Inductively Coupled Plasma Etching for Microlens Shape Control
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Solution Overview
Problem
Existing methods for forming microlenses on semiconductor substrates, such as photolithography and capacitively coupled plasma etching, face challenges in increasing light collection efficiency due to limitations in reducing the distance between microlenses, particularly in the diagonal direction, and often result in a roughened surface that reduces light collection efficiency.
Innovation Solution
An inductively coupled plasma etching process using a mixture of CF4 and CHF3 gases is employed to modify the lens shape of microlenses on a semiconductor substrate, allowing for independent control of ion energy and density, and the use of a grounded Faraday shield to prevent capacitive coupling, resulting in a smoother surface and increased light collection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If photolithography techniques are used to form microlenses, then the manufacturing process is simple, but the distance between microlenses cannot be sufficiently reduced
Solution Approach 1:
The patent changes the etching process parameters by using inductively coupled plasma instead of capacitively coupled plasma, and by adjusting gas flow rates and pressure, to achieve both reduced microlens spacing and smooth surface finish. The inductive coupling mode allows independent control of ion density and energy, enabling precise parameter optimization.
Solution Approach 2:
The patent replaces the photolithography-based microlens formation with a plasma etching process that directly modifies the microlens shape. This substitution enables better control over microlens geometry and spacing through plasma process parameters rather than relying on photolithographic resolution limits.
2Length of moving object
If capacitively coupled plasma etching is used to reduce microlens distance, then the distance between microlenses is reduced, but the microlens surface becomes roughened
Solution Approach 1:
The patent substitutes capacitively coupled plasma etching with inductively coupled plasma etching. This replacement fundamentally changes the plasma-surface interaction mechanism, allowing independent control of ion density and ion energy. The inductive coupling mode produces lower ion energy at the substrate, reducing sputtering-induced surface roughening while maintaining effective etching for spacing reduction.
Solution Approach 2:
The patent changes the plasma coupling mode from capacitive to inductive, which fundamentally alters the relationship between ion density and ion energy. In inductive coupling, these parameters can be independently controlled through separate RF power settings, enabling optimization where high ion density achieves spacing reduction while low ion energy preserves surface smoothness.
3Productivity
If expensive etching gases such as SF6 and C4F8 are used, then the etching rate increases and microlens area increases, but the processing cost increases
Solution Approach 1:
The patent replaces expensive specialty etching gases (SF6, C4F8) with a mixture of cheaper, more common gases (CF4 and CHF3). This substitution maintains effective etching performance while significantly reducing processing costs. The CHF3 component provides sufficient etching rate without requiring the expensive fluorocarbon compounds.
Solution Approach 2:
The patent changes the chemical composition of the etching gas mixture to use more cost-effective components. By optimizing the ratio of CF4 to CHF3 and adjusting flow rates, the process achieves high etching rates comparable to expensive gases while using cheaper, more readily available gas components.
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
The inductively coupled plasma etching process effectively increases the size of microlenses while reducing the distance between them, enhancing light collection efficiency and maintaining a smooth surface, thus overcoming the limitations of previous techniques.
Implementation Method 1
performing a plasma etching process with the process gas on the substrate to modify the lens shape of the microlens objects on the substrate
Implementation Method 2
energizing the at least one inductive element to generate a substantially inductive plasma within the interior of the processing chamber
Implementation Method 3
providing a process gas to the interior of the processing chamber. The process gas includes a mixture of CF4 and CHF3. The method includes energizing the at least one inductive element to generate a substantially inductive plasma within the interior of the processing chamber
Data Source
AI summary
Methods for forming microlenses on a semiconductor substrate are provided. An inductively coupled plasma etch process using a process gas that includes a mixture of CF4 and CHF3 can be used to modify the lens shape of a plurality of microlens objects located on a semiconductor substrate to meet microlens specifications in terms of curvature, height, length, shape, and/or distance between adjacent microlens objects on the substrate. The inductively coupled plasma process can be performed in an inductively coupled plasma processing apparatus that includes a grounded Faraday shield to prevent any capacitive coupling during the plasma etching process to reduce sputtering of the microlens surface.