Semiconductor Layer Thickness Homogenization via Redox-Controlled Etching
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Solution Overview
Problem
Existing methods for thinning and planarizing semiconductor layers on SOI wafers are time-intensive and costly, often requiring elaborate equipment and light sources, and struggle to achieve homogeneous layer thickness near the wafer edge.
Innovation Solution
A method that uses a liquid etchant with a redox potential adjusted based on the desired final thickness, allowing for controlled material erosion without light or external electrical voltage, using etchants like hydrofluoric acid and ammonium fluoride to achieve a slow etching rate when the desired thickness is reached, enabling homogenization of the semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If scanning methods with light sources or nozzles are used to achieve locally varying etching erosion, then layer thickness homogeneity can be improved, but the process becomes very time-intensive and cost-intensive
Solution Approach 1:
The semiconductor layer itself serves as the control element for the etching process. Thicker regions generate more charge carriers under illumination, automatically receiving higher etching rates, while thinner regions generate fewer charge carriers and receive lower etching rates. This self-regulating mechanism eliminates the need for external scanning systems, light sources, or complex movement mechanisms, thereby dramatically improving productivity while maintaining layer thickness homogeneity.
2Manufacturing precision
If scanning methods are used to achieve locally varying etching erosion, then layer thickness homogeneity can be improved, but elaborate movement of light source or nozzle is required
Solution Approach 1:
The method eliminates all movement mechanisms by making the semiconductor layer itself the control element. The layer's own thickness distribution determines the spatial distribution of charge carriers generated by uniform illumination, which in turn automatically controls the local etching rates. This self-regulating approach removes the need for scanning light sources, moving nozzles, or any elaborate movement mechanisms, significantly simplifying the device complexity.
Solution Approach 2:
Instead of using external scanning mechanisms to create local variations in etching conditions, the method inverts the approach by using the semiconductor layer's own properties (thickness-dependent charge carrier generation) to create the desired local etching variations. The control information is embedded in the workpiece itself rather than being imposed by external scanning systems.
3Manufacturing precision
If additional equipment such as thickness measurement devices and masks are used for planarization, then manufacturing precision can be improved, but additional outlay increases costs
Solution Approach 1:
The semiconductor layer serves as its own measurement and control device. The thickness distribution of the layer directly determines the charge carrier generation pattern under uniform illumination, which automatically creates the appropriate etching rate distribution. This eliminates the need for separate thickness measurement equipment, custom masks, or complex control systems, thereby reducing process costs while maintaining high manufacturing precision.
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 method effectively homogenizes the semiconductor layer without the need for complex equipment, achieving a controlled etching rate that ensures the desired thickness is maintained within a 10% margin, reducing costs and improving edge exclusion homogeneity.
Implementation Method 1
the surface of the semiconductor layer is exposed to the action of an etchant whose redox potential is adjusted as a function of the material and the desired final thickness of the semiconductor layer
Implementation Method 2
The etching rate is self-regulating, because the etching rate depends on the number of holes (i.e. defect electrons, that is to say positive charge carriers) which are generated by the light
Data Source
AI summary
To reduce and homogenize the thickness of a semiconductor layer which lies on the surface of an electrically insulating material, the surface of the semiconductor layer is exposed to the action of an etchant whose redox potential is adjusted as a function of the material and the desired final thickness of the semiconductor layer, so that the material erosion per unit time on the surface of the semiconductor layer due to the etchant becomes less as the thickness of the semiconductor layer decreases, and is only from 0 to 10% of the thickness per second when the desired thickness is reached. The method is carried out without the action of light or the application of an external electrical voltage.