JPH08293503A - Bipolar type semiconductor device and its manufacture - Google Patents

Abstract

PURPOSE: To reduce a width of a depletion layer in an interface between a first conductivity type semiconductor substrate and a second conductivity type epitaxial layer by making a carrier concentration of the second conductivity type epitaxial layer between the first conductivity type semiconductor substrate and a second conductivity type buried impurity layer lower than that of the second conductivity type buried impurity layer. CONSTITUTION: Silane compound and phosphorus compound are decomposed and reacted at a high temperature on a P-type semiconductor substrate 10. An insulation film 103 is formed on an N-type epitaxial layer 102 and an insulation film 103 on a buried diffusion layer formation region is removed. The ion implantation of antimony, for example, is performed for the N-type epitaxial layer 102 by using the insulation film 103 as a mask. The N-type epitaxial layer 102 is thermally diffused and an N-layer buried diffusion layer 104 is formed. A width of a depletion layer formed in an interface of the N-type epitaxial layer 102 whose concentration is lower than that of an N-type buried impurity layer below the N-type buried diffusion layer 104 becomes small in this way.

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semi-bipolar semiconductor device and a method of manufacturing the same, and more particularly to reduction of leak current and prevention of latch-up in a bipolar semiconductor device. 2. Description of the Related Art FIGS. 2A to 2F show an example of a method of manufacturing a bipolar semiconductor device using a conventional technique. For example, the insulating film 203 is formed on the P-type semiconductor substrate 201 by the thermal oxidation method. Next, the insulating pattern 203 is photoetched to remove the region where the embedded pattern is to be formed to expose the semiconductor substrate 201. Next, for example, antimony is ion-implanted into the semiconductor substrate 201 and then thermally diffused to form an N-type buried diffusion layer.
Form 204. This state is shown in Fig. 2 (a). Next, the insulating film 203 is removed, and then the semiconductor substrate
On the 201 and the N type buried diffusion layer 204, a silane compound and a phosphorus compound are thermally decomposed at a high temperature to form an N type epitaxial layer 205 by a chemical vapor deposition method. The buried diffusion layer 204 also grows in the N-type epitaxial layer 205 by heat.
This state is shown in Fig. 2 (b). Next, an insulating film 206 is formed on the N-type epitaxial layer 205 by a thermal oxidation method. Next, the insulating film 206 and the N-type epitaxial layer 205 are formed by photoetching.
Is removed to expose the semiconductor substrate 201, and the element isolation region 207 is removed.
To form. This state is shown in Fig. 2 (c). Next, for insulation on the surface of the element isolation region 207,
The insulating film 208 is formed by the sputtering method. Next, the insulating film 20
8 Polycrystalline polysilicon layer 209 by chemical vapor deposition method
To form. This state is shown in Fig. 2 (d). Next, the insulating film 20 is formed by the photoetching method.
Remove 6. Next, an insulating film 215 having an opening is formed in the area where the guaranteed diffusion layer is to be formed. In the bipolar semiconductor device, the collector electrode of the transistor on the integrated circuit must be taken out from the surface of the semiconductor device, so that the collector current path becomes long, the collector series resistance becomes large, and the operating speed of the transistor becomes slow. Therefore, it is necessary to form the guarantee diffusion layer in a form of connecting the buried layer immediately below the collector region and the collector electrode. Next, using the insulating film 215 as a mask, boron ions are implanted into the N-type epitaxial layer 205 and thermally diffused to form an N-type guaranteed diffusion layer 210. This state is shown in Fig. 2 (e). Next, the insulating film 21 is formed by photoetching.
Remove 5. Next, the insulating film 217 is formed on the N-type epitaxial layer 205 having the base opening. Next, using the insulating film as a mask, boron is used as an N-type epitaxial layer, for example.
Ion implantation into 205. Next, heat diffusion, base diffusion layer
Form 211. Next, similarly to the base diffusion, a new insulating film is formed by photoetching, and an emitter opening is formed in this insulating film. Next, using this insulating film as a mask, for example, phosphorus is ion-implanted into the N-type epitaxial layer 205 and thermally diffused to form an emitter diffusion layer 212. Next, an insulating film 217 having openings is formed in the electrode formation region. Next, for example, aluminum is formed on the entire surface as a metal film for electrodes by a vapor deposition method, and the wiring is patterned by a photoetching method. Next, a protective film (not shown) is formed to complete the bipolar semiconductor device. This state is shown in Fig. 2 (f).
As shown in. In the conventional bipolar semiconductor device, at the interface between the first conductivity type semiconductor substrate and the second conductivity type buried diffusion layer,
A depletion layer having a large width is formed. This is because the concentration of the second conductivity type buried diffusion layer is high, so that a PN junction surface having a large potential barrier is formed at the interface of the first conductivity type semiconductor substrate. The PN junction having a large potential barrier has various adverse effects on the bipolar semiconductor device. In the manufacturing process of the bipolar type semiconductor device and the bi-CMOS type semiconductor device, the parasitic capacitance of the semiconductor substrate, such as NPN junction, PNP junction, capacitor, etc. during the operation of a small current, Also, the generation of leak current becomes a problem. Parasitic capacitance is formed everywhere on the surface of the semiconductor substrate by the wiring conductor-insulating film-semiconductor. This is because the width of the depletion layer formed between the buried impurity layer and the semiconductor substrate is large. Therefore, in order to reduce the width of the depletion layer, it is necessary to lower the carrier concentration, but the buried impurity layer cannot lower the concentration because it lowers the resistance of the collector. Although it is conceivable to increase the depth of the epitaxial layer, this is not desirable in terms of downsizing the semiconductor device. According to the present invention, the width of the depletion layer formed between the buried impurity layer and the semiconductor substrate is reduced without lowering the carrier concentration of the buried impurity layer and without increasing the depth of the epitaxial layer. This reduces the parasitic capacitance and leak current between the semiconductor substrate and the buried impurity layer. As a result, it is an object to manufacture a semiconductor device which operates at high speed and operates at low current. A first conductivity type semiconductor substrate, a second conductivity type first epitaxial layer formed on the first conductivity type semiconductor substrate, and a second conductivity type first epitaxial layer. A second conductivity type buried impurity layer having a higher concentration than the second conductivity type first epitaxial layer formed therein, and a second conductivity formed on the second conductivity type buried impurity layer and the second conductivity type first epitaxial layer; Type second epitaxial layer and a bipolar transistor formed in the second conductivity type second epitaxial layer. A second conductivity type epitaxial layer is provided between the first conductivity type semiconductor substrate and the second conductivity type buried impurity layer, and the second conductivity type epitaxial layer has a concentration higher than that of the second conductivity type buried impurity layer. Is low, the width of the depletion layer generated at the interface between the first conductivity type semiconductor substrate and the second conductivity type epitaxial layer becomes small. As a result, it is possible to provide a bipolar semiconductor device having a small parasitic capacitance and leak current value between the buried impurity layer and the semiconductor substrate. 1 (a) to 1 (g) are sectional views sequentially showing a bipolar semiconductor device shown in the present invention as an example of a manufacturing method. First, for example, a silane compound and a phosphorus compound are decomposed at a high temperature on a P-type semiconductor substrate 101 to form an N-type epitaxial layer 102 by a chemical vapor deposition method. This state is shown in Fig. 1 (a). Next, an insulating film 103 is formed on the N-type epitaxial layer 102 by a thermal oxidation method, and the insulating film 103 on the buried diffusion layer forming region is removed by a photoetching method. Next, using the insulating film 103 as a mask, the N-type epitaxial layer 102 is ion-implanted with, for example, antimony. Next, the N-type epitaxial layer 102 is thermally diffused at about 1200 ° C.
The layer-embedded diffusion layer 104 is formed. This state is shown in Fig. 1 (b). Next, the insulating film 103 is removed. Next, a silane compound and a phosphorus compound are decomposed at a high temperature on the N-type buried diffusion layer 104 and the N-type epitaxial layer 102 to form an N-type epitaxial layer 105 by a chemical vapor deposition method. N
The type buried diffusion layer 104 is grown and formed in the N type epitaxial layer 105 when the N type epitaxial layer 105 is formed. This state is shown in Fig. 1 (c). Next, the insulating film 106 is formed on the entire surface by a thermal oxidation method. Next, the insulating film 106 is formed by photoetching.
, N type epitaxial layer 105, N type epitaxial layer 1
02 is removed to expose the semiconductor substrate 101. The concave portion formed by this photoetching becomes the element isolation region 107. Here, the element isolation region is preferably deep enough to reach the semiconductor substrate 101 below the N-type epitaxial layer 102. If the element isolation region does not reach the semiconductor substrate 101, N
The type epitaxial layer 102 becomes conductive with the adjacent transistor portion. This state is shown in Fig. 1 (d). Next, using the insulating film 106 as a mask, an insulating film 108 is formed on the surface of the element isolation region 107 by the sputtering method. Next, using the insulating film 106 as a mask, the polycrystalline polysilicon film 10 is formed on the element isolation region 107 by the chemical vapor deposition method.
Forming 9 This state is shown in Fig. 1 (e). Next, the insulating film 106 is removed. Next, an insulating film 115 is formed by a thermal oxidation method, and a hole is formed on the N-type guaranteed diffusion layer forming region by a photo etching method. In the bipolar semiconductor device, the collector electrode of the transistor on the integrated circuit must be taken out from the surface of the semiconductor device, so that the collector current path becomes long, the collector series resistance becomes large, and the operating speed of the transistor becomes slow. for that reason,
It is necessary to form a guaranteed diffusion layer in a form of connecting the buried layer directly below the collector region and the collector electrode. Next, the insulating film 115
Is used as a mask, and after ion implantation of boron into the N-type epitaxial layer 105, the N-type epitaxial layer 105 is thermally diffused and reaches the N-type buried diffusion layer 104.
Form 0. This state is shown in Fig. 1 (f). Next, the insulating film 115 is removed. Next, as in the case of forming the N-type guarantee diffusion layer, an insulating film is formed by the thermal oxidation method, and the diffusion layer forming the transistor, for example, the insulating film on the base diffusion layer forming region is removed by the photoetching method. Each time a transistor element is formed, the oxide film on the surface is removed and a new oxide film is formed. After the antimony is ion-implanted into the N-type epitaxial layer 105 by using the insulating film as a mask, the N-type epitaxial layer 105 is heated at about 1200 ° C. to form the P-type diffusion layer 111 serving as a base diffusion layer. Next, similarly to the base diffusion, the insulating film when the base diffusion layer is formed is removed and a new insulating film is formed. Next, the emitter forming region of this insulating film is removed by photoetching, and phosphorus is ion-implanted into the P-type epitaxial layer 105 using the insulating film as a mask. Next, the N-type epitaxial layer 105 is heated at about 1200 ° C. to form the N-type diffusion layer 112 which will become the emitter diffusion layer. Next, the insulating film 117 is formed by the thermal oxidation method, and the electrode formation planned region is removed by the photoetching method. Next, for example, aluminum is formed as an electrode on the entire surface of the insulating film 117 by a vapor deposition method, and a collector, base, and emitter electrodes are formed by a photoetching method. This state is shown in Fig. 1 (g). Next, an interlayer insulating film (not shown), contact hole openings, upper layer wiring patterning, protective film formation and bonding are performed to complete a bipolar semiconductor device. According to this embodiment, under the N-type buried diffusion layer 104, N
Since the N type epitaxial layer 102 having a lower concentration than the type buried impurity layer is formed, the width of the depletion layer formed at the interface between the semiconductor substrate 101 and the N type epitaxial layer 102 becomes small.
Therefore, the parasitic capacitance between the semiconductor substrate and the buried diffusion layer can be reduced, and the leak current can be prevented. As a result, it is possible to prevent a problem such as a latch-up of a bipolar semiconductor device, which has been a conventional problem. In this embodiment, the P-type semiconductor substrate is used to describe the P-type bipolar semiconductor device, but an N-type bipolar semiconductor device using the N-type semiconductor substrate is also shown in this embodiment. It is possible to manufacture by the technology mentioned above. Although a bipolar transistor is used in this embodiment, a field effect semiconductor device can also be used. As a specific method, for example, a depletion layer is formed at the boundary between the source / drain diffusion layer and the semiconductor substrate. Therefore, a low-concentration diffusion layer having the same carrier as the source / drain diffusion layer is formed between the source / drain diffusion layer and the semiconductor substrate. As a result, the width of the depletion layer at the interface can be reduced. According to the present invention, a second conductivity type epitaxial layer is provided between a first conductivity type semiconductor substrate and a second conductivity type buried impurity layer, and the second conductivity type epitaxial layer is Since the concentration is lower than that of the 2-buried impurity layer, the width of the depletion layer generated at the interface between the first conductivity type semiconductor substrate and the second conductivity type epitaxial layer becomes smaller. As a result, it is possible to provide a bipolar semiconductor device having a small parasitic capacitance and leak current value between the buried impurity layer and the semiconductor substrate.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross section showing a method of manufacturing a bipolar semiconductor device according to an embodiment of the present invention as an example. FIG. 2 is a cross-sectional view showing a conventional method for manufacturing a bipolar semiconductor device as an example. [Explanation of reference numerals] 101, 201 Semiconductor substrates 102, 105, 205 Epitaxial layers 103, 203 Insulating films 104, 204 Buried diffusion layers 106, 206 Insulating films 107, 207 Element isolation 108, 208 Insulating films 109, 209 Polycrystalline polysilicon 110, 210 Guaranteed diffusion layer 111, 211 Base diffusion layer 112, 212 Emitter diffusion layer 113, 213 Wiring 115, 215 Insulation film 117, 217 Insulation film

Claims (1)

Claims: 1. A semiconductor substrate of the first conductivity type, a first epitaxial layer of the second conductivity type formed on the semiconductor substrate of the first conductivity type, and a first epitaxial film of the second conductivity type. A second conductivity type buried impurity layer having a higher concentration than the second conductivity type first epitaxial layer formed in the layer, and formed on the second conductivity type buried impurity layer and the second conductivity type first epitaxial layer. And a bipolar transistor formed in the second epitaxial layer of the second conductivity type. 2. The bipolar transistor formed in the second epitaxial layer of the second conductivity type is isolated by a recess, and the recess reaches the semiconductor substrate of the first conductivity type. The semiconductor device according to claim 1. 3. A step of forming a second conductive type first epitaxial layer on a first conductive type semiconductor substrate, and a second conductive type buried impurity layer in the second conductive type first epitaxial layer. And a step of forming a second conductive type second epitaxial layer on the second conductive type buried impurity layer and the second conductive type first epitaxial layer, and the second conductive type second epitaxial layer And a step of forming a bipolar transistor therein. 4. The method for manufacturing a bipolar semiconductor device according to claim 3, wherein the transistor is suspended by element isolation, and the element isolation reaches the first conductivity type semiconductor substrate.