JP2009206349A - Semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device whose breakdown voltage property is improved without increasing a MIM capacitor area, and whose sticking is prevented. <P>SOLUTION: A first lower electrode 12-1, a first dielectric thin film 13 and a first upper electrode 14 are stacked on a semiconductor substrate to form a capacitor. A first ground electrode 15-1 and a first upper electrode 14 are mutually connected with a wiring electrode 16. A second lower electrode 17 connected with the first lower electrode 12-1 is formed on the semiconductor substrate. A portion of the surface of the second lower electrode 17 is covered with a second dielectric thin film 18, and a plurality of protrusions 23 is formed on the remaining portion. Insulation members 24, higher than protrusions 23, are formed between the protrusions 23. A second upper electrode 19 is formed on the second dielectric thin film 18. One end of a flexible strip conductor 22 is connected to the second upper electrode 19. The other end of the flexible strip conductor 22 is connected to the second ground electrode 21-1 connected to the first ground electrode 15-1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor device including a monolithic microwave integrated circuit using a compound semiconductor.

Conventionally, when a parallel plate type capacitor (MIM capacitor) is formed on a monolithic microwave integrated circuit (MMIC) using GaAsFET as an active element, a dielectric such as Si ₃ N _{4 is used} as an interlayer film between both electrodes. Although a film is widely used, in such a MIM capacitor structure, it has been difficult to improve breakdown voltage characteristics without increasing the area of the MIM capacitor.

  Therefore, a semiconductor device in which a flexible strip-like conductor is formed is known as a semiconductor device that can improve the breakdown voltage resistance without increasing the area of the MIM capacitor (Patent Document 1).

  That is, a semiconductor device provided with a ground electrode connected by wiring on a GaAs substrate on which a capacitor is formed by sequentially laminating a lower electrode, a dielectric thin film, and an upper electrode, at a position separated from the upper electrode The upper electrode and the grounding electrode are formed above the lower electrode via an air layer, and are connected to each other by a flexible strip conductor disposed at a position parallel to the wiring.

  According to this apparatus, since the flexible strip conductor has a function of contacting the lower electrode with desired electrostatic energy, the upper and lower electrodes are directly connected even when a breakdown voltage of the capacitor is applied due to a surge or the like. As a result, the applied voltage is grounded, so that failure of the capacitor can be avoided.

However, this semiconductor device has a problem that sticking that prevents the flexible strip-shaped conductor from returning to its original state while being in contact with the lower electrode occurs due to arc welding, moisture, or the like.
Japanese Patent Application No. 2007-273604

  An object of the present invention is to provide a semiconductor device capable of improving the breakdown voltage property without increasing the area of the MIM capacitor and preventing sticking.

  A semiconductor device according to the present invention includes a first lower electrode formed on a semiconductor substrate, a first dielectric thin film laminated on the first lower electrode, and a lamination on the first dielectric thin film. The formed first upper electrode, the first grounding electrode connected to the first upper electrode and formed on the semiconductor substrate, the first grounding electrode and the first upper electrode A wiring electrode disposed opposite to the first dielectric thin film, a second lower electrode formed on the semiconductor substrate and connected to the first lower electrode, and A second dielectric thin film laminated so as to cover a part of the surface of the second lower electrode; a second upper electrode laminated on the second dielectric thin film; and A flexible strip conductor with one end connected to the electrode and the other end of this flexible strip conductor are connected. And a second grounding electrode connected to the first grounding electrode, wherein the flexible strip-shaped conductor is disposed on the second lower electrode via an air layer, and The lower electrode has a structure having a plurality of protrusions formed on the surface other than the portion covered with the second dielectric thin film, the protrusions being separated from each other. An insulator is formed higher than the body.

  ADVANTAGE OF THE INVENTION According to this invention, the semiconductor device which can improve withstand voltage property without increasing the area of a MIM capacitor, and can prevent sticking can be provided.

  Embodiments of the present invention will be described below with reference to FIGS.

  FIG. 1 shows the structure of the semiconductor device according to the present embodiment. FIG. 1A is a top view showing the semiconductor device, and FIG. 1B is a broken line AA ′ in FIG. FIG. 3C is a structural cross-sectional view taken along the broken line BB ′ in FIG.

  In the semiconductor device according to the embodiment of the present invention, a first lower electrode 12 is formed on a GaAs substrate 11, and a first dielectric thin film 13 is laminated on the first lower electrode 12-1. A first upper electrode 14 is further laminated on the first dielectric thin film 13, and has a laminated structure of the first lower electrode 12-1, the first dielectric thin film 13, and the first upper electrode 14. The capacitor is formed. Further, a first grounding electrode 15-1 is formed on the GaAs substrate 11 at a position spaced from the first upper electrode 14, and further on the first grounding electrode 15-1, A lead electrode 15-2 of one grounding electrode 15-1 is formed. The first upper electrode 14 and the lead electrode 15-2 for the first ground electrode are connected to each other by the wiring electrode 16 disposed at a position facing the first dielectric thin film 13 with the air layer interposed therebetween. The air bridge wiring structure is formed.

  On the other hand, the second lower electrode 17 is formed integrally with the first lower electrode 12-1, and the first dielectric thin film 13 is formed on a part of the surface of the second lower electrode 17. And a second dielectric thin film 18 formed integrally with each other. A second upper electrode 19 is laminated on the second dielectric thin film 18. On the GaAs substrate 11, a second grounding electrode 21-1 connected to the first grounding electrode 15-1 through a high resistance layer 20 formed on the surface of the substrate 11 is formed. ing. Further, an extraction electrode 21-2 for the second grounding electrode 21-1 is formed on the second grounding electrode 21-1. The second upper electrode 19 and the lead electrode 21-2 for the second grounding electrode are opposed to the second dielectric thin film 13 across the air layer and are arranged in parallel with the wiring electrode 16. The conductors 22 are connected to each other.

  In the above-described semiconductor device, it is desirable that the wiring electrode 16 and the flexible strip-shaped conductor 22 are disposed close to each other in order to cope with high-speed operation. Therefore, the first upper electrode 14 connected to one end of the wiring electrode 16 and the second upper electrode 19 connected to one end of the flexible strip-shaped conductor 22 are formed close to each other, and the other end of the wiring electrode 16 is formed. The lead electrode 15-2 of the first ground electrode connected to the lead electrode 15-2 and the lead electrode 21-2 of the second ground electrode connected to the other end of the flexible strip conductor 22 are formed close to each other as described above. It is desirable that

  Furthermore, it is desirable that the high resistance layer 20 has a resistance value that is high enough to suppress the current flowing through the flexible strip conductor 22 to a negligible level during the operation of the semiconductor device described above.

  In the semiconductor device according to the present embodiment, the lead electrode 12-2 of the first lower electrode 12-1 is formed on the first lower electrode 12-1, and the lower surface of the GaAs substrate 11 is formed on the lower surface of the GaAs substrate 11. A through hole 25 is formed, and a grounding lower electrode 26 is formed on the entire lower surface of the GaAs substrate 11.

  Here, the second lower electrode 17 of the semiconductor device according to the present embodiment has a structure having a plurality of protrusions 23 on the surface of the electrode 17 other than the portion covered with the second dielectric thin film. It is a feature. Further, the plurality of protrusions 23 are formed apart from each other, and an insulator 24 made of polyimide is formed higher than the protrusions 23 between the protrusions 23.

  In the semiconductor device described above, when an excessive voltage such as a surge voltage is supplied to the lower electrodes 12-1 and 17, the flexible strip-shaped conductor 22 is moved by the electrostatic attraction as shown in FIG. 2 is attracted to the lower electrode 17, and a discharge phenomenon occurs from the tip of the protrusion 24 of the second lower electrode 17 to the flexible strip-shaped conductor 22, thereby making electrical contact. For example, when the voltage of the lower electrodes 12-1 and 17 drifts up to 100V due to a surge voltage, for example, the phenomenon described above occurs when a voltage exceeding about 50V is applied. Thereby, since the breakdown voltage of the first and second dielectric thin films 13 and 18 is about 80 V, the supply voltage is grounded before the dielectric thin films 13 and 18 are broken, so that the MIM capacitor is damaged. Can be prevented. As described above, since the breakdown voltage property can be maintained without increasing the thickness of the MIM capacitor, the capacitance value can be maintained without increasing the area of the MIM capacitor. In addition, since the flexible strip-shaped conductor 22 that is in electrical contact is not physically in direct contact with the insulator 24 formed on the second lower electrode 17, arc welding or adsorption to the second lower electrode 17 It becomes possible to prevent sticking such as moisture. Then, after the excessive voltage is cut off, the original shape is restored by the restoring force of the flexible strip-shaped conductor 22, so that the function as the MIM capacitor is restored.

  Next, a method for manufacturing the semiconductor device according to the present embodiment will be described.

  3 to 8 are explanatory views for explaining a manufacturing process of the semiconductor device according to the present embodiment. FIGS. 3 and 8A are top views, and FIG. It is structural sectional drawing along the broken line BB 'of (a). 4 to 7 are diagrams for explaining a processing method of the second lower electrode, and show a main part of the structural cross-sectional view along the broken line BB 'in FIG.

  The method for manufacturing the semiconductor device according to the present embodiment is the same as the method for manufacturing the semiconductor device having the conventional flexible strip-shaped conductor 22 described above, except for the step of forming the second lower electrode 17. Here, the manufacturing process of the second lower electrode 17 will be described in detail.

First, as shown in FIG. 3, the high resistance layer 20 is formed by ion implantation or mesa etching, and then the first and second grounding electrodes 15-1, 21-1 and the first, first, On the GaAs substrate 11 on which the two lower electrodes 12-1 and 17 are formed, an Si ₃ N ₄ film is deposited to a thickness of 100 nm as the first and second dielectric thin films 13 and 18 by plasma CVD, Unnecessary portions including the ground region of the flexible strip-shaped conductor 22 are removed by etching. The first and second grounding electrodes 15-1 and 21-1 are formed by, for example, depositing Ni / AuGe at 50 nm / 200 nm, respectively, and performing heat treatment at 440 ° C. for 3 minutes in a nitrogen atmosphere after lift-off. The first and second lower electrodes 12-1 and 17 are formed, for example, by vapor-depositing Au / Pt / Ti at 500 nm / 10 nm / 500 nm, respectively, and performing lift-off.

  Next, processing is performed on the second lower electrode 17 formed on the GaAs substrate 11 as described above. Below, the process of processing the 2nd lower electrode 17 is demonstrated.

  First, as shown in FIG. 4, a photoresist 27 is formed on the second lower electrode 17.

  Next, as shown in FIG. 5, the second lower electrode 17 is patterned, and the Au and Pt on the second lower electrode 17 are etched by ion milling to obtain the second A protrusion 23 is formed on the lower electrode 17.

  Next, as shown in FIG. 6, after removing the photoresist 27, an insulator 24 made of photosensitive polyimide is coated with a desired thickness, and a photoresist 28 is formed on the insulator 24.

  Next, as shown in FIG. 7, a desired insulator 24 can be obtained by performing a pattern PEP process on the insulator 24.

  As described above, the second lower electrode 17 of the semiconductor device according to the present embodiment is formed.

  After the second lower electrode 17 having the protrusions 23 is formed, as shown in FIG. 8, the first and second upper electrodes 14 and 19, the first lower electrode lead electrode 12-2, and As the lead electrodes 15-2 and 21-2 of the first and second grounding electrodes 15-1 and 21-1, for example, Au / Pt / Ti is vapor-deposited by 500 nm / 10 nm / 10 nm, respectively, and lift-off is performed. Then, after forming an air bridge wiring under resist 29, 1000 nm of Au is vapor-deposited as the wiring electrode 16 and the flexible strip conductor 22, and lift-off is performed. At this time, the wiring electrode 16 is formed to have a spatial distance of, for example, 1.0 μm with respect to the tip of the protrusion 23 on the second lower electrode.

  Finally, the back surface of the GaAs substrate 11 is polished to 100 μm, a through hole 25 is formed under the first grounding electrode 15-2 using RIE, and then the grounding lower electrode 26 is formed on the entire back surface of the GaAs substrate 11. For example, by depositing Au / Ti at 1000 nm / 10 nm, respectively, and removing the under-wire resist 29 for the bridge wiring, the semiconductor device shown in FIG. 1 can be manufactured.

  Although the semiconductor device according to the embodiment of the present invention has been described above, the embodiment is not limited thereto. For example, in the above-described embodiment, the flexible strip conductor is connected to the second upper electrode 19, but the same effect can be obtained by connecting to the second lower electrode 17. is there.

The structure of the semiconductor device according to the present embodiment is shown, FIG. 6A is a top view showing the semiconductor device, and FIG. 5B is a structural cross section taken along the broken line AA ′ in FIG. FIG. 4C is a structural cross-sectional view taken along the broken line BB ′ in FIG. The operation of the semiconductor device according to the present embodiment is shown. FIG. 11A is a top view showing the operation of the semiconductor device, and FIG. 11B is along the broken line BB ′ in FIG. FIG. It is explanatory drawing for demonstrating the manufacturing process of the semiconductor device which concerns on this embodiment, The figure (a) shows a top view, The figure (b) is the broken line BB 'of the figure (a). FIG. It is a figure explaining the processing method of a 2nd lower electrode, and shows the principal part of structure sectional drawing along broken line BB 'in FIG. It is a figure explaining the processing method of a 2nd lower electrode, and shows the principal part of structure sectional drawing along broken line BB 'in FIG. It is a figure explaining the processing method of a 2nd lower electrode, and shows the principal part of structure sectional drawing along broken line BB 'in FIG. It is a figure explaining the processing method of a 2nd lower electrode, and shows the principal part of structure sectional drawing along broken line BB 'in FIG. It is explanatory drawing for demonstrating the manufacturing process of the semiconductor device which concerns on this embodiment, The figure (a) shows a top view, The figure (b) is the broken line BB 'of the figure (a). FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... GaAs substrate 12-1 ... 1st lower electrode 12-2 ... Extraction electrode 13 of 1st lower electrode ... 1st dielectric thin film 14 ... 1st upper electrode 15-1... First grounding electrode 15-2... First grounding electrode lead electrode 16... Wiring electrode 17 .. Second lower electrode 18. Dielectric thin film 19 ... second upper electrode 20 ... high resistance layer 21-1 ... second grounding electrode 21-2 ... lead electrode 22 of second grounding electrode ... Flexible strip-shaped conductor 23 ... Projection body 24 ... Insulator 25 ... Through hole 26 ... Grounding lower electrodes 27 and 28 ... Photoresist 29 ... Under resist for air bridge wiring

Claims (5)

A first lower electrode formed on a semiconductor substrate;
A first dielectric thin film laminated on the first lower electrode;
A first upper electrode laminated on the first dielectric thin film;
A first grounding electrode connected to the first upper electrode and formed on the semiconductor substrate;
A wiring electrode that connects the first grounding electrode and the first upper electrode to each other, and is disposed opposite to the first dielectric thin film;
A second lower electrode formed on the semiconductor substrate and connected to the first lower electrode;
A second dielectric thin film laminated so as to cover a part of the surface of the second lower electrode;
A second upper electrode laminated on the second dielectric thin film;
A flexible strip conductor having one end connected to the second upper electrode;
A second grounding electrode connected to the first grounding electrode, the other end of the flexible strip conductor being connected, and
The flexible strip conductor is disposed on the second lower electrode through an air layer,
The second lower electrode has a structure having a plurality of protrusions formed separately from each other on a surface other than the portion covered with the second dielectric thin film,
A semiconductor device is characterized in that an insulator is formed between the protrusions so as to be higher than the protrusions.   The semiconductor device according to claim 1, wherein the flexible strip-shaped conductor is formed in close proximity to and parallel to the wiring electrode.   3. The first grounding electrode and the second grounding electrode are connected to each other through a high resistance layer formed on the semiconductor substrate. Semiconductor device. 4. The semiconductor device according to claim 1, wherein the semiconductor substrate is a GaAs substrate, and the first dielectric thin film and the second dielectric thin film are Si ₃ N ₄ films. .   The semiconductor device according to claim 1, wherein the insulator is photosensitive polyimide.

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