JPH04329873A - Sputtering apparatus - Google Patents

Abstract

PURPOSE:To form Al-Si layer on a substrate at a low cost by improving effective utilizing rate without developing unevenness in composition in the Al-Si layer. CONSTITUTION:An Al-made target 1 bored with plural holes 1a is fixed to a plate 4 through four supports 4a made of Al so as to have the same potential as the plate 4. Plural laying tables 3 made of Al are laid on plural projecting lines 4b on the plate 4 and positioned between the target 1 and the plate 4. On each mounting table 3, an Si-made sub-target 2 is laid so that each sub-target 2 has the same potential as the plate 4. While shifting each mounting table 3 toward the arrow mark A direction, Dc voltage is impressed to the plate 4. A part of sputtered particles of target 1 is flown toward the faced substrate (not shown in the figure) and stuck to the substrate. On the other hand, another part of the sputtered particles of sub-target 2 is flown toward the substrate after passing through each hole 1a in the target 1 and stuck to the substrate. The other sputtered particles are obstructed with the target 1 and do not reach the substrate.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a sputtering apparatus for forming a reflective layer made of aluminum and silicon on a metal substrate for a solar cell by sputtering a target made of aluminum and a sub-target made of silicon. Regarding.

0002

[Prior Art] In order to increase the conversion efficiency of a solar cell in which an active layer of amorphous silicon is provided on a substrate made of metal such as stainless steel, optical reflective properties are applied between the active layer and the substrate. It is also known to further provide a reflective layer made of silver or aluminum having excellent electrical conductivity, and a reflective layer made of aluminum is said to be preferable because aluminum is inexpensive. However, since aluminum migrates into the active layer of amorphous silicon and deteriorates the characteristics of the active layer, it is possible to prevent this migration by mixing less than 20% silicon into aluminum to increase the hardness of the reflective layer. is being carried out.

FIG. 7 is a sectional view of a conventional solar cell using aluminum mixed with silicon (hereinafter referred to as "Al-Si") as a reflective layer. solar cell 401
is an Al substrate 407 made of ferritic stainless steel.
-Si layer (reflection layer) 406, amorphous silicon (hereinafter referred to as "a-Si") N-type layer 405, a-Si
It has a structure in which an intrinsic layer (or non-doped layer) 404, an a-SiP type layer 403, and an ITO transparent electrode layer 402 are laminated in this order. In actual use, unillustrated extraction electrodes, protective films, connection terminals, etc. are attached.

[0004] If the substrate 407 is an inexpensive one, there may be scratches or irregularities on the surface caused by rolling, so in order to uniformly form the a-SiN type layer 405 with a thickness of about 100 Å to prevent the occurrence of shunts. usually includes an Al-Si layer 406
It is said that it is necessary to form the film with a thickness of 2000 to 3000 Å or more. Further, in order to obtain the well-known optical confinement effect of the Al-Si layer 406, irregularities may be actively formed in the Al-Si layer 406.

FIG. 6 shows Al on a metal substrate for solar cells.
- FIG. 2 is a schematic diagram of a conventional example of a sputtering apparatus for forming a Si layer.

The interior of the grounded chamber 10 is divided by a partition plate into a delivery chamber 10a, a sputtering chamber 10b, and a winding chamber 10c in order from the left side of the figure, and sputtering gas (argon, etc.) is not allowed to flow inside the chamber 10. The gas is introduced from the illustrated gas inlet and is evacuated by an exhaust system (not illustrated) while maintaining a predetermined degree of vacuum. The strip-shaped substrate 12 wound around the roll 11a in the delivery chamber 10a passes through the sputtering chamber 10b via a guide/tension roller 11b.
Winding chamber 10 via guide/tension roller 11c
It is wound up on the roll 11d of c. Each roll 11a, 1
1d rotates in synchronization with each other to rotate the substrate 12.
is transported from the delivery chamber 10a to the winding chamber 10c. A plurality of lamp heaters 13 are installed above the substrate 12 in the sputtering chamber 10b, and a reflection plate 14 is installed above each lamp heater 13. The substrate 12 passing through the sputtering chamber 10b is heated by radiant heat from each lamp heater 13 and the reflection plate 14 and maintained at a predetermined temperature.

Below the substrate 12 passing through the sputtering chamber 10b, a backing plate 42 made of copper with excellent thermal conductivity is placed so that a plate-shaped target 41 made of an alloy of aluminum and silicon faces the substrate 12. It is closely attached using indium etc. In order to prevent unnecessary sputtering in areas other than the target 41, an adhesion prevention plate 15 is provided to surround the target 41 and the backing plate 42 inside the dark space generated around the target 41 during sputtering. . The backing plate 42 is attached to one end of the outer tube 16a of the double pipe 16 that enters the sputtering chamber 10b. One side of the inner pipe 16b of the double pipe 16 is attached to the backing plate 42.
back side (the side opposite to the side where the target 41 comes into close contact)
The other end is connected to a cooling water circulation system (not shown) via a supply pipe 17. Also, double pipe 16
The outer pipe 16a is connected to the cooling water circulation system via the discharge pipe 18. Cooling water is supplied by a cooling water circulation system.
It is supplied from the open end of the inner pipe 16b via the supply pipe 17 to fill the inside of the outer pipe 16a, and is discharged from the discharge pipe 18 toward the cooling water circulation device. The target 41 is cooled through the backing plate 42 by the cooling water directly contacting the backing plate 42 and cooling the backing plate 42 . Outer pipe 1 of double pipe 16
A plurality of magnets 19 for confining DC plasma are provided near the back surface of the backing plate 42 inside the magnet 6a. The target 41 includes the cathode of the DC power supply 20 whose anode is grounded, and the outer tube 1 of the double pipe 16.
6a and a backing plate 42 in order. Target 41 and backing plate 4 described above
2. Another set of the double pipe 16 and the plurality of magnets 19 having the same structure is provided adjacent to each other.

When a DC voltage is applied to each target 41 by the DC power supply 20, each target 41 is sputtered, and an Al-Si layer is formed on the target 41 side of the substrate 12 moving in the sputtering chamber 10b. is formed and DC magnetron sputtering is performed.

[0009]

[Problems to be Solved by the Invention] In the conventional sputtering apparatus described above, the ratio (erosion rate) that can be used for sputtering of the target, which is an alloy of aluminum and silicon, is less than 50%, and the sputtering rate from the target is less than 50%. The rate at which sputtered particles are deposited on the substrate (substrate deposition rate) is about 60%. Therefore, the rate at which the target can be used as a deposited layer (effective utilization rate) is 20 to 30%, which is a major obstacle to cost reduction.

In order to increase the effective utilization rate, methods such as arranging the target diagonally or rotating the magnet periodically have been proposed, but even so, the erosion rate exceeds 70% and the substrate still exceeds 80%. Deposition rates are difficult to achieve.

[0011] Also, binary sputtering is known that uses a target made of aluminum and a target made of silicon, but this has the advantage that each target is inexpensive compared to expensive alloy targets. However, since the sputtering rates of aluminum and silicon are different, there is a drawback that the composition of the Al--Si layer formed on the substrate varies. In order to overcome this drawback, it is necessary to arrange a large number of small targets, resulting in new drawbacks such as increased cost and poor maintainability of the device.

The object of the present invention is to use an inexpensive target for binary sputtering instead of an expensive alloy target, and to
It is an object of the present invention to provide a sputtering apparatus that can increase the effective utilization rate of a target without causing variations in the composition of the l-Si layer and form an Al-Si layer on a substrate at a low cost.

[0013]

SUMMARY OF THE INVENTION The sputtering apparatus of the present invention has a sub-target made of silicon disposed at a distance from the substrate, and a plurality of sub-targets disposed facing the substrate between the substrate and the sub-target. The target is made of plate-shaped aluminum and has holes in it.

[0014] Furthermore, a backing plate made of aluminum and to which a DC voltage is applied is placed opposite to the substrate with a gap therebetween, and a sub-plate made of silicon is placed on the backing plate between the substrate and the backing plate. It has a target, and a target made of plate-shaped aluminum with a plurality of holes, which is attached to a backing plate facing the substrate between the substrate and the sub-target, and the sub-target and the target are connected to the backing plate. Some are equipotential.

[0015] Furthermore, the sub-target moving means may be made of aluminum and movable on the backing plate on which the sub-target is placed. Some devices include a sub-target mounting table and a drive device for moving the sub-target mounting table.

[0016]

[Operation] Sputtered aluminum particles sputtered from a target made of aluminum fly toward the opposing substrate and adhere to the substrate. Further, some of the silicon sputtered particles sputtered from the silicon sub-target fly toward the substrate through a plurality of holes formed in the target, and adhere to the substrate. The remaining ones are blocked by the target and do not reach the substrate. As a result, the substrate contains Al with a composition that follows the aperture ratio and distribution of the multiple holes drilled in the target.
- A Si layer is formed.

When the backing plate is made of aluminum, even if the backing plate is sputtered and the sputtered particles fly through a plurality of holes in the target and adhere to the substrate, since the sputtered particles are aluminum, Impurities are not mixed into the Si layer.

In the case where the sub-target moves between the target and the backing plate, the portion of the sub-target exposed from each hole of the target is not sputtered locally, but is sputtered uniformly.

[0019]

Embodiments Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic diagram of a sputtering apparatus according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of the vicinity of a backing plate of this embodiment, and FIG. 3 is a sectional view of the backing plate of this embodiment and its vicinity. be.

1 and 3, those designated by the same reference numerals as those in FIG. 6 are the same as those of the conventional device shown in FIG. 6, and therefore their explanation will be omitted.

As shown in FIG. 2, a plurality of rectangular holes 1a are bored in a rectangular plate-shaped target 1 made of aluminum. The holes 1a are arranged at equal intervals in a plurality of rows along a direction perpendicular to the direction in which the sub-target 2 moves (direction of arrow A), which will be described later. Each hole 1a on one row are alternately arranged so as to be located at corresponding positions between two adjacent holes 1a on adjacent rows. On the other hand, four pillars 4a made of aluminum are provided on the upper surface of a backing plate 4 made of aluminum, which is arranged to face the substrate 12 with a gap in between, and the tips of each pillar 4a touch the four corners of the target 1. The target 1 is attached to the backing plate 4 with a space between the targets 1 and the upper surface of the backing plate 4 by being fitted into and fixed to the respective support holes 1b. The target 1 is also electrically connected via each support 4a and has the same potential as the backing plate 4. In addition, cooling of the target 1 during sputtering is performed by each support 4a.
And cooling water (pure water having a resistivity of 1 MΩcm or more) is used to contact the back surface of the backing plate 4 via the backing plate 4. As above,
As shown in FIG. 1, two targets 1 are attached to two backing plates 4, one each to face a substrate 12.

On the top surface of each backing plate 4, as shown in FIG.
As shown in FIG. 3, a plurality of protruding stripes 4b are formed, and each protruding strip 4b is arranged so as to be hidden below the target 1 without being exposed from each hole 1a of the target 1. .

Each target 1 and each backing plate 4
A plurality of disc-shaped sub-target mounting stands 3 made of aluminum are slidably mounted on the plurality of protrusions 4b between the two. A hollow columnar recess is formed in the upper surface of each sub-target mounting table 3, and a sub-target 2 (disk-shaped silicon wafer) made of silicon is placed in each recess. Note that each sub-target 2 is electrically connected via a sub-target mounting table 3 and has the same potential as the backing plate 4. Further, each sub-target 2 is cooled by cooling water that comes into contact with the back surface of the backing plate 4 via each sub-target mounting table 3 and backing plate 4.

As explained above, each sub-target 2
are arranged at a distance from the substrate 12, and each target 1 is arranged facing the substrate 12 between the substrate 12 and each sub-target 2.

Next, sub-target moving means for moving each sub-target 2 between each target 1 and each backing plate 4 will be explained.

The plurality of sub-target mounting tables 3 are indicated by arrow A.
They are arranged in a plurality of rows along the direction, and two adjacent sub-target mounting tables 3 in each row are connected by links 8 made of aluminum. Further, two adjacent sub-target mounting tables 3 placed on different backing plates 4 are connected by an aluminum link 9, as shown in FIG. One end (left side in FIGS. 1 and 3) of the sub-target mounting tables 3 in each row lined up in the direction of arrow A is connected to an aluminum drive lever 6 of a known drive device 5. By moving the drive lever 6 in the direction of arrow A or the opposite direction, the sub-target mounting tables 3 in each row aligned along the direction of arrow A are moved in the direction of arrow A or the opposite direction. The drive lever 6 is connected to the chamber 1
The drive lever 6 is inserted into the chamber 10 from the outside through a hole drilled in the wall of the chamber 10, and the gap between the drive lever 6 and the hole is sealed by a bellows 7. Note that a magnetic seal may be used instead of the bellows 7.

Next, the operation of the sputtering apparatus of this embodiment will be explained.

The substrate 12 is moved in the direction of arrow A at a speed of, for example, about 20 cm per minute, and the driving device 5 is driven to move each sub-target 2 in the direction of arrow A at a speed of about 1 cm per hour. At the same time, each target 1
When a DC voltage is applied to each sub-target 2 by the DC power supply 20, each target 1 and each sub-target 2 are sputtered.

[0030] Sputtering gas particles collide with the target 1 to sputter the target 1, and the sputtered particles fly toward the substrate 12 and adhere to the substrate 12. The particles of the sputtering gas that have passed through the holes 1a of the target 1 collide with the sub-target 2, and the sub-target 2 is sputtered. It flies toward the substrate 12 and attaches to the substrate 12. The remaining sputtered particles of sub-target 2 are blocked by target 1 and do not reach substrate 12 . As a result, the substrate 12 has an Al-
A Si layer is formed, and by changing the aperture ratio and distribution of the plurality of holes 1a of the target 1, Al with a desired composition is formed.
- A Si layer can be formed.

Since each column 4a supporting the target 1, each sub-target mounting table 3, each link 8, 9, and the drive lever 6 are made of aluminum, they are sputtered and the sputtered particles adhere to the substrate 12. Also Al-
There is no problem of impurities being mixed into the Si layer.

Each sub-target 2 is moved between each target 1 and each backing plate 4 by the drive device 5 in the direction of arrow A.
Since the sub-targets 2 are moved in the direction, the portions of each sub-target 2 exposed from each hole 1a of each target 1 are not locally sputtered, and are sputtered evenly without warping or the like. As a result, each sub-target 2 made of expensive silicon can be used effectively.

A plurality of protruding stripes 4b are formed on the upper surface of each backing plate 4, and each sub-target mounting table 3 slides on the upper surface of each protruding strip 4b. The frictional resistance during movement can be reduced compared to the case where the protruding strip 4b is not provided on the upper surface. Moreover, since each protruding strip 4b is arranged so as to be hidden below the target 1, each protruding strip 4b is sputtered and shaped by the sputtering gas particles passing through each hole 1a of the target 1. Changes are prevented.

The composition of the Al--Si layer formed on the substrate 12 is influenced by the arrangement of the magnets 19, the thickness of the target 1, etc., but the aperture ratio of the target 1 (each hole 1a of the target 1 is The ratio of the opening area of all holes 1a to the area before drilling) is 1 to 80%.
, preferably 5 to 40%.

The shape of each hole to be drilled in the target does not have to be rectangular, and instead of the rectangular hole 1a, a circular hole 21a may be formed as shown in FIG. The circular hole 21a has the advantage of being easier to process than the rectangular hole 1a.

[0036] Furthermore, the inner diameter of each hole drilled in the target is
They do not have to be identical; for example, instead of drilling holes 1a or 21a of the same inner diameter, as shown in FIG.
A plurality of holes 31a may be formed so that the inner diameter gradually increases as the substrate 12 moves in the direction of movement (direction of arrow A). That is, the aperture ratio of the target 31 may be increased as the substrate 12 moves in the direction of movement. In this case, the composition of the Al--Si layer formed on the substrate 12 increases in silicon content as the distance from the substrate 12 increases. Alternatively, the aperture ratio of the target 31 may be decreased in the direction in which the substrate 12 moves. Furthermore, the change may be made along a direction perpendicular to the direction in which the substrate 12 moves; in this case, A
The composition of the l-Si layer corresponds to the change in the aperture ratio along the direction perpendicular to the direction of movement of the substrate 12.

[0037] There is no need for the number of targets 1 to be two;
The number may be 1 or 3 or more. Further, although an example has been shown in which the targets 1 are arranged along the direction in which the substrate 12 moves, the present invention is not limited to this, and multiple rows may be arranged in parallel to the direction in which the substrate 12 moves.

The direction in which the sub-target 2 is moved does not have to be the same direction as the direction in which the substrate 12 is moved; it may be moved in a direction perpendicular to the direction in which the substrate 12 is moved, or it may be moved in other directions. You may move it to

Although the sub-target mounting table 3 is shown as having a disc shape with a cylindrical recess, it is not limited to this, and may have other shapes such as a rectangular plate shape. good.

[0040] Although an example has been shown in which one sub-target 2 is placed on each sub-target mounting table 3, there is no need to limit it to this, and each sub-target placing table 3 can be manufactured in a large size.
A plurality of sub-targets 2 may be placed.

The sub-target moving means for moving the sub-target 2 connects a plurality of sub-target mounting tables 3 on which the sub-targets 2 are placed by links 8 and 9, and drives the plurality of connected sub-target mounting tables 3. Device 5
Although the configuration in which the robot is moved by the above is shown, it is not limited to this, and other configurations may be used.

Next, using the sputtering apparatus of this example,
A manufacturing example in which an Al--Si layer is formed on the substrate 12 will be described. (Manufacturing Example 1) The substrate 12 is made of ferritic stainless steel SUS430, which has undergone bright annealing treatment, and has a length of 100 m, a width of 30 cm, and a thickness of 0.2 mm, which is then cleaned with alkali. It was used.

Target 1 is made of aluminum with a purity of 4N and has a length of 30 cm, a width of 40 cm, and a thickness of 5 mm.
Prepare a 2cm square rectangular hole 1a in it as shown in Figure 2.
Two pieces of 20 pieces were used in the same arrangement as shown in . These two targets 1 were attached one by one to each of the two backing plates 4 so as to be parallel to the direction in which the substrate 12 moves.

The two backing plates 4 have a purity of 4N.
A board made of aluminum with a length of 32 cm and a width of 42 cm was prepared, and on each upper surface, a plurality of protrusions 4b with a length of 50 mm, a width of 1 mm, and a height of 2 mm were provided perpendicular to the direction in which the substrate 12 moves. Multiple rows were formed in the direction. Column spacing is 1
They were equally spaced in cm.

The sub-target mounting table 3 was prepared by hollowing out a cylindrical recess of 80 mm in inner diameter and 3 mm in depth in a disk-shaped one made of aluminum with a purity of 4N and having an outer diameter of 100 mm and a height of 10 mm. Eight sub-target mounting tables 3 were arranged between each target 1 and each backing plate 4.

[0046] Sub-target 2 is N type and 1k.
Disc-shaped silicon wafers having a resistivity of Ωcm, a thickness of 0.2 mm, and an outer diameter of 3 inches were used, and one silicon wafer was placed on each sub-target mounting table 3.

The links 8, 9 and the drive lever 9 were each made of aluminum with a purity of 4N.

The interior of the sputtering chamber 10b of the chamber 10 is 4×10 −6
The pressure was reduced to Torr, and then argon (20 sccm
) while increasing the internal pressure of the sputtering chamber 10b to 2x10-
It was maintained at 4 Torr.

The moving speed of the substrate 12 was set at 20 cm per minute, and the temperature of the substrate 12 moving within the sputtering chamber 10b was maintained at 100° C. by heating with a lamp heater 9.

Each sub-target mounting table 3 has a driving device 5.
The substrate 12 was moved at a speed of 1 cm per hour in a direction perpendicular to the direction in which it was moved.

A formed on the substrate 12 under the above conditions
The thickness of the l-Si layer was 3000 Å, and the surface of the Al-Si layer was flat. Further, the silicon content was 7%. (Production Example 2) As the substrate 12, an electrolytically polished martensitic stainless steel SUS304 was used after being cleaned with a solvent. The target has the same arrangement as shown in FIG. 5, and has 20 circular holes 31a arranged in three rows in a direction perpendicular to the direction in which the substrate 12 moves. As the inner diameter progresses in the direction in which the substrate 12 moves, it becomes φ3 cm, φ1.5 cm,
The diameter was decreased to 1 cm in order for each row. The moving speed of the substrate 12 is 10c/min, which is slower than in production example 1.
The temperature of the substrate 12 moving in the sputtering chamber 10b was set at 180° C., which was higher than that in Production Example 1. Other conditions were the same as in Production Example 1.

A formed on the substrate 12 under the above conditions
The thickness of the l-Si layer was 6000 Å, and the surface of the Al-Si layer was formed into a rough surface having unevenness without whiskers, that is, a shape excellent in light confinement effect. Further, the average silicon content was 6%.

As described in Production Example 1 and Production Example 2,
The sputtering apparatus of this embodiment can form the thickness of the Al--Si layer and the surface of the Al--Si layer to desired values as before, without impairing the conventional functions.

[0054]

[Effects of the Invention] As explained above, the present invention has the following effects.

[0055] A sub-target made of silicon is placed with a space between it and the substrate, a plurality of holes are made in a plate-shaped target made of aluminum, and this target is placed between the substrate and the sub-target so as to face the substrate. By doing so, it is possible to form an Al--Si layer on the substrate with a composition that follows the aperture ratio and distribution of the plurality of holes in the target, without arranging many small targets as in conventional binary sputtering. In other words, there is no need to particularly process the sub-target made of expensive silicon, and by simply changing the aperture ratio and distribution of multiple holes in the target made of cheap aluminum, an Al-Si layer with a desired composition can be formed on the substrate at a low cost. can be formed into

According to the second aspect of the invention, even when the backing plate is sputtered and the sputtered particles pass through each hole of the target and adhere to the substrate, since the backing plate is made of aluminum, the A of the substrate is
This does not mean that impurities are mixed into the l-Si layer.

According to the third aspect of the present invention, only the portion of the sub-target exposed from each hole of the target is not sputtered locally, but the sub-target made of expensive silicon is evenly sputtered and effectively utilized. rate can be increased.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a sputtering apparatus according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the vicinity of the backing plate of the same embodiment.

FIG. 3 is a sectional view of the backing plate and its vicinity in the same embodiment.

FIG. 4 is a perspective view of another example of the target of the same embodiment.

FIG. 5 is a perspective view of another example of the target of the same embodiment.

FIG. 6 is a schematic diagram of a conventional sputtering apparatus.

FIG. 7 is a cross-sectional view of a conventional solar cell using an Al-Si layer as a reflective layer.

[Explanation of symbols]

1, 21, 31 Targets 1a, 21a, 31a Holes 1b, 21b, 31b Support hole 2 Sub-target 3 Sub-target mounting table 4 Backing plate 4a Support 4b Projection strip 5 Drive device 6 Drive lever 7 Bellows 8, 9 Links 10 Chamber 10a Delivery chamber 10b Sputtering chamber 10c Winding chambers 11a, 11d Rolls 11b, 11c Guide/tension roller 12
Board 13 Lamp heater 14 Reflector 15 Anti-adhesive plate 16 Double pipe 16a Outer pipe 16b Inner pipe 17 Supply pipe 18 Discharge pipe 19 Magnet 20 DC power supply

Claims (4)

[Claims] 1. A sputtering apparatus for forming a layer made of aluminum and silicon on a substrate by a sputtering method, comprising: a sub-target made of silicon disposed with a space between the substrate and the sub-target; 1. A sputtering apparatus comprising a plate-shaped aluminum target with a plurality of holes, the target being disposed facing the substrate in between. 2. A sputtering apparatus for forming a layer made of aluminum and silicon on a substrate by a sputtering method, wherein a D is disposed facing the substrate with a gap therebetween.
A backing plate made of aluminum to which a C voltage is applied; a sub-target made of silicon placed on the backing plate between the substrate and the backing plate; and a sub-target made of silicon placed between the substrate and the sub-target. and a plate-shaped aluminum target with a plurality of holes formed therein, which is attached to the backing plate facing the sub-target, and the sub-target and the target are at the same potential as the backing plate. sputtering equipment. 3. The sputtering apparatus according to claim 2, further comprising subtarget moving means for moving the subtarget between the target and the backing plate. 4. The sub-target moving means includes a sub-target mounting table made of aluminum and movable on the backing plate on which the sub-target is mounted, and a drive device for moving the sub-target mounting table. The sputtering apparatus according to claim 3.