KR20090089963A - Silicon film formation method - Google Patents

Abstract

The present invention provides a method for stabilizing not only the surface of the silicon film but also the incomplete bonding therein at the same time as the silicon film is formed. The silicon film forming method according to the invention during the depositing the amorphous or crystalline silicon (CN) ^- ions not only by providing a silicon film surface from the inside of the silicon film is stabilized through a Si-CN bond.

Description

Silicon film formation method {Fabrication method of silicon layer}

The present invention relates to a method for forming a silicon film, and more particularly, to a method capable of stabilizing simultaneously with the formation of a silicon film.

Amorphous or polycrystalline silicon can be used for pn junction diodes and transistors, as well as for LCDs, solar cells, organic LEDs, radio-frequency identification tags, and x-ray detectors that utilize or serve as base elements. ), Color detectors, ultra-violet light detectors, infrared detectors, thin-film position sensitive detectors in the form of 1D / 2D / 3D It is a widely used material. By the way, amorphous or polycrystalline silicon contains many defects on its own. This is caused by the presence of an atomically incomplete bond, unlike single crystal silicon.

Defects present in amorphous or polycrystalline silicon include weak bonds and dangling bonds, and these defects are trap sites or recombination centers in the bandgap. It acts as a cause of deteriorating the characteristics of the manufactured device. In order to stabilize such a defect, conventionally, the hydrogen bond is formed from the silicon dangling bond by performing hydrogen heat treatment at the temperature of 300-500 degreeC (so-called hydrogenated amorphous-Si, hereinafter a-Si: H). However, since the binding energy of the Si-H bond is about 3.6 eV, the bond is broken when exposed to light or subjected to heat treatment of 600 ° C. or higher, thereby deteriorating characteristics. For example, as is well known in thin-film solar cells made of silicon, the exposure to light results in the deterioration of the characteristics (Staebler-Wronski Effect), which increases the Si-H bonds that are exposed to light and break with increasing use time. As a result, the photoelectric conversion efficiency is reduced by 15 to 35%.

In addition, a method of stabilizing defects through cyanide (CN) pretreatment in addition to hydrogen heat treatment is known. Cyanide forms Si-CN bonds from silicon dangling bonds, which are more stable since Si-CN bond energy is 1 eV or more higher than Si-H bonds at about 4.6 eV. However, the conventional method of forming a Si-CN bond is to deposit silicon on a substrate, and then dip it into a KCN or HCN solution, and the deposition and stabilization of the silicon film are performed in a separate process. Because it is a surface treatment technology that stabilizes only, there is a disadvantage that it can be applied only to metal-oxide-semiconductor (MOS) devices in which device characteristics depend on interface characteristics.

The thin film solar cell made of silicon has a pin structure in which an intrinsic a-Si: H light absorption layer containing no impurities is inserted between p-type a-Si: H and n-type a-Si: H having high doping concentration. Will have In an ideal device, an electric field is generated uniformly inside, and drift of an electron-hole pair is smoothly generated. In real devices, however, defects in intrinsic silicon increase the space charge density at the p-type and n-type silicon interfaces and decrease the electric field in the intrinsic silicon. This phenomenon, after prolonged exposure to light, increases the dangling bond density inside the silicon and decreases the internal electric field, further accelerating the recombination of electron-hole pairs generated by light, leading to deterioration of solar cell characteristics. As a result, the short lifespan of the solar cell is largely caused by defects in the silicon, and thus there is a problem that the conventional cyanide pretreatment that stabilizes only the surface cannot be improved.

The problem to be solved by the present invention is to provide a method for stabilizing the inside of the silicon film in the deposition of amorphous or crystalline silicon to form a silicon film.

The silicon film forming method according to the invention in order to solve the above problems while depositing an amorphous or crystalline silicon (CN) ^- provided the ion to stabilize the defects with Si-CN bond from the inside of the silicon film, as well as the silicon film surface Promote.

While depositing an amorphous or polycrystalline silicon according to the present invention (CN) ^- in order to provide ion, KCN, HCN, or (CN) and a _second gas the silicon source in the deposition of silicon using a method such as CVD or ALD are independent inlet It may be put into the deposition chamber through, or these gases are passed through the plasma generating apparatus to form a more highly reactive plasma form into the deposition chamber.

According to the present invention, not only the surface of the silicon film but also the inside of the silicon film can achieve stabilization of defects through Si-CN bonding. Therefore, not only a device having an important interfacial property but also a device having important properties such as a solar cell, a color detector, a thin film position sensor, or the like, may be improved. The solar cell, can prevent the deterioration of the characteristics over time.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in many different forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Accordingly, the shape of the elements in the drawings and the like are exaggerated to emphasize a clearer description.

1 is a schematic diagram of a thin film deposition apparatus suitable for carrying out the method of forming a silicon film according to the present invention.

Referring to FIG. 1, the thin film deposition apparatus 1 is made of quartz, metal, or the like, and has a deposition chamber 2 having an internal space, and is installed to be elevated in an internal space of the deposition chamber 2 and has a substrate 10. ) And a shower head for injecting a source of silicon and a reaction gas into the deposition chamber 2 so that a thin film is formed on the substrate block 3 to heat the substrate block 3 and the substrate 10 disposed on the substrate block 3. (4) is provided. The gas supply unit 7 supplies a gas or purge gas for adjusting the pressure in the deposition chamber 2.

The thin film deposition apparatus 1 is for depositing silicon on a substrate 10 such as a silicon wafer for semiconductor, a glass substrate for LCD, or a metal substrate, and the like to the deposition chamber 2 through the gas lines 5a and 5b. Also included are gas supply devices 6a, 6b for supplying a silicon source and a reaction gas. In this embodiment, an example of using one silicon source and one reaction gas is given. If necessary, other types of silicon sources may be further supplied. In the case of using two or more kinds of silicon sources, a configuration may be pre-mixed and supplied to the showerhead or may be separately supplied.

The thin film deposition apparatus 1 may also supply KCN, HCN or (CN) ₂ gas through an inlet 8 independent of the silicon source to provide (CN) ⁻ ions to the deposition chamber 2. The gas line 5c and the gas supply device 6c are also provided so that 2) can be put in.

Referring to the method of forming a silicon film according to the present invention using the thin film deposition apparatus 1 as follows.

First, the substrate 10 is loaded onto the substrate block 3 of the thin film deposition apparatus 1, and then the silicon source and the reaction gas are supplied through the gas supply devices 6a and 6b and the gas lines 5a and 5b. By supplying it to the deposition chamber 2 to deposit silicon on the substrate 10. At this time, the silicon source may be SiH ₄ , the reaction gas may be H ₂ . Silicon is deposited amorphous or crystalline depending on other process variables such as deposition temperature. The silicon source and the reactant gas may be transported and supplied by a carrier gas such as Ar. The carrier gas may be made of N ₂ or He, or a combination thereof in addition to Ar. The deposition method of silicon in the present invention may be CVD or ALD, according to the specifications of the apparatus plasma-enhanced chemical vapor deposition (PECVD), remote plasma CVD (RPCVD), high density PECVD (HD-PECVD), ECR Can be implemented by CVD, plasma enhanced atomic layer deposition (PEALD), and the like. Meanwhile, a method of depositing silicon through pyrolysis by supplying only a silicon source without a reaction gas is also possible. Hydrogen, the reaction gas supplied in this embodiment, not only breaks the bond of the silicon source, but also serves to stabilize the defect through the Si-H bond.

In particular, during the deposition of silicon on the substrate 10 in the deposition chamber 2 in accordance with the present invention, in order to provide (CN) ⁻ ions to form Si—CN bonds not only on the surface of the silicon film but also inside, the substrate 10 It provides an ^ion-over (CN) during the deposition of silicon. To this end, KCN, HCN or (CN) ₂ gas is introduced into the deposition chamber 2 through an injection hole 8 independent of the silicon source. At this time, a method such as nitrogen bubbling may be used. (CN) ^- provided the ion may be formed in sequence and the time difference between two or done at the same time as the supply of the silicon source.

On the other hand, in order to put KCN, HCN or (CN) ₂ gas into the deposition chamber 2 in a more reactive state, the thin film deposition apparatus 1 'as shown in FIG. 2 can be used. This apparatus 1 'is similar to the thin film deposition apparatus 1 of FIG. 1, with the addition of a plasma generating apparatus 20 on the gas line 5c. With this device 1 ', KCN, HCN or (CN) ₂ gas passes through the plasma generating device 20 to form a more reactive plasma and then is supplied to the deposition chamber 20, thereby depositing and stabilizing silicon. The reaction can be further activated.

According to the invention, during the deposition of silicon (CN) ^-, because it provides the ions are deposited on the silicon substrate as well as a silicon film forming surface from the inside is possible to form a Si-CN bond. Thus, not only the silicon film surface but also the weak bonds, recombination centers, etc. present in the silicon film can be removed. Si-CN bonds do not completely replace Si-H bonds, but form Si-H bonds and Si-CN bonds. In addition, since the Si-CN bond is "defect passivation" by a higher bonding force than the conventional method using hydrogen, it is possible to improve the characteristics, reliability, device stability, etc. of the device fabricated based on amorphous or crystalline silicon Will be.

If the conventional cyanide pretreatment method is a method in which silicon is deposited on a substrate and then deposited in a KCN or HCN solution, a process separate from the deposition of silicon, the present invention provides Si-H in a Si bond network during the deposition of silicon. In this case, the Si-CN bond is partially added, so the method is completely in-situ. In addition, since the conventional pretreatment method is a surface treatment technology that stabilizes only the surface portion of the silicon film, there is a disadvantage that the present invention can be applied only to MOS devices whose device characteristics are influenced by the interfacial properties. It does not have this disadvantage because it forms a Si-CN bond. Therefore, it can be applied to the element which a characteristic fall generate | occur | produces with defects in silicon like a thin film type | mold solar cell using a p-i-n structure, and can lengthen the lifetime.

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications are possible by those skilled in the art within the technical idea of the present invention. Is obvious. Embodiments of the present invention have been considered in all respects as illustrative and not restrictive, including the scope of the invention as indicated by the appended claims rather than the detailed description therein, the equivalents of the claims and all modifications within the means. I want to.

1 is a schematic diagram of a thin film deposition apparatus suitable for carrying out the method of forming a silicon film according to the present invention.

2 is a schematic view of another thin film deposition apparatus suitable for carrying out the method of forming a silicon film according to the present invention.

<Explanation of symbols for the main parts of the drawings>

1, 1 '... thin film deposition apparatus 2 ... deposition chamber

3 ... substrate block 4 ... shower head

5a, 5b, 5c ... gas line 6a, 6b, 6c ... gas supply

7.Gas supply part 8 ... Inlet

10 ... substrate 20 ... plasma generator

Claims (3)

While depositing silicon on a substrate in the deposition chamber (CN) ^- by providing the ions, the silicon film surface as well as the silicon film forming method which comprises forming a Si-CN bond from the inside. The method of claim 1, wherein KCN, HCN, or (CN) ₂ gas is introduced into the deposition chamber through an injection hole independent of a silicon source to provide the (CN) ⁻ ions. 2. The method of claim 1, wherein KCN, HCN, or (CN) ₂ gas is passed through a plasma generating device into the deposition chamber to provide the (CN) ⁻ ions.

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