Method and apparatus for precleaning a substrate surface prior to epitaxial growth

Embodiments of the present invention generally relate to methods for removing contaminants and native oxides from substrate surfaces. The methods generally include removing contaminants disposed on the substrate surface using a plasma process, and then cleaning the substrate surface by use of a remote plasma assisted dry etch process.

BACKGROUND

Field

Embodiments of the present invention generally relate to methods and apparatuses for removing contaminants and oxides from a substrate surface.

Description of the Related Art

Integrated circuits are formed in and on silicon and other semiconductor substrates. In the case of single crystal silicon, substrates are made by growing an ingot from a bath of molten silicon, and then sawing the solidified ingot into multiple wafers. An epitaxial silicon layer may then be formed on the monocrystalline silicon wafer to form a defect free silicon layer that may be doped or undoped. Semiconductor devices, such as transistors, are manufactured from the epitaxial silicon layer. The electrical properties of the formed epitaxial silicon layer will generally be better than the properties of the monocrystalline silicon substrate.

Surfaces of the monocrystalline silicon and the epitaxial silicon layer are susceptible to contamination when exposed to typical wafer fabrication facility ambient conditions. For example, a native oxide layer may form on the monocrystalline silicon surface prior to deposition of the epitaxial layer. Additionally, contaminants present in the ambient environment may deposit on the monocrystalline surface. The presence of a native oxide layer or contaminants on the monocrystalline silicon surface negatively affects the quality of an epitaxial layer subsequently formed on the monocrystalline surface. While present cleaning methods remove some of the native oxides and contaminants from the monocrystalline silicon surface, some contaminants still remain.

Therefore, there is a need for a method and apparatus for cleaning a substrate surface, especially for cleaning a substrate surface prior to performing an epitaxial deposition process.

SUMMARY

Embodiments of the present invention generally relate to methods for removing contaminants and native oxides from substrate surfaces. The methods generally include removing contaminants disposed on the substrate surface using a plasma process, and then cleaning the substrate surface by use of a remote plasma assisted dry etch process.

In one embodiment, a method for cleaning a surface of a substrate is disclosed. The method includes removing contaminants from the surface of the substrate, wherein the contaminants are removed by a reducing process, then cleaning the surface of the substrate by use of a plasma etch process, wherein at least one process gas is used during the plasma etch process, and forming an epitaxial layer on the surface of the substrate.

In another embodiment, a method for forming an epitaxial layer on a surface of a substrate is disclosed. The method includes removing contaminants from the surface of the substrate, wherein the contaminants are removed by a reducing process, then cleaning the surface of the substrate by use of a plasma etch process, and then forming an epitaxial layer on the surface of the substrate.

In another embodiment, a method for cleaning a surface of a substrate is disclosed. The method includes removing contaminants from the surface of the substrate, wherein the contaminants are removed by a reducing process, cleaning the surface of the substrate by use of a plasma etch process, wherein at least one of process gases used during the plasma etch process comprises fluorine, and forming an epitaxial layer on the surface of the substrate.

In another embodiment, an apparatus for forming an epitaxial layer on a surface of a substrate is disclosed. The apparatus includes a first processing chamber coupled to a first transfer chamber, wherein the first processing chamber is configured to perform a reducing process to remove contaminants from the surface of the substrate, a cleaning chamber coupled to the first transfer chamber, wherein the cleaning chamber is configured to perform a plasma etch process to remove an oxide layer, a second transfer chamber coupled to the first transfer chamber by a second processing chamber, and a plurality of third processing chambers coupled to the second transfer chamber, wherein the plurality of third processing chambers are configured to deposit an epitaxial layer on the surface of the substrate.

DETAILED DESCRIPTION

Embodiments of the present invention generally relate to methods for removing contaminants and native oxides from substrate surfaces. The methods generally include removing contaminants disposed on the substrate surface using a plasma process, and then cleaning the substrate surface by use of a remote plasma assisted dry etch process.

FIG. 1illustrates a processing sequence100in accordance with one embodiment of the present invention. The process sequence100begins at step102. In step102, contaminants on a surface of a substrate are removed. The substrate may include a silicon containing material and the surface may include a material, such as silicon (Si), germanium (Ge) or silicon germanium alloys (SiGe). In some embodiments, the Si, Ge, or SiGe surface may have contaminants and an oxide layer, such as native oxide layer, disposed thereon. Due to the sensitivity of epitaxial deposition processes to contaminants, such as carbon containing contaminants, exposure to most typical cleanroom environments for a few hours will allow a significant amount of contaminants to reaccumulate on the surface of the substrate such that the accumulated contaminants will affect the quality of the subsequently formed epitaxial layer.

In some embodiments of step102, contaminants may be removed from a surface of the substrate using a reducing process102A and/or an oxidizing process102B. There are several reducing processes that may be suitable for contaminant removal, which are described herein. In one embodiment, contaminants are removed using a hydrogen containing plasma. The plasma may contain hydrogen gas (H2) and/or argon (Ar) and ammonia (NH3) gases. The plasma may be inductively or capacitively coupled, or the plasma may be energized by a microwave source. In one embodiment, the plasma is inductively coupled, the processing temperature may be about 400 degrees Celsius (° C.) and the processing pressure may be about 20 milliTorr (mTorr). A processing chamber that can be adapted to perform a reducing process using an inductively coupled plasma is illustrated inFIG. 2.FIG. 3illustrates a processing chamber that can be adapted to perform a reducing process using a capacitively coupled plasma.FIG. 4illustrates a processing chamber that can be adapted to perform a different reducing process using an inductively coupled plasma.

After removing the contaminants, as shown in step104, the surface of the substrate is cleaned using a cleaning process. The cleaning process may include a plasma etching process, which is discussed more below. In some embodiments, the plasma etching process may use a fluorine containing plasma. A processing chamber that can be adapted to perform the plasma etch process is illustrated inFIG. 5.

Next, in step106, an epitaxial layer is deposited on the surface of the substrate. Steps102,104and106may be performed in one processing system, such as a cluster tool illustrated inFIG. 6. Alternatively, step102may be performed in a processing chamber that is not within a processing system that contains processing chambers in which steps104and106are performed, as illustrated inFIG. 7.

FIG. 2is a cross sectional view of a processing chamber200according to one embodiment. The processing chamber200is an inductively coupled plasma processing chamber that is adapted to perform at least some of the processes found in step102A, and thus removes contaminants, such as carbon or hydrocarbons accumulated on a surface201of a substrate202. In one embodiment, the processing chamber200is a modified Decoupled Plasma Nitridation (DPN) Chamber that is available from Applied Materials Inc. of Santa Clara, Calif.

The processing chamber200generally comprises a radio frequency (RF) source assembly291, a process chamber assembly293, and a substrate support assembly294. The process chamber assembly294generally comprises multiple components that are used to form a vacuum in a processing region222so that a plasma process can be performed therein. In general the process chamber assembly293comprises a chamber base227, chamber walls228and a chamber lid229that sealably enclose the processing region222. The processing region222can be evacuated to a desired vacuum pressure by the use of a vacuum pump210that is connected to the processing region222through the chamber base227and/or chamber walls228. Generally, the chamber walls228and chamber base227may be formed from a metal, such as aluminum, or other suitable material.

In one embodiment, the chamber walls228and chamber lid229may be temperature controlled. Conventional methods and/or heat exchanging devices may be used to heat and cool various chamber components. For example, the chamber walls228and chamber lid229may be heated by heaters (not shown), such as lamp arrays, positioned outside the process chamber assembly293. In another example, cooling gases may be circulated outside the process chamber assembly293to cool the chamber walls228and chamber lid229. In another example, heating and/or cooling conduits, which may be embedded in the chamber walls228and chamber lid229, may be connected to a fluid heater/chiller device to control the temperature.

In one embodiment, the RF source assembly291is an inductive type RF source that generally contains an RF generator208and an RF match circuit208A that are connected to a coil209. The coil209is positioned adjacent to the chamber lid229. In one embodiment, the RF generator208may operate at between about 0 and about 3000 W at a frequency between about 400 kHz and about 60 MHz. In one example, the RF generator208operates at a frequency of 13.56 MHz. In one embodiment, the RF generator208may provide pulses of RF energy to the coil209to generate a plasma that has a reduced energy level and/or plasma density. Use of a reduced energy hydrogen containing plasma may help to prevent roughening of the surface201of the substrate202during this processing step. Roughening of the surface201may negatively affect device properties and may cause gate leakage or poor subthreshold voltage. In some cases where an oxide layer, such as a native oxide layer, has been formed on the surface201of the substrate202, the formed oxide layer may be advantageously used to help prevent the roughening of the surface during step102A. The low energy level hydrogen containing plasma may be generated with a low RF power, such as between 10 W and 500 W, at a frequency between about 400 kHz and about 60 MHz, such as a frequency of about 13.56 MHz. Source RF powers can be operated in continuous wave mode, always on, or can be operated in pulsed mode, where the source power is on and off at a frequency of 100 Hz to 100 kHz.

The chamber lid229is generally a dielectric component (e.g., quartz, ceramic material (e.g., alumina)) that is adapted to allow the RF energy delivered from the inductive RF source assembly291to form a plasma in the processing region222. The plasma may be formed outside of the processing region222and then introduced into the processing region222. Processing gases exposed to remote plasma typically have a reduced energy level compare to processing gases that are exposed to an in-situ generated plasma at the same RF power level. Therefore, in some configurations, plasmas generated by a remote plasma source can be used to prevent roughening of the surface201of the substrate202.

In one embodiment, the process chamber assembly293also contains a gas delivery system250that is adapted to deliver one or more process gasses into the processing region222. In one embodiment, the processing region222is circumscribed with one or more shields230that are intended to protect the chamber walls228and/or the chamber lid229from the generated plasma and preparation processes performed in the chamber. In one embodiment, the gas delivery system is adapted to deliver a reactive gas, such as a hydrogen containing gas (e.g., H2or NH3), and/or a fluorine containing gas, such as fluorine gas (F2), nitrogen trifluoride (NF3) or anhydrous HF, to name just a few. In one embodiment, the gas delivery system250is adapted to deliver an inert gas, such as argon (Ar), helium (He), krypton (Kr) and/or nitrogen (N2). In one embodiment, the gas delivery system250is adapted to deliver a reactive gas and an inert gas. The pressure in the processing region222can be controlled by adjusting the flow rate of gas delivered by the gas delivery system250and the pumping speed of the vacuum pump210. A throttle valve211may be used to adjust the pumping speed of the vacuum pump210. The processing pressure may be between about 1 mTorr and about 500 mTorr, such as a pressure of about 20 mTorr.

The substrate support assembly294generally includes a substrate support262that contains a substrate supporting member262A. The substrate supporting member262A may be a conventional electrostatic chuck that can be used to actively hold the substrate during processing, or comprise a simple substrate support. A temperature controller261is generally adapted heat and/or cool the substrate supporting member262A to a desired temperature by use of temperature controller261and a heat exchanging device, such as embedded resistive heating elements or fluid cooling channels that are coupled to a conventional heat exchanger (not shown). In one embodiment, the temperature controller261is adapted to operate and heat the substrate202positioned on the substrate supporting member262A to a temperature between about 20° C. and about 800° C., such as about 400° C. The substrate202is not biased during processing because biasing may causing the surface201to be roughened.

Delivering RF energy from the RF generator208to the processing region222causes the gas atoms in the processing region222to become ionized. When the substrate202is exposed to plasma generated in or distributed to the processing region222during operation, the radicals and/or ions generated in the plasma will interact with the contamination disposed on the surface201of the substrate202causing it to desorb or be physically removed therefrom. In some configurations the plasma may knock off or cause the contaminants to desorb from the surface due to the energy transferred by the ionized atoms in the plasma striking the surface201of the substrate202. As noted above, in some embodiments, it is desirable to minimize the amount of energy the plasma generated species have to reduce the chance of roughening the surface201during processing. In some embodiments, it is desirable to form a larger percentage of gas radicals versus energetic ionized species.

In one example of a process performed in step102A, a hydrogen containing plasma may be generated with an RF power of between 10 W and 500 W at an RF frequency of 13.56 MHz, while the substrate202is maintained at a temperature of between about 15 and about 500° C. and the processing pressure in the processing region222is maintained at a pressure of 20 mTorr. In this example, the hydrogen (H2) gas in inert gas concentration during processing may be between 2% and 100%.

In some embodiments of step102A, the reducing process is at least partially preformed using a capacitively coupled plasma that is used to remove contaminants from the surface of the substrate.FIG. 3schematically illustrates a cross sectional side view of a processing chamber300in accordance with another embodiment of the present invention. The processing chamber300is a capacitively coupled plasma generating chamber. The processing chamber300comprises a chamber lid assembly330sealably coupled to the process chamber assembly396and defining a process region333. The processing region333can be evacuated to a desired vacuum pressure by the use of a vacuum pump310that is connected to the processing region333through the chamber base327and/or chamber walls328. A throttle valve311may be used to adjust the pumping speed of the vacuum pump210. Generally, the chamber walls328and chamber base327may be formed from a metal, such as aluminum, or other suitable material.

In this configuration, the chamber lid assembly330comprises a gas distribution plate (also known as a shower head)332and a base plate331having a blocker plate334substantially parallel to the gas distribution plate332. The gas distribution plate332is isolated from the chamber walls328using an electric insulator335. The chamber lid assembly330is connected to the gas delivery assembly350. Reactant and/or cleaning gases from the gas delivery system350may be delivered to the process region333through a gas passage336. The RF source assembly391is coupled to the base plate331to provide RF power for plasma generation to the processing region333. An RF source for capacitive plasma generation generally comprises a radio frequency (RF) power source308, for example, a 13.56 MHz RF generator, and an RF match circuit308A. During processing, the substrate supporting member362may be grounded or may electrically float. The bias potential between the chamber walls328and the base plate331may be used to form a plasma in the process region333. Activated species in the plasma can be used to process the substrate302. Again a hydrogen containing plasma can be used, in this embodiment of the reducing process, to remove contaminants on the surface301of the substrate302. In one example of a process performed in step102A, a hydrogen containing plasma may be generated with an RF power of between 10 W and 500 W at an RF frequency of 13.56 MHz, while the substrate302is maintained at a temperature of between about 15 and about 500° C. and the processing pressure in the processing region333is maintained at a pressure of 500 mTorr. In this example, the hydrogen (H2) gas in inert gas concentration during processing may be between 2% and 100%.

In another embodiment of step102A, the reducing process is performed using an inductively coupled plasma to remove contaminants disposed on a surface of a substrate. In one embodiment, the inductively coupled plasma may contain H2or a gas mixture containing nitrogen gas (N2) and H2or NH3gases. In some configurations, the inductively generated plasma is remotely generated. In one example, the processes performed in step102A may include generating an inductively coupled plasma using an RF power of between 10 W and 500 W at an RF frequency of 13.56 MHz, while the substrate is maintained at a temperature of between about 15 and about 500° C. and the processing pressure in the processing region is maintained at a pressure of about 700 mTorr. In this example, the hydrogen (H2) gas in inert gas concentration during processing may be between 2% and 100%. This reducing process may be performed in a processing chamber or in a support chamber. In configuration, the support chamber is a load lock chamber, or a similar chamber that is adapted to store or act as an interface between different regions of a cluster tool, which are discussed below. An exemplary load lock chamber for performing this reducing process is illustrated inFIG. 4.

FIG. 4depicts one embodiment of the load lock chamber400utilized to perform a reducing process to remove contaminants from a surface of a substrate. The load lock chamber400generally comprises a chamber body402, a first substrate holder404, a second substrate holder406, a temperature control pedestal440and a heater module470. The chamber body402may be fabricated from a singular body of material such as aluminum. The chamber body402includes a first side wall408, a second side wall410, a top414and a bottom416that define a chamber volume418. A window450typically comprised of quartz, is disposed in the top414of the chamber body402and is at least partially covered by the heater module470.

The pressure of the chamber volume418may be controlled so that the load lock chamber400may be evacuated to substantially match the environment of a transfer chamber436and be vented to substantially match the environment of a factory interface401. Additionally, the pressure of the chamber volume418may be controlled within a predetermined range that facilitates performing the contaminants removal process, as further described below. The chamber body402includes one or more vent passages430and a pump passage432. The vent passage430and the pump passage432are positioned at opposite ends of the chamber body402to induce laminar flow within the chamber volume418during venting and evacuation to minimize particulate contamination. In one embodiment, two vent passages430are disposed through the top414of the chamber body402, while the pump passage432is disposed through the bottom416of the chamber body402. The passages430,432typically are coupled to a valve412to selectively allow flow into and out of the chamber volume418.

The vent passage430may be additionally coupled to a gas source452through a valve440to provide a gas mixture into the chamber volume418. In one embodiment, the vent passage430may be configured as a gas distribution ring wherein the gas mixture may be distributed from adjacent the walls410,408through an array of holes to optimize the flow uniformity. In another embodiment, the gas mixture may be supplied to the load lock chamber400through a gas distribution plate (not shown) disposed below the heater module470. The gas distribution plate may be fabricated by a material transmissive to the heat generated from the heater module470such as not to substantially interfere with the heating of the substrates positioned on the substrate holders404,406. Examples of gases that may be supplied from the gas source452include N2, Ar, H2, helium (He), oxygen (O2), ozone (O3), wafer vapor (H2O), and the like.

In one embodiment, a remote plasma source (RPS)448may be alternatively coupled to the vent passage430to assist in removing contaminants from the substrate surfaces. The remote plasma source448provides plasma formed from the gas mixture provided by the gas source452to the load lock chamber400. In embodiment the RPS448is present, a diffuser (not shown) may be disposed at the outlet of the vent passage430to facilitate delivery the generated plasma into the load lock chamber400.

A first loading port438is disposed in the first wall408of the chamber body402to allow a substrate424to be transferred between the load lock chamber400and the factory interface401, which is discussed further below in conjunction withFIG. 6. A first slit valve444selectively seals the first loading port438to isolate the load lock chamber400from the factory interface401. A second loading port439is disposed in the second wall410of the chamber body402to allow the substrate424to be transferred between the load lock chamber400and the transfer chamber436, which is discussed further below in conjunction withFIG. 6. A second slit valve446which is substantially similar to the first slit valve444selectively seals the second loading port439to isolate the load lock chamber400from the vacuum environment of the transfer chamber436.

The first substrate holder404is concentrically coupled to (i.e., stacked on top of) the second substrate holder406that is disposed above the chamber bottom416. The substrate holders404,406are generally mounted to a hoop420that is coupled to a shaft482that extends through the bottom416of the chamber body402. Typically, each substrate holder404,406is configured to retain one substrate. The shaft482is coupled to a lift mechanism496disposed exterior to the load lock chamber400that controls the elevation of the substrate holders404and406within the chamber body402. A bellows484is coupled between the hoop420and the bottom416of the chamber body402and disposed around the shaft482to provide a flexible seal between the second substrate holder406and the bottom416, thus preventing leakage from or into the chamber body402and facilitating raising and lowing of the substrate holders404,406without compromising the pressure within the load lock chamber400.

The first substrate holder404is utilized to hold an unprocessed substrate from the factory interface401while the second substrate holder406is utilized to hold a processed substrate returning from the transfer chamber436. The flow within the load lock chamber400during venting and evacuation is substantially laminar due to the position of the vent passage430and pump passage432and is configured to minimize particulate contamination.

The processing/load lock chambers described above uses either inductively coupled plasma or capacitively coupled plasma to remove contaminants from a surface of a substrate. In another embodiment, a processing chamber may use microwave energy source to generate a reducing gas containing plasma (e.g., hydrogen containing plasma) that is used to perform the contaminants removal process of step102A.

The reducing methods described above generally use a hydrogen containing plasma to remove contaminants from a substrate. Another approach to remove contaminants from the surface of a substrate is to use an oxidation process102B. Oxidation processes may be suitable for use on silicon (Si) and germanium (Ge) surfaces, but may not be suitable for removing contaminants from a SiGe surface. Oxidation of a SiGe surface may result in compositional disturbance at the surface. In one embodiment, the oxidation process102B utilizing an inductively coupled oxygen containing plasma at room temperature and 20 mTorr is performed to remove the contaminants. In another embodiment, a radical oxidation process is performed at a temperature of between about 50 and about 600° C., such as about 400° C. to remove the contaminants.

In another embodiment, the oxidation process102B utilizes an inductively coupled oxygen containing plasma to remove the contaminants from the surface of the substrate. The radicals and/or ions generated in the oxygen containing plasma will interact with the contamination disposed on the surface of the substrate causing it to desorb or be physically removed therefrom. In some configurations the plasma may knock off or cause the contaminants to desorb from the surface due to the interaction of the energized oxygen containing gas atoms and the contaminants found on the surface of the substrate. The oxygen containing plasma may also form a thin oxide layer on the surface of the substrate which protects the surface from being roughened. The plasma may contain O2and N2and be remotely generated. The processing temperature may be about 250° C. and the processing pressure may be about 700 mT. In one example, an oxygen containing plasma may be generated using an RF power of between 100 W and 5000 W at an RF frequency of 13.56 MHz, while the substrate is maintained at a temperature of between about 15 and about 500° C. and the processing pressure in the processing region is maintained at a pressure of 700 mTorr. In this example, the oxygen containing gas in inert gas concentration may be between 2% and 100%. In one embodiment, this oxidation process102B is performed in the load lock chamber400, in which a remote plasma containing O2and N2is introduced through a quartz diffuser disposed at the outlet of the vent passage430.

Referring back toFIG. 1, at step102, the contaminants may be removed by one of the above mentioned reducing102A and/or oxidation102B contamination removal processes. Thus, the contaminants may be removed by an oxidation process102B, a reducing process102A, or a reducing process102A followed by an oxidation process102B. In some cases, the contaminants may be removed by performing an oxidation process102B followed by a reducing process102A. The oxidation/reducing processes102B,102A help removing contaminants such as carbon or hydrocarbons from a Si, Ge, or SiGe surface of a Si substrate prior to a cleaning process (step104). In some cases, the contaminant free surface may comprise an oxide layer that is formed during step102or formed prior to step102. The oxide layer may be a result of the oxidation process102B described above, or a native oxide layer. At step104, the surface of the substrate is further cleaned (e.g., removing the oxide layer) using a plasma etch process. The plasma etch process performed during at least a part of step104may be fluorine based.

In one embodiment, the plasma etch process is a remote plasma assisted dry etch process which involves the simultaneous exposure of a substrate to NF3and NH3plasma by-products. In one example, the plasma etch process may be similar to or may include a SiCoNi™ etch process that is available from Applied Materials, Inc. of Santa Clara, Calif. In some configurations that use remote plasma excitation of the gas species allows plasma-damage-free substrate processing. The remote plasma etch can be largely conformal and selective towards silicon oxide layers, and thus does not readily etch silicon regardless of whether the silicon is amorphous, crystalline or polycrystalline. The remote plasma process will generally produce solid by-products which grow on the surface of the substrate as substrate material is removed. The solid by-products can be subsequently removed via sublimation when the temperature of the substrate is raised. The plasma etch process results in a substrate surface having silicon-hydrogen (Si—H) bonds thereon.

In one embodiment, a plasma etch process may include an NF3flow rate within a range of about 1 sccm to about 20 sccm, such as about 5 sccm, as well as an NH3flow rate within a range of about 50 sccm to about 200 sccm, such as about 100 sccm. The plasma etch process may be performed at a pressure of about 5 Torr, and an RF power setting of about 30 W may be utilized to ionize the NF3and the NH3. By-products may then be sublimated from the surface of the substrate by annealing the substrate at a temperature of about 120° C. or more for about 5 seconds to about 100 seconds, such as about 60 seconds. Other embodiments of fluorine based cleaning involve, reacting NH3gas and F2or anhydrous HF gas in either plasma or thermal heat to etch SiO2native oxides. Examples of gas flow ratios would be 1:1 to 1:10 gas flow ratio of fluorine gas to NH3gas at temperatures of 15° C. to 130° C.

FIG. 5is a schematic cross sectional view of a cleaning chamber500that may be adapted to perform step104. The chamber500may be particularly useful for performing a thermal or plasma-based oxidation process and/or a plasma assisted dry etch process. The chamber500includes a chamber body512, a lid assembly514, and a support assembly516. The lid assembly514is disposed at an upper end of the chamber body512, and the support assembly516is at least partially disposed within the chamber body512. A vacuum system can be used to remove gases from chamber500. The vacuum system includes a vacuum pump518coupled to a vacuum port521disposed in the chamber body512.

The lid assembly514includes at least two stacked components configured to form a plasma volume or cavity there between. A first electrode520is disposed vertically above a second electrode522confining a plasma volume. The first electrode520is connected to a power source524, such as a radio frequency (RF) power supply, and the second electrode522is connected to ground or a source return, forming a capacitance between the first electrode520and the second electrode522. The lid assembly514also includes one or more gas inlets526for providing a cleaning gas to a substrate surface through blocker plate528and gas distribution plate530. The cleaning gas may be an etchant or ionized active radical, such as ionized fluorine, chlorine, or ammonia, or an oxidizing agent, such as ozone. Additionally, the chamber500includes a controller502for controlling processes within the chamber500.

The support assembly516may include a substrate support532to support a substrate510thereon during processing. The substrate support532may be coupled to an actuator534by a shaft536which extends through a centrally-located opening formed in a bottom surface of the chamber body512. The actuator534may be flexibly sealed to the chamber body512by bellows (not shown) that prevent vacuum leakage from around the shaft536. The actuator534allows the substrate support532to be moved vertically within the chamber body512between a process position and a lower, transfer position. The transfer position is slightly below the opening of a slit valve formed in a sidewall of the chamber body512.

The substrate support532has a flat, or a substantially flat, surface for supporting a substrate to be processed thereon. The substrate support532may be moved vertically within the chamber body512by actuator534coupled thereto by shaft536. In operation, the substrate support532may be elevated to a position in close proximity to the lid assembly514to control the temperature of the substrate510being processed. As such, the substrate510may be heated via radiation emitted or convection from the distribution plate530.

A different cleaning process may be utilized to clean the substrate surface. In one embodiment, a remote plasma containing He and NF3is introduced into a processing chamber through a gas distribution plate, such as a showerhead. NH3is directly injected into the chamber via a separate gas inlet.

In one example of process sequence100, the clean process (step104) may be performed in the SiCoNi™ cleaning chamber, available from Applied Materials, Inc. of Santa Clara, Calif. Chambers available from other manufacturers may also be used to practice embodiments described herein. In one embodiment, both steps102and104may be performed in a single processing chamber, such as one of the chambers shown inFIGS. 2-5. In one example, the both steps102and104are performed in a SiCoNi™ cleaning chamber.

Next, at step106, after the cleaning process is performed, an epitaxial silicon layer may be formed on the surface of the substrate. The surface of the substrate is contaminant free which improves the quality of the epitaxial layer subsequently formed on the surface of the substrate. In one example, the epitaxial deposition may be a selective epitaxial deposition process performed at a temperature that is less than 800° C. In this example, the temperature is set such that it will not exceed 800° C., in order to limit the wafer thermal budget for delicate features that may distort or diffuse if overheated. In one embodiment, the epitaxial layer is deposited using a high temperature chemical vapor deposition (CVD) process. In this thermal CVD process, processing gases such as dichlorosilane, silane, disilane, germane, hydrogen chloride, or combinations thereof are used to deposit the epitaxial layer. The processing temperature is under 800° C. and the processing pressure is between 5 and 600 Torr. When steps102,104and106are performed, contaminants at interfaces have been reduced and the epitaxial layer formed is relatively defect free.

FIG. 6illustrates a processing system600that can be used to complete the processing sequence100illustrated inFIG. 1, according to embodiments of the invention. As shown inFIG. 6, a plurality of processing chambers602is coupled to a first transfer chamber604. The first transfer chamber604is also coupled to a first pair of processing chambers606. The first transfer chamber604has a centrally disposed transfer robot (not shown) for transferring substrates between the processing chambers606and the processing chambers602. The processing chambers606are coupled to a second transfer chamber610, which is coupled to a processing chamber614for removing contaminants (step102) and a cleaning chamber616for cleaning the substrate (step104). The second transfer chamber610has a centrally disposed transfer robot (not shown) for transferring substrates between a set of load lock chamber612and the processing chamber614or the cleaning chamber616. A factory interface620is connected to the second transfer chamber610by the load lock chambers612. The factory interface620is coupled to one or more pods630on the opposite side of the load lock chambers612. The pods630typically are front opening unified pods (FOUP) that are accessible from the clean room.

During operation, a substrate is first transferred to the processing chamber614in a reducing process, an oxidation process, or a reducing process followed by an oxidation process, or vice versa, is performed to remove contaminants such as carbon or hydrocarbons from the substrate surface. The contaminants removal process is described inFIG. 1under step102. Then the substrate is transferred to the cleaning chamber616in which step104is performed. The queue time between step102and step104may be 8 to 12 hours. In one embodiment, the queue time between step102and step104is about 2 to 3 hours. Queue time is generally defined as the time a substrate can be exposed to the atmospheric or other contaminants after a first process has been completed on the substrate before a second process must be completed on the substrate to prevent some adverse affect on the fabricated device's performance.

The clean substrate is then transferred to one or more processing chambers602in which the epitaxial deposition, as described under step106is performed. Because all three steps102,104and106are performed within the same processing system, vacuum is not broken as the substrate is transferred to various chambers, which decreases the chance of contamination and improves the quality of the deposited epitaxial film.

In another embodiment, the contaminants removal step102is performed in a chamber that is not a part of the processing system that contains the cleaning chamber616and the one or more processing chambers602. As shown inFIG. 7, contaminants on the substrate surface are removed in a processing chamber702. The substrate is then transferred to the processing system700, which is the processing system600without the processing chamber614. The substrate is transferred to the cleaning chamber616in which step104is performed. Then the substrate is transferred to at least one of the processing chambers602in which step106is performed.

In summary, methods of removing contaminants from a substrate surface and cleaning the substrate prior to epitaxial deposition are disclosed. The contaminants removal process may be a reducing process, an oxidizing process, or a processing sequence that includes a reducing process and an oxidizing process. Then a fluorine containing plasma etch is performed on the substrate to remove an oxide layer. Since the fluorine containing plasma etch may be ineffective in removing the contaminants which can be hydrocarbon or carbon based, the removal process prior to the plasma etch helps removing the contaminants, which in turn improves the quality of the epitaxial layer subsequently deposited on the substrate.