JPH02283029A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a main part of a transistor structure by using one mask by a method wherein, by side-etching a mask which has been used for field oxidation, a base leading-out electrode is formed, and then an emitter region is formed. CONSTITUTION:On a semiconductor wafer 10 provided with a buried layer 2 of an inverse conductivity type and an epitaxial layer 3 of an inverse conductivity type on a semiconductor substrate 1 of a conductivity type, masks of a nitride film 4a and a oxide film 5a are formed, and a thick field oxide mask 8 is formed by performing field oxidation. After the field oxidation, by side- etching the masks of the nitride film 4a and the oxide film 5a, small masks 4b, 5b whose side surfaces are retreated are formed, and a part of the surface of the epitaxial layer 3 is exposed. By applying a bias voltage to the semiconductor wafer, silicon Si is subjected to bias sputtering. The whole surface of a polycrystalline silicon film 9 which is grown so as to have a flat surface is etched, and the masks of the nitride film 4b and the oxide film 5b are exposed.

Description

[Detailed Description of the Invention] [l! 1 Requirements Regarding a semiconductor device manufacturing method that uses one mask to form both the field oxide film and the emitter region of a co-bipolar transistor, there is no need to perform delicate control etching, and the field oxide film and emitter region can be formed using one mask. The purpose of the present invention is to provide a method for manufacturing a semiconductor device that can form an oxide film and an emitter region.This process involves forming a pattern of a nitride film and an oxide film on a semiconductor wafer, and using this pattern as a mask to form a field oxide film. and a step of performing side etching to reduce the side surfaces of the patterned nitride film and oxide film to form a nitride film and oxide film with a reduced area. The method includes the steps of depositing a polycrystalline silicon film on a semiconductor wafer by sputtering until it has a substantially flat surface, and etching the polycrystalline silicon film until the pattern-shaped oxide film is exposed.

[Industrial Application Field] The present invention relates to a method of manufacturing a semiconductor device including a bipolar transistor, and particularly to a method of manufacturing a semiconductor device in which both field oxide film formation and emitter region formation of a bipolar transistor are performed using one mask. Regarding.

[Prior Art 7] FIGS. 3(A) to 3(1) show a conventional method for manufacturing a semiconductor device in which field oxide film formation and emitter region formation are performed using one mask.

In FIG. 3(A), an n+ type buried region 52 is formed on the surface of an n-type silicon substrate 51, and a thick nitride film is formed on a semiconductor wafer 60 on which an n-type epitaxial layer 53 is formed. Form oxide film and photoresist layer,
A photoresist layer pattern 56 is formed, and the layer below it is patterned to form a mask of nitrided WA 54a and hot oxide film 55.

Referring to FIG. 3B, after removing resist film 56, field oxidation is performed using nitride H54a and oxide film 55a as masks to form field oxidation pA58. Thereafter, side etching is performed on the nitride film 54a and the thick oxide film 55a, and the side surfaces are recessed to form the nitride film 54b and the oxidized WA 55b with reduced areas, and the surface of the epitaxial layer 53 is partially exposed.

As shown in FIG. 3C, a polycrystalline silicon layer 59 is formed on the structure thus formed, and a photoresist layer 65 is further applied thereon. Polycrystalline silicon layer 59 is produced, for example, by CVD, and has a surface that follows the shape of the underlying layer. The photoresist layer 65 is formed using a spinner or the like to form a substantially flat surface.

As shown in FIG. 3(D), the laminated structure now having a substantially flat surface is subjected to controlled etching to expose the surface of the oxide film pattern 55b.

By carefully controlling the etching, the polycrystalline silicon layer 59 becomes a polycrystalline silicon layer 59b having a substantially flat surface.

Next, as shown in FIG. 3E, boron ions B+, for example, are implanted into the polycrystalline silicon layer 59b whose thickness has been reduced by etching. The polycrystalline silicon layer 59b implanted with boron ions B1 exhibits n-type conductivity.

As shown in FIG. 3(F), a thick oxide film pattern 55
b is removed, and the surface of polycrystalline silicon layer 59b is oxidized. In this way, oxide [62] is formed on the surface of polycrystalline silicon 7W59b.

Next, as shown in FIG. 3(G), the nitride film 54b is removed, the exposed surface of the epitaxial layer 53 is oxidized to form an oxide film 64, and n-type impurities such as boron ions B are ion-implanted. do. In this way, the polycrystalline silicon layer 5
A P-type internal base region 66 is formed within the region surrounded by 9b.

An oxide film is deposited on the surface of the semiconductor wafer 60 and anisotropically etched.

Then, as shown in FIG. 3H, the deposited oxide film is removed except for the portion 68 on the sidewall of the polycrystalline silicon layer 59b, and the exposed central portion of the oxide film 64 is removed, forming the epitaxial layer 153. is exposed. A polycrystalline silicon layer 70 is deposited thereon, and n-type impurities such as ^S+ ions are ion-implanted into the polycrystalline silicon layer 70.

The polycrystalline silicon layer 70 into which As ions are implanted exhibits n-type conductivity.

Referring to FIG. 3(I), polycrystalline silicon layer 70 is selectively etched to leave only a portion 70a above the emitter region, and a window for base electrode contact is formed in oxide film 62. An electrode layer such as AI is formed on this and patterned to form the emitter iEC electrode 72, base electrode 74, etc.

In this way, a bipolar transistor is manufactured by forming a field oxide film and forming an emitter region using one mask.

[Problems to be Solved by the Invention] As described above, when forming a field oxide film and an emitter region using one mask, when forming a region for extracting the pole from the base, the polycrystalline silicon layer may have a step difference. Therefore, after coating the photoresist, it was necessary to perform controlled etching, which requires delicate control.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device that does not require delicately controlled etching and can form a field oxide film and an emitter region using one mask.

[Means to solve the problem] FIGS. 1A to 1C are diagrams explaining the principle of the present invention.

In FIG. 1(A), a nitride film 4a and an oxide film 5a are placed on a semiconductor wafer 10 having a semiconductor substrate 1 of one conductivity type, a buried layer 2 of an opposite conductivity type, and an epitaxial layer 3 of an opposite conductivity type. A mask is made and field oxidation is performed to form a thick field oxide WA8.

In FIG. 1(B), after field oxidation, the nitride film 4a
Then, the mask of the oxide film 5a is side-etched to form small masks 4b and 5b with recessed sides to partially expose the surface of the epitaxial layer N3. This exposed portion of the epitaxial layer 3 is a region that becomes an external base region.

As shown in Figure 1 (C), a bias voltage is applied to the semiconductor wafer and bias sputtering of silicon Si is performed.81 particles flying from the Si target are deposited on the wafer surface, but the parts that will become protrusions are , the surface is gradually flattened by ^r1 ions in the sputtering atmosphere.

The polycrystalline silicon WA9 grown in this way to have a flat surface is then etched over the entire surface, and the nitrided WA4
b, exposing the mask of the oxide film 5b. Furthermore, the nitride film 4b
A bipolar transistor is formed by removing oxide film 5b, forming an internal base region, and further forming an emitter region.

[Operation] Side-etch the mask used for field oxidation, -
By first forming the base extraction electrode, and then forming the emitter region by performing surface oxidation, silicon oxide layer deposition, anisotropic etching, polycrystalline silicon layer deposition, etc., the main part of the transistor structure can be formed with a single mask. can be formed.

Furthermore, when creating the base lead-out electrode, by forming the polycrystalline silicon 1 film 9 by performing bias sputtering with the substrate biased, a flat surface can be easily formed, and the base lead-out electrode can be manufactured with high precision. I can do it. This facilitates the manufacture of the transistor structure itself.

[Embodiment PA] FIGS. 2A to 2K show a method for manufacturing a semiconductor device including a bipolar transistor according to an embodiment of the present invention.

In FIG. 1(A), a semiconductor substrate 1 made of P-type silicon, etc.
A nitrided WA 14 and a thick oxide film 15 are formed on the main surface of a semiconductor wafer 20 having an n1-type buried region 12 and an n-type epitaxial layer 13 thereon. Nitride film 14 acts as a mask against oxidation.

A photoresist layer 16 is applied to the surface of the oxidized WA 15,
The pattern is baked to form a photoresist pattern 16a. Using this photoresist pattern 16a as a mask, the underlying oxide film 15 and nitride film 14 are etched.
- type epitaxial layer 13 is exposed. After etching, the resist mask 16a is removed.

In FIG. 2C, using the patterns of the nitride film 14a and the oxide film 15a as masks, the exposed surface of the epitaxial layer 13 is field oxidized to form a field oxide film 1B. Field oxide film! is nitrided IN! 14a, forming a so-called bird's beak, but it is simply shown in the figure.

In FIG. 2 (D>), the nitride film 14a and the oxide film 15a are side-etched to expose the surface of the epitaxial layer 13 that is not covered with the field oxide film.This exposed epitaxial layer surface serves as the external base region and base extraction. It becomes the contact surface with the electrode.

In FIG. 2E, the semiconductor wafer 20 is negatively biased and bias sputtering of polycrystalline silicon is performed using an S1 target, and the atmosphere is Ar gas. A
Si particles, which are ejected from the target by the impact of r'' ions, fly to the wafer surface and deposit there.At the same time, Ar
The + ions bombard the surface and knock out the deposited Si particles on the protrusions again.

The bombardment effect of Ar+ ions is stronger on protruding parts than on flat parts due to the atmosphere, etc., so the growing surface gradually becomes flat. In this way, nitrided WA1
4b, a polycrystalline silicon film 19 having a flat surface is formed covering the oxide film 15b.

In FIG. 2(F), the grown polycrystalline silicon l
The entire surface of 1119 is etched. The surface of the polycrystalline silicon rIA 19 gradually lowers and eventually becomes an oxide film 15b.
is exposed. The polycrystalline silicon film at this time is indicated by 19a.

In FIG. 2(G), B+ ions, which are n-type impurities, are ion-implanted into the polycrystalline silicon film 19a which has been etched over the entire surface. The polycrystalline silicon wA19a doped with n-type impurities is given p-type conductivity. This n-type impurity diffuses into the epitaxial layer 13 to form an external base region.

Referring to FIG. 2(H), remove the thick oxide film 15b,
A thermal oxide film 21 is formed by thermally oxidizing the surface of the polycrystalline silicon film 19a.

Referring to FIG. 2(1), the remaining nitride film 14b is removed, thermal oxidation is performed to form thermal oxidation film 21a, and B1 ions, which are n-type impurities, are ion-implanted. In this way,
An internal base region 23 doped with n-type impurities is formed.

Referring to Figure 2 (J), CVD silicon oxide film is applied to the surface.
A sidewall oxide film 25 is formed by depositing at step D and performing anisotropic etching to leave only the side surface portion of the base lead-out electrode 19a, which has a large thickness in the vertical direction, and remove the rest. At this time,
Thermal oxide film! The central portion of 21a is also removed, exposing the internal base region 23.

Referring to FIG. 2(K), polycrystalline silicon WA 27 is deposited on the semiconductor wafer in which the internal base region 23 is partially exposed, and As'' ions, which are n-type impurities, are ion-implanted. is diffused inside the P-type internal base region 23 to form an emitter region.

Referring to FIG. 2(L), the emitter electrode 27 is patterned by patterning the polycrystalline silicon film 27 doped with n-type impurities.
Let it be a. Further, a window 29 for base electrode contact is formed in the thermal oxide film 21. After that, a ^1 electrode layer is formed,
The emitter electrode 31, base electrode 33, etc. are formed by patterning.

In this way, the main part of the bipolar transistor structure can be formed with one mask.

[Effects of the Invention] As explained above, according to the present invention, there is no need to perform delicately controlled etching when forming a base extraction electrode.

The field oxide film and the main parts of the bipolar transistor can be formed using a single mask, and by increasing alignment accuracy, parasitic capacitance can be reduced, and high-performance transistors can be manufactured with high yield.

[Brief explanation of drawings]

FIGS. 1(A) to 1(C) are diagrams explaining the principle of the present invention, and FIG. 1(A) is a sectional view showing the field oxidation process.
Figure (B) is a cross-sectional view showing the side etching process.
FIG. 2(C) is a cross-sectional view showing the process of bias sputtering, and FIGS. 2(A) to 2(L) show embodiments of the present invention, and are diagrams of a semiconductor device for explaining various steps of the semiconductor device manufacturing method. 3A to 3I are cross-sectional views of a semiconductor device showing the prior art and for explaining various steps of a method for manufacturing a semiconductor device. 4a, 4b a 5b 1 Semiconductor substrate of conductivity type Buried layer of opposite conductivity type Epitaxial layer of opposite conductivity type Nitride film Oxide film Field oxide film Polycrystalline silicon film Semiconductor wafer substrate Buried region Epitaxial layer Nitride film Thick oxide film Photoresist LayerField OxidePolycrystalline Silicon Semiconductor WaferThermal OxideInternal Base RegionSidewall OxidePolycrystalline Silicon FilmWindow ElectrodeSubstrateBuried AreaEpitaxial LayerNitride OxideResist LayerField OxidePolycrystalline Silicon WaferOxidation Resist LayerInternal Base Region sidewall oxide film polycrystalline silicon (A field) (A) i-oxide film, oxide film formation b (B) Side etching (B) Selective etching <C> Vanoas sputtering (C) Field oxidation (D) Side etching (I) Nitride film removal, acid deposition, ion implantation (J) Oxide film CVD, anisotropic etching (K) Bo! J
SiliicVD, ion implantation (L) Electrode formation (B) Field oxidation Q <C) Poly5i3CVD, photoresist coating (D) Controlled etching (E) Ion implantation (F) Thick oxide film removal, oxidation Conventional technology Figure 3 (Part 2 (G'J nitriding:! A removal acid oxidation ion 2 (I) Electrode formation conventional technology Figure 3 (Part 3)

Claims (1)

[Claims] (1) A step of forming a pattern of a nitride film (4a) and an oxide film (5a) on a semiconductor wafer (10) and using this pattern as a mask to form a field oxide film (8); The side surfaces of the film (4a) and oxide film (5a) are set back to form a nitride film (4) with a reduced area.
b) A step of performing side etching to form an oxide film (5b), and sputtering a silicon target while applying a predetermined bias voltage to the semiconductor wafer (10) to form a polycrystalline silicon film (5b) on the semiconductor wafer (10). 9) until it has a substantially flat surface; and etching the polycrystalline silicon film (9) until the patterned oxide film (5b) is exposed.