JPH10163177A - Equipment and method for substrate plasma cleaning - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma cleaning equipment of a substrate and a plasma cleaning method wherein the load of a vacuum pump which vacuum-sucks the inside of a chamber in which a substrate is accommodated for plasma cleaning is reduced, and generation of oil mist can be restrained. SOLUTION: A pipe 12 is connected with a chamber 5, a vacuum pump P, a tank 16 and a first branch pipe 14 for introducing the outside air are connected with a pipe 12, and a first valve V1, a second valve V2, a third valve V3 and a fourth valve V4 are arranged. After the tank 16 is vacuum- sucked with the vacuum pump P, and pressure in the tank 16 is reduced, the tank 16 is continuously connected with the chamber 5, chamber pressure of the chamber 5 is reduced to the approximate target value at a stretch. After that, the chamber 5 is vacuum-sucked with the vacuum pump, P chamber pressure is reduced to a target value, and plasma cleaning of a board 1 in the chamber 5 is performed. During the process, the vacuum pump P is continuously operated, vacuum-sucked the tank 16 and prepared for the next work.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma cleaning apparatus and a plasma cleaning method for cleaning a substrate on which electronic components are mounted.

[0002]

2. Description of the Related Art Electrodes of circuit patterns on boards such as printed boards and lead frames on which electronic components are mounted are easily stained. When the electrodes of the circuit pattern become dirty, the electrical connectivity of the electronic component becomes poor. Therefore, the substrate is cleaned prior to performing an electronic component mounting operation such as wire bonding or outer lead bonding.

As a substrate cleaning apparatus, a plasma cleaning apparatus is known (for example, Japanese Patent Application Laid-Open No. Hei 3-1).
No. 59143). Plasma cleaning equipment for substrates
After the substrate is housed in the chamber and the inside of the chamber is evacuated with a vacuum pump, a high voltage is applied to the electrodes to generate plasma in the chamber, and plasma molecules and plasma ions collide with the surface of the substrate to produce a plasma. This is for cleaning the surface.

[0004]

The plasma cleaning apparatus opens and closes the chamber, stores the substrate in the chamber, evacuates the inside of the chamber by a vacuum pump, generates plasma, and completes the cleaning. The chamber is returned to normal pressure (atmospheric pressure) and the substrate is taken out of the chamber. Therefore, conventionally, when the substrate is stored in the chamber, the vacuum pump is turned on to perform vacuum suction in the chamber, and when the substrate is taken out of the chamber after cleaning is completed, the vacuum pump is turned off, and the pressure in the chamber is reduced to normal pressure. Had been returned to.

[0005] As described above, in the conventional plasma cleaning apparatus, the on / off of the vacuum pump is frequently switched every time the substrate is cleaned. The load on the vacuum pump is greatest during the process of reducing the pressure in the chamber from a normal pressure to a target vacuum pressure. As a result, an excessive load is applied to the vacuum pump, and a large amount of oil mist is generated from the vacuum pump, and the oil evaporates and is lost, so that the oil consumption becomes extremely large, and environmental pollution is promoted due to the oil mist. There was a point.

[0006] Further, every time the substrate is cleaned, it is necessary to perform vacuum suction from the normal pressure state to a target vacuum pressure inside the chamber, so that a considerable time is required for vacuum suction, and this vacuum suction time is lost time. As a result, there is a problem that work efficiency does not increase.

Accordingly, the present invention reduces the load on the vacuum pump and suppresses the generation of oil mist, and significantly reduces the time required to vacuum-evacuate the interior of the chamber to a target vacuum pressure. It is an object to provide a cleaning device and a plasma cleaning method.

[0008]

According to the first aspect of the present invention, there is provided an openable / closable chamber for accommodating a substrate, gas supply means for supplying a plasma generating gas to the chamber, and plasma generation in the chamber. A voltage application means, a vacuum suction means for vacuum suctioning the inside of the chamber, and an outside air introduction unit for returning the inside of the chamber from a vacuum state to normal pressure, wherein the vacuum suction means is freely communicateable with the chamber; ,
The chamber and a vacuum pump for vacuum-sucking the tank were provided, and the vacuum pump was capable of selectively vacuum-suctioning the chamber and the tank.

The invention according to claim 2 includes a step of reducing the tank pressure by vacuum suctioning the inside of the tank with a vacuum pump, a step of preliminarily reducing the chamber pressure by communicating the tank with the chamber, Depressurizing the chamber pressure to a target value by vacuum suction, generating plasma in the chamber to clean the surface of the substrate housed in the chamber, and returning the chamber to normal pressure to return the substrate to normal pressure. And a step of vacuum-sucking the inside of the tank with a vacuum pump while the substrate is being taken in and out.

[0010]

According to the first and second aspects of the present invention, when plasma is generated in the chamber to clean the substrate, the vacuum pump is continuously driven to vacuum-evacuate the tank. deep. After the cleaning is completed, the chamber is opened and the substrate is taken in and out.When the chamber is closed again and the cleaning of the next substrate is started, the tank and the chamber which have been suctioned by the vacuum pump and in a reduced pressure state until then are removed. By communicating,
The inside of the chamber is preliminarily depressurized from normal pressure, and thereafter, the pressure is quickly depressurized to a target value by a vacuum pump, so that cleaning of the substrate can be restarted.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a plasma cleaning apparatus for a substrate according to an embodiment of the present invention, and FIG. 2 is a timing chart of the same operation. In FIG. 1, reference numeral 1 denotes a substrate, which is transported rightward on a transport path 2. The transport path 2 is provided with an electrode 3. An AC power supply 4 as a voltage applying means is connected to the electrode 3, and a high voltage is applied.

A chamber 5 is provided on the electrode 3 so as to be openable and closable. The upper surface of the chamber 5 is the rod 7 of the cylinder 6
Is joined to. When the rod 7 of the cylinder 6 protrudes and retracts, the chamber 5 moves up and down, and opens and closes the chamber 5. When the chamber 5 is raised and the chamber 5 is opened (refer to the chamber 5 indicated by a chain line), the substrate 1 is set on the electrode 3 in the chamber 5, and the substrate 1 after the plasma cleaning is removed from the chamber 5. It is taken out to the right.

The inside of the chamber 5 is connected to gas supply means 11 through a tube 10. Gas supply means 1
1 supplies a plasma generating gas such as an argon gas into the chamber 5.

A pipe 12 is connected to the chamber 5. A rotary vacuum pump P as a vacuum suction means is connected to the pipe 12. A first branch pipe 14 and a second branch pipe 15 are connected in the middle of the pipe 12.
The first branch pipe 14 serves as an outside air introduction unit communicating with outside air. Further, a tank 16 is connected to the second branch pipe 15. The second branch pipe 15 is provided with a first valve V1. The pipe 12 between the first branch pipe 14 and the second branch pipe 15
Is provided with a second valve V2. Pipe 12
Is provided with a third valve V3 for opening and closing the vacuum pump P, and a first branch pipe 14 is provided with a fourth valve V4. As will be described later, the first valve V1 to the fourth valve V4 are individually turned on and off to change the pressure state in the chamber 5.

The apparatus for cleaning a plasma of a substrate has the above-described configuration. Next, a plasma cleaning method will be described with reference to a timing chart of FIG. In FIG. 2, PT is the tank pressure in the tank 16, and PC is the chamber pressure in the chamber 5.

At first, the first valve V1 to the fourth valve V4
Are all closed. At the timing t1, the first valve V1 and the third valve V3 are opened, the vacuum pump P is connected to the tank 16, and the vacuum pump P is turned on (hereinafter, the vacuum pump P keeps on). Then, the tank pressure PT of the tank 16 is gradually reduced. Meanwhile, chamber 5
Is opened and closed to store the substrate 1 in the chamber 5. When the tank pressure PT is reduced to a predetermined value, the third valve V3 is closed (timing t2), and immediately thereafter, the second valve V2 is opened (timing t3). Then, the chamber 5 communicates with the depressurized tank 16, and the chamber pressure PC is preliminarily depressurized from normal pressure (timing t4). The capacity of the tank 16 is much larger than the capacity of the chamber 5 so that the chamber 5 can be preliminarily depressurized from normal pressure by connecting the chamber 16 and the chamber 5.

Next, the first valve V1 is closed and the third valve V3 is closed.
(Timing t5), the vacuum pump 13
And the tank 16 are shut off, and the vacuum pump P evacuates only the chamber 5 to reduce the chamber pressure PC to the target value (timing t6). During that time, a gas for plasma generation is supplied from the gas supply unit 11 into the chamber 5. When the chamber pressure PC decreases to the target value, a high voltage is applied to the electrode 3. Then, plasma molecules and plasma ions are generated in the chamber 5 and collide with the surface of the substrate 1 to etch and clean the electrodes of the circuit pattern.

When the plasma cleaning is completed (timing t7), the application of the voltage to the electrode 3 is stopped, the second valve 2 is closed, and the vacuum suction in the chamber 5 is stopped. Next, immediately after that, the first valve V1 and the fourth valve V4 are opened (timing t8), outside air is introduced into the chamber 5 through the first branch pipe 14, and the chamber pressure PC is returned to normal pressure. Vacuum suction of the tank 16 is performed. During that time, if the chamber pressure PC returns to the normal pressure (timing t9), the chamber 5 is opened and closed,
The substrate 1 after the plasma cleaning is carried out of the chamber 5 and the next substrate 1 is carried into the chamber 5. When the substrate 1 is set on the electrode 3, the above operation is repeated.

As shown in the timing chart of FIG.
If the vacuum pump P is turned on at the timing t1,
Thereafter, since the on state is basically continued, the on / off operation is not frequently repeated as in the related art, and therefore, no excessive load is applied to the vacuum pump P to generate oil mist. In addition, during the preparatory period between timings t1 and t2, the tank 16 having a larger capacity than the chamber 5 is preliminarily depressurized, so that the chamber pressure PC can be preliminarily depressurized from normal pressure in a short time between timings t3 and t4. Since the chamber pressure PC can be reduced to the target value in a short time from the timing t5 to t6, the time for reducing the chamber pressure PC to the target value can be greatly reduced, and the work efficiency can be improved accordingly.

[0020]

As described above, according to the present invention, the vacuum pump does not need to be repeatedly turned on and off frequently, so that no excessive load is applied to the vacuum pump and the generation of oil mist is suppressed. As a result, wasteful consumption of oil and environmental pollution can be eliminated. In addition, since the chamber pressure of the chamber can be reduced to the target vacuum pressure in a short time, the tact time can be greatly reduced, and the working efficiency can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a plasma cleaning apparatus for a substrate according to an embodiment of the present invention.

FIG. 2 is a timing chart of the operation of the substrate plasma cleaning apparatus according to one embodiment of the present invention;

[Description of Signs] 1 Substrate 3 Electrode 4 AC power supply 5 Chamber 11 Gas supply means 12 Pipe 16 Tank P Vacuum pump V1 First valve V2 Second valve V3 Third valve V4 Fourth valve

Claims (2)

[Claims] An openable and closable chamber for accommodating a substrate,
Gas supply means for supplying a plasma generating gas to the chamber, voltage applying means for generating plasma in the chamber, vacuum suction means for vacuum suction in the chamber, and return of the chamber from vacuum to normal pressure The vacuum suction means comprises a tank communicable with the chamber, a vacuum pump for vacuum suctioning the chamber and the tank, and the vacuum pump selects the chamber and the tank. A plasma cleaning apparatus for a substrate, characterized in that the substrate can be vacuum-suctioned freely. 2. A step of reducing the tank pressure by vacuum-suctioning the inside of the tank with a vacuum pump, a step of preliminarily reducing the chamber pressure by communicating the tank with the chamber, and a step of vacuum-suctioning the inside of the chamber by a vacuum pump. Reducing the chamber pressure to a target value, generating plasma in the chamber to perform plasma cleaning of the surface of the substrate housed in the chamber, and returning the chamber to normal pressure and loading and unloading the substrate. And a step of vacuum-sucking the inside of the tank with a vacuum pump while taking the substrate in and out,
A plasma cleaning method for a substrate, comprising: