JP2000294566A - Semiconductor device, method of manufacturing the same, and method of manufacturing a substrate - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce fluctuations in current amplification factor. A semiconductor device includes a heterojunction bipolar transistor having at least a collector layer, a base layer, and an emitter layer sequentially stacked on one surface side of a semiconductor substrate, wherein the base layer has a hydrogen concentration of 10 ¹⁸ cm.
And a ~ ³ above, wherein the base layer is large light irradiation treatment of the energy is being performed than the bandgap of the semiconductor constituting the base layer. A monolithic microwave integrated circuit including the heterojunction bipolar transistor is configured. The monolithic microwave integrated circuit is a high frequency power amplifier. Due to the circuit configuration, the base-emitter voltage of at least one heterojunction bipolar transistor is 1.3 V or less, and the time variation of the base current when the base-emitter voltage is applied is 1 to the base current at the start of measurement. Within 1% in time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device, a method for manufacturing the same, and a method for manufacturing a substrate. More particularly, the present invention relates to a heterojunction bipolar transistor as an element for an ultra-high-speed IC and a monolithic bipolar transistor incorporating the transistor.
The present invention relates to a technology effective when applied to a microwave integrated circuit (MMIC).

[0002]

2. Description of the Related Art A heterojunction bipolar transistor (HBT) is known as a semiconductor device having excellent high-speed performance and low power consumption performance. Such an HBT is used by being incorporated in a high-frequency power amplifier (RF power amplifier module) of a mobile communication terminal such as a mobile phone.

[0003] In the HBT, a sub-collector layer and a collector layer are sequentially laminated on one surface (main surface) of a semiconductor substrate, a base layer is partially formed on the collector layer, and a partial layer is formed on the base layer. The structure has an emitter layer formed of a semiconductor having a wide band gap.

In addition, in order to suppress a decrease in gain due to recombination of minority carriers between the emitter and the base, an IGaP layer is used as an emitter layer to reduce the current deterioration and to provide a highly reliable I
nGaP / GaAs HBTs are known. In addition, carbon (C), which hardly moves even at a large current operation, is used as a dopant for the base layer which becomes p-type in these HBTs.

[0005] "Hitachi Hyoron", published by Hitachi Hyoron-sha, No. 11, 1998
Nos. P47 to P52 describe GaAs-MMIC.

Japanese Unexamined Patent Publication No. Hei 6-333939 discloses that a collector current having a current density of 1 × 10 ⁴ A / cm ² or more is used in the manufacture of an HBT in order to improve the current amplification factor of a heterojunction bipolar transistor. There is disclosed a technique for reducing the surface recombination current in the peripheral portion of the emitter mesa edge by applying a current.

On the other hand, J. Appl. Phys., Vol. 47, No. 8, August
1976. pp3587-pp3591 discloses an annihilation reaction of a recombination center due to carrier recombination in a GaAs crystal.

[0008]

In the course of developing a heterojunction bipolar transistor for an RF power amplifier module, a phenomenon in which the current amplification factor of the HBT changes at the beginning of energization was found.

As one of commercially available substrates for forming a heterojunction bipolar transistor, a subcollector layer (n-type GaAs layer), a collector layer (n-type GaAs layer), and a base layer (n-type GaAs layer) are provided on one side of an insulating GaAs substrate. p-type GaAs
Layer), wide band gap emitter layer (n-type InG
A substrate in which an aP layer) and a cap layer (an n-type GaAs layer and an n-type InGaAs layer formed on this layer) are formed by metal organic chemical vapor deposition (MOCVD) is known.

[0010] Figure 20, the collector current I _C and base current I _B and the base of the HBT fabricated using a commercially available substrate which is formed by the MOCVD method - is a graph showing the correlation between the emitter voltage V _BE. Emitter size _SE is 2.5
μm × 20 μm, the collector-base voltage V _CB was 0 V, and the measurement was performed at room temperature. The first measurement result is a curve indicated by a dotted line, and the second measurement result is a curve indicated by a solid line.

[0011] Although the collector current I _C will hardly changes even if the first time and the second time, the base current I _B is the base - emitter voltage V _BE is 1.3V or less current in the measurement of the second time measurement variation Excessive size fluctuations occur and become smaller. However, the results of the third and subsequent measurements were almost the same as the results of the second measurement, and it was found that the current would no longer fluctuate.

The present inventor manufactured a substrate having the above-mentioned layer structure by a molecular beam epitaxy (MBE) method,
A BT was manufactured, and the HBT was inspected. In this case, it was found that a phenomenon in which the current amplification factor changed in the initial stage of energization hardly occurred.

A commercially available MOCVD substrate and an MBE
As a result of analyzing and inspecting the difference between the substrates by the method, it was found that the fluctuation of the base-emitter voltage V _BE , that is, the fluctuation of the current amplification factor was caused by the residual hydrogen concentration in the base layer.

[0014] Commercially available substrates are generally manufactured by the MOCVD method because they are excellent in mass productivity and can achieve cost reduction. When considering GaAs containing 4 × 10 ¹⁹ cm to ³ of carbon (C), which is usually used as a base layer, the hydrogen concentration is 10 ¹⁸ to 10 ¹⁹ cm to ³ , although there are some differences depending on the crystal growth conditions. About.

On the other hand, the hydrogen concentration of the base layer of the substrate manufactured by the MBE method is about 10 ¹⁷ cm- ³ .

[0016] As can be seen from the graph of FIG. 20, the base - variation will not occur between the first time measurement and the second measurement of the emitter voltage V _BE exceeds 1.3V base current I _B . Therefore, the base-emitter voltage V
It can be seen that the current amplification factor can be stabilized when _BE is used from the beginning at a voltage exceeding 1.3 V, or by applying a voltage exceeding 1.3 V between the base and the emitter before use.

In the conventional method for stabilizing the current amplification factor, a collector current having a current density of 1 × 10 ⁴ A / cm ² or more is supplied in the manufacture of the HBT.

However, it takes time to supply a collector current of a certain current density or more to all the transistors including the bias circuit, which leads to an increase in product cost.

Also, depending on the circuit type, some transistors cannot supply a collector current of a certain current density or higher as described above.

Therefore, the inventor of the present invention makes use of the technology of annihilation reaction of recombination centers by carrier recombination disclosed in the above-mentioned document, thereby making it possible to perform the stage of the substrate before manufacturing the HBT or the initial stage of manufacturing the HBT. The present invention has been made with the intention of eliminating the recombination centers caused by residual hydrogen in the semiconductor layer serving as the base layer at the stage of (1).

It is an object of the present invention to provide a heterojunction bipolar transistor in which the current amplification factor hardly fluctuates, a semiconductor device incorporating the heterojunction bipolar transistor, and a method of manufacturing the same.

Another object of the present invention is to provide a monolithic microwave integrated circuit incorporating a heterojunction bipolar transistor.

It is another object of the present invention to provide a monolithic high frequency power amplifier incorporating a heterojunction bipolar transistor.

Another object of the present invention is to provide a suitable substrate for a heterojunction bipolar transistor.

The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

[0026]

The following is a brief description of an outline of typical inventions disclosed in the present application.

(1) A semiconductor device comprising a heterojunction bipolar transistor having at least a collector layer, a base layer, and an emitter layer provided sequentially on one surface side of a semiconductor substrate, wherein the base layer has a hydrogen concentration of 10 ¹⁸
cm to ³ or more, and the base layer has been subjected to light irradiation treatment with energy having a larger energy than the forbidden band width of the semiconductor constituting the base layer. The base layer contains carbon as a conductivity type determining impurity. A monolithic microwave integrated circuit including the heterojunction bipolar transistor is configured. The monolithic microwave integrated circuit is a high frequency power amplifier. A semiconductor device comprising a plurality of heterojunction bipolar transistors,
The hydrogen concentration of the base layer of at least one of the heterojunction bipolar transistors is 10 ¹⁸ cm ³ or more, the base-emitter voltage is 1.3 V or less, and the base current The time variation is within 1% for one hour with respect to the base current at the start of the measurement.

Such a semiconductor device is manufactured by the following method. Forming at least one collector layer, a base layer, and a semiconductor layer serving as an emitter layer sequentially on one surface side of the semiconductor substrate; and transmitting light having energy larger than the forbidden band width of the semiconductor constituting the base layer to the semiconductor substrate. A step of irradiating from one surface side and a step of processing each of the semiconductor layers to form an emitter layer, a base layer, and a collector layer include forming a heterojunction bipolar transistor at least partially. A plurality of the heterojunction bipolar transistors are formed, and some of the heterojunction bipolar transistors are low-voltage transistors having a base-emitter voltage applied to the circuit of about 1.25 V or less. The base layer contains carbon and hydrogen, and the hydrogen concentration is 10 ¹⁸ cm- ³ or more. The wavelength of the light used for the light irradiation is 365 nm. A monolithic microwave integrated circuit (high-frequency power amplifier) including the heterojunction bipolar transistor is formed.

A substrate used in manufacturing such a semiconductor device is manufactured by the following method. At least one collector layer, a base layer, and a semiconductor layer serving as an emitter layer are sequentially formed on one surface side of a semiconductor substrate by metal organic chemical vapor deposition, and the base layer is formed by adding carbon as a conductivity type determining impurity. A method of manufacturing a substrate for manufacturing a junction bipolar transistor, comprising a step of irradiating light having energy larger than a forbidden band width of a semiconductor forming the base layer from one surface side of the semiconductor substrate. The hydrogen concentration of the base layer is 10 ¹⁸ cm- ³ or more.

(2) In the configuration of the means (1), at least a collector layer, a base layer,
Forming a semiconductor layer to be an emitter layer in order, forming the emitter layer by processing the semiconductor layer, and emitting light having energy larger than the forbidden band width of the semiconductor forming the base layer to the semiconductor layer. Irradiating from one surface side of the substrate with the electrons generated by the light to be introduced into the base layer directly below the emitter layer; and processing the semiconductor layers to form a base layer and a collector layer.

According to the means (1), (a) the hydrogen concentration of the base layer is 10 ¹⁸ cm ³ or more, but the base layer has a larger energy than the forbidden band width of the semiconductor constituting the base layer. Due to the light irradiation treatment, electron-hole pairs are generated by photons in the base layer, and the energy released by the recombination of these electron-hole pairs causes recombination due to residual hydrogen. The center can be extinguished. As a result, it is possible to suppress the occurrence of a change in the base current, that is, the current amplification factor.

(B) In a high-frequency power amplifier, a monolithic microwave integrated circuit, or the like having a plurality of heterojunction bipolar transistors, the base of at least one heterojunction bipolar transistor is required in terms of circuit configuration.
Even when the emitter-to-emitter voltage is 1.3 V or less, the hydrogen concentration in the base layer of the heterojunction bipolar transistor is 1
0 ¹⁸ cm to ³ or more, the recombination center caused by the residual hydrogen can be eliminated by the light irradiation treatment. As a result, the time variation of the base current when the base-emitter voltage is applied is measured. The base current at the start can be controlled within 1% in one hour, and a stable operation of the heterojunction bipolar transistor can be achieved. As a result, the reliability of the high-frequency power amplifier, the monolithic microwave integrated circuit, and the like can be improved.

(C) Even if the substrate is manufactured by the MOCVD method, the residual hydrogen in the semiconductor layer serving as the base layer does not become a recombination center by light irradiation, and the substrate is suitable for manufacturing a heterojunction bipolar transistor. Becomes

According to the means (2), in manufacturing a heterojunction bipolar transistor, a semiconductor layer serving as a collector layer, a base layer, and an emitter layer is sequentially formed on one surface side of a semiconductor substrate, and then the semiconductor layer is formed. To form an emitter layer, and then irradiate light having energy larger than the band gap of the semiconductor constituting the base layer from one surface side of the semiconductor substrate to the base layer immediately below the emitter layer. The recombination center caused by the residual hydrogen in the semiconductor layer serving as the base layer can be eliminated because electrons generated due to the current are circulated, and the current amplification factor is increased in the same manner as in the means (1). Can be provided.

[0035]

Embodiments of the present invention will be described below in detail with reference to the drawings. In all the drawings for describing the embodiments of the present invention, components having the same functions are denoted by the same reference numerals, and their repeated description will be omitted.

(Embodiment 1) FIGS. 1 to 16 relate to a heterojunction bipolar transistor (HBT) according to an embodiment (Embodiment 1) of the present invention.

In the first embodiment, an example in which the present invention is applied to the manufacture of a monolithic microwave integrated circuit as a semiconductor device, specifically, a high-frequency power amplifier will be described.

FIG. 14 is a block diagram showing the configuration of a high-frequency power amplifier incorporating the HBT manufactured by the manufacturing method of the first embodiment, FIG. 15 is an equivalent circuit diagram, and FIG. 16 is a monolithic component of the high-frequency power amplifier. FIG. 2 is a schematic plan view showing a microwave integrated circuit chip (semiconductor chip).
FIG. 13 is a schematic sectional view of a part of a semiconductor chip showing a part of a high-frequency power amplifier circuit.

As shown in FIG. 14, the high-frequency power amplifier 40 has an input terminal Pin and an output terminal as external electrode terminals.
Pout, a control terminal Vapc, a bias terminal Vbias, a power supply voltage Vcc, and a ground terminal GND (see FIGS. 15 and 16).

The rectangular portions arranged around the semiconductor chip 39 in FIG.

The high-frequency power amplifier 40 includes a first-stage transistor (Q1) 41 and an output-stage transistor (Q2), each of which is constituted by a heterojunction bipolar transistor.
42, first stage transistor 41 and output stage transistor 4
2, an input matching circuit 44 for input matching of the first-stage transistor, an input bias circuit 45 for controlling the first-stage transistor 41, and an output bias circuit 46 for controlling the output-stage transistor 42. are doing.

The input terminal Pin is connected to the input matching circuit 44, the output terminal Pout is connected to the output transistor 42, and the control terminal Vapc and the bias terminal Vbias are connected to the input bias circuit 45 and the output bias circuit 46, respectively. .

As shown in FIG. 16, the high-frequency power amplifying device 40 constitutes a multistage amplifier in which heterojunction bipolar transistors are connected in two stages, and two bias circuits for each of the transistors are used. HBTs (Q3-Q6) are monolithically incorporated. As shown in FIG. 16, capacitors (C1 to C10), bypass capacitors (CB), and resistors (R1 to R8) are provided on the semiconductor chip 39 constituting the high-frequency power amplifier 40 for the purpose of matching or potential adjustment. ), Inductor (L
1, L2) are incorporated.

FIG. 13 is a schematic sectional view showing a part of a semiconductor chip in which a high-frequency power amplifier circuit is incorporated in the manufacture of the semiconductor device of the first embodiment. As shown in the figure, the semiconductor chip 39 is provided with HBT, C (capacitance), R (resistance), and L (inductor), and has a structure in which the wiring 15 is partially exposed at the edge of the semiconductor chip 39. The structure is such that an electrode pad 38 is provided.

Next, referring to FIG. 1 to FIG.
The high-frequency power amplifier 40 having a BT, a capacitance, a resistance, an inductor and the like will be described.

As shown in FIG. 1, first, a substrate 30 for a heterojunction bipolar transistor is prepared. This substrate 30 is manufactured by the MOCVD method, and may be a commercially available substrate.

The substrate 30 includes a semiconductor substrate (semi-insulating GaAs substrate) 1 made of semi-insulating GaAs having a thickness of about 600 μm, and one surface (main surface) of the semi-insulating GaAs substrate 1.
N-type GaAs sequentially formed on the side by MOCVD
Subcollector layer 2 (Si concentration 5 × 10 ¹⁸ cm ~ ³ : thickness 6)
00 nm), n-type GaAs collector layer 3 (Si concentration 1 ×
10 ¹⁶ cm ^-3 : thickness 700 nm, p-type GaAs base layer 4 (C concentration 4 × 10 ¹⁹ cm ^-3 : thickness 70 nm), n-type InGaP emitter layer 5 (InP molar ratio 0.5: Si concentration 3 × 10 ¹⁷ cm ~ ^3: thickness 30 nm), n-type GaAs cap layer 6 (Si concentration 5 × 10 ¹⁸ cm ~ ^3: thickness 70n
m), and an n-type InGaAs cap layer 7 (InAs molar ratio 0.5: Si concentration 4 × 10 ¹⁹ cm ~ ³ : thickness 50 nm). Each of these semiconductor layers becomes a subcollector layer 2, a collector layer 3, a base layer 4, an emitter layer 5, a cap layer 6, and a cap layer 7 in the HBT portion by processing described later.

Next, the entire surface of the substrate 30 is irradiated with the light 8 to perform a defect annihilation process by carrier recombination.

That is, in the case of GaAs containing 4 × 10 ¹⁹ cm to ^{3 of} carbon commonly used as a base layer, depending on the crystal growth method, the MOCVD method usually has a maximum of 1 × 10 ¹⁹ cm to ³ residual carbon. Contains hydrogen. For a typical base layer thickness of 70 nm, the sheet concentration of residual hydrogen is 7
× 10 ¹³ cm ~ ² . When a similar number of photons reach the base layer, electron-hole pairs are generated and they recombine via the carrier recombination centers, resulting in energy released during the recombination. Recombination centers due to residual hydrogen will disappear. As a result, it is possible to suppress the occurrence of a change in the base current, that is, the current amplification factor.

Therefore, in the first embodiment, light irradiation is performed with light having energy larger than the forbidden band width of the semiconductor constituting the base layer. An example is wavelength 3
A light 8 of 65 nm is irradiated with 1 cm ² at an intensity of 400 mJ / s / cm ^2.
Irradiation for 4 seconds.

In order to effectively perform light irradiation, p-type Ga
N-type InGaP emitter layer 5 on As base layer 4
The total thickness of the type GaAs cap layer 6 and the n-type InGaAs cap layer 7 is 150 nm.

FIG. 2 shows the correlation between the required minimum light irradiation time (second) and the thickness of the semiconductor layer on the base layer (cap layer thickness + emitter layer thickness). As can be seen from the graph, the required minimum light irradiation time sharply increases as the film thickness increases from about 150 nm before. Therefore, it is desirable that the semiconductor layer on the base layer 4 be irradiated with light at 150 nm or less.

In the first embodiment, the wavelength is 365 nm.
Irradiates with the light from the i-line stepper, which is usually used in the photolithography process, and can be used in a clean room environment. No new equipment is required, and there is no problem of generation of dust. Thus, there is an effect that a semiconductor device can be manufactured with a high yield without using it.

The substrate 30 having been subjected to the light irradiation can be provided as a substrate for a heterojunction bipolar transistor, and the above manufacturing method is also a method of manufacturing a substrate.

Next, as shown in FIG. 3, the emitter electrode 9 is selectively formed on the main surface of the substrate 30. FIGS. 1 and 3 to 5 show only a single HBT, so that only one emitter electrode 9 is provided. However, as shown in FIG. 13, the emitter electrode 9 is provided corresponding to the HBT forming portion.

The emitter electrode 9 is, for example, 2.5 μm
It is formed in a size of × 20 μm. This emitter electrode 9
Is a 300 nm thick tungsten silicide (WSi)
It is formed with.

Next, as shown in FIG. 3, n-type InGaAs is formed by using the emitter electrode 9 as an etching mask.
The cap layer 7 and the n-type GaAs cap layer 6 are etched with a mixed solution of phosphoric acid + hydrogen peroxide + water. Also,
Subsequently, the n-type InGaP emitter layer 5 is etched with a hydrochloric acid aqueous solution to expose the surface of the p-type GaAs base layer 4.

Next, as shown in FIG.
After selectively forming a 300 nm thick base electrode 10 formed of Pt / Ti / Mo / Ti / Pt / Au formed on the p-type GaAs base layer 4 by a lift-off method, a conventional photolithography technique is used. The p-type GaAs base layer 4 and the n-type GaAs collector layer 3 are etched by wet etching with a mixed solution of phosphoric acid + hydrogen peroxide + water and the n-type GaAs sub-collector layer 2
Expose the surface.

Next, as shown in FIG. 5, the lowermost layer is made of Au.
After a collector electrode 11 of AuGe / W / Ni / Au formed of Ge and having a thickness of 300 nm is selectively formed on the n-type GaAs subcollector layer 2 by a lift-off method, an alloy is formed at 350 ° C. for 30 minutes. I do. Thereafter, n is obtained by a conventional photolithography technique and wet etching using a mixed solution of phosphoric acid + hydrogen peroxide + water.
The type GaAs subcollector layer 2 is selectively wet-etched to expose the surface of the semi-insulating GaAs substrate 1.
This etching separates the HBT. That is, as will be described later, each part of the upper layer of the n-type GaAs subcollector layer 2 is covered with an insulating film made of a polyimide resin or the like, and is electrically insulated and separated from other elements (see FIG. 9).

Next, as shown in FIGS. 7 and 8, the main surface of the semi-insulating GaAs substrate 1 is covered with an insulating film 14 made of, for example, an insulating polyimide resin, and the insulating film 14 is cured. After the contact hole is formed, a conductive layer made of gold or the like is selectively formed on the contact hole portion or on the insulating film 14 to form the wiring 15.

FIG. 6 is a diagram showing a pattern of the wiring 15 in the HBT portion. A horizontally long rectangular portion shown in the center is the p-type GaAs base layer 4, and a portion crossing the right side of the p-type GaAs base layer 4 so as to overlap with the wiring 15 is
(Emitter wiring 15E), the outer frame of the double frame portion shown in the center of the intersection shows the contour of the emitter electrode 9, and the inner rectangular portion is the emitter contact 16E.

A portion overlapping the left side portion of the p-type GaAs base layer 4 is a wiring 15 (base wiring 15B).
The outer frame of the double frame portion shown at the center of the overlapping portion shows the outline of the base electrode 10, and the inner rectangular portion is the base contact 16B.

A portion indicated by a two-dot chain line surrounding the p-type GaAs base layer 4 in a U-shape from the right side is a collector electrode 11, which overlaps the right side portion of the collector electrode 11 and extends rightward. This is the wiring 15 (collector wiring 15C), and a rectangular collector contact 16C indicated by a two-dot chain line is provided at the center of the overlapping portion between the collector wiring 15C and the collector electrode 11.

FIG. 9 shows a cross section of a portion where a capacitor (C), a resistor (R), an inductor (L) and the like other than the HBT are formed. 9 to 13, since the HBT portion has the structure shown in FIG. 7, the reference numerals of the respective parts of the HBT are omitted.

In the portion where the capacitance (C), the resistance (R), the inductor (L) and the like are formed, a structure in which the n-type InGaAs cap layer 7 extends directly under the insulating film 14 unless otherwise required. It has become. The wiring 15
Are the capacitance (C), resistance (R), and inductor (L)
Are formed in a predetermined pattern. That is, these capacitance (C), resistance (R), inductor (L)
In the part, the wiring 15 is electrically connected to the capacitance, the resistance, and the inductor, respectively, so that the wiring 15 has a discontinuous structure.

Next, as shown in FIG. 10, in the resistance forming portion, a resistance layer 20 having a predetermined specific resistance is formed between the interrupted wirings 15 to form a resistance R. With such a structure, all the resistors shown in FIGS. 15 and 16 are formed. The resistance layer 20 is formed of, for example, tungsten silicide nitride (WSiN).

Next, as shown in FIG.
An interlayer insulating film 21 is selectively formed on the main surface side of the aAs substrate 1. The interlayer insulating film 21 forms a dielectric layer forming a capacitor in a portion where a capacitor is formed. The interlayer insulating film 21
Is formed, for example, a laminated film of a silicon / silicon nitride / silicon dioxide _{(SiO 2 / Si 3 N 4} / SiO 2). In the resistance forming portion, the resistance layer 20 is completely covered by the interlayer insulating film 21.

In the part where the inductor is formed, an interlayer insulating film 21 is provided so that the end portions of the interrupted wiring 15 are exposed to form a spiral inductor.

In the capacitance forming portion, one end of the interrupted wiring 15 is formed so as to be exposed.

Next, as shown in FIG.
A conductor layer 25 is selectively formed on the main surface side of the aAs substrate 1. This conductor layer 25 has one wiring 1 in the capacity forming portion.
The capacitor C is provided over the interlayer insulating film 21 extending from the exposed portion 5 to the end portion of the other wiring 15. With such a structure, all the capacitors shown in FIGS. 15 and 16 are formed. The conductor layer 25 is formed of, for example, a laminated film of molybdenum / gold / molybdenum (Mo / Au / Mo).

The spiral inductor L is formed in the inductor forming portion. One end on the center side of the spiral inductor is connected to one wiring 15, and the outer peripheral end is connected to the other wiring 15. With such a structure, FIG.
And all the inductors shown in FIG. 16 are formed.

Next, a passivation film 26 made of an insulating film is formed over the entire area of the main surface of the semi-insulating GaAs substrate 1, and a portion of the passivation film 26 where an electrode pad is to be formed and an interlayer insulating film thereunder. Membrane 21
Is etched away in a rectangular shape to form an electrode pad 38 exposing the surface of the wiring 15.

Next, the rear surface of the semi-insulating GaAs substrate 1 is etched away by a predetermined thickness, and the thickness of the semi-insulating GaAs substrate 1 is changed from 600 μm to 30 μm. The substrate 30 is divided vertically and horizontally to form a semiconductor chip 39 as shown in FIGS.

Although not shown, such a semiconductor chip 39 is incorporated in a predetermined package to make it easy to handle, that is, a high-frequency power amplifier.

This high-frequency power amplifier has a circuit configuration as shown in FIG. In this circuit,
Resistors R1 to R6 are connected to the transistors Q3 and Q4 that constitute the bias circuit and the transistors Q5 and Q6 that perform automatic power control.

In an application example to a portable telephone, Vcc = 3.5 V
In general, Vbias and Vapc are both 2.8 V
It is necessary to design below and allow for a margin for fluctuations in the power supply voltage of the battery. In such a case, the transistors Q3 to Q6
Up to a maximum of 1.25 V is applied to the base-emitter junction of each transistor.

Therefore, in a structure using a conventional substrate which does not perform a process for eliminating the recombination center caused by residual hydrogen due to light irradiation, the transistors Q3 to Q6 are connected to the base-emitter junction at a maximum of 1.25V. Since the voltage is applied only to the above, the base current fluctuates as can be seen from the graph of FIG.

However, in the case of the first embodiment,
Since the process for eliminating the recombination center caused by the residual hydrogen due to the light irradiation is performed, the fluctuation of the base current hardly occurs, and the characteristics of the high-frequency power amplifier become stable and the reliability increases.

[0079] Figure 17 is the collector current I _C and base current I _B and the base of the heterojunction bipolar transistor manufactured by the manufacturing method of the embodiment 1 - is a graph showing the correlation between the emitter voltage V _BE. Emitter size S _E
Is 2.5 μm × 20 μm, collector-base voltage V _CB
Is 0 V, and the measurement was performed at room temperature. The first measurement result is a curve indicated by a dotted line, and the second measurement result is a curve indicated by a solid line. The conditions for this measurement are the same as in FIG.

[0080] In the case of the HBT Embodiment 1, a conventional collector current I _C as the base current I _B also can be seen that the first time and the second time also hardly changes as course.
Further, the measurement results after the third measurement are almost the same as those of the second measurement and do not change.

Therefore, from this, even if the hydrogen concentration of the base layer is as high as about 10 ¹⁸ cm ³ or more,
It can be seen that the recombination center caused by the residual hydrogen can be eliminated by the light irradiation treatment.

As a result, even in a circuit configuration in which only a maximum of 1.25 V is applied to the base-emitter junction of the transistors Q3 to Q6 as in the case of the first embodiment, the temporal fluctuation of the base current does not change between the base and the emitter. It was within 1% for one hour with respect to the base current at the start of voltage application.
Here, 1 hour and 1% are values that are normally determined as “no fluctuation”. Also, in a circuit configuration different from the bias circuit shown in FIG. 15, the voltage applied to the base-emitter junction of the transistor in the bias circuit is 1.
It was also found that when the voltage was 3 V or less, the temporal variation of the base current was within 1% in one hour with respect to the base current at the start of measurement.

This means that in the monolithic microwave integrated circuit manufactured by performing the light irradiation treatment, the characteristics related to the base current hardly fluctuate, and the residual hydrogen concentration of the base layer is reduced to 10 ¹⁷ cm- ³ . Even if it exceeds 10 ¹⁸ cm to about ³ or more, the voltage between the base and the
Even when the voltage is set to 1.2 V, 1.25 V, 1.3 V, or the like, the variation of the characteristic [current amplification factor] related to the base current is 1% or less at the start of the measurement, which is in the category of non-defective products.

The high-frequency power amplifier 40 of the first embodiment
Is, for example, a transmission frequency for 800 MHz to 2 GHz, a power supply voltage of 2.7 to 4.2 V, and an output of 28 to 32 dB.
m, efficiency is 55-70%.

According to the first embodiment, the following effects can be obtained.

(1) The hydrogen concentration of the base layer is 10 ¹⁸ cm ³
However, since the base layer 4 has been subjected to light irradiation treatment with light having an energy larger than the forbidden band width of the semiconductor (GaAs) constituting the base layer, electron-holes due to photons are contained in the base layer. As the pair is generated, the recombination center caused by the residual hydrogen can be eliminated by the energy released by the recombination of the electron-hole pair through the carrier recombination center. As a result, the base current I _B, i.e. can be suppressed variation occurrence in the current gain.

(2) In a high-frequency power amplifier or a monolithic microwave integrated circuit, the base of at least one heterojunction bipolar transistor is required in terms of circuit configuration.
Even when the voltage between the emitters is 1.3 V or less,
As described above, since the base layer 4 is irradiated with light, even when the voltage between the base and the emitter is applied, the time variation of the base current and the current amplification factor is within 1% in one hour, and the initial operation is performed. The fluctuation of the current amplification factor in the state hardly occurs, and the reliability can be improved.

(3) According to the above (2), according to the present embodiment, stable operation of all the heterojunction bipolar transistors can be achieved regardless of the circuit type.

[0089] (4) Although the conventional in order to improve the current amplification factor is performed energized constant current density than the collector current I _C, current processing operation time many take according to the present embodiment is not required Product cost reduction can be achieved.

(5) Even if the substrate 30 is manufactured by the MOCVD method, the residual hydrogen in the semiconductor layer serving as the base layer 4 does not become a recombination center by light irradiation, and is suitable for manufacturing a heterojunction bipolar transistor. Substrate. In addition, the processing time of this substrate is as short as several seconds and the equipment is simple, so that the processing cost is reduced. This substrate can also be provided as an inexpensive and suitable substrate for manufacturing heterojunction bipolar transistors.

(Embodiment 2) FIG. 18 is a diagram related to a method of manufacturing an HBT according to another embodiment (Embodiment 2) of the present invention.

The second embodiment is an example in which the light irradiation is performed after the emitter mesa is performed instead of performing the light irradiation in the state of the substrate.

That is, as in the first embodiment, semiconductor layers to be the sub-collector layer 2, the collector layer 3, the base layer 4, the emitter layer 5, the cap layers 6, and 7 are sequentially formed on one surface side of the semiconductor substrate 1. After that, the emitter electrode 9 is selectively formed on the cap layer 7. In this case, the width of the emitter electrode 9 is formed to be narrower than that of the first embodiment. For example, the width of the emitter electrode 9 is 1 μm or less.

Next, as shown in FIG. 18, the cap layers 7, 6 and the emitter layer 5 are etched using the emitter electrode 9 as an etching mask in the same manner as in the first embodiment to expose the surface of the base layer 4.

Next, as in the first embodiment, light 8 having energy larger than the forbidden band width of the semiconductor constituting the base layer is irradiated from one surface side of the semiconductor substrate 1. As a result, the diffusion distance of the electrons generated in the region not covered by the emitter layer 5 is about 0.5 μm.
Since the width of the emitter electrode 9 is as narrow as 1 μm or less,
Recombination centers caused by hydrogen remaining in the base layer 4 immediately below the emitter layer 5 can be eliminated by the electrons diffused in the lateral direction.

Thereafter, processing is performed in the same manner as in the first embodiment to form a heterojunction bipolar transistor. FIG. 19 is a schematic sectional view of a substrate on which an emitter mesa, a base mesa, and a collector mesa are formed.

In the second embodiment, the first embodiment is also used.
As in the case of (1), it is possible to provide a heterojunction bipolar transistor which does not cause a change in the current amplification factor.

Although the invention made by the inventor has been specifically described based on the embodiment, the invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention. Needless to say.

In the above description, the invention made mainly by the present inventor is based on the application field of InG
Although the semiconductor device having the aP / GaAs heterojunction structure has been described, the invention can be applied to an optical device and the like. Further, the present invention can be similarly applied to a heterojunction bipolar transistor made of another material.

The present invention can be applied to at least a semiconductor device having a heterojunction structure.

[0101]

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.

(1) The hydrogen concentration of the GaAs base layer is 10
¹⁷ be as high as cm ~ ³ a exceeds 10 ¹⁸ cm ~ ³ about or more electrons to the base layer by irradiation with high light energy than the band gap of the semiconductor composing the base layer - caused the hole pairs The energy released by the recombination of the electron-hole pairs can eliminate the recombination center caused by the residual hydrogen. As a result, it is possible to suppress the fluctuation occurrence of the base current I _B and the current amplification factor.

(2) In a monolithic microwave integrated circuit in which a plurality of heterojunction bipolar transistors are formed monolithically, the base-emitter voltage of some of the heterojunction bipolar transistors is 1.3 V or less due to the circuit configuration. Even in such a case, by performing light irradiation in the manufacture thereof, the operation of each heterojunction bipolar transistor can be stabilized, and the reliability of the monolithic microwave integrated circuit can be improved.

(3) As a technique for improving the current amplification factor, light irradiation for several seconds is sufficient, so that the product cost can be reduced by shortening the working time.

(4) According to the present invention, an inexpensive and suitable substrate for a heterojunction bipolar transistor can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a state in which a carrier recombination center in a base layer is annihilated by light irradiation in a method for manufacturing a semiconductor device having a heterojunction bipolar transistor according to an embodiment (Embodiment 1) of the present invention; FIG. 3 is a schematic sectional view of FIG.

FIG. 2 is a graph showing a correlation between a light irradiation time in the light irradiation and a thickness of a semiconductor layer on a base layer.

FIG. 3 is a cross-sectional view of an HB in the manufacture of the semiconductor device according to the first embodiment;
FIG. 3 is a schematic sectional view of a substrate on which a T emitter mesa is formed.

FIG. 4 is a cross-sectional view of a semiconductor device according to the first embodiment,
FIG. 3 is a schematic cross-sectional view of a substrate on which a T base mesa is formed.

FIG. 5 is a cross-sectional view of an HB in the manufacture of the semiconductor device according to the first embodiment;
FIG. 4 is a schematic cross-sectional view of a substrate on which a T collector mesa is formed.

FIG. 6 is a diagram illustrating the HB in the manufacture of the semiconductor device according to the first embodiment;
FIG. 3 is a partial schematic plan view showing a T electrode pattern.

FIG. 7 is a sectional view taken along the line AA of FIG. 6;

FIG. 8 is a sectional view taken along the line BB of FIG. 6;

FIG. 9 is a cross-sectional view of an HB in the manufacture of the semiconductor device according to the first embodiment;
FIG. 3 is a partial schematic cross-sectional view showing a state of forming a wiring for connecting T, a capacitance, a spiral inductor, a resistor, etc. to each other.

FIG. 10 is a partial schematic cross-sectional view showing a state where a conductor layer is formed for resistance formation in the manufacture of the semiconductor device of the first embodiment.

FIG. 11 is a partial schematic cross-sectional view showing a state where an insulating film including a dielectric layer for forming a capacitor is formed in the manufacture of the semiconductor device of the first embodiment.

FIG. 12 is a partial schematic cross-sectional view showing a state where a conductor layer for forming a capacitor and a spiral inductor is formed in the manufacture of the semiconductor device of the first embodiment.

FIG. 13 is a schematic cross-sectional view showing a part of a semiconductor chip in which a high-frequency power amplifier circuit is incorporated in manufacturing the semiconductor device of the first embodiment.

FIG. 14 is an HBT manufactured by the manufacturing method according to the first embodiment.
FIG. 2 is a block diagram showing a configuration of a high-frequency power amplifier incorporating the above.

FIG. 15 is an equivalent circuit diagram of the high-frequency power amplifier of the first embodiment.

FIG. 16 is a schematic plan view showing a monolithic / microwave integrated circuit chip included in the high-frequency power amplifier according to the first embodiment.

FIG. 17 is an HBT manufactured by the manufacturing method according to the first embodiment.
3 is a graph showing the correlation between the current of FIG.

FIG. 18 is a schematic cross-sectional view of a substrate showing a state in which a carrier recombination center in a base layer is annihilated by light irradiation in a method of manufacturing an HBT according to another embodiment (Embodiment 2) of the present invention. is there.

FIG. 19 is a schematic cross-sectional view of a substrate on which an emitter mesa, a base mesa, and a collector mesa are formed in the manufacture of the HBT according to the second embodiment.

FIG. 20 is a graph showing the correlation between the current of the HBT and the base-emitter voltage revealed by the present inventors.

[Explanation of symbols]

1: semiconductor substrate (semi-insulating GaAs substrate) 2: n-type G
aAs sub-collector layer, 3 ... n-type GaAs collector layer,
4 ... p-type GaAs base layer, 5 ... n-type InGaP emitter layer, 6 ... n-type GaAs cap layer, 7 ... n-type InGa
As cap layer, 8 ... light, 9 ... emitter electrode, 10 ... base electrode, 11 ... collector electrode, 14 ... insulating film, 15 ...
Wiring, 15B: Base wiring, 15C: Collector wiring, 1
5E: emitter wiring, 16B: base contact, 16
C: collector contact, 16E: emitter contact, 20: resistance layer, 21: interlayer insulating film, 25: conductor layer,
26 ... passivation film, 30 ... substrate, 38 ... electrode pad, 39 ... semiconductor chip, 40 ... high frequency power amplifier, 41 ... first stage transistor (Q1), 42 ... output stage transistor (Q2), 43 ... interstage matching circuit 44: input matching circuit, 45: input bias circuit, 46: output bias circuit.

Claims (14)

[Claims] 1. A semiconductor device comprising a heterojunction bipolar transistor, wherein the base layer of the heterojunction bipolar transistor has a hydrogen concentration of 10 ¹⁸ cm to ³ or more, and the base layer is a semiconductor layer forming a base layer. A semiconductor device in which irradiation treatment with light having energy larger than the forbidden band width is performed. 2. A semiconductor device comprising a plurality of heterojunction bipolar transistors, wherein at least one of the heterojunction bipolar transistors has a base layer having a hydrogen concentration of 10 ¹⁸ cm to ³ or more, and a base-emitter voltage. Is less than or equal to 1.3 V, and the time variation of the base current when the base-emitter voltage is applied is within 1% of the base current at the start of the measurement in one hour. 3. The semiconductor device according to claim 1, wherein the base layer contains carbon as a conductivity type determining impurity. 4. The semiconductor device according to claim 1, wherein a monolithic microwave integrated circuit including said heterojunction bipolar transistor is formed. 5. The monolithic microwave integrated circuit is a high frequency power amplifier.
3. The semiconductor device according to claim 1. 6. A step of sequentially forming at least one semiconductor layer serving as a collector layer, a base layer, and an emitter layer on one surface side of a semiconductor substrate, and forming light having a larger energy than a forbidden band width of a semiconductor forming the base layer. A semiconductor device having a step of irradiating the semiconductor substrate from one surface side and a step of processing each of the semiconductor layers to form an emitter layer, a base layer, and a collector layer, and forming a heterojunction bipolar transistor at least partially. Manufacturing method. 7. A step of sequentially forming at least one semiconductor layer serving as a collector layer, a base layer, and an emitter layer on one surface side of a semiconductor substrate, a step of processing the semiconductor layer to form an emitter layer, Irradiating light having a larger energy than the forbidden band width of the semiconductor constituting the layer from one surface side of the semiconductor substrate to allow electrons generated due to the light to flow into the base layer immediately below the emitter layer; ,
Forming a base layer and a collector layer by processing each of the semiconductor layers, wherein a heterojunction bipolar transistor is formed at least in part. 8. A plurality of heterojunction bipolar transistors are formed, and some of the heterojunction bipolar transistors are low-voltage transistors having a base-emitter voltage applied to a circuit of about 1.25 V or less. The method for manufacturing a semiconductor device according to claim 6 or 7, wherein 9. The semiconductor according to claim 6, wherein said base layer contains carbon and hydrogen, and said hydrogen concentration is about 10 ¹⁸ cm to about ³ or more. Device manufacturing method. 10. The wavelength of light used for the light irradiation is 36.
The method of manufacturing a semiconductor device according to claim 6, wherein the thickness is 5 nm. 11. A monolithic microwave integrated circuit including said heterojunction bipolar transistor is formed.
13. The method for manufacturing a semiconductor device according to the above item. 12. The method according to claim 11, wherein a high-frequency power amplifier is formed. 13. A semiconductor layer to be at least a collector layer, a base layer, and an emitter layer is sequentially formed on one surface side of a semiconductor substrate by metal organic chemical vapor deposition, and carbon is added to the base layer as a conductivity type determining impurity. A method of manufacturing a substrate for manufacturing a hetero-junction bipolar transistor formed by forming a substrate, comprising a step of irradiating light having energy larger than the forbidden band width of a semiconductor constituting the base layer from one surface side of the semiconductor substrate. A method for manufacturing a substrate, comprising: 14. The hydrogen concentration of the base layer is 10 ¹⁸ cm.
14. The method for manufacturing a substrate according to claim 13, wherein the number is about ³ or more.