Microwave plasma reactors
View Patent ↗Microwave plasma assisted reactors, for example chemical vapor deposition (MPCVD) reactors, are disclosed. The disclosed reactors operate at high pressures (>180-320 Torr) and high power densities (>150 W/cm3), and thereby enable high deposition rate CVD processes that rapidly deposit materials. In particular, reactor design examples are described that, when operating in the 180-320 Torr pressure regime, rapidly CVD synthesize high quality polycrystalline (PCD) and single crystal diamond (SCD). The improved reactors include a radial contraction in the vicinity of the plasma chamber (and optionally a combined expansion in the vicinity of the electromagnetic wave source, followed by the contraction) in the main microwave chamber as electromagnetic energy propagates from an electromagnetic wave source to a plasma/deposition chamber.
1. A microwave plasma assisted reactor comprising:
(a) a first microwave chamber having a reference plane at a reference axial location Zo and extending in an axial direction z>Zo, wherein the first microwave chamber comprises:
(i) a first cylindrical waveguide section positioned adjacent the reference axial location Zo, extending in the axial direction z>Zo away from the reference axial location Zo, and having a radius of R 1 a;
(ii) a second cylindrical waveguide section positioned adjacent the first cylindrical waveguide section, extending in the axial direction z>Zo away from the first cylindrical waveguide section, and having a radius of R 1 b such that R 1 b /R 1 a is greater than 1; and
iii) an electromagnetic wave source;
(b) a plasma chamber having an outer wall defining a cylindrical cross section with radius of R 2 , the plasma chamber extending into the first cylindrical waveguide section of the first microwave chamber such that at least a portion of the plasma chamber is located at z>Zo;
(c) a conductive stage defining a cylindrical cross section with radius of R 3 and having a reference surface extending into the plasma chamber and defining a second microwave chamber in the plasma chamber (i) at z<Z.sub. 0 and (ii) between the plasma chamber outer wall and the conductive stage; and
(d) a conducting short adjustably disposed in the second microwave chamber below Zo and in electrical contact with and movable with respect to the plasma chamber outer wall and the conductive stage, the axial distance between the conducting short and Zo being L 2 , and the axial distance between the conducting short and the reference surface of the conductive stage being L 1 ;
wherein:
R 3 /R 2 is 0.5 or less; and
geometric scales of the reactor are configured such that, during operation of the reactor, electromagnetic fields are produced in the vicinity of Zo and in the plasma chamber, the electromagnetic fields comprising one or more of a TM 01 mode, a TEM 001 mode, and evanescent modes.
2. A reactor kit comprising a microwave plasma assisted reactor according to claim 1 , wherein the first microwave chamber comprises a plurality of separate, interconnected chamber sections each having a different radius and corresponding to a waveguide section of the first microwave chamber.
3. The microwave plasma assisted reactor of claim 1 , wherein R 3 /R 2 is in a range from 0.05 to 0.4.
4. The microwave plasma assisted reactor of claim 1 , wherein R 3 /R 2 is in a range from 0.05 to 0.3.
5. The microwave plasma assisted reactor of claim 1 , wherein L 2 and L 1 are capable of adjustment in the reactor by moving the conducting short.
6. The microwave plasma assisted reactor of claim 5 , wherein the conductive stage is movable such that both L 1 and L 2 are capable of independent adjustment during operation of the reactor by moving one or both of the conducting short and the conductive stage.
7. The microwave plasma assisted reactor of claim 1 , wherein the conducting short is slidable in an axial direction.
8. The microwave plasma assisted reactor of claim 7 , wherein the conductive stage is movable and slidable in the axial direction.
9. A process for depositing a component on a substrate, the process comprising:
(a) providing a microwave plasma assisted reactor according to claim 1 , the reactor further comprising a deposition substrate mounted above an upper surface of the conductive stage;
(b) operating the reactor at a pressure ranging from about 10 Torr to about 760 Torr to generate a plasma discharge in the plasma chamber; and
(c) depositing a component on the substrate.
10. The process of claim 9 , wherein:
(i) operating the reactor comprises feeding a source gas comprising a hydrogen source gas and a methane source gas to the plasma chamber; and
(ii) the component is selected from the group consisting of single-crystal diamond, microcrystalline polycrystalline diamond, nanocrystalline polycrystalline diamond, and combinations thereof.
11. The process of claim 9 , wherein, during parts (b) and (c) of operating the reactor and depositing the component on the substrate, electromagnetic fields are produced in the vicinity of Z 0 and the deposition substrate in the plasma chamber, the electromagnetic fields comprising one or more of a TM 01 mode, a TEM 001 mode, and evanescent modes.