JPH03295277A - Semiconductor device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, particularly a semiconductor device having a Zener diode in a part thereof, and relates to a technique that is effective when applied to a semiconductor device that drives a display, for example. .

[Conventional technology]

As one of the semiconductor devices, for example, Japanese Patent Laid-Open No. 51-781
As described in No. 81, there is a semiconductor device in which a transistor, a Zener diode (constant voltage diode) as a protection element, and a damper diode are monolithically formed.

This semiconductor device has a structure in which a Zener diode is provided between the base (B) and collector (C) of the transistor, and a damper diode is provided between the collector and emitter (E). A Zener diode 3° transistor 4. It has a structure including a diode (damper diode) 5 and an n←-shaped guard ring 6 around it. A plurality of p-type layers 10 are provided in the surface layer part of the epitaxial layer 2, and a pair of adjacent p-type layers 1
An n1 type layer 11 is provided between 0 and 0, and a p+ type layer 12 is formed on the surface of this n+ type layer 11, thereby forming a Zener diode 3. Further, a P-type layer 10 (the second P-type layer from the left in the figure) in contact with the n-type layer 11 and the P-type layer 12 of the Zener diode 3 constitutes a base region 15 of the transistor 4. In the center of the surface layer of this base region 15, an emitter region 16 made of an n++ type layer is formed. Therefore, the epitaxial layer 2 and the substrate 1 become the collector region 17, and although not shown, a collector electrode is provided on the lower surface of the substrate 1.

The damper diode 5 is formed by the n-type epitaxial layer 2 and one p-type layer 10. Further, a p-type layer 20 for an ohmink contact is formed on the surface layer of the p-type layer 10. Note that in this figure, an insulating film wiring layer, a passivation film, etc. are omitted.

Furthermore, the Zener diode formed in the epitaxial layer 2 is formed by ion implantation or thermal diffusion.

[Problem to be solved by the invention]

As described above, the conventional Zener diode is formed by stacking different impurity layers on the epitaxial layer 2 by ion implantation or thermal diffusion. However, the inventors have found that with such a structure, it is difficult to maintain a constant Zener breakdown voltage.

In other words, when an impurity layer is formed by ion implantation or thermal diffusion, the impurity profile of each impurity layer is as follows: the horizontal axis in Figure 10 is the diffusion depth (μm), and the vertical axis is the impurity concentration (cm-'). As shown in the graph, the impurity profiles of the n-type layer 11 and the p"-type layer 12 have a slope.

In manufacturing, the emitter region of the transistor 4 is formed after the process of forming the Zener diode 3, and the current amplification factor hF of the transistor is determined by controlling the diffusion time for forming the emitter region. Therefore, when forming this emitter region, the p
In the + type layer 12, the impurity diffusion further spreads. Therefore, at the end of the emic diffusion, the impurity profile of the p1 type layer 12 changes as shown by the dotted line in the graph of FIG. As a result, the pn junction changes from A to B, and since there is a slope in the impurity profile of the n-domain layer 11, the impurity concentration of the pn junction also changes, becoming lower from N to N. Therefore, if the specifications change and the current amplification factor hFE of the transistor is changed, the Zener breakdown voltage will also change.

An object of the present invention is to provide a semiconductor device in which the Zener breakdown voltage of a monolithically formed Zener diode can always be kept constant.

The above and other objects and novel features of the present invention include:
It will become clear from the description of this specification and the accompanying drawings.

(Means for Solving the Problems) A brief overview of typical inventions disclosed in this application is as follows.

That is, in manufacturing the semiconductor device in which the transistor, Zener diode, and damper diode of the present invention are monolithically formed, epitaxial growth is selectively performed on the surface layer of the epitaxial layer so that the impurity concentration is constant at each depth. After forming the 10-type layer, a Zener diode is formed by forming an n-10 layer on the surface of the n4 layer by diffusion, and then an emitter region of a transistor is formed.

[Effect]

According to the above means, the semiconductor device in which the transistor Zener diode and damper diode of the present invention are formed into a monolink can be manufactured by selectively epitaxially growing an n-type semiconductor device in which the impurity concentration is uniform at each depth. Since the structure has an n-type layer formed on the surface layer, when forming the emitter region to determine the TFT amplification factor of the transistor, diffusion of the p3-type layer progresses, and the position of the p-n junction increases. Even if the (depth) changes, the impurity concentration in the n-type layer is constant at each depth, so the Zener breakdown voltage is always constant.

Therefore, both the current amplification factor hyt and the Zener breakdown voltage can be controlled with high precision. This also makes it possible to support a wide range of current amplification factors hrt for transistors, and by selecting processing conditions during manufacturing, semiconductors that always have a constant Zener withstand voltage and a desired current amplification factor 2. You will be able to obtain the device.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the main parts of a semiconductor device according to an embodiment of the present invention, FIG. 2 is an equivalent circuit diagram, FIG. 3 is a graph showing the impurity profile of a Zener diode, and FIG. A schematic circuit diagram showing an example of a circuit in which the semiconductor device of the invention is used, FIGS. FIG. 6 is a cross-sectional view of a substrate on which a p-type layer is selectively formed in the base region, and FIG. 7 is a cross-sectional view of a substrate on which a p-type layer is selectively formed. 8 are cross-sectional views of a substrate on which an n←-type layer such as an emitter region is selectively formed.

A semiconductor device in which a transistor, a Zener diode, and a damper diode of this embodiment are monolithically formed has a transistor 4 as shown in the equivalent circuit of FIG.
A Zener diode 3 is installed between the base (B) and collector (C) of the device, and a damper diode 5 is installed between the emitter (E) and collector, resulting in a structure as shown in FIG. Note that in FIG. 1, an insulating film, a wiring layer, a passivation film, etc. are omitted.

As shown in FIG. 1, this semiconductor device 30 includes a Zener diode 3. Transistor 4. It has a structure including a diode (damper diode) 5 and an n-> type guard ring 6 around it. A plurality of p-type layers 10 are provided in the surface layer part of the epitaxial layer 2, and a pair of adjacent p-type layers 1
An n+ type layer 11 is provided between 0 and 0, and a P1 type layer 12 is formed on the surface of this n+ type layer 11, thereby forming a Zener diode 3. In addition, a P-type layer 10 (two from the left in the figure
The third P-type layer) constitutes the base region 15 of the transistor 4.

An emitter region 16 made of an n'' type layer is formed in the center of the surface layer of the base region 15. Therefore, the epitaxial layer 2 and the substrate 1 serve as a collector region 17, and although not shown, the emitter region 16 is made of an n'' type layer. A collector electrode will be provided on the bottom surface.

The damper diode 5 is formed by the n-type epitaxial layer 2 and one p-type layer 10. Further, a p-type layer 20 for ohmic contact is formed on the surface layer of the p-type layer 10.

Incidentally, this is one of the features of the present invention, and the n-type layer 11 of the Zener diode 3 is composed of a selectively formed epitaxial layer. Further, as shown in FIG. 3, this epitaxial layer is formed so that the impurity concentration is substantially constant over the entire NA and its depth. As a result, in manufacturing this semiconductor device 30, heat is applied again after the p+ type layer 12 is formed, and the diffusion front of the p+ type 7112 changes from A (DA) to C (D
.

), the impurity concentration of the n-type layer 11 is uniform in the depth direction, so the impurity concentration at the pn junction is always constant at NA. Therefore, in order to control the current amplification factor hFE of the transistor,
Even if the diffusion time of the p-type 12 layer 12 is changed, the Zener breakdown voltage does not change, and the characteristics of the Zener diode are stabilized.

Next, a method for manufacturing such a semiconductor device 30 will be explained.

In manufacturing the semiconductor device 30, as shown in FIG. 5, a substrate 1 having an epitaxial layer 2 on its main surface is prepared. This substrate 1 and epitaxial layer 2 are both n
It has a conductivity type, and the impurity concentration is 1 when the substrate l is
0"cm-", epitaxial layer 2 is about 10"cm-
'It has become about. The thickness of the epitaxial layer 2 is about 10 to 15 μm, and the total thickness of the substrate 1 and epitaxial layer 2 is about 160 μm in the finished product, and about 350 μm when manufactured. Note that the term "substrate" refers to the substrate 1 itself or the substrate 1 having the epitaxial layer 2.

In such a substrate, an n+ type layer 11 for forming a Zener diode is first selectively formed on the surface layer of the substrate. That is, after an insulating film 21 made of a SiO□ film or the like is provided over the entire main surface of the substrate, this insulating film 21 is partially removed and patterned by common photolithography. Thereafter, etching is performed using the patterned insulating film 21 as a mask, and a recess with a depth of about 1 μm is provided in the surface layer of the epitaxial layer N2. Next, in this depression, an n-shaped layer 1 is formed so as to close the depression.
1 is formed by an epitaxial growth method such as MOCVD (metal organic pyrolysis). During this epitaxial growth, as an impurity, for example, phosphorus (P) is added at a desired concentration, resulting in the formation of the n♦-type layer 11 having an impurity concentration of about 1017c+ff-'.

Next, as shown in FIG. 6, an insulating film 22 with a new pattern is formed on the main surface side of the substrate 1, and impurities such as boron are implanted into predetermined locations using this insulating film 22 as a mask. A plurality of p-type layers 10 are formed by thermal diffusion (annealing). This p-type layer 10 has a depth of about 3 pm. The insulating film 22 is formed by patterning a newly provided insulating film after removing the insulating film 21 or an insulating film provided overlying the insulating film 21. These p-type Iw10 are connected to the base region 15 of the transistor 40 and the P type of the damper diode 5.
This becomes a shadow area, etc. Further, the substrate 1 and the epitaxial layer 2 become the collector region 17 of the transistor 4.

Next, as shown in FIG. 7, an insulating film 23 is partially formed on the main surface side of the substrate 1 in the same manner as described above, and a p+ type layer, which is the upper layer of the Zener diode 3, is formed by ion implantation and thermal diffusion. 12 and a p+ type layer 20 for contacting the damper diode 5 are formed. This p
The +-type layer 12 and the p-type layer 20 are formed to a depth of about 0.6 μm.

Next, as shown in FIG. 8, an insulating film 24 is partially formed on the main surface side of the substrate 1 in the same manner as described above, and the impurity concentration is reduced to 1019 to 1 by ion implantation and thermal diffusion.
An n+♦-shaped layer having a thickness of about 0t0cm-' is formed. This n'' type layer constitutes an emitter region 16 provided on a part of the surface layer of the base region 15 and a guard ring 6 provided on the periphery of the surface layer of the substrate 1.

Thereafter, although not particularly illustrated, electrodes for each element are provided on the main surface side of the substrate 1, and a collector ti is provided on the lower surface side of the substrate 1.

Note that, prior to forming the collector electrode, the lower surface of the substrate 1 is etched or polished to adjust the thickness.

In this way, a semiconductor device ff30 having an equivalent circuit as shown in FIG. 2 is manufactured.

Such a semiconductor device 30 is used by being incorporated into a circuit as shown in FIG. 4, for example. This circuit is a display drive circuit composed of light emitting diodes (LEDs), and is a drive circuit for a display made up of light emitting diodes (LEDs).
) The output of the CMO 531 is connected to the it pole via the resistor 32 to drive the LED. Note that 33 shown in the figure is a ground.

According to such an embodiment, the following effects can be obtained.

(1) In the semiconductor device of the present invention, since the Zener diode is formed of an epitaxial layer with a uniform impurity concentration in the depth direction and an impurity layer provided in the surface layer of this epitaxial layer, Even if the impurity layer in the surface layer of the epitaxial layer during manufacturing is diffused during thermal diffusion to determine the current amplification factor hI of the transistor, the impurity concentration in the pn junction of the Zener diode does not change and is always maintained constant. Effects can be obtained.

(2) According to the above (1), according to the present invention, a semiconductor device with stable Zener breakdown voltage can be manufactured with good reproducibility.

(3) According to the above (1), according to the present invention, even if a semiconductor device having a desired 1!1 current amplification factor hFE is manufactured by controlling the emitter diffusion of a transistor, the semiconductor device always has a constant Zener breakdown voltage. The effect is that the device can be obtained.

(4) According to the above (3), according to the present invention, the current amplification factor hF corresponding to each design specification can be obtained without reducing the Zener breakdown voltage of the Zener diode that protects the transistor.
The effect is that a semiconductor device having E can be manufactured.

(5) The semiconductor device of the present invention has a transistor base
Since the Zener diode is monolithically formed between the collector and the damper diode between the emitter and collector, the number of parts can be reduced and the device can be made compact.

(6) According to the above (1) to (5), according to the present invention, a semiconductor device having a constant Zener breakdown voltage can be reproducibly produced regardless of the length of the processing time for controlling the current amplification factor hyt of the transistor. Can be manufactured well. Therefore, according to the present invention, it is possible to provide a wide range of products (grade products) that maintain a constant Zener breakdown voltage and have different current amplification factors hrt.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the above Examples and can be modified in various ways without departing from the gist thereof. For example, even if the epitaxial layer that is selectively provided is provided after forming the impurity layer that will become the base region of the transistor, the same effect as in the embodiment described above can be obtained. Furthermore, fluctuations in the Zener breakdown voltage can be suppressed by forming the n-doped layer by ion implantation and thermal diffusion, and by increasing the depth of the impurity layer and flattening the impurity concentration gradient in the depth direction. You can also do it.

The above explanation has mainly been about the application of the invention made by the present inventor to the manufacturing technology of semiconductor devices monolithically incorporating protection diodes, which is the background field of application, but the invention is not limited thereto. .

The present invention can be applied to manufacturing techniques for semiconductor devices having at least two or more different types of impurity layers.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

In the semiconductor device of the present invention, the Zener diode is formed by providing a diffusion layer by diffusing an impurity of another conductivity type into the surface layer of an impurity layer selectively formed by epitaxial growth. Since the impurity concentration of the pn junction does not change depending on the layer depth,
Zener breakdown voltage is always constant. Further, according to the present invention, it is possible to provide a wide range of products with constant Zener breakdown voltage and different current amplification factors.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the main parts of a semiconductor device according to an embodiment of the present invention, Fig. 2 is an equivalent circuit diagram, Fig. 3 is a graph showing the impurity profile of a Zener diode, and Fig. 4 is the same. FIG. 5 is a schematic circuit diagram showing an example of a circuit in which the semiconductor device of the present invention is used; FIG. Figure 6 is a cross-sectional view of a substrate on which a p-type layer is selectively formed, such as in the Haas area, Figure 7 is a cross-sectional view of a substrate on which a p◆-type layer is selectively formed, and Figure 8 is a cross-sectional view of a substrate on which a p-type layer is selectively formed, such as the emitter area. FIG. 9 is a schematic cross-sectional view showing the main parts of a conventional semiconductor device; FIG. 10 is a graph showing the impurity profile of a Zener diode. . DESCRIPTION OF SYMBOLS 1... Substrate, 2... Epitaxial layer, 3... Pan Ener diode, 4... Transistor, 5... Damper diode, 6... Guard ring, 10...
P type layer, 11...n4- type layer, 12...P+ type layer,
15...Base region, 16...Emitter region, 17
... Collector region, 20 ... P+ type layer, 21 to 23
...Insulating film, 30...Semiconductor device, 31...CM
O5, 32...Resistance, 33...Figure 11-? L1 cedar 1 12.20-7" cedar 1 1-substrate 10-P Akira 1 2-processing degree 9 x 1 shi 1 11-7L" type layer 12-r cedar 1

Claims (1)

[Claims] 1. A semiconductor device in which at least a transistor and a Zener diode incorporated between the base and collector of the transistor are monolithically formed on the main surface of a substrate made of a semiconductor, the Zener diode being A semiconductor device characterized in that a pn junction is formed by a selective epitaxial layer selectively provided on a main surface of a substrate and an impurity layer formed on a surface layer of the selective epitaxial layer. 2. The semiconductor device according to claim 1, wherein the impurity concentration of the selective epitaxial layer is uniform at each depth.