AGITATION OF ELECTROLYTIC SOLUTION IN ELECTRODEPOSITION
In a reverse pulse plating of a substrate (110), the electrolytic solution is agitated with a greater power on forward pulses (210) than on reverse pulses (220). An ultrasound agitation source (170) can be positioned at the bottom of the substrate (110) if the anode (134) is at the top. The ultrasound source may contact the substrate's bottom. Other features are also provided.
The present invention relates to agitation of electrolytic solution in electrodeposition.
If the metal is to be electroplated into a via 160 in the substrate surface, the electrodeposition rate near the via bottom can be lower than at the top, and the metal 150 may close the via at the top before a desired amount of metal 150 is deposited into the via. An unwanted closed void may occur in the via as a result.
To increase the plating rate at the via bottom, the solution 140 can be agitated during the plating process to improve the metal ion delivery into the via 160. Agitation may involve mechanical stirring (e.g. using air bubbles or eductors) or ultrasonic energy. For example, ultrasonic energy source 170 can be positioned between the anode 134 and the substrate 110 so as to align the axis of ultrasound propagation with the central axis of via 160, thus allowing the ultrasonic energy to reach the via bottom. See U.S. Pat. No. 6,746,590 B2 issued Jun. 8, 2004 to Zhang et al.
Another technique used to improve the electrodeposition uniformity is periodic reverse pulse plating. This technique slows down the electrodeposition rate at the top relative to the via bottom.
This section summarizes some features of the invention. Other features are described in the subsequent sections. The invention is defined by the appended claims which are incorporated into this section by reference.
In some embodiments of the invention, the net plating rate is made more uniform by turning off agitation during the positive pulses or at least reducing the agitation power during the positive pulses. Turning off or reducing the agitation power during deplating makes the deplating rate less uniform, i.e. the ratio of the deplating rate at the top to the deplating rate at the via bottom increases. Hence, more metal can be deplated at the top per a given amount of metal deplated at the via bottom. The deplating non-uniformity provides better compensation for the plating non-uniformity during the negative pulses.
In some embodiments, the agitation source is placed at the substrate's side opposite to anode terminal 134 not to interfere with the metal ions' movement at the side adjacent to terminal 134. The agitation energy source (e.g. ultrasound source) can be placed close to the substrate, possibly in contact with the substrate.
The invention is not limited to the features and advantages described above. Other features are described below. The invention is defined by the appended claims.
The embodiments described in this section illustrate but do not limit the invention. The invention is defined by the appended claims.
The agitation can also be provided by mechanical stirring or perhaps in other ways.
The embodiment of
The invention is not limited to a particular placement of agitation energy sources. In
The source 170 may be moved relative to substrate 170 during electroplating. See the aforementioned U.S. Pat. No. 6,746,590 B2. Multiple sources 170, some moving and some not, can be provided.
The power supply 130 and the agitation energy sources 170, 410 can be controlled by a controller 420. Controller 420 may be a hardwired circuit and/or may include a computer processor or processors executing computer instructions to control the devices 170, 410. Controller 420 may include a computer readable medium storing computer instructions and/or data to control the devices 170, 410.
The invention is not limited to the embodiments described above. For example, the invention is not limited to flat substrates 110. If the substrate is flat, it can be positioned horizontally as in
Some embodiments of the present invention provide an electrodeposition method comprising: (1) immersing a substrate into an electrolytic solution; (2) providing a voltage between at least a portion of the substrate and an electrode (e.g. 134) spaced from the substrate to effect the electrodeposition onto the substrate, wherein providing the voltage comprises: (2A) providing one or more voltage pulses (e.g. 210) of a first polarity (e.g. negative polarity) in each of a plurality of first periods of time (e.g. 210T) to provide a net electrodeposition of metal onto the substrate in each first period of time (even though the voltage may become positive in a single period 210T between the negative pulses 210 or before the first pulse 210 or after the last pulse 210, the negative pulses dominate in each period 210 in the sense that the net result is electrodeposition); and (2B) providing one or more voltage pulses of a second polarity in each of a plurality of second periods of time (220T) alternating with the first periods of time to provide a net deplating off the substrate in each second period of time; (3) during a first time interval comprising a plurality of the first periods of time and a plurality of the second periods of time (the first interval of time may include a whole or a part of the electrodeposition time), operating one or more agitation sources (e.g. 170 and/or 410) to agitate said solution, wherein at least one of the one or more agitation sources is operated in a first mode during each first period of time and in a second mode during each second period of time. For example, an agitation source 170 or 410 (or both) may provide agitation power PA for the solution in each first period of time but not in the second periods of time. In another example, an agitation source provides agitation power for the solution both in each first period of time and in at least one of the second periods of time, but a maximum of the agitation power in each first period of time is greater than in any of the second periods of time.
In some embodiments, in each first period of time in the first time interval, the one or more voltage pulses of the first polarity are provided only while the at least one of the agitation sources agitates said solution. For example, in
In some embodiments, in each first period of time in the first time interval, the at least one of the agitation sources starts agitating said solution before a start of the one or more voltage pulses of the first polarity. For example, in
In some embodiments, in each first period of time in the first time interval, the one or more voltage pulses of the first polarity are started only when the solution agitation at the substrate has reached its maximum in the first period of time. For example, in
In some embodiments, in each first period of time in the first time interval, the one or more voltage pulses of the first polarity stop no later than the at least one of the agitation sources stops providing agitation power to said solution. For example, in
In some embodiments, in each first period of time in the first time interval, the solution agitation at the substrate becomes zero by the end of the first period of time (e.g. PAS becomes zero by the end of period 210T).
In some embodiments, at least some of ultrasound provided by an ultrasound source is coupled from the ultrasound source directly into the substrate (for example, when source 170 contacts the substrate 110), propagating through the substrate to reach the solution.
In some embodiments, the substrate comprises a via, and the electrodeposition comprises electrodeposition into the via. In some embodiments, at a start of the electrodeposition, the via has an aspect ratio of at least 1:1.
Some embodiments provide an electrodeposition method comprising: (1) immersing a substrate into an electrolytic solution; (2) providing a voltage between at least a portion of the substrate and an electrode spaced from the substrate to effect the electrodeposition onto the substrate, wherein providing the voltage comprises: (2A) providing one or more voltage pulses of a first polarity but no pulses of a second polarity opposite to the first polarity in each of a plurality of first periods of time; and (2B) providing one or more voltage pulses of the second polarity but no pulses of the first polarity in each of a plurality of second periods of time alternating with the first periods of time; (3) during a first time interval comprising a plurality of the first periods of time and a plurality of the second periods of time, providing a greater maximum agitation power for the solution in each first period of time than in any of the second periods of time.
In some embodiments, the agitation power is zero in each second period of time.
Some embodiments provide an electrodeposition method comprising: (1) immersing a substrate into an electrolytic solution; (2) providing a voltage between at least a portion of the substrate and a first electrode spaced from the substrate to effect the electrodeposition onto the substrate, the first electrode being positioned at a first side of the substrate (e.g. top side in
Some embodiments provide an apparatus for performing electrodeposition onto a substrate, the apparatus comprising: a first electrode (e.g. 124) for connection to the substrate; a second electrode (e.g. 134); and at least one ultrasound source; wherein a region for containing the substrate is located between the first electrode and the ultrasound source (in
Other embodiments and variations are within the scope of the invention, as defined by the appended claims.
Claims
1. An electrodeposition method comprising:
- (1) immersing a substrate into an electrolytic solution;
- (2) providing a voltage between at least a portion of the substrate and an electrode spaced from the substrate to effect the electrodeposition onto the substrate, wherein providing the voltage comprises: (2A) providing one or more voltage pulses of a first polarity in each of a plurality of first periods of time to provide a net electrodeposition of metal onto the substrate in each first period of time; and (2B) providing one or more voltage pulses of a second polarity in each of a plurality of second periods of time alternating with the first periods of time to provide a net deplating of the metal off the substrate in each second period of time;
- (3) during a first time interval comprising a plurality of the first periods of time and a plurality of the second periods of time, operating one or more agitation sources to agitate said solution, wherein at least one of the one or more agitation sources is operated in a first mode during each first period of time and in a second mode during each second period of time.
2. The method of claim 1 wherein in operation (3), the at least one of the agitation sources provides agitation power for the solution in each first period of time but not in the second periods of time.
3. The method of claim 2 wherein in each first period of time in the first time interval, the one or more voltage pulses of the first polarity are provided only while the at least one of the agitation sources agitates said solution.
4. The method of claim 2 wherein in each first period of time in the first time interval, the at least one of the agitation sources starts agitating said solution before a start of the one or more voltage pulses of the first polarity.
5. The method of claim 4 wherein in each first period of time in the first time interval, the one or more voltage pulses of the first polarity are started only when the solution agitation at the substrate has reached its maximum in the first period of time.
6. The method of claim 2 wherein in each first period of time in the first time interval, the one or more voltage pulses of the first polarity stop no later than the at least one of the agitation sources stops providing agitation power to said solution.
7. The method of claim 2 wherein in each first period of time in the first time interval, the solution agitation at the substrate becomes zero by the end of the first period of time.
8. The method of claim 1 wherein in operation (3), the at least one of the agitation sources provides agitation power for the solution both in each first period of time and in at least one of the second periods of time, but a maximum of the agitation power in each first period of time is greater than in any of the second periods of time.
9. The method of claim 1 wherein the at least one of the agitation sources is an ultrasound source.
10. The method of claim 9 wherein at least some of ultrasound provided by the ultrasound source is coupled from the ultrasound source directly into the substrate, propagating through the substrate to reach the solution.
11. The method of claim 1 wherein the substrate comprises a via, and the electrodeposition comprises electrodeposition into the via.
12. The method of claim 11 wherein at a start of the electrodeposition, the via has an aspect ratio of at least 1:1.
13. An electrodeposition method comprising:
- (1) immersing a substrate into an electrolytic solution;
- (2) providing a voltage between at least a portion of the substrate and an electrode spaced from the substrate to effect the electrodeposition onto the substrate, wherein providing the voltage comprises: (2A) providing one or more voltage pulses of a first polarity but no pulses of a second polarity opposite to the first polarity in each of a plurality of first periods of time; and (2B) providing one or more voltage pulses of the second polarity but no pulses of the first polarity in each of a plurality of second periods of time alternating with the first periods of time;
- (3) during a first time interval comprising a plurality of the first periods of time and a plurality of the second periods of time, providing a greater maximum agitation power for the solution in each first period of time than in any of the second periods of time.
14. The method of claim 13 wherein in operation (3), the agitation power is zero in each second period of time.
15. The method of claim 14 wherein in each first period of time in the first time interval, the one or more voltage pulses of the first polarity are started only while the agitation power is positive.
16. The method of claim 14 wherein in each first period of time in the first time interval, the agitation power becomes positive before a start of the one or more voltage pulses of the first polarity.
17. The method of claim 16 wherein in each first period of time in the first time interval, the one or more voltage pulses of the first polarity are provided only when the solution agitation at the substrate has reached its maximum in the first period of time.
18. The method of claim 14 wherein in each first period of time in the first time interval, the one or more voltage pulses of the first polarity stop while the agitation power is at its maximum for the first period of time.
19. The method of claim 14 wherein the solution agitation at the substrate is zero throughout each second period of time in the first time interval.
20. The method of claim 13 wherein the agitation power is ultrasonic.
21. The method of claim 20 wherein at least some of the agitation power is coupled directly into the substrate, propagating through the substrate to reach the solution.
22. The method of claim 13 wherein the substrate comprises a via, and the electrodeposition comprises electrodeposition into the via.
23. The method of claim 22 wherein at a start of the electrodeposition, the via has an aspect ratio of at least 1:1.
24. An electrodeposition method comprising:
- (1) immersing a substrate into an electrolytic solution;
- (2) providing a voltage between at least a portion of the substrate and a first electrode spaced from the substrate to effect the electrodeposition onto the substrate, the first electrode being positioned at a first side of the substrate;
- (3) during at least a part of operation (2), operating an ultrasound source to emit ultrasound at a second side of the substrate opposite to the first side of the substrate.
25. The method of claim 22 wherein the substrate comprises a via in a first side of the substrate, the via is not a through via, and the electrodeposition comprises electrodeposition into the via.
26. The method of claim 25 wherein a deepest point of the via is closer to the second side of the substrate than to the via's opening at the first side of the substrate.
27. The method of claim 24 wherein at least some of the ultrasound enters the substrate before entering the solution, and reaches the solution through the substrate.
28. A controller for controlling electrodeposition, the controller comprising circuitry and/or comprising a computer readable medium with computer instructions and/or data, the circuitry and/or the computer instructions and/or data being for:
- (i) providing a voltage between a terminal to be connected to a substrate immersed into an electrolytic solution and an electrode to be spaced from the substrate to effect the electrodeposition onto the substrate, wherein providing the voltage comprises: (A) providing one or more voltage pulses of a first polarity in each of a plurality of first periods of time to provide a net electrodeposition of metal onto the substrate in each first period of time; and (B) providing one or more voltage pulses of a second polarity in each of a plurality of second periods of time alternating with the first periods of time to provide a net deplating of the metal off the substrate in each second period of time;
- (ii) during a first time interval comprising a plurality of the first periods of time and a plurality of the second periods of time, operating one or more agitation sources to agitate said solution, wherein at least one of the one or more agitation sources is operated in a first mode during each first period of time and in a second mode during each second period of time.
29. The controller of claim 28 wherein in operation (ii), the at least one of the agitation sources provides agitation power for the solution in each first period of time but not in the second periods of time.
30. The controller of claim 29 wherein in each first period of time in the first time interval, the one or more voltage pulses of the first polarity are started only while the at least one of the agitation sources agitates said solution.
31. The controller of claim 29 wherein in each first period of time in the first time interval, the at least one of the agitation sources starts agitating said solution before a start of the one or more voltage pulses of the first polarity.
32. The controller of claim 29 wherein in each first period of time in the first time interval, the one or more voltage pulses of the first polarity stop no later than the at least one of the agitation sources stops providing agitation power to said solution.
33. The controller of claim 28 wherein in operation (ii), the at least one of the agitation sources provides agitation power for the solution both in each first period of time and in at least one of the second periods of time, but a maximum of the agitation power in each first period of time is greater than in any of the second periods of time.
34. The controller of claim 28 wherein the at least one of the agitation sources is an ultrasound source.
35. A controller for controlling electrodeposition, the controller comprising circuitry and/or comprising a computer readable medium with computer instructions and/or data, the circuitry and/or the computer instructions and/or data being for:
- (i) providing a voltage between a terminal to be connected to a substrate immersed into an electrolytic solution and an electrode to be spaced from the substrate to effect the electrodeposition onto the substrate, wherein providing the voltage comprises: (A) providing one or more voltage pulses of a first polarity but no pulses of a second polarity opposite to the first polarity in each of a plurality of first periods of time; and (B) providing one or more voltage pulses of the second polarity but no pulses of the first polarity in each of a plurality of second periods of time alternating with the first periods of time;
- (ii) during a first time interval comprising a plurality of the first periods of time and a plurality of the second periods of time, providing a greater maximum agitation power for the solution in each first period of time than in any of the second periods of time.
36. The controller of claim 35 wherein in operation (3), the agitation power is zero in each second period of time.
37. The controller of claim 36 wherein in each first period of time in the first time interval, the one or more voltage pulses of the first polarity are provided only while the agitation power is positive.
38. The controller of claim 36 wherein in each first period of time in the first time interval, the agitation power becomes positive before a start of the one or more voltage pulses of the first polarity.
39. The controller of claim 36 wherein in each first period of time in the first time interval, the one or more voltage pulses of the first polarity stop while the agitation power is at its maximum for the first period of time.
40. The controller of claim 35 wherein the agitation power is ultrasonic.
41. An apparatus for performing electrodeposition onto a substrate, the apparatus comprising:
- a first electrode for connection to the substrate;
- a second electrode; and
- at least one ultrasound source;
- wherein a region for containing the substrate is located between the first electrode and the ultrasound source.
Type: Application
Filed: May 3, 2007
Publication Date: Nov 6, 2008
Inventors: Sergey Savastiouk (San Jose, CA), Valentin Kosenko (Palo Alto, CA), Alexander J. Berger (Palo Alto, CA)
Application Number: 11/744,046
International Classification: C25D 21/10 (20060101); C25D 17/00 (20060101); C25D 21/12 (20060101);