JPH0497534A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent damage to a silicon substrate caused by etching by etching a first polysilicon film on an emitter layer in such a way that it is left somewhat without removing it completely and by implanting impurities for the base layer via an oxide film. CONSTITUTION:When a second oxide film 111 and a first polysilicon film 100 are etched with a first resist film 700 as a mask. the first polysilicon film 100 is left somewhat without removing it completely. The first polysilicon film which is left is denoted by reference numeral 100A. Next. the left film 100A is oxidized completely and an oxide film 100B is formed. A P-type impurity is implanted into an epitaxial layer 3 under the film 100B in an active region of a transistor via the film 100B. and an intrinsic base layer 7 is formed. As this prevents damage to a silicon substrate caused by etching, leak current of a transistor can be reduced and transistor characteristics can be improved. In addition, the performance of transistors can be increased because thin junction is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing a high-performance bipolar transistor.

[Prior Art] FIGS. 2(^) to 2(E) are cross-sectional views showing the main manufacturing steps for manufacturing a conventional semiconductor device, such as a bipolar transistor, in order of steps.

As shown in FIG. 2(^), first, a high concentration n-type collector buried layer 2 is formed on a low impurity concentration P type semiconductor substrate such as a silicon substrate 1, and then a semiconductor layer such as a low concentration n type collector layer 2 is formed thereon. A type epitaxial layer 3 is grown. In addition,
In this epitaxial layer 3, a zero-order element isolation groove 4 in which the active region of a bipolar transistor is formed is formed from the surface of the epitaxial layer 3 through the collector buried layer 2 to the inside of the silicon substrate 1, and the element isolation groove 4 is formed in the epitaxial layer 3. After forming a P-type layer 5 for channel cutting in the silicon substrate 1 near the tip of the silicon substrate 4, an oxide film 6 for isolation is filled in the isolation groove 4 between elements. After that, the device is oxidized to perform a first oxidation process on the entire surface of the epitaxial layer 3 and isolation oxide film 6! form lA110,
A portion of the epitaxial layer 3 is removed to determine the active region and collector all region of the transistor.
After partially exposing the first polysilicon M1, the entire surface is covered with the first polysilicon M1.
00, a second oxide film 111 is deposited. After that, the first resist film 700 is patterned.

As shown in FIG. 2(B), using the first polysilicon film 700 as a mask, the second oxide film 111 and the first polysilicon film 111 are bonded together. [10
After etching 0 to expose the epitaxial layer 3 in the active region, the first resist film 700 is removed.

Thereafter, a P-type impurity is ion-implanted into the exposed epitaxial layer 3 while masking the collector all region using a resist mask (not shown) to form an intrinsic base layer 7. Then, without masking the active region using another resist mask (not shown), n-type impurity ions are implanted into the collector all region from above the second oxide film 111, and heat treatment is performed to form the epitaxial layer 3. A collector all layer 6 is formed.

As shown in FIG. 2(C), the third oxide film 11 is again applied to the entire surface.
2, a sidewall oxide film 112a, which will become apparent later, is left behind by a full-surface etch-back process.

As shown in FIG. 2(D), a second polysilicon film 101 with an emitter as a pole is deposited on the entire surface, and after implanting n-type impurities into this second polysilicon film 101, a second resist film 701 is deposited. Second polysilicon film 10 as a mask
The first and third oxide films 112 are etched. (The second resist film 701 is left without being removed), the third resist film 702 is patterned, and P-type impurities are implanted into the first polysilicon film 100 for the base electrode.

As shown in FIG. 2E, an extrinsic base layer 9 is then formed in the epitaxial layer 3 and an emitter layer 10 is formed in the intrinsic base layer 7 by performing heat treatment. after that,
After removing the second resist film 701 and the third resist 703, depositing a fourth oxide film, for example, a PSG film 400, and baking it to form a contact hole, an emitter electrode 600 is formed on the second polysilicon film 101. At the same time, a base electrode 601 and a contour electrode 602 are formed on the first polysilicon Igloo.

[Problems to be Solved by the Invention] In the conventional semiconductor device manufacturing method, when etching the first polysilicon film, the underlying silicon surface is etched. There were problems such as causing severe damage.

The present invention has been made to solve these problems, and an object of the present invention is to provide a method for manufacturing a semiconductor device that can avoid damage to a silicon substrate caused by etching.

[Means for Solving the Problems] A method for manufacturing a semiconductor device according to the present invention includes a step of leaving a portion of the first polysilicon film on the emitter layer without etching it to the underlying silicon surface, and etching the remaining first polysilicon film. This method includes a step of oxidizing a silicon film to form an oxide film, and a step of forming an intrinsic base layer by injecting impurities through the oxide film.

[Function] In the present invention, since the first polysilicon film on the emitter layer is etched so as to be removed without completely removing it, damage to the silicon substrate is avoided, and the remaining first polysilicon film is removed. Since the impurity for the base layer is implanted through the oxide film formed by oxidation, it is expected that the performance of the bipolar transistor will be improved.

[Embodiment] FIGS. 1(^) to 1(C) are sectional views showing the main steps of an embodiment of the present invention in order of steps.

As shown in FIG. 1(^), it is manufactured in the same manner as the conventional example until it reaches the same state as shown in FIG. 2(^).

As shown in FIG. 1B, using the first polysilicon film 700 as a mask, the second oxide film 111 and the first polysilicon film 110 are
0, but at that time, the first polysilicon film 1
The first polysilicon film 00 is not completely removed, but is left slightly, and the remaining first polysilicon film is indicated by the reference numeral 100^.

As shown in FIG. 1C, the remaining first polysilicon film 100^ is entirely oxidized to form an oxide film 100B.

P-type impurities are implanted into the underlying epitaxial layer 3 through the oxide film 100B in the active region of the transistor to form the intrinsic base layer 7. Thereafter, a collector all layer 8, an external base layer 9, and an emitter layer 10 are sequentially formed in the same manner as in the conventional example.

[Effects of the Invention] As explained in detail above, the present invention includes a step in which the first polysilicon film on the emitter layer is left slightly etched without being etched to the underlying silicon surface, and a step in which the remaining first polysilicon film is etched. The process includes a step of oxidizing to form an oxide film and a step of forming an intrinsic base layer by injecting impurities through the oxide film, thereby avoiding damage to the silicon substrate due to etching and reducing transistor leakage current. etc., thereby improving transistor characteristics, and forming a shallow junction to realize higher performance of the transistor.

[Brief explanation of drawings]

FIGS. 1(^) to (C) are cross-sectional views explaining one embodiment of the present invention, and FIGS. 2(^) to (E) are cross-sectional views of main steps explaining a conventional method of manufacturing a semiconductor device. . In the figure, 1 is the silicon substrate, 3 is the epitaxial layer, 7 is the intrinsic base layer, 8 is the collector all layer, 9 is the external base layer, 10 is the emitter layer, 100 is the first polysilicon film, and 100^ is the remaining layer. first polysilicon film, 10
0B is an oxide film, and 111 is a second oxide film. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] In a method of manufacturing a semiconductor device having a bipolar transistor, a first polysilicon film on an emitter layer in a semiconductor layer in which an active region of the bipolar transistor is formed is not completely removed but is left slightly. a step of etching; a step of oxidizing the remaining first polysilicon film to form an oxide film; and a step of forming an intrinsic base layer by injecting impurities into the semiconductor layer through the oxide film. A method for manufacturing a semiconductor device, comprising: