KR100734393B1 - method for forming silicon film by Atomic Layer Deposition - Google Patents

Abstract

The present invention relates to a method for depositing an atomic layer of a silicon thin film, and in particular, by alternately supplying a silicon precursor and a plasma into a reaction tube, the silicon thin film can be formed even at a temperature below 500 ° C., and atomic layer deposition is repeatedly performed. The present invention relates to an atomic layer deposition method of a silicon thin film capable of depositing a silicon thin film having a desired thickness.

The constituent means constituting the method for depositing the atomic layer of the silicon thin film of the present invention, after flowing the substrate into the reaction tube, by supplying a silicon (Si) precursor while maintaining the inside of the reaction tube at a predetermined pressure and temperature to react The first step, the second step of performing the pumping and purging to remove the remaining silicon (Si) precursor and reaction by-products without reacting in the reaction tube, by reducing the silicon (Si) precursor adsorbed on the substrate surface A third step of supplying a reducing plasma into the reaction tube to form a solid silicon (Si). And a fourth step of performing pumping and purging to remove the various ions and reaction by-products remaining without reacting in the reaction tube.

Atomic layer, crystalline, silicon thin film

Description

Method for forming silicon film by Atomic Layer Deposition

1 is a flowchart of forming a silicon thin film using an excimer laser crystallization method.

2 is a process chart for forming a silicon thin film using an excimer laser crystallization method.

3 is a flowchart of depositing an atomic layer of a silicon thin film according to an embodiment of the present invention.

4 is a process diagram for depositing an atomic layer of a silicon thin film according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

1, 100: reaction tube 2, 110: substrate

3: SiH ₄ molecule 4: H ₂ molecule

5 laser beam 120 silicon precursor

121: silicon atom 130, 140: reaction by-product

150: atomic layer silicon thin film

The present invention relates to a method for depositing an atomic layer of a silicon thin film, and in particular, by alternately supplying a silicon precursor and a plasma into a reaction tube, the silicon thin film can be formed even at a temperature below 500 ° C., and atomic layer deposition is repeatedly performed. The present invention relates to an atomic layer deposition method of a silicon thin film capable of depositing a silicon thin film having a desired thickness.

Most active matrix liquid crystal display (AMLCD) active devices, electroluminescent devices, switching devices and peripheral circuits are made of polycrystalline silicon thin film devices.

Currently, polycrystalline silicon thin films are first deposited with amorphous silicon, followed by solid phase crystallization (SPC), rapid thermal annealing (RTA), continuous wave ar laser annealing, and excimer laser crystallization (ELA). and excimer laser annealing).

The solid phase purification method is a method of producing a polycrystalline silicon thin film by heat treatment for a long time at a high temperature of 600 ℃ or more. However, a method using high temperature heat treatment requires a high crystallization temperature and a long heat treatment time. In addition, there are many defects inside the crystal grains crystallized by this method, making it difficult to fabricate the device, and there is a problem that glass substrates cannot be used due to high crystallization temperature.

In addition, the rapid heat treatment method and the continuous wavelength laser crystallization method 500 ^It is not applicable to the case of using a glass substrate that causes thermal deformation in the above temperature range because a process temperature of more than C is required.

On the other hand, the excimer laser crystallization method is currently the most widely applied technology in production. This will be described with reference to the accompanying drawings.

1 is a flow chart for forming a polycrystalline silicon thin film using a conventional excimer laser crystallization method, Figure 2 is a flow chart for explaining this.

First, an amorphous silicon (Si) thin film is deposited on a substrate by plasma-enhanced chemical vapor deposition (PECVD) (S10). To this end, as shown in FIG. 2A, when SiH ₄ molecules 3 and H ₂ (4) are supplied into the reaction tube 1 and plasma is generated under predetermined conditions, silicon atoms (Si) 3a are generated. ) And hydrogen (H) atoms 3b are deposited on the substrate 2 to form an amorphous silicon thin film.

After the amorphous silicon thin film is formed on the substrate 2 as described above, a dehydrogenation treatment for removing hydrogen 3b contained in the amorphous silicon (Si) thin film is performed (S20). In this dehydrogenation process, as shown in b of FIG. 2, hydrogen 3b escapes between the silicon atoms 3a.

After removing the hydrogen 3b sandwiched between the silicon atoms 3a as described above, only the surface of the amorphous silicon (Si) thin film on the substrate 2 is irradiated by irradiating the pulsed excimer laser beam 5. By crystallization by heating the crystallized silicon (Si) thin film while minimizing damage to the glass substrate (S30) (see Fig. 2c).

However, when the polycrystalline silicon thin film is to be formed on the substrate by the excimer laser crystallization method as described above, an expensive excimer laser apparatus is required, and the process is performed by scanning a large area substrate with a laser beam. The disadvantage is that the time is relatively long and the silicon (Si) grain size is not uniform.

In addition, the deposition of amorphous silicon (Si) thin film, RTA (rapid thermal anneal) to remove the hydrogen in the thin film and laser crystallization in the vacuum process has the disadvantage that the process is complicated.

The present invention was devised to solve the above problems of the prior art, and by supplying the silicon precursor and the plasma alternately into the reaction tube, it is possible to form a silicon thin film at a temperature of less than 500 ℃, atomic layer deposition It is an object of the present invention to provide a method for depositing an atomic layer of a silicon thin film which can be easily deposited by repeatedly performing a silicon thin film having a desired thickness.

The constituent means of the atomic layer deposition method of the silicon thin film of the present invention proposed in order to achieve the technical problem as described above, in the atomic layer deposition method of the silicon thin film, after flowing the substrate into the reaction tube, the inside of the reaction tube In the first step of supplying and reacting a silicon (Si) precursor at a predetermined pressure and temperature, pumping and purging are performed to remove the remaining silicon (Si) precursor and reaction by-products without reacting inside the reaction tube. A second step of performing a third step of supplying a reducing plasma into the reaction tube in order to reduce the silicon (Si) precursor adsorbed on the substrate surface to form a solid silicon (Si). And a fourth step of performing pumping and purging to remove the various ions and reaction by-products remaining without reacting in the reaction tube.

In addition, the first to fourth steps are repeated to form a silicon thin film having a predetermined thickness on the substrate. By repeatedly depositing the silicon of the atomic layer on the substrate, a silicon thin film having a desired thickness can be formed.

In addition, the silicon (Si) precursor is characterized in that the halogen compound of silicon (Si). That is, the silicon precursor is preferably any 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 .

In addition, the pressure of the reaction tube for reacting the silicon precursor is preferably in the range of 10 mTorr ~ 10 Torr, the silicon precursor is preferably supplied into the reaction tube for a range of 1 second to 10 minutes. Do.

In addition, hydrogen (H 2) or deuterium (D 2) is used as a gas for forming the reducing plasma. The reducing plasma source may be capacitively-coupled plasma (CCP), inductively-coupled plasma (ICP), microwave plasma, ECR plasma (ECR plasma, electron cyclotron plasma). And it is preferable to use any one of the helicon plasma (helicon plasma).

In addition, in the case of using the inductively coupled plasma, the plasma power is maintained in the range of 100 W to 20 kW, the pressure is maintained in the range of 5 mTorr to 5 Torr, and the flow rate of the gas for forming the reducing plasma. Is characterized by maintaining a range between 100 Sccm and 50 Slpm.

In addition, the purge is characterized by using an inert gas or hydrogen (H ₂ ) gas. That is, inert gases such as nitrogen, argon and helium or hydrogen gas are used to remove reaction by-products and the like.

In addition, the temperature of the substrate is characterized in that it maintains a range between 300 ~ 500 ℃. In addition, it is preferable to use any one of a resistance heating method, an induction heating method, and a lamp heating method for heating the substrate.

Hereinafter, with reference to the accompanying drawings will be described in detail the operation and preferred embodiment of the method for depositing the atomic layer of the silicon thin film of the present invention consisting of the above configuration means.

The present invention is a technique for depositing a silicon (Si) thin film, which depends on the characteristics of a TFT, which is the basis technology of the next-generation flat panel display device, by atomic layer deposition (ALD) method. It is possible to lower the temperature and to improve the TFT characteristics, thereby producing a high-performance display device. In addition, the present invention can be applied to other display elements such as a flexible display as well as a flat panel display, and can be applied to energy fields such as solar cells.

3 is a flow chart of depositing an atomic layer of a silicon thin film according to an embodiment of the present invention, Figure 4 is a flow chart for explaining this.

As shown in FIG. 3, in order to deposit an crystalline silicon thin film of an atomic layer on a substrate, first, the substrate is introduced into a reaction tube, and the silicon (Si) is maintained while maintaining the inside of the reaction tube at a predetermined pressure and temperature. The precursor is supplied and reacted (S110).

As such, when the silicon (Si) precursor 120 is supplied into the reaction tube 100 and the inside of the reaction tube 100 is maintained at a predetermined pressure and temperature, the silicon (Si) precursor 120 reacts with the chemical reaction. To form a silicon (Si) atom 121 on the substrate 110 (see FIG. 4A).

The silicon (Si) precursor 120 is preferably a halogen compound of silicon (Si). For example, the silicon precursor 120 corresponds to any 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 .

In FIG. 4A, when SiH ₂ Cl ₂ is used as the silicon precursor 120, a silicon precursor in which two Cl 123 and two H 125 are bonded around the silicon atom 121 is formed in the reaction tube. (100) is supplied inside, reacts at a predetermined pressure and temperature to deposit a silicon atom 121 and a halogen atom Cl (123) on the substrate 110, and some silicon precursor 120 and the reaction by-product 130 ) Will remain inside the reaction tube (100).

The pressure inside the reaction tube 100 for reacting the silicon precursor 120 should be at least 10 mTorr, most preferably in the range between 10 mTorr and 10 Torr. In addition, the silicon precursor 120 supplied into the reaction tube 100 is preferably supplied for a range of 1 second to 10 minutes.

When the silicon atoms are deposited on the substrate 110 as described above, the silicon precursor 120 and the reaction by-product 130 remaining without reacting inside the reaction tube 100 are shown in FIG. It is removed (S120). As such, pumping and purging are performed to remove the remaining silicon precursor 120 and the reaction by-product 130 without reacting. As the purge gas, it is preferable to use an inert gas such as N ₂ , Ar, He, or hydrogen (H ₂ ) gas.

As described above, after the remaining silicon precursor 120 and the reaction by-product 130 are not reacted in the reaction tube 100, the silicon precursor adsorbed on the surface of the substrate 110 is reduced to form solid silicon. In order to supply a reducing plasma to the reaction tube (100) (S130).

Hydrogen (H 2) or deuterium (D 2) is preferably used as a gas for forming the reducing plasma, and a capacitively coupled plasma (CCP, capacitively) as a reducing plasma source for generating plasma using the plasma gas. It is preferable to use any one of -coupled plasma, inductively-coupled plasma (ICP), microwave plasma, microwave plasma (ECR plasma) and helicon plasma. Do.

If the inductively coupled plasma is used, the plasma power is maintained in the range of 100 W to 20 kW, the pressure is maintained in the range of 5 mTorr to 5 Torr, and the flow rate of the gas for forming the reducing plasma is 100. It is desirable to maintain a range between Sccm and 50 Slpm.

In order to form a reducing plasma as described above, hydrogen (H ₂ ) gas is supplied into the reaction tube 100, and when the plasma treatment is performed, the halogen atoms Cl adsorbed on the substrate 121 are separated from the hydrogen. Couplings remain as reaction byproducts 140, and reacted hydrogen 125 is bonded to silicon atoms adsorbed on the substrate 121 (see FIG. 4C).

As described above, after the reducing plasma is supplied into the reaction tube 100 to reduce the silicon precursor adsorbed on the surface of the substrate 110 to form solid silicon, each species remaining without reacting inside the reaction tube 100 is formed. Ions and reaction byproducts 140 are removed as shown in FIG. 4 (d) (S140).

Thus, pumping and purging are performed to remove the various ions and reaction by-products 140 remaining without reacting. As the purge gas, it is preferable to use an inert gas such as N ₂ , Ar, He, or hydrogen (H ₂ ) gas.

In order to form a crystalline silicon thin film according to the above process, the substrate 110 is preferably heated to maintain a range between 300 ~ 500 ℃. The temperature of such a substrate is different from the conventional method of directly depositing a crystalline silicon thin film at a high temperature of 600 ° C or higher. Although the method of heating the substrate to a predetermined temperature varies, it is preferable to use any one of a resistance heating method, an induction heating method, and a lamp heating method.

In addition, the steps S110 to S140 described above may be repeated several times. That is, as shown in FIG. 4E, the steps S110 to S140 may be repeated several times to form the silicon thin film 150 having a desired thickness on the substrate. That is, under the assumption that the steps S110 to S140 are performed to form a silicon thin film having an atomic layer of 0.2 nm, the steps S110 to S140 may be repeatedly performed 50 times to deposit a 10 nm thick silicon thin film.

Even when the steps S110 to S140 are repeatedly performed, the conditions for reacting the silicon precursor with the silicon precursor, the reducing plasma gas, the reducing plasma source, and the plasma processing conditions are the same as those when the steps S110 to S140 are performed. Do.

According to the atomic layer deposition method of the silicon thin film of the present invention having the above-described configuration, operation, and preferred embodiments, the crystalline silicon (Si) thin film is less than 500 ^o C which is a temperature range in which the silicon thin film is not formed by the conventional method. There is an effect that can be deposited directly.

In addition, when manufacturing the low-temperature polycrystalline silicon (Si) TFT by applying the present invention, compared to the case of forming a polycrystalline silicon (Si) thin film by using an excimer laser, the process is simple and the productivity is greatly improved. have.

In addition, when the present invention is applied to the fabrication of amorphous silicon (Si) TFT, since the silicon (Si) thin film formed by the method of the present invention has higher field effect mobility and higher driving current than the amorphous silicon (Si) thin film, the TFT LCD driver circuit can be embedded on the panel and reliability can be improved.

Claims (12)

In the atomic layer deposition method of a silicon thin film, A first step of flowing the substrate into the reaction tube and then supplying and reacting a silicon (Si) precursor while maintaining the inside of the reaction tube at a predetermined pressure and temperature; A second step of performing pumping and purging to remove remaining silicon (Si) precursor and reaction by-products without reacting inside the reaction tube; Supplying a reducing plasma into the reaction tube in order to reduce silicon (Si) precursor adsorbed on the substrate surface to form solid silicon (Si); A fourth step of performing pumping and purging to remove various ions and reaction by-products remaining without reacting in the reaction tube; And repeating the first to fourth steps to form a silicon thin film having a predetermined thickness on the substrate. delete The method according to claim 1, And the silicon (Si) precursor is a halogen compound of silicon (Si). The method according to claim 3, The silicon precursor is any 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 . The method according to claim 4, The pressure of the reaction tube for reacting the silicon precursor is a method of atomic layer deposition of a silicon thin film, characterized in that the range of 10 mTorr ~ 10 Torr. The method according to claim 4, The silicon precursor is supplied to the inside of the reaction tube for a range between 1 second to 10 minutes. The method according to claim 1, A method of depositing an atomic layer of a silicon thin film, characterized in that hydrogen (H 2) or deuterium (D 2) is used as a gas for forming the reducing plasma. The method according to claim 7, The reducing plasma source is capacitively-coupled plasma (CCP), inductively-coupled plasma (ICP), microwave plasma, microwave plasma (ECR plasma), and electron cyclotron plasma (HEL). A method of depositing an atomic layer of a silicon thin film, using any one of a helicon plasma. The method according to claim 8, wherein when using the inductively coupled plasma, The plasma power is maintained in the range of 100 W to 20 kW, the pressure is maintained in the range of 5 mTorr to 5 Torr, and the flow rate of the gas for forming the reducing plasma is maintained in the range of 100 Sccm to 50 Slpm. An atomic layer deposition method of a silicon thin film, characterized in that. The method according to claim 1, The purge is an atomic layer deposition method of a silicon thin film, characterized in that using an inert gas or hydrogen (H ₂ ) gas. The method according to claim 1, The temperature of the substrate is the atomic layer deposition method of the silicon thin film, characterized in that it maintains the range between 300 ~ 500 ℃. The method according to claim 11, The heating of the substrate is an atomic layer deposition method of a silicon thin film, characterized in that using any one of resistance heating method, induction heating method and lamp heating method.

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