Patent Application
20180272390
Embodiments of the disclosure generally relate to an improved batch processing load lock chamber, and a method for processing semiconductor substrates using the same.
A cluster tool allows for automatic transfer of a substrate between process chambers for use in different processes like chemical vapor deposition, physical vapor deposition, etching and the like. The cluster tool is used for parallel processing of multiple substrates to increase throughput and productivity. Typical configuration includes a conventional load lock chamber for loading substrates, a transfer chamber, and several process chambers which can perform the deposition and etching processes. In some applications, one or more of the processing chambers is replaced by a pre-clean chamber. The substrates are transferred between chambers under vacuum using a transfer mechanism to prevent exposure to air which prevents oxidation and contamination.
The load lock chamber is an auxiliary chamber in a cluster tool used to introduce substrates into the transfer chamber without exposing the vacuum condition inside the transfer chamber to the air outside the cluster tool. A vacuum pumping system connected to the load lock chamber pumps down the pressure inside the load lock chamber to a level compatible with the pressure inside the transfer chamber of the cluster tool. The load lock chamber may include a cassette for holding a plurality of substrates.
Prior to processing, the substrates are cleaned in a pre-clean chamber attached to the transfer chamber. During the pre-clean process, impurities such as native oxides, organic materials are removed from the substrates in order to prepare them for subsequent processing. The impurities affect the electrical properties of the substrates. For example, silicon oxide films formed by exposure of silicon substrates to oxygen, are electrically insulating and hence undesirable.
The presence of the pre-clean chamber reduces the number of processing chambers that can attach to the transfer chamber. Thus the flexibility to run different processes and the throughput is reduced.
Embodiments of the disclosure generally relate to an improved batch processing load lock chamber, a cluster tool having the same and a method of using the improved load lock chamber to clean a plurality of substrates disposed within. In one embodiment, a load lock chamber includes a chamber body, a cassette disposed in the chamber body, a remote plasma source, a plurality of inlet nozzles and a plurality of outlet ports. The chamber body has a plurality of substrate transfer slots formed therein. The cassette has a plurality of substrate storage slots and is configured to move up and down within the chamber body. The plurality of inlet nozzles is coupled to the remote plasma source and faces a processing region defined within the chamber body. The plurality of outlet ports faces the plurality of inlet nozzles across the processing region.
In another embodiment of the disclosure, a load lock chamber includes a chamber body, a cassette disposed in the chamber body, a remote plasma source, a plurality of inlet nozzles, a plurality of outlet ports, a pump coupled to the plurality of outlet ports, one or more heating elements disposed around the chamber body, one or more cooling channels disposed around the chamber body, an inlet manifold, an outlet manifold and a lift actuator configured to raise and lower the cassette. The chamber body has a plurality of substrate transfer slots formed therein. The cassette has a plurality of substrate storage slots. The plurality of inlet nozzles is coupled to the remote plasma source and faces a processing region defined within the chamber body. The plurality of outlet ports faces the plurality of inlet nozzles across the processing region. The inlet manifold connects the remote plasma source to the plurality of inlet nozzles. The outlet manifold connects the plurality of outlet ports to the pump.
In yet another embodiment of the disclosure, a method for processing a plurality of substrates disposed in a load lock chamber is provided. The method includes loading a cassette disposed in a chamber body with a plurality of substrates through a first substrate transfer slot formed through the chamber body, flowing radicals from a remote plasma source horizontally across the plurality of substrates disposed in the cassette and transferring the plurality of substrates after exposure to the radicals out of the chamber body through a second substrate transfer slot formed through the chamber body.
So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of its scope, may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
Embodiments of the disclosure generally relate to an improved batch processing load lock chamber, a cluster tool having the same and a method of using the improved load lock chamber to clean a plurality of substrates disposed within.
The improved batch processing load lock chamber described herein increases both the speed of processing and yield of substrates processed within a cluster tool. Incorporation of a pre-clean capability in the load lock chamber increases system efficiency, resulting in an increase in the number of substrates that can be processed by the cluster tool in a given time, leading to an increased throughput.
The cassette 120 is supported onto a platform 130 by a shaft 128. The shaft 128 is coupled to a lift actuator 135a, which is capable of raising or lowering the cassette 120 disposed within the chamber 100 as needed. In some embodiments, the lift actuator 135a may be a lift motor. In the embodiment shown in
The cassette 120 has a top surface 122, a bottom surface 124 and a wall 126. The wall 126 of the cassette 120 has a plurality of substrate storage slots collectively referenced as 250. Each substrate storage slot 250 is configured to hold a substrate 200 therein. Each substrate storage slot 250 is evenly spaced along the wall 126 of the cassette 120. For example, in the embodiment shown in
The cassette 120 is operatively coupled to the lift actuator 135a and a rotary actuator 135b. The lift actuator 135a raises and lowers the cassette 120, thus moving the cassette 120 between a processing position in the processing region 150 and a transfer position that aligns each substrate storage slot 250 with the substrate transfer slots 112 and 114 formed on the chamber body 110. The rotary actuator 135b rotates the cassette 120, as the substrates 200 undergo processing in the processing position.
The inlet nozzles 160 on the chamber body 110 are connected to an inlet manifold 145. The inlet manifold 145 is connected to a remote plasma source 140 by an inlet pipe 142. The remote plasma source 140 is configured to generate gaseous radicals that flow through the inlet pipe 142 and the inlet nozzles 160 into the processing region 150 inside the chamber body 110. The inlet manifold 145 is configured for evenly distributing gaseous radicals through the inlet nozzles 160 into the processing region 150 of the chamber 100.
The remote plasma source 140 is operatively coupled to one or more gas sources, where the gas may be at least one of ammonia, hydrogen, nitrogen or an inert gas like argon or helium. The generation as well as the distribution of gaseous radicals activated in the remote plasma source 140 is controlled by a controller 190.
The outlet ports 170 of the chamber body 110 are connected to an outlet manifold 155. The outlet manifold 155 is connected to an on/off valve 174a in series with a throttle valve 174b by an outlet pipe 172 that is further connected to a pump 182, located downstream of the on/off valve 174a and the throttle valve 174b. The on/off valve 174a and the throttle valve 174b are configured to remove the gaseous radicals and byproducts from the processing region 150 through the outlet ports 170 utilizing the suction force of the pump 182. The operation of the on/off valve 174a and the throttle valve 174b is controlled by the controller 190 through the connecting wires 176a and 176b respectively.
The chamber body 110 includes an exhaust port 180a which is connected to the pump 182 by an exhaust pipe 184. The exhaust pipe 184 is connected to an on/off valve 188a in series with a throttle valve 188b and to the pump 182, located further downstream of the on/off valve 188a and the throttle valve 188b. The on/off valve 188a and the throttle valve 188b are configured to remove air from the processing region 150 through the exhaust port 180a utilizing the suction force of the pump 182, in order to pump down the processing region 150 to a vacuum. The operation of the on/off valve 188a and the throttle valve 188b is controlled by the controller 190 through the connecting wires 187a and 187b respectively.
The chamber body 110 further includes a vent port 180b which is connected to a vent valve 185 by a vent pipe 186. The vent valve 185 is configured to provide air into chamber 100. The operation of the vent valve 185 is controlled by the controller 190 through the connecting wire 189. The air pressure within the processing region 150 inside the chamber 100 is thus regulated by the pump 182 and the vent valve 186, which are controlled by the controller 190.
The chamber body 110 includes one or more heating elements 210 configured to heat the chamber 100. The heating element 210 is shown in both
One or more cooling channels 230 are disposed around the chamber body 110, as shown in
The controller 190 controls the operation of the load lock chamber 100 as well as the remote plasma source 140. The controller 190 is communicatively connected to the lift actuator 135a and the rotary actuator 135b by a connector 198. The controller 190 is communicatively connected to the pump 182 by a connector 183. The controller 190 is communicatively connected to the remote plasma source 140 by a connector 144 and to the heating element 210 and the cooling channel 230 on the chamber body 110 by the connector 116. The controller 190 includes a central processing unit (CPU) 192, a memory 194, and a support circuit 196. The CPU 192 may be any form of general purpose computer processor that may be used in an industrial setting. The memory 194 may be random access memory, read only memory, floppy, or hard disk drive, or other form of digital storage. The support circuit 196 is conventionally coupled to the CPU 192 and may include cache, clock circuits, input/output systems, power supplies, and the like.
The load lock chamber 100 advantageously incorporates a pre-clean capability that is unavailable in conventional load lock chambers. This advantage is demonstrated clearly in
The improved load lock chamber 100 is utilized for pre-cleaning a plurality of substrates before the substrates undergo processing in processing chambers within the cluster tool 600. Initially, the cassette 120 is raised by the lift actuator 135a so that each of the empty substrate storage slots 250 on the cassette 120 sequentially aligns with the substrate transfer slot 112 on the chamber body 110 of the chamber 100. Substrates 200 are loaded into the substrate storage slots 250 one substrate at a time by incrementally raising or lowering the cassette 120, until all the substrate storage slots 250 are occupied by substrates 200 and the cassette 120 is full. The operation of the lift actuator 135a is precisely controlled by the controller 190 such that the substrates 200 are efficiently and correctly loaded onto the respective substrate storage slots 250. Once the cassette 120 is full or otherwise ready for pre-cleaning, the cassette 120 is raised into the processing region 150 such that the substrate storage slots 250 in the cassette 120 is aligned with the inlet nozzles 160 and the outlet ports 170. The positioning of the substrate storage slots 250 laterally between the inlet nozzles 160 and the outlet ports 170 ensures that gaseous radicals distributed from the inlet nozzles 160 uniformly contact the surface of the substrates 200 before they exit through the outlet ports 170.
Once the cassette 120 is loaded with the substrates 200, the controller 190 turns on the on/off valve 188a and the throttle valve 188b to vacuum down the processing region 150 using the pump 182. The controller 190 maintains the desired pressure within the processing region 150 by regulating the inflow and evacuation of air from the processing region 150 through the vent valve 185 and the pump 182 respectively, during and after the pre-cleaning process.
The remote plasma source 140 produces gaseous radicals by activating a gas supplied by a gas source (not shown) operatively coupled to the remote plasma source 140. In one embodiment, the gas supplied to the remote plasma source 140 may be at least one of ammonia, hydrogen, nitrogen or an inert gas like argon or helium. The gaseous radicals activated in the remote plasma source 140 then travel through the inlet pipe 142 to the inlet manifold 145, from where they are distributed in the processing region 150 via the inlet nozzles 160. The cassette 120 is rotated by the rotary actuator 135b as the substrates are exposed to the gaseous radicals. While gaseous radicals flow horizontally from the inlet nozzles 160 and across the plurality of substrates 200, the chamber body 110 is heated to a temperature of about 300-350 degrees Celsius. The application of heat to the chamber body 110 ensures that the gaseous radicals remain sufficiently energized as they flow over the substrates 200. The controller 190 maintains the temperature of the chamber body 110 at the desired level by controlling the heating elements 210 and the cooling channels 230 through feedback received from temperature sensors (not shown).
As the gaseous radicals flow across the substrates, the reaction between the gaseous radicals and impurities such as a native oxide or organic material present on the surface of the substrates 200 creates a gaseous byproduct that removes the impurity and leaves the substrates 200 cleaned. In one embodiment, the gaseous byproduct may be a salt of the native oxide layer. The unreacted gaseous radicals and any gaseous byproducts are removed by the pump 182. The unreacted gaseous radicals and gaseous byproducts exit the processing region 150 through the outlet ports 170 and the outlet manifold 155. The controller 190 turns on the on/off valve 174a and the throttle valve 174b to remove the unreacted gaseous radicals and gaseous byproducts through the pump 182 connected to the outlet manifold 155 via the on/off valve 174a and the throttle valve 174b.
The substrates 200 are thus cleaned prior to subsequent processing in the processing chambers 640. The clean substrates are transferred out of the chamber body 110 through a second substrate transfer slot 114 formed through the chamber body 110. Each of the substrate storage slots 250 of the cassette 120 is sequentially aligned with the substrate transfer slot 114 by the lift actuator 135a. The substrates 200 are unloaded from the substrate storage slots 250 one substrate at a time by incrementally raising or lowering the cassette 120, until all the substrate storage slots 250 in the cassette 120 are emptied. The substrates 200 are efficiently unloaded from the respective substrate storage slots 250 into the transfer chamber 650 by the transfer mechanism (not shown). The transfer mechanism then places the substrates 200 into the processing chambers 640 for further processing. In one embodiment, the transfer mechanism is a robot.
At block 720, gaseous radicals are flown across the plurality of substrates disposed in the chamber body. The cassette is simultaneously rotated to provide uniform exposure across the substrates to the radicals. The gaseous radicals are produced in a remote plasma source by activating at least one of ammonia, hydrogen, nitrogen or an inert gas like argon or helium. The gaseous radicals flow from the remote plasma source and through an inlet manifold connected to one or more inlet nozzles on the chamber body to enter the chamber. While the radicals are flown horizontally from the inlet nozzles and across the plurality of substrates, the chamber is heated to a temperature of about 300-350 degrees Celsius. The temperature of the chamber body is maintained at the desired level by controlling the heat generated by heating element and the heat removed by the cooling channel disposed around the chamber body.
The flow of gaseous radicals across the plurality of substrates disposed in the chamber helps remove impurities present on the substrates such as a native oxide or an organic material. The energized radicals react with the impurities to form a byproduct that is readily removable from the substrate. For example, silicon oxides formed on a silicon substrate may be removed by flowing fluoride radicals over the silicon substrate to form a thin layer of a salt containing silicon and fluorine, which subsequently dissociates into volatile gaseous byproducts. The gaseous radicals and gaseous byproducts are removed by a pump connected to the outlet ports formed in the chamber body via an outlet manifold. The pre-cleaning process of removing impurities prepares the substrates for further processes such deposition, etching, etc.
At block 730, the plurality of substrates, after pre-cleaning, are transferred out of chamber body through a second substrate transfer slot formed through the chamber body. Each substrate storage slot on the cassette is aligned with the second substrate transfer slot in order to remove the substrates. The substrates are transferred out of the cassette and placed in the processing chamber for processing. After processing, the processed substrates are returned to the cassette. Once the cassette is filled with processed substrates, the processing region is vented and the substrates are removed from the load lock chamber into the factory interface.
The improved batch processing load lock chamber and the method for cleaning a plurality of substrates disposed within the load lock chamber increases the efficiency of the cluster tool utilized for processing substrates. Incorporation of a pre-clean capability in a load lock chamber increases system efficiency, resulting in an increase in the number of substrates that can be processed by the cluster tool over a given time. The pre-clean capability in the load lock chamber frees up space for one or more processing chambers that can accommodate additional substrates for processing. The pre-clean capability is incorporated by flowing gaseous radicals from a remote plasma source horizontally across the plurality of substrates disposed in the rotating cassette, removing the impurities as gaseous byproducts and leaving behind clean substrates that are removed for subsequent processing within processing chambers. Thus, a cluster tool incorporating the improved batch processing load lock chamber having a pre-cleaning capability has an increased throughput as compared to conventional systems. Equally importantly, the number of substrates processed in a given time would increase due to the availability of additional processing chambers in the cluster tool with the improved batch processing load lock chamber.
While the foregoing is directed to particular embodiments of the present disclosure, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments to arrive at other embodiments without departing from the spirit and scope of the present inventions, as defined by the appended claims.
