2. Manufacture of polycrystalline CVD-diamond materials

TWINN, LLC specialists have been practicing growing CVD-diamond polycrystalline films since 1997. Polycrystalline CVD-diamond is obtained by chemical vapor deposition of hydrogen and methane. The diamond is grown on polished silicon pads.

TWINN, LLC has two types of CVD-diamond growth equipment with MW generator power of 6 and 10 kW. The rate of growth of diamond film is 3-5 µm/hour. The equipment allows growing polycrystalline diamond films with thickness from 100 µm to 2 mm with diameter up to 100 mm. The physical appearance of the films is shown in fig.2.1 & fig.2.2. The diamond films are produced according to TU 6365-001-18107879-2013.

Fig.2.2. CVD-Diamond disks with 57, 75, 100 mm in diameter

TWINN, LLC has patent technology avoiding laser cutting for obtaining heat sinks of a required size (Patent RU #...). Fig.2.3 shows profiled silicon plate with a diamond film.

Fig 2.3. Profiled silica plate with a diamond film

The growing surface of CVD-diamond film is shown in fig. 2.4, diamond film in a cutaway - fig.2.5. The growing surface has polycrystalline structure (some cases require polishing/sanding), not growing surface is of 9-10 processing class and is determined by the surface of the substrate (polished silica).

CVD-diamond materials parameters:

- Thermal conductivity coefficient 800-1800 W/mK (depending on CVD-diamond type: black, grey, white);

- Thermal expansion coefficient 1x10^-6 K^-1

- Resistivity 1012 – 1014 Ohm·m

Fig.2.6 shows the Raman spectra for diamond film growing. Fig.2.7 shows the photoluminescence spectra of a grown film.

Thermal conductivity of CVD-diamond is 4-5 times greater than of copper..

Currently CVD-diamond is positioned as a material for laser diodes heat sinks, small MW integrated circuits, and high-speed reaction chips since active devices mounted on the diamond substrate can work better without overheating. Thereby the reliability of devices increases as thermal transition temperature will be substantially lower when chips are installed on the diamond pad.