Wafer Level Package Cavities Polymer Walls Blanket Film
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Solution Overview
Problem
Conventional wafer level packaging techniques for semiconductor devices are costly and inefficient, requiring numerous process steps and often resulting in yield loss due to challenges in forming and sealing cavities around active devices.
Innovation Solution
A wafer level package with cavities is created using polymer walls and a blanket film, where polymer walls are formed around active devices to support a ceiling and a blanket film is applied to enclose them in a single batch process, reducing the need for sacrificial layers and individual lid placement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional wafer level packaging techniques are used to create cavities around active devices, then the devices can be packaged with protective cavities, but the manufacturing cost increases significantly (40-90% of total device cost) and the process becomes complex requiring numerous steps
Solution Approach 1:
The patent combines multiple packaging functions into a single integrated process. The mold compound serves both as protective encapsulation and as the cavity-forming structure itself, eliminating the need for separate sacrificial layers and multiple sealing steps. This merging of functions directly reduces process complexity while maintaining device protection.
Solution Approach 2:
The mold compound performs multiple functions simultaneously: it provides mechanical protection, defines the cavity geometry, seals around the active devices, and eliminates the need for separate sacrificial materials. This multi-functionality reduces the overall number of materials and process steps required.
2Reliability
If conventional methods with sacrificial layers and release holes are used, then cavities can be formed around active devices, but the manufacturing time increases and yield loss occurs due to challenges in complete sacrificial layer removal
Solution Approach 1:
The patent extracts and eliminates the sacrificial layer step entirely from the process. Instead of adding a sacrificial layer that must subsequently be removed through release holes, the design directly forms cavities using the mold compound, removing the problematic intermediate step that causes yield loss and extends manufacturing time.
Solution Approach 2:
The patent skips the entire sacrificial layer deposition and removal sequence. By rushing through to direct cavity formation with mold compound, the process eliminates the time-consuming steps of layer deposition, release hole formation, and sacrificial material extraction, thereby improving manufacturing efficiency.
3Reliability
If individual lids are placed over each active device in a pick and place process, then each device can be individually sealed, but the manufacturing time becomes very time consuming and costly
Solution Approach 1:
The patent merges individual device sealing into a single batch process. The mold compound is applied once to encapsulate multiple active devices simultaneously, forming individual cavities for each device in parallel rather than sequentially. This eliminates the time-consuming pick-and-place operations while maintaining individual device sealing integrity.
Solution Approach 2:
The patent performs preliminary action by applying the mold compound to all devices before any individual handling or placement operations. This preliminary encapsulation step establishes all cavities and seals simultaneously, eliminating the need for subsequent individual lid placement operations.
Data Source
AI summary
According to one exemplary embodiment, a method for forming a wafer level package includes fabricating an active device on a substrate in a semiconductor wafer, forming polymer walls around the active device, and applying a blanket film over the semiconductor wafer and the polymer walls to house the active device in a substantially enclosed cavity formed by the polymer walls and the blanket film. By way of examples and without limitation, the active device can be a microelectromechanical systems (“MEMS”) device, a bulk acoustic wave (“BAW”) filter, or a surface acoustic wave (“SAW”) filter. According to one embodiment, solder bumps can be applied to interconnect traces of the active device, and the semiconductor wafer can then be diced to form an individual die. According to another embodiment, the semiconductor wafer can be diced to form an individual die, then the individual die is wire bonded to a circuit board.