Transient voltage suppression device and manufacturing method thereof

• US 9,257,421 B2
• Filed: 06/02/2015
• Issued: 02/09/2016
• Est. Priority Date: 06/13/2014
• Status: Expired due to Fees

• Current Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Original Assignee: Richtek Technology Corporation (MediaTek, Inc.)
• Inventors: Huang, Tsung-Yi, Lo, Kuo-Hsuan, Weng, Wu-Te
• Primary Examiner(s): Nguyen, Dao H
• Assistant Examiner(s): Nguyen, Tram H
• Application Number:
  US14/728,189
• Publication Number:
  US 20150364460A1
• Time in Patent Office: 252 Days
• Field of Search: 257/186, 257/199, 257481-482, 257/493, 257/589, 257603-606, 257/E31.063, 257/E29.18, 257E29334-E29335, 257/46, 257104-106, 257/E21.354, 257/E31.355, 257/E21.356, 257/E21.357, 438/91, 438/380, 438/983
• US Class Current: 1/1
• CPC Class Codes: H01L 21/76224 using trench refilling with dielectric materials trench filling with polycristalline silicon H01L21/763; together with vertical isolation, e.g. trench refilling in a SOI substrate H01L21/76264
• CPC Class Codes: H01L 27/0255 using diodes as protective elements
• CPC Class Codes: H01L 29/0649 Dielectric regions, e.g. SiO2 regions, air gaps
• CPC Class Codes: H01L 29/66106 Zener diodes
• CPC Class Codes: H01L 29/66136 PN junction diodes
• CPC Class Codes: H01L 29/861 Diodes
• CPC Class Codes: H01L 29/866 Zener diodes

Abstract

The present invention discloses a transient voltage suppression (TVS) device and a manufacturing method thereof. The TVS device limits a voltage drop between two terminals thereof not to exceed a clamp voltage. The TVS device is formed in a stack substrate including a semiconductor substrate, a P-type first epitaxial layer, and a second epitaxial layer stacked in sequence. In the TVS device, a first PN diode is connected to a Zener diode in series, wherein the series circuit is surrounded by a first shallow trench isolation (STI) region; and a second PN diode is connected in parallel to the series circuit, wherein the second PN diode is surrounded by a second STI region. The first STI region and the second STI region both extend from an upper surface to the second epitaxial layer, but not to the first epitaxial layer.

Claims

1. A transient voltage suppression (TVS) device, which has a first terminal and a second terminal, for limiting a voltage drop between the first terminal and the second terminal not to exceed a clamp voltage, the TVS device comprising:

a semiconductor substrate, which has a P-type conductivity, and is used as or is electrically connected to the second terminal;

a first epitaxial layer having the P-type conductivity, which is formed on and connected to the semiconductor substrate;

a second epitaxial layer, which is formed on and connected to the first epitaxial layer, the second epitaxial layer having an upper surface;

a cap layer having the P-type conductivity, which is formed in the first epitaxial layer, and is electrically connected to the second terminal;

a first buried layer having an N-type conductivity, which is formed on the cap layer;

a first N-type region having the N-type conductivity, which is formed in the second epitaxial layer on the first buried layer;

a first P-type region having the P-type conductivity, which is formed in the second epitaxial layer on the first N-type region, and is electrically connected to the first terminal;

a first shallow trench isolation (STI) region, which extends from the upper surface to the second epitaxial layer and connects the first buried layer, but the first STI region does not extend to the first epitaxial layer, and the first STI region surrounds the first N-type region and the first P-type region from a top view;

a second P-type region having the P-type conductivity, which is formed in the first epitaxial or the second epitaxial layer on the semiconductor substrate, and is electrically connected to the second terminal;

a second N-type region having the N-type conductivity, which is formed in the second epitaxial layer on and connected to the second P-type region, and is electrically connected to the first terminal; and

a second STI region, which extends from the upper surface to the second epitaxial layer, but the second STI region does not extend to the first epitaxial layer, and the second STI region surrounds the second N-type region and the second P-type region from the top view;

wherein a Zener diode includes the cap region and the first buried layer;

a first PN diode includes the first P-type region and the first N-type region;

a second PN diode includes the second P-type region and the second N-type region;

wherein the first PN diode and the Zener diode are connected in series, the first N-type region being electrically connected to the first buried layer, and the second PN diode is connected in parallel to the series circuit of the first PN diode and the Zener diode, wherein the second PN diode and the series circuit of the first PN diode and the Zener diode are isolated by the first STI region and the second STI region in a lateral direction.

2. The TVS device of claim 1, further comprising a second buried layer having the P-type conductivity, which is formed beneath the second STI region and extends to the first epitaxial layer, the second buried layer surrounding the second N-type region and the second P-type region.

3. The TVS device of claim 1, wherein the first STI region and the second STI region share a common part of STI region, and the second PN diode and the series circuit of the first PN diode and the Zener diode are isolated only by the common part of STI region in the lateral direction.

4. The TVS device of claim 1, wherein the second epitaxial layer has the P-type or the N-type conductivity.

5. The TVS device of claim 1, further comprising:

a P-type ohmic contact region having the P-type conductivity, which is formed in the second epitaxial layer on the first P-type region, for electrically connecting the first terminal and the first P-type region; and

an N-type ohmic contact region having the N-type conductivity, which is formed in the second epitaxial layer on the second N-type region, for electrically connecting the first terminal and the second N-type region.

6. A manufacturing method of a transient voltage suppression (TVS) device, which has a first terminal and a second terminal, for limiting a voltage drop between the first terminal and the second terminal not to exceed a clamp voltage, the manufacturing method comprising:

providing a semiconductor substrate having a P-type conductivity, is used as or is electrically connected to the second terminal;

forming a first epitaxial layer having the P-type conductivity on and connected to the semiconductor substrate;

forming a second epitaxial layer on and connected to the first epitaxial layer, the second epitaxial layer having an upper surface;

forming a cap layer having the P-type conductivity in the first epitaxial layer, the cap layer being electrically connected to the second terminal;

forming a first buried layer having an N-type conductivity on the cap layer;

forming a first N-type region having the N-type conductivity in the second epitaxial layer on the first buried layer;

forming a first P-type region having the P-type conductivity in the second epitaxial layer on the first N-type region, the first P-type region being electrically connected to the first terminal;

forming a first shallow trench isolation (STI) region, which extends from the upper surface to the second epitaxial layer and connects the first buried layer, but the first STI region does not extend to the first epitaxial layer, the first STI region surrounding the first N-type region and the first P-type region from a top view;

forming a second P-type region having the P-type conductivity in the first epitaxial or the second epitaxial layer on the semiconductor substrate, the second P-type region being electrically connected to the second terminal;

forming a second N-type region having the N-type conductivity in the second epitaxial layer, wherein the second N-type region is on and connected to the second P-type region, and is electrically connected to the first terminal; and

forming a second STI region, which extends from the upper surface to the second epitaxial layer, but the second STI region does not extend to the first epitaxial layer, the second STI region surrounding the second N-type region and the second P-type region from the top view;

wherein a Zener diode includes the cap region and the first buried layer;

a first PN diode includes the first P-type region and the first N-type region;

a second PN diode includes the second P-type region and the second N-type region;

wherein the first PN diode and the Zener diode are connected in series, the first N-type region being electrically connected to the first buried layer, and the second PN diode is connected in parallel to the series circuit of the first PN diode and the Zener diode, wherein the second PN diode and the series circuit of the first PN diode and the Zener diode are isolated by the first STI region and the second STI region in a lateral direction.

7. The manufacturing method of claim 6, further comprising:

forming a second buried layer having the P-type conductivity beneath the second STI region, wherein the second buried layer extends to the first epitaxial layer, and surrounds the second N-type region and the second P-type region.

8. The manufacturing method of claim 6, wherein the first STI region and the second STI region share a common part of STI region, and the second PN diode and the series circuit of the first PN diode and the Zener diode are isolated only by the common part of STI region in the lateral direction.

9. The manufacturing method of claim 6, wherein the second epitaxial layer has the P-type or the N-type conductivity.

10. The manufacturing method of claim 6, further comprising:

forming a P-type ohmic contact region having the P-type conductivity in the second epitaxial layer on the first P-type region, for electrically connecting the first terminal and the first P-type region; and

forming an N-type ohmic contact region having the N-type conductivity in the second epitaxial layer on the second N-type region, for electrically connecting the first terminal and the second N-type region.