JPH03169041A - Vacuum treatment apparatus - Google Patents

Abstract

PURPOSE:To separate an object to be treated within a short time by a method wherein a supply operation of a DC voltage of an inverse potential is stopped according to a detection result that a pressure of a gas has become a prescribed ratio with reference to a prescribed pressure. CONSTITUTION:An electrode 3 of an electrostatic chuck 1 is connected respectively to a DC power supply 4 of a positive potential and a DC power supply 5 of a negative potential via switches 6 and 7; a DC voltage of a prescribed potential is applied; an electrostatic attraction force is generated; an object 10 to be treated is attracted; in this state, a gas of a prescribed pressure is supplied into a gap. The gas is leaked into a vacuum chamber 34 as the attraction force is lowered; the pressure is lowered. Consequently, when the lowered pressure becomes a prescribed rate with reference to a prescribed pressure, the attraction force is lowered sharply. Accordingly, a supply operation of the DC voltage of an inverse potential is stopped. Thereby, the object 10 to be treated can be separated from the electrostatic chuck 1 within a minimum range of the attraction force without damaging the object to be treated; a time required to separate the object 10 to be treated can be shortened.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a vacuum processing apparatus that is used in the manufacturing process of semiconductor elements such as ICs and LSIs, and is equipped with an electrostatic adsorption device that adsorbs and holds objects to be processed. Regarding. [Prior Art] Conventionally, in the manufacturing process of semiconductor devices such as ICs and LSIs, a photolithography method has been adopted in which a pattern is formed by developing with a developer after exposure. However, in recent years, LSIs have become even more miniaturized, and the minimum dimension of a pattern to be formed on a substrate is entering the region of 1 μm or less. Even if a substrate with a stepped structure is used, sufficient resolution may not be obtained due to problems such as the influence of light reflection during exposure and the shallow depth of focus in the exposure system. The problem arises that it is not possible to As a method to solve such problems, JP-A-61-1
Publication No. 07346 (or corresponding EP Patent Publication No. 18)
No. 4567), instead of performing development using a developer in the photolithography method, development is performed by etching a pattern using a reactive ion etching device that generates gas plasma such as oxygen plasma. A dry development process has been proposed to form resist patterns. As an example of this reactive ion etching equipment,
No. 8-151028 (or corresponding U.S. Pat.
, No. 422,896) and JP-A-59-140375
No. 4,581,118 (or corresponding U.S. Pat. No. 4,581,118)
No.) is a reactive ion etching device in which the cathode, which is a support for the material to be etched and to which microwave power is applied, has a built-in means for generating a magnetic field parallel to the surface of the material to be etched. is listed. Furthermore, Japanese Patent Laid-Open No. 58-170018 describes a reactive ion etching apparatus in which a magnetic field is formed in a direction perpendicular to a cathode that is a support for a material to be etched. These reactive ion etching devices can increase the concentration of reactive species in the generated gas plasma, so using these devices increases the productivity compared to general parallel plate type reactive ion etching devices. high-speed etching. However, in these devices, although high-speed etching is possible by increasing the applied power, problems such as damage to the material to be etched, deformation and denaturation due to heat occur during etching. In order to prevent the temperature of the material to be etched from rising, there is a method of cooling the electrode and sample stage on which the material to be etched is placed using an appropriate coolant. However, if the material to be etched is simply placed on a cooled electrode or sample stand, a sufficient contact area cannot be obtained due to the roughness of the contact surface and the warpage of the material to be etched, resulting in insufficient cooling of the material to be etched. Become. Therefore, an electrostatic adsorption device is used as a means for fixing the etched material to ensure sufficient thermal contact between the etched material and the electrode or sample stage. This electrostatic adsorption device is usually constructed so that the upper surface of the electrode is covered with a dielectric material, and the object to be processed is placed on the dielectric material. Then, a voltage is applied between the object to be processed and the electrode, and the object to be processed is fixed by electrostatic force. [Problems to be Solved by the Invention] However, in a dry etching apparatus using such an electrostatic chuck device, for example, even if the application of voltage is stopped after processing the workpiece, the workpiece and There is a problem in that it takes a long time to remove the object to be processed from the electrostatic chuck device because the charge or polarization of the dielectric material of the electrostatic chuck device does not disappear in a short time and the adsorption force remains. especially,
This problem is noticeable in wafers having an oxide film or other oxide film on the surface. Therefore, in order to dissipate the charge on the object to be processed, after stopping the voltage application to the electrostatic chucking device, a method is proposed in which a bottle with one end grounded is brought into contact with the object to be processed, and a method is proposed in which the bottle, which is grounded at one end, is brought into contact with the object to be processed. Method of applying a potential opposite to the time
226, page 5, upper right column) has also been attempted, but has not achieved sufficient effects. It is an object of the present invention to provide a vacuum processing apparatus equipped with an electrostatic adsorption device that can eliminate such conventional problems, make it possible to remove objects to be processed within a short time, and improve productivity. It is in. [Means for Solving the Problem] In order to achieve the above object, the vacuum processing apparatus of the present invention has the following features:
When an electrostatic adsorption device is provided in a vacuum chamber and includes an electrode and a dielectric layer that covers the electrode and has a recess on the surface that forms a gap between the object and the object to be processed, means for supplying gas at a predetermined pressure to the void, means for detecting the pressure of the gas supplied to the void when the object to be treated is adsorbed, and a DC voltage of a predetermined potential is applied to the electrode for a predetermined time. a means for applying a DC voltage having an opposite potential to the predetermined potential; and a means for stopping application of the DC voltage having the opposite potential in response to a detection result in which the pressure of the gas is a predetermined ratio to the predetermined pressure. It is characterized by having the following. [Function] According to the present invention, by applying a DC voltage of a predetermined potential to the electrodes of the electrostatic adsorption device, electrostatic adsorption force is generated, and the object to be processed is adsorbed. In this state, gas at a predetermined pressure is supplied into the gap. When a predetermined process on the workpiece in the vacuum processing apparatus is completed, a DC voltage having a potential opposite to the above-described predetermined potential is applied to the electrode. Then, the charge and polarization of the object to be processed and the dielectric of the electrostatic adsorption device disappear, and the adsorption force decreases. On the other hand, if the application of the DC voltage with the opposite potential exceeds a certain time, the electrostatic attraction force based on the application of the DC voltage with the opposite potential increases. However, the gas that is being supplied at a predetermined pressure to the gap between the object to be processed and the dielectric layer leaks into the vacuum chamber as the adsorption force decreases, and its pressure decreases. Therefore, the fact that this reduced pressure has become a predetermined ratio to the above-mentioned predetermined pressure means that the adsorption force has decreased significantly, and accordingly, the application of a DC voltage of the opposite potential is necessary. By stopping the workpiece, it becomes possible to remove the workpiece from the electrostatic adsorption device within the minimum range of the adsorption force without damaging the workpiece. As a result, the required time for desorption of the object to be processed can be significantly shortened. [Examples] Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing the basic structure of an electrostatic chuck device used in the present invention. In FIG. 1, 1 indicates the entire electrostatic adsorption device, 2 is a dielectric layer made of ceramics, and there are flat electrodes 3 inside.
is provided. The flat plate electrode 3 is connected to a positive potential DC power source 4 and a negative potential DC power source 5 with switches 6 and 7, respectively.
It is connected via a 2000-pin, so that DC voltage can be applied to it. As shown in FIG. 2, the surface of the dielectric layer 2 is provided with a plurality of concentric gas introduction grooves 8 as recesses, leaving a dielectric surface 2A of an appropriate area, and each groove 8 has a radial direction. They are communicated by a linear groove 9. Incidentally, lO is the object to be treated, and in reality, unlike the state shown in FIG. 1, it is adsorbed to the dielectric surface 2A, which is shown hatched in FIG. 2, as will be described later. Based on FIGS. 3, 4, and 5, as a vacuum processing apparatus equipped with an electrostatic adsorption device, a means for applying a parallel magnetic field to a material to be etched as a processing object; We will explain a reactive ion etching device that has a path for flowing a coolant to the cathode to cool the material to be etched, and a means for filling the back side of the material to be etched with a coolant gas with high thermal conductivity such as helium. FIG. 3 is a perspective view of the cathode portion of the reactive ion etching apparatus, and FIGS. 4 and 5 are cross-sectional views showing its detailed structure. Reference numeral 11 indicates a cathode block constituting the cathode body, and an aluminum block 12 (hereinafter referred to as the aluminum block) is disposed on the upper surface of the cathode block 11, and an electrostatic adsorption device is mounted on the aluminum block 12. l is arranged. The electrostatic chuck device 1 is provided with an opening 15 through which a wafer receiving arm 14 of a lifting device for loading and unloading a material to be etched enters and exits. The cathode block 11 receives a refrigerant from the refrigerant population l6, such as water, an aqueous solution of an ethylene glycol compound, or a fluorine refrigerant (
Fluorinert (manufactured by 3M Co., Ltd.) or the like is introduced and cooled to a predetermined temperature by flowing it through a refrigerant passage 18 provided in the cathode block 11. As shown in FIG. 4, a rod-shaped permanent magnet 19 is disposed inside the cathode block 1l, and ball beads 20 and 21 made of a magnetic material are provided at both ends of the cathode, respectively. Further, an auxiliary magnet block is provided above the cathode block 11, which is composed of a permanent magnet 22 and ball pieces 23, 24, and is used to form an auxiliary magnetic field.
Due to the interaction between the permanent magnet 19 of No. 1 and the auxiliary magnet block, a magnetic field parallel to the surface of the material to be etched 27 is formed as shown by lines of magnetic force 26. The electrostatic adsorption device 1 is the fifth
As shown in the figure, the flat plate electrode 3 is buried inside the dielectric layer 2 as described above, and the upper surface of the dielectric layer 2 has a plurality of concentric refrigerant gas introduction grooves 8 as described above. Radial linear groove 9 communicating with concentric refrigerant gas introduction groove 8
is provided. The electrostatic adsorption device 1 is provided with a through hole 25, and this through hole 25 communicates with a refrigerant gas passage 30 provided in the aluminum block l2 and the cathode block 1.1. Refrigerant gas is introduced to the back surface of the material to be etched. The introduced refrigerant gas spreads over the entire back surface of the material to be etched through the linear grooves 9 and the concentric refrigerant gas introduction grooves 8, dissipating the heat of the material to be etched to the surface of the electrostatic adsorption device 1. The material to be etched is cooled. Here, the depth of the concentric refrigerant gas introduction groove 8 is usually 5.
It is from μm to 1 mm, preferably from 5 μm to 100 μm. The area occupied by the concentric refrigerant gas introduction grooves 8 on the surface of the electrostatic adsorption device 1 is usually 10 to 90%, preferably 30 to 80%. Note that the shape of the refrigerant gas introduction groove is not particularly limited as long as it can uniformly fill the refrigerant gas between the material to be etched and the electrostatic adsorption device 1; for example, it may be spiral or lattice-shaped. can also be suitably used. As shown in FIG. 5, a device 3l for lifting and lowering the material to be etched is provided in the center of the main body of the cathode block 11, and a shaft 32 passing through the aluminum block 12 and an opening of the electrostatic adsorption device 1 attached to the shaft 32 are provided. Part 15
The material to be etched is raised and lowered by raising and lowering the wafer receiving arm 14 disposed in the wafer receiving arm 14 . Here, the lifting device 3l includes a fluid pressure operated actuator, and is attached to the cathode block 11 in an airtight manner via a flange member 33, so that the refrigerant gas introduced to the back surface of the material to be etched does not leak into the reaction chamber. ．． Further, FIG. 6 schematically shows the entire configuration of a reactive ion etching apparatus as an example of a vacuum processing apparatus according to the present invention using a partially sectional view. In the reaction vessel 34, a #pole block 1l in which the electrostatic adsorption device 1 shown in FIG. 5 is disposed is arranged. Etched material 2
7 is supported on the electrostatic adsorption device 1. Electrostatic adsorption device 1
A DC voltage of a predetermined potential is applied to the electrode 3 via a high frequency filter 60 according to a sequence described later. An anode 111 is disposed facing the cathode block 1l, and the anode 111 and the reaction vessel 34 are at ground potential. Further, the above-mentioned auxiliary magnet block is provided on the back side of the anode 111, and in the wooden example, the permanent magnet 22 is housed in the magnet holding block 22^. #1 pole block l1
The terminal block 35 connected to the reaction vessel 34 is insulated from the reaction vessel 34 by an insulator 36 attached to the reaction vessel 34. By applying high frequency power between the anode 111 and the cathode block 11 by the high frequency power supply 37,
A gas plasma of the reactive gas introduced into the reaction vessel 34 is generated, and reactive species in this gas plasma contribute to etching. In this example, after the inside of the reaction container 34 is evacuated to a high vacuum by the turbo pump 40 and the mechanical bomb 4l, the reaction gas is pumped from the reaction gas container 42, or the inert gas is pumped together with the reaction gas from the inert gas container 43. Reaction vessel 34 via flow control valves 44 and 45
to be introduced within. Here, the flow rate of the reaction gas and the pressure inside the reaction container 34 are:
Controlled by flow control valves 44 and 45 and control valve 46. The progress of etching of the material to be etched 27 is detected by an etching detection device 47. In addition, in the device shown in the example, when the material to be etched 27 is a wafer, for example, the wafers are taken out one by one from a wafer cassette containing a plurality of wafers and placed in the preparation chamber 4.
The process can be carried out by loading a plurality of materials 27 into the reaction vessel 34 and sequentially introducing a plurality of materials 27 into the reaction vessel 34 via the gate valve 49. The above-mentioned lifting device 31 is equipped with an inert gas container 43 such as nitrogen.
Pressure gas is introduced from the wafer through, for example, an electromagnetic switching valve 50 to move the wafer receiving arm 14 up and down. Furthermore, 5l is a helium container as a refrigerant gas,
The above-mentioned cathode block l1 and aluminum block 1 are connected via the flow rate control valve 52 and the pressure control valve 53.
It communicates with the refrigerant gas introduction groove 8 of the electrostatic adsorption device 1 through the refrigerant gas passage 30 and the through hole 25 provided in the electrostatic adsorption device 1 . The pressure control valve 53 has two variable orifices 53A.
, 53B and a control valve 53C. Note that 54 is a pressure sensor that detects the pressure of the refrigerant gas supplied to the refrigerant gas introduction groove 8, and for example, a capacitance manometer is used. The conditions for etching the material to be etched 27 using the reactive ion etching apparatus shown in FIG. 6 are usually as follows:
It is as shown below. Distance between cathode block 11 and positive Fi 1111; 3~
20cn+ Power applied between cathode block 11 and anode 111: 10
W ~ 4 kW, preferably IOOW ~ 3 kW Temperature of cathode block 11: 0°C or less, preferably 0 ~ -40°C, particularly preferably -5 ~ -40°C Temperature of the material to be etched 27: 40°C or less near the material to be etched Magnetic field strength: lO~400 Gauss Reaction gas flow rate: 2~2005CCM 1 preferably 2~IOOsccM
Pressure during etching: 1 to 100 mTorr, preferably 2 to 80 mTorr
rReactant gas introduction method: In the example shown in FIG. 6, the reaction gas is introduced from the bottom surface of the reaction container 34, but instead of doing so, a hole is provided in the side surface of the reaction container 34 or in the anode 111, and the reaction gas is introduced from this hole. May be introduced. Reactive gas; oxygen, nitrogen oxide. Tetrafluoromethane. Inert gas such as hexafluoroethane and hexafluoropropane; nitrogen. Refrigerant gases such as helium and argon; nitrogen and helium. Refrigerant gas pressure in the gap between the material to be etched, such as argon or hydrogen, and the electrostatic adsorption device 1; 6 to 20 Torr. Heat-resistant materials containing at least 50% by weight, preferably at least 50% by weight, such as graphite; diamond: tetrafluoromethane, methanol. By covering with a plate, sheet, or film made of a plasma-polymerized polymer of ethanol, polyimide, poly-p-phenylene, polyacetylene, or other synthetic polymer; or a composite material of these materials, the anisotropy of etching with respect to the material to be etched can be improved. It can be further increased. In this case, these plates, sheets, or membranes are preferably removably fixed to the inner surface of the reaction vessel 34. Furthermore, the cover 150 is made of a material containing 30% by weight or more of carbon.
(See FIGS. 5 and 6) to cover the part of the surface of the cathode block 1l around the material to be etched 27,
The uniformity of etching on the surface of the material to be etched 27 can be further improved. The material to be etched 27 that can be etched by the reactive ion etching apparatus of this embodiment is glass. Examples include those in which a resist layer is provided on a substrate made of silicon, gallium arsenide, etc., and this resist layer is made by partially esterifying a hydroxyl group-containing resin such as novolak resin or hydroxystyrene resin with quinonediazide sulfonyl halide. Examples include those obtained by irradiating a radiation-sensitive resin with radiation and selectively silylating it with a silane compound such as hexamethyldisilazane or silyl chloride. An example of a sequence when performing ion etching processing on a wafer as an object to be processed using the ion etching apparatus of this embodiment having the above configuration will be described below with reference to the time chart shown in FIG. First, electric BN switching valve 5
By performing the switching operation of 0, pressurized nitrogen gas is introduced into the lifting device 31 and the wafer receiving arm 14 is raised. Then, the wafer 27 introduced into the reaction container 34 by a wafer introducing device (not shown) is received on the wafer receiving arm l4, and the arm 14 is subsequently lowered. Now, if the time point at which this lifting device 3l completes lifting is to, then
At this point in time, the switch 6 is turned on, and a positive DC voltage is applied to the electrode 3 of the electrostatic adsorption device 1 via the high frequency filter 60. The reason why voltage is applied in advance in this way is that it takes some time (about 10 to 30 seconds) for the electrostatic adsorption device to generate the maximum adsorption force. When 4 to 5 seconds have elapsed from the point in time when some adsorption force is generated in the electrostatic adsorption device 1, the above-mentioned electromagnetic switching valve 5 is activated.
0, the lifting device 31 is lowered and the wafer 27 is placed on the electrostatic chuck device 1. Then, at an appropriate time after t1 from the time when the wafer is placed on the electrostatic chuck device, the refrigerant gas introduction groove 8, that is, the wafer 27
The supply of refrigerant gas controlled to a predetermined pressure P by the pressure control valve 53 of the electrostatic adsorption device 1 is started. Once the refrigerant gas pressure within the gap reaches a predetermined pressure h, the control valve 53C is closed and the pressure within the gap is maintained at the predetermined pressure P1. This 1 is preferably 5 seconds≦1,≦30 seconds,
If it is less than 5 seconds, the adsorption force of the electrostatic adsorption device 1 has not yet been sufficiently generated and refrigerant gas will leak into the reaction chamber, which is undesirable, and if it exceeds 30 seconds, the throughput will decrease too much. . Next, the aforementioned reaction gas is introduced into the reaction vessel 34 after t2 from the time point t. This t2 is preferably O seconds≦t2≦10 seconds. This is because if the time exceeds 10 seconds, the throughput decreases too much. Further, high frequency power is applied from the high frequency power supply 37 to the wafer 27 after t after the elapse of t2, and etching is performed on the wafer 27. Preferably, t3 is 0 seconds≦t,≦30 seconds. If it exceeds 30 seconds, the throughput will drop too much, which is undesirable.In response to the detection by the etching detection device 47 that detects the progress of etching on the wafer 27, the reaction gas is introduced into the reaction vessel 34 and into the negative illumination. At the same time as the application of high frequency power is stopped, switch 6 is turned off and switch 7 is turned off.
is turned on, and instead of applying a positive voltage to the electrode 3, a negative voltage is applied. From this point on, the refrigerant gas pressure within the gap is monitored by the pressure sensor 54, and this pressure P2
The supply of refrigerant gas is stopped at the time when the refrigerant gas reaches a predetermined ratio to the predetermined pressure P, that is, 0.6 Pl≦P2≦0.9 P, and after t4 from this point, the application of the above-mentioned negative voltage is stopped. ．． The pressure P2 at the start of time t4 is the most important factor for stably detaching the wafer in a short time, and P2 < 0. 6 P l , the negative voltage is applied for too long and the adsorption force due to the negative voltage increases, so it takes time to detach the wafer 27 from the electrostatic adsorption device 1, and the throughput decreases. Therefore, if P2>0.9Pl, the adsorption force due to the residual charge of the electrostatic adsorption device 1 is large, and stable desorption operation cannot be performed. In addition, P, is as mentioned above<6Torr≦PI≦20Torr
r is preferable; if it is less than 6 Torr, cooling of the wafer 27 will be insufficient, and if it exceeds 20 Torr, it will be difficult to adsorb the wafer 27. Further, t4 is preferably 0 seconds≦t4≦5 seconds,
If it exceeds 5 seconds, the adsorption force will regenerate and the atom will be removed! This is because it becomes impossible to create a product. Then, after t from the stop of application of this negative voltage, the lifting device 3
Pressurized nitrogen gas is introduced into the wafer receiving arm l.
4 is lifted up, and the wafer 27 is detached from the electrostatic chuck device 1. This t, is preferably 0 seconds≦1s≦IO seconds,
If it exceeds 10 seconds, the throughput will drop too much. Experimental Examples 1 to 8 and Comparative Experiment 1 With the structure shown in FIGS.
An electrostatic adsorption device 1 having a diameter of 100 mm and having a thickness of A silicon wafer with an oxide film having a diameter of 4 inches was placed on the suction device 1 as the material to be etched 27 according to the sequence shown in the time chart of FIG. 7, and the wafer was fixed by suction. Table 1 shows the initial voltage applied to the plane electrode 8i3 at this time. and a refrigerant gas introduction groove 8;
That is, helium with a pressure of 10.5 Torr was supplied to the gap, and after the wafer was fixed by suction, the voltage was continued to be applied for 1 minute and 30 seconds, the voltage application was stopped, and various reverse voltages as shown in Table 1 were applied. did. Thereafter, the pressure within the system including the voids was detected and the pressure drop was measured. Then, when various pressure reduction states as shown in Table 1 are reached, the supply of helium is stopped, and 3 seconds later, the application of reverse voltage is stopped,
The time required from the time when a reverse voltage is applied until the wafer can be lifted by the wafer lifting device 3l without causing damage to the wafer or displacement due to peeling off the wafer (
(hereinafter referred to as desorption time) was measured. The results are shown in Table 1. Table 1◆1. OKV ◆ 1. OKV ◆1. OKV+1. OKV ◆ 1. OKV ◆2. OK KV - 2.5 KV - 3.0 KV Comparative Experiment Example 1 ◆1.0κV - 0.5 KV - 05 KV -0.5κV -05 κV - 1. OKV-1. OK V As mentioned above, sputtering equipment and C
It goes without saying that the present invention can also be applied to VD devices. [Effects of the Invention] As explained above, according to the present invention, the object to be treated can be desorbed in a short time, and the refrigerant gas can be filled between the object to be treated and the electrostatic adsorption device. Since it can also be used for processing, it is possible to effectively cool the processed material and perform highly accurate vacuum processing with high productivity.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the basic configuration of an electrostatic adsorption device according to an embodiment of the present invention, FIG. 2 is a plan view thereof, and FIG. 3. 4 and 5 are a perspective view, a cross-sectional view, and a cross-sectional view taken along a line perpendicular to FIG. 6 is an overall configuration diagram of a reactive ion etching apparatus according to an embodiment of the present invention, and FIG. 7 is a time chart showing the processing steps of the ion etching apparatus. DESCRIPTION OF SYMBOLS 1... Electrostatic adsorption device, 2... Dielectric layer, 3... Flat plate electrode, 6.7... Switch, 8... Refrigerant gas introduction groove, 11... Cathode block, 12. ... Aluminum block, 14... Wafer receiving arm, 15... Opening, l6... Coolant inlet, l7... Coolant outlet, l8... Coolant passage, l9... Permanent magnet, 20, 21, 23. 24...Ball piece, 22...
- Auxiliary permanent magnet, 30... Refrigerant gas passage, 3l... Wafer lifting device, 34... Reaction container, 35... Terminal block, 36... Insulator, 37... High frequency power supply, 42 ...Reaction gas container, 43...Inert gas container, 44,45.52...Flow rate control valve, 53...Pressure control valve, 54...Pressure sensor, 60...RF filter, 111... Anode, 150... Cathode cover Fig. 1 Fig. 2 Fig. 16 Fig. 3 Fig. 4

Claims (1)

[Claims] 1) An electrostatic adsorption device provided in a vacuum chamber, comprising an electrode and a dielectric layer covering the electrode and having a recessed portion on the surface to form a gap between the electrode and the object to be processed. a means for supplying gas at a predetermined pressure to the gap when the object to be processed is adsorbed; a means for detecting the pressure of the gas supplied to the gap when the object to be processed is adsorbed; After applying a DC voltage of potential for a predetermined time,
means for applying a DC voltage at a potential opposite to the predetermined potential; and means for stopping application of the DC voltage at the opposite potential in response to a detection result in which the pressure of the gas is a predetermined ratio to the predetermined pressure. A vacuum processing apparatus comprising: