JPH0287528A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To increase breakdown strength between an emitter and a base by a method wherein impurity is introduced for a base electrode in the manner in which high concentration impurity is introduced into a positioning part except a contact positioning part of the base electrode with an active region and its adjacent positioning part, through thermal diffusion, and low concentration impurity is introduced into a contact positioning part of the base electrode and its adjacent positioning part by ion implantation. CONSTITUTION:Boron is introduced into polysilicon 8 turning a base electrode, in the following manner. Deposition and ion implantation are used for a positioning part except a contact positioning part of the base electrode with an active region 3 and its adjacent positioning part. Ion implantation only is used for a contact positioning part of the base electrode with the active region 3 and its adjacent positioning part. The impurity concentration of the contact positioning part of the base electrode with the active region 3 and its adjacent positioning part is made middle. The impurity concentration of the other regions of the base electrode is made high. As a result, boron diffusion form the polysilicon 6 turning to the base electrode to the active region 3 becomes shallow, so that the concentration of a graft base 11 can be low as compared with the conventional ones, and at the same time, breakdown strength between an emitter and a base can be increased.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a technique that is effective when applied to a method of manufacturing a semiconductor device, such as forming a graft base in an active region by spreading from a base electrode. It relates to effective technology that can be used to

[Conventional technology] With the demand for higher speed and higher density of ultra-high-speed bipolar LSIs, in recent years, only the most important active region for transistor operation is formed in a single crystal substrate, and the reverse operation speed is reduced to the forward direction. S I CO5 (S
ideal 13ase ContactSt
structure) has been proposed.

Regarding the manufacturing process of this 5ICO8, for example, see "Ultra High Speed Bipolar Device" published by Baifukan Co., Ltd. on November 15, 1985, pages 272 to 2 of the first edition.
It is described on page 74.

An outline of an example of the manufacturing process of 5rcos will be explained as follows.

For example, when using a P-type silicon substrate as a semiconductor substrate, first, a 0+ type buried layer is formed on one main surface of the p-type silicon substrate, and an n-type epitaxial layer and 5JO2, 5JO2, 513N4, S i O2 3
Layer insulating films are sequentially formed.

Next, etching is performed so that a portion that will become the active region (device region) remains, a Si film and a Si, N film are formed on the side surfaces of the remaining convex active region, and thermal oxidation is performed to form a non-conductive layer. Form a thick field oxide in the active area. Thereafter, the Si and N4/S i O2 films on the side surfaces are removed, polysilicon is deposited, and boron is implanted as a p-type impurity, for example, to the extent of lXIO1'/C1112, and annealing is performed to form a p-type base. In addition to lowering the resistance, a graft base is formed in the active region in contact with the base electrode by diffusion of p-type impurities from the base electrode. After oxidizing the polysilicon surface, a p-type impurity is implanted and annealing is performed to form an intrinsic base, and an n-type impurity is implanted into the emitter region and annealing is performed to make the emitter region n-type. Thereafter, a contact I/window is opened in the base portion to form an electrode.

[Problems to be Solved by the Invention] However, the method for manufacturing a 5rcos type semiconductor device as described above has the following problems.

That is, for example, in order to prevent noise in linear 5ICO8, it is necessary to lower the resistance of the base electrode, but in that case, boron is used at a high concentration (I
O"/■28 degrees). As a result, the time required for the drive is very long, and therefore,
A problem arises in that the throughput becomes extremely poor and mass production is difficult.

In addition, when ions are implanted at a high concentration to lower the resistance of the base electrode as described above, the depth of the base (graph 1) formed by impurity diffusion from the base electrode increases, and the withstand voltage between the emitter and base increases. There is a problem in that the value decreases.

On the other hand, when trying to improve the breakdown voltage between the emitter and the base, the amount of impurity implanted into the base electrode can be reduced, which improves throughput compared to the above,5 but on the other hand, the resistance of the base electrode increases. It ends up.

It is also possible to introduce impurities into the base electrode by thermal diffusion, but in this case, the throughput is improved compared to ion implantation, but other problems are not solved. Furthermore, in this case, there is also the disadvantage that the diffusion depth of the graft base cannot be controlled more accurately than in the case of ion implantation.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a method for manufacturing a semiconductor device that can simultaneously optimize the resistance value of the base electrode, mass-produce semiconductor devices, and improve the breakdown voltage between the emitter and base. The purpose is

The above-mentioned and other objects and novel features of the present invention will become clear from the description in the Unknown aI book and the accompanying drawings.

[Means for Solving the Problems] Representative inventions disclosed in this application will be summarized as follows.

That is, a step of introducing an impurity by thermal diffusion into a portion of the base electrode other than a contact portion with the active region and a portion thereof; and a step of ion-implanting impurities into at least a contact portion of the base electrode with the active region and a portion adjacent thereto. and a step of introducing, by both steps,
The impurity concentration of the contact portion of the base electrode with the planar active region and the vicinity thereof is lower than the impurity concentration of the portion other than the contact portion of the base electrode with the active region and the vicinity thereof, and The graft base is formed in the active region by solid phase-solid phase diffusion of impurities from the base electrode after ion implantation.

[Operation] According to the above-mentioned means, the introduction of the impurity into the base' quasi-electrode is thermally expanded to regions other than the contact region with the active region of the base electrode and its vicinity. In high concentration through Il,
Since the base electrode is implanted at a low concentration into at least the contact area 1 with the active region and its vicinity, the resistance value of the base electrode is maintained at an appropriate level, and the ions from the base electrode are Due to the effect that the craft base formed by impurity diffusion can be formed shallowly, it is possible to optimize the resistance value of the base electrode and to improve the breakdown voltage between the emitter and the base.

Furthermore, since thermal diffusion, which has a relatively fast impurity introduction rate, is used to introduce impurities into areas where the impurity concentration must be increased, the overall impurity introduction time is shortened.

Throughput 1 to 1 on a semiconductor device manufacturing line can be improved.

[Example] Hereinafter, an example of the method for manufacturing a semiconductor device according to the present invention will be described with reference to the drawings.

Figure 1 (F) shows the so-called 5IC obtained by applying this example.
It represents an O3 type semiconductor device.

The manufacturing process of this 5ICO5 type semiconductor device is shown in Figure 1 (A
) to FIG. 1(E).

For example, when using a p-type silicon substrate as a semiconductor substrate, first, a SiO2 film is formed on the p-type silicon substrate 1 by thermal oxidation film, and a buried diffusion layer is placed at an appropriate position on this SiO2 film. A patterned hole is opened, and using this Si◯ film as a mask, an n-type impurity such as arsenic is introduced by, for example, a deposition method to partially form an n1-type buried layer 2. Next, the above Sj was used as a mask for embedding.

2 films are removed, and n.
A shaped epitaxial layer 3 is grown. Then, a SiO2 film 4 is formed on the surface by a thermal oxidation method, and a SiO2 film 4 is formed by a CVD method.
, N4 film 5 and 5102 film 6 are sequentially laminated. after that,
The third layer'#A edge film 6,5.4 is selectively removed, and the epitaxial layer 13 in the inactive region is removed by photoetching using the remaining three layer insulating film as a mask. As a result, the active region is divided by the grooves and elements are isolated, as shown in FIG. 1(A).

Next, after thermally oxidizing the surface, Si3N is formed by CVD method.
4 film is formed again, and the 5iJN41 pattern on the flat part is removed by etching. Then, thermal oxidation is performed using the remaining Si, N, and films exposed on the side surfaces of the active region as a mask.
A thick field oxide film (isolation film) 7 is formed in the inactive region. Next, the Si, N, and films adhering to the side surfaces of the active region are removed, and polysilicon 8 is deposited by CVD, followed by dry etching using a gas such as CF, etc., as shown in FIG. As shown in B), the surface of polysilicon 8 is made flat. This polysilicon 8 will be used as a future base electrode.

The following steps are the characteristics of the present invention. First, a Si, N4 film 9 is deposited on the entire surface by, for example, the CVD method, and then patterned, as shown in FIG. 1(C).
As shown in FIG. 2, the Si3N4 film 9 is left only on the upper part of the active region, the contact region of polysilicon 8 with the active region, and the vicinity thereof. Next, a material containing a p-type impurity, such as BSG (boron glass) 15, is deposited on the entire surface by, for example, a CVD method.
By thermal diffusion at a temperature of around 900°C, boron is concentrated at a high concentration in areas other than the contact area with the active region of polysilicon 8 and its vicinity, that is, areas not covered by the S1 and N4 films 9. Introduce.

After removing the B5G15 and Si3N film 9, the entire surface of the polysilicon 8 is doped with p-type impurities, for example, as shown in FIG.

Boron is implanted at a rate of about I x 10" to 5 x 10"/cm2, and annealing is performed to complete the reduction of the resistance of the polysilicon 9, that is, the base electrode, and solid phase-solid phase diffusion of boron from the base electrode by heat treatment , graph 1-base 1 in the active region contacting the base electrode.
form 1.

Here, the concentration of boron in the base electrode other than the contact area with the active region 11 and its vicinity determined by this thermal diffusion, ion implantation, and annealing is a value suitable for lowering the resistance of the base electrode, e.g. , lXl0”/
It is about σ2. Furthermore, the amount of boron implanted is a considerably smaller value than in the past.

After that, the Si○2 film 6. Si, N, film 5
are sequentially removed, and the surface of the polysilicon 8 that will become the base electrode is oxidized to form an oxide film 10, resulting in the state shown in FIG. After performing annealing to form the intrinsic base 12 and removing the SiO2 film 4, polysilicon 13 is deposited as shown in FIG. An n-type emitter region 16 is formed by implanting and annealing, and then an aluminum electrode 14 is formed on the polysilicon 13.

Contact lenses with an opening in the base! - Aluminum electrodes 15 are formed on each window, and a 5rcos type semiconductor device according to this embodiment is formed.

As a result, according to the method of manufacturing a semiconductor device of the above embodiment, the following effects can be obtained.

In other words, boron is introduced into the polysilicon 8 that will become the base electrode by deposition and ion implantation in areas other than the contact area with the active area of the base electrode and its vicinity. Only ion implantation is performed on the contact 11 region and its neighboring regions, so that the impurity concentration in the contact region with the active region of the base electrode and its neighboring regions is medium concentration, and the impurity concentration in other regions of the base electrode is reduced to a medium concentration. Since the concentration is set to be high, it is possible to maintain the resistance value of a 1m base electrode at the appropriate level as before, and the amount of boron implanted can be reduced compared to the conventional method, which reduces the implantation time. The graph becomes 1/2 to 1/10 that of the conventional one, making it possible to mass-produce semiconductor devices, and the diffusion of boron from the polysilicon 8, which forms the base'M pole, to the active region becomes shallower. The concentration of the base 11 can be lowered compared to the conventional one, and it is possible to simultaneously improve the breakdown voltage between the emitter, ivy, and base.

Although the inventions made by each of the present inventions have been specifically explained based on examples, it goes without saying that the present invention is not limited to the above-mentioned examples, and can be modified in various ways without departing from the gist thereof. Nor.

For example, in the above embodiment, boron is implanted into the entire base electrode after thermally diffusing the boron to areas other than the contact area with the active region of the base electrode and its vicinity, but the order can be reversed. After implanting 5 boron into the entire polysilicon 8 that will become the base electrode,
Boron may also be thermally diffused to other parts. Note that there are no restrictions on the method of thermal diffusion.

Further, in the above embodiment, boron is implanted into the polysilicon 8 that will become the base electrode, but the contact with the active region of the base electrode 1 is The boron implantation may be performed only in one area and its vicinity.The point is that the amount of boron implanted into the contact area of the base electrode with the active region and its vicinity is adjusted to the area where the base electrode contacts the active region and its vicinity. It is sufficient if the amount of boron introduced is smaller than that of other parts, and the amount of implantation can be made smaller than that of the conventional method.

[Effects of the Invention] The effects obtained by typical inventions disclosed in this application are briefly explained below.

That is, a step of introducing impurities by thermal diffusion into a region other than the contact region of the base electrode with the active region and its vicinity, and a step of introducing impurity ions into at least the contact region of the base electrode with the active region and its vicinity. and a step of implanting the impurity concentration in the contact portion of the base electrode with the active region and its vicinity. The graft base is formed in the active region by solid phase-solid phase diffusion of the impurity from the base electrode after the ion implantation, so that the concentration of impurities is lower than that of other regions. As the resistance value can be optimized and the amount of impurity ions implanted can be reduced, mass production of semiconductor devices can be achieved3.Furthermore, the diffusion of impurities from the electrodes to the active region becomes shallower, and as a result, the graft-based It is possible to lower the concentration and improve the breakdown voltage between the emitter and the base.

[Brief explanation of the drawing]

FIG. 1(A) to FIG. 1(F) are process diagrams of an embodiment of a method for manufacturing a semiconductor device according to the present invention.

Claims (1)

[Claims] 1. In reducing the resistance of the base electrode by introducing impurities and forming a graft base in the active region in contact with the base electrode by diffusion of the impurity from the base electrode, a step of introducing impurities into a portion of the base electrode other than the contact portion with the active region and its vicinity by thermal diffusion; and a step of introducing impurities into at least the contact portion of the base electrode with the active region and its vicinity by ion implantation. and introducing the impurity concentration of the base electrode at the contact portion with the active region and the vicinity thereof, and by both steps, the impurity concentration of the base electrode at the contact portion with the active region and the vicinity thereof is reduced. A method for manufacturing a semiconductor device, characterized in that the graft base is formed in the active region by solid phase-solid phase diffusion of the impurity from the base electrode after the ion implantation, with the concentration being lower than the impurity concentration. . 2. After thermally diffusing the impurity to a region other than the contact region of the base electrode with the active region and its vicinity, ion implantation of the impurity is further carried out into at least the contact region of the base electrode with the active region and its vicinity. 2. The method of manufacturing a semiconductor device according to claim 1, wherein: 3. The method of manufacturing a semiconductor device according to claim 1 or 2, wherein the ion implantation of the impurity into the base electrode is performed on the entire base electrode.