MEMS Chip Package With Concave Sidewall for Light Entry
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Solution Overview
Problem
In chip packages with a photosensitive function, the separation of the metal layer from the semiconductor substrate during manufacturing can damage the MEMS structure, and the presence of a semiconductor substrate portion between the opening and metal layer obstructs light entry, reducing sensing capability, while etching reactions produce pollutants.
Innovation Solution
A chip package design with a semiconductor substrate and metal layer featuring a concave sidewall and a staircase structure, along with a manufacturing method that includes forming through holes and etching to maintain the metal layer's integrity and minimize substrate removal, using specific gases for etching, and applying a patterned photoresist or oxide layer to control oxygen reaction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a portion of the semiconductor substrate is left remaining between the opening and the metal layer, then the metal layer is prevented from separating from the semiconductor substrate, but light entry into the MEMS structure is obstructed, reducing sensing capability
Solution Approach 1:
The patent removes the remaining semiconductor substrate portion between the opening and metal layer after the metal layer is formed, extracting the obstructing element while maintaining the metal layer attachment through the previously formed structure. This resolves the contradiction by eliminating the light obstruction while the metal layer remains attached due to the formation sequence.
Solution Approach 2:
The metal layer is formed on the semiconductor substrate before the opening is etched through the substrate. This preliminary formation of the metal layer ensures it remains attached during subsequent substrate removal, while allowing complete light entry after the opening is created.
2Productivity
If the metal layer forms the MEMS structure and the semiconductor substrate is etched, then the MEMS structure is created, but a large area of the metal layer reacts with oxygen, producing pollutants remaining in the manufacturing equipment
Solution Approach 1:
The patent applies a protective layer selectively to specific regions of the metal layer, creating local quality differences. The protective layer covers only the metal layer areas that would otherwise react with oxygen during etching, preventing pollutant formation in those specific locations while allowing the MEMS structure fabrication to proceed.
Solution Approach 2:
The patent converts the harmful oxygen reaction into a beneficial protective oxidation layer formed in advance. By deliberately forming an oxide layer on the metal layer before etching, the harmful oxygen reaction is controlled to create a protective barrier that prevents further unwanted reactions and pollutant formation during subsequent manufacturing steps.
3Loss of substance
If the metal layer is made thin to reduce material usage, then material cost is reduced, but the metal layer becomes more susceptible to separation from the semiconductor substrate
Solution Approach 1:
The metal layer is formed on the semiconductor substrate before the opening is etched through the substrate. This preliminary formation ensures that even thin metal layers remain attached to the substrate during subsequent processing, as the attachment is established before the substrate is thinned or opened.
Solution Approach 2:
The patent introduces an adhesive layer or protective layer as an intermediary between the thin metal layer and the semiconductor substrate or environment. This intermediary layer provides additional mechanical support and attachment strength to the thin metal layer, preventing separation while allowing minimal metal material usage.
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
Prevents metal layer separation and enhances light entry into the MEMS structure, improving sensing capability and reducing manufacturing pollutants by maintaining the metal layer's integrity and controlling oxygen reaction.
Implementation Method 1
Before the MEMS structure of the metal layer is formed and before the remaining portion of the semiconductor substrate is etched, a patterned photoresist or an oxide layer may be disposed on the metal layer. Thus, only a portion of the metal layer above the opening reacts with oxygen, and thus, pollutants remaining in a manufacturing equipment may be reduced.
Data Source
AI summary
A chip package includes a semiconductor substrate and a metal layer. The semiconductor substrate has an opening and a sidewall surrounding the opening, in which an upper portion of the sidewall is a concave surface. The semiconductor substrate is made of a material including silicon. The metal layer is located on the semiconductor substrate. The metal layer has plural through holes above the opening to define a MEMS (Microelectromechanical system) structure, in which the metal layer is made of a material including aluminum.