APPARATUS AND METHOD FOR UNIFORM METALLIZATION ON SUBSTRATE
An apparatus and method for uniform metallization on substrate are provided, achieving highly uniform metallic film deposition at a rate far greater than a conventional film growth rate in electrolyte solutions. The apparatus includes an immersion bath (3021), at least one set of electrode (3002), a substrate holder (3003), at least one ultra/mega sonic device (3004), a reflection plate (3005), and a rotating actuator (3030). The immersion bath contains at least one metal salt electrolyte (3020). The at least one set of electrode (3002) connects to an independent power supply. The substrate holder (3003) holds at least one substrate and electrically connects with a conductive side of the substrate. The conductive side of the substrate is exposed to face the electrode. The at least one ultra/mega sonic device (3004) and the reflection plate (3005) are disposed parallel for generating ultra/mega sonic standing wave in the immersion bath. The rotating actuator (3030) rotates the substrate holder (3003) along its axis in the standing wave field, so as to result in a uniform overall power intensity distribution across the substrate in an accumulated time.
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1. Field of the Invention
The present invention generally relates to an apparatus and a method for metallization on substrate from electrolyte solutions. More particularly, it relates to applying at least one ultra/mega sonic device to a metallization apparatus, incorporating a dynamical controlling mechanism of substrate motions for uniformly applying the acoustic wave across the substrate surface, to achieve highly uniform metallic film deposition at a rate far greater than a conventional film growth rate in electrolyte solutions.
2. The Related Art
Forming of a metallic layer onto a substrate bearing a thin conductive layer, usually copper, in an electrolyte environment, is implemented to form conductive lines during ULSI (ultra large scale integrated) circuit fabrication. Such a process is used to fill cavities, such as vias, trenches, or combined structures of both by electrochemical methods, with an overburden film covering the surface of the substrate. It is critical to obtain a uniform final deposition film because the subsequent process step, commonly a planarization step (such as CMP, chemical-mechanical planarization) for removing the excess conductive metal material, requires a high degree of uniformity in order to achieve an equal electrical performance from device to device at the end of a production line.
Currently, metallization from electrolyte solutions is also employed in filling TSV (through silicon via) to provide vertical connections to 3-D package of substrate stacks. In TSV application, a via opening has a diameter of a few micrometers or larger, with a via depth as deep as several hundreds of micrometers. The dimensions of TSV are orders of magnitude greater than those in a typical dual damascene process. It is a challenge in TSV technology to perform metallization of cavities with such high aspect ratio and depth close to the thickness approaching that of the substrate itself The deposition rates of metallization systems designed for use in the typical dual damascene process, usually a few thousand angstroms per minute, is too low to be efficiently applied in TSV fabrication.
To achieve the void-free and bottom-up gapfill in deep cavities, multiple organic additives are added in the electrolyte solutions to control the local deposition rate. During deposition, these organic additives often break down into byproduct species that may alter the desired metallization process. If incorporated into deposited film as impurities, they may act as nuclei for void formation, causing device reliability failure. Therefore, during the deposition process, high chemical exchange rate of feeding fresh chemicals and removing break-down byproducts in and near the cavities is needed. In addition, with high aspect ratio, vortex is formed inside the cavities below where steady electrolyte flow passes on top of the cavity openings. Convection hardly happens between the vortex and the main flow, and the transport of fresh chemicals and break-down byproducts between bulk electrolyte solution and cavity bottom is mainly by diffusion. For deep cavity such as TSV, the length of diffusion path is longer, further limiting the chemical exchange within the cavity. Moreover, the slow diffusion process along the long path inside TSV hinders the high deposition rate required by economical manufacturing. The maximum deposition rate by electrochemical methods in a mass-transfer limited case is related to the limiting current density, which is inversely proportional to diffusion double layer thickness for a given electrolyte concentration. The thinner the diffusion double layer is, the higher the limiting current density is, thus a higher deposition rate is possible. The PCT international application with the PCT publication number WO/2012/174732, and the PCT application number PCT/CN2011/076262 discloses an apparatus and method by using ultra/mega sonic in the substrate metallization to conquer the above issues.
In the plating bath with a piece of ultra/mega sonic device, the acoustic wave distribution across the ultra/mega sonic device length is not uniform, which is proved by the power intensity test of an acoustic sensor and other optical-acoustic inspection tool. If applying an acoustic wave on the substrate, the acoustic energy acts on each point of the substrate is not the same.
In addition, in the plating bath with an acoustic field, the wave energy lost occurs due to acoustic wave absorbed by the plating bath wall and diffraction around the additives and byproducts. So that the power intensity of acoustic wave in the areas near the acoustic source is different from the power intensity of acoustic wave in the areas far away from the acoustic source. A standing wave formed between two parallel planes maintains the wave energy within the plating bath to minimize the wave energy lost. And the energy transfer only occurs between the node and anti-node within a standing wave. However, the power intensity of acoustic wave at its node and anti-node are different, which leads to nonuniform acoustic performance across the substrate surface during process. What's more, it is difficult to control the standing wave formation during the process due to the difficulty in adjusting the parallelism and distance between the planes.
Therefore, a way of controlling uniformity of acoustic energy distribution further improving the uniformity of plating deposition is desired. And a way of controlling the acoustic field with low wave energy lost in the plating bath is further required.
SUMMARYThe present invention provides at least one ultra/mega sonic device in a metallization apparatus to achieve highly uniform metallic film deposition at a rate far greater than conventional film growth rate in electrolyte solutions. In the present invention, the substrate is dynamically controlled so that the position of the substrate passing through the entire acoustic wave field with different power intensity in each motion cycle, guaranteeing each location of the substrate to receive the same amount of overall sonic energy during the process time, and to accumulatively grow a uniform deposition thickness at a rapid rate.
In an embodiment of the present invention, an apparatus for uniform metallization on substrate includes an immersion bath, at least one set of electrode, a substrate holder, at least one ultra/mega sonic device, a reflection plate, and a rotating actuator. The immersion bath contains at least one metal salt electrolyte. The at least one set of electrode connects to an independent power supply. The substrate holder holds at least one substrate and electrically connects with a conductive side of the substrate. The conductive side of the substrate is exposed to face the electrode. The at least one ultra/mega sonic device and the reflection plate are disposed parallel for generating ultra/mega sonic standing wave in the immersion bath. The rotating actuator rotates the substrate holder along its axis in the standing wave field, so as to result in a uniform overall power intensity distribution across the substrate in an accumulated time.
In another embodiment of the present invention, an apparatus for uniform metallization on substrate includes an immersion bath, at least one set of electrode, a substrate holder, at least one ultra/mega sonic device, and a rotating actuator. The immersion bath contains at least one metal salt electrolyte. The at least one set of electrode connects to an independent power supply. The substrate holder holds at least one substrate and electrically connects with a conductive side of the substrate. The conductive side of the substrate is exposed to face the electrode. The at least one ultra/mega sonic device generates ultra/mega sonic wave in the immersion bath. The rotating actuator rotates the substrate holder along its axis in the acoustic wave field, so as to result in a uniform overall power intensity distribution across the substrate in an accumulated time.
According to an embodiment of the present invention, a method for uniform metallization on substrate includes the following steps: supplying at least one metal salt electrolyte into an immersion bath; transferring a substrate to a substrate holder that is electrically connected with a conductive side of the substrate and the conductive side of the substrate exposed to face an electrode connecting to an independent power supply; applying a first bias voltage to the substrate; rotating the substrate; immersing the substrate into the immersion bath; applying an electrical current to the substrate; turning on an ultra/mega sonic device; oscillating the substrate holder in the acoustic wave field, and meanwhile periodically changing the distance of space between the ultra/mega sonic device and a reflection plate; turning off the ultra/mega sonic device and stopping oscillation of the substrate holder and stopping periodically changing the distance of space between the ultra/mega sonic device and the reflection plate; applying a second bias voltage to the substrate; bringing the substrate out of the metal salt electrolyte; and stopping rotating the substrate.
The present invention will be apparent to those skilled in the art by reading the following description of embodiments thereof, with reference to the attached drawings, in which:
According to exemplary embodiments of the present invention, ultra/mega sonic devices are utilized, and an exemplary ultra/mega sonic device may be applied to a plating apparatus as described in U.S. Pat. No. 6,391,166 or WO/2009/055992.
Referring to
where λ is the wavelength of the acoustic wave and N is an integer. The standing wave with highest power intensity is formed within the space. Under the condition that the distance of the space approximates integer times of half wavelength, the standing wave is also formed but the power intensity of the standing wave is not that strong. The standing wave maintains the wave energy within the space with high uniformity along the wave propagating direction. The wave energy lost caused by the wave propagation in the electrolyte is minimized. In this case, the uniformity of acoustic power intensity distribution from the area near the acoustic source to that far away from the acoustic source is enhanced, and the efficiency of the acoustic generator is enhanced as well. In
However, the energy distribution within a particular wavelength of the standing wave is nonuniform, due to the energy transferring between the node and antinode of the standing wave.
where λ is the wavelength of the ultra/mega sonic wave and N is an integer. Each point of the substrate obtains equal overall power intensity of the ultra/mega sonic wave during an accumulation plating time. As the uniform ultra/mega sonic wave working across the substrate with low wave energy lost, the high plating rate and uniformity of the plated film may be achieved. In
where λ is the wavelength of the ultra/mega sonic wave and N is an integer. The substrate 3001 is horizontally oscillated along propagation direction of the ultra/mega sonic standing wave and at the same time rotating in the standing wave field, based on the theory disclosed in
where λ is the wavelength of the ultra/mega sonic wave and N is an integer. The lateral component movement along Y′ direction, an angle θ (0<θ<45) tilted from Y axis, leads each point on the substrate passing through the strips, and the lateral component movement along X′ direction, an angle θ (0<θ<45) tilted from X axis, leads each point on the substrate passing through node and antinode of the ultra/mega sonic wave in each oscillation cycle. Meanwhile, the reflection plate is oscillated along X′ direction with the amplitude of integer times of half wavelength, so as to ensure the overall power intensity in the space between the ultra/mega sonic device and the reflection plate in each oscillation cycle the same. Herein the oscillation speed of the reflection plate is faster than the oscillation speed of the substrate. This is a solution for the difficulty in the parallelism adjustment of the reflection plate to meet the best standing wave formation condition. It also makes the acoustic wave field in the plating bath stable between each oscillating period, if the condition of the plating bath is unstable by time. The application of above motion controlling mechanism is critical in the plating bath. In
where λ is the wavelength of the ultra/mega sonic wave and N is an integer. The reflection plate 6005 is made of one layer or multiple layers and a space may be provided between layers of the reflection plate 6005 for minimizing the acoustic energy lost. In order to keep the surface of the reflection plate 6005 parallel to the surface of the ultra/mega sonic device 6004, an adjusting mechanism is used to set the reflection plate 6005 position. An oscillating actuator 6006 is mounted to the backside of the reflection plate 6005 with a bellow component 6007 for flexible sealing. The oscillating actuator 6006 oscillates the reflection plate 6005 back and forth along X′ direction which is the standing wave propagation direction, so as to change the distance of the space between the ultra/mega sonic device 6004 and the reflection plate 6005. The oscillating actuator 6006 has a frequency operated from 1 to 10 Hz and amplitude equaling to N times of half wavelength of ultra/mega sonic wave, N is an integer from 1 to 10. The oscillating actuator 6006 works while the horizontal actuator 6013 horizontally oscillates the substrate and the rotating actuator 6030 rotates the substrate in the acoustic wave field. The oscillation speed of the oscillating actuator 6006 is faster than the oscillation speed of the horizontal actuator 6013. A vertical actuator moves the substrate holder 6003 up and down to load or unload the substrate into or out of the immersion bath 6021.
where λ is the wavelength of the ultra/mega sonic standing wave and N is an integer. Meanwhile, the lateral component ΔZ of oscillation along Z axis ensures each point on the substrate 7001 in the acoustic wave field can obtain the same overall power intensity of the ultra/mega sonic wave in each cycle of oscillation. In this case, the power intensity on each point of the substrate 7001 is uniform over the course of process. The vertical actuator 7012 moves the substrate holder 7003 up and down to load or unload the substrate 7001 into or out of the immersion bath 7021.
where λ is the wavelength of the ultra/mega sonic wave and N is an integer. Meanwhile, the lateral component ΔZ′ of oscillation along Z′ direction ensures each point on the substrate 8001 in the acoustic wave field can obtain the same overall power intensity. In this case, the power intensity on each point of the substrate 8001 is uniform over the course of process. The vertical actuator 8012 moves the substrate holder 8003 up and down to load or unload the substrate 8001 into or out of the immersion bath 8021.
It can be seen from
where λ is the wavelength of the ultra/mega sonic standing wave and N is an integer, θ is the angle between the substrate oscillation direction and the normal direction of propagation direction of the ultra/mega sonic standing wave.
A method for uniform metallization on substrate according to an embodiment of the present invention includes the following steps.
Process Sequence
Step 1: supplying at least one metal salt electrolyte into an immersion bath, wherein the metal is selected from a group of metals including Cu, Au, Ag, Pt, Ni, Sn, Co, Pd, Zn;
Step 2: transferring a substrate to a substrate holder that is electrically connected with a conductive side of the substrate and the conductive side of the substrate exposed to face an electrode connecting to an independent power supply;
Step 3: applying a first bias voltage to the substrate, wherein the first bias voltage is in the range of 0.1V to 10V;
Step 4: rotating the substrate with a rotation speed in the range of 10 rpm to 100 rpm;
Step 5: immersing the substrate into the immersion bath;
Step 6: applying an electrical current to the substrate, wherein the electrical current is in the range of 0.1 A to 100 A;
Step 7: turning on an ultra/mega sonic device, wherein the power intensity of the ultra/mega sonic device is in the range of 0.01 to 3 W/cm2 and the operating frequency of the ultra/mega sonic device is set between 20 KHz to 10 MHz;
Step 8: oscillating the substrate holder in the acoustic wave field, the oscillation amplitude is from 1 mm to 300 mm and the frequency is from 0.001 to 0.5 Hz; meanwhile, periodically changing the distance of space between the ultra/mega sonic device and a reflection plate, changing length of the distance of space between the ultra/mega sonic device and the reflection plate equals to
where λ is the wavelength of the ultra/mega sonic wave and N is an integer number from 1 to 10, and changing frequency is in range of 1 to 10 HZ;
Step 9: turning off the ultra/mega sonic device and stopping oscillation of the substrate holder and stopping periodically changing the distance of space between the ultra/mega sonic device and the reflection plate;
Step 10: applying a second bias voltage to the substrate, wherein the second bias voltage is in range of 0.1V to 5V;
Step 11: bringing the substrate out of the metal salt electrolyte;
Step 12: stopping rotating the substrate.
In the step 8, the amplitude of the substrate oscillation equals to
where λ is the wavelength of the ultra/mega sonic wave and N is an integer, θ is the angle between substrate oscillation direction and the normal direction of propagation direction of the ultra/mega sonic wave. The θ is in range of 0 to 45 degree. The frequency of the space distance changing periodically is larger than the frequency of substrate oscillation. Alternatively, the amplitude of the substrate oscillation in the acoustic wave field is controlled as integer times of quarter wavelength of the ultra/mega sonic wave. Alternatively, the substrate oscillates with an angle θ in range of 0 to 45 degree, tilted to the normal direction of propagation direction of the ultra/mega sonic wave, and the amplitude of the substrate oscillation equals to
where λ is wavelength of the ultra/mega sonic wave and N is an integer.
Although the present invention has been described with respect to certain embodiments, examples, and applications, it will be apparent to those skilled in the art that various modifications and changes may be made without departing from the invention.
Claims
1. An apparatus for uniform metallization on substrate comprising:
- an immersion bath containing at least one metal salt electrolyte;
- at least one set of electrode connecting to an independent power supply;
- a substrate holder holding at least one substrate and electrically connecting with a conductive side of the substrate, the conductive side of the substrate exposed to face the electrode;
- at least one ultra/mega sonic device and a reflection plate disposed parallel for generating ultra/mega sonic standing wave in the immersion bath; and
- a rotating actuator rotating the substrate holder along its axis in the standing wave field, so as to result in a uniform overall power intensity distribution across the substrate in an accumulated time.
2. The apparatus of claim 1, further comprising a horizontal actuator oscillating the substrate holder along propagation direction of the ultra/mega sonic standing wave.
3. The apparatus of claim 2, wherein the amplitude of the substrate oscillation equals to N · λ 4, N = 1, 2, 3 … where λ is the wavelength of the ultra/mega sonic standing wave and N is an integer.
4. The apparatus of claim 1, further comprising a horizontal actuator oscillating the substrate holder along a direction tilted an angle θ relative to normal direction of propagation direction of the ultra/mega sonic standing wave.
5. The apparatus of claim 4, wherein the amplitude of the substrate oscillation equals to N · λ 4 sin θ, N = 1, 2, 3 … where λ is the wavelength of the ultra/mega sonic standing wave and N is an integer, θ is the angle between the substrate oscillation direction and the normal direction of propagation direction of the ultra/mega sonic standing wave.
6. The apparatus of claim 4, wherein the θ is 0-45 degrees.
7. The apparatus of claim 1, further comprising a vertical actuator moving the substrate holder up and down to load or unload the substrate into or out of the immersion bath.
8. The apparatus of claim 1, further comprising a vertical actuator oscillating the substrate holder along a direction that an angle θ is formed between the substrate holder oscillation direction and normal direction of propagation direction of the ultra/mega sonic standing wave.
9. The apparatus of claim 8, wherein the amplitude of the substrate oscillation equals to N · λ 4 sin θ, N = 1, 2, 3 … where λ is the wavelength of the ultra/mega sonic standing wave and N is an integer, θ is the angle between the substrate oscillation direction and the normal direction of propagation direction of the ultra/mega sonic standing wave.
10. The apparatus of claim 8, wherein the vertical actuator moves the substrate holder up and down to load or unload the substrate into or out of the immersion bath.
11. The apparatus of claim 8, wherein the vertical actuator oscillates the substrate holder along the direction perpendicular to the horizontal plane.
12. The apparatus of claim 8, wherein the vertical actuator oscillates the substrate holder along the direction tilted an angle relative to the normal direction of the horizontal plane.
13. The apparatus of claim 12, wherein the substrate and the electrode are set with a tilted angle relative to the horizontal plane.
14. The apparatus of claim 1, wherein each set of electrode includes one piece of electrode or more pieces of electrodes with independent power control.
15. The apparatus of claim 1, further comprising at least one layer of permeable membrane being set between the substrate and the electrode.
16. The apparatus of claim 1, wherein the rotation speed of the rotating actuator is in the range of 10 to 100 rpm.
17. The apparatus of claim 1, wherein the ultra/mega sonic device and the reflection plate are mounted on opposite sidewalls of the immersion bath and tilt an angle θ relative to the substrate oscillation direction, and the substrate is set parallel to the horizontal plane, the substrate oscillation direction is perpendicular to the horizontal plane.
18. The apparatus of claim 1, wherein the ultra/mega sonic device and the reflection plate are mounted on opposite sidewalls of the immersion bath and perpendicular to the horizontal plane, the substrate and the electrode are set with a tilted angle relative to the horizontal plane, the substrate is oscillated along a direction tilted the angle relative to the normal direction of the horizontal plane.
19. The apparatus of claim 1, further comprising an adjusting mechanism for adjusting the surface of the reflection plate to be parallel to the surface of the ultra/mega sonic device.
20. The apparatus of claim 19, wherein the adjusting mechanism includes an oscillating actuator for oscillating the reflection plate along propagation direction of the ultra/mega sonic standing wave, the oscillation amplitude is equal to N times of half wavelength of the ultra/mega sonic standing wave, N is an integer number from 1 to 10.
21. The apparatus of claim 20, wherein the frequency of the oscillating actuator is 1 to 10 HZ.
22. An apparatus for uniform metallization on substrate comprising:
- an immersion bath containing at least one metal salt electrolyte;
- at least one set of electrode connecting to an independent power supply;
- a substrate holder holding at least one substrate and electrically connecting with a conductive side of the substrate, the conductive side of the substrate exposed to face the electrode;
- at least one ultra/mega sonic device for generating ultra/mega sonic wave in the immersion bath; and
- a rotating actuator rotating the substrate holder along its axis in the acoustic wave field, so as to result in a uniform overall power intensity distribution across the substrate in an accumulated time.
23. The apparatus of claim 22, further comprising a vertical actuator oscillating the substrate holder along normal direction of propagation direction of the ultra/mega sonic wave.
24. The apparatus of claim 22, further comprising an acoustic reflector placed with a tilted angle relative to the ultra/mega sonic device, avoiding forming standing wave across the surface of the substrate.
25. The apparatus of claim 24, wherein the acoustic reflector is tilted at its width direction to form the tilted angle relative to the ultra/mega sonic device, so as to reflect the acoustic wave upwards and out of the immersion bath.
26. The apparatus of claim 25, wherein the ultra/mega sonic device and the tilted acoustic reflector set the path where the acoustic stream flows horizontally and then out of the immersion bath.
27. A method for uniform metallization on substrate comprising:
- supplying at least one metal salt electrolyte into an immersion bath;
- transferring a substrate to a substrate holder that is electrically connected with a conductive side of the substrate and the conductive side of the substrate exposed to face an electrode connecting to an independent power supply;
- applying a first bias voltage to the substrate;
- rotating the substrate;
- immersing the substrate into the immersion bath;
- applying an electrical current to the substrate;
- turning on an ultra/mega sonic device;
- oscillating the substrate holder in the acoustic wave field, and meanwhile periodically changing the distance of space between the ultra/mega sonic device and a reflection plate;
- turning off the ultra/mega sonic device and stopping oscillation of the substrate holder and stopping periodically changing the distance of space between the ultra/mega sonic device and the reflection plate;
- applying a second bias voltage to the substrate;
- bringing the substrate out of the metal salt electrolyte; and
- stopping rotating the substrate.
28. The method of claim 27, wherein
- the first bias voltage is 0.1V to 10V;
- the electrical current is 0.1 A to 100 A;
- the ultra/mega sonic device has an operating frequency of 20 KHz to 10 MHz and a power intensity of 0.01 to 3 W/cm2;
- the substrate oscillates with an amplitude of 1 mm to 300 mm and a frequency of 0.001 to 0.5 Hz;
- the second bias voltage is 0.1V to 5V.
29. The method of claim 27, wherein the substrate rotates with a rotation speed in range of 10 rpm to 100 rpm.
30. The method of claim 27, wherein the amplitude of the substrate oscillation equals to N · λ 4 sin θ, N = 1, 2, 3 … where λ is the wavelength of the ultra/mega sonic wave and N is an integer, θ is the angle between substrate oscillation direction and the normal direction of propagation direction of the ultra/mega sonic wave.
31. The method of claim 27, wherein the frequency of the space distance changing periodically is larger than the frequency of substrate oscillation.
32. The method of claim 27, wherein the amplitude of the substrate oscillation in the acoustic wave field is controlled as integer times of quarter wavelength of the ultra/mega sonic wave.
33. The method of claim 27, wherein the substrate oscillates with an angle θ in range of 0 to 45 degree, tilted to the normal direction of propagation direction of the ultra/mega sonic wave, and the amplitude of the substrate oscillation equals to N · λ 4 sin θ, N = 1, 2, 3 … where λ is the wavelength of the ultra/mega sonic wave and N is an integer.
Type: Application
Filed: Nov 25, 2014
Publication Date: Sep 14, 2017
Applicant: ACM Research (Shanghai) Inc. (Shanghai)
Inventors: Xi Wang (Shanghai), Hui Wang (Shanghai)
Application Number: 15/529,285