METHOD AND APPARATUS FOR APPLYING A COATING ON A SUBSTRATE

Abstract: Improved method and apparatus for applying a coating (24) on one side of a substrate (14), moving in between media cushions through the passage (12) of a cabin section (10), with in the direction of movement of such substrate (14) through the passage (12) in at least the passage section (28) in front of the coating supply channel (22) the establishing and maintaining of a coating lock (34), which prevents superfluous coating to escape this passage section (28) in the direction of movement of this substrate (14).

Description: Method and apparatus for applying a coating on a substrate The invention relates to a method and apparatus to apply a coating on a flat surface. Thereby use is made of a sub-micron filtered gaseous environment for the surface during the applying thereon of this coating. The substrates or tape, in that way provided u/ith a coating, can be used in the micrα-electroπica. In the Dutch Patent Application No. 8 103 979 of the applicant a processing system is described, in which substrates are fed through a pas¬ sage of a cabin and whereby by means of media a "floating" processing of these substrates is established. Thereby in a coating station the applying of coating on the substra¬ te takes place, whereupon by means of whirling flows of gases excessive coating is removed. The disadvantages of this system are the following: 1, Thin fluid coating has to be used with a very small thickness of the applied coating layer, which is left behind on the substrate with in that way a successively applying of a great number of coating layers as a requirement; and 2 « Due to the forces of the whirling media, acting on the applied coating layer, the surface thereof is not smooth. The apparatus for coating appliance according to the invention, whereby use is made of this "floating" processing of the substrates or tapes in the cabin passage, now is characterized by having means, included therein, to enable that after the passing of the coating apply section the surface of such substrates or tape is free of excessive coating. A following positive characteristic of the apparatus is, that as seen in the direction of movement of the substrate or tape, immediately behind the coating apply channel a segmentwall section is included therein, ωhich for at least part thereof is at least near parallel to the substrate or tape, with the creation of a first coating passage. Also, that thereby before the coating supply channel a segmentwall section is included therein, which for at least part thereof is at least near parallel to the substrate or tape, with the creation of a second coa¬ ting passage, and under the influence of the media in the passage, acting on the substrate or tape, in this coating passage such a coating lock is created and maintained, that coating is prevented to displace therein with a higher speed as that of the substrate in the direction of substrate mo¬ vement. The first passage can also be constructed in that way, that therein a coating lock is created and maintained, which prevents the leakage of coating in a direction, which is opposite to the direction of movement of the substrates or tape. Consequently, by metering the volume of the supplied coating per second in combination with both coating locks a wanted thickness of the applied coating can be obtained. Such a metered coating supply apparatus can in particular be used with square substrates and tapes. With substrates, not completely filling the total cabin passage, such as with a ost circular substrates (wafers), inevitably at least peri¬ odically a leakage of coating occurs. In view of this, another positive structure of the apparatus accor¬ ding to the invention is, that as immediately behind the coating apply channel a vacumized discharge channel is located, such a channel can also function for the discharge of excessive coating. Furthermore, that as seen in the direction of movement of the sub¬ strate, the flow resistance of the coating passage between the coating supply channel and such a vacuum channel, positioned behind it, is cαnsi- derably smaller than that of the coating passage between the coating sup¬ ply channel and the supply channel in front of it, which functions for the urging of additional media towards the substrate. Furthermore, as such coating, applied in the second coating passage, functions as a coating lock far excessive coating, and displacing together with the substrate, via the first coating passage coating is urged towards the vacuum channel, in combination with the metered supply of coating per second, the passage width of both passages is determined and consequently the thickness of the coating layer, applied on the substrate. A following very positive characteristic of the apparatus is there- by, that in a segment separate branched channels for the supply of coating are positioned aside each other. These channels are an one end thereof connected with a common supply channel and on the other end thereof con¬ nected with at least one mouth and whereby in each of such branched chan¬ nels the same flow restriction is incorporated, being such, that the total thereof is at least as large as the flow restriction of the first coating passage. Furthermore, that the setting of the height of at least the medium cushions behind the coating supply section is such, that in case of no supply of coating, the substrate makes a mechanic contact with these r ^e*.p'a ting passage-walls. The coating, supplied under pressure, then establishes a coating gap against the reaction force of the substrate and the thrusts of the media. Each local narrowing of the passage width of the coating passage im- mediately establishes in that area an increased and correcting thrust of the coating supply and the same occurs oppositely. As a result, over the whole width of the substrate the gap width and consequently the thickness of the applied coating layer remains practically the same. Other characteristics of the coating apply system and apparatus fol- low from the description of the Figures, as described underneath. Figure 1 is a vertical longitudinal sectional view of a cabin, in which the coating apply apparatus according to the invention is incorpora¬ ted. Figure 2 shows the coating supply apparatus in an enlarged sectional view. Figure 3 shows in a heavily enlarged sectional view the outlet of the coating supply channel into the cabin passage. Figure 4 is a heavily enlarged sectional view of the coating appara¬ tus at the outlet of the supply channel of gaseous process medium, in front of the coating supply channel. Figure 5 is a cross—sectional view of the cabin at the segment, in which the parallel positioned branched channels for the supply of coating are situated. Figure 6 is a cabin section, whereby square substrates are passing through its passage. Figure 7 is the cabin section according to Figure 6, whereby a tape is fed through the passage. Figure 8 is a longitudinal sectional view of a coating apply sec¬ tion, which is applicable in the cabin according to Figure 6 or 7. Figure 9 shows in a longitudinal sectional view a coating apply ap¬ paratus, whereby a channel for the supply of coating thinner debouches into the high vacuum channel. Figure 10 is a longitudinal sectional view of a coating apply ap¬ paratus, in which a high temperature is maintained and whereby by means of a supply of evaporated thinner the drying of the coating, which is ap¬ plied on the substrate, and gatherings of coating in the passage are pre¬ vented. Figure 11 shows a substrate section with a stepped surface and on which a layer of fluid coating has been applied. 8 ' A Figure 11 shows the substrate section according to Figure 11 after oven drying thereof. F Fiigguurree 1122 shows a polished substrate section with a coating, applied thereon 8 A 5 Figure 12 shows the section according to Figure 12 after oven drying thereof. In Figure 1 a part of process cabin 10 is shown, with in the cen¬ tral section thereof the passage 12 for substrates or tape 14. On both sides of this passage segments 16 and 18 are positioned. 10 In this cabin the appliance of coating takes place on the substra¬ tes, passing through and such in station 20, see also Figure 2. Thereby through channel 22 coating 24 is urged towards coating passages 26 and 28, see also Figure 3,and applied on the substrate. Such appliance of coating takes place after the vacumizing of the apply section through 15 high vacuum channel 30. The length of passage 26 is restricted, for instance only 30 micro¬ meter, with consequently, even with a small passage height of 0.5 micro¬ meter,still a relatively low flow restriction thereof for the coating. The length of passage 28 however is in comparison very large, for 20 instance 1 mm, causing the flow restriction therein for the coating to be that high, that therein a coating lock 34 is established and maintained, which lock is taken along with the substrate and is continuously supple¬ mented with newly applied coating. As via channel 22 an over amount of coating is supplied, the urging 25 of excessive coating takes place via channel 26 towards the high vavuum channel 30. Through channel 36, see also Figure 4, gaseous medium is supplied. The coating, which, adhering to the substrate, leaves the passage 28, cannot stick to the back side 38 of the coating segment, because of: 301. the over pressure of the gaseous medium, as present in channel 36; 2. a relatively very high speed of the substrate with the applied coating, in cαmparaπce with the thickness of the coating layer; 3. a high viscosity of the coating; and 4. the sharply edged profile of the top section 40 of this back side 38. 35 If required, through channel 36 also thinner, whether or not in va¬ por phase, can be urged to move along the segment wall 38 towards the coa¬ ting layer and so helps to prevent an adhering of coating to the coating segment. The passage wall 42 of the coating segment is ultra polished, with a roughness, which preferably is smaller than 0.1 micrometer. Consequent¬ ly, the coating layer 44, as it is free, is extremely smooth and so al¬ most instantly an oven drying of this applied coating layer can take pla¬ ce. 5 The passage wall 46 of the following segment is situated on a rela¬ tively great distance from the substrate 14, with the creation of the pas¬ sage 48, having a relatively great height. Consequently, a contact of this wall with the coating layer 44, applied on the substrate, is prevented. As by means of a narrow discharge channel for the media, passing through the 10 passage, is extremely small, such media cannot negatively effect the coa¬ ting 44. In Figure 5 the cabin 10 is shown in a cross—section of the coating supply section 20. The main coating channel 50, located in segment 16, is connected with the supply channel 52, which is positioned in the sidewall 15 54 of the cabin. A great number of branched channels 65 are in open con¬ nection with this channel 50. Furthermore, these channels 50 are by means of their outlets 58 connected with an extremely small coating supply channel 22, of which the sections A through X correspond with those of passage 26. Thereby the com- 0 munication of the channel sections is kept very restricted. In the branched channels the channel sections 60 are located. The passage dimensions thereof are extremely small, for instance 30 microme¬ ter times 30 micrometer, whereas also the length of these sections is re¬ latively very large. Consequently, the flow restriction of such a channel 5 section 60 is very large and considerably larger than that of each of the A X passage sections 26 through 26 . A X Consequently, via each passage section 26 through 26 approximately the same amount of coating is urged towards the main vacuum channel 32, whereby every local smallest reduction in height instantly results in an 0 increase in urging pressure in the corresponding channel sectiαns22 X through 22 to still urge the volume of coating through these passage sections. This increase in urging pressure also increases the urging pressure in the entrance 64 of passage 28, see also Figure 3. 5 The resultant increased force on the substrate in upward direction overcomes the increase in forces, which locally have urged the substrate in downward direction. Oppositely, each local increase in height of a passage section imme¬ diately results in a decrease in urging pressure in a corresponding chan— A X πel section 22 through 22 and a resulting decreased force on the cor¬ responding section of the substrate in upward direction. In that way a stabilisation of forces on the substrate takes place with almost the same height of each section A through X of the coating passages 26 and 28 and consequently a practically constant thickness of the applied coating layer. In Figure 2 behind vacuum channel 30 the supply channel 32 for ga¬ seous and/or vaporized medium is located, see also Figures 9 and 10. The¬ reby this medium is urged towards the high vacuum channel 30 and through passage 164 towards the high vacuum channel 66, positioned behind it. Wear the high vacuum channel 30 the passage 62 has been narrowed. Thereby this passage section 70 is extremely small, as for instance 0.3 micrometer. Because the length of it, as seen in longitudinal direction of the passage way, is also very limited, for instance 20 micrometer, the flow restriction in this passae section is not large. The supply channel 32 has the same configuration of a great number of branched channels as is shown in Figure 5, causing the flow restric¬ tion therethrough to be considerably greater than that of the correspon¬ ding sections of this passage section 70. In that way the volume of me— dium, per second urged through the supply channel 32, is almost indepen¬ dent of the local presence of a substrate section, as is shown in Figure 10, with the passing through of almost circular substrates. By keeping low the volume of media, urged to flow through this nar¬ row passage 70 per second, the small passage height of 0.3 micrometer be— comes possible. Fluctuations in the pressure of the media in the cabin passage might change this height to a small extent. However, already with a reduction in height of 0.1 micrometer, the pressure thrusts in the medium passages 62 and 70 sharply increase. In that way by means of the resulting local in— creased forces on the substrate a levelling action is obtained. As a result, by extending this combination of passages 62 and 70 towards very close to the coating supply channel, and such to for instance 0.1 mm distance, a guidewall for the substrate 14 is obtained, which at least in combination or even possibly alone, can establish and maintain the height of the coating passages 26 and 28, as wanted. Due tα this feature, also the thickness of the coating 44, applied on the substrate 14, differs with these small values. In passage 164 also near the high vacuum channel 66 a passage nar¬ rowing 72 is positioned, whereby during the processing almost the same 0.3 micrometer gap height as with passage 70 can be valid. As a result, as seen in longitudinal direction of the cabin passage and substrate mo¬ vement, behind the coating supply section a guide area for the substrates has been created, which even with extremely thin substrates, having a 5 thickness of only 0.15 mm, ensures an even thickness af the applied coa¬ ting layer. Due to the extremely small gap height of the passage section 70, the discharge of medium towards the discharge channel 30 is very small 3 and amounts for instance only approximately 20 mm per second for a sub- 10 strate with a diameter of 125 mm. By also keeping the quantity of superfluous coating restricted and which through coating passage 26 flows towards this discharge channel 30 3 in the amount of only for instance 10 mm per second, a too large gathe¬ ring of coating and medium in the vacuum channel 30 is prevented and so 15 by means of this channel a vacuum near the substrate surface 74, see Figu¬ re 10, can succesfully be established and such before this surface is co¬ vered with the coating. Furthermore, due to the relatively low flow restriction of passages 26, 70 and 72 the process pressure in and around the coating apply section 20 can remain low with the following advantages: 1. a small and allowable wear-down of these passage walls; 2. the average pressure in the rest of the cabin passage can remain low; and 3. due to the low process pressure of the gaseous medium in the drying/ 25 oven section the influence of this medium on the coating layer is negli¬ gible, with no negative effect on the applied coating layer. Very thick coating can now be urged towards the substrate and whereby the superfluous coating, discharged through passage 26, can be thinned in the vacuum channel 30 by means of the thinner 78, supplied through channel 30 76, see Figure 9. Also, at least the coating section of the cabin can be maintained on a high temperature, up to for instance 80 C. Such to enable the percenta¬ ge of solids in the applied coating to be as high as possible. The high percentage on solids enable an ideal supply of a planarisa- 5 tion layer of coating on a stepped surface of the substrate 14, see Figure 11 , and whereby such planarisation after oven drying is still . Lunchanged B with a nearly complete diminishing of the steps, see Figure 11 Furthermore, after the oven drying the thickness of the coating 44', applied on a polished surface of the substrate 14', can still have _ OMPI approximately the same height, with a completely smooth top of the coating, A B as is shown in Figures 12 and 12 , In that way a perfect system for the applying of coatings on substra¬ tes is obtained, which cannot be met by any of the existing coating in- stallations. With the processing of square substrates 14" or tape 80, see Figures 6 and 7, such a periodic discharge of coating is not required. Thereby the structure according to Figure 8 is possible, whereby in both passage 26 and passage 28 the respective coating locks 34 and 82 are established with no escape of superfluous coating from passage 26 to the high vacuum chan¬ nel 30. In that case other safeguards can be part of the system to prevent coating to contaminate the cabin passage, A number of media channels 84 and 86, supplying the media cushions above the substrates, can also supply at least thinner 88 for the coating in whether or not vapor phase, see Figure 10. Thereby with almost circu¬ lar substrates 14 such a media are periodically urged into the open passage sections and move towards channel 30 under the taking along with them of the coating, urged from channel 22. In that way a gathering of coating in the passage 12 is prevented. Furthermore, during the under high temperature applying of coating on the substrates, the through channel 32 supplied medium can be a medium in vapor phase to prevent a sealing off of the high vacuum channel 30. Within the scope of the invention variations in the shown configu— rations of channels, process pressures, — temperatures and heights of the passages are possible. Furthermore, the apparatus embodies all installation components, as required for the correct supply and discharge of the media, whereby sen¬ sors can be installed in the supply channels of the various process media to command regulating systems. _iϊ-E

Claims: C L A I M S 1. Method for applying a coating on a substrate, moving through a passage of a cabin section, including: as seen in direction of movement of said substrate through said 5 cabin passage, through successive mouthes for supply and discharge of media the maintaining of media cushions in between the walls of said pas¬ sage and the flat sides of said substrate; through at least one supply mouth the urging of coating towards one process side of said substrate; and as seen in the direction of movement of said substrates through said cabin passage,by means of said coating in co-operation with other media, urging on said substrate, in at least the passage section in front of said coating supply and in between the coating supply-block and said substrate the establishing and at least periodically maintaining of a gap, filled with coating in such a way, that in said gap the velocity of said coating is not considerably larger than that of said substrate, 2, Method according to Claim 1 , wherein said cabin section is such, that in said gap the velocity of said coating through said gap is not larger than the velocity of said substrate. 3. Apparatus, in which the method according to one of foregoing Claims is embodied, wherein said cabin section has a narrow passage for substrates, on both sides of said passage in longitudinal direction there¬ of successive mouthes for supply and discharge of media are positioned in packages of segments and therein such means are included, that during the coating supply towards one of said substrates a with coating filled gap aside said substrate is obtained. 4. Apparatus according to Claim 3, wherein in direction of movement of said substrates through said cabin passage, immediately behind said coating supply channel a first segment wall-section is located such, that by means of the moving of said substrate through said passage a first coa¬ ting gap can be established, immediately in front of said coating supply channel a second segment wall-section, being at least for a part thereof at least almost parallel with said first segment wall-section, is located, such, that a second coating gap can be created and in said second coating gap under the influence of media in said cabin passage, urging on said substrate, a coating lock can be established and at least temporarily be maintained, 5. Apparatus according to Claim 4, wherein said first coating gap is dimensioned such, that therein also a coating lock can be established and at least temporarily can be maintained in that way, that said lock at least almost completely prevents coating to escape therefrom in a di¬ rection, opposite to the direction of movement of said substrate in said cabin passage. 5 6. Method αf coating appliance of said apparatus of Claim 5, whe¬ rein means for metering said coating supply in combination with said coa¬ ting locks provide the required thickness of the coating, applied on said substrates. 7. Substrates,to be used for such method according to Claim 6, whe— 10 rein said substrates are rectangular. 8. Tape, as a- series of substrates, being connected with each other, wherein said tape can be used in said method αf Claim 6. 9. Method according tα Claim 6, wherein successive substrates rest against each other and media in said cabin passage take care of the trans— 15 port of said substrates. 10. Apparatus according to one of foregoing Claims, wherein, as seen in direction αf movement of said substrate through said cabin passage, immediately behind said coating supply channel a vacuum discharge channel is positioned and said channel is such, that it is at least able to dis- 20 charge superfluous coating. 11. Apparatus according to Claim 10, wherein immediately in front αf said supply channel of coating a supply channel for urging of media to¬ wards said substrate is located, 12. Apparatus according to Claim 11, wherein in direction of move— 25 ment of said substrate through said cabin passage, the flow resistance of said first coating passage between said coating supply channel and said vacuum channel is smaller than said coating passage between said coating supply channel and said supply channel for other media. 13. Method of coating appliance of said apparatus according to Claim 3012, wherein as said coating in said second coating passage functions as a coating lock for superfluous coating, displacing together with said sub¬ strate, and through said first coating passage at least temporary coating is urged towards said vacuum channel, in combination with a metered sup¬ ply of said coating at least together with other means the gap width of 35 both passages is determined and therewith the thickness αf the coating layer, applied on said substrate. 14. Apparatus according to one of foregoing Claims, wherein in a seg¬ ment branched channels for said coating are located aside each other and separated from each other, said channels at one end thereof are connected with a common supply channel and at the other end thereof are connected with at least one mouth, said mouth being in open connection with said cabin passage and in each of said branched channels a similar flow res¬ triction is located with such a total flow restriction for all channels 5 together, that said total flow restriction is at least the same as the flow restriction of said first coating passage, 15. Apparatus according to Claim 14, wherein said total flow res¬ triction is at least five times larger than said flow restriction of said first created coating passage, 16, Apparatus according to Claim 14, wherein the width of said coating supply channel at the outlet mouth thereof in said cabin passage is smaller than 50 micrometer, 17. Apparatus according to Claim 16, wherein the structure of said apparatus is such, that the gap width of said first coating passage is smaller than said gap width of said second coating passage, 18. Method of coating appliance of said apparatus according to Claim 14, wherein the setting of the height of at least the media cushi¬ ons behind said coating supply section is such, that with no supply of said coating, said substrate still does not make a mechanic contact with said segment wall of said first coating passage. 19. Apparatus according to Claim 17, wherein said segment wall of said first coating passage extends farther than 0.5 micrometer into said cabin passage th -n said segment wall of said second coating passage. 20. Apparatus according to Claim 14, wherein the structure αf said apparatus is such, that the height of said coating passage, as created during the coating appliance, is smaller than 1 micrometer. 21. Apparatus according to one of foregoing Claims, wherein in di¬ rection of movement of said substrates through said cabin passage, at the processing side of said passage immediately behind said high vacuum chan- nel a substrate guide wall is located, consisting of at least one passage wall of a segment, positioned parallel to said segment wall of said first coating passage and whereby said wall extends farther into said cabin passage as said wall of said first coating passage. 22. Apparatus according to Claim 21 , wherein at said processing side αf said cabin passage behind said high vacuum discharge channel a supply channel is located to maintain a media cushion underneath said substrate and whereby said segment wall section of said cabin passage in between said supply channel and said high vacuum channel near said vacuum channel extends farther into said cabin passage as said segment wall section near said supply channel. 23. Apparatus according to Claim 22, wherein in direction of move¬ ment of said substrate through said cabin passage, the length of said segment wall section near said high vacuum channel is smaller than the length of said coating passage wall in between said high vacuum channel and said coating supply channel. 24. Method of coating appliance of said apparatus according to one αf foregoing Claims, wherein a coating is used, having at least a high percentage on solids. 25. Method according to Claim 24, wherein said percentage is larger than 50. 26. Method according to Claim 24, wherein said coating has a high temperature. 27. Method according to Claim 26, wherein during said coating ap- pliancε at least said cabin section at said coating supply has also a high temperature. 28. Method according to Claim 26, wherein said temperature is at least 50°C. 29. Method according to Claim 27, wherein during the passing of said substrates through said coating apply section, said substrates have been brought to at least approximately the temperature of said coating. 30. Apparatus according to one of foregoing Claims, wherein said apparatus contains means tα locally establish and maintain such a high temperature. 31. Method according to one of foregoing Claims, wherein as at least said coating apply section and said substrates locally are kept at a high temperature, said media to maintain said media cushion behind said high vacuum channel contain at least a thinning agent in vapor phase. 32. Method according to Claim 31 , wherein said media is only a thin- ning agent in vapor phase. 33. Apparatus, wherein said method according to Claim 31 is used, whereby at the process side of said cabin in direction of movement of said substrates through said cabin passage, behind said supply channel for at least thinning agent in vapor phase a high vacuum channel is located. 34. Apparatus according to Claim 33, wherein said segment wall- section of said cabin passage between said medium supply channel and said high vacuum channel, positioned behind it, extends near said vacuum chan¬ nel farther into said cabin passage as the segment wall—section near said Ol..:l medium supply channel. 35. Apparatus according to one of foregoing Claims, wherein in said supply channels for gaseous and vaporized medium also a great num¬ ber of branched channels are located separately from each other, with a 5 flow restriction, being at least larger than the flow restriction for said medium in corresponding passage sections, which during the proces¬ sing are created by said substrates and said segment walls between said supply and discharge channels. 36. Apparatus according to one of foregoing Claims, wherein in at 10 least said high vacuum channel also a great number of branched channels with a high flow restriction are located separately from each other. 37. Apparatus according to Claim 36, wherein said restrictions are that high, that during the discharge of gaseous medium from said coating passage the velocity of said medium in the inlet mouth is not larger than 15 100 mm per second. 38. Method of coating appliance of said apparatus according to one of foregoing Claims, wherein during said coating appliance at said pro¬ cessing side in said outlet mouth of said supply channel for the supply of at least gaseous medium and located in front of said coating supply 0 channel the pressure is at least approximately the same as the pressure in said outlet mouth αf said coating supply channel. 39. Apparatus according to one of fαrυgoiπg Claims, wherein the structure thereof is such, that during the coating appliance through supply channels at the other side of said cabin passage, being the non- 5 processing side, at least near the coating supply section also thinning agent in whether or not vapor phase is urged towards said cabin passage.

Inventors: BOK EDWARD, BOK, EDWARD
Applicants: BOK EDWARD, BOK, EDWARD
Application year: 1983
Main classification: B05C5
IPC codes: B05C5, B05D1, H01L21