Particle trap for a plasma source

A particle trap for a remote plasma source includes a body structure having an inlet for coupling to a chamber of a remote plasma source and an outlet for coupling to a process chamber inlet. The particle trap for a remote plasma source also includes a gas channel formed in the body structure and in fluid communication with the body structure inlet and the body structure outlet. The gas channel can define a path through the body structure that causes particles in a gas passing from a first portion of the channel to strike a wall that defines a second portion of the gas channel at an angle relative to a surface of the wall. A coolant member can be in thermal communication with the gas channel.

FIELD OF THE INVENTION

The invention relates generally to plasma generation and processing equipment. In particular, the invention relates to methods and apparatus for removing contaminant particles from an activated gas.

BACKGROUND

Plasmas are often used to activate gases placing them in an activated state such that the gases have an enhanced chemical reactivity. In some cases, the gases are activated to produce dissociated gases containing ions, free radicals, atoms and molecules. Dissociated gases are used for numerous industrial and scientific applications including processing solid materials such as semiconductor wafers, powders, and other gases. Properties of activated gases and conditions under which materials are exposed to the gases vary widely depending on the application. Significant amounts of power are sometimes required in the plasma for dissociation to occur.

Plasma sources generate plasmas by, for example, applying an electric potential of sufficient magnitude to a plasma gas (e.g., O2N2, Ar, NF3, H2and He), or a mixture of gases, to ionize at least a portion of the gas. Plasmas can be generated in various ways, including DC discharge, radio frequency (RF) discharge, and microwave discharge. DC discharge plasmas are achieved by applying a potential between two electrodes in a plasma gas. RF discharge plasmas are achieved either by capacitively or inductively coupling energy from a power supply into a plasma. Microwave discharge plasmas are achieved by directly coupling microwave energy through a microwave-passing window into a discharge chamber containing a plasma gas. Plasmas are typically contained within chambers that are composed of metallic materials such as aluminum or stainless steel or dielectric materials such as quartz, sapphire, yttrium oxide, zirconium oxide, and/or aluminum nitride.

A known problem in the art of plasma generation is that particles are often generated which can, for example, contaminate the plasma generator or chambers coupled to an output of the plasma chamber. A need therefore exists for decreasing the number of contaminant particles in activated gases generated by plasma generation equipment.

SUMMARY OF THE INVENTION

The invention generally features apparatus and methods that can provide reduced particle counts in an activated gas. One advantage is that the invention minimizes the introduction of particles or defects on the material (e.g., a semiconductor wafer) to be processed. Another advantage is that the invention provides a higher yield rate in the manufacturing of materials to be processed (e.g., a semiconductor wafer). Yet another advantage is that the invention provides an apparatus that can be replaceable to minimize manufacturing downtime. Another advantage is that the invention reduces particle count while minimizing recombination of the activated gas.

The invention, in one aspect, features a particle trap for a remote plasma source. The particle trap includes a body structure having an inlet for coupling to a chamber of a remote plasma source and an outlet for coupling to a process chamber inlet. The particle trap also includes a gas channel formed in the body structure and in fluid communication with the body structure inlet and the body structure outlet, the gas channel defining a path through the body structure that causes particles in a gas passing from a first portion of the channel to strike a wall that defines a second portion of the gas channel at an angle relative to a surface of the wall.

In some embodiments, the wall is a portion of an obstruction that is interior to exterior walls of the body structure. In some embodiments, the particle trap includes a plurality of obstructions. In some embodiments, the obstruction includes a cooling member in thermal communication with the surface of the wall of the obstruction. The cooling member can include a coolant channel to receive a fluid to cool the surface of the wall of the obstruction.

In some embodiments, the angle is between 45-135 degrees. In some embodiments, the first portion of the channel is at a substantially normal angle to the second portion of the channel. The gas channel can have a third portion and particles in the gas passing from the second portion strike a second wall that defines the third portion at a second angle relative to a second surface of the second wall. In some embodiments, the second angle is between approximately 45-135 degrees. In some embodiments, the first section and the second section define a curve. The surface of the wall can be at least one of irregular or textured. In some embodiments, the body structure is disposed in the remote plasma source. In some embodiments, a pressure drop between the body structure inlet and the body structure outlet is less than approximately 100 milliTor. In some embodiments, the particle trap includes a depression in the wall of at least one of the first portion or the second portion of the gas channel, the depression adapted to collect the particles in the gas.

In some embodiments, the particle trap includes a cooling member in thermal communication with the gas channel. The cooling member can include at least one coolant channel formed in the body structure to receive a fluid to cool at least a portion of the wall of the second portion of the gas channel. In some embodiments, the cooling member includes a cooling plate. In some embodiments, the cooling member indirectly cools at least a portion of the wall of the second portion of the gas channel. The cooling member can be disposed in the body structure. In some embodiments, a path of the at least one coolant channel is at least substantially parallel to the path of the gas channel.

The invention, in another aspect, features a particle trap for a remote plasma source. The particle trap includes a body structure having an inlet for coupling to a chamber of a remote plasma source and an outlet for coupling to a process chamber inlet. The particle trap also includes a gas channel formed in the body structure and in fluid communication with the body structure inlet and the body structure outlet, the gas channel defining a path through the body structure. The particle trap also includes a cooling member in thermal communication with the gas channel.

In some embodiments, the cooling member includes at least one coolant channel formed in the body structure to receive a fluid to cool at least a portion of a wall of the gas channel. In some embodiments, the cooling member includes a cooling plate. The cooling member can indirectly cool at least a portion of a wall of the gas channel. The cooling member can be disposed in the body structure.

In some embodiments, the path through the body structure causes particles in a gas passing from a first portion of the channel to strike a wall that defines a second portion of the gas channel at an angle relative to a surface of the wall. In some embodiments, the gas channel has a third portion and particles in the gas passing from the second portion strike a second wall that defines the third portion at a second angle relative to a second surface of the second wall. The body structure can be disposed in the remote plasma source. In some embodiments, the particle trap includes a depression in the wall of at least one of the first portion or the second portion of the gas channel, the depression adapted to collect the particles in the gas.

The invention, in another aspect, features a method for removing particles from a gas output by a plasma source. The method involves receiving at an inlet an activated gas generated by a plasma in a chamber. The method also involves directing the activated gas through a gas channel formed in a body structure configured to cause particles in the activated gas passing from a first portion of the gas channel to strike a wall that defines a second portion of the gas channel at an angle relative to a surface of the wall. The method also involves directing the activated gas exiting the gas channel to a process chamber.

The method can involve cooling at least a portion of the wall to cause particles in the activated gas to accumulate on the wall. In some embodiments, the method involves directing the activated gas through the gas channel of the body structure from the second portion of the channel to strike a second wall that defines a third portion of the channel at a second angle relative to a second surface of the second wall. The method can involve cooling at least a portion of the second wall to cause the particles in the activated gas to accumulate on the second wall. The method can involve flowing a fluid in a coolant channel in the body structure to cool at least a portion of the wall. In some embodiments, the wall is indirectly cooled. The method can involve regulating a temperature of the wall. In some embodiments, the method involves generating a signal when the particle count exceeds a predetermined limit. In some embodiments, the gas channel causes a pressure drop between an inlet of the body structure and an outlet of the body structure less than approximately 100 milliTor.

The invention, in another aspect, features a method for removing particles from a gas output by a plasma source. The method involves receiving at an inlet an activated gas generated by a plasma in a chamber. The method also involves directing the activated gas through a gas channel formed in a body structure. The method also involves cooling at least a portion of a wall of the gas channel to cause particles in the activated gas to accumulate on the wall.

In some embodiments, at least a portion of the wall is indirectly cooled. In some embodiments, the method involves regulating a temperature of the wall. In some embodiments, the method involves directing the activated gas through the gas channel of the body structure from a first portion of the channel to strike a second wall that defines a second portion of the channel at an angle relative to a surface of the wall. The method can involve cooling at least a portion of the second wall to cause the particles in the activated gas to accumulate on the second wall. In some embodiments, the method involves flowing a fluid in a coolant channel in the body structure to cool at least a portion of the wall.

The invention, in another aspect, features a system. The system includes a remote plasma source. The system also includes a body structure having an inlet for coupling to a chamber of a remote plasma source and an outlet for coupling to an inlet of a process chamber. The system also includes a gas channel formed in the body structure and in fluid communication with the body structure inlet and the body structure outlet, the gas channel defining a path through the body structure that causes particles in a gas passing from a first portion of the channel to strike a wall that defines a second portion of the gas channel at an angle relative to a surface of the wall.

The invention, in another aspect, features a method of manufacturing a particle trap. The method involves creating a gas channel in a body structure, the gas channel having an inlet capable of coupling to a chamber of a remote plasma source and an outlet capable of coupling to an inlet of a process chamber, the gas channel being configured to cause particles in a gas passing from a first portion of the channel to strike a wall that defines a second portion of the gas channel at an angle relative to a surface of the wall.

In some embodiments, the method involves thermally coupling a cooling member to the gas channel. In some embodiments, the method involves forming at least one coolant channel in the body structure to receive a fluid to cool at least a portion of the wall of the second portion of the gas channel.

The invention, in another aspect, features a particle trap for a remote plasma source. The particle trap includes a means for receiving at an inlet an activated gas generated by a plasma in a chamber. The particle trap also includes a means for directing the activated gas through a gas channel formed in a body structure configured to cause particles in the activated gas passing from a first portion of the gas channel to strike a wall that defines a second portion of the gas channel at an angle relative to a surface of the wall. The particle trap also includes a means for cooling at least a portion of the wall to cause particles in the activated gas to accumulate on the wall.

The invention, in another aspect, features a particle trap for a remote plasma source. The particle trap includes a body structure having an inlet for coupling to a chamber of a remote plasma source and an outlet for coupling to a process chamber inlet. The particle trap also includes at least one obstruction in the body structure. The at least one obstruction is configured to deflect a gas flowing from the inlet to the outlet to cause particles in the gas to strike a surface of the obstruction. In some embodiments, the at least one obstruction is a plurality of obstructions. In some embodiments, the at least one obstruction includes a cooling member in thermal communication with the surface of the at least one obstruction. The cooling member can include a coolant channel to receive a fluid to cool the surface of the at least one obstruction. In some embodiments, the at least one obstruction is a wall that is interior to exterior walls of the body structure.

DETAILED DESCRIPTION

FIG. 1is a schematic cross-sectional view of a plasma generation system100, according to an illustrative embodiment of the invention. The system100includes a remote plasma source110, a process chamber130, and a particle trap140. An outlet125of the remote plasma source110is coupled to an inlet135of the particle trap140. In some embodiments, the outlet125is directly coupled to the inlet135. In some embodiments, the outlet125is indirectly coupled to the inlet135by, for example, a conduit or other suitable structure. The plasma is produced in a chamber120of the plasma source110by, for example, applying an electric potential of sufficient magnitude to a plasma gas (e.g., O2, N2, Ar, NF3, H2and He), or a mixture of gases, to ionize at least a portion of the gas in the chamber120. The plasma is used to activate additional gases introduced into the chamber120of the plasma source110, placing the additional gases in an activated state such that the gases have, for example, an enhanced reactivity. The activated gases are directed out of the outlet125of the plasma source110and into the inlet135of the particle trap140.

A gas channel145is created in a body structure150of the particle trap140. The gas channel145is in fluid communication with the inlet135and an outlet155of the body structure150. An obstruction187is located interior to exterior walls105aand105bof the body structure150. The combination of the obstruction187and the exterior walls105aand105bdefines the gas channel145. The outlet155of the body structure150is coupled to an inlet160of the process chamber130. In some embodiments, the outlet155is directly coupled to the inlet160. In some embodiments, the outlet155is indirectly coupled to the inlet160by, for example, a conduit or other suitable structure. The gas channel145defines a path through the body structure150that causes particles in a gas directed from a first portion165of the channel145to strike a wall170of the obstruction187that defines a second portion175of the gas channel145at an angle Φ1(e.g., in this embodiment, approximately 90 degrees), relative to a surface180of the wall170. The momentum of the particles traveling along the first portion165(along the negative y-axis direction) of the gas channel145causes the particles to strike the surface180of the wall170when the path changes direction at the second portion175of the gas channel145(then traveling generally along the positive and negative x-axis directions). In some embodiments, the wall170is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the surface180of the wall170. In some embodiments the angle θ1is between approximately 45-135 degrees.

In this embodiment, the gas channel145has a third portion185. Particles in the gas directed from the second portion175of the gas channel145strike a second wall190at a second angle Φ2(e.g., in this embodiment, approximately 90 degrees) relative to a second surface192of the second wall190. The momentum of the particles traveling along the second portion175of the gas channel145causes the particles to strike the second surface192of the second wall190when the path changes direction at the third portion185of the gas channel145(then traveling along the negative y-axis direction). In some embodiments, the wall190is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the wall190. In some embodiments the second angle θ2is between approximately 45-135 degrees. In some embodiments, the particle trap is configured to provide a pressure drop between the inlet135and the outlet155of the body structure150that is less than approximately 100 milliTorr. High pressure drops can reduce the activity of the activated gas generated by the remote plasma source110, and therefore reduce the effectiveness and utility of the plasma generation system.

A cooling member195is in thermal communication with the gas channel145adjacent the second wall190. In this embodiment, the cooling member195is a cooling plate in a wall of the body structure150. In some embodiments, the particle trap140includes a plurality of cooling members. In some embodiments, the cooling member195is cooled by a fluid (e.g., water). The cooling member195cools the second surface192of the second wall190. In some embodiments, the second surface192of the second wall190is cooled to approximately 25-30° C. The particles entering the particle trap140via the inlet135have been thermally activated in the remote plasma source120. In some embodiments, the gas entering the particle trap140is approximately 2000° C. The difference in temperature between the thermally-activated particles and the second surface192of the second wall190results in a local temperature gradient in the gas. The magnitude of a typical temperature gradient is greater than approximately 1000° C./cm. Gas species that absorb more plasma power (e.g., oxygen, nitrogen, hydrogen) will have larger temperature gradients than those that absorb less plasma power (e.g., argon). The temperature gradient imparts a force to the thermally-activated particles, called the thermophoretic force, that acts in the direction of steepest temperature descent. The low temperature of the second surface192of the second wall190creates the temperature gradient in the gas, so the thermophoretic force acts to push particles toward the colder second surface192of the second wall190. Particles striking the second surface192of the second wall190accumulate due to a combination of the change in path direction, the high sticking properties of the material (e.g., quartz, aluminum, or aluminum oxide) of the second wall190, and the thermophoretic force associated with the local temperature gradient.

The obstruction187can include a cooling member in thermal communication with the surface180of the wall170of the obstruction187. In some embodiments, the cooling member includes a coolant channel to receive a fluid to cool the surface180of the wall170of the obstruction187. In some embodiments, the particle trap includes a plurality of obstructions187.

After the activated gas is directed through the particle trap140, the activated gas is directed to the process chamber130. Because particles accumulate on the surfaces180and192of the walls170and190, respectively, the activated gas entering the process chamber130has less particles than the activated gas entering the particle trap140.

In some embodiments, features incorporating principles of the invention are provided in (or, as a portion of) the plasma source110. In some embodiments, the plasma source110is adapted to accommodate various features of the particle trap140. For example, the gas channel145and walls170and190can be incorporated into the plasma source110, and, during operation, the walls170and190can accumulate particles as described previously herein. In some embodiments, the cooling member195is incorporated into a portion (e.g., a portion of a wall of an outlet of the chamber120of the plasma source110) creating a temperature gradient between the activated gases and a portion of the chamber to cause particles in the activated gases to migrate towards and adhere to the cooled portion of the chamber.

FIG. 2is a schematic cross-sectional view of a plasma generation system100without a cooling member, according to an illustrative embodiment of the invention. The system100includes a remote plasma source110, a process chamber130, and a particle trap140. An outlet125of the remote plasma source110is coupled to an inlet135of the particle trap140. In some embodiments, the outlet125is directly coupled to the inlet135. In some embodiments, the outlet125is indirectly coupled to the inlet135by, for example, a conduit or other suitable structure. Activated gases are directed out of the outlet125of the plasma source110and into the inlet135of the particle trap140.

A gas channel145is formed in a body structure150of the particle trap140. The gas channel145is in fluid communication with the inlet135and an outlet155of the body structure150. The outlet155of the body structure150is coupled to an inlet160of the process chamber130. In some embodiments, the outlet155is directly coupled to the inlet160. In some embodiments, the outlet155is indirectly coupled to the inlet160by, for example, a conduit or other suitable structure. The gas channel145defines a path through the body structure150that causes particles in a gas directed from a first portion165of the channel145to strike a wall170that defines a second portion175of the gas channel145at an angle Φ1(e.g., in this embodiment, approximately 90 degrees), relative to a surface180of the wall170. The momentum of the particles traveling along the first portion165(along the negative y-axis direction) of the gas channel145causes the particles to strike the surface180of the wall170when the path changes direction at the second portion175of the gas channel145(then traveling generally along the positive and negative x-axis directions). In some embodiments, the wall170is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the surface180of the wall170. In some embodiments the angle θ1is between approximately 45-135 degrees.

In this embodiment, the gas channel145has a third portion185. Particles in the gas directed from the second portion175of the gas channel145strike a second wall190at a second angle Φ2(e.g., in this embodiment, approximately 90 degrees) relative to a second surface192of the second wall190. The momentum of the particles traveling along the second portion175of the gas channel145causes the particles to strike the second surface192of the second wall190when the path changes direction at the third portion185of the gas channel145(then traveling along the negative y-axis direction). In some embodiments, the wall190is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the wall190. In some embodiments the second angle θ2is between approximately 45-135 degrees.

After the activated gas is directed through the particle trap140, the activated gas is directed to the process chamber130. Because particles accumulate on the surfaces180and192of the walls170and190respectively, the activated gas entering the process chamber130has less particles than the activated gas entering the particle trap140.

FIG. 3is a schematic cross-sectional view of a plasma generation system100, according to an illustrative embodiment of the invention. The system100includes a remote plasma source110, a process chamber130, and a particle trap340. An outlet125of the remote plasma source110is coupled to an inlet135of the particle trap340. In some embodiments, the outlet125is directly coupled to the inlet135. In some embodiments, the outlet125is indirectly coupled to the inlet135by, for example, a conduit or other suitable structure. Activated gases are directed out of the outlet125of the plasma source110and into the inlet135of the particle trap340.

A gas channel345is created in a body structure350of the particle trap340. The gas channel345is in fluid communication with the inlet135and an outlet155of the body structure350. The outlet155of the body structure350is coupled to an inlet160of the process chamber130. In some embodiments, the outlet155is directly coupled to the inlet160. In some embodiments, the outlet155is indirectly coupled to the inlet160by, for example, a conduit or other suitable structure. In some embodiments, the particle trap is configured to provide a pressure drop between the inlet135and the outlet155of the body structure150that is less than approximately 100 milliTor. High pressure drops can reduce the activity of the activated gas generated by the remote plasma source110.

A cooling member390is in thermal communication with the gas channel345adjacent a wall370. The cooling member390cools at least a portion of the wall370, including a surface380of the wall370. In some embodiments, the surface380of the wall370is cooled to approximately 25-30° C. The cooling member390has a plurality of cooling channels395. Coolant (e.g., water) flows through the channels395to cool the cooling member390and the wall370. Particles entering the particle trap340via the inlet135have been thermally activated in the remote plasma source120. In some embodiments, the gas entering the particle trap340is approximately 2000° C. The difference in temperature between the thermally activated particles and the surface380of the wall370results in a local temperature gradient. The magnitude of a typical temperature gradient is greater than approximately 1000° C./cm. Gas species that absorb more plasma power (e.g., oxygen, nitrogen, hydrogen) will have larger temperature gradients than those that absorb less plasma power (e.g., argon). The temperature gradient imparts a force to the thermally-activated particles, called the thermophoretic force, that acts in the direction of steepest temperature descent. The low temperature of the surface380of the wall370creates the temperature gradient in the gas, so the thermophoretic force acts to push particles toward the colder surface380of the wall370. In some embodiments, the wall370can be made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the surface380of the wall370.

After the activated gas is directed through the particle trap340, the activated gas is directed to the process chamber130. Because particles accumulate on the surface380of the wall390, the activated gas entering the process chamber130has less particles than the activated gas entering the particle trap340.

FIG. 4is a schematic cross-sectional view of a particle trap440, according to an illustrative embodiment of the invention. The particle trap440can be used in a plasma generation system (e.g., the plasma generation system100ofFIG. 1,2, or3). The particle trap440has an inlet135that can be coupled to an outlet of a remote plasma source (e.g., the outlet125of the remote plasma source110ofFIG. 1,2, or3). The particle trap440has an outlet155that can be coupled to the inlet of a process chamber (e.g., the inlet160of the process chamber130ofFIG. 1,2, or3). In some embodiments, the body structure150is disposed in a chamber (e.g., the chamber120ofFIG. 1,2, or3) of the remote plasma source (e.g., the remote plasma source110ofFIG. 1,2, or3).

A gas channel445is formed in a body structure450of the particle trap440and is in fluid communication with the inlet135and the outlet155. The gas channel145defines a path through the body structure450that causes particles in a gas passing from a first portion465of the gas channel445to strike a wall470that defines a second portion475of the gas channel445at an angle Φ4(in this embodiment, approximately 135 degrees) relative to a surface480of the wall470. The momentum of the particles traveling along the first portion465of the gas channel445causes the particles to strike the surface480of the wall470when the path changes direction at the second portion475of the gas channel445. In some embodiments, the wall470is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the wall470. In some embodiments, the first portion465is at a substantially normal angle (e.g., Φ4is substantially equal to 90 degrees) to the second portion475of the gas channel445. In some embodiments, θ4is between approximately 45-135 degrees.

Optional coolant channels495aand495b(collectively, cooling member495) are included in alternative embodiments of the invention. The cooling member495is in thermal communication with the gas channel445. The coolant channel495ais formed in the body structure450to receive a fluid (e.g., water) to cool at least a portion of the wall470, including the surface480of the wall470, of the second portion475of the gas channel445. In some embodiments, the surface480of the wall470is cooled to approximately 25-30° C. The particles entering the particle trap140have been thermally activated in the remote plasma source. In some embodiments, the gas entering the particle trap140is approximately 2000° C. The difference in temperature between the thermally-activated particles and the surface480of the wall470results in a local temperature gradient. The magnitude of a typical temperature gradient is greater than approximately 1000° C./cm. Gas species that absorb more plasma power (e.g., oxygen, nitrogen, hydrogen) will have larger temperature gradients than those that absorb less plasma power (e.g., argon). The local temperature gradient imparts a force to the thermally-activated particles, called the thermophoretic force, that acts in the direction of steepest temperature descent. The low temperature of the surface480of the wall470creates the temperature gradient in the gas, so the thermophoretic force acts to push particles toward the colder surface480of the wall470. Particles striking the surface480of the wall470accumulate due to a combination of the change in path direction, the high sticking properties of the material (e.g., quartz, aluminum, or aluminum oxide) of the wall490, and the thermophoretic force associated with the local temperature gradient.

In some embodiments, the coolant channel495ais disposed outside the particle trap440. In those embodiments, the coolant channel495aindirectly cools at least a portion of the wall470, including the surface480of the wall470, of the second portion475of the gas channel445through the body structure450. In one embodiment, the coolant channel495ais external to the particle trap440and is coupled to a wall of the particle trap with a thermally conductive bonding material. In some embodiments, the coolant channel495ais disposed orthogonally to the coolant channel depicted inFIG. 4, such that a path of the coolant channel495ais at least substantially parallel to the path of the gas channel adjacent the surface480of the wall470.

The coolant channel495bis formed in the body structure450to receive a fluid to cool at least a portion of the interior wall490. The difference in temperature between the thermally-activated particles and the interior wall490results in a second local temperature gradient. The second local temperature gradient causes the thermally-activated particles that were not attracted to the wall470to be attracted to the low temperature of the wall490due to a thermophoretic force associated with the second temperature gradient. In some embodiments, the coolant channel495bis disposed outside the particle trap440. In those embodiments, the coolant channel495aindirectly cools at least a portion of the wall490, including a surface492of the wall490, of the second portion475of the gas channel445through the body structure450. In some embodiments, the coolant channel495bis disposed orthogonally to the coolant channel depicted inFIG. 4, such that a path of the coolant channel495ais at least substantially parallel to the path of the gas channel445adjacent the surface492of the wall490.

After the activated gas is directed through the particle trap440, the activated gas can be directed to the process chamber. Because particles accumulate on the surfaces480and490of the walls470and490respectively, the activated gas entering the process chamber has less particles than the activated gas entering the particle trap440.

FIGS. 5A and 5Bare schematic cross-sectional views of different illustrative embodiments of a particle trap540. The particle trap540can be used in a plasma generation system (e.g., the plasma generation system100ofFIG. 1,2, or3). The particle trap540has an inlet135that can be coupled to an outlet of a remote plasma source (e.g., the outlet125of the remote plasma source110ofFIG. 1,2, or3). The particle trap540has an outlet155that can be coupled to the inlet of a process chamber (e.g., the inlet160of the process chamber130ofFIG. 1,2, or3). A gas channel545is formed in a body structure550of the particle trap540and is in fluid communication with the inlet135and the outlet155.

Referring toFIG. 5A, the gas channel545adefines a path through the body structure550that causes particles in a gas passing from a first portion565a(e.g., along a negative y axis) of the gas channel545ato strike a wall570athat defines a second portion575aof the gas channel545ahaving a local angle Φ5a(in this embodiment, approximately 135 degrees) relative to a surface580aof the wall570a. In this embodiment, the first portion565aand the second portion575aform a curved portion of the path of the channel545a. The momentum of the particles traveling along the first portion565aof the gas channel545acauses the particles to strike the surface580aof the wall570awhen the path changes direction at the second portion575aof the gas channel545a. In some embodiments, the wall570ais made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the surface580aof the wall570a. In some embodiments, the local angle Φ5ais between approximately 45-135 degrees.

After the activated gas is directed through the particle trap540, the activated gas can be directed to a process chamber. Because particles accumulate on the surface580aof the wall570a, the activated gas entering the process chamber has less particles than the activated gas entering the particle trap540.

Referring toFIG. 5B, the gas channel545bdefines a path through the body structure550that causes particles in a gas passing from a first portion565b(e.g., along the negative y axis) of the gas channel545bto strike a surface580bof a wall570bthat defines a second portion575bof the gas channel545bat an angle Φ5brelative to the surface580bof the wall570b. In this embodiment, the first portion565bof the gas channel545bis at a substantially normal angle to the second portion575b(e.g., Φ5bis substantially equal to 90 degrees). The momentum of the particles traveling along the first portion565bof the gas channel545bcauses the particles to strike the surface580bof the wall570bwhen the path changes direction at the second portion575bof the gas channel545b. In some embodiments, the wall570bis made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the surface580bof the wall570b.

After the activated gas is directed through the particle trap540, the activated gas can be directed to the process chamber. Because particles accumulate on the surface580aof the wall570a, the activated gas entering the process chamber has less particles than the activated gas entering the particle trap540.

FIG. 6is a schematic cross-sectional view of a particle trap640, according to an illustrative embodiment of the invention. The particle trap640can be used in a plasma generation system (e.g., the plasma generation system100ofFIG. 1,2, or3). The particle trap640has an inlet135that can be coupled to an outlet of a remote plasma source (e.g., the outlet125of the remote plasma source110ofFIG. 1,2, or3). The particle trap640has an outlet155that can be coupled to the inlet of a process chamber (e.g., the inlet160of the process chamber130ofFIG. 1,2, or3). A gas channel645is formed in a body structure650of the particle trap640and is in fluid communication with the inlet135and the outlet155. The gas channel645defines a path through the body structure650that causes particles in a gas passing from a first portion665of the gas channel645to strike a second surface680of a second wall670that defines a second portion675of the gas channel645at an angle Φ6(in this embodiment, approximately 135 degrees) relative to the second surface680of the wall670. The momentum of the particles traveling along the first portion665of the gas channel645causes the particles to strike the second surface680of the second wall670when the path changes direction at the second portion675of the gas channel645.

In this embodiment, a first surface615of a first wall610is irregular, providing a plurality of depressions620on the first surface615of the first wall610. The particles traveling along the first section665of the gas channel645strike the first surface615of the first wall610, including the depressions620. Particles in the gas traveling along the first portion665of the gas channel645are trapped by the depressions620. In some embodiments, the first wall610is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, which further facilitates to the accumulation of particles on the first surface615of the first wall610.

The second surface680of the second wall670is irregular, providing a plurality of depressions685on the second surface680of the second wall670. The particles traveling from the first section665of the gas channel645strike the second surface680of the second wall670in a distribution along the second surface680of the second wall670. Particles traveling along the second portion675of the gas channel645strike the second surface680of the second wall670, including the depressions685. Particles in the gas traveling along the second portion675of the gas channel645are trapped by the depressions685to prevent the particles from being dislodged by mechanical vibration in the system. In some embodiments, at least one of the surfaces615or680of the walls610or670respectively is at least partially irregular. In some embodiments, only one of the walls610or670is at least partially irregular. In some embodiments, at least one of the surfaces615or680is textured. A textured surface increases the likelihood that particles will adhere to the surfaces615or680because the textured surface has local pockets or depressions in which particles can be trapped.

In some embodiments, the second wall670is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the wall470. In some embodiments, the first portion665is at a substantially normal angle (e.g., θ6is approximately 90 degrees) to the second portion675of the gas channel645. In some embodiments, Φ6is between approximately 45-135 degrees.

After the activated gas is directed through the particle trap640, the activated gas can be directed to the process chamber. Because particles accumulate on the surfaces615or680of the walls610or670respectively, the activated gas entering the process chamber has less particles than the activated gas entering the particle trap640.

FIG. 7is a schematic cross-sectional view of a particle trap740, according to an illustrative embodiment of the invention. The particle trap740can be used in a plasma generation system (e.g., the plasma generation system100ofFIG. 1,2, or3). The particle trap740has an inlet135that can be coupled to an outlet of a remote plasma source (e.g., the outlet125of the remote plasma source110ofFIG. 1,2, or3). The particle trap740has an outlet155that can be coupled to the inlet of a process chamber (e.g., the inlet160of the process chamber130ofFIG. 1,2, or3).

A gas channel745is created in a body structure750of the particle trap740and is in fluid communication with the inlet135and the outlet155. An obstruction787is located interior to exterior walls705aand705bof the body structure750. The combination of the obstruction787and the exterior walls705aand705bdefines the gas channel145. The gas channel745defines a path through the body structure750that causes particles in a gas passing from a first portion765(e.g., along the negative y-axis direction) of the gas channel745to strike a surface780of a wall770of the obstruction787that defines a second portion775of the gas channel745at an angle Φ7a(in this embodiment, approximately 90 degrees) relative to the surface780of the wall770. The momentum of the particles traveling along the first portion765of the gas channel745causes the particles to strike the surface780of the wall770when the path changes direction at the second portion775of the gas channel745. In this embodiment, the wall770includes a depression735. Particles traveling along the second portion775(e.g., along the positive and negative x-axis directions) strike a surface730in the depression735of the wall770. The depression735traps the particles away from the gas flowing along the second portion775of the gas channel745, causing the particles to accumulate on the surface730of the depression735and serves to prevent the particles from being dislodged by mechanical vibration in the system. In some embodiments, the wall770is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the surface780of the wall770or the surface730of the depression735of the wall770. In some embodiments, the angle Φ7ais between approximately 45-135 degrees.

In some embodiments, the obstruction787includes a depression (e.g., the depression735). The obstruction787can include a cooling member in thermal communication with the surface780of the wall770of the obstruction787. In some embodiments, the cooling member includes a coolant channel to receive a fluid to cool the surface780of the wall770of the obstruction787. In some embodiments, the particle trap includes a plurality of obstructions787.

Still referring toFIG. 7, the gas channel745has a third portion785. Particles in the gas directed from the second portion775of the gas channel745(e.g., along the positive and negative x-axis directions) strike a second surface792of a second wall790at a second angle Φ7b(in this embodiment, approximately 90 degrees) relative to the second surface792of the second wall790. The momentum of the particles traveling along the second portion775of the gas channel745causes the particles to strike the second surface792of the second wall790when the path changes direction at the third portion785of the gas channel745. In some embodiments, the wall790is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the wall790. In some embodiments, the second angle Φ7bis between approximately 45-135 degrees. In some embodiments, the second wall790includes a depression.

Optional cooling member795is in thermal communication with the gas channel745adjacent the second wall790. The cooling member795indirectly cools the second surface792of the second wall790through the body structure750. In some embodiments, the second surface792of the second wall790is cooled to approximately 25-30° C. The particles entering the particle trap740are thermally activated from processing in the remote plasma source. In some embodiments, the gas entering the particle trap740is approximately 2000° C. The difference in temperature between the thermally-activated particles and the wall770results in a local temperature gradient. The magnitude of a typical temperature gradient is greater than approximately 1000° C./cm. Gas species that absorb more plasma power (e.g., oxygen, nitrogen, hydrogen) will have larger temperature gradients than those that absorb less plasma power (e.g., argon). The local temperature gradient imparts a force to the thermally-activated particles, called the thermophoretic force, that acts in the direction of steepest temperature descent. The low temperature of the second surface792of the second wall790creates the temperature gradient in the gas, so the thermophoretic force acts to push particles toward the colder second surface792of the second wall790. Particles striking the second surface792of the second wall790accumulate due to a combination of the change in path direction, the high sticking properties of the material (e.g., quartz, aluminum, or aluminum oxide) of the second wall790, and the thermophoretic force associated with the local temperature gradient.

After the activated gas is directed through the particle trap740, the activated gas can be directed to the process chamber. Because particles accumulate on the surfaces780,730, and792, the activated gas entering the process chamber has less particles than the activated gas entering the particle trap740.

FIG. 8is a schematic cross-sectional view of a particle trap840, according to an illustrative embodiment of the invention. The particle trap840can be used in a plasma generation system (e.g., the plasma generation system100ofFIG. 1,2, or3). The particle trap840has an inlet135that can be coupled to an outlet of a remote plasma source (e.g., the outlet125of the remote plasma source110ofFIG. 1,2, or3). The particle trap840has an outlet155that can be coupled to the inlet of a process chamber (e.g., the inlet160of the process chamber130ofFIG. 1,2, or3).

A gas channel845is formed in a body structure850of the particle trap840and is in fluid communication with the inlet135and the outlet155. An obstruction887is located interior to exterior walls805aand805bof the body structure850. The combination of the obstruction887and the exterior walls805aand805bdefines the gas channel845. The gas channel845defines a path through the body structure850that causes particles in a gas passing from a first portion865(e.g., along the negative y-axis direction) of the gas channel845to strike a surface880of a wall870of the obstruction887that defines a second portion875of the gas channel845at an angle Φ8a(e.g., in this embodiment, approximately 90 degrees) relative to a surface880of the wall870. The momentum of the particles traveling along the first portion865of the gas channel845causes the particles to strike the surface880of the wall870when the path changes direction at the second portion875of the gas channel845. In some embodiments, the wall870is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the surface880of the wall870. In some embodiments, the angle Φ8ais between approximately 45-135 degrees. In some embodiments, the first wall870includes at least one depression (e.g., the depression735ofFIG. 7).

Still referring toFIG. 8, the gas channel845has a third portion885. Particles in the gas directed from the second portion875of the gas channel845(e.g., along the positive and negative x-axis directions) strike a second surface892of a second wall890at a second angle Φ8b(e.g., in this embodiment, approximately 90 degrees) relative to the second surface892of the second wall890. The momentum of the particles traveling along the second portion875of the gas channel845causes the particles to strike the second surface892of the second wall890when the path changes direction at the third portion885of the gas channel845.

In some embodiments, the wall890is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the wall890. In some embodiments, the second angle Φ8bis between approximately 45-135 degrees. In some embodiments, the second wall890includes a depression.

In this embodiment, the third portion885includes a depression835in a third wall820. Particles traveling along the third portion885(e.g., along the negative y-axis direction) enter the depression835of the third wall820. The particles strike a third surface830of the third wall820. The depression835traps particles in the gas that flow along the third portion885of the gas channel845, causing the particles to accumulate on the third surface830of the depression835and serves to prevent the particles from being dislodged by mechanical vibration in the system. In some embodiments, the third wall820is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the third wall820. In some embodiments, a cooling member is in thermal communication with the depression835in the third wall820to enhance the particle trapping properties of the particle trap840.

After the activated gas is directed through the particle trap840, the activated gas can be directed to the process chamber. Because particles accumulate on the surfaces880,892, and830, the activated gas entering the process chamber has less particles than the activated gas entering the particle trap840.

FIG. 9is a schematic cross-sectional view of a particle trap940, according to an illustrative embodiment of the invention. The particle trap940can be used in a plasma generation system (e.g., the plasma generation system100ofFIG. 1,2, or3). The particle trap940has an inlet135that can be coupled to an outlet of a remote plasma source (e.g., the outlet125of the remote plasma source110ofFIG. 1,2, or3). The particle trap940has an outlet155that can be coupled to the inlet of a process chamber (e.g., the inlet160of the process chamber130ofFIG. 1,2, or3).

A gas channel945is formed in a body structure950of the particle trap940and is in fluid communication with the inlet135and the outlet155. An obstruction987is located interior to exterior walls905aand905bof the body structure950. The combination of the obstruction987and the exterior walls905aand905bdefines the gas channel945. The gas channel945defines a path through the body structure950that causes particles in a gas passing from a first portion965(e.g., along the negative y-axis direction) of the gas channel945to strike a surface980of a first wall970that defines a second portion975of the gas channel945at an angle Φ9a(e.g., in this embodiment, approximately 120 degrees) relative to the surface980of the first wall970. The momentum of the particles traveling along the first portion965of the gas channel945causes the particles to strike the surface980of the first wall970when the path changes direction at the second portion975of the gas channel945. In some embodiments, the first wall970is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the surface980of the wall970. In some embodiments, the angle Φ9ais between approximately 45-135 degrees. In some embodiments, the first wall970includes a depression (e.g., the depression735fromFIG. 7).

In some embodiments, the obstruction987includes a depression (e.g., the depression735fromFIG. 7). The obstruction987can include a cooling member in thermal communication with the surface980of the first wall970of the obstruction987. In some embodiments, the cooling member includes a coolant channel to receive a fluid to cool the surface980of the first wall970of the obstruction987. In some embodiments, the particle trap includes a plurality of obstructions987.

Still referring toFIG. 9, the gas channel945has a third portion985. Particles in the gas directed from the second portion975of the gas channel945strike a second surface992of a second wall990at a second angle Φ9b(e.g., in this embodiment, approximately 135 degrees) relative to the second surface992of the second wall990. The momentum of the particles traveling along the second portion975of the gas channel945causes the particles to strike the second surface992of the second wall990when the path changes direction at the third portion985of the gas channel945. In this embodiment, a portion of the second surface992of the second wall990defines a curve. In some embodiments, the wall990is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the wall990. In some embodiments, the second angle Φ9bis between approximately 45-135 degrees. In some embodiments, the second wall990includes a depression.

In this embodiment, the third portion985includes a depression in a third wall920. Particles traveling along the third portion985enter a depression935of the third wall920. The particles strike a surface930of the third wall920. The depression935traps particles in the gas that are flowing along the third portion985of the gas channel945, causing the particles to accumulate on the third surface930of the depression935and serves to prevent the particles from being dislodged by mechanical vibration in the system. In some embodiments, the third wall920is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the surface930of the third wall920. In some embodiments, a cooling member is in thermal communication with the depression in the third wall920.

After the activated gas is directed through the particle trap940, the activated gas can be directed to the process chamber. Because particles accumulate on the surfaces980,992, and930, the activated gas entering the process chamber has less particles than the activated gas entering the particle trap940.

FIG. 10is a schematic cross-sectional view of a particle trap1040, according to an illustrative embodiment of the invention. The particle trap1040can be used in a plasma generation system (e.g., the plasma generation system100ofFIG. 1,2, or3). The particle trap1040includes a body structure1050having an inlet135that can be coupled to an outlet of a remote plasma source (e.g., the outlet125of the remote plasma source110ofFIG. 1,2, or3). The body structure1050has an outlet155that can be coupled to the inlet of a process chamber (e.g., the inlet160of the process chamber130ofFIG. 1,2, or3). The particle trap includes at least one obstruction1010in the body structure1050. In some embodiments, the at least one obstruction1010is a plurality of obstructions1010. In this embodiment, the particle trap1040includes 8 obstructions1010. In some embodiments, the at least one obstruction1010has, or is, a wall (e.g., the wall170ofFIG. 1or2) that is interior to exterior walls1030aand1030bof the body structure1050. The at least one obstruction1010is configured to deflect a gas flowing from the inlet135to the outlet155to cause particles in the gas to strike a surface1015of the at least one obstruction1010. The momentum of the particles flowing from the inlet135to the outlet155of the body structure1050causes the particles to strike the surface1015of the at least one obstruction1010when the gas is deflected thereby. In some embodiments, the surface1015of the at least one obstruction1010is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the surface1015of the at least one obstruction1010. In some embodiments, the at least one obstruction1010includes a depression (e.g., the depression935ofFIG. 9).

The at least one obstruction1010includes a cooling member1020in thermal communication with the surface1015of the at least one obstruction1010. The cooling member1020can include a coolant channel to receive a fluid to cool the surface1015of the at least one obstruction1010. The surface1015of the at least one member1010can be cooled to approximately 25-30° C. The particles entering the particle trap1040are thermally activated from processing in the remote plasma source. In some embodiments, the gas entering the particle trap1040is approximately 2000° C. The difference in temperature between the thermally-activated particles and the surface1015of the at least one member1010results in a local temperature gradient. The magnitude of a typical temperature gradient is greater than approximately 1000° C./cm. Gas species that absorb more plasma power (e.g., oxygen, nitrogen, hydrogen) will have larger temperature gradients than those that absorb less plasma power (e.g., argon). The local temperature gradient imparts a force to the thermally-activated particles, called the thermophoretic force, that acts in the direction of steepest temperature descent. The low temperature of the surface1015of the at least one member1010creates the temperature gradient in the gas, so the thermophoretic force acts to push particles toward the cold surface1015of the at least one member1010.

FIG. 11is a schematic cross-sectional view of a particle trap1140, according to an illustrative embodiment of the invention. In this embodiment, a body structure1150of the particle trap1140is disposed in an outlet1160of a remote plasma source (e.g., the remote plasma source120ofFIG. 1,2, or3). The body structure1150includes a first end1130and a second end1135. The body structure1150has a channel1144with an inlet1132at the first end1130and an outlet1134at the second end1135. Gas entering the inlet1132flows through the channel1144to the outlet1134. In this embodiment, the body structure1150is substantially circular in cross section. A diameter d1of the inlet1132at the first end1130is greater than a diameter d2of the outlet1134at the second end1135. Particles traveling through the channel1144of the body structure1150strike an interior surface1152of the second end1135at an angle relative to the interior surface1152of the second end1135.

In some embodiments, the diameter d1of the first end1130is approximately equal to the diameter d2of the second end1135. In some embodiments, the diameter d1is approximately 4.6 centimeters (1.8 inches) and the diameter d2is approximately 3.8 centimeters (1.5 inches). In some embodiments, the body structure1150is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the interior surface of the body structure1150.

The body structure is coupled to a conduit1145. The conduit1145is coupled to an inlet1170of a process chamber (e.g., the process chamber130ofFIG. 1,2, or3). The conduit1145transports gas from the outlet1134of the body structure1150to the inlet1170of the process chamber. In this embodiment, the conduit1145is substantially cylindrical. In some embodiments, a length l of the conduit1145is approximately 10.2 centimeters (4 inches). The particle trap1140also includes a cooling member1195. The cooling member1195is in thermal communication with the conduit1145and the body structure1150. The cooling member1195cools an interior surface1175of the conduit1145. In some embodiments, the cooling member1195includes one or more coolant channels that are in the body of the cooling member1195through which coolant flows. In some embodiments, the interior surface1175of the conduit1145is cooled to approximately 25-30° C. The particles entering the conduit1145are thermally activated from processing in a remote plasma source. In some embodiments, the gas entering the conduit1145is approximately 2000° C. The difference in temperature between the thermally-activated particles and the interior surface1175of the conduit1145results in a local temperature gradient. The magnitude of a typical temperature gradient is greater than approximately 1000° C./cm. Gas species that absorb more plasma power (e.g., oxygen, nitrogen, hydrogen) will have larger temperature gradients than those that absorb less plasma power (e.g., argon). The local temperature gradient imparts a force to the thermally-activated particles, called the thermophoretic force, that acts in the direction of steepest temperature descent. The low temperature of the interior surface1175of the conduit1145creates the temperature gradient in the gas, so the thermophoretic force acts to push particles towards the colder interior surface1175of the conduit1145.

After the activated gas is directed through the particle trap1140, the activated gas can be directed to a process chamber. Because particles accumulate on the interior surfaces of the body structure1150and the conduit1145, the activated gas entering the process chamber has less particles than the activated gas entering the particle trap1140.

FIG. 12is a schematic cross-sectional three-dimensional view of a particle trap1240, according to an illustrative embodiment of the invention. In this embodiment, a body structure1250of the particle trap1240is an outlet1260of a remote plasma source (e.g., the remote plasma source120ofFIG. 1,2, or3). The body structure1250has a length l1aand includes a first end1230and a second end1235. A diameter d1aof the first end1230is greater than a diameter d2aof the second end1235. Particles traveling through the body structure1250strike an interior surface1220of the second end1235at an angle Φ12relative to the interior surface1220of the second end1235.

In some embodiments, the body structure1250is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing the particles to accumulate on the interior surface1220of the body structure1250.

In some embodiments, the diameter d1aof the first end1230is approximately equal to the diameter d2aof the second end1235. The effectiveness (e.g., number of particles trapped) of the particle trap1240increases as a ratio of the diameter d1ato the diameter d2aincreases (i.e., the angle Φ12increases). In some embodiments, the diameter d1ais approximately 4.6 centimeters (1.8 inches), the diameter d2ais approximately 3.8 centimeters (1.5 inches), and the length l1ais approximately 2.8 centimeters (1.1 inches). In some embodiments, the body structure1250is in thermal communication with a cooling member.

In some embodiments, the second end1235of the body structure1250is coupled to an inlet of a process chamber (e.g., the process chamber130ofFIG. 1,2, or3). In this embodiment, the second end1235of the body structure1250is coupled to a conduit1245. The conduit1245is substantially cylindrical. The conduit1245is coupled to an inlet of the process chamber (e.g., the process chamber130ofFIG. 1,2, or3). In some embodiments, the conduit1245is made out of a material (e.g., quartz, aluminum, or aluminum oxide) that has a high sticking coefficient, causing particles to accumulate on an interior surface1260of the conduit1245. The effectiveness (e.g., number of particles trapped) of the conduit1245increases as a length l2aincreases.

In some embodiments, the conduit1245is in thermal communication with a cooling member (not shown). The interior surface1260of the conduit1245can be cooled by the cooling member. The particles entering the conduit1245are thermally activated from processing in the remote plasma source. The difference in temperature between the thermally-activated particles and the interior surface1260of the conduit1245results in a local temperature gradient in the gas. The magnitude of a typical temperature gradient is greater than approximately 1000° C./cm. Gas species that absorb more plasma power (e.g., oxygen, nitrogen, hydrogen) will have larger temperature gradients than those that absorb less plasma power (e.g., argon). The local temperature gradient imparts a force to the thermally-activated particles, called the thermophoretic force, that acts in the direction of steepest temperature descent. The low temperature of the interior surface1260of the conduit1245creates the temperature gradient in the gas, so the thermophoretic force acts to push particles toward the colder interior surface1260of the conduit1245. In some embodiments, the length l2ais approximately 10.2 centimeters (4 inches). In some embodiments, the conduit1245is coupled to a subsequent particle trap.

After the activated gas is directed through the particle trap1240and the conduit1245, the activated gas can be directed to the process chamber. Because particles accumulate on the interior surface1220of the body structure1250and the interior surface1260of the conduit1245, the activated gas entering the process chamber has less particles than the activated gas entering the particle trap1240and the member1245.

Variations, modifications, and other implementations of what is described herein will occur to those of ordinary skill in the art without departing from the spirit and the scope of the invention and are considered to be encompassed thereby. Accordingly, the invention is not to be defined only by the preceding illustrative description.