JPH10132646A - Liquid phase surface treatment device, and method for measuring change in mass of a body to be treated using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a mass change in real time and accurately in a liquid phase surface treatment such as plating, that is accompanied with the mass change of a body to be treated. SOLUTION: A first quartz oscillator 2 with a mass change detection surface that is subjected to the same surface treatment for a body W to be treated and a second quartz oscillator 3 with the same vibration characteristics but a non-activated reference surface for the surface treatment are simultaneously dipped into a chemical liquid L. An amount of change Δf of a frequency that the first quartz oscillator 2 shows along with the advance of surface treatment is obtained as the sum (ΔfM+ΔfL) of an amount of change ΔfM due to mass increase and an amount of change ΔfL due to the fluctuation in liquid phase parameters. On the other hand, the amount of frequency change indicated by the second quartz oscillator 3 is only the amount of change ΔfL. Therefore, by performing information processing for subtracting the latter from the former by an operation processing device 6, only the amount of change ΔfM can be determined accurately.

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, and water-repellent treatment. The present invention relates to a liquid surface treatment apparatus capable of performing accurate and accurate measurement, and a method of measuring a change in mass using the same.

[0002]

2. Description of the Related Art Electroplating, electroless plating, anodic oxidation,
In a liquid surface treatment such as a water-repellent treatment, the mass of the object increases as a metal film, an oxide film, and a water-repellent material film grow on the surface of the object. The easiest way to manage the progress of such surface treatment is by time. For example, in the case of electroplating, a curve representing the relationship between time and the increase in mass accompanying the growth of a plating 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.

[0003] However, since the actual liquid phase surface treatment is performed in a chemical solution having a finite volume, the processing speed changes with the temporal change of the liquid phase parameter. For this reason, 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 processed must be taken out of the processing tank each time and washed with water, and if the desired mass has not been obtained, the object to be processed is returned to the processing tank again to continue the processing. 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 Patent Application Laid-Open No. 3-294500 discloses a plating film thickness gauge in which only one side of a crystal unit formed by depositing a metal film as an excitation electrode on both surfaces of a crystal disk is brought into contact with a plating solution. I have. According to the present 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 oscillator caused by the growth of the plating film on the contact surface with the plating solution.

[0005]

The measurement of mass change using a quartz oscillator is a technique that has been widely used for monitoring in the field of thin film formation by a vapor phase epitaxy method. However, when using a crystal oscillator 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 a conventional method to know the amount of frequency change purely due to mass change. Is not possible. Therefore, the present invention provides a liquid-phase surface treatment apparatus capable of measuring the mass change in real time and accurately in a liquid-phase surface treatment involving a mass change of an object to be processed, and a method for measuring the mass change using the same The purpose is to provide.

[0006]

According to the present invention, there is provided a liquid surface treatment apparatus comprising: a treatment tank filled with a chemical used for surface treatment of an object; and a treatment tank having at least one main surface immersed in the chemical. A first quartz oscillator having a mass change detection surface on which the same surface treatment as that of the body is performed, and a second crystal oscillator having at least one principal surface serving as a reference surface which is inactive with respect to the surface treatment with a chemical solution; A crystal oscillator, frequency measuring means for measuring a change in frequency between the first crystal oscillator and the second crystal oscillator with the progress of the surface treatment, and based on the measurement result of the frequency measuring means. The above-mentioned object is achieved by adopting a configuration provided with arithmetic processing means for judging the progress of surface treatment on the object to be processed.

The above-mentioned apparatus may be provided with control means for performing feedback control of a liquid phase parameter based on the calculation result of the calculation processing means so as to keep the frequency of the second quartz oscillator constant. good. Further, a temperature measuring means for measuring the temperature of the chemical solution may be provided so that the temperature among the liquid phase parameters can be independently controlled.

In order to measure the mass of an object to be processed using an apparatus provided with these control means, the first crystal oscillator and the second crystal oscillator are placed in a chemical solution used for liquid phase surface treatment. It may be immersed together with the object to be processed, and a change in mass occurring on the object to be processed may be detected based on a measurement result of a change in the frequency of the first crystal unit and the second crystal unit. .

Alternatively, attention is paid to the frequency of the second crystal oscillator, and feedback control is performed so as to keep the components contributing to the second crystal oscillator constant. It can also be used for This includes
The following three methods are conceivable. (A) The total frequency of the second crystal resonator is kept constant. (B) selecting at least one liquid phase parameter that changes over time, and subtracting a residual value obtained by subtracting a change amount due to the selected liquid phase parameter from a total change amount of the frequency of the second crystal resonator. 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 as to keep the amount of change in the frequency of the second crystal resonator caused by the liquid phase parameter selected in (b) constant.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic concept of the present invention is that a first quartz crystal unit to be subjected to the same surface treatment as that of an object to be treated and a frequency not to be subjected to the surface treatment but to other frequencies caused by immersion in a chemical solution. By comparing the change in the frequency with the frequency of the second quartz crystal unit, the change in the frequency purely due to the surface treatment alone, that is, only the change in mass resulting from the surface treatment, is extracted. is there.

In general, when a quartz oscillator is connected to an oscillation circuit, it vibrates at a fundamental frequency f ₀ depending on the thickness of the quartz plate, but this quartz oscillator is immersed in a liquid phase to perform 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 practice, the variation Δf of the resonance frequency includes the variation Δf _M of the frequency purely due to the weight change and the variation Δf _L of the frequency derived from the immersion itself in the liquid phase. Are superimposed. Assuming that the frequency of the crystal resonator after the weight change is F, 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. Could not be detected.

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

Accordingly, the difference between the two frequencies after the surface treatment is completed is expressed by the following equation: 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 given by selecting the fundamental frequencies f ₀₁ , f ₀₂ of both quartz oscillators equal to f ₀₁ −f
₀₂ = 0. Therefore, the equation [4] can be written as: F ₁ −F ₂ = Δf _M + (Δf _L1 −Δf _L2 ) (5)

On the other hand, assuming that the frequency change amounts Δf _L1 and Δf _L2 due to the immersion of the two crystal units in the liquid phase do not differ so much under ordinary processing conditions, (Δf _L1
−Δf _L2 ) can be set to approximately zero. However, in order to cancel this term exactly to zero, the first
It is preferable to set the areas of the mass change detection surface of the quartz oscillator and the reference surface of the second quartz oscillator to be equal to each other, and to equalize the changes received by the liquid phase immersion. This allows
[5] Equation becomes F ₁ −F ₂ = Δf _M. In this way, by subtracting the frequency generated in the second crystal resonator as the background value of the variation, it is possible to easily detect the variation of the frequency purely due to the weight change. The remainder of this specification will use Δf _L1
= Δf _L2 = Δf _L is described.

The present invention utilizes the fact that only the frequency change Δf _L2 due to the liquid phase immersion is reflected in the frequency F ₂ of the second crystal oscillator, and the second crystal oscillator is It can be actively used for 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 _A method of performing feedback control to keep ₂ constant at all times is conceivable. That is, this is given by Δf _L from equation [3].
Is constant. As a result, Δf _M can be detected with high accuracy from equation [2]. Of course, the quality of the surface treatment is improved by stabilizing the film forming conditions. As specific contents of the feedback control of the liquid phase parameter, control of the temperature of the chemical using a temperature adjusting means, or adjustment of the concentration, viscosity, pH, and electric conductivity by replenishment of the chemical or the solvent can be performed.

The above Δf _L is actually a collection of contributions of various liquid phase parameters. Therefore, if an arbitrary liquid phase parameter is selected from these liquid phase parameters and independently measured, and if the amount of change in frequency due to the selected liquid phase parameter can be individually estimated,
The influence of the change caused by these selected parameters is excluded from the change of the frequency of the second crystal resonator, and the constant is maintained by focusing only on the change caused by the remaining liquid phase parameters. Such liquid phase management can be performed. This is the second method of liquid phase management. For example, assuming that the temperature of a chemical solution is selected as an arbitrary liquid phase parameter, the change amount due to the temperature of the chemical solution is Δf _TEMP , and the change amount due to other liquid phase parameters is Δf _R , Δf _L becomes Δf _L = Δf _TEMP + Δf _R ... [6] At this time, the temperature of the chemical solution is monitored using the temperature measuring means, and the change amount Δf _TEMP resulting from this is monitored.
Can be estimated, liquid phase management should be performed so as to focus on only Δf _R and keep it constant.

Of course, feedback control may also be performed on the temperature of the chemical solution to keep Δf _TEMP constant at all times. This is the third method of liquid phase management. Δf _R and Δf
_If both _TEMP and _TEMP are kept constant, Δf _L will be kept constant from the equation [6], which is apparently the same as the above-described first method of liquid phase management. However, 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 simpler than the first method.

Hereinafter, specific embodiments of the present invention will be described. First Embodiment Here, a configuration example of a liquid phase surface treatment apparatus of the present invention will be described with reference to FIG. 1 and FIG. As shown in FIG. 1, this apparatus includes a treatment tank 1 for filling a chemical solution L used for surface treatment of a workpiece W, a first crystal unit 2 immersed in the chemical solution, and a second crystal unit. A vibrator 3, a thermometer 4 for measuring the temperature of the chemical liquid L, and a liquid phase maintaining device 5 for maintaining a constant liquid phase parameter are provided. The first crystal unit 2, the second crystal unit 3, the thermometer 4, and the liquid phase maintaining device 5 are a first crystal unit controller 12, a second crystal unit controller 13, and a thermometer controller, respectively. It is connected to the arithmetic processing unit 6 via the controller 14 and the liquid phase maintenance device controller 15, respectively. In the arithmetic processing unit 6, feedback control of all liquid phase parameters necessary for liquid phase surface treatment is collectively performed.

FIGS. 2 (a) and 2 (b) show structural examples of the first crystal unit 2 and the second crystal unit 3, respectively.
Each of these two vibrators has an excitation electrode 22 and an inactive excitation electrode 32 deposited on both principal surfaces of AT-cut circular quartz plates 21 and 31 having a diameter of 20 mm and a thickness of 0.17 mm, respectively, in a circular pattern. It was formed. Lead wires 23 and 33 soldered out from the excitation electrode 22 and the inactive excitation electrode 32 are connected to the controllers 12 and 13 shown in FIG. Further, the first and second crystal units 2,
3 is covered with casings 24 and 34 and sealed with resin, so that the excitation electrode 22 and the inactive excitation electrode 32 on this side do not come into contact with the chemical liquid L.

The surface not covered by the casing 24 is the mass change detecting surface 21 in the first crystal unit 2.
a, the reference surface 31a in the second crystal resonator 3, which is in direct contact with the chemical liquid L and is affected by various liquid phase parameters. First, the above-described mass change detection surface 21a is a surface on which the same processing as the surface processing performed on the workpiece W in the chemical liquid L is performed. If this surface treatment is, for example, plating or water-repellent treatment, a plating film or a water-repellent material film adheres to this surface to cause an increase in mass, and the frequency of the first crystal unit 2 changes accordingly. I do. This 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 reference surface 31a is a surface which is in contact with the chemical solution L but is inactive for surface treatment using the same. Ideally, the reference surface 31a is inactivated in some form over the entire surface of the reference surface. However, only the excitation electrode that closes most of the area of the reference surface 31a is inactivated. However, it is sufficient depending on the content of the surface treatment. FIG. 2B illustrates the inactive excitation electrode 32. 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 forcible potential operation. Will be described sequentially from the second embodiment. In any case, since the plating film or the water-repellent material film does not adhere to the reference surface 31a, a change in frequency due to a change in mass does not occur. However, it is affected by liquid phase parameters such as temperature, viscosity, pH, electric conductivity and the like, which are derived from the immersion itself in the chemical solution L, and a frequency change is caused by these. This change in the frequency 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 effect of the liquid phase parameter on the second crystal unit 3 is actually equally applied to the mass change detection surface 21a of the first crystal unit 2. Therefore, the frequency change generated in the second crystal resonator 3 is considered to be a background value in this surface treatment, and the difference between this value and the frequency change generated in the first crystal resonator 2 is obtained. In addition, it is possible to know a frequency change purely due to only a mass change. The above-described arithmetic processing unit 6 stores in advance the relationship between the frequency change of the first crystal resonator 2 and the mass change, the relationship between the mass change and the result of the surface treatment (eg, film thickness), and other necessary control information. It is stored so that the corresponding change in mass or film thickness can be known based on the difference between the frequencies.

The thermometer 4 is a temperature measuring means for measuring the temperature of the liquid medicine L. The information on the temperature 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 above-described 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 maintaining the temperature of the chemical solution L constant, or a concentration of the chemical solution L,
Solvent and / or to maintain constant pH and electrical conductivity
Alternatively, a member such as a pipe or a nozzle of a chemical solution supply system for adding a solute is incorporated. What directly controls the liquid phase maintenance device 5 is a liquid phase maintenance device controller 15. 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 operations such as turning on / off a switch of a heating / cooling unit and opening / closing a valve of a chemical liquid replenishing device.

For example, a procedure for performing feedback control of the temperature of the chemical solution in the apparatus shown in FIG. 1 is as follows. That is, first, based on the measurement result by the thermometer 4, the arithmetic processing device 6 raises the required
A temperature decrease width is determined, a control signal for determining an energizing time to the heating / cooling device or a refrigerant supply amount required for the liquid temperature adjustment is generated and transferred to the liquid phase maintaining device controller 15, and the liquid is controlled based on the signal. When the phase maintaining device controller 15 actually controls the switches and valves, the liquid phase maintaining device 5 maintains the liquid phase parameters. According to such an apparatus, since the temperature of the chemical liquid L is always kept constant, for example, the fluctuation in the frequency of the crystal resonator caused by the rise of the chemical liquid temperature accompanying the progress of plating is caused by other liquid phase parameters. It can be excluded from frequency fluctuation.

Alternatively, the arithmetic processing unit 6 can perform the feedback control of the liquid phase parameter based on the frequency of the second crystal resonator 3. That is, in order to always transfer the data of the frequency of the second crystal resonator 3 to the arithmetic processing unit 6 and to return the frequency to the reference value when the observed frequency deviates from the reference frequency. The required change amount of the liquid phase parameter is determined by the arithmetic processing unit 6, and the liquid phase maintaining device controller 1
The liquid phase parameters are changed by 5 and the liquid phase maintaining device 5.

Regardless of which method is used, according to the apparatus of the present invention, the state of progress of the surface treatment in real time is determined from the change in the frequency of the first quartz oscillator 2 while the first quartz oscillator 2 is immersed in the chemical solution L. You can know. In addition, by subtracting the frequency change caused by the liquid phase parameter indicated by the second crystal unit 3 for reference, the vibration caused by the mass change is selected from the frequency change indicated by the first crystal unit 2. Only the number changes can be easily separated, and the quality of the surface treatment can be improved and precise monitoring can be performed.

Second Embodiment Here, the excitation electrode is made inactive to the surface treatment due to the intrinsic characteristics of the metal material constituting the excitation electrode.
A description will now be given of the second crystal resonator 3 in which the reference surface is substantially inactivated. A schematic cross-sectional view of the second crystal resonator 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 electroless plating to proceed, it is necessary for the reversible potential of the metal electrode to be more noble than the redox potential of the reducing agent in terms of equilibrium theory. It is heavily dominated. It is known that the oxidation reaction rate greatly depends on the type of electrode metal. For example, “Metal Surface Technology”, Vol. 34, No. 12, p. 594-599 (1983), describes the anodic oxidation of hypophosphorous acid, which is widely used as a reducing agent in electroless plating baths of nickel and cobalt. Is evaluated from its oxidation onset potential, the catalytic activity of the electrode metal is Au>Ni>Pd>Co>Pt>Cu> A in order from higher to lower.
g.

Therefore, when hypophosphorous acid is used as a reducing agent for electroless plating, if the inert excitation electrode 32 is formed using Ag or a metal having a lower catalytic activity than Ag, the surface of The deposition of the plating film can be suppressed, and the second crystal resonator 3 does not change its mass. That is, the second crystal resonator 3 is in an inactive state with respect to the electroless plating, and shows only a frequency change caused by immersion in the chemical solution. When a reducing agent other than hypophosphorous acid is used, the excitation electrode may be formed using a metal having as low a catalytic activity as possible according to the magnitude 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. One of the water repellents,
There is a chlorosilane-based coupling agent that provides an excellent water repellent effect due to the water repellency of a fluoroalkyl group. This compound adheres to the surface of the object by forming a siloxane bond with an —OH group (hydroxyl group) present on the surface of the object. Therefore, in order to prevent the water-repellent treatment agent from adhering to the excitation electrode, it suffices that no -OH group exists on the surface. However, a normal metal whose surface is covered with a natural oxide film always has an -OH group because dangling bonds of oxygen atoms of the oxide film are terminated with H atoms. . In contrast, Pt,
If the excitation electrode is formed by using a noble metal such as Au which is not easily oxidized, the surface of the excitation electrode has almost no -OH group. Can be.

Third Embodiment Here, a description will be given of an example of the configuration of a second quartz-crystal vibrator in which a reference surface 31a is inactivated by forming a self-aligned inert protective film on an excitation electrode. FIG. 3 shows a schematic cross-sectional view of this electrode. The excitation electrode 35 and the inert protective film 36 formed on the surface thereof in a self-aligned manner function as an inert excitation electrode 37.

For example, electroless plating as a surface treatment,
Assuming either electroplating or anodic oxidation, a requirement common to these surface treatments is that at least the surface of the object to be processed 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, nitride, or 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 can be used. By performing an oxidation treatment, a nitridation treatment, or an oxynitridation treatment using an annealing furnace or a plasma apparatus, the surface layer can be changed to a thin insulating film.

Alternatively, the excitation electrode can be formed using a metal material that is passivated by a surface treatment. For example, it is known that in an anodizing treatment in which Ti is connected to an anode, once the surface of titanium is coated with a thin insulating titanium oxide film, the oxidation does not proceed further. Therefore, in the present invention, the inactive protective film 36 made of titanium oxide is formed by previously performing anodizing treatment on the second crystal resonator made of Ti for the excitation electrode 35.
Is formed, and the surface of the excitation electrode 35 is passivated.
By doing so, even when the anodic oxidation process is actually performed on the target object W, the reference surface 31a becomes inactive to the process.

The thickness of the inert protective film 36 is
While a sufficient surface inactivation effect can be obtained,
It is important to make a selection so as not to impair the original vibration characteristics of the crystal unit. The upper limit of the film thickness is preferably about 1/1000 or less of the thickness of the quartz plate 31 and １ ／ or less of the thickness of the excitation electrode 35. If the film thickness is larger than this, there is a large possibility that the detection of the background value reflecting the liquid phase parameter will be hindered. In particular, when anodizing is assumed as a surface treatment, in view of the fact that this anodizing is generally performed in a strongly acidic chemical such as a sulfuric acid bath, an inert protective material having acid resistance as well as insulating properties. Preferably, a film 36 is formed.

Fourth Embodiment The above-mentioned inert protective film is formed not only on the surface of the excitation electrode in a self-aligned manner but also on the entire surface of the reference surface as shown in FIG. May be. For example, when a 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, or CVD, and this is used as an inert protective film 38, electroless plating, A second crystal unit suitable for monitoring electroplating and anodic oxidation can be configured.

Further, by performing a water-repellent treatment on the entire surface of the reference surface, it is possible to prevent contact between the chemical liquid L and the reference surface 31a. For example, the second crystal unit 3 is replaced with a chlorosilane coupling agent CF ₃ (CF ₂ ) ₇ (CH ₂ )
_By immersing in ₂ SiCl ₃ to form a water-repellent film and using it as an inert protective film 38, the reference surface 31 a for the chemical solution L
Extremely decreases the wettability. Thereby, the reference surface 31
a can be made substantially inert to surface treatments such as electroless plating, electroplating, and water repellent treatment. The regulation on the thickness of the insulating film and the water-repellent film described in the present embodiment also
It conforms to the rules described in the third embodiment.

Unlike the configuration in which the inert protective film 36 is formed on the entire surface of the reference surface by modifying the surface of the excitation electrode 35 itself, the type of the excitation electrode 35 is different. There is a merit of not choosing. Therefore, for example, it is possible to purchase a commercially available quartz resonator on which excitation electrodes are deposited in advance and apply the inert protective film 38 on the surface of the quartz resonator, thereby increasing the degree of freedom in device design.

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

In the electroless plating, when the object W is immersed in a plating bath, the potential of the object W is set so that the current caused by the oxidation reaction of the reducing agent and the absolute value of the current caused by the reduction reaction of the metal become equal. The potential is set spontaneously, that is, the immersion potential, and the metal is deposited on the surface of the workpiece W without a current flowing. The immersion potential varies depending on the concentration of the reducing agent and the pH of the plating bath, but is approximately -0.5 to -0.7 V in the case of Ni plating. In the present embodiment, the potential of the excitation electrode 35 is set to be more noble than the immersion potential using the counter electrode 39, so that the deposition rate of the plating film on the excitation electrode 35 can be significantly reduced. . In particular, by setting more noble than the reversible potential,
The deposition rate of the plating film becomes so small as to be negligible, and the reference surface 31a is practically inactivated. The reversible potential of the electroless Ni plating is about -0.257V.

It is to be noted that the excitation electrode 35 is more noble than the immersion potential,
More preferably, when setting the potential higher than the reversible potential, attention must be paid to the generation of oxygen. If the potential of the excitation electrode 35 is more noble than the oxygen minimum overvoltage, electrolysis of water occurs on the electrode surface to generate oxygen, and the bubbles change the interface state between the reference surface and the liquid phase. Therefore, although the plating film does not deposit, noise is superimposed on the detected frequency, and precise monitoring becomes 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 type 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 preferable. In order to set the potential of the excitation electrode 35, a change in the frequency of the second quartz-crystal vibrator 3 is measured while gradually changing the potential from the immersion potential to a noble direction by a preliminary experiment, and the frequency due to the generation of bubbles is measured. It is preferable to confirm a potential region where the fluctuation of the potential does not become apparent. As long as the excitation electrode 35 is used within this potential region, the excitation electrode 35 is in a state inactivated with respect to electroless plating. Note that metals other than Ni, for example, Cu
The concept is the same for electroless plating of Co and Co.

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 apparatus configuration shown in FIG. 1, the first crystal unit and the second crystal unit are not entirely immersed in the chemical solution, but only the mass change detection surface and the reference surface are respectively brought into contact with the chemical solution. You may take a different setting style. Other details of the device configuration, electrode materials used,
For the types of surface treatments and their combinations,
It can be changed or selected as appropriate.

[0043]

As is clear from the above description, according to the present invention, the measurement of the mass change in the liquid phase surface treatment can be performed with good accuracy, reproducibility, and controllability. Processing quality and productivity can be significantly improved.

[Brief description of the drawings]

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

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

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

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

FIG. 5 is a schematic cross-sectional view showing a configuration example of a second quartz-crystal vibrator inactivated by forcible potential operation using a counter electrode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Processing tank 2 1st crystal oscillator 3 2nd crystal oscillator 4 Thermometer 5 Liquid phase maintenance device 6 Operation processing device 12 1st crystal oscillator controller 13 2nd crystal oscillator controller 14 Thermometer controller 15 Liquid phase maintenance device controller 21, 31 Quartz plate 21a Mass change detecting surface 22, 35 Exciting electrode 23, 33 Lead wire 24, 34 Casing 31a Reference surface 32, 37 Inactive exciting electrode 36, 38 Inactive protective film 39 Counter electrode L Chemical solution W Object

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G01N 5/02 G01N 5/02 A (72) Inventor Katsuyuki Okubo 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Yuji Miura 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd.

Claims (21)

[Claims] 1. A treatment tank filled with a chemical solution 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 for the object at the time of immersion in the chemical solution. 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 that is inactive with respect to surface treatment with the chemical solution; A first crystal unit and a second crystal unit
Frequency measurement means for measuring the change in frequency with the crystal resonator of, respectively, calculation processing means for determining the progress of the surface treatment on the object to be processed based on the measurement results of the frequency measurement means, A liquid phase surface treatment device comprising: 2. The liquid-phase surface treatment apparatus according to claim 1, wherein the first crystal unit and the second crystal unit have the same fundamental frequency in an initial state before performing the surface treatment. . 3. The liquid phase surface treatment apparatus according to claim 2, wherein the mass change detection surface and the reference surface have equal areas. 4. The liquid phase according to claim 1, further comprising control means for performing a feedback control of a liquid phase parameter based on a calculation result of said calculation processing means so as to keep a frequency of said second crystal resonator always constant. Surface treatment equipment. 5. The liquid phase surface treatment apparatus according to claim 4, further comprising a temperature measuring means for measuring a temperature of said chemical solution. 6. The liquid phase surface according to claim 1, wherein the excitation electrode exposed on the reference surface is formed using a metal having low catalytic activity for an oxidation reaction of a reducing agent contained in a chemical solution for electroless plating. Processing equipment. 7. An insulating film is formed on at least the surface of the excitation electrode exposed in the reference surface.
The liquid phase surface treatment device according to the above. 8. The liquid-phase surface treatment apparatus according to claim 7, wherein the insulating film is formed of a metal compound film formed in a self-aligned manner by modifying the surface of the excitation electrode. 9. The liquid 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 film is formed on the entire surface of the reference surface. 11. The liquid-phase surface treatment apparatus according to claim 7, wherein the insulating film has acid resistance. 12. The water repellency is applied to at least the surface of the excitation electrode exposed in the reference surface.
The liquid phase surface treatment device according to the above. 13. The liquid-phase surface treatment apparatus according to claim 1, wherein the excitation electrode exposed on the reference surface is formed using a hard-to-oxidize metal. 14. The potential of the excitation electrode on the reference surface is set to a potential nobler than the immersion potential in a chemical solution for electroless plating by a potential operation between the excitation electrode and the counter electrode disposed in the vicinity thereof. The liquid-phase surface treatment apparatus 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 the surface treatment performed on the object to be processed is performed. First with mass change measurement surface
And a second quartz oscillator having a reference surface inactivated with respect to the surface treatment are immersed in a chemical solution used for liquid phase surface treatment together with the object to be treated, and And 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 a frequency of the second crystal unit. 17. The fundamental frequency of the first crystal unit and the second crystal unit in an initial state before performing the surface treatment are set to be equal to each other, and both are set in accordance with the progress of the surface treatment. 17. The method for measuring a mass change 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 mass change measuring method according to claim 16, wherein the feedback control of the liquid phase parameter is performed so that the frequency of the second crystal resonator is always kept constant. 19. A liquid phase parameter that changes with the progress of the surface treatment is selected, and a change caused by the selected liquid phase parameter is determined from a change in the frequency of the second crystal resonator. 17. The mass change measuring method according to claim 16, wherein feedback control is performed on the remaining liquid phase parameter so as to keep the remaining value obtained by subtracting the remaining value constant. 20. The apparatus according to claim 19, wherein the feedback control is performed on the selected liquid phase parameter such that a change amount of the frequency of the second crystal resonator caused by the selected liquid phase parameter is kept constant. Measurement method of mass change 21. The method according to claim 19, wherein the selected liquid phase parameter is a temperature of a chemical solution.