JP3099175B2 - Film formation method by electrolysis - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming method by electrolysis, and more particularly, to a film forming method by electrolysis capable of producing a thin film of a charge transfer controlling element such as nickel, iron and cobalt. In particular, IC lead frames,
It is useful for manufacturing magnetic heads, coil cores, and the like.

[0002]

2. Description of the Related Art A film forming method by electrolysis is superior to other film forming methods such as sputtering in that the manufacturing cost becomes much lower. As a film formation method by electrolysis, there are a direct current electrolysis method and a pulse electrolysis method. In the pulse electrolysis method,
When current is interrupted, ions are replenished to the electrode surface, the diffusion layer is reduced, and spherical diffusion that causes dendritic crystal growth and powdery electrodeposition is suppressed, and a smooth electrodeposited film can be obtained. . However, the conventional pulse electrolysis method is used for forming a diffusion controlling element such as tin, silver, and cadmium, but is practically used for forming a charge transfer controlling element such as nickel, iron, and cobalt. Not been. The reason for this is that, in the case of the charge transfer rate controlling element, the diffusion layer is not thick and the diffusion overvoltage is not large unlike the diffusion rate controlling element, so that the function of the pulse electrolysis method does not work effectively.

[0003]

For the above reasons, DC electrolysis has been conventionally used for depositing charge transfer controlling elements such as nickel, iron and cobalt. However, when a film is formed by a direct current electrolysis method, a large number of hydrogen traces are generated on the film surface, and there is a problem that smoothness is impaired. Therefore, an object of the present invention is to provide a film forming method by electrolysis that can produce a thin film having excellent smoothness of a charge transfer rate-controlling element.

[0004]

In Means for Solving the Problems A first aspect, the present invention is a film forming method charge transfer process in the electrodeposition reaction is obtained by electrolysis membrane element comprising a rate-limiting reaction, Oyo said element
Potential and the pulse potential at which both crystal nuclei of hydrogen and hydrogen are generated
No crystal nuclei of the above elements and only hydrogen nuclei
And a pulse potential Elow to be applied alternately for a short time.
Provided is a method for forming a film by electrolysis, characterized in that an electrodeposited film without traces is generated .

According to a second aspect, the present invention provides a method for forming a film by electrolysis having the above-described structure, wherein the pulse potential is set to Ehigh, Ehigh.
low, the application time of the pulse potential Ehigh is Thigh, and the application time of the pulse potential Elow is Tlow.
-2500 mV, Ehigh-Elow ≦ -1000 mV, Thigh> 10 μs, and Tlow> 0 are provided.

In a third aspect, the present invention provides a method for forming a film by electrolysis having the above-described structure, wherein the pulse potential is set to Ehigh, Ehigh.
low, the application time of the pulse potential Ehigh is Thigh, and the application time of the pulse potential Elow is Tlow.
-2500 mV, Ehigh-Elow ≦ -1000 mV, and Tlow / Thigh <10, Tlow> 0 are provided.

According to a fourth aspect, the present invention is directed to a method for forming a film by electrolysis having the above-described structure, wherein the pulse potential is set to Ehigh, Ehigh.
low, Ehigh ≒ -2500mV, Ehigh-Elow ≦
A film forming method by electrolysis, characterized in that the film thickness is set to −1000 mV and the film thickness is set to less than 75 nm.

According to a fifth aspect, the present invention provides a method for forming a film by electrolysis having the above-described structure, wherein the pulse potential is set to Ehigh, Ehigh.
low, Ehigh ≒ -2500mV, Ehigh-Elow ≦
The present invention provides a film formation method by electrolysis, wherein the concentration is set to -1000 mV and the concentration of the element in the electrolytic solution is more than 0.05 mol / L.

In a sixth aspect, the present invention provides a method for forming a film by electrolysis having the above-described structure, wherein the pulse potential is set to Ehigh, Ehigh.
low, the application time of the pulse potential Ehigh is Thigh, and the application time of the pulse potential Elow is Tlow, Thigh>
A film forming method by electrolysis is provided, wherein 10 μs, Tlow> 0, and the concentration of the element in the electrolytic solution is greater than 0.05 mol / L.

According to a seventh aspect of the present invention, there is provided a film forming method by electrolysis having the above-described structure, wherein the pulse potential is set to Ehigh, Ehigh.
low, the application time of the pulse potential Ehigh is Thigh, and the application time of the pulse potential Elow is Tlow, Thigh>
10 μs, Tlow> 0, and Tlow / Thigh <
The present invention provides a film formation method by electrolysis, characterized in that the method is set to 10.

According to an eighth aspect, the present invention provides a method for forming a film by electrolysis having the above-described structure, wherein the pulse potential is set to Ehigh, Ehigh.
low, the application time of the pulse potential Ehigh is Thigh, the application time of the pulse potential Elow is Tlow, and Tlow / Thigh
= R, Ehigh ≒ -2500 mV, Ehigh-E
low ≦ −1000 mV and Thigh / r> 1
0, Tlow> 0 is provided.

[0012]

The inventor of the present invention has completed the present invention by focusing on the fact that there is a difference between potentials at which crystal nuclei of a charge transfer controlling element and hydrogen are generated as a result of intensive studies. That is, in the film forming method by electrolytic of the present invention, formation of the element and hydrogen
The pulse potential Ehigh at which both crystal nuclei are generated and the connection of the above elements
A pulse in which no nuclei are generated and only hydrogen nuclei are generated
The potential Elow and the potential Elow are alternately applied at short intervals . As described above, the action of the above-described pulse electrolysis method cannot be obtained for the charge transfer rate-limiting element. However, as shown in FIG. 1, when the pulse potential EHIGH, and Elow, EHIGH, were potential regulating Elow, pulsed potential EHIGH the charge transfer rate-determining element and hydrogen crystal nuclei are generated, the hydrogen in the pulse potential Elow If you like only crystal nuclei occurs, the pulse potential Ehi
At the application time Thigh of gh, as shown in FIG. 2, on the surface of the cathode electrode 1, the charge transfer rate-limiting element 2 and the hydrogen 3 of the fine bubbles 3a are simultaneously precipitated. Next, the pulse potential E
In the low application time Tlow, as shown in FIG. 3, only the hydrogen 3 of the relatively large bubbles 3b is generated on the surface of the cathode electrode 1. At this time, the fine bubbles 3a previously deposited are adsorbed by the relatively large bubbles 3b and grow into large bubbles. As a result, the enlarged bubbles 3b are separated from the surface of the cathode electrode 1 by buoyancy. Therefore, the next
During the application time of the loos potential Ehigh, the hydrogen bubbles 3a,
The charge transfer is carried out on the surface of the cathode electrode 1 from which the 3b has been separated.
The rate-limiting element 2 can be deposited. As a result, it becomes possible to deposit a smooth electrodeposited film with few hydrogen traces on the surface of the cathode electrode 1.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the embodiments shown in the drawings. It should be noted that the present invention is not limited by this. FIG. 4 is a configuration diagram of the constant potential pulse electrolysis system 100. The constant potential pulse electrolysis system 100 includes a container 101 containing an electrolytic solution 10 and a container 10.
1, a cathode electrode 1 made of Au, an anode electrode 102 made of Pt, which is a counter electrode of the cathode electrode 1, a reference electrode (saturated sweet pepper electrode: SEC) 103, and an electrodeposited film of the cathode electrode 1. QCM104 (quartz crystal microbalance device: MAXTEX Inc; PM740) for measuring film thickness
A control unit 105 connected to the CM 104;
, A pulse generator 107 (Hokuto Denko: HB-211) for generating a pulse, a function generator 108 for setting a cathode current-potential curve, and a pulse based on the pulse time (Thigh, Tlow) A potentiostat 109 (HA-305 manufactured by Hokuto Denko) for setting potentials (Ehigh, Elow), a recording unit 110 connected to the potentiostat 109, and a current probe 111 (SONY for monitoring the waveform during electrolysis) / TEK
TRONIX TM501, AM503) and oscilloscope 112
(Made by HEWLETT PACKARD: 54503A) and a plotter 113 connected to the oscilloscope 112.

[Experimental Conditions and Results] [Experiment 1] The surface of the deposited film was observed by changing the pulse potential Elow. [Experiment conditions] The electrolytic solution 10 contained NiSO ₄ .6H ₂ O (0.1 mol /
L) were used _{H 3 BO 3 (0.5mol / L} ) electrolyte.
The hydrogen ion concentration of this electrolytic solution 10 is pH 4 and the temperature is 25 ° C. The hydrogen ion concentration was adjusted with sulfuric acid. Here, L represents 1000 cm ³ . The pulse potential Ehigh was -2500 mV. This is because in normal constant potential plating, a relatively smooth electrodeposited film can be obtained when the potential is -2500 mV (there is little change even when the potential is -2500 mV or less). The application time Thigh is 100 μm.
s and pulse potential application time ratio r (= Tlow / Thigh)
= 1. The electrodeposition was performed until the film thickness of the electrodeposited film became 50 nm while monitoring with the QCM104. The surface of the deposited film after the deposition was observed with a scanning electron microscope (SEM: JEOL Ltd., JSM-T100). [Experimental Results] FIG. 5 is an SEM photograph showing the change of the surface state of the electrodeposited film when the pulse potential Elow was changed.
In the cases shown in FIGS. 5A to 5C, the remaining amount of hydrogen traces on the surface of the electrodeposited film is reduced. FIG. 5D shows the result of the DC electrolysis method for comparison. Hydrogen traces appear on the surface of the electrodeposited film.

[Experiment 2] The surface of the deposited film was observed by changing the application time Thigh = Tlow = T. [Experiment conditions] The application time T was set to 10 μs, 100 μs, 10 μs.
It was measured as 00 μs. As the electrolytic solution 10, the same electrolytic solution as described above was used. Pulse potential Ehigh is -2500m
V. The pulse potential Elow was -1000 mV.
The electrodeposition was performed until the film thickness of the electrodeposited film became 50 nm while monitoring with the QCM104. The surface of the electrodeposited film after electrodeposition was measured with a scanning electron microscope (SEM: JEOL Ltd., JS
M-T100). [Experimental Results] FIG. 6 is an SEM photograph showing the change of the surface state of the electrodeposited film when the application time T was changed. As shown in FIG. 6A, when the application time T is 10 μs, fine hydrogen traces exist. This is due to the application time T
Is considered to be too short to allow hydrogen gas bubbles to grow sufficiently. As shown in FIGS. 6B and 6C, when the application time T is equal to or longer than 100 μs, hydrogen traces on the surface of the electrodeposited film are reduced.

[Experiment 3] The pulse potential application time ratio r
(= Tlow / Thigh), the surface of the electrodeposited film was observed. [Experimental conditions] The pulse potential application time ratio r was 0.1, 1, 1
It was measured as 0. As the electrolytic solution 10, the same electrolytic solution as in Experiment 2 was used. Also, as in Experiment 2, the pulse potential Ehigh
Is −2500 mV, and the pulse potential Elow is −100.
0 mV. The surface of the deposited film after the deposition was observed with a scanning electron microscope (SEM: JEOL Ltd., JSM-T100). [Experimental Results] FIG. 7 is an SEM photograph showing a change in the surface state of the electrodeposited film when the pulse potential application time ratio r was changed. In the cases shown in FIGS. 7A and 7B, a smooth electrodeposited film with few hydrogen traces was obtained. As shown in FIG. 7C, when the pulse potential application time ratio r = 10, hydrogen traces remain on the surface of the electrodeposited film.

[Experiment 4] The surface of the deposited film was observed while changing the thickness of the deposited film. [Experiment conditions] The thickness of the electrodeposited film was 10 nm, 25 nm, 50 nm.
nm, 75 nm, and 100 nm. Electrolyte 1
For 0, the same electrolytic solution as in Experiment 2 was used. Experiment 2
Similarly, the pulse potential Ehigh was -2500 mV, and the pulse potential Elow was -1000 mV. The application time Thigh is 100 μs, and the pulse potential application time ratio r =
It was set to 1. The surface of the deposited film after electrodeposition was measured by a scanning electron microscope (SEM: JEOL Ltd., JSM-T100) and a scanning tunneling microscope (STM: Digital Instruments Nanosc).
opeII). [Experimental Results] FIG. 8 is an SEM photograph showing the change of the surface state of the electrodeposited film when the thickness of the electrodeposited film was changed. FIG.
In the cases shown in (a) to (c), smooth electrodeposited films with few hydrogen traces were obtained. As shown in (d) and (e) of FIG.
When the film thickness is 75 nm or more, hydrogen marks remain on the surface of the electrodeposited film. (A) to (d) of FIG. 9 are STM photographs corresponding to (a) to (d) of FIG.

[Experiment 5] The surface of the electrodeposited film was observed by changing the concentration of the electrolyte 10. [Experiment conditions] The concentration of the electrodeposited solution 10 was 1 mol / L, 0.5
mol / L, 0.1 mol / L, 0.05 mol / L,
It was measured as 0.01 mol / L. Other conditions of the electrolytic solution 10 were the same as those in the experiment 2. Further, as in Experiment 2, the pulse potential Ehigh was set at -2500 mV, and the pulse potential Elow was set at -1000 mV. In addition, the application time Thi
gh was 100 μs, and the pulse potential application time ratio r was 1. The surface of the electrodeposited film after electrodeposition was scanned with a scanning electron microscope (SE
M: Observed by JEOL Ltd., JSM-T100). [Experimental Results] FIG. 10 is an SEM photograph showing the change in the surface state of the electrodeposited film when the concentration of the electrodeposited solution 10 was changed. In the cases shown in FIGS. 10A to 10C, a smooth electrodeposited film with few hydrogen traces was obtained. As shown in (d) and (e) of FIG. 10, when the concentration was 0.05 mol / L or less, hydrogen traces remained on the surface of the electrodeposited film.

The data items resulting from the above are summarized. The order of the data items is the data identifier, Ni concentration (mol /
L), film thickness (nm), Ehigh (mV), Elow (m
V), Thigh (μs), Tlow (μs), r (= Tlow
/ Thigh), Ehigh-Elow (mV), Thigh / r (μ
s). [Data with few hydrogen traces] a, 0.1, 50, -2500, -500, 100, 100, 1, -2000, 100 b, 0.1, 50, -2500, -1000, 100, 100, 1, -1500, 100 c, 0.1,50, -2500, -1500,100,100,1, -1000,100d, 0.1,50, -2500, -1000,1000,1000,1, -1500,1000 e, 0.1,50 , -2500, -1000, 100, 10, 0.1, -1500, 1000 f, 0.1, 10, -2500, -1000, 100, 100, 1, -1500, 100 g, 0.1, 25, -2500, -1000 , 100,100,1, -1500,100h, 0.5,50, -2500, -1000,100,100,1, -1500,100i, 1.0,50, -2500, -1000,100,100,1 , -1500,100 [Data with many hydrogen traces] j, 0.1,50, -2500, -2500,100,100,1,0,100k, 0.1,50, -2500, -1000,10,10,1 , -1500,10 l, 0.1,50, -2500, -1000,100,1000,10, -1500,10 m, 0.1,75, -2500, -1000,100,100,1, -1500,100 n , 0.1,100, -2500, -1000,100,100,1, -1500,100 o, 0.05,50, -2500, -1000,100,100,1, -1500,100p, 0.01,5 0, -2500, -1000, 100, 100, 1, -1500, 100 The above data a to p were plotted on the graphs of FIGS.

As can be seen from FIG. 11, Ehigh ≒ -250
0 mV, Ehigh−Elow ≦ −1000 mV, Thigh> 10 μs, and Tlow> 0 are preferable. As can be seen from FIG. 12, Ehigh ≒ -2500 mV,
Ehigh−Elow ≦ −1000 mV and Tlow
/ Thigh <10, Tlow> 0 is preferable. As can be seen from FIG. 13, Ehigh ≒ -2500 mV, Ehigh
−Elow ≦ −1000 mV and a film thickness of 75 n
It is preferably less than m. As can be seen from FIG.
high ≒ -2500mV, Ehigh-Elow ≦ -1000m
V and the concentration of the element in the electrolyte is 0.05
It is preferably larger than mol / L. As can be seen from FIG. 15, it is preferable that Thigh> 10 μs and Tlow> 0, and the concentration of the element in the electrolyte be greater than 0.05 mol / L. As can be seen from FIG.
gh> 10 μs, Tlow> 0, and Tlow / Thi
Preferably, gh <10. As can be seen from FIG.
When Tlow / Thigh = r, Ehigh ≒ -2500m
V, Ehigh−Elow ≦ −1000 mV, and T
It is preferable that high / r> 10 and Tlow> 0.

[0021]

According to the film formation method by electrolysis of the present invention, a thin film of a charge transfer rate-controlling element such as nickel, iron, and cobalt can be produced without a trace of hydrogen. Further, since a low-concentration solution can be used, production costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a pulse waveform diagram.

FIG. 2 is an explanatory diagram showing a reduction state of nickel and hydrogen during an Ehigh application time.

FIG. 3 is an explanatory diagram showing a reduced state of hydrogen during an Elow application time.

FIG. 4 is a configuration diagram showing a constant potential pulse electrolysis system according to the present invention.

FIG. 5 is an SEM photograph showing a surface state of an electrodeposited film when a pulse voltage Elow is changed.

FIG. 6 is an SEM photograph showing a surface state of an electrodeposited film when an application time Thigh is changed.

FIG. 7 is an SEM photograph showing a surface state of an electrodeposited film when a pulse potential application time ratio r is changed.

FIG. 8 is an SEM photograph showing a surface state of an electrodeposited film when the film thickness is changed.

FIG. 9 is an STM photograph showing changes in the surface state of the electrodeposited film when the film thickness is changed.

FIG. 10 is an SEM photograph showing a change in the surface state of the electrodeposited film when the concentration of the electrodeposited solution is changed.

FIG. 11 is a graph in which data is plotted on coordinates of an (Ehigh-Elow) axis and a Thigh axis.

FIG. 12 is a graph in which data is plotted on coordinates of an (Ehigh-Elow) axis and an r-axis.

FIG. 13 is a graph in which data is plotted on coordinates of an (Ehigh-Elow) axis and a film thickness axis.

FIG. 14 is a graph in which data is plotted on coordinates of an (Ehigh-Elow) axis and a Ni concentration axis.

FIG. 15 is a graph in which data is plotted on coordinates of a Thigh axis and a Ni concentration axis.

FIG. 16 is a graph in which data is plotted on the coordinates of the Thigh axis and the r axis.

FIG. 17 is a graph in which data is plotted on coordinates of an (Ehigh-Elow) axis and a Thigh / r axis.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cathode electrode 2 Nickel 3 Hydrogen gas 3a, 3b Bubble 100 Constant potential pulse electrolysis system 10 Electrolyte 101 Container 102 Anode electrode 103 Reference electrode 104 QCM 105 Control unit 106 Printer 107 Pulse generator 108 Function generator 109 Potentiostat 110 Recording unit 111 Current probe 112 Oscilloscope 113 Plotter

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) C25D 5/18

Claims (1)

(57) [Claims] In a film forming method for obtaining, by electrolysis, a film of an element whose charge transfer process in the electrodeposition reaction is a rate-determining reaction, a pulse voltage generating both crystal nuclei of the element and hydrogen is provided.
No crystal nuclei of the element Ehigh and the above elements and hydrogen crystals
Alternating the pulse potential Elow that generates only nuclei for a short time
And forming an electrodeposited film having no hydrogen trace by electrolysis.