Distribution system for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate

Abstract

The invention relates to a distribution system for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate and a distribution method for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate. The distribution system comprises a substrate holder and an electric control unit. The substrate holder is configured to hold the substrate. The substrate holder is further configured to electrically contact the two substrate surfaces of the substrate and the electric control unit. The electric control unit is configured to control a flow of the electric current for each of the at least two different substrate surfaces individually to obtain different electrolytic surface treatments at the at least two different substrate surfaces.

Description

[0001] Distribution system for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate

[0002] Field of invention

[0003] The invention relates to a distribution system for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate. These different electrolytic surface treatments can be plating processes with different material thicknesses at a front side and a back side of a substrate. The invention further relates to a distribution method for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate.

[0004] Background of the invention

[0005] In many industrial production processes, especially in the high-volume manufacturing for semiconductor devices, electroplating of metallic / conductive material layers onto substrates used for the manufacturing or packaging of micro-, nano- or other types of electronic devices has become a standard practice.

[0006] In order to reduce the tool footprint, the required number of process steps and the number of substrate handling movements, as well as to improve the throughput, it is of outmost interest, that multiple sides (or surface areas) of a substrate can be plated simultaneously, which mostly means a front side and a back side of the substrate.

[0007] In very specific cases, it might be of interest to plate both or at least two sides of a substrate simultaneously with a material layer resulting in layers with different thicknesses, i.e. a thicker layer of a material on e.g. the front side and a thinner layer on e.g. the back side, or the other way around.

[0008] There are many challenges associated with simultaneous plating of two or more sides of a substrate with the goal of having a thicker layer on a first side and a thinner layer on a second side, and potentially an even thinner layer on a third side of a substrate. Summary of the invention

[0009] To achieve different layer thicknesses on different sides or surfaces of the substrate, each substrate surface needs to be placed under a different potential to achieve different current densities.

[0010] Hence, there may be a need to provide an improved distribution system for an electric current for different electrolytic surface treatments on or at at least two different substrate surfaces of a substrate, which in particular allows to obtain different electrolytic surface treatments on at least two different substrate surfaces.

[0011] This objective can be achieved by the subject-matters of the independent claims, wherein further embodiments are incorporated in the dependent claims. It should be noted that the aspects of the invention described in the following apply also to the distribution system for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate and the distribution method for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate.

[0012] According to the present invention, a distribution system for an electric current for different electrolytic surface treatments on or at at least two different substrate surfaces of a substrate is presented. The distribution system comprises at least one substrate holder and at least one electric control unit. The substrate holder is configured to hold at least one substrate. The substrate holder is further configured to electrically contact the two substrate surfaces of the substrate and the electric control unit. The electric control unit is configured to control a flow of the electric current for each of the at least two different substrate surfaces individually to obtain different electrolytic surface treatments at the at least two different substrate surfaces.

[0013] The invention provides an improved distribution system, which allows to obtain different electrolytic surface treatments at two different substrate surfaces. These different electrolytic surface treatments at the two different substrate surfaces may be applied simultaneously or at the same time. The different electrolytic surface treatments might be different material depositions, which e.g. differ in a thickness of a deposited material. The different electrolytic surface treatments may lead to different layer thicknesses at the at least two different substrate surfaces, e.g. a thicker front side and a thinner back side.

[0014] The distribution system according to the invention may further allow a highly precise and / or highly uniform surface treatment, e.g. an electroplating of a metallic and / or conductive layer onto at least two or multiple surfaces of a substrate. The distribution system according to the invention may provide for a high-volume manufacturing character and / or may be focused on minimum floor space requirements (CoO - Cost of Ownership), while enabling and maintaining full control on the plating results for each individual substrate surface.

[0015] In comparison to systems, which provide different surface treatments of different substrate surfaces one after the other (with changes at the surface treatment system and / or movements of the substrate), the distribution system according to the invention may reduce the tool footprint, the required number of process steps and / or the number of substrate handling movements. It may further improve the throughput.

[0016] Of course, different electrolytic surface treatments at more surfaces are possible, e.g. not only a first and a second surface, but also a third and / or a fourth surface, which might be lateral side(s) connecting the first / front and the second / back side. Even more than three or four different electrolytic surface treatments at different surfaces are possible. The surface can be a complete side of a substrate or only a portion of a side of the substate.

[0017] The substrate holder may be configured to electrically connect each of the at least two substrate surfaces of the substrate with the electric control unit. The substrate holder may be further configured to hold the substrate in a shared common electrolyte.

[0018] The distribution system may comprise more than one substrate holder, e.g. two substrate holders, each configured to hold at least one substrate. Each substrate holder may be further configured to electrically contact the at least two substrate surfaces of the at least one substrate and the electric control unit. The electric control unit is configured to control a flow of the electric current for each of the at least two different substrate surfaces individually to obtain different electrolytic surface treatments at the at least two different substrate surfaces.

[0019] The electric control unit may control the flow of the electric current for each of the at least two different substrate surfaces independently to obtain different electrolytic surface treatments at the at least two different substrate surfaces.

[0020] In an embodiment, the electric control unit is configured to control a continuous flow of electric current at one substrate surface. Simultaneously, the electric control unit is configured to control a pulsed flow of electric current at another substrate surface. This can be understood in that one substrate surface is plated continuously at a given current density, which then yields a deposition layer of a certain thickness, while the other substrate surface, required to yield a thinner deposition layer, is turned on and off for given time periods at the same power density to obtain a thinner deposition layer. In other words, one substrate side is plated continuously and one substrate side is plated in a pulsed mode.

[0021] In an embodiment, the electric control unit is configured to control the flow of electric current alternating between the at least two different substrate surfaces. This can be understood as surface treating a first substrate surface, e.g. electro -plating a first side of the substrate, for a certain time period, then switching to a second substrate surface, while turning off the electrical potential on the first substrate surface. Alternating can mean any form of alternation, for example 1 / 2 / 1 / 2, 1 / 1 / 2 / 1, 1 / 2 / 2 / 1, 1 / 1 / 1 / 2 / 1 / 2 / 1 / 1 / 1, etc. In this case, a potential increase in processing time due to the non-simultaneous plating of the at least two substrate surfaces might need to be compensated by e.g. increasing the individual current densities or the like.

[0022] To achieve different layer thicknesses on different surfaces of the substrate, each substrate surface needs to be placed under a different potential (or applying different currents, resulting in different potentials) to achieve different current densities resulting in different plating rates. This may result however, at a given electrolyte concentration and a given flow rate towards each substrate surface, in a stray current from the surface with higher potential (to achieve a faster plating) to the surface with a lower potential (to achieve a slower plating process). For highly uniform electroplated material layers, which are of different thickness on different surfaces of the substrate, this stray current needs to be eliminated or at least reduced. The stray current may cause a higher plating rate in specific areas of the substrate on the lower potential side and therefore a less uniform plating.

[0023] To control the stray current, at least one cross-talk-thief (cathode) can be applied. In an embodiment, the distribution system for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate further comprises a crosstalk-thief. The cross-talk-thief is configured to compensate a stray current flow between the at least two different substrate surfaces. The cross-talk-thief may be electrically controlled independently from the substrate potential. The cross-talk-thief can be understood as an additional cathode. It can be made from an electrically conductive material, which is preferably chemically resistant, as e.g. Titanium. The cross-talk-thief can have a shape of at least a plate, a rod, a cylinder or any other geometric contour.

[0024] One option is to apply one, a first cross-talk-thief. In an embodiment, the cross-talk-thief is a first cross-talk-thief. The first cross-talk-thief may be electrically connectable to a first substrate surface and spatially arranged closer to a second substrate surface than to the first substrate surface. In practice, the first cross-talk-thief may be electrically connected to the surface with the lower potential and placed close to and surrounding the substrate surface which is at a higher potential. As a result, the first cross-talk-thief may be electrically connected to the first substrate surface so that it is on the same potential as the first substrate surface to be plated, and may be physically located closer to the second substrate surface than to the first substrate surface.

[0025] Another option is to apply two cross-talk-thieves, the first cross-talk-thief as described above and a second cross-talk-thief. The second cross-talk-thief may be electrically connectable to a second substrate surface and spatially arranged closer to the first substrate surface than to the second substrate surface. In other words, the first cross-talk-thief may be electrically connected to the surface with the lower potential and placed close to and surrounding the substrate surface which is at a higher potential. The second cross-talk-thief cathode may be electrically connected to the surface with the higher potential and placed close to and surrounding the substrate surface which is at a lower potential. As a result, the second crosstalk-thief may be electrically connected to the second substrate surface so that it is on the same potential as the second substrate surface to be plated, and may be physically located closer to the first substrate surface than to the second substrate surface.

[0026] With one or two cross-talk-thieves, the stray current from the higher current density area (higher potential) escaping to the lower current density area can be stopped before reaching the surface area on a lower potential, while a potential stray current from the lower potential area (lower current density plating) is reduced or stopped in this area before reaching the higher current density area. As a result, the plating is most uniform.

[0027] In an embodiment, the at least one electric control unit is configured to measure an electron density at at least one of the substrate surfaces. The electric control unit may be further configured to calculate a corresponding amount of material deposited on this substrate surface. The electric control unit may be further configured to compensate for a deviation from a predetermined material deposition. Such electric control can be implemented by at least one ohmic control mechanism, which is added to one substrate surface or e.g. two ohmic control mechanisms, which are added to a first and a second substrate surface. The ohmic control mechanism may measure the absolute electron density having reached the individual surface of the substrate, may calculate the equivalent amount of material deposited on the individual surface, and may compensate for a deviation from a target material deposit by adjusting e.g. a plating time. This could mean reducing the plating time on a substrate side, where more has been deposited as targeted or increasing the plating time on a substrate side, where the amount of material deposition is below target. In an embodiment, the compensation is a variation of deposition time. The compensation may be an increase or decrease of deposition time. The compensation may also be an increase or decrease of current flowing, or any other method to control the relative current flowing to the various different substrate surfaces.

[0028] The ohmic control can be understood as to compensate for lost stray current through real-time current measurements and modelling. The ohmic control mechanism can be used with or without the cross-talk- thief / thieves.

[0029] Optionally, the substrate and / or the substrate holder may be moveable. In an embodiment, the electric control unit is configured to control a pulsed flow of electric current to at least one of the two different substrate surfaces based on a position of the substrate. The position of the substrate may be changed relative to a high speed plate for distributing the electrolyte and the current towards at least one substrate surface. The position of the substrate may also be changed relative to the anode, the chamber and / or the cross talk thieves.

[0030] According to the present invention, also a distribution method for an electric current for different electrolytic surface treatments on or at at least two different substrate surfaces of a substrate is presented. The distribution method comprises (not necessarily in this order):

[0031] - providing an electric control unit,

[0032] - providing a substrate holder holding the substrate and electrically contacting the two substrate surfaces of the substrate and the electric control unit, and

[0033] - controlling a flow of the electric current for each of the at least two different substrate surfaces individually to obtain different electrolytic surface treatments at the at least two different substrate surfaces.

[0034] The distribution method according to the invention allows to obtain different electrolytic surface treatments at two different substrate surfaces. The different electrolytic surface treatments might be different material depositions, which e.g. differ in a thickness of a deposited material. The different electrolytic surface treatments may lead to different layer thicknesses at the at least two different substrate surfaces, e.g. a thicker front side and a thinner back side. The distribution method according to the invention may further allow a highly precise and / or highly uniform surface treatment, e.g. an electroplating of a metallic and / or conductive layer onto at least two or multiple surfaces of a substrate. The distribution method according to the invention may provide a high-volume manufacturing character and / or may be focused on minimum floor space requirements, while enabling and maintaining full control on the plating results for each individual substrate surface.

[0035] It shall be understood that the system and the method according to the independent claims have similar and / or identical preferred embodiments, in particular, as defined in the dependent claims. It shall be understood further that a preferred embodiment of the invention can also be any combination of the dependent claims with the respective independent claim.

[0036] These and other aspects of the present invention will become apparent from and be elucidated with reference to the embodiments described hereinafter.

[0037] Brief description of the drawings

[0038] Exemplary embodiments of the invention will be described in the following with reference to the accompanying drawing:

[0039] Figure 1 shows schematically and exemplarily a front view of an embodiment of a distribution system for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate according to the invention.

[0040] Figure 2 shows schematically and exemplarily a detail of Fig. 1 and a top view of an embodiment of a distribution system for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate according to the invention.

[0041] Figure 3 shows an exemplary diagram of a position on a substrate surface in m at the x- axis versus an electric current magnitude in A / m2at the y-axis.

[0042] Figure 4 shows schematically and exemplarily an embodiment of a distribution system for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate according to the invention.

[0043] Figure 5 shows schematically and exemplarily an embodiment of a distribution method for an electric current for different electrolytic surface treatments on at least two different substrate surfaces of a substrate according to the invention. Detailed description of embodiments

[0044] Figure 1 shows schematically and exemplarily a front view of an embodiment of a distribution system 10 for an electric current for different electrolytic surface treatments on at least two different substrate surfaces 31, 32 of a substrate 30 according to the invention. The surface treatments are material depositions and the different electrolytic surface treatments at the at least two different substrate surfaces 31, 32 differ in a thickness of a deposited material.

[0045] The distribution system 10 comprises a substrate holder 11. The substrate holder 11 holds the substrate 30 in a shared common electrolyte 13. The substrate holder 11 may be moveable and may move and / or agitate the substrate 30 to change the position of the substrate 30 relative to an anode 40, the chamber etc.

[0046] The distribution system 10 further comprises an electric control unit 12. The substrate holder 11 electrically contacts the two substrate surfaces 31, 32 of the substrate 30 (only one shown in Fig. 1) and the electric control unit 12. The electric control unit 12 controls a flow of the electric current for each of the at least two different substrate surfaces 31, 32 individually to obtain different electrolytic surface treatments at the at least two different substrate surfaces 31, 32.

[0047] The electric control unit 12 may control a continuous flow of electric current at one substrate surface and, simultaneously, may control a pulsed flow of electric current at another substrate surface. The electric control unit 12 may also control the flow of electric current alternating between the at least two different substrate surfaces 31, 32. The electric control unit 12 may also control a pulsed flow of electric current to at least one of the two different substrate surfaces 31, 32 based on a position of the substrate 30.

[0048] The electric control unit 12 may measure an electron density at at least one of the substrate surfaces 31, 32. It may calculate a corresponding amount of material deposited on this substrate surface. It may compensate for a deviation from a predetermined material deposition. The compensation may be an increase or decrease of deposition time.

[0049] The different electrolytic surface treatments at the at least two different substrate surfaces 31, 32 differ in a thickness of a deposited material. To achieve different layer thicknesses on different surfaces of the substrate 30, each substrate surface needs to be placed under a different potential to achieve different current densities resulting in different plating rates. This may result however in a stray current from the surface with higher potential to the surface with a lower potential. To control the stray current, at least one cross-talk-thief 20 is applied. The cross-talk-thief is an additional cathode made from an electrically conductive and chemically resistant material. It compensates the stray current flow between the two different substrate surfaces 31, 32. The cross-talk-thief 20 may be electrically controlled independently from the substrate potential.

[0050] The cross-talk-thief 20 is electrically connected to a first substrate surface 31 and spatially arranged closer to a second substrate surface 32 than to the first substrate surface 31. In practice, the first cross-talk- thief 20 may be electrically connected to the surface with the lower potential and placed close to and surrounding the substrate surface which is at a higher potential. As a result, the first cross-talk- thief 20 may be electrically connected to the first substrate surface 31 so that it is on the same potential as the first substrate surface 31 to be plated, and may be physically located closer to the second substrate surface 32 than to the first substrate surface 31.

[0051] Figure 2 shows schematically and exemplarily a detail of Fig. 1 and a top view of a part of a distribution system 10 according to the invention. Fig. 2 shows an electric current distribution from each of the anodes 41, 42 (shown on top and bottom in the Fig.) through both distribution bodies 50 to the substrate 30 with its first substrate surface 31 and its second substrate surface 32. The substrate 30 forms the cathode. The current density at the first (in Fig. 2 upper) anode 41 may be higher than the current density at the second (in Fig. 2 lower) anode 42, e.g. by a factor in a range of 1 to 10, 3 to 7 or 4 to 6. The current density at the first (in Fig. 2 upper) anode 41 may be about five times higher than the current density at the second (in Fig. 2 lower) anode 42. The current density at the first (in Fig. 2 upper) anode 41 may be e.g. in a range of 500 A / m2. The current density at the second (in Fig. 2 lower) anode 42 may be e.g. in a range of 100 A / m2. The differences in current densities at the anodes lead to differences in the potentials at the first substrate surface 31 and the second substrate surface 32. The cross-talk- thief 20 leads to a cross-talk compensation of along the arrows 200 to compensate the stray current flow between the first substrate surface 31 and the second substrate surface 32.

[0052] Figure 3 shows an exemplary diagram of a position on a substrate surface in m at the x-axis versus an electric current magnitude in A / m2at the y-axis. The upper pair of lines corresponds to the first substrate surface 31 and an anode with higher current density (e.g. 500 Ampere pro square meter) compared to the lower pair of lines corresponding to the second substrate surface 32 and an anode with lesser current density (e.g. 100 Ampere pro square meter). The solid line shows a situation without cross-talk- thief 20. The broken line shows a situation with cross-talk- thief 20. The gap 201 between solid and broken line each shows the positive effect of the cross-talk- thief 20.

[0053] Figure 4 shows a distribution system 10 with two cross-talk-thieves 20 to compensate a stray current flow between the at least two different substrate surfaces 31, 32. The first cross-talkthief 21 is electrically connected to the first substrate surface 31 and spatially arranged closer to the second substrate surface 32 than to the first substrate surface 31. The second cross-talkthief 22 is electrically connected to the second substrate surface 32 and spatially arranged closer to the first substrate surface 31 than to the second substrate surface 32.

[0054] Figure 5 shows a distribution method for an electric current for different electrolytic surface treatments on at least two different substrate surfaces 31, 32 of a substrate 30, comprising:

[0055] In step SI, providing an electric control unit 12,

[0056] In step S2, providing a substrate holder 11 holding the substrate 30 and electrically contacting the two substrate surfaces 31, 32 of the substrate 30 and the electric control unit 12, and

[0057] In step S3, controlling a flow of the electric current for each of the at least two different substrate surfaces 31, 32 individually to obtain different electrolytic surface treatments at the at least two different substrate surfaces 31, 32.

[0058] It has to be noted that embodiments of the invention are described with reference to different subject matters. In particular, some embodiments are described with reference to method type claims whereas other embodiments are described with reference to the system type claims. However, a person skilled in the art will gather from the above and the following description that, unless otherwise notified, in addition to any combination of features belonging to one type of subject matter also any combination between features relating to different subject matters is considered to be disclosed with this application. However, all features can be combined providing synergetic effects that are more than the simple summation of the features.

[0059] While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing a claimed invention, from a study of the drawings, the disclosure, and the dependent claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single processor or other unit may fulfil the functions of several items re-cited in the claims. The mere fact that certain measures are re-cited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

Claims1. A distribution system (10) for an electric current for different electrolytic surface treatments on at least two different substrate surfaces (31, 32) of a substrate (30), comprising:- a substrate holder (11), and- an electric control unit (12), wherein the substrate holder (11) is configured to hold the substrate (30), wherein the substrate holder (11) is further configured to electrically contact the two substrate surfaces (31, 32) of the substrate (30) and the electric control unit (12), and wherein the electric control unit (12) is configured to control a flow of the electric current for each of the at least two different substrate surfaces (31, 32) individually to obtain different electrolytic surface treatments at the at least two different substrate surfaces (31, 32).

2. The distribution system (10) according to claim 1, wherein the substrate holder (11) is further configured to hold the substrate (30) in a shared common electrolyte (13).

3. The distribution system (10) according to one of the preceding claims, wherein the surface treatments are material depositions and the different electrolytic surface treatments at the at least two different substrate surfaces (31, 32) differ in a thickness of a deposited material.

4. The distribution system (10) according to one of the preceding claims, wherein the electric control unit (12) is configured to control a continuous flow of electric current at one substrate surface and, simultaneously, to control a pulsed flow of electric current at another substrate surface.

5. The distribution system (10) according to one of the preceding claims, wherein the electric control unit (12) is configured to control the flow of electric current alternating between the at least two different substrate surfaces (31, 32).

6. The distribution system (10) according to one of the preceding claims, further comprising a cross-talk-thief (20) configured to compensate a stray current flow between the at least two different substrate surfaces (31, 32).

7. The distribution system (10) according to the preceding claim, wherein the cross-talkthief is a first cross-talk-thief (21) electrically connectable to a first substrate surface (31) and spatially arranged closer to a second substrate surface (32) than to the first substrate surface (31).

8. The distribution system (10) according to the preceding claim, further comprising a second cross-talk-thief (22) electrically connectable to a second substrate surface (32) and spatially arranged closer to the first substrate surface (31) than to the second substrate surface (32).

9. The distribution system (10) according to one of the preceding claims, wherein the electric control unit (12) is configured to measure an electron density at at least one of the substrate surfaces (31, 32), to calculate a corresponding amount of material deposited on this substrate surface, and to compensate for a deviation from a predetermined material deposition.

10. The distribution system (10) according to the preceding claim, wherein the compensation is an increase or decrease of deposition time.

11. The distribution system (10) according to one of the preceding claims, wherein the electric control unit (12) is configured to control a pulsed flow of electric current to at least one of the two different substrate surfaces (31, 32) based on a position of the substrate (30).

12. A distribution method for an electric current for different electrolytic surface treatments on at least two different substrate surfaces (31, 32) of a substrate (30), comprising:- providing an electric control unit (12), - providing a substrate holder (11) holding the substrate (30) and electrically contacting the two substrate surfaces (31, 32) of the substrate (30) and the electric control unit (12), and- controlling a flow of the electric current for each of the at least two different substrate surfaces individually to obtain different electrolytic surface treatments at the at least two different substrate surfaces.

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