  700 . A die is an individual pattern, typically rectangular, on a substrate that contains circuitry, or integrated circuit devices, to perform a specific function. Semiconductor die  710  has at least one titanium nitride layer planarized in accordance with the invention. A semiconductor wafer will typically contain a repeated pattern of such dies containing the same functionality. Die  710  may contain circuitry for the inventive memory device, as discussed above. Die  710  may further contain additional circuitry to extend to such complex devices as a monolithic processor with multiple functionality. Die  710  is typically packaged in a protective casing (not shown) with leads extending therefrom (not shown) providing access to the circuitry of the die for unilateral or bilateral communication and control.  
      Circuit Modules  
      As shown in  FIG. 5 , two or more dies  710  may be combined, with or without protective casing, into a circuit module  800  to enhance or extend the functionality of an individual die  710 . Circuit module  800  may be a combination of dies  710  representing a variety of functions, or a combination of dies  710  containing the same functionality. Some examples of a circuit module include memory modules, device drivers, power modules, communication modems, processor modules and application-specific modules and may include multilayer, multichip modules. Circuit module  800  may be a subcomponent of a variety of electronic systems, such as a clock, a television, a cell phone, a personal computer, an automobile, an industrial control system, an aircraft and others. Circuit module  800  will have a variety of leads  810  extending therefrom and coupled to the dies  710  providing unilateral or bilateral communication and control.  
       FIG. 6  shows one embodiment of a circuit module as memory module  900 . Memory module  900  generally depicts a Single Inline Memory Module (SIMM) or Dual Inline Memory Module (DIMM). A SIMM or DIMM is generally a printed circuit board (PCB) or other support containing a series of memory devices. While a SIMM will have a single in-line set of contacts or leads, a DIMM will have a set of leads on each side of the support with each set representing separate I/O signals. Memory module  900  contains multiple memory devices  910  contained on support  915 , the number depending upon the desired bus width and the desire for parity. Memory module  900  may contain memory devices  910  on both sides of support  915 . Memory module  900  accepts a command signal from an external controller (not shown) on a command link  920  and provides for data input and data output on data links  930 . The command link  920  and data links  930  are connected to leads  940  extending from the support  915 . Leads  940  are shown for conceptual purposes and are not limited to the positions shown in  FIG. 6 .  
      Electronic Systems  
       FIG. 7  shows an electronic system  1000  containing one or more circuit modules  800 . Electronic system  1000  generally contains a user interface  1010 . User interface  1010  provides a user of the electronic system  1000  with some form of control or observation of the results of the electronic system  1000 . Some examples of user interface  1010  include the keyboard, pointing device, monitor and printer of a personal computer; the tuning dial, display and speakers of a radio; the ignition switch and gas pedal of an automobile; and the card reader, keypad, display and currency dispenser of an automated teller machine. User interface  1010  may further describe access ports provided to electronic system  1000 . Access ports are used to connect an electronic system to the more tangible user interface components previously exemplified. One or more of the circuit modules  800  may be a processor providing some form of manipulation, control or direction of inputs from or outputs to user interface  1010 , or of other information either preprogrammed into, or otherwise provided to, electronic system  1000 . As will be apparent from the lists of examples previously given, electronic system  1000  will often contain certain mechanical components (not shown) in addition to circuit modules  800  and user interface  1010 . It will be appreciated that the one or more circuit modules  800  in electronic system  1000  can be replaced by a single integrated circuit. Furthermore, electronic system  1000  may be a subcomponent of a larger electronic system.  
       FIG. 8  shows one embodiment of an electronic system as memory system  1100 . Memory system  1100  contains one or more memory modules  900  and a memory controller  1110 . Memory controller  1110  provides and controls a bidirectional interface between memory system  1100  and an external system bus  1120 . Memory system  1100  accepts a command signal from the external bus  1120  and relays it to the one or more memory modules  900  on a command link  1130 . Memory system  1100  provides for data input and data output between the one or more memory modules  900  and external system bus  1120  on data links  1140 .  
       FIG. 9  shows a further embodiment of an electronic system as a computer system  1200 . Computer system  1200  contains a processor  1210  and a memory system  1100  housed in a computer unit  1205 . Computer system  1200  is but one example of an electronic system containing another electronic system, i.e., memory system  1100 , as a subcomponent. Computer system  1200  optionally contains user interface components. Depicted in  FIG. 9  are a keyboard  1220 , a pointing device  1230 , a monitor  1240 , a printer  1250  and a bulk storage device  1260 . It will be appreciated that other components are often associated with computer system  1200  such as modems, device driver cards, additional storage devices, etc. It will further be appreciated that the processor  1210  and memory system  1100  of computer system  1200  can be incorporated on a single integrated circuit. Such single package processing units reduce the communication time between the processor and the memory circuit.  
     CONCLUSION  
      Planarizing solutions, and their methods of use, for removing titanium nitride from the surface of a substrate using a fixed-abrasive planarizing pad type are disclosed. The planarizing solutions may take the form of an etchant solution or an oxidizing solution. The etchant solutions are aqueous solutions containing an etchant and a buffer. The etchant contains one or more etching agents selective to titanium nitride. The oxidizing solutions are aqueous solutions containing an oxidizer and a buffer. The oxidizer contains one or more oxidizing agents selective to titanium nitride. In either solution, i.e., etchant or oxidizing solution, the buffer contains one or more buffering agents. Titanium nitride layers planarized in accordance with the invention may be utilized in the production of integrated circuits, and various apparatus utilizing such integrated circuits.  
      Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. Many adaptations of the invention will be apparent to those of ordinary skill in the art. For example, other planarizing machine formats may be utilized with the invention. Furthermore, titanium nitride layers planarized in accordance with the invention may be utilized as conductor lines, barrier layers or other structures in addition to the contacts described herein. Accordingly, this application is intended to cover any adaptations or variations of the invention. It is manifestly intended that this invention be limited only by the following claims and equivalents thereof.