WO2019048693A1 - Method for etching a silicon containing surface - Google Patents

Method for etching a silicon containing surface Download PDF

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Publication number
WO2019048693A1
WO2019048693A1 PCT/EP2018/074401 EP2018074401W WO2019048693A1 WO 2019048693 A1 WO2019048693 A1 WO 2019048693A1 EP 2018074401 W EP2018074401 W EP 2018074401W WO 2019048693 A1 WO2019048693 A1 WO 2019048693A1
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Prior art keywords
reaction
substrate
forming
radicals
chamber
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French (fr)
Inventor
Elie SCHAPMANS
Clement Merckling
Francesco BUTTITTA
Sergej PASKO
M. Ziaul Karim
Maxim Kelman
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Aixtron SE
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Aixtron SE
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P70/00—Cleaning of wafers, substrates or parts of devices
    • H10P70/10—Cleaning before device manufacture, i.e. Begin-Of-Line process
    • H10P70/12—Cleaning before device manufacture, i.e. Begin-Of-Line process by dry cleaning only
    • H10P70/125—Cleaning before device manufacture, i.e. Begin-Of-Line process by dry cleaning only with gaseous HF
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/20—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials
    • H10P14/29—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials characterised by the substrates
    • H10P14/2901—Materials
    • H10P14/2902—Materials being Group IVA materials
    • H10P14/2905—Silicon, silicon germanium or germanium
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/20—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials
    • H10P14/34—Deposited materials, e.g. layers
    • H10P14/3402—Deposited materials, e.g. layers characterised by the chemical composition
    • H10P14/3414—Deposited materials, e.g. layers characterised by the chemical composition being group IIIA-VIA materials
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P14/00—Formation of materials, e.g. in the shape of layers or pillars
    • H10P14/20—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials
    • H10P14/36—Formation of materials, e.g. in the shape of layers or pillars of semiconductor materials characterised by treatments done before the formation of the materials
    • H10P14/3602—In-situ cleaning
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P50/00—Etching of wafers, substrates or parts of devices
    • H10P50/20—Dry etching; Plasma etching; Reactive-ion etching
    • H10P50/28—Dry etching; Plasma etching; Reactive-ion etching of insulating materials
    • H10P50/282—Dry etching; Plasma etching; Reactive-ion etching of insulating materials of inorganic materials
    • H10P50/283—Dry etching; Plasma etching; Reactive-ion etching of insulating materials of inorganic materials by chemical means
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10P—GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
    • H10P70/00—Cleaning of wafers, substrates or parts of devices
    • H10P70/10—Cleaning before device manufacture, i.e. Begin-Of-Line process
    • H10P70/12—Cleaning before device manufacture, i.e. Begin-Of-Line process by dry cleaning only

Definitions

  • the invention relates to a method of manufacturing thin films and coatings on a silicon-containing surface of a substrate or a layer grown on a substrate.
  • the method removes native oxides, as S1O2 from the surface and leaves a smooth surface.
  • the etching method forms a pre-process for a subsequent process for depositing a layer, in particular a III-V-layer on a clean, smooth surface of silicon.
  • US 8,501,629 B2 discloses a method of etching a silicon-containing layer by flowing a fluorine-containing precursor and a hydrogen-containing precursor into a remote plasma region.
  • the hydrogen to fluorine atomic flow ratio is greater than 5:1.
  • the state of the art prefers as fluorine containing precursor nitrogen tri-fluoride and as hydrogen-containing precursor ammonia.
  • the method of the state of the art forms solid adducts, which have to be removed by sublimation at temperatures above 1000°C.
  • the method of the invention comprises the following steps: Flowing NF3 and H 2 into a plasma activation zone of a cleaning chamber,
  • the method of the invention comprises additionally the following features:
  • the first reaction comprises first subsequent reactions of NF 2 with H- radicals and NF with H-radicals,
  • the first reaction comprises second subsequent reactions forming NH4F
  • the first reaction comprises third subsequent reactions forming molecules comprising NH and F,
  • the substrate is maintained at a temperature between room temperature and 1050°C during the etching operation, and a plasma is used for activating NF3 and H 2 .
  • a plasma decomposes at least molecular hydrogen into hydrogen radicals.
  • NF3 maybe decomposed in decomposition products as well.
  • the activation zone is preferably located inside of a cleaning system or chamber.
  • the plasma activation zone can be located outside of a vacuum chamber in which a process chamber is located wherein the substrate rests on a susceptor, which can be heated to elevated temperatures.
  • a remote plasma source is connected with a showerhead via a conduit, which transports the reactive radicals. The latter is located inside the vacuum chamber.
  • the following overall reaction takes place in the activation zone: [0008] The following overall reaction takes place on the surface: 4HF + Si0 2 ⁇ S1F4 + 2H2O (2)
  • HF is flown from the activation zone to a process zone of the cleaning chamber in an etching operation, wherein the substrate is located and kept at room temperature or at a temperature in a range between room temperature and 1050°C and especially below 30°C.
  • the gaseous HF reacts with solid S1O2 to form gaseous S1F 4 and gaseous H2O, which are removed by a carrier gas, which is flown into the process zone of the cleaning chamber as well.
  • the carrier gas can be flown into the vacuum chamber by use of separate conduit. Preferable two separate conduits are connected to a gas inlet of a showerhead for flowing gas into the process chamber wherein the substrate rests on a heatable susceptor.
  • the cleaning system or chamber can be part of a clustered III-V epitaxial chamber, wherein in a growth chamber of a growth reactor a III-V- layer or a SiGeSn layer may be deposited on the pre-cleaned silicon containing layer, which may be the surface of a silicon wafer.
  • the III-V-layer can be GaAs or any other binary, ternary or quaternary compound based on Al, Ga, In as group-Ill elements and N, P, As, Sb as group- V elements.
  • NH 4 F which is formed in (1) may decompose in reaction (3) into NH 3 .
  • Reaction (4) shows the formation of H-radicals in the activation zone by the plasma.
  • the reactions (5) to (7) are first subsequent reactions to form HF- molecules, which etch Si0 2 on the surface, but not the Si-atoms of the surface.
  • Second subsequent reactions (8) and (10) form NH 3 in a reaction of nitrogen- containing reaction products with hydrogen atoms.
  • Reaction (11) shows a parallel reaction to reaction (5), wherein NF 3 reacts to NHF 3/ which decomposes in third subsequent reactions (12) to (14) into fluorine atoms (F-radicals).
  • the formation of fluorine atoms should be avoided as much as possible, since fluorine may destroy the silicon-containing surface. It is therefore proposed, that the gas ratio of NF 3 to the total precursor flow is less than 0.3.
  • Reaction (16) shows a subsequent reaction to reaction (13).
  • Reaction (17) shows a subsequent reaction of reaction (14).
  • Figure 1 shows the different flows of NF 3 + H 2 keeping a constant total flow of 750 seem, which was tested by flowing into the plasma activation zone.
  • Figure 2 shows the Si etch rate in function of NF 3 /(NF 3 + H 2 ) ratio, showing low Si-etch rate below 0.28 due to formation of HF-vapor (so a selective etch process to Silicon). Above 0.28 due to atomic F-formation the Si- etching is strongly enhanced.
  • Figures 3a shows SIMS profiles of the oxygen O-level measured in GaAs/Si hetero-structures with low bake temperature (650°C in the process growth chamber) on a pre cleaned substrate, at different NF 3 /H 2 plasma etch time.
  • Figure 3b shows the (004) XRD FWHM at different NF 3 /H 2 plasma etch time.
  • Figure 4 shows SIMS profiles of the O-level measured in GaAs/Si hetero structures with low bake temperature (650°C in the process growth chamber) showing the lower O-concentration at GaAs/Si interface by using in- situ NF3/H2 plasma compared to other ex-situ and in-situ etch treatments.
  • Figure 5 compares FWHM from (004) XRD scans of GaAs/Si hetero structure on a pre clean substrate after various ex-situ and in-situ etch treatments showing that similar crystal quality (i.e. low Full Width Half Maximum) can be obtained with low (650C) and high (950C) bake temperature by using in-situ NF3/H2 plasma preclean process at flow ratio ⁇ 0.28.
  • Figure 6 shows schematic of a Cleaning system or chamber comprising gas inlet manifold, eventually heated susceptor, showerhead and vacuum pump; this is also equipped with Remote Plasma Source fed with NF 3/ H 2 and/ or Ar and additional separate carrier gases.
  • a cluster process system unit comprises a growth chamber comprising a gas inlet device, a heated susceptor and a vacuum equipment.
  • a pre-cleaned substrate comprising a silicon surface is transferred through a load lock into the growth chamber and is placed on the susceptor.
  • the susceptor is heated to a process temperature.
  • Volatile precursors comprising III- and V-elements are flown into the growth chamber.
  • a III-V-layer is grown on the pre-cleaned substrate.
  • a cleaning system or chamber comprises a vessel, comprising a gas inlet device, an eventually heated susceptor, and a vacuum chamber which can be evacuated by means of a vacuum pump.
  • Fig. 6 shows schematic of such a system or chamber equipped with Remote Plasma Source fed with NF 3 , H 2 and/ or Ar.
  • the vessel is directly connected via the load lock with the growth chamber.
  • the growth chamber and the cleaning chamber are connected with a transfer chamber of a cluster process system, wherein the transfer chamber can be evacuated or flushed with an inert gas.
  • the cleaning system or chamber comprises an activation zone, especially a plasma activation zone, which is remote from an etching zone.
  • the cleaning system comprises electrodes to create a plasma by high frequency such as radio frequency or Remote Plasma Source (RPS).
  • NF 3 and H 2 are flown into the activation zone in a space between the electrodes.
  • a noble gas (such as Ar) can be used as a carrier gas to dilute the precursors.
  • the plasma activates the precursors to form gaseous HF and as less as possible fluorine atoms.
  • the reaction products of the reactions in the plasma zone are flown into the etching zone, in which a substrate is located on a support. In the embodiment the temperature of the substrate is room temperature.
  • SiF 4 and H2O reacts with Si0 2 on the surface of the substrate to form SiF 4 and H2O.
  • the total pressure in the cleaning system is far below atmospheric pressure: at these conditions SiF 4 and H2O are vapors. Gaseous SiF 4 and gaseous H2O are removed by the carrier gas out of the etching zone. [0029] The pressure conditions are kept at 1 Torr to obtain a clean O-free Si surface.
  • Figure 2 shows that the Si etch rate increases dramatically at ratios over 0.28 due to an increased atomic F generation. At lower ratios the etch rate of silicon is nearly constant at a low level due to HF-vapor generation. [0031] After cleaning the surface from the oxide, the substrate is carried through the load lock directly into the process chamber to grow the III-V-layer on top of the surface.
  • the substrate can be baked, prior to the growth of the III-V-layer, at an elevated temperature in particular at 650°C (which is close to the III-V layer growth). This may be processed in the process growth chamber of the cluster.
  • Figure 3a and 3b show a good agreement between XRD- and SIMS- analysis. It shows the crystal quality degradation with residual native oxide after in situ NF3/H2 plasma process. The 30 seconds' process shows lower O contamination at the interface and lower XRD FWHM.
  • the cleaning system or chamber shown in figure 6 comprises a vacuum chamber 1 having an inlet 2 for flowing process gases into a process chamber located in the vacuum chamber 1.
  • Two separate conduits 2', 2" are connected with the gas inlet 2 through which gas flows from outside of the vacuum chamber 1 into the vacuum chamber 1.
  • a gas inlet manifold 4 comprises a H 2 -Source, an Ar-Source and an NF 3 -Source.
  • a remote Plasma Source 3 is located between the gas inlet manifold 4 and a showerhead 5 which is located inside the vacuum chamber 1 to flow the process gases into process chamber.
  • the gas conduit 2' connects the plasma source 3 with the gas inlet 2.
  • a separate carrier gas source 9 is able to flow Argon or Hydrogen through a conduit 2" into the gas inlet 2.
  • a Susceptor 7 forms the bottom of the process chamber.
  • a substrate 6 is located on a surface of the Susceptor 7 which faces a gas outlet surface of the showerhead 5.
  • the susceptor 7 comprises heating elements to heat the substrate 6.
  • a gas outlet 8 is connected with a vacuum pump to evacuate the vacuum chamber 1.
  • All disclosed features are essential to the invention (taken in isolation, but also in combination with each other).
  • the disclosure of the application hereby also includes the disclosure content of the accompanying/ attached priority documents (copy of preliminary application) in its entirety, also for the purpose of also incorporating features of these documents into the claims of the present application.
  • the features in the subclaims characterize independent inventive further developments of prior art, in particular so as to generate partial applications based upon these claims.

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Abstract

A Method for etching a silicon-containing surface of a substrate or a layer deposited on a substrate without forming solid adducts, wherein the method comprising: Flowing NF3 and H2 into an activation zone of a cleaning system or chamber, activating NF3 and H2 in the activation zone by forming H-radicals, forming gaseous HF in a first reaction of the H-radicals with NF3 and reaction products of NF3, flowing the gaseous HF to the surface and forming gaseous SiF4 in a second reaction of HF with SiO2 of the surface. The flow ratio of R=(NF3)/(NF3+H2) is less than 0.3 or is between 0.2 and 0.3. The substrate is maintained at a temperature between room temperature and 1050°C during the etching operation. The first reaction comprises first subsequent reactions of NF2 with H-radicals and NF with H-radicals. The first reaction comprises second subsequent reactions forming NH3. The first reaction comprises third subsequent reactions forming molecules comprising NH and F and F-radicals.

Description

Description
Method for etching a silicon containing surface Field of the Invention
[0001] The invention relates to a method of manufacturing thin films and coatings on a silicon-containing surface of a substrate or a layer grown on a substrate. [0002] The method removes native oxides, as S1O2 from the surface and leaves a smooth surface. The etching method forms a pre-process for a subsequent process for depositing a layer, in particular a III-V-layer on a clean, smooth surface of silicon.
State of the Art
[0003] US 8,501,629 B2 discloses a method of etching a silicon-containing layer by flowing a fluorine-containing precursor and a hydrogen-containing precursor into a remote plasma region. The hydrogen to fluorine atomic flow ratio is greater than 5:1. The state of the art prefers as fluorine containing precursor nitrogen tri-fluoride and as hydrogen-containing precursor ammonia. The method of the state of the art forms solid adducts, which have to be removed by sublimation at temperatures above 1000°C.
Summary of the Invention
[0004] It is an object of the invention to improve a dry etching method to avoid the additional sublimation step.
[0005] The method of the invention comprises the following steps: Flowing NF3 and H2 into a plasma activation zone of a cleaning chamber,
activating NF3 and H2 in the plasma activation zone by forming H- radicals,
forming gaseous HF in a first reaction of the H-radicals with NF3 and reaction products of NF3,
flowing the gaseous HF to the surface and forming gaseous S1F4 in a second reaction of HF with Si02 of the surface.
[0006] Optionally the method of the invention comprises additionally the following features:
the first reaction comprises first subsequent reactions of NF2 with H- radicals and NF with H-radicals,
the first reaction comprises second subsequent reactions forming NH4F
Figure imgf000004_0001
the first reaction comprises third subsequent reactions forming molecules comprising NH and F,
the flow ratio of R=(NF3)/(NF3+H2) is less than 0.3 and preferably is between 0.2 and 0.3,
the substrate is maintained at a temperature between room temperature and 1050°C during the etching operation, and a plasma is used for activating NF3 and H2.
[0007] In the activation zone a plasma decomposes at least molecular hydrogen into hydrogen radicals. NF3 maybe decomposed in decomposition products as well. The activation zone is preferably located inside of a cleaning system or chamber. The plasma activation zone can be located outside of a vacuum chamber in which a process chamber is located wherein the substrate rests on a susceptor, which can be heated to elevated temperatures. A remote plasma source is connected with a showerhead via a conduit, which transports the reactive radicals. The latter is located inside the vacuum chamber. The following overall reaction takes place in the activation zone:
Figure imgf000005_0001
[0008] The following overall reaction takes place on the surface: 4HF + Si02 → S1F4 + 2H2O (2)
[0009] NH4F can decompose with the following reaction into NH3:
Figure imgf000005_0002
[0010] HF is flown from the activation zone to a process zone of the cleaning chamber in an etching operation, wherein the substrate is located and kept at room temperature or at a temperature in a range between room temperature and 1050°C and especially below 30°C.
[0011] The gaseous HF reacts with solid S1O2 to form gaseous S1F4 and gaseous H2O, which are removed by a carrier gas, which is flown into the process zone of the cleaning chamber as well. The carrier gas can be flown into the vacuum chamber by use of separate conduit. Preferable two separate conduits are connected to a gas inlet of a showerhead for flowing gas into the process chamber wherein the substrate rests on a heatable susceptor.
[0012] The cleaning system or chamber can be part of a clustered III-V epitaxial chamber, wherein in a growth chamber of a growth reactor a III-V- layer or a SiGeSn layer may be deposited on the pre-cleaned silicon containing layer, which may be the surface of a silicon wafer. The III-V-layer can be GaAs or any other binary, ternary or quaternary compound based on Al, Ga, In as group-Ill elements and N, P, As, Sb as group- V elements.
[0013] The following subsequent reactions may occur:
H2 2H (4)
H + NF3 HF + NF2 (5)
H + NF2 HF + NF (6)
H + NF HF + N (7)
H + N NH (8)
H + NH NH2 (9)
H + NH3 NH3 (10)
H + NF3 NHF3 (11)
NHF3 NHF2 + F (12)
NHF2 NHF + F (13)
H + NHF2 NH2F + F (14)
H + NHF2 HF + NHF (15)
H + NHF HF + NH (16)
H + NH2F HF + NH2 (17)
[0014] NH4F, which is formed in (1) may decompose in reaction (3) into NH3.
[0015] Reaction (4) shows the formation of H-radicals in the activation zone by the plasma. The reactions (5) to (7) are first subsequent reactions to form HF- molecules, which etch Si02 on the surface, but not the Si-atoms of the surface. Second subsequent reactions (8) and (10) form NH3 in a reaction of nitrogen- containing reaction products with hydrogen atoms. [0016] Reaction (11) shows a parallel reaction to reaction (5), wherein NF3 reacts to NHF3/ which decomposes in third subsequent reactions (12) to (14) into fluorine atoms (F-radicals). The formation of fluorine atoms should be avoided as much as possible, since fluorine may destroy the silicon-containing surface. It is therefore proposed, that the gas ratio of NF3 to the total precursor flow is less than 0.3.
[0017] Reactions (15) to (16) show a parallel reaction to reaction (13) of NHF2, formed in reaction (12).
[0018] Reaction (16) shows a subsequent reaction to reaction (13). [0019] Reaction (17) shows a subsequent reaction of reaction (14). Brief description of the drawings
[0020] Figure 1 shows the different flows of NF3 + H2 keeping a constant total flow of 750 seem, which was tested by flowing into the plasma activation zone.
[0021] Figure 2 shows the Si etch rate in function of NF3/(NF3 + H2) ratio, showing low Si-etch rate below 0.28 due to formation of HF-vapor (so a selective etch process to Silicon). Above 0.28 due to atomic F-formation the Si- etching is strongly enhanced.
[0022] Figures 3a shows SIMS profiles of the oxygen O-level measured in GaAs/Si hetero-structures with low bake temperature (650°C in the process growth chamber) on a pre cleaned substrate, at different NF3/H2 plasma etch time. In relation to this Figure 3b shows the (004) XRD FWHM at different NF3/H2 plasma etch time. [0023] Figure 4 shows SIMS profiles of the O-level measured in GaAs/Si hetero structures with low bake temperature (650°C in the process growth chamber) showing the lower O-concentration at GaAs/Si interface by using in- situ NF3/H2 plasma compared to other ex-situ and in-situ etch treatments. [0024] Figure 5 compares FWHM from (004) XRD scans of GaAs/Si hetero structure on a pre clean substrate after various ex-situ and in-situ etch treatments showing that similar crystal quality (i.e. low Full Width Half Maximum) can be obtained with low (650C) and high (950C) bake temperature by using in-situ NF3/H2 plasma preclean process at flow ratio <0.28. [0025] Figure 6 shows schematic of a Cleaning system or chamber comprising gas inlet manifold, eventually heated susceptor, showerhead and vacuum pump; this is also equipped with Remote Plasma Source fed with NF3/ H2 and/ or Ar and additional separate carrier gases.
Detailed Description of the invention
[0026] A cluster process system unit comprises a growth chamber comprising a gas inlet device, a heated susceptor and a vacuum equipment. A pre-cleaned substrate comprising a silicon surface is transferred through a load lock into the growth chamber and is placed on the susceptor. The susceptor is heated to a process temperature. Volatile precursors comprising III- and V-elements are flown into the growth chamber. A III-V-layer is grown on the pre-cleaned substrate.
[0027] A cleaning system or chamber comprises a vessel, comprising a gas inlet device, an eventually heated susceptor, and a vacuum chamber which can be evacuated by means of a vacuum pump. Fig. 6 shows schematic of such a system or chamber equipped with Remote Plasma Source fed with NF3, H2 and/ or Ar. The vessel is directly connected via the load lock with the growth chamber. In an alternative embodiment the growth chamber and the cleaning chamber are connected with a transfer chamber of a cluster process system, wherein the transfer chamber can be evacuated or flushed with an inert gas.
[0028] The cleaning system or chamber comprises an activation zone, especially a plasma activation zone, which is remote from an etching zone. The cleaning system comprises electrodes to create a plasma by high frequency such as radio frequency or Remote Plasma Source (RPS). NF3 and H2 are flown into the activation zone in a space between the electrodes. A noble gas (such as Ar) can be used as a carrier gas to dilute the precursors. The plasma activates the precursors to form gaseous HF and as less as possible fluorine atoms. The reaction products of the reactions in the plasma zone are flown into the etching zone, in which a substrate is located on a support. In the embodiment the temperature of the substrate is room temperature. HF reacts with Si02 on the surface of the substrate to form SiF4 and H2O. The total pressure in the cleaning system is far below atmospheric pressure: at these conditions SiF4 and H2O are vapors. Gaseous SiF4 and gaseous H2O are removed by the carrier gas out of the etching zone. [0029] The pressure conditions are kept at 1 Torr to obtain a clean O-free Si surface.
[0030] Figure 2 shows that the Si etch rate increases dramatically at ratios over 0.28 due to an increased atomic F generation. At lower ratios the etch rate of silicon is nearly constant at a low level due to HF-vapor generation. [0031] After cleaning the surface from the oxide, the substrate is carried through the load lock directly into the process chamber to grow the III-V-layer on top of the surface.
[0032] To remove oxygen, which possibly adsorb on the silicon surface, the substrate can be baked, prior to the growth of the III-V-layer, at an elevated temperature in particular at 650°C (which is close to the III-V layer growth). This may be processed in the process growth chamber of the cluster.
[0033] Figure 3a and 3b show a good agreement between XRD- and SIMS- analysis. It shows the crystal quality degradation with residual native oxide after in situ NF3/H2 plasma process. The 30 seconds' process shows lower O contamination at the interface and lower XRD FWHM.
[0034] The cleaning system or chamber shown in figure 6 comprises a vacuum chamber 1 having an inlet 2 for flowing process gases into a process chamber located in the vacuum chamber 1. Two separate conduits 2', 2" are connected with the gas inlet 2 through which gas flows from outside of the vacuum chamber 1 into the vacuum chamber 1.
[0035] A gas inlet manifold 4 comprises a H2-Source, an Ar-Source and an NF3-Source. A remote Plasma Source 3 is located between the gas inlet manifold 4 and a showerhead 5 which is located inside the vacuum chamber 1 to flow the process gases into process chamber. The gas conduit 2' connects the plasma source 3 with the gas inlet 2. A separate carrier gas source 9 is able to flow Argon or Hydrogen through a conduit 2" into the gas inlet 2.
[0036] A Susceptor 7 forms the bottom of the process chamber. A substrate 6 is located on a surface of the Susceptor 7 which faces a gas outlet surface of the showerhead 5. The susceptor 7 comprises heating elements to heat the substrate 6.
[0037] A gas outlet 8 is connected with a vacuum pump to evacuate the vacuum chamber 1. [0038] All disclosed features are essential to the invention (taken in isolation, but also in combination with each other). The disclosure of the application hereby also includes the disclosure content of the accompanying/ attached priority documents (copy of preliminary application) in its entirety, also for the purpose of also incorporating features of these documents into the claims of the present application. The features in the subclaims characterize independent inventive further developments of prior art, in particular so as to generate partial applications based upon these claims.

Claims

Method for etching a silicon-containing surface of a substrate or a layer deposited on a substrate without forming solid adducts, wherein the method comprising:
Flowing NF3 and H2 into an activation zone of a cleaning system or chamber,
activating NF3 and H2 in the activation zone by forming H-radicals, forming gaseous HF in a first reaction of the H-radicals with NF3 and reaction products of NF3,
flowing the gaseous HF to the surface and forming gaseous S1F4 in a second reaction of HF with Si02 of the surface, characterized in that the ratio of the mass flows R=(NF3)/(NF3+H2) is lower than 0,3 and in that the substrate is maintained at a temperature between room temperature and 1050°C during the second reaction.
Method of claim 1, wherein the flow ratio of R=(NF3)/(NF3+H2) is between 0.2 and 0.3.
Method of claim 1, wherein the flow ratio of R=(NF3)/(NF3+H2) is between 0.2 and 0.28.
Method of any of claims 1 to 3, wherein the first reaction comprises second subsequent reactions forming NH3.
Method of any of claims 1 to 4, wherein the first reaction comprises third subsequent reactions forming molecules comprising NH and F and F- radicals. The method of any of claims 1 to 5, wherein the substrate is maintained at a temperature between room temperature to 650°C during the etching operation.
The method of any of claims 1 to 6, wherein the substrate is maintained at a temperature below 30°C during the etching operation.
The method of any of claims 1 to 7, wherein activating NF3 and H2 is performed in a plasma or other activating sources.
PCT/EP2018/074401 2017-09-11 2018-09-11 Method for etching a silicon containing surface Ceased WO2019048693A1 (en)

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Citations (2)

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