CN1127381C - Apparatus and method for providing pulsating fluid - Google Patents

Abstract

The invention provides a system for supplying pulsating fluid to a pressure vessel (54), the system comprising: at least one reservoir (10, 12) for storing a fluid to be pulsed; valved conduits (14, 16, 20) connecting the reservoirs (10, 12) to at least one pump (24); a conduit (26) with a control valve (28) extending from the pump (24) to one or more tanks (36, 38, 40), wherein the control valve (28) is capable of directing fluid flow to each of the ballast tanks (36, 38, 40) sequentially or intermittently; conduits (42, 44, 46) extending from each ballast tank (36, 38, 40) to a control valve (48); and an injection valve (50) that injects fluid from the conduits (42, 44, 46), respectively from each of the ballast tanks (36, 38, 40), into the high pressure processing vessel (54) where material to be contacted by the pulsating fluid is contacted by the fluid. To recirculate the process fluid, conduits (60, 64) from the high pressure process vessel (54) may be connected to a separation vessel (66), a secondary process vessel, or a storage vessel.

Description

Apparatus and method for providing pulsating fluid

This application claims the benefit of US Patent Provisional Application No. 60/079,918, filed March 30, 1998, and US Patent Provisional Application No. 60/079,919, filed March 30, 1998.

Technical Field of the Invention

This invention relates to apparatus and methods for providing pulsating fluids. It is particularly useful in supplying pulses of supercritical fluid to a coated surface to be treated with supercritical fluid.

This invention was made with Government support under contract awarded by the U.S. Department of Energy (Contract No. W-7405-ENG-36). The government has certain powers with respect to this invention.

Prior Art of the Invention

Many scientific and industrial processes today require the transfer of fluids to a surface in order to treat that surface or remove soluble materials from that surface. In some of these applications, the fluid needs to be delivered in a pulsating manner. In some of these applications, the fluid has to remain in a supercritical state while the surface is in contact with the fluid.

A particularly suitable use of the apparatus of the present invention is the patent application for invention filed on the same date as this application for the protection of certain fluids to be used to remove photoresist material from substrates used in the manufacture of integrated circuits or other electronic components introduced in.

During the manufacture of integrated circuits, commonly referred to as semiconductor chips or microchips, a photolithographic process repeated several times is used. In this manufacturing process, the conductive ion-doped gate in the conductive barrier layer, such as silicon dioxide, silicon nitride or metal, is first passed through several appropriate processes such as thermal oxidation, chemical vapor deposition, sputtering, ion implantation or Either vacuum evaporation deposits on substrates such as silicon or gallium arsenide wafers.

After forming or depositing the conductive barrier layer, the photoresist material is applied to the wafer by any suitable means, including but not limited to spin coating to evenly distribute the liquid photoresist over the surface of the wafer.

This is usually followed by heating the photoresist material coating the wafer in a "soft bake" or pre-bake stage in order to improve adhesion and removal of the photoresist material to the substrate surface and/or barrier layer. Solvent in polymeric photoresist materials.

After the photoresist is low-temperature baked on the barrier layer, the part of the photoresist coating on the wafer that has been low-temperature baked is selectively exposed to high-energy light such as high-intensity ultraviolet rays according to the desired pattern defined by the photolithographic mask. under the light. The portions of the photoresist material exposed to high energy light are then developed with a developer.

When using a positive photoresist material, through exposure and development, the developed part of the photoresist material is solubilized and then washed away, and the part of the barrier layer left on the coated wafer is exposed, while the barrier layer is used The remainder of the coated wafer underlies the remaining unexposed and undeveloped photoresist layer.

Conversely, when a negative photoresist material is used, undeveloped portions of the photoresist material are selectively removed to expose selected portions of the barrier layer of the coated substrate in a desired pattern.

Once the photoresist pattern is established on the wafer, the wafer is subjected to a "hard bake" to densify and toughen the photoresist material and improve adhesion to the barrier layer. The exposed substrate and/or barrier material is then etched (removed) by any of several suitable methods (depending on the material used as the barrier layer). Processes such as wet chemical etching, dry etching, plasma etching, sputter etching or reactive ion etching can be used. The etch process removes the barrier material that is not protected by the photoresist, leaving bare wafer portions and wafer portions with a layered coating of the barrier layer and the photoresist material that protects the underlying barrier layer from subject to etching on the wafer surface.

The wafer having the pattern of barrier layer material coated with photoresist material on its surface is then processed through an etching step to remove the high temperature baked photoresist material from the remaining pattern of barrier layer material. Conventionally this is done by washing with a solvent such as a mixture of halogenated hydrocarbons, sulfuric acid and hydrogen peroxide or a strongly basic mixture of hydroxide and an activator. Use of any of these solvent mixtures will generate large and undesirable waste streams.

After removal of the high temperature baked photoresist material, in a final step the substrate with the patterned surface layer on it is washed with deionized water to ensure that all traces of photoresist are removed from the wafer surface. Glue cleaner. This photolithographic process is repeated as many times as necessary to produce as many differently patterned conductive barrier layers on the substrate as desired, often resulting in a large stream of contaminated waste water.

Therefore, there is a need for methods of efficiently removing photoresist material which will reduce undesirable waste flow.

More generally, there is a need for an apparatus and method for supplying pulsating fluids to reaction sites or surfaces to be treated with those fluids; more specifically, there is a need for a device and method for providing pulsating supercritical fluids to The supercritical fluid treats the surface.

It is therefore an object of this invention to provide an apparatus and method for supplying a pulsating fluid to a reaction site or a surface to be treated with the fluid.

Another object of this invention is a method and apparatus for removing photoresist material used in the manufacture of integrated circuits or other electronic components such as circuit boards, optical waveguides and flat panel displays.

Additional objects, advantages and novel features of the present invention will be partially stated in the following introduction, and those skilled in the art may make these additional objects, advantages and novel features partially apparent by studying the following content, or These additional objects, advantages and novel features can be learned by practice of the invention. The objects and advantages of the invention may be realized and accomplished by means of the instrumentalities and combinations particularly pointed out in the claims. The claims are intended to cover all changes and modifications that do not depart from the spirit and scope of the invention.

Summary of the invention

To accomplish the foregoing and other objects, and in accordance with the objects of the present invention, as embodied and broadly described herein, means for supplying a pulsating fluid to a pressure vessel comprises: at least one reservoir for the fluid to be pulsated; valved piping connecting said reservoir to the pumping means; piping extending from the pumping means to one or more ballast storage tanks, provided with at least one control valve capable of directing fluid flow sequentially or intermittently into each ballast tank; a conduit extending from each ballast tank to a control/injection valve that transfers fluid from and to each ballast tank The tubing of the storage tank injects into the high pressure processing vessel where the material to be in contact with the pulsating fluid comes into contact with the fluid.

In order to recycle the treatment fluid, the piping from the high pressure treatment vessel can be connected to a single or multi-unit separation vessel, secondary treatment vessel or storage vessel, whereby the treatment fluid can be returned to the reservoir for reuse in the treatment, Or be directed elsewhere for other purposes.

Brief description of the drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the presentation, serve to explain the principles of the invention. In these drawings,

Figure 1 is a schematic diagram of an apparatus of the present invention for use in contacting a photoresist material on a substrate with a mixture of a dense phase fluid and a dense phase fluid modifier;

Figure 2 is a schematic illustration of an apparatus for supplying pulsating fluid to a pressure vessel in accordance with the present invention.

Detailed description of the invention

A device has been invented which is capable of delivering a pulsating fluid to a reaction site or surface of material to be treated with the pulsating fluid.

The invention comprises: at least one reservoir for fluid; valved piping connecting each reservoir to a pumping device; several control valves extending from the pumping device to one or more ballast storage tanks; Piping for valves, wherein said control valve is capable of directing fluid flow sequentially or intermittently into each ballast tank; piping extending from each ballast tank to a control/injection valve, wherein said control The /injection valve injects fluid from the piping from each ballast storage tank into the high pressure processing vessel where the reaction site or material to be treated is in contact with the fluid. In addition, there may be lead piping extending from a control valve connected to one or more ballast storage tanks to the process vessel in order to provide a means to flow one of several feed fluids or a non-pulsating fluid Or the fluid flow of the fluid mixture is directly introduced into the process vessel, thereby providing a bypass for the ballast storage tank.

If processing with pulsating supercritical fluid is required, such as when using a pulsating supercritical fluid mixture to remove photoresist material from a substrate surface, a high pressure process vessel and pump capable of generating and maintaining high pressure will be used.

If desired, the feedstock fluid or fluid mixture, as well as any contaminants from the reacted or processed materials, can simply be directed out of the process and then treated, stored or transported as desired.

In order to recirculate the treatment fluid, the piping from the treatment vessel can be connected to a separation vessel, a multi-unit separation vessel or several separation vessels in series. In such separation vessels, the treatment fluid or fluid mixture with any contaminants therein can be treated in any of several ways, depending on the desired product, economic factors and equipment, space and engineering capabilities.

For example, in pulsing a supercritical mixture of a dense phase fluid and a dense phase fluid modifier against a substrate coated with a photoresist material using the apparatus of the present invention, at least three different separation vessel designs are available to select different process method.

In the first case, a single separate vessel can be used to contain the mixture while adjusting the temperature and pressure to a value at which the photoresist material is no longer soluble and precipitates out. The remaining dense phase fluid is then recycled together with the dense phase fluid modifier.

In the second case, a separation vessel or a compartment of a separation vessel can be used to contain the mixture while reducing the pressure and raising the temperature so that they reach values at which the supercritical dense phase fluid will evaporate, leaving Mixture of lower dense phase fluid modifier and photoresist material. The dense phase fluid in the gaseous state is then recondensed into a liquid and reused in the process. Instead, the dense phase fluid modifier and photoresist material will be separated in another vessel or in another compartment of a single separation vessel.

In the third case, the currently preferred case, a multi-unit separation vessel is used so that the temperature and pressure of the mixture are first adjusted so that the photoresist material is no longer soluble and precipitates, and then in the second unit by reducing the pressure and raising the The high temperature evaporates the dense phase fluid leaving the dense phase fluid modifier.

As required in this example of removal of photoresist material using the apparatus of the present invention, conduits are provided by which the dense phase fluid modifier can be directed to the channel for separating dissolved photoresist material. device, and then return the cleaned dense phase fluid modifier to the dense phase fluid modifier reservoir for reuse in the process of the present invention, or direct the dense phase fluid modifier to other places for other purposes .

Again, in this example, some piping can also be provided as required by the device, because the evaporated supercritical fluid will be directed to a condenser to condense there and then return to the dense phase fluid reservoir for the purpose of the present invention. re-used in the process or directed elsewhere for other purposes.

In general, the number of ballast tanks required is sufficient to provide as continuous and efficient a process as possible, since a simple alternate selection of tanks will provide a ready and reliable source of compressed fluid whenever required .

While one or more embodiments of the device of the present invention can be used in virtually all applications that require contacting a reactive site or surface with a pulsating fluid, the device of the present invention is useful in the manufacture of electronic components, including integrated circuits and circuit boards, that have never been It is especially useful to remove the high temperature baked photoresist material from the substrate treated by coating the conductive barrier layer and photoresist material, preheating, selective exposure and development, etching and high temperature baking.

At the beginning of the last step of the photolithography process usually used to manufacture integrated circuits and circuit boards, the conductive barrier material layer and the high temperature baked photoresist material layer (this layer has been etched on the conductive barrier material during the etching step of the photolithography process) The pattern of protection) remains on the substrate. In accordance with this invention, high temperature baked photoresist material is removed by subjecting it to a mixture of at least one dense phase fluid and at least one dense phase fluid modifier using the apparatus and method of the present invention Multiple shock contacts.

Dense-phase fluids in the liquid state are most convenient to use as starting components, but for the present example, the temperature and pressure will be high enough to maintain the fluid in a supercritical state so that it behaves like a liquid (in Density) acts like a gas (in terms of diffusivity) and is capable of dissolving dense phase fluid modifiers. The necessary temperature and pressure will depend on the dense phase fluid used.

Dense phase fluids useful for this purpose are generally those in which the selected modifier is dissolved in sufficient quantities to effectively remove the photoresist material. Carbon dioxide is currently most preferred because it is non-flammable, non-toxic, has an easily achieved critical phase and is an excellent solvent for ethers.

The amount of dense phase fluid is sufficient to dissolve the selected amount of modifier and to satisfy the requirements of the area contacting the photoresist material.

Generally speaking, as the dense phase fluid modifier, the cyclic compound compounds with the functional groups shown in the figure below are preferred:

and ethers with the functional groups shown in the diagram below,

Because they have relatively high boiling point, high polarity, low toxicity and biodegradability.

In general, presently preferred dense phase fluid modifiers include, but are not limited to, ethers within the range of the formula:

wherein R ₁ , R ₂ , R ₃ and R ₄ are substituents selected from hydrogen, hydrocarbon groups having 1 to 10 carbon atoms, halogen and halogenated hydrocarbon groups having 1 to 10 carbon atoms, and wherein each R ₁ , R ₂ , R ₃ and R ₄ can be the same or different substituents; and ethers within the scope of the following formula:

wherein R ₁ , R ₂ , R ₃ and R ₄ are substituents selected from hydrogen, hydrocarbon groups having 1 to 10 carbon atoms, halogen and halogenated hydrocarbon groups having 1 to 10 carbon atoms, and wherein each R ₁ , R ₂ , R ₃ and R ₄ can be the same or different substituents;

Cyclic ethers are generally considered more useful because of the lower likelihood of steric hindrance than open-chain ethers.

Presently preferred dense phase fluid modifiers include, but are not limited to, propylene carbonate (1,3-dioxalane-2-one, 4-methyl), ethylene carbonate, butyl carbonate, dimethyl sulfoxide, and γ-butyl Lactone (2,4-dioxalane-3-one).

Dense-phase fluid modifiers that are fully soluble in selected dense-phase fluids are particularly useful because complete solubility in dense-phase fluids facilitates incorporation of the modifier on the treated surface into the dense phase in one step. Fluid cleans up together.

The amount of dense phase fluid modifier is sufficient to break the chemical bonds in the photoresist polymer to the extent that removal of the photoresist material is facilitated.

A solvent solution that maintains a single supercritical phase is formed when the dense phase fluid modifier is virtually completely soluble in the supercritical fluid.

A mixture of a dense phase fluid forming a single supercritical phase of the solvent and a dense phase fluid modifier is prepared by combining the two selected phases while maintaining a pressure and temperature sufficient to maintain the single phase supercritical fluid in a supercritical state. Quantitative compound pooling. Depending on the choice of compound, various pressures and temperatures can be used to maintain the compound in a single supercritical phase. For example, selecting carbon dioxide as the dense phase fluid and ethylene carbonate as the dense phase fluid modifier requires a pressure of at least 1080 psi and a temperature of at least 31°C acting between both the dense phase fluid and the dense phase fluid modifier superior.

A substrate having a patterned coating of a conductive barrier material and a high temperature baked photoresist material may first be mixed with a composition according to the invention in selected proportionate amounts during a soak cycle touch. During immersion the coated substrate is submerged in a static supercritical fluid mixture at a temperature and pressure sufficient to maintain the fluid mixture in a supercritical state.

The strip coating is then exposed to sequential pressure-driven impingement of a mixture of supercritical fluids at a temperature that maintains the fluid in a supercritical state. The pressure sequence is typically followed by a high pressure fluid impingement followed by an intermittent period of time during which the pressure of the fluid in contact with the substrate being processed is allowed to drop to a lower but still elevated pressure. A presently preferred high pressure pulse of fluid is generally in the range of about 550 psi to about 10,500 psi to contact the coated substrate with sufficient force to remove solubilized or softened photoresist material. Presently more preferred are high pressure pulses of fluid in the range of about 1500 psi to about 5000 psi, depending on what solvent solution composition and what temperature is used. High pressure pulses of fluid in the range of about 2000 psi to about 4000 psi are presently most preferred when using carbon dioxide as the dense phase fluid and ethylene carbonate as the dense phase fluid modifier.

During soaking, if a soaking period is used, the pressure is maintained in the range of about 500 psi to about 10,000 psi while simply filling the high pressure vessel with the adhesive removal fluid.

The pressure of the stripping fluid typically ranges from about 500 psi to about 10,000 psi during the low pressure contact cycle. Presently more preferred are fluid low pressure cycles at pressures in the range of about 1,100 psi to about 2,000 psi.

During both the soak cycle and the low pressure cycle of contact, the modified supercritical fluid softens the high temperature baked photoresist material and breaks free from the conductive barrier material layer on the substrate.

When the pressure of the supercritical processing fluid in contact with the coated substrate is sufficiently increased, the softened and debonded photoresist material is dissolved and cleaned by the supercritical processing fluid during exposure to several high pressure shocks, leaving the coated substrate Substrate.

Utilizing the apparatus of the present invention, after the photoresist has been removed to a level consistent with or better than existing wafer industry standards, a final rinse of the substrate with unmodified supercritical fluid can be performed to remove residual modifiers.

Figure 1 schematically illustrates an exemplary embodiment of the invention in which an apparatus with three ballast tanks is used to remove photoresist material from a coated substrate.

Referring to Figure 1, separate reservoirs 10 and 12 are provided for the dense phase fluid and the dense phase fluid modifier, respectively. These two reservoirs also function as long-term storage facilities for these ingredients. Additionally, a single reservoir may be used in order to contain the mixture of dense phase fluid and dense phase fluid modifier.

Conduit 14 connects dense-phase fluid reservoir 10 to control valve 18, which introduces a selected amount of dense-phase fluid corresponding to the amount dispensed from dense-phase fluid modifier reservoir 20 through conduit 16 to control valve 18. The amount of dense phase fluid modifier is proportional. The control valve 18 is connected to a high-pressure pump 24 via a line 20 . Control valve 18 may also be used to distribute unmodified dense phase fluid to line 20 for flushing the system with unmodified dense phase fluid or for a final rinse step if desired.

The high pressure pump 24 has the ability to generate the required fluid pressure and high volumetric flow.

The wafers to be processed are positioned and secured within the high pressure processing vessel 54 by any suitable means. For example, the wafer may be attached to a rack suspended in the high pressure processing vessel 54 by means of retaining clips. The wafer is positioned such that the fluid pulses directly impinge on the photoresist material to be removed.

In order to place wafers into and remove wafers from the high pressure processing vessel 54, the high pressure processing vessel 54 is first isolated and then depressurized.

In order for the photoresist material to soften and start to dissolve, a first soaking step may be used. If it is desired to use a soaking step, the mixture of the present invention, which is dispensed through control valve 18 proportional to the amount of dense phase fluid to the amount of dense phase fluid modifier, can be pumped directly through fixture 56 into high pressure processing vessel 54 using high pressure pump 24 . Autoclave vessel 54 is maintained at a temperature and pressure sufficiently high to maintain the solvent mixture of the present invention in the supercritical phase.

In such a soak step, the wafer is allowed to soak in the static supercritical mixture in the high pressure processing vessel 54 for a period of time in the range of about 30 seconds to about 10 minutes in order to soften and/or remove the photoresist material to be removed. or degradation.

A high pressure pump 24 is then used to pump the selected mixture of dense phase fluid and dense phase fluid modifier of the present invention through line 26 into a control valve 28 which can be sequentially or intermittently passed through three lines 30, Each of bars 32 and 34 releases a predetermined portion of the mixture of dense phase fluid and dense phase fluid modifier. Three contacts in the control valve 28 can be activated by an electronic circuit to control the pressure of the mixture released into each of the three conduits 30 , 32 and 34 . Three pipelines 30, 32 and 34 are connected to three ballast storage tanks 36, 38 and 40 respectively. In general, it is preferred that at least one ballast tank is fully pressurized while at least one other ballast tank is releasing pressure due to fluid flowing from it into the multi-port control valve 48, wherein the multi-port The port control valve will inject fluid through injection valve 50 and conduit 52 into high pressure processing vessel 54 .

For example, still referring to FIG. 1, when pressurized fluid enters ballast storage tank 36 from line 30 to pressurize ballast storage tank 36, valve 48 closes line 42 from ballast storage tank 36, and at the same time, Pressurized fluid from ballast tank 38 is being released through line 44 into multi-port control valve 48 which is now allowing pressurized fluid from ballast tank 38 to inject valve 50 for injection into the high pressure process vessel 54. In this example, ballast storage tank 40 may be being pressurized with fluid from line 34 while line 46 to multi-port control valve 48 is closed during pressurization. Additionally, fluid may be being released from ballast tank 40 through line 46 into multi-port control valve 48 for injection through injection valve 50, depending on pressure-on-pressure requirements to produce the desired time interval and pulse of fluid into high-pressure process vessel 54. High pressure processing vessel 54 .

The supercritical fluid mixture is pumped in alternating high-pressure pulses and low-pressure pulses to impinge on the surface of the photoresist-coated substrate. The length of the pressure pulse is the time required for the ballast tank to deliver the pressure pulse to bring its pressure down to equilibrium with the pressure in the high pressure process vessel 54 when using the apparatus described herein.

The fluid mixture that has been in contact with the photoresist on the substrate in the high pressure processing vessel 54 is directed away from the high pressure processing vessel 54 after each impact of the fluid mixture of the present invention on the wafer in the high pressure processing vessel 54 . This is accomplished by opening the control valve 62 on the line 60 to release the pressure build up in the autoclave 54 until the pressure in the autoclave 54 drops back to the steep cycle pressure level.

The photoresist-coated substrate will be treated in a high pressure processing vessel with the single phase supercritical solvent mixture of the present invention for a period of time sufficient to allow complete removal of the photoresist material. Depending on the pulse pressure, temperature, velocity and volume and proportional amounts of the dense phase fluid and dense phase fluid modifier, a period of at least about 1 minute is typically required. It is generally not necessary for the time period to be longer than about 30 minutes if other factors are optimized.

While thus releasing the pressure of the high pressure processing vessel 54 , the fluid mixture directed out of the high pressure processing vessel 54 through the conduit 60 with the valve 62 is conveyed through the conduit 64 into the separation vessel 66 .

Separation vessel 66 may have any suitable configuration to meet the requirements of separating the dense phase fluid from the dense phase fluid modifier having the photoresist material dissolved therein and, if desired, separating the dissolved photoresist material from the dense phase fluid modifier. Dense Phase Fluid Modifier Separate Requirements. One example of a useful separation vessel 66 is a three-stage multistage separation apparatus with means for independently controlling the heating of each of the three sections 66A, 66B and 66C of the separation vessel 66 .

In this example of a separation vessel, the first portion 66A of the multipolar separation apparatus 66 is used to preheat the supercritical fluid mixture of the present invention comprising dissolved photoresist material. After the temperature is raised to a temperature sufficient to allow the miscible mixture of dense phase fluid and dense phase fluid modifier to "cook off" the photoresist material, the mixture is conveyed to the second section 66B of the separation apparatus.

In the second portion 66B of the separation device 66 of this example, the pressure is controlled sufficiently to allow precipitation of the photoresist material from the single-phase miscible mixture of dense phase fluid and dense phase fluid modifier. Precipitation of photoresist material from a miscible mixture of dense phase fluid and dense phase fluid modifier is due to the inability of this single phase miscible mixture to retain the photoresist material at reduced pressure. in solution.

The third section 66C of the multi-stage separation device 66 of this example is then used to separate the dense phase fluid and the dense phase fluid modifier. In the third section 66C, the temperature and/or pressure will be further controlled for the difference in vapor pressure of the two fluids so that the two fluids separate into two phases.

Depending on which dense phase fluid is selected, the temperature of separation vessel 66 is maintained in the range of about 0°C to about 100°C. For example, when using carbon dioxide as the dense phase fluid and propylene carbonate as the dense phase fluid modifier, the temperature of separation vessel 66 is maintained within a range of about 0°C to about 25°C. This step is accomplished in the first stage 66A of the separation vessel 66 when a multi-stage separation vessel is used.

The drop in pressure causes the supercritical or critical components of the dense phase fluid mixture to separate as a gas and exit separation vessel 66 through line 68 . Conduit 68 passes the fluid in the gas phase to condenser 70 where the fluid in the gas phase is liquefied. The liquefied dense phase fluid can then be returned to the dense phase fluid reservoir 10 via conduit 72 for reuse in the process of the present invention if desired. Additionally, the dense phase fluid can also be removed from the reactor loop.

A device 66B for separating photoresist material dissolved or mechanically entrained in the dense phase fluid modifier may be incorporated into the separation vessel 66 . In this example, the dense phase fluid modifier from which the photoresist material has been removed may be returned to dense phase fluid modifier reservoir 12 via conduit 78 if desired. Any separated photoresist material is directed through conduit 74 to means 76 for collecting the separated photoresist material. Additionally, the dense phase fluid modifier containing dissolved photoresist material can also be pumped out of the reactor loop from separation device 66 for separation at a remote facility.

After impacting the coated substrate with the fluid mixture of the present invention a number of times sufficient to remove the photoresist, a final rinse of the substrate wafer with the unmodified fluid is accomplished by removing the unmodified fluid from the dense phase fluid reservoir 10. The modified dense phase fluid is pumped through the "three-way" valve 28 and a separate line 58 bypassing the ballast tank directly into the multi-port control valve 48 for injection into the high pressure process vessel 54 .

Use of the apparatus and method of the present invention renders unnecessary the final step in which the substrate with the conductive pattern thereon will be rinsed with deionized water to ensure that all traces of organic solvents and sulfates are removed from the wafer surface . The supercritically treated fluid solution does not leave behind any dense phase fluid modifiers because the dense phase fluid modifiers are completely soluble in the supercritical fluid.

The device and method of the present invention are suitable or readily adaptable to a large number of applications, as the device and method are applicable to a wide variety of pressures, volumes, temperatures, times and sequences of any fluid pulses that may be pumped through the device.

Example 1

To demonstrate the operability of the present invention, an inventive run was made with a device providing a single pulse of ballast fluid. In order to carry out the inventive operation described in this example, the apparatus was constructed as shown schematically in FIG. 2 .

To remove photoresist material from silicon substrates of semiconductor chips, carbon dioxide was used as the dense phase fluid and propylene carbonate was used as the dense phase fluid modifier.

A mixture of 5% propylene carbonate and 95% carbon dioxide supplied by H.PGas Products Ltd in standard size Type A siphon cylinders was used as feed from the propylene carbonate and carbon dioxide reservoir 11. The pressure in a siphon cylinder is about 900 psi at room temperature, which is enough to keep the contents of the cylinder liquid. -

The propylene carbonate and carbon dioxide reservoirs 11 are connected via line 13 to an ISCO ^™ Model 260D Syringe Pump 15 which in turn is connected via line 17 to a Whitey ^™ Model 304L-HDF4 1000 ml High Pressure Sampling on the bottle. The line 17 between the syringe pump 15 and the ballast storage tank 21 has a pressure relief valve 19 .

Downstream of the ballast tank 21, 1/4 inch OD stainless steel pipe 23 connects the ballast tank 21 to a DUR-O-LOK ^TM type quick start high pressure filter housing which has been modified to serve as Purification container 27. A DUR-O-LOK ^™ filter housing manufactured by CF Technologies, Inc. was retrofitted by adding a relief port and machining the inside of the vessel to allow for tie down points for special wafer holders. The modified container is re-certified to meet the ASMECode, Sec.VIII, Div.1 standards.

The positioning jig is designed for fixing silicon wafers in the cleaning container 27 . The wafer positioning fixture is a stainless steel plate approximately 2 inches in diameter that is bored to accept a second plate with a wafer mounted therein.

The effective volume of the cleaning container 27 is about 320 ml.

The high pressure input through conduit 23 to the cleaning vessel 27 is positioned so as to allow direct injection of the dense phase fluid mixture onto the wafer surface.

High power heater 29, thermocouple 31, pressure relief valve 33 and pressure reducing valve 35 are all installed on the quick start high pressure filter housing that serves as cleaning container 27 through transformation.

High-pressure tubing (304 stainless steel hard pipe and Swagelok ^TM stainless steel wire braided polytetrafluoroethylene hose) is used as the pipeline 37 to connect the cleaning container 27 with the high-pressure filter housing made by AutoclaveEngineers. The high-pressure filter housing The body is modified to act as a buffer tank 41. A precision micrometer bellows needle valve 39 is installed on the pipe 37 to allow the controlled release of excess pressure from the purge container 27 while maintaining the pressure inside the purge container 27 above the critical point.

The high pressure filter housing retrofitted as surge tank 41 has a volume of 2 liters and allows sufficient room for expansion pressure from purge vessel 27 .

A valved pipe 43 connects the buffer tank 41 to a 5 liter storage tank suitable as a sparge tank 47 to collect the propylene carbonate in the gas mixture released from the buffer tank 41 . A line 49 from the sparger tank 47 directs clean carbon dioxide out of the sparger tank 47 for release into the atmosphere. The water in solution with the propylene carbonate is drained from the sparge tank 47 as needed.

The ballast storage tank 21 and purge vessel 27 were preheated to 50°C prior to commencing pressurization for this demonstration run. Two variable transformers are used to control the temperature of the ballast storage tank 21 and the cleaning vessel 27 respectively.

A mixture of carbon dioxide and propylene carbonate is flowed into the system and allowed to fill the high pressure syringe pump 15 , ballast storage tank 21 and purge container 27 . The final pressure was about 900 psi and the fill time was about two full minutes.

Once filled, the high pressure syringe pump 15 is used to raise the pressure of the purge vessel 27 and ballast tank 21 to about 1100 psi, which is the critical pressure. Then, the valve 25 between the ballast storage tank 21 and the purge vessel 27 is closed and the pump 15 is run for approximately 5 minutes to pressurize the ballast storage tank 21 to approximately 1600 psi. This 5 minute time period becomes the "wafer soak time" in the cleaning vessel 27 .

Once ballast storage tank 21 is pressurized to 1600 psi, valve 25 is opened to release the pressure into purge vessel 27 . The pressure differential between the ballast tank 21 (1600 psi) and the cleaning vessel 27 (1100 psi) causes a dense phase fluid mixture of carbon dioxide and propylene carbonate to be injected directly onto the wafer with high pressure and velocity, thereby cleaning the photolithography from the wafer. glue. We think it will become a solution in a dense fluid mixture of carbon dioxide and propylene carbonate.

The pressure in the ballast storage tank 21 and the cleaning container 27 tends to be balanced, and the balanced pressure is about 1400 psi. After the ballast tank 21 and purge vessel 27 pressures have equilibrated, the downstream micrometer bellows needle valve 39 is opened for a time sufficient to allow the ballast tank 21 and purge vessel 27 pressures to drop to 1100 psi (approximately 1 minute ).

Then, the micrometer bellows needle valve 39 and the valve 25 between the ballast storage tank 21 and the purge container 27 are closed. With the micrometer bellows needle valve 39 and the valve 25 between the ballast storage tank 21 and the cleaning container 27 closed, the high-pressure injection pump 15 is activated to pressurize the ballast storage tank 21 again to repeat the above procedure, Another pressure pulse is applied to the silicon wafer in the cleaning container 27 . This procedure was repeated 3 times in total.

After completing 3 pressure pulses, reduce the pressure of the whole system, take out the special jig holding the silicon wafer from the cleaning container 27, and rinse the whole system with filtered deionized water.

Wafer analysis indicated that essentially all photoresist material had been removed from the wafer by the pulse of fluid.

Although the process and article of manufacture of this invention have been described in detail for purposes of illustration, the process and article of manufacture of this invention are not limited thereto. This patent is intended to cover all changes and modifications within its spirit and scope.

industrial application

The apparatus and process of the present invention can be used in any application where it is desirable to impinge a surface with a fluid, in particular for impinging a surface with a supercritical fluid to remove substances soluble in that particular solvent.

The apparatus and process of the present invention can be used to remove photoresist material from metallized and non-metallized substrates during the manufacture of electronic devices, particularly semiconductor chips and wafers. The apparatus and process of the present invention can also be used in other manufacturing processes that require photoresist masks, such as the production of optical waveguides and flat panel displays.

Claims (31)

1. A device for providing a pulsating fluid to a treatment vessel, the device comprising: (A) at least one reservoir for storing the fluid to be pulsed; (B) at least one line with a valve connecting the reservoir to the pumping device; (C) at least one pipeline provided with a control valve extending from said pumping means to one or more ballast storage tanks, wherein said control valve is capable of sequentially or intermittently introducing fluid flow into said one or each of a plurality of ballast tanks; (D) piping extending from each ballast storage tank to a control/injection valve, wherein said control/injection valve is connected from the piping connected to each of said one or more ballast storage tanks The fluid is injected into the processing vessel, where the material intended to be in contact with the pulsating fluid contacts the fluid; Wherein the processing vessel is a high-pressure processing vessel, and the pumping device can generate and maintain high pressure. 2. The apparatus according to claim 1, wherein at least one conduit directly connects said at least one reservoir for storing a fluid to be pulsed to said processing vessel, thereby providing a direct introduction of fluid into said processing vessel. Said means for processing vessels thereby bypassing said one or more ballast storage tanks. 3. The apparatus of claim 1, wherein said high pressure is sufficient to maintain the fluid in a supercritical state. 4. The apparatus according to claim 1, wherein said processing vessel is connected by piping to a storage vessel located downstream of said processing vessel. 5. The apparatus of claim 1, wherein said processing vessel is connected by piping to at least one additional processing vessel located downstream of said processing vessel. 6. The apparatus according to claim 5, wherein said at least one additional processing container is a separator and has at least one connection between said at least one additional processing container and said reservoir for storing the fluid to be pulsated. Connected conduits and at least one conduit directing a substance other than the fluid to be pulsed leaves said at least one additional processing vessel. 7. Apparatus according to claim 6, wherein said separator has been connected to cooling means and a valve, wherein said valve is adjustable to allow the pressure to be reduced therein. 8. The device according to claim 5, wherein said at least one additional processing container has two separate compartments, wherein the first compartment is not only connected with cooling equipment and a valve capable of reducing the pressure in the compartment through adjustment, but also connected with a channel leading to the receiving chamber. The pipe connection of the condensation chamber of the gas discharged from the first isolation chamber; and the second chamber may contain liquid and solid substances. 9. Apparatus according to claim 5, wherein said at least one additional processing vessel is a multi-unit separation vessel having a first isolated compartment which is connected to a cooling device and a valve which can be adjusted to reduce the pressure in the compartment connected to and in fluid communication with a second isolation compartment, wherein said second isolation compartment has a heater coupled thereto to vaporize fractions of a fluid contained therein. 10. Apparatus according to claim 9, wherein said second isolated compartment is connected by a conduit to said at least one reservoir for fluid to be pulsed and leads non-evaporating fluid and solids away from said at least one reservoir by another conduit. The second isolation compartment mentioned above. 11. The apparatus according to claim 8, wherein said coalescer is connected to said at least one reservoir for the fluid to be pulsed through a conduit so that the fluid to be condensed can flow back to said reservoir for the fluid to be pulsed. Reservoir for fluid use. 12. The apparatus according to claim 1 having two ballast storage tanks. 13. The apparatus of claim 1 having three ballast storage tanks. 14. The apparatus of claim 1, wherein said reservoir for fluid to be pulsed is connected to a temperature controller and means for maintaining pressure in said reservoir for fluid to be pulsed . 15. The apparatus of claim 14, wherein said temperature controller and means for maintaining the pressure in said reservoir for fluid to be pulsed are sufficient to maintain the fluid therein in a supercritical state. 16. Apparatus according to claim 1 having two separate reservoirs for fluid to be pulsed, wherein each reservoir is connected to said pumping means by a valved conduit. 17. The apparatus of claim 1 further having preprogrammable control means on said at least one valved conduit connecting the reservoir to the pumping means. 18. The apparatus of claim 1 further having preprogrammable control equipment on said piping extending from said pumping means to said one or more ballast storage tanks. 19. The apparatus of claim 1 further having preprogrammable control equipment on said piping extending from each ballast storage tank to said control/injection valve. 20. The apparatus of claim 2 further having pre-programmable control means on said conduits directing fluid into said processing vessel. 21. The apparatus of claim 5 further having valves and preprogrammable control devices on said conduit to said at least one additional processing vessel located downstream of said processing vessel. 22. The apparatus according to claim 6 further comprising a valve and a preprogrammable control device on said conduit connecting said at least one additional processing vessel to said reservoir for fluid to be pulsed . 23. The apparatus of claim 8 further having a valve and a preprogrammable control device on said conduit to said condensation chamber receiving gas exhausted from said first isolation chamber. 24. The apparatus of claim 10 further having valves and preprogrammable control means on said conduit to said at least one reservoir for fluid to be pulsed. 25. The apparatus of claim 11 further having valves and preprogrammable control means on said conduit to said reservoir for fluid to be pulsed. 26. The apparatus of claim 16 further having valves and pre-programmable control means on said conduit leading to said valved conduit leading to said pumping means. 27. A method of producing a pulsating fluid on the surface of a material to be treated, the method comprising: (A) containing the treatment fluid under pressure in a reservoir connected to the pump; (B) pumping said treatment fluid under pressure into one or more ballast storage tanks; (C) releasing said treatment fluid from one of said one or more ballast tanks into a treatment vessel in which the material to be treated is located; (D) directing process fluid away from said process vessel after the pressure in one of said one or more ballast storage tanks has equilibrated with the pressure in said process vessel; then, (E) releasing another pulse of said treatment fluid from one of said one or more ballast storage tanks into said treatment vessel; (F) directing process fluid away from said process vessel after the pressure in one of said one or more ballast storage tanks has equilibrated with the pressure in said process vessel. 28. The method according to claim 27, wherein one of said one or more ballast storage tanks is to be filled and pressurized with said treatment fluid in step (E) and simultaneously removed from said treatment fluid in step (C) releasing said treatment fluid from one of said one or more ballast storage tanks. 29. The method of claim 27, wherein said process fluid is directed into a separator after being directed out of said process vessel. 30. The method of claim 29, wherein the gaseous portion of said process fluid from said separator is returned to said reservoir. 31. The method of claim 27, wherein said treatment fluid is maintained in a supercritical state in said reservoir and in a dense phase state in said ballast tank.

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