JP3470786B2 - Liquid phase surface treatment apparatus and method for measuring mass change of workpiece using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid phase surface treatment involving a change in mass of an object to be processed, such as electroplating, electroless plating, anodic oxidation, water repellent treatment, etc. The present invention also relates to a liquid surface treatment apparatus that enables accurate measurement and a method for measuring mass change using the same.

[0002]

2. Description of the Related Art Electroplating, electroless plating, anodic oxidation,
In liquid phase surface treatment such as water repellent treatment, the mass of the object to be treated increases with the growth of the metal film, the oxide film, and the water repellent material film on the surface of the object to be treated. The simplest way to control the progress of such surface treatments is time control. For electroplating, for example, a curve representing the relationship between time and mass increase due to growth of the plated film is created in advance after setting various liquid phase parameters such as chemical concentration, temperature, and current density to known values. The plating film thickness and plating speed can be estimated based on this curve.

However, since the actual liquid surface treatment is carried out in a chemical solution having a finite volume, the processing speed also changes as the liquid phase parameters change with time. Therefore, it is not possible to measure the mass change with high accuracy only by time management. Further, when measuring the mass, the object to be treated must be taken out of the treatment tank and washed with water each time, and if the desired mass is not obtained, the object to be treated is returned to the treatment tank again to continue the treatment. There is a need. That is, the surface treatment and the mass measurement cannot be performed in real time, which causes a decrease in throughput.

Japanese Unexamined Patent Publication (Kokai) No. 3-294500 discloses a plating film thickness meter in which only one side of a crystal resonator, which is formed by vapor-depositing a metal film serving as an excitation electrode on both sides of a crystal disk, is brought into contact with a plating solution. There is. According to this invention, it is said that the plating film thickness can be measured in real time by utilizing the change in the frequency of the crystal resonator caused by the growth of the plating film on the contact surface with the plating solution.

[0005]

The measurement of mass change using a crystal oscillator is a technique that has been widely used for monitoring in the field of thin film formation by vapor phase epitaxy. However, when using the crystal unit in contact with the liquid phase,
The contribution of liquid phase parameters such as temperature, viscosity, density, pH, and electrical conductivity of the chemical solution is superimposed on the frequency measurement result, and it is possible to know the amount of change in frequency purely due to mass change by the conventional method. Is impossible. Therefore, the present invention is a liquid phase surface treatment apparatus capable of accurately measuring the mass change in real time in a liquid phase surface treatment accompanied by a mass change of an object to be processed, and a mass change measuring method using the same. The purpose is to provide.

[0006]

The liquid surface treatment apparatus of the present invention comprises a treatment tank filled with a chemical used for the surface treatment of an object to be treated, and at least one main surface of the vessel to be treated when immersed in the chemical. A first crystal unit, which is a mass change detection surface that is subjected to the same surface treatment as the body surface treatment, and a second crystal surface, at least one main surface of which is a reference surface inert to the surface treatment with a chemical solution. Based on a crystal unit, a frequency measuring unit that measures a change in the frequency of the first crystal unit and the second crystal unit with the progress of the surface treatment, and the measurement result of the frequency measuring unit. It is intended to achieve the above-mentioned object by adopting a configuration including arithmetic processing means for determining the progress of the surface treatment on the object to be treated.

The apparatus may be provided with control means for performing feedback control of the liquid phase parameter so that the frequency of the second crystal oscillator is always kept constant based on the calculation result of the calculation processing means. good. Further, among the liquid phase parameters, temperature measuring means for measuring the temperature of the chemical liquid may be provided so that the temperature can be independently controlled.

In order to measure the mass of the object to be processed by using the apparatus equipped with these control means, the first crystal unit and the second crystal unit are placed in a chemical solution used for liquid surface treatment. It may be soaked with the object to be processed, and a mass change generated on the object to be processed may be detected based on a measurement result of a change in frequency of the first crystal unit and the frequency of the second crystal unit. .

Alternatively, by paying attention to the frequency of the second crystal oscillator and performing feedback control so as to keep the component contributing to this constant, the second crystal oscillator is actively managed in the liquid phase. It can also be used for. This includes
The following three methods are possible. (A) Keep the total frequency of the second crystal unit constant. (B) At least one liquid phase parameter that changes with time is selected, and a residual value obtained by subtracting the amount of change due to the selected liquid phase parameter from the total amount of change in the frequency of the second crystal resonator is set. Feedback control is performed on the remaining liquid phase parameters so as to keep it constant. (C) Feedback control is performed on the selected liquid phase parameter so that the amount of change in the frequency of the second crystal unit caused by the liquid phase parameter selected in (b) is kept constant.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The basic idea of the present invention is to use a first crystal oscillator that is subjected to the same surface treatment as that of the object to be treated, and a frequency that is not subjected to the surface treatment but is associated with other chemical liquid immersion. Is compared with the frequency of the second crystal oscillator that occurs, and it is intended to extract only the change in frequency purely due to the surface treatment, that is, the mass change resulting from the surface treatment. is there.

Generally, when a crystal unit is connected to an oscillation circuit, it vibrates at a fundamental frequency f ₀ which depends on the thickness of the crystal plate. However, the crystal unit is immersed in a liquid phase for a predetermined surface treatment. As a result, when the weight changes due to the deposited or adhered substance, the resonance frequency changes by Δf. However, in reality, the amount of change in resonance frequency Δf includes the amount of change in frequency Δf _M , which is purely due to weight change, and the amount of change in frequency Δf _L, which is due to immersion in the liquid phase itself. Are superimposed. If the frequency of the crystal unit after the change in weight is F, then this relationship is expressed by the following equation. F = f ₀ + Δf = f ₀ + (Δf _M + Δf _L ) ... [1] However, since only one crystal resonator is used in the conventional method, Δf _M and Δf _L are separated. It could not be detected.

In the present invention, in order to solve this problem,
A second crystal oscillator for reference is used. However, since the main surface of the second crystal oscillator is inactive to the surface treatment, the frequency does not change due to the weight change (Δf _M = 0). Here, the above equation [1] is changed to the first
In terms of both the crystal unit and the second crystal unit, F ₁ = f ₀₁ + (Δf _M + Δf _L1 ) ... [2] F ₂ = f ₀₂ + (0 + Δf _L2 ) ... [ 3] where F ₁ = frequency after surface treatment of the first crystal unit F ₂ = frequency after surface treatment of the second crystal unit Δf ₀₁ = fundamental frequency Δf of the first crystal unit ₀₂ = fundamental frequency of second crystal unit Δf _L1 = amount of change in frequency caused by liquid phase immersion of first crystal unit Δf _L2 = frequency of liquid crystal immersed in second crystal unit It is the amount of change.

Therefore, after the surface treatment, the difference between the two frequencies is expressed by the following formula F ₁ −F ₂ = (f ₀₁ −f ₀₂ ) + Δf _M + (Δf _L1 −Δf _L2 ) ... [4] expressed. Here, the fundamental frequency f of both crystal units
_{Since 01} and f ₀₂ are known, (f ₀₁ −f ₀₂ ) is a known constant. This term is f ₀₁ -f by selecting the fundamental frequencies f ₀₁ and f ₀₂ of both crystal oscillators to be equal.
₀₂ becomes 0. Therefore, the equation [4] can be written as F ₁ −F ₂ = Δf _M + (Δf _L1 −Δf _L2 ) ... [5].

On the other hand, if it is assumed that the amounts of frequency changes Δf _L1 and Δf _L2 due to the liquid phase immersion of both crystal oscillators do not differ so much under normal processing conditions, (Δf _L1
It is also possible to put −Δf _L2 ) approximately at zero. However, in order to exactly offset this term to zero, the first
It is preferable to set the areas of the mass change detection surface of the crystal oscillator and the reference surface of the second crystal oscillator to be equal to each other so that the changes caused by the liquid phase immersion are equal. This allows
The formula [5] is F ₁ −F ₂ = Δf _M. Thus, by subtracting the frequency generated in the second crystal unit as the background value of the amount of change, it is possible to easily detect the amount of change in frequency purely due to the weight change. The subsequent description of this specification is Δf _L1.
Description will be made on the assumption that = Δf _L2 = Δf _L.

By the way, in the present invention, the fact that only the frequency change Δf _L2 caused by the liquid phase immersion is reflected in the frequency F ₂ of the second crystal unit is used to make the second crystal unit liquid. It is possible to positively contribute to phase management. As a first method of such liquid phase management, a control means capable of executing feedback control of liquid phase parameters is installed in the surface treatment apparatus of the present invention, and the frequency F of the second crystal oscillator is used by using this control means. _A method of performing feedback control that keeps ₂ always constant is conceivable. In other words, this is Δf _L from equation [3]
It is nothing but keeping constant. As a result, it becomes possible to detect Δf _M with high accuracy according to the equation [2]. Needless to say, the quality of the surface treatment is improved by stabilizing the film forming conditions. As the specific contents of the feedback control of the liquid phase parameter, the temperature of the chemical liquid can be controlled using the temperature adjusting means, or the concentration, viscosity, pH and electric conductivity can be adjusted by supplementing the chemical liquid or solvent.

The above Δf _L is actually a collection of contributions of various liquid phase parameters. Therefore, if any liquid phase parameter among these liquid phase parameters can be selected and measured independently, and if the amount of change in frequency due to these selected liquid phase parameters can be individually estimated,
The influence of the change amount caused by these selected parameters is excluded from the change amount of the frequency of the second crystal oscillator, and only the change amount caused by the remaining liquid phase parameters is focused on and kept constant. Such liquid phase management can be performed. This is the second method of liquid phase management. For example, when the temperature of the chemical liquid is selected as an arbitrary liquid phase parameter, the change amount due to the temperature of the chemical liquid is Δf _TEMP , and the change amount due to other liquid phase parameters is Δf _R , Δf _L is Δf _L = Δf It can be expressed as _TEMP + Δf _R ... [6]. At this time, the temperature of the chemical liquid is monitored using the temperature measuring means, and the change amount Δf _TEMP resulting from this is monitored.
If it is possible to estimate, then it suffices to focus only on Δf _R and perform liquid phase management so as to keep this constant.

Of course, feedback control may also be performed with respect to the temperature of the chemical liquid so that Δf _TEMP is always kept constant. This is the third method of liquid phase management. Δf _R and Δf
_When both _TEMP and _TEMP are kept constant, Δf _L is kept constant as a result of the equation [6], and at first glance, it is the same as the first method of liquid phase management described above. But this third
In the method (1), Δf _L is kept constant after the temperature and other liquid phase parameters are independently controlled, and the control method is more specific and simple compared to the first method.

A mode of a concrete embodiment of the present invention will be described below. 1st Embodiment Here, the structural example of the liquid phase surface treatment apparatus of this invention is demonstrated, referring FIG.1 and FIG.2. As shown in FIG. 1, this apparatus includes a treatment tank 1 filled with a chemical liquid L used for the surface treatment of an object to be treated W, a first crystal oscillator 2 and a second crystal that are immersed in the chemical liquid. A vibrator 3, a thermometer 4 for measuring the temperature of the chemical liquid L, and a liquid phase maintaining device 5 for maintaining constant liquid phase parameters are provided. The first crystal oscillator 2, the second crystal oscillator 3, the thermometer 4, and the liquid phase maintenance device 5 are respectively a first crystal oscillator controller 12, a second crystal oscillator controller 13, and a thermometer controller. 14 and the liquid phase maintenance device controller 15 are respectively connected to the arithmetic processing device 6. The arithmetic processing unit 6 collectively performs feedback control of all liquid phase parameters necessary for liquid surface treatment.

Examples of the configurations of the first crystal unit 2 and the second crystal unit 3 are shown in FIGS. 2 (a) and 2 (b), respectively.
Each of these two vibrators has a diameter of 20 mm, a thickness of 0.17 mm, and AT-cut circular quartz plates 21 and 31 on both main surfaces of which an excitation electrode 22 and an inert excitation electrode 32 are vapor-deposited in a circular pattern. It was formed. From the excitation electrode 22 and the inactive excitation electrode 32, soldered lead wires 23 and 33 are led out and connected to the controllers 12 and 13 shown in FIG. In addition, these first and second crystal units 2,
One main surface of No. 3 is covered with casings 24 and 34 and resin-sealed so that the excitation electrode 22 and the inactive excitation electrode 32 on this surface side do not come into contact with the chemical liquid L.

The surface not covered by the casing 24 is the mass change detection surface 21 of the first crystal unit 2.
a, the reference surface 31a of the second crystal unit 3 is in direct contact with the chemical liquid L and is affected by various liquid phase parameters. First, the mass change detection surface 21a is a surface on which the same surface treatment as that performed on the object W in the chemical liquid L is performed. If this surface treatment is, for example, plating or a water repellent treatment, the plating film or the water repellent material film adheres to this surface to increase the mass, and the frequency of the first crystal resonator 2 changes accordingly. To do. The change in the frequency is measured by the first crystal oscillator controller 12, which is one of the frequency measuring means, converted into an electric signal, and transferred to the arithmetic processing unit 6.

On the other hand, the above-mentioned reference surface 31a is a surface which is in contact with the chemical liquid L but inactive to the surface treatment using the same. The deactivation of the reference surface 31a is ideally performed on the entire surface of the reference surface in some form, but only the excitation electrode that closes most of the area of the reference surface 31a is deactivated. However, it is sufficient depending on the content of the surface treatment. In FIG. 2B, the inert excitation electrode 32 is illustrated. Note that the inactivation of the inactive excitation electrode can be performed by various methods such as selection of the electrode material itself, surface modification of the electrode material, surface coating of the electrode material, and forced potential operation. Will be sequentially described in the second and subsequent embodiments. In any case, since the plating film or the water repellent material film is not attached to the reference surface 31a, the frequency change due to the mass change does not occur. However, it is affected by liquid phase parameters such as temperature, viscosity, pH, and electrical conductivity, which are derived from the immersion itself in the chemical liquid L, and a frequency change caused by these is generated. This frequency change is also measured by the second crystal oscillator controller 13, which is one of the frequency measuring means, converted into an electric signal, and transferred to the arithmetic processing unit 6.

The influence of the liquid phase parameter exerted on the second crystal oscillator 3 is actually equally exerted on the mass change detection surface 21a of the first crystal oscillator 2. Therefore, the frequency change generated in the second crystal unit 3 is considered to be the background value in this surface treatment, and the difference between this value and the frequency change generated in the first crystal unit 2 is obtained. , It is possible to know the frequency change purely due to the mass change. The arithmetic processing unit 6 described above stores in advance the relationship between the frequency change of the first crystal unit 2 and the mass change, the relationship between the mass change and the surface treatment result (for example, the film thickness), and other necessary control information. It is stored, and the corresponding mass change or film thickness can be known based on the above-mentioned difference in frequency.

The thermometer 4 is a temperature measuring means for measuring the temperature of the chemical liquid L. The temperature information measured by the thermometer 4 is converted into an electric signal by the thermometer controller 14 and transferred to the arithmetic processing unit 6. Also,
The liquid phase maintaining device 5 is a device that directly acts on the chemical liquid L to maintain the liquid phase parameter at a predetermined condition. For example, a heating / cooling device for keeping the temperature of the chemical liquid L constant, or a concentration of the chemical liquid L,
Solvent and / or to keep pH and conductivity constant
Alternatively, it has a built-in member such as a pipe and a nozzle of a chemical liquid supply system for adding a solute. It is the liquid phase maintenance device controller 15 that directly controls the liquid phase maintenance device 5. This liquid phase maintenance device controller 15
Receives the command signal generated by the arithmetic processing unit 6 based on the measurement result of the liquid phase parameter, and performs an operation such as turning on / off a switch of the heating / cooling device or opening / closing a valve of the chemical liquid replenishing device.

For example, the procedure for performing feedback control of the temperature of the chemical liquid in the apparatus shown in FIG. 1 is roughly as follows. That is, first, based on the measurement result of the thermometer 4, the arithmetic processing unit 6 needs to raise the temperature of the chemical liquid required /
A control signal that determines the temperature drop range and determines the energization time or the refrigerant supply amount to the heating / cooling device necessary for such liquid temperature adjustment is generated and transferred to the liquid phase maintenance device controller 15, and based on this signal, the liquid The liquid phase parameters are maintained by the liquid phase maintaining device 5 by the phase maintaining device controller 15 actually controlling the switches and valves. According to such an apparatus, the temperature of the chemical liquid L is always maintained constant, so that, for example, the vibration frequency fluctuation of the crystal unit due to the increase in the chemical liquid temperature accompanying the progress of plating is caused by other liquid phase parameters. It can be excluded from frequency fluctuations.

Alternatively, the arithmetic processing unit 6 can be made to perform feedback control of liquid phase parameters based on the frequency of the second crystal unit 3. That is, the frequency data of the second crystal unit 3 is always transferred to the arithmetic processing unit 6, and when the observed frequency deviates from the reference frequency, the frequency is returned to the reference value. The amount of change in the required liquid phase parameter is determined by the arithmetic processing unit 6, and the liquid phase maintenance device controller 1 is determined according to this determination.
5 and the liquid phase maintenance device 5 change the liquid phase parameter.

Whichever method is adopted, according to the apparatus of the present invention, the surface treatment progresses in real time from the change in the frequency of the first crystal oscillator 2 while being immersed in the chemical liquid L. You can know. Moreover, by subtracting the frequency change caused by the liquid phase parameter indicated by the second crystal oscillator 3 for reference, the vibration caused by the mass change among the frequency changes indicated by the first crystal oscillator 2 is subtracted. Only a few changes can be easily separated, which enables quality improvement of surface treatment and precise monitoring.

Second Embodiment Here, the excitation electrode is made inactive with respect to the surface treatment due to the inherent characteristics of the metal material forming the excitation electrode,
The second crystal unit 3 whose reference surface is substantially inactivated by this will be described. A model cross-sectional view of the second crystal unit 3 is as shown in FIG.

As an example, a case where electroless plating is assumed as the surface treatment will be described. In order for the electroless plating to proceed, the reversible potential of the metal electrode must be nobler than the redox potential of the reducing agent in terms of equilibrium, but in reality, it depends on the anodic oxidation reaction rate of the reducing agent. It is heavily controlled. It is known that this oxidation reaction rate greatly depends on the type of electrode metal. For example, “Metal Surface Technology”, Volume 34, No. 12, p. 594-599 (1983), describes the anodic oxidation reaction of hypophosphorous acid, which is widely used as a reducing agent for electroless plating baths of nickel and cobalt. Is evaluated from its oxidation onset potential, the catalytic activity of the electrode metal is in order from higher to lower Au>Ni>Pd>Co>Pt>Cu> A.
It has been shown to be g.

Therefore, when hypophosphorous acid is used as a reducing agent for electroless plating, if the inert excitation electrode 32 is made of Ag or a metal having a lower catalytic activity than Ag, the surface of this surface can be reduced. The deposition of the plated film can be suppressed, and the second crystal unit 3 does not change its mass. That is, the second crystal unit 3 becomes inactive with respect to the electroless plating, and shows only the frequency change due to the immersion in the chemical solution. When a reducing agent other than hypophosphorous acid is used, the excitation electrode may be formed by using a metal having as low a catalytic activity as possible according to the magnitude relationship of the catalytic activity according to the reducing agent.

As another example, a case where a water repellent treatment is assumed as the surface treatment will be described. As one of the water repellent treatment,
There is a chlorosilane-based coupling agent that can obtain an excellent water repellent effect due to the water repellency of the fluoroalkyl group. This compound adheres to the surface of the object to be processed by forming a siloxane bond with the —OH group (hydroxyl group) existing on the surface of the object to be processed. Therefore, in order to prevent the water-repellent treatment agent from adhering to the excitation electrode, it is sufficient that no -OH group is present on the surface thereof. However, a normal metal whose surface is covered with a natural oxide film always has a -OH group because dangling bonds of oxygen atoms in this oxide film are terminated by H atoms. . On the other hand, Pt,
If the excitation electrode is made of a noble metal which is extremely hard to be oxidized, such as Au, the -OH group is scarcely present on the surface of the excitation electrode. Therefore, the inert excitation electrode 32 that is inert to the water repellent treatment should be formed. You can

Third Embodiment Here, a configuration example of a second crystal oscillator in which the reference surface 31a is inactivated by forming a self-aligning inactive protective film on the excitation electrode will be described. A schematic cross-sectional view of this electrode is shown in FIG. The excitation electrode 35 and the inert protective film 36 formed on the surface of the excitation electrode 35 in a self-aligning manner are integrated and function as an inert excitation electrode 37.

For example, as the surface treatment, electroless plating,
Assuming either electroplating or anodic oxidation, a requirement common to these surface treatments is that at least the surface of the object to be treated has conductivity. Therefore, it is preferable to use a thin insulating film as the inert protective film 36 in the present embodiment. At this time,
If a material that forms an insulating oxide, a nitride, or an oxynitride is selected as the metal material forming the excitation electrode 35, the excitation electrode 35 deposited on the surface of the quartz plate 31 will be By performing an oxidation treatment, a nitriding treatment, or an oxynitriding treatment using an annealing furnace or a plasma apparatus, the surface layer portion can be changed to a thin insulating film.

Alternatively, the excitation electrode can be formed by using a metal material that is passivated by surface treatment. For example, it is known that in the anodizing treatment in which Ti is connected to the anode, once the surface of titanium is covered with a thin insulating titanium oxide film, the oxidation does not proceed any further. In view of this, in the present invention, the inactive protective film 36 made of titanium oxide is formed by subjecting the second crystal oscillator, in which the excitation electrode 35 is made of Ti, to anodization in advance.
Are formed, and the surface of the excitation electrode 35 is passivated.
By doing so, even when the anodizing treatment is actually performed on the target object W, the reference surface 31a is inactive to the treatment.

The thickness of the above-mentioned inert protective film 36 is
While sufficient surface deactivation effect can be obtained,
It is important to select so that the original vibration characteristics of the crystal unit are not impaired. The upper limit of the film thickness is preferably about 1/1000 or less of the thickness of the crystal plate 31 and 1/3 or less of the thickness of the excitation electrode 35. If the film thickness is larger than this, there is a great possibility that the detection of the background value reflecting the liquid phase parameter will be hindered. In addition, in particular, when anodizing treatment is assumed as the surface treatment, in consideration of the fact that this anodizing treatment is generally performed in a strong acid chemical solution such as a sulfuric acid bath, inert protection with insulation and acid resistance is also taken into consideration. Forming the membrane 36 is preferred.

Fourth Embodiment The above-mentioned inert protective film is formed not only in a self-aligned manner on the surface of the excitation electrode, but also so as to cover the entire reference surface as shown in FIG. May be. For example, when the thin insulating film as described in the third embodiment is formed by using a vapor phase thin film forming technique such as sputtering, vapor deposition, and CVD, and this is used as the inert protective film 38, electroless plating, A second crystal oscillator suitable for monitoring electroplating and anodic oxidation can be configured.

It is also possible to prevent contact between the chemical liquid L and the reference surface 31a by subjecting the entire reference surface to a water repellent treatment. For example, the second crystal unit 3 is replaced with a chlorosilane coupling agent CF ₃ (CF ₂ ) ₇ (CH ₂ ).
_When a water repellent film is formed by dipping in ₂ SiCl ₃ , and this is used as an inert protective film 38, a reference surface 31a for the chemical liquid L is formed.
The wettability of is extremely reduced. Thereby, the reference surface 31
a can be made substantially inert to surface treatments such as electroless plating, electroplating and water repellent treatment. The regulations regarding the film thickness of the insulating film and the water-repellent film described in this embodiment also
It complies with the regulations described in the third embodiment.

Unlike the structure in which the inert protective film 36 is formed on the entire surface of the reference surface by the surface modification of the exciting electrode 35 itself, the type of the exciting electrode 35 is different. There is an advantage of not choosing. Therefore, for example, it is possible to purchase a commercially available crystal oscillator in which the excitation electrode is vapor-deposited in advance and to apply the inert protective film 38 on the surface thereof, which increases the degree of freedom in device design.

Fifth Embodiment Here, assuming electroless plating as the surface treatment, the second crystal unit in which the reference surface 31a is inactivated by the forced potential operation using the counter electrode, This will be described with reference to FIG. In the second crystal unit 3, the lead wire 33 led out from the excitation electrode 35 on the reference surface 31a side.
In addition, the counter electrode 39 facing the excitation electrode 22 is connected to the power source 40.
Are connected in parallel via. The surface area of the counter electrode 39 is substantially equal to the reference surface 31a of the second crystal unit 3, and the distance between the excitation electrode 35 and the counter electrode 39 is about 10 mm.

In electroless plating, when the object W to be treated is immersed in a plating bath, the potential of the object W to be treated is made equal to the absolute value of the current due to the oxidation reaction of the reducing agent and the current due to the reduction reaction of the metal. Potential is set spontaneously, that is, the immersion potential, and the metal is deposited on the surface of the object W to be processed without the flow of current. The immersion potential varies depending on the concentration of the reducing agent and the pH of the plating bath, but is about -0.5 to -0.7 V in the case of Ni plating. In the present embodiment, the counter electrode 39 is used to set the potential of the excitation electrode 35 to be nobler than the immersion potential, whereby the deposition rate of the plating film on the excitation electrode 35 can be significantly reduced. . In particular, by setting it more noble than the reversible potential,
The deposition rate of the plated film becomes so small that it can be ignored, and the reference surface 31a is practically in an inactivated state. The reversible potential of electroless Ni plating is about −0.257V.

It should be noted that the excitation electrode 35 is more noble than the immersion potential,
More preferably, it is necessary to pay attention to the generation of oxygen when setting the noble potential higher than the reversible potential. When the potential of the excitation electrode 35 is nobler than the oxygen minimum overvoltage, electrolysis of water occurs on the electrode surface and oxygen is generated, and the bubbles greatly change the interface state between the reference surface and the liquid phase. Therefore, although the plating film is not deposited, noise is superimposed on the detected frequency, making precise monitoring impossible. Therefore, the potential of the excitation electrode 35 needs to be lower than the oxygen minimum overvoltage.

However, since the oxygen minimum overvoltage depends on the kind of metal, it is effective to select a metal material having a large value as the metal material forming the excitation electrode 35. For example, Au, Ag and Pt (smooth platinum) are suitable. In order to set the potential of the excitation electrode 35, a change in the frequency of the second crystal oscillator 3 is measured while gradually changing the potential from the immersion potential to the noble direction in a preliminary experiment, and the frequency due to generation of bubbles is measured. It is advisable to confirm the potential region in which the fluctuation of is not apparent. As long as the excitation electrode 35 is used in this potential region, the excitation electrode 35 is in a state of being inactivated by the electroless plating. Note that metals other than Ni, such as Cu
The concept of electroless plating of Co and Co is exactly the same.

Although the seven embodiments of the present invention have been described above, the present invention is not limited to these embodiments. For example, in the device configuration shown in FIG. 1, the first crystal unit and the second crystal unit are not soaked in the entire chemical solution, but only the mass change detection surface and the reference surface are brought into contact with the chemical solution, respectively. You can take various installation styles. Details of other device configurations, electrode materials used,
For surface treatment types and combinations of these,
It can be changed or selected as appropriate.

[0043]

As is clear from the above description, according to the present invention, it is possible to measure the mass change in the liquid surface treatment with good accuracy, reproducibility and controllability. It is possible to significantly improve the processing quality and productivity.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing one configuration example of a liquid surface treatment apparatus of the present invention.

2 is an enlarged cross-sectional view of the crystal unit of FIG. 1, (a)
Represents a first crystal unit, and (b) represents a second crystal unit.

FIG. 3 is a schematic cross-sectional view showing a configuration example of a second crystal oscillator using a self-aligned inert protective film.

FIG. 4 is a schematic cross-sectional view showing a configuration example of a second crystal unit in which an inactive protective film is entirely formed on a reference surface.

FIG. 5 is a schematic cross-sectional view showing a configuration example of a second crystal unit that is inactivated by a forced potential operation using a counter electrode.

[Explanation of symbols]

1 processing tank 2 First crystal unit 3 Second crystal unit 4 thermometer 5 Liquid phase maintenance device 6 Processor 12 First crystal oscillator controller 13 Second crystal oscillator controller 14 Thermometer controller 15 Liquid phase maintenance device controller 21, 31 Crystal plate 21a Mass change detection surface 22,35 Excitation electrode 23, 33 lead wire 24, 34 casing 31a reference surface 32,37 Inert excitation electrode 36,38 Inert protective film 39 Counter electrode L chemical W object

Front page continuation (51) Int.Cl. ⁷ Identification code FI G01N 5/02 G01N 5/02 A (72) Inventor Katsuyuki Okubo 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd. (72 ) Inventor Yuji Miura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) Reference JP-A-3-294500 (JP, A) JP-A-54-153059 (JP, A) Actual Kaihei 2-32007 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01G 17/04 C23C 18/31 C25D 21/12 G01B 17/02 G01G 3/16 G01N 5/02

Claims (21)

(57) [Claims] 1. A treatment tank filled with a chemical used for surface treatment of an object to be treated, and at least one main surface is subjected to the same surface treatment as the surface treatment to the object to be treated when immersed in the chemical. A first crystal unit serving as a mass change detection surface; a second crystal unit having at least one main surface serving as a reference surface inert to the surface treatment with the chemical solution; The first crystal unit and the second unit according to the progress
A vibration frequency measuring means for respectively measuring a change in the vibration frequency of the crystal oscillator, and an arithmetic processing means for judging the progress of the surface treatment on the object based on the measurement result of the frequency measuring means, A liquid-phase surface treatment device provided with. 2. The liquid phase surface treatment apparatus according to claim 1, wherein the first crystal oscillator and the second crystal oscillator have fundamental frequencies that are equal to each other in an initial state before performing the surface treatment. . 3. The liquid surface treatment apparatus according to claim 2, wherein the mass change detection surface and the reference surface have the same area. 4. The liquid phase according to claim 1, further comprising control means for performing feedback control of the liquid phase parameter so as to always keep the frequency of the second crystal oscillator constant based on the calculation result of the calculation processing means. Surface treatment equipment. 5. The liquid surface treatment apparatus according to claim 4, further comprising temperature measuring means for measuring the temperature of the chemical liquid. 6. The liquid surface according to claim 1, wherein the excitation electrode exposed on the reference surface is formed by using a metal having a low catalytic activity for the oxidation reaction of the reducing agent contained in the chemical solution for electroless plating. Processing equipment. 7. The insulating film is formed on at least the surface of the excitation electrode exposed in the reference surface.
The liquid surface treatment apparatus described. 8. The liquid surface treatment apparatus according to claim 7, wherein the insulating coating is a metal compound film formed in a self-aligned manner by surface modification of the excitation electrode. 9. The liquid phase surface treatment apparatus according to claim 8, wherein the metal compound is one of a metal oxide film, a metal nitride film, and a metal oxynitride film. 10. The liquid surface treatment apparatus according to claim 7, wherein the insulating coating is formed on the entire surface of the reference surface. 11. The liquid-phase surface treatment apparatus according to claim 7, wherein the insulating coating has acid resistance. 12. The water repellency is imparted to at least the surface of the excitation electrode exposed in the reference surface.
The liquid surface treatment apparatus described. 13. The liquid phase surface treatment apparatus according to claim 1, wherein the excitation electrode exposed on the reference surface is formed by using a non-oxidizing metal. 14. The potential of the excitation electrode of the reference surface is set to a potential nobler than the immersion potential in the chemical solution for electroless plating by the potential operation between the excitation electrode and the counter electrode arranged in the vicinity thereof. The liquid-phase surface treatment device according to claim 1. 15. The liquid surface treatment apparatus according to claim 14, wherein the potential of the excitation electrode on the reference surface is set to be lower than the minimum oxygen overvoltage of the excitation electrode. 16. A mass change measuring method for measuring a mass change of an object to be processed due to a liquid phase surface treatment, wherein the same surface treatment as that performed on the object to be treated is performed. First having a mass change measurement surface
And a second crystal oscillator having a reference surface inactivated by the surface treatment are dipped together with the object to be treated in a chemical solution used for liquid-phase surface treatment, A mass change measuring method for determining a mass change occurring on the object to be processed based on a measurement result of a change in frequency of the crystal unit and the second crystal unit. 17. The fundamental frequencies of the first crystal oscillator and the second crystal oscillator in the initial state before the surface treatment are set to be equal to each other, and both are accompanied by the progress of the surface treatment. 17. The mass change measuring method according to claim 16, wherein the mass change is determined based on a difference in the amount of change in the vibration frequency. 18. The method for measuring mass change according to claim 16, wherein feedback control of a liquid phase parameter is performed so that the frequency of the second crystal oscillator is always kept constant. 19. At least one liquid phase parameter that changes with the progress of the surface treatment is selected, and the amount of change due to the selected liquid phase parameter is selected from the amount of change in the frequency of the second crystal oscillator. The method for measuring a mass change according to claim 16, wherein feedback control is performed on the remaining liquid phase parameter so that the remaining value obtained by subtracting is constant. 20. The feedback control relating to the selected liquid phase parameter is performed so that the amount of change in the frequency of the second crystal unit caused by the selected liquid phase parameter is kept constant. Method for measuring the mass change of. 21. The mass change measuring method according to claim 19, wherein the selected liquid phase parameter is the temperature of the chemical liquid.