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Acid copper electroplating bath and method for electroplating low internal stress and good ductility copper deposits

Inactive Publication Date: 2017-03-09
ROHM & HAAS ELECTRONICS MATERIALS LLC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The patent describes a method for electroplating copper onto substrates with a low internal stress and high ductility. The plating process uses a special electroplating bath that includes copper ions, electrolytes, polyallylamines, a specific chemical, and a suppressor. The resulting copper deposits have good strength and ductility, making them resistant to cracking and bowing when placed on thin substrates. This method allows for the production of reliable, high-quality copper films on a variety of materials.

Problems solved by technology

This stress and its relief can be problematic.
Stress can lead to poor adhesion of the deposit to the substrate resulting in blistering, peeling or cracking.
This is especially the case for difficult to adhere substrates, such as semiconductor wafers or those with relatively smooth surface topography.
In general, the magnitude of stress is proportional to deposit thickness thus it can be problematic where thicker deposits are required or indeed may limit the achievable deposit thickness.
Transformation of the grain structure during such self annealing concurrently results in a change in the deposit stress, often increasing it.
Not only is internal stress problematic in itself but is typically subject to change on aging as the deposit self anneals with time resulting in unpredictability.
Such empirical means of reducing stress have been employed though typically are not consistent or compromise the efficiency of the electroplating process.
Ideally, a copper deposit has a relatively low internal stress and a high ductility; however, there is typically a tradeoff between internal stress and ductility.

Method used

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  • Acid copper electroplating bath and method for electroplating low internal stress and good ductility copper deposits
  • Acid copper electroplating bath and method for electroplating low internal stress and good ductility copper deposits
  • Acid copper electroplating bath and method for electroplating low internal stress and good ductility copper deposits

Examples

Experimental program
Comparison scheme
Effect test

example 1

[0033]The following aqueous acid copper electroplating baths were prepared.

TABLEComponentBath 1Bath 2Bath 3Bath 4Copper sulfate160g / L160g / L160g / L160 g / LSulfuric acid150 g / L150g / L150g / L150g / LChloride (as60ppm60ppm60 ppm60ppmhydrochloric acid)Bis-sodium04ppm4 ppm4ppmsulfopropyl-disulfide3-mercapto-1-06ppm06ppmpropane sulfonicacid, sodium salt(O-175 ppm000Ethydithio-carbonato)-S-(3-sulfopropyl)-ester, potassium saltPolyoxy-alkylene0.15g / L0.15g / L0.15g / L0.15 g / Lglycol (PolyMax ™PA-66 / LC solution)Polyethylene 0.18g / L0.18g / L0.18g / L0.18g / Lglycol(PEG 12000)Polyallylamine 1.25ppm000(Mw = 15000)Linear0000.75 ppmpolyethyleneimine(Mw = 2000)

[0034]The components of the copper electroplating baths were made up using conventional laboratory procedures where organics were added to water followed by adding the inorganic components. Stirring or agitation with heat application at temperatures of below 30° C. was done to be certain that all of the components were solubilized in the water. The baths were...

example 2

[0035]Two flexible copper alloy foil test strips were coated on one side with a dielectric to enable single sided plating on the uncoated side. The test strips were taped to a support substrate with platers tape and placed in a haring cell containing an acid copper plating bath having the formulation of Bath 1 of the table in Example 1. The bath was maintained at room temperature. A copper metal strip was used as an anode. The test foil strips and anode were connected to a rectifier. The test foil strips were copper plated at an average current density of 2 ASD to deposit a thickness of 5 μm of copper on the uncoated side of each strip. After plating was completed the test strips were removed from the haring cell, rinsed with wafer, dried and the platers tape was removed from the test strips. The internal stress of the copper deposit on the strips was determined to be 838 psi. The stress was determined using the equation S=U / 3TxK, where S is stress in psi, U is number of increments ...

example 3

Comparative

[0037]Two flexible copper / beryllium alloy foil test strips were coated on one side with a dielectric to enable single sided plating on the uncoated side. The test strips were taped to a support substrate with platers tape and placed in a haring cell containing acid copper plating Bath 2. The bath was at room temperature. A copper metal strip was used as an anode. The test foil strips and anode were connected to a rectifier. The test foil strips were copper plated at an average current density of 2 ASD to deposit a copper thickness of five μm on the uncoated side of each strip. After plating was completed the test strips were removed from the haring cell, rinsed with wafer, dried and the platers tape was removed from the test strips. The test strips were inserted at one end into screw clamps of the deposit stress analyzer. The internal stress of the copper deposit on the strips was determined to be 211 psi. The stress was determined using the equation S=U / 3TxK, where S is ...

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Abstract

Acid copper electroplating baths provide improved low internal stress copper deposits with good ductility. The acid copper electroplating baths include one or more polyallylamines and certain sulfur containing accelerators. The acid copper electroplating baths may be used to electroplate thin films on relatively thin substrates to provide thin film copper deposits having low internal stress and high ductility.

Description

FIELD OF THE INVENTION[0001]The present invention is directed to a copper electroplating bath for electroplating low internal stress copper deposits having good ductility. More specifically, the present invention is directed to a copper electroplating bath for electroplating low internal stress copper deposits having good ductility where the acid copper electroplating bath includes polyallylamine in combination with certain sulfur containing accelerators.BACKGROUND OF THE INVENTION[0002]Internal or intrinsic stress of electrodeposited metals is a well known phenomenon caused by imperfections in the electroplated crystal structure. After the electroplating operation such imperfections seek to self correct and this induces a force on the deposit to contract (tensile strength) or expand (compressive stress). This stress and its relief can be problematic. For example, when electroplating is predominantly on one side of a substrate it can lead to curling, bowing and warping of the substr...

Claims

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Application Information

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IPC IPC(8): C25D3/38
CPCC25D3/38C25D7/12C25D7/00C25D1/04
Inventor WEI, LINGYUNKAO, YU HUAHAZEBROUCK, REBECCACORONA, ROBERTLEFEBVRE, MARK
Owner ROHM & HAAS ELECTRONICS MATERIALS LLC