Sample processing method and apparatus

Abstract: A method and apparatus for processing a sample comprises etching the sample by means (10; 11-14) of an etching plasma, and then treating the sample by means (20-21) of a second plasma, to remove residual corrosive compounds formed by the etching plasma. Removal of the residual corrosive compounds and prevention of corrosion is much improved by contacting (30, 31) the surface of the sample after the second plasma treatment with at least one liquid in order to effect at least one of (a) removal of the residual corrosive compounds and (b) passivation of said surface exposed by steps, and drying (41) the sample.

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of processing a sample including an etching step, and to an apparatus for carrying out such a method, and more particularly to a processing method and apparatus which is suitable for processing a sample in the manufacture of a semiconductor device or other device including miniaturized components. 2. Description of the Prior Art A sample such as a semiconductor device substrate is etched by a chemical solution or by plasma, for example. Sufficient care must be paid to corrosion protection of the sample after etching processing. A corrosion-proofing technique after etching is disclosed, for example, in US-A-4487678. This prior art technique subjects a resist film, after etching by plasma inside an etching chamber, to removal in a second plasma processing chamber connected to the etching chamber. The second plasma treatment removes chlorine compounds which are corrosive components remaining in the resist film or at the etched surface. It is also known to heat the sample after etching to at least 200°C in order to promote evaporation of chlorides that are residual corrosive components. Japanese Laid-Open Patent Publication No. JP-A-61-133388 discloses a method in which a sample after plasma etching is transferred to a heat-treating chamber in which hot air is blown at it to remove corrosive compounds. Thereafter the sample is washed with water and dried. The present applicants have found that these prior art techniques involve the problem that sufficient corrosion-proofing performance cannot be obtained, at least for certain kinds of samples. For instance, the techniques described above are believed effective in some cases for corrosion-proofing of a single metallic film such as an aluminium (Al) wiring film. However, they fail to provide a sufficient corrosion-proofing effect after etching of a sample having metals having mutually different ionization tendencies such as films of Al, Cu, W, Ti, Mo, etc. and their alloys or laminates. With a remarkable progress in miniaturization in recent years, wiring films have been more and more miniaturized, and an Al-Cu-Si alloy film having a few percents of Cu content in place of the conventional Al-Si alloy film and a laminate structure of the Al-Cu-Si alloy film and a refractory metal film such as titanium tungsten (TiW), titanium nitride (TiN) and molybdenum silicon (MoSi) film for reducing contact resistance have gained wide application as the wiring film in order to prevent breakage due to electromigration and stress migration. In such a wiring film structure, ionization tendencies of Al and Cu, W, Ti, Mo or the like are different so that a kind of battery action develops due to water components as a medium and corrosion of the wiring film is accelerated by so-called "electrolytic corrosion". Even if corrosive materials generated by etching are removed by utilizing plasma at a high temperature of 200°C or above, corrosion occurs due to the effect of moisture on remaining corrosive compounds within some minutes or several hours after the sample is withdrawn into atmosphere. SUMMARY OF THE INVENTION It is an object of the present invention to provide a sample processing method and apparatus which can prevent sufficiently corrosion of a sample after etching irrespective of the kind of sample. In one aspect, the invention provides a method of processing a sample which comprises a substrate and on said substrate a layer which is subjected to the etching of step (i), said layer being selected from (a) a laminate comprising metals of different ionization tendencies and (b) an alloy of metals of different ionization tendencies, the method comprising the steps of: (i) etching the sample by means of an etching plasma formed using a chlorine-containing gas (i.e. a gas containing chlorine itself or chlorine compound), the etching being performed through a mask on said sample, (ii) after step (i), treating the sample by means of a second plasma, to effect removal of said mask and to remove residual corrosive compounds formed in step (i), said second plasma being formed in a gas atmosphere which is different from that of the etching plasma, (iii) contacting a surface of said sample exposed by steps (i) and (ii) with at least one aqueous liquid in order to effect at least one of (a) removal of residual corrosive compounds from step (i) and (b) passivation of said surface exposed by steps (i) and (ii), and (iv) after step (iii), drying the sample. As discussed more below, it has surprisingly been found that the combination of steps (ii) and (iii) provides remarkably improved corrosion resistance of a plasma-etched sample. The plasma of step (ii) is preferably formed in an oxygen-containing gas atmosphere. Preferably washing in step (iii) is selected from (a) washing with water, (b) washing first with an alkaline liquid and then with water, (c) washing first with an acidic liquid and then with water, and (d) washing first with a mixture of nitric acid and hydrofluoric acid and then with water. Suitably, to avoid contact with air, step (iii) is performed in an inert gas atmosphere. Likewise, step (iv) may be performed in an inert gas atmosphere. In particular the invention is applicable when a layer which is subjected to the etching of step (i) is (a) a laminate comprising metals of different ionization potentials or (b) an alloy of metals of different ionization potentials. More generally, the etched layer may be selected from films made of Al, Cu, W, Ti, Mo, other refractory metals, alloys thereof (including alloys containing Si), silicides of refractory metals, TiN and TiW and laminates of at least two such films. In another aspect, the invention provides apparatus for processing a sample, comprising (i) means for effecting plasma etching of the sample, including supply means adapted to supply a first plasma-forming gas for the plasma etching, (ii) means for effecting plasma treatment of the sample after the plasma etching, including supply means for supplying a second plasma-forming gas for the plasma treatment, said second gas being preferably an oxygen-containing gas and being different from said first gas, (iii) means for contacting the surface of the sample exposed by the plasma etching and the plasma treatment with a liquid adapted to effect at least one of (a) removal of residual corrosive compounds formed in the plasma etching and (b) passivation of said surface, and (iv) means for drying said sample following contact with said liquid. Preferably the means for plasma etching is magnetic field-type microwave plasma etching apparatus, and the means for the subsequent plasma treatment is non-magnetic field-type microwave plasma etching apparatus. The apparatus may comprise first and second units which are detachable from each other. The first unit includes the plasma etching means and the means for plasma treatment, while the second unit includes the means for contacting with liquid and the drying means. The apparatus further includes means for transfer of a sample from said first unit to said second unit, preferably mounted on said second unit. Preferably a sample receiving station for receiving a sample to be processed and a sample discharge station for discharging a sample after the processing are on the same side of the apparatus. In this description, the plasma treatment step after etching is called post-processing, the liquid treatment step is called wet-processing and the drying step is called dry-processing, for convenience. In the invention, therefore, a sample is etched by use of plasma. After etching, the sample is post-processed by plasma post-processing means by utilizing plasma under a reduced pressure. The post-processed sample from the plasma post-processing means is wet-processed by wet-processing means. The wet-processed sample is dry-processed by dry-processing means. Since post-processing using plasma and wet-processing are both carried out, the corrosive materials that occur due to etching can be removed sufficiently from the etched sample. Therefore, even when the etched sample is withdrawn into external air, for example, its corrosion can be sufficiently prevented irrespective of the kind of sample. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention will be described below by way of non-limitative example with reference to the accompanying drawings, in which:- Fig. 1 is a block diagram of a sample processing apparatus in accordance with one embodiment of the present invention; Fig. 2 is a diagrammatic plan view of the apparatus of Fig. 1; Fig. 3 is a diagrammatic longitudinal side view of the apparatus shown in Fig. 2; Figs. 4A-4G illustrate details of structure and operation of one part of the apparatus of Figs. 2 and 3; Figs. 5A and 5B illustrate details of structure and operation of a second part of the apparatus of Figs. 2 and 3; Fig. 6 is a sectional view showing an example of a sample; Fig. 7 is a perspective view showing an example of occurrence of corrosion; Fig. 8 is a diagram showing the relation between processing modes after etching and the time till occurrence of corrosion; and Fig. 9 is a block diagram of a sample processing apparatus in accordance with a second embodiment of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS In Fig. 1, the sample processing apparatus includes a processing apparatus 10 for etching a sample, a plasma post-processing apparatus 20, a wet-processing apparatus 30 and a dry-processing apparatus 40 and is equipped at least with means 50, 60, 70 for transferring the sample between these processing apparatuses. In Fig. 1, an apparatus for processing, such as etching, the sample by utilizing plasma under a reduced pressure is used as the processing apparatus 10. Examples of the plasma etching apparatuses which may be employed are a plasma etching apparatus, a reactive sputter etching apparatus, a non-magnetic field type microwave plasma etching apparatus, a magnetic field type microwave plasma etching apparatus, an electron cyclotron resonance (ECR) type microwave plasma etching apparatus, a photo-excitation plasma etching apparatus, a neutral particle etching apparatus, and the like. Besides the apparatuses described above, it is possible to employ an apparatus which wet-etches the sample and an apparatus which etches the sample by use of a corrosive gas. In Fig. 1, the plasma post-processing apparatus 20 post-processes, such as ashes i.e. removes photoresist by oxidation, the processed sample processed by the processing apparatus 10, by utilizing plasma under a reduced pressure. Examples of the ash-processing apparatuses which may be employed are a plasma ashing apparatus, non-magnetic field type and magnetic field type microwave plasma ashing apparatuses, an ECR type microwave plasma ashing apparatus, a photo-excitation plasma ashing apparatus, and the like. In Fig. 1, the wet-processing apparatus 30 wet-processes the post-processed sample from the plasma post-processing apparatus 20, such as a spinning wet-processing apparatus. In the spinning wet-processing apparatus, the post-processed sample is subjected to spinning washing with water, for example, or to spinning washing sequentially with chemical solutions and water. In this case, the chemical solution is selected suitably in accordance with the materials to be removed from the post-processed sample. An inert gas atmosphere such as nitrogen gas or an atmospheric atmosphere is used as the processing atmosphere. Dry-processing such as water removal is sometimes conducted under this state after wet-processing. In Fig. 1, an apparatus for dry-processing the wet-processed sample from the wet-processing apparatus 30, such as an apparatus for heating and drying the wet-processed sample or an apparatus for blowing a dry gas to the wet-processed sample to dry it, is used as the dry-processing apparatus 40. A nitrogen gas atmosphere or atmospheric atmosphere is used as the processing atmosphere. In Fig. 1, the sample transfer means 50 has the function of transferring the processed sample between a processing station (not shown) of the processing apparatus 10 and a processing station (not shown) of the plasma post-processing apparatus 20. The sample transfer means 60 has the function of transferring the post-processed sample between a processing station (not shown) of the plasma post-processing apparatus 20 and a processing station (not shown) of the wet-processing apparatus 30. The sample transfer means 70 has the function of transferring the wet-processed sample between a processing station of the wet-processing apparatus 30 and a processing station (not shown) of the dry-processing apparatus 40. The sample transfer means 50 can deliver and receive the sample between the processing station of the processing apparatus 10 and that of the plasma post-processing apparatus 20. The sample transfer means 60 can deliver and receive the sample between the processing station of the plasma post-processing apparatus 20 and that of the wet-processing apparatus 30. The sample transfer means 70 can deliver and receive the sample between the processing station of the wet-processing apparatus 30 and that of the dry-processing apparatus 40. Known transfer means are used as the sample transfer means 50, 60, 70. Examples of such means include an arm conveyor equipped with sample scooping members that pick up and hold the sample which are rotated or reciprocated mechanically, electrically or magnetically, or with sample grippers or sample adsorbers that grip and hold the sample at their outer peripheral edge by electromagnetic adsorption or vacuum adsorption, for example, a belt conveyor having an endless belt spread between a driving roller and a driven roller, an apparatus for transferring the sample by blow force of gas, and the like. If the processing apparatus 10 is the apparatus which processes the sample by utilizing plasma under a reduced pressure, the sample transfer means 50 is disposed in such a manner that the processed sample can be transferred inside a reduced pressure space without being exposed to the external air. In this case, there are shown disposed in Fig. 1 the sample transfer means 80 which transfers the sample to be processed by the processing apparatus 10 thereto and the sample transfer means 90 for transferring the sample dry-processed by the dry-processing apparatus 40 to a recovery cassette (not shown), for example. Sample transfer means analogous to the sample transfer means 50, 60 are used as these sample transfer means 80 and 90. If the processing apparatus 10 in Fig. 1 processes the sample by utilizing plasma under a reduced pressure, for example, the sample processing atmosphere of the processing apparatus 10 can be put in communication with, and cut off from, the space in which the sample to be processed by the processing apparatus 10 is transferred thereto and the space in which the processed sample is transferred. The sample processing atmosphere of the plasma post-processing apparatus 20, the space in which the processed sample is transferred and the space in which the post-processed sample is transferred can be put in communication with, and cut off from, one another. The space in which the post-processed sample is transferred, the sample wet-processing atmosphere of the wet-processing apparatus 30, the space in which the wet-processed sample is transferred, the sample dry-processing atmosphere of the dry-processing apparatus 40 and the space in which dry-processed sample is transferred may be maintained in communication with one another or may be put in communication with, and cut off from, one another. In Fig. 1, the processing station is disposed in the sample processing atmosphere of the processing apparatus 10. If the sample processing apparatus 10 processes the sample by utilizing plasma under a reduced pressure, the processing station is a sample table (not shown). The sample table (not shown) is disposed as the processing station in each of the processing atmosphere of the plasma post-processing apparatus 20, the wet-processing apparatus 30 and the dry-processing apparatus 40. One or a plurality of samples can be put on each sample table. In the processing apparatus 10 and in the plasma post-processing apparatus 20, each sample table is sometimes used as one of the constituent elements forming the sample processing atmosphere. An embodiment of the present invention will be explained in further detail with reference to Figs. 2 and 3. In Figs. 2 and 3, an apparatus for processing the sample by utilizing plasma under a reduced pressure is used as the processing apparatus in this case. In Figs. 2 and 3, four openings 101a, 101b, 101c and 101d are formed in the top wall of a buffer chamber 100. An exhaust nozzle 102a is disposed on the bottom wall of the buffer chamber 100. One of the ends of an exhaust pipe (not shown) is connected to the exhaust nozzle 102a and its other end, to a suction port of an evacuation apparatus (not shown) such as a vacuum pump. The planar shape of the buffer chamber 100 is substantially L-shaped. The buffer chamber 100 is made of a stainless steel in this case. When the buffer chamber 100 is viewed on a plan view, the openings 101a, 101b, 101c are formed from the major side to minor side of the L shape and the opening 101d is formed on the minor side of the L shape. The openings 101a - 101d have predetermined gaps between the adjacent pairs of them. An arm 81 is disposed rotatably inside the buffer chamber 100. The arm 81 can rotate in one plane in the buffer chamber 100. A sample scooping member 82 is disposed at the rotating end of the arm 81. The sample scooping member 82 has shaped elements opposed in a plane. The orbit of rotation substantially at the center of the sample scooping member 82 is positioned in such a manner as to substantially correspond to the center of each opening 101a, 101b. In other words, the support point of rotation of the arm 81 is positioned so that almost the center of the sample scooping member 82 describes the orbit of rotation described above. The support point of rotation of the arm 81 is positioned at the upper end of a rotary shaft 83 whose upper end projects at that position into the buffer chamber 100, whose lower end projects outside the buffer chamber 100 and which is disposed rotatably on the bottom wall of the buffer chamber 100 while keeping air-tightness. The lower end of the rotary shaft 83 is connected to rotation driving means (not shown) which is disposed outside the buffer chamber 100 in such a manner as to correspond to the bottom wall of the buffer chamber 100. An arm 51 is disposed rotatably inside the buffer chamber 100 at a position different from that of the arm 81 and on the opposite side of the sample path. The arm 51 can rotate in the same plane in the buffer chamber 100 as the arm 81. A sample scooping member 52 is disposed at the rotating end of the arm 51. The planar shape of the sample scooping member 52 is substantially the same as that of the sample scooping member 82. The arm 51 is disposed in such a manner that the orbit of rotation at the center of the sample scooping member 52 corresponds substantially to the center of each opening 101b, 101c, 101d. In other words, the support point of rotation of the arm 51 is positioned at such a position where almost the center of the sample scooping member 52 describes the orbit of rotation described above. The support point of rotation of the arm 51 is positioned at the upper end of a rotary shaft 53 which is disposed rotatably on the bottom wall of the buffer chamber 100 while keeping air-tightness inside the buffer chamber 100 with its upper end projecting at that position into the buffer chamber 100 and with its lower end projecting outside the buffer chamber 100. The lower end of the rotary shaft 53 is connected to a driving shaft of rotation driving means disposed outside the buffer chamber 100 so as to correspond to the bottom wall of the buffer chamber 100, such as a driving shaft of a motor 54. In Fig. 3, a sample table 110 and a cover member 111 are disposed in such a manner as to interpose the opening 101a between them. The sample table 110 has a sample disposition surface on its surface. The planar shape and size of the sample table 100 are such that they can close the opening 101a. The sample table 110 is disposed inside the buffer chamber 100 in such a manner as to be capable of opening and closing the opening 101a and in this case, capable of moving up and down. An elevation shaft 112 has its center of axis at the center of the opening 101a with its upper end projecting into the buffer chamber 100 and with its lower end projecting outside the same and is disposed on the bottom wall of the buffer chamber 100 in such a manner that it can move up and down while keeping air-tightness inside the buffer chamber 100. The sample table 110 is disposed substantially horizontally at the upper end of the elevation shaft 112 with its sample disposition surface being the upper surface. The lower end of the elevation shaft 112 is connected to elevation driving means, such as a cylinder rod of a cylinder 113, which is disposed outside the buffer chamber 100 in such a manner as to correspond to the bottom wall of the latter. A seal ring (not shown) is disposed around the outer periphery of the upper surface of the sample table 110 or the inner surface of the top wall of the buffer chamber 100 opposed the former, that is, on the inner surface of the top wall of the buffer chamber 100 around the opening 101a. A sample delivery member (not shown) is disposed on the sample table 110. The sample delivery member is disposed in such a manner as to be capable of moving up and down between a position lower than the sample disposition surface of the sample table 110 and a position which projects outward from the opening 101a when the opening 101a is closed by the sample table 110. The planar shape and size of the cover member 111 are such that they can close the opening 101a. The cover member 111 is disposed outside the buffer chamber 100 in such a manner as to be capable of opening and closing the opening 101a and in this case, capable of moving up and down. In this case, an elevation shaft 114 is disposed outside the buffer chamber 100 in such a manner as to be capable of moving up and down with its axis being substantially in conformity with that of the elevation shaft 112. The cover member 111 is disposed substantially horizontally at the lower end of the elevation shaft 114. The upper end of the elevation shaft 114 is connected to elevation driving means, such as a cylinder rod of a cylinder 115, which is disposed above the cover member 111 outside the buffer chamber 100. A seal ring (not shown) is disposed around the outer periphery of the lower surface of the cover member 111 or the outer surface of the top wall of the buffer chamber 100 opposed the former, or in other words, around the outer surface of the top wall of the buffer chamber 100 around the opening 101a. The sample table 110 and the cover member 111 are thus doors of an entry airlock of the buffer chamber 100. A discharge tube 11, whose shape is substantially semi-spherical in this case, is shown disposed hermetically on the top wall of the buffer chamber 100 in Fig. 3. The shape and size of the opening of the discharge tube 11 are substantially the same as those of the opening 101b, and the opening of the discharge tube 11 is substantially in agreement with the opening 101b. The discharge tube 11 is made of an electric insulator such as quartz. A waveguide 12a is disposed outside the discharge tube 11 to surround it. A magnetron 13 as microwave oscillation means and the waveguide 12a are connected by a waveguide 12b. The waveguides 12a and 12b are made of an electric conductor. The waveguide 12b has an isolator 12c and a power monitor 12d. A solenoid coil 14 as magnetic field generation means is disposed outside and around the waveguide 12b. A sample table 15 is disposed movably up and down inside the space defined inside the buffer chamber 100 and the discharge tube 11. The axis of an elevation shaft 16 is substantially in agreement with the axis of the discharge tube 11 in this case. The elevation shaft 16 is disposed on the bottom wall of the buffer chamber 100 movably up and down with its upper end projecting into the buffer chamber 100 and with its lower end projecting outside the buffer chamber 100 while keeping air-tightness inside the buffer chamber 100. More details of this part of the apparatus are given in Figs. 5A and 5B, to which reference should be made also. The sample table 15 has a sample disposition surface on its surface. The planar shape and size of the sample table 15 are such that the sample table 15 can penetrate through the opening 101b. The sample table 15 is disposed substantially horizontally at the upper end of the elevation shaft 16 with its sample disposition surface being its upper surface. The lower end of the elevation shaft 16 is connected to elevation driving means, such as a cylinder rod of a cylinder (not shown), which is disposed outside the buffer chamber 100 in such a manner as to correspond to the bottom wall of the same. In this case, the lower end portion of the elevation shaft 16 is connected to a bias power source, for example, a radio frequency power source 18. The radio frequency power source 18 is disposed outside the buffer chamber 100 and is grounded. In this case, the sample table 15 and the elevation shaft 16 are under an electrically connected state but the buffer chamber 100 and the elevation shaft 16 are electrically isolated. A sample delivery member 15a (Fig. 5A) is disposed on the sample table 15. The sample delivery member 15a is disposed at a position below the sample disposition surface of the sample table 15 and in such a manner as to be capable of moving up and down with respect to the sample scooping members 82, 52 when the sample disposition surface of the sample table 15 is moved down below the sample scooping member 82 of the arm 81 and the sample scooping member 52 of the arm 51. The sample table 15 has means for control of the temperature. A heat medium flow path is defined inside the sample table 15, for example, and a cooling medium as a heat medium such as cooling water, liquid ammonium, liquid nitrogen, or the like, or a heating medium such as heating gas is supplied to the flow path. Heat generation means such as a heater, for example, is disposed on the sample table 15. Flanges 120 and 121 are disposed around the sample table 15 and the elevation shaft 16 inside the buffer chamber 100. The inner diameter and shape of each flange 120, 121 are substantially in conformity with those of the opening 101b. The flange 120 is disposed air-tight on the inner surface of the bottom wall of the buffer chamber 100 with the axis of the elevation shaft 16 being substantially its center. The flange 121 is disposed in such a manner as to oppose the flange 120. Metallic bellows 122 as extension-contraction cut means are disposed in such a manner as to bridge these flanges 120 and 121. An elevation shaft 122a is disposed movably up and down with its upper end projecting into the buffer chamber 100 and with its lower end projecting outside the buffer chamber 100 while keeping air-tightness inside the buffer chamber 100. The flange 121 is connected to the upper end of the elevation shaft. The lower end of the elevation shaft is connected to elevation driving means such as a cylinder rod of a cylinder (not shown) disposed outside the buffer chamber 100 in such a manner as to correspond to the bottom wall of the buffer chamber 100. A seal ring is disposed on the upper surface of the flange 121 or the inner surface of the top wall of the buffer chamber 100 opposing the former, or in other words, on the inner surface of the top wall of the buffer chamber 100 around the opening 101b. An exhaust nozzle 102b is disposed on the bottom wall of the buffer chamber 100 more inward than the flange 120. One of the ends of an exhaust pipe (not shown) is connected to the exhaust nozzle 102b and its other end, to the suction port of an evacuation apparatus (not shown) such as a vacuum pump. A switch valve (not shown) and a pressure regulating valve such as a variable resistance value (not shown) are disposed in the exhaust pipe. One of the ends of a gas introduction pipe (not shown) is connected to a processing gas source (not shown) and its other end opens into the discharge tube 11, or the like. A switch valve and a gas flow rate regulator (not shown) are disposed in the gas introduction pipe. In Fig. 3, the plasma post-processing chamber 21 is hermetically disposed on the top wall of the buffer chamber 100. The shape and size of the opening of the plasma post-processing chamber 21 are substantially in agreement with those of the opening 101c and the opening of the plasma post-processing chamber 21 is substantially in agreement with the opening 101c. A sample table 22 is disposed in the space defined by the interior of the buffer chamber 100 and that of the plasma post-processing chamber 21. A support shaft 23 in this case uses the axis of the plasma post-processing chamber 21 as its axis. It is disposed on the bottom wall of the buffer chamber 100 with its upper end projecting into the buffer chamber 100 and with its lower end projecting outside the buffer chamber 100 while keeping air-tightness inside the buffer chamber 100. The sample table 22 has a sample disposition surface on its surface. The planar shape and size of the sample table 22 are smaller than those of the opening 101c in this case. The sample table 22 is disposed substantially horizontally at the upper end of the support shaft 23 with its sample disposition surface being the upper surface. The sample disposition surface of the sample table 22 is positioned below the sample scooping member 52 of the arm 51. A sample delivery member (not shown) is disposed on the sample table 22. In other words, the sample deliver member is disposed movably up and down between a position lower than the sample disposition surface of the sample table 22 and a position higher than the sample scooping member 52 of the arm 51. Flanges 125 and 126 are disposed outside the sample table 22 and the support shaft 23 but inside the buffer chamber 100. The inner diameter and shape of each flange 125, 126 are substantially in conformity with those of the opening 101c. The flange 125 is disposed hermetically on the inner surface of the bottom wall of the buffer chamber 100 substantially coaxial with the axis of the support shaft 23. The flange 126 opposes the flange 125. Metallic bellows as extension-contraction cut means bridge between these flanges 125 and 126. An elevation shaft (not shown) is disposed movably up and down on the bottom wall of the buffer chamber 100 with its upper end projecting into the buffer chamber 100 and with its lower end projecting outside the buffer chamber 100 while keeping air-tightness inside the buffer chamber 100. The flange 126 is connected to the upper end of the elevation shaft. The lower end of the elevation shaft is connected to elevation driving means such as a cylinder rod of a cylinder (not shown) which is disposed outside the buffer chamber 100 so as to correspond to the bottom wall of the buffer chamber 100. A seal ring (not shown) is disposed on the upper surface of the flange 126 or the inner surface of the top wall of the buffer chamber 100 opposing the upper surface of the flange 126, or in other words, on the inner surface of the top wall of the buffer chamber 100 around the opening 101c. An exhaust nozzle 102c is disposed on the bottom wall of the buffer chamber 100 which is more inward than the flange 125. One of the ends of an exhaust pipe (not shown) is connected to the exhaust nozzle 102c and its other end, to the suction port of an evacuation apparatus (not shown) such as a vacuum pump. In Fig. 3, a sample table 130 and a cover member 131 are disposed in such a manner as to interpose the opening 101d between them. This part of the apparatus and its operation are shown in more detail in Figs. 4A-G, to which reference should be made also. The sample table 130 has a sample disposition surface on its surface. The planar shape and size of the sample table 130 are such that the sample table 130 can sufficiently close the opening 101d. The sample table 130 is disposed movably up and down, in this case, inside the buffer chamber 100 in such a manner as to be capable of opening and closing the opening 101d. In this case, an elevation shaft 132 is disposed movably up and down on the bottom wall of the buffer chamber 100 with its upper end projecting into the buffer chamber 100 and with its lower end projecting outside the buffer chamber 100 while keeping air-tightness inside the buffer chamber 100. The sample table 130 is disposed substantially horizontally at the upper end of the elevation shaft 132 with its sample disposition surface being the upper surface. The lower end of the elevation shaft 132 is connected to elevation driving means such as a cylinder rod of a cylinder 133 which is disposed outside the buffer chamber 100 in such a manner as to correspond to the bottom wall of the buffer chamber 100. A seal ring is disposed around the outer peripheral edge of the upper surface of the sample table 130 (as shown) or the inside of the top wall of the buffer chamber 100 opposing the outer peripheral edge, that is, on the inner surface of the top wall of the buffer chamber 100 around the opening 101d. A sample delivery member 130a is disposed on the sample table 130. It is disposed movably up and down between a position lower than the sample disposition surface of the sample table 130 and a position projecting outward from the opening 101d under the state where the opening 101d is closed by the sample table 130. The planar shape and size of a cover member 131 are such that the cover member 131 can open and close the opening 101d. It is disposed movably up and down, in this case, outside the buffer chamber 100. The axis of an elevation shaft 134 is substantially in agreement with that of the elevation shaft 132, in this case. This elevation shaft 134 is disposed movably up and down outside the buffer chamber 100. The cover member 131 is disposed substantially horizontally at the lower end of the elevation shaft 134. The upper end of the elevation shaft 134 is connected to elevation driving means such as a cylinder rod of a cylinder 135 which is disposed at a position above the cover member 131 outside the buffer chamber 100. A seal ring is disposed around the outer peripheral edge of the lower surface of the cover member 131 (as shown) or the outer surface of the top wall of the buffer chamber 100 opposing the former, that is, the outer surface of the top wall of the buffer chamber 100 around the opening 101d. The sample table 130 and the cover member 131 thus constitute doors of an exit airlock for the buffer chamber 100. A cassette table 140 is disposed movably up and down in such a manner as to correspond to the side surface of the L-shaped major side of the buffer chamber 100 outside the buffer chamber 100. A guide 141 is disposed outside the buffer chamber 100 in such a manner as to extend linearly along the side surface of the L-shaped major side in its transverse direction. The edge of this guide 141 on the side of the cassette table 140 is extended so as to correspond to the center of the cassette table 140, in this case. An arm 142 is a linear member in this case, and one of its ends is disposed on the guide 141 in such a manner as to be capable of reciprocation while being guided by the guide 141. A sample scooping member 143 is disposed at the other end of the arm 142. The cassette table 140 is disposed substantially horizontally at the upper end of an elevation shaft 144 with the cassette disposition surface being its upper surface. The lower end of the elevation shaft 144 is connected to elevation driving means 145. The wet-processing chamber 31, the dry-processing chamber 41 and a sample recovery chamber 150 are disposed outside the buffer chamber 100, in this case. They form a unit connectable to and disconnectable from the buffer chamber unit. The wet-processing chamber 31, the dry-processing chamber 41 and the sample recovery chamber 150 are aligned sequentially along the side walls on the side of the openings 101c, 101d of the buffer chamber 100 in this case. Among them, the wet-processing chamber 31 is disposed at the position closest to the opening 101d. A sample table 32 is disposed inside the wet-processing chamber 31. A support shaft 33 is disposed rotatably on the bottom wall of the wet-processing chamber 31 with its upper end projecting into the wet-processing chamber 31 and with its lower end projecting outside the wet-processing chamber 31 in such a manner as to keep air-tightness and water-tightness inside the wet-processing chamber 31 in this case. The lower end of the support shaft 33 is connected to a rotary shaft of a motor (not shown) as rotation driving means, for example. The sample table 32 has a sample disposition surface on its surface. The sample table 32 is disposed substantially horizontally at the upper end of the support shaft 33 with the sample disposition surface being its upper surface. The sample disposition surface of the sample table 32 is positioned below a sample scooping member 52 of an arm 51. The sample table 32 is equipped with a sample delivery member (not shown). The sample delivery member is disposed movably up and down between a position below the sample disposition surface of the sample table 32 and a position above the sample scooping member 52 of the arm 61. A processing liquid feed pipe (not shown) is disposed inside the wet-processing chamber 31 in such a manner as to be capable of supplying a processing solution to the sample disposition surface of the sample table 32. A processing solution feed apparatus (not shown) is disposed outside the wet-processing chamber 31. The processing solution feed pipe is connected to this processing solution feed apparatus. A waste liquor discharge pipe (not shown) is connected to the wet-processing chamber 31. In this case, inert gas introduction means (not shown) for introducing an inert gas such as nitrogen gas into the wet-processing chamber 31 are provided. In Figs. 2 and 3, the arm 61 is disposed rotatably so as to correspond to the sample tables 130 and 32. The arm 61 can rotate on the same plane outside the buffer chamber 100. The sample scooping member 62 is disposed at the rotating end of the arm 61. The planar shape of the sample scooping member 62 is substantially the same as those of the sample scooping members 52 and 82. The arm 61 is disposed in such a manner that the orbit of rotation of the center of the sample scooping member 62 corresponds substantially to the centers of the sample tables 130 and 32, respectively. In other words, the support point of rotation of the arm 61 is positioned to a position where almost the center of the sample scooping member 62 describes the orbit of rotation described above. The support point of rotation of the arm 61 is disposed at the upper end of the rotary shaft 63 disposed rotatably outside the buffer chamber 100 and outside the wet-processing chamber 31. The lower end of the rotary shaft 63 is connected to the driving shaft of a motor 64, for example, as rotation driving means. An opening 34 is bored on the side wall of the wet-processing chamber 31 that corresponds to the rotation zones of the arm 61 and sample scooping member 62. The size and position of the opening 34 are such that they do not prevent the entry and exit operations of the arm 61 and sample scooping member 62 with respect to the wet-processing chamber 31. The opening 34 can be opened and closed by switch means (not shown) in this case. A sample table 42 is disposed inside the dry-processing chamber 41. The sample table 42 has a sample disposition surface on its surface. It is disposed substantially horizontally on the bottom wall of the dry-processing chamber 41. A heater 43 is used as heating means in this case. The heater 43 is disposed on the back of the sample table 42 in such a manner as to be capable of heating the sample table 42. It is connected to a power source (not shown). The sample disposition surface of the sample table 42 is positioned below a sample scooping member 72 of an arm 71. A sample delivery member (not shown) is disposed on the sample table 42. In other words, the sample delivery member is disposed movably up and down between a position below the sample disposition surface of the sample table 42 and a position above the sample scooping member 72 of the arm 71. In this case, the sample delivery member, too, is capable of moving up and down between a position below the sample disposition surface of the sample table 32 and a position above the sample scooping member 72 of the arm 71. In this case, there is provided inert gas introduction means (not shown) for introducing an inert gas such as nitrogen gas into the dry-processing chamber 41. A cassette table 151 is disposed inside a sample recovery chamber 150. An elevation shaft 152 is disposed movably up and down on the bottom wall of the sample recovery chamber 150 with its upper end projecting into the sample recovery chamber and with its lower end projecting outside the sample recovery chamber 150. The cassette table 151 is disposed substantially horizontally at the upper end of the elevation shaft 152 with its cassette disposition surface being the upper surface. The lower end of the elevation shaft 152 is disposed on elevation driving means 153. In this case, inert gas introduction means (not shown) are arranged so as to introduce an inert gas such as nitrogen gas into the sample recovery chamber 150. In Fig. 2, a guide 73 is disposed along the inner wall surface of each of the wet-processing chamber 31, the dry-processing chamber 41 and the sample recovery chamber 150. The guide 73 has a linear shape. In other words, the line passing through the centers of the sample tables 32, 42 and the cassette table 151 is a straight line and the guide 73 is disposed substantially parallel to this line. The arm 71 is a linear member in this case and one of its ends is disposed on the guide 73 so as to be capable of reciprocation while being guided by the guide 73. A sample scooping member 72 is disposed at the other end of the arm 71. Openings (not shown) are formed on the side walls of the wet- and dry-processing chambers 31, 41 and the sample recovery chamber 150 corresponding to the reciprocation zones of the arm 71 and the sample scooping member 72, respectively, so that the arm 71 and the sample scooping member 72 are not prevented from coming into and out from the wet-processing chamber 31, the dry-processing chamber 41 and the sample recovery chamber 150, respectively. These openings can be opened and closed by switch means (not shown), respectively. An opening for loading and discharging a cassette and a door (not shown) are disposed in the sample recovery chamber 150. A cassette 160 is disposed on a cassette table 140. It can store a plurality of samples 170 one by one stacked in the longitudinal direction, and one of its side surfaces is open in order to take out the samples 170 from the cassette 160. The cassette 160 is disposed on the cassette table 140 with its sample take-out side surface facing the opening 101a. The cassette table 140 supporting the cassette 160 thereon is moved down, for example, under this state. Descent of the cassette table 140 is stopped at the position where the sample 170 stored at the uppermost stage of the cassette 160 can be scooped up by the sample scooping member 143. The operation of this apparatus is as follows:- The openings 101a and 101d are closed by the sample tables 110 and 130, respectively, and when an evacuation apparatus is operated under this state, the inside of the buffer chamber 100 is evacuated to a predetermined pressure. Thereafter, the cover member 111 is moved up and this ascent is stopped at the position where the sample scooping member 143 for scooping up the sample 170 is not prevented from reaching the opening 101a. The arm 142 is moved towards the cassette 160 under this state and this movement is stopped at the position where the sample scooping member 143 corresponds to the back of the sample 170 stored at the lowermost stage of the cassette 160, for example. Thereafter the cassette 160 is moved up by the distance at which the sample scooping member 143 can scoop up the sample 170. In this manner the sample 170 is scooped up on its back by the sample scooping member 143 and delivered to the sample scooping member 143. When the sample scooping member 143 receives the sample 170, the arm 142 is moved towards the opening 101a. This movement of the arm 142 is stopped at the point where the sample scooping member 143 having the sample 170 reaches the position corresponding to the opening 101a. Under this state the sample delivery member of the sample table 110 is moved up so that the sample 170 is delivered from the sample scooping member 143 to the sample delivery member. Thereafter, the sample scooping member 143 is retreated to the position, at which it does not prevent descent of the sample delivery member receiving the sample 170, by the movement of the arm 142. Thereafter the sample delivery member having the sample 170 is moved down and the sample 170 is delivered from the sample delivery member to the sample table 110 and placed on its sample disposition surface. Then, the cover member 111 is moved down. Accordingly, the opening 101a is closed by the cover member 111 and its communication with the outside is cut off. Thereafter, the sample table 110 having the sample 170 is moved down and this downward movement is stopped at the point where the sample table 110 reaches the position at which the sample 170 can be exchanged between the sample delivery member of the sample table 110 and the sample scooping member 82 of the arm 81. The flange 121 and the metallic bellows 122 are moved down by the shaft 122a lest they prevent the rotation of the arm 81 and the sample scooping member 82 and the sample table 15 is moved down to the position where its sample delivery member 15a and the sample scooping member 82 of the arm 81 can exchange the sample 170 between them. Under this state the sample delivery member 15a is moved up so that it can exchange the sample 170 with the sample scooping member 82 of the arm 81. The arm 81 is then rotated in the direction of the sample table 110 and the sample scooping member 82 is located at the position which corresponds to the back of the sample 170 held by the sample delivery member of the sample table 110 and at which it can scoop up the sample 170. Under this state the sample delivery member of the sample table 110 is moved down and the sample 170 is delivered to the sample scooping member 82 of the arm 81. After scooping up the sample 170, the sample scooping member 82 is rotated in the direction of the sample table 15 while passing between the flange 121 and the inner surface of the top wall of the buffer chamber 100 as the arm 81 is rotated in the direction of the sample table 15. The sample table 110 is moved up once again so that the opening 101a is closed by the sample table 110. The rotation of the sample scooping member 82 described above is stopped when the sample scooping member 82 reaches the position where the sample 170 can be exchanged between the sample scooping member 82 and the sample delivery member 15a of the sample table 15. The sample delivery member 15a of the sample table 15 is moved up under this stage so that the sample 170 is delivered from the sample scooping member 82 to the sample delivery member 15a of the sample table 15. Thereafter, when the arm 81 is rotated to the position betwen the openings 101a and 101b, the sample scooping member 82 is brought into the stand-by state to prepare for the next delivery of the sample between the sample tables 110 and 15. Thereafter the flange 121 and the metallic bellows 122 are moved up by the shaft 122a so that communication of the buffer chamber 100 in the metallic bellows 122 and the inside of the discharge tube 11 with the interior of the buffer chamber 100 outside the metallic bellows 122 is cut off. When the sample delivery member 15a of the sample table 15 receiving the sample 170 is moved down, the sample 170 is delivered from the sample delivery member 15a of the sample table 15 to the sample table 15 and is placed on the sample disposition surface of the sample table 15. After receiving the sample 170 on its sample disposition surface, the sample table 15 is moved up to a predetermined position (see Fig. 5A) inside the space where communication with the buffer chamber 100 outside the metallic bellows 122 is cut off. A predetermined processing gas is introduced at a predetermined flow rate from the processing gas source into the space in which communication with the buffer chamber 100 outside the metallic bellows 122 is cut off. Part of the processing gas introduced into this space is exhausted outside the space due to the operations of the evacuation apparatus and the variable resistance valve. In this manner the pressure of this space is controlled to a predetermined pressure of etching treatment. The magnetron 13 oscillates a 2.45 GHz microwave in this case. The microwaves thus oscillated propagate through the waveguides 12b and 12a through the isolator 12c and the power monitor 12d and are absorbed by the discharge tube 11, thereby generating a radio frequency field containing the microwave. At the same time, the solenoid coil 14 is operated to generate a magnetic field. The processing gas existing inside the space where communication with the buffer chamber 100 outside the metallic bellows 122 is cut off is converted to plasma due to the synergistic operations of the radio frequency field containing the microwave and the magnetic field. The sample 170 disposed on the sample table 15 is etched by utilizing this plasma. Thereafter the sample table 15 and the flange 121 are moved downwardly (Fig. 5B) and the sample delivery member 15a is moved upwardly. The rotation of the sample scooping member 52 is stopped at the point when the sample scooping member 52 reaches the position where the etched sample 170 can be exchanged between the sample scooping member 52 and the sample delivery member 15a of the sample table 15. The sample delivery member 15a of the sample table 15 is moved down under this state and the etched sample 170 is delivered from the sample delivery member 15a of the sample table 15 to the sample scooping member 52 of the arm 51. After scooping up the etched sample 170, the sample scooping member 52 is rotated in the direction of the sample table 22 while passing between the flange 121 and the inner surface of the top wall of the buffer chamber 100 as the arm 51 is rotated in the direction of the sample table 22. A new sample in the cassette 160 is placed by the operations described above on the sample table 15 from which the etched sample 170 is removed. The new sample placed on the sample table 15 is subsequently etch-processed due to the operations described above. Before, or during, the rotation of the sample scooping member 52 having the etched sample 170, the flange 126 and the metallic bellows 127 are moved down lest they prevent the rotation of the arm 51 and the sample scooping member 52. The radio frequency power source 18 is operated at the time of etching of the sample 170, a predetermined radio frequency power is applied to the sample table 15 through the elevation shaft 16 and a predetermined radio frequency bias is applied to the sample 170. The sample 170 is adjusted to a predetermined temperature through the sample table 15. The operations of the magnetron 13, solenoid coil 14 and radio frequency power source 18, and the like, are stopped at the point where etching of the sample 170 is complete and introduction of the processing gas into the space whose communication with the inside of the buffer chamber 100 outside the metallic bellows 122 is cut off is stopped. After evacuation of this space is conducted sufficiently, the switch valve constituting the evacuation means is closed. Thereafter, the flange 121 and the metallic bellows 122 are moved down so as not to prevent the rotation of the arm 51 and the sample scooping member 52 and the sample table 15 is moved down to the position where its sample delivery member and the sample scooping member 52 of the arm 51 can exchange the etched sample 170. The sample delivery member of the sample table 15 is then moved up so that it can exchange the etched sample 170 with the sample scooping member 52 of the arm 51. When the arm 51 is rotated under this state in the direction of the sample table 15, the sample scooping member 52 passes between the flange 121 and the inner surface of the top wall of the buffer chamber 100 and is rotated in the direction of the sample table 15. The sample scooping member 52 having the etched sample 170 is rotated in the direction of the sample table 22 while passing between the flange 126 and the inner surface of the top wall of the buffer chamber 100 when the arm 51 is rotated further in the direction of the sample table 22. Such a rotation of the sample scooping member 52 is stopped when the sample scooping member 52 reaches the position where the etched sample 170 can be exchanged between the sample scooping member 52 and the sample delivery member of the sample table 22. The sample delivery member of the sample table 22 is moved up under this state and the etched sample 170 is delivered from the sample scooping member 52 to the sample delivery member of the sample table 22. Thereafter the sample scooping member 52 is rotated to the position between the openings 101c and 101d and is brought into the stand-by state. Thereafter, the flange 126 and the metallic bellows 127 are moved up and the interior of the buffer chamber 100 inside the metallic bellows 127 and the interior of the plasma post-processing chamber 21 are cut off from communication with the interior of the buffer chamber 100 outside the metallic bellows 127. When the sample delivery member of the sample table 22 receiving the etched sample 170 is moved down, the etched sample 170 is delivered from the sample delivery member of the sample table 22 to the sample table 22 and is placed on the sample disposition surface of the sample table 22. The post-processing gas is introduced at a predetermined flow rate into the space whose communication with the interior of the buffer chamber 100 outside the metallic bellows 127 is cut off, and part of the post-processing gas is exhausted from this space. In this manner the pressure of this space is adjusted to a predetermined post-processing pressure. Thereafter, the post-processing gas existing in this space is converted in this case to plasma due to the operation of the radio frequency field containing the microwaves. The etched sample 170 placed on the sample table 22 is post-processed by utilizing this plasma. After the post-processing of the etched sample is thus complete, introduction of the post-processing gas into the space, which is cut off from the interior of the buffer chamber 100 outside the metallic bellows 127, and conversion to plasma of the post-processing gas are stopped. Then, the flange 126 and the metallic bellows 127 are moved down lest they prevent the rotation of the arm 51 and the sample scooping member 52. The sample scooping member 52 that is under the stand-by state between the openings 101c and 101d is rotated to the position which does not prevent the rise of the post-processed sample 170 on the sample table 22 and which has passed the sample table 22. The sample delivery member of the sample table 22 is moved up under this state so that the post-processed sample 170 placed on the sample table 22 is delivered to the sample delivery member of the sample table 22. Then, when the arm 51 is rotated in the direction of the sample table 22, the sample scooping member 52 is located to the position at which it can scoop up the sample 170, so as to correspond to the back of the post-processed sample 170 held by the sample delivery member of the sample table 22. The sample delivery member of the sample table 22 is moved down under this state and the post-processed sample 170 is delivered from the sample delivery member of the sample table 22 to the sample scooping member 52 of the arm 51. After receiving the post-processed sample 170, the sample scooping member 52 is rotated in the direction of the sample table 130 while passing between the flange 126 and the inner surface of the top wall of the buffer chamber 100 when the arm 51 is rotated in the direction of the sample table 130. After the post-processed sample 170 is removed, the next etched sample is placed on the sample table 22 and is then post-processed by utilizing plasma. Before, or during, the rotation of the sample scooping member 52 having the post-processed sample 170 as described above, the sample table 130 is moved down to the position at which its sample delivery member 130a and the sample scooping member 52 of the arm 51 can exchange the post-processed sample 170. The rotation of the sample scooping member 52 is stopped when it reaches the position at which the post-processed sample 170 can be exchanged between the sample scooping member 52 and the sample delivery member 130a of the sample table 130 (Fig. 4A). The sample delivery member 130a of the sample table 130 is moved up under this state so that the post-processed sample 170 is delivered from the sample scooping member 52 to the sample delivery member 130a of the sample table 130 (Fig. 4B). Thereafter, when the arm 51 is rotated to the position between the openings 101b and 101c, the sample scooping member 52 is brought into the stand-by state at that position in order to transfer the next etched sample to the sample table 22. After receiving the post-processed sample 170, the sample delivery member 130a of the sample table 130 is moved down. Accordingly, the post-processed sample 170 is delivered from the sample delivery member 130a of the sample table 130 to the sample table 130 and placed on its sample disposition surface (Fig. 4C). The sample table 130 having the post-processed sample 170 is moved up so that the opening 101d is closed air-tight by the sample table 130 (Fig. 4D). The cover member 131 is moved up under this state. The rise of the cover member 131 is stopped when it reaches the position (Fig. 4E) at which the rise of the sample delivery member 130a of the sample table 130 is not prevented and moreover, the sample scooping member 62 of the arm 61 is not prevented from reaching the position where it can receive the post-processed sample 170 from the sample delivery member 130a of the sample table 130. Under this stage, the sample delivery member 130a of the sample table 130 is first moved up. Accordingly, the post-processed sample 170 is delivered from the sample table 130 to its sample delivery member 130a (Fig. 4F). Next, when the arm 61 is rotated in the direction of the sample table 130, the sample scooping member 62 is rotated in the direction of the sample table 130. This rotation of the sample scooping member 62 is stopped when it reaches the position where the post-processed sample 170 can be exchanged between it and the sample delivery member 130a of the sample table 130 or in other words, the position which corresponds to the back of the post-processed sample 170 held by the sample delivery member 130a of the sample table 130 (Fig. 4G). The sample delivery member 130a of the sample table 130 is then moved down so that the post-processed sample 170 is delivered from the sample delivery member 130a of the sample table 130 to the sample scooping member 62. After receiving the post-processed sample 170, the sample scooping member 62 is rotated towards the sample table 32 inside the wet-processing chamber 31 when the arm 61 is rotated in the direction of the wet-processing chamber 31. After delivering the post-processed sample 170 to the sample scooping member 62, the sample delivery member 130a of the sample table 130 is further moved down to the position which is below the sample disposition surface of the sample table 130. The cover member 131 is thereafter moved down and the opening 101d is closed air-tight by the cover member 131. The sample table 130 is again moved down under this state and the next post-processed sample is delivered to and placed on this sample table 130. The rotation of the sample scooping member 62 having the post-processed sample 170 is stopped when it reaches the position at which it can exchange the post-processed sample 170 between it and the sample delivery member of the sample table 32. The sample delivery member of the sample table 32 is moved up under this state. Accordingly, the post-processed sample 170 is delivered from the sample scooping member 62 to the sample delivery member of the sample table 32. After delivering the post-processed sample 170, the sample scooping member 62 is moved outside the wet-processing chamber 31 in order to prepare for acceptance of the next post-processed sample. The opening 34 is then closed. The sample delivery member of the sample table 32 is moved down after receiving the post-processed sample 170. Accordingly, the post-processed sample 170 is delivered from the sample delivery member of the sample table 32 to the sample table 32 and is placed on its sample disposition surface. The processing solution is then supplied at a predetermined flow rate from the processing solution feed apparatus to the processed surface of the post-processed sample 170 placed on the sample table 32 through the processing solution feed pipe. At the same time, the post-processed sample 170 is rotated by the operation of the motor. In this manner, wet-processing of the post-processed sample 170 is executed. Nitrogen gas, for example, is introduced into the wet-processing chamber 31 by the inert gas introduction means so that wet-processing is carried out in the nitrogen gas atmosphere. The waste liquor generated by this wet-processing is discharged outside the wet-processing chamber 31 through the waste liquor discharge pipe. After such a wet-processing is complete, the supply of the processing solution, the rotation of the sample 170, and the like, are stopped, and the sample delivery member of the sample table 32 is moved up. During this rise, the wet-processed sample 170 is delivered from the sample table 32 to its sample delivery member. The rise of the sample delivery member receiving the wet-processed sample 170 is stopped at the position where this sample 170 can be exchanged between the sample delivery member and the sample scooping member 72. The sample scooping member 72 is moved under this state towards the sample table 32. This movement is stopped when the sample scooping member 72 reaches the position where the wet-processed sample 170 can be exchanged between the sample scooping member 72 and the sample delivery member of the sample table 32. The sample delivery member of the sample table 32 is then moved down. Accordingly, the wet-processed sample 170 is delivered to the sample scooping member 72. After the wet-processed sample 170 is removed, the sample delivery member of the sample table 32 prepares for the acceptance of the next post-processed sample. The sample scooping member 72 having the wet-processed sample 170 is further moved to the dry-processing chamber 41 from the wet-processing chamber 31 passing through the opening towards the sample table 42 through the arm 71. This movement is stopped when the sample scooping member 72 reaches the position at which the wet-processed sample 170 can be exchanged between the sample scooping member 72 and the sample delivery member of the sample table 42. The sample delivery member of the sample table 42 is then moved up. Accordingly, the wet-processed sample 170 is delivered to the sample delivery member of the sample table 42. After the wet-processed sample 170 is removed, the sample scooping member 72 is once moved back and the sample delivery member of the sample table 42 is moved down. Accordingly, the wet-processed sample 170 is delivered from the sample delivery member of the sample table 42 to the sample table 42 and is placed on its sample disposition surface. The sample table 42 is heated externally by supply of power to the heater 43 and the wet-processed sample 170 is heated through the sample table 42. The temperature of the wet-processed sample 170 is controlled to a predetermined temperature by adjusting the feed quantity to the heater 43. Thus the wet-processed sample 170 is dry-processed. Nitrogen gas, for example, is introduced into the dry-processing chamber 41 by the inert gas introduction means and dry-processing is carried out in the nitrogen gas atmosphere. After dry-processing is thus complete, the sample delivery member of the sample table 42 is moved up. During this rise, the dry-processed sample 170 is delivered from the sample table 42 to its sample delivery member. The rise of the sample delivery member of the sample table 42 receiving the dry-processed sample 170 is stopped when the dry-processed sample 170 can be exchanged between it and the sample scooping member 72. Under this state, the sample scooping member 72 is again moved towards the sample table 42 through the arm 71. This movement is stopped when the sample scooping member 72 reaches the position at which the dry-processed sample 170 can be delivered between the sample scooping member 72 and the sample delivery member of the sample table 42. The sample delivery member of the sample table 42 is then moved down. Accordingly, the dry-processed sample is transferred to the sample scooping member 72. The sample delivery member of the sample table 42 from which the dry-processed sample 170 is removed prepares for acceptance of the next wet-processed sample. The sample scooping member 72 having the dry-processed sample 170 is further moved from the dry-processing chamber 41 to the sample recovery chamber 150 through the opening towards the cassette table 151 through the arm 71. This movement is stopped when the sample scooping member 72 reaches the position where the dry-processed sample 170 can be delivered between it and the cassette 161 placed on the cassette table 151. The cassette 161 has a plurality of storage grooves in the direction of height, for example, and is positioned so that the uppermost groove can accept and store the sample. The cassette 161 is intermittently moved down by a predetermined distance under this state. Accordingly, the dry-processed sample is supported by the uppermost groove of the cassette 161 and is recovered and stored therein. Nitrogen gas, for example, is introduced into the sample recovery chamber 150 by the inert gas introduction means so that the dry-processed sample 170 is stored in the nitrogen gas atmosphere and is once preserved in the sample recovery chamber 150. Recovery of the dry-processed samples into the cassette 161 is sequentially conducted and after this recovery is complete, the cassette 161 is discharged outside the sample recovery chamber 150. The sample thus taken out from the sample recovery chamber 150 while stored in the cassette 161 is transferred to the next step. EXAMPLE The following sample is prepared several times. First, a 3,000 A-thick silicon dioxide film 172 is formed on a Si substrate 171 such as shown in Fig. 6, a laminate wiring of a TiW layer 173 and an Al-Cu-Si film 174 is formed on the former and a photo-resist 175 is used as a mask. This sample is processed by use of the apparatus shown in Figs. 2 to 5. The etching conditions are BCl 3 + Cl 2 as the processing gas, with a flow rate of the processing gas of 150 sccm (standard cm 3 per minute), a processing pressure of 16 mTorr, a microwave output of 600 W and a radio-frequency bias of 60 W. The samples which are passed through all the subsequent steps without any processing after etching are referred to as (A), those which are etched, plasma post-processed but are not passed through the wet- and dry-processings are referred to as (B), those which are subjected to the predetermined processings at all the steps are referred to as (D) and those which are not plasma post-processed after etching but are wet- and dry-processed are referred to as (C). The corrosion-proofing effects of these samples are then compared. The processing conditions in the plasma post-processing chamber are O 2 + CF 4 as the processing gas, with a flow rate of the processing gas of 400 sccm (O 2 ) and 35 sccm (CF 4 ) and a processing pressure of 1.5 Torr, and the plasma is generated by use of a 2.45 GHz microwave. In this case, the plasma post-processing is mainly intended to ash (remove) the photo-resist and to remove chlorides remaining on the protective film on the pattern sidewall and the pattern bottom portion, and ashing is conducted for about 30 seconds and additional processing under the same condition is conducted for about one minute. In wet-processing, spinning water wash treatment with pure water is conducted for one minute and spinning drying is conducted for 30 seconds. Furthermore, the sample table is heated to 150°C in the nitrogen gas atmosphere and the wet-processed sample is left standing for the minute for dry-processing. When those samples (B) which are etched and then plasma post-processed but are not passed through the wet-processing, that is, water washing treatment and dry-processing, are observed through an optical microscope, spot-like matters analogous to corrosion can be observed within about one hour. Accordingly, they are observed in further detail by SEM. Fan-like corrosion products 180 starting from the boundary between the TiW layer and the Al-Cu-Si layer are observed as shown in Fig. 7. Even though the mixing ratio of CF 4 with respect to O 2 is changed to from 5 to 20%, the processing pressure is changed to from 0.6 to 2 Torr and the sample temperature is raised to 250°C, corrosion analogous to that described above is observed within a few hours in each case. It is therefore believed that particularly in a laminate layer wiring, or alloy wiring, containing different kinds of metals having mutually different ionization potentials, corrosion is generated and accelerated by so-called electrolytic corrosion due to battery operation. To sufficiently prevent the occurrence of such corrosion, it has been found that plasma post-processing alone after etching is not sufficient and even limited amounts of chlorine components must be removed completely. As described above, therefore, processing was carried out under various conditions to examine the time till the occurrence of corrosion after processing. The result is shown in Fig. 8. As can be seen from Fig. 8, in the case of wiring materials such as the laminate layer wiring in which corrosion is vigorous, the plasma post-processing such as resist ashing after etching, or water washing processing and drying processing after etching without carrying out plasma post-processing cannot provide a sufficient corrosion-proofing effect. A high corrosion-proofing effect for more than 30 hours can only be obtained by carrying out in series the etch-processing, the plasma post-processing such as ashing of the resist, the water washing processing and the dry-processing. Besides the washing process described above, the same effect of inhibition of corrosion can be obtained by passivation processing with a mixture of nitric acid and hydrogen fluoride or nitric acid, which also serves to remove any residues after plasma etching, before the water washing processing. In order to remove the reactive products on the pattern sidewall that cannot be removed sufficiently by the plasma post-processing, it is advisable to conduct liquid processing by use of a weakly alkaline solution or a weakly acidic solution (e.g. acetic acid) after plasma post-processing subsequent to etching and then to carry out the water washing processing and dry-processing. In this manner, the chlorine components can be removed more completely and the corrosion-proofing effect can be further improved. In the embodiment described above, the time till completion of the wet-processing of the plasma post-processed sample is limited to about one hour because corrosion occurs within about one hour as shown in Fig. 8 in the case of the sample shown in Fig. 6. However, wet-processing is preferably completely as quickly as possible. In other words, the plasma post-processed sample is preferably transferred immediately after completion of plasma post-processing from the plasma post-processing apparatus to the wet-processing apparatus. Though the plasma post-processed sample is transferred inside the atmosphere in the embodiment described above, it may be transferred in vacuum or in an inert gas atmosphere. Transfer in such an atmosphere is extremely effective when the time from plasma post-processing till the start of wet-processing is longer than the corrosion occurrence time in the atmosphere, for example. In such a case, means may be disposed between the plasma post-processing apparatus and wet-processing apparatus for preserving the plasma post-processed sample in vacuum or in the inert gas atmosphere. Fig. 9 explains a second embodiment of the present invention. The difference of this embodiment from the first embodiment shown in Fig. 1 lies in that a passivation-processing apparatus 190 is additionally disposed on the downstream side of the dry-processing apparatus 40. In this case, the sample transfer means 90 has the function of transferring the dry-processed sample from the dry-processing chamber (not shown) of the dry-processing apparatus to a passivation-processing chamber (not shown) of the passivation-processing apparatus 190. Additionally, sample transfer means 200 for transferring the passivated sample to a recovery cassette (not shown), for example, is disposed. Like reference numerals are used to identify like constituents as in Fig. 1 and their explanation will be omitted. In Fig. 9, the etched, plasma post-processed sample (not shown) is transferred into the wet-processing chamber (not shown) of the wet-processing apparatus 30 by the sample transfer means 60 and is placed on the sample disposition surface of the sample table (not shown) as the wet-processing station inside the wet-processing chamber. The plasma post-processed sample placed on the sample table in the wet-processing chamber is subjected to development solution processing. Residues, and the reactive products on the pattern sidewall, after etching are completely removed by such wet-processing. If the sample contains Al as its component, Al, too, is partly dissolved. When such a sample is dry-processed and taken out into the atmosphere, for example, oxidation as a form of corrosion will occur disadvantageously. Therefore, the sample subjected to development and dry-processed in the dry-processing chamber of the dry-processing apparatus 40 is transferred into the passivation-processing chamber of the passivation-processing apparatus 190 and is placed on the sample disposition surface of the sample table (not shown) as the processing station in the passivation-processing apparatus 190. Gas plasma for passivation-processing or oxygen gas plasma in this case is generated in or introduced into the passivation-processing chamber. Ozone may be used instead of oxygen. The dry-processed sample placed on the sample table in the passivation-processing chamber is passivation-processed by the oxygen gas plasma. The passivation-processed sample is transferred from the passivation-processing chamber to the recovery cassette by the sample transfer means and recovered and stored therein. Passivation-processing may use nitric acid, besides the chemicals described above. Since the present invention can sufficiently remove the corrosive materials generated by etching of the sample, it provides the effect that corrosion of the sample after etching can be prevented sufficiently irrespective of the type of sample.

Claims: A method of processing a sample which comprises a substrate and on said substrate a layer which is subjected to the etching of step (i), the method comprising the steps of: (i) etching the sample by means of an etching plasma formed using a chlorine-containing gas, the etching being performed through a mask on said sample, (ii) after step (i), treating the sample by means of a second plasma, to effect removal of said mask and to remove residual corrosive compounds formed in step (i), said second plasma being formed in a gas atmosphere which is different from that of the etching plasma, characterised by (iii) contacting a surface of said sample exposed by steps (i) and (ii) with at least one aqueous liquid in order to effect at least one of (a) removal of residual corrosive compounds from step (i) and (b) passivation of said surface exposed by steps (i) and (ii), and (iv) after step (iii), drying the sample, said layer which is subjected to etching being said layer being selected from (a) a laminate comprising metals of different ionization tendencies and (b) an alloy of metals of different ionization tendencies. A method according to claim 1 wherein step (ii) is performed in a different chamber from step (i). A method according to claim 1 or claim 2 wherein said plasma of step (ii) is formed in a gas atmosphere containing oxygen. A method according to any one of claims 1 to 3 wherein step (iii) comprises, to effect removal of residual corrosive compounds from step (i), (a) washing with water, (b) washing with an alkaline liquid and thereafter with water, (c) washing with an acidic liquid and thereafter with water, or (d) washing first with a mixture of nitric acid and hydrofluoric acid and thereafter with water. A method according to any one of claims 1 to 3 wherein step (iii) comprises passivation effected by one of (a) a mixture of with nitric acid and hydrogen fluoride and (b) nitric acid. A method according to any one of claims 1 to 5 wherein said step (iii) is performed in an inert gas atmosphere. A method according to any one of claims 1 to 6 wherein said step (iv) is performed in an inert gas atmosphere. A method according to any one of claims 1 to 7 including subjecting said sample to passivation of said surface after step (iv). A method according to any one of claims 1 to 8 wherein said layer which is etched in step (i), is selected from laminates of at least two films made of Al, Cu, W, Ti, Mo, other refractory metals, alloys thereof (including alloys containing Si), silicides of refractory metals, TiN and TiW, Apparatus for processing a sample, comprising (i) means (10; 11-14) for effecting plasma etching of said sample, including supply means adapted to supply a first plasma-forming gas for the plasma etching, (ii) means (20; 21) for effecting plasma treatment of said sample after the plasma etching, including supply means for supplying a second plasma-forming gas for the plasma treatment, said second gas being different from said first gas, characterized by (iii) means (30; 31) for contacting a surface of the sample exposed by the plasma etching and the plasma treatment with a liquid adapted to effect at least one of (a) removal of residual corrosive compounds formed in the plasma etching and (b) passivation of said surface, and (iv) means (41) for drying said sample following contact with said liquid. Apparatus according to claim 10 wherein said means for plasma etching comprises a first chamber (12) and means (13, 14) for forming a plasma therein, and said means for effecting plasma treatment comprises a second chamber (21), which is different from said first chamber, and means for forming a plasma therein. Apparatus according to claim 11 wherein said means for plasma etching is magnetic field-type microwave plasma etching apparatus. Apparatus according to claim 11 or claim 12 wherein said means for plasma treatment is non-magnetic field-type microwave plasma etching apparatus. Apparatus according to any one of claims 10 to 13 which comprises first and second units which are detachable from each other, said first unit (100) including said plasma etching means (11-14) and said means (21) for effecting plasma treatment, and said second unit including said means (31) for contacting with liquid and said drying means (41), the apparatus further including means (61) for transferring said sample from said first unit to said second unit. Apparatus according to any one of claims 10 to 14 having a sample receiving station (160) for receiving a sample to be processed and a sample discharge station (161) for discharging said sample after the processing, said sample receiving station and said sample discharge station being on the same side of the apparatus. Apparatus according to claim 11 having a sample transfer station (15) between said means (21) for effecting plasma treatment and said means (31) for contacting with liquid, and wherein said transfer means (51) comprises a rotating arm adapted to transfer said sample from said first plasma chamber (12) to said second plasma chamber (21) and from said second plasma chamber (21) to said transfer station (15). Apparatus according to any one of claims 10 to 16 having means (190) for applying passivating liquid for passivating said surface of said sample after drying thereof by said drying means (41). Apparatus according to any one of claims 10 to 17 having transfer means (52,130,61) for transferring said sample between said means (20,21) for effecting plasma treatment after plasma etching and said means (30,31) for contacting the sample with said liquid, while maintaining reduced pressure in said means (20,21) for effecting plasma treatment after plasma etching. Apparatus according to claim 10, adapted for sequentially processing samples (170) one-by-one from a supply cassette (160) to a discharge cassette (161), which cassettes hold a plurality of said samples, each sample having a metal layer and a resist layer on the metal layer, said means (10; 11-14) for plasma etching effecting etching of said metal and resist layers, said means (20;21) for plasma treatment effecting ashing of said resist layer, said apparatus further including:- first transfer means (142, 110, 81) for transferring each said sample in said supply cassette (160) to said means (10; 11-14) for plasma etching one-by-one; second transfer means (52) for transferring each said sample from said means (10; 11-14) for plasma etching to said means (20; 21) for plasma treatment one-by-one; third transfer means (52, 130, 61) for transferring each said sample from said means (20; 21) for plasma treatment to said means (30; 31) for contacting said sample with said liquid one-by-one; and fourth transfer means (71) for transferring each said sample from said means (30; 31) for contacting said sample with said liquid to said discharge cassette (161) one-by-one; whereby said samples pass sequentially from said supply cassette (160) to said discharge cassette (161) in a path via said means (10; 11-14) for plasma etching, said means (20; 21) for plasma treatment and said means (31; 31) for contacting said sample with said liquid. Apparatus according to claim 10, adapted for sequentially processing samples (170) one-by-one from a supply cassette (160) to a discharge cassette (161), which cassettes hold a plurality of said samples, each sample having a metal layer and a resist layer on the metal layer, said means (10; 11-14) for plasma etching effecting etching of said metal and resist layers, said means (20;21) for plasma treatment effecting ashing of said resist layer, said apparatus further including:- first transfer means (142, 110, 81) for transferring each said sample in said supply cassette (160) to said means (10; 11-14) for plasma etching one-by-one; second transfer means (52) for transferring each said sample from said means (10; 11-14) for plasma etching to said means (20; 21) for plasma treatment one-by-one; third transfer means (52, 130, 61) for transferring each said sample from said means (20; 21) for plasma treatment to said means (30; 31) for contacting said sample with said liquid one-by-one; and fourth transfer means (71) for transferring each said sample from said means (30; 31) for contacting said sample with said liquid to said discharge cassette (161) one-by-one; said apparatus including said first, second, third and fourth transfer means being adapted and arranged so that at least two said samples are processed simultaneously in a path via said means (10; 11-14) for plasma etching, said means (20; 21) for plasma treatment and said means (30; 31) for contacting said sample with said liquid.

Inventors: FUKUYAMA RYOOJI, KAWAHARA HIRONOBU, KAWASAKI YOSHINAO, NOJIRI KAZUO, SATO YOSHIAKI, TORII YOSHIMI, FUKUYAMA, RYOOJI, KAWAHARA, HIRONOBU, KAWASAKI, YOSHINAO, NOJIRI, KAZUO, SATO, YOSHIAKI, TORII, YOSHIMI
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1990
Main classification: C23F4
IPC codes: H01L21, H01J37, C23F4