Abstract:
A fluid injection device. The device includes a substrate, a structural layer formed thereon, a manifold installed in the substrate to supply fluid, a plurality of chambers with the same length formed between the substrate and the structural layer to hold injected fluid, and a plurality of nozzles through the structural layer to inject fluid, wherein each chamber connects with the manifold by a channel and the nozzles connect to the chambers.

Description:
BACKGROUND  
       [0001]     The present invention relates to a semiconductor device, and more specifically to a fluid injection device.  
         [0002]     Currently, the fluid injection technique is widely used in various products, such as ink jet printheads, fuel oil injection devices, or drug injection mechanism.  
         [0003]     A related art fluid injection device is disclosed for example, in U.S. Pat. No. 6,102,530 and illustrated in  FIG. 1 . The fluid injection device comprises a silicon substrate  38 , a manifold  26  to transport fluid, a plurality of chambers  14  installed on one side of the manifold  26  to hold fluid, a plurality of nozzles  18  installed on the surface of the chambers  14  to inject fluid, and injection elements  20  and  22  installed around the nozzles  18 .  
         [0004]     A fabrication process for the above chamber  14  is disclosed in the following. Referring to  FIG. 2   a,  a substrate  38  comprising an upper protective layer  42  and a lower protective layer  44  is provided, wherein a sacrificial layer is installed between the substrate  38  and the upper protective layer  42 . Subsequently, referring to  FIG. 2   b,  the back of the substrate  38  is etched by anisotropic wet etching to form a manifold  26 , exposing the sacrificial layer  40  (not shown). The sacrificial layer  40  (not shown) is then removed by HF. Finally, the substrate  38  is repeatedly etched with KOH to enlarge the vacant volume thereof, thus forming the chamber  14 , as shown in  FIG. 2   c.    
         [0005]      FIG. 3   a  shows an original chamber pattern design on a mask and  FIG. 3   b  shows an etching result of the chambers. Referring to  FIG. 3   b,  when the chambers  14  are formed by anisotropic wet etching, the portion  30  of the substrate isolating each chamber  14  may also be etched. As a result, various chamber lengths may be provided from the original design (as shown in  FIG. 3   a ) because anisotropic etching has various etching rates for different crystal planes, thus resulting in cross-talk among the chambers  14 . Additionally, stress may concentrate on a point, when an etching peak  31  is formed, thus deteriorating structural strength and reducing active lifetime of a device. The above situation may worsen with reduced device size.  
       SUMMARY  
       [0006]     In order to solve problems related to the conventional technology, the invention provides a fluid injection device having chambers with the same length to eliminate cross-talk while chambers are refilled with fluid.  
         [0007]     The invention provides a fluid injection device comprising a substrate, a structural layer formed on the substrate, a manifold installed in the substrate to supply fluid, a plurality of chambers with the same length formed between the substrate and the structural layer to hold injected fluid, a plurality of channels formed between the chambers and the manifold, and a plurality of nozzles through the structural layer and connected with the chambers to inject fluid, wherein the manifold is connected to the chambers by the channels.  
         [0008]     Based on the above device structure, when the chambers are refilled with fluid, cross-talk between adjacent chambers can be avoided due to the narrow channels between the chambers and the manifold.  
         [0009]     The invention also provides a fluid injection device comprising a substrate, a structural layer formed on the substrate, a manifold installed in the substrate to supply fluid, a plurality of chambers formed between the substrate and the structural layer and connected with the manifold to hold injected fluid, a neck structure installed between the manifold and each chamber, and a plurality of nozzles through the structural layer, connecting the chambers to inject fluid.  
         [0010]     The invention further provides a fluid injection device comprising, a substrate, a structural layer formed on the substrate, a manifold installed in the substrate to supply fluid, a plurality of chambers formed between the substrate and the structural layer and connected with the manifold to hold injected fluid, a neck structure installed between the manifold and each chamber, wherein the neck structures have different widths which increase as distances from the chambers to the manifold increase, and a plurality of nozzles through the structural layer, connecting the chambers to inject fluid.  
         [0011]     A detailed description is given in the following embodiments with reference to the accompanying drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:  
         [0013]      FIG. 1  is a cross section of a fluid injection device as disclosed in U.S. Pat. No. 6,102,530.  
         [0014]      FIGS. 2   a ˜ 2   c  are cross sections illustrating fabrication process of a fluid injection device as disclosed in U.S. Pat. No. 6,102,530.  
         [0015]      FIG. 3   a  shows a related mask pattern.  
         [0016]      FIG. 3   b  illustrates anisotropic etching performance.  
         [0017]      FIGS. 4   a ˜ 4   b  are cross sections of the method of fabricating a fluid injection device of the invention.  
         [0018]      FIGS. 4   c ˜ 4   d,    5   a ˜ 5   b,    6   a ˜ 6   b,  and  7   a ˜ 7   b  show various mask patterns and etching results of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0019]     Referring to  FIG. 4   d,  the first feature of the fluid injection device of the invention is the installation of the narrow channels  430  between the chambers  420  and the manifold  410  to form the chambers  420  with the same length (Lc).  
         [0020]     The above device structure is illustrated in  FIG. 4   b  (a cross section) and  FIG. 4   d  (a top view), wherein  FIG. 4   b  is a cross section along the tangent line  4   b - 4   b  of  FIG. 4   d.  Referring to  FIG. 4   b,  the fluid injection comprises a substrate  400 , a manifold  410 , a plurality of chambers  420 , a plurality of channels  430 , a structural layer  440 , a resist layer  450 , an isolation layer  460 , a conductive layer  470 , a protective layer  480 , a plurality of signal transmission line contacts  490 , and a plurality of nozzles  495 . The manifold  410  is formed in the substrate  400 , and the chambers  420  and the channels  430  are formed between the substrate  400  and the structural layer  440 . Lengths of the chambers  420  are equal due to the installation of the channels  430 , as shown in  FIG. 4   d.    
         [0021]     The structural layer  440  covers the substrate  400 , the channels  430 , and the chambers  420 . The resist layer  450  is installed on the structural layer  440  and on both sides of the nozzles  495 . The resist layer  450  represents a plurality of fluid actuators, such as heaters, thereby driving fluid out of the nozzles  455 . The isolation layer  460  covers the substrate  400 , the structural layer  440 , and the resist layer  450 , exposing a portion of the resist layer  450  to form heater contacts. The conductive layer  470  covers the isolation layer  460  and fills heater contacts to form signal transmission lines.  
         [0022]     The protective layer  480  covers the isolation layer  460  and the conductive layer  470 , exposing a portion of the conductive layer  470  to form a plurality of signal transmission line contacts  490 , thereby facilitating subsequent packaging process. A plurality of nozzles  495  are formed through the protective layer  480 , the conductive layer  470 , the resist layer  450 , and the structural layer  440 , and connected to the chambers  420 .  
         [0023]     Referring to  FIG. 4   a ˜ 4   d,  a method of fabricating the fluid injection device is provided. First, referring to  FIG. 4   a,  a substrate  400  such as a silicon substrate is provided. The thickness of the substrate  400  is about 625˜675 μm. Subsequently, a critical step of fabricating a patterned sacrificial layer  405  is performed. First, a sacrificial layer is formed on a first plane  4001  of the substrate  400 . Next, the sacrificial layer is exposed by a mask having channel patterns and chamber patterns, as shown in  FIG. 4   c.  Finally, a patterned sacrificial layer  405  comprising channel patterns and chamber patterns is formed after developing, wherein lengths of the chamber patterns are equal.  
         [0024]     The sacrificial layer  405  comprises BPSG, PSG, or silicon oxide, preferably PSG. The thickness of the sacrificial layer  405  is about 1˜2 μm.  
         [0025]     Next, a patterned structural layer  440  is formed on the substrate  400  to cover the patterned sacrificial layer  405 . The structural layer  440  may be silicon oxide nitride formed by CVD. The thickness of the structural layer  440  is about 1.5˜2 μm. Additionally, the structural layer  440  is a low-stress material, and the stress thereof is about 100˜200 MPa.  
         [0026]     Subsequently, a patterned resist layer  450  is formed on the structural layer  440 , as fluid actuators, such as heaters, thereby driving fluid out of subsequently formed nozzles. The resist layer  450  comprises HfB 2 , TaAl, TaN, or TiN, and is preferably TaAl.  
         [0027]     A patterned isolation layer  460  is then formed to cover the substrate  400 , the structural layer  440 , and the resist layer  450 , forming heater contacts. Subsequently, a patterned conductive layer  470  is formed on the isolation layer  460 , and filled heater contacts to form signal transmission lines. Finally, a protective layer  480  is formed on the isolation layer  460  and the conductive layer  470 , exposing the conductive layer  470 , thereby forming signal transmission line contacts  490  to facilitate a subsequent packaging process.  
         [0028]     Subsequently, referring to  FIG. 4   b,  a series of etching steps are performed. First, a second plane  4002  of the substrate  400  is etched to form a manifold  410  by anisotropic wet etching using TMAH, KOH, or NaOH as an etching solution, exposing the sacrificial layer  405 .  
         [0029]     The narrow opening width of the manifold  410  is about 160˜200 μm, and the wide opening width thereof is about 100˜1200 μm. The included angle between the side wall of the manifold  410  and a horizontal factor is about 54.74°. Therefore, after etching, a manifold  410  with a back opening larger than a front opening is formed. Additionally, the manifold  410  connects to a fluid storage tank.  
         [0030]     Next, the sacrificial layer  405  is removed by HF, and the substrate  400  is subsequently etched with a basic etching solution, such as KOH or NaOH, to enlarge the vacant volume thereof, forming the chambers  420  and the channels  430 , wherein the channels  430  are formed between the chambers  420  and the manifold  410 , and lengths (Lc) of the chambers are equal, as shown in  FIG. 4   d.    
         [0031]     Finally, referring to  FIG. 4   b,  the protective layer  480 , the isolation layer  460 , and the structural layer  440  are etched in order by plasma etching, chemical vapor etching, laser etching, or reactive ion etching (RIE) to form the nozzles  495  connecting to the chambers  420 .  
         [0032]     The invention provides a specific connection design such as a manifold-channel-chamber on a photomask to compensate for more rapidly etched portion of a substrate to form chambers with the same length to solve the cross-talk problem when chambers are refilled with fluid.  
         [0033]     Referring to  FIG. 5   b,  the second feature of the fluid injection device of the invention are the installation of the neck structures  525  between the chambers  520  and the manifold  510  to form the chambers  520  with the same length (Lc) and the formation of the same connection width (Wch) of the neck structures  525  and the manifold  510 . The distinction between  FIG. 5   b  and  FIG. 4   d  is that the latter merely discloses forming the chambers  420  with the same length, but  FIG. 5   b  discloses forming the same connection width  530  of the neck structures  525  and the manifold  510  in addition to forming the chambers  520  with the same length.  
         [0034]     The fabrication methods for the injection devices illustrated in  FIG. 5   b  and  FIG. 4   d  are similar. The distinction therebetween is merely the pattern formation on a sacrificial layer, for example, after a sacrificial layer is formed on a first plane of the substrate, the sacrificial layer is exposed by a mask having neck structure patterns and chamber patterns, as shown in  FIG. 5   a,  to form a patterned sacrificial layer comprising neck structure patterns and chamber patterns after developing, wherein lengths of the chamber patterns are equal.  
         [0035]     After deposition steps for each semiconductor layer are finished, a series of etching steps are performed to finally form a fluid injection device. The chambers  520  and the neck structures  525  are formed by etching, wherein the neck structures  525  are formed between the chambers  520  and the manifold  510  to form the chambers  520  with the same length (Lc), and the connections of the neck structures  525  and the manifold  510  have the same width, as shown in  FIG. 5   b.    
         [0036]     The invention provides a specific connection design such as a manifold-neck structure-chamber on a photomask to form chambers with the same length and solve cross-talk problems by forming connections with the same width between the neck structures and the manifold. Additionally, the invention also prevents the formation of etching peaks due to increasing the isolation area  30  as shown in  FIG. 3   b.    
         [0037]     Referring to  FIG. 6   b,  the third feature of the fluid injection device of the invention is the installation of neck structures  625  with the same length (Ln) between the chambers  620  and the manifold  610  to form chambers  620  with the same length (Lc). The distinction between  FIG. 6   b  and  FIG. 5   b  is that the latter does not set the lengths of the neck structure  525 , but  FIG. 6   b  discloses forming the neck structures  625  with the same length.  
         [0038]     The fabrication methods for the injection devices illustrated in  FIG. 6   b  and  FIG. 5   b  are similar. The distinction therebetween is merely the pattern formation on a sacrificial layer, for example, after a sacrificial layer is formed on a first plane of the substrate, the sacrificial layer is exposed by a mask having neck structure patterns and chamber patterns, as shown in  FIG. 6   a,  to form a patterned sacrificial layer comprising neck structure patterns and chamber patterns after developing, wherein lengths of the chamber patterns and the neck structure patterns are respectively equal.  
         [0039]     After deposition steps for each semiconductor layer are finished, a series of etching steps are performed to finally form a fluid injection device. The chambers  620  and the neck structures  625  are formed by etching, wherein the neck structures  625  are formed between the chambers  620  and the manifold  610  to form the chambers  620  with the same length (Lc), and the lengths thereof are also equal, as shown in  FIG. 6   b.    
         [0040]     The invention provides a specific connection design such as a manifold-neck structure-chamber on a photomask to form chambers with the same length and solve the cross-talk problem and control the flow resistance by forming the neck structures with the same length.  
         [0041]     Referring to  FIG. 7   b,  the fourth feature of the fluid injection device of the invention are the installation of the neck structures  725  with the same length (Ln) between the chambers  720  and the manifold  710  to form the chambers  720  with the same length (Lc) and the design of the altered neck structure widths (Wn 1 ˜Wn 3 ) which increase as distances from the chambers  720  to the manifold  710  increase. The distinction between  FIG. 7   b  and  FIG. 6   b  is that the latter does not set the widths of the neck structures  625 , but  FIG. 7   b  discloses forming the neck structures  725  with altered widths which increase as distances from the chambers  720  to the manifold  710  increase.  
         [0042]     The fabrication methods for the injection devices illustrated in  FIG. 7   b  and  FIG. 6   b  are similar. The distinction therebetween is merely the pattern formation on a sacrificial layer, for example, after a sacrificial layer is formed on a first plane of the substrate, the sacrificial layer is exposed by a mask having neck structure patterns and chamber patterns, as shown in  FIG. 7   a,  to form a patterned sacrificial layer comprising neck structure patterns and chamber patterns after developing, wherein lengths of the chamber patterns and the neck structure patterns are respectively equal, and the widths of the neck structure patterns are increased as distances from the chamber patterns to the subsequently formed manifold increase.  
         [0043]     After deposition steps for each semiconductor layer are finished, a series of etching steps are performed to finally form a fluid injection device. The chambers  720  and the neck structures  725  are formed by etching, wherein the neck structures  725  are formed between the chambers  720  and the manifold  710  to form the chambers  720  with the same length (Lc), the lengths thereof are also equal, and the widths of the neck structures  725  are increased as distances from the chambers  720  to the manifold  710  increase, such as Wn 3 &gt;Wn 2 &gt;Wn 1 , as shown in  FIG. 7   b.    
         [0044]     The invention provides a specific connection design such as a manifold-neck structure-chamber on a photomask to form chambers with the same length and effectively control the flow resistance by forming the neck structures with the altered widths, significantly improving the injection quality.  
         [0045]     While the invention has been described by way of example and in terms of preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art) Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.