US20080029028A1 - Systems and methods for depositing material onto microfeature workpieces in reaction chambers - Google Patents

Abstract

Systems and methods for depositing material onto a microfeature workpiece in a reaction chamber are disclosed herein. In one embodiment, the system includes a gas supply assembly having a first gas source, a first gas conduit coupled to the first gas source, a first valve assembly, a reaction chamber, and a gas distributor carried by the reaction chamber. The first valve assembly includes first and second valves that are in fluid communication with the first gas conduit. The first and second valves are configured in a parallel arrangement so that the first gas flows through the first valve and/or the second valve. It is emphasized that this Abstract is provided to comply with the rules requiring an abstract. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Description

TECHNICAL FIELD
• The present invention is related to systems and methods for depositing material in thin film deposition processes used in the manufacturing of microfeatures.
BACKGROUND
• Thin film deposition techniques are widely used in the manufacturing of microfeatures to form a coating on a workpiece that closely conforms to the surface topography. The size of the individual components in the workpiece is constantly decreasing, and the number of layers in the workpiece is increasing. As a result, both the density of components and the aspect ratios of depressions (i.e., the ratio of the depth to the size of the opening) are increasing. The size of workpieces is also increasing to provide more real estate for forming more dies (i.e., chips) on a single workpiece. Many fabricators, for example, are transitioning from 200 mm to 300 mm workpieces, and even larger workpieces will likely be used in the future. Thin film deposition techniques accordingly strive to produce highly uniform conformal layers that cover the sidewalls, bottoms, and corners in deep depressions that have very small openings.
• One widely used thin film deposition technique is Chemical Vapor Deposition (CVD). In a CVD system, one or more precursors that are capable of reacting to form a solid thin film are mixed while in a gaseous or vaporous state, and then the precursor mixture is presented to the surface of the workpiece. The surface of the workpiece catalyzes the reaction between the precursors to form a solid thin film at the workpiece surface. A common way to catalyze the reaction at the surface of the workpiece is to heat the workpiece to a temperature that causes the reaction.
• Although CVD techniques are useful in many applications, they also have several drawbacks. For example, if the precursors are not highly reactive, then a high workpiece temperature is needed to achieve a reasonable deposition rate. Such high temperatures are not typically desirable because heating the workpiece can be detrimental to the structures and other materials already formed on the workpiece. Implanted or doped materials, for example, can migrate within the silicon substrate at higher temperatures. On the other hand, if more reactive precursors are used so that the workpiece temperature can be lower, then reactions may occur prematurely in the gas phase before reaching the substrate. This is undesirable because the film quality and uniformity may suffer, and also because it limits the types of precursors that can be used.
• Atomic Layer Deposition (ALD) is another thin film deposition technique.FIGS. 1A and 1B schematically illustrate the basic operation of ALD processes. Referring toFIG. 1A, a layer or partial layer of gas molecules A_xcoats the surface of a workpiece W. The layer of A_xmolecules is formed by exposing the workpiece W to a precursor gas containing A_xmolecules and then purging the chamber with a purge gas to remove excess A_xmolecules. This process can form a monolayer or partial monolayer of A_xmolecules on the surface of the workpiece W because the A_xmolecules at the surface are held in place during the purge cycle by physical adsorption forces at moderate temperatures or chemisorption forces at higher temperatures. Referring toFIG. 1B, the layer of A_xmolecules is then exposed to another precursor gas containing B_ymolecules. The A_xmolecules react with the B_ymolecules to form an extremely thin layer of solid material on the workpiece W. The chamber is then purged again with a purge gas to remove excess B_ymolecules.
• FIG. 2 illustrates the stages of one cycle for forming a thin solid layer using ALD techniques. A typical cycle includes (a) exposing the workpiece to the first precursor A_x, (b) purging excess A_xmolecules, (c) exposing the workpiece to the second precursor B_y, and then (d) purging excess B_ymolecules. In actual processing, several cycles are repeated to build a thin film on a workpiece having the desired thickness. For example, each cycle may form a layer or partial layer having a thickness of approximately 0.1-1.0 Å, and thus several cycles are required to form a solid layer having a thickness of approximately 60 Å.
• FIG. 3 schematically illustrates a single-wafer ALD reactor10 having areaction chamber20 coupled to agas supply30 and avacuum40. Thereactor10 also includes aheater50 that supports the workpiece W and agas dispenser60 in thereaction chamber20. Thegas dispenser60 includes aplenum62 operably coupled to thegas supply30 and adistributor plate70 having a plurality ofholes72. In operation, theheater50 heats the workpiece W to a desired temperature, and the gas supply30 selectively injects the first precursor A_x, the purge gas, and the second precursor B_y, as shown above inFIG. 2. Thevacuum40 maintains a negative pressure in the chamber to draw the gases from thegas dispenser60 across the workpiece W and then through an outlet of thereaction chamber20.
• One drawback of ALD processing is that it has a relatively low throughput compared to CVD techniques. For example, each A_x-purge-B_y-purge cycle can take several seconds. This results in a total process time of several minutes to form a single thin layer of only 60 Å. In contrast to ALD processing, CVD techniques require only about one minute to form a 60 Å thick layer. The low throughput of existing ALD techniques limits the utility of the technology in its current state because ALD may be a bottleneck in the overall manufacturing process.
• Another drawback of ALD and pulsed CVD processing is the downtime required to service the valves that control the flow of precursor into the reaction chamber. The flow of each precursor is controlled by a single, quick-action valve that actuates at least once per cycle to provide the precursor to the gas dispenser. For example, the valves can actuate between 100-2000 times to build a single 200 Å thick layer. Accordingly, the high frequency of actuations causes the valves to wear out relatively quickly. Replacing and servicing these valves requires downtime, increases operating costs, and causes an associated reduction in throughput. Therefore, there is a significant need to reduce the downtime for servicing components in CVD and ALD reactors.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIGS. 1A and 1B are schematic cross-sectional views of stages in ALD processing in accordance with the prior art.
• FIG. 2 is a graph illustrating a cycle for forming a layer using ALD techniques in accordance with the prior art.
• FIG. 3 is a schematic representation of a system including a reactor for depositing material onto a microfeature workpiece in accordance with the prior art.
• FIG. 4 is a schematic representation of a system for depositing material onto a microfeature workpiece in accordance with one embodiment of the invention.
• FIG. 5 is a schematic isometric view of a valve assembly for use in the system shown inFIG. 4 in accordance with another embodiment of the invention.
• FIG. 6 is a schematic side cross-sectional view of a valve assembly for use in the system shown inFIG. 4 in accordance with yet another embodiment of the invention.
DETAILED DESCRIPTION
• A. Overview
• The following disclosure describes several embodiments of systems and methods for depositing material onto microfeature workpieces in reaction chambers. Many specific details of the invention are described below with reference to single-wafer reactors for depositing material onto microfeature workpieces, but several embodiments can be used in batch systems for processing a plurality of workpieces simultaneously. The term “microfeature workpiece” is used throughout to include substrates upon which and/or in which microelectronic devices, micromechanical devices, data storage elements, read/write components, and other features are fabricated. For example, microfeature workpieces can be semiconductor wafers such as silicon or gallium arsenide wafers, glass substrates, insulative substrates, and many other types of materials. Furthermore, the term “gas” is used throughout to include any form of matter that has no fixed shape and will conform in volume to the space available, which specifically includes vapors (i.e., a gas having a temperature less than the critical temperature so that it may be liquefied or solidified by compression at a constant temperature). Several embodiments in accordance with the invention are set forth inFIGS. 4-6 and the following text to provide a thorough understanding of particular embodiments of the invention. A person skilled in the art will understand, however, that the invention may have additional embodiments, or that the invention may be practiced without several of the details of the embodiments shown inFIGS. 4-6.
• One aspect of the invention is directed to a system for depositing material onto a microfeature workpiece in a reaction chamber. In one embodiment, the system includes a gas supply assembly having a first gas source, a first gas conduit coupled to the first gas source, a first valve assembly, a reaction chamber, and a gas distributor carried by the reaction chamber. The first valve assembly includes first and second valves that are in fluid communication with the first gas conduit. The first and second valves are configured in a parallel arrangement so that the first gas flows through the first valve and/or the second valve.
• In one aspect of this embodiment, the system further includes a controller configured to operate the first and second valves simultaneously or in an alternating sequence. In another aspect of this embodiment, the first valve assembly further includes first and second gas passageways in fluid communication with the first gas conduit. The first valve can be configured to control the first gas flow through the first passageway, and the second valve can be configured to control the first gas flow through the second passageway. In another aspect of this embodiment, the first valve assembly further includes a third valve in fluid communication with the first gas conduit. The first, second, and third valves can be arranged symmetrically so that the first, second, and third valves are spaced apart from a portion of the gas distributor by at least approximately the same distance.
• In another embodiment, the system includes a gas supply assembly having a first gas source, a first gas conduit coupled to the first gas source, a first valve and a second valve each in fluid communication with the first gas conduit, a reaction chamber, and a gas distributor carried by the reaction chamber. The first and second valves are operable independently to individually and/or jointly provide pulses of the first gas downstream from the first and second valves. The gas distributor is in fluid communication with the first and second valves to receive the pulses of the first gas.
• In another embodiment, the system includes a gas supply assembly having a first gas source, a first gas conduit coupled to the first gas source, a valve assembly, a reaction chamber, and a gas distributor carried by the reaction chamber. The valve assembly includes a body with first and second gas passageways, a first valve stem configured to control the flow of the first gas through the first gas passageway, and a second valve stem configured to control the flow of the first gas through the second gas passageway. The first and second gas passageways are in fluid communication with the first gas conduit and are configured in a parallel arrangement.
• Another aspect of the invention is directed to a method of depositing material onto a microfeature workpiece in a reaction chamber. In one embodiment, the method includes flowing a first pulse of a first gas through a first gas conduit and a first valve into the reaction chamber. The method further includes flowing a second pulse of the first gas through the first gas conduit and a second valve into the reaction chamber without flowing the second pulse of the first gas through the first valve. In one aspect of this embodiment, flowing the first pulse of the first gas includes controlling the first valve to dispense the first pulse of the first gas into the reaction chamber, and flowing the second pulse of the first gas includes controlling the second valve to dispense the second pulse of the first gas into the reaction chamber.
• B. Deposition Systems
• FIG. 4 is a schematic representation of asystem100 for depositing material onto a microfeature workpiece W in accordance with one embodiment of the invention. In this embodiment, thesystem100 includes areactor110 having areaction chamber120 coupled to agas supply130 and avacuum140. Thereactor110 also includes agas distributor160 coupled to thereaction chamber120 and thegas supply130 to dispense gas(es) into thereaction chamber120 and onto the workpiece W.
• Thegas supply130 includes a plurality of gas sources132 (identified individually as132a-c) and a plurality of upstreammain lines136 coupled to the gas sources132. The gas sources132 can include afirst gas source132afor providing a first gas, asecond gas source132bfor providing a second gas, and athird gas source132cfor providing a third gas. The first and second gases can be first and second precursors, respectively. The third gas can be a purge gas. The first and second precursors are the gas and/or vapor phase constituents that react to form the thin, solid layer on the workpiece W. The purge gas can be a suitable type of gas that is compatible with thereaction chamber120 and the workpiece W. In other embodiments, thegas supply130 can include a different number of gas sources132 for applications that require additional precursors or purge gases. In additional embodiments, the gas sources132 can include one or more etchants for deposition onto a microfeature workpiece during etching.
• In the illustrated embodiment, thereactor110 also includes aworkpiece support150 to hold the workpiece W in thereaction chamber120. In one aspect of this embodiment, theworkpiece support150 can be heated to bring the workpiece W to a desired temperature for catalyzing the reaction between the first gas and the second gas at the surface of the workpiece W. For example, theworkpiece support150 can be a plate with a heating element. Theworkpiece support150, however, may not be heated in other applications.
• Thesystem100 of the illustrated embodiment further includes a plurality of valve assemblies168 (identified individually as168a-c) coupled to the upstreammain lines136 and a plurality of downstreammain lines139 coupled to the valve assemblies168 and thegas distributor160. The valve assemblies168 can include a plurality of branch lines137 (identified individually as137a-b) attached to the upstream and downstreammain lines136 and139 and a plurality of valves170 (identified individually as170a-b) attached to the branch lines137. The branch lines137 flow the gases from the upstreammain lines136 to the downstreammain lines139, and the valves170 control the flow of the gases through the branch lines137. In the illustrated embodiment, the first and second valves170a-bare configured in a parallel arrangement, and accordingly, each portion of gas flows through either thefirst valve170aor thesecond valve170bof the corresponding valve assembly168. In other embodiments, such as those described below with reference toFIGS. 5 and 6, the valve assemblies can have a different configuration and/or a different number of valves. For example, several valve assemblies168 can be combined into a single valve assembly, and/or the valve assemblies168 can be carried by thereaction chamber120.
• The valve assemblies168 are operated by acontroller142 that generates signals for controlling the flow of gases into thereaction chamber120 for ALD and CVD applications. For example, thecontroller142 can be programmed to operate the valve assemblies168 to pulse the gases individually through thegas distributor160 in ALD applications or mix selected precursors in thegas distributor160 in CVD applications. More specifically, in one embodiment of an ALD process, thecontroller142 actuates thefirst valve170aof a first valve assembly168ato dispense a pulse of the first gas (e.g., the first precursor) into thereaction chamber120. Next, thecontroller142 actuates thefirst valve170aof athird valve assembly168cto dispense a pulse of the third gas (e.g., the purge gas) into thereaction chamber120. Thecontroller142 then actuates thefirst valve170aof asecond valve assembly168bto dispense a pulse of the second gas (e.g., the second precursor) into thereaction chamber120. Next, thecontroller142 actuates thesecond valve170bof thethird valve assembly168cto dispense a pulse of the third gas into thereaction chamber120. In the next cycle, the process is repeated except thecontroller142 actuates thesecond valves170b(rather than thefirst valves170a) of the first and second valve assemblies168a-bto dispense pulses of the first and second gases into thereaction chamber120.
• In one embodiment of a pulsed CVD process, thecontroller142 actuates thefirst valves170aof the first and second valve assemblies168a-bto dispense a pulse of the first and second gases (e.g., the first and second precursors) into thereaction chamber120. Next, thecontroller142 actuates thefirst valve170aof thethird valve assembly168cto dispense a pulse of the third gas (e.g., the purge gas) into thereaction chamber120. In the next cycle, thecontroller142 actuates thesecond valves170b(rather than thefirst valves170a) of the first and second valve assemblies168a-bto dispense a pulse of the first and second gases into thereaction chamber120. Thecontroller142 then actuates thesecond valve170bof thethird valve assembly168cto dispense a pulse of the third gas into thereaction chamber120. In other embodiments, thecontroller142 can actuate the valves170 in other sequences.
• One feature of the illustrated embodiment is that each gas source is coupled to a valve assembly with a plurality of valves. By coupling several valves to each gas source, the frequency with which each valve is actuated to dispense gas is reduced. For example, if each gas source is coupled to a valve assembly with two valves, the frequency that each valve is actuated may be reduced by one half. One advantage of this feature is that the life of the valve assembly is extended because the valves do not wear out as quickly. When the valves wear out or otherwise fail, the system is shut down to replace and/or service the valves. Accordingly, the system of the illustrated embodiment reduces the downtime to replace and/or service the valves and thereby increases the throughput.
• In other embodiments, thecontroller142 can simultaneously actuate the first and second valves170a-bof a single valve assembly168 to dispense a portion of the corresponding gas into thereaction chamber120. One advantage of this arrangement is that if one valve fails, the other valve in the valve assembly will continue to dispense gas for deposition onto the workpiece W.
• C. Other Valve Assemblies
• FIG. 5 is a schematic isometric view of avalve assembly268 for use in thesystem100 shown inFIG. 4 in accordance with another embodiment of the invention. Thevalve assembly268 includes a plurality of valves270 (identified individually as270a-c) and a plurality of branch lines237 (identified individually as237a-c) coupling the valves270 to the upstream and downstreammain lines136 and139. In one aspect of this embodiment, the branch lines237 and the valves270 are arranged symmetrically so that the valves270 provide pulses of gas to the reaction chamber120 (FIG. 4) at a consistent pressure and with a consistent response time. For example, the branch lines237 can include afirst portion243 coupled to the upstreammain line136, asecond portion244 coupled to thefirst portion243 and the valve270, athird portion245 coupled to the valve270, and afourth portion246 coupled to thethird portion245 and the downstreammain line139. Thefirst portions243 can be oriented at generally the same angle relative to the upstreammain line136, and thefourth portions246 can be oriented at generally the same angle relative to the downstreammain line139. The second andthird portions244 and245 can be generally parallel to the upstream and downstreammain lines136 and139. Moreover, theportions243,244,245 and246 in each branch line237 can have approximately the same length as the corresponding portions in the other branch lines237. In this embodiment, the symmetric arrangement can ensure that each valve270 provides consistent and uniform pulses of gas to the reaction chamber120 (FIG. 4). In other embodiments, thevalve assembly268 may have other configurations, including asymmetric arrangements. For example, the valve assembly can include a body with gas passageways, such as in the embodiment described below with reference toFIG. 6, or the valve assembly can include a different number of valves.
• FIG. 6 is a schematic side cross-sectional view of avalve assembly368 for use in thesystem100 shown inFIG. 4 in accordance with another embodiment of the invention. Thevalve assembly368 includes avalve body372 having afirst gas passageway338aand asecond gas passageway338b, afirst valve stem380ain thevalve body372, and asecond valve stem380bin thevalve body372. Thevalve body372 includes aninlet374 configured for attachment to the upstream main line136 (FIG. 4), anoutlet376 configured for attachment to the downstream main line139 (FIG. 4), a plurality ofvalve seats383, and a plurality ofcavities378. The first and second valve stems380a-binclude afirst portion381 configured to engage thevalve seat383 and asecond portion382 configured to be received in thecavity378. The first and second valve stems380a-bare movable in a direction D between a first position (illustrated by thefirst valve stem380a) in which thefirst portion381 engages thevalve seat383 and a second position (illustrated by thesecond valve stem380b) in which thesecond portion382 is received in thecavity378. The position of the first and second valve stems380a-bcontrols the flow of gas through the gas passageways338.
• In operation, a gas flow “F” enters thevalve body372 through theinlet374 and is split into two separate flows at ajunction347 of the first and second gas passageways338a-b. The first and second gas passageways338a-bare configured in a parallel arrangement so that each portion of gas flows through either thefirst gas passageway338aor thesecond gas passageway338b. When one or both of the valve stems380a-bare in the second position, the gas flows past the valve stems380a-band exits thevalve body372 through theoutlet376. In one embodiment, a controller can actuate the valve stems380 in an alternating sequence so that when one valve stem380 is in the second position, the other valve stem380 is in the first position. In other embodiments, a controller can actuate the valve stems380 simultaneously so that both of the valve stems380 can be in the second position at the same time. In additional embodiments, thevalve assembly368 can include a different number of valve stems380 and gas passageways338. For example, a valve assembly can include four gas passageways and four valve stems.
• 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 spirit and scope of the invention. Accordingly, the invention is not limited, except as by the appended claims.

Claims (18)

1. A system for depositing material onto a microfeature workpiece in a reaction chamber, the system comprising:

a gas supply assembly having a first gas source for containing a first gas;

a first gas conduit coupled to the first gas source;

a first valve assembly including first and second valves in fluid communication with the first gas conduit, the first and second valves configured in a parallel arrangement so that the first gas flows through the first valve and/or the second valve;

a reaction chamber; and

a gas distributor carried by the reaction chamber and in fluid communication with the first valve assembly.

2. The system ofclaim 1, further comprising a controller configured to operate the first and second valves in an alternating sequence.

3. The system ofclaim 1, further comprising a controller configured to operate the first and second valves at least partially simultaneously.

4. The system ofclaim 1 wherein the first valve assembly further comprises first and second gas passageways in fluid communication with the first gas conduit, the first valve being configured to control the first gas flow through the first passageway, and the second valve being configured to control the first gas flow through the second passageway.

5. The system ofclaim 1 wherein the first valve assembly further comprises a third valve in fluid communication with the first gas conduit, the first, second, and third valves being arranged symmetrically so that the first, second, and third valves are spaced apart from a portion of the gas distributor by at least approximately the same distance.

6. The system ofclaim 1 wherein the gas supply assembly further comprises a second gas source for containing a second gas, and wherein the system further comprises:

a second gas conduit coupled to the second gas source and in fluid communication with the gas distributor; and

a second valve assembly including third and fourth valves in fluid communication with the second gas conduit, the third and fourth valves being configured in a parallel arrangement so that the second gas flows through the third valve and/or the fourth valve.

7. A system for depositing material onto a microfeature workpiece in a reaction chamber, the system comprising:

a gas supply assembly having a first gas source containing a first gas;

a first gas conduit coupled to the first gas source;

a first valve and a second valve each in fluid communication with the first gas conduit, the first and second valves being operable independently to individually and/or jointly provide pulses of the first gas downstream from the first and second valves;

a reaction chamber; and

a gas distributor carried by the reaction chamber and in fluid communication with the first and second valves to receive the pulses of the first gas.

8. The system ofclaim 7, further comprising a controller configured to operate the first and second valves in an alternating sequence.

9. The system ofclaim 7, further comprising a controller configured to operate the first and second valves simultaneously.

10. The system ofclaim 7, further comprising first and second gas passageways coupled to the first gas conduit, the first valve configured to control the first gas flow through the first passageway, and the second valve configured to control the first gas flow through the second passageway.

11. The system ofclaim 7, further comprising a third valve in fluid communication with the first gas conduit, the first, second, and third valves being arranged symmetrically so that the first, second, and third valves are spaced apart from a portion of the gas distributor by at least approximately the same distance.

12. The system ofclaim 7 wherein the gas supply assembly further comprises a second gas source for containing a second gas, and wherein the system further comprises:

a second gas conduit coupled to the second gas source and in fluid communication with the gas distributor; and

a third valve and a fourth valve each in fluid communication with the second gas conduit, the third and fourth valves being operable independently to individually and/or jointly provide pulses of the second gas downstream from the third and fourth valves.

13. A system for depositing material onto a microfeature workpiece in a reaction chamber, the system comprising:

a gas supply assembly having a first gas source for providing a first gas;

a first gas conduit coupled to the first gas source to carry the first gas from the first gas source;

a valve assembly including a body with first and second gas passageways in fluid communication with the first gas conduit, a first valve stem configured to control the flow of the first gas through the first gas passageway, and a second valve stem configured to control the flow of the first gas through the second gas passageway, the first and second gas passageways configured in a parallel arrangement;

a reaction chamber; and

a gas distributor carried by the reaction chamber and in fluid communication with the first gas conduit.

14. The system ofclaim 13, further comprising a controller configured to operate the first and second valve stems in an alternating sequence.

15. The system ofclaim 13, further comprising a controller configured to operate the first and second valve stems simultaneously.

16. The system ofclaim 13 wherein:

the body of the valve assembly further comprises a third gas passageway in fluid communication with the first gas conduit; and

the valve assembly further comprises a third valve stem configured to control the flow of the first gas through the third gas passageway.

17. The system ofclaim 13 wherein:

the valve assembly comprises a first valve assembly;

the body comprises a first body;

the gas supply assembly further comprises a second gas source for providing a second gas; and

the system further comprises—

a second gas conduit coupled to the second gas source and in fluid communication with the gas distributor; and

a second valve assembly including a second body having third and fourth gas passageways in fluid communication with the second gas conduit, a third valve stem configured to control the flow of the second gas through the third gas passageway, and a fourth valve stem configured to control the flow of the second gas through the fourth gas passageway, the third and fourth gas passageways configured in a parallel arrangement.

18-39. (canceled)

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