Patent Application
20170053781
The present embodiments relate to semiconductor wafer processing equipment tools, and more particularly, multi-station chambers with symmetric grounding plate for improved wafer-to-wafer non-uniformity matching.
There are many types of film deposition processes commonly used in the semiconductor fabrication field. One example process is referred to as a plasma-enhanced chemical vapor deposition (PECVD), which is a type of plasma deposition that is used to deposit thin films from a gas state (i.e., vapor) to a solid state on a substrate such as a wafer. PECVD systems convert a liquid precursor into a vapor precursor, which is delivered to a chamber. PECVD systems may include a vaporizer that vaporizes the liquid precursor in a controlled manner to generate the vapor precursor.
Another example film deposition process is referred to as atomic layer deposition (ALD), which also utilizes plasma energy to facilitate the deposition. ALD systems are used to produce very thin films that are highly conformal, smooth, and possess excellent physical properties. ALD uses volatile gases, solids, or vapors that are sequentially introduced (or pulsed) over a heated substrate. A first precursor is introduced as a gas, which is absorbed (or adsorbed) into the substrate and the reactor chamber is cleared of the gaseous precursor. A second precursor is introduced as a gas, which reacts with the absorbed precursor to form a monolayer of the desired material. By regulating this sequence, the films produced by ALD are deposited a monolayer at a time by repeatedly switching the sequential flow of two or more reactive gases over the substrate.
Chambers used to process PECVD and ALD processes require highly engineered structural construction so that the resulting films deposited on substrates are as uniform as possible and processes are repeatable from wafer-to-wafer. In such chambers, radio frequency (RF) power is supplied to enable excitation of gases in the form of a plasma, which leads to the deposition of a material film. The delivery of RF power is typically applied to either the substrate support (i.e., the pedestal) or the showerhead. In either configuration, RF power applied to the chamber needs to have an RF return to ground. Commonly, the chamber walls are grounded and RF power turns to ground via one or more conductive paths.
This process has worked well for some time, but as the demand continues to push for the manufacture of smaller feature sizes, more stringent demands are continually made upon chamber construction and engineered geometries. For example, some chamber designs usable for PECVD as well as ALD include multi-station designs. Multi-station designs are those that enable deposition processes to occur in multiple stations at the same time. Such multi-station designs have added complexities associated with neighboring processing by other stations. Furthermore, the RF return to ground from the individual stations may not be symmetric, which may introduce additional challenges in overcoming inherent wafer-to-wafer non-uniformity mismatch.
It is in this context that inventions arise.
Embodiments of the disclosure provide embodiments of a process chamber, used for processing semiconductor wafers. In one implementation, a ground plate is provided that provides for symmetric radio frequency (RF) ground return paths during processing, such as thin film deposition processing in plasma chambers.
A multi-station chamber having a symmetric ground plate is disclosed. The multi-station chamber includes four stations, and the four stations are arranged in a square configuration with a rotating mechanism in a center location. A pedestal for supporting a substrate is provided for each of the four stations, each pedestal is disposed in a lower chamber body, and each pedestal includes a carrier ring. In some embodiments, the carrier ring is referred to as a plasma focus ring. The lower chamber body includes outer walls and inner walls to define a space for each of the pedestals of the four chambers. A ground plate is disposed over the inner walls and attached to the outer walls. The ground plate has a center opening and a process opening for each station. The center opening is configured to receive the rotating mechanism at the center location. The process opening has a diameter that is larger than a diameter of the carrier ring at each station, and a symmetric gap is defined between an edge of each process opening defined by the ground plate and an outer edge of a carrier ring. The chamber further includes an upper chamber body. The upper chamber body is configured to mate over the lower chamber body. The upper chamber body includes four showerheads and each of the four showerheads is configured to be aligned over a respective pedestal of a respective station. Wherein when a radio frequency (RF) power is provided to either the showerhead or the pedestal of each station, the RF power is provided with an RF ground return via the ground plate that symmetrically surrounds each process opening of each station.
In some embodiments, a top surface of the ground plate is positioned at a first height relative to an inner floor of the lower chamber. The first height is about equal to or slightly less than a second height of a top surface of the pedestal relative to the inner floor of the lower chamber. A top surface of a substrate when present over any one of the four stations is substantially coplanar with the top surface of the ground plate.
In some embodiments, the ground plate covers a top surface of the lower chamber, except for the center opening and the process opening for each station.
In some embodiments, the rotating mechanism includes a plurality of spider forks, and each of the spider forks is associated with each of the four of stations and is configured to lift and move a respective one of carrier rings from each station in order to lift and move a respective substrate when present over a respective pedestal.
In some embodiments, the symmetric gap provides a separation to a ground potential provided by the ground plate, the ground potential is symmetrically arranged around each substrate when disposed over a respective pedestal of each station.
In some embodiments, a pump is disposed below the lower chamber body. The pump is configured to provide evacuation of process gases from a space between the inner floor and an under surface of the ground plate. Further, process gases flow through the gap at each station that is symmetrically maintained around and between the process openings in the ground plate and the carrier ring of each station.
In some embodiments, two pumps are provided in a symmetric orientation below the lower chamber body.
In another embodiment, a multi-station chamber is disclosed. The multi-station chamber includes a lower chamber body that has a plurality of stations arranged around a rotating mechanism. Each station includes a pedestal for supporting a substrate and a carrier ring that surrounds the pedestal. The carrier ring of each station is configured to be lifted and moved by the rotating mechanism. The lower chamber body has an inner floor disposed below each pedestal of each of the plurality of stations. The lower chamber body has outer walls that surround a perimeter of each of the plurality of stations. The outer walls have a support step. The lower chamber body has inner walls that laterally separate respective ones of the plurality of stations. The outer walls and the inner walls extend up from the inner floor. The chamber further includes a ground plate disposed over the support step of the outer walls and over the inner walls. The ground plate has a center opening and a process opening for each station. The process opening defined for each pedestal has the carrier ring. The process opening surrounds the carrier ring of each process station so that gap is symmetrically maintained around and between the ground plate and the carrier ring of each station. Wherein the ground plate provides a symmetric RF return path to ground for RF power supplied to any one of the stations of the multi-station chamber.
One advantage of providing a symmetric RF return path to ground is that deposition of ALD films results in substantial reductions in wafer-to-wafer (WtW) non-uniformity mismatch. Without being bound by theory, it has been hypothesized that this mismatch was due to differences in RF or thermal grounding for each station. Integration of a symmetric grounding plate has resulted in improved WtW matching. These and other advantages will be discussed below and will be appreciated by those skilled in the art upon reading the specification, drawings and the claims.
Embodiments of the disclosure provide embodiments of a process chamber, used for processing semiconductor wafers. A ground plate is disclosed that is configured to symmetrically surround each station of a multi-station chamber, such that a symmetric radio frequency (RF) return to ground is provided around each station. The symmetry provided by the ground plate enables for uniform processing of thin films being deposited and also improves station-to-station uniformity as well as wafer-to-wafer uniformity.
In one embodiment, a multi-station chamber having a symmetric ground plate is disclosed. The multi-station chamber includes four stations, and the four stations are arranged in a square configuration with a rotating mechanism in a center location. A pedestal for supporting a substrate is provided for each of the four stations, each pedestal is disposed in a lower chamber body, and each pedestal includes a carrier ring. The lower chamber body includes outer walls and inner walls to define a space for each of the pedestals of the four chambers. A ground plate is disposed over the inner walls and attached to the outer walls. The ground plate has a center opening and a process opening for each station. The center opening is configured to receive the rotating mechanism at the center location. The process opening has a diameter that is larger than a diameter of the carrier ring at each station, and a symmetric gap is defined between an edge of each process opening defined by the ground plate and an outer edge of a carrier ring. For applied radio frequency power, an RF ground return is provided via the ground plate that symmetrically surrounds each process opening of each station.
In one configuration, a chamber then will include four spider forks and a carrier ring will be disposed around respective pedestals of each of the stations. In this configuration, the spider forks can simultaneously lift each of the four carrier rings (and any wafer disposed thereon), and rotate all of the carrier rings and wafers to the next station (e.g., for additional or different processing). In one configuration, the chamber has loading and unloading stations when one wafer is loaded at a time or can include parallel loading and unloading stations where two wafers are loaded and unloaded at a time. As noted above, in some embodiments, the carrier ring may be referred to as a plasma focus ring. In such embodiments, the plasma focus ring functions to focus or optimize the plasma processing across the surface of the substrate, including the edges of the substrate. Generally speaking a plasma focus ring works to extend the outer surface of the substrate so that non-uniformities due to the substrate edge are extended to the outer surface edge of the plasma focus ring (i.e., instead of the substrate edge). In this manner, the edge of the substrate is more uniformly processed, as it will see less or reduced process non-uniformities.
It should be appreciated that the present embodiments can be implemented in numerous ways, such as a process, an apparatus, a system, a device, or a method. Several embodiments are described below.
The center column is also shown to include lift pins 120, which are controlled by lift pin control 122. The lift pins 120 are used to raise the wafer 101 from the pedestal 140 to allow an end-effector to pick the wafer and to lower the wafer 101 after being placed by the end end-effector. The substrate processing system 100 further includes a gas supply manifold 112 that is connected to process gases 114, e.g., gas chemistry supplies from a facility. Depending on the processing being performed, the control module 110 controls the delivery of process gases 114 via the gas supply manifold 112. The chosen gases are then flown into the shower head 150 and distributed in a space volume defined between the showerhead 150 face that faces that wafer 101 and the wafer 101 resting over the pedestal 140.
Further, the gases may be premixed or not. Appropriate valving and mass flow control mechanisms may be employed to ensure that the correct gases are delivered during the deposition and plasma treatment phases of the process. Process gases exit chamber via an outlet. A vacuum pump (e.g., a one or two stage mechanical dry pump and/or a turbomolecular pump) draws process gases out and maintains a suitably low pressure within the reactor by a close loop controlled flow restriction device, such as a throttle valve or a pendulum valve.
Also shown is a carrier ring 200 that encircles an outer region of the pedestal 140. The carrier ring 200 is configured to sit over a carrier ring support region that is a step down from a wafer support region in the center of the pedestal 140. The carrier ring includes an outer edge side of its disk structure, e.g., outer radius, and a wafer edge side of its disk structure, e.g., inner radius, that is closest to where the wafer 101 sits. The wafer edge side of the carrier ring includes a plurality of contact support structures which are configured to lift the wafer 101 when the carrier ring 200 is lifted by spider forks 226. The carrier ring 200 is therefore lifted along with the wafer 101 and can be rotated to another station, e.g., in a multi-station system. More detail regarding the ground plate used to improve symmetric RF ground return is provided below with reference to
In this illustration, a grounding plate 290 is provided. However, grounding plate 290 has a non-symmetric configuration around the pedestal 140. As shown, grounding plate 290 has portions 290a and 290b that non-symmetrically extend a body of ground away from the pedestal 140. Portions 290c and 290d have a thinner separation with less body for providing ground return to RF power. As such, this configuration, although useful for some processes, is not optimized for efficient and symmetric RF ground return, especially in more demanding ALD processes that require ever stringent film performance.
The depicted processing chamber 102b comprises four process stations, numbered from 1 to 4 in the embodiment shown in
In the configuration of
In some embodiments, a “ring-less” substrate transfer may also be employed. In such embodiments, the “carrier ring” or “plasma focusing ring” remains fixed on one station. The substrate is moved by lifting the substrate off of the pedestal with pins, inserting a paddle under the wafer, and then lowering the substrate on pins thus ensuring direct contact with the paddle to substrate. At this point, the substrate is indexed using the paddle to another station. Once the substrate is at the new station, the substrate is lifted off of the paddle with pins, the paddle is rotated or moved out and the pins are lowered ensure direct contact of the substrate to the pedestal. Now, the substrate processing can proceed at the new station for the indexed (i.e., moved) substrate. When the system has multiple stations, each of the substrates (i.e., those present at stations) can be transferred together, e.g., simultaneously, in the similar fashion for ring-less substrate transfers.
In this illustration, the showerhead 150 is configured to deliver deposition gases in accordance with the desired deposition process. The deposition gases, depending on the deposition process (e.g. PECVD, ALD, etc.) will be disposed over the surface of the substrate 101. When plasma is activated by the delivery of RF power, the deposition gases will be activated to cause the formation of a film. In some processes, the deposition process includes a number of steps, such as reactant absorption, purge, and plasma activated deposition reactants. Vacuum pumps 160a and 160b are provided and interfaced with the lower chamber body 102a. The vacuum pumps 160 are configured to provide for sufficient gas flow to remove process gases and/or to provide pressure control within the chamber. Typically, the gas flow is allowed to flow over the substrate 101 and over the edges of the pedestal 140, thus defining flows 402. As will be defined below in more detail, a process opening is defined as a circular opening in the ground plate 404 around each one of the stations, such that the gap between the inner edge of the process opening of the ground plate 404 and the outside edge of the pedestal 140 that includes the carrier ring 200 is provided. The gap is configured so that a gas flow is still provided along 402, while also providing for a uniform coupling of RF power return to ground, once RF power is provided to either the pedestal 140 or the showerhead 150, depending on the configuration.
It should be noted that the ground plate 404 provides a substantially symmetric ground potential around the process opening defined by diameter D1, such that the return path to ground is the same all the way around the substrate during processing, which improves process uniformities as well as achieves more stringent control of deposition films. Still further, by improving the ground plate 404 and providing the uniform in substantial symmetric configuration, it is possible to control and reduce non-uniformities between wafers processed in the different stations. This adds to the control of wafer to wafer uniformity as well as repeatability of process in the various stations and during wafer process cycles.
In one embodiment, the ground plate 404 is a conductive ground plate defined from an alumina material. In some embodiments, the ground plate can be stainless steel. In other embodiments, the ground plate can be a conductive material that is coded with a material. In some examples, the ground plate 404 is defined from any aluminum material, and in one particular example, any non-ferrous material.
In this example, a first height H1 is defined between the inner floor 102c and a top surface of the ground plate 404. In one embodiment, H1 can have a dimension that is between about 114 mm and about 137 mm. In one configuration, H1 will be about 132 mm.
Also shown is a second height H2 that is defined between the inner floor 102c and a top surface of the pedestal 140. In one embodiment, H1 can have a dimension that is between about 125 mm and about 140 mm. In one configuration, H1 will be about 135.13 mm.
Further shown is a third height H3, that is defined between the inner floor 102c and a top surface of the carrier ring 200. In one embodiment, H3 can have a dimension that is between about 125 mm and about 140 mm. In one configuration, H3 will be about 135.65″ mm.
In one embodiment, a gap 406 will have a dimension D3 that is between about 5 mm and about 30 mm. In one configuration, 406 D3 will be about 20 mm. In still another embodiment, a gap 408 will have a dimension D4 that is between about 0 mm and about 5 mm. In one configuration, 408 D4 will be about 2 mm. By providing the ground plate 404 proximate and surrounding the pedestal 140, the symmetry provided by the gap 406 will enable for a more substantial uniform RF return path the power provided to the chamber, such as the RF returned to ground 430 from the plasma during processing.
Again it should be understood that the above dimensions are provided to provide a detailed understanding of one particular example, and the example relates to 300 mm wafers being processed in the multi-station chamber 102. Suitable adjustments in height and ranges should be considered for chambers that are manufactured to process larger wafers, such as 450 mm wafers, or larger, or even smaller wafer such as 200 mm wafers.
The control module 800 may control activities of the precursor delivery system and deposition apparatus. The control module 800 executes computer programs including sets of instructions for controlling process timing, delivery system temperature, pressure differentials across the filters, valve positions, mixture of gases, chamber pressure, chamber temperature, wafer temperature, RF power levels, wafer chuck or pedestal position, and other parameters of a particular process. The control module 800 may also monitor the pressure differential and automatically switch vapor precursor delivery from one or more paths to one or more other paths. Other computer programs stored on memory devices associated with the control module 800 may be employed in some embodiments.
Typically there will be a user interface associated with the control module 800. The user interface may include a display 818 (e.g. a display screen and/or graphical software displays of the apparatus and/or process conditions), and user input devices 820 such as pointing devices, keyboards, touch screens, microphones, etc.
Computer programs for controlling delivery of precursor, deposition and other processes in a process sequence can be written in any conventional computer readable programming language: for example, assembly language, C, C++, Pascal, Fortran or others. Compiled object code or script is executed by the processor to perform the tasks identified in the program.
The control module parameters relate to process conditions such as, for example, filter pressure differentials, process gas composition and flow rates, temperature, pressure, plasma conditions such as RF power levels and the low frequency RF frequency, cooling gas pressure, and chamber wall temperature.
The system software may be designed or configured in many different ways. For example, various chamber component subroutines or control objects may be written to control operation of the chamber components necessary to carry out the inventive deposition processes. Examples of programs or sections of programs for this purpose include substrate positioning code, process gas control code, pressure control code, heater control code, and plasma control code.
A substrate positioning program may include program code for controlling chamber components that are used to load the substrate onto a pedestal or chuck and to control the spacing between the substrate and other parts of the chamber such as a gas inlet and/or target. A process gas control program may include code for controlling gas composition and flow rates and optionally for flowing gas into the chamber prior to deposition in order to stabilize the pressure in the chamber. A filter monitoring program includes code comparing the measured differential(s) to predetermined value(s) and/or code for switching paths. A pressure control program may include code for controlling the pressure in the chamber by regulating, e.g., a throttle valve in the exhaust system of the chamber. A heater control program may include code for controlling the current to heating units for heating components in the precursor delivery system, the substrate and/or other portions of the system. Alternatively, the heater control program may control delivery of a heat transfer gas such as helium to the wafer chuck.
Examples of sensors that may be monitored during deposition include, but are not limited to, mass flow control modules, pressure sensors such as the pressure manometers 810, and thermocouples located in delivery system, the pedestal or chuck (e.g. the temperature sensors 814). Appropriately programmed feedback and control algorithms may be used with data from these sensors to maintain desired process conditions. The foregoing describes implementation of embodiments of the invention in a single or multi-chamber semiconductor processing tool.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the invention, and all such modifications are intended to be included within the scope of the invention.
Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications can be practiced within the scope of the appended claims. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the embodiments are not to be limited to the details given herein, but may be modified within their scope and equivalents of the claims.
This application claims priority from U.S. Provisional Patent Application No. 62/206,829, filed Aug. 18, 2015, and entitled “MULTI-STATION CHAMBER HAVING SYMMETRIC GROUNDING PLATE.” This provisional application is herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62206829 | Aug 2015 | US |
