Plasma uniformity control by gas diffuser hole design

A gas distribution plate assembly for a plasma processing chamber, comprising:

• a diffuser plate element having an edge, a center, an upstream side and a downstream side;
• and
• inner and outer gas passages passing between the upstream and downstream sides of the diffuser plate element from the center to the edge of the diffuser plate element, each gas passage having:
• an orifice hole having a first diameter, wherein a length of the orifice divided by the first diameter is between 2 and 3.33;
• and
• a hollow cathode cavity that is downstream of the orifice hole and is at the downstream side, the hollow cathode cavity having a cone or cylinder shape and a second diameter at the downstream side that is greater than the first diameter, the second diameters or the depths or a combination of both of the cones or cylinders increases from the center to the edge of the diffuser plate element, the first diameters are substantially uniform from the center to the edge of the diffuser plate element, and the hollow cathode cavity surface area density of the inner gas passages is less than the hollow cathode cavity surface area density of the outer gas passages.

A gas distribution plate assembly for a plasma processing chamber, comprising:

• a diffuser plate element having an edge, a center, an upstream side and a down stream side;
• and
• a plurality of gas passages passing between the upstream and downstream sides of the diffuser plate element from the center to the edge of the diffuser plate element, each gas passage having:
• an orifice hole having a first diameter, wherein a length of the orifice divided by the first diameter is between 2 and 3.33;
• and
• a hollow cathode cavity that is downstream of the orifice hole and intersects the downstream side of the diffuser plate element, the hollow cathode cavity having a cone or cylinder shape and a second diameter at the downstream side that is greater than the first diameter, the second diameters or the depths or a combination of both of the cones or cylinders increases from the center to the edge of the diffuser plate element, the first diameters are substantially uniform from the center to the edge of the diffuser plate element, the densities of the hollow cathode cavities increase from the center to the edge of the diffuser plate element, and the hollow cathode cavity volume density or the hollow cathode cavity surface area density increases from the center to the edge of the diffuser plate element.

A plasma processing chamber, comprising:

• a planar diffuser plate element having an edge, a center, an upstream side and a downstream side, wherein the upstream side and the downstream side are parallel;
• a RF power source coupled to the diffuser plate element;
• inner and outer gas passages passing between the upstream and downstream sides of the diffuser plate element from the center to the edge of the diffuser plate element, each gas passage having:
• an orifice hole having a first diameter;
• and
• a hollow cathode cavity that is downstream of the orifice hole and is at the downstream side, the hollow cathode cavity having a cone or cylinder shape and a second diameter at the downstream side that is greater than the first diameter, the second diameters or the depths or a combination of both of the cones or cylinders increases from the center to the edge of the diffuser plate element, the first diameters are substantially uniform from the center to the edge of the diffuser plate element, and the size of the hollow cathode cavities of the inner gas passages is less than the size of the hollow cathode cavities of the outer gas passages;
• and
• a substrate support adjacent the downstream side of the diffuser plate element.

A plasma processing chamber, comprising:

• a diffuser plate element having an edge, a center, an upstream side and a downstream side;
• a RF power source coupled to the diffuser plate element;
• inner and outer gas passages passing between the upstream and downstream sides of the diffuser plate element from the center to the edge of the diffuser plate element, each gas passage having:
• an orifice hole having a first diameter, wherein a length of the orifice divided by the first diameter is between 2 and 3.33;
• and
• a hollow cathode cavity that is downstream of the orifice hole and is at the downstream side, the hollow cathode cavity having a cone or cylinder shape and a second diameter at the downstream side that is greater than the first diameter, the second diameters or the depths or a combination of both of the cones or cylinders increases from the center to the edge of the diffuser plate element, the first diameters are substantially uniform from the center to the edge of the diffuser plate element, and the hollow cathode cavity surface area density of the inner gas passages is less than the hollow cathode cavity surface area density of the outer gas passages;
• and
• a substrate support adjacent the downstream side of the diffuser plate element.

A plasma processing chamber, comprising:

• a planar diffuser plate element having an edge, a center, an upstream side and a down stream side, wherein the upstream side and the down stream side are parallel;
• a RF power source coupled to the diffuser plate element;
• a plurality of gas passages passing between the upstream and downstream sides of the diffuser plate element from the center to the edge of the diffuser plate element, each gas passage having:
• an orifice hole having a first diameter;
• and
• a hollow cathode cavity that is downstream of the orifice hole and is at the downstream side, the hollow cathode cavity having a cone or cylinder shape and a second diameter at the downstream side that is greater than the first diameter, the second diameters or the depths or a combination of both of the cones or cylinders increases from the center to the edge of the diffuser plate element, the first diameters are substantially uniform from the center to the edge of the diffuser plate element, and surface area densities of hollow cathode cavities of the plurality of gas passages increase from the center to the edge of the diffuser plate element;
• and
• a substrate support adjacent the downstream side of the diffuser plate element.

A gas distribution plate assembly for a plasma processing chamber, comprising:

• a planar diffuser plate element having an edge, a center, an upstream side and a downstream side and the diffuser plate is divided into a number of concentric zones, wherein the upstream side and the downstream side are parallel;
• and
• a plurality of gas passages passing between the upstream and downstream sides of the diffuser plate element from the center to the edge of the diffuser plate element, each gas passage having:
• an orifice hole having a first diameter;
• and
• a hollow cathode cavity that is downstream of the orifice hole and is at the downstream side, the hollow cathode cavity having a cone or cylinder shape and a second diameter at the downstream side that is greater than the first diameter, the second diameters or the depths or a combination of both of the cones or cylinders increases from the center to the edge of the diffuser plate element, the first diameters are substantially uniform from the center to the edge of the diffuser plate element, the gas passages in each zone are identical and the volume or surface area of hollow cathode cavities of gas passages in each zone gradually increase from the center to the edge of the diffuser plate element.

A diffuser plate, comprising:

• a body having an edge, a center, a top surface and a bottom surface, wherein the bottom surface is concave;
• a plurality of gas passages between the top surface and the bottom surface, from the center to the edge of the body wherein each gas passage has:
• an orifice hole having a first diameter, wherein a length of the orifice divided by the first diameter is between 2 and 3.33;
• and
• a hollow cathode cavity that is downstream of the orifice hole and intersects the bottom surface, the hollow cathode cavity having a cone or cylinder shape and a second diameter at the downstream side that is greater than the first diameter, the second diameters or the depths or a combination of both of the cones or cylinders increases from the center to the edge of the diffuser plate, the first diameters are substantially uniform from the center to the edge of the diffuser plate, and the size of the hollow cathode cavities increases from the center to the edge of the diffuser plate;
• and
• an outer region and an inner region wherein the body between the top and the bottom of the outer region is thicker than the body between the top and the bottom of the inner region.