TWI516644B - Electroplating method - Google Patents

Description

Plating method

The present invention relates to an electroplating method for simultaneously plating the front and back sides of a substrate having a through-hole vertically passing through the inside thereof to plate a metal (for example, copper or the like). The membrane is filled with the perforations.

A technique of forming a plurality of metal through-vias vertically through a substrate is conventionally a method of electrically connecting layers in a multilayer stack composed of a plurality of substrates (e.g., semiconductor substrates). It is customary to form a vertical through hole of a substrate by simultaneously plating the front and back surfaces of the substrate through which the perforations are vertically passed, thereby filling the metal plating film into the perforations.

There is known an electroplating apparatus for making a through hole (refer to Japanese Patent No. 4138542). The electroplating apparatus includes a substrate holder for holding the substrate while exposing certain areas on the front and back sides, and surrounding areas surrounding the certain areas, and a pair of anodes respectively configured to be held by the substrate holding member Face to face, face to face. The substrate held by the substrate holding member and the anode are immersed in the plating solution, and then a voltage is applied between the substrate and the anode to simultaneously plate the front and back surfaces of the substrate defined by the vertical perforations, which can be embedded in the metal ( For example, copper) is in the perforation.

The sequence of process steps shown in Figs. 1A to 1D illustrates a method for filling a plating film into a perforation defined in a substrate to form a via hole therein (refer to Japanese Patent No. 4248353).

As shown in FIG. 1A, a preliminary substrate W includes a base 100 in which a vertical through hole 100a is defined, and a barrier layer 102 made of titanium or the like and used as a feed layer ( An electric feed layer) and a seed layer 104 covering all surfaces of the base 100, including the inner surface of the perforations 100a. At the same time, the plating film 106 of the metal (for example, copper or the like) is deposited on the front and back sides of the substrate W on the front and back surfaces of the substrate W and the perforations 100a as shown in FIG. 1B. The plating film 106 in the perforation 100a has a maximum thickness at the center in the depth direction. Then, as shown in FIG. 1C, the growth plating film 106 is connected to each other at the center of the perforation 100a in the depth direction up to the tip end of the plating film 106 layer which has been formed by the wall surface of the perforation 100a. The center of the perforation 100a along the depth direction is thus blocked by the plating film 106, and a recess 108 is formed above and below the closed area. The plating process is further continued to grow the plating film 106 in the recess 108 until the plating film 106 fills the recess 108 as shown in FIG. 1D. In this way, a through hole composed of the plating film 106 is generated in the substrate W.

A plating method in which a perforation defined on a substrate is filled with a metal plating film has been proposed (refer to Japanese Patent Laid-Open Publication No. 2008-513985). According to this plating method, a forward pulse current is supplied to flow between a substrate as a cathode, an anode, and a reverse pulse current having a flow direction opposite to a forward pulse current is also supplied to flow between the substrate and the anode, This completely or substantially completely fills the center of the perforation.

A method for preventing whisker generation when plating a printed wiring board or the like with copper has also been proposed (refer to Japanese Patent Laid-Open Publication No. 2010-95775). According to this method, the DC power source for applying a DC voltage between the cathode and the anode has a reversible polarity. The printed wiring board is electroplated under alternating normal DC voltages, reverse DC voltages, that is, the normal electrolysis period in which the printed wiring board is used as a cathode alternately, and the reverse electrolysis period in which the printed wiring board is used as an anode.

In order to form a through hole in the form of a defect-free plating film of, for example, voids or the like in the substrate, as shown in FIGS. 1A to 1D, it is desirable that the perforation is at the center in the depth direction. The plating film is preferentially grown until the center of the perforation 100a is blocked by the plating film 106, and then the plating process is continued. However, in practice, it is generally difficult to attempt to meet the desired requirements while efficiently filling the plating film into the perforations to shorten the time required to complete the plating process. In other words, the conventional electroplating process fails to achieve a high average plating current during plating, ideally filling the perforated film with the plating film and efficiently filling the plating film into both of the perforations.

The present invention has been made in view of the above circumstances. Accordingly, it is an object of the present invention to provide an electroplating method for efficiently filling a plating film into a perforation with a higher average plating current during plating to shorten the time required to complete the plating process and also desirably The plated film is filled with perforations.

In order to achieve the above object, the present invention provides a plating method comprising the steps of: dipping a substrate having a perforation defined therein into a plating solution in a plating bath; and being in the plating solution of the plating tank. a pair of anodes are disposed to face the front and back sides of the substrate in the plating solution, respectively; for the front and back sides of the substrate, the pulse current is supplied to the front surface of the substrate and the anodes Between one of the front sides of the substrate, and between the opposite side of the substrate and the other of the opposite sides of the substrate facing the substrate, performing a plurality of plating processes each continuing for a predetermined period of time; Between the adjacent processes of the plating process, the positive and negative faces of the substrate are respectively supplied to the substrate in the front surface of the substrate and the anodes by supplying currents opposite to the pulse currents of the plating processes. A reverse electrolysis process is performed between one of the front faces and between the opposite side of the substrate and the other of the opposite sides of the anode facing the substrate.

For the positive and negative sides of the substrate, by supplying a pulse current between the front surface of the substrate and one of the front faces of the substrate facing the substrate, and the opposite side of the substrate and the anodes Between the other of the opposite sides of the substrate, a plurality of plating processes each continuing for a predetermined period of time are performed, so that it is possible to efficiently fill the plating film with the perforation with an increasing average current value, thereby shortening the finish plating. The time required to overwrite the process. The reverse electrolysis process performed between the plating processes effectively dissolves the plating film deposited on the corners of the perforations. Therefore, it is possible to ideally fill the perforation with the plating film by preferentially growing the plating film at the center of the perforation in the depth direction.

In a preferred aspect of the invention, each of the pulse currents comprises a PR pulsed current that is represented by an alternating repetition of a forward flow current and a reverse flow current.

The reverse electrolysis process is repeatedly performed between plating processes using PR pulse currents, thereby preventing fine irregularities generated by abnormal deposition on the microscopic surface of the plating film to prevent the formation of the plating film due to fine irregularities. The fine holes caused.

In a preferred aspect of the invention, each of the pulsed currents comprises an on/off pulse current presented in alternating repetitions of supply current and no supply of forward flow plating current.

Since the on/off pulse current provides a non-plating period in the plating process that does not supply the plating current, the metal ion concentration of the plating solution in the perforation is restored during the non-plating period by the plating film. Defects are formed, for example, voids or the like.

In a preferred aspect of the invention, each of the pulsed currents comprises a combined pulse current presented in combination of one of two pulsed currents having different current values.

Since the plating film continues to grow in the plating process having the combined pulse current, the plating process prevents the plating film from being dissolved in the plating solution.

In a preferred aspect of the invention, the plating process and the reverse electrolysis process are performed together to gradually increase the average current density as the plating of the substrate progresses.

When the plating process causes the perforations to gradually fill the plating film, the substantial aspect ratio of the perforations also changes. When the substantial high aspect ratio of the perforations is changed, it is possible to efficiently fill the perforations with the plating film by increasing the average current density of the plating process in a manner that matches the substantially high aspect ratio of the perforations. As a result, the time required to plate the substrate can be further shortened.

In a preferred aspect of the invention, the reverse electrolysis process is performed a plurality of times before and after the normal electrolysis cycle of the forward supply pulse current.

For example, the reverse electrolysis process is performed with a negative cathode current density between -30 and -40 ASD with a pulse spacing of between 0.1 and 10 milliseconds. Depending on the high aspect ratio of the perforations defined on the substrate, it may not be possible to preferentially fill the plating film in the center of the perforation along the depth direction according to the reverse electrolysis process with a pulse pitch of less than 1.0 msec. However, if the reverse electrolysis process is repeated a plurality of times at a pulse pitch of less than 1.0 msec before and after the normal electrolysis cycle of supplying the pulse current in the forward direction, it is possible to desirably fill the perforation with the plating film.

According to the present invention, as described above, the positive and negative sides of the substrate are respectively supplied with a pulse current between the front surface of the substrate and one of the front surfaces of the anode facing the substrate, and the substrate Between the reverse side and the other of the anodes facing the opposite side of the substrate, a plurality of plating processes each continuing for a predetermined period of time are performed. Therefore, it is possible to efficiently fill the plating film into the perforations with increasing average current values, thereby shortening the time required to complete the plating process. The reverse electrolysis process performed between the plating processes effectively dissolves the plating film deposited on the corners of the perforations. Therefore, it is possible to ideally fill the perforation with the plating film by preferentially growing the plating film at the center of the perforation in the depth direction.

The above and other objects, features and advantages of the present invention will become apparent from the description of the appended claims.

Preferred embodiments of the present invention will now be described with reference to the drawings. The vertical cross-sectional front view of Fig. 2 schematically shows an electroplating apparatus 50 for carrying out the electroplating method of the present invention. As shown in FIG. 2, the plating apparatus 50 includes a plating tank 51 in which the plating solution Q is stored, and a holding substrate W (for example, a semiconductor wafer or the like) and vertically suspended in the plating liquid Q. The substrate holder 10 in the middle. The plating solution Q in which the substrate holder 10 is immersed has a horizontal plane L at the upper end of the plating tank 51 as shown in Fig. 2. The two insoluble anodes 52 each supported on the anode holder 58 are disposed in the plating tank 51 to face the both faces (i.e., the front and back sides) of the substrate W held by the substrate holding member 10, respectively. As shown in Fig. 3, the substrate holder 10 includes a first holding member 11 in which the circular hole 11a is defined and a second holding member 12 in which the circular hole 12a is defined. The first holding member 11 and the second holding member 12 are used to hold the substrate W therebetween. The insoluble anode 52 is circular and has substantially the same size as the circular holes 11a, 12a of the first and second holding members 11, 12.

Two adjustment plates 60 made of an insulating material are disposed between the substrate holder 10 and the respective insoluble anodes 52 in the plating tank 51. The adjustment plates 60 each have a circular hole defined therein and have a shape similar to that of the circular holes 11a, 12a of the first and second holding members 11, 12. The insoluble anodes 52 are electrically connected to respective electric wires 61a extending from the terminals of the plating power source 53, each of which can change the direction of the supply current and thereby also change the current value. The plating power source 53 has the other terminal electrically connected to the electric wire 61b, and the electric wires 61b are each connected to the terminal plates 27, 28 of the substrate holder 10 (refer to Fig. 3). The plating power source 53 is also electrically connected to the controller 59 that individually controls the plating power source 53.

The two agitating pastes 62 are disposed between the substrate W held by the substrate holder 10 and the respective adjustment plates 60 in the plating tank 51. The agitating paddle 62 is movable back and forth in parallel with the substrate W held by the substrate holder 10 to agitate the plating solution Q. The plating apparatus 50 also includes an outer tank 57 disposed around the plating tank 51 for holding the plating liquid Q overflowing the plating tank 51. The plating solution Q that has overflowed the plating tank 51 into the outer tank 57 is circulated from the bottom portion back to the plating tank 51 by the plating liquid circulation pump 54 through the constant temperature unit 55 and the filter 56.

FIG. 3 is a front view of the substrate holder 10. 4 is a plan view of the substrate holder 10. FIG. 5 is a bottom view of the substrate holder 10. Fig. 6 is a cross-sectional view taken along line K-K of Fig. 3. Fig. 7 is a view showing the substrate holder 10 drawn with the arrow A of Fig. 6 as a line of sight. Fig. 8 is a view showing the substrate holder 10 drawn with the arrow B of Fig. 6 as a line of sight. Fig. 9 is a view showing the substrate holder 10 drawn with the arrow C of Fig. 6 as a line of sight. Figure 10 is a cross-sectional view taken along line D-D of Figure 7. Figure 11 is a cross-sectional view taken along line E-E of Figure 7. Fig. 12 is a cross-sectional view taken along line F-F of Fig. 3. Figure 13 is a cross-sectional view taken along line G-G of Figure 7. Fig. 14 is a cross-sectional view taken along line H-H of Fig. 8.

As shown in FIG. 3, the first holding member 11 and the second holding member 12 (each in a planar shape) of the substrate holder 10 are each pivotally coupled to each other with a lower end of a hinge mechanism 13. The pivoting mechanism 13 has two hooks 13-1 made of synthetic resin (for example, HTPVC) and fixed to the second holding member 12. The hook 13-1 is angularly movably supported on the lower end of the first holding member 11 by a hook pin 13-2 made of stainless steel (for example, SUS 303). The first holding member 11 is made of a synthetic resin (for example, HTPVC) and has a substantially pentagonal shape. The circular hole 11a is defined in the center of the first holding member 11, as shown in Fig. 7. As shown in FIG. 3, a T-shaped hanger 14 made of a synthetic resin (for example, HTPVC) is integrally formed with the upper end of the first holding member 11. The second holding member 12 is made of a synthetic resin (for example, HTPVC) and has a substantially pentagonal shape. The circular hole 12a is defined in the center of the second holding member 12.

When the first holding member 11 and the second holding member 12 are rotated to overlap each other with the pivoting mechanism 13 as the center, that is, when the substrate holding member 10 is closed, the first holding member 11 and the second holding member 12 are left, The right clamps 15, 16 are clamped together. The left and right clamps 15, 16 each made of a synthetic resin (for example, HTPVC) each have a recess 15a, 16a for accommodating the both side edges of the first holding member 11 and the second holding member 12 which are overlapped with each other. among them. The lower ends of the left and right clamps 15, 16 are each angularly movably supported by the lower ends of the opposite sides of the first holding member 11 by the pins 17, 18.

As shown in Fig. 7, the seal ring 19 is mounted on the surface of the first holding member 11 facing the second holding member 12, and extends around the hole 11a. As shown in Fig. 9, the seal ring 20 is mounted on the surface of the second holding member 12 facing the first holding member 11, and extends around the hole 12a. The seal rings 19, 20 are made of rubber, for example, silicone rubber. The O-ring 29 is mounted on the surface of the second holding member 12 facing the first holding member 11, and extends around the sealing ring 20.

The seal rings 19, 20 each having a rectangular cross-sectional shape each have ridges 19a, 20a projecting and extending radially inward from the inner periphery thereof. When the first holding member 11 and the second holding member 12 overlap each other with the substrate W interposed therebetween, the ridges 19a, 20a each press the surface of the substrate W and maintain close contact therewith, which is in the O-ring 29 and the radial direction. A watertight space free of the plating solution Q is defined between the ridges 19a, 20a outside the holes 11a, 12a. As shown in FIGS. 7 and 10, eight substrate guide pins 21 for positioning the substrate W are attached to the surface of the first holding member 11 facing the second holding member 12, radially outside the hole 11a. And protruding through the seal ring 19.

As shown in Figs. 7, 11, and 12, six conductive plates 22 are mounted around the hole 11a in the first holding member 11 facing the surface of the second holding member 12. As shown in FIG. 11, three of the six conductive plates 22 pass through the conductive pin 23 and the seed layer 104 on one side (for example, the front surface) of the substrate W (refer to FIGS. 1A to 1D). Keep electrical contact. As shown in Fig. 12, the other three conductive plates 22 are in electrical contact with the seed layer 104 on the other side (e.g., the reverse side) of the substrate W via the conductive pins 23.

Maintaining electrical contact with the seed layer 104 on one of the sides (eg, the front side) of the substrate W. The three conductive plates 22 are electrically connected to each other by the insulated covered wires 26 extending through the wire slots 25 (refer to FIG. 13). The electrode terminals 27a, 27b, and 27c on the terminal block 27 of the pylon 14 (refer to Fig. 4). The other three conductive plates 22 that are in electrical contact with the seed layer 104 on the other side (e.g., the reverse side) of the substrate W are electrically connected by the insulated covered wires 26 extending through the wire slots 25 (refer to Fig. 13). It is connected to the electrode terminals 28a, 28b, 28c provided on the other terminal plate 28 of the pylon 14 (refer to FIG. 4). As shown in Figs. 7 and 13, the insulated covered electric wire 26 is fixed by a wire holder 30 made of a synthetic resin (for example, PVC).

The operation of the substrate holder 10 is as follows: when the first holding member 11 and the second holding member 12 are rotated apart from each other with the pivoting mechanism 13 as being centered, that is, when the substrate holding member 10 is opened, the substrate W is located at the first holding The member 11 is in a region surrounded by eight substrate guide pins 21. The substrate W is now fixed on the first holding member 11. The first holding member 11 and the second holding member 12 are turned toward each other centering on the pivoting mechanism 13, that is, the substrate holding member 10 is closed. Then, the left and right clamps 15, 16 are angularly moved about the pins 17, 18 until the side edges of the first and second holding members 11 and 12 are inserted into the grooves 15a of the left and right clamps 15, 16 respectively. 16a. The substrate W fixed to the first holding member 11 is now sandwiched between the first holding member 11 and the second holding member 12.

The O-ring 29 together with the ridges 19a, 20a of the seal rings 19, 20 define a watertight space in which there is no plating solution Q therebetween. At this time, the outer peripheral edge region of the substrate W (radially outside the ridges 19a, 20a) is located in the watertight space, and the surface regions of both surfaces of the substrate W (the holes 11a of the first holding member 11 and the second holding member 12, 12a is coextensive) exposed to the holes 11a, 12a. Among the six conductive plates 22, three conductive plates 22 that are in electrical contact with the seed layer 104 on one side of the substrate W are electrically connected to the electrode terminals 27a, 27b, 27c provided on the terminal plate 27 of the pylon 14. And three other conductive plates 22 that are in electrical contact with the seed layer 104 on the other side of the substrate W are electrically connected to the electrode terminals 28a, 28b, 28c provided on the terminal block 28 of the pylon 14.

Fig. 15 is a front elevational view showing the anode holder 58 in which the insoluble anode 52 is held in the electroplating apparatus of Fig. 2, and Fig. 16 is a cross-sectional view of Fig. 15. In this embodiment, in order to prevent the anode from being dissolved by the additive (or several) of the plating solution, the anode bodies are each made of titanium and coated with an insoluble anode 52 such as ruthenium oxide.

As shown in FIGS. 15 and 16, each of the anode holders 58 includes a holder body 70 defined therein with a center hole 70a, and a closing plate 72 disposed on the reverse side of the holder body 70 and closing the center hole 70a. a circular support plate 74 disposed in the center hole 70a of the holder main body 70 and holding the insoluble anode 52 on the surface thereof so that the insoluble anode 52 is located in the center hole 70a, and mounted on the front surface of the holder main body 70 and surrounding the center hole Annular anode shield 76 of 70a. The support plate 74 has a passage 74a defined therein, and the passage 74a houses a conductive plate 78 electrically connected to the electric wire 61a extending from the plated power source 53 therein. The conductive plate 78 extends to a central region of the support plate 74 where the conductive plate 78 is electrically connected to the insoluble anode 52.

The separator film 80 in the form of a neutral film is configured to cover the surface of the insoluble anode 52 located at the center hole 70a of the holder body 70. The separator 80 has a periphery sandwiched by the holder body 70 and the anode shield 76, and is fixed to the holder body 70. The anode shield 76 is fixed to the holder main body 70 with a screw 82, and the closing plate 72 is also screwed to the holder main body 70.

When the anode holder 58 is immersed in the plating solution Q, the plating solution Q enters a gap between the insoluble anode 52 and the support plate 74 in the center hole 70a of the holder main body 70.

The reason for using the insoluble anode 52 and the separator film 80 is as follows: The additive to be added to the plating solution Q contains a component for promoting formation of a monovalent copper, which may impair the function of other additives because it causes oxidative decomposition of other additives. As a result, a soluble anode cannot be used. When an insoluble anode is used, the insoluble anode generates oxygen in the vicinity thereof, and the generated oxygen is partially dissolved in the plating solution Q to increase the concentration of dissolved oxygen. An increase in the concentration of dissolved oxygen tends to cause oxidative decomposition of the additive. Therefore, it is desirable to arrange the barrier film 80 in the form of a neutral film in a covering relationship with the surface of the insoluble anode 52 to prevent adverse effects on the components of the additive near the substrate W even if they are in the vicinity of the insoluble anode 52. Subject to oxidative decomposition.

Another desirable way is to supply a permeate (for example, a vent tube, not shown) with air or nitrogen to fill the plating solution Q near the insoluble anode 52 with bubbles or gas to prevent the dissolved oxygen concentration from being on the insoluble anode 52 side. Not rising properly.

Since the surface of the insoluble anode 52 held by the anode holder 58 is covered with the separator film 80, the insoluble anode 52 is configured to allow the separator film 80 to face the substrate W held by the substrate holder 10 and disposed in the plating tank 51, When the plating solution Q is filled with bubbles and gas, it is possible to prevent oxygen from being generated in the vicinity of the insoluble anode 52 and dissolved in the plating solution to prevent an increase in the concentration of dissolved oxygen in the plating solution Q.

The plating apparatus 50 constructed in this manner operates as follows: the substrate holding member 10 holding the substrate W exposed to the front and the back is placed in the plating solution Q of the plating tank 51 so that one side (for example, the front surface) of the substrate W is insoluble. One of the anodes 52, and the other side of the substrate W (e.g., the reverse side) faces the other insoluble anode 52. The plating power source 53 is each provided between the front surface of the substrate W and the insoluble anode 52 facing the front surface of the substrate W, and between the reverse side of the substrate W and the insoluble anode 52 facing the reverse side of the substrate W, and the plating current controlled by the controller 59 is supplied. Thereby, the front and back sides of the substrate W are simultaneously plated. If necessary, when the front and back sides of the substrate W are plated, the stirring slurry 62 is moved back and forth in parallel with the substrate W to agitate the plating solution Q. In this manner, as shown in FIGS. 1A to 1D, the plating film 106 is grown in the substrate W perforation 100a.

The enlarged cross-sectional views of Figs. 17 to 19 each illustrate another substrate holder drawn along different cross sections. The substrate holders shown in FIGS. 17 to 19 are different from the substrate holders as follows: As shown in FIG. 17, the substrate holders each include a proximal end fixed to the first holding member 11 and a second holding member. The resilient conductive plates 90, 92 of the member 12 are instead of the conductive pins 22, 23 of Figures 11 and 12. When the substrate W is held by the first holding member 11 and the second holding member 12, the distal free ends of the elastic conductive plates 90, 92 respectively elastically abut against the front and back surfaces of the substrate W and the front and back surfaces of the substrate W. The seed layer 104 (refer to FIGS. 1A through 1D) maintains electrical contact.

As shown in Figures 18 and 19, the substrate holder also includes seal ring retainers 94, 96 for holding the seal rings 19, 20, respectively. The seal ring holders 94, 96 are each fixed to the first holding member 11 and the second holding member 12. The seal ring holders 94, 96 each have an array of alternating guide teeth 97, 98 for positioning the substrate W instead of the substrate guide pins 21 illustrated in Figures 7 and 10. The guide teeth 97, 98 are each disposed at each position along the circumferential direction of the seal ring holders 94, 96. The guide teeth 97, 98 each have a tapered surface 97a, 98a on the inner peripheral surface near the free end. When the substrate W is held by the first holding member 11 and the second holding member 12, the outer peripheral edge of the substrate W is kept in contact with and guided by the tapered surfaces 97a, 98a to position the substrate W.

Figure 20 is a graph showing cathode current density versus time for an embodiment of a plating current supplied between the surface of the substrate W and the insoluble anode 52 (which is disposed to face the surface of the substrate W). The plating current supplied between the reverse side of the substrate W and the insoluble anode 52 facing the reverse side of the substrate W is synchronized with the plating current supplied between the front surface of the substrate W and the insoluble anode 52 facing the front surface of the substrate W. However, the plating currents need not be synchronized with each other, and thus the invention should not be limited to whether the above plating currents are synchronized. For the plating current supplied between the surface of the substrate W and the insoluble anode 52 facing the surface of the substrate W, Fig. 20 illustrates the relationship between the cathode current density and time.

The embodiment of Fig. 20 alternately repeats the following two processes: a plating process A for supplying a pulse current between the surface of the substrate W and the insoluble anode 52 for plating the surface of the substrate W for a predetermined period of time; and reverse electrolysis Process B, the direction of the supply current is opposite to the current supplied between the surface of the substrate W and the insoluble anode 52 during the plating process A. Therefore, the predetermined period of time during which the plating process A is performed is in the range of 50 to 100 milliseconds, for example, and the predetermined period of time for performing the reverse electrolytic process B is in the range of 0.1 to 10 milliseconds, or preferably in the range of 0.5 to 1 millisecond. .

As shown by the broken line in Fig. 20, a quiescent period C of, for example, 0.05 msec can be inserted after the reverse electrolysis process B and before the plating process A, at which time there is no current supply between the surface of the substrate W and the insoluble anode 52. . The stationary phase C can homogenize the metal ion distribution of the plating solution Q in the perforations for efficiently filling the plating film into the perforations. It is advantageous to insert a stationary phase C in other embodiments described below.

In the embodiment of Fig. 20, the plating process A is performed using the PR pulse current having the following alternating repetition period: a normal electrolysis cycle, for example, a pulse pitch of P ₁ , and a plated current is flowing forward (ie, plating) Direction), the positive cathode current density D _{1 is} between 1 and 3 ASD (A/dm); and the reverse electrolysis period, for example, the pulse spacing is P ₂ , the plating current flows countercurrently, and the negative cathode current density D _{2 is} at - Between 0.05 and -4 ASD. For example, the pulse pitch P ₂ of the reverse electrolysis period of the PR pulse current is 0.5 msec. For example, the reverse electrolysis process B is carried out with a single pulse having a pulse pitch P ₃ between 0.1 and 10 milliseconds (0.5 to 1 millisecond is preferred) and a negative cathode current density D ₃ between -30 and -40 ASD.

Since the reverse electrolytic process B is performed after the plating process A with a negative cathode current density D ₃ of, for example, between -30 and -40 ASD, as shown by the broken line in Fig. 21, the plating is easily deposited on the corner of the perforation 100a. The film 106a is dissolved in the plating solution Q, thereby allowing the plating film 106 to preferentially grow in the depth direction at the corner of the perforation 100a as shown by the solid line in FIG.

As shown in Fig. 22, in the plating process, abnormal deposition on the microscopic surface of the plating film 106 is liable to cause fine irregularities 106b. However, for example, according to the embodiment of Fig. 20, the fine irregularity 106b can be prevented from being generated by the reverse electrolysis period in which the negative cathode current density D _{2 is} between -0.05 and -4 ASD. Fine irregularities 106b caused by abnormal deposition may be interconnected in other ways to form fine voids in the plating film.

Figure 23 is a graph showing cathode current density versus time for another embodiment of the plating current supplied between the surface of the substrate W and the insoluble anode 52 (configured to face the surface of the substrate W). The embodiment of Fig. 23 differs from the embodiment of Fig. 20 in that the pulse pitch P _{4 is} between 0.1 and 10 milliseconds before and after the normal electrolysis cycle in which the forward plating current is applied (0.5 to 1.0 msec is preferred). The two pulses of the reverse electrolysis process B _{1 are performed} .

The reverse electrolysis process B, in which the negative cathode current density D _{3 is} between -30 and -40 ASD, as shown in Fig. 20, is carried out with a single pulse with a pulse pitch P _{3 of} between 0.1 and 10 msec. If the pulse pitch P _{3 is} greater than 1 millisecond, as shown in Fig. 24A, the plating film 106 is excessively dissolved in the plating solution to form the excessive dissolution region 112. As shown in Fig. 24B, the excessive dissolution zone 112 causes the open end to be closed to easily produce a cat-eyed void 114 in the plating film 106 embedded in the perforation 110a. Therefore, the pulse pitch P ₃ is preferably in the range of 0.1 to 1.0 msec, more preferably in the range of 0.5 to 1.0 msec.

However, depending on the high aspect ratio of the perforations defined on the substrate W, it is possible to ideally embed the plating film in the depth direction of the perforation center with a single pulse having a pulse pitch of less than 1.0 msec depending on the reverse electrolysis process. Process. As shown in Fig. 23, the reverse electrolysis process B ₁ which is carried out by applying two pulses each having a pulse pitch P ₄ of less than 1.0 msec makes it possible to ideally fill the perforated film with the plating film.

Figure 25 is a graph showing cathode current density versus time for another embodiment of the plating current supplied between the surface of the substrate W and the insoluble anode 52 (configured to face the surface of the substrate W). Embodiment of FIG. 25 embodiment includes three different plating processes, i.e., the plating process (a first plating process) A ₁ in the first region 100a in the depth direction along the perforation 100a through perforations 106 in the center of the plated film In the substantial connection, as shown in FIGS. 1A to 1C, the plating process (second plating process) A ₂ is used in the second region to embed the plating film 106 in the recess 108 of the through hole 100a to a predetermined thickness. As shown in FIGS. 1C and 1D, and the plating process (third plating process) A ₃ in the third zone is a risk of reducing pinch-off after the stage of FIG. 1D.

In Fig. 25, the first plating process A ₁ , the second plating process A ₂ and the third plating process A ₃ are illustrated as being performed once before and after the reverse electrolysis process B (refer to Fig. 20). . However, each of the first plating process A ₁ , the second plating process A _{2 ,} and the third plating process A ₃ may be performed several times before and after the reverse electrolytic process B. This also applies to other embodiments described below.

In the embodiment of FIG. 25, each of the first plating process A ₁ , the second plating process A _{2 ,} and the third plating process A ₃ is performed by using an on/off pulse current, which is alternately heavy. The plating current is supplied to the ground and the plating current is not supplied to the forward flow (i.e., the plating direction), and there is a positive cathode current density D ₁ between, for example, 1 to 3 ASD. The pulse pitch P ₅ of the on/off pulse current of the first plating process A ₁ is smaller than the pulse pitch P ₆ (P ₅ <P ₆ ) of the on/off pulse current of the second plating process A ₂ , and the second plating The pulse pitch P ₆ of the on/off pulse current of the process A ₂ is smaller than the pulse pitch P ₇ of the on/off pulse current of the third plating process A ₃ (P ₆ <P ₇ ). The on/off pulse currents of the first, second, and third plating processes A ₁ , A ₂ , and A ₃ have equal downtime pitches P ₈ , P ₉ , and P ₁₀ (P ₈ = P ₉ = P ₁₀ ). Therefore, the average value of the cathode current density is gradually increased. Alternatively, the average value of the cathode current density can be linearly increased.

Since the on/off pulse current provides a non-plating period in which the plating current is not supplied to the entire plating process, the metal ion concentration of the plating solution in the perforation is restored during the non-plating period, thereby preventing the plating film from being formed such as a void. defect. In the plating process, as the perforations gradually fill the plating film, the substantial aspect ratio of the perforations also changes. When the substantial high aspect ratio of the perforations is changed, it is possible to efficiently fill the perforations with the plating film by increasing the average cathode current density of the plating process in a manner that matches the substantially high aspect ratio of the perforations. As a result, the time required to plate the substrate can be further shortened.

It is well known in the art to gradually increase the plating current density as the plating process progresses. However, it is difficult to suppress the generation of monovalent copper in the entire range of the plating current density from the low plating current density to the high plating current density. According to this embodiment, since the cathode current density has a constant peak to suppress the generation of the monovalent copper, the plating solution can be prevented from being deteriorated.

Figure 26 is a graph showing cathode current density versus time for another embodiment of the plating current supplied between the surface of the substrate W and the insoluble anode 52 (configured to face the surface of the substrate W). The difference between the embodiment of Fig. 26 and the embodiment of Fig. 25 is that the image is applied by applying two pulses each having a pulse pitch P ₄ of between 0.1 and 10 milliseconds (preferably between 0.5 and 1.0 milliseconds). The reverse electrolysis process B ₁ shown in Fig. 23, instead of performing the reverse electrolysis process B of Fig. 25, with a single pulse such as a pulse pitch P _{3 of} between 0.1 and 10 msec (preferably between 0.5 and 1 msec) .

Figure 27 is a graph showing cathode current density versus time for another embodiment of the plating current supplied between the surface of the substrate W and the insoluble anode 52 (configured to face the surface of the substrate W). The difference between the embodiment of Fig. 27 and the embodiment of Fig. 25 is that the first, second and third plating processes A ₁ , A ₂ , A ₃ have processing times equal to each other, and the first plating process A ₁ pulse interval on / off pulse current P ₅ is smaller than the second plating process a the opening ₂ of the / pulse interval off pulse current _{P 6 (P 5 <P 6} ), a second plating process a ₂ of the on / off pulse current The pulse pitch P _{6 is} smaller than the pulse pitch P ₇ (P ₆ <P ₇ ) of the on/off pulse current of the third plating process A ₃ , and the shutdown pitch P ₈ of the on/off pulse current of the first plating process A ₁ shut off the pitch distance apart greater than the second plating process of ₂ a / off pulse current _{P 9 (P 8> P 9} ), and a second plating process a ₂ of the opening / closing of the pulse current is greater than the third plating P ₉ The shutdown interval P ₁₀ (P ₉ > P ₁₀ ) of the on/off pulse current of the process A ₃ is overwritten. Therefore, the average value of the cathode current density is gradually increased.

Figure 28 illustrates a graph of cathode current density versus time for another plated current embodiment applied between the surface of substrate W and insoluble anode 52 (configured to face the surface of substrate W). 28 embodiment of the first embodiment of FIG. 25 where a different embodiment of FIG embodiment is characterized by using a combination of a pulsed power supply, for example, to a cathode current density value D ₁ of the first plating current between 1 and 3 ASD, and a cathode value e.g. The second plating current of the current density D _{4 is} between 0.1 and 0.5 ASD, instead of being supplied by the repeated supply and not supplying the forward flow (ie, the plating direction) and the positive cathode current density D ₁ at 1 A plating current between 3 ASDs to supply a power source for turning on/off the pulse current.

Since the combined pulsed power supply is used to continuously supply a weak current, for example, between 0.1 and 0.5 ASD, instead of stopping the supply of the plating current, the plating film continues to grow during the plating process. Therefore, it is possible to prevent the plating film from being dissolved in the plating solution of the plating process.

Figure 29 is a graph showing cathode current density versus time for another embodiment of the plating current supplied between the surface of the substrate W and the insoluble anode 52 (configured to face the surface of the substrate W). The difference between the embodiment of Fig. 29 and the embodiment of Fig. 25 is that the supply of the PR pulse current is repeated by performing, for example, a normal electrolysis period of a positive cathode current density D ₁ between 1 and 3 ASD, and for example, negative The value of the cathode current density D _{2 is} in the reverse electrolysis cycle between -0.05 and -4 ASD, rather than being supplied by re-feeding and not supplying a plating current such as a positive cathode current density between 1 and 3 ASD. / off pulse current.

Figure 30 illustrates a graph of cathode current density versus time for another embodiment of the plating current supplied between the surface of the substrate W and the insoluble anode 52 (configured to face the surface of the substrate W). The difference between the embodiment of Fig. 30 and the embodiment of Fig. 25 is that it sequentially implements the first and second sums by supplying a DC plating current such as a positive cathode current density D ₁ between 1 and 3 ASD. The third plating process A ₁ , A ₂ , A ₃ , the first, second and third plating processes A ₁ , A ₂ , A ₃ have sequential processing times (A ₁ <A ₂ <A ₃ ) .

Depending on the high aspect ratio of the perforations, the structure of the underlying plating, the nature of the plating solution, and the like, it may not be necessary to provide a stationary period between the reverse electrolysis processes. If the stationary period is not required, the surface of the substrate W and the insoluble anode 52 can supply a plating current to achieve the relationship between the cathode current density and time in FIG. 30, thereby shortening the time required to complete the plating process to efficiently fill the plating film. Into the perforation.

Figure 31 is a graph showing cathode current density versus time for another embodiment of the plating current supplied between the surface of the substrate W and the insoluble anode 52 (which is disposed to face the surface of the substrate W). The embodiment of Fig. 31 differs from the embodiment of Fig. 20 in that when the recess 108 of the perforation 100a of the plating film 106 is embedded in a predetermined thickness, as shown in Fig. 1D, thereby reducing the risk of pinching, for example, reverse After the electrolytic process B, the plating process A ₄ is carried out by supplying a DC plating current of, for example, a positive cathode current density D _{1 of} between 1 and 3 ASD. At the stage of reducing the risk of pinching, the perforations 100a of the plating film embedded in the substrate W are substantially completed, as shown in Fig. 1D, and finally filled with dimples remaining on the surface of the substrate. At this time, it is not necessary to supply a DC plating current to make the cathode current density equal to the previous pulse peak current density, but a DC plating current can be supplied to make the cathode current density higher than the previous pulse peak current density, thereby shortening the completion of the plating process. Time required.

Figure 32 is a graph showing cathode current density versus time for another embodiment of the plating current supplied between the surface of the substrate W and the insoluble anode 52 (configured to face the surface of the substrate W). The difference between the embodiment of Fig. 32 and the embodiment of Fig. 27 is that the third plating process A ₃ is performed by supplying a DC plating current of, for example, a positive cathode current density D _{1 of} between 1 and 3 ASD, thereby Shorten the time required to complete the plating process.

While the preferred embodiment of the present invention has been shown and described, it is understood that various modifications and changes may be made without departing from the scope of the appended claims.

10. . . Substrate holder

11. . . First holding member

11a, 12a. . . Round hole

12. . . Second holding member

13. . . Pivot mechanism

13-1. . . hook

13-2. . . Hook pin

14. . . T-shaped rack

15,16. . . clamp

15a, 16a. . . Groove

17, 18. . . plug

19, 20. . . Sealing ring

19a, 20a. . . Ridge

twenty one. . . Substrate guide pin

twenty two. . . Conductive plate

twenty three. . . Conductive pin

25. . . Wire slot

26. . . Insulated covered wire

27, 28. . . Terminal board

27a, 27b, 27c, 28a, 28b, 28c. . . Electrode terminal

29. . . O ring

30. . . Wire holder

50. . . Plating equipment

51. . . Plating tank

52. . . Insoluble anode

53. . . Plating power supply

54. . . Plating liquid circulation pump

55. . . Thermostatic unit

56. . . filter

57. . . Outer slot

58. . . Anode holder

59. . . Controller

60. . . Adjustment board

61a, 61b. . . wire

62. . . Stirring slurry

70. . . Holder body

70a. . . Center hole

72. . . Closed plate

74. . . Circular support plate

74a. . . aisle

76. . . Annular anode shield

78. . . Conductive plate

80. . . Isolation film

82. . . Screw

90, 92. . . Elastic conductive plate

94, 96. . . Seal ring retainer

97, 98. . . Guide tooth

97a, 98a. . . Conical surface

100. . . Base

100a. . . Vertical perforation

102. . . Barrier layer

104. . . Seed layer

106, 106a. . . Plating film

108. . . Recess

112. . . Excessive zone

114. . . Cat's eye cavity

A ₁ , A ₂ , A ₃ . . . Plating process

Bx. . . Reverse electrolysis process

D ₁ . . . Positive cathode current density

D ₂ . . . Negative cathode current density

D ₃ . . . Negative cathode current density

D ₄ . . . Positive cathode current density

L. . . level

P ₁ -P ₇ . . . Pulse spacing

P ₈ -P ₁₀ . . . Shutdown interval

Q. . . Plating solution

W. . . Substrate

The sequence of process steps shown in FIGS. 1A to 1D illustrate a method for filling a plating film into a perforation defined in a substrate to form a via hole therein;

2 is a vertical cross-sectional front view schematically showing an electroplating apparatus for carrying out the electroplating method of the present invention;

Figure 3 is a front elevational view of the substrate holder in the electroplating apparatus of Figure 2;

Figure 4 is a plan view of the substrate holder in the electroplating apparatus of Figure 2;

Figure 5 is a bottom view of the substrate holder in the electroplating apparatus of Figure 2;

Figure 6 is a cross-sectional view taken along line K-K of Figure 3;

Figure 7 is a diagram showing a substrate holder drawn by the arrow A of Figure 6;

Figure 8 is a diagram showing a substrate holder drawn by the arrow B of Figure 6;

Figure 9 is a view showing the substrate holder drawn by the arrow C of Figure 6;

Figure 10 is a cross-sectional view taken along line D-D of Figure 7;

Figure 11 is a cross-sectional view taken along line E-E of Figure 7;

Figure 12 is a cross-sectional view taken along line F-F of Figure 3;

Figure 13 is a cross-sectional view taken along line G-G of Figure 7;

Figure 14 is a cross-sectional view taken along line H-H of Figure 8;

Figure 15 is a front elevational view showing the anode holder in which the insoluble anode is held in the electroplating apparatus of Figure 2;

Figure 16 is a cross-sectional view showing the anode holder in which the insoluble anode is held in the electroplating apparatus of Figure 2;

Figure 17 is an enlarged cross-sectional view showing the main portion of another substrate holder;

Figure 18 is an enlarged cross-sectional view showing the main portion of the substrate holder of Figure 17;

Figure 19 is an enlarged cross-sectional view showing the main portion of the substrate holder of Figure 17;

Figure 20 is a graph showing a relationship between a cathode current density and a time of an embodiment of a plating current supplied between a substrate surface and an anode;

FIG. 21 is an enlarged partial cross-sectional view showing a manner of preferentially growing a plating film at a center of a perforation along a depth direction when performing a reverse electrolysis process after a plating process;

Figure 22 is an enlarged partial cross-sectional view showing the fine irregularity caused by the abnormal deposition of the microscopic surface of the plating film in the plating process;

Figure 23 is a graph showing cathode current density versus time for another embodiment of plating current supplied between the surface of the substrate and the anode;

24A and 24B are schematic enlarged cross-sectional views showing the manner in which the plating film embedded in the perforation is excessively dissolved into the plating solution until a void is finally formed in the plating film;

Figure 25 is a graph showing cathode current density versus time for another embodiment of plating current supplied between the surface of the substrate and the anode;

Figure 26 is a graph showing cathode current density versus time for another embodiment of plating current supplied between the surface of the substrate and the anode;

Figure 27 is a graph showing cathode current density versus time for another embodiment of plating current supplied between the surface of the substrate and the anode;

Figure 28 is a graph showing cathode current density versus time for another embodiment of plating current supplied between the surface of the substrate and the anode;

Figure 29 is a graph showing cathode current density versus time for another embodiment of plating current supplied between the surface of the substrate and the anode;

Figure 30 is a graph showing cathode current density versus time for another embodiment of plating current supplied between the surface of the substrate and the anode;

Figure 31 is a graph showing cathode current density versus time for another embodiment of the plating current supplied between the surface of the substrate and the anode;

Figure 32 is a graph showing cathode current density versus time for another embodiment of plating current supplied between the surface of the substrate and the anode.

10. . . Substrate holder

14. . . T-shaped rack

27, 28. . . Terminal board

50. . . Plating equipment

51. . . Plating tank

52. . . Insoluble anode

53. . . Plating power supply

54. . . Plating liquid circulation pump

55. . . Thermostatic unit

56. . . filter

57. . . Outer slot

58. . . Anode holder

59. . . Controller

60. . . Adjustment board

61a, 61b. . . wire

62. . . Stirring slurry

L. . . level

Q. . . Plating solution

W. . . Substrate

Claims (11)

An electroplating method comprising the steps of: immersing a substrate having a perforation defined therein in a plating solution in a plating bath; and configuring a pair of anodes in the plating solution of the plating tank to be respectively The front and back sides of the substrate in the plating solution face each other; between the front surface of the substrate and one of the front surfaces of the anode facing the substrate, and the opposite side of the substrate and the anode Between the other of the opposite sides of the substrate, a normal electrolysis period in which a pulse current flows forward at a predetermined current density at a constant peak to fill a metal inside the perforation, and a pulse current is reversed at a first current density a first reverse electrolysis process that prevents fine irregularities generated on the surface of the aforementioned metal, and as the plating progresses, the positive and negative faces of the substrate are each performed for a predetermined period of time in a manner of gradually increasing the average current density. a plurality of plating processes; and between adjacent ones of the substrates, between the front side of the substrate and one of the front faces of the substrate facing the substrate, and Between the opposite side of the substrate and the other of the opposite sides of the substrate facing the substrate, a second reverse electrolysis process for dissolving the current in the second current density to dissolve the metal deposited in the perforated corner is performed; The second current density is greater than the first current density. The electroplating method according to claim 1, wherein the second reverse electrolysis is performed a plurality of times before and after the normal electrolysis cycle. Process. An electroplating method comprising the steps of: immersing a substrate having a perforation defined therein in a plating solution in a plating bath; and configuring a pair of anodes in the plating solution of the plating tank to be respectively The front and back sides of the substrate in the plating solution face each other; between the front surface of the substrate and one of the front surfaces of the anode facing the substrate, and the opposite side of the substrate and the anode Between each other of the opposite sides of the substrate, a pulse current having a constant peak value is supplied, and as the plating progresses, the flow time of the pulse current is lengthened to perform a plurality of plating for each of the front and back surfaces of the substrate for a predetermined period of time. Between the adjacent processes of the plating process, between the front side of the substrate and one of the front faces of the substrate facing the substrate, and the opposite side of the substrate A reverse electrolysis process in which an opposite current to the plating is applied to the other of the opposite sides of the substrate in the anode is supplied. The electroplating method of claim 3, wherein each of the pulse currents comprises a PR pulse current that is represented by an alternating repetition of a forward flow current and a reverse flow current. The electroplating method of claim 3, wherein each of the pulse currents comprises an on/off pulse current presented in alternating repetitions of supply current and no supply of forward flow plating current. An electroplating method as described in claim 3, wherein the pulses Each of the currents comprises a combined pulse current presented in combination of one of two pulsed currents having different current values. The electroplating method according to claim 3, wherein the plating process is performed in such a manner as to gradually increase the average current density before and after the reverse electrolysis process as the plating progress of the substrate progresses. The electroplating method according to claim 3, wherein the reverse electrolysis process is performed a plurality of times before and after a normal electrolysis cycle in which a pulse current is supplied in the forward direction. The electroplating method according to claim 5, wherein the time during which the forward current is not supplied is shortened as the plating progresses. The electroplating method according to claim 5, wherein the time of the forward current supply is lengthened as the plating progresses. The electroplating method according to claim 10, wherein the time during which the forward current is not supplied is constant.