Classifications

• • 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
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
  • C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
  • C23C18/18—Pretreatment of the material to be coated
  • C23C18/20—Pretreatment of the material to be coated of organic surfaces, e.g. resins
  • C23C18/28—Sensitising or activating
  • C23C18/30—Activating or accelerating or sensitising with palladium or other noble metal
• • 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
  • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
  • H10P14/40—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials
  • H10P14/46—Formation of materials, e.g. in the shape of layers or pillars of conductive or resistive materials using a liquid

Definitions

• the .surfacemust When a metal such as nickel is electrolessly deposited on a surface which is not normally a catalyst for such deposition, the .surfacemust first be activated by treating it with a catalyst. Although a number of metals catalyze the electroless deposition of nickel, the one mostoften used is palladium. A very thirifdiscontinuous film of palladium particles is deposited asa catalyzing medium by reducing a solution of a palladium salt which is in contact with the surface to be plated. If the palladium film is non-uniform, a non-uniform layer of nickel results.
• the palladium film When the palladium film is first deposited under conventional, carefully controlled-conditions, it is usually substantially uniform. But,- during the conventional step of rinsing with deionized water between deposition of the palladium and the subsequent nickel plating, non-uniformity of the palladium is often introduced, and this then causes difficulties with the nickel plating operation. There are often areas where nickel does not deposit and others where the nickel is too thin or too thick.
• the palladium-coated surface usually becomes dewetted.
• droplets of water form on the surface and these tend to pull the palladium into clumps.
• the coated surface is immersed in the nickel plating bath, the palladium particles are further moved around on the surface. Too much nickel may be deposited on the areas where the palladium is "clumped" and too little or none where the palladium is missing.
• the present invention is based on the discovery that, if a wetting agent of a particular type is included in the rinsing solution which is applied between the palladium deposition step and the nickel plating step, the original palladium deposit is not disturbed during the rinsing operation and uniformity of the nickel plating is considerably enhanced.
• the wetting agent must be one which does not interfere with the nickel plating operation.
• Glacial acetic acid 950 ml/liter 48% HF 50 ml/liter by wt.
• PdClg 2 ml/liter The amount of PdClsolution may be varied between 1 about 05 and ml/liter. If too much PdCl is present, the'deposit of palladium metal tends to become nonuniform and this leads to'non-uniformity in the nickel 5 deposit.
• the amount of 48% HF can be varied between about ml and 150m].
• the glacial acetic acid and the hydrofluoric acid improve the wetting of the silicon sur-' face by the -palladium solution and thus permit more uniform deposition of palladium at low concentration. This requires less palladium.
• the slices are immersed in the above catalyst solution for 20 seconds at C.
• the time can be varied'between about 5 seconds and 60 seconds.
• the solution is reduced by the silicon and palladium deposits mostly on the silicon and not on the silicon dioxide. However, some palladium does occasionally deposit on the oxide.
• the slices are immersed in this solution for 25 seconds at 25C.
• the propanol is used as a wetting agent.
• Other wetting agents such as other lower molecular weight alcohols (i.e., up to C which do not interfere with the subsequent nickel deposition, may be substituted. Higher molecular weight alcohols can also be used.
• the presence of the wetting agent prevents water droplets from forming and thus it prevents the rather loosely held palladium from being moved around on the surface.
• the amount used should be at least about 10% by volume of the rinsing solution. As the molecular weight rises, the amount of the alcohol used can be correspondingly less.
• the slices are immersed in a nickel plating bath which may have a composition such as the following, per liter of solution.
• the solvent used is deionized water.
• the slices are immersed in this solution for 3 minutes at 80C.
• the glycolate and the acetate are chelating agents. Other chelating agents may be used.
• the ammonium acetate is included to complex any palladium salt that may have been dragged over from the palladium catalyst solution despite thorough rinsing.
• the glycolate complexes the nickel. Any soluble nickel salt may be used and the concentration is not critical. Any conventional reducing agent for nickel may be used in place of the hypophosphite. Other examples are amine boranes and hydrazine.
• the pH range may be either 3.8 5.1 or 7.5 10.5.
• a coating of a sensitizing agent such as tin, must first be deposited. This must be ladium, in an aqueous solution containing a wetting agent that does not interfere with the subsequent electroless deposition of said metal on said surface.

Landscapes

• Chemical & Material Sciences (AREA)
• General Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Chemically Coating (AREA)

Priority Applications (3)

Applications Claiming Priority (1)

Publications (1)

Family

ID=23398564

Family Applications (1)

Country Status (3)

Cited By (12)

Citations (6)

• 1973
  • 1973-04-30 US US355720A patent/US3877981A/en not_active Expired - Lifetime
• 1974
  • 1974-04-24 JP JP49047042A patent/JPS5239766B2/ja not_active Expired
  • 1974-04-29 BE BE143758A patent/BE814359A/fr unknown

Patent Citations (6)

Also Published As

Similar Documents