JP3486349B2 - Manufacturing method of bipolar transistor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a bipolar transistor, and more particularly to a method for manufacturing a bipolar transistor in which a substrate temperature is improved when forming a second conductivity type and a first conductivity type Si film film.

[0002]

2. Description of the Related Art Conventionally, an npn-type three-layer bipolar transistor having a structure shown in FIG. 3 is known.

Reference numeral 1 in the figure is an n-type Si substrate (collector). On the Si substrate 1, a p-type Si film (base) 2 and an n-type Si film (emitter) 3 are sequentially formed. The emitter 3, the base 2, and the Si substrate 1 are R
The opening 4 is formed by being appropriately etched by IE. An emitter electrode 5 is formed on the emitter 3, a base electrode 6 is formed on the base 2 exposed from the opening 4, and a collector electrode 7 is formed on the Si substrate 1.

By the way, the bipolar transistor having such a structure is manufactured by, for example, a vapor phase growth method.
In this method, as shown in FIG. 4, the Si substrate 1 is placed in a vacuum container 13 having a gas inlet 11 and a gas outlet 12, and S
While heating the i substrate 1, Si hydride gas such as silane (SiH ₄ ) or disilane (Si ₂ H ₆ ) which is a raw material gas and phosphine (PH ₃ ) or diborane (B) which is a material gas for doping. ₂ H ₆ ) is introduced to form a film.

When forming an npn type bipolar transistor, a p type Si film or Si is formed on an n type Si substrate.
A Ge film is laminated, and then an n-type Si film is laminated.
These film formations form an npn-type three-layer structure in the same vacuum container by switching the introduced gas species. Further, by etching the three-layer structure to form electrodes on the respective layers, the substrate is a collector, the p-layer is a base, and an n-type Si is formed.
A bipolar transistor is formed that functions as an emitter with the film. In order to increase the current amplification factor of such a transistor, the doping concentration of the emitter should be 10 ¹⁹ / cm ^3.
In this way, the doping concentration of the base needs to be 10 ¹⁷ / cm ³ or less.

[0006]

By the way, in manufacturing the above-mentioned bipolar transistor, phosphine is used as a material gas for doping. This phosphine has a high adsorption coefficient to the inner wall of the vacuum container and the pipe, and this remains as a gas release in the vacuum container. As a result, even if phosphine is not introduced when forming the p-type layer, a phenomenon occurs in which a certain level is automatically mixed into the film (autodoping phenomenon).

In particular, phosphine (PH₃) And so
The decomposed species (PHx, x = 0 to 2) has a vacuum partial pressure of 1
0^-TenIf there is a Torr stand in a vacuum vessel, 10¹⁷/
cm ³If it mixes with the film grown on the table, in that case,
The base layer doped at a concentration below
N-type due to doping,
Function is impaired.

For this reason, it is necessary to sufficiently evacuate the film before film formation to sufficiently lower the partial pressure of the molecular species related to phosphorus, but this has led to a decrease in throughput. In addition, another vacuum container is prepared for the p-type layer and the n-type layer,
There is also a method of transporting the two between them to form an npn three-layer structure, but in this case, the cost of the apparatus increases.

The present invention has been made in consideration of the above circumstances. When the second conductivity type Si film or the SiGe film is formed, the substrate temperature is raised and the first conductivity type Si film is formed.
It is an object of the present invention to provide a method for manufacturing a bipolar transistor which can avoid a change in conductivity type of a second conductivity type Si film due to autodoping by lowering the substrate temperature when forming a film.

[0010]

According to the present invention, a second-conductivity-type Si film or SiGe film and a first-conductivity-type Si film are sequentially laminated on a first-conductivity-type Si substrate. In the method of manufacturing a bipolar transistor in which electrodes are respectively formed on the Si film and the Si substrate after etching, the substrate temperature is raised when the second conductivity type Si film or SiGe film is formed, and The first conductivity type S
A method of manufacturing a bipolar transistor is characterized in that the substrate temperature is lowered when forming the i film.

In the present invention, the mechanism for suppressing P (phosphorus) autodoping is as follows. When depositing an n-type Si film, a mixed gas of Si ₂ H ₆ and PH ₃ is introduced from a gas inlet, and when depositing a p-type Si film, Si ₂ H ₆ and B ₂ H are introduced from a gas inlet. Introduce mixed gas of ₆ . At this time, if the substrate is heated to 600 ° C. or higher, S containing phosphorus or boron present on the substrate due to a chemical reaction.
The i-film grows.

Concentration C _P (atom /
cm ³ ) is the partial pressure of the PH ₃ vacuum container P _p (Tor)
r), when the film forming rate of Si is A (nm / s), it is expressed by the following formula.

C _p = P _p × 4.1 × 10 ²⁰ × 0.135
/ A × S _p ÷ 6.8 × 10 ¹⁴ × 4.99 × 10 ²² where 4.1 × 10 ²⁰ is a conversion coefficient, 0.135 is an atomic layer-layer thickness, and 6.8 × 10 ¹⁴ is an atom. Layer-layer atomic density,
4.99 × 10 ²² is the number of atoms in 1 cm ³ , S _p is PH ₃
-The probability that a molecule will react and come into the film when it comes to the Si surface. This formula is based on the assumption that the substrate is Si and the crystal growth is on the (100) plane.

The concentration of boron mixed in the film is C _{B, which} is the same as in the above equation. When the partial pressure of B ₂ H _{6 in} the vacuum container is P _B , C _B = P _B × 4. 1 × 10 ²⁰ × 0.135 / A × S _B ÷
It is represented by 6.8 × 10 ¹⁴ × 4.99 × 10 ²² .

The probability of incorporation of B and P in the Si film formation and the film formation temperature have a certain relationship. As an example, when the growth rate of Si is 0.5 nm / s, B ₂
Assuming that the partial pressure of H _{6 in} the vacuum container is 4.4 × 10 ^-9 Torr and the substrate temperature during film formation is 750 ° C., boron is mixed at 2.5 × 10 ¹⁷ / cm ³ from the above formula. The grown Si film can grow.

Autodoping occurs when PH ₃ remains in the vacuum container. If the base of the transistor is doped with 1 × 10 ¹⁷ / cm ³ of boron, the residual partial pressure of PH ₃ is 2.4 × 10 4 at 750 ° C.
If there is ^-9 Torr, the amount of phosphorus mixed will be equal to that of boron. In other words, in order to make the transistor function properly normally, in this case, the partial pressure of PH ₃ is 2.4 ×
It must be below 10 ^-9 Torr.

In the present invention, the mixing ratio of phosphorus is lowered by raising the film forming temperature without lowering the residual partial pressure of PH ₃ . If the substrate temperature is 780 ° C., the residual partial pressure does not change, and the phosphorus concentration can be reduced by 30%.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION n according to an embodiment of the present invention will now be described.
Manufacturing method of pn-type bipolar transistor
This will be described with reference to (A) to (C) and FIG. However, FIG. 2 shows a plan view of FIG. A vacuum container as shown in FIG. 3 was used for manufacturing the transistor.

First, a p-type Si film (base) 22 was formed on an n-type Si substrate 21. At this time, a mixed gas of Si ₂ H ₆ and B ₂ H ₆ was introduced from the gas inlet 11 and the substrate temperature was 780 ° C. Subsequently, an n-type Si film (emitter) 23 was formed on the base 22 (see FIG. 1A).
At this time, a mixed gas of Si ₂ H ₆ and PH ₃ was introduced from the gas inlet 11 and the substrate temperature was 750 ° C. Next, the respective Si films 23 and 22 are subjected to reactive ion etching (RIE).
By the method, etching was performed until the pn junction surfaces of the Si film 23 and the film 22 were exposed to form an opening 24 (see FIG. 1B). In the production of the base 22 and the emitter 23, the partial pressure of the phosphorus-related species in the vacuum chamber 13 is on the order of 10 ⁻¹⁰ Tor, and the concentration of phosphorus doped in the base 22 is 1 × 10 ¹⁷ / cm 3.
^{Was 3} . Further, Al is constantly deposited on the entire surface, and then patterned by a conventional method to form a comb-shaped emitter electrode 25 on the p-type Si film 23, the n-type Si 22 exposed from the opening 24, and the Si substrate 21. , The base electrode 26 and the collector electrode 27 are respectively formed to manufacture an npn-type bipolar transistor (see FIGS. 1C and 2).

According to the above embodiment, the substrate temperature is set to 780 ° C. when the p-type Si film (base) 22 is formed, and the substrate temperature is set to the n-type Si film (emitter) 23. 7
Since the film is formed with a temperature difference of 50 ° C., the concentration of phosphorus auto-doped in the base 22 can be suppressed to 5 × 10 ¹⁶ / cm ³ or less, and the base 22 can be prevented from becoming an n-type.

In the above embodiment, the substrate temperature was set to 780 ° C. when forming the base film and the substrate temperature was set to 750 ° C. when forming the emitter film. However, the temperature is not limited to these values. The difference may be about 30 ° C.

In the above embodiment, the case where the invention is applied to the case of the npn type bipolar transistor has been described, but the present invention is not limited to this, and the same can be applied to the case of the pnp type bipolar transistor.

[0023]

As described above in detail, according to the present invention, the substrate temperature is raised when forming the second conductivity type Si film or SiGe film, and the first conductivity type Si film is formed. At this time, by lowering the substrate temperature, it is possible to provide a method for manufacturing a bipolar transistor capable of avoiding a change in the conductivity type of the second conductivity type Si film or SiGe film due to autodoping.

[Brief description of drawings]

FIG. 1 is a sectional view showing a method of manufacturing a bipolar transistor according to an embodiment of the present invention in the order of steps.

FIG. 2 is a plan view of FIG.

FIG. 3 is a cross-sectional view of a conventional npn-type three-layer bipolar transistor.

FIG. 4 is an explanatory view of the principle of a vacuum container used when vacuum processing a substrate.

[Explanation of symbols]

21 ... n-type Si substrate (collector), 22 ... p-type Si film (base), 23 ... n-type Si film (emitter), 24 ... Emitter electrode, 25 ... Base electrode, 26 ... Collector electrode.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Sakamoto, 8-chome, 1-chome, Koura, Kanazawa-ku, Yokohama-shi, Kanagawa 1 Mitsubishi Heavy Industries, Ltd. Basic Technology Research Institute (56) Reference Japanese Patent Laid-Open No. 9-186172 (JP, A) ) JP-A-9-181091 (JP, A) JP-A-5-347313 (JP, A) JP-A-4-230037 (JP, A) JP-A-4-102334 (JP, A) JP-A-7- 130978 (JP, A) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 29/73

Claims (2)

(57) [Claims] 1. A second conductivity type Si film or SiGe film and a first conductivity type Si film are sequentially laminated on a first conductivity type Si substrate, and the respective Si films are further etched, and then the respective S
In a method of manufacturing a bipolar transistor in which electrodes are respectively formed on an i film and a Si substrate, when forming the second conductive type Si film or SiGe film, a substrate temperature is raised and the first conductive type Si film is formed. A method for manufacturing a bipolar transistor, which comprises lowering a substrate temperature when forming a film. 2. The second conductivity type Si film or SiGe
The substrate temperature is set to 780 ° C. or more when forming the film, and the substrate temperature is set to 30 ° C. or more lower than the substrate temperature when forming the second conductivity type Si film when forming the first conductivity type Si film. The method for manufacturing a bipolar transistor according to claim 1, wherein