Abstract:
A method for fabricating a monolithic fluid injection device. The method includes providing a substrate with a patterned sacrificial layer thereon. Next, a patterned support layer and a patterned resistive layer, as a heating element, are formed on the substrate sequentially. A patterned insulating layer having a heating element contact via and a first opening is formed on the support layer. A patterned conductive layer is formed on the support layer and fills the heating element contact via as a signal transmitting circuit. A patterned protective layer having a signal transmitting circuit contact via and a second opening corresponding to the first opening is formed on the substrate. A manifold is formed by wet etching the back of the substrate to expose the sacrificial layer. A chamber is formed by removing the sacrificial layer in the wet etching process. Finally, an opening connecting the chamber is formed by etching the support layer along the second opening.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to thermal ink-jet (TIJ) technology, and more particularly, to a method for fabricating a monolithic fluid injection device.  
           [0003]    2. Description of the Related Art  
           [0004]    The conventional fabrication technique of a monolithic fluid injection device typically includes standard integrated circuit (IC) technology and micro-electro-mechanical system (MEMS) technology for both front-end and back-end processes. The front-end process comprises formation of wafer driving circuits and heating elements in an IC foundry. The subsequent back-end process forms fluid chambers and orifices on said wafer in a MEMS foundry.  
           [0005]    Both the IC and MEMS processes require one or several thin-film processing techniques, such as metal deposition, dielectric deposition, or etching of dielectric openings. Production costs and the probability of defects, however, increase with repeated thin-film processes.  
           [0006]    Conventionally, a monolithic fluid injection device with various components, such as a fluid chamber, a heater, a driving circuit, and an orifice, is formed on a silicon wafer using a MEMS process without requiring packaging and thus results in higher yield and lower cost.  
           [0007]    [0007]FIGS. 1A and 1B are schematic illustrations of a conventional monolithic fluid injection device fabrication process, wherein FIG. 1A shows the front-end IC process and FIG. 1B shows the back-end MEMS process. Referring to FIG. 1A, a substrate  10  (e.g., silicon wafer) having a first surface and a second surface is provided, and a monolithic fluid injection device is formed thereon. In a typical processing sequence, a patterned sacrificial layer  20  is formed on the first surface of the substrate  10 . A patterned structure layer  30  is formed on the first surface of the substrate  10  and covers the patterned sacrificial layer  20 . A patterned resistive layer  40  is formed on the structure layer  30  as a heater. A patterned insulating layer  50  having a heater contact opening  45  is formed over the structure layer  30 . A patterned conductive layer  60  is formed overlying the structure layer  30  and fills the heater contact opening  45  as a signal transmitting circuit  62 . A patterned protective layer  70 , having a signal transmitting circuit contact opening and covering the insulating layer  50  and the conductive layer  60 , is formed overlying the substrate  10 .  
           [0008]    Referring to FIG. 1B, the IC processed wafer is then subjected to wet etching. A fluid channel  80  is formed in the second surface of the substrate  10  and exposes the sacrificial layer  20 . The sacrificial layer  20  is then removed to form a fluid chamber  90 . Thereafter the protective layer  70 , the insulating layer  50 , the structure layer  30 , an orifice  90  connecting the fluid chamber  95  are formed sequentially by lithographic etching. Thus, formation of a monolithic fluid injection device is complete.  
           [0009]    The above described formation of the orifice  90  minimally requires etching of the protective layer  70 , the insulating layer  50 , and the structure layer  30 . The front-end process, however, also requires etching of the protective layer  70  and the insulating layer  50  to form an electrical connection between the signal transmitting circuit  62  and the heater  40  to form a signal transmitting contact.  
           [0010]    A monolithic fluid injection device combining IC and MEMS processes is disclosed in U.S. Pat. No. 6,102,530. In this method, a structure layer is suspended over the fluid chamber; hence, the process must be precisely controlled to improve production yield and reliability.  
         SUMMARY OF THE INVENTION  
         [0011]    An object of the present invention is to provide a less complex method of fabricating a monolithic fluid injection device. By merging part of back-end MEMS process with the front-end IC process, overall process efficiency is improved.  
           [0012]    According to the object mentioned above, the present invention provides a method for fabricating a monolithic fluid injection device. A substrate having a first surface and a second surface is provided. A patterned sacrificial layer is formed on the first surface of the substrate. A patterned structure layer is formed on the first surface of the substrate and covers the patterned sacrificial layer. A patterned resistive layer is formed on the structure layer as a heater. A patterned insulating layer having a heater contact opening and a first opening is formed on the structure layer, wherein at least a portion of the heater is exposed through the heater contact opening. A patterned conductive layer is formed overlying the structure layer and connecting the heater via the heater contact opening to form a signal transmitting circuit. A patterned protective layer having a signal transmitting circuit contact opening and a second opening corresponding to the first opening is formed overlying the substrate and covers the insulating layer and the conductive layer. A fluid channel in the second surface of the substrate, opposing the first surface, is formed and exposes the sacrificial layer. The sacrificial layer is removed to form a fluid chamber. The structure layer is etched along the second and the first opening to form an orifice connecting the fluid chamber.  
           [0013]    According to the object mentioned above, the present invention provides another method for fabricating a monolithic fluid injection device. A substrate having a first surface and a second surface is provided. A patterned sacrificial layer is formed on the first surface of the substrate. A patterned structure layer is formed on the first surface of the substrate and covers the patterned sacrificial layer. A patterned resistive layer is formed on the structure layer as a heater. A patterned insulating layer having a heater contact opening is formed on the structure layer, wherein at least a portion of the heater is exposed through the heater contact opening. A patterned conductive layer is formed overlying the structure layer and connecting the heater via the heater contact opening to form a signal transmitting circuit. A patterned protective layer is formed overlying the substrate and covers the insulating layer and the conductive layer. A fluid channel in the second surface of the substrate, opposing the first surface, is formed and exposes the sacrificial layer. The sacrificial layer is removed to form a fluid chamber. The protective layer, the insulating layer, and the structure layer are etched to form an orifice connecting the fluid chamber  
           [0014]    The present invention provides still another method for fabricating a monolithic fluid injection device. A substrate having a first surface and a second surface is provided. A patterned sacrificial layer is formed on the first surface of the substrate. A patterned structure layer is formed on the first surface of the substrate and covers the patterned sacrificial layer. A patterned resistive layer is formed on the structure layer as a heater. A patterned insulating layer having a heater contact opening is formed on the structure layer, wherein at least a portion of the heater is exposed through the heater contact opening. A patterned conductive layer is formed overlying the structure layer and fills the heater contact opening to form a signal transmitting circuit. A patterned protective layer is formed overlying the substrate and covers the insulating layer and the conductive layer. The protective layer and the insulating layer are etched to form an opening. A fluid channel is formed in the second surface of the substrate, opposing the first surface, and exposes the sacrificial layer. The sacrificial layer is removed to form a fluid chamber. The structure layer is etched along the opening to form an orifice connecting the fluid chamber  
           [0015]    The present invention further provides another method for fabricating a monolithic fluid injection device. A substrate having a first surface and a second surface is provided. A patterned sacrificial layer is formed on the first surface of the substrate. A patterned structure layer is formed on the first surface of the substrate and covers the patterned sacrificial layer. A conductive layer is formed on the structure layer. A patterned resistive layer is formed on the conductive layer as a heater. The conductive layer is patterned to form a signal transmitting circuit. A protective layer is formed overlying the substrate and covers the structure layer, the conductive layer, and the resistive layer. The protective layer is etched to form an opening. A fluid channel is formed in the second surface of the substrate, opposing the first surface, and exposes the sacrificial layer. The sacrificial layer is removed to form a fluid chamber. The structure layer is etched along the opening to form an orifice connecting the fluid chamber.  
           [0016]    The present invention provides yet another method for fabricating a monolithic fluid injection device. A substrate having a first surface and a second surface is provided. A patterned sacrificial layer is formed on the first surface of the substrate. A patterned structure layer is formed on the first surface of the substrate and covers the patterned sacrificial layer. A conductive layer is formed on the structure layer. A patterned resistive layer is formed on the conductive layer as a heater. The conductive layer is patterned to form a signal transmitting circuit. A protective layer is formed overlying the substrate and covers the structure layer, the conductive layer, and the resistive layer. A fluid channel is formed on a second surface of the substrate, opposing the first surface, and exposing the sacrificial layer. The sacrificial layer is removed to form a fluid chamber. The protective layer and the structure layer is etched sequentially to form an orifice connecting the fluid chamber  
           [0017]    The advantage of the present invention is providing a hybrid integrated process for fabricating the orifice of a monolithic fluid injection device. More specifically, integrating portions of the back-end MEMS and front-end IC processes, reduces process cost improves yield.  
         BRIEF DESCRIPTION OF THE DRAWINGS  
         [0018]    The present invention can be more fully understood by reading the subsequent detailed description in conjunction with the examples and references made to the accompanying drawings, wherein:  
           [0019]    [0019]FIGS. 1A and 1B are schematic illustrations of the conventional monolithic fluid injection device fabrication process, wherein FIG. 1A shows the front-end IC process and FIG. 1B shows the back-end MEMS process;  
           [0020]    [0020]FIGS. 2A to  2 F are cross-sections illustrating the manufacture of a monolithic fluid injection device according to the first embodiment of the invention, wherein FIGS. 2A to  2 D show the front-end IC process and FIGS. 2E to  2 F show the back-end MEMS process;  
           [0021]    [0021]FIGS. 3A to  3 C are cross-sections illustrating the manufacture of a monolithic fluid injection device according to the second embodiment of the invention, wherein FIG. 3A shows the front-end IC process and FIGS. 3B and 2C show the back-end MEMS process;  
           [0022]    [0022]FIGS. 4A to  4 C are cross-sections illustrating the manufacture of a monolithic fluid injection device according to the third embodiment of the invention, wherein FIG. 4A shows the front-end IC process and FIGS. 4B and 4C show the back-end MEMS process; and  
           [0023]    [0023]FIGS. 5A to  5 D are cross-sections illustrating the manufacture of a monolithic fluid injection device according to the fourth embodiment of the invention, wherein FIGS. 5A and 5B show the front-end IC process and FIGS. 5C and 5D show the back-end MEMS process. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]    First Embodiment  
         [0025]    [0025]FIGS. 2A to  2 F are cross-sections illustrating the manufacture of a monolithic fluid injection device according to the first embodiment of the invention, wherein FIGS. 2A to  2 D show the front-end IC process and FIGS. 2E to  2 F show the back-end MEMS process. Referring to FIG. 2A, a patterned sacrificial layer  120  is formed on a substrate  100  (e.g. a silicon wafer) having a first surface and a second surface. The sacrificial layer  120  comprises borophosphosilicate glass (BPSG), phosphosilicate glass (PSG), or silicon oxide. The sacrificial layer  120  may be deposited using a CVD or LPCVD process. In a typical processing sequence, a structure layer  130  is conformally formed on the first surface of the substrate  100  and covers the patterned sacrificial layer  120 . The structure layer  130  comprises silicon oxide. The structure layer  130  may be deposited using a CVD or a LPCVD process. A patterned resistive layer  140  is formed on the structure layer  130  as a heater. The resistive layer  140  comprises HfB 2 , TaAl, TaN, or TiN. The resistive layer  140  may be deposited using a PVD process, such as evaporation, sputtering, or reactive sputtering. A blanket insulating layer  150  is formed on the Structure layer  130 .  
         [0026]    Referring to FIG. 2B, lithographic etching is performed to define the insulating layer  150  to form a heater contact opening  145  and a first opening  195   a . The first opening  195   a  maybe a precursor of an orifice of a monolithic fluid injection device.  
         [0027]    Referring to FIG. 2C, a patterned conductive layer  162 , comprising Al, Cu, or alloys thereof, is formed overlying the structure layer  130  and fills the heater contact opening  145  to form a signal transmitting circuit  162 . The conductive layer  162  may be deposited using a PVD process, such as evaporation, sputtering, or reactive sputtering.  
         [0028]    Referring to FIG. 2D, a protective layer  170  is formed overlying the substrate  100 . Next, lithographic etching is performed to define the protective layer  170 . Therefore, a signal transmitting circuit contact opening  175  is formed and exposes the underlying conductive layer  162  for subsequent packaging. The insulating. layer  150  is etched along the first opening  195   a  and transformed to a second opening  195   b  as a precursor of the orifice of the monolithic fluid injection device.  
         [0029]    Referring to FIG. 2E, a fluid channel  180  is formed in the second surface of the substrate  100  and exposes the sacrificial layer  120 . The sacrificial layer  120  is then removed to form a fluid chamber  190 .  
         [0030]    Referring to FIG. 2F, the structure layer  130  is etched by lithography along the second opening  195   b  to form an orifice  190  connecting the fluid chamber  195 . The lithographic etching comprises plasma etching, chemical dry etching, reactive ion etching, and laser etching. Thus, formation of a monolithic fluid injection device is complete.  
         [0031]    Second Embodiment  
         [0032]    [0032]FIGS. 3A to  3 C are cross-sections illustrating the manufacture of a monolithic fluid injection device according to the second embodiment of the invention, wherein FIG. 3A shows the front-end IC process and FIGS. 3B and 2C show the back-end MEMS process. Referring to FIG. 3A, a patterned sacrificial layer  120  is formed on a substrate  100  (e.g. a silicon wafer) having a first surface and a second surface. The sacrificial layer  120  comprises borophosphosilicate glass (BPSG), phosphosilicate glass (PSG), or silicon oxide. The sacrificial layer  120  may be deposited using a CVD or LPCVD process. In a typical processing sequence, a structure layer  130  is conformally formed on the first surface of the substrate  100  and covers the patterned sacrificial layer  120 . The structure layer  130  comprises silicon oxide. The structure layer  130  may be deposited using a CVD or LPCVD process. A patterned resistive layer  140  is formed on the structure layer  130  as a heater. The resistive layer  140  comprises HfB 2 , TaAl, TaN, or TiN. The resistive layer  140  may be deposited using a PVD process, such as evaporation, sputtering, or reactive sputtering. A blanket insulating layer  150  is formed on the structure layer  130 .  
         [0033]    Next, lithographic etching is performed to define a heater contact opening  145 . Thereafter, a patterned conductive layer  162 , comprising Al, Cu, or alloys thereof, is formed overlying the structure layer  130  and fills the heater contact opening  145  to form a signal transmitting circuit  162 . The conductive layer  162  may be deposited using a PVD process, such as evaporation, sputtering, or reactive sputtering. A protective layer  170  is formed overlying the substrate  100  and covers the insulating layer  150  and the signal transmitting circuit  162 .  
         [0034]    Referring to FIG. 3B, a fluid channel  180  is formed in the second surface of the substrate  100  and exposes the sacrificial layer  120 . The sacrificial layer  120  is then removed to form a fluid chamber  190 .  
         [0035]    Referring to FIG. 3C, lithographic etching is performed to sequentially penetrate the protective layer  170 , insulating layer  150 , and the structure layer  130 , forming an orifice  190  to connect the fluid chamber  195 . Alternately, a signal transmitting circuit contact opening  175  is simultaneously formed exposing the underlying conductive layer  162  for subsequent packaging. The lithographic etching comprises plasma etching, chemical dry etching, reactive ion etching, or laser etching. Thus, formation of a monolithic fluid injection device is complete.  
         [0036]    Third Embodiment  
         [0037]    [0037]FIGS. 4A to  4 C are cross-sections illustrating the manufacture of a monolithic fluid injection device according to the third embodiment of the invention, wherein FIG. 4A shows the front-end IC process and FIGS. 4B and 4 c  show the back-end MEMS process. Referring to FIG. 2A, a patterned sacrificial layer  120  is formed on a substrate  100  (e.g. a silicon wafer) having a first surface and a second surface. The sacrificial layer  120  comprises borophosphosilicate glass (SPSG), phosphosilicate glass (PSG), or silicon oxide. The sacrificial layer  120  may be deposited using a CVD or LPCVD process. In a typical processing sequence, a structure layer  130  is conformally formed on the first surface of the substrate  100  and covers the patterned sacrificial layer  120 . The structure layer  130  comprises a silicon nitride. The structure layer  130  may be deposited using a CVD or LPCVD process. A patterned resistive layer  140  is formed on the structure layer  130  as a heater. The resistive layer  140  comprises HfB 2 , TaAl, TaN, or TiN. The resistive layer  140  may be deposited using a PVD process, such as evaporation, sputtering, or reactive sputtering. A blanket insulating layer  150  is formed on the structure layer  130 . Thereafter, lithographic etching is performed to define the insulating layer  150  and form a heater contact opening  145 .  
         [0038]    Next, a patterned conductive layer  162 , comprising Al, Cu, or alloys thereof, is formed overlying the structure layer  130  and fills the heater contact opening  145  to form a signal transmitting circuit  162 . The conductive layer  162  may be deposited using a PVD process, such as evaporation, sputtering, or reactive sputtering. A protective layer  170  is formed overlying the substrate  100 . Lithographic etching is then performed to define the protective layer  170 , thereby forming a signal transmitting circuit contact opening  175  and exposing the underlying conductive layer  162  for subsequent packaging. The protective layer  170  and the insulating layer  150  are etched to form a second opening  195   b  as a precursor of the orifice of the monolithic fluid injection device.  
         [0039]    Referring to FIG. 4B, a fluid channel  180  is formed in the second surface of the substrate  100  and exposes the sacrificial layer  120 . The sacrificial layer  120  is then removed to form a fluid chamber  190 .  
         [0040]    Referring to FIG. 4C, the structure layer  130  is etched by lithography along the second opening  195   b  to form an orifice  190  connecting the fluid chamber  195 . Thus, formation of a monolithic fluid injection device is complete.  
         [0041]    Fourth Embodiment  
         [0042]    [0042]FIGS. 5A to  5 D are cross-sections illustrating the manufacture of a monolithic fluid injection device according to the fourth embodiment of the invention, wherein FIGS. 5A and 5B show the front-end IC process and FIGS. 5C and 5D show the back-end MEMS process. Referring to FIG. 5A, a patterned sacrificial layer  120  is formed on a substrate  100  (e.g. a silicon wafer) having a first surface and a second surface. The sacrificial layer  120  comprises borophosphosilicate glass (BPSG), phosphosilicate glass (PSG), or silicon oxide. The sacrificial layer  120  may be deposited using a CVD or LPCVD process. In a typical processing sequence, a structure layer  130  is conformally formed on the first surface of the substrate  100  and covers the patterned sacrificial layer  120 . The structure layer  130  is composed of silicon oxide. The structure layer  130  may be deposited using a CVD or LPCVD process. Next, a conductive layer  162 , comprising Al, Cu, or alloys thereof, is formed overlying the structure layer  130 . The conductive layer  162  may be deposited using a PVD process, such as evaporation, sputtering, or reactive sputtering. A resistive layer  140  is formed on the structure layer  130  as a heater. The resistive layer  140  comprises HfB 2 , TaAl, TaN, or TiN. The resistive layer  140  may be deposited using a PVD process, such as evaporation, sputtering, or reactive sputtering. The resistive layer  140  is patterned to form a signal transmitting circuit  162 . A blanket protective layer  170  is formed on the structure layer  130  and covers the resistive layer  140  and the signal transmitting circuit  162 .  
         [0043]    Referring to FIG. 5B, lithographic etching is performed to define the protective layer  170  to form a heater contact opening  145 . During the etching process, the signal transmitting circuit  162  may be used as an etch stopper. Simultaneously, the protective layer  170  is etched to form an opening  195   b  as a precursor of the orifice of the monolithic fluid injection device.  
         [0044]    Referring to FIG. 5C, a fluid channel  180  is formed in the second surface of the substrate  100  and exposes the sacrificial layer  120 . The sacrificial layer  120  is then removed to form a fluid chamber  190 .  
         [0045]    Referring to FIG. 5D, the structure layer  130  is etched by lithography along the opening  195   b  to form an orifice  190  connecting the fluid chamber  195 . The lithographic etching comprises plasma etching, chemical dry etching, reactive ion etching, and laser etching. Thus, formation of a monolithic fluid injection device is complete.  
         [0046]    Fifth Embodiment  
         [0047]    Referring again to FIG. 5A, a patterned sacrificial layer  120  is formed on a substrate  100  (e.g. a silicon wafer) having a first surface and a second surface. The sacrificial layer  120  comprises borophosphosilicate glass (BPSG), phosphosilicate glass (PSG), or silicon oxide. The sacrificial layer  120  may be deposited using a CVD or LPCVD process. In a typical processing sequence, a structure layer  130  is conformally formed on the first surface of the substrate  100  and covers the patterned sacrificial layer  120 . The structure layer  130  comprises silicon oxide. The structure layer  130  may be deposited using a CVD or LPCVD process. Next, a conductive layer  162 , comprising Al, Cu, or alloys thereof, is formed overlying the structure layer  130 . The conductive layer  162  may be deposited using a PVD process, such as evaporation, sputtering, or reactive sputtering. A resistive layer  140  is formed on the structure layer  130  as a heater. The resistive layer  140  comprises HfB 2 , TaAl, TaN, or TiN. The resistive layer  140  may be deposited using a PVD process, such as evaporation, sputtering, or reactive sputtering. The resistive layer  140  is patterned to form a signal transmitting circuit  162 . A blanket protective layer  170  is formed on the structure layer  130  and covers the resistive layer  140  and the signal transmitting circuit  162 .  
         [0048]    Referring again to FIG. 5C, a fluid channel  180  is formed in the second surface of the substrate  100  and exposes the sacrificial layer  120 . The sacrificial layer  120  is then removed to form a fluid chamber  190 .  
         [0049]    Next, lithographic etching is performed to define the protective layer  170 , and form a heater contact opening  145 . During the etching process, the signal transmitting circuit  162  may be used as an etch stopper. The protective layer  170  and the structure layer  130  are simultaneously etched to form an orifice  190  connecting the fluid chamber  195 . The lithographic etching comprises plasma etching, chemical dry etching, reactive ion etching, and laser etching. Thus, formation of a monolithic fluid injection device is complete.  
         [0050]    The primary advantage of the described preferred embodiments lies in the hybrid integrated process for fabricating the orifice of a monolithic fluid injection device.  
         [0051]    More specifically, the invention integrates portions of the back-end MEMS and front-end IC processes, thus reducing overall process costs and increasing yield. Additionally, the orifice of the monolithic fluid injection device can also be improved.  
         [0052]    Finally, while the invention has been described by way of example and in terms of the above, it is to be understood that the invention is not limited to the disclosed embodiments. On 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.