JPH0645892B2 - Deposited film formation method - Google Patents

Description

The present invention relates to a functional film, in particular, an electronic device such as a semiconductor device, a photosensitive device for electrophotography, an optical input sensor device for an optical image input device, and the like. The present invention relates to a method for forming a functional deposited film useful for an application.

[Conventional technology]

Conventionally, an amorphous or polycrystalline functional film such as a semiconductor film, an insulating film, a photoconductive film, a magnetic film, or a metal film is individually formed from the viewpoint of desired physical characteristics or intended use. The method has been adopted.

For example, amorphous or polycrystalline non-single-crystal silicon (hereinafter referred to as "NON-Si (H)" in which unpaired electrons are compensated with a compensating agent such as a hydrogen atom (H) or a halogen atom (X), if necessary. ，
X) ”, and in particular,“ A—Si (H, X) ”indicates amorphous silicon, and“ poly-Si (H, X) ”indicates polycrystalline silicon. A silicon deposited film such as a film (the so-called microcrystalline silicon is
It is needless to say that it falls within the category of A-Si (H, X)) for forming a vacuum vapor deposition method, a plasma CVD method, a thermal CVD method, a reaction sputtering method, an ion plating method, a photo CVD method. Have been tried, and in general,
The plasma CVD method is widely used and commercialized.

[Problems to be solved by the invention]

However, the reaction process for forming a silicon deposited film by the plasma CVD method, which has been generalized in the past, is considerably complicated as compared with the conventional CVD method, and the reaction mechanism has few unclear points. Absent. In addition, there are many formation parameters of the deposited film (for example, substrate temperature, introduced gas flow rate and ratio, formation pressure, high frequency power, electrode structure, reaction vessel structure, exhaust speed, plasma generation method, etc.). Due to the combination of many parameters, the plasma was sometimes in an unstable state and had a significant adverse effect on the formed deposited film. In addition, it is difficult to generalize the manufacturing conditions because it is necessary to select a device-specific parameter for each device.

On the other hand, in order to develop a silicon deposited film that can sufficiently satisfy electrical and optical characteristics for each application, it is currently best formed by the plasma CVD method.

However, depending on the application of the silicon deposited film, it is necessary to achieve a large area, film thickness uniformity, and film quality uniformity for mass production with reproducibility.
In forming a silicon deposited film by the D method, a large amount of capital investment is required for a mass production device, the management items for the mass production are complicated, the control allowance is narrow, and the adjustment of the device is delicate. However, these are pointed out as problems to be improved in the future.

Further, in the case of the plasma CVD method, plasma is directly generated by high frequency or microwave in the film forming space in which the substrate to be formed is arranged, so that electrons and a large number of ion species are generated. Causes damage to the film during the film formation process, which causes deterioration of film quality and nonuniformity of film quality.

A method proposed as an improvement on this point is an indirect plasma CVD method.

In the indirect plasma CVD method, plasma is generated by microwaves or the like at an upstream position away from the film formation space, and the plasma is transported to the film formation space to selectively use chemical species effective for film formation. It is measured so that it can be done.

However, even in such a plasma CVD method, the transport of plasma is indispensable, so that the lifetime of the chemical species effective for film formation must be long, and naturally, the gas species used are limited, and various kinds of deposition are deposited. There are problems such as not being able to obtain a film, requiring a large amount of energy to generate plasma, and being essentially unable to control the generation and amount of chemical species effective for film formation under simple control. I have left over.

In contrast to the plasma CVD method, the photo CVD method is advantageous in that it does not generate ion species or electrons that damage the film quality and film quality, but there are not so many types of light sources, and the wavelength of the light source is large. Is also deviated to the ultraviolet, a large light source and its power source are required for industrialization, and the window for introducing the light from the light source into the film formation space is coated during film formation. There is a problem that the light from the light source is not incident on the film formation space.

As described above, there are still points to be solved in the formation of the silicon deposited film, and while maintaining the practicable characteristics and uniformity, it is possible to mass-produce by saving energy with a low-cost device. It is eagerly desired to develop a forming method capable of forming. These can be mentioned as similar problems to be solved in other functional film formations such as a silicon nitride film, a silicon carbide film and a silicon oxide film.

〔Purpose〕

An object of the present invention is to provide a novel deposited film forming method which does not rely on the conventional forming method while removing the second point of the deposited film forming method described above.

Another object of the present invention is to provide a deposited film forming method which can save energy and can easily control the film quality and can obtain a deposited film having uniform characteristics over a large area.

Still another object of the present invention is to provide a deposited film forming method which is excellent in productivity and mass productivity, and which can easily obtain a film having high quality and excellent physical properties such as electrical, optical and semiconductor properties. is there.

[Means for solving problems]

The method for forming a deposited film of the present invention to achieve the above object is a gaseous raw material containing at least silicon atoms and hydrogen atoms for forming a deposited film, and a gaseous halogen having a property of oxidizing the raw material. By introducing a system oxidant into the reaction space and bringing them into contact with each other, a plurality of precursors including a plurality of precursors including excited state precursors are generated with light emission, and at least one of these precursors is generated. In a deposited film forming method for forming a deposited film on a substrate in a film formation space by using one precursor as a supply source of a deposited film constituent, light emission by Si-H and light emission by Si-X (X: halogen atom) Is characterized by setting the intensity ratio ([Si-H] / [Si-X]) of 1 or less.

[Action]

According to the above-described deposited film forming method of the present invention, energy saving as well as large area, film thickness uniformity, and film quality uniformity are sufficiently satisfied to simplify management and mass production, and to be used in a mass production apparatus. It does not require a large capital investment, the management items for its mass production are clarified, the management allowance range is wide, and the adjustment of the device is easy.

In the deposited film forming method of the present invention, the gaseous raw material used for forming the deposited film contains at least silicon atoms and hydrogen atoms, and further has an oxidizing action by contact with a gaseous halogen-based oxidizing agent. Light emission of Si-H and Si-X (X:
It emits light of a halogen atom), and is appropriately selected according to the desired type, characteristics, intended use, etc. of the deposited film. In the present invention, the above-mentioned gaseous raw material and the substrate-like halogen-based oxidant may be those that are made gaseous at the time of chemical contact, and in the usual case, they are gas, liquid or solid. But it doesn't matter.

When the raw material for forming the deposited film or the halogen-based oxidant is a liquid or a solid, a carrier gas such as Ar, He, N ₂ or H ₂ is used, and bubbling is performed while adding heat as necessary. As a result, the raw material for forming the deposited film and the halogen-based oxidizing agent are introduced into the reaction space in a gaseous state.

At this time, the partial pressure and mixing ratio of the gaseous raw material and the gaseous halogen-based oxidant are adjusted by adjusting the flow rate of the carrier gas or the vapor pressure of the raw material for forming the deposited film and the gaseous halogen-based oxidant. Is set.

Examples of the raw material for forming a deposited film used in the present invention include linear and branched chain silane compounds if a semiconductor or electrically insulating silicon deposited film is obtained. Cyclic silane compounds and the like can be mentioned as effective ones.

Specifically, SinH is used as the linear silane compound.
_{2n + 2} (n = 1,2,3,4,5,6,7,8), as the branched chain silane compound, SiH ₃ SiH (Si
H _{3) SiH} 2 _{SiH 3} and the like.

Of course, these raw material substances may be used alone or in combination of two or more.

The halogen-based oxidant used in the present invention is gasified when introduced into the reaction space, and at the same time, only by chemical contact with a gaseous raw material for forming a deposited film which is introduced into the reaction space. It has the property of effectively oxidizing,
Examples of the halogen gas include F ₂ , Fcl, Cl ₂ , Br ₂ , and I ₂ .

These halogen-based oxidants are gaseous, and are introduced into the reaction space at a desired flow rate and supply pressure together with the gas of the raw material for forming the deposited film, and are mixed and collided with the raw material. The raw materials are brought into contact with each other to oxidize, and effectively generate a plurality of kinds of precursors including excited precursors. The excited state precursors and other precursors that are produced serve as a source of constituents of the deposited film, at least one of which is formed.

The produced precursor decomposes or reacts to become a precursor in another excited state or a precursor in another excited state, or releases energy as needed but is formed in its original form. A deposited film having a three-dimensional network structure is created by touching the surface of the substrate arranged in the film space.

The excited energy level is preferably an energy level accompanied by light emission in the process of energy transition of the precursor in the excited state to a lower energy level or change to another chemical species. The deposited film forming process of the present invention proceeds more efficiently and more energy saving by forming an activated precursor including a precursor in an excited state accompanied by light emission in such energy transition.
A deposited film having uniform and better physical properties is formed over the entire surface of the film.

When forming a deposited film by contacting a gaseous source material (containing at least silicon atoms and hydrogen atoms) for forming a deposited film with a gaseous halogen-based oxidizing agent having a property of oxidizing the gaseous source material For example, taking the reaction of SiH ₄ and F ₂ as an example, it is known that the oxidation reaction of SiH ₄ by F ₂ includes the following processes.

SiH ₂ + F → SiH * + HF (1) SiH + F ₂ → SiF * + HF (2) Si + F ₂ → SiF * + F (3) (* indicates emission species) Thus, the oxidation of SiH ₄ by F ₂ is F Si by ₂
Extraction of hydrogen from H _{4 is} followed by an exchange reaction of SiH with fluorine.

SiH ₄ and _{F 2} and the reaction proceeds in order to SiH ₄ is not deposited is when SiF ₄ is oxidized to SiF _4, it can not be obtained deposited film.

Therefore, it is important to control the progress of the oxidation reaction.

In the present invention, SiH and SiX (x:
As a result of repeated intensive studies focusing on the fact that halogen atoms) emit light, it was found that the emission ratio of SiH and SiX has an important influence on the characteristics and reproducibility of the deposited film.

In order to obtain a deposited film with good characteristics with good reproducibility, the emission ratio of SiH and the emission ratio of SiX ([SiH] / [SiX]) are preferably 1 or less, more preferably 0.8 or less, and most preferably. It is desirable to set it to 0.5 or less.

In the present invention, the deposited film forming process proceeds smoothly, a film having high quality and desired physical properties can be formed, and as a film forming factor, in combination with the kinds of the raw material and the halogen-based oxidizing agent, The mixing ratio, the pressure during mixing, the flow rate, the film forming space internal pressure, the gas flow pattern, and the film forming temperature (the substrate temperature and the ambient temperature) are appropriately selected as desired. These film forming factors are organically related, and are not determined individually but are determined according to each other under mutual relation. In the present invention, the ratio of the amounts of the gaseous raw material substance for forming a deposited film and the gaseous halogen-based oxidant introduced into the reaction space is related to the film forming factors related to the above film forming factors. However, the flow rate of introduction is preferably 1
/ 100 to 100/1 is suitable, and more preferably 1
/ 50 to 50/1 is desirable.

The pressure at the time of mixing when introduced into the reaction space is preferably higher in order to stochastically enhance the chemical contact between the gaseous raw material and the gaseous halogen-based oxidant, but the reactivity is higher. Considering the above, it is preferable to appropriately determine the optimum value as desired. The pressure at the time of mixing is determined as described above, but the pressure at each introduction is preferably 1 × 10 ⁻⁷ atm to 10 atm, more preferably 1 × 10 ⁷ atm.
^It is desirable that the pressure is ^-6 atm to 3 atm.

The pressure in the film-forming space, that is, the pressure in the space where the substrate on which the film is to be formed is disposed, is the precursor (E) in the excited state generated in the reaction space and the precursor in some cases. The precursor (D) derived from the body (E) is appropriately set as desired so as to effectively contribute to film formation.

The internal pressure of the film formation space is such that when the film formation space is open and continuous with the reaction space, the introduction and introduction of the substrate-like raw material for forming the deposited film and the gaseous halogen-based oxidant into the reaction space are performed. In relation to the flow rate, it can be adjusted by adding a device such as a differential exhaust or using a large exhaust device.

Alternatively, when the conductance of the connecting portion between the reaction space and the film formation space is small, an appropriate exhaust device is provided in the film formation space,
The pressure in the film forming space can be adjusted by controlling the exhaust amount of the apparatus. Further, when the reaction space and the film formation space are integrated and the reaction position and the film formation position are spatially different from each other, differential evacuation is performed as before, or a large size with sufficient evacuation capacity. It suffices if an exhaust device is provided.

As described above, the pressure in the film formation space is determined by the relationship between the gaseous raw material introduced into the reaction space and the introduction pressure of the gaseous halogen-based oxidant, but preferably 0.001
Torr to 100 Torr, more preferably 0.01 Torr
It is desirable that it is r to 30 Torr, optimally 0.05 to 10 Torr.

Regarding the gas flow type, when the raw material for forming the deposited film and the halogen-based oxidant are introduced into the reaction space, these are uniformly and efficiently mixed, and the precursor (E) is efficiently mixed. It is necessary to design in consideration of the geometrical arrangement of the gas inlet, the substrate and the gas outlet so that the film can be properly formed and the film can be properly formed. One suitable example of this geometric arrangement is shown in FIG.

The substrate temperature (Ts) at the time of film formation is individually set as desired according to the gas species used, the number of species of the deposited film to be formed and the required characteristics. In order to obtain the above, it is preferable that the temperature is from room temperature to 450 ° C, more preferably 50 to 400 ° C. In particular, when forming a silicon deposited film having better semiconductor properties and photoconductivity, the substrate temperature (Ts) is preferably 70 to 350 ° C. Further, when a polycrystalline film is obtained, the temperature is preferably 200 to 650 ° C., more preferably 30.
It is desirable that the temperature be 0 to 600 ° C.

As the ambient temperature (Tat) of the film formation space, the generated precursor (E) and the precursor (D) do not change into chemical species unsuitable for film formation, and the precursor (E) is efficiently generated. ) Is appropriately determined as desired in relation to the substrate temperature (Ts).

The substrate used in the present invention may be either conductive or electrically insulating as long as it is appropriately selected according to the intended use of the deposited film to be formed. As the conductive substrate, for example, NiCr, stainless steel, Al, C
r, Mo, Au, Ir, Nb, Ta, V, Ti, Pt,
Examples include metals such as Pd and alloys thereof.

As the electrically insulating substrate, a film or sheet of synthetic resin such as polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene and polyamide, glass, ceramics, paper and the like are usually used. It is preferable that at least one surface of these electrically insulating substrates is subjected to a conductive treatment, and another layer is provided on the surface subjected to the conductive treatment.

For example, in the case of glass, the surface is NiCr, Al, C
r, Mo, Au, Ir, Nb, Ta, V, Yi, Pt,
_{Pd, In 2 O 3, SnO} 2, ITO (In 2 O 3 + S
nO ₂ ), a conductive film is provided by providing a thin film, or a synthetic resin film such as a polyester film is NiCr, Al, Ag, Pb, Zn, Ni, Au,
A metal such as Cr, Mo, Ir, Nb, Ta, V, Ti, Pt is vacuum-deposited, electron-beam-deposited, sputtered, or the like, or laminated with the metal, and the surface thereof is subjected to a conductive treatment. The shape of the support may be any shape such as a cylindrical shape, a belt shape and a plate shape, and the shape is determined as desired.

The substrate is preferably selected from the above in consideration of the adhesion and reactivity between the substrate and the film. Furthermore, if the difference in thermal expansion between the two is large, a large amount of strain may occur in the film, and a good quality film may not be obtained. Therefore, select and use a substrate with a close difference in thermal expansion between the two. Is preferred.

Further, since the surface condition of the substrate is directly related to the structure (orientation) of the film and the generation of the conical structure, it is necessary to treat the surface of the substrate so that the film structure and the film structure can obtain desired characteristics. Is desirable.

FIG. 1 shows an example of an apparatus suitable for embodying the deposited film forming method of the present invention.

The deposited film forming apparatus shown in FIG. 1 is roughly divided into three parts: an apparatus main body, an exhaust system and a gas supply system.

A reaction space and a film formation space are provided in the apparatus body.

101 to 108 are cylinders filled with gas used for film formation, 101a to 108a are gas supply pipes, 101b to 108b are mass flow controllers for adjusting gas flow rates from the cylinders, 101c.
To 108c are gas pressure gauges, 101d to 108d, respectively.
And 101e to 108e are valves, and 101f to 10e, respectively.
Reference numerals 8f are pressure gauges showing the pressures inside the corresponding gas cylinders.

Reference numeral 120 denotes a vacuum chamber having a structure in which a gas introducing pipe is provided in an upper portion thereof, and a reaction space is formed in the downstream of the pipe, and the substrate 1 faces the gas outlet of the pipe.
It has a structure in which a film formation space in which the base holder 112 is provided so that 18 is installed is formed. The gas introduction pipe has a triple concentric circle arrangement structure, and the first gas introduction pipe 109 into which the gas from the gas cylinders 101 and 102 is introduced and the second gas from the gas cylinders 103 to 105 are introduced from the inside. Gas introduction pipe 110 and gas cylinder 1
It has a third gas introduction pipe 111 into which the gas from 06 to 108 is introduced.

For the gas discharge to the reaction space of each gas introduction pipe, it is designed such that the inner pipe is located farther from the surface position of the substrate. That is, the respective gas introduction pipes are arranged so that the outer pipes surround the inner pipes.

The supply of gas from the pipe cylinders to the respective introduction pipes is performed by gas supply pipelines 123 to 125, respectively.

The gas introduction pipes, the gas supply pipelines, and the vacuum chamber 120 are vacuum-exhausted by a vacuum exhaust device (not shown) via the main vacuum valve 119.

The substrate 118 is installed at a desired distance from the position of each gas introduction pipe by moving the substrate holder 112 up and down.

In the case of the present invention, the distance between the substrate and the gas outlet of the gas introduction pipe is in an appropriate state in consideration of the type of the deposited film to be formed, its desired characteristics, the gas flow rate, the internal pressure of the vacuum chamber, etc. However, it is preferably several mm
20 cm, more preferably 5 mm to 15 cm is desirable.

Reference numeral 113 denotes a substrate heating heater that heats the substrate 118 to an appropriate temperature during film formation, preheats the substrate 118 before film formation, and further heats after film formation to anneal the film. is there.

The substrate heater 113 is connected to the power source 115 via the conductor 114.
Is supplied with electric power.

Reference numeral 116 is a thermocouple for measuring the temperature of the substrate temperature (Ts), which is electrically connected to the temperature display device 117.

The light emission due to the oxidation reaction between the raw material gas for forming the deposited film and the halogen-based oxidant is monitored by being dispersed by the emission spectroscope 127 through the window 126.

Hereinafter, the present invention will be specifically described with reference to Examples.

Example 1 Using the film forming apparatus shown in FIG. 1, a deposited film was formed by the method of the present invention under the conditions shown in Table 1 as follows.

The flow rate of the SiH ₄ gas filled in the cylinder 101 is 20
The F ₂ gas filled in the cylinder 106 is supplied through the gas introduction pipe 109 at a sccm of 10 sccm and the cylinder 107.
The H ₂ gas filled in was introduced into the vacuum chamber 102 through the gas introduction pipe 111 at a flow rate of 500 sccm.

At this time, the pressure in the vacuum chamber 120 was adjusted to 400 mTorr by adjusting the opening / closing degree of the vacuum valve 119. Quartz glass (15 cm × 15 cm) was used as the substrate, and the distance between the gas inlet 111 and the substrate was set to 3 cm. In this way, the ratio of Si—H emission to SiF emission was set to 0.1.

The substrate temperature (Ts) was set to 300 ° C.

When gas is flowed for 3 hours in this state, S with a film thickness of 2.0 μm
An i: H: F film was deposited on the substrate.

The unevenness of the film thickness distribution was within ± 5%. It was confirmed by electron beam diffraction that each of the formed Si: H: F films was amorphous.

Further, when the ESR of the formed Si: H: F film was measured, the spin density was −5 × 10 ¹⁶ 4 / cm ₃ , which was a localized level density sufficient for practical use.

Example 2 Using the film forming apparatus shown in FIG.
Under the conditions shown in the table, a Si: H: F film having a film thickness of 2.0 μm was deposited on the substrate.

ESR measurement is performed on each Si: H: F film,
The results shown in Table 3 were obtained.

[Effect] From the above detailed description and each example, according to the deposited film forming method of the present invention, it is possible to achieve energy saving and at the same time easily control the film quality and to obtain a deposited film having uniform physical properties over a large area. Obtained with good reproducibility. Further, it is possible to easily obtain a film which is excellent in productivity and mass productivity and has high quality and excellent physical properties such as electrical, optical and semiconductor properties.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a film forming apparatus used in an example of the present invention. 101-108 ... Gas cylinder, 101a-108a ... Gas introduction pipe, 101b-108b ... Mass flow meter, 101c-108c ... Gas pressure gauge, 101d-108d and 101e-108e ... Valve, 101f-108f ... ... Pressure gauge, 109, 110, 111 ... Gas introduction pipe, 112 ... Substrate holder, 113 ... Substrate heating heater, 116 ... Substrate temperature monitoring thermocouple, 118 ... Substrate, 119 ... Vacuum exhaust valve , 126 ... Window, 127 ... Emission spectroscope, respectively.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location H01L 29/78 31/04

Claims (14)

[Claims] 1. A reaction space containing a gaseous raw material containing at least silicon atoms and hydrogen atoms for forming a deposited film, and a gaseous halogen-based oxidizing agent having a property of oxidizing the raw material. When introduced and brought into contact with each other, a plurality of precursors including a precursor in an excited state are generated with light emission, and at least one of these precursors is used as a supply source of deposited film constituents to form a film formation space. In a deposited film forming method for forming a deposited film on a substrate inside, an intensity ratio of light emitted by Si-H and light emitted by Si-X (X: halogen atom) ([Si-H] / [Si-X]) To 1 or less. 2. The deposited film forming method according to claim 1, wherein the gaseous raw material is a chain silane compound. 3. The deposited film forming method according to claim 2, wherein the chain silane compound is a straight chain silane compound. 4. The linear silane compound has the general formula Sin.
The deposited film forming method according to claim 3, wherein the method is represented by H2n + 2 (n is an integer of 1 to 8). 5. The deposited film forming method according to claim 2, wherein the chain silane compound is a branched chain silane compound. 6. The deposited film forming method according to claim 1, wherein the gaseous raw material is a silane compound having a silicon ring structure. 7. The deposited film forming method according to claim 1, wherein the gaseous halogen-based oxidizing agent contains a halogen gas. 8. The deposited film forming method according to claim 1, wherein the gaseous halogen-based oxidizing agent contains a fluorine gas. 9. The deposited film forming method according to claim 1, wherein the gaseous halogen-based oxidizing agent contains chlorine gas. 10. The gas-based halogen-based oxidizing agent is a gas containing a fluorine atom as a constituent.
The method for forming a deposited film according to item. 11. The deposited film forming method according to claim 1, wherein the gaseous halogen-based oxidizing agent contains halogen in a nascent state. 12. The substrate according to claim 1, wherein the substrate is arranged at a position opposed to a direction in which the gaseous raw material substance and the gaseous halogen-based oxidant are introduced into the reaction space. Method for forming deposited film. 13. The method for forming a deposited film according to claim 1, wherein the gaseous raw material and the gaseous halogen-based oxidant are introduced into the reaction space through a multi-tube structure transport pipe. 14. The method according to claim 1, wherein the gaseous raw material and the gaseous halogen-based oxidant are diluted with an inert gas H ₂ gas and N ₂ gas and introduced into the reaction space. Method for forming deposited film.