International Business Machines Corporation

Globalfoundries Inc.

Invensas LLC

Charles C Goldsmith

Eric D Perfecto

Suryanarayana Kaja

Patrick William Dehaven

Michele S Legere

Mukta G Farooq

Emanuel Israel Cooper

Sung Kwon Kang

Henry Atkinson Nye, Iii

Stephen James Kilpatrick

Jeffery L Hurd

Carmen M Mojica

Chih-Chao Yang

Ping-Chuan Wang

Charles Leon Arvin

Ronald G Filippi

Da-Yuan Shih

Minhua Lu

Thomas Anthony Wassick

Kaushik Chanda

Krystyna Waleria Semkow

Donald W Henderson

Srinivasa S N Reddy

Karl J Puttlitz, Sr

Timothy A Gosselin

Muta G Farooq

Kenneth Bird

Jeffrey L Hurd, Deceased

Thomas Lester Nunes

Clare J McCarthy

Won K Choi

Sung K Kang

Embodiments of the invention include a lead-free solder interconnect structure and methods for making a lead-free interconnect structure. The structure includes a semiconductor substrate having a last metal layer, a copper pedestal attached to the last metal layer, a barrier layer attached to the copper pedestal, a barrier protection layer attached to the barrier layer, and a lead-free solder layer contacting at least one side of the copper pedestal.

Electromigration-resistant lead-free solder interconnect structures

Recrystallization and grain growth of metal, such as Cu, is achieved at higher anneal temperatures of 150&#xb0; C. to 400&#xb0; C., for example, for short anneal times of five to sixty minutes by forming a metal stress locking layer on the Cu before anneal and chemical-mechanical polishing. The stress locking layer extends the elastic region of the Cu by suppressing atom diffusion to the free surface, resulting in near zero tensile stress at room temperature after anneal. Stress voiding, which creates reliability problems, is thereby avoided. Improved grain size and texture are also achieved. The stress locking layer is removed after anneal by chemical-mechanical polishing leaving the Cu interconnect with low stress and improved grain size and texture.

Stress locking layer for reliable metallization

Methods of forming and assemblies having hybrid interconnection grid arrays composed of a homogenous mixture of Pb-free solder joints and Pb-containing solder paste on corresponding sites of a printed board. The aligned Pb-free solder joints and Pb-containing solders are heated to a temperature above a melting point of the Pb-free solder joint for a sufficient time to allow complete melting of both the Pb-free solder joints and Pb-containing solder paste and the homogenous mixing thereof during assembly. These molten materials mix together such that the Pb from the Pb-containing solder disperses throughout substantially the entire Pb-free solder joint for complete homogenization of the molten materials to form the homogenous hybrid interconnect structures of the invention.

Structure and method to gain substantial reliability improvements in lead-free BGAs assembled with lead-bearing solders

A first metal is plated onto a substrate comprising a second metal by immersing the substrate into a bath comprising a compound of the first metal and an organic diluent. The second metal is more electropositive than the first metal. The organic diluent has a boiling point higher than a eutectic point in a phase diagram of the first and second metals. The bath is operated above the eutectic point but below the melting point of the second metal. For example, bismuth is immersion plated onto lead-free tin-based solder balls, and subsequently redistributed by fluxless reflow. Plated structures are also provided.

Immersion plating and plated structures

A solder composition and associated method of formation. The solder composition comprises a substantially lead-free alloy that includes tin (Sn), silver (Ag), and copper. The tin has a weight percent concentration in the alloy of at least about 90%. The silver has a weight percent concentration X in the alloy. X is sufficiently small that formation of Ag Sn plates is substantially suppressed when the alloy in a liquefied state is being solidified by being cooled to a lower temperature at which the solid Sn phase is nucleated. This lower temperature corresponds to an undercooling &dgr;T relative to the eutectic melting temperature of the alloy. Alternatively, X may be about 4.0% or less, wherein the liquefied alloy is cooled at a cooling rate that is high enough to substantially suppress Ag Sn plate formation in the alloy. The copper has a weight percent concentration in the alloy not exceeding about 1.5%.

Lead-free tin-silver-copper alloy solder composition

A process for controlling grain growth in the microstructure of thin metal films (e.g., copper or gold) deposited onto a substrate. In one embodiment, the metal film is deposited onto the substrate to form a film having a fine-grained microstructure. The film is heated in a temperature range of 70-100&deg; C. for at least five minutes, wherein the fine-grained microstructure is converted into a stable large-grained microstructure. In another embodiment, the plated film is stored, after the step of depositing, at a temperature not greater than &minus;20&deg; C., wherein the fine-grained microstructure is stabilized without grain growth for the entire storage period.

Device produced by a process of controlling grain growth in metal films

A process for controlling grain growth in the microstructure of thin metal films (e.g., copper or gold) deposited onto a substrate. In one embodiment, the metal film is deposited onto the substrate to form a film having a fine-grained microstructure. The film is heated in a temperature range of 70-100&deg;C. for at least five minutes, wherein the fine-grained microstructure is converted into a stable large-grained microstructure. In another embodiment, the plated film is stored, after the step of depositing, at a temperature not greater than &minus;20&deg; C., wherein the fine-grained microstructure is stabilized without grain growth for the entire storage period.

Process of controlling grain growth in metal films

A process for controlling grain growth in the microstructure of thin metal films (e.g., copper or gold) deposited onto a substrate. In one embodiment, the metal film is deposited onto the substrate to form a film having a fine-grained microstructure. The film is heated in a temperature range of 70-100.degree. C. for at least five minutes, wherein the fine-grained microstructure is converted into a stable large-grained microstructure. In another embodiment, the plated film is stored, after the step of depositing, at a temperature not greater than -20.degree. C., wherein the fine-grained microstructure is stabilized without grain growth for the entire storage period.

A process for producing a low-stress electrolessly deposited layer of nickel yielding a clean nickel film and having a wettable surface is described. Diffusion is performed in a non-oxidizing environment, using a gas mixture containing nitrogen. The diffusion temperature is optimally set at a temperature of at least 500.degree. C., i.e., at least 150.degree. C. below typical prior art diffusion temperatures. The presence of nitrogen during diffusion changes the direction of the outgoing born away from the surface of the film, and eliminates the requirement that the nickel film be plated on refractory metal that contains glass, which was previously required to provide a media for the boron to diffuse into it for its subsequent removal.

Method for producing a low-stress electrolessly deposited nickel layer

Growing community of inventors

Poughkeepsie, NY, United States of America

Charles C Goldsmith