Patent Application
20240258072
The following relates to impedance matching, radio-frequency matching, and sub-atmospheric pressure chemical vapor deposition. In chemical vapor deposition processing, radio frequency is used in the generation of plasma within the process chamber. High and low radio frequencies produced by radio frequency generators may interfere with each other. A radio frequency match is used to control the impedance and alleviate this interference.
Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.
The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.
Numerical values in the specification and claims of this application should be understood to include numerical values which are the same when reduced to the same number of significant figures and numerical values which differ from the stated value by less than the experimental error of conventional measurement technique of the type described in the present application to determine the value. All ranges disclosed herein are inclusive of the recited endpoint.
The term “about” can be used to include any numerical value that can vary without changing the basic function of that value. When used with a range, “about” also discloses the range defined by the absolute values of the two endpoints, e.g., “about 2 to about 4” also discloses the range “from 2 to 4.” The term “about” may refer to plus or minus 10% of the indicated number.
In the fabrication of semiconductor microelectronic circuits, chemical vapor deposition processes are employed to fill deep narrow openings or high aspect ratio (HAR) openings, such as isolation trenches and deep contacts. The aspect ratio (the height to diameter ratio) may range from 5:1 to greater than 10:1. Several processes have been employed for this purpose, including sub-atmospheric chemical vapor deposition (SACAVD), plasma enhanced chemical vapor deposition (PECVD) and high density plasma chemical vapor deposition (HDPCVD).
The SACVD process, when used to deposit a silicon dioxide film, typically uses a metal-organic silicide gas a vacuum chamber containing the silicon wafer. The deposition reaction is a thermal reaction carried out at an elevated wafer temperature (e.g., about 500° C.), in which the heat dissociates free oxygen from the ozone gas and silicon from the TEOS molecules, and promotes surface mobility of deposited atoms on the coating. The deposition reaction is conformal, forming a coating of a nearly uniform thickness on both horizontal and vertical surfaces on the semiconductor wafer. Although the reaction is carried out in a vacuum, the chamber pressure is high (e.g., a few hundred Torr) relative to other CVD processes. This relatively high pressure is required to compensate for the slow deposition rate of the SACVD process. Although the wafer temperature is elevated during the deposition to about 500° C., the deposited coating must be annealed at about 700°−900° C.
The SACVD utilizes an RF power supply to provide high and low radio frequency power to the chamber for plasma processing. In each of these plasma processes, a gas is first introduced into a reaction chamber and then plasma is generated from the gas. This is accomplished by dissociation of the gas into ions, free radicals, and electrons by using an RF (radio frequency) power supply or generator, which includes one or more electrodes. The electrodes are accelerated in an electric field generated by the electrodes, and the energized electrons strike gas molecules to form additional ions, free radicals, and electrons, which strike additional gas molecules, and the plasma eventually becomes self-sustaining. The RF power supply may utilize a high frequency RF source and a low frequency RF source. In some instances, the high RF power is supplied to a gas distribution manifold within the chamber and the low RF power is supplied to an electrode that may be embedded in the pedestal or substrate holder within the chamber. Interference between the high and low frequency RF power is minimized across the top and bottom plasma sheaths by an external RF match unit that which matches the impedance at high frequency RF and the impedance of the decoupled low frequency. Otherwise, the interference would produce high voltages at the electrodes and potentially result in arcing at the gas distribution system damaging the showerhead. The use of a low frequency bottom plasma sheath and a predominantly high frequency top plasma sheath induces a harmonic oscillation frequency that may be increased or decreased by the external RF circuit as desired. The external RF match unit may be connected to the chamber through an RF match strap that couples a chamber lid strap (conductive strip of material) from the RF match strap to the process chamber.
In a typical RF coupling arrangement for providing RF power to an SACVD chamber or other process chamber, an RF match strap provides a low impedance RF connection to the RF match unit. The RF match strap includes an electrical conductor surrounded by an electrically nonconductive column providing electrical insulation. A separate chamber lid strap includes two parts: a fixed (i.e., rigid) chamber lid strap that secures to the top of the RF match strap, and a flexible chamber lid strap that runs from the fixed chamber lid strap to an RF port of the process chamber. The RF port is typically located on the lid of the process chamber.
As recognized herein, this multi-component RF coupling arrangement has some disadvantages. Each time the lid of the process chamber is opened or closed, the flexible chamber lid strap flexes against the fixed chamber lid strap, which in turn flexes against its connection with the top of the RF match strap. This produces cyclical stress over time at the connection between the chamber lid strap and the top of the RF match strap, which over time can lead to shifting of the chamber lid strap position and impaired RF coupling between the chamber lid strap and the top of the RF match strap. This in turn lead to reduced RF power transfer, reflected RF high power issues that may cause product defects, RF arcing, and the like.
In various embodiments disclosed herein, a robust RF coupling arrangement is disclosed which alleviates the foregoing issues. In some improved arrangements, a one-piece RF match strap is provided, which eliminates the connection of the fixed chamber lid strap to the RF match strap. The one-piece RF match strap comprises a rod, which fits into an electrically nonconductive column providing electrical insulation. The rod-shaped one-piece RF match strap is configured at its lower end to connect with the RF match unit, and is configured at its upper end to connect directly with the flexible chamber lid strap thus eliminating the RF coupling between the fixed chamber lid strap and the RF match strap, so that the RF power is efficiently transferred from the RF match unit through the one-piece RF match strap directly to the flexible chamber lid strap. The one-piece RF match strap provides additional structural rigidity (in addition to structural support provided by the electrically nonconductive column) and provides a continuous RF power transfer path from the RF match unit to the flexible chamber lid strap.
Turning now to
The RF match strap assembly 100 depicted in
Removably coupled to the top fixed column 104 is a bottom fixed (i.e. rigid) column 106, which is also electrically insulating for the RF power being conveyed, and includes a bottom fixed column flange 108 positioned on one end of the bottom fixed column 106 opposite the end to which the top fixed column 104 is coupled. The bottom fixed column flange 108 is suitably configured to secure the RF match strap assembly 100 to an RF match unit 504, as discussed in greater detail below. Extending through the top fixed column 104 and the bottom fixed column 106 is a one-piece RF match strap 110, which extends through the end of the bottom fixed column 106 corresponding to the bottom fixed column flange 108. According to some embodiments contemplated herein, the one-piece RF match strap 110 is configured to interact with internal components of the RF match 504, as discussed in greater detail below.
Referring now to
The top fixed column 104 is depicted as generally cylindrical in shape, having a hollow center 302 therethrough. The skilled artisan will appreciate that the cylindrical depiction of the top fixed column 104 is intended solely as an example, and other shapes, e.g., hexagonal, squared, oval, and the like, may also be utilized in accordance with vary aspects of the subject application.
The bottom fixed column 106 is also illustrated in
The bottom fixed column 106 further includes a central hole or passageway 312 extending therethrough, i.e., extending longitudinally from the top (i.e., the tab component 306) downward to the end to which the flange 108 is affixed. In accordance with one embodiment, the central hole 312 of the bottom fixed column 106 is configured to receive the one-piece RF match strap 110, as discussed in greater detail below. In varying embodiments contemplated herein, the top fixed column cover 102, the top fixed column 104, the bottom fixed column 106, and/or the flange 108 may be constructed of a suitable electrically nonconductive material. Suitable nonconductive materials may include, for example and without limitation, plastics, thermoplastics (e.g., polyoxymethylene), ballistic plastics, acrylics, and/or other suitable nonconductive materials as will be appreciated by those skilled in the art. Not shown in
Turning now to
According to one embodiment, the body extension 404 has a diameter 410 smaller than the diameter 412 of the main body 402. In some embodiments, the diameter 412 of the main body 402 is suitably configured smaller than the inner diameter 310 of the fixed bottom column 106. In the illustrative embodiment the main rod 402 and rod extension 404 has a circular cross-section suitably described by a diameter. In other embodiments, these rod components 402, 404 may have other cross-sectional shapes, e.g. hexagonal or octagonal, and can be suitably described by another cross-sectional dimension suitable to that cross-sectional shape. Further, in such embodiments, the height 406 of the main body 402 and the head 400 is less than or equal to the combined heights of the top fixed column 104 and the bottom fixed column 106 when these two components are joined together. Thus, the skilled artisan will appreciate that the main body 402 and head 400 of the one-piece RF match strap 110 are enclosed within the top fixed column 104 and the bottom fixed column 106, while the body extension 404 extends outward from the bottom of the bottom fixed column 104.
In some embodiments, the one-piece RF match strap 110 is formed from a single piece of electrically conductive material, e.g., forged, milled from a single billet, created via additive manufacturing (i.e. sintering, 3D printing, etc.). Suitable examples of such conductive material include, for example and without limitation, aluminum, aluminum alloys, copper, copper alloys, and other suitable conductive materials, metals and alloys, as will be understood by one skilled in the art. It will further be appreciated that the head 400 and main body 402 cooperate to retain the flexible chamber lid strap (not shown) within the slot 112 formed by the top fixed column cover 102 and the top fixed column 104. The skilled artisan will further appreciate that such retention enables constant and sustained contact between the conductive material of the one-piece RF match strap 110 and the chamber match strap (not shown), as will be illustrated in
Referring now to
The example embodiment illustrated in
The exemplary embodiment of
In accordance with one embodiment, the RF generator 506 provides both high and low radio frequency power to the process chamber 502 for plasma-enhanced processes. Interference between the high and low frequency RF power is minimized by the RF match unit 504, which matches the impedance at high RF and the impedance of the low (decoupled) frequency, to avoid the production of high voltages at the electrodes resulting in arcing at the gas distribution system. In order to ensure such matching is effective, the RF match unit 504 using the RF match assembly 100 is coupled to the process chamber 502 via the flexible chamber lid strap, as illustrated in
As shown in
Turning now to
The top fixed column 104 is then slidably engaged onto the bottom fixed column 106 that has been mounted to the top of the RF match unit 504 at 706. In accordance with one embodiment, the top fixed column 104 is frictionally secured to the tab component 308 of the bottom fixed column 106. According to some embodiments contemplated herein, the top fixed column 104 is rotatable on the bottom fixed column 106 around the tab component 308, thereby enabling alignment of the slot 112 with the process chamber 502 and the flexible chamber lid strap 600.
At 708, the flexible chamber lid strap 600 is coupled to contact points on the top of the process chamber 502. It will be appreciated by those skilled in the art that the contact points are adjacent to the orifice 508, in close proximity thereto, or otherwise accessible to the RF match assembly 100. The skilled artisan will appreciate that the flexible chamber lid strap 600 may be a rigid conductive material, pre-shaped or bent into the appropriate configuration to couple the process chamber 502 to the RF match assembly 100 of the RF match unit 504. It will be appreciated by those skilled in the art that steps 706 and 708 may be performed in either order, as the rotatable coupling of the top fixed column 104 and the bottom fixed column 106 referenced above allow movement of the top fixed column 104 into the proper position.
At 710, an end of the flexible chamber lid strap 600 that is not secured to the top of the process chamber 502 is inserted to slot 112 partially formed by the top fixed column 104 that has been secured to the bottom fixed column 106. As discussed above, the end of the flexible chamber lid strap 600 to be connected to the RF match strap 110 may include a suitable opening through which the RF match strap 110 may pass, or alternatively may extend partially into the hole 302 of the top fixed column 104. At 712, the RF match strap 110 is inserted into the hole 302 of the top fixed column 104 and through the passageway 312 of the bottom fixed column 106 into the RF match unit 504. It will be appreciated that at this step, the head 400 of the RF match strap 110 contacts the end of the flexible chamber lid strap 600 inserted into the slot 112 of the top fixed column 104. That is, the underside of the head 400 is in contact with the flexible chamber lid strap 600, either circumferentially (via a hole through the flexible chamber lid strap 600) or with a portion of the flexible chamber lid strap 600 that has extended into the hole 302 of the top fixed column 104.
At 714, the bottom fixed column cover 114 is inserted around the one-piece RF match strap 110 within the interior of the RF match unit 504 and threaded into the bottom fixed column 106, as discussed above. According to one embodiment, this step may be used when no fasteners are used to secure the flange 108 to the top of the RF match unit 504, i.e., when predrilled holes are not available or when use of metallic fasteners may have a negative impact on function of the RF match 504. In such an embodiment, the bottom fixed column cover 114 is utilized to secure the bottom fixed column 106 to the top of the RF match unit 504, i.e., the lip 420 extends around the hole through the top of the RF match unit 504 and the cover 114 is screwed/tightened to provide a secure coupling of the RF match assembly 100 to the RF match 504.
After securing the bottom fixed column cover 114, the RF match strap 110 is connected to the internal impedance circuitry of the RF match unit 504 at 716. It will be appreciated by those skilled in the art that such connection may include any suitable electrical connection known in the art to ensure proper conductivity, e.g., circuit block, friction connection, solder connection, or the like. After the one-piece RF match strap 110 has been connected to the internal components of the RF match unit 504, operations proceed to 718, whereupon the top fixed column cover 102 is positioned on the top fixed column 104. At 720, fasteners are inserted into the holes 116A, 116B, and 116C of the top fixed column cover 102 to engage holes 300A, 300B, and 300C, respectively, of the top fixed column 104.
In accordance with one embodiment contemplated herein, the RF match assembly 100 enables contact between the RF match unit 504 and the process chamber 502 via secure coupling of the flexible chamber lid strap 600. The one-piece RF match strap 110 reduces RF power decay, reflected RF high power issues that may cause product defects, wafer arcing, and the like. Further, the aforementioned one-piece RF match strap 110 maintains constant and secure connection with the flexible chamber lid strap 600, even as the lid of the process chamber is repeatedly opened and closed providing less than 1 W of RF reflection.
In accordance with a first embodiment, there is provided a radio frequency (RF) match assembly for connecting RF power from an RF match unit to a process chamber. The assembly includes a top electrically insulating column and a bottom electrically insulating column. The assembly further includes a one-piece RF match strap that has a head, a main body and a body extension. The main body of the one-piece RF match strap is configured to extend through the top electrically insulating column and the bottom electrically insulating column. In addition, a top of the one-piece RF match strap is configured to electrically contact an associated flexible chamber lid strap of the process chamber and a bottom of the one-piece RF match strap is configured to electrical connect with the RF match unit.
In accordance with a second embodiment, there is provided a semiconductor manufacturing system. The system includes a process chamber, an RF match unit, an RF generator in electrical communication with the RF match unit, and an RF match assembly affixed to the RF match unit. The RF match assembly includes a top electrically insulating column, a bottom electrically insulating column coupled to a top of the RF match unit, and a one-piece RF match strap. The one-piece RF match strap includes a head, a main body and a body extension, with the main body extending through the top electrically insulating column and the bottom electrically insulating column into the RF match unit. The system further includes a flexible chamber lid strap connecting between a top of the one-piece RF match strap assembly and the process chamber.
In accordance with a third embodiment, there is provided a method of coupling an RF match strap assembly to a semiconductor manufacturing apparatus that includes an RF match unit, a process chamber, and an RF generator. The method includes securing a bottom electrically insulating column of the RF match strap assembly to the RF match unit. The method further includes attaching a top electrically insulating column to the bottom electrically insulating column, and connecting a flexible chamber lid strap to the process chamber. The method also includes inserting the flexible chamber lid strap into a slot of the top electrically insulating column, and inserting a one-piece RF match strap into the top electrically insulating column and the bottom electrically insulating column contacting the flexible chamber lid strap. In addition, the method includes attaching a bottom fixed column cover around the one-piece RF match strap to the bottom electrically insulating column within the RF match unit, and attaching a top fixed column cover to the top electrically insulating column to secure the one-piece RF match strap therein.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.
This application is a Continuation Patent Application of patent application Ser. No. 17/585,703, filed Jan. 27, 2022, and entitled RADIO FREQUENCY MATCH STRAP ASSEMBLY, which claims the benefit of U.S. Provisional Application Ser. No. 63/212,435 filed Jun. 18, 2021 and entitled ONE PIECE RF MATCH STRAP FOR SACVD RF MATCH, both of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63212435 | Jun 2021 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17585703 | Jan 2022 | US |
| Child | 18601155 | US |
