A millimeter waveguide and a circuit apparatus using the same

BACKGROUND OF THE INVENTION

1. Field of the Invention

0001This invention relates to a millimeter waveguide for transmitting millimeter waves and a circuit apparatus using the same.

2. Description of the Prior Art

0002A millimeter waveguide for transmitting millimeter waves is known. As a such a waveguide, a shielded membrane microstrip is disclosed in 1996 IEEE MTT-S Digest at pages 797 to 800.

0003Fig. 10 is a cross-sectional side view of this prior art millimeter waveguide.

0004Silicon dioxide 802 is formed on a silicon substrate 801 and a microstrip line 803 is formed on the silicon dioxide 802. The silicon substrate 801 is sandwiched by a carrier substrate 804 on which a metal is formed and a silicon substrate 805 subjected to micromachining processing, so that the microstrip line 803 is shielded.

SUMMARY OF THE INVENTION

0005The aim of the present invention is to provide an improved millimeter waveguide and an improved circuit apparatus using the same.

0006According to the present invention a first millimeter waveguide is provided which comprises: a first single crystal substrate having a groove therein; a conductor film to be grounded on a surface of the groove and a surface of the first single crystal substrate connecting to the surface of groove; a second single crystal substrate covering the conductor film; and a microstrip line on a surface of the second single crystal substrate, exposed to a cavity defined by the conductor film and the second crystal substrate.

0007In the first millimeter waveguide, the first and second single crystal substrates comprise silicon substrates.

0008In the first millimeter waveguide, the conductor film comprises: a first conductor layer on the first crystal substrate, covering the groove; a conductive connecting layer on the first conductor layer; a second conductor film on the conductive connecting layer extending from one edge of the groove; and a third conductor film on the conductive connecting layer extending from another edge of the groove.

0009In this case the first and second conducting layers comprise nickel chromium and the conductive connecting layer comprises gold.

0010In the first millimeter waveguide, the first single crystal substrate may further comprise a protruding portion on a bottom surface of the groove at a middle of the bottom surface, extending along the groove to confront the microstrip line, the first conducting film covering a surface of the protruding portion.

0011In the first millimeter waveguide, the second single crystal substrate has a via hole and the first millimeter waveguide further comprises a second microstrip line on an opposite surface of the second single crystal substrate, connecting to the microstrip line via the via hole for coupling the microstrip line to an external circuit.

0012In the first millimeter waveguide the microstrip line comprises a foundation layer on the surface of the second signal crystal substrate and a conductive layer on the foundation layer. In this case, the foundation layer comprises nickel chromium and the conductive layer comprises gold.

0013A second millimeter waveguide is provided which comprises: a first single crystal substrate; a conductor film on the first single crystal substrate; a second single crystal substrate on the second conductor film, having a groove on side of the first crystal substrate; and a microstrip line on a bottom surface of the groove.

0014In the second millimeter waveguide, the first and second single crystal substrates comprise silicon substrates.

0015In the second millimeter waveguide, the conductor film comprises: a first conductor layer on the first crystal substrate; a conductive connecting layer on the first conductor layer; and a second conductor film on the conductive connecting layer extending from one edge of the groove; a third conductor film on the conductive connecting layer extending from another edge of the groove.

0016In the second millimeter waveguide, the first and second conducting layers comprise nickel chromium and the conductive connecting layer comprises gold.

0017In the second millimeter waveguide, the microstrip line comprises a foundation layer on the bottom surface of the groove and a conductive layer on the foundation layer. In this case, the foundation layer comprises nickel chromium and the conductive layer comprises gold.

0018According to this invention, a third millimeter waveguide is provided which comprises: a first single crystal substrate having a groove therein; a conductor film to be grounded on a surface of the groove and a surface of the first single crystal substrate connected to the surface of the groove; a second single crystal substrate covering the second conductor film and having a protrusion toward the groove; and a microstrip line on a surface of the protrusion, exposed to a cavity defined by the conductor film and the second crystal substrate, a height of the protrusion being less than a depth of the groove.

0019In the third millimeter waveguide, the first and second single crystal substrates comprise silicon substrates.

0020In the third millimeter waveguide, the conductor film comprises: a first conductor layer on the first crystal substrate, covering the groove; a conductive connecting layer on the first conductor layer; a second conductor film on the conductive connecting layer extending from one edge of the groove; and a third conductor film on the conductive connecting layer extending from another edge of the groove.

0021In the third millimeter waveguide, the first and second conducting layers comprise nickel chromium and the conductive connecting layer comprises gold.

0022In the third millimeter waveguide, the microstrip line comprises a foundation layer on the surface of the protrusion and a conductive layer on the foundation layer. In this case, the foundation layer comprises nickel chromium and the conductive layer comprises gold.

0023According to this invention, a fourth millimeter waveguide is provided which comprises: a first single crystal substrate having a hollow portion therein; a first conductor film to be grounded on a surface of the hollow portion and a surface of the first single crystal substrate connecting to the surface of the hollow portion; a second conductor film covering the hollow portion and the surface of the first single crystal substrate, having a first through hole above the hollow portion; a second single crystal substrate on the second conductor film, having a second through hole connecting to the first hole; and a microstrip line on a surface of the second single crystal substrate opposite to the first crystal substrate; and a probe extending from the microstrip line through the first and second through holes, exposed to a cavity defined by the first and second conductor films.

0024In the fourth millimeter waveguide, the microstrip line comprises a foundation layer on the surface of the second single crystal substrate and a conductive layer on the foundation layer. In this case, the foundation layer comprises nickel chromium and the conductive layer comprises gold.

0025According to this invention, a fifth millimeter waveguide is provided which comprises: a first single crystal substrate having a groove therein; a first single crystal substrate having a hollow portion therein; a first conductor film to be grounded on a surface of the hollow portion and a surface of the first single crystal substrate connecting to the surface of the hollow portion; a second conductor film covering the hollow portion and the surface of the first single crystal substrate, having a slot above the hollow portion; a second single crystal substrate on the second conductor film; and a microstrip line on a surface of the second single crystal substrate opposite to the first crystal substrate, confronting a cavity defined by the first and second conductor films through the slot and the second single crystal substrate to electromagnetically couple to the cavity.

0026In the fifth millimeter waveguide, the microstrip line comprises a foundation layer on the surface of the second signal crystal substrate and a conductive layer on the foundation layer. In this case, the foundation layer comprises nickel chromium and the conductive layer comprises gold.

0027According to this invention, a first circuit apparatus is provided which comprises: a millimeter waveguide including a first single crystal substrate having a groove therein, a conductor film to be grounded on a surface of the groove and a surface of the first single crystal substrate connecting to the surface of groove, a second single crystal substrate covering the conductor film and having a via hole, a first microstrip line on a surface of the second single crystal substrate, exposed to a cavity defined by the conductor film and the second crystal substrate, a second microstrip line on an opposite surface of the second single crystal substrate, connecting to the first microstrip line via the via hole, and a third microstrip line on the opposite surface apart from the second microstrip line; an active circuit chip for performing a predetermined circuit operation; and a connecting portion for mechanically and electrically connecting the active circuit to the third microstrip line and to the second microstrip line, wherein there is a responsive relation between the first and third microstrip lines through the active circuit, the second microstrip line, and the via hole. The connecting portion comprises micro-bumps through a flip-chip bonding.

0028In the first circuit apparatus, the first microstrip line comprises a foundation layer on the surface of the second signal crystal substrate and a conductive layer on the foundation layer. In this case, the foundation layer comprises nickel chromium and the conductive layer comprises gold.

0029According to this invention, a second circuit apparatus is provided which comprises: a millimeter waveguide including a first single crystal substrate, a conductor film to be grounded on a surface of the first single crystal substrate, a second single crystal substrate on the second conductor film, having a groove on side of the first crystal substrate and a via hole, and a first microstrip line on a bottom surface of the groove, a second microstrip line on a surface of the second single crystal substrate opposite to the groove, connecting to the first microstrip line via the via hole; and a third microstrip line on the surface of the second signal crystal substrate apart from the second microstrip line, an active circuit chip for performing a predetermined circuit operation; and a connecting portion for mechanically and electrically connecting the active circuit to the third microstrip line and to the second microstrip line, wherein there is a responsive relation between the first and third microstrip lines through the active circuit, the second microstrip line, and the via hole. The connecting portion comprises micro-bumps through a flip-chip bonding.

0030In the second circuit apparatus, the first microstrip line comprises a foundation layer on the bottom surface of the groove and a conductive layer on the foundation layer. In this case, the foundation layer comprises nickel chromium and the conductive layer comprises gold.

0031According to this invention, a third circuit apparatus is provided which comprises: a millimeter waveguide including a first single crystal substrate having a groove therein, a conductor film to be grounded on a surface of the groove and a surface of the first single crystal substrate connecting to the surface of the groove, a second single crystal substrate covering the second conductor film and having a protrusion toward the groove and a via hole therein, and a first microstrip line on a surface of the protrusion, exposed to a cavity defined by the conductor film and the second crystal substrate, a height of the protrusion being less than a depth of the groove, a second microstrip line on a surface of the second single crystal substrate opposite to the protrusion, connecting to the first microstrip line via the via hole, and a third microstrip line on the surface of the second single crystal substrate apart from the second microstrip line; an active circuit chip for performing a predetermined circuit operation; and a connecting portion for mechanically and electrically connecting the active circuit to the third microstrip line and to the second microstrip line, wherein there is a responsive relation between the first and third microstrip lines through the active circuit, the second microstrip line, and the via hole. The connecting portion comprises micro-bumps through a flip-chip bonding.

0032In the third circuit apparatus, the first microstrip line comprises a foundation layer on the surface of the protrusion and a conductive layer on the foundation layer. In this case, the foundation layer comprises nickel chromium and the conductive layer comprises gold.

BRIEF DESCRIPTION OF THE DRAWINGS

0033The object and features of the present invention will become more readily apparent from the following detailed description taken in conjunction with the accompanying drawings in which: <ul id="ul0001" list-style="none" compact="compact"><li>Fig. 1A is a cross-sectional side view of a millimeter waveguide of a first embodiment in a condition before connection;</li><li>Fig. 1B is a cross-sectional side view of the millimeter waveguide of the first embodiment in a connected condition;</li><li>Fig. 2 is a cross-sectional side view of a millimeter waveguide of a second embodiment;</li><li>Fig. 3 is a cross-sectional side view of a millimeter waveguide of a third embodiment;</li><li>Fig. 4A is a cross-sectional side view of a millimeter waveguide of a fourth embodiment in a condition before connection;</li><li>Fig. 4B is a cross-sectional side view of the millimeter waveguide of the fourth embodiment in a connected condition;</li><li>Fig. 5 is a cross-sectional side view of a circuit apparatus of a fourth embodiment using the millimeter waveguide of the first embodiment;</li><li>Fig. 6 is a cross-sectional side view of a circuit apparatus of a sixth embodiment using the millimeter waveguide of the third embodiment;</li><li>Fig. 7 is a cross-sectional side view of a circuit apparatus of a seventh embodiment using the millimeter waveguide of the fourth embodiment;</li><li>Fig. 8A is a cross-sectional side view of a millimeter waveguide apparatus of an eighth embodiment;</li><li>Fig. 8B is a plan view of the millimeter waveguide apparatus of the eighth embodiment;</li><li>Fig. 9A is a cross-sectional side view of a millimeter waveguide apparatus of a ninth embodiment;</li><li>Fig. 9B is a plan view of the millimeter waveguide apparatus of the ninth embodiment; and</li><li>Fig. 10 is a cross-sectional side view of a prior art millimeter waveguide.</li></ul>

0034The same or corresponding elements or parts are designated with like references throughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

0035Hereinbelow will be described a first embodiment of this invention.

0036Fig. 1A is a cross-sectional side view of a millimeter waveguide of the first embodiment in a condition before connection. Fig. 1B is a cross-sectional side view of the millimeter waveguide of the first embodiment in a connected condition.

0037A millimeter waveguide 100 of the first embodiment comprises a single crystal substrate 101 having a groove 109 therein, a ground conductor film 110 on a surface of the groove 109 and a surface of the single crystal substrate 101 connecting to the surface of the groove 109, a single crystal substrate 104 covering the conductor film 110, and a microstrip line 108 on a surface of the single crystal substrate 108, exposed to a cavity 111 defined by the conductor film 110, the microstrip line 108, and the crystal substrate 104.

0038The single crystal substrate 101 comprises a silicon substrate. The single crystal substrate 104 comprises a silicon substrate also.

0039The ground conductor film 110 comprises: a conductor layer 102 on a surface of the crystal substrate 101 and a surface of the groove 109, a conductive connecting layer 112 on the conductor layer 102, a conductor film 105a on the conductive connecting layer 112 extending from an edge of the groove 109, and a conductor film 105b on the conductive connecting layer 112 extending from another edge of the groove 109.

0040The conductor layers 102, 105a and 105b comprise nickel chromium.

0041The microstrip line 108 comprises a foundation layer 105c on the surface of the second signal crystal substrate 104 and a conductive layer 106c on the foundation layer 105c. In this case, the foundation layer 105c comprises nickel chromium and the conductive layer 106c comprises gold.

0042The conductive connecting layer 112 comprises gold.

0043The groove 109 is formed in the single crystal substrate 101 made of a silicon by the anisotropic etching. The conductor layer 102 made of nickel chromium is formed on the surface of the single crystal substrate 101 and a surface of the groove 109. The conductive connecting layer 103 is formed on the conductor layer 102 with gold.

0044The conductor layers 105a, 105b, 105c are formed on the surface of the single crystal substrate 104 with nickel chromium. Conductive connecting layers 106a and 106b are formed with gold. Then, both substrates 1 and 2 are connected by the thermo-compression bonding.

0045This structure extends in the depth direction of the drawing as required.

0046This structure provide a microstrip line with shielding. The shield structure can reduce a loss due to radiation in the millimeter band.

0047Generally, it is difficult to directly form gold on the surface of the crystal substrates 101 and 104. Therefore, after forming the conductor layers 102 and 105a and 105b, the gold is formed on the conductor layers 102 and 105a, 105b, and 105c. In this structure, almost all of current flows through the microstrip line 108 on the side near the bottom surface of the ground conductor film 110 (the groove 109), that is, almost all of the current flows through the microstrip line 108 made of gold not through the foundation layer 105c made of nickel chromium, so that a loss can be reduced.

0048A second embodiment will be described.

0049Fig. 2 is a cross-sectional side view of a millimeter waveguide of the second embodiment.

0050The millimeter waveguide of the second embodiment has substantially the same structure as that of the first embodiment. The difference is that a protruding portion 209 is formed on a bottom surface of the groove 219 at a middle of the bottom surface, extending along edges of the groove 219 in the depth direction of the drawing of Fig. 2. The conductor film 202 and the conductive connecting layer 203 cover a surface of the protruding portion 209.

0051In the structure of the first embodiment, the current concentrates on both sides of the microstrip line 108. On the other hand, in the structure of the second embodiment, the current tends to flow through the middle portion of the microstrip line 108, so that a current density can be dispersed. Then, a loss in the microstrip line 108 can be further reduced.

0052A third embodiment will be described.

0053Fig. 3 is a cross-sectional side view of a millimeter waveguide of the third embodiment.

0054The millimeter waveguide of the third embodiment comprises: a single crystal substrate 404, a conductor film 410 on a surface of the single crystal substrate 404, a single crystal substrate 401 on the conductor film 410, having a groove 409 on the side of the crystal substrate 404, and a microstrip line 408 on a bottom surface 409a of the groove 409.

0055That is, the difference from the first embodiment is that the microstrip line 408 is formed on the bottom surface of the groove 409 instead the crystal substrate 101. Therefore, the operation is similar to the first embodiment. However, the extent that the grounded conductor film surrounds the microstrip line is different between the first and third embodiments.

0056A fourth embodiment will be described.

0057Fig. 4A is a cross-sectional side view of a millimeter waveguide of the fourth embodiment in a condition before connection. Fig. 4B is a cross-sectional side view of the millimeter waveguide of the fourth embodiment in a connected condition.

0058The millimeter waveguide of the third embodiment comprises a single crystal substrate 504 having a groove 509 therein, a conductor film 510 on a surface of the groove 509 and a surface of the single crystal substrate 504 connecting to the surface of the groove 509, a second crystal substrate 501 covering the conductor film 510 and the groove 509 and having a protrusion 511 toward the groove 509, and a microstrip line 508 on a surface of the protrusion 511, exposed to a cavity 513 defined by the conductor film 503 and the crystal substrate 501. A height H of the protrusion 511 is less than a depth D of the groove 509. In this embodiment, the height H is about a half of the depth D. Therefore, the protrusion 511 is formed such that the protrusion fits into the groove 509, wherein the cavity 513 is formed.

0059The basic operation is similar to the first embodiment. The difference is that a shielding effect is higher than that of the first embodiment because the microstrip line 508 is surrounded by the conductor film 510, so that a loss due to radiation at millimeter band can be reduced.

0060A fifth embodiment will be described.

0061Fig. 5 is a cross-sectional side view of a circuit apparatus of the fourth embodiment using the structure of the millimeter waveguide 100 of the first embodiment.

0062The crystal substrate 104' is processed to form a via hole 312 therein and then, microstrip lines 309 and 313 are formed in addition to forming the microstrip line 108 and the conductor films 105a to 105c and the conductive connecting films 106a and 106b as similar to the first embodiment. Then, the substrate 1' and 2 are connected by the thermo compression bonding. Then, the active circuit 310 is connected to the microstrip lines 309 and 313 with micro-bumps 311 by the flip chip bonding.

0063The microstrip line 309 on the second single crystal substrate 104' is connected to the microstrip line 108 via the via hole 312. The active circuit chip 310 performs a predetermined circuit operation, such as an amplifying. The micro-bumps 111 mechanically and electrically connect the active circuit 310 to the microstrip line 313 and to the microstrip line 309. The microstrip line 313 is used for inputting an external signal to the active circuit or outputting a signal from the active circuit 310. Therefore, there is a responsive relation between the microstrip lines 108 and 313 through the active circuit 310, the via hole 312 and a microstrip line 309.

0064The microstrip line 108 comprises the foundation layer 105c on the surface of the second signal crystal substrate 104' and the conductive layer 106c on the foundation layer 105c. In this case, the foundation layer 105c comprises nickel chromium and the conductive layer 106c comprises gold.

0065A sixth embodiment will be described.

0066Fig. 6 is a cross-sectional side view of a circuit apparatus of the sixth embodiment using the millimeter waveguide of the third embodiment.

0067The structure of the sixth embodiment is similar to that of the fifth embodiment. The difference is that the structure of the millimeter waveguide of the third embodiment is used instead of that of the first embodiment.

0068A seventh embodiment will be described.

0069Fig. 7 is a cross-sectional side view of a circuit apparatus of the seventh embodiment using the millimeter waveguide of the fourth embodiment.

0070The structure of the seventh embodiment is similar to that of the fifth embodiment. The difference is that the structure of the millimeter waveguide of the fourth embodiment is used instead of that of the first embodiment.

0071An eighth embodiment will be described.

0072Fig. 8A is a cross-sectional side view of a millimeter waveguide apparatus of the eighth embodiment. Fig. 8B is a plan view of the millimeter waveguide apparatus of the eighth embodiment.

0073A millimeter waveguide of the eighth embodiment comprises a single crystal substrate 601 having a hollow portion 611 therein, a conductor film 612 on a surface of the hollow portion 611 and a surface of the single crystal substrate 601 connecting to the surface of the hollow portion 611, a conductor film 613 covering the hollow portion 611 and the conductor film 612, having a through hole 614 above the hollow portion 611, a single crystal substrate 604 on the conductor film 613, having a through hole 615 connected to the first hole 614, and a microstrip line 609 on a surface of the second single crystal substrate 604 opposite to the crystal substrate 601, and a probe 610 extending from the microstrip line 609 through the through holes 614 and 615, exposed to a cavity (611) defined by the conductor films 612 and 613.

0074The probe 610 is connected to the microstrip line 609 as follows:

0075The probe 610 has a dielectric substance 616 surrounding the probe 610. A tip of the dielectric substance 616 is stripped and is pierced through a through hole formed in the microstrip line 609. Then, the probe 610 is soldered.

0076The microstrip line 609 comprises a foundation layer 609a on the surface of the second single crystal substrate 604 and a conductive layer 609b on the foundation layer. The foundation layer 609a comprises nickel chromium and the conductive layer 609b comprises gold.

0077A ninth embodiment will be described.

0078Fig. 9A is a cross-sectional side view of a millimeter waveguide apparatus of the ninth embodiment. Fig. 9B is a plan view of the millimeter waveguide apparatus of the ninth embodiment.

0079A millimeter waveguide of the ninth embodiment has substantially similar to the eighth embodiment. The difference is that the through hole 615 is not formed and a slot 710 having a rectangular shape in the drawing of Fig. 9B instead the through hole 614. The microstrip line 709 is electromagnetically coupled to the cavity through the slot 710.

0080This structure eliminates the necessity of fixing the probe 610 to the crystal.