阅读说明：本技术 晶体管及其制备方法 (Transistor and preparation method thereof ) 是由 杨健 魏鸿基 王勇 郑坤 于 2019-11-29 设计创作，主要内容包括：本申请提供了一种晶体管及其制备方法,涉及半导体和通信技术领域。所述晶体管包括衬底和依次形成在所述衬底上的基极平台和基极接触电极；所述基极平台的两侧边缘设置有缺口,以使所述基极接触电极超出所述基极平台顶面的边缘。这样,能够在后续加工中对应减小Cbc的面积,提高功率增益。(The application provides a transistor and a preparation method thereof, and relates to the technical field of semiconductors and communication. The transistor comprises a substrate, and a base electrode platform and a base electrode contact electrode which are sequentially formed on the substrate; and notches are arranged on the edges of the two sides of the base electrode platform, so that the base electrode contact electrode exceeds the edge of the top surface of the base electrode platform. Thus, the area of Cbc can be reduced correspondingly in the subsequent processing, and the power gain can be improved.)

1. A transistor, characterized in that it comprises a substrate (110) and a base mesa (111) and a base contact electrode (124) formed in succession on said substrate (110); notches (120) are provided at both side edges of the base mesa (111) so that the base contact electrode (124) exceeds the edge of the top surface of the base mesa (111).

2. The transistor of claim 1, wherein the distance between the edge of the base mesa (111) and the edge of the base contact electrode (124) is D1, and D1 has a value in the range of: 0.2-0.8 μm.

3. The transistor of claim 1, wherein the notch (120) comprises a first notch (140), an edge of the first notch (140) meeting an edge of the base contact electrode (124).

4. The transistor of claim 3, wherein the notch (120) comprises a second notch (150), the second notch (150) being disposed at a side of the first notch (140), an edge of the second notch (150) being spaced apart from an edge of the base contact electrode (124) by a distance D2, D2 having a value in a range of: 0.2-0.8 μm.

5. Transistor according to claim 1, characterized in that the base mesa (111) comprises a collector contact electrode (112), a pedestal (113) and an epitaxial layer (114) arranged in this order from bottom to top.

6. A preparation method of a transistor is characterized by comprising the following steps:

sequentially forming a base mesa (111) and a base contact electrode (124) on a substrate (110);

and etching off partial materials on two side edges of the top surface of the base platform (111) to form a gap (120) so that the base contact electrode (124) exceeds the edge of the top surface of the base platform (111).

7. The method for manufacturing the transistor according to claim 6, wherein the notch (120) comprises a first notch (140) and a second notch (150), the second notch (150) is disposed at a side of the first notch (140), and the second notch (150) is formed by wet etching.

8. The preparation method of the transistor according to claim 7, wherein in the solution adopted in the wet etching, the ratio range of phosphoric acid to hydrogen peroxide is as follows: 3: 1-30: 1.

9. the method for manufacturing a transistor according to claim 7, wherein in the wet etching, a range of a ratio of a forward etching rate to a lateral etching rate is: 1: 1-5: 1.

Technical Field

The application relates to the technical field of semiconductors and communication, in particular to a transistor and a preparation method thereof.

Background

The existing power amplifier adopts a gallium arsenide heterojunction bipolar transistor (GaAsHBT), and has the advantages of high-frequency characteristic, high power density, high working efficiency, good linearity and the like. Among them, one of the main reasons for limiting the linearity of the Heterojunction Bipolar Transistor (HBT) is that the collector junction capacitance (Cbc) inside the HBT has a large area.

However, in the HBT, the area of Cbc is closely related to the area of the base mesa, and in the current mainstream process, no matter wet etching or dry etching is adopted, the edge of the top surface of the base mesa exceeds the edge of the base contact electrode, so the area of the base mesa is also large, and the area of Cbc is also large, thereby resulting in a small Power Gain (Power Gain).

Disclosure of Invention

In view of the above, the present application provides a transistor and a method for fabricating the same to improve the above-mentioned problems.

The embodiment of the application provides a transistor, which comprises a substrate (110), and a base platform (111) and a base contact electrode (124) which are sequentially formed on the substrate (110); notches (120) are provided at both side edges of the base mesa (111) so that the base contact electrode (124) exceeds the edge of the top surface of the base mesa (111).

In the transistor of the above embodiment, the distance between the edge of the base mesa (111) and the edge of the base contact electrode (124) is D1, and the value range of D1 is: 0.2-0.8 μm.

In the transistor of the above embodiment, the notch (120) includes a first notch (140), and an edge of the first notch (140) is connected to an edge of the base contact electrode (124).

In the transistor of the above embodiment, the notch (120) includes a second notch (150), the second notch (150) is disposed on a side of the first notch (140), a distance between an edge of the second notch (150) and an edge of the base contact electrode (124) is D2, and a value range of D2 is: 0.2-0.8 μm.

In the transistor of the above embodiment, the base platform (111) includes a collector contact electrode (112), a pedestal (113), and an epitaxial layer (114) sequentially disposed from bottom to top.

The embodiment of the application provides a preparation method of a transistor, which comprises the following steps:

sequentially forming a base mesa (111) and a base contact electrode (124) on a substrate (110);

and etching off partial materials at two side edges of the base platform (111) to form a gap (120) so that the base contact electrode (124) exceeds the edge of the top surface of the base platform (111).

In the preparation method of the transistor according to the above embodiment, the notch (120) includes a first notch (140) and a second notch (150), the second notch (150) is disposed on a side surface of the first notch (140), and the second notch (150) is formed by wet etching.

In the preparation method of the transistor in the above embodiment, in the solution used in the wet etching, the ratio of phosphoric acid to hydrogen peroxide is in the range: 3: 1-30: 1.

in the method for manufacturing a transistor according to the embodiment, in the wet etching, a range of a ratio of a forward etching rate to a lateral etching rate is as follows: 1: 1-5: 1.

the transistor and the preparation method thereof provided by the embodiment of the application have the beneficial effects that:

the base electrode platform is firstly positioned on the two side edges of the base electrode platform (111) to form notches, so that the width of the base electrode platform is reduced, the area of the base electrode platform is reduced, the base electrode contact electrode (124) exceeds the edge of the top surface of the base electrode platform (111), the area of Cbc can be correspondingly reduced in subsequent processing, and the power gain (Powergain) is improved.

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

Fig. 1 is a flowchart of a method for manufacturing a transistor according to an embodiment of the present disclosure.

Fig. 2 is a flow chart of forming a base mesa and a base.

Fig. 3 to 9 are schematic structural diagrams in the process of manufacturing a transistor.

Icon: 100-transistors; 110-a substrate; a 111-base mesa; 112-collector contact electrode; 113-a base; 114-an epitaxial layer; 120-notch; 121-emitter mesa; 122-emitter contact electrode; 123-a silicon nitride layer; 124-base contact electrode; 130-a photoresist layer; 140-a first gap; 150-second notch.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all the embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

At present, in the HBT manufacturing process, no matter wet etching or dry etching is adopted, the edge of the top surface of the base mesa exceeds the edge of the base contact electrode, so the area of the base mesa is also large, and the area of Cbc is also large, resulting in a small Power Gain (Power Gain).

Note that the area referred to in this embodiment refers to the area corresponding to the cross section of the layer structure, i.e., the area of a section perpendicular to the paper surface in fig. 3 to 9. For example, the area of the base mesa refers to the area of the top surface of the base mesa.

Embodiments of the present application provide a transistor and a method for manufacturing the same, which can enable a base contact electrode to exceed an edge of a top surface of a base platform, and accordingly can correspondingly reduce an area of Cbc in subsequent processing, and improve power gain (PowerGain).

Referring to fig. 1, a method for manufacturing a transistor 100 provided in this embodiment includes the following steps:

s1: base mesa 111 and base contact electrode 124 are sequentially formed on substrate 111.

In this embodiment, base mesa 111 is defined to include collector contact electrode 112, pedestal 113 and epitaxial layer 114, which are sequentially disposed from bottom to top, so S1 specifically includes the following steps, please refer to fig. 2:

s11: referring to fig. 3, a substrate 110 is provided.

The material of the substrate 110 may be gallium arsenide (GaAs) or indium phosphide (InP). In this embodiment, the material of the substrate 110 is gallium arsenide (GaAs). The substrate 110 may be annealed and surface cleaned.

S12: a collector contact electrode 112 is formed on the substrate 110.

The material of the collector contact electrode 112 may be gallium arsenide (GaAs) or indium gallium arsenide (InGaAs). Preferably, the material of the collector contact electrode 112 is different from that of the substrate 110.

S13: a pedestal 113 is formed on the collector contact electrode 112.

The material of the pedestal 113 may be gallium arsenide (GaAs) or indium gallium arsenide (InGaAs). The pedestal 113 is p-doped, where the p-doping may be carbon doping.

S14: an epitaxial layer 114 is formed on the pedestal 113.

The material of the epitaxial layer 114 may be the same as the material of the pedestal 113, and the doping type of the epitaxial layer 114 may also be the same as the doping type of the pedestal 113.

S15: referring to fig. 4, a base contact 124, an emitter mesa 121, and an emitter contact 122 are formed on epitaxial layer 114.

Wherein the emitter mesa 121 serves to support the emitter contact electrode 122 to be formed. The number of base contact electrodes 124 is two, and the two base contact electrodes 124 are distributed on both sides of the emitter mesa 121.

The material of the emitter contact electrode 122 is selected from aluminum gallium arsenide (AIGaAs), indium gallium phosphide (GaInP), indium phosphide (InP), or aluminum indium phosphide (InAlP).

S16: a silicon nitride layer 123 is deposited over base mesa 111, emitter mesa 121 and emitter contact electrode 122.

Wherein silicon nitride layer 123 is deposited on the top surface of the resulting structure of the device, such that silicon nitride layer 123 overlies base mesa 111, emitter mesa 121 and emitter contact 122.

S17: a photoresist layer 130 is coated on the silicon nitride layer 123.

Photoresist layer 130 is applied for exposure and development to pattern base platform 111.

S18: referring to fig. 5, the silicon nitride layer 123 is etched away around the photoresist layer 130.

Here, the etching is dry etching, light is exposed from the direction of the arrow in fig. 5, and the portion of the silicon nitride layer 123 not covered by the photoresist layer 130 is etched away to expose the portion of the epitaxial layer 114. The periphery of the photoresist layer 130 is the area not covered by the photoresist layer 130.

S2: referring to fig. 6, portions of the material on the two side edges of the base mesa 111 are etched away to form a first gap 140.

The etching here is dry etching, light is exposed from the direction of the arrow in fig. 6, the portion of the epitaxial layer 114 and the base 113 not covered by the photoresist layer 130 is etched away to form a first gap 140, and the edge of the first gap 140 is connected to the edge of the base contact electrode 124.

The side surface of the first notch 140 is a slope inclined with respect to a vertical surface, and the bottom surface of the first notch 140 becomes narrower as the depth of the first notch 140 becomes deeper. Here, the depth direction of the first notch 140 is the vertical direction in fig. 6, and the lateral direction of the first notch 140 is the horizontal direction in fig. 6.

The depth of the first notch 140, i.e. the depth of the etching, may be in the range of: 2000A-8000A, according to different design requirements of the device, the etching depth can be flexibly adjusted.

In this embodiment, the first notch 140 is formed by etching away a portion of the material from the epitaxial layer 114 and the base 113. In other embodiments, the first notch 140 may also be formed by etching away only a portion of the material from the epitaxial layer 114, or may also be formed by etching away only a portion of the material from the epitaxial layer 114, the base 113, and the substrate 110.

S3: referring to fig. 7, the side surfaces of first opening 140 are etched to form second opening 150, such that base contact electrode 124 extends beyond the edge of the top surface of base mesa 111.

Wherein, the second notch 150 is formed by wet etching. In the solution adopted by the wet etching, the proportion range of the phosphoric acid and the hydrogen peroxide is as follows: 3: 1-30: 1. the wet etching direction is the depth direction and the lateral direction of the first notch 140, and the range of the ratio of the forward (depth direction) etching rate to the lateral etching rate is as follows: 1: 1-5: 1. thus, the second notch 150 can be formed at the side of the first notch 140, which further reduces the area of the epitaxial layer 114, the area of the pedestal 113, and the width of the collector contact electrode 112. The Power Gain (Power Gain) can be improved by correspondingly reducing the area of Cbc in subsequent processing.

Referring to fig. 8, experimental tests show that the lateral etching amount of the second notch 150 can reach a distance between the edge of the second notch 150 and the edge of the base contact electrode 124 of 0.8 μm, and the distance between the edge of the second notch 150 and the edge of the base contact electrode 124 can also reach a distance of 0.2 μm by using a general conventional wet etching, so that the distance between the edge of the second notch 150 and the edge of the base contact electrode 124 is defined as D2, and the value range of D2 is: 0.2-0.8 μm. Defining the distance between the edge of the base mesa 111 and the edge of the base contact electrode 124 as D1, D1 equals D2, and D1 also has the following value: 0.2-0.8 μm.

In this embodiment, the first notch 140 and the second notch 150 may be collectively referred to as the notch 120, and it is within the scope of the present application as long as the notches 120 are disposed on both side edges of the top surface of the base mesa 111 so that the base contact electrode 124 extends beyond the edge of the top surface of the base mesa 111.

It is noted that, as long as the base contact electrode 124 can be made to exceed the edge of the top surface of the base mesa 111, the area of Cbc can be correspondingly reduced in the subsequent processing, and the Power Gain (Power Gain) can be improved. Therefore, the lateral depth of the second notch 150 is larger than zero, provided that the edge of the first notch 140 is connected to the edge of the base contact electrode 124. It can be appreciated that whatever the lateral depth of the second notch 150 is, the concept of the present application should fall within the scope of the claimed invention.

In this embodiment, wet etching is used to simultaneously etch from the forward direction and the lateral direction of first notch 140, so as to obtain the effect of reducing the area of base mesa 111. In other embodiments, wet etching may be used to etch only from the lateral direction of first notch 140, so as to directly reduce the area of base mesa 111.

S4: referring to fig. 9, the photoresist layer 130 is removed.

After the second opening 150 is formed, the remaining photoresist layer 130 is removed, and the base mesa 111 is processed to form the transistor 100.

The present embodiment further provides a transistor 100 manufactured by the above manufacturing method, wherein the transistor 100 includes a substrate 110, and a base platform 111 and a base contact electrode 124 sequentially formed on the substrate 110; notches 120 are formed in two side edges of the top surface of base mesa 111, notches 120 include a first notch 140 and a second notch 150, the edge of first notch 140 is connected to the edge of base contact electrode 124, and second notch 150 is formed in the side surface of first notch 140, so that base contact electrode 124 extends beyond the edge of the top surface of base mesa 111. Base mesa 111 includes a collector contact electrode 112, a pedestal 113, and an epitaxial layer 114, which are sequentially disposed from bottom to top.

The features of each layer structure formed in the above manufacturing method are included in each layer structure of the transistor 100, and are not described again here.

The transistor 100 and the method for manufacturing the same provided in this embodiment can be suitable for being processed into a heterojunction bipolar transistor HBT, which includes a heterojunction indium gallium phosphide transistor device (InGaP HBT), a heterojunction indium phosphide transistor device (InP HBT), and a heterojunction aluminum gallium arsenide transistor device (AlGaAs HBT).

The transistor 100 and the preparation method thereof provided by the embodiment have the following beneficial effects:

first, a first notch 140 is formed at a position on the base mesa 111 at the periphery of the base contact electrode 124, and then, a second notch 150 is formed by etching the side surface of the first notch 140, so that the width of the base mesa 111 is reduced, the area of Cbc can be correspondingly reduced in subsequent processing, and the Power Gain (Power Gain) is improved.

The technical core mainly expressed in the embodiment is as follows: after one dry etch of base mesa 111, one more wet etch is performed, and the direction of the wet etch includes the lateral direction, such that base contact electrode 124 extends beyond the edge of the top surface of base mesa 111. The method and the product which only use the technical core are all within the protection scope of the claims of the application.

Only an example of applying the manufacturing method of the transistor 100 to the manufacturing method of the HBT is described in detail in this application, and the manufacturing method of the transistor 100 provided in this application may also be applied to the manufacturing of transistors with other structural forms, which is not described herein again, and it is within the scope of the present application to claim as long as the concept of reducing the area of the base platform 111 by wet etching on the basis of the first notch 140 in this application is applied.

The transistor 100 formed by the manufacturing method provided in the present application should also fall within the scope of the present application, and the transistor formed by the manufacturing method can also be applied to a power amplifier or other electrical appliances.

It should be noted that the numerical values mentioned in the present application, including the length value, the ratio range, the etching rate ratio, etc., are only reliable numerical values obtained by the applicant through experiments and calculation, and are not limited to only these values. Those skilled in the art may make further experiments based on the scheme of the present application to obtain other values with similar effects, which do not depart from the core of the present application and should also fall within the scope of the protection claimed in the present application.

The materials used for the layer structures and the precursors in the present application are only the more reliable materials obtained by the applicant through experiments, and are not strictly limited to only use these materials. Those skilled in the art may make further experiments based on the solution of the present application to obtain other materials with similar effects, which do not depart from the core of the present application and should fall within the protection scope of the present application.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.