Patent Application
20070199509
1. Field of the Invention
This invention relates to the coating of substrates, and in particular to an apparatus and process for the efficient coating of substrates using chemical vapor reaction.
2. Description of the Related Art
The application of coatings onto substrates and other workpieces is required as a process step in many industrial fields. An example of such a process is the coating of a silicon wafer with a layer of Hexamethyldisalizane (HMDS). This coating process is used to promote the adhesion of organic layers such as photoresist to the inorganic silicon wafer. The HMDS molecule has the ability to adhere to the silicon wafer and also to be adhered to by an organic additional layer. For example, silicon wafers would be baked for 30 minutes in a 150 C oven for 30 minutes to dehydrate them. The silicon wafers would then be sprayed with HMDS. The excess HMDS would then be spun off of the silicon wafer. A typical process of this type would result in a HMDS monolayer on the surface of the silicon wafer.
A problem encountered with the above mentioned process was that if the silicon wafer was not sufficiently dry prior to the application of HMDS, then residual moisture would interfere with the reaction of the HMDS to the silicon wafer. This would result in variations in the HMDS layer reaction and then could lead to voids in the subsequently applied next layer. Another problem with a process of this type is that HMDS would rapidly deteriorate when exposed to air and moisture, and thus such a process required a large amount of HMDS to provide a small amount of reaction.
Because of the problems relating to variations in the HMDS monolayer, processes for the coating of substrates with HMDS evolved. Later processes more thoroughly dehydrated the silicon wafer substrate prior to the application of HMDS, and limited the HMDS from much, if any, exposure to air and moisture. An example of such a process would be as follows. Silicon wafers would be placed in a vacuum chamber and cycled back and forth between vacuum and preheated hot dry nitrogen in order to dehydrate the silicon wafer. For example, the silicon wafer would be exposed to a vacuum of 10 Torr for 2 minutes. At this pressure water boils at about 11 C. The vacuum chamber would then be flooded with preheated nitrogen at 150 C. This part of the process would heat the surface of the silicon wafer so that the high temperature of the wafer would assist in the dehydration process as vacuum was once again applied. After 3 complete cycles, a vacuum of 1 Torr would be applied to complete the dehydration process.
The next step in such a process is to open a valve between the vacuum chamber and a canister of HMDS. At room temperature the HMDS boils at approximately 14 Torr and thus the chamber is flooded with 14 Torr of HMDS vapor. In this process the HMDS is not exposed to air or moisture and the silicon wafer is significantly dryer prior to being coated.
Some coating processes based on the above mentioned type of process require a higher pressure. The HMDS is preheated to create a higher vapor pressure. Typical figures are preheating of the HMDS to 100 C to produce up to 400 Torr pressure or HMDS vapor while limiting the pressure in the process oven at 300 Torr to avoid condensation of the HMDS.
Processes involving the preheating of the deposition chemicals have the drawback that if the deposition chemicals degrade with exposure to heat then the bulk preheating of these chemicals may result in the loss of the unused residual chemical. These chemicals are often very expensive. Also, many of these chemicals are hazardous materials. The less of these chemicals actually being used in the process at any time reduces the potential risk for processing facilities.
The coating of substrates for biotech applications may require sufficiently dehydrated substrates and insertion into the process chamber of one or more deposition chemicals which have been preheated and/or vaporized prior to insertion. Some coatings for biotech applications are quite expensive. Some coatings are difficult to vaporize and vaporization requires a combination of low pressure and high temperature. Without reduced pressure, the temperature required for vaporization may be too high to retain stability of the chemical to be vaporized. Biotech applications may require silane deposition onto glass and/or other substrates as a bridge to organic molecules. Among the silanes used are amino silanes, epoxy silanes, and mercapto silanes. These silanes are used in the adhesion layer between glass substrates and oligonucleotides. Oligonucleotides are a short DNA monomer. Substrates are coated with a monolayer of silane as a bridge between the inorganic substrate and the organic oligonucleotide. A silane coated substrate with an oligonucleotide layer is now a standard tool used in biotech test regimens. One area where this oligonucleotide layer is used is in the formation of DNA microarrays. A uniform and consistent silane layer leads to a more uniform and consistent top surface of the oligonucleotide layer, which in turn leads to more useful test results.
What is called for is a process and apparatus which withdraws deposition chemicals from a bulk storage container and then preheats and/or vaporizes this portion separately prior to delivery into the process chamber, allowing for the introduction of deposition chemicals at high temperatures and/or vapor pressures into a process chamber, without requiring preheating of bulk amounts of the deposition chemicals.
Substrates coated with such a process have more consistent monolayers with better bonds to the substrate, allowing for a more consistent oligonucleotide layer. This consistent substrate, used in DNA microarray tests, leads to more accurate test results
A process for the coating of substrates comprising insertion of a substrate into a process oven, dehydration of the substrate, withdrawal of a metered amount of one or more chemicals from one or more chemical reservoirs, vaporizing the withdrawn chemicals in one or more vapor chambers, and transfer of the vaporized chemicals into a process oven, thereby coating the substrate. An apparatus for the coating of substrates comprising a process oven, a metered chemical withdrawal subsystem, a vacuum subsystem, and a vaporization subsystem.
In one embodiment of the present invention, as seen in
Chemicals in the fluid reservoirs 106, 107, are withdrawn into fluid input portion 102 by syringe pumps 108, 109. Although syringe pumps are used in this embodiment, other methods of withdrawal may be used, including peristaltic pumps and other appropriate methods. Chemical withdraw valves 116, 117, provide isolation between fluid reservoirs 106, 107, and syringe pumps 108, 109. Chemical withdraw valves 116, 117, are opened prior to withdrawal of chemicals from fluid reservoirs 106, 107.
Chemical infusion valves 113, 114 provide isolation between syringe pumps 108, 109, and the vapor chamber 110. The vapor chamber 110 is surrounded by vapor chamber heater 118. Although the vapor chamber heater is external to the vapor chamber in this embodiment, the vapor chamber heater may be internal to the vapor chamber or integral to the vapor chamber. The vapor chamber heater 110 may be P/N MBH00233 manufactured by Tempco, of Wood Dale, Ill., or other suitable heater. The vapor chamber 110 is fluidically coupled to process oven 104 by heated vapor line 111. The vapor chamber 110 may be isolated from process oven 104 by the operation of heated vapor valve 115. An example of such a heated vapor valve is valve P/N SS-8BK-VV-1C by Swagelok of Sunnyvale, Calif., with heater P/N 030630-41 by Nor-Cal Products of Yreka, Calif. The vapor chamber manometer 112 monitors the pressure inside vapor chamber 110. The process oven 104 may contain one or more trays 105.
In one embodiment of the present invention, as seen in
After withdrawal of chemicals into the syringe body 209, the chemical withdraw valve 116 may be closed to isolate the delivery pipe 203. The chemical infusion valve 113 may then be opened to link the syringe body 209 to the vapor chamber 110. An example of such a chemical infusion valve 113 is P/N 6LVV-DP11811-C manufactured by Swagelok of Sunnyvale, Calif. The syringe pump mechanism 207 may then re-insert the syringe plunger 208 partially or fully into the syringe body 209, forcing the chemical within the syringe body 209 through the T-coupler 205 and then through pipe 210. With the chemical infusion valve 113 open, the chemical then may enter the vapor chamber 110 via pipe 215. Pressure within the vapor chamber 110 is monitored with the vapor chamber manometer 112. An example of such a manometer is a 0-100 Torr heated capacitance manometer P/N 631A12TBFP manufactured by MKS of Andover, Md.
The fluid reservoir 106 is secured with a spring clamp 212 within a source bottle tray 213. The source bottle tray 213 may also act as a spill containment vessel.
One of skill in the art will understand that the fluid input portion may have other embodiments that may use the above described elements in different types of combinations, or may use different typed of elements.
In one embodiment of the present invention, as seen in
The high pressure gas inlet 403 provides gas via a line 464 to the chemical reservoirs 502, 503, and also provides the pressure to actuate valves 463 and valves 480-484. Solenoids 421-427 are directed by a logic controller at I/O locations 440-445 to actuate valves 480-485 using solenoids 421-427. The gas from the high pressure gas inlet 403 is reduced in pressure to 4 psig by a pressure reducer 460 to be fed to the chemical reservoirs.
The solenoid acutated valves 430, 431 are triggered by directions from a logic controller at I/O interfaces 454, 455 to allow for purging of the chemical source bottle feed line 490.
When the solenoid 421 is directed by the logic controller via the I/O interface 440, high pressure gas is directed through a line 471 to actuate the chemical infusion valve 480, which connects the fluid line 510 from the syringe pump 512 to the vaporization chamber 501. When the solenoid 422 is directed by the logic controller via the I/O interface 441, high pressure gas is directed through the line 470 to actuate the chemical infusion valve 481, which connects the fluid line 511 from the syringe pump 513 to the vapor chamber 501.
When the solenoid 426 is directed by the logic controller via the I/O interface 444, high pressure gas is directed through the line 467 to actuate valve 483 which allows for the introduction into the process chamber 500 of gas from the inlet 404. When the solenoid 425 is directed by the logic controller via the I/O interface 443, high pressure gas is directed through the line 465 to actuate the valve 485, which allows for the introduction into the process chamber 500 of gas from the inlet 405.
When the solenoid 427 is directed by the logic controller via the I/O interface 445, high pressure gas is directed through a line 468 to actuate the heated vapor valve 484, which allows for the introduction into the process chamber 500 of vaporized chemical from the vapor chamber 501 via line 554. Temperature indicating controller 524 and temperature alarm high switch are coupled to I/O interface 451.
Solenoid operated valves 428, 429 allow the opening and closing of lines between the chemical reservoirs 502, 503 and the syringe pumps 512, 513. I/O interfaces 458, 459 control the operation of the solenoid operated valves 428, 429.
The level of chemical left in the chemical reservoirs 502, 503 is monitored with level sensors 514, 515 and routed to the logic controller via the I/O interfaces 456, 457. Level sensors 514, 515 are capacitance level switches P/N KN5105 by IFM Effector of Exton, Pa., in this embodiment.
The vapor chamber pressure switch 464 is linked directly by a line 472 to a solenoid actuated valve 423, which, when triggered, in turn triggers the gas actuated overpressurization limit relief valve 463. The overpressurization limit relief valve 463 connects the vapor chamber 501 to the vacuum line inlet 406. The vapor chamber pressure switch 464 triggers when the pressure in the vapor chamber 501 exceeds a preset pressure, which is 650 Torr in this embodiment.
The process oven manometer 461 feeds its signal to the logic controller via an analog interface (not shown). Overtemperature alarm 551 feeds its signal to the logic controller via I/O interface 448. An I/O interface 442 controls the solenoid actuated valve 424, which in turn can trigger the gas actuated heated vacuum valve 482 via a line 466, which links the process oven 500 to the vacuum inlet 406. A temperature monitor 527 monitors the vacuum line temperature and is linked to the logic controller via an I/O interface 460. Temperature alarm high switch 552 is linked to the logic controller via an I/O interface 460.
Temperature monitors 520, 521, 522, 523 monitor the temperature in the process oven 500. Temperature monitors 520, 521, 522, 523 are linked to the logic controller by an RS-485 interface (not shown). Alarms are present in the temperature monitoring system and are linked to the logic controller by I/O interfaces 446, 447, 449, 450.
Temperature monitors 524, 525 connected to I/O interfaces 451, 453 are also used to monitor the temperature of the heated vapor line 526 and the vapor chamber 501. A pressure monitor 462 is linked to the logic controller by an analog interface and overtemperature alarm 553 is linked to the logic controller by an I/O interface 452.
A logic controller may be used to control this apparatus in some embodiments. An example of such a controller is Control Technology Corporation Model 2700 of Hopinkton, Mass. One of skill in the art will understand that the apparatus may be controlled using a variety of suitable methods.
In one embodiment of the present invention, as seen in
A low pressure gas distribution manifold 733 distributes gas such as dry nitrogen for use in dehydration cycles. Inert gas such as dry nitrogen may be used in these lines. A purge manifold 732 allows for the purging of the fluid reservoirs and lines. The low pressure gas input line 522 is split at a T-coupler 723 into two serpentine lines 720. Gas line heaters 721 allow for the pre-heating of the gas prior to delivery of the process chamber. T-couplers 724, 729 further divide the delivery lines prior to input to the chamber at the gas inlets 725, 726, 727, 728.
A high pressure gas distribution manifold 731 provides gas for purge manifold 732 which inserts low pressure nitrogen into the fluid reservoirs 106, 107. A line 730 routes gas to a fluidic coupler 211 in order to replace the volume voided by chemical withdrawal. Inert gas such as dry nitrogen may be used in these lines. The regulator 741 reduces the pressure from manifold 731 upstream from purge manifold 732.
High pressure gas distribution manifold 731 provides high pressure gas that is routed to the gas actuated valves by the triggering of solenoid actuated valves in valve bank 740.
An alternative process gas distribution inlet 734 provides another inlet for process gas that may be used in some processes using this embodiment of the present invention. In this embodiment, the process gas lines are fluidically coupled to the low pressure gas lines upstream of the serpentine lines 720.
As seen in
A process for the coating of substrates in a process chamber, which may include dehydrating the substrate, and vaporizing the chemical to be reacted prior to its entry into the process chamber.
A substrate for the chemical deposition of different chemicals may be of any of a variety of materials. For biotech applications, a glass substrate, or slide, is often used. Glass substrates may be borosilicate glass, sodalime glass, pure silica, or other types. Substrate dehydration may be performed as part of some processes. The glass slide is inserted into the process chamber. The slide is then dehydrated. Residual moisture interferes with the adhesion of chemicals during the deposition process. Alternatively, dehydration of the slide allows for later rehydration in a controlled fashion. The dehydration process alternates exposing the glass slide to vacuum and then to heated nitrogen, either once or multiple times. For example, the glass slide would be exposed to a vacuum of 10 Torr for 2 minutes. At this pressure water boils at about 11 C. The vacuum chamber would then be flooded with preheated nitrogen at 150 C. This part of the process would heat the surface of the glass slide so that the high temperature of the slide would assist in the dehydration process as vacuum was once again applied. After 3 complete cycles, a vacuum of 1 Torr would be applied to complete the dehydration process.
After the completion of the dehydration cycle, the slide is ready for chemical reaction. Chemical reservoirs, such as manufacturer's source bottles, provide the chemical for the deposition process. For many processes, silanes are used. Among the silanes used are amino silanes, epoxy silanes, and mercapto silanes. Chemical may be withdrawn directly from the reservoir. A metered amount of chemical is withdrawn from the chemical reservoir. This may be done by opening a valve between the chemical reservoir and a withdrawal mechanism. The withdrawal mechanism may be a syringe pump. Chemical is withdrawn from the reservoir, enters the syringe pump, and then the valve between the chemical reservoir and the syringe pump is closed. The chemical reservoirs may be purged with an inert gas such as nitrogen. This purging allows for the filling of the volume of fluid removed with an inert gas, minimizing contact between the chemical in the reservoir and any air or moisture.
Next, a valve between the syringe pump and a vaporization chamber is opened. The vapor chamber may be pre-heated. The vapor chamber may be a reduced pressure. The syringe pump then pumps the previously withdrawn chemical from the syringe pump to the vaporization chamber. The vapor chamber may be at the same vacuum level as the process oven. In parallel to this delivery of chemical to the vaporization chamber, a second chemical may be undergoing the same delivery process. The two chemicals may vaporize at substantially the same time. Additionally, more chemicals may also be delivered to the vaporization chamber, or to another vaporization chamber.
The reduced pressure in the vapor chamber, and/or the elevated temperature in the vapor chamber may allow for the vaporization of chemicals at pre-determined pressure levels and temperatures.
The vaporized chemical, or chemicals, are then delivered to the process chamber. This may be done by opening a valve between the vaporization chamber and the process oven after the chemical has vaporized in the vaporization chamber. Alternatively, the valve between the vaporization chamber and the process oven may already be open when the chemical, or chemicals, are delivered to the vaporization chamber. The chemical then proceeds into the process chamber and reacts with the substrate.
As evident from the above description, a wide variety of embodiments may be configured from the description given herein and additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader aspects is, therefore, not limited to the specific details, representative apparatus and illustrative examples shown and described. Accordingly, departures from such details may be made without departing from the spirit or scope of the applicant's general invention.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10656840 | Sep 2003 | US |
| Child | 11489236 | Jul 2006 | US |
