晶圆级单晶金刚石的常用工艺

Large size single crystal diamond (SCD) wafer has been strongly desired for various of advancedapplications, while two major potential approaches, including mosaic growth and heteroepitaxybased on chemical vapor deposition method, are both stuck with respective technical barriers.This paper reveals and summarizes the essential commonality of the two schemes, anddenominates the concept of “coessential-connection” (CC) growth. Such generalized conceptinvolved the nature of the single crystal and polycrystalline diamond film deposition with similarmechanism and processes. The principle of CC growth process with detailed classification waselaborated, and influence of nucleus size and orientation mismatch was clarified, which isregarded as the core problem of large area SCD film growth via coessential-connection process.

Diamond, the king of jewelries with incomparablebeauty and brilliancy, loved by people from ancient royaland nobles, to the tokens of marriage today. It has beenregarded as the most valuable treasures by humans, andbrought about numerous of stories through thousandsof years. In recent decades, a world-renowned marketingcampaign let by De Beers, the giant diamond company,with the phrase “a diamond is forever” impressed thelovers all over the world, indicating a forever lasting love,being supposed to the only pledge, carrying the best loveof the new couples.

While in the point of view of material science, thebeautiful attribute of diamond seems to be at the bottomof its values, as it holds various of other excellent properties. The most well-known and used nature of diamond is the superhard, with the Mohs hardness of 10and elasticity modulus of >1000GPa. Such super largehardness makes diamond capable for cutting tools, drills[1], core of drawing die [2] and high pressure anvils [3].Besides, diamond also has super high thermal conductivity, up to 2380W/mK for single crystals [4] and up to2000W/mK for polycrystalline films and wafers [5, 6],depending on its quality. What’s more, the ultra-wideelectromagnetic wave transparent window from UV toradio waves together with the high thermal conductivity and irradiation hardness make diamond very competitive candidate for the windows of high-power laser,microwave, and synchrotron radiation facilities. Largeband gap (5.4 eV) together with rather high carriermobility (>2000 cm2V−1 s−1) qualifies diamond excellentsemiconductor property, which is honored as the leaderof the 3rd generation semiconductor materials for highpower devices, computing chips and 5G stations, etc.Advanced applications in industry are regarded morevaluable than the jewelry, the most traditional use ofdiamond. Praises such as “ultimate semiconductor,” “the21st century is a century of diamond,” expressing enoughprospect of this fundamental material.

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However, the harshest problem restricting the fullpotential of diamond is the limited crystal size and highcost. It is well known that diamond is precious andexpensive, with a whopping price as high as tens of millions of dollars especially for large natural crystals withgood qualities and special colors. As a result, syntheticof diamond has becoming a dream of human to producelarger and more perfect diamond with lower cost, insteadof digging and drilling accompanied by serious pollutionand environmental disruption. After decays of researchand development, synthetic diamond has become possible and nowadays even played an important role inmodern industries.

By the year of 1770s, the perplexing question “What isdiamond?” finally solved by famous chemist A. Lavoisier,who proved diamond was consist of pure carbon element. However, to make a diamond from carbon source,such as graphite, is so hard and many attempts failed. Itwas not until 1950 that Rossini et al. [7] summarized thetemperature and pressure equilibrium phase diagram ofgraphite-diamond through theoretical analysis. Thiswork finally pointed out the direction for the technicalproblem of manufacturing diamond crystal: about2500–3000K, 5–10GPa pressure is needed to imitate theformation process of diamond in nature.