Semiconductor Through Electrode Formation via Back-Surface Paste Embedding
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Solution Overview
Problem
Conventional methods for forming through electrodes in semiconductor chips face issues such as bump adhesion to adhesives during wafer peeling, leading to yield degradation and process complexity, especially when thinning semiconductor wafers.
Innovation Solution
The method involves forming electrode forming holes and bump holes on both surfaces of a semiconductor wafer, aligning and embedding conductive paste using bump forming masks, detaching the masks, and dividing the wafer to form through electrodes and bumps without adhesion-related issues, simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the front surface of the semiconductor wafer is attached onto the support table using adhesive to form through electrodes, then the through electrodes and bumps can be formed, but the bumps on the front surface adhere to the adhesive and are hard to peel off, causing dropping off of bumps and cracking of the wafer
Solution Approach 1:
The patent applies preliminary action by forming through electrodes and bumps on the back surface of the wafer before peeling it from the support table. The conductive paste is embedded and cured while the wafer is still attached, ensuring bumps are formed on the back surface rather than the front surface that contacts the adhesive. This preliminary formation of electrical connections eliminates the adhesion problem during peeling.
Solution Approach 2:
The patent inverts the conventional approach by forming through electrodes and bumps on the back surface of the wafer instead of the front surface. The bump forming mask is applied to the back surface, and conductive paste is embedded from the back surface side. This inversion ensures that bumps are formed on the surface away from the adhesive contact, preventing adhesion issues during peeling.
2Reliability
If conventional methods are used to form through electrodes with bumps on the front surface, then electrical connections are established, but the process becomes complex requiring back surface planarization and multiple masking steps
Solution Approach 1:
The patent performs preliminary actions by forming the entire through electrode structure including bumps on the back surface before wafer peeling. The bump forming mask is applied, conductive paste is embedded and cured, and through electrodes are formed all while the wafer remains attached to the support table. This eliminates the need for subsequent back surface planarization and reduces process complexity.
Solution Approach 2:
The patent merges multiple process steps into a single integrated flow. The formation of through electrodes and bumps is combined with the wafer attachment state, eliminating the need for separate back surface planarization and re-attachment steps. The bump forming mask serves dual purposes as both the masking layer and the template for bump formation.
3Length of moving object
If the wafer is thinned to 30 μm to 70 μm thickness, then chip thinning is achieved, but the wafer becomes more susceptible to cracking and bump adhesion issues during the through electrode formation process
Solution Approach 1:
The patent applies preliminary action by completing all through electrode and bump formation operations while the wafer is still attached to the support table in its thinned state. The conductive paste is embedded and cured before peeling, ensuring that the thinned wafer does not undergo mechanical stress from subsequent processing steps. This protects the mechanically vulnerable thinned wafer.
Solution Approach 2:
The patent inverts the process sequence by forming bumps on the back surface of the thinned wafer rather than the front surface. This inversion allows the thinned wafer to maintain its mechanical integrity during processing, as the bump formation occurs on the surface away from the adhesive contact that would cause stress concentration and cracking in thinned wafers.
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 prevents bump dropping and wafer cracking, enhances yield, and eliminates the need for back surface planarization, thereby simplifying the through electrode formation process in semiconductor chips.
Implementation Method 1
embedding conductive paste into the bump holes of the bump forming masks superimposed over the front and back surfaces and the electrode forming holes of the semiconductor wafer
Data Source
AI summary
A method for manufacturing a semiconductor chip having through electrodes includes forming, in a semiconductor wafer, a plurality of electrode forming holes for forming through electrodes, superimposing bump forming masks formed with a plurality of bump holes over the front and back surfaces of the semiconductor wafer respectively so that the electrode forming holes and the bump holes are brought into alignment, placing the semiconductor wafer with the bump forming masks superimposed thereon over a stage, embedding conductive paste into the bump holes and the electrode forming holes from the bump forming mask disposed over the surface on the side opposite to the stage, of the semiconductor wafer, detaching the bump forming masks from the semiconductor wafer after the conductive paste has been embedded, and dividing the semiconductor wafer into fractions after the bump forming masks have been detached.