Diamond Substrate Separation via Ion Implantation and AC Etching
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Solution Overview
Problem
Current methods for separating large single-crystal diamond substrates are inefficient, limiting their size to around 5×5 mm due to slow etching rates and surface damage from ion implantation, and require multiple steps to achieve satisfactory purity and separation.
Innovation Solution
A method involving ion implantation to form a non-diamond layer followed by etching with an alternating-current (AC) voltage in an electrolytic solution, which allows for rapid separation of the diamond surface layer or grown layer, enabling the production of large single-crystal diamond substrates exceeding 5×5 mm in size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If oxygen ions are implanted at high energy levels to form a non-diamond layer for separation, then the etching rate initially increases, but the supply of oxygen decreases as etching proceeds farther inside, reducing the etching rate
Solution Approach 1:
The patent applies preliminary action by implanting oxygen ions at high energy levels (several MeV) before the etching process to pre-form a non-diamond layer throughout the crystal. This preliminary ion implantation ensures that oxygen is distributed throughout the crystal structure in advance, allowing the etching process to proceed uniformly and deeply without the supply of oxygen becoming a limiting factor as etching progresses inward.
2Length of stationary object
If a sufficient amount of oxygen ions are implanted beforehand to enable deep etching, then the etching can proceed farther inside the crystal, but the surface layer of the diamond is damaged by radiation
Solution Approach 1:
The patent applies parameter changes by carefully controlling the ion implantation parameters, specifically using oxygen ions at high energy levels (several MeV) with optimized dosing. This parameter optimization allows the ion beam to penetrate deeply into the crystal to form the non-diamond layer throughout the bulk, while the high energy disperses the damage over a larger volume, minimizing surface layer damage compared to lower energy implantation that would concentrate damage near the surface.
3Reliability
If electrochemical etching is performed by applying DC voltage to remove the non-diamond layer, then the diamond film can be separated from the substrate, but as the substrate size increases, the etching rate inside the crystal decreases, requiring a very long period of time for etching
Solution Approach 1:
The patent applies mechanics substitution by replacing the conventional DC electrochemical etching method with an AC voltage application method. The AC voltage (at frequencies such as 60 Hz or higher) creates alternating electric fields that enhance the etching efficiency throughout the crystal volume, substituting the slow, diffusion-limited DC process with a more dynamic process that maintains higher etching rates even in larger substrates, thereby significantly reducing the overall etching time.
4Productivity
If a large single-crystal diamond substrate is used for vapor-phase synthesis, then large single-crystal substrates can be produced at high growth rate and yield, but separation of the large single-crystal substrate from the vapor-phase synthetic diamond in reusable form is strongly desired
Solution Approach 1:
The patent applies the blessing in disguise principle by utilizing the harmful non-diamond layer formed by high-energy oxygen ion implantation as a beneficial separation interface. The ion implantation creates a distinct non-diamond layer that serves as a preferential etching plane, allowing the vapor-phase grown diamond layer to be easily and cleanly separated from the seed crystal substrate. This converts the potentially harmful radiation damage into a useful feature that facilitates substrate reuse.
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 enables the efficient separation of large single-crystal diamond substrates in a short period, allowing for the reuse of seed crystals and increasing substrate production quantities while maintaining low costs and high purity.
Implementation Method 1
oxygen ions accelerated to a high energy level of several megaelectron volts are implanted into a diamond to form a non-diamond layer
Implementation Method 2
the non-diamond layer is removed by annealing in an oxygen atmosphere, thereby separating a single-crystal film with a thickness of the order of about microns from the substrate
Implementation Method 3
etching the non-diamond layer in the diamond by applying an alternating-current voltage across electrodes in an electrolytic solution
Data Source
AI summary
The present invention provides a method for separating a surface layer of a diamond, which comprises implanting ions into a diamond to form a non-diamond layer near a surface of the diamond; and etching the non-diamond layer in the diamond by applying an alternating-current voltage across electrodes in an electrolytic solution; and a method for separating a grown layer of a diamond, which further comprises the step of growing a diamond by a vapor-phase synthesis method, after forming a non-diamond layer according to the above-described method. The invention is applicable to various single-crystal and polycrystal diamonds. More specifically, even with a large single-crystal diamond, a portion of the single-crystal diamond can be efficiently separated in a reusable form in a relatively short period of time.