Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K3/00—Materials not provided for elsewhere
  • C09K3/14—Anti-slip materials; Abrasives
  • C09K3/1454—Abrasive powders, suspensions and pastes for polishing
  • C09K3/1463—Aqueous liquid suspensions
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09G—POLISHING COMPOSITIONS; SKI WAXES
  • C09G1/00—Polishing compositions
  • C09G1/02—Polishing compositions containing abrasives or grinding agents
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23F—NON-MECHANICAL REMOVAL OF METALLIC MATERIAL FROM SURFACE; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL; MULTI-STEP PROCESSES FOR SURFACE TREATMENT OF METALLIC MATERIAL INVOLVING AT LEAST ONE PROCESS PROVIDED FOR IN CLASS C23 AND AT LEAST ONE PROCESS COVERED BY SUBCLASS C21D OR C22F OR CLASS C25
  • C23F3/00—Brightening metals by chemical means
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
  • H10P52/00—Grinding, lapping or polishing of wafers, substrates or parts of devices
  • H10P52/40—Chemomechanical polishing [CMP]
  • H10P52/403—Chemomechanical polishing [CMP] of conductive or resistive materials

Definitions

• the present invention relates to processes for the chemical-mechanical polishing of substrates, especially those comprising an insulator, a metal and titanium. More especially it relates to the polishing of substrates comprising silicon dioxide, tungsten, and titanium.
• CMP chemical-mechanical polishing
• this structure is planarized to expose the insulating base before proceeding with subsequent steps in the manufacture of the integrated circuit.
• Rutten et al. (“Pattern Density Effects in Tungsten CMP", June 27-29, 1995 NMIC Conference, ISMIC - 104/95/0491) discusses the problems encountered when planarizing a structure in which tungsten, titanium and titanium nitride are used. Ideally, the titanium and titanium nitride layers should be removed at a rate comparable to the rate for tungsten removal.
• iodate such as potassium iodate has become a common oxidant for use in tungsten planarization. It has replaced the earlier use of hydrogen peroxide, H 2 O 2 , as the oxidant because although H 2 O 2 provides a high removal rate for both tungsten and titanium, the removal from the center portion of tungsten in a via may be so great that dishing occurs as shown in Figure lb. Also, a void created in the metal layer during deposition may be exposed as shown in Figure lc creating a "keyhole" in the metal structure. This is particularly undesirable.
• the rate of removal of the insulating layer, silicon dioxide should be as low as possible.
• compounds which suppress the rate of removal of silica are included in the polishing slurries. Such compounds are described by Brancaleoni et al. in USPatent 5,391,258 and USPatent 5,476,606.
• a process for polishing a composite comprised of an insulating layer, a metal and titanium comprising placing the composite in a polishing machine having a polishing pad; and polishing the composite with the polishing pad in the presence of a slurry comprising water, submicron abrasive particles, an iodate and a peroxide.
• a process for polishing a composite comprised of an insulating layer, a metal and titanium comprising placing the composite in a polishing machine having a polishing pad; and polishing the composite with the polishing pad in the presence of a slurry comprising water, submicron abrasive particles, an iodate as the oxidant for the metal wherein, when titanium is present on the surface of the composite being polished, the slurry also comprises about 0.5% to about 10% hydrogen peroxide by weight.
• Another aspect of the invention is the processes above also comprising the addition of a base to the slurry stream exiting the polishing machine to bring the pH of the used slurry to about 7 or higher while the polishing processes are carried out.
• a further aspect of the invention is the process above wherein the slurry further comprises a compound or compounds which suppress the rate of removal of silica.
• the metals in the composite with titanium may be tungsten, copper or aluminum.
• 1 a Cross section of a semiconductor wafer via comprising a metal, titanium nitride, and titanium in an insulator.
• lb Cross section of 1 a after polishing wherein dishing occurs.
• lc Cross section of la after polishing wherein a keyhole is formed.
• the wafer 3 in a wafer carrier 4 is pressed against the surface of the polishing pad 2 while there is relative motion between the pad and the wafer.
• An abrasive slurry is provided to the surface of the polishing pad via a means 5.
• the slurry provided to the polishing process is shown in this example to flow across the circular rotating pad and exit from the edge of the pad into a catch basin 6.
• the catch basin directs the used slurry to a waste holding tank 8.
• the layers to be removed in the process of this invention are first tungsten 24 then titanium nitride 23 and then titanium 22. It is most advantageous to use KIO 3 as the oxidant in the slurry during the first step.
• a slurry with a constant composition comprising both an iodate and a peroxide can be used throughout the polishing process thereby making it unnecessary to change the composition during the process. In such a case it may be advantageous to neutralize the effluent from the polishing machine so that the iodate is not easily oxidized in the waste stream.
• a first polishing slurry 9 had the following composition (by weight): about 3% potassium iodate, about 2.5% ammonium hydrogen phthalate, about 5.0% submicron alumina and the remaining being deionized water.
• the 6 inch wafers were coated with tungsten, titanium, or silicon oxide. Removal rate for each coating was determined by measuring the change in thickness of the coating over a given time period. Table 1 shows the results of polishing with the polishing slurry 9 described above and with the addition of 30% hydrogen peroxide to give a slurry as used comprising about 1.5% and about 3%> hydrogen peroxide.
• the removal rate of Ti can be brought up to the rate at which W is removed when using slurry #9 by simply adding hydrogen peroxide to slurry #9. Under these conditions the rate of tungsten removal will be increased somewhat, but overall the rates of tungsten and titanium removal will be near 1 to 1.
• the amount of hydrogen peroxide added to the incoming slurry is in the amount to give a slurry comprising about 0.5% to 10%) by weight hydrogen peroxide. More preferably, the incoming slurry comprises about 1% to 5% by weight hydrogen peroxide. Also, the rate of silicon oxide removal is maintained low so that the selectivity of tungsten to silicon oxide removal rates remains above 20.
• the slurries used in this invention may contain compounds which suppress the rate of removal of silica.
• Compounds which act as complexing agents or chelating agents for SiO 2 and, therefore, suppress the rate of removal of silica are described in great detail in U. S. Patent 5391258 and U. S. Patent 5476606. These compounds must have at least two acid groups present in the structure which can affect complexation to the silica. Acid species are defined as those functional groups having a dissociable proton. These include, but are not limited to, carboxylate, hydroxyl, sulfonic and phosphonic groups. Carboxylate and hydroxyl groups are preferred as these are present in the widest variety of effective species.
• Particularly effective are structures which possess two or more carboxylate groups with hydroxyl groups in an alpha position, such as straight chain mono- and di-carboxylic acids and salts including, for example, malic acid and malates, tartaric acid and tartarates and gluconic acid and gluconates. Also effective are tri- and polycarboxylic acids and salts with secondary or tertiary hydroxyl groups in an alpha position relative to a carboxylic group such as citric acid and citrates.
• these complexing agents are used in slurries for CMP at about 2% to about 7% by weight.
• Examples of such compounds are potassium hydrogen phthalate and ammonium hydrogen phthalate.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Mechanical Treatment Of Semiconductor (AREA)
• Weting (AREA)

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• 1997
  • 1997-05-20 US US08/859,132 patent/US6001269A/en not_active Expired - Fee Related
• 1998
  • 1998-05-19 WO PCT/US1998/010252 patent/WO1998053488A1/en not_active Ceased
  • 1998-05-19 JP JP55053798A patent/JP2002511192A/ja not_active Ceased

Patent Citations (8)

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