Bipolar transistor structure and radio frequency amplifier

Abstract

The embodiment of the utility model provides a bipolar transistor structure and a radio frequency amplifier, and the bipolar transistor structure comprises a semiconductor layer which is provided with a first surface and comprises a collector electrode layer, a base electrode layer and an emitter electrode layer which are laminated in sequence; the emitting electrode structure is arranged on the first surface and comprises an emitting electrode step and emitting electrode metal which are stacked in sequence; the dielectric layer at least covers the part, exposed out of the emitter structure, of the first surface; the dielectric layer has a first opening; the base metal layer is partially positioned in the first opening so as to be connected to the base layer through the first opening, and partially extends to the upper part of the dielectric layer towards the periphery; the base metal layer comprises a first metal layer in contact with the dielectric layer, and the first metal layer comprises a peripheral part which is located on the dielectric layer and surrounds the first opening; the thickness of the peripheral portion is less than or equal to 18 nanometers. According to the embodiment of the utility model, cracking and layering between the base metal layer and the dielectric layer can be prevented, and the reliability of the device is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of semiconductor, especially to a bipolar transistor structure and radio frequency amplifier. BACKGROUND

[0002] The bipolar transistor is commonly known as a triode, and with the development of technology, people have put forward higher and higher requirements on the performance of the triode. High-frequency high-power performance and high reliability are both relatively important performances. However, some existing schemes for improving the high-frequency high-power performance of the bipolar transistor cannot take into account the high reliability of the device. For example, the high-frequency high-power performance of the bipolar transistor can be improved by changing the base region platform area, the base-emitter junction capacitance, and reducing the base metal width. However, directly reducing the spacing between the base metal and the emitter platform will reduce the reliability of the device.

[0003] Therefore, how to design the bipolar transistor structure to take into account the high-frequency high-power performance and high reliability of the bipolar transistor is a problem to be solved. SUMMARY

[0004] Therefore, to overcome at least some of the defects in the prior art, the utility model embodiment provides a bipolar transistor structure and a radio frequency amplifier, which can prevent cracking and delamination between the base metal layer and the dielectric layer and improve the reliability of the device.

[0005] One embodiment of the utility model provides a bipolar transistor structure, comprising: a semiconductor layer having a first surface, the semiconductor layer comprising a collector layer, a base layer and an emitter layer which are sequentially stacked; the first surface is the surface of the emitter layer facing away from the base layer; an emitter structure is provided on the first surface and comprises an emitter step and an emitter metal which are sequentially stacked; a dielectric layer covers at least part of the first surface exposed outside the emitter structure; the dielectric layer has a first opening; a base metal layer is partially located in the first opening to be connected to the base layer through the first opening and partially extends to above the dielectric layer; the base metal layer comprises a first metal layer in contact with the dielectric layer, and the first metal layer comprises a peripheral part located above the dielectric layer and surrounding the first opening; the thickness of the peripheral part is less than or equal to 18 nanometers.

[0006] One embodiment of the utility model provides a radio frequency amplifier comprising the aforementioned bipolar transistor structure.

[0007] The above embodiments of the utility model have at least one or more of the following beneficial effects: the base metal layer part is connected with the base layer and extends partially above the dielectric layer, which can reduce the distance between the part of the base metal layer above the dielectric layer and the emitter structure, and maintain a proper base and emitter step effective spacing, so that the base region step area can be made smaller and the BC junction area is smaller, thus improving the frequency characteristics. The thickness of the part of the base metal layer in contact with the dielectric layer is designed to prevent stress cracking between the base metal layer and the dielectric layer, which can improve high frequency characteristics while ensuring high reliability. BRIEF DESCRIPTION OF DRAWINGS

[0008] The specific embodiments of the utility model will be described in detail below with reference to the drawings. The drawings only show the spatial relationship of the structures of the parts, and not the essential thickness, size or relative proportional relationship of the structures of the parts.

[0009] Figure 1 The utility model provides the top view structure schematic diagram of bipolar transistor structure.

[0010] Figure 2 For Figure 1 The local amplification schematic view of C area.

[0011] Figure 3 For Figure 1 The A-A section schematic view of.

[0012] Figure 4 For Figure 1 The B-B section schematic view of.

[0013] Figure 5 For Figure 3 The local amplification schematic view of one embodiment of D area.

[0014] Figure 6 For Figure 3 The local amplification schematic view of another embodiment of D area.

[0015]

Explanation of reference signs

[0016] 11, semiconductor layer; 111, collector layer; 112, base layer; 113, emitter layer; 1131, first surface; 1132, second opening; 114, substrate; 115, sub-collector layer; 116, etch stop layer; 1101, semiconductor side surface; 12, emitter structure; 121, emitter step; 122, emitter metal; 13, dielectric layer; 131, first opening; 132, first dielectric layer; 133, second dielectric layer; 14, base metal layer; 141, first metal layer; 1411, middle part; 1412, peripheral part; 142, second metal layer; 143, third metal layer; 144, fourth metal layer; 15, collector metal; 16, first alloy layer. DETAILED DESCRIPTION

[0017] In order to make the above objectives, features and advantages of the present application more apparent, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0018] In order to make the above objectives, features and advantages of the present application more apparent, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0019] It should be noted that the terms "first", "second" and the like in the description and in the claims of the present application are intended to distinguish between similar objects, but are not necessarily used to describe a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of practical implementation in other than the presented orders. Moreover, the terms "comprising", "having", "including" and "containing" are to be construed open-ended, i.e., meaning "including, but not limited to", "comprising, but not limited to", "having, but not limited to", or "including, but not limited to", respectively, unless otherwise noted.

[0020] It should also be noted that the division of the embodiments in the present application is only for the convenience of description, and should not constitute a special limitation. The features in various embodiments can be combined with each other and mutually referenced, without contradiction.

[0021] The utility model discloses an embodiment provides a bipolar transistor structure, wherein the bipolar transistor structure is a transistor structure with a semiconductor laminated structure, for example, can be HBT (heterojunction bipolar transistor) device, also can be integrated HBT device (integrated passive device on HBT device).

[0022] Figure 1 The utility model discloses an embodiment provides the overhead structure schematic diagram of bipolar transistor structure, Figure 3 For Figure 1 The schematic diagram of A-A section in, refer to Figure 1 And Figure 3 The bipolar transistor structure has a semiconductor layer 11, an emitter structure 12, a dielectric layer 13 and a base metal layer 14. In order to facilitate the structure inside the exhibition, Figure 1 The dielectric layer 13 is transparently handled and the position of the first opening 131 is marked with a dashed line in the embodiment. The semiconductor layer 11 has a first surface 1131, and the semiconductor layer 11 includes a collector layer 111, a base layer 112 and an emitter layer 113 which are sequentially laminated. The first surface 1131 is the surface of the emitter layer 113 away from the base layer 112. The emitter structure 12 is arranged on the first surface 1131 and includes an emitter step 121 and an emitter metal 122 which are sequentially laminated. It should be noted that although the width of the emitter metal 122 is less than the width of the emitter step 121 as shown in the embodiment, the embodiment is not limited thereto, and in some embodiments, the width of the emitter metal 122 can be equal to or substantially consistent with the width of the emitter step 121. Figure 1 And Figure 3 The width of the emitter metal 122 can be equal to or substantially consistent with the width of the emitter step 121.

[0023] The dielectric layer 13 covers at least the part of the first surface 1131 exposed outside the emitter structure 12, and the dielectric layer 13 has a first opening 131. In some embodiments, the dielectric layer 13 also covers the top surface of the emitter structure 12 away from the first surface 1131 and the sidewall of the emitter structure 12. The orthographic projection of the first opening 131 on the first surface 1131 is located in the area of the first surface 1131 exposed outside the emitter structure 12.

[0024] The base metal layer 14 can also be referred to as a base electrode. The base metal layer 14 is partially located within the first opening 131 to connect to the base layer 112 through the first opening 131, and partially extends to above the dielectric layer 13 to the periphery. The portion of the base metal layer 14 located within the first opening 131 connects to the base layer 112 through an opening in the emitter layer 113 or an alloy layer. Specifically, the base metal layer 14 includes a first metal layer 141 in contact with the dielectric layer 13, the first metal layer 141 including a peripheral portion 1412 located above the dielectric layer 13 and surrounding the first opening 131, the peripheral portion 1412 having a thickness less than or equal to 18 nanometers.

[0025] The semiconductor layer 11 further includes, for example, a substrate 114, a sub-collector layer 115, and an etching stop layer 116, which are sequentially stacked, and the collector layer 111 is provided on the etching stop layer 116.

[0026] The substrate 114 can be, for example, a III-V semiconductor, such as any one or a combination of GaN, AlGaN, AlN, GaAs, AlGaAs, InP, InGaAs, and InAlAs.

[0027] The sub-collector layer 115 can be, for example, a III-V semiconductor, such as any one or a combination of GaN, AlGaN, AlN, GaAs, AlGaAs, InP, InGaAs, and InAlAs.

[0028] The etching stop layer 116 can be, for example, a III-V semiconductor, such as any one or a combination of InGaP, InGaAs, GaAsP, AlGaAs, InAlAs, and GaSb.

[0029] The collector layer 111 can be, for example, a III-V semiconductor, such as any one or a combination of GaN, AlGaN, AlN, GaAs, AlGaAs, InP, InGaAs, and InAlAs.

[0030] The base layer 112 can be, for example, a III-V semiconductor, such as any one or a combination of GaN, AlGaN, AlN, GaAs, AlGaAs, InP, InGaAs, and InAlAs.

[0031] The emitter layer 113 can be, for example, a III-V semiconductor, such as any one or a combination of GaN, AlGaN, AlN, GaAs, AlGaAs, InP, InGaAs, InAlAs, and InGaP. The emitter layer 113 can be a multi-layer structure.

[0032] The doping type of the sub-collector layer 115, the collector layer 111 and the emitter layer 113 is the first doping type, and the doping type of the base layer 112 is the second doping type. When the first doping type is n-type, the second doping type is p-type. When the first doping type is p-type, the second doping type is n-type.

[0033] Referring to Figure 1 and Figure 3 , the bipolar transistor structure further comprises a collector metal 15, which is connected to the sub-collector layer 115. The collector metal 15 can be AuGe / Ni / Au or Au / Ge / Ni / Au structure.

[0034] The emitter metal 122 can be Ti, Pt, Au, Al, Cu, W, Ni, Ge, etc.

[0035] The material of the dielectric layer 13 can be any one or a combination of multiple of the following insulating materials: SiN, Si3N4, Si2N3, SiO2, SiON, Al2O3, AlN, PI (polyimide), BCB (benzocyclobutene), PBO (polybenzoxazole), etc. The dielectric layer 13 can be single layer or multiple layers. For example, referring to Figure 3 and Figure 4 , the dielectric layer 13 comprises a first dielectric layer 132 and a second dielectric layer 133. The semiconductor layer 11 comprises a semiconductor side surface 1101 adjacent to the first surface 1131. The first dielectric layer 132 further covers the top surface and the sidewall of the emitter structure 12. The second dielectric layer 133 covers the first dielectric layer 132 and extends to cover the semiconductor side surface 1101.

[0036] The material of the first dielectric layer 132 and the second dielectric layer 133 can be the same or different, and the thickness of the first dielectric layer 132 and the second dielectric layer 133 can be the same or different. In some embodiments, the thickness of the first dielectric layer 132 and the second dielectric layer 133 ranges from 20 nm to 100 nm. In some embodiments, at least one of the material and the thickness of the first dielectric layer 132 and the second dielectric layer 133 is different, for example, the material of the first dielectric layer 132 and the second dielectric layer 133 is the same but the thickness is different, for example, the material of the first dielectric layer 132 and the second dielectric layer 133 is different but the thickness is the same, for example, the material and the thickness of the first dielectric layer 132 and the second dielectric layer 133 are both different. The arrangement of the first dielectric layer 132 can form passivation on the surface of the emitter layer 113, and can protect the emitter layer 113 from being affected during the preparation process of the bipolar transistor structure (specifically, the step of etching the base region platform), thereby improving the reliability of the structure. Moreover, when the reliability is higher, a smaller base-emitter step effective spacing can be designed, thereby reducing the area of the device and further reducing the BC junction area, and improving the high-frequency characteristics of the device.

[0037] The side wall of the dielectric layer 13 towards the first opening 131 can be arranged obliquely, and the first surface 1131 is located in a sub-region of the first opening 131 as the bottom surface of the first opening 131. The included angle between the side wall of the dielectric layer 13 towards the first opening 131 and the bottom surface of the first opening 131 is greater than or equal to 90°. The oblique angles of the first dielectric layer 132 and the second dielectric layer 133 towards the side wall of the first opening 131 can be the same or different. For example, refer to Figure 6 , the oblique angles of the first dielectric layer 132 and the second dielectric layer 133 towards the side wall of the first opening 131 are the same, and the width of the first opening 131 gradually increases from bottom to top. Refer to Figure 5 , the oblique angles of the first dielectric layer 132 and the second dielectric layer 133 towards the side wall of the first opening 131 are different. The included angle α2 between the side wall of the second dielectric layer 133 towards the first opening 131 and the bottom surface of the first opening 131 is greater than the included angle α1 between the side wall of the first dielectric layer 132 towards the first opening 131 and the bottom surface of the first opening 131, that is, the side wall of the first dielectric layer 132 towards the first opening 131 is steeper.

[0038] The base metal layer 14 can adopt a commonly used base metal material, for example, Pt is used as the bottom layer metal (i.e., the first metal layer 141) to form an ohmic contact connection with the base layer 112. According to the pattern of the base metal layer 14, the base metal layer 14 further includes a plurality of fingers and a connecting portion connecting the plurality of fingers, for example, refer to Figure 1 , the base metal layer 14 includes three fingers extending along the first direction, and in Figure 3 , 3 fingers can also be observed. Refer to Figure 1The base metal layer 14 includes a connecting portion extending in the second direction and connected to one end of the three finger portions, and Figure 4 The connecting portion can also be observed in the middle.

[0039] Referring to Figure 3 The base metal layer 14 has a portion connected to the base layer 112 through the first opening 131, and a portion extending above the dielectric layer 13 beyond the edge of the first opening 131 and covering the portion of the dielectric layer 13 adjacent to the first opening 131. The overall width of the base metal layer 14 is greater than the overall width of the first opening 131. When the width of the base metal layer 14 is non-uniform and / or the width of the first opening 131 is non-uniform, the maximum width of the portion of the base metal layer 14 above the dielectric layer 13 is greater than the maximum width of the first opening 131. Specifically, the width of the portion of the base metal layer 14 above the dielectric layer 13 is greater than the width of the base metal layer 14 in contact with the base layer 112. The maximum width of the first opening 131 is 200-1000 nm.

[0040] Referring to Figure 2W1 represents the base-emitter step effective distance, and W1 represents the distance between the part of the base metal layer 14 in contact with the base layer 112 and the emitter step 121. Through the structure of the embodiment, the distance W2 between the base metal layer 14 (the part above the dielectric layer 13) and the emitter step 121 can be smaller while the base-emitter step effective distance and other sizes (the width of the base metal layer 14, the width of the emitter structure 12, etc.) remain unchanged. For example, W1 can be 200-1000 nm, and W2 can be 0-1000 nm. The difference between W1 and W2 ranges from 100-1000 nm. That is, even if the distance between the part of the base metal layer 14 above the dielectric layer 13 and the emitter structure 12 is reduced, a suitable base-emitter step effective distance can still be maintained, so that the base region step area of the bipolar transistor structure provided by the embodiment can be made smaller, the BC junction area is smaller, and thus the frequency characteristic can be improved. The inventors have found in practice that when the part of the base metal layer 14 extending beyond the first opening 131 has a large thickness and is in direct contact with the dielectric layer 13, the material of the base metal layer 14 and the material of the dielectric layer 13 are prone to stress cracking at high temperatures, leading to moisture intrusion, and the metal of the base metal layer 14 and the gallium arsenide material of the semiconductor layer 11 are prone to electrochemical reaction in the presence of moisture, which will cause the reliability of the bipolar transistor structure to fail. In the embodiment, the thickness of the peripheral portion 1412 is set to be relatively thin, so that the stress between the base metal layer 14 and the upper surface of the dielectric layer 13 is small, which can prevent the base metal layer 14 and the dielectric layer 13 from cracking and delaminating, and further prevent the problem of stress cracking between the base metal layer 14 and the dielectric layer 13 leading to moisture intrusion, so that high frequency characteristics can be improved while ensuring high reliability.

[0041] With reference to Figure 6 In some embodiments, the first metal layer 141 includes a middle portion 1411 located in the first opening 131. The peripheral portion 1412 is located above the dielectric layer 13 and surrounds the middle portion 1411. The middle portion 1411 and the peripheral portion 1412 are made of the same material. The middle portion 1411 and the peripheral portion 1412 can be integrally formed. That is, the middle portion 1411 and the peripheral portion 1412 can be formed simultaneously in the preparation process, and the middle portion 1411 and the peripheral portion 1412 can be made of the same material, so that no additional material needs to be provided, and the process difficulty and cost are low.

[0042] In some embodiments, the base metal layer 14 further includes a second metal layer 142, a third metal layer 143, and a fourth metal layer 144 sequentially stacked on the first metal layer 141.

[0043] In a more specific embodiment, the thickness of the peripheral portion 1412 ranges from 3 to 10 nm. For example, the thickness of the peripheral portion 1412 can be 4 nm, 5 nm, 7 nm, 8 nm, etc. The third metal layer 143 can be the same material as the first metal layer 141, for example, both are Pt. Specifically, the thickness of the peripheral portion 1412 is less than or equal to half of the thickness of the third metal layer 143. The second metal layer 142 can be Ti, and the fourth metal layer 144 can be Au. In one specific embodiment, the thickness of the peripheral portion 1412 is 10 nm, the central portion 1411 is Pt, the second metal layer 142, the third metal layer 143, and the fourth metal layer 144 are a Ti / Pt / Au stack structure, and the thicknesses of the layers in the stack structure are 50 nm, 30 nm, and 320 nm, respectively. In another specific embodiment, the thickness of the peripheral portion 1412 is 10 nm, the central portion 1411 is Pt, the second metal layer 142, the third metal layer 143, and the fourth metal layer 144 are a Ti / Pt / Au stack structure, and the thicknesses of the layers in the stack structure are 50 nm, 25 nm, and 500 nm, respectively. In the above two specific embodiments, by providing a thinner peripheral portion 1412, the separation between the base metal layer 14 and the dielectric layer 13 can be prevented, thereby ensuring high reliability.

[0044] With continued reference to Figure 6 In some embodiments, a first alloy layer 16 is formed in the base layer 112 near the first opening 131, a second opening 1132 is formed in the emitter layer 113, and the central portion 1411 connects the first alloy layer 16 through the first opening 131 and the second opening 1132. The second opening 1132 in the emitter layer 113 can be formed by dry or wet etching after the dielectric layer 13 is formed and before the base metal layer 14 is formed. By providing the second opening 1132 in the emitter layer 113, the central portion 1411 can directly contact the base layer 112 through the second opening 1132 to form the first alloy layer 16 by alloying reaction, which can ensure better ohmic contact between the base layer 112 and the emitter layer 113 and ensure the reliability of the device.

[0045] In some embodiments, with reference to Figure 6 The thickness H1 of the first alloy layer 16 is greater than half of the difference between the width of the first alloy layer 16 and the width D1 of the bottom of the second opening 1132, i.e., H1 > [(D2-D1) / 2], which means that the width of the first alloy layer 16 extending horizontally beyond the second opening 1132 in the base layer 112 is less than the depth of the first alloy layer 16 extending in the thickness direction into the base layer 112. This can prevent the horizontal diffusion of the first alloy layer 16 from reducing the effective spacing between the base and the emitter steps, thereby ensuring higher reliability.

[0046] In some embodiments, the utility model embodiments also provide a radio frequency amplifier, the radio frequency amplifier includes any one of the foregoing bipolar transistor structures, the radio frequency amplifier has the same effect as the foregoing bipolar transistor structure, and here is not repeated.

[0047] The above is only the preferred embodiment of the utility model, and does not limit the utility model in any form, although the utility model has disclosed as above with the preferred embodiment, however, is not used to limit the utility model, any skilled person in the art, within the scope of the technical scheme of the utility model, can make some changes or modifications to the equivalent embodiments of equivalent changes by using the disclosed technical content, but as long as it does not deviate from the technical scheme of the utility model, according to the technical essence of the utility model, any simple modification, equivalent change and modification of the above embodiment, still belongs to the scope of the technical scheme of the utility model.

Claims

1. A bipolar transistor structure, characterized in that, include: A semiconductor layer (11) has a first surface (1131). The semiconductor layer (11) includes a collector layer (111), a base layer (112), and an emitter layer (113) stacked sequentially. The first surface (1131) is the surface of the emitter layer (113) facing away from the base layer (112). An emitter structure (12) is disposed on the first surface (1131) and includes an emitter step (121) and an emitter metal (122) stacked sequentially. A dielectric layer (13) at least covers the portion of the first surface (1131) exposed outside the emitter structure (12); the dielectric layer (13) has a first opening (131); A base metal layer (14) is partially located within the first opening (131) to be connected to the base layer (112) through the first opening (131), and partially extends peripherally over the dielectric layer (13); the base metal layer (14) includes a first metal layer (141) in contact with the dielectric layer (13), the first metal layer (141) including a peripheral portion (1412) located over the dielectric layer (13) and surrounding the first opening (131); the thickness of the peripheral portion (1412) is less than or equal to 18 nanometers.

2. The bipolar transistor structure as described in claim 1, characterized in that, The first metal layer (141) also includes a central portion (1411) located within the first opening (131) and connected to the peripheral portion (1412).

3. The bipolar transistor structure as described in claim 2, characterized in that, The central part (1411) and the peripheral part (1412) are integrally formed and connected.

4. The bipolar transistor structure as described in claim 2, characterized in that, The base metal layer (14) further includes a second metal layer (142), a third metal layer (143) and a fourth metal layer (144) sequentially stacked on the first metal layer (141); the thickness of the peripheral portion (1412) is less than or equal to half the thickness of the third metal layer (143).

5. The bipolar transistor structure as described in claim 1, characterized in that, The dielectric layer (13) includes a first dielectric layer (132) and a second dielectric layer (133); the semiconductor layer (11) also includes a semiconductor side surface (1101) adjacent to the first surface (1131); the first dielectric layer (132) also covers the top surface and sidewalls of the emitter structure (12); the second dielectric layer (133) covers the first dielectric layer (132) and extends to cover the semiconductor side surface (1101).

6. The bipolar transistor structure as described in claim 5, characterized in that, The thickness and material of the first dielectric layer (132) and the second dielectric layer (133) are different.

7. The bipolar transistor structure as described in claim 2, characterized in that, A first alloy layer (16) is formed in the base layer (112) on the side near the first opening (131), and a second opening (1132) is formed in the emitter layer (113). The middle part (1411) is connected to the first alloy layer (16) through the first opening (131) and the second opening (1132).

8. The bipolar transistor structure as described in claim 7, characterized in that, The thickness of the first alloy layer (16) is greater than half the difference between the width of the first alloy layer (16) and the bottom width of the second opening (1132).

9. The bipolar transistor structure according to any one of claims 1 to 8, characterized in that, The thickness of the peripheral portion (1412) ranges from 3 to 10 nanometers.

10. A radio frequency amplifier, characterized in that, Includes the bipolar transistor structure as described in any one of claims 1 to 9.

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