Flow controllers for diamond production

Good reliability and reproducibility are the main features for Bronkhorst mass flow controllers and pressure controllers that are used in the manufacturing of synthetic, lab-grown diamonds using chemical vapor deposition. After all, a single batch to grow these shiny gems will take as long as 300 to 600 hours, and during this entire period the process conditions need to be the same to obtain a consistent good quality of the diamonds.

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Flow controllers in lab-grown diamonds manufacturing

Traditionally, diamonds were formed deep down below our feet in the earth’s mantle. Millions of years at high temperature and extreme pressure allowed the carbon atoms present there to be densified into the characteristic diamond crystal structure. Volcanic eruptions swept them to the earth's surface, ready to be mined. Quite a journey for these precious gems ...

In recent decades, natural diamonds have been given synthetic counterparts - even grown from the vapor phase. Synthetic lab-grown diamonds which are manufactured using microwave plasma chemical vapor deposition (CVD) technology are gaining traction. Mainly as jewelry, but also for industrial cutting and polishing purposes due to their extremely good materials properties, and in the future for semiconductor wafers.

India is a front runner in this matter, and Bronkhorst has cooperated for many years with leading machine and system building players in the field by supplying mass flow controllers and pressure controllers for growing high-quality CVD diamonds.

Requirements for lab-grown diamond production

To manufacture lab-grown diamonds, gaseous reactants such as methane and hydrogen are fed to a low-pressure reactor. Microwave radiation converts these gases into reactive compounds (a plasma) that deposit onto tiny diamond seed crystals present in the reactor chamber. The deposit follows the structure of the seed crystal, thereby forming a larger diamond, layer by layer. This process typically takes 300 to 600 hours – quite some time, but very much shorter than in the case of natural diamonds. After cutting and polishing, these lab-grown diamonds have the same physical, chemical and optical properties as natural diamonds.

For the batch CVD process, a constant, very low pressure (high vacuum) is required. Moreover, the gaseous reactants need to be supplied to the reactor with the same constant flow throughout the entire process.

Important topics

Good reliability and reproducibility of mass flow controllers and pressure controllers
Consistent good quality of diamonds over a long period during manufacturing
Understanding of the CVD process