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High Power Density Microwave Plasmas

Diamond deposition at high power densities has yielded more than one-of-magnitude improvement of the linear growth rates previously possible in similar reactors at lower power densities. In this new system, diamond deposition rates of up to 60 mg/hour have been demonstrated. Linear growth rates of 15micro meter/hour near the center of the sample have been measured.

 

Figure 1 shows a cross-section of a diamond film grown at such rates. Note the columnar structure characteristic of high growth rate depositions.  
    Figure 1. SEM cross-section of diamond film grown at 15 micro meter per hour.
 

 

 
Figure 2 shows a top view of the films. Nicely faced material is obtained. At these high rates, thick free-standing films are possible within a few hours of deposition.  
    Figure 2. Surface of diamond film shown in Figure 1.
     
Figure 3 shows preferential alignment of the crystals along the [100] direction which is obtained under some deposition conditions. Preferential alignment of the facets can have applications for these CVD films in active electronics.

The thermal conductivity of diamond films samples grown at rates near 3micro meter m/hour was measured using two different techniques. The measurements yielded values of the thermal conductivity in the 10 to 20 W/cm-K range. This high thermal conductivity value makes such films ideal for heat sink applications.

 
Figure 3. SEM of diamond film grown at 5micro meter per hour, showing preferential [100] alignment.
     
As an example, the Raman spectrum for one of these films is shown in Figure 4. The FWHM of the diamond line near 1332cm-1 was measured at 6cm-1. This value is close to the width for natural diamond (approximately 2 cm-1). Such narrow width lines are characteristic of high quality CVD diamond.  
    Figure 4. Raman spectrum of typical diamond film.


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Microwave Plasma Applications

Model AX5000/AX5200

Model AX5250/AX5400

Model AX6550/6560

Model AX6600

High Power Density Microwave Plasmas

Advanced Materials