Method for Controlling Stress in a Substrate During Laser Deposition

Abstract

The invention relates to a method for controlling stress in a substrate during laser deposition. The method includes the steps of: providing a laser deposition device including a chamber with a target holder with a target, a substrate holder with a substrate facing the target and a window, the laser deposition device further including a laser beam directed through the window of the chamber onto a spot at the target for generating a plasma plume of target material and depositing the target material onto a surface portion of the substrate in order to form a thin film of target material, wherein the target spot is movable relative to the substrate in order to deposit target material onto a plurality of surface portions of the substrate; defining a plurality of discrete surface portions on the substrate; aligning the target spot one after the other with each of the plurality of discrete surface portions and generating a plasma plume to deposit target material on each of the plurality of discrete surface portions; and adjusting at least one of the parameters of the deposition process depending on the discrete surface portion with which the target spot is aligned, which parameters include temperature, pressure, laser beam pulse duration, laser beam power, distance of target to substrate.

Claims

1. A method for controlling stress in a thin film on a substrate during laser deposition, which method comprises the steps of: providing a laser deposition device comprising a chamber with a target holder with a target, a substrate holder with a substrate facing the target and a window, the laser deposition device further comprising a laser beam directed through the window of the chamber onto a spot at the target for generating a plasma plume of target material and depositing the target material onto a surface portion of the substrate in order to form a thin film of target material, wherein the target spot is movable relative to the substrate in order to deposit target material onto a plurality of surface portions of the substrate; defining a plurality of discrete surface portions on the substrate; aligning the target spot one after the other with each of the plurality of discrete surface portions and generating a plasma plume to deposit target material on each of the plurality of discrete surface portions; and adjusting at least one of the parameters of the deposition process depending on the discrete surface portion with which the target spot is aligned, which parameters comprise temperature, pressure, laser beam pulse duration, laser beam power, distance of target to substrate, spotsize and RF ionization energy.

2. The method according to claim 1, wherein the plurality of discrete surface portions are defined as a two-dimensional grid, for example in longitudinal and transverse direction or in radial and tangential direction.

3. The method according to claim 1, further comprising the steps of: measuring the stress in the deposited thin film on the substrate; comparing the stress measurements with a desired stress profile for the thin film; and taking into account the comparison while adjusting at least one of the parameters of the deposition process.

4. The method according to claim 3, wherein the stress in the thin film is measured in situ with a stress measuring device, such as a wafer bow meter.

5. The method according to claim 1, further comprising the steps of: depositing target material on a first substrate, while maintaining the parameters of the deposition process constant; measuring ex situ the stress in the deposited thin film on the first substrate; calculating adjustments per discrete surface portion based on the stress measurements; performing the steps of claim 1 on a second substrate, while using the calculated adjustments in the step of adjusting at least one of the parameters of the deposition process depending on the discrete surface portion with which the target spot is aligned.

6. The method according to claim 1, wherein the temperature of the substrate at the discrete surface portion with which the target spot is aligned is controlled by irradiating the substrate with a laser beam.

7. The method according to claim 1, wherein the laser deposition device further comprises at least one nozzle, directed towards the discrete surface portion with which the target spot is aligned, and wherein the nozzle is supplied with a controlled gas flow in order to adjust the pressure for the deposition process.

8. The method according to claim 2, further comprising the steps of: measuring the stress in the deposited thin film on the substrate; comparing the stress measurements with a desired stress profile for the thin film; and taking into account the comparison while adjusting at least one of the parameters of the deposition process.

9. The method according to claim 8, wherein the stress in the thin film is measured in situ with a stress measuring device, such as a wafer bow meter.

10. The method according to claim 2, wherein the temperature of the substrate at the discrete surface portion with which the target spot is aligned is controlled by irradiating the substrate with a laser beam.

11. The method according to claim 3, wherein the temperature of the substrate at the discrete surface portion with which the target spot is aligned is controlled by irradiating the substrate with a laser beam.

12. The method according to claim 4, wherein the temperature of the substrate at the discrete surface portion with which the target spot is aligned is controlled by irradiating the substrate with a laser beam.

13. The method according to claim 5, wherein the temperature of the substrate at the discrete surface portion with which the target spot is aligned is controlled by irradiating the substrate with a laser beam.

14. The method according to claim 8, wherein the temperature of the substrate at the discrete surface portion with which the target spot is aligned is controlled by irradiating the substrate with a laser beam.

15. The method according to claim 9, wherein the temperature of the substrate at the discrete surface portion with which the target spot is aligned is controlled by irradiating the substrate with a laser beam.

16. The method according to claim 2, wherein the laser deposition device further comprises at least one nozzle, directed towards the discrete surface portion with which the target spot is aligned, and wherein the nozzle is supplied with a controlled gas flow in order to adjust the pressure for the deposition process.

17. The method according to claim 3, wherein the laser deposition device further comprises at least one nozzle, directed towards the discrete surface portion with which the target spot is aligned, and wherein the nozzle is supplied with a controlled gas flow in order to adjust the pressure for the deposition process.

18. The method according to claim 4, wherein the laser deposition device further comprises at least one nozzle, directed towards the discrete surface portion with which the target spot is aligned, and wherein the nozzle is supplied with a controlled gas flow in order to adjust the pressure for the deposition process.

19. The method according to claim 5, wherein the laser deposition device further comprises at least one nozzle, directed towards the discrete surface portion with which the target spot is aligned, and wherein the nozzle is supplied with a controlled gas flow in order to adjust the pressure for the deposition process.

20. The method according to claim 8, wherein the laser deposition device further comprises at least one nozzle, directed towards the discrete surface portion with which the target spot is aligned, and wherein the nozzle is supplied with a controlled gas flow in order to adjust the pressure for the deposition process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] These and other features of the invention will be elucidated in conjunction with the accompanying drawings.

[0045] FIG. 1 shows a schematic view of a laser deposition device for a method according to the invention.

[0046] FIG. 2A and 2B show a schematic top view of two embodiments of substrates for a method according to the invention.

[0047] FIG. 3 shows a diagram of a first embodiment of the method according to the invention.

[0048] FIG. 4 shows a diagram of a second embodiment of the method according to the invention.

DESCRIPTION OF THE INVENTION

[0049] FIG. 1 shows a laser deposition device 1 for a method according to the invention. The laser deposition device 1 has a chamber 2, in which a target holder with a target 3 and a substrate holder and a substrate 4 are arranged. The target 3 is rotatable by a motor 5 and the substrate 4 is rotatable by a motor 6.

[0050] The chamber 2 is provided with a first window 7 through which a laser beam 8 of a laser 9 is directed onto the target 3 at a target spot 10 to generate a plasma plume 11, which is deposited onto the substrate 4. The laser 9 is movable in radial direction, such that the target spot 10 is moved in radial direction relative to the substrate 4.

[0051] The substrate 4 is heated by a heater 12, which has discrete heating elements 13, such that only a part of the substrate 4 can be heated.

[0052] A drain 14 with a vacuum pump 15 is connected to the chamber 2 in order to obtain a low pressure in the chamber 2. A gas supply 16 with a valve 17 is also connected to the chamber 2 to provide an atmosphere of a certain gas in the chamber 2.

[0053] Furthermore a wafer bow meter 18, 19 is provided, which directs a laser beam 21 through a second window in the chamber 2 to measure the bending of the substrate 4 and derive therefrom the stress of the deposited thin film on the substrate 4.

[0054] A controller 22 is provided to control the movement of the laser 9, the rotation of the target 3, the rotation of the substrate 4, control the vacuum pump 15 and the gas supply 16 in order to perform the method according to the invention. Also the measurements of the wafer bow meter 18, 19 are supplied to the controller 22 to provide feed back of the thin film stress on the substrate 4.

[0055] FIG. 2B shows a top view of a rectangular substrate 30 with defined discrete surface portions 31, which compose a grid in longitudinal and transverse direction. Typically, such a rectangular substrate 30 is moved in X and Y direction in order to align each of the discrete surface portions 31 with the target spot.

[0056] FIG. 2A shows a top view of a disc shaped substrate 4 with defined discrete surface portions 23, which compose a grid in radial and tangential direction. Typically such a disc shaped substrate 4 is rotated in order to move the target spot above each of the discrete surface portions 23.

[0057] FIG. 3 shows a diagram 40 of a first embodiment of the method according to the invention. The diagram 40 starts with the step 41 of providing a laser deposition device, such as shown in FIG. 1. Then the method defines in step 42 a plurality of discrete surface portions 23 on the substrate 4 as shown in FIG. 2A.

[0058] The target spot 10 is then, in step 43, aligned with a discrete surface portion 23 on the substrate 4 and a plasma plume of target material 3 is generated and deposited onto the discrete surface portion 23.

[0059] Then the parameters of the deposition process are adjusted for the next discrete surface portion 23 in step 44, after which step 43 is repeated. The adjustment of the parameters of the deposition process could be adjusting the temperature of the substrate with the heater 12, 13, supplying gas with the gas supply 16 or controlling the vacuum with the vacuum pump 14. The adjustment of the parameters could be controlled by the measurements of the wafer bow meter 18, 19.

[0060] FIG. 4 shows a diagram 50 of a second embodiment. In this method 50, a deposition device 1 as shown for example in FIG. 1 is provided in step 51. Then in step 52 a first substrate is provided in the deposition device 1, on which a plurality of discrete surface portions 23 are defined in step 53 and as shown in FIG. 2A.

[0061] In step 54 the target spot is aligned one after the other with each of the plurality of discrete surface portions 23 and a plasma plume is generated to deposit target material on each of the plurality of discrete surface portions. During this deposition on the first substrate the parameters of the deposition process are kept constant.

[0062] After the deposition process has covered all of the plurality of discrete surface portions 23, the stress of the first substrate is measured in step 55. These measurements are then compared with a desired stress profile and adjustment parameters are calculated therefrom in step 56 and stored in a database 57.

[0063] Then with a second substrate, the deposition process is repeated for each discrete surface portion 23 in step 58, wherein after each deposition on a discrete surface portion 23 the parameters for the deposition process are adjusted with the parameters stored in the database 57 in step 59. The adjusting and deposition is then repeated for each discrete surface portion 23 on order to cover the whole second substrate and reduce the thin film stress on the substrate.