Photosensitive Mold Structures for TSV Encapsulation
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Solution Overview
Problem
Encapsulation techniques during semiconductor device manufacturing often result in mold compound flowing onto the circuit side of through-substrate vias (TSV) dies, causing 'mold flash' that can lead to poor electrical connections or opens, making it difficult and costly to remove without damaging the circuitry.
Innovation Solution
A method using a photosensitive mold compound backed by a supporting base film, which is patterned and formed into controlled volume structures to prevent mold flash by using a press die under controlled pressure and heat, ensuring the mold compound does not flow over the TSV surfaces during curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If encapsulation is performed using conventional mold compound application, then the TSV die is protected and electrical connections are established, but mold compound flows onto the circuit side causing mold flash that degrades electrical connections
Solution Approach 1:
A photosensitive mold compound is applied to the TSV die before mounting, and a protective layer is formed over the circuit side. The photosensitive compound is then cured through the protective layer using UV radiation, creating a cured mold compound structure that prevents flash during subsequent encapsulation processes. This preliminary curing action establishes the mold compound in a controlled state before the harmful flash can occur.
Solution Approach 2:
A protective layer acts as an intermediary between the mold compound and the circuit side of the TSV die. This protective layer allows UV radiation to pass through for curing the photosensitive mold compound while preventing the mold compound from flowing onto the circuit side during encapsulation, thus mediating between the need for electrical connection protection and the need to prevent mold flash.
2Productivity
If back grinding is used to thin the wafer to expose TSV tips, then the substrate thickness is reduced efficiently, but mechanical damage and contamination are generated
Solution Approach 1:
The invention changes the physical state and properties of the mold compound by using a photosensitive material that can be cured through UV radiation. This parameter change allows the mold compound to be applied in a uncured state for easy formation, then transformed to a cured state that provides protection without requiring aggressive back grinding, thereby reducing mechanical damage and contamination while maintaining productivity.
Solution Approach 2:
The invention replaces the mechanical back grinding process with a chemical/photchemical approach using photosensitive mold compound that cures through UV exposure. This substitution eliminates or reduces the need for mechanical substrate removal, thereby reducing mechanical damage and contamination while achieving the desired substrate thinning and TSV exposure through the curing process instead.
3Reliability
If a protective layer is formed over the back side to expose TSV during singulation, then TSV protection is achieved, but the process complexity increases
Solution Approach 1:
The photosensitive mold compound serves multiple functions: it acts as the encapsulation material, provides the protective layer structure, enables UV curing through the protective layer, and prevents mold flash during encapsulation. This multi-functionality reduces the need for separate protective layers and process steps, thereby reducing overall process complexity while maintaining TSV protection.
Solution Approach 2:
The invention merges the mold compound application and protective layer formation into a single step by applying the photosensitive mold compound that will be cured through the protective layer. This combining of steps reduces process complexity while achieving both TSV protection and encapsulation functionality simultaneously.
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 reduces electrical opens, decreases rework and scrap, and lowers manufacturing costs by containing the mold compound and preventing it from covering the TSV surfaces, allowing for reliable electrical connections.
Implementation Method 1
A layer of photosensitive mold compound is exposed to patterned radiation, such as ultraviolet (UV) radiation
Implementation Method 2
The press die is urged toward the TSV die and receiving substrate with controlled pressure and heat to flow the mold structures
Data Source
AI summary
A method for forming a semiconductor device can include providing a patterned layer of mold compound having a plurality of individual mold compound structures overlying a base film. The plurality of mold compound structures are aligned with a plurality of semiconductor dice to interpose the individual mold compound structures between the plurality of semiconductor dice. A pressure is applied to the individual mold compound structures to fill spaces between each of the plurality of semiconductor dice with the mold compound. The mold compound structures can be formed on the base film using a photosensitive mold compound. The mold compound structures can also be formed through the use of a patterned mask and a screen printing process.