JPH04373179A - Voltage regulator diode - Google Patents

Abstract

PURPOSE:To prevent irregularity of breakdown voltage of a voltage regulator diode in a semiconductor wafer surface, and improve yield. CONSTITUTION:The title diode has a first semiconductor layer having the same conductivity type as a semiconductor substrate 1, on the semiconductor substrate having a conductivity type, and a second semiconductor layer 4 having a conductivity type opposite to the substrate 1, on the first semiconductor layer, and the breakdown voltage is obtained by a PN junction of the first and the second semiconductor layers. The breakdown voltage is determined by the impurity concentration of the first semiconductor layer 2 formed by a deposition method. Almost uniform distribution of impurity concentration can be obtained in the semiconductor wafer surface. Thereby irregularity of resistivity can be restrained and irregularity of breakdown voltage is reduced.

Description

[Detailed description of the invention] [Industrial application field]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a constant voltage diode, and more particularly to a constant voltage diode that prevents deterioration in diode quality due to variations in breakdown voltage within the plane of a semiconductor wafer.

0002

2. Description of the Related Art FIG. 3 is a longitudinal sectional view of a conventionally known constant voltage diode. After the N-type semiconductor substrate 21 is subjected to high-temperature treatment to form a silicon thermal oxide film 23 on the entire surface of the N-type semiconductor substrate 21, diffusion windows are selectively formed using photoresist. Next, silicon doped with boron is grown over the entire surface of the N-type substrate 21, and then the peripheral portion is etched by plasma processing to obtain a P+-type semiconductor layer 22. At this time, the portion in contact with the semiconductor substrate 21 within the diffusion window is configured as a single crystal layer. After that, DHD (do
An Ag bump electrode 25 is formed by plating on the P+ type semiconductor layer 22 as an electrode for sealing in the container (heatsink diode), and an Ag electrode 26 is further formed on the back surface of the N type semiconductor substrate 21.

The voltage regulator diodes manufactured in this way mainly have a breakdown voltage of 7 V or more, and are designed to improve the current-voltage characteristics at breakdown (harden the breakdown waveform in the Zener breakdown region). It is something. The breakdown voltage of this constant voltage diode depends on the concentration gradient of the P+N junction formed by the N-type semiconductor substrate 21 and the P+-type semiconductor layer 22.

0004

[Problems to be Solved by the Invention] In the conventional voltage regulator diode described above, the factor that determines the breakdown voltage is P+N
It depends on the concentration gradient of the junction, which is determined by the impurity concentration of the N-type semiconductor substrate 21 on the low impurity concentration side. However, when manufacturing normal semiconductor substrates, for example, a phosphorus-doped semiconductor wafer with a resistivity of 0.005 Ωcm (the breakdown voltage in this case is approximately 5V) is processed into a 3-inch diameter semiconductor wafer using the CZ method. When pulled up, the variation in impurity concentration within the semiconductor wafer surface is approximately 6 to 15%.
The resistivity depending on the impurity concentration has a distribution such that it is high at the periphery of the semiconductor wafer and low at the center. This variation in resistivity causes variation in the breakdown voltage of each voltage regulator diode formed at each location within the surface of the semiconductor wafer, reducing the yield for obtaining a voltage regulator diode with a predetermined breakdown voltage. I have a problem. An object of the present invention is to provide a constant voltage diode that prevents variations in breakdown voltage within the plane of a semiconductor wafer and improves the yield when obtaining a required breakdown voltage.

[0005]

[Means for Solving the Problems] A constant voltage diode of the present invention has a first semiconductor layer of the same conductivity type as the semiconductor substrate on a semiconductor substrate having one conductivity type, and has a different conductivity type on the first semiconductor layer. A second semiconductor layer having a conductivity type is provided, and a breakdown voltage is obtained by a PN junction between the first and second semiconductor layers. The first and second semiconductor layers are formed by growing polysilicon and making it a single crystal semiconductor layer.

[0006]

[Operation] According to the present invention, since the breakdown voltage is determined by the impurity concentration of the first semiconductor layer formed by the deposition method, it is possible to achieve a substantially uniform impurity concentration distribution within the semiconductor wafer surface, suppressing variations in resistivity. to reduce variations in breakdown voltage.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained with reference to the drawings. FIG. 1 is a longitudinal sectional view of a first embodiment of a constant voltage diode according to the present invention. When trying to obtain a breakdown voltage of 5V, silicon doped with phosphorus is deposited on an N-type semiconductor substrate 1 having a resistivity of 0.005 Ωcm so that it has the same conductivity type as the N-type semiconductor substrate 1. , an N+ type first semiconductor layer 2 having a thickness of 2 μm is formed over the entire surface. After that, CVD
A plasma nitride film 3 with a thickness of 1.5 μm is formed by the method, and windows are selectively opened using photoresist.

Next, boron-doped silicon is deposited to form a P+ type second semiconductor layer 4. The second semiconductor layer 4 is formed into a single crystal at a portion in contact with the first semiconductor layer 2 within the window of the plasma nitride film 3. Thereafter, the surrounding area is plasma-treated and etched. Further, A is formed by plating on the second semiconductor layer 4 as an electrode for sealing in the DHD container.
A G bump electrode 5 is formed, and an Ag electrode 6 is formed on the back surface of the N-type semiconductor substrate 1.

According to the constant voltage diode having this configuration, the breakdown voltage is the lower the impurity concentration of the P+/N+ junction formed by the first semiconductor layer 2 and the second semiconductor layer 4, the lower the impurity concentration.
It is determined by the resistivity of the semiconductor layer 2. Since the first semiconductor layer 2 is formed by a deposition method, the variation in resistivity within the plane of the semiconductor wafer is about 4 to 10%, and the variation in breakdown voltage is smaller than that of a conventional constant voltage diode.

FIG. 2 is a longitudinal sectional view of a second embodiment of the present invention. By forming silicon doped with phosphorus over the entire surface of the N-type semiconductor substrate 11 and etching the periphery by plasma treatment, an N+-type first semiconductor layer 12 having the same conductivity type is formed. Next, silicon doped with boron is formed over the entire surface, and the periphery is etched by plasma processing to form a P+ type second semiconductor layer 14. At this time, the second semiconductor layer 14 is made into a single crystal on the first semiconductor layer 12. Furthermore, a plasma nitride film 13 with a thickness of 1.5 μm is formed on the entire surface, an Ag bump electrode 15 is formed by plating on the second semiconductor layer 14 as an electrode for sealing the DHD container, and an N-type semiconductor substrate is formed. An Ag electrode 16 is formed on the back surface of 11.

In this embodiment, there are two junctions: a P+/N+ junction between the first and second semiconductor layers 12 and 14, and a P+/N junction between the semiconductor substrate 11 and the second semiconductor layer 14. However, since the P+/N+ junction has a lower breakdown voltage and the first semiconductor layer 12 is formed by a deposition method, variations in resistivity within the semiconductor wafer surface are suppressed,
Similar to the first embodiment, variations in breakdown voltage can be reduced. Also, the P+/N junction acts as a guard ring. Furthermore, since the plasma nitride film 13 is used as a mask when forming the Ag bump electrodes 15, it is possible to obtain effects that could not be obtained in the first embodiment, such as requiring one less window opening process using photoresist. .

0012

As explained above, in the constant voltage diode according to the present invention, the breakdown voltage is determined by the resistivity of the first semiconductor layer, and the variation in the resistivity within the semiconductor wafer surface is approximately 4 to 10. %, which is smaller than the variation in resistivity of about 6 to 15% in conventional semiconductor substrates, which has the effect of improving the yield of the required breakdown voltage.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a first embodiment of a constant voltage diode of the present invention.

FIG. 2 is a longitudinal cross-sectional view of a second embodiment of the voltage regulator diode of the present invention.

FIG. 3 is a longitudinal cross-sectional view of an example of a conventional constant voltage diode.

[Explanation of symbols]

1, 11 N-type semiconductor substrate 2, 12 First semiconductor layer (N+ type) 3, 13 Plasma nitride film 4, 14 Second semiconductor layer (P+ type) 5, 15 A
g bump electrode 6, 16 Ag electrode

Claims (2)

[Claims] 1. A first semiconductor layer having the same conductivity type as the semiconductor substrate on a semiconductor substrate having one conductivity type, and a second semiconductor layer having a different conductivity type on the first semiconductor layer. , a constant voltage diode characterized in that a breakdown voltage is obtained by a PN junction between these first and second semiconductor layers. 2. The constant voltage diode according to claim 1, wherein the first and second semiconductor layers are formed by growing polysilicon and making it a single crystal.