One-way silicon controlled electrostatic protection device triggered by Schottky diode and manufacturing method of one-way silicon controlled electrostatic protection device

Abstract

The invention discloses a Schottky diode triggered one-way silicon controlled rectifier electrostatic protection device and a manufacturing method thereof. The Schottky diode triggered one-way silicon controlled rectifier electrostatic protection device is improved on the basis of one-way silicon controlled rectifiers. A Schottky diode is embedded in an NW of a one-way silicon controlled rectifier, a P + area is embedded in a PW, and the Schottky diode is connected with the embedded P + area through a metal wire. According to the invention, a reverse Schottky diode trigger structure is embedded on the basis of a traditional unidirectional silicon controlled rectifier electrostatic protection device, so that the trigger voltage of the SCR can be effectively reduced; the Schottky diode is introduced, so that the distance between the cathode and the anode of the one-way silicon controlled rectifier is increased, and the maintaining voltage of the SCR and the heat dissipation capability of the device can be effectively improved; the silicon rectifier electrostatic discharge device has the advantages of being high in maintaining voltage, high in failure current and low in trigger voltage, the latch-up effect can be effectively avoided, and meanwhile the high protection level can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of electrostatic protection, and in particular to a unidirectional thyristor electrostatic protection device triggered by a Schottky diode with low trigger voltage and high failure current, and a manufacturing method thereof. Background Art

[0002] With the advancement of semiconductor manufacturing technology, the failure of integrated circuit chips and electronic products caused by ESD has become more and more serious. ESD protection for electronic products and integrated circuit chips has become one of the main problems faced by product engineers.

[0003] The failure modes caused by ESD include hard failure, soft failure, and potential failure. The causes of these failures can be divided into electrical failure and thermal failure. Thermal failure refers to the current of several amperes to tens of amperes generated locally on the chip when the ESD pulse comes. It lasts for a short time but generates a lot of heat, causing the local metal connection to melt or causing hot spots on the chip, resulting in secondary breakdown. Electrical failure refers to the electric field strength formed by the voltage applied to the gate oxide layer being greater than the dielectric strength, causing surface breakdown or dielectric breakdown. As the threat posed by ESD to chips becomes more and more serious, research on its physical mechanism is receiving more and more attention.

[0004] The cross-section diagram of the traditional unidirectional thyristor electrostatic protection device is shown in Figure 1 , its equivalent circuit diagram is shown in Figure 2 . When an ESD pulse is applied to the anode of the unidirectional SCR, the first N-well and the first P-well form a reverse-biased PN junction. When the pulse voltage is higher than the avalanche breakdown voltage of the PN junction, a large amount of avalanche current will be generated inside the device. The current flows through the first P-well and flows to the cathode through the parasitic resistance. The voltage drop across the parasitic resistance of the first P-well is equivalent to the base voltage drop of the transistor NPN. When this voltage is higher than the forward conduction voltage of the vertical NPN transistor, the transistor is turned on. After this transistor is turned on, it provides base current for the horizontal PNP transistor. After the horizontal PNP transistor is also turned on, it further provides base current for the vertical NPN transistor, forming a positive feedback mechanism to fully open the SCR path. Therefore, even if there is no avalanche current afterwards, the large current can be discharged due to the conduction of the transistor. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a Schottky diode triggered unidirectional thyristor electrostatic protection device and a manufacturing method thereof, and is applied to the design of an ESD protection network with an operating voltage of 0 to 5.5V.

[0006] The technical solution of the present invention to solve the above problems is:

[0007] In a first aspect, an embodiment of the present invention provides a Schottky diode-triggered unidirectional thyristor electrostatic protection device, comprising a P-type substrate; a first N-well and a first P-well are provided above the substrate; a first N-well and a first P-well are provided on the P-type substrate in sequence from left to right; a first N+ injection, a first P+ injection, a second P+ injection, a first metal and a third P+ injection are provided on the first N-well in sequence from left to right; a fourth P+ injection, a second N+ injection and a fifth P+ injection are provided in sequence from left to right in the first P-well;

[0008] The two electrodes of the first N+ injection and the second P+ injection in the first N well are connected together and serve as the anode of the device; the second P+ injection and the third P+ injection in the first N well have no electrodes and are in a floating state; the second N+ injection and the fifth P+ injection in the first P well are connected together and serve as the cathode of the device; the first metal in the first N well and the fourth P+ injection of the first P well are connected together through a metal wire and are not connected to a potential.

[0009] Preferably, there are five field oxygen isolation regions; the first field oxygen isolation region is between the first N+ injection and the first P+ injection region, the second field oxygen isolation region is between the first P+ injection and the second P+ injection, the third field oxygen is between the third P+ injection and the fourth P+ injection, the fourth field oxygen is between the fourth P+ injection and the second N+ injection, and the fifth field oxygen is between the second N+ injection and the fifth P+ injection.

[0010] Preferably, the first field oxygen isolation region and the second field oxygen isolation region are located on the surface of the first N-well; the third field oxygen isolation region is located between the first N-well and the first P-well; the fourth field oxygen isolation region and the fifth field oxygen isolation region are located on the surface of the first P-well.

[0011] Preferably, when the ESD pulse reaches the anode of the device and the cathode of the device is connected to a low potential, its breakdown surface is between the first N-well and the first metal; at this time, the first N-well and the first metal constitute a Schottky diode D1, and the first N+ injection, the first N-well, the first metal, the fourth P+ injection, the first P-well, and the fifth P+ injection constitute a trigger current path one of the device. After D1 undergoes an avalanche breakdown and is turned on, the trigger current path one will provide a trigger current.

[0012] Preferably, when the ESD pulse reaches the anode of the device and the cathode of the device is connected to a low potential, the first P+ injection, the first N-well and the first P-well constitute a parasitic transistor PNP, the first N-well, the first P-well and the second N+ injection constitute a parasitic transistor NPN, and after D1 undergoes avalanche breakdown, a trigger current is formed to flow through R2 in the first P-well. When the voltage drop through the resistor R2 is greater than 0.7V, the PN junction formed by the first P-well and the second N+ injection is turned on, and then the parasitic transistor NPN on the right is turned on and provides base current to the parasitic transistor PNP on the left, thereby promoting its conduction. When the parasitic transistor PNP and the parasitic transistor NPN are turned on, a forward SCR path is formed, forming a positive feedback effect, and the device is successfully triggered.

[0013] Preferably, the base width S1 of the parasitic transistor PNP is adjustable, and when S1 increases, the sustaining voltage increases.

[0014] In a second aspect, an embodiment of the present invention provides a method for manufacturing a Schottky diode-triggered unidirectional thyristor electrostatic protection device, comprising the following steps:

[0015] Step 1: generating a first N-well and a first P-well in a P-type substrate;

[0016] Step 2: Generate a first N+ injection, a first P+ injection, a second P+ injection, a third P+ injection and a first metal on the first N well from left to right; generate a fourth P+ injection, a second N+ injection and a fifth P+ injection on the first P well from left to right;

[0017] Step 3: forming a first field oxygen isolation region between the first N+ injection and the first P+ injection on the first N well, generating a second field oxygen between the first P+ injection and the second P+ injection on the first N well, bridging a third field oxygen between the first N well and the first P well, generating a fourth field oxygen between the fourth P+ injection and the second N+ injection on the first P well, and generating a fifth field oxygen between the second N+ injection and the fifth P+ injection on the first P well;

[0018] Step 6: Anneal all implanted areas to eliminate the migration of impurities in the implanted areas;

[0019] Step 7: Connect the first N+ injection and the first P+ injection together and use them as the anode of the device, connect the N well between the second P+ injection and the third P+ injection and the fourth P+ injection together without connecting the potential, and connect the second N+ injection and the fifth P+ injection together and use them as the cathode of the device.

[0020] Preferably, before forming the N-well and the P-well on the P-type substrate, the method further comprises:

[0021] A silicon dioxide film is grown on a P-type substrate, and then a silicon nitride layer is deposited; a photoresist layer is spin-coated on the wafer, and a mask is added to expose and develop it to form an isolation shallow groove; the silicon dioxide, silicon nitride and isolation shallow groove are etched to remove the photoresist layer, a silicon dioxide layer is deposited, and then chemical mechanical polishing is performed until the silicon nitride layer is reached to remove the silicon nitride layer.

[0022] The beneficial effects of the present invention are:

[0023] 1. The present invention adjusts the breakdown surface and introduces a Schottky diode on the basis of a traditional unidirectional thyristor electrostatic protection device to change the breakdown surface from the well breakdown of the first N well and the first P well to the Schottky junction breakdown formed by the first N well and the first metal, thereby effectively reducing the trigger voltage of the device and making the device easier to turn on.

[0024] 2. In order to better exert the performance of the unidirectional thyristor, the present invention increases the base width of the parasitic transistors PNP and NPN by embedding a Schottky junction in the first N well and embedding the second N+ injection in the first P well, which will weaken the positive feedback effect of the SCR path, thereby suppressing the latch effect, and thus improving the holding voltage of the device.

[0025] 3. The width S1 of the second P+ injection of the present invention is adjustable. When S1 increases, it is equivalent to widening the base width of the parasitic transistor NPN and the parasitic transistor PNP, thereby weakening the emitter injection effect of the parasitic transistor, suppressing the positive feedback effect of the SCR path, and maintaining the voltage increase. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a cross-sectional view of a traditional unidirectional SCR electrostatic protection device.

[0027] Figure 2 This is the equivalent circuit diagram of the traditional unidirectional SCR electrostatic protection device.

[0028] Figure 3 It is a cross-sectional view of an embodiment of the present invention.

[0029] Figure 4 2 is an equivalent circuit diagram of an embodiment of the present invention.

[0030] Figure 5 A simulation diagram of the total current density distribution of a Schottky diode-triggered unidirectional thyristor electrostatic protection device provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0031] The ESD protection design of the analog switch chip applied to the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0032] like Figure 3As shown, a Schottky diode triggered unidirectional thyristor electrostatic protection device includes a P-type substrate 101; an N-well 201 and a P-well 202 are provided in the substrate; a first N+ injection 301, a first P+ injection 302, a second P+ injection 303, and a fourth P+ injection 304 are provided above the N-well 201 from left to right; a fourth P+ injection 305, a second N+ injection 306, and a fifth P+ injection 307 are provided above the first P-well from left to right; the first N+ injection 301 and the second P+ injection 302 in the first N-well 201 are both connected together and serve as the anode of the device; the second N+ injection 306 and the fifth P+ injection 307 in the first P-well 202 are connected together and serve as the cathode of the device; the N-well between the second N+ injection 303 and the third P+ injection 304 in the first N-well 202 and the fourth P+ injection 305 in the first P-well 202 are connected together through metal wires without being connected to a potential. In this way, the first N-well 201 and the first metal 501 are in Schottky contact and form a Schottky diode D1. When a positive ESD pulse is applied to the anode of the device, the breakdown surface changes from the original first N-well 201 / first P-well 202 to the first N-well 201 / first metal 501, which will reduce the trigger voltage of the device and increase the maintenance voltage of the device.

[0033] In one embodiment, the Schottky diode triggered unidirectional thyristor electrostatic protection device has five field oxygen isolation regions; there are five field oxygen isolation regions; the first field oxygen isolation region 401 is between the first N+ injection 301 and the first P+ injection 302, the second field oxygen isolation region 402 is between the first P+ injection 302 and the second P+ injection 303, the third field oxygen 403 is between the third P+ injection 304 and the fourth P+ injection 305, the fourth field oxygen 404 is between the fourth P+ injection 305 and the second N+ injection 306, and the fifth field oxygen 405 is between the second N+ injection 306 and the fifth P+ injection 307.

[0034] In one embodiment, the first field oxygen isolation region 401 and the second field oxygen isolation region 402 are located on the surface of the first N-well 201 ; the third field oxygen isolation region 403 is between the first N-well 201 and the first P-well 202 ; the fourth field oxygen isolation region 404 and the fifth field oxygen isolation region 405 are located on the surface of the first P-well 202 .

[0035] In one embodiment, if Figures 4 to 5As shown, when the high-voltage ESD pulse reaches the anode of the device and the cathode of the device is connected to a low potential, its breakdown surface is between the first N-well 201 and the first metal 501; at this time, the first N-well 201 and the first metal 501 constitute a Schottky diode D1, and the first N+ injection 301, the first N-well 201, the first metal 501, the fourth P+ injection 305, the first P-well 202, and the fifth P+ injection 307 constitute the trigger current path one of the device. After D1 undergoes avalanche breakdown and is turned on, the trigger current path one will provide a trigger current.

[0036] When the ESD pulse reaches the anode of the device and the cathode of the device is grounded, the first P+ injection 302, the first N-well 201 and the first P-well 202 constitute a parasitic transistor PNP, and the first N-well 201, the first P-well 202 and the second N+ injection 306 constitute a parasitic transistor NPN. After D1 undergoes avalanche breakdown, a trigger current is formed to flow through R2 in the first P-well 202. When the voltage drop across the resistor R2 is greater than 0.7V, the PN junction formed by the first P-well 202 and the second N+ 306 injection is turned on, and then the parasitic transistor NPN on the right is turned on and provides base current to the parasitic transistor PNP on the left, thereby promoting its conduction. When the parasitic transistor PNP and the parasitic transistor NPN are turned on, a forward SCR path is formed, forming a positive feedback effect, and the device is successfully triggered.

[0037] According to the requirements of the ESD design window in different application scenarios, the base width S1 of the parasitic transistor PNP of the device can be adjusted. When S1 increases, the base width of the parasitic transistor PNP increases, thereby reducing the current gain coefficient β, thereby increasing the holding voltage.

[0038] The embodiment of the present invention also provides a method for manufacturing a Schottky diode triggered unidirectional thyristor electrostatic protection device, comprising the following steps:

[0039] Step 1: generating a first N-well 201 and a first P-well 202 in a P-type substrate 101;

[0040] Step 2: Generate a first N+ injection 301, a first P+ injection 302, a second P+ injection 303, a third P+ injection 304 and a first metal 501 from left to right on the first N well 201; generate a fourth P+ injection 305, a second N+ injection 306 and a fifth P+ injection 307 from left to right on the first P well 202;

[0041] Step 3: forming a first field oxygen isolation region 401 between the first N+ implantation 301 and the first P+ 302 implantation on the first N well 201, generating a second field oxygen 402 between the first P+ implantation 302 and the second P+ 303 implantation on the first N well 201, bridging a third field oxygen 403 between the first N well 201 and the first P well 202, generating a fourth field oxygen 404 between the fourth P+ implantation 305 and the second N+ 306 implantation on the first P well 202, and generating a fifth field oxygen 405 between the second N+ implantation 306 and the fifth P+ implantation 307 on the first P well 202;

[0042] Step 6: Anneal all implanted areas to eliminate the migration of impurities in the implanted areas;

[0043] Step seven: Connect the first N+ injection 301 and the first P+ injection 302 together and use them as the anode of the device, connect the N well between the second P+ injection 303 and the third P+ injection 304 and the fourth P+ injection 305 together without connecting the potential, and connect the second N+ injection 306 and the fifth P+ injection 307 together and use them as the cathode of the device.

[0044] The manufacturing method of a Schottky diode-triggered unidirectional thyristor electrostatic protection device of the present invention is simple in process and easy to operate. In order to better exert the performance of the unidirectional thyristor, the present invention adjusts the breakdown surface, based on the traditional unidirectional thyristor electrostatic protection device, by introducing a Schottky diode, the breakdown surface is changed from the well breakdown of the first N well and the first P well to the Schottky junction breakdown formed by the first N well and the first metal, which effectively reduces the trigger voltage of the device and makes the device easier to turn on. The invention increases the base width of the parasitic transistors PNP and NPN by embedding a Schottky junction in the first N well and the first P well into the second N+ injection, which will weaken the positive feedback effect of the SCR path, thereby suppressing the latch effect, thereby increasing the holding voltage of the device, and effectively improving the protection performance of the device. The device can be used in the ESD protection design of the I / O port of 0 to 5.5V. The example device of the present invention adopts a 0.18μm CMOS process.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A Schottky diode triggered unidirectional thyristor electrostatic protection device, characterized in that: include: A P-type substrate, with a first N-well and a first P-well disposed above the P-type substrate; The P-type substrate is provided with a first N-well and a first P-well from left to right in sequence; the first N-well is provided with a first N+ injection, a first P+ injection, a second P+ injection, a first metal and a third P+ injection in sequence from left to right; The first P well is provided with a fourth P+ injection, a second N+ injection and a fifth P+ injection from left to right; The first N+ injection and the second P+ injection electrodes in the first N well are connected together and serve as the anode of the device; The second P+ injection and the third P+ injection in the first N well have no electrodes and are in a floating state; The second N+ injection and the fifth P+ injection electrodes in the first P well are connected together and serve as the cathode of the device; The first metal in the first N-well and the fourth P+ injection of the first P-well are connected together through a metal wire without being connected to a potential.

2. The Schottky diode-triggered unidirectional thyristor electrostatic protection device according to claim 1, characterized in that: Also includes: five field oxygen isolation zones; The first field oxygen isolation region is between the first N+ injection and the first P+ injection region, the second field oxygen isolation region is between the first P+ injection and the second P+ injection, the third field oxygen is between the third P+ injection and the fourth P+ injection, the fourth field oxygen is between the fourth P+ injection and the second N+ injection, and the fifth field oxygen is between the second N+ injection and the fifth P+ injection.

3. The Schottky diode-triggered unidirectional thyristor electrostatic protection device according to claim 2, characterized in that: The first field oxygen isolation region and the second field oxygen isolation region are located on the surface of the first N-well; the third field oxygen isolation region is between the first N-well and the first P-well; the fourth field oxygen isolation region and the fifth field oxygen isolation region are located on the surface of the first P-well.

4. The Schottky diode triggered unidirectional thyristor electrostatic protection device according to claim 1, characterized in that: When a high-voltage ESD pulse reaches the anode of the device and the cathode of the device is connected to a low potential, its breakdown surface is between the first N-well and the first metal; at this time, the first N-well and the first metal constitute a Schottky diode D1, and the first N+ injection, the first N-well, the first metal, the fourth P+ injection, the first P-well, and the fifth P+ injection constitute the trigger current path one of the device. After D1 undergoes an avalanche breakdown and is turned on, the trigger current path one will provide a trigger current.

5. The Schottky diode triggered unidirectional thyristor electrostatic protection device according to claim 1, characterized in that: When the high-voltage ESD pulse reaches the anode of the device and the cathode of the device is connected to a low potential, the first P+ injection, the first N-well and the first P-well constitute a parasitic transistor PNP, and the first N-well, the first P-well and the second N+ injection constitute a parasitic transistor NPN. After D1 undergoes avalanche breakdown, a trigger current is formed to flow through R2 in the first P-well. When the voltage drop through the resistor R2 is greater than 0.7V, the PN junction formed by the first P-well and the second N+ injection is turned on, and then the parasitic transistor NPN on the right is turned on and provides base current to the parasitic transistor PNP on the left, thereby promoting its conduction. When the parasitic transistor PNP and the parasitic transistor NPN are turned on, a forward SCR path is formed, forming a positive feedback effect, and the device is successfully triggered.

6. The Schottky diode triggered unidirectional thyristor electrostatic protection device according to claim 1, characterized in that: The base width S1 of the parasitic transistor PNP is adjustable, and when S1 increases, the sustaining voltage increases.

7. A method for manufacturing a Schottky diode triggered unidirectional thyristor electrostatic protection device, comprising the following steps: Step 1: generating a first N-well and a first P-well in a P-type substrate; Step 2: Generate a first N+ injection, a first P+ injection, a second P+ injection, a third P+ injection and a first metal on the first N well from left to right; Generating a fourth P+ implant, a second N+ implant, and a fifth P+ implant in sequence from left to right on the first P well; Step 3: forming a first field oxygen isolation region between the first N+ injection and the first P+ injection on the first N well, generating a second field oxygen between the first P+ injection and the second P+ injection on the first N well, bridging a third field oxygen between the first N well and the first P well, generating a fourth field oxygen between the fourth P+ injection and the second N+ injection on the first P well, and generating a fifth field oxygen between the second N+ injection and the fifth P+ injection on the first P well; Step 6: Anneal all implanted areas to eliminate the migration of impurities in the implanted areas; Step 7: Connect the first N+ injection and the first P+ injection together and use them as the anode of the device, connect the N well between the second P+ injection and the third P+ injection and the fourth P+ injection together without connecting the potential, and connect the second N+ injection and the fifth P+ injection together and use them as the cathode of the device.

8. The method for manufacturing the Schottky diode triggered unidirectional thyristor electrostatic protection device according to claim 7, characterized in that: The following steps are also included before step one: growing a layer of silicon dioxide film on a P-type substrate, and then depositing a layer of silicon nitride; spin coating a photoresist layer on the wafer, exposing and developing it with a mask to form an isolation shallow groove; etching the silicon dioxide, silicon nitride and the isolation shallow groove to remove the photoresist layer, depositing a layer of silicon dioxide, and then performing chemical polishing until the silicon nitride layer is formed to remove the silicon nitride layer.

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