JPS58142575A - Preparation of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a high density and high speed bipolar transistor by executing selective oxidation after etching the Si layer with the oxidation resistant film used as the mask and by providing the emitter with the side placed in contact with almost vertically formed isolation oxide film. CONSTITUTION:After the N type epitaxial layer 35 and SiO2 36 on the P type Si substrate having the N<+> type buried layer are vertically etched by the reactive sputtering method using Si3N4 layer as the mask 37, the SiO2 39 and Si3N4 40 are stacked on the N layer 35. These are vertically etched and left at the side. When an insulating isolation film 41 is formed in contact with the buried layer by oxidation, a bird's beak is not generated thanks to the film 40. An opening is provided on the mask 37 and thereby the SiO2 film 42 is formed and the P layer 43 is selectively formed. The surface is covered with the poly-Si 44, the Si3N4 mask 45 is provided and an opening is provided on the film 44, the P layer 43 is etched in the shallow depth, the surface is covered with the SiO2 46, the mask 45 is removed, ion is implanted selectively, and the N emitter 47, collector connecting layer 48, and inactive base 48 are sequentially formed and the electrodes are attached. According to this structure, there is no bird's beak, parasitic capacitance at the side of emitter and a high density and high speed device can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device including an isolation type bipolar transistor.

Bipolar transistors are also becoming denser, similar to MoS transistors. As a method for this purpose, insulation isolation is often used because it can make the size of the transistor extremely small.The so-called LOCO8 method is often used for this insulation isolation, in which an oxidation-resistant film such as Si3H4 is coated only on the part that will become the active region. Are known.

However, this LOCO8 method has the drawback of creating a bird's beak where the oxide film invades the active region. An example of the LOCO8 method with bird's beak is shown in FIG. 1st
In the figure, 1 is a thick oxide film and serves as an isolation region. 2 is a bird's beak extending into the island region like the beak of the island; 03B n+ buried layer; 4 is a p-type substrate; 5 is a collector region; 6 is an oxide film separating the base and collector contact; 7
is an oxide film separating the base 8 and emitter 9.

As shown in FIG. 1, if a bipolar transistor is formed in an island region separated by an insulator 1 where a bird's beak 2 is formed, there will be the following drawbacks.

That is, even if the emitter 9 is formed in contact with the isolation region 1, the side surface of the isolation region 1 is not perpendicular to the substrate 4, so the side surface of the emitter 9 is hardly covered with the oxide film 1. . Therefore, the side surface of the emitter 9 is in direct contact with the base 8, so that the capacitance between the emitter and the base becomes large. Furthermore, since the side surfaces of the emitter 9 are not covered with the oxide film 1, the shape of the emitter 9 which is spread in the lateral direction when it is formed remains unchanged, and as a result, the edge portion of the emitter 9 has an elliptical shape. As a result, the base width at the periphery of the emitter 9 becomes wider than at the center of the emitter 9, resulting in deterioration of the high frequency characteristics, and at the same time, the transistor current increase rate also decreases. As described above, a bipolar transistor in which an emitter is formed in contact with an isolation region where a bird's beak occurs has various drawbacks.

In view of the above-mentioned drawbacks, the present invention provides a method for manufacturing a rectangular conductor device including an isolated bipolar transistor having good high frequency characteristics and no deterioration in current amplification factor.

Hereinafter, the configuration of the present invention will be explained in detail based on examples.

FIG. 2A is a cross-sectional view of the structure of a bipolar transistor formed by the manufacturing method according to the present invention, and FIG. 2A is a plan view thereof. In FIG. 2, 21 is a thick element isolation oxide film, 22 is an end of the oxide film 21, 23 is an n+ buried layer, 2
4 is a p-type substrate, 26 is an n-type collector, 26 is a collector-base isolation oxide film, 27 is a base-emitter isolation oxide film, 28 is a base, 29 is an emitter, and 3o is a contact portion of the collector 25.

As is clear from the figure, the separation membrane 21 has almost no bird's beak and is formed almost vertically.

Therefore, the side surfaces of the emitter 29 are completely covered with the insulator 21, and furthermore, only the flat portion of the bottom surface of the emitter 29 is in contact with the base 28.

Hereinafter, the manufacturing method according to the present invention will be explained based on FIG.

(a) An n-type epitaxial layer 35 is formed on a p-type substrate 34 on which an n+ buried layer 33 is formed. After this, 5io23s on the epitaxial layer ACS.

5i3N437 is sequentially formed. Kokote, b 1023
6 is a film that relieves the stress of 5i3N437.

This is usually called ``Put'' S t 02.

(1)) A resist 38 is coated on the Si3N437 to form an island region, and the resist 38 is used as a mask.
Pad on the part that will become the separation area b * 0236 +b
Etch 13N43y. Furthermore, the epitaxial layer 36 is vertically etched using the same resist mask 38 using a reactive spanometer emitter method. Since the reactive sputter etching method enables anisotropic etching, etching does not proceed in the lateral direction with respect to the resist mask 38, but etching occurs almost perpendicularly to the resist mask 38.

(c) Next, after removing the resist film 38, the exposed epitaxial layer 36 is oxidized to form a second pad b iO2
39 is formed on the side. Furthermore, a second b s is applied to the entire surface.
After forming 3N440, vertical etching was performed using a reactive etching method to form a second pan on only the sides of 35-1.
440 left.

(d) 5i3N436 and 2nd (7) b i3N
Using a 40 as a mask, oxidation is performed to form the insulating isolation film 4.
Form 1. The depth of this separation [41] is formed so as to be in contact with the buried portion 33. In this case, since the oxidation-resistant film 40 (second 5i3N4) is formed on the side surface of the island region 36-1, the oxide film 41 does not penetrate into the island region. Proceed only in the vertical direction of the oxidized epitaxial layer 35. Therefore, the side surface of the isolation oxide film 41 comes into contact with the island region 35-1 on a plane perpendicular to the substrate 34. Furthermore, since there is no lateral intrusion, bird's beaks do not occur.

(e) By selectively removing Si3N437 and performing heat treatment in an oxidizing atmosphere, an oxide film 42 separating the base and collector is formed. The mace 43 is selectively formed by ion implantation using a resist or the like as a mask.

(1) Deposit polycrystalline 5i44 on the entire surface. Next 513
Region 46 where N446 is deposited and partially becomes an emitter
-1 base contact region 45-2. Si3N4 in the region 46-3 which becomes the collector coretact is left.

(g) Polycrystalline 514 using 5t3N445 as a mask
4 is performed, and the base 43 between the base and the emitter is further removed. Next, 5i3N446-1.45-
Selective oxidation is performed using 3 as a mask to form a BE isolation film 46 that separates the emitter and base contacts. This B
Since the E separation film 46 is also formed shallowly, it is almost perpendicular to the substrate 34. Here, 44-1.44-2.44-
3 is polycrystalline Si for emitter, base, and collector contacts, respectively. Next, polycrystalline Si 44-1
．． 44-3 is exposed, and the other surfaces are covered with resist or the like. Thereafter, an impurity such as 8 is ion-implanted into the polycrystalline Si 44-1.44-3, the resist is removed, and heat treatment is performed to form the emitter 47. A collector contact 48 is formed. At this time, the side surface of the emitter 47 is b 102 film 4
6 and 41. Furthermore, since the side faces b 102 films 46 and 41 have a shape perpendicular to the substrate 34, only the bottom surface of the emitter 47 comes into contact with the emitter 47, so that the bottom surface becomes flat. Therefore, the active base formed directly below has a uniform width.

(h) Polycrystalline Si on collector contact 48
After covering 44-3 with at least a resist or the like, an impurity such as boron is ion-implanted at low energy and high dose, followed by annealing to form a highly concentrated inert base 49. At this time, a highly concentrated inert base 49 is formed only in the vicinity directly below the emitter 47, and does not come into direct contact with the bottom and side surfaces of the emitter. In particular, since the isolation oxide film 41 is formed perpendicularly to the substrate 34 without bird's bead on the side surface of the emitter 47 in contact with the thick oxide film 41, a high concentration of boron is applied to the side surface of the emitter 47 and 0 (i) Emitter electrode 50 that does not enter from the bottom. Base electrode 61. A collector electrode 52 is formed.

The bipolar transistor formed by the manufacturing method of the present invention has the following effects.

(1) Even if the emitter is formed in contact with the oxide film, the side surfaces of the isolation oxide film are perpendicular to the substrate.
The sides of the emitter are completely covered with oxide. Therefore, the parasitic capacitance on the emitter side surface is reduced and high-speed operation is possible.

Since the side surfaces of the emitter are vertical, the bottom surface of the emitter has a flat structure. Therefore, Emi”/2
Since a uniform base width is formed over the entire area immediately below, the high frequency characteristics of the transistor are improved. Furthermore, the current amplification factor is also improved.

(3) When a highly doped external base is formed by self-line using ion implantation or the like, the high doped external base does not come into direct contact with the emitter, so the withstand voltage between the emitter and base does not deteriorate.

As described above, the present invention has high industrial value because it can manufacture a semiconductor device including a bipolar transistor suitable for high density and high speed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the structure of a bipolar transistor manufactured by the conventional manufacturing method, FIG. 2(a) is a cross-sectional view of the structure of a bipolar transistor manufactured by the manufacturing method of the present invention, FIG. (-) to (i) are process cross-sectional views showing the manufacturing method according to the present invention. 41--Isolation oxide film, 42--Collector base isolation oxide film, 43--Active base, 46--Emitter base isolation oxide film,
47--------Eminota, 48-----Collector contact, 49--111 inert base. Name of agent: Patent attorney Toshio Nakao and 1 other person @3
I51 @ 3 Figure

Claims (2)

[Claims] (1) A step of forming an oxidation-resistant film on the active region forming portion of the semiconductor layer, a step of etching a predetermined amount of the semiconductor layer other than the active region forming portion, and etching the oxidation-resistant film using the oxidation-resistant film as a mask. A semiconductor device comprising the steps of: oxidizing an exposed portion of a semiconductor layer to form an isolation oxide film substantially perpendicular to the active region forming portion; and forming an emitter so that its angled surface is in contact with the isolation oxide film. Production method. (2) The method of manufacturing a semiconductor device according to claim 1, wherein an oxidation-resistant film is formed on the side surface of the semiconductor layer that has been etched by a predetermined amount, and then the exposed portion of the semiconductor layer is oxidized.