JP3071660B2 - Method of forming transparent electrode thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a structure with a conductive oxide
The present invention relates to a method for forming a transparent electrode thin film to be formed.

[0002]

2. Description of the Related Art Semiconductor devices such as photovoltaic devices include:
A transparent electrode such as SnO ₂ , ITO or ZnO or A
A metal electrode of g, Al, platinum, copper-titanium alloy or the like is formed as a thin film. These electrode thin films are mainly formed by a sputtering method using those electrode materials as targets. The sputtering method is, for example, a method in which argon ions collide with a target serving as a cathode during glow discharge, and particles ejected therefrom are deposited on a substrate arranged opposite to the target. In recent years, a magnetron sputtering method has been devised to improve the throughput. The magnetron sputtering method is a method in which a generated plasma is confined in the vicinity of a target by arranging a magnetic field orthogonal to an electric field to increase the sputtering efficiency and the deposition rate.

FIG. 5 is a schematic diagram showing a schematic configuration of an apparatus for performing a conventional thin film forming method. Chamber 11
An exhaust device 112 is connected to 1 so that the pressure in the chamber 111 can be reduced when sputtering is performed.
Further, in the chamber 111, a rotating plate 181 and a rotating shutter 113 are arranged at predetermined intervals in a vertical direction, and are each independently rotated about a rotating shaft 115.

A substrate electrode 121 is provided on the lower surface of the rotating plate 181. A bias power supply 161 is connected to the substrate electrode 121. In addition, the substrate electrode 1
A substrate 122 is set on 21.

The rotary shutter 113 has an opening 113
a is formed. The opening 113a has an opening shape corresponding to the substrate 122. Therefore, when the rotary shutter 113 rotates and the opening 113a is positioned below the substrate 122, the shutter state of the rotary shutter 113 with respect to the substrate 122 is released. In addition, by forming the shutter state, it is possible to prevent a problem in the discharge state control at the start of the discharge.

At a lower position in the chamber 111,
A first target electrode 131 and a second target electrode 132 are provided. First target electrode 131
Is connected to the RF power supply 151 and the second target electrode 1
32 is connected to the RF power supply 152. And the first
The first target 191 is set on the target electrode 131, and the second target 192 is set on the second target electrode 132.

In such an apparatus, the thin film made of the material of the first target 191 and the second target 192
Can be formed on the substrate 22.

By the way, the above sputtering method
When a transparent electrode thin film is formed, it is necessary to change the amount of a dopant (for example, Al) with respect to a main electrode material (for example, ZnO) in order to control the conductivity of the transparent electrode. However, since the amount of the dopant is very small with respect to the main electrode material, conventionally, several kinds of targets having different amounts of the dopant are prepared, and the amount of the dopant is adjusted by replacing the target itself. I was Alternatively, two or more targets having different dopant amounts (for example, two dopant amounts of 1% and 5%) are installed, and the applied voltage is adjusted to perform simultaneous sputtering, thereby adjusting the dopant amount. Was like that. In addition, when forming a multilayer film in which the doping amount is continuously changed, it is necessary to prepare an electrode targeting a solid as a raw material of each layer.

[0009]

However, as in the above-described conventional case, if a number of types of targets are prepared and replaced, the production efficiency is reduced and the production cost is increased. Also, in the method of adjusting the amount of dopant by adjusting the applied power when performing simultaneous sputtering for two or more targets, it is difficult to obtain a desired thin film because the adjustment control is difficult, and the productivity is low. Is reduced.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a method for forming a thin film in which fine adjustment of a dopant amount or the like can be easily performed without requiring several kinds of targets having different dopant amounts.

[0011]

The transparent electrode thin film of the present invention is
In order to solve the above-mentioned problem, the formation method is to form a transparent electrode.
Dopin prepared separately from the main target consisting of the main material
Impacts ions on a slave target composed of
The particles of the slave target that was hit by the impact
A first step of depositing on the get,
The ions collide with the primary target on which the
Primary Target Particles and Secondary Targets
Depositing particles of the cutout on the substrate.
Bias voltage to the slave target when performing the first step
The doping amount in the transparent electrode thin film by adjusting the
Is adjusted.

Further, when performing the first step, a slave
The bias voltage to the target
Pressure and the second target
Bias voltage to the main target
Enlarge and continue both processes while maintaining the discharge state
It may be performed afterwards.

[0013]

According to the above arrangement, in the first step , the first step is performed.
By adjusting the assault voltage, the slave target
By varying the degree of sputtering on the get, the amount of secondary target particles deposited on the primary target can be adjusted. Then, in the sputtering from the main target to the substrate in the second step, the main target particles and the sub target particles are deposited on the substrate at a component ratio reflecting the deposition amount of the sub target particles.

Therefore, the component ratio of the thin film deposited on the substrate can be easily adjusted by adjusting the deposition amount of the sub target material in the first step, so that several types of targets having different dopant amounts are prepared. Fine adjustment of the dopant amount and the like can be easily performed without performing. In addition, in the repetition of the first step and the second step, the deposition amount of the target material is made different according to the degree of the repetition, whereby a multilayer film having a different component ratio can be easily formed. If a plurality of slave targets and main targets are prepared, a multilayer film made of different materials can be formed.

The transition from the first step to the second step or the transition from the second step to the first step may be performed by temporarily stopping the discharge state and causing the discharge state again. However, in this case, the film quality may be slightly deteriorated due to the influence of the initial discharge when the discharge is restarted.

If the first step and the second step are performed continuously while maintaining the discharge state, the influence of the initial discharge can be avoided.

[0017]

【Example】

(Embodiment 1) Hereinafter, the present invention will be described with reference to the drawings showing the embodiment.

FIG. 1 is a schematic diagram showing a schematic configuration of an apparatus for performing the method of forming a thin film according to the present invention. Chamber 1
An exhaust device 12 is connected to 1 so that the pressure in the chamber 11 can be reduced when sputtering is performed. In the chamber 11, a first rotating plate 81 and a second rotating plate 82 also serving as a shutter are arranged at predetermined intervals in the vertical direction.
, Each of which is separately rotated.

On the lower surface of the first rotating plate 81,
Of the secondary target electrode 41 and the substrate electrode 21 are provided. The first sub target electrode 41 is connected to a bias power source 71.
, And the substrate electrode 21 is connected to a bias power supply 61. The first sub target electrode 41 has the first
Are set, and the substrate 22 is set on the substrate electrode 21.

The lower surface of the second rotating plate 82 has a second
Are provided. The second sub target electrode 42 is connected to a bias power supply 72. Then, a second slave target 94 is set on the second slave target electrode 42. The second rotating plate 82 has an opening 82a. The opening 82a has an opening shape corresponding to the first slave target 93 and the substrate 22. Therefore, the second
Of the rotating plate 82 is rotated to move the opening 82a to the first position.
Is located below the slave target 93 or the substrate 22, the shutter state of the second rotary plate 82 with respect to the slave target 93 or the substrate 22 is released.

At a lower position in the chamber 11, a first main target electrode 31 and a second main target electrode 32 are arranged. The first main target electrode 31 is connected to the RF power source 51 and the second main target electrode 32
Are connected to an RF power supply 52. The first main target 91 is set on the first main target electrode 31, and the second main target 92 is set on the second main target electrode 32.

The method for forming a thin film according to the present invention using the above apparatus will be described. In the present embodiment, ZnO is used as the first main target 91, Al is used as the second main target 92, and Al ₂ O _{3 is used} as the first sub target 93.
And Al as the second slave target 94.

In the method of forming a thin film according to the present embodiment, first, Ar is introduced into the chamber 11 to a predetermined pressure, and then the RF power is supplied from the RF power source 51 to the main target electrode 31.
Apply power and create a discharge state. Then, Ar ions collide with the first slave target 93, and the particles of the slave target 93 struck out by the impact are deposited on the first main target 91. Hereinafter, this step is referred to as a first step. In this first step, the first rotary plate 81 is rotated by 180 ° from the state shown in FIG. 1, and the first slave target 93 is moved to the opening 82a of the second rotary plate 82.
Turn to. The particles hit from the first slave target 93 are deposited on the first main target 91 through the opening 82a.

Next, ions collide with the first main target 91 on which the particles of the first sub target 93 are deposited, and the particles of the first main target 91 and the first sub target which are struck out by the impact are struck. 93 particles are deposited on the substrate 22. Hereinafter, this step is referred to as a second step. In the second step, the state shown in FIG. 1, that is, the substrate 22 is directed to the opening 82 a of the second rotating plate 82. The particles of the first main target 91 and the particles of the first sub target 93 deposited in the first step are deposited on the substrate 22 through the opening 82a.

The first step and the second step are performed by the second step.
By rotating the first rotating plate 81 while the rotating plate 82 is fixed, the operation can be repeated while maintaining the discharge state. Then, the particles of the first main target 91 and the particles of the first slave target 93 can be uniformly (approximately ± 3%) deposited on the substrate 22 by the sputtering while rotating. Also, in the repetition of the first step and the second step while rotating,
In the first step, the potential difference between the electrodes suitable for it is adjusted, and in the second step, the potential difference between the electrodes suitable for it may be adjusted.
The first step and the second step can be performed without changing the potential difference between the electrodes.

Table 1 below shows various conditions regarding the substrate temperature and the like in the first step and the second step. The numbers in the table correspond to the member numbers in FIG. The self-bias of the first main target electrode 31 was -250V. The unit film thickness on the substrate 22 formed per one rotation of the first rotating plate 81 was 5 angstroms. Then, the final film thickness formed on the substrate 22 was 3000 Å.

[0027]

[Table 1]

FIG. 2 is a graph showing the relationship between the bias voltage applied to the sub target electrode 41 in the first step and the resistivity of the ZnO thin film formed on the substrate.

When the bias voltage applied to the slave target electrode 41 is -200 to -300 V, the difference between the self-bias voltage (-250 V) at the time of discharge of the main target electrode 31 and the difference is about 50 V at most. Therefore, particles of the sub target 93 hardly accumulate on the first main target 91. Therefore, the resistivity of the obtained film is almost the same as the case where only undoped ZnO is targeted.

On the other hand, when the bias voltage of the sub target electrode is -350 V or less, the sub target (Al ₂
O ₃₎ from the primary target (doped ZnO film sputtering is performed on the substrate to ZnO) is formed. The doped ZnO film is formed on the substrate because not only the sputtering from the slave target to the main target but also the sputtering from the main target to the substrate is performed alternately and continuously. That is, the first step and the second step are performed alternately and continuously without changing the potential difference between the electrodes.
However, since the second rotating plate 82 is fixed and the film is formed while rotating the first rotating plate 81 as in this embodiment, the first rotating plate 81 is rotated every half rotation.
And the second step are switched.

By changing the bias voltage of the slave target electrode, the degree of sputtering from the slave target to the main target in the first step can be adjusted. FIG.
Then, as the bias voltage of the slave target electrode becomes lower, the doping amount of Al increases and Z
It can be seen that the resistivity of the nO film decreases. Therefore, the doping amount of the formed ZnO film can be easily changed in the film thickness direction only by changing the bias voltage of the slave target electrode. However, when the bias voltage of the slave target electrode is set lower than -600 V, the resistivity increases because the crystallinity of the film obtained due to excessive doping decreases.

The bias voltage of the slave target electrode is equal to the self-bias voltage (−2) when the main target electrode is discharged.
If it is higher than 50 V), it becomes difficult to maintain the discharge in the first step, and thus the controllability of the film characteristics deteriorates, which is not preferable.

Here, when sputtering from the second slave target 94 to the first main target (ZnO) 91 using Al, a ZnO thin film having a higher doping amount than the case of FIG. Thus, although the resistivity is increased as a result, when a multilayer film is formed, the advantage that the contact resistance between adjacent layers can be reduced can be obtained.

When the second slave target (Al) 94 is used, the first rotating plate 81 is fixed so that the substrate 22 faces the first main target 91, and the second rotating plate 82 is rotated. What should be done is. However, as described above, when forming a multilayer film using the second slave target (Al) 94, the second rotating plate 82 is not simply rotated for forming each film, but is rotated every half rotation. The rotation is temporarily stopped so that the second slave target 94 or the substrate 22 faces the first main target 91 for a certain period of time, and the first step and the second step are performed separately in time.

Therefore, in the first step, it is important to adjust the potential difference between the electrodes suitable for it, and in the second step, it is important to adjust the potential difference between the electrodes suitable for it. Since the switching is performed for each process, the productivity of film formation is reduced. On the other hand, since rotation is temporarily stopped to form a film under conditions suitable for each process, controllability of sputtering is improved, and a high-quality multilayer film can be formed by uniform film formation.

The present invention is applied to a case where a multilayer film of ZnO and Al is used as a back electrode of an amorphous silicon solar cell, and the results are shown below. Note that, as a first step, sputtering was performed from the second slave target (Al) 94 to the first main target (ZnO) 91. At this time, the bias voltage to the second secondary target electrode 42 was set to -550 V, and the other conditions were the same as in Table 1. Under such conditions, an interface layer of 20 Å was formed at the interface between ZnO and Al. As a result, the series resistance is reduced by 20% and the conversion efficiency of the amorphous silicon solar cell is reduced from 11.5% to 12.2% as compared with the back electrode of the multilayer film composed of ZnO and Al formed by the conventional device. Improved.

As described above, in the first step, the sub target 93 (or 94) is switched from the main target 91 to the main target 91.
By changing the degree of sputtering to (or 92), the amount of particles of the slave target 93 (or 94) deposited on the main target 91 (or 92) can be adjusted. And the main target 9 in the second step
In sputtering from 1 (or 92) to the substrate 22,
The main target particles and the sub target particles are deposited on the substrate 22 at a component ratio reflecting the deposition amount of the sub target particles.

Therefore, the component ratio of the thin film deposited on the substrate 22 can be easily adjusted only by adjusting the deposition amount of the slave target material in the first step. Then, as can be seen from FIG. 2, the adjustment of the component ratio can be performed only by adjusting the bias voltage to the slave target electrode.
Also, by repeating the first step and the second step,
Multilayer films having different component ratios can be easily formed. In addition, by preparing a plurality of sub-targets for one main target or preparing a plurality of main targets themselves, a multilayer film having not only a component ratio but also a main material itself can be easily formed.

Further, if the transition between the two steps is performed by the potential difference between the substrate electrode, the main target electrode, and the sub target electrode, the effect of the initial discharge can be eliminated and a thin film of higher quality can be formed.

FIG. 3 is a schematic diagram showing a schematic configuration of an apparatus having another configuration for implementing the thin film forming method of the present invention. 1 is that the apparatus of FIG. 1 has the second secondary target electrode 42 and the second secondary target 94 on the second rotating plate 82, whereas the apparatus of FIG. The point is that the second sub target electrode 42 and the second sub target 94 are provided on the plate 85.

The slide plate 85 is provided in the chamber 11
The second part is configured to move linearly in the horizontal direction within the second part.
Of the secondary target 94 can be put into or taken out of the plasma region. Second
In a state where the secondary target 94 is placed in the plasma region, the spread of the plasma to the substrate electrode 21 can be blocked, and the sputtering from the second secondary target 94 to the first main target 91 can be performed. In a state where the sub target 94 is taken out of the plasma region, the spread of the plasma to the substrate electrode 21 is released, and the sputtering from the first main target 91 to the substrate 22 can be performed.

In this apparatus, the insertion of the first step and the second step in the series of film forming steps is performed by the slide plate 85.
The mechanical control is simplified as compared with the control of the rotation of the rotary plate and its stoppage.

FIG. 4 is a schematic diagram showing a schematic configuration of an apparatus having another configuration for performing the method of forming a thin film according to the present invention. In the apparatus shown in FIG. 4, the chamber 11 has two chamber chambers 11a and 11b arranged side by side and close to each other. A substrate loading chamber (not shown) and a substrate unloading chamber (not shown) are formed at both ends of the chamber 11, and a substrate transport path (not shown) is secured on the mutually adjacent surfaces of the chamber chambers 11a and 11b.
The substrate 22 can be transferred in both chambers 11a and 11b. Then, similarly to the apparatus of FIG. 3, the second sub target electrode 42 and the second
Of the slide plate 8
6, a first sub target electrode 41 and a second sub target 93 are provided. Further, each of the chambers 11a, 11
The shutters 13 'are provided in b.

With the use of such an apparatus, the formation of a multilayer film on the substrate 22 can be continuously performed by sequentially transporting the substrate 22 linearly, thereby improving the productivity of film formation.

[0045]

As described above, according to the present invention,
In a series of steps of forming a thin film, a first step of performing sputtering from a slave target to a main target and a second step of performing sputtering from a main target to a substrate are appropriately incorporated, and the first step is performed. In the above, the component ratio of the thin film deposited on the substrate can be easily adjusted only by adjusting the deposition amount of the slave target material, so that fine adjustment of the dopant amount can be easily performed without preparing several kinds of targets having different dopant amounts. It has the effect of being able to do so.

Further, when the transition between the two steps is performed by the mutual potential difference between the substrate electrode, the main target electrode and the sub target electrode, the stop of the discharge state can be avoided. There is an effect that a higher quality thin film can be formed without the thin film.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of an apparatus for performing a thin film forming method of the present invention.

FIG. 2 is a graph showing a relationship between a bias voltage applied to a slave target electrode and the resistivity of a formed film.

FIG. 3 is a schematic diagram showing a schematic configuration of an apparatus having another configuration for performing the method of forming a thin film of the present invention.

FIG. 4 is a schematic diagram showing a schematic configuration of an apparatus having another configuration for performing the method of forming a thin film of the present invention.

FIG. 5 is a schematic view showing a schematic configuration of an apparatus for performing a conventional thin film forming method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Chamber 21 Substrate electrode 22 Substrate 31 1st main target electrode 32 2nd main target electrode 41 1st sub target electrode 42 2nd sub target electrode 51 RF power supply 52 RF power supply 61 Bias power supply 71 Bias power supply 72 Bias power supply 91 first main target 92 second main target 93 first sub target 94 second sub target

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 14/00-14/58 H01L 21/203

Claims (2)

(57) [Claims] 1. A method of forming a transparent electrode film on a substrate by sputtering phenomenon, or the main material of the transparent electrode
Doping material prepared separately from the main target
A first step of bombarding the configured secondary target with ions and depositing the secondary target particles hit by the impact on the primary target, and causing the primary target particles on which the secondary target particles are deposited to collide with the ions; look-containing particles with a particle and secondary targets of the main targets dislodged by the impact and a second step of depositing on the substrate, the first
Adjust the bias voltage to the slave target when performing the process of
Adjust the doping amount in the transparent electrode thin film
Forming a transparent electrode thin film . 2. The method according to claim 1, wherein the first step is performed by a slave target.
The bias voltage to the target
When performing the second step,
Bias voltage is greater than bias voltage to main target
Thus, the two steps are continuously performed while maintaining the discharge state.
The transparent electrode thin film according to claim 1, wherein
Forming method .