Solder Reflow Thermal Conductivity Control

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Solution Overview

Problem

In semiconductor device manufacturing, the existing methods for reflow processing of bumps, such as soldering, often result in surface unevenness and air bubbles, leading to reduced connecting strength and durability due to fine unevenness and air bubbles introduced during the process, which can be exacerbated by thermal stress in three-dimensional mounting and TSV technology.

Innovation Solution

A method involving a substrate processing apparatus that uses a reducing gas to remove the natural oxide film from the solder and a thermally conductive gas to melt the solder while maintaining specific thermal conductivities in the processing chamber, ensuring precise temperature control and minimizing thermal stress, thereby improving the quality and uniformity of the reflow process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the solder is heated to melting point to planarize the surface, then the surface uniformity is improved, but air bubbles are introduced and connecting strength decreases

Engineering Contradiction:

Improvesurface uniformityVSAvoidconnecting strength

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies preliminary action by removing the oxide film from the solder surface before heating to melting point. This is achieved by controlling the atmospheric composition (using reducing atmosphere or vacuum) prior to the reflow heating process. By eliminating the oxide film in advance, the subsequent melting process planarizes the surface without introducing air bubbles, thus maintaining connecting strength while achieving surface uniformity.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If conventional reflow processing is used, then the solder surface is planarized, but fine unevenness remains and air bubbles are trapped

Engineering Contradiction:

Improvesurface planarizationVSAvoidair bubbles and fine unevenness

Core Design Contradiction:

Manufacturing precisionVSObject-generated harmful factors

Solution Approach 1:

The patent applies parameter changes by modifying the atmospheric parameters (composition, pressure, thermal conductivity) during the reflow process. Specifically, it controls the atmosphere to be reducing or vacuum state, and adjusts the thermal conductivity of the atmosphere to optimize heat transfer. These parameter changes enable complete oxide removal and prevent air bubble formation during melting, achieving superior surface planarization without the harmful effects of conventional reflow.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If high thermal conductivity gas is used during melting, then heating efficiency is improved, but thermal stress on substrate increases

Engineering Contradiction:

Improveheating efficiencyVSAvoidthermal stress

Core Design Contradiction:

ProductivityVSStress or pressure

Solution Approach 1:

The patent applies local quality by creating different atmospheric conditions in different spatial zones or at different stages of the process. It uses high thermal conductivity atmosphere (such as hydrogen or helium) specifically during the melting phase where efficient heat transfer is critical, while controlling the overall thermal profile to protect the substrate. The atmosphere composition and thermal conductivity are optimized locally at the solder region without uniformly heating the entire substrate, thus achieving high heating efficiency while minimizing thermal stress.

Inventive Principle:

Principle #3Local quality

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach effectively removes natural oxide films, planarizes the solder surface, prevents substrate damage, and reduces thermal stress, enabling uniform processing even for substrates in a dice state, while enhancing manufacturing quality and throughput by controlling thermal conductivity and heat flux.

Implementation Method 1

reducing the oxygen-containing film by supplying a reducing gas into the processing chamber

Methodology Applied

Scientific EffectChemical reduction: Reduction

Implementation Method 2

melting the solder by supplying a thermally conductive gas into the processing chamber while maintaining the thermal conductivity of the inner atmosphere of the processing chamber at a second thermal conductivity higher than the first thermal conductivity

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Data Source

PatentUS9974191B2Method of manufacturing semiconductor device, substrate processing apparatus and recording medium

Publication Date: 2018.05.15 KOKUSAI DENKI KK

AI summary

Manufacturing quality of a semiconductor device can be improved, and manufacturing throughput can be improved. A method of manufacturing a semiconductor device includes (a) placing a substrate on a substrate supporting unit installed in a processing chamber, the substrate having thereon a solder with an oxygen-containing film on a surface thereof, (b) reducing the oxygen-containing film by supplying a reducing gas into the processing chamber while maintaining a thermal conductivity of an inner atmosphere of the processing chamber at a first thermal conductivity, and (c) melting the solder by supplying a thermally conductive gas into the processing chamber while maintaining the thermal conductivity of the inner atmosphere of the processing chamber at a second thermal conductivity higher than the first thermal conductivity.