JP2002363744A - Multi-layered film manufacturing apparatus, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-layered film manufacturing apparatus and a multi- layered film manufacturing method for manufacturing a selective reflecting film of a conductive multi-layered structure with excellent transparency and conductivity. SOLUTION: The multi-layered film manufacturing apparatus comprises a first chamber having a first sputtering film deposition unit, a third chamber having a second sputtering film deposition unit, and a second chamber provided between the first chamber and the third chamber and having a high vacuum exhaust mechanism and a substrate heating mechanism. Each chamber has a substrate carrying mechanism for moving the substrate between the chambers. Mutual diffusion of atmospheric gas is considerably reduced by performing the heating and high evacuation by the second chamber when moving the substrate between the first chamber and the third chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for producing a multilayer film, and more particularly, to a method for producing a conductive multilayer selective reflection film used for an intermediate layer of a stacked photoelectric conversion element. Apparatus and method.

[0002]

2. Description of the Related Art As a low-cost, high-conversion-efficiency solar cell suitable for photovoltaic power generation, a stacked-type photovoltaic cell such as a silicon tandem photovoltaic cell in which two or more photovoltaic cells of different materials are stacked. An element is used.

In order to further increase the efficiency of photoelectric conversion of the stacked photoelectric conversion element, a first photoelectric conversion section on the light incident surface side;
A device has been devised to insert an intermediate layer made of a conductive transparent film between the first photoelectric conversion unit and the second photoelectric conversion unit connected in series. That is, by utilizing the reflection characteristics exhibited by the intermediate layer formed of the conductive transparent film, the light in the short wavelength region is reflected on the surface of the intermediate layer and returned to the first photoelectric conversion unit,
The amount of light absorbed by the first photoelectric conversion unit is increased, and light in a long wavelength region is transmitted through the intermediate layer and absorbed by the second photoelectric conversion unit. It is known that such a selective reflection characteristic of the intermediate layer makes it possible to improve the balance of the light generation current between the first photoelectric conversion unit and the second photoelectric conversion unit, thereby improving the photoelectric conversion efficiency.

[0004] Methods for forming an intermediate layer formed of a conductive transparent film include a vapor deposition method and a sputtering method. Among them, the sputtering method is widely used because it is easy to control and can form a large area film. I have. Known techniques relating to sputter film formation include JP-A-60-35580 and JP-A-61-35580.
No. 127847, JP-A-62-84570, JP-A-6-84570
There are methods and apparatuses as disclosed in JP-A-3-77167 and JP-A-63-6882.

For example, in JP-A-63-6882,
A transparent conductive layer made of an ITO film is inserted between the first photoelectric conversion unit and the second photoelectric conversion unit, and a short wavelength region (300 nm to 80 nm) is inserted.
0 nm) is reflected to the first photoelectric conversion unit and is reflected in a long wavelength region.
The use of an intermediate layer having a reflection characteristic of transmitting light (800 nm to 1200 nm) through the transparent conductive layer and absorbing the light in the second photoelectric conversion unit is disclosed.

In order to improve the selective reflection characteristics in the intermediate layer of the stacked solar cell, Japanese Patent Application Laid-Open No.
Japanese Patent No. 37172 discloses that an ITO single film intermediate layer is formed between a crystalline silicon photoelectric conversion element on the lower side (substrate side) and an amorphous silicon photoelectric conversion element on the upper side (light receiving surface side). Further, the thickness of the ITO film is about 250.
It is also disclosed that by setting the thickness to about nm, there is a peak of reflection at a wavelength of about 600 nm, and an intermediate layer having a selective reflection characteristic in which the reflectance at long wavelengths is suppressed low.

[0007] Also, the second solar power generation world conference (2nd
WORLD CONFERENCE AND EXHIB
ITION ON PHOTOVOLTAIC SOLA
R ENERGY CONVERSION, July, 1
998, VIENNA, AUSTRIA)
According to a report from Neuchatel University (pp. 728-731), a transparent conductive film of zinc oxide was inserted between the first photoelectric conversion part of amorphous silicon and the second photoelectric conversion part of the polycrystalline thin film to form the amorphous silicon. 1 indicates that the reflection on the back surface of the photoelectric conversion unit is enhanced.

Further, by optimizing the thickness of the zinc oxide thin film,
The short-circuit current of the first photoelectric converter is 0.7 mA / cm ² when the surface is flat, and 2.0 mA when the surface is textured.
/ Cm ² has also been reported.

On the other hand, a technique for producing a conductive transparent film or the like with a sputtering film forming apparatus has been established. As a method for improving the film thickness uniformity of the conductive transparent film, Japanese Patent Application Laid-Open No.
And a method of moving and rotating a target or a substrate as described in JP-A-61-235561. Further, as described in Japanese Patent Application Laid-Open No. 7-90569, a second shutter having a hole smaller than the target diameter is provided below a shutter in a conventional magnetron rf sputtering apparatus to prevent impurity contamination in sputter deposition. In addition, there is a method of correcting the film thickness distribution.

[0010]

Conventionally, a conductive transparent film (a zinc oxide film or an ITO film) is used as an intermediate layer of a stacked photoelectric conversion element.
Film) was used. However, even when actually trying to optimize the thickness of the single-layer film, it has not been possible to obtain a conductive transparent film having selective reflection characteristics that is optimal for improving solar cell characteristics in a stacked photoelectric conversion element. Was.

That is, when an intermediate layer composed of a single-layer film is used, there is a certain limit to the range in which the reflectance at the interface with the intermediate layer can be adjusted even if the thickness of the intermediate layer is optimized. Yes, the reflectance of the stacked photoelectric conversion element in the short wavelength region cannot be sufficiently increased, and a remarkable increase in light absorption in the first photoelectric conversion unit due to reflection from the interface with the intermediate layer is impossible. Met. On the other hand, since the reflectance in the long wavelength region does not decrease so much, there is a fatal problem that the amount of light transmitted to the second photoelectric conversion unit is reduced, and the effective use of sunlight is not sufficient.

It is also known that a film having selective reflection characteristics can be manufactured by forming a multilayer structure film in which two types of transparent films having different refractive indexes are laminated. However, there is no suitable multilayer-structure selective reflection film that can be used as an intermediate layer of the stacked photoelectric conversion element. The main factor is that the intermediate layer of the stacked photoelectric conversion element is required to have excellent electrical characteristics as well as excellent electrical characteristics, and it is technically difficult to produce a multilayer structure film that satisfies both. It is mentioned. In particular, when a transparent film is formed by a conventional sputtering apparatus, it has been extremely difficult to satisfy the reduction of the resistivity of the thin film and the uniformity of the in-plane distribution of the film thickness.

For example, it is conceivable to prepare a multilayer structure selective reflection film using two types of conductive transparent films. To form a multilayer structure film having selective reflection characteristics, the film thickness of the laminated films is considered. Must be controlled accurately and the film thickness distribution must be uniform. In addition, in order to reduce the resistivity of the multilayer structure film, it is necessary to select a material that can reduce the resistivity. A multilayer structure film that satisfies such demands is difficult from the viewpoint of material selection and also from the viewpoint of a film forming technique for performing uniform film formation, and a multilayer structure selective reflection film having conductivity is used for a photoelectric conversion element. It was not used as an intermediate layer.

Further, Japanese Patent Application Laid-Open No. 61-15966 described above is disclosed.
JP-A-61-235561, JP-A-7-9056
In any of the methods described in No. 9, it is difficult to control the film thickness distribution at such a small film thickness, and it is difficult to produce a multilayer selective reflection film having excellent characteristics using this material. could not.

Accordingly, an object of the present invention is to provide a method and an apparatus for manufacturing a conductive multilayer selective reflection film having excellent optical and electrical characteristics which can be used for an intermediate layer of a stacked solar cell. The purpose is to do. Further, a second object of the present invention is to provide a manufacturing apparatus which can provide a good film thickness distribution even when laminating very thin films such as respective films forming each layer of a multilayer structure film. The purpose is to do.

[0016]

Means for Solving the Problems A multilayer film manufacturing apparatus, which is one of the present inventions made to solve the above-mentioned problems, has the following features.
A first chamber provided with a sputter film forming unit, a third chamber provided with a second sputter film forming unit, and a high vacuum evacuation mechanism and a substrate heating mechanism provided between the first chamber and the third chamber; Each of these chambers has a substrate transfer mechanism for moving a substrate between the chambers.

According to the present invention, after the first thin film is formed in the first chamber, the substrate is transferred to the second chamber. In the second chamber, the substrate is heated and the chamber is evacuated to a high vacuum. Thus, the residual gas (eg, oxygen) from the first chamber can be drastically reduced, and then the substrate is transferred to the third chamber to form a second thin film. In this way, a plurality of films are stacked in a state in which the mutual diffusion of the atmospheric gas is drastically reduced.

In particular, when a conductive transparent film is formed as the first thin film and then a semiconductor film is formed as the second thin film, oxygen gas is introduced at the time of forming the conductive transparent film. After forming the first thin film, the oxygen gas remaining in the second chamber is evacuated and evacuated while being actively heated.
By moving to the chamber, a high-quality semiconductor film can be stacked.

Here, as the main component of the conductive transparent film used for the conductive multilayer structure selective reflection film, zinc oxide, tin oxide, ITO, titanium oxide and the like are preferable. These films become films having light transmittance and conductivity by containing oxygen, and are made of a group III element such as aluminum (Al),
It is preferable to increase the conductivity by adding a metal impurity such as gallium (Ga) or indium (In).

[0020] Among the conductive transparent films, zinc oxide is superior in hydrogen plasma resistance to other materials (tin oxide, ITO, titanium oxide). When a process using is performed, it is preferable that zinc oxide be the main component. For example, in the case where a conductive transparent film is used as an intermediate layer of a stacked photoelectric conversion element in which the first photoelectric conversion unit is an amorphous silicon film, the amorphous silicon film is exposed to hydrogen plasma when forming the amorphous silicon film. It is preferred to use zinc.

As a semiconductor film used for the conductive multilayer structure selective reflection film, a silicon (Si) film in a polycrystalline state, a microcrystalline state, a mixed state of amorphous and microcrystalline, or a silicon carbon ( SiC)
A membrane is preferred. Then, the group III element (B,
The semiconductor film contains impurities imparting conductivity, such as Al, Ga) and group V elements (P, As).

Particularly when a silicon film is used, the impurity concentration is preferably 5 × 10 ¹⁸ cm ⁻³ or more, but 1 × 10 ²⁰
When the density is more than cm ^−3, the light absorption rate of the silicon thin film increases, and the impurity concentration becomes 5 × 10 ¹⁸ cm ^−3.
Is preferably in the range of 1 × 10 ²⁰ cm ⁻³ to 1 × 10 ²⁰ cm ⁻³ .

Further, in order to solve the above-mentioned problems, a sputtering film forming section of another multilayer film manufacturing apparatus according to the present invention has a target attached to a position facing a substrate conveyed into a chamber, and A film thickness correction plate made of the same material as that of the target is provided in the vicinity immediately above the periphery of the target.

According to the present invention, the angle of the film thickness compensating plate attached to the periphery of the target with respect to the target is made appropriate, and the electric potential is applied to the film thickness compensating plate so that the uniformity of the electric field distribution on the film forming surface is improved. Can be improved, so that the film thickness distribution can be improved. Further, since the film thickness correction plate itself is made of the same material as the target, there is no problem of particles sputtered from the correction plate.

The film thickness compensating plate is configured so that the mounting angle with respect to the target can be adjusted and connected to a power supply whose voltage can be adjusted so that the film thickness distribution can be adjusted to be optimal. This is more preferable because it becomes possible.

Further, the method for manufacturing a multilayer film according to one aspect of the present invention includes a first chamber having a first sputter film forming section, a third chamber having a second sputter film forming section, A second chamber provided between the third chambers and having a high vacuum evacuation mechanism and a substrate heating mechanism, each of these chambers being a multilayer having a substrate transfer mechanism for moving a substrate between the chambers; Using a film manufacturing apparatus, (a) forming a first layer film on a substrate in a first sputter film forming section of a first chamber, and (b) transporting the substrate to a second chamber to provide a high vacuum evacuation mechanism and a substrate. (C) transporting the substrate to the third chamber to form a second layer film in the second sputtering film forming section, and thereafter, when further increasing the number of layers, the first chamber and the When transferring the substrate to and from the third chamber, the substrate is transferred from one chamber to the second chamber. Transported to Nba by operating the high vacuum evacuation system and the substrate heating mechanism for producing the film is transported to the other chamber from. According to this method, after the first thin film is formed in the first chamber, the substrate is transferred to the second chamber. In the second chamber, the substrate is heated and the chamber is evacuated to a high vacuum. Thereby, the first
Since the residual gas (eg, oxygen) from the chamber can be sharply reduced, the substrate is then transferred to a third chamber to form a second thin film. In this manner, a plurality of films can be stacked in a state in which the mutual diffusion of the atmospheric gas is drastically reduced.

In the first sputter deposition section of the first chamber, if the conductive transparent film is formed in an oxygen / argon mixed gas atmosphere having an oxygen mixture ratio in the range of 0.5 to 3%, the conductive A conductive transparent film having a good balance between the transmittance and the transmittance can be formed.

[0028]

Embodiments of the present invention will be described below.

First, a multilayer film to be formed by the manufacturing apparatus and the manufacturing method of the present invention will be described. What is required for a multilayer film is conductivity and selective reflection characteristics.
A method for calculating the selective reflectance of the multilayer film will be described. The formula is O.
S. Heavens, "Optical Properties of Thin Solid Fil
ms ", a conventional calculation formula as described in Butterworths Science (1955). In the case of normal incidence, the reflectance R (λ) of the multilayer film is represented by the following formula (1).

[0030]

(Equation 1) A (λ) = η ₀ (m ₁₁ + η _{l + 1} m ₁₁ )-(m ₂₁ + η _{l +1} m ₂₂ ) B
(Λ) = η ₀ (m ₁₁ + η _{l + 1} m ₁₁ ) + (m ₂₁ + η _{l + 1} m ₂₂ )

[0031]

(Equation 2)

[0032]

(Equation 3)Where M_jIs the characteristic matrix of the homogeneous j-th layer monolayer, and M is the homogeneous multilayer
Membrane characteristic matrix m₁₁, M ₁₂, M_{twenty one}, M_{twenty two}Corresponds to each layer
Diagonal element of product matrix of characteristic matrix, η₀, Η_{l + 1}And η_jIs in
The effective refractive indices of the medium on the emitting side, silicon and the j-th layer film
Multi-refractive index N for absorptive media_j= N_j-With iK
You can change it. δ_j= (2π / λ) N_jd_jAnd d_jIs the j-th layer film
It is a film thickness.

For a stacked photoelectric conversion element composed of an amorphous silicon first photoelectric conversion unit and a crystalline silicon second photoelectric conversion unit, the optimum film thickness of the first type material and the second type material is expressed by the following equation (1). （(3). Here, zinc oxide (ZnO) was used as the first type material, and polycrystalline silicon was used as the second type material. As a result, the optimal value of the thickness of zinc oxide (ZnO) as the first type material is 70 nm, and the optimal value of the thickness of the polycrystalline silicon film as the second type material is 3 nm.
0 nm.

Therefore, the film thickness of the entire multilayer film is 170 nm (70 × 2 + 30) in the case of a laminated structure of two zinc oxide films and one silicon film, and three zinc oxide films and two silicon films. 270 nm (70 × 3 + 30)
× 2) is a preferable value. Of course, it is also possible to perform a multi-layer film formation more than this, and in that case, the total film thickness increases according to the number of layers.

The reflection characteristic of the intermediate layer by the multilayer structure selective reflection film having two layers of zinc oxide film and one layer of silicon film is about 70%.
A high reflection region exists in a short wavelength region of 0 nm or less, and its reflectance peak is about 87%.
nm to 1200 nm) can be low (≦ 11%). As the number of layers in the multilayer structure increases, the short wavelength region of the reflection characteristics gradually converges, and the reflectance in this wavelength range increases. 700n if there are three or more structural layers
The reflectance in the wavelength region of m or less is 90% or more.

FIG. 4 shows the calculated data of the reflectance of the intermediate layer formed by the selective reflection film having a multilayer structure in which three zinc oxide films and two silicon films are combined. As shown by the reflection characteristics in FIG. 4, the silicon laminate photoelectric conversion element has a high reflectance in the wavelength region of 400 nm to 700 nm, which is most effective for the first photoelectric conversion portion, and a low reflectance in the wavelength region of 750 nm or more. And has good selective reflection characteristics of transmitting long-wavelength light.

The conductivity of the conductive transparent film constituting the conductive multilayer structure selective reflection film is substantially determined by the content of metal impurities (metal impurities such as aluminum). If the content of metal impurities is more than a certain amount (> 4.5%), the conductivity can be increased only up to about 6 × 10 ³ Ω · cm, but the transmittance will be reduced.

Since the transmittance of interest here is the transmittance in the wavelength range of 400 to 700 nm, the transmittance used in the following description is in principle unless otherwise specified.
The transmittance in this range is referred to.

On the other hand, when the content of metal impurities is a certain amount (<1
%), The transmittance can be improved, but when the conductivity becomes 6 × 10 ² Ω · cm or less, the resistance value of the multilayer selective reflection film as a whole increases.

Therefore, as a selective reflection film which is required to have conductivity and transparency like an intermediate layer of a stacked photoelectric conversion element, the conductivity of the film is from 6 × 10 ² Ω · cm to 6 × 10 ³ Ω · cm. Is appropriate.

As described above, it is necessary to adjust the balance between conductivity and transparency. In the case of sputter deposition, the composition of the sputter atmosphere gas, that is, the mixing ratio of argon gas to oxygen gas is adjusted. The conductivity and transmittance can be adjusted.

FIG. 5 is a diagram showing the relationship between the conductivity and the transmittance based on the oxygen partial pressure. The conductivity tends to decrease as the oxygen content increases, but by setting the oxygen partial pressure ratio in the range of 0.5% to 3%, the conductivity of the film becomes 6 × 10 5
^{In addition} to the range of 2 Ω · cm to 6 × 10 ³ Ω · cm, the transmittance of the film can be 77% or more. That is, both conductivity and transparency can be achieved.

As described above, a thin film having good optical characteristics (selective reflection characteristics) and good electric characteristics (good conductivity) is required for use as an intermediate layer of a stacked photoelectric conversion element. There is a need. As a film structure for satisfying these requirements, it has been found that a conductive multilayer structure selective reflection film combining a conductive transparent film and a semiconductor film is effective.How to make this multilayer film By further studying the above, the manufacturing apparatus and the manufacturing method of the present invention were made. In other words, in order to form a high-quality conductive multilayer structure selective reflection film, it is necessary to form a conductive transparent film and a semiconductor film in a stable and clean plasma atmosphere, respectively. A suitable manufacturing device and manufacturing method were created. Specifically, when forming the conductive transparent film and the semiconductor film alternately, it is assumed that the film formation residual gas can be sufficiently removed after each film formation, and that the semiconductor film has a very small film thickness. Can be performed uniformly.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an apparatus for manufacturing a multilayer film according to an embodiment of the present invention. This multilayer film manufacturing apparatus is suitable for manufacturing a conductive multilayer structure selective reflection film.

In the drawing, reference numeral 19 denotes a load chamber used when a substrate is taken in and out of the apparatus, 20 denotes a first chamber for forming a conductive transparent film as a first thin film, and 2 denotes a first chamber.
1 is a second chamber for switching the ambient gas, 22
Is a third chamber for forming a semiconductor film as a second thin film.

A door 40 is provided between the load chamber 19 and the first chamber 20 to separate the chambers from each other. Similarly, a door 42 and a second door are provided between the first chamber 20 and the second chamber 21. A door 45 is provided between the second chamber 21 and the third chamber 22.

In the load chamber 19, 18 is a door for carrying out the substrate, and 26 is a nitrogen gas introduction line. The load chamber is provided with a roughing vacuum pump (not shown) for bringing the atmospheric pressure into a vacuum.

In the first chamber 20, 23 is a high vacuum evacuation system (a turbo molecular pump is used as a main evacuation pump), 27 is a high-purity argon gas introduction line, and 31 is a high-purity oxygen gas line. Reference numeral 28 denotes an electrode shield for limiting a discharge space at the time of sputtering to a space on the substrate side, reference numeral 29 denotes a target for producing a conductive transparent film, reference numeral 30 denotes a shutter, and reference numeral 43 denotes a heater. 41 are configured. Note that zinc oxide (ZnO) is used as a target material. In addition, tin oxide (S
nO ₂ ), ITO, titanium oxide (TiO ₂ ), or the like may be used. In the chamber, the substrate 48 is transported by a transport mechanism described later.
Is carried into a position facing the target 29.

In the second chamber 21, reference numeral 24 denotes a high-speed exhaust system (using a cryopump as a main exhaust pump); 32, a high-purity argon gas introduction line;
4 is an infrared heating lamp.

In the third chamber 22, reference numeral 25 denotes a high vacuum evacuation system (a turbo molecular pump is used as a main evacuation pump), and reference numeral 34 denotes an argon gas introduction line. 35,
Reference numeral 38 denotes a film thickness correction plate, which will be described later, reference numeral 36 denotes a silicon target for producing a semiconductor film, reference numeral 37 denotes an electrode shield, reference numeral 39 denotes a shutter, and reference numeral 52 denotes a heater. Reference numeral 50 denotes a DC power supply, and 51 denotes a low-pass filter, which is connected to the film thickness correction plates 35 and 38. Note that silicon or silicon carbon is used as the target material. In this embodiment, a target made of n-type silicon containing phosphorus and having a resistivity of 3 × 10 ⁻³ Ω · cm is used.

Each of the chambers 19 to 22 is provided with a transport belt 49 for automatically transporting the substrate 48. In the first and third chambers, the substrate can be stopped at positions facing the targets 29 and 36.

A radio frequency (RF) power supply 5 for generating a discharge required for sputtering is provided to the targets 29 and 36.
6, 57 are connected. Further, since the magnetron sputtering method in which a magnetic field is applied to the target surface in order to increase the film forming rate is employed, the targets 29 and 36 are used.
The magnets 54 and 55 are attached to the back of. In addition,
DC power supplies 58 and 59 may be provided instead of the high frequency power supplies 56 and 57 to perform DC discharge. Furthermore, a high frequency power supply 5
The plasma may be adjusted by simultaneously providing the DC power supplies 6 and 57 and the DC power supplies 58 and 59 and applying a DC bias when generating a high-frequency discharge. That is, it is used as an apparatus of a high frequency / DC coupling bias sputtering method. Each power supply is provided with low-pass filters 60, 61, 62, 63 for noise cut.

Next, the film thickness correction plate of the third chamber will be described. Second sputter deposition unit 4 in third chamber
In No. 7, it is required that the in-plane film thickness distribution be made uniform by performing precise control on an extremely thin film thickness. Therefore, a film thickness correction plate is attached.

In general, when a negative voltage or a high-frequency voltage is applied to a target electrode to generate glow discharge and generate plasma, ions in the plasma are accelerated in a sheath portion immediately before the target to become high-energy particles and become high-energy particles. It strikes 36 surfaces at various angles. Among the sputtered particles hit by the collision, those having various particle energies (5 to 10 eV) exist, pass through the space between the target 36 and the substrate 48,
Deposition of the film is achieved by reaching the substrate at various angles. At this time, the film thickness distribution is influenced by the potential gradient between the target 36 and the substrate 48 and the like.

With the conventional apparatus and method, it is extremely difficult to precisely control the in-plane film thickness. Therefore, an angle-variable thickness correction plate 35 is provided between the target 36 and the shutter 39.
38 are arranged. The angle with respect to the target is set to about 30 degrees so as to improve the uniformity of the electric field distribution on the film formation surface by plasma. Film thickness correction plate 3
The same material as the target 36 is disposed on the surfaces of the substrates 5 and 38 on the substrate side. For example, in the case of forming a silicon thin film, if an n-type silicon material having a resistivity of 3 × 10 ⁻³ Ω · cm is used as the target 36, the thickness correction plate 3
5 and 38 are also composed of n-type silicon substrates of the same material.

Although only two film thickness correction plates are shown in FIG. 1, a total of four film thickness correction plates are arranged around the square target so as to correspond to each side. The plasma potential of the film formation chamber is controlled by adjusting the potentials of the film thickness correction plates 35 and 38. That is, by adjusting the installation angles and potentials of the film thickness correction plates 35 and 38, the plasma potential and sputtered particles are physically controlled, and the film thickness of the semiconductor thin film is precisely controlled.

Next, a procedure for forming a conductive multilayer structure film using this manufacturing apparatus will be described. Loading the substrate First, the first chamber 20, second chamber 21, third chamber 22, may be held in a high vacuum state, respectively, the door 4
With the 0 closed, nitrogen is introduced into the load chamber 19 to return to atmospheric pressure, the door 18 is opened, and the substrate 48 is placed on the transport belt 49 in the chamber. In the case of manufacturing a stacked photoelectric conversion element in which the first photoelectric conversion unit and the second photoelectric conversion unit are stacked via an intermediate layer, the substrate-side photoelectric conversion unit must be formed first on the substrate. become. Subsequently, the load chamber is evacuated by a roughing vacuum pump (not shown). When a vacuum is established, the door 40 is opened, the substrate 48 is moved to the first chamber 20, and the door 40 is closed.

[0058]Formation of the first conductive transparent film Subsequently, a first-layer conductive transparent film is formed. Of FIG.
Argon gas introduction line 27 in first chamber 20, oxygen
Each gas is introduced from the gas introduction line 31 and
As a mixed atmosphere of gon (Ar) and oxygen (O),
Power is about 6 × 10 ^-3 While controlling to about Torr,
Forming a 70-nm zinc oxide thin film
To achieve. The film formation conditions are as follows: substrate temperature is 200 ° C, target
Is zinc oxide (containing 2% Al or 3.5% Ga), R
The power density of F magnetron sputtering is 2W /
cm^TwoControl to the degree of conductivity and transparency of the conductive transparent film.
Mixed gas of oxygen and argon to balance
Adjust the volume. Specifically, as described in FIG.
Is set in the range of 0.5% to 3%.

Atmosphere Switching After the first layer of the zinc oxide thin film is formed, the door 42 is opened to transport the sample to the second chamber 21, and then the door 42 is closed. The vacuum degree 3 × 10
Wait until the pressure reaches ^-6 Torr or less, preferably about 2 × 10 ^-6 Torr, open the door 45, transport the substrate to the third chamber 22, and close the door 45. By simultaneously heating during high vacuum evacuation, the release of the adsorbed gas is promoted.

After the formation of the second semiconductor film , a silicon thin film is formed in the third chamber 22. The potential of the film thickness correction plate is adjusted to a range of about 0 to -45V. The pressure range of the argon atmosphere is 1 mTorr to 10 mTorr. RF frequency is 100MHz,
High frequency power density is 0.6 W / cm ² , film formation speed is about 5 n
m / min. The film forming temperature is set to 300 ° C., and the film thickness is controlled by the opening time of the shutter 39.

Formation of Third and Subsequent Layers After forming the first-layer conductive transparent film and the second-layer silicon thin film and further laminating them, it is necessary to send the substrate to the first chamber again. For this reason, the door 45 is opened, the wafer is transported to the second chamber 21, heated to a high vacuum state once, and then transported to the first chamber 20 again. The third layer of zinc oxide thin film is formed on the above-mentioned second layer of silicon thin film under the same film forming conditions as the first layer of zinc oxide thin film. Further, the fourth-layer silicon thin film is formed under the same film-forming conditions as the second-layer silicon thin film.

Thereafter, similar film formation is continued until the required number of layers is reached. After the formation of the required number of multilayer films is completed, annealing is performed in an argon atmosphere at 200 ° C. for about 20 minutes in the second chamber 21 to form a conductive multilayer structure selective reflection film composed of alternate single films.

Characteristics of the Conductive Multilayer Structure Film The sheet resistance of the conductive transparent film was 30 Ω · cm or less (film thickness: about 70 nm), and the transmittance in the wavelength region of 700 nm or more was 82% or more. Further, as a result of reducing the residual oxygen in the film formation atmosphere at the time of forming the silicon thin film to 10 ppm or less, the impurity concentration of the formed silicon thin film becomes 5 × 10 ¹⁸
-10 ¹⁹ cm ^-3 . The resistivity of the formed silicon thin film at this time is about 5 × 10 ⁻³ Ω · cm, and it is possible to obtain a low-resistance thin film substantially similar to the resistivity (5 × 10 ⁻³ Ω · cm) of the target material. did it. This satisfies the electrical characteristics required for the intermediate layer of the stacked photoelectric conversion element. Further, the film thickness distribution of the silicon thin film was optimized by arranging the film thickness compensating plate, so that the in-plane film thickness distribution could be suppressed to ± 3.0 nm or less, which was greatly improved.

Next, regarding the characteristics of the multilayer structure film, as the number of layers of the multilayer structure film formed by alternately depositing two types of single films increases, the width of the short wavelength region where the reflectivity is high decreases. However, the reflectance in this short wavelength region was high. When the number of layers is three or more, the wavelength 700
A reflectance of 90% or more in a region of nm or less was obtained. At the same time, the conductivity characteristics of the entire multilayer film were also improved by the improvement of the film quality.

The atmosphere is switched by the second chamber,
Since the residual gas mixed with the fine powder generated when the silicon thin film is formed in the third chamber can be removed, a cleaning effect is also achieved.

[0066]

Next, a description will be given of an embodiment in which a conductive multilayer structure selective reflection film is formed using the apparatus of the present invention, and this is used as an intermediate layer of a laminated photoelectric conversion element.

FIG. 2 is a sectional view of a stacked silicon photoelectric conversion element having an intermediate layer formed by using the apparatus of the present invention. This element can be roughly classified into a first photoelectric conversion unit 11 on the light incident side, an intermediate layer 5, and a second photoelectric conversion unit 12.

The first photoelectric conversion portion 11 is made of an amorphous silicon material pi-
It has an n structure. The intermediate layer 5 is a conductive multilayer structure selective reflection film composed of two materials having different refractive indexes. on the other hand,
The second photoelectric conversion unit 12 has a basic structure of a polycrystalline silicon solar cell. These three parts constitute a stacked photoelectric conversion element.

The second photoelectric conversion section 12 has a crystal face (10
0), an n-type silicon substrate 3 having a resistivity of 0.5 Ω · cm is used. After RCA cleaning the n-type silicon substrate 3,
Immediately after boron diffusion is performed to form the p-type polycrystalline silicon layer 4 and form a pn junction, a surface protective film (BSG) is formed on the diffusion layer in an oxygen atmosphere in the same oxidation furnace.
Subsequently, only the diffusion layer on one side is protected by a resin mask and removed by chemical etching. Dry etching can be performed instead of the chemical wet etching. Further, phosphorus diffusion is performed on the surface to be etched away by a thermal diffusion method to a thickness of about 0.3 μm and an impurity concentration of 1.2 × 10 ^20.
An n-type silicon layer 2 of cm ^-3 is formed. Further, after removing the surface silicon oxide, the Ti / Pd / Ag three-layer metal electrode 1 is deposited and annealed in a nitrogen atmosphere to form the second photoelectric conversion unit 12.

Next, the intermediate layer 5 of the conductive multilayer structure selective reflection film is laminated on the second photoelectric conversion section 12 by using the above-described apparatus of the present invention. FIG. 3 shows the detailed structure of the intermediate layer 5 to be laminated. The first layer 13 and the third layer 1 of the intermediate layer 5
The fifth and fifth layers 17 are made of a zinc oxide (ZnO) thin film, and the second and fourth layers are made of a silicon thin film.

First, the first layer is formed in a first chamber 20 of the apparatus shown in FIG. 1 by using an atmosphere of a mixed gas of argon and oxygen and controlling the film forming pressure to about 6 × 10 ⁻³ Torr while controlling the film thickness. A 70 nm zinc oxide thin film is formed. As the film forming conditions, the substrate temperature was 200 ° C., and the target was zinc oxide (Al: 2).
%), The power density of RF magnetron sputtering was 2 W / cm ² , and the partial pressure ratio of oxygen was 1.4%. The sheet resistivity at a thickness of 70 nm was 28 Ω · cm, and the transmittance of the film was 83%. First layer zinc oxide thin film 1
After the film 3 is formed, the door 42 is opened, the substrate is transferred to the second chamber 21, and then the door 42 is closed. Evacuation is performed by the high-speed exhaust system 24, and the degree of vacuum is 2 × 10 ⁻⁶ Torr.
Then, the door 45 is opened, the substrate is transferred to the third chamber, and the door 45 is closed.

In the third chamber 22, a silicon thin film as a semiconductor film is formed. Film thickness correction plate 35 during sputtering,
The potential of 38 is adjusted to -43 V, and the pressure of the argon atmosphere is adjusted to 5 mTorr. RF frequency is 100MHZ
z, high frequency power density is 0.6 W / cm ² , film formation temperature is 3
Set to 00 ° C.

The thickness of the formed silicon thin film is about 30 n
m, the in-plane film thickness distribution was ± 2.5 nm or less, and the impurity concentration of the silicon thin film was 8 × 10 ¹⁸ cm ⁻³ . After forming the second-layer silicon thin film 14 (FIG. 3), the door 4
5 is opened, transported to the second chamber, heated to a high vacuum state d, and then transported to the first chamber.

The third and fifth zinc oxide thin films 15
(FIG. 3) is formed under the same conditions as the first-layer zinc oxide thin film 13 described above.
The film is formed under the same conditions as the silicon film 14 of the layer. After forming the fifth layer of zinc oxide thin film 17 in this manner,
At 200 ° C. in an argon atmosphere in the second chamber 21
Annealing is performed for about 0 minutes to form an intermediate layer 5 composed of a conductive multilayer structure selective reflection film composed of three alternate single films.

Further, the upper photoelectric conversion unit 11 (FIG. 2)
Is formed on the intermediate layer 5 by a plasma CVD method. The substrate temperature during film formation by plasma CVD was 16
The pressure at the time of film formation was about 0.3 Torr, the energy supplied to the plasma was 30 mW / cm ² , and the source gases were SiH ₄ (silane), H ₂ (high-purity hydrogen), and B ₂ H.
₆ (diborane) and PH ₃ (phosphine) are used. The upper photoelectric conversion unit 11 includes an n-type amorphous silicon semiconductor 6,
A hydrogenated amorphous i-type silicon semiconductor 7 (thickness: about 300 nm) and a p-type amorphous silicon semiconductor 8 are stacked in this order.

Subsequently, a conductive transparent film (ITO) 9 was deposited to a thickness of 107 nm by sputtering, and an Ag surface collector 10 was formed by electron beam evaporation.
This stacked photoelectric device was completed.

The laminated photoelectric conversion element prepared in this embodiment is
Has a five-layer structure as described above (three zinc oxide layers, silicon layer
An intermediate layer 5 (two layers) is formed. With this structure
Can be absorbed by the amorphous silicon first photoelectric conversion unit 11
For the light region (300-700 nm), the reflectivity is about
85% or more, while ~ 700 nm or less
It is necessary to keep the reflectance low for light in the long wavelength region above.
Now you can do it. Improve this selective reflection characteristic
The photocurrent of the first photoelectric conversion unit 11
Increases, and the photocurrent of the second photoelectric conversion unit 12 decreases.
The first photoelectric conversion unit 11 and the second photoelectric conversion
The photocurrent of the switching section 12 was able to approach the equilibrium state.
As a result, the photocurrent density under AM1.5 irradiation was about 1
2A / cm ^TwoFrom 18 mA / cm^TwoReach the degree
did. The conversion efficiency of a silicon stacked solar cell is about 1
Significantly improved from 2% to about 18%, effective for incident sunlight
Was available to

In this embodiment, zinc oxide is used as the first material (conductive transparent film) of the intermediate layer 5. However, if the intermediate layer 5 is conductive and has high transparency to long-wavelength light, it may be used. By optimizing the film thickness according to the above film, similar characteristics can be provided. For example, the same effect can be obtained when an ITO film (a material containing several weight% of tin in indium oxide), a tin oxide film, a titanium oxide film, a silicon oxide film, or the like is used.

However, when the first photoelectric conversion section 11 is formed by high-frequency plasma such as an amorphous silicon material, considering that the outermost surface of the intermediate layer 5 is exposed to hydrogen plasma, the first photoelectric conversion section 11 has high hydrogen plasma resistance. A material containing zinc oxide, which is an excellent material, as a main component is desirable.

The same effect can be obtained by a DC method or an RF-DC combined sputtering method as a sputtering method used for forming a zinc oxide thin film. However, in order to reduce plasma damage and control film thickness uniformity, an RF method is used. It is more desirable to use.

Although a polycrystalline silicon thin film is used as the second material (semiconductor film) of the intermediate layer 5, any material having a low absorption coefficient for long-wavelength light and having conductivity can be used.
Other materials can be used by optimizing the film thickness. For example, the same effect can be obtained by using an amorphous silicon film and amorphous or microcrystalline silicon carbon.

[0082]

According to the multilayer film manufacturing apparatus of the present invention, the first
After the thin film is formed, the substrate is transferred to the second chamber. In the second chamber, the substrate is heated and the inside of the chamber is evacuated to a high vacuum, so that the residual gas (eg, oxygen) from the first chamber is removed. When the substrate is transferred to the third chamber to form the second thin film, a plurality of films can be stacked in a state where the mutual diffusion of the atmospheric gas is sharply reduced. A film could be formed. In particular, in the case where the first thin film is a conductive transparent film formed using oxygen and the second thin film is a semiconductor film, high quality can be obtained because oxygen incorporated in the semiconductor film can be sharply reduced. A multilayer film could be manufactured.

Further, the plasma potential and the sputtered particles can be controlled by arranging the film thickness correction plate and adjusting the installation angle and the potential of the film thickness correction plate, so that the film thickness of the semiconductor thin film can be precisely controlled. An intermediate layer of a conductive multilayer structure selective reflection film having selective reflection characteristics was obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an apparatus for manufacturing a multilayer structure film according to one embodiment of the present invention.

FIG. 2 is a sectional configuration diagram of a stacked silicon photoelectric conversion element according to an embodiment of the present invention.

FIG. 3 is a schematic cross-sectional view of the intermediate layer in FIG. 2;

FIG. 4 is a view showing selective reflection characteristics of a three-layer structure intermediate layer in which a zinc oxide thin film and a polycrystalline silicon thin film are combined.

FIG. 5 is a graph showing the dependency of the transmittance and the conductivity on the mixed oxygen partial pressure of a conductive transparent film using zinc oxide.

[Explanation of symbols]

 1: Ti / Pd / Ag back electrode 2: n-type silicon layer 3: n-type polycrystalline silicon substrate 4: p-type polycrystalline silicon 5: intermediate layer 6: n-type amorphous amorphous Si: H semiconductor layer 7: i-type amorphous Amorphous Si: H semiconductor layer 8: p-type amorphous amorphous Si: H semiconductor layer 9: ITO transparent electrode 10: Ag surface collecting electrode 11: first photoelectric conversion unit 12: second photoelectric conversion unit 13: first layer zinc oxide Thin film 14: Second layer silicon thin film 15: Third layer zinc oxide thin film 16: Fourth layer silicon thin film 17: Fifth layer zinc oxide thin film 18, 40, 42, 45: Door 19: Load chamber 20: First chamber 21: Second chamber 22: Third chamber 23, 24, 25: High vacuum evacuation system 26: Nitrogen gas introduction line 27, 32, 34: High purity argon gas introduction Line 29: Target (zinc oxide) 30, 39: Shutter 31: High-purity oxygen gas introduction line 33, 44: Infrared heating lamp 35, 38: Film thickness correction plate 36: Target (silicon) 48: Substrate 49: Transport belt 50 , 58, 59: DC power supply 43, 52: Substrate heater 56, 57: RF power supply 51, 60, 61, 62, 63: Low-pass filter

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K029 AA06 BA35 BA43 BA47 BA48 BA49 BA50 BA56 BB02 BC07 BD01 CA05 DA01 DA02 DA08 DB05 EA01 EA05 KA01 5F051 AA02 AA05 CB15 CB20 DA03 DA04 DA17 HA20 5F103 AA08 BB49 BB59 DD RR10

Claims (8)

[Claims] A first chamber having a first sputter film forming section; a third chamber having a second sputter film forming section;
A second chamber provided between the chamber and the third chamber and provided with a high vacuum exhaust mechanism and a substrate heating mechanism;
Each of these chambers is a multilayer film manufacturing apparatus provided with a substrate transfer mechanism for moving a substrate between the chambers. 2. The multilayer according to claim 1, wherein the first sputter deposition unit uses a conductive transparent film material as a target, and the second sputter deposition unit uses a semiconductor film material as a target. Film production equipment. 3. The main component of a target material for a conductive transparent film in a first sputter deposition portion is any one of zinc oxide, tin oxide, ITO, and titanium oxide. The multilayer film manufacturing apparatus according to claim 2, further comprising: 4. The method according to claim 1, wherein the target material for the semiconductor film in the second sputter deposition part is either silicon or silicon carbon, and the target material contains impurities for imparting conductivity. The multilayer film manufacturing apparatus according to claim 2. 5. A target is attached to the second sputter deposition section at a position facing the substrate conveyed into the chamber, and a film thickness correction plate made of the same material as the target is provided immediately above the periphery of the target. The multilayer film manufacturing apparatus according to any one of claims 1 to 4, wherein: 6. The multilayer film manufacturing apparatus according to claim 5, wherein the film thickness correction plate is configured to be capable of adjusting a mounting angle with respect to a target, and is connected to a power source capable of adjusting an applied voltage. . 7. Use of the device according to claim 1, wherein (a)
Forming a first layer film on the substrate in the first sputtering film forming section of the first chamber, and (b) transporting the substrate to the second chamber to operate the high vacuum exhaust mechanism and the substrate heating mechanism, and (c) ) The substrate is transported to the third chamber to form a second layer film in the second sputtering film forming section. Thereafter, when the number of layers is further increased, the substrate is moved between the first chamber and the third chamber. A method of manufacturing a multilayer film, wherein a substrate is transferred from one chamber to a second chamber when the substrate is transferred, a high vacuum evacuation mechanism and a substrate heating mechanism are operated, and then transferred to the other chamber to form a film. 8. A conductive transparent film is formed in an oxygen / argon mixed gas atmosphere having an oxygen mixing ratio in a range of 0.5 to 3% in a first sputtering film forming section of a first chamber. A method for producing the multilayer film according to the above.