Etch‐pit formation mechanism induced on HPHT and CVD diamond single crystals by H₂/O₂ plasma etching treatment

Abstract

H2/O2 plasma treatments offer advantages over other etching processes of diamond as a technique to prepare the substrate surface prior to chemical vapor deposition (CVD) diamond growth. It allows removing defects induced on the surface by polishing, thus leading to an improved morphology and limiting the stress within the grown crystal. Moreover, they present the advantage to be performed in situ just before the CVD diamond growth. In this work, H2/O2 plasma treatments were performed so that threading dislocations and other defects are etched preferentially, thus leaving typical etch‐pits. The defect densities in several high pressure high temperature (HPHT) and CVD diamond crystals were then quantified and compared; in particular defects originating from polishing could be distinguished from extended defects inside the crystal. Furthermore, the defect density was found to be of the order of 105/cm2 for HPHT crystals, which was approximately one order of magnitude lower than that measured in low cost commercial CVD monocrystals. The use of laser microscopy also allowed observing the morphology, size and depth of different etch‐pits of 〈001〉‐oriented and misoriented crystals and their evolution with etching time in order to get a better understanding of defect density and formation during CVD growth.

Three-dimensional kinetic Monte Carlo simulations of diamond chemical vapor deposition

“…This is very similar to the shape and size of etch pits seen experimentally when etching diamond with O 2 mixtures. 13 Reducing b to 1000, as in Fig. 6(b), lowers the relative defect etch rate and produces shallower rectangular etch pits with flat bottoms, which more closely resemble those seen when etching diamond in H 2 , 12 as seen previously in Fig.…”

“…[10][11][12] Indeed, counting etch pits is often used as a method to determine the number density and distribution of dislocations at a diamond surface. 13 These observations all support the idea that isolated sp 3 hydrocarbon species on flat diamond terraces are etched away faster than those adjacent to a step-edge, 8 so hydrocarbon species preferentially reside and accumulate at step-edges. This "preferential etching" 14 is an alternative explanation for apparent step-edge growth.…”

Fabrication of Low Dislocation Density, Single-Crystalline Diamond via Two-Step Epitaxial Lateral Overgrowth

“…Figure 4 shows images of the surface of the first ELO layer after plasma etching by MPCVD for 15 min. H 2 /O 2 plasma etching treatments under relatively high pressure/power (>100 mbar, >2000 W) and with a low amount of added oxygen (<4%), usually lead to very selective etching of the (100) diamond surface [6]. Thus, defects such as dislocations located near the diamond surface typically appear as inverted pyramids with a square base after selective plasma etching.…”

“…For crystals formed via chemical vapor deposition (CVD), dislocations mainly stem from extended defects related to the substrate, such as defects in the substrate surface and defects in the bulk of the substrate. Dislocations tend to thread through the CVD film almost parallel to the growth direction [6]. Epitaxial lateral overgrowth (ELO) is a useful method to suppress the dislocation density and has been used for the growth of GaN [7][8][9][10].…”

“…Moreover, it is very difficult to distinguish areas of different growth quality for the purpose of fabricating a metal mask by the ELO process, since the differences can be seen only under the observation of heavy equipment. Since lattice defects, such as vacancies, dislocations, and impurities, serve as preferential sites for etching, plasma etching treatment can be used to characterize and distinguish different growth areas by dislocation density [6]. As etch-pits are formed after plasma etching treatment, it is quite convenient to assess the growth quality in different areas.…”