Patent Publication Number: US-2012032297-A1

Title: Electronic Device and Method for Fabricating the Same, Spiral Inductor Device and Method for Fabricating the Same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This Application claims priority of Taiwan Patent Application No. 099126041, filed on Aug. 4, 2010, the entirety of which is incorporated by reference herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an electronic device, and in particular relates to an electronic device with an opening. 
     2. Description of the Related Art 
     Many digital and analog elements and circuits have been successfully applied to semiconductor integrated circuits. Such elements may include passive components, such as resistors, capacitors, or inductors. Typically, a semiconductor integrated circuit includes a silicon substrate. One or more dielectric layers are formed on the substrate, and one or more metal layers are formed in the dielectric layers or thereon. The metal layers may be employed to form on-chip elements, such as on-chip inductors, by current semiconductor technologies. 
     Conventionally, an on-chip inductor is formed on an insulating layer on a substrate, wherein the inductor is electrically connected to an external circuit by the conductive plugs, the conductive layers and the signal output/input conductive traces. A principle advantage of the planar spiral inductor device is an increased level of circuit integration due to the reduced number of off-chip circuit elements and the complex interconnections required thereby. 
     In spiral inductor devices, there are three factors to estimate the quality factor (Q value) of the inductor devices, including skin effect, substrate eddy current and coil eddy current. 
     To reduce the skin effect loss, spiral conductive traces are widened or thickened. To improve the substrate eddy current loss, use of a grounding metal shielding layer, interposed between the spiral conductive trace and the semiconductor substrate, has been proposed. However, there is currently no way to improve the coil eddy current loss. 
     Since the performance of the inductor devices is based on the Q value, there is a need to develop an inductor device so that the coil eddy current loss can be improved. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides an electronic device, comprising: a substrate; and a conductive trace pattern formed on the substrate, wherein the conductive trace pattern has an opening to expose the substrate. 
     The invention also provides a spiral inductor device, comprising: a substrate; and a spiral conductive trace pattern with at least one turn formed on the substrate, wherein the spiral conductive trace pattern has an opening to expose the substrate. 
     The invention also provides a method for fabricating an electronic device, comprising: providing a substrate; and forming a conductive trace pattern on the substrate, wherein the conductive trace pattern has an opening to expose the substrate. 
     The invention also provides a method for fabricating a spiral inductor device, comprising: providing a substrate; and forming a spiral conductive trace pattern on the substrate, wherein the spiral conductive pattern has an opening to expose the substrate. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
         FIG. 1A  shows a top-view schematic representation of an electronic device in accordance with an embodiment of the invention; and 
         FIG. 1B-1C  show a cross-sectional schematic representations of an electronic device in accordance with an embodiment of the invention; 
         FIG. 1D  shows a top-view schematic representation of an electronic device in accordance with an embodiment of the invention; 
         FIG. 2A  shows a top-view schematic representation of a spiral inductor device in accordance with an embodiment of the invention; 
         FIG. 2B  show a cross-sectional schematic representation of a spiral inductor device in accordance with an embodiment of the invention; and 
         FIG. 2C  shows a top-view schematic representation of a spiral inductor device in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
     Refer to  FIGS. 1A to 1C , in which  FIG. 1A  is a top view of an embodiment of an electronic device,  FIG. 1B  shows a cross section along  1 B- 1 B′ line shown in  FIG. 1A , and  FIG. 1C  shows a cross section along  1 C- 1 C′ line shown in  FIG. 1A . 
     Referring to  FIG. 1A  and  FIG. 1B , the invention provides an electronic device, wherein an opening is formed in a conductive trace pattern of the electronic device to change the amplitude of the magnetic field of the electronic device. The electronic device comprises: a substrate  10 ; and a conductive trace pattern  20  formed on the substrate  10 , wherein the conductive trace pattern  20  has an opening  30  to expose the substrate  10 . 
     The substrate  10  may include a silicon substrate or other well-known semiconductor substrates. The substrate  10  may include various elements, such as transistors, resistors, or other well-known semiconductor elements. Moreover, the substrate  10  may also include other conductive layers (e.g. copper, aluminum or alloy thereof) and insulating layers (e.g. silicon oxide, silicon nitride or low-k dielectric materials). Hereinafter, to simplify the diagram, only a flat substrate is depicted. 
     The conductive trace pattern  20  is a single conductive trace, or a number of parallel or parallel conductive traces. The material of the conductive trace pattern  20  may comprise copper, aluminum or alloy thereof. The conductive trace pattern  20  has a first end  20   a  and a second end  20   b  to input/output signals. According to actual application needs, the first end  20   a  and the second end  20   b  separately connect to other interconnect structures (not shown in figures). 
     The opening  30  is formed in the conductive trace pattern  20  and the conductive trace pattern is divided into a first part  21  and a second part  22 , wherein a width of the first part  21  may be larger, equal to or smaller than a width of the second part  22 . Referring to  FIG. 2B , the width W A  of the first part  21  is equal to the width W B  of the second part  22 . 
     The opening  30  is extended from the first end  20   a  to the second end  20   b . The opening  30  is extended from the top surface of the conductive trace pattern  20  down to the depth D which is the same as that of the thickness d of the conductive trace pattern  20 . Thus, the substrate  10  below the opening  30  is exposed. Referring to  FIG. 1C , note that the conductive trace pattern  20  is divided into the first part  21  and the second part  22 , but the opening  30  does not pass through the first end  20   a  and second end  20   b . Therefore, the first part  21  and the second part  22  electrically connect to each other by the first end  20   a  and the second end  20   b.    
     Additionally, the opening  30  comprises a continuous structure or a discontinuous structure, wherein the opening  30  is divided into a plurality of sections to form the discontinuous structure. Referring to  FIG. 1A , the opening  30  is a continuous structure. Alternatively, in another embodiment, referring to  FIG. 1D  the opening  30  is a discontinuous structure which is divided into two sections  30   a  and  30   b.    
     Moreover, referring to  FIG. 1A , the opening  30  is formed along the conductive trace pattern  20 , and a length L o  of the opening  30  is smaller than a length L c  of the conductive trace pattern  20 . Furthermore, the conductive trace pattern  20  comprises an arc shape or a rectangular shape. In one embodiment, the conductive trace pattern  20  is a spiral conductive trace. 
     According to Ampere&#39;s Law, as current flows through the electronic device, magnetic field is produced by the current. And, as the magnetic field passes through the conductive trace, an unwanted eddy current is induced. Because the original current and the eddy current interact with each other, the performance of the electronic device is reduced. In order to solve the above problems, an opening is formed in the conductive trace pattern of the electronic device of the invention, so that the amplitude of the magnetic field is changed by adjusting the position of the opening. Thus, the current of the conductive trace pattern is uniformly distributed to improve the performance of the electronic device. 
     The electronic device of the invention may be an inductor or other passive electronic devices, such as a transmission line or an energy storage device. All electronic devices in which performance may be affected by the uneven current are within the scope of the invention. Note that according to the shape and length of the conductive trace pattern, the position of the opening may be adjusted by those skilled in the art to change the amplitude of the magnetic field of the conductive trace pattern. 
     Refer to  FIGS. 2A to 2B , in which  FIG. 2A  is a top view of an embodiment of a spiral inductor device, and  FIG. 2B  shows a cross section along  2 B- 2 B′ line shown in  FIG. 2A . 
     Referring to  FIG. 2A , the invention provides a spiral inductor device, which comprises: a substrate  100  and a spiral conductive trace pattern  200 , wherein the spiral conductive trace pattern  200  is formed on the substrate  100  and has an opening  300 . The material of the substrate  100  is the same as that of the first embodiment; thus, repeated description is omitted. 
     The spiral conductive trace pattern  200  has at least one turn and comprises an inner end  200   a  and an outer end  200   b . All of the spiral conductive trace pattern  200  may substantially be in the same plane or not in the same plane. According to actual application needs, the first end  200   a  and second end  200   b , separately connect to other interconnect structures (not shown in figures). In this embodiment, the spiral conductive trace pattern  200  extends from the outer end  200   b  to the inner end  200   a  clockwise. In other embodiment, the spiral conductive trace pattern  200  may extend counterclockwise. In  FIG. 2A , the spiral conductive trace pattern  200  comprises 2.5 turns, but may comprises more turns as required. 
     The spiral conductive trace pattern  200  may comprise a circular, rectangular, hexagonal, octagonal or polygonal shape, and comprises a rectangular shape as shown in the preferred embodiment in  FIG. 2A . The material of the spiral conductive trace pattern  200  may comprise copper, aluminum or alloy thereof. 
     The opening  300  extends from the inner end  200   a  to the outer end  200   b . The opening  300  is extended from the top surface of the conductive trace pattern  200  down to the depth which is the same as that of the thickness of the conductive trace pattern  200 . Thus, the substrate  100  below the opening  300  is exposed. 
     Referring to  FIG. 2B , note that the opening  300  does not pass through the inner end  200   a . Although the conductive trace pattern  200  is divided into two parts by the opening  300 , the two parts still electrically connect to each other (by the inner end  200   a  and the outer end  200   b ). 
     Moreover, the opening  300  is formed along the spiral conductive trace pattern  200 , and a length of the opening  300  is smaller than a length of the spiral conductive trace pattern  200 . Furthermore, the opening  300  comprises a continuous structure or a discontinuous structure, wherein the opening  300  is divided into a plurality of sections to form the discontinuous structure. Referring to  FIG. 2A , the opening  300  is a continuous structure. Alternatively, in another embodiment, referring to  FIG. 2C , the opening  300  is a discontinuous structure and the opening  30  is divided into three sections. 
     Referring to  FIG. 2B , the spiral conductive trace pattern  200  has a width W m , the pitches between neighboring turns of the spiral conductive trace pattern  200  has a value P, and the opening  300  has a width S. The spiral conductive trace pattern  200  is divided into a first part  210  (a width of W 1a ),  230  (a width of W 1b ) and a second part  220  (a width of W 2a ),  240  (a width of W 2b ) by the opening  300 , wherein the first part  210 ,  230  is nearer to the inner end  200   a  than that of the second port  220 ,  240 . The sum of the width (W 1a , W 1b ) of the first part, the width (W 2a , W 2b ) of the second part and the width (S) of the opening  300  is the width (W m ) of the spiral conductive trace pattern  200 , and is represented as W m =W 1a,1b +W 2a,2b +S. 
     In prior art, when the current flows through the adjacent coils of the inductor, the magnetic field is generated in the adjacent coils (according to Ampere&#39;s law). When the magnetic field passes through the adjacent coil, an eddy current surrounding the coil is produced. The uneven current distribution of the coils caused by the eddy current will degrade the quality factor (Q value) of the inductor. Thus, the invention provides a spiral inductor, in which the opening is formed in the spiral conductive trace pattern to divide the spiral conductive trace pattern into two parts. The magnetic fields which are generated by the two parts, cancelled each other out to avoid eddy current. Thus, the current of the spiral conductive trace pattern is uniformly distributed, and quality factor of the inductor (Q value) is improved. 
     For example, referring to  FIG. 2B , when designing the position of the opening  300 , the two adjacent spiral conductive trace patterns are divided into four parts  210 ,  220 ,  230 ,  240  from left to right, respectively. When the second part  220  is centered, the magnetic fields generated by the left side  210  and the right side  230 , cancel each other out. When the first part  230  is centered, the magnetic field generated by the left side  220  and the right side  240  cancel each other out. Thus, preventing an unwanted eddy current. Regarding the design of the position of the opening, according to Lenz&#39;s Law and Ampere&#39;s Law, the width W m  of the spiral conductive trace pattern, the pitches P between neighboring turns of the spiral conductive trace pattern, the width S of the opening, the width W 1a,1b  of the first part and the width W 2a,2b  of the second part may be designed by those skilled in the art by computer simulated calculations to cancel the magnetic fields generated from the left and right sides of the divided spiral conductive trace pattern and further eliminate eddy current. 
     The width (W 1a,1b ) of the first part  210 ,  230  may be larger than, equal to or smaller than the width (W 2a,2b ) of the second part  220 ,  240 . In one embodiment, referring to  FIG. 2B , the width (W 1a,1b ) of the first part  210 ,  230  is smaller than the width (W 2a,2b ) of the second part  220 ,  240 . However, the widths of the first part or the second part are not limited to a specific size. As long as the magnetic field of the divided spiral conductive trace pattern cancels each other out, other sizes of the width are within the scope of the invention. 
     The invention also provides a method for fabricating an electronic device. The method comprises the following steps. A substrate is firstly provided and the material of the substrate is described above, so repeated description is omitted. Then, a conductive trace pattern is formed on the substrate, wherein the conductive trace pattern has an opening to expose the substrate. The conductive trace pattern with the opening is formed by coating a photoresist on the substrate, applying a photolithography technique (known to those skilled in the art), forming a specific pattern on the substrate, applying a deposition process (such as chemical deposition method or sputter method) to form the conductive trace pattern, and then removing the photoresist. 
     The invention also provides a method for fabricating a spiral conductive trace inductor. A substrate is firstly provided and a spiral conductive trace pattern is formed on the substrate, wherein the spiral conductive trace pattern has at least one turn and an opening to expose the substrate. The method for forming the spiral conductive trace pattern with the opening is the same as that of the above embodiments, so, repeated description is omitted. 
     The invention provides an electronic device and a spiral inductor device, in which an opening is formed in the conductive trace pattern. When current flows through the electronic device or the spiral inductor device, the magnetic field of the conductive trace pattern or the spiral conductive trace pattern is changed by the design of the opening to avoid an eddy current. Therefore, the performance of the electronic device and the quality factor (Q value) of the spiral inductor device are improved. 
     Embodiment 
     Comparative Embodiment 
     In the comparative embodiment, the width W m  of the spiral conductive trace pattern is about 25 μm and the spiral conductive trace pattern has 2.5 turns. The pitch P between neighboring turns of the spiral conductive trace pattern is about 3 μm. Note that there is no opening in the spiral conductive trace pattern. 
     Embodiment 1 
     In the embodiment 1, the width W m  of the spiral conductive trace pattern was about 25 μm and the spiral conductive trace pattern had 2.5 turns. The pitch P between neighboring turns of the spiral conductive trace pattern was about 3 μm. The width S of the opening was about 6 μm, the width W 1a,1b  of the first part was about 6.5 μm and the width W 2a,2b  of the second part was about 12.5 μm. 
     According to a computer calculated data, the quality factor of the embodiment 1 was higher than the comparative embodiment by about 25%. 
     Embodiment 2 
     In the embodiment 2, the width W m  of the spiral conductive trace pattern was about 25 μm and the spiral conductive trace pattern had 3.5 turns. The pitch P between neighboring turns of the spiral conductive trace pattern was about 2 μm. The width S of the opening was about 6 μm, the width W 1a,1b  of the first part was about 6.5 μm and the width W 2a,2b  of the second part was about 12.5 μm. 
     While the invention has been described by way of example and in terms of the 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.