ATOMIC LAYER DEPOSITION APPARATUS

Abstract

Disclosed is apparatus for atomic layer deposition including a frame, an injector head with longitudinal slots supplying gases to deposition spaces confined by the longitudinal slots and a substrate. The slots are transverse to a movement in a first direction of the substrate, a subframe suspending the injector head; a movable carrier supporting the substrate for movement in the first direction; and gas pads at the subframe outside the injector head between the subframe and the moveable carrier, bearing the subframe on the carrier for the movement in the first direction. Actuators suspend the injector head from the subframe, and a control device connected to the actuators controls the actuators to adjust a working distance between a reference plane of the injector head and the surface of the substrate corresponding to a predetermined distance and to adjust an orientation of the injector head corresponding to an orientation of the substrate.

Claims

1. Apparatus (1) for atomic layer deposition comprising a frame (2) and an injector head (40) provided with longitudinal slots for respectively supplying gasses to respective deposition spaces (41,42,43,44,45,46,47) confined by the longitudinal slots (48,49) and a substrate (8), wherein the longitudinal slots are directed transverse to a movement in a first direction (X) of the substrate (8) with respect to the injector head (40), the apparatus further comprising a sub frame (52) arranged to suspend the injector head; a movable carrier (30) arranged to support the substrate (8) for the movement in the first direction (X); and gas pads (53,54,55) positioned at the sub frame 52 outside the injector head (40) between the sub frame 52 and the moveable carrier (30) to bear the sub frame (52) on the moveable carrier (30) for the movement in the first direction (X) of the substrate (8) under the injector head (40), wherein the apparatus further comprises actuators (60,61,62) for suspending the injector head (40) from the sub frame (52); and a control device (100) connected to the actuators (60,61,62) and arranged to control the actuators to adjust a working distance between a reference plane of the injector head (40) and the surface of the substrate (8) corresponding to a predetermined distance and to adjust an orientation of the injector head (40) corresponding to an orientation of the substrate (8).

2. Apparatus according to claim 1, wherein the apparatus further comprises: a measuring device (70) arranged to determine the distance between a reference plane of the injector head (40) and a surface of the substrate(8) in a second direction (Z);

3. Apparatus according to claim 1, wherein the carrier (8) is provided with bearing surfaces arranged at a border of the carrier opposite the gas pads (53,54,55) to allow a movement of the substrate (8) under the respective longitudinal slots of the injector head (40) in the first direction (X).

4. Apparatus according to claim 1, wherein the apparatus comprises a slab (31) for supporting the carrier, the slab being provided with a guide to direct the carrier in the first direction and a further gas bearing (32,33,34) positioned between the slab (31) and the carrier (30) for bearing the carrier.

5. Apparatus according to claim 4, wherein the further gas bearing is provided with a first longitudinal slot (32) directed in the first direction (X) in a first side of the carrier facing the slab; a second slot (33) circumferential around the first longitudinal slot (32) in the first side; and exhaust holes (34) outside the second slot arranged in the first side.

6. Apparatus according to claim 2, wherein the actuators (60,61,62) comprise a motor (64,65,66) and a spindle (67,68,69) mechanically connected to the motor.

7. Apparatus according to claim 2, wherein the measuring device (70) comprises a radiation source (72) arranged to radiate a beam of coherent radiation, a radiation guide (74,75,76) arranged to direct the beam to and from a surface of the substrate (8) wherein the radiation guide further comprises a reference glass (77,78,79) provided at an exit of the radiation guide in a surface of the injector head (40) faced to the substrate (8); a beam splitter (730,731) positioned between the radiation source and the radiation guide arranged to direct the radiation beam to the radiation guides and to direct a radiation beam reflected from respectively the reference glass and the substrate to a radiation sensor (800) arranged to receive the reflected radiation beams and to convert the received radiation beams in an electrical signal wherein the measuring device is further arranged to determine a distance between the reference glass (77,78,79) and the substrate (8) from the electric signal and to determine an orientation of the substrate (8) with respect to the injector head (40);

8. Apparatus according to claim 7; wherein the radiation guide (74,75,76) comprises an optical fibre to conduct the radiation beam from the radiation source to a guide tube (85), wherein one end of the guide tube (85) is positioned outside of the apparatus (1) facing away from the substrate(8) and the other end of the guide tube (85) is positioned in the injector head opposite to the surface of the substrate (8), wherein the reference glass (77) is arranged at the other end in the injector head facing the substrate (8).

9. Apparatus according to claim 8, wherein the reference glass (77) is integrated in the injector head (40).

10. Apparatus according to claim 7, wherein the control device is arranged, in a first pass, to move the substrate (8) forth and back in the first direction relatively with respect to the injector head (40) and to determine a height map from the measured distances.

11. Apparatus according to claim 10, wherein the control device is further arranged to determine from the height map the working distance between the surface of the substrate (8) and the injector head (40) and to control the actuators (60,61,62) to adjust the injector head in correspondence with the determined working distance.

12. Apparatus according to claim 10, wherein the control device is further arranged to determine an orientation of the substrate(8) and to control the actuators (60,61,62) to adjust the injector head in correspondence with the determined orientation of the substrate (8).

13. Apparatus according to claim 2, wherein the carrier (8) is provided with bearing surfaces arranged at a border of the carrier opposite the gas pads (53,54,55) to allow a movement of the substrate (8) under the respective longitudinal slots of the injector head (40) in the first direction (X).

14. Apparatus according to claim 2, wherein the apparatus comprises a slab (31) for supporting the carrier, the slab being provided with a guide to direct the carrier in the first direction and a further gas bearing (32,33,34) positioned between the slab (31) and the carrier (30) for bearing the carrier.

15. Apparatus according to claim 3, wherein the apparatus comprises a slab (31) for supporting the carrier, the slab being provided with a guide to direct the carrier in the first direction and a further gas bearing (32,33,34) positioned between the slab (31) and the carrier (30) for bearing the carrier.

16. Apparatus according to claim 13, wherein the apparatus comprises a slab (31) for supporting the carrier, the slab being provided with a guide to direct the carrier in the first direction and a further gas bearing (32,33,34) positioned between the slab (31) and the carrier (30) for bearing the carrier.

17. Apparatus according to claim 3, wherein the actuators (60,61,62) comprise a motor (64,65,66) and a spindle (67,68,69) mechanically connected to the motor.

18. Apparatus according to claim 4, wherein the actuators (60,61,62) comprise a motor (64,65,66) and a spindle (67,68,69) mechanically connected to the motor.

19. Apparatus according to claim 5, wherein the actuators (60,61,62) comprise a motor (64,65,66) and a spindle (67,68,69) mechanically connected to the motor.

20. Apparatus according to claim 13, wherein the actuators (60,61,62) comprise a motor (64,65,66) and a spindle (67,68,69) mechanically connected to the motor.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0024] The invention will be described in more detail with reference to the attached drawings, in which:

[0025] FIG. 1 diagrammatically shows a first view of an embodiment of an Atomic Layer Deposition, ALD, apparatus according to the invention;

[0026] FIG. 2 diagrammatically shows a second view of the embodiment of ALD apparatus;

[0027] FIGS. 3A and 3B diagrammatically shows a carrier and a slab of an ALD apparatus;

[0028] FIG. 4 diagrammatically shows an embodiment of an injector head for an ALD apparatus;

[0029] FIG. 5 diagrammatically shows a sub frame, a carrier and an injector head;

[0030] FIG. 6 diagrammatically shows a first perspective view of the sub frame, and the injector head;

[0031] FIG. 7 diagrammatically shows a second perspective view of the sub frame, and the injector head;

[0032] FIG. 8 diagrammatically shows a distance measuring device; and

[0033] FIG. 9 diagrammatically shows a control device for an ALD apparatus.

DETAILED DESCRIPTION OF THE PRESENT INVENTION

[0034] FIG. 1 and FIG. 2 diagrammatically show a first embodiment of atomic layer deposition, ALD, apparatus 1 according to the invention. The ALD apparatus can be used in the manufacturing of photovoltaic solar cells from a substrate. The substrate may contain, for example, glass and have a size of, for example, 60×40 cm, 120×60 cm, or 110×140 cm. The apparatus 1 comprises a housing (not shown) of layered material, for example, a stack of sheet steel, a heatproof insulating material, for example rock wool, and a graphite layer.

[0035] Furthermore, the ALD apparatus 1 may be provided with a frame 2 provided with an inlet port or load lock 3. The load lock 3 can be sealed and are provided with doors for allowing a substrate 8 in or out the ALD apparatus. The inlet port may also be made of steel, graphite, borosilicate or fused silica. The ALD apparatus 1 may furthermore be provided with electric heating elements, for example quartz elements 9 between the load lock and the injector head for producing a desired temperature. The temperature range within can be set in a range of, for example, 80 to 500° C.

[0036] FIG. 1 further shows a coordinate system with an X, Y and Z-axis. The X-axis is directed in a longitudinal direction in a horizontal plane, the Y-axis is perpendicular to the X-axis in the horizontal plane and the Z-axis is perpendicular to both the X and Y-axis. The ALD apparatus 1 is further provided with transport rollers 15 positioned in the frame 2 for transport of the substrate within the ALD apparatus in the X-direction. The transport rollers 15 may be made of fused silica and have a length of 80 cm and a diameter of 100 mm. Some of the transport rollers 15 may be provided with a drive (not shown). The transport rollers 15 can be rotably attached to the frame 2 to enable transport of the substrate 8 inside the ALD apparatus 1 to the gripper station 10.

[0037] In an embodiment the ALD apparatus 1 is provided with a carrier 30 for supporting the substrate 8 and two dummy plates 11, 12 of the same material as the substrate and having an equal thickness of the substrate, for, example glass. Furthermore, the ALD apparatus comprises a gripper station 10. The gripper station 10 is arranged to pick up the substrate 8 and to transport the substrate to the carrier 30.

[0038] The ALD apparatus 1 can be further provided with a slab 31 for supporting the carrier 30 and a gas bearing between the slab 30 and the carrier 31 for bearing the carrier on the slab in the X-direction. The gas can be for example nitrogen.

[0039] FIG. 3A shows schematically a bottom view of the carrier 30 and FIG. 3B shows schematically a top-side view of the carrier 30 and the slab 31. The carrier 30 can be a rectangular metal plate. The slab 31 can be provided with a guide to direct the carrier 30 in the X-direction. The gas bearing between carrier 30 and the slab 31 is provided with a longitudinal slot 32 in a first side of the carrier 30 directed to slab 31. The longitudinal slot 32 is directed in the X-direction and through the centre of the first side of the carrier, a zero-slot 33 that can be, for example, circumferentially provided around the longitudinal slot 32 and exhaust holes or vacuum pads 34 provided outside the zero-slot 33. The carrier 30 is further provided with a first channel connected to the longitudinal slot 32 for receiving pressurized gas at a first pressure higher than 1033 hPa, a second channel connected to the zero-slot 33 for receiving gas at a pressure of 1 hPa, and a third channel to connect the exhaust holes or the vacuum pads 34 to each other and to a vacuum. The vacuum, i.e. pressure is lower than 1 hPa.

[0040] In operation, a gas flow maintained through the gap between the flat surface of the slab 31 and the carrier 30 provides lift to the carrier and simultaneously acts as a seal because the gas flow from the area of high pressure towards the vacuum is restricted by the small dimensions of the gap so that the high pressure in the zero-slot 32 can be maintained. The gas flow can be used to pre-set the gas bearing i.e. gap height.

[0041] The opposite side of the first side of the carrier 30 for supporting the substrate is provided with exhaust holes 35 which are connected to each other and to a second vacuum via a fourth channel for clamping the substrate 8 on the carrier 30.

[0042] The ALD apparatus 1 is further provided width a drive belt 21 and a motor 20 connected to a control device 100 for moving the carrier 31 back and forth in the X-direction on the slab 31 of the ALD apparatus. The ALD apparatus 1 further comprises an injector head 40.

[0043] FIG. 4 shows an embodiment of the injector head 40 provided with eight longitudinal slots 48, 49 for respectively defining seven deposition spaces 41,42,43,44,45,46,47. The first deposition spaces 41,42,46,47 can be further provided with reactant supplies for supply of a first material deposition. The second deposition spaces 43, 44, 45 can be provided with precursor supplies. The longitudinal slots 48, 49 are arranged for supplying an inert gas flow to separate the deposition spaces from each other and the remainder of the space in the ALD apparatus. The longitudinal slots are directed in the Y-direction perpendicular to a moving direction, X-direction, of the substrate.

[0044] The inert gas can be nitrogen. The injector head wherein the deposition space are formed by inert gas flows is known per see from patent NL 2010893. However, in the known injector head the inert gas flows are also used for height adjustment between the injector head and the substrate, however the variation in height that can be adjusted is limited due to restriction in the gasflow through the longitudinal slots. Whereas, in the embodiment of the ALD apparatus according to the invention the precursor and reactant supplies can be designed without substantial flow restrictions to allow for plasma deposition. Thus, towards a surface of the substrate 8, plasma flow is unhindered by any flow restrictions.

[0045] Alternatively or additionally, at least one of a reactant gas, a plasma, laser generated radiation, and ultraviolet radiation, may be provided in the deposition space for reacting the precursor with the reactant gas after deposition of the precursor gas on at least part of the substrate surface in order to obtain the atomic layer on the at least part of the substrate surface.

[0046] In an embodiment of the ALD apparatus according to the invention the ALD apparatus is provided with a sub frame 52 for suspending the injector head 40.

[0047] FIG. 5 shows a schematic side view of the arrangement of sub frame 52, the injector head 40, the carrier 30 and the slab 31.

[0048] FIGS. 6 and 7 show diagrammatically different side views of the arrangement of the sub frame 52, the slab 31, the carrier 30 and the injector head 40. The sub frame 52 is further provided with three gas pads 53, 54, 55, for lifting the sub frame 52from the carrier 30. The gas pads 53, 54, 55 are positioned outside the injector head 40 and opposite a border of the carrier 30 outside the space for supporting the substrate 8. For example, two gas pads 53, 54 can be positioned at a first border in longitudinal direction and a third gas pad 55 can be positioned at the opposite border. The gas pads can be connected to a supply of nitrogen via a central channel.

[0049] Furthermore, the control device 100 comprises a gas flow control unit 101 for adjusting the gas flow through the gas pads to set a predetermined height between a reference surface of the sub frame and the carrier.

[0050] The carrier 52 is further provided with bearing surfaces 57, 58 at the borders opposite to the gas pads 53, 54, 55 of the sub frame 52, so that the substrate 8 can be moved forth and back under the respective longitudinal slots of the injector head 40 along the X-direction.

[0051] The side of the carrier 52 supporting the substrate 8 can be further provided with additional spaces for supporting the additional substrates 11, 12 or dummy substrates, the additional spaces are positioned in a longitudinal direction at opposite sides of the space for supporting the substrate 8. The dummy substrates 11, 12 confine the deposition spaces between the borders of the substrate and the injector head when the borders of the substrate 8 are moving under the injector head.

[0052] The sub frame 52 can be further provided with three actuators 60, 61, 62 to suspend the injector head 40 from the sub frame 52. The actuators 60,61,62 may comprise a motor 64,65,66, for example a stepper motor and a spindle 67,68,69 mechanically coupled to the stepper motor. The control device 100 is further electrically connected to the actuators 60, 61, 62 and arranged to adjust the distances of between the sub frame 52 and the reference surface of the injector head 40 via the three actuators and therewith the height between the injector head 40 and the substrate 8 and the orientation of the injector head 40 with respect to the surface of the substrate 8. This arrangement of actuators 60, 61, 62 can adjust the height between the injector head and the surface of the substrate independently from the gasflows through the respective longitudinal slots 48, 49 and the gas flow through the gas pads 53, 54, 55.

[0053] In the embodiment according to the invention, the height of a deposition space formed between the substrate 8 and the injector head 40 can independently adjusted from the gas flow through the longitudinal slots 48,49 for supplying nitrogen for separating the deposition spaces and the flow of precursor and reaction gasses.

[0054] In an embodiment the ALD apparatus is further provided with a distance measuring device 70 for measuring the distance between a position on the surface of the substrate 8 and a reference plane of the injector head 40. The distance measuring device can be an optical distance measuring device. The reference plane can be a surface of the injector head facing the substrate.

[0055] FIG. 8 shows diagrammatically the optical measuring device 70. The optical measuring device can comprise three interferometers. The interferometers can be provided with a radiation source 72 for example, a solid state laser device arranged outside of the ALD apparatus 1, because an operating temperature inside the ALD apparatus may be higher than the maximum operating temperature of the solid state laser devices. The operating temperature inside the ALD apparatus can be, for example 350° C. The radiation sources can generate radiation with a wavelength between 400 to 1200 nm, including infra-red radiation.

[0056] The interferometer is further provided with two beam splitters 730,731 for obtaining three radiation beams and three radiation guides 74, 75, 76 arranged to direct the respective radiation beams from the beam splitters 730,731 to the surface of the substrate 8 faced to the injector head 40 and to direct the reflected radiation beams from the surface of the substrate 8 back to the beam splitters 730,731. The beam splitters 730,731,732 are further arranged to direct the reflected radiation beams to a radiation sensor 80. The radiation guides 74, 75, 76 may comprise optical fibres, e.g. glass fibres, and guide tubes.

[0057] The guide tubes can be positioned in the ALD apparatus, wherein the ends of the guide tubes facing the substrate 8 on the carrier can be arranged to coincide with the corner points of a triangle. FIG. 6 shows one of the guide tubes 85 mounted in the sub frame 52, one end of the guide tube 85 is positioned at an upper side of the ALD apparatus 1 facing away from the substrate 8 and the other end at the side of the injector head 80 directed to the substrate 8. The guide tubes 85 can be internally coated with a radiation absorbing coating to prevent mutual interference of the radiation beams and influence of infra-red radiation.

[0058] The radiation guides, for example, at the end of the guide tube 85 outside the ALD apparatus, can be further provided with a lens 81,82,83 for adjusting the focus of the respective radiation beams at the surface of the substrate 8. The radiation guides can be further provided with reference glass plates 77, 78, 79. The reference glass plate 77, 78,79 are arranged to reflect a part of the incoming radiation beam a reference radiation beam to the radiation sensor 70 via the beam splitter 730,731. The reference glass plates 77,78,79 can be incorporated in the injector head 40 at the side facing to the substrate 8, outside and near the outer longitudinal slots for supplying nitrogen gas. In this arrangement the nitrogen gas flow can be directed along the reference glass plate in order to prevent parasitic deposition on the reference glass plate.

[0059] The radiation sensor 80 is further electrically coupled to the sensor control device 71. The radiation sensor 80 is arranged to convert the incident radiation beams from the beam splitter 73 into an electric signal.

[0060] In operation, the radiation beam is direct to the substrate and a reference radiation beam reflected from the reference substrate interferes with the reflected radiation beam from the substrate 8 at the radiation sensor 80. The radiation sensor 80 converts the incoming interference pattern in the electric signal. The sensor control device 71 is further arranged to determine from the electric signal distances between the reference glasses 77,78,79 of the sub frame and the surface of the substrate 8. The optical distance measuring device is known per see and can be obtained from Precitec, Germany. The optical distance measuring device can measure differences in height of the substrate between 0 and 8 mm. The resolution of the optical measuring device is typically 1 to 2 micrometre.

[0061] The ALD apparatus may comprise a control device.

[0062] FIG. 9 shows diagrammatically a control device 100 for an ALD apparatus. Furthermore, FIG. 9 shows schematically the actuators 60,61,62, the gas flow controller 101 and the stepper motor 20. The control device can comprise a microcomputer for executing the operating programs. The control device 100 is electrically connected to the actuators 60,61,62, the optical measuring device 71, the air flow control controller 101 to control respectively the gas flow through the bearing pads 53,54,55 and/or the stepper motor 20 to adjust the direction and speed of the carrier 30.

[0063] In operation, in a first step the gripper station 10 in the ALD apparatus places a substrate 8 on the carrier 30 and, in a further step, the ALD apparatus is measuring, in a first pass of the substrate under the injector head 40, distances between three positions of the reference plane of the sub frame and the surface of the substrate at predetermined time intervals, while the substrate 8 is moving forth and back under the injector head 40 with a speed of, for example, 1 m/s. The control device 100 is further arranged to determine a height map of the surface of the substrate 8 from the measured distances and to determine a minimum distance of the injector head 40 to the substrate 8 at which the substrate 8 can be moved freely under the injector head. Furthermore, the orientation of the reference plane of the injector head can be determined from the determined height map.

[0064] In a next step, the control device 100 adjusts the working distance between the reference plane of the injector head 40 and the carrier 8 according to the determined minimum distance and the orientation of the reference plane. In this way, when in a next step, the substrate and carrier are moved back and forth under the injector head 40 the deviations in the height of reaction spaces formed between the respective longitudinal slots of the injector head 40 and the surface of the substrate 8 are minimized.

[0065] In the further steps the substrate 8 can be subsequently passed under the injector head 40, each portion of the surface of the substrate 8 is subsequently exposed to the respective precursor and reaction gasses received via the subsequent longitudinal slots of the injector head.

[0066] In a single pass a (sub) monolayer of the target material can be applied on the substrate, the thickness of that (sub) monolayer is typically between 0.005 and 0.2 nm. In practice, the thickness of a functional layer about 25 nm. The number of passes to obtain that thickness can be for example 125 and 500.

[0067] The speed at which the substrate 8 and the carrier 30 moves under the injector head can be for example 1 m/s.

[0068] The present invention is not limited to the preferred embodiments thereof which are described herein. Rather, the rights sought are defined by the following claims, which allow for numerous modifications.