The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.
It is to be noted, however, that the appended drawings illustrate only exemplary embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
Embodiments of the present invention generally provide methods for fabricating dielectric materials used in a variety of applications, such as a gate dielectric layer used in field effect transistors fabrication. The improved gate dielectric layer fabricated by the present invention may include a silicon nitride layer deposited over a silicon oxide layer having a total thickness less than about 30 Å, such as less than about 25 Å, while maintaining low equivalent oxide thickness (EOT), low leakage current and high charge carrier mobility in channel regions.
The tool 100 includes a vacuum-tight processing platform 101, a factory interface 104, and a system controller 102. The platform 101 comprises a plurality of processing chambers 114A-D and load-lock chambers 106A-B, which are coupled to a vacuum substrate transfer chamber 103. The factory interface 104 is coupled to the transfer chamber 103 by the load lock chambers 106A-B.
In one embodiment, the factory interface 104 comprises at least one docking station 107, at least one factory interface robot 138 to facilitate transfer of substrates. The docking station 107 is configured to accept one or more front opening unified pod (FOUP). Four FOUPS 105A-D are shown in the embodiment of
Each of the loadlock chambers 106A-B have a first port coupled to the factory interface 104 and a second port coupled to the transfer chamber 103. The loadlock chamber 106A-B are coupled to a pressure control system (not shown) which pumps down and vents the chambers 106A-B to facilitate passing the substrate between the vacuum environment of the transfer chamber 103 and the substantially ambient (e.g., atmospheric) environment of the factory interface 104.
The transfer chamber 103 has a vacuum robot 113 disposed therein. The vacuum robot 113 is capable of transferring substrates 121 between the loadlock chamber 106A-B and the processing chambers 114A-D.
In one embodiment, the processing chambers coupled to the transfer chamber 103 may be a chemical vapor deposition (CVD) chamber 114D, a Decoupled Plasma Nitridation (DPN) chamber 114C, a Rapid Thermal Process (RTP) chamber 114B, or an atomic layer deposition (ALD) chamber 114A. Alternatively, different processing chambers, including at least one ALD, CVD, MOCVD, PVD, DPN, RTP chamber, may be interchangeably incorporated into the integrated tool 100 in accordance with process requirements. Suitable ALD, CVD, PVD, DPN, RTP, and MOCVD processing chambers are available from Applied Materials, Inc., among other manufacturers.
In one embodiment, an optional service chamber (shown in 116A-B) may be coupled to the transfer chamber 103. The service chambers 116A-B may be configured to perform other substrate processes, such as degassing, orientation, cool down and the like.
The system controller 102 is coupled to the integrated processing tool 100. The system controller 102 controls the operation of the tool 100 using a direct control of the process chambers 114A-D of the tool 100 or alternatively, by controlling the computers (or controllers) associated with the process chambers 114A-D and tool 100. In operation, the system controller 102 enables data collection and feedback from the respective chambers and system to optimize performance of the tool 100.
The system controller 102 generally includes a central processing unit (CPU) 130, a memory 134, and support circuit 132. The CPU 130 may be one of any form of a general purpose computer processor that can be used in an industrial setting. The support circuits 132 are conventionally coupled to the CPU 130 and may comprise cache, clock circuits, input/output subsystems, power supplies, and the like. The software routines, such as a method 200 for gate dielectric layer deposition described below with reference to
The method 200 begins at step 202 by providing a substrate 121 utilized to form a gate dielectric layer utilized in a gate structure. The substrate 121, as shown in
At an optional step 204, precleaning of the substrate 121 may be performed. In one of the processing chambers 114A-D of the tool 100. The precleaning step 204 is configured to cause compounds that are exposed on the surface of the substrate 121 to terminate in a functional group. Functional groups attached and/or formed on the surface of the substrate 121 include hydroxyls (OH), alkoxy (OR, where R=Me, Et, Pr or Bu), haloxyls (OX, where X=F, Cl, Br or I), halides (F, Cl, Br or I), oxygen radicals and aminos (NR or NR2, where R=H, Me, Et, Pr or Bu). The precleaning process may expose the surface of the substrate 121 to a reagent, such as NH3, B2H6, SiH4, SiH6, H2O, HF, HCl, O2, O3, H2O, H2O2, H2, atomic-H, atomic-N, atomic-O, alcohols, amines, plasmas thereof, derivatives thereof or combination thereof. The functional groups may provide a base for an incoming chemical precursor to attach on the surface of the substrate 121. In one embodiment, the precleaning process may expose the surface of the substrate 121 to a reagent for a period from about 1 second to about 2 minutes. In another embodiment, the exposure period may be from about 5 seconds to about 60 seconds. Precleaning processes may also include exposing the surface of the substrate 121 to an RCA solution (SC1/SC2), an HF-last solution, peroxide solutions, acidic solutions, basic solutions, plasmas thereof, derivatives thereof or combinations thereof. Useful precleaning processes are described in commonly assigned U.S. Pat. No. 6,858,547 and co-pending U.S. patent application Ser. No. 10/302,752, filed Nov. 21, 2002, entitled, “Surface Pre-Treatment for Enhancement of Nucleation of High Dielectric Constant Materials,” and published as US 20030232501, which are both incorporated herein by reference in their entirety.
In an exemplary embodiment of a precleaning process, a native oxide layer 302, as shown in
At step 206, a silicon oxide layer 304 is formed on the substrate 121, as shown in
In one embodiment, the silicon oxide layer 304 is a thermal oxide layer deposited with an RTP process at a temperature from about 650 degrees Celsius to about 980 degrees Celsius, such as from about 750 degrees Celsius to about 950 degrees Celsius. The silicon oxide layer 304 is deposited having a thin thickness less than about 30 Å, such as less than about 20 Å, for example, about 15 Å or less. A process gas mixture including oxygen gas (O2) is supplied into the chamber between about 0.5 slm to about 10 slm, such as about 2 slm. The process pressure may be regulated between about 0.5 Torr and about 50 Torr, such as 2 Torr. The deposition process may be performed between about 5 seconds to about 30 seconds. Examples of process chamber used to deposit silicon oxide layer 304 include Radiance® system available from Applied Materials, Inc., such as RTP chamber 114A-D, as shown in
At an optional step 208, a plasma treatment step may be performed on the silicon oxide layer 304. The plasma treatment step is performed to treat the silicon oxide layer while forming plasma-treated layer 306, as depicted in
In one embodiment, the plasma treatment step 208 is performed in one of the chambers 114A-D that is configured as a DPN chamber. The silicon oxide layer 304 is bombarded with ionic nitrogen formed by flowing nitrogen (N2) into the DPN chamber. Gases that may be used in the plasma process include nitrogen containing gas, such as N2 or NH3, argon (Ar), helium (He), neon, xenon or combinations thereof. The nitrogen gas flowed into the DPN chamber nitridizes the silicon oxide layer 304, forming the treated layer 306 on the upper surface of the silicon oxide layer 304. In one embodiment, the nitrogen concentration treated on the silicon oxide layer 304 may be between about 2E15 atomic weight percent per square centimeters (at/cm2) and about 8E15 atomic weight percent per square centimeters (at/cm2).
In one embodiment, the plasma process proceeds for a time period from about 10 seconds to about 300 seconds, for example, from about 30 seconds to about 240 seconds, and in one embodiment, from about 60 seconds to about 180 seconds. Also, the plasma process is conducted at a plasma power setting from about 500 watts to about 3,000 watts, for example, from about 700 watts to about 2,500 watts, for example, from about 900 watts to about 1,800 watts. Generally, the plasma process is conducted with a duty cycle of about 10 percent to about 90 percent, and at a pulse frequency at about 10 kHz. The DPN chamber may have a pressure from about 10 mTorr to about 80 mTorr. The inert gas may have a flow rate from about 10 standard cubic centimeters per minute (sccm) to about 5 standard liters per minute (slm), or from about 50 sccm to about 750 sccm, or from about 100 sccm to about 500 sccm.
At step 210, a silicon nitride layer 308 is deposited on the silicon oxide layer 304, as shown in
In embodiments depicted in
In one embodiment, the silicon nitride layer 308 is deposited with a Thermal-CVD process at a temperature from about 400 degrees Celsius to about 800 degrees Celsius, such as from about 500 degrees Celsius to about 700 degrees Celsius, for example, about 600 degrees Celsius. A process gas mixture including a nitrogen containing gas and a silicon containing gas, such as SiH4, is supplied into the chamber. Suitable nitrogen containing gases include, but not limited to, NH3, N2, N2O, and the like. Suitable silicon containing gases include, but not limited to, SiH4, Si2H6, dichlorosilane (DCS), tetrachlorosilane (TCS), or hexachlorodisilane (HCD) and the like. In one embodiment, the gas mixture may be supplied by a predetermined ratio of the nitrogen containing gas and silicon containing gas ranging between about 1:1 to about 1000:1 into the process chamber. In another embodiment, the gas mixture may be supplying by controlling the gas flow of nitrogen containing gas between about 10 sccm and about 1000 sccm, for example, between about 10 sccm and about 100 sccm, such as about 25 sccm, and silicon containing gas between about 1 sccm and about 100 sccm, for example, between about 1 sccm and about 50 sccm, such as 10 sccm. The process pressure may be regulated between about 0.5 Torr and about 50 Torr, for example, between about 1 Torr and about 25 Torr, such as 5 Torr. The deposition process may be performed between about 30 seconds to about 1800 second.
At an optional step 212, another plasma treatment step, which may be substantially similar to the plasma treatment step 208, may be performed on the silicon nitride layer 308. The plasma step 212 is performed to densify the silicon nitride layer 308 while forming plasma-treated layer 310, as depicted in
At step 214, the deposited silicon oxide layer 304 and the silicon nitride layer 308 disposed on the substrate 121 is exposed to a thermal annealing process. An example of a suitable RTP chamber in which step 214 may be performed is the CENTURA™ RADIANCE™ RTP chamber, available from Applied Materials, Inc., among others. The thermal annealing process step 214 may be performed in one of the process chambers 114A-D described in
In one embodiment, the substrate 121 may be thermally heated to a temperature from about 600 degrees Celsius to about 1,200 degrees Celsius. In another embodiment, the temperature may be from about 700 degrees Celsius to about 1,150 degrees Celsius, such as between about 800 degrees Celsius about 1,000 degrees Celsius. The thermal annealing process may have different durations. In one embodiment, the duration of the thermal annealing process may be from about 1 second to about 180 seconds, for example, about 2 seconds to about 60 seconds, such as about 5 seconds to about 30 seconds. At least one annealing gas is supplied into the chamber for thermal annealing process. Examples of annealing gases include oxygen (O2), ozone (O3), atomic oxygen (O), water (H2O), nitric oxide (NO), nitrous oxide (N2O), nitrogen dioxide (NO2), dinitrogen pentoxide (N2O5), nitrogen (N2), ammonia (NH3), hydrazine (N2H4), derivatives thereof or combinations thereof. The annealing gas may contain nitrogen and at least one oxygen-containing gas, such as oxygen. The chamber may have a pressure from about 0.1 Torr to about 100 Torr, for example, about 0.1 to about 50 Torr, such as 0.5 Torr. In one example of a thermal annealing process, substrate 121 is heated to a temperature of about 1,000 degrees Celsius for about 15 seconds within an oxygen atmosphere. In another example, substrate 121 is heated to a temperature of about 1,100 degrees Celsius for about 10 seconds to about 25 seconds within an atmosphere containing equivalent volumetric amounts of nitrogen and oxygen during the annealing process.
The thermal annealing process of step 214 converts the silicon oxide layer 304 and the silicon nitride layer 308 to a post anneal layer 312, as depicted in
At step 216, a gate structure may be formed on the substrate 121, as shown in
Thus, methods for fabricating a gate dielectric material that may be used for gate fabrication for field effect transistors have been provided. The method produces an integrated silicon nitride layer and a silicon oxide layer having a total thickness less than 30 Å, such as less than 25 Å, while having a desired low while maintaining low equivalent oxide thickness (EOT), low leakage current and high charge carrier mobility in channel regions.
While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.