JP2001284332A - Device and method for processing work by plasma - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for processing work by plasma capable of moving electrodes closer to each other, to increase an etching rate, when plasma- processing a work and of increasing a gap between the electrodes, when putting the work into or out of the gap between the electrodes after the plasma process is finished. SOLUTION: A vacuum chamber 1 has a top electrode 2 and a bottom electrode 3. The top electrode is moved in the vertical directions by a cylinder 7 to adjust the gap T between the top and bottom electrodes. A holding head 57 of a work 20 is put into or out of the vacuum chamber 1, through an opening 40 to place the work 20 on the bottom electrode 3 and to pick up and take out the work 20 from the vacuum chamber 1. When the work 20 is processed by a plasma, the gap T is reduced to increase the density of plasma to increase the etching rate. When the work 20 is put into or out of the vacuum chamber 1, the gap T is increased so as to facilitate placing the holding head 57 into or out of the vacuum chamber 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a work plasma processing apparatus for etching or cleaning the surface of a work.

[0002]

2. Description of the Related Art It is known to perform a plasma treatment for etching a wafer surface or cleaning a printed circuit board surface. The plasma processing apparatus accommodates a work such as a wafer or a printed circuit board between two electrode portions of a vacuum chamber, generates a plasma by applying a high-frequency voltage between the electrode portions, and generates ions and the like on the surface of the work. The plasma processing is performed by causing the gas to collide with the gas.

[0003]

In this type of plasma processing apparatus, in order to increase the etching rate (etching power), the distance between the electrode portions is reduced by bringing the electrode portions as close as possible to reduce the distance between the electrode portions. It is desirable to increase the plasma density of the substrate.

On the other hand, a workpiece, such as a wafer or a printed circuit board, which is an object of plasma processing, is held by a holding head and is taken in and out between electrode portions. Therefore, if the electrode portions are brought closer to each other to increase the etching rate and the distance between the electrode portions is reduced, it is difficult or impossible to put the work in and out of the holding head. Accordingly, it is an object of the present invention to provide a plasma processing apparatus for a workpiece that can increase the etching rate by bringing the electrode portions close to each other during plasma processing.

[0005]

According to the present invention, there is provided a plasma processing apparatus for a workpiece, comprising: a vacuum chamber to which a plasma generating gas is supplied; an upper electrode portion and a lower electrode provided in the vacuum chamber at intervals above and below; Part, a high-frequency power supply for applying a high-frequency voltage between the upper electrode part and the lower electrode part, an interval changing means for changing the size of the interval between the upper electrode part and the lower electrode part, And a work taking-in / out means having a work holding head for taking the work in and out between the electrode portions.

Further, the plasma processing method of the present invention is a step of supplying a workpiece onto the lower electrode when the distance between the lower electrode and the upper electrode is widened, and the distance between the lower electrode and the upper electrode is suitable for the plasma processing. The vacuum chamber, depressurizing the vacuum chamber, supplying plasma generating gas into the depressurized vacuum chamber, and applying a high-frequency voltage between the upper and lower electrodes. Generating the plasma, stopping the application of the high-frequency voltage and the supply of the plasma generating gas and returning the inside of the vacuum chamber to atmospheric pressure, and performing plasma generation from above the lower electrode in a state where the distance between the upper electrode and the lower electrode is widened. This includes a step of removing the processed work.

According to the present invention, the upper electrode portion and the lower electrode portion are brought closer to each other during the plasma processing to increase the etching rate. The work can be taken in and out by increasing the size.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a plasma processing apparatus according to an embodiment of the present invention, and FIGS. 2, 3, 4, 5, 6, and 7 are cross-sectional views of the plasma processing apparatus according to an embodiment of the present invention. FIG. 8 and FIG. 8 are pressure change diagrams in one embodiment of the present invention.

First, the overall configuration of the plasma processing apparatus will be described with reference to FIG. Inside the vacuum chamber 1, an upper electrode portion 2 and a lower electrode portion 3 as two electrode portions are disposed so as to face each other with a vertical interval T therebetween. The upper electrode part 2 is grounded to the ground part 4, and the vacuum chamber 1 is also grounded.

The upper electrode unit 2 is connected to the lower end of a vertical shaft 5 that penetrates the upper wall of the vacuum chamber 1 vertically. The upper end of the shaft 5 is connected to a rod 8 of a cylinder 7 via an arm 6. Therefore, when the rod 8 of the cylinder 7 protrudes and retracts, the shaft 5 and the upper electrode portion 2 move up and down, and the size of the interval T between the upper electrode portion 2 and the lower electrode portion 3 is changed. That is, the cylinder 7 serves as an interval changing unit that changes the size of the interval T by adjusting the relative height of the upper electrode unit 2 with respect to the lower electrode unit 3. Of course, in addition to the cylinder 7, a feed screw mechanism or the like can be applied as a means for moving the upper electrode unit 2 up and down. Further, in the present embodiment, by moving the upper electrode portion 2 up and down with respect to the lower electrode portion 3, the interval T
Has been changed, but the lower electrode 3
May be moved up and down. The vacuum chamber may also serve as the upper electrode portion. In this case, the interval T is changed by moving the lower electrode portion up and down.

In FIG. 1, a shaft 5 is a gas supply unit 1.
0 through a valve 11. The shaft 5 is a hollow pipe, and when the valve 11 is opened, a gas for plasma generation is supplied from the gas supply unit 10 to the upper electrode unit 2 through the hole 5a at the center of the shaft 5, and the gas is supplied to the upper electrode unit 2 Are blown out toward the lower electrode portion 3 from a plurality of gas blowout holes 9 formed on the lower surface of the substrate. The gas outlet 9
As a forming method, a porous member having an irregular number of gas blowing holes may be attached to the lower surface of the upper electrode portion 2 and gas may be blown from the porous member.

In FIG. 1, the lower electrode 3 is supported by a joint 12. The joint 12 is mounted on the lower wall of the vacuum chamber 1. A cooling device 13 circulates a coolant such as cold water through a pipe 14, 15 through a coolant passage (not shown) formed inside the lower electrode portion 3, and heats the lower electrode portion 3 during plasma processing and the lower electrode portion 3. Is cooled. Reference numeral 16 denotes a high-frequency power supply for applying a high-frequency high voltage between the upper electrode unit 2 and the lower electrode unit 3, and is connected to the lower electrode unit 3. The frequency of the high-frequency voltage applied to the lower electrode unit 3 is 13.56 MHz.
It is.

The work 20 is placed on the lower electrode section 3. A plurality of suction holes 17 are formed on the upper surface of the lower electrode portion 3, and are connected to a first vacuum pump 21 as first vacuum suction means via a suction path 23. By sucking the suction holes 17 with the first vacuum pump 21, the work 20 is vacuum-adsorbed and fixed on the lower electrode portion 3. 22
Is the suction path 2 between the first vacuum pump 21 and the lower electrode unit 3
3, which opens and closes the suction passage 23.

Reference numeral 24 denotes an atmospheric pressure release unit connected to the suction passage 23 via a valve 25. When the valve 25 is opened, the vacuum state in the suction hole 17 is broken and returns to atmospheric pressure.
The vacuum suction state of the work 20 by the suction hole 17 is released. Reference numeral 26 denotes a second vacuum pump, which is a second vacuum suction means for suctioning the inside of the vacuum chamber 1, and reference numeral 27 denotes an atmospheric pressure release unit for returning the inside of the vacuum chamber 1 to the atmospheric pressure.
Each is connected to the suction path 30 of the vacuum chamber 1 via valves 28 and 29. Reference numeral 18 denotes a hole of the vacuum chamber 1 to which the suction path 30 is connected. 31 is a pressure measuring device for measuring the pressure in the suction hole 17 of the lower electrode portion 3, 32 is a pressure measuring device for measuring the pressure in the vacuum chamber 1,
The suction passages 23 and 30 are provided respectively. Reference numeral 33 denotes a control unit which receives measurement signals from the pressure measuring devices 31 and 32, performs necessary arithmetic processing, etc., and connects the high-frequency power supply 16 connected by broken lines and the vacuum pump 2 serving as vacuum suction means.
Each element such as 1, 26 is controlled.

Referring to FIG. 1, a side wall of the vacuum chamber 1 has an opening 40 for taking in and out the work 20. A cover plate 41 is attached to the access opening 40. The cover plate 41 includes a rod 43 of a cylinder 42.
Are connected, and when the rod 43 protrudes and retracts, the cover plate 4
1 moves up and down to open and close the entrance 40. That is,
The cover plate 41 and the cylinder 42 constitute opening / closing means of the access port 40.

Work loading / unloading means 50 for loading / unloading the workpiece 20 into / from the vacuum chamber 1 is provided beside the vacuum chamber 1. The work loading / unloading means 50 includes a movable unit 51. The movable unit 51 includes an X table 52, a Y table 53, and a Z table 54. A rod 55 is erected on the Z table 54, and a horizontal arm 56 connected to the upper end of the rod 55 is provided.
The holding head 57 is attached to the tip of the. The holding head 57 holds the work 20 in a suction hole formed in the lower surface thereof.
The work 20 is detachably held, for example, by vacuum suction. When the X table 52 and the Y table 53 are driven, the holding head 57 moves horizontally in the X direction and the Y direction, and moves up and down when the Z table 54 is driven. Each element such as the cylinder 42 and the work loading / unloading means 50 is also controlled by the control unit 33.

This plasma processing apparatus has the above-described configuration. Next, a plasma processing method will be described. 2 to 7 show the plasma processing in the order of steps. FIG. 8 shows changes in the pressure P1 of the suction hole 17 and the pressure P2 of the vacuum chamber 1 in the plasma processing.

FIG. 2 shows a state where the plasma processing is being performed. The upper electrode part 2 descends and approaches the lower electrode part 3, and the interval T is small. A work 20 is placed on the lower electrode unit 3. In FIG. 2, first,
The vacuum suction in the suction hole 17 is started by the vacuum pump 21 (timing (1) in FIG. 8), and if the pressure in the suction hole 17 decreases to the set pressure 1 (for example, about 100 Pa) (timing (2) )), Vacuum suction in the vacuum chamber 1 is started by the second vacuum pump 26 (timing (3)), and vacuum suction is performed until the pressure in the vacuum chamber 1 reaches the set pressure 2 (for example, about 500 Pa). As described above, the set pressure 1 is slightly lower than the set pressure 2, and the pressure P1 in the suction hole 17 by the first vacuum pump 21 is higher than the pressure P2 in the vacuum chamber 1 by the second vacuum pump P2. These vacuum pumps 21 are always set to be small (that is, the suction force of the first vacuum pump 21 is larger than the suction force of the second vacuum pump 26).
26 is controlled by the control unit 33. In this way, the work 20 can be reliably fixed on the lower electrode portion 3 using an inexpensive vacuum pump. If the suction force of the first vacuum pump 21 is smaller than the suction force of the second vacuum pump 26, the work 20 on the lower electrode unit 3 floats and performs a stable plasma process. It is not possible.

The pressure P1 in the suction hole 17 and the vacuum chamber 1
The pressure P2 is monitored by the pressure measuring devices 31 and 32, and the control unit 33 controls the vacuum pumps 21 and 26 while observing the pressure measurement results of the pressure measuring devices 31 and 32.
The control unit 33 also performs setting and setting of the set pressure 1 and the design value 2 and calculations and determinations necessary for executing the program. Finally, the pressure of the suction hole 17 is reduced to 10 Pa or less.

When the pressure P2 in the vacuum chamber 1 drops to the set pressure 2, the gas for plasma generation is blown out from the gas blowing holes 9 of the upper electrode part 2 to the lower electrode part 3 (timing (4)), and When the pressure falls within the processing pressure range, a high-frequency voltage is applied to the lower electrode portion 3 (timing (5)). Then, plasma is generated between the upper electrode portion 2 and the lower electrode portion 3, and the ions collide with the upper surface of the work 20 and act to perform plasma processing. In this case, by setting the interval T small, the upper electrode portion 2
The plasma density between the first electrode 3 and the lower electrode portion 3 can be increased, whereby isotropic etching is performed to increase the etching rate (etching rate), and the predetermined plasma processing can be completed quickly in a short time. During the transition from timing (4) to timing (5), the pressure P2
Rises because the supply of the plasma generation gas has started. (5) and (6) are during the plasma processing while supplying the gas. During this time, the pressure P2 in the vacuum chamber 1 maintains the processing pressure range.

When the plasma processing is completed, the supply of the plasma generating gas is stopped (timing (6)), the pressure P2 reaches the set pressure 2, and the exhaust of the plasma generating gas in the vacuum chamber 1 is confirmed. Then, the valve 28 is opened to break the vacuum state in the vacuum chamber 1 and return to the atmospheric pressure (timing (7)). Subsequently, the valve 22 is opened to break the vacuum state in the suction hole 17 to break the vacuum state. Return to atmospheric pressure (timing (8)). In this way, if the vacuum state in the vacuum chamber 1 is first broken and then the vacuum state in the suction hole 17 is broken, the work 20 on the lower electrode portion 3 does not rattle. The reason why the pressure P2 decreases during the transition from the timing (5) to the timing (6) is that the supply of the plasma generating gas is stopped.

By the way, in the conventional plasma processing apparatus,
The work is fixed on the lower electrode portion by the electrostatic chuck means. However, the electrostatic chuck means is extremely expensive, which has contributed to an increase in cost. Therefore, in the plasma processing apparatus of the present embodiment, by operating the apparatus as described above, the work 20 can be fixed using the inexpensive vacuum pumps 21 and 26.

When the plasma processing is completed, the rod 8 of the cylinder 7 is protruded to raise the upper electrode portion 2 as shown in FIG. Make it large enough to not interfere. Further, the cover plate 41 is lowered by pulling the rod 43 of the cylinder 42 and the access port 40 is opened. Holding head 57
Is waiting at the side of the inlet / outlet 40, enters the vacuum chamber 1 through the inlet / outlet 40, performs a lowering / elevating operation on the lower electrode part 3, and The work 20 is picked up by vacuum suction on its lower surface (FIG. 5). In this case, since the interval T is increased by raising the upper electrode portion 2, the holding head 57 moves into the interval T (between the upper electrode portion 2 and the lower electrode portion 3) or moves within the interval T. Up and down movement can be performed without difficulty. The operation of the holding head 57 as described above is performed by operating the movable table 50 to cause the holding head 57 to move horizontally or vertically.

Next, as shown in FIG.
Retreats and escapes from the vacuum chamber 1 to transfer the work 20 to the collection unit 58 and collect it. Next, the holding head 57 picks up the next work 20 waiting at the supply unit (not shown), reenters the vacuum chamber 1 and lowers the lower electrode unit 3.
Transfer to the top. Next, as shown in FIG.
Is retracted out of the vacuum chamber 1, the cover plate 41 is raised to close the access port 40, and the upper electrode portion 2 is lowered to reduce the interval T to an interval suitable for plasma processing.
Then, the above-described operation is repeated.

The plasma processing apparatus of the present embodiment can be used for processing various works. Next, a case where the back surface of the silicon wafer on which the semiconductor circuit is formed (the back surface of the circuit formation surface) is subjected to plasma processing will be described as an example. The back side of the silicon wafer is processed by mechanical polishing,
A stress layer (a layer in which cracks are generated by mechanical grinding for thinning etc.) exists on the mechanically ground surface. Since this stress layer causes a decrease in the strength of the silicon wafer, it is necessary to remove the back surface of the silicon wafer by deep etching (for example, 5 μm). Since the conventional plasma processing apparatus has a structure for performing anisotropic etching, the plasma density is low and the etching rate is low (0.1 μm / min).
Therefore, it takes a long time to perform such a deep etching, so that it is difficult to use and unusable.
In the present embodiment, a mixed gas of SF ₆ (sulfur hexafluoride) and He (helium) is used as a plasma generating gas, and the distance between the upper electrode portion and the lower electrode portion is, for example, 5 mm to 1 mm.
The plasma processing was performed by reducing the diameter to about 5 mm.
The plasma processing apparatus of the present invention can increase the plasma density by narrowing the interval between the electrodes and perform isotropic etching, so that the etching rate can be 1.0 μm / min to 2.5 μm / min. Therefore, according to the plasma processing apparatus of the present invention, the removal of the stress layer on the back surface of the wafer can be removed in a short time by the plasma processing.

[0026]

As described above, according to the present invention, during plasma processing, the upper electrode portion and the lower electrode portion are brought close to each other to increase the etching rate, and after the plasma processing is completed, the workpiece is moved to the upper electrode portion and the lower electrode. When taking in and out between the parts, the interval can be increased, so that a predetermined plasma processing can be performed quickly in a short time by increasing the etching rate, and the upper electrode part and the lower electrode by a work taking in / out means such as a holding head. The work can be taken in and out of the department without difficulty. Also, since the interval between the upper electrode portion and the lower electrode portion can be made as small as possible to increase the plasma density and increase the etching rate, deep etching is required for thinning the wafer and removing the stress layer. It is particularly advantageous as a plasma processing apparatus.

According to the second aspect of the present invention, the work can be firmly fixed on the lower electrode portion using inexpensive vacuum suction means, and stable plasma processing can be performed.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 3 is a sectional view of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 4 is a sectional view of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 5 is a sectional view of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 6 is a sectional view of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 7 is a sectional view of a plasma processing apparatus according to an embodiment of the present invention.

FIG. 8 is a diagram showing a change in pressure according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Upper electrode part 3 Lower electrode part 16 High frequency power supply 17 Suction hole 20 Work 21 First vacuum pump 26 Second vacuum pump 33 Control part 50 Work taking-in / out means 57 Holding head

Claims (16)

[Claims] 1. A vacuum chamber to which a gas for plasma generation is supplied, an upper electrode portion and a lower electrode portion provided in the vacuum chamber at intervals above and below, and a space between the upper electrode portion and the lower electrode portion. A high-frequency power supply for applying a high-frequency voltage;
A space changing means for changing the size of the space between the upper electrode portion and the lower electrode portion; and a work taking-in / out means having a work holding head for taking a work in and out between the upper electrode portion and the lower electrode portion. A plasma processing apparatus for a workpiece. 2. The distance changing means increases the distance between the lower electrode and the upper electrode when the holding head enters between the lower electrode and the upper electrode, and decreases the distance when performing the plasma processing. The plasma processing apparatus for a workpiece according to claim 1, wherein: 3. The interval when performing plasma processing is 5 m.
The plasma processing apparatus for a workpiece according to claim 2, wherein the diameter is from m to 15 mm. 4. A plasma processing apparatus for a workpiece according to claim 1, further comprising holding means for holding the workpiece on an upper surface of said lower electrode. 5. The work plasma processing apparatus according to claim 4, wherein the lower electrode is provided with a plurality of suction holes for vacuum-sucking the work. 6. A vacuum suction means for vacuum-suctioning the suction hole to hold a workpiece on the lower electrode, a second vacuum suction means for vacuum-suctioning the inside of the vacuum chamber, and 6. A control device for controlling the first vacuum suction means and the second vacuum suction means so that the pressure of the suction hole is lower than the pressure of the vacuum chamber. A plasma processing apparatus for the work described in the above. 7. The plasma processing apparatus for a workpiece according to claim 1, wherein said high-frequency power supply is connected to said lower electrode. 8. The frequency of the high frequency voltage applied to the lower electrode is 13.56 MHz.
A plasma processing apparatus for the work described in the above. 9. The plasma processing apparatus for a workpiece according to claim 1, wherein a plurality of gas blowing holes for blowing the plasma generating gas are provided on a lower surface of the upper electrode. 10. An upper electrode portion and a lower electrode portion which are provided in a vacuum chamber at an interval above and below, and a gas for generating plasma is supplied to the vacuum chamber and a space between the upper electrode portion and the lower electrode portion is provided. A plasma processing method for a workpiece in which a high-frequency voltage is applied to the workpiece to perform plasma processing on the workpiece held on the lower electrode, wherein the workpiece is placed on the lower electrode when the distance between the lower electrode and the upper electrode is widened. A step of supplying; a step of reducing the interval to a distance suitable for plasma processing; a step of vacuum-suctioning the inside of the vacuum chamber to reduce the pressure; and a step of supplying a plasma generating gas into the reduced-pressure vacuum chamber and Generating a plasma by applying a high-frequency voltage between an electrode and the lower electrode; and stopping the application of the high-frequency voltage and the supply of a plasma generation gas. A step of returning the inside of the vacuum chamber to atmospheric pressure, and a step of taking out a plasma-processed work from above the lower electrode in a state where the distance between the upper electrode and the lower electrode is widened. Plasma processing method. 11. The plasma processing apparatus according to claim 1, wherein the interval is 5 times.
The method according to claim 10, wherein the thickness is in the range of 15 mm to 15 mm. 12. The method according to claim 10, wherein the work is held on the lower electrode by vacuum suction by a plurality of suction holes on the lower electrode. 13. The pressure of the vacuum chamber is reduced when the pressure of the suction hole drops to a predetermined pressure, and the pressure of the suction hole is always kept lower than the pressure of the vacuum chamber during plasma processing. The method for plasma processing a workpiece according to claim 12. 14. The method according to claim 10, wherein the frequency of the high-frequency voltage applied to the lower electrode is 13.56 MHz. 15. The method according to claim 10, wherein a plasma generating gas is blown from a lower surface of the upper electrode to supply the plasma generating gas into the vacuum chamber. 16. The method according to claim 10, wherein the surface of the work is removed by isotropic etching.