JPH09134926A - Bipolar semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable this device to be used optionally as a resistor for negative feedback interposed between a base and a collector, not to mention that this can be used as a ballast resistor, by building in a resistor, making use of the process of forming an emitter electrode. SOLUTION: On a semiconductor device 21 are an epitaxial growth semiconductor layer 22, a resistor made by emitter electrode formation process, an interlayer insulating film 24, and a metallic wiring 25 made severally. Here, the resistor 23 has just the same constitution as that of the emitter electrode not shown in the Figure, and it is one where a part of the electrode material film for formation of the emitter electrode is diverted, and is made at the same time at formation of the emitter electrode. Accordingly, the emitter electrode has to be stacked in such thickness that the sheet resistance required by the resistor 23 can be obtained. Hereby, the resistor can be built easily in the bipolar semiconductor device, and the resistor can be used optionally as a resistor or the like in a base input part, not to mention that it can be used as a ballast resistor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bipolar semiconductor device in which current concentration due to thermal runaway does not occur.

For example, a heterojunction bipolar transistor (heterojunction bipolar)
Transistor (HBT) is an amplifier for mobile phones, which has excellent high-frequency characteristics and high-speed switching characteristics, has a large power gain in the microwave band and high efficiency as compared with conventional semiconductor elements. However, there are still problems to be solved such as prevention of destruction due to current concentration, and the present invention can meet this.

[0003]

2. Description of the Related Art In a portable electronic device such as a mobile phone, a power source is a battery. Therefore, the amplifier is required to be capable of obtaining a large output at a low bias voltage.

Generally, in order to obtain a large output with a low bias voltage, it is essential to pass a large current.

Since the HBT is, of course, a bipolar transistor, when a large current is applied, current concentration due to thermal runaway easily occurs, which may lead to destruction.

In order to suppress this current concentration, it is effective to insert a series resistor between the emitter and ground.
This series resistance is called a ballast resistance and is an essential element for a small area and high output bipolar transistor.

Normally, the value of the ballast resistance required for an HBT made of a compound semiconductor such as GaAs is about 4 [Ω] to 5 when the emitter area is 60 [square μm].
It is about [Ω].

This ballast resistor is formed in the substrate as an epitaxial growth layer and is located above the emitter layer (if necessary, "Emitter ballastin" is used).
gresistor design for, and
current handling capabili
ty of AlGaAs / GaAs powerhe
terrojunction bipolar tran
sisters "IEEE Trans. on El
electron Devices vol. 38 No.
2 Feb. 1991 pp. 185-196) or separately formed of a metal layer.

[0009]

Among the above-mentioned conventional techniques, when the epitaxial growth layer is used as the resistance layer, the resistance layer always exists immediately above the emitter, and the emitter and the resistance layer can be separated. Even if it is necessary to ground the emitter, such a configuration cannot be taken.

Also, since one side of the resistance layer is always an emitter, it cannot be used as a negative feedback resistance inserted between the base and collector, or a resistance in the base input section. In short, when trying to obtain a high-output transistor amplifier circuit, it is not possible to obtain a multi-stage amplifier circuit by using the resistance layer according to the conventional technique.

Among the above-mentioned conventional techniques, when forming a resistor with a metal layer, the steps of depositing a metal layer and forming a pattern are required, so that an increase in the number of steps is inevitable.

According to the present invention, a resistor is built in a semiconductor device,
The resistor can be used not only as a ballast resistor but also as a resistor for negative feedback inserted between the base and collector or a resistor in the base input section. Moreover, the number of steps for forming the resistance is not increased.

[0013]

According to the present invention, it is fundamental to form a resistor by utilizing the step of forming an emitter electrode in a bipolar semiconductor device.

FIG. 1 is a side sectional view showing a main part of a bipolar semiconductor device for explaining the principle of the present invention.

In the figure, 21 is a semiconductor substrate, 22 is an epitaxially grown semiconductor layer, 23 is a resistor formed by an emitter electrode forming process, 24 is an interlayer insulating film, 25
Indicate metal wirings, respectively.

Here, the resistor 23 has exactly the same structure as the emitter electrode (not shown), and a part of the electrode material film for forming the emitter electrode is diverted. Is created at the same time as the creation of.

Therefore, the emitter electrode must be deposited in such a thickness that the sheet resistance required by the resistor 23 can be obtained. Further, the resistor 23 may be etched into a desired shape.

Not only the resistor 23, but also the surroundings and the underlying structure are all produced at the same time in the process of producing the bipolar semiconductor device and especially the emitter, and therefore the resistor 23 and its vicinity. Is almost the same as the other parts of the bipolar semiconductor device.

In particular, the resistor 23 is the metal itself used as the emitter electrode. Strictly speaking, the same metal material film as the emitter electrode and the multi-layered semiconductor layer below it are used as the resistor.

However, in reality, the sheet resistance of the metal material film is about 1/50 of that of the underlying multilayer semiconductor layer.
Since it is below, most of the electric current will flow through the metal material film, so the sheet resistance of the metal material film and the resistor 2
The plane shape of 3 determines the resistance value.

From the above, in the bipolar semiconductor device according to the present invention, required semiconductor layers (for example, sub-collector layer 1, collector layer 2, base layer 3, emitter layer 4, first cap layer 5). Second cap layer 6: FIG.
A vertical bipolar transistor having a mesa shape in which a device electrode (for example, an emitter electrode 7) is formed on a surface of a semiconductor layer (for example, a second cap layer 6) which is an uppermost layer, A mesa-shaped base for forming each of the semiconductor layers stacked to form the vertical bipolar transistor, and an electrode material film formed on the base to serve as an element electrode on the surface of the uppermost semiconductor layer. And a resistor (for example, resistor 7A) in which a part of the above is patterned.

By adopting the above means, the resistor can be easily formed in the bipolar semiconductor device, and
The resistor can be used as a ballast resistor, and of course it is formed separately from the emitter, so a resistor for negative feedback inserted between the base and collector or a resistor in the base input section. It is also possible to use any of the above, and to make the resistor, the manufacturing process of the emitter incorporated in the manufacturing process of the bipolar semiconductor device is mainly used. There is no increase in numbers.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a side sectional view showing a main part of a semiconductor device including an HBT for explaining an embodiment of the present invention.

In the figure, 1 is a sub collector layer, 1A
Is a high resistance layer, 2 is a collector layer, 3 is a base layer, 4 is an emitter layer, 5 is a first cap layer, 6 is a second cap layer, 7
Is an emitter electrode, 7A is a resistor, 8 is a sidewall, 9 is a base electrode, 10 is a collector electrode, 11 is an interlayer insulating film, 11A to 11F are electrode contact holes,
Reference numeral 12 is a wiring, and 20 is a substrate.

Here, the main data regarding each part in the bipolar semiconductor device shown in the figure is exemplified as follows.

(1) Sub-collector layer 1 Material: n ⁺ -GaAs Impurity: Si Impurity concentration: 3 × 10 ¹⁸ [cm ^-3 ] Thickness: 500 [nm]

(2) Regarding the high resistance layer 1A Material: Proton (H ⁺ ) injection into the sub-collector layer 1

(3) Collector layer 2 Material: n-GaAs Impurity: Si Impurity concentration: 3 × 10 ¹⁶ [cm ⁻³ ] Thickness: 600 [nm] Sheet resistance: 20 [Ω] / □

(4) Regarding the base layer 3 Material: p ⁺ -GaAs Impurity: C Impurity concentration: 4 × 10 ¹⁹ [cm ^-3 ] Thickness: 70 [nm] Sheet resistance: 300 [Ω] / □

(5) Regarding Emitter Layer 4 Material: n-AlGaAs Impurity: Si Impurity concentration: 3 × 10 ¹⁷ [cm ⁻³ ] Thickness: 180 [nm] Sheet resistance: 30 [Ω] / □

(6) Regarding the first cap layer 5 Material: n ⁺ -GaAs Impurity: Si Impurity concentration: 3 × 10 ¹⁸ [cm ^-3 ] Thickness: 150 [nm]

(7) Second Cap Layer 6 Material: n ⁺ -InGaAs Impurity: Si Impurity concentration: 3 × 10 ¹⁹ [cm ⁻³ ] Thickness: 110 [nm]

(8) Regarding the emitter electrode 7 Material: WSi _x Thickness: 400 [nm] Sheet resistance: 0.5 [Ω] / □ Contact: Schottky

(9) Resistor 7A Material: WSi _x Thickness: 400 [nm]

(10) Side Wall 8 Material: SiON Thickness: 100 [nm]

(11) Regarding the base electrode 9 Material: Ti / Pt / Au Thickness: 10 [nm] / 50 [nm] / 100 [nm]

(12) Collector electrode 10 Material: AuGe / Au Thickness: 20 [nm] / 300 [nm]

(13) Interlayer insulating film 11 Material: SiO ₂ Thickness: 1100 [nm]

(14) Wiring 12 Material: Au Thickness: 4 [μm]

(15) Substrate 20 Material: Semi-insulating GaAs

The process of manufacturing the bipolar semiconductor device shown in FIG. 2 will be described below.

(1) Metalorganic chemical vapor deposition (metal)
organic chemical vapor d
The sub-collector layer 1, the collector layer 2, the base layer 3, the emitter layer 4, the first cap layer 5, and the second cap layer 6 are grown on the substrate 20 by applying the deposition (MOCVD) method.

(2) A WSi _x film is formed on the second cap layer 6 by applying the sputtering method.

[0044] (3) in the resist process in lithography, and etching gas or etchant CF ₄ + O ₂ mixed gas (for WSi _x) H ₂ O ₂ + phosphoric acid + H ₂ O mixture (for InGaAs ) A SiCl ₄ + CF ₄ mixed gas (for GaAs) H ₂ O ₂ + phosphoric acid + H ₂ O mixed solution (for AlGaAs) is used to apply the dry etching method or the wet etching method, and the above step (2) is performed. The so-called emitter / mesa is formed by etching the WSi _x film, the second cap layer 6, the first cap layer 5, and the emitter layer 4 formed in the above step.

[0045] Depending on this, the resistor 7A made of WSi emitter electrode 7 made of _x, WSi _x is formed.

(4) Chemical vapor deposition (chemical)
A SiON film is formed on the entire surface by applying a vapor deposition (CVD) method.

(5) By applying a dry etching method using CHF ₃ as an etching gas, anisotropic etching of the SiON film formed in the above step (4) is performed to cover only the side surface of the mesa. The wall 8 is formed.

(6) By applying a resist process in the lithography technique and an ion implantation method, proton implantation for element isolation is performed to selectively increase the resistance of the sub-collector layer 1. The high resistance layer 1A is generated.

(7) The base electrode 9 is formed on the base layer 3 by applying a resist process, a vacuum deposition method, and a lift-off method in the lithography technique.
The base electrode 9 is an emitter including the emitter layer 4.
Since it corresponds to the mesa, it is unnecessary around the emitter mesa associated with the resistor 7A.

(8) The resist process in the lithography technique and the etching gas are SiCl ₄ +
By applying a dry etching method using CF ₄ mixed gas (for GaAs), etching is performed to reach the sub collector layer 1 from the surface of the base layer 3 to form a so-called base mesa. The base layer 3 and the collector layer 2 are not necessary around the emitter / mesa associated with the resistor 7A and may be removed.

(9) The collector electrode 10 is formed on the sub-collector layer 1 by applying a resist process in the lithography technique, a vacuum deposition method, and a lift-off method.

(10) By applying the CVD method,
An interlayer insulating film 11 is formed on the entire surface.

(11) By applying a resist process in the lithography technique and a dry etching method using CHF ₃ gas as an etching gas, the interlayer insulating film 11 is etched and electrode contact
The holes 11A to 11F are formed.

(12) After forming a thin Au film by applying a vapor deposition method, a thick Au film is formed by applying a plating method using the patterned resist film as a mask, and a lift-off method is applied. Patterning the thick Au film, then
Ion milling of the thin Au film is performed to form the wiring 12.

As described above, the bipolar semiconductor device incorporating the HBT and the resistor is completed. The wiring 12
By selecting the pattern for forming the
The circuit can be arbitrarily configured not only with ballast resistors such as 7 and 7B but also as resistors for negative feedback, resistors in the base input section, and the like.

[0056]

In the bipolar semiconductor device according to the present invention, a vertical bipolar transistor having a mesa shape in which semiconductor layers are laminated and an element electrode is formed on the surface of the uppermost semiconductor layer, and a vertical bipolar transistor Patterning a mesa-shaped base of each semiconductor layer laminated to form a transistor and a part of an electrode material film formed for the element electrode on the surface of the uppermost semiconductor layer provided on the base Equipped with a resistor.

By adopting the above structure, the resistor can be easily formed in the bipolar semiconductor device, and
The resistor can be used as a ballast resistor, and of course it is formed separately from the emitter, so a resistor for negative feedback inserted between the base and collector or a resistor in the base input section. It is also possible to use any of the above, and to make the resistor, the manufacturing process of the emitter incorporated in the manufacturing process of the bipolar semiconductor device is mainly used. There is no increase in numbers.

[Brief description of the drawings]

FIG. 1 is a fragmentary side view showing a bipolar semiconductor device for explaining the principle of the present invention.

FIG. 2 is an HB for explaining an embodiment of the present invention.
It is a principal part cutting side view showing the semiconductor device containing T.

[Explanation of symbols]

 1 Sub-collector layer 1A High resistance layer 2 Collector layer 3 Base layer 4 Emitter layer 5 First cap layer 6 Second cap layer 7 Emitter electrode 7A Resistor 8 Side wall 9 Base electrode 10 Collector electrode 11 Interlayer insulating film 11A to 11A 11F Electrode Contact Hole 12 Wiring 20 Substrate 21 Semiconductor Substrate 22 Epitaxial Growth Semiconductor Layer 23 Resistor Created by Emitter Electrode Creating Process 24 Interlayer Insulating Film 25 Metal Wiring

Claims (1)

[Claims] 1. A vertical bipolar transistor having a mesa shape in which required semiconductor layers are stacked and a device electrode is formed on the surface of the uppermost semiconductor layer, and the vertical bipolar transistor is formed. A mesa-shaped base for laminating the respective semiconductor layers for this purpose, and a resistor formed by patterning a part of an electrode material film formed on the base to serve as an element electrode on the surface of the uppermost semiconductor layer. A bipolar semiconductor device comprising: