Semiconductor Bonding Structure Copper Pillar Diffusion
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Solution Overview
Problem
The existing semiconductor flip-chip bonding process using solder faces challenges such as inability to reduce solder diameter effectively, leading to increased pitch between metal pillars, warpage of chips due to high-temperature reflow, and oxidation of metal pillars, which are costly to mitigate in vacuum environments.
Innovation Solution
A semiconductor bonding structure and process that employs copper pillars with diffusion layers of titanium, allowing copper-to-copper bonding at low temperatures without solder, reducing pitch and preventing warpage through interdiffusion and oxide formation at specific interfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If solder is used for bonding in flip-chip process, then bonding is achieved, but the pitch between metal pillars cannot be effectively reduced
Solution Approach 1:
The invention extracts and eliminates the solder material from the bonding process, achieving direct copper-to-copper bonding between pillars. This removal of solder enables finer pitch between metal pillars while maintaining bonding effectiveness through diffusion bonding mechanisms at low temperatures.
Solution Approach 2:
The invention changes the bonding temperature parameter from high temperature (above 300°C for solder reflow) to low temperature (below 200°C for diffusion bonding). This parameter change enables direct metal bonding without solder, allowing reduced pitch between pillars while avoiding warpage issues.
2Reliability
If high-temperature reflow is performed to melt solder, then bonding is achieved, but chips warp and metal pillars oxidize
Solution Approach 1:
The invention changes the bonding temperature from high (above 300°C) to low (below 200°C), eliminating warpage and oxidation problems while achieving reliable bonding through diffusion mechanisms. The low temperature prevents thermal stress that causes warpage and avoids oxidation of metal pillars.
Solution Approach 2:
The invention introduces a diffusion layer as an intermediary between copper pillars, enabling bonding at low temperatures without direct high-temperature contact. This diffusion layer mediates the bonding process, allowing atomic diffusion to create strong bonds without the harmful effects of high temperature.
3Object-affected harmful factors
If high-temperature bonding is performed in vacuum environment to prevent oxidation, then oxidation is reduced, but manufacturing cost increases and warpage remains
Solution Approach 1:
The invention changes the temperature parameter to low temperature (below 200°C), which inherently prevents oxidation without requiring vacuum environments. This eliminates the need for costly vacuum equipment while also preventing warpage, achieving both oxidation protection and cost reduction.
Solution Approach 2:
The invention extracts and eliminates the requirement for vacuum environments by using low-temperature diffusion bonding. This removal of the vacuum requirement significantly reduces manufacturing cost while maintaining protection against oxidation through the low-temperature process.
4Manufacturing precision
If solder diameter is decreased to reduce pitch, then pitch between pillars is reduced, but solder becomes difficult to handle and bond reliably
Solution Approach 1:
The invention extracts solder from the bonding process entirely, using direct copper-to-copper diffusion bonding instead. This eliminates the limitations of solder diameter and enables consistent reliable bonding at fine pitches without the handling and bonding difficulties associated with small solder balls.
Solution Approach 2:
The invention replaces the mechanical solder ball placement and reflow melting process with a diffusion bonding mechanism. This substitution enables precise pitch control through direct metal contact and atomic diffusion, achieving reliable bonding at fine pitches without the constraints of solder ball handling.
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
Achieves fine-pitch copper-to-copper bonding at low temperatures, preventing warpage and oxidation, while eliminating the need for vacuum environments, resulting in a robust bonding effect with high thrust test values.
Implementation Method 1
the first metal of the first pillar is diffused towards the second pillar, the first metal of the second pillar is diffused towards the first pillar
Implementation Method 2
an oxide of a second metal, wherein the content percentage of the first metal in the first interface is less than that of the first metal in the intermediate area
Data Source
AI summary
The disclosure relates to a semiconductor bonding structure and process and a semiconductor chip. The semiconductor bonding structure includes a first pillar, a first interface, an intermediate area, a second interface and a second pillar in sequence. The first pillar, the second pillar and the intermediate area include a first metal. The first interface and the second interface include the first metal and an oxide of a second metal. The content percentage of the first metal in the first interface and the second interface is less than that of the first metal in the intermediate area.