JP2000226671A - Electroless plating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroless plating device which is capable of reducing incomplete plating or irregular plating, small in degradation of a plating solution and change in concentration of the composition of the plating solution, capable of keeping the plating temperature at a specified temperature, stable in plating quality, and capable of avoiding the increase in the cost in disposing the solution and the excessive burden on the environment. SOLUTION: In an electroless plating device to form a metallic plating film on a surface to be plated by bringing the electroless plating solution in contact with a surface of a substrate to be plated, the surface of the substrate 1 to be plated is faced upward, a space in which the surfaces to be plated are opposite to each other and sealed is formed in a plating cell 22, the electroless plating solution is fed into the sealed space from an initial make-up tank through a plating solution feed valve 9, and the plating is achieved by feeding the pressure pulsation to the sealed space from a pressure pulsation generation part 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroless plating apparatus for performing electroless metal plating such as copper plating on a substrate to be plated such as a semiconductor wafer.

[0002]

2. Description of the Related Art In recent years, wiring layers and the like of substrates such as semiconductor substrates have been formed by electroless copper plating. In this electroless copper plating, hydrogen gas is generated, and the hydrogen gas causes an inconvenience in plating. For example, the deposition reaction of electroless copper plating using formalin (HCHO) as a reducing agent is as follows: Cu ²⁺ + 2HCHO + 4OH ⁻ → Cu ²⁺ + 2HCOO ⁻ +
H ₂ + 2H ₂ O + 2e ⁻ → Cu + 2HCOO + H ₂ + 2H ₂
O _{2 and} hydrogen gas (H ₂ ) is always generated.

For this reason, as shown in FIG. 1, when plating is performed on a substrate 101 having fine grooves or holes 102 formed on its surface, as shown in FIG.
When plating is performed with the plating surface 01a facing down or the plating surface 101a raised as shown in FIG. 1B, hydrogen gas (H ₂ ) bubbles 103 generated in the plating solution Q in the fine grooves and holes 102 are generated. It is not possible to escape and the plating chip 104 is generated.

Further, due to the characteristics of electroless plating, generation of hydrogen gas cannot be avoided as described above. In conventional electroless copper plating, plating is performed while stirring a plating solution with a pump or air. Therefore, the hydrogen gas bubbles 103 generated on the plating surface move on the plating surface by this stirring. Since the portion where the hydrogen gas bubbles 103 stay on the plating surface is not plated, as shown in FIG. 2, the plating surface 101a of the substrate 101 to be plated is moved in the direction in which the hydrogen gas bubbles 103 move (the direction of the arrow 106). There is a problem that plating unevenness 105 occurs.

Also, hydrogen gas bubbles 1 on the plating surface 101a
Conventionally, in order to remove 03, the substrate to be plated is hung between the plating jigs in a sandwiched manner, and an external impact is applied to the jig to release bubbles from the plating surface 101a. However, this method is not a preferable method for plating the substrate 101 to be plated because it involves a risk of damaging the plating jig and the substrate to be plated.

In conventional electroless copper plating,
A plating tank and a plating solution circulation tank were provided, and plating was performed by circulating the plating solution. Further, the bath for plating solution is provided with a bathtub dedicated to bathing, and bathing is performed in this bathtub or in a circulation bath. For this reason, immediately after the bathing, inconvenient reactions peculiar to electroless copper plating (Cannizzuro reaction,
Disproportionation reaction) occurs in the electroless plating solution, and there are problems such as deterioration of the plating solution and change in the concentration of the plating solution composition.

As shown in FIG. 3, the conventional electroless copper plating apparatus includes a pretreatment tank 111, a washing tank 112, a plating tank 113, a washing tank 114, and a drying tank 115, and is held between jigs 120. Alternatively, the suspended plating target substrate 101 is sequentially immersed in each tank to perform plating.
For this reason, the installation area of the apparatus becomes large. In particular, when the apparatus is installed in a clean room of a semiconductor manufacturing facility, floor load, installation area, and the like become problems. In FIG. 3, reference numeral 117 denotes a pump for circulating the pretreatment liquid in the pretreatment tank 111, and 118 denotes a pump.
Is a pump for circulating the plating solution through the plating tank 113;
9 is a blower for sending dry air to the drying tank 115.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to eliminate the above-mentioned conventional problems, to reduce chipping and uneven plating, to reduce plating solution deterioration and plating solution. An object of the present invention is to provide an electroless plating apparatus capable of performing stable plating with a small change in the composition concentration.

Further, even if the plating solution that has been plated is treated as a waste solution in order to perform plating of extremely stable quality, it is possible to avoid an increase in cost due to the waste solution and an excessive burden on the environment. It is an object of the present invention to provide an electroless plating apparatus that is suitable for being installed in a plating apparatus and that can maintain a plating temperature at a predetermined constant temperature.

[0010]

According to a first aspect of the present invention, an electroless plating solution is brought into contact with a plating surface of a substrate to be plated to form a metal plating film on the plating surface. A closed space forming means for forming a closed space in which the plating surface of the substrate to be plated faces upward, and the plating surface faces and is sealed, and an electroless plating solution is provided in the closed space. A plating solution supply means for supplying an electroless plating solution to the enclosed space to perform electroless plating.

As described above, when the plating surface of the substrate to be plated is directed upward, hydrogen gas bubbles generated in the plating solution in electroless plating always move upward due to buoyancy. The number and amount of hydrogen gas bubbles remaining in the surface, the fine grooves and the holes are reduced, and the chipping of the plating can be reduced.

The invention described in claim 2 is the first invention.
In the electroless plating apparatus described in the above, the minimum amount of electroless plating solution necessary to apply a predetermined plating to the substrate to be plated in the closed space is supplied, and the electroless plating solution can be electrolessly plated in a stationary state. It is characterized by having such a configuration.

As described above, by supplying a minimum necessary amount of the electroless plating solution to the closed space and plating in a stationary state, hydrogen gas bubbles do not move on the plating surface. Plating unevenness occurring on the plating surface can be minimized.

[0014] The invention according to claim 3 provides the invention according to claim 1.
Alternatively, in the electroless plating apparatus described in 2, the pressure in the closed space is higher than the atmospheric pressure, and pressure pulsation means for pulsating the pressure is provided.

As described above, the pressure in the closed space to which the electroless plating solution is supplied by the pressure pulsating means is made higher than the atmospheric pressure,
Since the pressure is pulsated, the dissolution of the hydrogen gas bubbles in the electroless plating solution is promoted by pressurization, and the release of the hydrogen gas bubbles can be promoted by pulsating the pressure. That is, as shown in FIG. 4A, the hydrogen gas bubbles 103 adhered to the plating surface 101a of the substrate 101 to be plated contract by pressurization as shown in FIG. 4B and separate from the plating surface 101a. FIG. 4
As shown in (c), it expands and completely separates from the plating surface 101a.

The invention described in claim 4 is the first invention.
In the electroless plating apparatus according to any one of Items 1 to 3, a building bath is provided in the vicinity of the closed space, and a minimum necessary amount of the electroless plating solution built in the closed space can be supplied immediately before performing the electroless plating. It is characterized by having such a configuration.

As described above, just before plating, bathing is performed in a building bath provided near the closed space (plating processing section), and a minimum necessary plating solution is supplied to the closed space immediately after building bath to perform plating. By doing so, inconvenient reactions (cannizzuro reaction, disproportionation reaction) peculiar to electroless copper plating immediately after building bath
Occurs, and the plating is completed before the deterioration of the plating solution and the change in the concentration of the plating solution composition occur, so that plating with extremely stable quality can be performed.

The invention described in claim 5 is the first invention.
In the electroless plating apparatus according to any one of (1) to (4), after plating with a minimum necessary amount of the electroless plating solution, the electroless plating solution is treated as a waste solution without being recycled. Features.

As described above, since the electroless plating solution after plating is treated as a waste solution without being circulated and reused, plating with extremely stable quality can be performed.
In addition, the amount of the electroless plating solution consumed for each film formation (film formation of a plating film) can be suppressed to a necessary minimum. Therefore, it is possible to avoid an increase in cost due to a waste solution and an excessive burden on the environment.

Further, in the electroless plating apparatus according to any one of claims 1 to 5, the substrate to be plated is held on a turntable, and after plating is finished, the substrate is washed with water while being held on the turntable. , So that drying can be performed.

As described above, the substrate to be plated is held on the turntable, and after plating, the substrate to be plated is washed and dried with the substrate held on the turntable. Therefore, plating, washing and drying are performed. It can be performed in one place, and the installation space of the apparatus can be reduced, and the apparatus is suitable for installation in a clean room.

Further, in the electroless plating apparatus according to any one of the first to fifth aspects, a water temperature tank for keeping heat is provided near an upper portion of the closed space, and a heater for keeping heat is provided below the substrate to be plated. Features.

As described above, by providing a water temperature tank for keeping heat above the closed space and a heater for keeping heat below the substrate to be plated, the quality of electroless plating (thickness uniformity, reproducibility, conductivity of plating film) can be improved. Etc.) can be kept constant, which is the most important factor affecting the plating temperature.

Further, in the electroless plating apparatus according to any one of claims 2 to 5, the minimum necessary amount of the electroless plating solution is a solute which is 1.5 to 20 times as large as a predetermined equivalent number of deposited metal. It is characterized in that it is within the range of the liquid amount contained as.

Further, in the electroless plating apparatus according to any one of claims 3 to 5, the pressure pulsation means has a function of causing pressure pulsation in a range of a pressure amplitude of 0 to 1 MPa and a frequency of 0 to 10 Hz. It is characterized by the following.

[0026]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 is a diagram showing a configuration example of the electroless plating apparatus according to the present invention. In FIG. 5, reference numeral 2 denotes a turntable for holding a substrate to be plated 1 such as a semiconductor substrate on an upper surface, and a heater 3 for keeping heat is provided inside the turntable 2. The turntable 2 is configured to be able to move up and down by a motor 16 via a ball screw 15 and to be rotatable by a motor 14 via a timing belt 13.

A plating cell 22 having an open lower surface is disposed above the turntable 2, and a plating target substrate 1 held by a housing 26 is provided on the outer periphery of the lower end of the plating cell 22.
The seal packing 21 is provided in close contact with the seal packing 21. That is, while the turntable 2 is raised and the surface of the substrate 1 to be plated is brought into close contact with the seal packing 21, the plating cell 2
2 is a closed space. As will be described in detail later, the closed space has a capacity for storing a minimum amount of a plating solution (electroless plating solution) necessary for performing predetermined plating on the substrate 1 to be plated.

A construction bath 4 is arranged near the upper portion of the plating cell 22, and a plating solution A, a plating solution B,
A plating solution C and pure water D are supplied,
Inside, a stirring blade 6a extending from the stirrer 6 is arranged, and a heater 11 is arranged. In addition, building tub 4
The plating solution in the plating cell 2 is passed through the plating solution supply valve 9.
2.

A hot water tank 5 is disposed near the outer periphery of the building bath 4, and a stirring blade 7 a extending from the stirrer 7 is disposed in the hot water tank 5, and a heater 12 is disposed therein. 10
Is a plating solution discharge valve for discharging the plating solution after plating in the plating cell 22, and the plating solution discharge valve 10
The plating solution discharged through the tank flows into the waste liquid tank 23. Reference numeral 8 denotes a pressure supply valve for supplying pressure into the plating cell 22.
The pressure in the plating cell 22 can be pulsated from the pressure pulsation generator 24 through the pulsation.

The pressure pulsation generator 24 includes a high-pressure pressure regulating valve 17, a low-pressure pressure regulating valve 18, a pressure switching switching valve 19, and a pneumatic pressure source 20.
Pressure pulsation can be performed in the range of 0 to 10 Hz in MPa and frequency. Note that P ₁ and P ₂ are pressure gauges, respectively.

In the electroless plating apparatus having the above configuration, when plating is performed, the substrate 1 to be plated is positioned and held on the upper surface of the turntable 2 located below the plating cell 22. In this state, the turntable 2 is raised by the motor 16 via the ball screw 15 and the substrate 1 to be plated is
Is brought into close contact with the seal packing 21,
The opening at the lower end of the plating cell 22 is closed to make the inside a closed space. In this state, the plating solution supply valve 9 is opened, and the
Is supplied into the plating cell 22.

The inside of the plating cell 22 has a volume capable of storing a minimum required amount of plating solution Q for applying predetermined plating to the substrate 1 to be plated. Is accommodated. Here, the minimum necessary amount of the electroless plating solution is 1.times.
The range of the amount of liquid containing 5 to 20 times as many ions as a solute is set. In plating, pressure pulsation is applied from the pressure pulsation generator 24 to the plating cell 22 at a predetermined pressure amplitude and a predetermined frequency via the pressure supply valve 8 as described above.

Since the substrate 1 to be plated is held on the upper surface of the turntable 2 with the plating surface facing upward, hydrogen gas bubbles generated in the plating solution Q in electroless plating move upward due to buoyancy. The number and amount of bubbles remaining in the plating surface, the fine grooves and the holes of the substrate 1 to be plated are reduced, and the chipping of the plating is reduced. In addition, by supplying the minimum necessary plating solution Q to the enclosed space in the plating cell 22 and performing plating in a stationary state, hydrogen gas bubbles do not move on the plating surface, so that plating unevenness generated on the plating surface is reduced. Can be kept to a minimum.

The pressure in the sealed space in the plating cell 22 is made higher than the atmospheric pressure by the pressure pulsation generator 24 to pulsate the pressure. Dissolution into the inside is promoted, and pulsation of the pressure can promote release of hydrogen gas bubbles from the plating surface (see FIG. 4).

Further, the bath 4 is placed near the upper side of the plating cell 22, and a minimum necessary amount of plating solution immediately after bathing in the bath 4 is applied to the plating cell 22 immediately before plating the substrate 1. Since the plating is carried out by supplying, the undesirable reactions (Canitzuro reaction, disproportionation reaction) peculiar to the electroless copper plating occur immediately after the bathing, and the plating is performed before the deterioration of the plating solution and the change in the concentration of the plating solution composition occur. Since the plating is completed, plating with extremely stable quality can be performed.

The plating solution Q in the plating cell 22 after plating is discharged through the plating solution discharge valve 10 into the waste liquid tank 2.
3 and is treated as a waste liquid, so that plating can be performed with extremely stable quality, and the amount of plating solution consumed for each film formation is minimized.
It is possible to avoid an increase in cost due to waste liquid and an excessive burden on the environment. Since the hot water tank 5 is provided above the plating cell 22 and the heater 3 is provided below the turntable 2, the quality of electroless plating (film thickness uniformity, reproducibility, plating film conductivity, etc.) is improved. The plating temperature, which is the most important factor, can be kept constant.

After the plating is completed, the plating solution discharge valve 10 is opened as described above, the plating solution in the plating cell 22 is discharged to the waste solution tank 23, and the turntable 2 is lowered by the motor 16 via the ball screw 15. Cleaning water (mainly pure water) is sprayed from the cleaning nozzle 25 shown in FIG. 6 onto the plating surface of the plated substrate 1 on which plating has been completed to clean the plating surface. In this cleaning, the cleaning is performed while oscillating the cleaning nozzle 25 and slowly rotating the substrate 1 to be plated via the timing belt 13 by the motor 14.

After the completion of the cleaning, the substrate 1 is rotated at a high speed, and the washing liquid attached to the substrate 1 is scattered by the centrifugal force and dried, that is, spin-dried.

In the above embodiment, the example in which the plating treatment and the drying treatment are performed by the electroless plating apparatus is described. However, a pretreatment liquid tank is provided in the vicinity of the plating cell, and the plating tank is placed in the plating cell 22 before the plating treatment. A pre-treatment liquid is supplied from the pre-treatment liquid tank, the pre-treatment is performed, then the pre-treatment is performed, and the plating, the cleaning, and the drying are performed. , Cleaning, plating, cleaning, and drying can be performed, and a small-sized apparatus with a small installation space can be provided, in which all of the processing can be performed by one apparatus.

In the above-described embodiment, an example in which electroless copper plating is performed has been described. However, the electroless plating apparatus according to the present invention is not limited to this, and is applicable to electroless plating of other metals. Available.

[0041]

As described above, according to the invention described in each claim, the following excellent effects can be obtained.

According to the first aspect of the present invention, since the plating surface of the substrate to be plated faces upward, the hydrogen gas bubbles generated in electroless plating always move upward by buoyancy. The number and amount of hydrogen gas bubbles remaining in the plating surface, the fine grooves and the holes are reduced, and the chipping of the plating can be reduced.

According to the second aspect of the present invention, the required minimum amount of the electroless plating solution is supplied to the closed space and plating is performed in a stationary state, so that hydrogen gas bubbles move on the plating surface. Without this, it is possible to minimize plating unevenness occurring on the plated surface.

According to the third aspect of the present invention, the pressure in the closed space to which the electroless plating solution is supplied by the pressure pulsating means is made higher than the atmospheric pressure and the pressure is pulsated, so that the hydrogen gas is pressurized and pressurized. Dissolution of the bubbles in the electroless plating solution is promoted, and pulsation of the pressure can promote release of the hydrogen gas bubbles.

According to the fourth aspect of the present invention, the bath solution is laid in a tub provided near the sealed space (plating section) immediately before plating, and the minimum necessary plating solution is applied immediately after the bathing. By supplying to the enclosed space and performing plating, the disadvantageous reactions (Cannizzuro reaction, disproportionation reaction) peculiar to electroless copper plating occur immediately after the bathing, causing deterioration of the plating solution and change in the concentration of the plating solution composition. Before plating finishes,
Extremely stable plating can be performed.

According to the fifth aspect of the present invention, the electroless plating solution after plating is treated as a waste solution without being circulated and reused, so that extremely stable plating can be performed. Since the amount of the electroless plating solution consumed for each film formation (forming of a plating film) is minimized, it is possible to avoid an increase in cost due to the waste solution and an excessive burden on the environment.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams for explaining the behavior of hydrogen gas bubbles during electroless plating. FIG. 1A shows a case where a plating surface of a substrate to be plated is arranged downward, and FIG. The case where the plating surface is arranged vertically is shown.

FIG. 2 is a view for explaining a state of plating unevenness generated on a plating surface of a substrate to be plated due to the behavior of hydrogen gas bubbles during electroless plating.

FIG. 3 is a diagram showing an outline of a conventional apparatus for performing pretreatment, cleaning processing, plating processing, cleaning processing, and drying processing.

FIG. 4 is a diagram for explaining the behavior of hydrogen gas bubbles when pressure pulsation is applied to a sealed space containing an electroless plating solution in the electroless plating apparatus according to the present invention.

FIG. 5 is a diagram showing a configuration example of an electroless plating apparatus according to the present invention.

FIG. 6 is a diagram showing a configuration example of an electroless plating apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate to be plated 2 Turntable 3 Heater 4 Building bath 5 Hot water tank 6 Stirrer 7 Stirrer 8 Pressure supply valve 9 Plating solution supply valve 10 Plating solution discharge valve 11 Heater 12 Heater 13 Timing belt 14 Motor 15 Ball screw 16 Motor 17 Pressure regulating valve 18 Pressure regulating valve 19 Switching valve 20 Pneumatic pressure source 21 Seal packing 22 Plating cell 23 Waste liquid tank 24 Pressure pulsation generator 25 Cleaning nozzle 26 Housing

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Mishima, Inventor Koji Mishima 11-1 Haneda Asahimachi, Ota-ku, Tokyo Ebara Corporation (72) Inventor Hiroaki Inoue 11-1, Haneda Asahimachi, Ota-ku, Tokyo Co., Ltd. Ebara Corporation (72) Inventor Shuichi Okuyama 11-1 Haneda Asahimachi, Ota-ku, Tokyo F-term in Ebara Corporation (reference) 4K022 AA42 BA08 DA01 DB14 DB15 DB20 DB24 DB30 EA02 4M104 BB04 DD53

Claims (5)

[Claims] 1. An electroless plating apparatus in which an electroless plating solution is brought into contact with a plating surface of a substrate to be plated and a metal plating film is formed on the plating surface, wherein the plating surface of the substrate to be plated faces upward. A closed space forming means for forming a closed space in which the plating surface faces and is sealed; and a plating solution supply means for supplying an electroless plating solution to the closed space, wherein the electroless plating solution is provided in the closed space. An electroless plating apparatus characterized in that an electroless plating is carried out by supplying an electroless plating. 2. The electroless plating apparatus according to claim 1, wherein a minimum amount of electroless plating solution necessary for applying a predetermined plating to the substrate to be plated is supplied to the closed space, and the electroless plating solution is supplied. An electroless plating apparatus characterized in that electroless plating can be performed in a stationary state. 3. The electroless plating apparatus according to claim 1, wherein the pressure in the closed space is higher than the atmospheric pressure, and pressure pulsation means for pulsating the pressure is provided. apparatus. 4. The electroless plating apparatus according to claim 1, wherein a building bath is provided near the enclosed space, and the bath is built in the enclosed space immediately before performing the electroless plating. An electroless plating apparatus characterized in that it can supply a minimum amount of electroless plating solution. 5. The electroless plating apparatus according to claim 1, wherein after plating with the minimum necessary electroless plating solution, the electroless plating solution is recycled without being recycled. An electroless plating apparatus characterized in that it is configured to be processed as.