SiC Substrate Backside Dislocation Control for Yield
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for manufacturing silicon carbide semiconductor devices fail to sufficiently improve yield due to inadequate control of dislocation density, particularly on the backside surface of the substrate, leading to warpage and positional misalignment issues during thermal and film-forming processes.
Innovation Solution
A method involving a silicon carbide substrate with a hexagonal crystal structure, where the backside surface has an off-angle of ±8° or smaller relative to the {0001} plane, and is characterized by a low density of luminous regions in specific wavelength ranges when irradiated with excitation light, ensuring reduced dislocation density and minimal warpage, thereby improving yield by reducing positional misalignment in lithography steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If only the density of dislocations in the front-side surface of the substrate is reduced, then the dislocation density in the epitaxial film is reduced, but the yield of the semiconductor device is not sufficiently improved due to warpage and positional misalignment caused by high dislocation density in the backside surface
Solution Approach 1:
The patent applies local quality by differentiating the quality requirements between the front-side surface and backside surface of the substrate. Specifically, it requires reducing dislocation density in both surfaces but with different target values: the front-side surface (where the epitaxial film is formed) requires dislocation density of 1×10^8 cm^-2 or less, while the backside surface (where electrodes are formed) requires dislocation density of 5×10^3 cm^-2 or less. This localized differentiation of quality standards resolves the contradiction by addressing the specific needs of each surface to simultaneously achieve low dislocation density and high device yield.
Solution Approach 2:
The patent applies preliminary action by performing dislocation density measurement and evaluation on the backside surface before the device forming process. By measuring the density of luminous regions (which correlate with dislocation density) in advance using photoluminescence measurement, and selecting substrates that meet the specified criteria (off-angle of ±8° or less and luminous region density indicating 5×10^3 cm^-2 or less dislocation density), the patent prevents warpage and positional misalignment issues from occurring during subsequent thermal and lithography processes, thereby ensuring high device yield.
2Stability of the object's composition
If the dislocation density in the backside surface is high, then the substrate undergoes warpage during thermal processes, but controlling the off-angle and reducing dislocation density increases manufacturing complexity
Solution Approach 1:
The patent replaces direct mechanical measurement of dislocation density with photoluminescence measurement. Instead of using complex mechanical or optical microscopy methods to directly observe and count dislocations, the patent uses photoluminescence measurement to detect the density of luminous regions, which correlate with dislocation density. This substitution simplifies the measurement process while providing sufficient information to control substrate warpage and ensure device yield.
Solution Approach 2:
The patent changes the measurement parameter from direct dislocation density (which is difficult to measure) to luminous region density via photoluminescence (which is easier to measure). By establishing the correlation between luminous region density and dislocation density, and setting appropriate thresholds for luminous region density, the patent transforms a complex measurement problem into a simpler optical measurement task, thereby reducing manufacturing complexity while maintaining warpage control.
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 method effectively reduces the change in substrate warpage and improves yield by ensuring a low density of dislocations on the backside surface, leading to fewer positional misalignments and enhanced manufacturing efficiency.
Implementation Method 1
when irradiated with excitation light having energy equal to or greater than a band gap of silicon carbide, luminous regions in a wavelength range of 750 nm or greater are generated in the first main surface
Data Source
AI summary
A method for manufacturing a silicon carbide semiconductor device includes the following steps. There is prepared a silicon carbide substrate having a first main surface and a second main surface. On the first main surface, an electrode is formed. The silicon carbide substrate has a hexagonal crystal structure. The first main surface has an off angle of ±8° or smaller relative to a {0001} plane. The first main surface has such a property that when irradiated with excitation light having energy equal to or greater than a band gap of silicon carbide, luminous regions in a wavelength range of 750 nm or greater are generated in the first main surface at a density of 1×104 cm−2 or smaller. In this way, a yield of a silicon carbide semiconductor device can be improved.