JPH05346586A - Ito film and its production - Google Patents

Abstract

PURPOSE:To obtain an equal conductivity to conventional manner by dissolving tin in a solid soln. state with a periodically specific concn. into an In2Ox layer and thereby forming an indium oxide layer on a substrate. CONSTITUTION:This device consists of a vacuum chamber 11 evacuated by an evacuating system 9, a polygonal rotation substrate holder 1 which can be heated, several substrates 2 mounted on the holder 1, and plural number of In target 2 and Sn target 4 disposed on the inner wall of the chamber surrounding the rotating substrates 2. An indium oxide layer is formed on the substrate 2 in a manner that tin is dissolved with a periodically specific concn. in an In2Ox layer. Thereby, tin oxide SnOy is diffused in the indium oxide In2Ix to form an ITO film in which the tin concn. is periodically varied from high concn. area to low concn. area. In this process, Sn<4+> ion becomes donor by substituting it for In<3+> lattice atom to generate free electrons at high concn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ITO (Indium T) used for display panels, solar cells and the like.
in Oxide) film and its manufacturing method.

[0002]

2. Description of the Related Art An ITO film is a chemical vapor deposition (CVD) method,
The film is formed using a vacuum deposition method, a sputtering method, or the like.
Among them, I prepared by the dc magnetron sputtering method using an In ₂ O ₃ —SnO ₂ target I
The TO film is widely used because of its good controllability and reproducibility. The conductivity of the ITO film depends on the donor that is an oxygen vacancy generated when the stoichiometric composition of the In ₂ O ₃ crystal shifts and the donor when the Sn ⁴⁺ ion, which is a dopant, replaces the In ³⁺ lattice atom. .. The conductivity of the ITO film is achieved by heating the substrate during film formation to enhance crystallinity and mobility. The Sn / In ratio is about 10%, the typical carrier mobility is 30 cm ² / Vs, the carrier density is 10 ²⁰ to 10 ²¹ cm ^-3 , and the specific resistance is 1 to 2 × 10 ^-4 Ω.・
cm.

[0003]

However, in the conventional method for manufacturing an ITO film as described above, the substrate temperature is raised to 300 to 400 ° C. to enhance the crystallinity and lower the specific resistance, but at the same time the surface morphology has irregularities. There is a problem in that the film becomes large and the smoothness of the film surface is reduced, the stability and reliability of the device are impaired, and electrode processing is difficult in device manufacturing.

Further, the ITO film has low stability against environmental changes, and oxidation progresses to a high resistance in a high temperature atmosphere in which oxygen exists, and when heated in a vacuum, oxygen deficiency progresses to blacken the film. There was also a problem. Also, SnO ₂ (nesa film), which was once the mainstream, is low in cost and has better environment resistance than the ITO film, but pinholes are generated on the surface of the film formed by the spray method. In addition, there is a problem that the electric resistance is higher than that of the ITO film, and it is difficult to chemically etch the electrode during processing.

The present invention has been made in view of the above-mentioned points, and an object thereof is to improve the manufacturing method and structure of the ITO film so that the electric resistance is similar to that of the conventional ITO film and the surface morphology is smooth. A membrane and a method for manufacturing the membrane are provided.

[0006]

According to the first aspect of the present invention, there is provided an indium oxide layer on a substrate, the indium oxide layer being a layer made of In ₂ Ox and containing tin at a predetermined periodic concentration. According to the second invention, both of the first step and the second step are alternately repeated, and the first step is an atmosphere containing an In-based target containing oxygen gas. The second step is a step of sputtering in a gas to form a film on a substrate having a predetermined temperature. The second step is a step of sputtering an Sn-based target in an atmosphere gas containing oxygen gas to form a film on a substrate having a predetermined temperature. Is achieved.

[0007]

[Function] The first step and the second step are repeated at a predetermined substrate temperature.
When returned, indium oxide In ₂Tin oxide Sn in Ox
Oy diffuses and the low concentration from the high concentration region in the indium oxide layer
ITO film whose tin concentration changes periodically over the concentration region
Is obtained. The obtained ITO film is crystalline. this
When Sn⁴⁺Ion is In³⁺Substitute with a lattice atom to serve as a donor
Free electrons are generated at high concentration. Mobility of the generated electron
It is estimated that the degree does not change much.

Indium oxide I on tin oxide SnOy
When n ₂ Ox is grown, a crystal plane that gives a smooth crystal surface grows.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a layout view showing a carousel type sputtering apparatus used in manufacturing an ITO film according to an embodiment of the present invention. In this apparatus, a plurality of substrates 2 are mounted on a heatable polygonal rotary substrate holder 1 provided in a vacuum chamber 11 evacuated by an exhaust system 9, and a plurality of substrates 2 are mounted on an inner wall of a chamber surrounding the rotary substrate 2. In-based target 3 and Sn-based target 4 are arranged. The number of substrates and the number of targets can be increased as much as the device allows.

Ar gas is used as the sputtering gas, oxygen gas is used as the reaction gas, and a slight amount of hydrogen gas is added using the gas system 5. Direct current (d
c) can be done using a power supply 7 or a high frequency (rf) power supply 6, dc magnetron sputtering or rf
A film is formed on a rotating substrate by magnetron sputtering.

The substrate is heated to a predetermined temperature by using the heater 10. Example 1 In metal and Sn metal were used as targets. In ₂ Ox and SnOy were alternately laminated by dc magnetron sputtering at a total gas pressure of 0.5 Pa. The total film thickness is 150 nm and the substrate temperature is 300 ° C.

The alternately laminated In ₂ Ox and SnOy are mutually diffused to obtain an ITO film in which SnOy is dissolved in the In ₂ Ox crystal. SnOy does not form a solid solution uniformly, and high concentration regions and low concentration regions of Sn ⁴⁺ appear periodically. Sn ⁴⁺ ions replace In ³⁺ lattice atoms to become electron donors. FIG. 2 shows I according to an embodiment of the present invention.
It is a diagram which shows the film thickness ratio dependence of the light transmittance by making oxygen partial pressure into a parameter about TO film. Thickness ratio (In ₂ Ox / S
nOy) is a set value at the time of manufacturing the ITO film. The oxygen partial pressure is set to a magnitude of A <B <C.

FIG. 3 is a diagram showing the film thickness ratio dependence of the electrical resistance of the ITO film according to the embodiment of the present invention with the oxygen partial pressure as a parameter. It is almost transparent at a film thickness ratio of 5 to 50 for any oxygen partial pressure, and is 10 to 2
It can be seen that about 0 has the smallest specific resistance. Under the condition of A where the oxygen partial pressure is small, the amount of black InO is large and the light transmittance of the film is low. Further, in C having a large oxygen partial pressure, the generation of oxygen vacancies is suppressed, the carrier density is lowered, and the specific resistance is increased. The minimum value of the specific resistance was at the same level as the conventional one, and a value of 1.6 × 10 ⁻⁴ Ω · cm was obtained.
When heated in air, the transparency increased slightly but the specific resistance decreased. It is considered that this is due to a microscopic change in crystal due to heating. There is little deterioration of the film due to environmental changes.

When the surface of the film was observed with a scanning electron microscope, it was found that there was almost no unevenness and the surface smoothness was excellent. The conventional chemical etching characteristics ((40
0) orientation). Example 2 An In ₂ O ₃ sintered body and Sn metal were used as targets. In ₂ Ox and SnOy were alternately laminated by dc magnetron sputtering at a total gas pressure of 0.5 Pa. Overall film thickness is 150 nm, substrate temperature is 300 ° C
Is. The power was adjusted so that the film formation rate was 30 / min. The film thickness ratio (In ₂ Ox / SnOy) was determined by obtaining the element ratio of In and Sn by optical emission spectroscopy.

Since the In ₂ O ₃ sintered body is used as the target, the oxygen gas as the reaction gas is kept lower than in the case of Example 1. When the oxygen concentration is high, oxygen vacancies decrease, the carrier density of the ITO film decreases, and the electric resistance increases. FIG. 4 is a diagram showing the film thickness ratio dependence of the specific resistance of ITO films according to different embodiments of the present invention. The resistivity becomes the smallest when the film thickness ratio is about 10 to 20. The specific resistance value was 1.5 × 10 ⁻⁴ Ω · cm. When the film thickness ratio becomes small, blackening occurs due to an increase in Sn metal, and the specific resistance increases significantly.

Light transmittance, surface smoothness, etching characteristics,
The environmental stability and the like were almost the same as those in Example 1. Example 3 An In ₂ O ₃ sintered body and a SnOx sintered body were used as targets. In ₂ Ox and SnOy were alternately laminated by dc magnetron sputtering at a total gas pressure of 0.5 Pa. Total film thickness is 150 nm, substrate temperature is 30
It is 0 ° C. The power was adjusted so that the film formation rate was 30 / min. The film thickness ratio (In ₂ Ox / SnOy) was determined by obtaining the element ratio of In and Sn by optical emission spectroscopy.

The oxygen concentration was adjusted so that the specific resistance of the ITO film was minimized. The same applies to the substrate temperature. FIG. 5 is a diagram showing the film thickness dependence of the specific resistance of ITO films according to further different embodiments of the present invention. Minimum specific resistance is 1.3
It was × 10 ^-4 . The light transmittance, surface smoothness, etching characteristics, environmental stability, etc. were almost the same as in Example 1.

[0018]

According to the first aspect of the present invention, the indium oxide layer is provided on the substrate, and the indium oxide layer is a layer of In ₂ Ox, and tin is solid-dissolved at a predetermined periodic concentration. Sn ⁴⁺ ions substitute for In ³⁺ lattice atoms to serve as donors to generate free electrons at a high concentration and to generate conductivity equivalent to that of a conventional ITO film in which tin is uniformly dissolved.

According to the second invention, the first step,
The two steps of the second step are alternately repeated, and the first step is I
This is a step of sputtering an n-type target in an atmosphere gas containing oxygen gas to form a film on a substrate at a predetermined temperature. The second step is sputtering an Sn-type target in an atmosphere gas containing oxygen gas. Since this is a process of forming a film on a substrate at a predetermined temperature, indium oxide In is formed on tin oxide SnOy.
_{As 2} Ox grows, a crystal plane that gives a smooth crystal surface grows, and there is no unevenness in terms of surface morphology.
A TO film is obtained.

[Brief description of drawings]

FIG. 1 is a layout view showing a carousel-type sputtering apparatus for manufacturing an ITO film according to an embodiment of the present invention.

FIG. 2 is a diagram showing the film thickness ratio dependency of light transmittance with the oxygen partial pressure as a parameter for the ITO film according to the example of the present invention.

FIG. 3 is a diagram showing the film thickness ratio dependence of the specific resistance with the oxygen partial pressure as a parameter for the ITO film according to the example of the present invention.

FIG. 4 is a diagram showing the film thickness ratio dependence of the specific resistance of ITO films according to different embodiments of the present invention.

FIG. 5 is a diagram showing the film thickness dependence of the specific resistance of ITO films according to further different embodiments of the present invention.

[Explanation of symbols]

 1 rotating substrate holder 2 substrate 3 In-based target 4 Sn-based target 5 gas system 6 rf power supply 7 dc power supply 8 magnet 9 exhaust system 10 heater 11 bell jar

Claims (4)

[Claims] 1. An ITO having an indium oxide layer on a substrate, the indium oxide layer being a layer made of In ₂ Ox, in which tin is solid-dissolved at a predetermined periodic concentration.
film. 2. The ITO film according to claim 1, wherein In /
An ITO film having an average atomic ratio of Sn in a concentration range of 1 to 50. 3. The first step and the second step are alternately repeated, and the first step is to sputter an In-based target in an atmosphere gas containing oxygen gas onto a substrate having a predetermined temperature. The second step is a step of forming a film, and the second step is a step of forming an Sn-based target in a gas atmosphere containing oxygen gas by sputtering to form a film on a substrate at a predetermined temperature. .. 4. The method of manufacturing an ITO film according to claim 3, wherein the In-based target is In ₂ O ₃ or In metal, and the Sn-based target is In ₂ Ox-SnOy mixed sintered body or Sn metal. A method for producing an ITO film, characterized by being present.