Efficient negative ion production in rf plasmas using a mesh grid bias method

Abstract

Using a grid bias method for plasma parameter control, volume production of hydrogen negative ions H − is studied in pure hydrogen rf plasmas. Relationship between the extracted H − ion currents and plasma parameters is discussed. It is confirmed that both high and low electron temperature T e plasmas are produced in the separated regions when the grid is negatively biased. In addition, with changing grid potential V g , values of n e increase while T e decrease in their values. The negative ion production depends strongly on the grid potential and related plasma conditions.

Utilizing upper hybrid resonance for high density plasma production and negative ion generation in a downstream region

“…To further reduce the electron temperature, an insulated mesh grid is attached to the magnetic filter. 39,40 The axial variation of T e and electron density n e in the attachment chamber at 1.2 mTorr, with the grid in place is shown in Fig. 7.…”

Efficient production of negative hydrogen ions in RF plasma by using a self-biased grid electrode

“…Therefore, it is difficult to keep e fixed at most suitable electron temperature. In the latter case, it is difficult to suppress RF electric-field penetration into the downstream low e region, which disturbs negative ion production [13]. To overcome these faults, cesium is needed for seeding additionally to the discharge chamber to raise the ratio − / + [27].…”

“…We also applied this method to negatve-ion production in RF hydrogen plasma, where the negative hydrogen ion production was enhanced by the decrease in e [11]. In the case of RF discharge plasma, the grid bias method was found to be quite suitable for optimizing the plasma conditions for negative ion production, compared with the magnetic filter method [12,13].…”