Patent Application
20130008601
The present disclosure is directed generally to systems and methods for oscillating the exposure of a semiconductor workpiece to multiple chemistries, for example, to remove particles from the workpiece, and/or to conduct other processes on the workpiece.
Many chemical processes are required to manufacture semiconductor devices. These processes include deposition processes, photolithography processes, etching processes, chemical mechanical polishing (CMP) processes and/or electrochemical mechanical polishing (ECMP) processes, among others. As a result of carrying out the foregoing processes, the semiconductor workpiece on which the processes are conducted typically becomes contaminated with particulate residue. Accordingly, the workpiece must be periodically rinsed and dried to prevent the particulate residue from interfering with subsequent process steps.
Several existing techniques have been developed for rinsing semiconductor workpieces. One such technique includes a rinse bath in which the workpiece is immersed in a volume of rinse solution and then dried. A drawback with this technique is that it requires a large volume of rinse liquid which then becomes contaminated with particulate matter and must be disposed of in accordance with proper handling procedures. The larger the volume of liquid that must be disposed of, the more time-consuming and/or expensive the disposal process becomes. Accordingly, other techniques that require smaller volumes of rinse liquid have been developed. One such technique includes a spin rinse/dry process in which the rinse liquid is disposed on the workpiece and the workpiece is then spun at high speed to both remove the rinse liquid and dry the workpiece. Another technique includes a proximity cleaning technique in which a rinse fluid is delivered to a local region of the workpiece and then removed (along with contaminating particulate matter) by suction. A representative device for carrying out such a process is disclosed in U.S. Pat. No. 7,045,018 to Ravkin, et al., assigned to Lam Research Corporation of Fremont, Calif.
While the foregoing techniques have generally proven to be effective, there is a continual need to improve the efficiency with which workpieces are cleaned, e.g., by reducing the number of particulates left by such techniques. There is also a continual need to reduce the volume of fluid required by such techniques. Furthermore, there is a need to improve the efficiency with which other semiconductor chemical processes are conducted.
Specific details of several embodiments of the disclosure are described below with reference to semiconductor workpieces and systems for processing the workpieces. The workpieces can include micromechanical components, data storage elements, optics, read/write components, or other features. For example, the workpieces can include wafers having dies including SRAM, DRAM (e.g., DDR-SDRAM), flash-memory (e.g., NAND flash-memory), processor, imager, and/or other dies. Although many of the embodiments are described below with respect to semiconductor devices that have integrated circuits, other embodiments include other types of devices manufactured on other types of substrates. Several other embodiments of the invention can have configurations, components, or procedures different than those described in this section. A person of ordinary skill in the art, therefore, will accordingly understand that the invention may have other embodiments with additional elements, or the invention may have other embodiments without several of the elements shown and described below with reference to
A particular method for processing a semiconductor workpiece includes sequentially exposing a portion of the workpiece surface to a first chemistry having a first chemical composition and a second chemistry having a second chemical composition different than the first. Prior to rinsing the portion of the workpiece surface, it is sequentially exposed to the first and second chemistries again. The method further includes removing the first and second chemistries and rinsing and drying the portion after sequentially exposing the portion to each of the first and second chemistries at least twice, and removing the first and second chemistries. In further particular embodiments, the first and second chemistries can be selected to have different pHs so as to facilitate removing particles from the surface of the workpiece. In other embodiments, the first and second chemistries can have different surfactant characteristics. In yet further embodiments, one of the chemistries can include an oxidizing chemistry and the other can include an acidic chemistry for etching or otherwise removing material from the workpiece.
An apparatus in accordance with a particular embodiment, and suitable for carrying out the foregoing methods, can include a workpiece support and a process head, at least one of which is linearly movable relative to the other. The process head includes at least one fluid delivery port and at least one fluid removal port. A valve can be coupled in fluid communication with a first source of chemistry, a second source of chemistry, and the fluid delivery port. The controller can be operatively coupled to the valve and programmed with instructions directing the valve to change between a first state and a second state at particular intervals, for example, ten seconds or less. In the first state, the valve directs a first fluid from the first source to exit through the process head, and in the second state, the valve directs a second fluid from the second source to exit through the process head. By alternating between the first and second chemistries, the workpiece can be rapidly exposed to both chemistries, which can enhance or facilitate particulate removal from the workpiece, and/or produce other effects at the workpiece.
In a particular embodiment, the support 110 translates linearly, as indicated by arrow T, beneath a chemical delivery/removal head 120. The head 120 can span the diameter (or other dimension) of the workpiece 102 so that the support 110 need translate along only one axis to treat the entire workpiece 102. As the semiconductor workpiece 102 passes beneath the head 120, the head dispenses and removes multiple chemistries using a “proximity” treatment technique in which limited portions of the semiconductor workpiece 102 are treated in a sequential manner without immersing the entire workpiece 102. The head 120 can be coupled to multiple chemical sources 101, including a first source 101a that delivers a first chemistry A, a second source 101b that delivers a second chemistry B, a third source 101c that delivers a rinse fluid R, and a fourth source 101d that delivers a drying fluid D. The first and second sources 101a, 101b can be coupled to a valve 150 that delivers the chemistries to a chemistry manifold 121 for ultimate delivery to the semiconductor workpiece 102. The rinse fluid R can be connected to a corresponding rinse manifold 122, and the drying fluid D can be coupled to a drying manifold 135. Flow through the rinse manifold 122 and the drying manifold 135 can also be controlled with valves, which are not shown in
The chemistry element 123 can include a chemistry delivery port 125 and two chemistry vacuum ports, illustrated as a leading chemistry vacuum port 126a and a trailing chemistry vacuum port 126b. Chemistry is provided via the chemistry delivery port 125 to a chemistry zone 129 at the surface S of the workpiece 102, and is removed via the vacuum ports 126a, 126b. The chemistry zone 129 moves over the surface S of the workpiece 102 due to the relative motion between the head 120 and the support 110. A chemistry fluid volume 138 (e.g., a meniscus) formed between the vacuum ports 126a, 126b includes a leading edge 130 proximate to the leading vacuum port 126a, and a trailing edge 131 proximate to the trailing vacuum port 126b. A point Q on the surface S of the workpiece 102 first encounters the leading edge 130 as the workpiece 102 moves from left to right, and then encounters the trailing edge 131.
The rinse element 124 can be arranged in a manner generally similar to that of the chemistry element 123. Accordingly, the rinse element 124 can include a rinse delivery port 127 that delivers a rinse fluid (e.g., deionized water) to a rinse zone 132. A rinse fluid volume 139 (e.g., another meniscus) has a leading edge 130 and a trailing edge 131. A leading rinse vacuum port 128a and a trailing rinse vacuum port 128b together confine the rinse fluid volume 139 to the rinse zone 132 between these two ports. Optionally, the leading rinse vacuum port 128a can be combined with the trailing chemistry vacuum port 126b, for example, when mixing the fluid exiting the rinse zone 132 and the fluid exiting the chemistry zone 129 is not undesirable.
The drying element 136 can include a drying fluid delivery port 137 configured to provide an appropriate drying fluid, for example, a mixture of isopropyl alcohol and nitrogen. The drying fluid can be provided in gaseous form and therefore, a removal port is not required to remove the drying chemistry from the workpiece 102. A given portion of the workpiece surface S may be in the chemistry zone 129 receiving chemistry via the chemistry delivery port 125, while another portion is in the rinse zone 132 receiving rinse fluid from the rinse delivery port 127, and while a third portion is being dried, and while still other portions of the workpiece surface S are not exposed to the chemistry, the rinse liquid or the drying fluid.
In a particular embodiment, the pHs of the first and second chemistries A, B can be different. By rapidly changing the pH of the fluid in the chemistry fluid volume 138, the electrostatic charge on particles P at or near the surface S of the workpiece 102 can also change rapidly. The result can be a rapid change in the zeta-potential and in particular, the polarity of the electrostatic charge of either the particles P or the workpiece surface S. In a particular example, the workpiece surface S can include a silicon dioxide layer with an electrostatic charge of −60 mV. The particles P can be aluminum oxide particles with an electrostatic charge of +50 mV. Accordingly, (at least initially) an attractive electrostatic force exists between the particles P and the surface S. If the pH of the chemistry fluid volume 138 is rapidly changed from pH 7 to pH 11, the electrostatic charge on the surface S can change to −110 mV and the electrostatic charge on the particles P can change to −50 mV. When the particles P and the surface S have electrostatic charges of the same polarity, the particles P can be repelled from the surface S and are accordingly more likely to be removed, either via the vacuum ports 126a, 126b, or by the rinse fluid that follows.
In the foregoing example, the relative polarity between the particles P and the surface S changed. However, such a change is not required. In general, it is expected that the attraction between the particles P and the surface S will be disturbed by a rapid perturbation of the electrostatic environment (thereby increasing the likelihood for hydrodynamic shear), whether or not the electrostatic polarity between the particles P and the surface S reverses.
The particles P in any of the foregoing embodiments can be relatively small, e.g., on the order of a micron or less. Accordingly, the changes in pH value can have a significant effect on the forces that attract and repel the particles P. The pH values can have values other than those described above in other embodiments. For example, the pH can oscillate between a value of about 5 or less and a value of about 7 or more, and in a more particular embodiment, between a value of about 2 and a value of about 10. Representative chemistries include dilute hydrochloric acid and dilute ammonia.
The change in the electrostatic force experienced by the particles P may in some cases be experienced by only some of the particles P, or the change may not have an effect that lasts long enough for a given particle P to be removed. Accordingly, the chemical composition of the chemistry fluid volume 138 can be changed multiple times so that any point within the chemistry zone 129 is exposed to multiple changes in chemistry. For example, in a particular embodiment, any point in the chemistry zone 129 is exposed to chemistry A, then chemistry B, then chemistry A again, and then chemistry B again before passing out of the chemistry zone 129. In other embodiments, any point in the chemistry zone 129 can be exposed to more cycles.
The maximum number of cycles that can be experienced by any point within the chemistry zone 129 will be limited by the length L of the chemistry zone, the amount of fluid in the chemistry fluid volume 138 (e.g., the length L, height H, and width of the chemistry fluid volume 138), the maximum actuation rate of the valve 150, and the speed of the workpiece 102. In at least some instances, it is desirable to fix the speed of the workpiece at a value that allows the rinse and dry processes to be fully executed (e.g., about 20 mm/second or less). Accordingly, the maximum number of cycles experienced by each point within the chemistry zone 129 can be controlled by the remaining variables. While the maximum number of cycles is a function of the speed of the workpiece 102, the number of cycles actually implemented can be changed independently of the speed of the workpiece 102 by simply changing the rate at which the valve 150 oscillates between chemistry A and chemistry B. In this manner, the system can provide adequate time for rinsing and drying the workpiece 102 (by setting the workpiece speed), while also oscillating the chemistry at a frequency sufficient to facilitate removal of the particles P. This frequency can have any of a variety of suitable values, for example, in a range of less than once every ten seconds up to several times (e.g., five to ten times) per second. In a representative case, the chemistry oscillates every two seconds. In any of these embodiments, the frequency can be low enough so that the composition of the chemistry fluid volume 138 completely turns over before the next change. The frequency can be high enough that each point within the chemistry zone 129 receives multiple “shocks” resulting from rapid fluid turnover.
In other embodiments, the different chemistries can be delivered to the workpiece surface in a similar oscillating manner, using other techniques. For example, referring now to
The apparatus 700 can have other arrangements in other embodiments. For example, the apparatus 700 can include rinse and dry components that are generally similar to those shown in
In a particular aspect of several of the embodiments described above, the first and second chemistries have different pHs so as to change the electrostatic potential (and, in a particular embodiment, the relative polarities) of the workpiece surface and/or particles that are targeted for removal from the workpiece surface. In other embodiments, the chemistries can have other characteristics. For example, the chemistries can have different surfactant characteristics which may also provide a “shock” (e.g., a surface tension shock) to the particles and may facilitate the removal of the particles from the workpiece surface. In still further embodiments, different chemistries can be used in a manner generally similar to that described above, but to produce results other than particulate removal. For example, the first chemistry can include an oxidizing chemistry and the second chemistry can include an acidic chemistry or an alkaline chemistry. By sequentially exposing the surface of the workpiece to an oxidant and an acid (or a base), the surface of the workpiece can be etched. As was described above with reference to the pH and surfactant embodiments, shocking the surface with sudden changes in chemistry (e.g., from an oxidant to an acid or base and back) can facilitate the rate at which material is etched from the workpiece. Furthermore, limiting the volume of chemistry to which the surface is exposed can allow for precise control of the etching process, and reduced consumption of the chemicals required to etch the surface.
One feature of at least some of the foregoing embodiments is that the chemistry to which a workpiece is exposed can be changed quickly and repeatedly using a proximity process. Unlike other processes (e.g., batch processes or spin processes), this arrangement can consume very small amounts of process fluid. This arrangement can also subject the workpiece to a series of chemical “shocks” e.g., rapid changes in chemistry. As a result, this arrangement can reduce attractive forces between the workpiece and residue/particles (for example, when the pH and/or surfactant characteristics of the chemistry are rapidly changed), which in turn facilitates cleaning the workpiece. In settings other than cleaning settings (for instance, during an etch process), the chemical shock can also facilitate processes for removing constituents of the workpiece, in addition to or in lieu of removing particles carried by the workpiece.
Another feature of at least some of the foregoing embodiments is that they can include oscillating a chemistry to which the workpiece is exposed, without affecting other associated processes. For example, the chemistry can be cycled at a rapid rate without changing the rate at which the workpiece is rinsed and dried. This aspect can enhance the versatility and applicability of the process.
From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the invention. For example, in the illustrated embodiments, two process chemistries (aside from the rinse chemistry and the drying chemistry) are provided to the workpiece. In other embodiments, more than two chemistries may be provided, and the valve may be arranged to cycle among the multiple chemistries in any of a wide variety of manners. As described above, each point on the surface of the workpiece can be exposed to the multiple chemistries twice before undergoing a rinse process, and in other embodiments, can be exposed to the multiple chemistries more than twice, and up to any suitable value that produces the desired effect and allows other processes (e.g., the rinsing and drying processes) to be performed. In still further embodiments, the head can include slots or other apertures rather than the circular holes shown in
Certain aspects of the invention described in the context of particular embodiments may be combined or eliminated in other embodiments. For example, the rinse and dry elements shown in
This application is a divisional of U.S. application Ser. No. 11/766,632 filed Jun. 21, 2007, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11766632 | Jun 2007 | US |
| Child | 13619566 | US |
