Device for pulsed laser deposition and a substrate with a substrate surface for reduction of particles on the substrate

Abstract

The invention relates to a device for pulsed laser deposition and a substrate with a substrate surface, which device includes: a substrate holder for holding the substrate; a target arranged facing the substrate surface of the substrate; a velocity filter arranged between the substrate and the target; a pulsed laser directed onto the target at a target spot for generating a plasma plume of target material; and a plasma hole plate arranged between the target and the substrate. The plasma hole plate has a plasma passage opening divided in an upstream section and a downstream section by a dividing plane. The target spot coincides with the dividing plane, and the surface area of the upstream section is larger than the surface area of the downstream section.

Claims

1. A device for pulsed laser deposition, comprising: a substrate holder for holding a substrate; a target arranged facing a substrate surface of the substrate; a pulsed laser configured to direct a laser beam onto the target at a target spot for generating a plasma plume of target material, wherein the surface of the target at the target spot faces the substrate surface; a velocity filter arranged between the substrate and the target, the velocity filter comprising a rotating body with at least one filter passage opening, the rotating body configured to rotate with respect to the target spot; and a plasma hole plate arranged between the target and the substrate, the plasma hole plate comprising a plasma passage opening that is stationary relative to the target spot during a pulsed laser deposition process, wherein the plasma passage opening is divided in an upstream section and a downstream section by a dividing plane which is perpendicular to the direction of rotation of the velocity filter, wherein the target spot coincides with the dividing plane, wherein the dividing plane is fixed with respect to the target spot and the plasma passage opening, and wherein the upstream section of the plasma passage opening has a larger surface area than the downstream section of the plasma passage opening.

2. The device according to claim 1, wherein a length of the upstream section of the plasma passage opening in the direction of rotation of the velocity filter is larger than the length of the downstream section of the plasma passage opening in the direction of rotation of the velocity filter.

3. The device according to claim 2, wherein the plasma hole plate is arranged between the velocity filter and the substrate.

4. The device according to claim 2, wherein, in use, a part of the generated plasma plume is shielded by the plasma hole plate on the downstream section side of the dividing plane.

5. The device according to claim 2, wherein the surface of the target at the target spot is substantially parallel to the substrate surface.

6. The device according to claim 1, wherein the plasma hole plate is arranged between the velocity filter and the substrate.

7. The device according to claim 6, wherein, in use, a part of the generated plasma plume is shielded by the plasma hole plate on the downstream section side of the dividing plane.

8. The device according to claim 6, wherein the surface of the target at the target spot is substantially parallel to the substrate surface.

9. The device according to claim 1, wherein, in use, a part of the generated plasma plume is shielded by the plasma hole plate on the downstream section side of the dividing plane.

10. The device according to claim 9, wherein the dividing plane is perpendicular to the surface of the target at the target spot.

11. The device according to claim 9, wherein the surface of the target at the target spot is substantially parallel to the substrate surface.

12. The device according to claim 1, wherein the surface of the target at the target spot is substantially parallel to the substrate surface.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other features of the invention will be elucidated in conjunction with the accompanying drawings.

(2) FIGS. 1A-1D show a schematic cross-sectional view of a first embodiment of a device according to the invention in four different positions.

(3) FIGS. 2A-2I show different shapes for the plasma passage opening.

(4) FIGS. 3A-3D show a schematic cross-sectional view of a second embodiment of a device according to the invention in four different positions.

DESCRIPTION OF THE INVENTION

(5) FIG. 1A shows a substrate 1 with a substrate surface 2. The substrate 1 is typically arranged in a substrate holder (not shown). A target 3 is arranged facing the substrate surface 2. The target 3 has a target spot 4 on which a laser beam 5 is directed. Typically the laser beam 5 is moved over the target and the substrate 1 is moved, for example rotated, such that a larger area of the substrate surface 2 can be treated.

(6) A velocity filter 6, which is a disc with a filter passage opening 7, rotates between the substrate 1 and the target 3. Furthermore a plasma hole plate 8 with a plasma passage opening 9 is arranged between the velocity filter 6 and the substrate 1. The plasma passage opening 9 is arranged stationary relative to the target spot 4. So, if the laser beam 5 is moved over the target 3 to treat a larger surface of the substrate 1, then the plasma passage opening 9 moves along with the target spot 4.

(7) The pulsed laser 5 is fired at the target spot 4 when the filter passage opening 7 is positioned over the target spot 4 and the generated plasma plume 10 can freely pass the velocity filter 6 through the filter passage opening 7 (See FIG. 1A).

(8) After the laser beam 5 has been fired, the plasma plume 10 will move towards the substrate surface 2 via the filter passage opening 7 and the plasma passage opening 9.

(9) Also particles 11 will start to be expelled from the surface of the target spot 4 in random direction, where the target spot 4 can be considered a point source (see FIG. 1B).

(10) A dividing plane 12, which is perpendicular to the direction of rotation R of the velocity filter 6 and wherein the target spot 4 coincides with the dividing plane 12, divides the space between the substrate 1 and the target 3 in an upstream part U and a downstream part D.

(11) Because the velocity filter 6 rotates, the filter passage opening 7 moves away from the target spot 4, such that particles 11 having a direction into the upstream part U will encounter the velocity filter 6 sooner, than the particles 11 having a direction into the downstream part D (i.e. particles 11 having a directional component in the direction of rotation R of the velocity filter 6).

(12) The plasma passage opening 9 has an upstream section 13 which is larger than the downstream section 14. Due to the smaller downstream section 14, part of the plasma plume 10 will deposit onto the plasma hole plate 8 and will be lost, while the remaining part of the plasma plume 10 passes the upstream section 13 and will be deposited on the substrate surface 2.

(13) When more time passes, the velocity filter 6 will have rotated further, such that the filter passage opening 7 has fully passed beyond the dividing plane 12. Any particles 11 having a direction towards the upstream part U will be caught by the velocity filter 6, while some of the particles 11 having a direction towards the downstream part D could pass through the filter passage opening 7 but will be caught by the plasma hole plate 8 (see FIG. 1C).

(14) After the emission of particles 11 from the target spot 4 has stopped, the velocity filter 6 will have rotated even further and has caught a large part of the particles 11. The particles 11 with a direction towards the downstream part and which managed to pass the filter passage opening 7 will have been caught by the plasma hole plate 8. The plasma plume 10 will have formed a deposit layer of target material onto the substrate surface 2 (see FIG. 1D).

(15) Thus, by reducing the plasma passage opening 9 on the downstream part D, particles 11 managing to pass the filter passage opening 7 will still be filtered by the plasma hole plate 8. This reduces the contamination by particles 11 of the substrate surface 11 and the layer of target material deposited thereon.

(16) FIGS. 2A-2I show different shapes for the plasma passage opening 9 in the plasma hole plate 8 of the device according to FIG. 1. Clearly each plasma passage opening 9 has an upstream section 13 with a larger surface than the downstream section 14. In FIG. 2D even a shape is proposed, where the downstream section 14 has a surface area of zero.

(17) It will be clear that the shape of the plasma passage opening 9 can be determined by a person skilled in the art merely based on an optimization of for example filtering action of the plasma hole plate 8 and the reduction of the depositing rate by the plasma hole plate 8.

(18) FIG. 3A shows a second embodiment of a device according to the invention. A substrate 21 with a substrate surface 22 is arranged in a substrate holder (not shown). A target 23 is provided opposite of the substrate 21. A target spot 24 is irradiated by a pulsed laser 25 such that a plasma plume 30 is generated.

(19) Furthermore, a velocity filter 26 with a filter passage opening 27 is rotated in the direction R between the substrate 21 and target 23.

(20) Also a plasma hole plate 28 with a plasma passage opening 29 is arranged between the substrate 21 and the velocity filter 26. In this embodiment the plasma hole plate 28 is also rotated but in direction O opposite of the direction R of the velocity filter 26. The plasma passage opening 29 can be symmetrical, for example circular.

(21) As shown in FIG. 3A, the pulsed laser 25 generate a plasma plume 30 when the filter passage opening 26 and plasma passage opening 29 align over the target spot 24.

(22) A dividing plane 32, which is perpendicular to the direction of rotation R of the velocity filter 26 and wherein the target spot 24 coincides with the dividing plane 32, divides the space between the substrate 21 and the target 23 in an upstream part U and a downstream part D.

(23) After the target spot 24 has been irradiated by the laser 25, the plasma plume 30 will leave the target 23 towards the substrate 21 via the filter passage opening 27 and the plasma passage opening 29. The plasma plume 30 will be trailed by undesired particles 31.

(24) As the velocity filter 26 rotates further in the direction R, the filter passage opening 27 will no longer be aligned over the target spot, which is the point source of the particles 31, such that particles 31 directed towards the upstream part U will be caught by the velocity filter 26.

(25) At the same time, the plasma hole plate 28 will have rotated in the opposite direction O, such that the plasma passage opening 29 has, relative to the dividing plane 32, an upstream section 33 with a larger surface area than the surface area of the downstream section 34. Although the reduced size of the downstream section 34 cuts of part of the plasma plume 30, it will also reduce the possibility of particles 31 passing through the plasma passage opening 29 and contaminating the substrate surface 22 (see FIG. 3B).

(26) In FIG. 3C the velocity filter 26 has rotated further, such that the filter passage opening 27 has fully past the dividing plane 32, while the plasma hole plate 28 has rotated further such that the plasma passage opening 29 is also past the dividing plane 32. This ensures that no particles 31 can reach any longer the substrate surface 21 and that all remaining particles 31 are caught by either the velocity filter 26 or the plasma hole plate 28.

(27) FIG. 3D shows the position in which the plasma plume 30 has been deposited onto the substrate 21 and wherein the last particles 31 are caught by the plasma hole plate 28.