Patent Grant
7178905
1. Field of the Invention
The present invention relates to an ink-jet printhead. More particularly, the present invention relates to a thermally-driven, monolithic ink-jet printhead, in which a plurality of nozzles is densely disposed to implement high-resolution printing, and a method of manufacturing the same.
2. Description of the Related Art
In general, ink-jet printheads are devices for printing a predetermined image, color or black, by ejecting a small volume droplet of ink at a desired position on a recording sheet. Ink-jet printheads are generally categorized into two types depending on which ink ejection mechanism is used. A first type is a thermally-driven ink-jet printhead, in which a heat source is employed to form and expand a bubble in ink to cause an ink droplet to be ejected due to an expansive force of the formed bubble. A second type is a piezoelectrically-driven ink-jet printhead, in which an ink droplet is ejected by a pressure applied to the ink and a change in ink volume due to a deformation of a piezoelectric element.
An ink droplet ejection mechanism of a thermally-driven ink-jet printhead will now be explained in detail. When a pulse current is supplied to a heater formed of a resistive heating material, the heater generates heat and ink near the heater is instantaneously heated to boiling. The boiling of the ink causes bubbles to be generated, thereby expanding and exerting pressure on the ink filling an ink chamber. As a result, ink in a vicinity of a nozzle is ejected from the ink chamber in the form of a droplet.
A thermal ink-jet printhead is classified into a top-shooting type, a side-shooting type; and a back-shooting type, depending on a growth direction of a bubble and an ejection direction of a droplet. In a top-shooting type printhead, a bubble grows in the same direction in which an ink droplet is ejected. In a side-shooting type of printhead, a bubble grows in a direction perpendicular to a direction in which an ink droplet is ejected. In a back-shooting type of printhead, a bubble grows in a direction opposite to a direction in which an ink droplet is ejected.
An ink-jet printhead using the thermal driving method should satisfy the following requirements. First, manufacturing of the ink-jet printheads should be simple, costs should be low, and should facilitate mass production thereof. Second, in order to obtain a high-quality image, cross talk between adjacent nozzles should be suppressed while a distance between adjacent nozzles should be narrow; that is, in order to increase dots per inch (DPI), a plurality of nozzles should be densely positioned. Third, in order to perform a high-speed printing operation, a period in which the ink chamber is refilled with ink after being ejected from the ink chamber should be as short as possible and the cooling of heated ink and heater should be performed quickly to increase an operating frequency.
In the above structure, if a pulse current is supplied to the heater 22 and heat is generated by the heater 22, ink in the ink chamber 16 boils and bubbles are generated and continuously expand. Due to this expansion, pressure is applied to ink filling the ink chamber 16. As a result, ink is ejected in droplet form through each of the plurality of nozzles 10. Subsequently, ink flows into the ink chamber 16 from the ink reservoir 12 through the through hole 2 formed in the cover plate 3. Thus, the ink chamber 16 is refilled with ink.
In this first conventional ink-jet printhead 20, however, a depth of the ink chamber 16 is almost the same as a thickness of the substrate 11. Thus, unless a very thin substrate is used, the size of the ink chamber 16 increases. Accordingly, pressure generated by bubbles for ejecting ink is dispersed by the ink, resulting in degradation to an ejection performance. When a thin substrate is used to reduce the size of the ink chamber 16, it becomes more difficult to process the substrate 11. By way of example, a depth of the ink chamber 16 in a typical conventional ink-jet printhead is about 10–30 μm. In order to form an ink chamber having this depth, a silicon substrate having a thickness of 10–30 μm should be used. It is virtually impossible, however, to process a silicon substrate having such a thickness using existing semiconductor processes.
Further, in order to manufacture an ink-jet printhead 20 having the above structure, the substrate 11, the cover plate 3, and the ink reservoir 12 are bonded together. Thus, a process of manufacturing such an ink-jet printhead becomes complicated, and an ink passage which significantly affects an ejection property, cannot be very elaborate due to potential misalignment during the bonding process.
In this second conventional monolithic ink-jet printhead having the above structure, the silicon substrate 30 and the nozzle plate 40 form a single body such that a process of manufacturing the ink-jet printhead is simplified and misalignment may be prevented.
In this configuration, however, in order to form the ink chamber 32, the substrate 30 is isotropically etched through the nozzle 47. As a result, the ink chamber 32 has a hemispherical shape. Thus, in order to form an ink chamber 32 having a predetermined volume, a constant radius of the ink chamber 32 should be maintained. As a result, there is a limitation in narrowing a distance between adjacent nozzles 47 and disposing the nozzles 47 more densely. More specifically, in order to narrow a distance between adjacent nozzles 47, a radius of the ink chamber 32 should be reduced. Such a reduction results in a decrease in a volume of the ink chamber 32, and such a decrease is not preferable.
Accordingly, there is a limitation in densely disposing a plurality of nozzles using the structure of the second conventional monolithic ink-jet printhead, with respect to meeting the requirement for the ink-jet printhead with high DPI to print an image with high-resolution.
In this third conventional ink-jet printhead, since the ink chamber 61 is formed using the insulating layer 60 stacked on the substrate 70, the ink chamber 61 may have a variety of shapes, and a backflow of ink may be suppressed.
When manufacturing this third conventional ink-jet printhead, however, a method of depositing the thick insulating layer 60 on the silicon substrate 70, etching the insulating layer 60, and forming the ink chamber 61 is generally used. This method has the following problems. First, it is difficult to stack a thick insulating layer on a substrate using existing semiconductor processes. Second, it is difficult to etch a thick insulating layer. Thus, there is a limitation on the depth of the ink chamber. As shown in
The present invention is therefore directed to a thermally-driven monolithic ink-jet printhead having an ink chamber in which a distance between adjacent nozzles is narrowed to print a high-resolution image, and a method of manufacturing the same, which substantially overcome one or more of the problems due to the limitations and disadvantages of the related art.
It is therefore a feature of an embodiment of the present invention to provide a monolithic ink-jet printhead including a substrate, an ink chamber to be filled with ink to be ejected being formed on a front surface of the substrate, a manifold for supplying ink to the ink chamber being formed on a rear surface of the substrate, and an ink channel in flow communication between the ink chamber and the manifold; the ink chamber including sidewalls formed to a predetermined depth from the front surface of the substrate for defining side surfaces of the ink chamber, and a bottom wall formed parallel to the front surface of the substrate at the predetermined depth from the front surface of the substrate for defining a bottom surface of the ink chamber; a nozzle plate formed on the front surface of the substrate, the nozzle plate including a plurality of passivation layers formed of an insulating material, a heat dissipating layer formed of a material having good thermal conductivity, the heat dissipating layer being stacked on the plurality of passivation layers, and a nozzle for ejecting ink out of the monolithic ink-jet printhead in flow communication with the ink chamber; a heater, which is disposed between adjacent layers of the plurality of passivation layers of the nozzle plate, the heater being positioned above the ink chamber and heating ink in the ink chamber; and a conductor, which is disposed between adjacent layers of the plurality of passivation layers of the nozzle plate, the conductor being electrically connected to the heater and delivering a current to the heater.
The sidewalls and the bottom wall may be formed of a material other than a material of the substrate. The sidewalls and the bottom wall may be silicon oxide.
The ink chamber may be surrounded by sidewalls defining a substantially rectangular shape. The predetermined depth may be about 10–80 μm.
The substrate may be a silicon-on-insulator (SOI) substrate comprising a lower silicon substrate, an insulating layer, and an upper silicon substrate, which are sequentially stacked. The ink chamber and the sidewalls may be formed in the upper silicon substrate of the SOI substrate, and the insulating layer of the SOI substrate may form the bottom wall.
The heater may be disposed above the ink chamber and separated from the nozzle. For example, the nozzle may be disposed at a position corresponding to a center of the ink chamber, and the heater may be disposed on opposite sides of the nozzle. The nozzle may be offset from a lengthwise center of the ink chamber in a first direction and the heater may be offset from the lengthwise center of the ink chamber in a second direction, wherein the first direction and the second direction are opposite.
The ink channel may be vertically formed through the substrate and may be disposed at a location corresponding to where the ink chamber and the manifold are in flow communication. The printhead may further include a plurality of ink channels, wherein ink is supplied to the ink chamber from the manifold through the plurality of ink channels.
The plurality of passivation layers may include at least one passivation layer disposed between the substrate and the heater and at least one passivation layer disposed between the heater and the heat dissipating layer.
The plurality of passivation layers may include at least one passivation layer disposed between the substrate and the conductor and at least one passivation layer disposed between the conductor and the heat dissipating layer.
The passivation layers may be formed on upper portions of the heater and the conductor and at portions adjacent thereto.
A lower portion of the nozzle may be formed through the plurality of passivation layers, and an upper portion of the nozzle may be formed through the heat dissipating layer. The upper portion of the nozzle formed through the heat dissipating layer may have a tapered shape such that a diameter thereof decreases in a direction toward an outlet. The upper portion of the nozzle formed through the heat dissipating layer may have a pillar shape.
The heat dissipating layer may be formed of at least one metallic layer, and each of the at least one metallic layer is formed of at least one material selected from the group consisting of nickel (Ni), copper (Cu), aluminum (Al), and gold (Au). The heat dissipating layer may be formed to a thickness of about 10–100 μm. The heat dissipating layer may thermally contact the front surface of the substrate via a contact hole formed through the plurality of passivation layers.
The printhead may further include a seed layer for electroplating the heat dissipating layer formed on the passivation layers and at least a portion of the substrate. The seed layer may be formed of at least one metallic layer, and each of the at least one metallic layer is formed of at least one material selected from the group consisting of copper (Cu), chromium (Cr), titanium (Ti), gold (Au), and nickel (Ni).
It is another feature of an embodiment of the present invention to provide a method of manufacturing a monolithic ink-jet printhead, the method comprising forming a sacrificial layer surrounded by sidewalls and a bottom wall on a front surface of a substrate; sequentially stacking a plurality of passivation layers on the front surface of the substrate and forming a heater and a conductor connected to the heater between adjacent layers of the plurality of passivation layers; forming a heat dissipating layer on the plurality of passivation layers and forming a nozzle through which ink is ejected through the plurality of passivation layers and the heat dissipating layer to form a nozzle plate on the front surface of the substrate, the nozzle plate including the plurality of passivation layers and the heat dissipating layer; forming an ink chamber, which is defined by the sidewalls and the bottom wall, by etching the sacrificial layer exposed through the nozzle using the sidewalls and the bottom wall as an etch stop; forming a manifold for supplying ink by etching a rear surface of the substrate; and forming an ink channel by etching the substrate between the manifold and the ink chamber to provide flow communication between the manifold and the ink chamber.
Forming the sacrificial layer may include etching the front surface of the substrate to form a groove having a predetermined depth; oxidizing the front surface of the substrate in which the groove is formed to form the sidewalls and the bottom wall; filling the groove surrounded by the sidewalls and the bottom wall with a predetermined material to form the sacrificial layer; and planarizing the front surface of the substrate and the sacrificial layer. Filling the groove with the predetermined material may include epitaxially growing polysilicon in the groove.
Forming the sacrificial layer may include etching an upper silicon substrate of a silicon-on-insulator (SOI) substrate to a predetermined depth to form a trench; and filling the trench with a predetermined material to form the sidewalls. The predetermined material may be silicon oxide.
Forming the plurality of passivation layers may include forming a first passivation layer on the front surface of the substrate; forming the heater on the first passivation layer; forming a second passivation layer on the first passivation layer and the heater; forming the conductor on the second passivation layer; and forming a third passivation layer on the second passivation layer and the conductor. The third passivation layer may be formed on upper portions of the heater and the conductor and at portions adjacent thereto.
The heat dissipating layer may be formed of at least one metallic layer, and each of the at least one metallic layer is formed by electroplating at least one material selected from the group consisting of nickel (Ni), copper (Cu), aluminum (Al), and gold (Au). The heat dissipating layer may be formed to a thickness of about 10–100 μm.
Forming the heat dissipating layer and the nozzle may include forming a lower nozzle by etching the plurality of passivation layers formed on the sacrificial layer; forming a plating mold for forming an upper nozzle vertically from the inside of the lower nozzle; forming the heat dissipating layer on the plurality of passivation layers by electroplating; and removing the plating mold to form the nozzle having the upper nozzle and the lower nozzle.
The lower nozzle may be formed by dry etching the plurality of passivation layers by a reactive ion etching (RIE), and the plating mold may be formed of a photoresist or photosensitive polymer.
Forming the heat dissipating layer and the nozzle further may include forming a seed layer for electroplating the heat dissipating layer on the plurality of passivation layers. The seed layer may be formed of at least one metallic layer, and each of the at least one metallic layer is formed by depositing at least one metallic material selected from the group consisting of copper (Cu), chromium (Cr), titanium (Ti), gold (Au), and nickel (Ni).
The method may further include planarizing an upper surface of the heat dissipating layer by a chemical mechanical polishing (CMP) process, after forming the heat dissipating layer.
Forming the ink channel may include dry etching the substrate from a rear surface of the substrate having the manifold.
The ink chamber may have a substantially rectangular shape.
According to an embodiment of the present invention, because an ink chamber having an optimum planar shape and depth, which is defined by sidewalls and a bottom wall that serve as an etch stop, is formed, a distance between adjacent nozzles is narrowed and a monolithic ink-jet printhead with high DPI that is capable of printing a high-resolution image is implemented. In addition, since a nozzle plate is formed integrally with a substrate having an ink chamber and an ink channel, the monolithic ink-jet printhead can be implemented by a series of processes on a single wafer without any subsequent processes, thereby improving a yield of the monolithic ink-jet printhead and simplifying a manufacturing process of the monolithic ink-jet printhead.
The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail exemplary embodiments thereof with reference to the attached drawings in which:
Korean Patent Application No. 2003-36332, filed on Jun. 5, 2003, in the Korean Intellectual Property Office, and entitled: “Monolithic Ink-Jet Printhead and Method of Manufacturing the Same,” is incorporated by reference herein in its entirety.
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the figures, the dimensions of layers and regions are exaggerated for clarity of illustration. It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout.
Referring to
The ink chamber 106 to be filled with ink is formed on a front surface of a substrate 110 to a predetermined depth, preferably, about 10–80 μm. Side surfaces of the ink chamber 106 are defined by sidewalls 111 that define the planar shape and a width of the ink chamber 106. A bottom surface of the ink chamber 106 is defined by a bottom wall 112 formed parallel to the front surface of the substrate that defines a depth of the ink chamber 106. The sidewalls 111 and the bottom wall 112 serve as an etch stop during formation of the ink chamber 106 by etching the substrate 110, as will be described later. Thus, the ink chamber 106 can be precisely formed to desired dimensions using the sidewalls 111 and the bottom wall 112. In other words, the ink chamber 106 may have an optimum volume, i.e., an optimum cross-section and depth, at which the ejection performance of ink droplets is improved.
The ink chamber 106 defined by the sidewalls 111 may have a variety of planar shapes. In particular, the ink chamber 106 may have a substantially rectangular shape, e.g., a substantially rectangular shape in which a width of a nozzle disposition direction, i.e., a direction in which a plurality of nozzles is arranged, as shown in
The sidewalls 111 and the bottom wall 112 are formed of materials other than a material used to form the substrate 110. This difference of materials allows the sidewalls 111 and the bottom wall 112 to serve as an etch stop during formation of the ink chamber 106. Thus, when the substrate 110 is formed of a silicon wafer, the sidewalls 111 and the bottom wall 112 may be formed of silicon oxide.
The manifold 102 is formed on a rear surface of the substrate 110, which is opposite to the front surface of the substrate 110, and is in flow communication with an ink reservoir (not shown) for storing ink. Thus, the manifold 102 supplies ink to the ink chamber 106 from the ink reservoir.
The ink channel 104 is vertically formed through the substrate 110 between the ink chamber 106 and the manifold 102. In the drawings, the ink channel 104 is formed at a position corresponding to a center of the ink chamber 106. Alternatively, the ink channel 104 may be formed at any position that provides flow communication between the ink chamber 106 and the manifold 102. The ink channel 104 may have a variety of cross-sectional shapes, such as a circular shape and a polygonal shape. In addition, one or a plurality of ink channels 104 may be formed depending on a desired ink supply speed.
A nozzle plate 120 is disposed on the substrate 110 on which the ink chamber 106, the ink channel 104, and the manifold 102 are formed. The nozzle plate 120 forms an upper wall of the ink chamber 106. A nozzle 108, which is in flow communication with the ink chamber 106 and through which ink is ejected from the ink chamber 106, is vertically formed through the nozzle plate 120.
The nozzle plate 120 may be formed of a plurality of material layers, i.e., passivation layers, stacked on the substrate 110. The plurality of material layers may include a first passivation layer 121, a second passivation layer 123, a third passivation layer 125, and a heat dissipation layer 128. A plurality of heaters 122 may be disposed between the first passivation layer 121 and the second passivation layer 123. A conductor 124 may be disposed between the second passivation layer 123 and the third passivation layer 125.
The first passivation layer 121 is a lowermost material layer of the plurality of material layers, which are components of the nozzle plate 120, and is formed on the front surface of the substrate 110. The first passivation layer 121 is formed to provide insulation between the heater 122 and the substrate 110 and to protect the heater 122. The first passivation layer 121 may be formed of silicon oxide or silicon nitride.
The heater 122, which heats ink in the ink chamber 106, is disposed on the first passivation layer 121 formed on the ink chamber 106. The heater 122 may be formed of a resistive heating material, such as impurity-doped polysilicon, tantalum-aluminum alloy, tantalum nitride, titanium nitride, or tungsten silicide. The heater 122 is disposed above the ink chamber 106 and separated from the nozzle 108. Specifically, the heaters 122 may be disposed at both sides of the nozzle 108 and may have a substantially rectangular shape, e.g., a substantially rectangular shape having a longer length parallel to a disposition direction of the nozzle 108. Alternatively, only one heater 122 may be formed, and the disposition or shape thereof may be different from that shown in
The second passivation layer 123 is formed on the first passivation layer 121 and the heater 122. The second passivation layer 123 is formed to provide insulation between the heat dissipating layer 128 formed thereon and the heater 122 formed thereunder and to protect the heater 122. The second passivation layer 123 may be formed of silicon nitride or silicon oxide, like the first passivation layer 121.
The conductor 124, which is electrically connected to the heater 122 and delivers a pulse current to the heater 122, is formed on the second passivation layer 123. A first end of the conductor 124 is connected to both ends of the heater 122 via a first contact hole C1 formed through the second passivation layer 123, and a second end of the conductor 124 is electrically connected to a bonding pad (101 of
The third passivation layer 125 is formed on the conductor 124 and the second passivation layer 123. The third passivation layer 125 may be formed of tetraethylorthosilicate (TEOS) oxide or silicon oxide. Preferably, the third passivation layer 125 is formed so that an insulation function of the third passivation layer 125 is not damaged. Further, the third passivation layer 125 is formed on upper portions of the heater 122 and the conductor 124 and at portions adjacent thereto and is not formed at the remaining portions, e.g., at portions beyond an upper portion of the ink chamber 106 in which the conductor 124 is not installed. This selective placement facilitates narrowing a distance between the heat dissipating layer 128 and the substrate 110, thereby reducing thermal resistance and further improving a heat dissipating capability of the heat dissipating layer 128. In addition, the third passivation layer 125 may be formed to a predetermined thickness, e.g., about 0.5–3 μm, so that when a current is applied to the heater 122, a larger amount of heat generated by the heater 122 is transferred to ink within the ink chamber 106 and after delivery of a current to the heater 122 is completed, heat generated by the heater 122 and remaining around the heater 122 is smoothly dissipated to the substrate 110 through the heat dissipating layer 128.
The heat dissipating layer 128 is formed on the third passivation layer 125 and the second passivation layer 123 and thermally contacts the front surface of the substrate 110 via a second contact hole C2 formed through the second passivation layer 123 and the first passivation layer 121. The heat dissipating layer 128 may be formed of a material having good thermal conductivity, e.g., a metallic material, such as nickel (Ni), copper (Cu), aluminum (Al), or gold (Au). In addition, the heat dissipating layer 128 may be formed of one or a plurality of metallic layers. The heat dissipating layer 128 may be formed to a relatively large thickness of about 10–100 μm by electroplating the above-described metallic material on the third passivation layer 125 and the second passivation layer 123. To accomplish this electroplating, a seed layer 127 for electroplating the above-described metallic material may be formed on the third passivation layer 125 and the second passivation layer 123. The seed layer 127 may be formed of a metallic material having good electrical conductivity, such as copper (Cu), chromium (Cr), titanium (Ti), gold (Au), and nickel (Ni). In addition, the seed layer 127 may be formed of at least one metallic layer.
As described above, since the heat dissipating layer 128 formed of metal is formed by electroplating, the heat dissipating layer 128 may be formed integrally with the other elements of the ink-jet printhead and may be formed to a relatively large thickness to dissipate heat effectively.
In operation, the heat dissipating layer 128 dissipates heat generated by the heater 122 and remaining around the heater 122 while contacting the front surface of the substrate 110 via the second contact hole C2. More specifically, heat generated by the heater 122 and remaining around the heater 122 after ink is ejected is dissipated to the substrate 110 and out of the printhead via the heat dissipating layer 128. Thus, heat is dissipated after ink is ejected, and the temperature around the nozzle 108 rapidly decreases so that printing can be performed stably at a high driving frequency.
As described above, since the heat dissipating layer 128 may be formed to a relatively large thickness, the nozzle 108 can be formed to have a sufficient length. Thus, a stable high-speed operation can be performed, and a linearity of ink droplets ejected through the nozzle 108 is improved, i.e., ink droplets can be ejected in a direction exactly perpendicular to the substrate 110.
In this particular embodiment, each of the plurality of nozzles 108 includes a lower nozzle 108a and an upper nozzle 108b formed through the nozzle plate 120. The lower nozzle 108a has a cylindrical shape and is formed through the first, second, and third passivation layers 121, 123, and 125. The upper nozzle 108b is formed through the heat dissipating layer 128. Although the upper nozzle 108b may have a cylindrical shape, the upper nozzle 108b may have a tapered shape such that a diameter thereof decreases in a direction of an outlet, as shown in
Referring to
Referring to
Referring to
An operation of ejecting ink from the monolithic ink-jet printhead shown in
Referring to
Referring to
A meniscus at the surface of the ink 131 in the nozzle 108 after the droplets 131′ are separated retreats toward the ink chamber 106. In this configuration, because the nozzle 108 is formed to have a sufficient length by the nozzle plate 120, the meniscus retreats only into the nozzle 108 and does not retreat into the ink chamber 106. Thus, air is prevented from flowing into the ink chamber 106, the meniscus is quickly returned to an initial state thereof, and high-speed ejection of the droplets 131′ can be performed stably. In addition, since heat generated by the heater 122 and remaining around the heater 122 after the droplets 131′ are ejected is dissipated to the substrate 110 and out of the printhead via the heat dissipating layer 128, the temperature of the heater 122, the nozzle 108, and the temperature around the heater 122 and the nozzle 108 decrease rapidly.
Referring to
A method of manufacturing a monolithic ink-jet printhead having the above structure according to the first embodiment of the present invention will now be described.
While
An etch mask 114 for defining a portion of the substrate 110 to be etched is formed on an upper, i.e., the front, surface of the silicon substrate 110. A photoresist is coated on the upper surface of the substrate 110 to a predetermined thickness and is patterned, thereby forming the etch mask 114.
Subsequently, the substrate 110 exposed by the etch mask 114 is etched, thereby forming a groove 116 having the predetermined depth. The substrate 110 may be etched by a dry etching, such as a reactive ion etching (RIE). The groove 116 defines an area in which the ink chamber is to be formed. Preferably, the groove 116 has a depth of about 10–80 μm. The groove 116 may have a variety of shapes depending on the shape in which the front surface of the substrate 110 is etched by designing the planar shape of the ink chamber. Thus, the ink chamber can be formed to have desired size and shape, e.g., having a planar, substantially rectangular shape. After the groove 116 is formed, the etch mask 114 is removed from the substrate 110.
Subsequently, as shown in
Specifically, for this particular embodiment, a polysilicon layer is formed in the groove 116, and the polysilicon layer is epitaxially grown, thereby forming the sacrificial layer 119 completely filling the groove 116. Subsequently, an upper surface of the sacrificial layer 119 and the front surface of the substrate 110 are planarized, e.g., by a chemical mechanical polishing (CMP) process. Here, the silicon oxide layer 117 formed on the front surface of the substrate 110 is removed, but the sidewalls 111 and the bottom wall 112, which will serve as an etch stop as described above, remain on the sides and bottom surface of the groove 116.
Specifically, the first passivation layer 121 may be formed by depositing silicon oxide or silicon nitride on the front surface of the substrate 110 and the sacrificial layer 119.
Subsequently, the heater 122 is formed on the first passivation layer 121 formed on the front surface of the substrate 110 and the sacrificial layer 119. The heater 122 may be formed by depositing a resistive heating material, such as impurity-doped polysilicon, tantalum-aluminum alloy, tantalum nitride, or tungsten silicide, on the entire surface of the first passivation layer 121 to a predetermined thickness and patterning the deposited material in a predetermined shape, e.g., in a substantially rectangular shape. Specifically, impurity-doped polysilicon may be formed to a thickness of about 0.7–1 μm by depositing polycrystalline silicon together with impurities, e.g., a source gas of phosphorous (P), by low-pressure chemical vapor deposition (LP-CVD). When the heater 122 is formed of tantalum-aluminum alloy, tantalum nitride, or tungsten silicide, the heater 122 may be formed to a thickness of about 0.1–0.3 μm by depositing tantalum-aluminum alloy, tantalum nitride, or tungsten silicide by sputtering or chemical vapor deposition (CVD). The deposition thickness of the resistive heating material may be varied to have proper resistance in consideration of the width and length of the heater 122. Subsequently, the resistive heating material deposited on the entire surface of the first passivation layer 121 is patterned by a photolithographic process using a photomask and a photoresist and an etch process using a photoresist pattern as an etch mask.
Next, as shown in
Next, the third passivation layer 125 is formed on upper surfaces of the second passivation layer 123 and the conductor 124. The third passivation layer 125 is a material layer that provides insulation between the conductor 124 and the heat dissipating layer, which will be formed later. The third passivation layer 125 may be formed to a thickness of about 0.5–3 μm by depositing TEOS oxide using plasma enhanced chemical vapor deposition (PE CVD). Subsequently, a portion of the third passivation layer 125 is etched to expose a portion of the second passivation layer 123 away from upper portions of the heater 122 and the conductor 124 and portions adjacent to the heater 122 and the conductor 124 within a range in which an insulation function of the third passivation layer 125 is not damaged. In this embodiment, at least portions of the second passivation layer 123 out of the upper portion of the ink chamber 106 in which the conductor 124 is not disposed are exposed. Simultaneously, the substrate 110 is also exposed via the second contact hole C2. As a result, a distance between the heat dissipating layer and the substrate 110 is narrowed, thermal resistance is reduced, and a heat dissipating capability of the heat dissipating layer is improved.
Next, as shown in
Subsequently, a plating mold 109 for forming an upper nozzle is formed. The plating mold 109 may be formed by coating a photoresist on the entire surface of the seed layer 127 to a predetermined thickness and patterning a coated photoresist in the shape of the upper nozzle. Meanwhile, the plating mold 109 may be formed of a photoresist or photosensitive polymer. Specifically, a photoresist is coated on the entire surface of the seed layer 127 to a thickness greater than the height of the upper nozzle. In this embodiment, the photoresist is also filled in the lower nozzle 108a. Subsequently, the photoresist is patterned, and only portions in which the upper nozzle is to be formed and portions filled in the lower nozzle 108a are left. In this particular embodiment, the photoresist is patterned to have a tapered shape such that a diameter thereof decreases in an upward direction. The patterning step may be performed by proximity exposure in which the photoresist is exposed through a photomask, which is isolated a predetermined distance from an upper surface of the photoresist. In this embodiment, light that has passed through the photomask is diffracted. As a result, an interface between an exposed portion and an unexposed portion of the photoresist is formed to be inclined. The inclination degree of the interface and an exposure depth may be adjusted by the distance between the photomask and the photoresist and an exposure energy. Alternatively, the upper nozzle may have a pillar shape. In this alternative embodiment, the photoresist is patterned in the pillar shape.
Alternatively, the step of forming the plating mold 109 may be divided into two steps, that is, a first step of filling an interior of the lower nozzle 108a with a photoresist to form a lower plating mold and a second step of forming an upper plating mold to form an upper nozzle 108b. In this embodiment, the step of forming the seed layer 127 may be performed between the first step and the second step.
Next, as shown in
The surface of the heat dissipating layer 128 after electroplating is completed, is uneven due to the presence of the material layers formed under the heat dissipating layer 128. Thus, the surface of the heat dissipating layer 128 may be planarized by CMP.
Subsequently, the plating mold 109 is removed, and then, a portion of the seed layer 127 exposed by removing the plating mold 109 is removed. The plating mold 109 may be removed by a general method of removing a photoresist, e.g., using acetone. The seed layer 127 may be etched by a wet etching using an etchant capable of selectively etching the seed layer 127 in consideration of an etch selectivity of the metallic material used in forming the heat dissipating layer 128 to the metallic material used in forming the seed layer 127. For example, when the seed layer 127 is formed of copper (Cu), an acetic acid based etchant may be used. When the seed layer 127 is formed of titanium (Ti), a hydrofluoric acid (HF) based etchant may be used. Then, as shown in
By performing the above-described steps, the monolithic ink-jet printhead having the structure shown in
As shown in
Subsequently, the front surface of the upper silicon substrate 530 is etched, thereby forming a trench 540 having a predetermined shape so that the insulating layer 520 is exposed. The upper silicon substrate 530 may be etched by dry etching such as RIE. The trench 540 is formed to surround portions in which an ink chamber is to be formed. The trench 540 is formed to a width of several micrometers (μms) so that it may easily be filled with a predetermined material.
Next, as shown in
Subsequent steps are the same as the above-described steps shown in
As described above, the monolithic ink-jet printhead and the method of manufacturing the same according to the present invention have several advantages. First, an ink chamber, which has an optimum planar shape and depth defined by sidewalls and a bottom wall that serve as an etch stop is formed such that a distance between adjacent nozzles is narrowed and a monolithic ink-jet printhead with high DPI that is capable of printing a high-resolution image is implemented. Second, since a heat dissipating capability is improved by a heat dissipating layer formed of metal having a relatively large thickness, ejection performance is improved and a driving frequency is increased. In addition, a nozzle can be formed to have a sufficient length. Thus, a meniscus at the surface of ink in the nozzle can be maintained in the nozzle, an ink refill operation can be stably performed, and a linearity of ink droplets ejected through the nozzle may be improved. Third, the shape and dimensions of a heater, a nozzle, an ink chamber, and an ink channel are not closely connected with one another, and a degree of freedom in designing and manufacturing the monolithic ink-jet printhead is high. Thus, ejection performance can be improved, and a driving frequency can easily be increased. Fourth, since a nozzle plate is formed integrally with a substrate having the ink chamber and the ink channel, the monolithic ink-jet printhead can be implemented by a series of processes on a single wafer without any subsequent processes, thereby improving the yield of the monolithic ink-jet printhead and simplifying the process of manufacturing the monolithic ink-jet printhead.
Exemplary embodiments of the present invention have been disclosed herein and, although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. For example, materials used in forming each element of an ink-jet printhead according to the present invention may be varied. Accordingly, a substrate may be formed of a material having a good processing property other than silicon, and the case of the substrate may also be applied to sidewalls, a bottom wall, a heater, a conductor, passivation layers, and a heat dissipating layer. In addition, methods for depositing and forming each element may be modified. Furthermore, specific dimensions exemplified in each step may be adjusted within the range in which the manufactured printhead operates normally. In addition, the order in which steps of a method of manufacturing the ink-jet printhead are performed may be changed. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.
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