TWI824399B - Interdigitated varactor diode and manufacturing method thereof - Google Patents

Abstract

An interdigital varactor diode includes a substrate, an epitaxial structure, an electrode unit, and a dielectric unit. The epitaxial structure is disposed on the substrate and includes a top surface, a first-type doped epitaxial layer sequentially downward from the top surface, a second-type doped epitaxial layer, and a plurality of first-type doped epitaxial layers sequentially downward from the top surface. Grooves are extended and spaced apart from each other, and a plurality of convex portions are spaced apart from each other by the grooves, and the second type doped epitaxial layer is exposed from the grooves. The electrode unit includes a plurality of bottom electrodes disposed in the grooves and a plurality of top electrodes disposed on the protrusions. The top and bottom electrodes respectively form ohmic contact with the epitaxial structure and are connected in parallel. form of external electrical connection. The dielectric unit covers the epitaxial structure and the electrode unit, and exposes part of the surface of the top electrodes.

Description

Interdigitated varactor diode and manufacturing method thereof

The present invention relates to a varactor diode and a manufacturing method thereof, in particular to a varactor diode with an interdigitated structure and a manufacturing method thereof.

The varactor diode element is mainly based on the variable capacitance principle of the PN interface of the semiconductor (that is, when a reverse bias voltage is applied to the PN interface, its capacitance value will change with different voltages) and becomes a frequency radio circuit. Or tuned circuits and other common components in circuit design, and are widely used in wireless communications, aerospace and other fields. Currently, the varactor element generally includes a semiconductor epitaxial layer with a platform (msea) structure, an anode disposed on the platform structure and connected to the p-type epitaxial layer of the semiconductor epitaxial layer. , and a cathode ring disposed on the platform structure and connected to the n-type epitaxial layer of the semiconductor epitaxial layer.

However, the parasitic resistance of the varactor element itself will cause losses during operation, and subsequently generate resistance-capacitance delay (RC-Delay), which will affect the overall circuit design. Therefore, how to reduce the parasitic resistance of the varactor element and improve its Q value has become the focus of research in related fields.

Therefore, the purpose of the present invention is to provide an interdigitated varactor diode to reduce the overall parasitic resistance and improve the Q value.

Therefore, the interdigitated varactor diode of the present invention includes a substrate, an epitaxial structure, an electrode unit, and a dielectric unit.

The epitaxial structure is disposed on the substrate and includes a first-type doped epitaxial layer, a second-type doped epitaxial layer, and multiple A plurality of strip-shaped grooves extending downward from the top surface and spaced apart from each other along the same direction, and a plurality of strip-shaped convex portions spaced apart from each other by the grooves, and the second type doping The epitaxial layer will be exposed from the grooves.

The electrode unit includes a plurality of strip-shaped bottom electrodes respectively disposed in the grooves, and a plurality of top electrodes respectively disposed on the top surfaces of the protrusions. The top electrodes are respectively connected with the first type doped The hybrid epitaxial layer forms an ohmic contact and is electrically connected to the outside in a parallel manner. The bottom electrodes respectively form an ohmic contact with the second type doped epitaxial layer and are electrically connected to the outside in a parallel manner.

The dielectric unit covers the epitaxial structure and the electrode unit, and the top electrodes and the bottom electrodes can be electrically connected to the outside through the dielectric unit.

Another object of the present invention is to provide a method for manufacturing an interdigitated varactor diode.

Therefore, the manufacturing method of the interdigitated varactor diode of the present invention includes a providing step, a contact pad forming step, a first dielectric layer forming step, a bottom electrode setting step, and a second dielectric layer forming step. , and a top electrode setting step.

The providing step is to provide an epitaxial semi-finished product. The epitaxial semi-finished product has a substrate and an epitaxial laminated layer disposed on the surface of the substrate. The epitaxial laminated layer has a second type doped epitaxial layer sequentially upward from the surface of the substrate. a crystal laminated layer, and a first type doped epitaxial laminated layer.

The step of forming contact pads is to form a plurality of contact pads made of conductive material and in ohmic contact with the epitaxial layer at predetermined positions of the epitaxial layer, and etching from the top surface of the epitaxial layer corresponding to the The areas other than the contact pads are etched downward to expose the second-type doped epitaxial layer, forming a plurality of elongated grooves spaced apart from each other in the same direction, and a plurality of grooves spaced apart from each other. Arrange and grow strip-shaped protrusions to obtain an epitaxial structure, and corresponding contact pads formed on the top surfaces of the protrusions of the epitaxial structure, and then form a plurality of conductive materials in the grooves. , and form a contact pad in ohmic contact with the epitaxial structure.

The first dielectric layer forming step is to use a dielectric insulating material to form a first dielectric layer covering the epitaxial structure and the contact pads.

The bottom electrode setting step is to form a plurality of first openings in the first dielectric layer to expose the surfaces of the contact pads located in the grooves, and to make contacts in the grooves through the first openings. A plurality of bottom electrode portions made of conductive material are provided on the exposed surface of the pad to form a plurality of bottom electrodes respectively located in the grooves and defined by the corresponding contact pads and the bottom electrode portion.

The second dielectric layer forming step is to use a dielectric insulating material to form a second dielectric layer covering the first dielectric layer, the bottom electrodes, and the contact pads located on the protrusions.

The top electrode disposing step is to form a plurality of second openings penetrating the second dielectric layer and the first dielectric layer to expose the surfaces of the contact pads located on the protrusions, and forming from the exposed contact pads. A plurality of top electrode portions are defined together with corresponding contact pads to form a plurality of top electrodes for external electrical connection.

The effect of the present invention is that the interdigitated varactor diode of the present invention can reduce the anode (i.e., the The overall resistance of the top electrode), thereby reducing the overall anode parasitic resistance of the interdigitated varactor diode, slowing down the impact of resistor-capacitance delay during operation, and improving the overall Q value.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are designated with the same numbering. The relevant technical contents, features and effects of the present invention will be clearly presented in the following detailed description of the embodiments with reference to the drawings. In addition, it should be noted that the drawings of the present invention only represent the relative structure and/or positional relationship between components, and are not related to the actual size of each component.

1 and 2 together, the interdigitated varactor diode of the present invention includes a substrate 2, an epitaxial structure 3, an electrode unit 4, and a dielectric unit 5. Among them, Fig. 1 shows the top view structure of the interdigital varactor diode, and Fig. 2 is the cross-sectional structure along the II-II cut plane line in Fig. 1.

The epitaxial structure 3 is disposed on the substrate 2 and includes a top surface 31 opposite to the substrate 2, a first-type doped epitaxial layer 32 sequentially downward from the top surface 31, a second-type doped epitaxial layer 32, and a second-type doped epitaxial layer 32. A plurality of hybrid epitaxial layers 33 extend downward from the top surface 31 to the second-type doped epitaxial layer 33 and grow into strips along a first direction X, and along a line intersecting the first direction X. The grooves 34 are spaced apart from each other in the second direction Y, and a plurality of strip-shaped convex portions 35 are spaced apart from each other through the grooves 34 . In this embodiment, the second type doped epitaxial layer 33 is an n-type epitaxial layer, and the first type doped epitaxial layer 32 is a p-type epitaxial layer, so the grooves 34 are formed from the p-type epitaxial layer. The surface of the n-type epitaxial layer extends downward to expose the n-type epitaxial layer.

The electrode unit 4 is made of conductive material and includes a plurality of bottom electrodes 41 and a plurality of top electrodes 42 . In this embodiment, the bottom electrodes 41 are used as cathodes and the top electrodes 42 are used as anodes, but the present invention is not limited thereto.

In detail, the bottom electrodes 41 are respectively disposed in the grooves 34 and extend along the first direction A contact pad 411 that is in ohmic contact with the second type doped epitaxial layer 33 (that is, the n-type epitaxial layer), and a bottom electrode portion 412 formed on the top surface of the contact pad 411 for external electrical connection, And the bottom electrodes 41 are electrically connected to the outside in a parallel manner.

The top electrodes 42 are respectively disposed on the protrusions 35 and extend in a strip shape along the first direction The epitaxial layer) forms a contact pad 421 with ohmic contact, and a top electrode portion 422 formed on the top surface of the contact pad 421 for external electrical connection, and the top electrodes 42 are electrically connected to the outside in a parallel manner. It should be noted that in this embodiment, the contact pads 411 and 421 that are in ohmic contact with the n-type epitaxial layer and the p-type epitaxial layer respectively are made of different conductive materials. Since the selection of relevant conductive materials to form ohmic contacts with different semiconductor materials is well known to those in the art and is not the focus of the present invention, it will not be described in detail.

It should be noted that the bottom and top electrodes 41 and 42 are each extended into a long interdigitated shape and intertwined with each other, and one side of the bottom and top electrodes 41 and 42 can respectively be wired or wired (not shown in the figure) They are connected in parallel to each other so that the bottom and top electrodes 41 and 42 can be electrically connected to the outside in parallel. However, in actual implementation, as long as the bottom and top electrodes 41 and 42 can be electrically connected to the outside in parallel. , but not limited to the above examples.

The dielectric unit 5 covers the epitaxial structure 3 and the electrode unit 4, and can expose part of the surfaces of the bottom electrodes 41 and the top electrodes 42. In detail, the dielectric unit 5 includes a first dielectric layer 51 and a second dielectric layer 52 . The first dielectric layer 51 can be selected from dielectric insulating materials such as nitride, oxide or oxynitride, covering the epitaxial structure 3 and the electrode unit 4, and allowing part of the surface of each bottom electrode 41 to pass through A corresponding first opening 511 is exposed for external electrical connection. The second dielectric layer 52 is made of the same or different dielectric insulating material as the first dielectric layer 51 , covering the first dielectric layer 51 , the bottom electrodes 41 and the top electrodes 42 , and The top electrodes 42 can be electrically connected to the outside through a plurality of second openings 521 penetrating the first dielectric layer 51 and the second dielectric layer 52 . Through the arrangement of the dielectric unit 5 , electrical insulation can be maintained between the top electrodes 42 and the bottom electrodes 41 , and crosstalk effects between each other during operation can be reduced.

Compared with the conventional varactor diode, it only has an anode arranged on a mesa structure and connected to the p-type epitaxial layer, and a ring arranged on the anode and connected to the n-type epitaxial layer. Cathode, the interdigitated varactor diode of the present invention can maintain the interdigitated structure by arranging the bottom and top electrodes 41 and 42 of the electrode unit 4 alternately to form an interdigitated structure. The total area is to maintain the existing P-N junction capacitance characteristics, and at the same time, the top electrodes 42 (anode) are connected in parallel to reduce the overall resistance of the anode, thereby reducing the overall anode parasitic resistance of the interdigitated varactor diode. , slow down the impact of resistor-capacitor delay (RC Delay) during operation, improve the overall Q value, and reduce circuit losses.

Referring to FIG. 3 , in another embodiment, the electrode unit 4 further includes a flat-shaped common electrode 43 connected to the top electrodes 42 so that the top electrodes 42 can be connected in parallel through the common electrode 43 form of external electrical connection. The common electrode 43 can be selected from titanium gold alloy with a thickness of 2 μm to 4 μm, or metallic copper with a thickness of 2 μm to 15 μm.

It should be noted that when the top electrodes 42 are electrically connected to the outside through the common electrode 43, the interdigitated varactor diode also includes an insulating support layer 6. The insulating support layer 6 will fill the grooves 34 and extend to cover part of the surface of the convex portions 35 so that the top surface of the insulating support layer 6 can have substantially the same height as the top electrodes 42, and A relatively flat surface can be provided to support the common electrode 43 .

The interdigitated varactor diode of the present invention uses the common electrode 43 to connect the top electrodes 42 in parallel, which can further reduce the junction resistance of the interdigitated varactor diode, thereby further reducing circuit losses and improving The Q value can also increase the thickness of the anode (ie, the common electrode 43 and the top electrodes 42 ), which helps dissipate heat and improve the impact of thermal effects.

With reference to Figure 4, the manufacturing method of the aforementioned interdigitated varactor diode will be described below. The manufacturing method includes a providing step 81, a contact pad forming step 82, a first dielectric layer forming step 83, a bottom electrode setting step 84, a second dielectric layer forming step 85, and an insulating support layer forming step 86. , and a top electrode setting step 87.

The providing step 81 is to provide an epitaxial semi-finished product (not shown). The epitaxial semi-finished product has the substrate 2 and an epitaxial laminated layer disposed on the surface of the substrate 2 , and the epitaxial laminated layer has an epitaxial layer extending from the surface of the substrate 2 . A second-type doped epitaxial layer 33 (ie, an n-type epitaxial layer) and a first-type doped epitaxial layer 32 (ie, a p-type epitaxial layer) are arranged upward.

The contact pad forming step 82 is to form a plurality of contact pads 421 made of conductive material and in ohmic contact with the epitaxial layer at predetermined positions of the epitaxial layer, and then etching from the epitaxial layer. The top surface and the area corresponding to the contact pads 421 are etched downward to expose the second-type doped epitaxial layer 33 , forming strips arranged at intervals along the second direction Y and extending along the first direction X. The grooves 34 and the grooves 34 are spaced apart from each other and grow into strip-shaped protrusions 35 to obtain the epitaxial structure 3 and a plurality of corresponding protrusions formed on the epitaxial structure 3 The contact pads 421 on the top surface of the part 35 are then formed on the bottom surfaces of the grooves 34. A plurality of contact pads 411 made of conductive material and in ohmic contact with the epitaxial structure 3 are formed. That is, the grooves 34 are Extend downward from the surface of the p-type epitaxial layer (ie, the top surface 31 of the epitaxial structure 3) to expose the n-type epitaxial layer, and the contact pads 421 are respectively located on the protrusions 35, and It is in ohmic contact with the p-type epitaxial layer, and the contact pads 411 located in the grooves 34 are in ohmic contact with the n-type epitaxial layer. Since the process method and material selection for forming ohmic contact between the conductive material and the semiconductor material are well known in the art and are not the focus of the present invention, they will not be described in detail. In this embodiment, at least one side of the grooves 34 is connected to each other.

The first dielectric layer forming step 83 is to deposit a dielectric insulating material to form the first dielectric layer 51 covering the epitaxial structure 3 and the contact pads 411 and 421 .

The bottom electrode setting step 84 is to use etching to form a plurality of first openings 511 on the first dielectric layer 51 to expose the surfaces of the contact pads 411 located in the grooves 34, and through the first openings 511 forms a plurality of bottom electrode portions 412 made of conductive material by deposition on the exposed surfaces of the contact pads 411 in the grooves 34, so that the bottom electrode portions 412 are jointly defined with the corresponding contact pads 411. The bottom electrodes 41 are obtained.

The second dielectric layer forming step 85 is to deposit a dielectric insulating material to completely cover the first dielectric layer 51 , the bottom electrodes 41 , and the contact pads 421 located on the protrusions 35 . second dielectric layer 52.

The insulating support layer forming step 86 is to fill the grooves 34 with a polymer material and cover the second dielectric layer 52 to form the insulating support layer 6 with a flat top surface.

The top electrode setting step 87 is to form a plurality of second openings 521 from the top of the insulating support layer 6 facing the corresponding convex portions 35 downward to expose the corresponding contact pads 421, and then respectively from the corresponding convex portions 35. Two openings 521 are deposited to form a plurality of top electrode portions 422 that are electrically connected to the contact pads 421, so that the top electrode portions 422 and the corresponding contact pads 421 are jointly defined as the top electrodes 42 for external electrical connection. , and then deposit a conductive material to form the common electrode 43 covering the surface of the insulating support layer 6 and electrically connected to the top electrode portions 422, thereby obtaining the interdigitated varactor diode as shown in Figure 3.

In addition, it should be noted that when the interdigital varactor diode is not provided with the common electrode 43 as shown in FIG. 2 , the top electrode setting step 87 is directly performed from the second dielectric layer 52 The second openings 521 are formed on the top surface and corresponding to the positions of the protrusions 35 downward to expose the corresponding contact pads 421 to the outside. After that, electrical contacts with the contact pads 421 are formed through deposition from the second openings 521 respectively. A plurality of top electrode portions 422 are connected to form the top electrodes 42, and the interdigitated varactor diode as shown in FIG. 2 can be obtained.

It should be noted that in some embodiments, depending on the process requirements, when performing the bottom electrode setting step 84 , a plurality of ? The openings of the corresponding contact pads 421 are exposed to the outside, and at the same time as the bottom electrode portions 412 are formed, the top electrode portions 422 are formed with conductive materials to prepare the bottom and top electrodes 41 and 42. After that, The second dielectric layer forming step 85 is performed to form a second dielectric layer 52 covering the bottom and top electrodes 41 and 42, and to sequentially form the insulating support layer 6, the second openings 521, and the The common electrode 43 is not limited to the above-mentioned process sequence.

To sum up, the interdigitated varactor diode of the present invention can be connected in parallel by arranging the epitaxial junction structure 3 and the electrode units 4 disposed thereon in an alternating arrangement (for example, interdigitated type). To reduce the overall resistance of the anode, thereby reducing the overall anode parasitic resistance of the interdigitated varactor diode, slowing down the impact of resistance and capacitance delays during operation, and improving the overall Q value. In addition, by configuring the common electrode 43, the junction resistance of the interdigitated varactor diode can be further reduced to reduce circuit losses, improve the Q value, and also improve the connection between the anode (that is, the common electrode 43) and the The thickness of the top electrode 42) helps to dissipate heat and improve the impact of thermal effects, so the purpose of the present invention can indeed be achieved.

However, the above are only examples of the present invention and should not be used to limit the scope of the present invention. All simple equivalent changes and modifications made based on the patent scope of the present invention and the content of the patent specification are still within the scope of the present invention. within the scope covered by the patent of this invention.

2: Substrate 3: Epitaxial structure 31: Top surface 32: First type doped epitaxial layer 33: Second type doped epitaxial layer 34: Groove 35: Projection 4: Electrode unit 41: Bottom electrode 411: Contact pad 412: bottom electrode part 42: top electrode 421: contact pad 422: top electrode part 43: common electrode 5: dielectric unit 51: first dielectric layer 511: first opening 52: second dielectric layer 521: Second opening 6: Insulating support layer 81: Providing step 82: Contact pad forming step 83: First dielectric layer forming step 84: Bottom electrode setting step 85: Second dielectric layer forming step 86: Insulating support layer forming step 87 : Top electrode setting steps X: First direction Y: Second direction

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, in which: Figure 1 is a top view schematic diagram illustrating an epitaxial structure of the interdigitated varactor diode of the present invention, and an The relative position of the electrode unit; Figure 2 is a schematic side view, illustrating the cross-sectional structure of the interdigitated varactor diode corresponding to the II-II cut plane line in Figure 1; Figure 3 is a schematic side view, illustrating Another structural aspect of the interdigitated varactor diode; and FIG. 4 is a flow chart illustrating the manufacturing method of the interdigitated varactor diode of the present invention.

34: Groove

35:convex part

4:Electrode unit

41: Bottom electrode

42:Top electrode

5: Dielectric unit

X: first direction

Y: second direction

Claims (7)

An interdigital varactor diode includes: a substrate; an epitaxial structure, which is disposed on the substrate and includes a first-type doped layer that is opposite to the top surface of the substrate and sequentially downward from the top surface. A hybrid epitaxial layer, a second type doped epitaxial layer, a plurality of elongated grooves extending downward from the top surface and spaced apart from each other along the same direction, and a plurality of grooves spaced apart from each other , and form strip-shaped convex portions, and the second-type doped epitaxial layer will be exposed from the grooves; an electrode unit includes a common electrode, a plurality of strips respectively arranged in the grooves A shaped bottom electrode, and a plurality of top electrodes respectively disposed on the top surfaces of the protrusions. The top electrodes are in ohmic contact with the first type doped epitaxial layer and are electrically connected to the outside in a parallel manner. The bottom electrodes are in ohmic contact with the second type doped epitaxial layer and are electrically connected to the outside in parallel. The common electrode is flat and connected to the top electrodes; and a dielectric unit is coated on The epitaxial structure and the electrode unit, and the top electrodes and the bottom electrodes can be electrically connected to the outside through the dielectric unit. The interdigitated varactor diode according to claim 1, wherein the dielectric unit includes a first dielectric layer and a second dielectric layer, and the first dielectric layer covers the epitaxial layer. The structure, and the electrode unit, has a plurality of first openings that can expose part of the surface of the bottom electrodes for external electrical connection, the second dielectric layer covers the bottom electrodes, and the first dielectric layer, and have a plurality of holes penetrating the first dielectric layer and the second dielectric layer so that the top electrodes can be exposed to the outside. The second opening. The interdigitated varactor diode according to claim 1 further includes an insulating support layer filled in the grooves, and the common electrode is formed on the insulating support layer and the surface of the convex portions, and electrically connected to the top electrodes. The interdigitated varactor diode as claimed in claim 1, wherein the second type doped epitaxial layer is an n-type epitaxial layer, the first type doped epitaxial layer is a p-type epitaxial layer, and the The grooves extend downward from the surface of the p-type epitaxial layer to expose the n-type epitaxial layer. The bottom electrodes are respectively disposed in the grooves to form ohmic contact with the n-type epitaxial layer. The interdigitated varactor diode of claim 1, wherein the common electrode is selected from titanium gold alloy with a thickness of 2 μm to 4 μm or metallic copper with a thickness of 2 μm to 15 μm. A method for manufacturing an interdigital varactor diode, including: a step of providing an epitaxial semi-finished product, the epitaxial semi-finished product having a substrate, and an epitaxial laminated layer disposed on the surface of the substrate, the epitaxial laminated layer having A second type doped epitaxial layer and a first type doped epitaxial layer are sequentially upward from the surface of the substrate; a contact pad forming step is to form a plurality of contact pads at predetermined positions on the top surface of the epitaxial layer. Contact pads made of conductive material and in ohmic contact with the epitaxial layer are etched downward from the top surface of the epitaxial layer and corresponding to areas other than the contact pads to make the second type doped epitaxial layer The crystal layer is exposed, forming a plurality of grooves spaced apart from each other in the same direction and elongated into strips, and a plurality of convex portions spaced apart from each other in the same direction and elongated into strips, thereby obtaining an epitaxial structure, and corresponding formed in the epitaxial structure The contact pads on the top surface of the convex portion are then respectively formed with a plurality of contact pads made of conductive material and in ohmic contact with the epitaxial structure in the grooves; a first dielectric layer forming step is used to dielectrically insulate The material forms a first dielectric layer covering the epitaxial structure and the contact pads; a bottom electrode is provided to form a plurality of surfaces on the first dielectric layer to expose the surfaces of the contact pads located in the grooves. first openings, and a plurality of bottom electrode parts made of conductive material are respectively disposed on the exposed surfaces of the contact pads in the grooves through the first openings, so as to form a plurality of bottom electrode parts respectively located in the grooves, and a bottom electrode defined by the corresponding contact pad and the bottom electrode part; a second dielectric layer forming step, using a dielectric insulating material to form a layer covering the first dielectric layer and the bottom electrodes, and a second dielectric layer located on the contact pads of the protrusions; and a top electrode disposing step to form a plurality of contact pads located on the protrusions through the second dielectric layer and the first dielectric layer A second opening is exposed on the surface, and a plurality of top electrode portions are formed from the exposed contact pads, so that the top electrode portions and corresponding contact pads are jointly defined to form a plurality of top electrodes for external electrical connection. The method for manufacturing an interdigitated varactor diode as claimed in claim 6, further comprising an insulating support layer forming step between the second dielectric layer forming step and the top electrode arranging step, wherein the insulating The step of forming the support layer is to use a polymer material to form an insulating support layer that fills the grooves and covers the second dielectric layer. The step of arranging the top electrode is to form it from the top surface of the insulating support layer downward to the bottom of the second dielectric layer. The contact pads of the protrusions are exposed to the and second openings, and form a plurality of top electrode portions connected to the contact pads from the second openings, and then deposit a common electrode portion on the surface of the insulating support layer, the protrusions and the top electrode portions. electrode.

Images