CN-121992496-A - Method for stripping polycrystalline diamond by low-stress growth

Abstract

The invention provides a method for stripping polycrystalline diamond by low-stress growth, which adopts the principle that the substrate and transition layer are in low mismatch with the polycrystalline diamond, and simultaneously utilizes the strong etching capability of hydrogen to etch the substrate after the polycrystalline diamond grows so as to avoid the intervention of extra stress, thereby reducing the cracking of the polycrystalline diamond. The solution is effective in reducing cracking of polycrystalline diamond during peeling as compared with the prior art, and is applicable to solve the problem of low yield of industrial MPCVD polycrystalline diamond due to cracking.

Inventors

• ZHANG CHAOQI
• GAN JUNWEI
• ZHENG XUPENG
• MAO LI

Assignees

• 湖北瑞华科技有限公司

Dates

Publication Date

20260508

Application Date

20260109

Claims (9)

1. 1. A method of low stress growth of exfoliated polycrystalline diamond comprising the steps of: Providing a substrate, wherein the upper surface and the lower surface of the substrate are respectively a growth surface and an etching surface; Covering the growth surface and etching surface of the substrate with a mask, and placing the substrate into PVD equipment; Plating a metal layer on the side edge of the substrate by using PVD equipment; Placing the substrate into an acetone solution, and ultrasonically cleaning to remove a mask; Placing the etched surface of the substrate in an embedded molybdenum holder; Placing a molybdenum support carrying a substrate in MPCVD equipment, introducing high-purity methane, and forming a transition layer of the substrate and polycrystalline diamond on the growth surface of the substrate; Placing the substrate and the transition layer into diamond nucleation liquid for ultrasonic nucleation; putting the obtained substrate into MPCVD equipment again to grow polycrystalline diamond films; And turning over the substrate, placing the etched surface upwards into MPCVD equipment, and introducing high-purity hydrogen to etch the substrate layer on the back of the polycrystalline diamond to obtain the polycrystalline diamond.
2. 2. The method of claim 1, wherein the substrate is graphite or glassy carbon.
3. 3. The method of claim 1, wherein the substrate is ultrasonically cleaned in acetone, ethanol, and ultra-pure water, respectively, to remove organic impurities on the surface of the substrate, and the cleaned substrate is dried with nitrogen gas before being placed in the PVD apparatus.
4. 4. The method of claim 1, wherein plating the metal layer on the side of the substrate with the PVD apparatus comprises plating a plating material on the side of the substrate by magnetron sputtering, wherein the plating material is one of molybdenum, titanium, and tungsten.
5. 5. The method of claim 1 or 4, wherein the metal layer has a thickness of 10-50um.
6. 6. The method of claim 1, wherein placing the etched surface of the substrate in the embedded molybdenum support comprises the embedded molybdenum support fully immersing the substrate into the molybdenum support, the substrate growth surface having a height differential from the surface of the molybdenum support of between-0.5 mm and 0 mm.
7. 7. The method of claim 1, wherein the transition layer has a thickness of 50-100um and comprises an amorphous carbon having an Sp 3 bond.
8. 8. The method of claim 1, wherein the purity of methane, hydrogen, nitrogen and argon is greater than 99.9999%, and the growth flow rates are 480Sccm, 20Sccm, 0.01Sccm and 5Sccm, respectively, during the process of re-placing the obtained substrate into the MPCVD apparatus to grow the polycrystalline diamond film.
9. 9. The method of claim 1, wherein turning the substrate, placing the etched surface upwards into an MPCVD device, and etching the back substrate layer of the polycrystalline diamond to obtain the polycrystalline diamond comprises turning the substrate, placing the growth surface of the substrate downwards, placing the etched surface upwards, repeating the operation of the MPCVD device, introducing hydrogen with the flow of 500sccm into the cavity, etching the substrate at the etching temperature of 600-800 ℃, obtaining the polycrystalline diamond after the substrate is completely etched, and adopting a slow cooling mode to prevent the polycrystalline diamond from being broken due to cooling, wherein the cooling time is more than 3 hours, so as to obtain the polycrystalline diamond.

Description

Method for stripping polycrystalline diamond by low-stress growth Technical Field The invention relates to the technical field of film growth, in particular to a method for low-stress growth stripping polycrystalline diamond. Background Polycrystalline diamond is an aggregate formed by covalent bonding of micro-or nano-scale diamond grains. The performance of the diamond is similar to that of single crystal diamond, and the diamond has extremely high hardness, excellent heat conductivity, stable chemical property and good optical property, and can meet the industrial requirement of large-size diamond materials. Based on these excellent properties, polycrystalline diamond has been widely used in key industrial fields such as machining, optical window, thermal power dissipation, and the like. Currently, the predominant method of polycrystalline diamond production is chemical vapor deposition. The method decomposes a carbon-containing gas (e.g., methane) with hydrogen at a high temperature under low pressure conditions and deposits polycrystalline diamond on the surface of the substrate. Subsequently, common methods of stripping polycrystalline diamond from a substrate mainly include strong acid and alkali etching (for silicon substrates) and high temperature annealing (for molybdenum substrates). However, both of these exfoliation processes introduce stresses that are the primary cause of cracking of the polycrystalline diamond. Specifically, after growing polycrystalline diamond using silicon as a substrate, the silicon substrate is usually removed using a strong corrosive agent such as concentrated sulfuric acid, hydrofluoric acid, or high concentration sodium hydroxide. In the etching process, the concentration of the etchant in the area close to the silicon wafer is lower than that in other areas due to reaction consumption, so that a concentration gradient is formed, the polycrystalline diamond is stressed unevenly in the stress release process, and additional stress is introduced. In addition, there is a difference in thermal expansion coefficient between silicon and polycrystalline diamond, and after the substrate is corroded, residual stress originally constrained by the substrate is released, which easily causes the polycrystalline diamond to warp or even directly crack. On the other hand, if metallic molybdenum is used as the growth substrate, the delamination process is typically accomplished by high temperature annealing, which is a process in which polycrystalline diamond is suddenly reduced from the growth temperature (800-900 ℃) to room temperature within a few minutes, and is delaminated using a thermal stress difference. However, abrupt changes in temperature are also likely to cause cracking of the polycrystalline diamond. Thus, the current industry has a low success rate for stripping polycrystalline diamond, especially in large area materials, and the problem of cracking during stripping is one of the key factors limiting mass production. To solve the above problems, researchers have proposed various improvement methods. The stripping is more commonly performed by laser ablation, but the method is limited in laser processing range and is only applicable to small-size polycrystalline diamond. In patent document CN119243330B, a proposal for preparing a sacrificial layer is made to achieve the peeling of polycrystalline diamond by spin coating the sacrificial layer and breaking it by cooling. However, this method may cause residual impurities inside the polycrystalline diamond due to the introduction of additional sacrificial layer materials, affecting the purity of the material. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a low-stress and high-integrity polycrystalline diamond stripping method, which aims to solve the problems of stress concentration, material rupture, impurity pollution and the like caused by chemical corrosion, quenching or external sacrificial layer in the existing stripping process. To achieve the above object, the present invention provides a method for low stress growth delamination of polycrystalline diamond, the method comprising at least: Providing a substrate, wherein the upper surface and the lower surface of the substrate are respectively a growth surface and an etching surface; Covering the growth surface and etching surface of the substrate with a mask, and placing the substrate into PVD equipment; Placing the substrate into an acetone solution, and ultrasonically cleaning to remove a mask; Plating a metal layer on the side edge of the substrate by using PVD equipment; Placing the etched surface of the substrate in an embedded molybdenum holder; Placing a molybdenum support carrying a substrate in MPCVD equipment, introducing high-purity methane, and forming a transition layer of the substrate and polycrystalline diamond on the growth surface of the substrate; Placing the substrate and the transition layer into diamond