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
  • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
  • C23C10/06—Solid state diffusion of only metal elements or silicon into metallic material surfaces using gases
• • 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
  • C23C10/00—Solid state diffusion of only metal elements or silicon into metallic material surfaces
  • C23C10/60—After-treatment
• • 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
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/06—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the coating material
  • C23C14/14—Metallic material, boron or silicon
• • 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
  • C23C14/00—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material
  • C23C14/22—Coating by vacuum evaporation, by sputtering or by ion implantation of the coating forming material characterised by the process of coating
  • C23C14/34—Sputtering
• • 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
  • C23C16/56—After-treatment

Definitions

• the present invention relates to a method for forming a poly crystalline silicon thin film, and more particularly, to a method for forming a polycrystalline silicon by two- step deposition: supplying silicon precursors and plasma alternately to the inside of a plasma reaction tube to forming a crystalline silicon thin film of atom layer at a lower temperature than 500 0 C; and forming a separate upper silicon thin film on the crystalline silicon thin film functioning as a seed layer.
• the present invention can form a polycrystalline silicon thin film at relatively low temperature by such two-step deposition.
• elements employing polycrystalline silicon thin films are used for active elements for active matrix liquid crystal displays and switching elements and peripheral circuits for electro-luminescence elements.
• a polycrystalline silicon thin film can be obtained by applying a method such as a solid phase crystallization method(SPC), a rapid thermal annealing method(RTA), a continuous wave Ar laser annealing method, an excimer laser annealing method(ELA), etc. on a substrate deposited with amorphous silicon.
• a method such as a solid phase crystallization method(SPC), a rapid thermal annealing method(RTA), a continuous wave Ar laser annealing method, an excimer laser annealing method(ELA), etc.
• the solid phase crystallization method carries out a heat treatment at a high temperature more than 600 0 C for a long time to form a polycrystalline silicon thin film.
• the method using a high temperature heat treatment like this requires a long and high temperature heat treatment.
• there occur many defects in the grains crystallized by this method thus making it difficult to make an element, and a substrate made of glass can not be employed due to high crystallization temperature.
• the rapid thermal annealing method and continuous wave Ar laser annealing method also require a process temperature more than 500 0 C, thereby making it impossible to be applicable to a glass substrate, which can cause thermal deformation.
• FIG. 1 is a flow chart forming a polycrystalline silicon thin film using an excimer laser annealing method according to the prior art
• FIG. 2 is a process flow diagram for illustrating the flow chart of FIG. 1.
• an amorphous silicon thin film is deposited on a substrate using a plasma- enhanced chemical vapor deposition (PECVD) method (SlO).
• PECVD plasma- enhanced chemical vapor deposition
• SiH molecules 3 and H molecules 4 supplied to the inside of a reaction tube 1 and generating plasma at a predetermined condition make silicon atoms 3a and hydrogen atoms 3B deposited on the substrate 2, thus forming the amorphous silicon thin film as shown in FIG. 2(a).
• pulsed excimer laser beams 5 are illuminated to the dehydrogenated silicon atoms 3 a to locally heat and crystallize only the surface of the amorphous silicon thin film on the substrate 2, thus allowing the silicon thin film to be crystallized while minimizing the damage to the glass substrate (S30) (see FIG. 2(c)).
• the process may become complicated since the laser crystallization should be proceeded under vacuum after the deposition of the amorphous silicon thin film has been complete and hydrogen have been removed in the thin film using the rapid thermal annealing method(RTA).
• RTA rapid thermal annealing method
• an object of the present invention is to provide a method for forming a polycrystalline silicon through two-step deposition: supplying silicon precursor and plasma alternately to the inside of a plasma reaction tube to forming a crystalline silicon thin film of an atom layer at a lower temperature than 500 0 C; and forming a separate upper silicon thin film with the crystalline silicon thin film as a seed layer.
• the present invention can form a polycrystalline silicon thin film at relatively low temperature by the two-step deposition.
• a method of forming a polycrystalline silicon thin film by two-step deposition which includes: sequentially supplying silicon precursors and reductive plasma into the inside of a reaction tube having a substrate placed therein to deposit a crystalline silicon thin film of atom layer having a predetermined thickness on the substrate; and depositing an upper silicon thin film on the crystalline silicon thin film functioning as a seed layer.
• Said depositing the crystalline silicon thin film of atom layer may includes: (a) supplying silicon precursors into the inside of a reaction tube having a substrate placed therein to make the silicon precursors react with the substrate while maintaining the inside of the reaction tube at a predetermined pressure and a temperature; (b) pumping and purging to remove silicon precursors not having reacted and reaction byproducts remaining inside the reaction tube; (c) supplying reductive plasma into the inside of the reaction tube to form solid state silicon by reducing the silicon precursors deposited on the substrate; and (d) pumping and purging to remove various ions not having reacted and reaction byproducts remaining inside the reaction tube.
• steps (a) to (d) may be repeated to form the crystalline silicon thin film having the predetermined thickness on the substrate.
• the silicon precursors each may be a halogen compound, and the silicon precursors each may J be any J one of SiCl 4 , SiF 4 , SiH 2 Cl 2 , SiHCl 3 , SiH 3 Cl, SiI 4 , Si 2 Cl 6 , and Si 2 F 6.
• a pressure inside the reaction tube may range from lOmTorr to lOTorr to cause the silicon precursors to react, and the silicon precursors may be supplied into the inside of the reaction tube during a time from 1 second to 10 minutes.
• H or D may be used as a gas to form the reductive plasma.
• any one of ca- pacitively-coupled plasma(CCP), inductively-coupled plasma(ICP), microwave plasma, electron cyclotron (ECR) plasma, and helicon plasma may be used as a source for the reductive plasma.
• a plasma power may be maintained between 100 watts and 20 kirowatts, a pressure may be maintained between 5mTorr and 5Torr, and a flow rate of a gas for generating the reductive plasma may be maintained between 100 Seem and 50 Slpm.
• An inert gas or H may be used for said purging, and temperature of the substrate may be maintained between 300 and 500 0 C. And, the substrate may be heated using any one of a resistance heating technique, an induction heating technique, and a ramp heating technique.
• a thickness of the crystalline silicon thin film of atom layer may range from lnm to lOOnm.
• the upper silicon thin film may be formed using any one of a PECVD method, a
• LPCVD method an APCVD method, and a sputtering method.
• silicon precursors, H , and inert gases may be simultaneously supplied into the inside of the reaction tube, plasma may be applied to the inside of the reaction tube, and a temperature of the substrate may be maintained between 200 and 500 0 C.
• the silicon precursors each may be any one of SiH , Si H , SiCl , SiF , SiH Cl ,
• SiHCl , SiH Cl, SiI , Si Cl and Si F any one of capacitively-coupled plasma(CCP), inductively-coupled plasma(ICP), microwave plasma, electron cyclotron (ECR) plasma, and helicon plasma may be used as a source for generating the plasma.
• CCP capacitively-coupled plasma
• ICP inductively-coupled plasma
• ECR electron cyclotron
• helicon plasma any one of capacitively-coupled plasma(CCP), inductively-coupled plasma(ICP), microwave plasma, electron cyclotron (ECR) plasma, and helicon plasma may be used as a source for generating the plasma.
• CCP capacitively-coupled plasma
• ICP inductively-coupled plasma
• microwave plasma microwave plasma
• ECR electron cyclotron
• helicon plasma helicon plasma
• silicon precursors, H , and inert gases may be simultaneously supplied into the inside of the reaction tube, and a temperature of the substrate may be maintained between 300 and 500 0 C.
• the silicon precursors each may be any one of SiH , Si H , SiCl , SiF , SiH Cl ,
• FIG. 1 is a flow chart for forming a silicon thin film using an excimer laser annealing method
• FIG. 2 is a process flow diagram for forming a silicon thin film using an excimer laser annealing method
• FIG. 3 is a process flow diagram for forming a polycrystalline silicon thin film through two-step deposition according to an embodiment of the present invention
• FIG. 4 is a flow chart for forming a silicon thin film of atom layer according to an embodiment of the present invention.
• FIG. 5 is a process flow diagram for forming a silicon thin film of atom layer according to an embodiment of the present invention.
• FIG. 6 is a graph showing a degree of crystallinity for a polycrystalline silicon thin film formed according to an embodiment of the present invention. Mode for the Invention
• the present invention is a technique of depositing a silicon thin film, which decides the properties of TFTs, using an atomic layer deposition method(ALD) called a base technology of next generation flat panel display apparatuses.
• ALD atomic layer deposition method
• the present invention can conduct a process at lower temperature and improve the properties of TFTs, thus making it possible to manufacture high capability display devices.
• the present invention can be applicable to other display devices such as flexible displays as well as flat panel displays, and also applicable to the energy fields such as solar cells.
• a crystalline silicon thin film 150 of atom layer having a predetermined thickness is deposed on a substrate 110 to make a poly- crystalline silicon thin film according to a method of the present invention. More specifically, the crystalline silicon thin film 150 is firstly deposited on the substrate 110 placed inside a reaction tube. A silicon precursor and reductive plasma need to be sequentially or repeatedly supplied alternately to the inside of the reaction tube so that the crystalline silicon thin film 150 of atom layer can be deposited on the substrate 110.
• a separate upper silicon thin film 160 is deposited on the crystalline silicon thin film 150 of atom film.
• the upper silicon thin film 160 is deposited using an existing deposition method. Because the crystalline silicon thin film 150 deposited prior to the deposition of the upper silicon thin film 160 functions as a seed layer, however, the upper silicon thin film 160 starts to be crystallized by the seed layer, i.e. crystalline silicon thin film 150.
• the substrate in order to deposit the crystalline silicon thin film on the substrate, the substrate is placed inside a reaction tube and reacted with a silicon precursor supplied into the reaction tube with the inside of the reaction tube maintained at a given pressure and a temperature (Sl 10).
• the silicon precursor 120 is preferably a halogen compound of silicon.
• the silicon precursor 120 is any one of SiCl , SiF , SiH Cl , SiHCl , SiH Cl,
• SiH Cl is used as the silicon precursor 120 in FIG. 5(a)
• silicon precursors each of which is composed of a silicon atom 121 and two Cl atoms 123 and two H atoms 125 bonded to the silicon atom 121, are supplied to the inside of the reaction tube 100 and react with the substrate 110 at a predetermined pressure and a temperature, so that silicon atoms 121, halogen atoms, and Cl atoms 123 are deposited on the substrate 110 and part of the silicon precursors 120 and reaction byproducts 130 remains inside the reaction tube 100.
• Pressure of the inside of the reaction tube 100 should be more than lOmTorr, most preferably in the range from lOmTorr to lOTorr, to cause a reaction on the precursors 120. It is desirable that the silicon precursors 120 are supplied into the inside of the reaction tube 100 for 1 second- 10 minutes.
• silicon precursors 120 not having reacted and reaction byproducts 130 inside the reaction tube 100 are removed (S 120). Pumping and purging are performed to remove the silicon precursors 120 not having reacted and reaction byproducts 130. It is desirable to use inert gases such as N , Ar, He, etc., or H gas as a purge gas.
• H or D it is desirable to use H or D as a gas to form the reductive plasma, and it is desirable to use any one of capacitively-coupled plasma (CCP), inductively-coupled plasma (ICP), microwave plasma, electron cyclotron (ECR) plasma, and helicon plasma as a source for the reductive plasma.
• CCP capacitively-coupled plasma
• ICP inductively-coupled plasma
• ECR electron cyclotron
• the inductively-coupled plasma it is desirable to maintain the plasma power between 100 watts and 20 kirowatts, the pressure between 5mTorr and 5Torr, and the flow rate of gas for generating reductive plasma between 100 Seem to 50 Slpm.
• the present invention makes a difference from a prior art that directly deposits a crystalline silicon thin film at a high temperature more than 600 0 C. While various heating techniques can be employed to heat the substrate, it is desirable to use any one of a resistance heating technique, an induction heating technique, and a ramp heating technique.
• the steps Sl 10-S140 can be repeatedly performed several times. That is, the steps Sl 10-S140 can be repeated several times to form a crystalline silicon thin film 150 of atom layer having a desired thickness on a substrate as shown in FIG. 5(e). Assuming that a crystalline silicon thin film of ID atom layer is formed in case of carrying out the steps Sl 10-S140, it is enough to conduct the steps Sl 10-S140 five times in order to deposit a crystalline silicon thin film of 5D thickness of atom layer.
• the silicon precursors used, the conditions to cause the silicon precursors to react, the gases for reductive plasma, the source for reductive plasma, and conditions to process the plasma are the same as the case of performing the step SI lO-S 140.
• the thickness of the crystalline silicon thin film of atom layer deposited by the above processes can be changed variously, it is desirable to be in the range between lnm and lOOnm. That is, it is desirable that the crystalline silicon thin film of atom layer is formed to have a thickness within the above range by either performing the steps SI lO-S 140 or repeating the steps SI lO-S 140 several times.
• a separate upper silicon thin film 160 is formed by various deposition methods using the crystalline silicon thin film 150 as a seed layer.
• the upper silicon thin film 160 can be deposited on the crystalline silicon thin film 150 as a seed layer using any one of a PECVD method, a LPCVD method, an APCVD method, and a sputtering method.
• the upper silicon thin film 160 is deposited by the PECVD method
• plasma having a predetermined condition is applied to the reaction tube filled with silicon precursors, H , and inert gases.
• the temperature of the substrate is preferably maintained in the range from 200 to 500 0 C.
• SiI , Si Cl , and Si F as the precursors supplied into the inside of the reaction tube, and it is desirable to use any one of capacitively-coupled plasma (CCP), inductively- coupled plasma (ICP), microwave plasma, electron cyclotron (ECR) plasma, and helicon plasma as a source for causing the plasma.
• CCP capacitively-coupled plasma
• ICP inductively- coupled plasma
• ECR electron cyclotron
• helicon plasma a source for causing the plasma.
• the upper silicon thin film 160 is deposited by the LPCVD method, it is desirable to maintain the temperature of the substrate between 300 and 500 0 C, with the reaction tube filled with silicon precursors, H , and inert gases. [62] At this time, it is desirable to use any one of SiH , Si H , SiCl , SiF , SiH Cl , SiHCl
• the present invention is a novel low-temperature crystallization method, which can directly form a crystalline silicon thin film even at the temperature range where existing methods can not form crystalline thin films by firstly forming a crystalline silicon thin film as a seed layer and secondly growing up an upper silicon thin film on the crystalline silicon thin film.
• the crystalline silicon thin film of atom layer is firstly deposited on the substrate to function as a seed layer, the upper silicon thin film on the seed layer has an improved degree of crystallization accordingly.
• FIG. 6 is a graph showing a degree of crystallinity of a silicon thin film using
• FIG. 6(a) is a graph showing a degree of crystallinity of a silicon thin film formed by an existing PECVD method
• FIG. 6(b) is a graph showing a degree of crystallinity of a silicon thin film formed by sequentially applying an ALD method and a PECVD method according to the present invention
• the former the ALD method
• the PECVD method for forming an upper silicon thin film to be crystallized.
• the degree of crystallinity of the crystalline silicon thin film formed by the present invention is even much better than that of the crystalline silicon thin film by the conventional method.
• the method of forming a polycrystalline silicon thin film by two-step deposition according to the present invention produces the following effects.
• the crystalline silicon thin film of atom layer even at the temperature lower than 500 0 C, at which silicon thin films can not be formed by existing methods, can be directly formed.
• the silicon thin film formed by the present invention has higher electric field mobility and driving current than an amorphous silicon thin film, thereby improving the reliability as well as making LCD drivers built in a TFT panel when being applied to the manufacturing process of TFTs.

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• 2005
  • 2005-11-28 KR KR1020050114401A patent/KR100773123B1/ko not_active IP Right Cessation
• 2006
  • 2006-11-28 WO PCT/KR2006/005064 patent/WO2007061273A1/en active Application Filing
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