JP2011007074A - Micropump and method of manufacturing micropump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a micropump having a flow passage shape capable of providing an efficient flow speed.SOLUTION: In this micropump, a pressurizing chamber 3, a suction side flow passage 4 and a delivery side flow passage 5 communicating with the pressurizing chamber 3, are formed on a silicon substrate 2 having crystal plane orientation of <100>. At least a part of an inner wall of the pressurizing chamber 3, the suction side flow passage 4 and the delivery side flow passage 5 is a <111> surface, and a width and the depth of the pressurizing chamber 3, the suction side flow passage 4 and the delivery side flow passage 5 are different, and an opening width S and a width larger than a width of the deepest part, are formed in a position shallower than the deepest part in respective positions of the pressurizing chamber 3, the suction side flow passage 4 and the delivery side flow passage 5.

Description

  The present invention relates to a micropump and a manufacturing method of the micropump.

  2. Description of the Related Art Conventionally, liquid transport apparatuses such as a droplet discharge head (inkjet recording head) and a micropump used as a recording head in an inkjet recording apparatus used as an image forming apparatus such as a printer, a facsimile machine, and a copying machine are known.

  As the micro pump, for example, the volume of the pressurizing chamber (also referred to as a pump chamber) is changed by an actuator (using a piezo element or the like), and the change rate of the flow path resistance with respect to the generated differential pressure change In order to achieve this, a micropump has been proposed in which the cross-sectional area and the shape of the flow path before and after the pressurization chamber are differently connected before and after the pressurization chamber. As such a micro pump having different flow channel volumes before and after the pressurizing chamber, a micro pump in which the width dimension and the cross-sectional area of the flow channel are changed as means for changing the flow channel volume has been proposed. A micro pump having a movable valve in the middle of the flow path has also been proposed. In such a micro pump, the valve moves as a check valve, and sends out fluid in one direction in accordance with the movement of the actuator.

  For example, Patent Document 1 discloses an ink jet printer head in which grooves for forming an orifice, an ink flow path, and an ink chamber are integrally formed on the surface of a (100) silicon substrate. In Patent Document 1, anisotropic wet etching is performed using a silicon substrate having a crystal plane orientation <100> for the purpose of producing ink flow paths and ink chambers having different cross-sectional areas with good dimensional control in one step. By doing so, it is disclosed that the flow path depth by the etch stop is controlled by controlling the <111> plane that develops at an angle of 54.7 ° with the progress of etching by the etching mask width dimension. Yes.

  Patent Document 2 discloses a semiconductor microstructure in which channels having different widths and depths are formed adjacently by performing anisotropic wet etching using a silicon substrate having a crystal plane orientation <100>. A manufacturing method is disclosed.

  However, in the configuration in which the width dimension and the cross-sectional area of the flow path are changed, the larger the flow path width and the cross-sectional area, the more space is required on the plane, which is disadvantageous for miniaturization of the micropump. It was.

  The technique described in Patent Document 1 is intended to control the flow path depth. However, in this technique, the flow path depth can be manufactured only at the same depth in the ink flow path and the ink chamber. However, if you want to change the depth in each flow path when you want to increase the flow rate or obtain an efficient flow rate, etc., it is necessary to increase the number of steps, making the manufacturing complicated, and cost and dimensional controllability. There was a problem that the advantage of was lost.

  Here, if the flow path depth can be formed in multiple stages, the volume in the depth direction increases, so that a space on the plane is not required, which can lead to micro pump miniaturization. The production leads to an increase in steps and complications, and there is a problem that the control of the depth dimension and the cost are disadvantageous. Moreover, although the example of the technique of the said patent document 2 from which the width | variety and depth of an adjacent flow path (V type) differ is disclosed, the flow path connected to the pressurization chamber and this pressurization chamber is disclosed. The flow path depth cannot be formed in multiple stages, and the above-described problems cannot be solved.

  Accordingly, the present invention provides a micropump in which a pressurizing chamber and a channel communicating with the pressurizing chamber are formed on a silicon substrate having a crystal plane orientation of <100>, and at least a part of the inner walls of the pressurizing chamber and the channel Is the <111> plane, the width and depth of the pressurizing chamber and the flow path are different, and the width greater than the opening width and the deepest width at each position of the pressurizing chamber and the flow path is the deepest portion An object is to provide a micropump formed at a shallower position. It is another object of the present invention to provide a method for manufacturing a micropump in which the micropump is manufactured by a simple process including two steps of anisotropic dry etching and crystal anisotropic wet etching.

  In order to achieve this object, the micropump according to claim 1 is a micropump in which a pressure chamber and a flow path communicating with the pressure chamber are formed on a silicon substrate having a crystal plane orientation of <100>. At least a part of the inner walls of the pressurizing chamber and the flow path is a <111> plane, the width and depth of the pressurizing chamber and the flow path are different, and the opening width at each position of the pressurizing chamber and the flow path In addition, a width larger than the width of the deepest portion is formed at a position shallower than the deepest portion.

  According to a second aspect of the present invention, in the micropump according to the first aspect, the width and depth of the flow path differ in stages from the suction side to the discharge side of the flow path.

  The micropump manufacturing method according to claim 3 is a micropump manufacturing method in which a pressurizing chamber and a flow path communicating with the pressurizing chamber are formed on a silicon substrate having a crystal plane orientation of <100>. Then, anisotropic dry etching is performed to a predetermined etching depth so that the opening width of the etching mask formed on the silicon substrate is stepwise changed at a plurality of positions in the pressurization chamber and the flow path, and then the crystal difference is changed. A step of performing anisotropic wet etching is included.

  According to the present invention, the pressurization chamber and the flow paths before and after the pressurization chamber (also referred to as the suction-side flow path and the discharge-side flow path) have different volumes on the plane and in the depth direction. By making the width larger than the opening width and the width of the deepest part at a position shallower than the deepest part at each position of the path, it is possible to efficiently obtain the flow velocity generated by the fluctuation of the pressure chamber in a certain direction. it can.

  In addition, by making the width and depth of the flow path in the suction side flow path and the discharge side flow path gradually different from the suction side to the discharge side of the flow path, the flow rate can be made more efficient in a certain direction. Obtainable. For example, by forming a shape that is wide and deep on the discharge side, the pressure difference between the suction side and the discharge side that occurs due to fluctuations in the pressurizing chamber can be reduced, while the resistance on the suction side is large and the resistance on the discharge side is reduced. It becomes possible, and it becomes easier to obtain a flow rate in a certain direction.

  In addition, by two steps of anisotropic dry etching and crystal anisotropic wet etching, the pressure chamber and the flow path before and after the pressurization chamber are different in volume on the plane and in the depth direction. Can be formed in multiple stages so that the width and depth of the film differ stepwise.

It is an example of explanatory drawing of anisotropic dry etching and crystal | crystallization anisotropic wet etching. It is another example of explanatory drawing of anisotropic dry etching and crystal anisotropic wet etching. It is an example of the plane schematic diagram of the micropump concerning the present invention. It is an example of the cross-sectional schematic diagram of the micropump shown in FIG. It is another example of the cross-sectional schematic of the micropump shown in FIG.

  Hereinafter, the configuration according to the present invention will be described in detail based on the embodiment shown in FIGS.

  The micropump according to the present embodiment changes the volume of the pressurizing chamber with an actuator, and the flow rate before and after the pressurizing chamber is set to make the flow rate resistance change rate relative to the generated differential pressure change a constant flow rate. The micropump is connected so that the cross-sectional area and the flow path shape are different between before and after the pressurizing chamber, and more specifically, the silicon substrate 2 having a crystal plane orientation of <100> and the pressurizing chamber 3 In the micropump in which the suction side flow path 4 and the discharge side flow path 5 communicating with the pressurization chamber 3 are formed, at least part of the inner walls of the pressurization chamber 3, the suction side flow path 4, and the discharge side flow path 5 are formed. The <111> plane has different widths and depths between the pressurizing chamber 3 and the suction side flow path 4 and the discharge side flow path 5, and the pressurization chamber 3, the suction side flow path 4, and the discharge side flow path. In each of the positions 5, the opening width S and the width larger than the deepest portion are formed at positions shallower than the deepest portion. Is shall.

  In the micropump manufacturing method according to the present embodiment, first, using the silicon substrate 2 having a crystal plane orientation of <100>, the pressurizing chamber 3, the suction side flow path 4, and the discharge side flow are formed on the surface of the silicon substrate 2. A pattern of the etching mask 1 for forming the path 5 is formed. The etching mask 1 may be any one that can be applied as a mask for anisotropic etching by dry etching, but a nitride film is preferable when it is applied as it is as a mask for anisotropic wet etching. Here, the etching mask 1 is formed by changing the widths of the pressurizing chamber 3, the suction-side flow path 4, and the discharge-side flow path 5. First, etching is performed in the vertical direction by dry etching, and regions having different widths are formed. Etch to the same depth. Thus, side surfaces having the same height (common depth) and bottom surfaces having different widths are formed. Next, when etching is performed with an alkaline anisotropic wet etchant, the <111> crystal orientations appear on the side surfaces and the bottom surface of the pressurizing chamber 3, the suction side flow path 4, and the discharge side flow path 5, respectively. By forming it at an angle of 54.7 °, it is possible to form the flow path depth in multiple steps by changing the width dimension of the etching mask 1 in a stepwise manner. In addition, by simultaneously increasing the channel volume in the depth direction, the channel volume can be formed with good control in a space-saving manner.

(Anisotropic dry etching and crystal anisotropic wet etching)
First, anisotropic dry etching (hereinafter also simply referred to as dry etching) and crystalline anisotropic wet etching (hereinafter also simply referred to as wet etching) will be described with reference to FIGS. Since the micropump according to the present embodiment uses the silicon substrate 2 having a crystal plane orientation <100>, if alkaline anisotropic etching (crystal anisotropic etching) is performed, the etching is caused by the difference in etching rate depending on the crystal plane. A <111> plane that is practically not etched appears at an angle of about 54.7 ° from the surface of the silicon substrate 2 from the boundary surface with the mask 1.

  For example, as shown in FIGS. 1 (a) and 2 (a), a nitride film is formed by CVD (Chemical Vapor Deposition) on the entire surface of the silicon substrate 2 having a crystal plane orientation <100> and then partially patterned. The nitride film is removed. In the present embodiment, the etching mask opening width (also simply referred to as opening width) S is set to S3 = 280 μm and S4 = 500 μm.

  Anisotropic dry etching is performed using the remaining nitride film as an etching mask 1, and etching is performed by d 1 in a direction perpendicular to the silicon substrate 2. In the present embodiment, d1 = 100 μm.

  Next, the silicon substrate is treated with an alkaline aqueous solution such as KOH (potassium hydroxide) for 100 μm etching time. At this time, the silicon substrate 2 having the <100> crystal plane orientation is etched at an angle of about 54.7 ° at which the <111> crystal plane orientation appears as described above. Etching into a shape as shown in FIG.

(Micro pump manufacturing method)
The configuration of the micropump and the method for manufacturing the micropump according to the present invention will be specifically described with reference to FIGS.

  Here, FIGS. 3A to 3D are schematic plan views of the micropump according to the present embodiment. FIG. 3A shows the patterning of the nitride mask, and FIG. After dry etching using the nitride film mask, FIG. 3C shows the state after wet etching, and FIG. 3D shows the state after the nitride film mask is removed.

  4A is between A-A 'in FIG. 3A, FIG. 4B is between A-A' in FIG. 3B, and FIG. 4C is in FIG. 3C. FIG. 4D is a schematic cross-sectional view taken along the line A-A ′ in FIG. 5 (a) is between BB 'in FIG. 3 (d), FIG. 5 (b) is between CC' in FIG. 3 (d), and FIG. 5 (c) is in FIG. 3 (d). FIG. 5D is a schematic cross-sectional view taken along line EE ′ in FIG.

  The flow rate (direction in which the liquid such as the recording liquid flows) in the micropump of the present embodiment is from A to A ′ shown in FIG. In order to form the pressurizing chamber 3, the suction side channel 4 and the discharge side channel 5 connected to the pressurizing chamber 3 in the micropump having such a flow rate, first, on the silicon substrate 2 with the crystal plane orientation <100> A nitride film formed by CVD is formed on the entire surface with a thickness of 1 μm, for example, and then a resist mask is formed thereon. First, a part of the nitride film is removed by etching, and the nitride film is patterned. Next, the resist is removed and a nitride film mask 1 is formed. These can be formed by known lithography and etching techniques (FIGS. 3A and 4A).

  At this time, in order to simultaneously form the etching depth in multiple stages, as shown in FIGS. 5A to 5D, the etching mask opening width S is changed at each position of the flow path and the pressurizing chamber. Like that. Specifically, for example, the etching mask opening widths are set to S1 = 60 μm, S2 = 100 μm, S3 = 280 μm, and S4 = 500 μm, respectively. Here, S1, S2, and S3 are the width of the flow path, and S4 is the width of the pressurizing chamber.

  Using this nitride film as a mask 1, the silicon substrate 2 is etched by dry etching. This dry etching may be a known anisotropic etching, and the etching proceeds in a direction perpendicular to the silicon substrate 2. In this embodiment, as shown in FIG. 3B, the nitride film mask is formed by changing the width in the flow path direction, but the depth (d1) by dry etching is the same in any width portion. is there. In the present embodiment, the depth d1 = 100 μm (FIG. 4B).

  Next, after dry etching, the silicon substrate 2 is left in an alkaline aqueous solution such as KOH (potassium hydroxide), TMAH (tetramethylammonium hydroxide), EDP (ethylenediamine pyrocatechol) or the like while leaving the mask 1 of the nitride film. Is processed for 100 μm etching time.

  At this time, the silicon substrate 2 having a crystal plane orientation of <100> is anisotropically etched at an angle of about 54.7 ° at which the crystal plane orientation of <111> appears, so that the side and bottom surfaces (the deepest) Is also etched in an inclined shape. Here, in S3 and S4 having a wide opening width, the bottom surface is formed in a flat shape by setting the etching time.

  At this time, since the etching depth expands in a forward taper shape in the flow velocity direction, a shape in which the flow velocity in the discharge direction can be easily obtained can be obtained (FIGS. 3C and 4C). In this embodiment, since the etching mask opening width S is set to S1 = 60 μm, S2 = 100 μm, S3 = 280 μm, and S4 = 500 μm, the specific etching amount in S1 is 100 μm after dry etching in the depth direction. In the lateral direction of 21 μm, the left and right sides of 71 μm are etched in a triangular shape (FIG. 5A). Similarly, in S2, after dry etching of 100 μm, the left and right sides of 71 μm are etched in a triangular shape in the depth direction of 35 μm (FIG. 5B). Further, in S3, after dry etching of 100 μm, the bottom surface of the 100 μm surface is flat and the periphery is inclined in the depth direction, and 71 μm is etched in a triangular shape on the left and right sides in the lateral direction (FIG. 5C). In S4, after dry etching of 100 μm, the bottom surface of the 100 μm surface is flat and the periphery is inclined in the depth direction, and 71 μm is etched in a triangular shape on the left and right sides in the lateral direction (FIG. 5D).

  The width of the flat region on the bottom surface is larger in S4 than in S3. For S1 and S2, etching is practically stopped when V-groove shapes having different etching depths depending on the etching mask opening width are formed. However, since S3 and S4 are wide, the etching mask opening width is large. This is because it depends on the etching time. Further, since the relationship of S1 <S2 <S3 <S4 is satisfied, the depth d is d2> d4> d3.

  For the etching mask 1, a film type having selectivity in etching speed with the silicon substrate 2 may be formed into an etching mask 1 with respect to an alkaline aqueous solution such as an oxide film or a nitride film. Since the film is less selective with respect to the silicon substrate 2 with respect to the alkaline aqueous solution than the nitride film, the nitride film is preferably used as the etching mask 1 from the viewpoint of dimensional control.

  After the steps shown in FIGS. 3C and 4C, the nitride film etching mask 1 is removed (FIGS. 3D and 3D). The removal of the etching mask 1 may be removed by dry etching having selectivity with Si, or wet etching such as hydrofluoric acid or hot phosphoric acid, depending on the type of etching mask, and is not particularly limited. .

  After the above steps, another silicon substrate, a glass substrate, or the like is pasted on the silicon substrate 2 using a bonding technique such as anodic bonding or direct bonding, and an actuator element such as PZT (lead zirconate titanate). A micro pump can be manufactured by sticking.

  In the above embodiment, the example in which the flow path depth is controlled in four stages has been described. However, the present invention is not limited to this, and a desired number of etching masks having different etching mask width dimensions are arranged. Thus, the flow path depth can be created at an arbitrary stage.

  In the above embodiment, the dry etching depth, the channel width, and the wet etching time are values that can be arbitrarily set. By appropriately adjusting these values, it is possible to create channels with various cross-sectional shapes, and the degree of freedom in the configuration of the channels is greatly increased, making it easier to find the optimal channel and pressure chamber structure. It is.

  In addition, the above-described micropump according to the present invention is used as a liquid transport device, and a droplet discharge head configured by communicating with a liquid chamber filled with ink from an ink tank and a discharge hole for discharging ink to the outside. It is suitable to apply to. Furthermore, it is also suitable to apply to an image forming apparatus provided with the droplet discharge head configured as described above as a recording head.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

1 Etching mask (nitride film mask)
2 Silicon substrate 3 Pressurizing chamber 4 Suction side flow path 5 Discharge side flow path d1 Depth of dry etching d2, d3, d4 Depth of wet etching S1, S2, S3, S4 Opening width of etching mask

Japanese Patent Laid-Open No. 3-158242 JP 2001-38698 A

Claims (3)

In a micropump in which a pressure chamber and a flow path communicating with the pressure chamber are formed on a silicon substrate having a crystal plane orientation of <100>,
At least part of the inner walls of the pressurization chamber and the flow path is a <111> plane, and the width and depth of the pressurization chamber and the flow path are different,
In addition, the micropump is characterized in that a width larger than the opening width and the width of the deepest portion is formed at a position shallower than the deepest portion at each position of the pressurizing chamber and the flow path.   2. The micropump according to claim 1, wherein the width and depth of the flow path differ stepwise from the suction side to the discharge side of the flow path. In a method of manufacturing a micropump in which a pressure chamber and a flow path communicating with the pressure chamber are formed on a silicon substrate having a crystal plane orientation of <100>,
After performing anisotropic dry etching to a predetermined etching depth so that the opening width of the etching mask formed on the silicon substrate differs stepwise at a plurality of positions in the pressure chamber and the flow path, A method of manufacturing a micropump comprising a step of performing crystal anisotropic wet etching.