JPS63292621A - Method and apparatus for forming deposited film - Google Patents

Abstract

PURPOSE:To so control that a plasma of an activating space for activated material gas by a high frequency does not arrive at a substrate surface and to reduce the damage of the surface of a deposited film by providing a control electrode near a boundary between the activating space and a film growing space in which the substrate is disposed. CONSTITUTION:Material gases A, B are respectively introduced into quartz inner and outer tubes 1 and 2, and activated in activating spaces 3 to generate decomposited products, active seeds and pretreated materials of the gases A, B used to form a deposited film. A microwave 11 is introduced from a high frequency oscillator 10 through a waveguide 7 into the spaces 3. Since the high frequency is simultaneously propagated in an applicator 9 when a plasma is generated in the space 3, the plasma frequently arrives at a substrate 5 disposed in a reaction chamber 12. Then, an arbitrary potential is applied from a power source 14 to a conductive meshlike screen electrode 13 of a control electrode to prevent the plasma from arriving at the substrate 5.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a deposited film forming method and apparatus, and particularly to a deposited film forming method in which a deposited film is formed by chemically reacting a precursor and the active species. and its apparatus.

INDUSTRIAL APPLICATION This invention is suitably used for the formation of the semiconductor deposited film used for a'a film transistor, a photovoltaic element, a photoconductive member for electrophotography, etc.

[Conventional technology and its problems]

For example, the amorphous silicon film (hereinafter referred to as Si film) that constitutes the photoelectric conversion layer of a photovoltaic element can be formed using vacuum evaporation, plasma CVD, CVN, reactive sputtering, or ion beam deposition. Rating methods, optical CVD methods, etc. have been tried, and in general, plasma CVD methods are widely used and commercialized.

However, the photoelectric conversion layer composed of a-5i has poor electrical and optical properties, fatigue properties during repeated use, use environment properties, and productivity and mass production, including uniformity and reproducibility. There is still room for further improvement of the overall characteristics.

a- by plasma CVD method which has been widely used
The reaction process in forming the 5i-based photoelectric conversion layer is as follows:
It is considerably more complicated than the conventional CVD method, and the reaction mechanism is still unclear.

In addition, there are many formation parameters for the deposited film (for example,
(substrate temperature, flow rate and ratio of introduced gas, pressure during formation, high-frequency electrode, electrode structure, reaction vessel structure, pumping speed, plasma generation method, etc.), sometimes the plasma becomes unstable and formation This often caused significant damage to the deposited film. Furthermore, it is necessary to select parameters unique to each device, making it difficult to generalize manufacturing conditions.

On the other hand, in order to develop a photoelectric conversion layer made of Si that has electrical and optical properties that fully satisfy various uses, it is currently considered best to form it by plasma CVD.

However, in the case of photovoltaic elements, it is now necessary to achieve mass production with high reproducibility by satisfying the requirements of large area, uniformity of film thickness, and uniformity of film quality. In this respect, in the formation of A-5i-based photovoltaic converters using the conventional plasma CVD method, a large amount of capital investment is required for mass production equipment, and the management items for mass production are also complicated, resulting in a management tolerance. Problems that need to be improved in the future include the fact that the area is narrower and the adjustment of the equipment is delicate.

On the other hand, the conventional technique using the normal CVD method requires high temperatures and has not been able to provide a deposited film with practically usable characteristics.

As mentioned above, in the formation of a-5i-based photoelectric conversion, it is strongly desired to develop a formation method and apparatus that can be mass-produced using low-cost equipment while maintaining practical characteristics and uniformity.

The same can be said of the other layers constituting the photoelectric conversion layer, such as a silicon nitride film, a silicon carbide film, and a silicon oxide film.

As a solution to the above problems, JP-A-60-41
In 047, a plurality of gases are introduced into the film forming space, and some of them are activated in advance by energy such as light, heat, plasma, etc., and a deposited film is formed on the substrate placed in the film forming space. Formation method (hereinafter referred to as 11R)
It is written as CVD method. ) is folded. An advantage of such a method is that, for example, when depositing a-5i films, Si
Deposition is performed by combining Fi gas and hydrogen radicals (hereinafter referred to as H''), and depending on the concentration of ``■'', it is possible to grow not only amorphous silicon but also polycrystalline silicon at a low temperature.

In general, energy such as light, heat, and plasma can be used as the activation method, but in terms of activation efficiency, yield, and difficulty in causing contamination,
Excellent excitation by microwave discharge.

However, IIRCVD due to this microwave discharge
After examining the law, the following problems were found.

In other words, due to the shape, material, surface condition, etc. of the film forming space where the substrate is placed and the wall surrounding the activation space where the raw material gas is activated, the plasma discharge caused by microwaves may not be stable, and the film deposition rate and electrical・Problems remain with the reproducibility of optical properties. Furthermore, the plasma state in the activation space is likely to fluctuate, and afterglow may reach the substrate surface and affect the deposited film.

[Means for solving problems]

The method for forming a deposited film according to the present invention includes activating a first source gas to generate a precursor, activating a second source gas to generate active species, and combining the precursor and the active species. In a deposited film forming method for forming a deposited film by chemical reaction, an activation space for activating the first raw material gas and the second raw material gas, and a film forming space for forming the deposited film on a substrate; A control electrode is provided near the boundary of the activation space and the film forming space to electrically control the activation space and the film forming space.

Further, the deposited film forming apparatus according to the present invention includes an activation space in which the first source gas is activated to generate a precursor, and the second source gas is activated to generate active species; A deposited film forming apparatus having a film forming space in which a deposited film is formed on a substrate by contacting the activated species, characterized in that a control electrode is disposed near the boundary between the activation space and the film forming space. do.

The term "precursor" in the present invention refers to something that can serve as a raw material for a deposited film to be formed. In addition, "active species" means chemical interactions with the precursors, such as giving energy to the precursors, or chemically reacting with the precursors, thereby converting the precursors into deposited films more efficiently. It refers to something that has the role of bringing things into a state where they can be formed.

Therefore, the active species may include constituent elements constituting the deposited film to be formed, or may not include such constituent elements.

The precursor used in the present invention is a precursor that causes a chemical reaction by causing molecular collision with the above-mentioned active species in the space where the substrate to be deposited exists, and forms a deposit on the substrate. It is more desirable to select a chemical species that spontaneously generates chemical species that contribute to the formation of the film, but in its normal state of existence, the active species are inert or If there is no active species, excitation energy strong enough to prevent the precursor from dissociating may be applied to the precursor before or during film formation to bring the precursor into an excited state where it can chemically react with the active species. A compound that is necessary and can be brought into such an excited state is employed as one of the precursors used in the present invention.

[Effect]

The present invention is capable of controlling plasma in the activation space so that it does not reach the surface of the substrate by providing a control electrode near the boundary between the activation space where source gas is activated by high frequency and the film formation space where the substrate is placed. This reduces damage to the surface of the deposited film.

Note that if a heating means is provided in addition to the control electrode, activation can be performed again to increase the number of active species and precursors that contribute to deposition, and as a result, the control electrode is placed between the substrate and the substrate. By doing so, the plasma moves away from the substrate, suppressing the reduction of active species and precursors that contribute to deposition, and making it possible to uniformly form high-quality deposited films with good reproducibility without reducing the degree of deposition. .

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic diagram of a first embodiment of a deposited film forming apparatus according to the present invention.

In the figure, raw material gases A and B are introduced into the quartz inner cylinder 1 and the quartz outer cylinder 2, respectively, and the activation space 3 is
The decomposition products, active species, and precursors of the source gases A and H used for forming the deposited film are generated.

The activation space 3 is a space in which energy such as plasma can be supplied, and in FIG. , a microwave 11 is introduced from a high frequency oscillator 10 through a waveguide 7.

If the cross section created by intersecting the applicator 9 and the waveguide 7 has a diameter below the cutoff wavelength of the high frequency (microwave, etc.) being used, the high frequency energy within the applicator 9 moves away from the m-wave tube 7. The activation space 3 is attenuated as the temperature increases, and the activation space 3 retreats into the interior of the applicator 9.

Also, a high frequency cutoff wave plate used by the applicator 9]
In the case of the second diameter, the high frequency wave is propagated to the discharge port and then discharged into the film forming space 4 in the reaction chamber 12 connected to the applicator 9 . However, regardless of the diameter, once plasma is generated in the activation space 3, although there is reflection of high frequency waves by the plasma, propagation of high frequency waves within the applicator 9 also occurs at the same time. More or less plasma often reaches the substrate 5 placed in the reaction chamber 12.

Therefore, the plasma can be prevented from reaching the substrate 5 by applying an arbitrary potential to the conductive mesoche-like screen electrode 13 serving as the control electrode using the power source 14.

Further, a heating means 15 is arranged directly below the screen electrode 13 to activate the raw material gas and its separation products whose activity level has decreased due to separation from the plasma or which have not been sufficiently activated in the activation space 3. . This heating means 15 is connected to a power source 816, and is controlled to an arbitrary temperature. However, it is sufficient for the heating means 15 to play an auxiliary role in activation, and high temperatures are not required. Furthermore, when a metal having a catalytic action is used, the temperature may be even lower.

As the heating means 15, a wire made of a material such as tungsten, thorium tungsten, platinum, nickel, or chromium, or a wire made of platinum, Connel alloy, tungsten, or nickel coated with barium, strontium, or calcium oxide is used.

Further, at least a part of the screen electrode 13 may also serve as the heating means 15. The screen electrode 13 may be made of any material and shape as long as it is conductive and has holes through which gas can pass, but it is more preferable that the screen electrode 13 has good corrosion resistance against the gas used and good i1 plasma properties.

Examples of such materials are stainless steel and nickel.

Aluminum etc. can be used.

Further, the substrate 5 is supported by a substrate holder 6, and a heater (not shown) is built into the substrate boulder 6 so that the substrate 5 can be maintained at a temperature as required.

Source gases A and B are determined by the film to be deposited on substrate 5.

For example, when forming an a-3i photoconductive layer, if the precursor is the decomposition product of the raw material gas that is the main constituent element of the deposited film, and the active species is the decomposition product of the raw material gas B that chemically reacts with the precursor. In this case, 11□ is used as the raw material gas B for generating active species in the activation space 3.

5i114+5i113F, 5i113CI, 5i11
3Br+5i) I: In addition to +I etc., 11e.

Examples include rare gases such as Ne and Ar.

On the other hand, as the raw material gas 8 for producing the precursor, one in which an atom or atomic group with high electron-withdrawing property, or a polar group is bonded to a silicon atom is used.

As such, for example, Sl nX2h+z (n=L 2.3...' +
X=F + CI lBr + I) + (SiXz
)n (n≧3.X=F, CI, Br,
f).

SI, +11Xz, l++ (n=1+2+3”・+
X=F+CI+Br1l)+Si,II□×zn (
n=1+2+3''+X=F+CI, Br+I), etc.

Specifically, for example, 5il14. (SiFz) 5+
(SiFz) 61(SiFz) 41St zFb+
S+1lF3+ 5IH2F21 SiCI a (
SiCI 2) 5+SiBr4+ (SiBr2)
Examples include those in a gaseous state or those that can be easily gasified, such as s. Also, 5ill□(C6+15)2゜5iH
2(CN)z and the like may also be used depending on the intended use of the deposited film to be formed.

Examples of the deposited film forming method according to the present invention will be specifically described below using the first embodiment of the deposited film forming apparatus according to the present invention. Here, a case will be described in which an a-3i film is formed as the deposited film.

First, in FIG. 1, the distance between the substrate 5 and the screen electrode 13 is 123 = 20 mm, the distance between the screen electrode 13 and the quartz inner cylinder 1 (t + = 50 mm, and the distance between the screen electrode 13 and the end of the applicator 9 ρz = ] Omm.

Incidentally, a tungsten wire is used for the heating means 15, and
The temperature was controlled by a power source 16 to be 0 to 900°C.

The screen electrode is made of stainless steel and has a voltage of +50 (V) ~
The experiment was conducted by changing the voltage to 100 (V) and the power supply 14.

The distance between the screen electrode 13 and the heating means I5 is about 10 mm, and as the raw material gas A, SiH4 is heated for 50 sec.
m, raw material gas B was introduced at 11° at 40 sccm and Ar at 450 seconds, and the internal pressure was set at 0.4 Lo.
It was set to rr. As the substrate 5, a 7059 Corning glass substrate whose surface was coated with ITO was used.

As for the high frequency, a microwave 11 of 2.45 Go2 was oscillated from a high frequency oscillator 10 and propagated to the applicator 9 through a waveguide 7 made of aluminum. The microwave output at this time was 200 (W). Cylindrical applicator 9
The diameter of the circular cross section formed by passing through the waveguide 7 is 50 mm, which is less than the cutoff wavelength of the microwave used, 62.8 mm, but the microwave is transmitted from the open end of the applicator 9 to the film forming space 4 due to the plasma discharge. It has been confirmed that the plasma has been propagated to some extent and has reached the substrate 5 in the absence of the screen electrode 13.

Now, under the above conditions, amorphous silicon (hereinafter referred to as a
-5t) was deposited, and a-5 showed good electrical properties with no damage at the substrate-deposited film interface.
I was able to deposit. The deposition rate at this time was 6 persons/sec. The potential of the screen electrode 13 in this case is →-50~
-50 (V) is appropriate; -100 (V) increases the deposition rate but causes significant damage; conversely, when it is higher than +50V, the deposition rate decreases.

Note that when 100 V or more was applied, low voltage arc discharge occurred between the heating means 15 and the screen electrode 13, but this was resolved by separating the screen electrode 13 further.

The relationship between the voltage applied to the screen electrode 13 and the film quality is determined by the internal pressure,
Although it varies depending on the raw material gas flow rate and microwave output, good electrical characteristics without damage can be obtained by applying a potential so that even if light emission due to plasma discharge is observed on the substrate side of the screen electrode 13, it does not reach the substrate 5. I found out that it can be done.

Furthermore, the temperature of the heating means 15 is set auxiliary in consideration of the influence on the material deposited film on the substrate 5, but depending on the types of raw material gases A and B, the decomposition excitation may be more effective than the high frequency 11 in the activation space 3. It does not matter if the setting has many roles.

The second example is a schematic configuration diagram of a second embodiment of the deposited film forming apparatus according to the present invention. Note that the same members as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In the figure, raw material gas A and raw material gas B pass through a quartz tube 16 and a quartz tube 17, respectively, into a pair of cylindrical water-cooled metal applicators 9 coupled to a pair of independently provided waveguides 7. introduced through.

The only difference from the first embodiment is that raw material gas A and raw material gas B are independently decomposed and excited by microwaves 11;
As in the first embodiment, the film forming space 4 is set according to the target gas phase reaction.

However, if the decomposition and excitation of source gas A and/or source gas B is delicate, it is necessary to set the conditions of the activation space 3 independently as shown in FIG. Furthermore, in the case of doping or deposition of multi-element compounds, one or both of the applicators 9 and the quartz tube 16 in FIG. 2 can be made into a double tube as in FIG. 1.

2 differs from FIG. 1 in that the screen electrode 13 also serves as a heating means, but its role as a screen electrode and heating means are the same as in the first embodiment. However, although either alternating current or direct current may be used (the figure shows the case of alternating current), any material that can be heated at a low voltage and has a high melting point can be used.

Such materials include tungsten, thorium/tungsten wire, platinum, Conel alloy, tungsten, nickel, barium, and strontium.

A wire coated with calcium oxide is used, but thorium tungsten or the like is preferable because it has a low work function, easily emits thermionic electrons at low voltage, and has a long life.

As shown in FIG. 2, this screen electrode 13 applies a voltage as the above-mentioned heating means, and is also connected to an electric current a17 to which a DC voltage can be applied for electrically controlling plasma discharge.

Examples of the deposited film forming method and apparatus according to the present invention will be specifically described below using the second embodiment of the deposited film forming apparatus according to the present invention. A case will be described in which an a-3i film is formed as the deposited film in the same manner as in the first embodiment.

In FIG. 2, the distance between the substrate 5 and the end of the applicator 9' l + n z = 50 mm, the distance between the substrate 5 and the screen electrode 13 1!3 = 15 mm, and the raw material gases are SiSiH41Osc, ArAr30se, and raw materials. As gas B, H□20sccm, ArAr40s
e was allowed to flow, and the internal pressure of the film forming space 4 was set to 0.3 torr. As the high frequency introduced into the activation space 3, 2.45GI
+2 microwaves at 150 (W) and 200 respectively
(W) and propagated to applicator 9. The screen electrode 13 is made of a thorium-tungsten wire stretched in a sieve shape with a diameter of 800 mm.
The temperature was controlled by the power supply 17 so that the temperature was -900°C, and at the same time, the DC voltage was varied in the range of +200 to -300 (V). Other conditions are the same as in the first example.

When a-3i was deposited under the following conditions, it was found that the a-3i had good electrical properties with no damage at the interface between the substrate and the deposited film.
-5i was deposited.

The DC voltage applied to the screen electrode 13 at this time is -5
A large-area a-5i film with good electrical properties and no plasma damage was obtained at 0 (V) and 0-100 (V). The deposition rate at this time was 10 persons/sec.

Since the heating means 15 in FIG. 1 is not used and the screen electrode 13 is used, low voltage arcs do not occur and the range of DC voltage that can be applied to the screen electrode I3 is from +200 to -
It became possible to expand the voltage to 300 (V).

As a result, we were able to approach deposition conditions that were more suited to our purposes.

〔Effect of the invention〕

As explained in detail above, according to the deposited film forming method and apparatus according to the present invention, an activation space for activating source gas;
Damage to the surface of the deposited film can be reduced by providing a control electrode near the boundary with the film-forming space where the substrate is placed and controlling the plasma in the activation space so that it does not reach the surface of the substrate.

In addition, by arranging a heating means and performing activation again in order to increase the number of active species and precursors that contribute to deposition, a high-quality deposited film can be produced with good reproducibility without reducing the deposition rate.
, it is possible to form a uniform film.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a first embodiment of a deposited film forming apparatus according to the present invention. FIG. 2 is a schematic diagram of a second embodiment of the deposited film forming apparatus according to the present invention. 1... Quartz inner cylinder, 2... Quartz outer cylinder, 3... Activation space. 4...Nation space, 5...Substrate, 7...Waveguide,
9... Applicator, 10... Microwave oscillator,
11...Microwave, 12...Reaction chamber, 1
3...Screen electrode. 14.16.17... Power supply, 15... Heating means.

Claims (5)

[Claims] (1) Activating the first source gas to generate a precursor,
A method for forming a deposited film, in which a deposited film is formed by activating a second source gas to generate active species, and causing a chemical reaction between the precursor and the active species, comprising: the first source gas and the first source gas; A control electrode is provided near the boundary between the activation space for activating the raw material gas No. 2 and the film-forming space for forming the deposited film on the substrate, and the activation space and the film-forming space are electrically controlled. A deposited film forming method characterized by: (2) A heating means is provided near the boundary with the film forming space in which the deposited film is formed on the substrate, and at least one of the active species, the precursor, the first source gas, and the second source gas is provided. The deposited film forming method according to claim 1, characterized in that activation is performed. (3) Bringing the precursor and the active species into contact with an activation space in which the first source gas is activated to generate a precursor and the second source gas is activated to generate active species. What is claimed is: 1. A deposited film forming apparatus having a film forming space for forming a deposited film on a substrate by a method, wherein a control electrode is disposed near a boundary between the activation space and the film forming space. (4) Claim 3, characterized in that a heating means is arranged near the boundary between the activation space and the film forming space.
Deposited film forming apparatus as described in 2. (5) The deposited film forming apparatus according to claim 4, wherein at least a portion of the control electrode also serves as heating means.