JPS6331156A - semiconductor equipment - Google Patents

Abstract

PURPOSE:To prevent emitter resistance from increasing and hfe from decreasing by a method wherein a bipolar transistor emitter electrode polycrystalline silicon film may be rendered thinner than a MOSFET gate polycrystalline silicon film. CONSTITUTION:A bipolar transistor emitter electrode polycrystalline silicon film is rendered thinner than a field effect transistor gate polycrystalline silicon film. On a silicon substrate 1, a MOSFET constituted of a source 4, drain 5, gate oxide film 6'', and gate 6, and the impurity-diffused region of a bipolar transistor base 7 are covered by a PSG film 3. Next, a contact window is pro vided in an oxide film 2 on the base 7 and PSG film 3. A polycrystalline silicon film is attached to the entire surface of a semiconductor chip, impurity ions are implanted into the polycrystalline silicon film, etching is accomplished by photolithography for patterning the polycrystalline silicon film into an emitter electrode 9, and then thermal diffusion is accomplished for the formation of an impurity-diffused layer for an emitter 8 under the emitter electrode 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to a semiconductor device in which bipolar transistors and field effect transistors are mixedly formed on the same semiconductor substrate.

[Conventional technology]

Conventionally, insulated gate field effect transistor (hereinafter referred to as MO3
By changing the gate from an aluminum layer to a polycrystalline silicon film, FETs (FETs) can form source and drain impurity diffusion layers in self-alignment with the gate, which allows for high-density semiconductor devices and internal It has become possible to suppress manufacturing variations in device characteristics.

On the other hand, bipolar transistors have changed from an emitter electrode structure in which an aluminum layer is deposited directly on the surface of the impurity diffusion layer of the emitter to a polycrystalline silicon film in which impurities are introduced into the surface of the region where the emitter is formed by ion implantation, etc. This is used as an emitter impurity diffusion source to form an emitter impurity diffusion layer by thermal diffusion under the polycrystalline silicon film, and then an aluminum layer is deposited in a predetermined pattern on the polycrystalline silicon film to form an aluminum layer. It forms the emitter electrode of. In such a structure, (i) Since a polycrystalline silicon film electrode is interposed between the aluminum electrode and the emitter impurity diffusion layer, alloy spikes occur due to mutual diffusion between aluminum and the silicon of the impurity diffusion layer. This improves reliability by preventing

(ii) There is an advantage that the impurity diffusion layer of the emitter can be formed extremely thin.

Therefore, in a semiconductor device in which a bipolar transistor and a MOSFET are formed on the same semiconductor substrate, by using a polycrystalline silicon film for the emitter electrode of the bipolar transistor and the gate of the MOSFET, it is possible to increase the density of internal elements and increase the density of the semiconductor device. Reliability can be achieved.

Furthermore, in order to simplify the manufacturing process, conventionally, in such semiconductor devices, the emitter electrode of the bipolar transistor and the gate of the MOSFET were formed using the same polycrystalline silicon film, so that both had the same film thickness. .

[Problem that the invention seeks to solve]

However, in the conventional semiconductor device described above, MOSFET
Since the source and drain of the gate are formed in a self-aligned manner by ion implantation using the gate as a mask, the polycrystalline silicon film of the gate needs to have a thickness of at least 4000 nm to function as a mask, and therefore, the bipolar The thickness of the polycrystalline silicon film of the emitter electrode of the transistor is also at least 4000 nm. As a result, there is a drawback that the emitter resistance of the bipolar transistor increases and hre is difficult to increase.

An object of the present invention is to provide a high-density, high-reliability semiconductor device in which bipolar transistors and MOSFETs are mixedly formed on the same semiconductor substrate, with an increase in emitter resistance and a decrease in hre of bipolar transistors. It's about doing.

[Means for solving problems]

In the semiconductor device of the present invention, in a semiconductor device in which a bipolar transistor and a field effect transistor are formed on the same semiconductor substrate, the thickness of the polycrystalline silicon film of the emitter electrode of the bipolar transistor is the same as that of the field effect transistor. It is thinner than the polycrystalline silicon of the gate.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1(a) and 1(b) are cross-sectional views of a semiconductor chip shown in the order of steps for explaining the manufacturing method of the first embodiment of the present invention. In the manufacturing method of this example, first, the manufacturing method shown in FIG.
As shown in Fig. a>, sources 4.
A phosphosilicate glass (hereinafter referred to as PSG) film 3 is formed by 3000 people on the impurity diffusion of the base 7 of the MOSFET constituted by the drain 5° gate oxide film 6'' and the gate 6 and the bipolar transistor covered with the oxide film. Here, source 4 and drain 5 of MOSFET
is formed by ion implantation using the gate 6 of a 4,000-layer polycrystalline silicon film as a mask.

Next, as shown in FIG. 1(b), a contact window is opened in the oxide film 2 and PSG film 3 on the base 7, and a polycrystalline silicon film is deposited to a thickness of 2500 nm over the entire surface of the semiconductor chip. After introducing impurities into the polycrystalline silicon film by ion implantation, it is etched into a predetermined pattern using photolithography technology to form the emitter electrode 9 of the polycrystalline silicon film, and then the emitter electrode 9 is formed by thermal diffusion. A first embodiment of the present invention is obtained by forming an impurity diffusion layer of the emitter 8 below.

FIGS. 2(a) and 2(b) are cross-sectional views of a semiconductor chip shown in order of steps for explaining a manufacturing method according to a second embodiment of the present invention.

In this embodiment, first, as shown in FIG. 2(a), polycrystalline silicon 6a' is formed in a predetermined pattern to a thickness of 2000 nm so as to cover a gate insulating film 6 on a silicon substrate 1. , a contact window is opened in the oxide film 2 on the base 7 of the impurity diffusion layer, a polycrystalline silicon film 6b' is deposited on the entire surface of the semiconductor chip to a thickness of 2500 nm, and impurities are implanted on top of the polycrystalline silicon film 6b' by ion implantation. is introduced, and further an impurity diffusion layer of the emitter 8 is formed by thermal diffusion.

Next, as shown in FIG. 2(b), the polycrystalline silicon films 6b' and 6a' are sequentially etched by photolithography to form a gate 6' with a thickness of 4500 and a gate 6' with a thickness of 2.
By forming 500 emitter electrodes 9',
A second embodiment of the invention is now available.

〔Effect of the invention〕

As explained above, the present invention improves the thickness of the polycrystalline silicon film of the emitter electrode of a bipolar transistor by
By forming it thinner than the polycrystalline silicon film of the gate of T, there is an effect that an increase in emitter resistance and a decrease in hfe can be prevented, and a semiconductor device with good characteristics, high density, and high reliability can be provided.

[Brief explanation of drawings]

FIGS. 1 and 2 (a) and (b) are the first embodiment of the present invention, respectively.
FIG. 2 is a cross-sectional view of a semiconductor chip shown in the order of steps for explaining the manufacturing method of the second embodiment. 1... Silicon substrate, 2... Oxide film, 3... PS
G film, 4...source, 5...drain, 6.6'・
...Gate, 6P...Gate oxide film, 6a', 6b
'... Polycrystalline silicon film, 7... Base, 8...
Emitter, 9, 9'...emitter electrode. (αjiriku I concave Csu (b)

Claims (1)

[Claims] In a semiconductor device in which a bipolar transistor and a field effect transistor are formed together on the same semiconductor substrate, the polycrystalline silicon film of the emitter electrode of the bipolar transistor is thicker than the polycrystalline silicon film of the gate of the field effect transistor. A semiconductor device characterized by its thinness.