Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
  • C23C16/24—Deposition of silicon only
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
  • C23C16/455—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
  • C23C16/44—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating
  • C23C16/455—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the method of coating characterised by the method used for introducing gases into reaction chamber or for modifying gas flows in reaction chamber
  • C23C16/45557—Pulsed pressure or control pressure

Definitions

• This application relates generally to a method and apparatus for creating solar cells and, more specifically to method and apparatus for depositing microcrystalline silicon layers on a substrate for thin-film solar cells.
• Photovoltaic devices also referred to as photoelectric conversion devices or solar cells, are devices that convert light, especially sunlight into direct current (DC) electrical power.
• DC direct current
• thin-film solar cells are of particular interest since they allow glass, glass ceramics or other rigid or flexible materials to be used as a substrate instead of crystalline or polycrystalline silicon.
• the solar cell structure i.e., the layer sequence responsible for, or capable of, producing the photovoltaic effect is deposited in thin layers on the substrate. This deposition may take place under atmospheric or vacuum conditions. Deposition techniques are widely known in the art, such as PVD, CVD, PECVD, APCVD, etc ., each of which is used in the production of semiconductor devices.
• a thin-film solar cell generally includes a first electrode, one or more semiconductor thin-film p-i-n junctions, and a second electrode, which are successively stacked on a substrate.
• the i-type layer which is a substantially intrinsic semiconductor layer, occupies a majority of the thickness of the thin-film p-i-n junction and is primarily responsible for the photoelectric conversion performed by the solar cell.
• This significant portion of the hydrogen (H 2 ) diluting agent does not otherwise contribute to the formation of layers on the substrate of the solar cell, and is exhausted as a waste product requiring disposal.
• the total flow of gas during deposition is one of the primary factors influencing the size of pumps, tubes, gas supplies and amount of waste materials requiring disposal for such processes, contributing to expensive production costs.
• Another function of a large hydrogen (H 2 ) volumetric flow rate in conventional processes such as that describe above is to flush out silicon (Si)-containing products formed in the plasma volume.
• the large hydrogen (H 2 ) volumetric flow rate also entrains and removes non-dissociated (or not-fully dissociated) silane (S1H 4 ) from the deposition chamber.
• This premature removal of silane (S1H 4 ) gas from the deposition chamber causes silane (SiH 4 ) gas to be inefficiently consumed and excess amounts of silane (S1H 4 ) gas (and partially-dissociated silane (S1H 4 )) to be exhausted, requiring disposal. Both conditions add to the overall product cost of thin-film solar cells.
• Dopant gases such as Phosphine (PH 3 ) and Trimethylboron (B(CH 3 ) 3 ) negatively influence the nucleation of microcrystalline silicon when preparing doped microcrystalline silicon layers according to conventional fabrication processes.
• P-type and n-type doped microcrystalline silicon layers therefore have traditionally been prepared at an increased hydrogen dilution and lower total volumetric silane (S1H 4 ) flows compared to the preparation of intrinsic microcrystalline silicon.
• S1H 4 total volumetric silane
• the subject application involves a deposition system for producing a photovoltaic cell, including a deposition chamber that substantially encloses a reaction space where a semiconductor material is to be deposited onto a substrate to form a microcrystalline layer of the semiconductor material on the substrate.
• a substrate conditioner provides a heating effect to the substrate, provides a cooling effect to the substrate, or provides heating and cooling effects to the substrate to establish a desired temperature of the substrate for deposition of the semiconductor material.
• First and second electrodes that oppose each other are separated by a distance D, and are operatively connected to a power source to be energized for igniting a plasma and maintaining the plasma in the reaction space during at least a portion of the deposition.
• a vacuum subsystem at least partially evacuates the deposition chamber, and a delivery subsystem introduces a process gas to the reaction space.
• the process gas includes a semiconductor-containing gas from a semiconductor source and a diluting agent from a dilution source.
• a controller is programmed to control operation of at least one of the vacuum subsystem and the delivery subsystem to maintain the sub- atmospheric pressure during at least a portion of the deposition of the semiconductor material at a pressure that is less than or equal to:
• the distance D separating the first and second electrodes is expressed in mm.
• the controller is also programmed to establish a concentration of the semiconductor- containing gas in the process gas of at least fifty (50%) percent by volume during at least a portion of the deposition of the semiconductor material.
• the subject application involves a method of depositing a semiconductor material onto a substrate in a deposition chamber of a deposition system.
• the deposition system also includes a substrate conditioner that provides one or both of a heating effect and a cooling effect to the substrate, first and second electrodes separated by a distance D and operatively connected to a power source for establishing a plasma in the deposition chamber, a vacuum subsystem for at least partially evacuating the deposition chamber, and a delivery subsystem for introducing a process gas to the deposition chamber.
• the method includes, with a controller, receiving a sub-atmospheric pressure to be established within the deposition chamber during at least a portion of the deposition of the semiconductor material.
• the sub-atmospheric pressure is less than or equal to:
• the distance D separating the first and second electrodes is expressed in mm.
• the method also includes transmitting a pressure signal that controls operation of the vacuum subsystem to at least partially evacuate the deposition chamber and establish the sub- atmospheric pressure received with the controller. Also with the controller, a target temperature of the substrate for the deposition is received. A temperature signal that controls the substrate conditioner to elevate, lower or both elevate and lower a temperature of the substrate to a temperature approaching or approximately equal to the target temperature is transmitted from the controller. A plasma signal that controls the power source to energize the first and second electrodes and establish the plasma within the deposition chamber is also transmitted from the controller.
• a flow signal that controls operation of a delivery subsystem is transmitted from the controller to introduce a semiconductor-containing gas and a suitable quantity of a diluting agent into the deposition chamber to establish a concentration of the semiconductor-containing gas within the deposition chamber of at least fifty (50%) percent by volume during at least a portion of the deposition.
• the subject application involves a method of depositing a semiconductor material onto a substrate in a deposition chamber of a deposition system.
• the deposition system also includes a substrate conditioner that provides one or both of a heating effect and a cooling effect to the substrate, and first and second electrodes separated by a distance D and operatively connected to a power source for establishing a plasma in the deposition chamber.
• a vacuum subsystem is provided to at least partially evacuate the deposition chamber, and a delivery subsystem introduces a process gas to the deposition chamber.
• the method includes establishing a sub- atmospheric pressure within the deposition chamber during at least a portion of the deposition of the semiconductor material, the sub-atmospheric pressure being less than or equal to:
• the distance D separating the first and second electrodes is expressed in mm.
• a temperature of the substrate is elevated, lowered or both elevated and lowered to a temperature approaching, or approximately equal to a target temperature within a range from about 120°C to about 280°C.
• the power source at least one of the first and second electrodes is energized to establish the plasma within the deposition chamber.
• a semiconductor-containing gas and a suitable amount of the diluting agent are introduced to the deposition chamber to establish a concentration of the semiconductor- containing gas within the deposition chamber of at least fifty (50%) percent by volume during at least a portion of the deposition.
• the subject application involves a method of depositing a semiconductor material onto a substrate in a deposition chamber of a deposition system.
• the deposition system also includes a substrate conditioner that provides one or both of a heating effect and a cooling effect to the substrate, first and second electrodes separated by a distance D and operatively connected to a power source for establishing a plasma in the deposition chamber, a vacuum subsystem for at least partially evacuating the deposition chamber, and a delivery subsystem for introducing a process gas to the deposition chamber.
• the method includes establishing a sub- atmospheric pressure within the deposition chamber during at least a portion of the deposition of the semiconductor material, the sub-atmospheric pressure being less than or equal to:
• the distance D separating the first and second electrodes is expressed in mm and is greater than or equal to about 10 mm but less than or equal to about 30 mm.
• a temperature of the substrate is elevated, lowered, or both elevated and lowered to a temperature approaching, or approximately equal to a target temperature within a range from about 120°C to about 280°C.
• the power source at least one of the first and second electrodes is energized to establish the plasma within the deposition chamber.
• a semiconductor-containing gas and a suitable amount of the diluting agent are introduced to the deposition chamber for the deposition to be performed.
• FIG. 1 shows a schematic view of a deposition system according to an illustrative embodiment
• FIG. 2 shows illustrative arrangements of intrinsic and extrinsic microcrystalline layers for single-junction and multi-junction solar cells
• FIG. 3 is a flow diagram schematically depicting an automated method of depositing a semiconductor material onto a substrate.
• FIG. 4 is a flow diagram schematically depicting a general method of depositing a semiconductor material onto a substrate.
• the phrase "at least one of, if used herein, followed by a plurality of members herein means one of the members, or a combination of more than one of the members.
• the phrase "at least one of a first widget and a second widget” means in the present application: the first widget, the second widget, or the first widget and the second widget.
• “at least one of a first widget, a second widget and a third widget” means in the present application: the first widget, the second widget, the third widget, the first widget and the second widget, the first widget and the third widget, the second widget and the third widget, or the first widget and the second widget and the third widget.
• FIG. 1 shows an illustrative embodiment of a plasma-enhanced chemical vapor deposition ("PECVD") system 10 for producing a photovoltaic cell.
• the illustrative embodiment of the deposition system 10 includes a deposition chamber 12 that substantially encloses a reaction space 14, where at least one layer, and optionally a plurality of microcrystalline layers of a semiconductor material are to be deposited onto a substrate 16.
• An example of a physical arrangement of such a deposition chamber 12 can be found in the model KAI-1200 deposition reactor, from Oerlikon Solar AG, of Triibbach, Switzerland.
• microcrystalline layer is referred to as an n-type or p-type doped microcrystalline layer.
• Microcrystalline layers deposited without a dopant are said to be intrinsic microcrystalline layers.
• a pedestal or other suitable substrate support 18 supports the substrate 16 at a location within the reaction space 14 suitable for deposition.
• a substrate conditioner 20 can be provided adjacent to the substrate support 18 to adjust and substantially maintain the temperature of the substrate 16 at a desired level for the deposition of the semiconductor material onto the substrate 16.
• the substrate conditioner 20 can be operable to heat the substrate 16, cool the substrate 16, or both heat and cool the substrate 16 during the deposition described herein.
• the substrate conditioner 20 can include a heating element that generates thermal energy in any manner such as resistive heating, inductive heating, radiant heating, and the like.
• the thermal energy required for providing a heating effect to the substrate 16 can optionally be provided, at least in part, by the plasma generated as described herein.
• the substrate conditioner 20 can include portions of a refrigeration circuit that removes thermal energy owing at least in part to phase changes of a refrigerant, a conduit that transports a coolant at a lower temperature than the substrate 16 to remove thermal energy from the substrate 16, or any other suitable apparatus for providing the desired cooling effect to the substrate 16 during deposition.
• the desired temperature of the substrate 16 as established by the substrate conditioner 20 can depend on the particular semiconductor material to be deposited, as well as other process conditions. However, according to the present embodiment, the desired temperature can be any temperature, including any sub-range of temperatures, within a range from about 120°C to about 280°C. According to alternate embodiments the range of temperatures in which the desired temperature falls is from about 140°C to about 220°C, preferably 180°C to about 200°C.
• the substrate support 18 is formed, at least in part, from a metal, metal alloy or other suitable electrically-conductive material to form a first electrode that opposes a second electrode 22.
• the second electrode 22 is substantially parallel to the substrate support 18 which, according to the present embodiment is also the first electrode, and is separated from the substrate support 18 by a distance D that is normal to the substrate support 18 and the second electrode 22.
• the distance D separating the first electrode/substrate support 18 and the second electrode 22 can be greater than or equal to about 10 mm and less than or equal to about 30 mm, although other values of the distance D are also within the scope of the present disclosure.
• the substrate support 18 is the first electrode in the embodiment shown and described with reference to FIG. 1, other embodiments can optionally include a separate first electrode that is distinct from the substrate support 18.
• the first electrode/substrate support 18 and the second electrode 22 in FIG. 1 are operatively connected to a power source 24 for igniting a plasma 26 and maintaining the plasma 26 within the reaction space 14 during at least a portion of the deposition of the semiconductor material onto the substrate 16.
• the power source 24 includes a RF generator that can supply RF power having a frequency that is greater than or equal to 13.56 MHz or harmonics of it, such as about 28MHz or 40 MHz, or any other suitable frequency for example.
• at least one of the first electrode/substrate support 18 and the second electrode has a substantially-planar surface 28 facing the opposite electrode, and comprising a predetermined surface area.
• the surface area of the planar surface 28 can be selected in conjunction with the power source 24 to establish a desired power density for the particular deposition to be performed.
• the surface area of the planar surface 28 of the second electrode 22 and the RF generator can collectively establish a power density that is greater than or equal to 0.1 W per cm 2 of surface area of the second electrode 22.
• a vacuum subsystem 29 can also be provided to establish a sub- atmospheric pressure within the reaction space 14.
• the vacuum subsystem 29 can include any device that is operable to at least partially evacuate the deposition chamber 12 to lower the pressure within the reaction space 14 to less than 1 atmosphere.
• the vacuum subsystem 29 can be operated in cooperation with a process gas delivery subsystem 30 introducing a process gas to the reaction space 14 to maintain the sub-atmospheric pressure within the reaction space 14 at a desired deposition pressure for at least a portion of the deposition of the semiconductor material.
• suitable deposition pressures include any pressure that is less than or equal to:
• the distance D separating the first and second electrodes 18, 22 is expressed in millimeters (mm).
• the pressure, expressed in millibar (mbar) within the reaction space 14 multiplied by the distance D, expressed in millimeters (mm), separating the first electrode/substrate support 18 from the second electrode 22 is less than or equal to about 50 mbar*mm.
• the delivery system 30 includes a flow regulator 32, which can be any adjustable device such as a valve, for example, that can regulate, and optionally meter entry of a process gas into the reaction space 14.
• the delivery system 30 can also optionally include a mixer 50 that defines a volume in which the components of the process gas can be combined prior to being introduced to the reaction space 14.
• Individual valves 52 or other flow regulator for each of the various sources 34, 36, 38 can also optionally be disposed along plumbing that establishes fluid communication between the various sources 34, 36, 38 and the reaction space 14. The individual valves 52, if present, can be adjusted to regulate the flow rate of the semiconductor-containing gas, diluting agent and dopant introduced into the reaction space 14.
• the process gas can include at least one of: a semiconductor-containing gas from a semiconductor source 34, a diluting agent from a dilution source 36, and a dopant from a dopant source 38.
• the semiconductor-containing gas can be any gas that includes a semiconducting substance such as silane (S1H4), for example, which includes silicon.
• the most common diluting agent for the purpose of semiconductor deposition in photovoltaic applications is hydrogen, although any other suitable diluting agent for diluting the concentration of the semiconductor-containing gas is also within the scope of the present disclosure.
• the dopant includes a material that, when deposited, affects the electrical conductivity of the deposited layer of a semiconducting material. Examples of the dopant include, but are not limited to Phosphine (PH3), Diborane (B 2 3 ⁇ 4), and
• Trimethylboron (B(CH 3 )3).
• the embodiment shown in FIG. 1 and described below includes silane (S1H 4 ) as the semiconductor-containing gas, and Hydrogen (H 2 ) as the diluting agent.
• Silane S1H 4
• Hydrogen H 2
• Phosphine PH 3
• Doborane B 2 H 6
• other suitable P-type and N-type dopants are within the scope of the present disclosure.
• a controller 40 is provided to control operation of at least one of: the power source 24 in supplying RF power to the first electrode/substrate support 18 and second electrode 22 to ignite and maintain the plasma 26, the vacuum subsystem 29 in evacuating at least a portion of the deposition chamber's contents from the reaction space 14, and the delivery subsystem 30 in introducing the process gas to the reaction space 14.
• the controller 40 can be a microprocessor-based embedded system with access to a non- transitory, computer-readable memory 42, for example. According to such an
• computer-executable instructions stored in the computer-readable memory 42 can be executed by a microprocessor 46 which, in turn, emits control signals via control lines 44 to portions of the delivery subsystem 30, vacuum subsystem 29 and power supply 24 to be controlled by the controller 44.
• the controller 40 can be hardwired to perform the various control steps regulating operation of the delivery subsystem 30, vacuum subsystem 29 and power supply 24.
• the controller 40 can include one or more application-specific integrated circuits.
• FIG. 2 is a schematic representation of a single-junction solar cell 60 and a multi-junction (dual-junction in the present example) solar cell 62 arranged side- by-side on a common glass substrate 16.
• the single-junction solar cell 60 includes a P-type microcrystalline layer 64, on which is deposited an intrinsic
• a front contact 70 and a back contact 72 made from an electrically-conductive material form the terminals of the single-junction solar cell 60 through which a DC current is generated in response to the single-junction cell 60 being exposed to light 74.
• the front contact 70 is substantially transparent to transmit most of the light 74 imparted on the front contact 70 to the microcrystalline layers of the semiconductor.
• the doped microcrystalline layer 64 is a P-type layer since it includes atoms that have at least one fewer valence electrons than the semiconductor material deposited to form the microcrystalline material.
• a dopant containing boron for example, can be introduced to the reaction space 14.
• Diborane (B 2 H 6 ) and trimethylboron (B(CH 3 )3) mentioned above are two examples of suitable dopants for depositing the P-type extrinsic microcrystalline layer 64.
• the doped microcrystalline layer 68 is an N-type since it is negatively-doped to include atoms that have at least one more valence electron than the semiconductor material deposited to form the microcrystalline layer.
• the microcrystalline layer 68 is made of silicon as the semiconductor material deposited from silane (SiH 4 )
• a dopant containing phosphorous for example, can be introduced to the reaction space 14.
• Phosphine (PH 3 ) mentioned above, is an example of a suitable dopant for depositing the N-type extrinsic microcrystalline layer 68.
• the intrinsic layer 66 between the P-type microcrystalline layer 64 and the N-type microcrystalline layer 68 is a deposited layer of silicon that has not been intentionally doped during deposition. Thus, the electric conductivity of the intrinsic layer 66 is not altered by the introduction of a dopant.
• the multi-junction solar cell 62 appearing in FIG. 2 is similar to the single-junction solar cell 60, but includes a plurality of repeating stacks comprising P- type, I-type (intrinsic) and N-type layers.
• solar cells such as those appearing in FIG. 2 are characterized as amorphous (a-Si) or
• Microcrystalline layers refer to layers comprising a significant fraction of crystalline silicon - so called micro- crystallites - in an amorphous matrix.
• the controller 40 can execute the computer-executable instructions in the memory 42 to perform a method of depositing a semiconductor material onto a substrate 16 disposed in the deposition chamber 12.
• the controller 40 can be hard wired to perform such a method, or some or all of the method steps can be performed manually without departing from the scope of the present application.
• Illustrative embodiments of such automated methods can be understood with reference to the flow diagrams appearing in FIG. 3. The order in which the steps appear in FIG. 3 is not necessarily the order in which the steps are required to be performed unless specified otherwise.
• FIG. 3 One example of the PECVD process is schematically depicted in FIG. 3 for depositing intrinsic and/or doped microcrystalline-silicon layers using a standard deposition machine such as the model KAI-1200 deposition system commercially available from Oerlikon Solar AG.
• a standard deposition machine such as the model KAI-1200 deposition system commercially available from Oerlikon Solar AG.
• silane SiH 4
• the diluting agent in the present example includes hydrogen (H 2 ), and for embodiments where a doped
• a dopant such as phosphine (PH ), diborane (B 2 H 6 ), or trimethylboron (B(CH 3 ) 3 ) can be added.
• PH phosphine
• B 2 H 6 diborane
• B(CH 3 ) 3 trimethylboron
• the flow rate of the process gas being introduced to the reaction space 14 during deposition is low in the present example, less than 0.03 sccm/cm 2 of surface area of the planar surface 28 (FIG. 1) of the second electrode 22. Further, the sub-atmospheric pressure within the deposition chamber in the present example is maintained at or below normalized pressures of 50 mbar*mm
• the method includes receiving, with the controller 40, a sub-atmospheric pressure to be established within the deposition chamber 12 during at least a portion of the deposition of the semiconductor material at step 100.
• the sub- atmospheric pressure can be programmed into the controller 40 during construction of the deposition system 10, input by a user operating the deposition system 10, or otherwise input to the controller 40. Regardless of the way the sub-atmospheric pressure is specified, the sub-atmospheric received can be less than or equal to:
• the distance D separating the first and second electrodes is expressed in millimeters (mm).
• the distance D separating the first and second electrodes is greater than or equal to about 10 mm and less than or equal to about 30 mm.
• the sub-atmospheric pressure received by the controller 40 at step 100 is at least 0.8 mbar, but not greater than 3.0 mbar.
• the sub-atmospheric pressure received by the controller 40 at step 100 to be at least 1.0 mbar, but not greater than 2.0 mbar.
• the controller 40 can subsequently transmit a pressure signal to be delivered along control lines 44 that controls operation of the vacuum subsystem 29 at step 1 10 in FIG. 3 to at least partially evacuate the deposition chamber 12 and establish the sub-atmospheric pressure received.
• the controller 40 also receives a target temperature of the substrate 16 for the deposition process to be performed at step 120.
• the target temperature can be programmed into the controller 40 during construction of the deposition system 10, input by a user operating the deposition system 10, or otherwise input to the controller 40.
• the target temperature received for the present example is at least 120°C, but not greater than 280°C.
• the received target temperature is at least 140°C but not greater than 220°C, and preferably from about 180°C to about 200°C.
• the controller 40 subsequently transmits a temperature signal to be delivered along the control lines 44 (FIG. 1) to control operation of the substrate conditioner 20 at step 130 in FIG. 3 to elevate or lower the temperature of the substrate 16 to a temperature approaching the received target temperature.
• the delivery system 30 can optionally introduce an ignition gas at step 140 in FIG. 3 to the reaction space 14 prior to introduction of the process gas, and prior to ignition of the plasma 26.
• the ignition gas can be a gas such as hydrogen (H 2 ) from the dilution source 36 (FIG. 1) or an inert gas, for example.
• the controller 40 can transmit a plasma signal at step 150 that causes the power source to energize the first and second electrodes 18, 22 and establish the plasma 26 within the deposition chamber 12 in the presence of the ignition gas.
• the power source comprises a RF generator that provides RF power having a frequency that is at least 13.56 MHz or a harmonic of that frequency, such as about 28MHz or 40 MHz, for example.
• the frequency can be at least 35 MHz, or at least 40 MHz.
• the RF power supplied comprises a power density that is greater than or equal to 0.1 W per cm of the surface area of a planar surface 28 of the second electrode 22.
• the controller 40 transmits a flow signal via control lines 44 at step 160 that controls operation of the delivery system 30 to introduce the process gas comprising at least silane (SiH 4 ) and a suitable quantity of hydrogen (H 2 ) into the deposition chamber 12.
• Operation of the delivery system 30 establishes a concentration of silane (SiH 4 ) in the reaction space 14 of at least fifty (50%) percent by volume during at least a portion of the deposition, and possibly during a majority or all of the deposition.
• the concentration of silane (SiH 4 ) can be at least seventy (70%) percent by volume, or at least seventy-five (75%) percent by volume. Regardless of the concentration of silane (S1H 4 ), the controller can be further programmed to adjust a portion of the delivery subsystem 30 to establish a flow rate for the process gas being introduced to the reaction space 14 of about 0.03 seem per cm 2 of surface area A of the planar surface 28 of the first and/or second electrodes 18, 22. Deposition of
• microcrystalline layers according to such a method yield growth rates of at least 5 A/sec (50 nm/s).
• the method described with reference to FIG. 3 is an example of an automated method. As mentioned above, however, one or more steps can be performed manually or by means other than the controller 40, without departing from the scope of the application. So regardless of the entity performing such steps, the general method of controlling deposition of a semiconductor material described herein using the deposition system 10 can be understood with reference to FIG. 4.
• a sub-atmospheric pressure is established at step 200 within the deposition chamber 12, and the sub-atmospheric pressure is maintained during at least a portion of the deposition of the semiconductor material.
• the sub-atmospheric can be less than or equal to:
• the distance D separating the first and second electrodes is expressed in mm.
• the distance D separating the first and second electrodes is at least about 10 mm, but not greater than about 30 mm.
• the sub- atmospheric pressure to be established is at least 0.8 mbar, but not greater than 3.0 mbar.
• the sub-atmospheric pressure established at step 200 can be at least 1.0 mbar, but not greater than 2.0 mbar. Regardless of its value, the sub- atmospheric pressure can be established by controlling operation of at least one of the vacuum subsystem 29 and the delivery subsystem 30.
• a temperature of the substrate 16 is adjusted (i.e., elevated, lowered or maintained) at step 210 of FIG. 4 to a temperature approaching, or approximately equal to a target temperature for the particular deposition process being performed.
• the target temperature can be programmed into the controller 40, input by an operator via a control panel, or otherwise specified.
• the target temperature is at least 120°C, but not greater than 280°C.
• the target temperature is at least 140°C, but not greater than 220°C, and preferably from about 180°C to about 200°C.
• the delivery system 30 can optionally introduce the ignition gas at step 220 in FIG. 4 to the reaction space 14 prior to introduction of the silane (S1H 4 ) or other semiconductor-containing gas, and prior to ignition of the plasma 26.
• the ignition gas can be a gas such as hydrogen (H 2 ) or an inert gas from the dilution source 36 (FIG. 1), for example, that does not deposit a significant quantity of, or optionally any unwanted solids in the presence of the plasma 26, once ignited.
• the power source 24 (FIG. 1) is used at step 230 to energize the first and second electrodes 18, 22 to establish the plasma 26 within the deposition chamber 12, optionally in the presence of the ignition gas.
• the power source comprises a RF generator that provides RF power having a frequency of 13.56 MHz or a harmonic of that frequency, such as about 28MHz or 40 MHz, for example.
• the frequency can be at least 35 MHz, or at least 40 MHz.
• the RF power supplied comprises a power density that is greater than or equal to 0.1 W per cm of the surface area of a planar surface 28 of the first and/or second electrodes 18, 22.
• a portion of the delivery subsystem 30 (such as the flow regulator 32) is adjusted at step 240 to introduce the process gas comprising at least silane (S1H 4 ) and a suitable quantity of hydrogen (H 2 ) into the deposition chamber 12. Operation of the delivery subsystem 30 establishes a concentration of silane (S1H 4 ) in the reaction space 14 of at least fifty (50%) percent by volume during the deposition.
• the concentration of silane (S1H 4 ) can be at least seventy (70%) percent by volume, or at least seventy-five (75%) percent by volume, diluted by hydrogen (H 2 ) as the diluting agent.
• the concentration of silane (SiH 4 ) in the reaction space 14 can be established as at least fifty (50%) percent by volume during the deposition, and the composition of the combination of the dopant and hydrogen (H 2 ) can be at least 30%.
• the combination of the dopant and hydrogen (H 2 ) can include a dopant concentration of less than 1% by volume, diluted with the hydrogen (H 2 ).
• the delivery subsystem 30 can be controlled to establish a flow rate for the process gas being introduced to the reaction space 14 of about 0.03 seem per cm 2 of surface area A of the planar surface 28 of the first and/or second electrodes 18, 22.
• the total flow rate of the process gas introduced to the reaction space 14 can be maintained at less than 500 seem.
• the process gas comprised about 75% SiH 4 and about 25% H 2 .
• Total flow rate of the process gas introduced to the reaction space during deposition was about 2.5 sccm/(100cm of surface area of the planar electrode surface 28), which for the present example amounted to a process gas volumetric flow rate of about 330 seem SiH 4 and about 100 seem 3 ⁇ 4.
• the energy supplied by the power source 24 was RF power that had a frequency of about 40 MHz RF frequency and a power density of about 0.17 W/(cm of surface area of the planar electrode surface 28), which amounted to about 3,000 W per deposition chamber in the present example.
• the substrate temperature was maintained between 120°C and 280°C during deposition.
• silane (SiH 4 ) i.e., process gas that includes silane concentrations of less than 10% by volume diluted with about 90% hydrogen by volume
• hydrogen (H 2 ) consumption was reduced by about 95%
• silane (S1H 4 ) usage efficiency increased by approximately 35%
• the growth rate of the microcrystalline layer increased by approximately 35% over such conventional deposition processes.
• the process gas comprised about 67% SiH 4 and about 33% dopant gas comprising phosphine (PH 3 ), wherein the dopant gas comprised approximately 0.5% phosphine (PH 3 ) by volume diluted in hydrogen (H 2 ).
• the total flow rate of the process gas introduced to the reaction space 14 during deposition was about 2.5 sccm/( 100cm 2 of surface area of the planar electrode surface 28), which for the present example amounted to a process gas volumetric flow rate of about 300 seem S1H4 and about 150 seem of the dopant gas.
• the energy supplied by the power source 24 was RF power that had a frequency of about 40 MHz RF frequency and a power density of about 0.2 W/(cm of surface area of the planar electrode surface 28), which amounted to about 3,500 W per deposition chamber 12 in the present example.
• the substrate temperature was maintained between 120°C and 280°C during deposition.

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