KR20030070954A - Micropump for transporting fluid and manufacturing method thereof - Google Patents

Abstract

PURPOSE: A micro pump and a manufacturing method thereof are provided to allow for a mass production and reduction of manufacturing costs, while permitting silicon semiconductor elements to be integrated on a single chip. CONSTITUTION: A micro pump comprises a lower substrate(100); a heat generating layer formed into a predetermined pattern on the lower substrate so as to generate a heat and control the pressure of the fluid; a cavity(170) formed on the heat generating layer; membranes(140,150,160) formed on the cavity in such a manner that the membranes expand by the heat generated from the heat generating layer; a fluid transfer path(230) including the membranes and an upper substrate as a boundary; and the upper substrate which is patterned to form the boundary of the fluid transfer path. The membranes expands by heating a certain part of the heat generating layer formed beneath a fluid outlet port(310), and the fluid is transferred by using expansions of the membranes.

Description

Fluid transport micro pump and its manufacturing method {MICROPUMP FOR TRANSPORTING FLUID AND MANUFACTURING METHOD THEREOF}

The present invention relates to a micro-pump for fluid transport using a semiconductor manufacturing process technology and a method for manufacturing the same, and in particular, instead of using a fluid inlet / outlet valve having a mechanical function normally required for a pump function, an instantaneous external temperature increase is achieved. The present invention relates to a micro pump for fluid transport which induces a flow of a stopped fluid in one direction due to an increase in pressure of a closed fluid.

Recently, microstructures having a micro unit size necessary for sensing or actuating are fabricated using semiconductor manufacturing process technology, and signal processing circuits are integrated therein to provide a high performance, multifunctional microelectromechanical system (Micro Electro). Mechanical System, hereinafter referred to as 'MEMS' is implemented. Using this MEMS technology, Lab-on-Chip, a micro-integrator of biochips, medical and microfluidic analyzers on a few centimeters of chips, is a medical microcontroller for biological, chemical, medical and genetic engineering applications. Many studies have been conducted to utilize the diagnostic and drug injection system. In particular, micropumps that can be applied to lab-on-chip microfluidic devices for injecting, mixing, and analyzing fluids are used in the microfluidic fluid transport and control field. Such micro pumps include electrostatic, piezoelectric, electrolytic, shape memory alloy, and electromagnetic force methods.

Hereinafter, the problem according to the driving method of the micro pump will be briefly described. First, the electrostatic type is simple in structure but difficult to obtain a relatively large force, and the piezoelectric type can be driven by using the piezoelectric effect of piezoelectric ceramics to generate a relatively large force, but it is structurally large because a high applied voltage is required. . On the other hand, the electrolysis type can produce a large displacement without heat generation even with relatively low energy, but has a problem that the gas removal time generated through the chemical reverse reaction is long and the driving speed is slow. The shape memory alloy can produce great force with strong tensile force, but it is difficult to manufacture due to unidirectional characteristics. In addition, the electromagnetic force method has a merit that a large displacement can be obtained at a low voltage, and the frequency response is fast, but it is difficult to miniaturize.

Compared to the micro pump having such a driving method, the thermopneumatic type repeatedly drives the air inside the cavity repeatedly for heating and cooling, so that the response is rather slow, but a large force can be obtained due to a large displacement at a relatively low voltage. It has an advantage for the transfer of fluid. For example, thermopneumatic micropumps are disclosed in US Pat. No. 5,375,979.

However, the conventional thermopneumatic micropump is difficult to realize the capping of the buried heater and the membrane suspended in several microcavities of the silicon substrate at the same time, so that two or more pieces of silicon or glass substrates are used. The pump structure was manufactured by manufacturing a closed space. Therefore, the micropump of this structure is very difficult to realize the integrated MEMS device in which fluid transfer and analysis work together with electronic circuits on one chip in the future, like the lab-on-chip concept, and it is difficult to mass-produce. The unit price is high and uneconomical.

Therefore, in order to solve the above problems, a pump having a space structure sealed by a general semiconductor process using a sacrificial layer dry etching method using hydrogen fluoride, which is easy to process and has excellent reproducibility, can be manufactured. To fabricate a micropump capable of integrating silicon semiconductor devices.

In addition, an object of the present invention is to produce a micropump with a sealed space structure by a general manufacturing process such as a semiconductor CMOS process and a surface micromachining method, the electronic circuit can be produced on a silicon substrate on the same chip, the flow path and the water tank Micro-channels such as to bond the etched glass to reduce the production cost and mass production.

1 is a schematic diagram of a micropump according to an embodiment of the present invention.

2A and 2B are conceptual views illustrating a driving principle of a micropump according to an embodiment of the present invention.

3A to 3E are views illustrating a manufacturing process of a micro pump according to an embodiment of the present invention.

FIG. 4 is a view illustrating an etching hole formed in the polysilicon membrane during the manufacturing process of FIG. 3.

FIG. 5 is a view illustrating a situation in which the plasma oxide film inside the cavity is completely removed during the manufacturing process of FIG. 3.

FIG. 6 is an SEM photograph showing that the etching holes formed in the polysilicon membrane are capped with photoresist during the manufacturing process of FIG. 3.

FIG. 7 is a SEM photograph showing that an etching hole formed in the polysilicon membrane is capped with a plasmid oxide layer during the manufacturing process of FIG. 3.

8 is a photograph showing a fluid pump micro pump actually manufactured according to an embodiment of the present invention.

FIG. 9 is a graph illustrating the displacement of the polysilicon membrane (μm) according to the voltage applied to the heater in the micropump manufactured by the manufacturing process of FIG.

* Description of the main parts of the drawings

100: substrate 110, 120: electrode pad

130: heater 140,150,160: membrane

170: cavity 200: glass substrate

210, 250: Water tank 220: Nozzle

230: fluid transport path 240: diffuser

300: fluid inlet 310: fluid outlet

400,420,460: thermal oxide film 410: nitride film

430,450 polysilicon film

As a means for achieving the above object, the present invention provides a heat generating layer, a heat generating layer upper portion formed in a predetermined pattern on the lower substrate in order to generate heat according to the application of the lower substrate, the voltage and thereby control the pressure of the fluid A cavity formed in the cavity, a membrane formed to expand according to the heat generated in the heat generating layer, a fluid transportation path formed by including a membrane and an upper substrate as a boundary, and an upper substrate patterned to form a boundary of the fluid transportation path And partially heating the heat generating layer formed below the fluid discharge port at the fluid inlet of the fluid transport path, thereby expanding the membrane and providing a micro pump for transporting fluid using the same.

As a means for achieving another object, the present invention comprises the steps of forming a heat generating layer on the lower substrate in a predetermined pattern on the lower substrate to generate heat in response to the application of voltage and thereby control the pressure of the fluid Forming an insulating film on the heat generating layer; forming a membrane on the insulating film so as to expand according to the heat generated in the heat generating layer; forming an etching hole on the surface of the membrane, and forming an insulating layer through the etching hole. Forming a cavity by etching all or a portion of the membrane; and forming an upper substrate on the upper portion of the membrane to form a fluid transportation path including the membrane and the upper substrate as a boundary. to provide.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Hereinafter, the basic configuration and operating principle of the micropump will be described with reference to FIG. 1. 1 is a schematic diagram of a micropump according to an embodiment of the present invention.

The micro pump includes a lower substrate 100, a heater 130, corrugated membranes 140, 150, and 160, a cavity 170, and a glass substrate 200. Preferably, the water tank 210, 250, and nozzle 220 are provided. ), A fluid transport path 230, a diffuser 240, a fluid inlet 300 and a fluid discharge port 310.

First, assuming that the fluid is filled between the flow path discharge port 310 (C) in the flow path injection section (300) (A), in such a situation, the fluid will be stopped between the flow path because there is no change in the pressure difference .

When a potential difference is applied between the pads 110 and 120 for electrodes in order to move the fluid stopped in this state, heat generated by resistance is generated in the heater 130 disposed in the cavity 170 and thus the cavity 170. ) Expands the air therein, thereby swelling the polysilicon membrane 140 to the upper, and the fluid is sent to the intermediate membrane 150. Then, when the intermediate membrane 150 is operated and sent to the last membrane 160, the fluid is transferred in a three phase sequence method in which power supply to the polysilicon membrane 140 is cut off and the fluid is sucked again. Let's do it.

In this case, the nozzle 220 reduces the backflow while naturally inducing the inflow of the fluid, and the diffuser 240 serves to reduce the backflow while smoothly releasing the fluid. The water tanks 210 and 250, the nozzles 220, the flow paths 230, and the diffuser 240 are formed under the glass 200 to allow fluid to pass therethrough. In addition, the upper portion of the water tank (210, 250) is penetrated so that the fluid inlet 300 and the fluid discharge port 310 can be connected by a hose, the electrode connecting window to the polysilicon heater 130 to the electrode pad (110, 120) It is penetrated to supply power.

2A and 2B, the principle of movement of a fluid according to an embodiment of the present invention will be described in detail. FIG. 2A is a schematic cross-sectional view of the X-X 'of FIG. 1 for explaining the principle of fluid transfer, in which the membrane is expanded according to the heating of the polysilicon (140, 150, 160), and polysilicon in the proper order. By heating the 140, 150, and 160, the fluid can be transported.

First, when the power is applied in an interlocked manner by an electrical signal input, the air inside the cavity 170 expands or contracts by adding or subtracting heat generated from the heater 130. As a result, when the membrane moves up and down, the fluid may move upward and downward. Flow in the C direction through the flow path 230 in the A direction. FIG. 2 illustrates an example of a sequence in which the polysilicon membranes 140, 150 and 160 are expanded by heating, and the heating sequence is not necessarily limited thereto. The pumping principle of the fluid uses the principle that the internal pressure increases when the fluid filled in the enclosed space receives heat from the outside instantaneously, and the internal pressure causes the flow toward the side with less flow resistance. On the other hand, in order to maximize the driving of the membrane to form a wrinkle in a circular shape in a proper position.

Hereinafter, a manufacturing process of the micro pump will be described in detail with reference to FIGS. 3A to 3E. 3A to 3E are views illustrating a manufacturing process of a thermally driven micropump using a silicon surface micromachining method.

Referring to FIG. 3A, the substrate 100 is subjected to a standard cleaning operation of a 5-inch p-type silicon wafer having a resistivity of 1 to 30 Ω · cm, and then the thermal oxide film 400 is approximately 1000 on the substrate 100. The nitride film 410 is deposited to a thickness of 2000 μm by a low pressure chemical vapor deposition (LPCVD) method. Thereafter, a low-temperature oxide film 420 having a thickness of 2000 μm and a polysilicon layer 430 having a thickness of 8000 μm are deposited and doped by POCl ₃ diffusion for 30 minutes at 900 μm to pattern polysilicon for use as an electrode. . At this time, the low temperature oxide film 420 is also patterned. Thereafter, the oxide film 440 was changed to 1000 ° C. by the plasma chemical vapor deposition method. After the deposition, the polysilicon film 450 is deposited to a thickness of 2000 μm by a low pressure chemical vapor deposition method.

Referring to FIGS. 3B to 3D, the low temperature oxide film 440 is then patterned to open the polysilicon film 430 which becomes a heater by reactive ion etching. Let this be exposed. Thereafter, the low temperature oxide film 460 is deposited to a thickness of 2 to 6 μm, and a corrugation of 0.8 to 2 μm thick is formed on the upper surface thereof. In the process of forming the wrinkles, the upper surface of the low-temperature oxide film 460 is coated with photoresist, and the photoresist is left at a predetermined site through a series of processes such as exposure and development, and the thickness is 0.8 to 2 μm with an etching mask. Etch to form wrinkles.

Such wrinkles are formed to more effectively expand (displace) the membranes 140, 150, and 160 when heat is generated through the heater, and the purpose of the present embodiment may be achieved even if the wrinkle forming process is omitted. However, if wrinkles are not formed, the voltage applied to the heater 130 is further increased to obtain the same expansion (displacement).

The polysilicon membranes 140, 150, and 160 are deposited to a thickness of 1 to 2 μm by using a silane gas (SiH ₄ ) at 650 degrees and 200 mtorr on the corrugations by low pressure chemical vapor deposition (FIG. 3 (c)). Thereafter, dry etching and 6: 1 BHF wet etching are performed on the membranes 140, 150, and 160 to form etching holes EH having a diameter of about 1 μm at intervals of 5 μm. 4 is a view illustrating etching holes formed by the above process.

Thereafter, although not shown in FIG. 3, metal pads for electrodes (110 and 120 in FIG. 1) made of Al-1% silicon were deposited by sputtering to a thickness of 1.0 μm, and nitrogen was removed to remove residual stress of the polysilicon thin film. And a 400 degree annealing process in a hydrogen atmosphere. Meanwhile, the plasma oxide layer 460 inside the cavity 170 of the polysilicon membranes 140, 150, and 160 is completely removed without hydrogenation through a hydrogen fluoride vapor phase etching process through the etching holes EH. FIG. 5 is a diagram illustrating a situation in which the plasma oxide film 460 in the cavity 170 is completely removed without the sticking phenomenon. It can be seen that the plasma oxide film 460 is removed in comparison with FIG. 4.

The principle that the sticking phenomenon is removed is as follows. In general, when the oxide film is used as a sacrificial layer and the silicon film is used as a microstructure, the oxide film is mostly removed by hydrogen fluoride wet etching, followed by washing and drying with a deionized water, methanol, isopropyl alcohol, and the like. Capillary forces are generated by the surface tension due to residual cleaning liquid present in the microscopic gaps between the substrates. If this force is greater than the restoring force generated in the microstructure, the microstructure is attached first, and this temporary adhesion is caused by the capillary force caused by the liquid, even if the residual cleaning liquid evaporates completely. Even if it evaporates completely, permanent surface adhesion occurs due to capillary force caused by liquid, which is called sticking phenomenon. As the water generated by the chemical reaction is condensed, the oxide layer, which is a sacrificial layer, is not etched completely due to debris and side wall polymerization on the etched surface without vaporization, and residues of various shapes remain. Until now, in order to remove such sticking phenomenon to the substrate, the surface was roughened, made non-hydrophilic, that is, hydrophobic, or the cleaning liquid was transferred to the supercritical region to convert the gas and liquid into an intermediate state, and then to a constant temperature. Supercritical CO ₂ drying method, which utilizes phase-transfer characteristics to supercritical fluids by lowering the pressure in the system, converts the cleaning solution into a solid and passes through the liquid state without sublimation of butyl alcohol or dichlorobenzene. (p-DCB; dicholorobenzene) or the like has been produced by a sublimation method (sublimation). However, this method is difficult to handle specimens and the process is very complicated and uneconomical, mass production is difficult.

Therefore, in the embodiment according to the present invention, in order to etch the sacrificial layer oxide film, the gas phase etching process using anhydrous hydrogen fluoride is used to remove the thermodynamic properties of H ₂ O to effectively remove the water generated during the process. Process at 50torr, 35 ?? Low process pressures and high flow rates of hydrogen fluoride gas are required to minimize oxidation hazards. Alcohol is believed to act as an etchant and an intermediary instead of water. The advantage of alcohol is known to be the ability to control the condensation concentration of water in the condensed surface reaction layer. Therefore, by excluding water on the oxide film, it is known that alcohol has the ability to continuously remove the most volatile species during the etching reaction to control the condensation concentration of water in the surface reaction layer. Water has the lowest vapor pressure, followed by isopropyl alcohol (IPA), ethanol, methanol, and anhydrous hydrogen fluoride. In particular, the methanol additive has a very low etching rate of 55 kW / min for the thermal oxide film, and thus can be applied to remove several tens of kW of the natural oxide film in the dry cleaning field. On the other hand, since isopropyl alcohol has the lowest vapor pressure among alcohols, it is very advantageous because it has the highest etching rate for removing various sacrificial layers in surface micromachining.

Finally, referring to FIG. 3E, the polysilicon membranes 140, 150, and 160 completely cap the etching hole EH with a photoresist or a plasma oxide film. 6 and 7 are scanning electron microscope (SEM) photographs showing that the etching holes are capped, and show a case where the etching holes are capped using a photoresist and a plasma oxide film, respectively.

Finally, referring to FIG. 3E, the channel 230 is formed to the glass substrate 200 to a depth of about 40 μm, and a fluid transport path is formed by bordering the glass substrate 200 and the membranes 140, 150, and 160. Although not shown in the drawing, it is obvious that the glass substrate 200 is partially formed to form a fluid inlet and a fluid outlet.

8 is a photograph showing a fluid pump micro pump manufactured in this manner. You can guess the size through the coins in the picture.

Meanwhile, the resistance of the polysilicon heater 130 manufactured as described above is 450 to 1400 Ω, and when the fluid is air, the maximum bending degree of the center of the membrane when the fluid is 30 V is about 63.5 μm. That is, when the position of the center of the membrane in the state without applying heat is 0, the position of the center of the membrane in the state where the voltage is applied is 63.5 µm. It is apparent that the higher the displacement, the easier the transport of the fluid. 9 is a graph showing the displacement (μm) according to the applied voltage measured through a displacement measuring system. This graph shows a steep increase in the displacement in the section above 20V.

On the other hand, the wrinkles of the membrane, etc. in the drawings are exaggerated to emphasize the clear explanation. In addition, when a film is described as "on" another film or substrate, the film may be present in direct contact with the other film or substrate, or a third film may be interposed therebetween.

In addition, although the technical spirit of the present invention has been described in detail according to the above-described preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

Since the pump is manufactured in a closed space structure using the semiconductor device manufacturing process, it can be manufactured on the surface of the silicon wafer in a planar manner. Simultaneous production with electronic circuits is possible on the same substrate. Only by etching the glass, the production cost can be reduced and mass production is possible.

In addition, the micro-pump according to the present invention enables the implementation of a lab-on-a-chip such as a medical micro diagnostic and drug injection system by integrating a silicon semiconductor device such as a signal processing circuit on the same chip.

Claims (10)

Lower substrate; A heat generating layer formed and buried in a predetermined pattern on the lower substrate to generate heat according to the application of a voltage and thereby control the pressure of the fluid; A cavity formed on the heat generating layer; A membrane formed on the cavity to expand in accordance with heat generated from the heat generating layer; A fluid transport path including the membrane and the upper substrate as a boundary; And an upper substrate patterned to define a boundary of the fluid path; Micro-fabricated by surface micromachining, in which the membrane is inflated and partially transported by transporting the buried heat generating layer formed under the fluid outlet at the fluid inlet of the fluid transport passage. Pump. The fluid pump of claim 1, wherein the upper surface of the membrane has a pleat shape. The micropump for fluid transport according to claim 1 or 2, wherein the heat generating layer and the membrane are made of polysilicon. 3. The micropump according to claim 1 or 2, wherein the lower substrate is a silicon substrate and the upper substrate is a glass substrate. Forming a heat generating layer on the lower substrate in a predetermined pattern to generate heat according to the application of voltage and thereby control the pressure of the fluid; Forming an insulating film on the heat generating layer; Forming a membrane on the insulating layer, the membrane expanding in accordance with heat generated from the heat generating layer; Forming a hole in the surface of the membrane to form a cavity by etching all or part of the insulating layer through the hole for etching; And And forming an upper substrate on the membrane to form a fluid transportation path including the membrane and the upper substrate as a boundary. 6. The fluid of claim 5, further comprising, after forming the membrane, applying a photoresist to form wrinkles on the upper surface of the membrane, and partially performing an etching process. Method for manufacturing a micro pump for transport. The method of claim 5 or 6, wherein after the cavity is formed, the etching hole is capped with a photoresist, an insulating film, a polymer, or the like. The method of claim 5 or 6, wherein the forming of the cavity is performed by a gas phase etching method including hydrogen anhydride and alcohols. The method of claim 5 or 6, wherein the heat generating layer and the membrane are formed of polysilicon. The method of claim 5 or 6, wherein the lower substrate is a silicon substrate, and the upper substrate is a glass substrate.