A device for improving the total dose radiation effect of bipolar devices and its fabrication method.

Abstract

This invention discloses a device and its fabrication method for improving the total dose radiation effect of bipolar devices, belonging to the field of semiconductor device radiation hardening technology. This invention forms a higher concentration of the first conductivity type base buried well region within the first conductivity type deep well region of a traditional bipolar device. This changes the base current path from being flush with the lower surface of the shallow trench isolation structure to having a certain distance from it, causing it to flow more along the lower resistance of the first conductivity type base buried well region to the second conductivity type emitter well region. This moves the current away from SiO2-Si surface defects, weakens surface recombination, and reduces the generation of excess base current. This invention can effectively reduce the excess base current after total dose radiation of bipolar devices, reduce the degree of current gain damage, and improve the radiation resistance of bipolar devices.

Description

Technical Field

[0001] This invention relates to the field of radiation hardening technology for semiconductor devices, and in particular to a device and its fabrication method for improving the total dose radiation effect of bipolar devices. Background Technology

[0002] In bipolar devices, the SiO2 oxide layer covering the emitter-base region is thick and of relatively low quality, typically with a high hydrogen content, thus containing various types of neutral oxygen vacancy defects and hydrogenation defects. When the device is subjected to total dose radiation, the radiation loses energy in the SiO2 oxide layer through ionization radiation, generating electron-hole pairs. Since the mobility of electrons is much greater than that of holes, electrons leave the oxide layer, while holes concentrate in the oxide layer. Holes are transported to the vicinity of the Si-SiO2 interface and are captured in a trap region of about 100 nm at the interface, thus forming oxide trap charges. Ionization radiation also breaks some silicon-hydrogen bonds, forming interface states (traps) at the Si-SiO2 interface on the emitter-base junction. These traps do not contribute to the surface current when on an undepleted surface, but as the positive charge in the oxide layer increases, the surface depletion region increases, exposing more interface traps. When interface traps are on the depleted surface, they become effective recombination centers, increasing the surface recombination rate at the interface. These two damage mechanisms work together on the space charge region at the emitter-base junction surface. As a result, while oxide charge and interface traps increase only sublinearly or linearly with total dose, the base current increases superlinearly with increasing total dose, reducing the base transport coefficient, increasing excess base current, and decreasing current gain. Currently, the main approach in the industry to improve the total dose radiation effect of bipolar devices is to reinforce the masking oxide layer on the emitter-base junction surface—the sensitive location for total dose radiation—to reduce the impact of total dose radiation at its source. For example, this can be achieved by thinning the masking oxide layer or changing its material composition. However, changing the oxide layer significantly alters the manufacturing process, severely impacting the normal performance of other devices.

[0003] Through extensive research, we have discovered another approach to improve the total dose radiation effect of bipolar devices: optimizing the base current path and reducing the surface current density of the emitter-base junction. This allows the base current to flow primarily from the bottom of the emitter-base junction to the emitter, thus moving it away from surface defects, weakening surface recombination, and reducing the generation of excess base current. This cleverly bypasses the significant process changes required for directly reinforcing the Si-SiO2 interface region. Summary of the Invention

[0004] The purpose of this invention is to provide a device and its fabrication method for improving the total dose radiation effect of bipolar devices, so as to reduce the excess base current after total dose radiation of bipolar devices.

[0005] The technical solution to achieve the purpose of this invention is as follows: a device for improving the total dose radiation effect of bipolar devices, comprising, from bottom to top, a first conductivity type substrate, a second conductivity type buried layer, and a second conductivity type collector deep well region, wherein a first conductivity type base deep well region is disposed above the interior of the second conductivity type collector deep well region, and a first conductivity type base buried layer well region is disposed inside the first conductivity type base deep well region, wherein the first conductivity type base buried layer well region divides the first conductivity type base deep well region into upper and lower parts;

[0006] A second type of collector well region is provided above the periphery of the second type of collector well region, and a second type of collector injection region is provided above the second type of collector well region. The area of ​​the second type of collector injection region is smaller than that of the second type of collector well region.

[0007] A first type of base well region is provided above the periphery of the first type of base deep well region. The lower surface of the first type of base well region forms an electrical contact with the upper surface of the first type of base buried layer well region. A first type of base injection region is provided above the first type of base well region. The area of ​​the first type of base injection region is smaller than that of the first type of base well region.

[0008] A second type of emitter well region is provided above the base deep well region of the first type of conductivity. The lower surface of the second type of emitter well region forms an electrical contact with the upper surface of the base buried layer well region of the first type of conductivity. A second type of emitter injection region is provided above the second type of emitter well region. The area of ​​the second type of emitter injection region is smaller than that of the second type of emitter well region.

[0009] Electrical isolation between the emitter injection region of the second conductivity type and the base injection region of the first conductivity type, and between the base injection region of the first conductivity type and the collector injection region of the second conductivity type, is achieved through STI shallow trench isolation structures. The outer side of the collector injection region of the second conductivity type is electrically isolated from other devices through STI shallow trench isolation structures.

[0010] A method for fabricating a device that improves the total dose radiation effect of a bipolar device includes the following steps:

[0011] Step 1: Provide a silicon substrate of the first conductivity type, perform photolithography and doping ion implantation on its surface, and anneal to form a buried layer of the second conductivity type; perform photolithography and doping ion implantation on the upper surface of the buried layer of the second conductivity type, and anneal to form a collector deep well region of the second conductivity type; perform photolithography and doping ion implantation on the upper surface of the collector deep well region of the second conductivity type to form a base deep well region of the first conductivity type.

[0012] Step 2: Photolithography is performed on the surface of the first conductivity type base deep well region to expose the area window for buried layer implantation, high-energy doped ion implantation is performed, and annealing is performed to form the first conductivity type base buried well region; the first conductivity type base buried well region divides the first conductivity type base deep well region into upper and lower parts.

[0013] Step 3: An oxide layer and a SiN layer are grown on the surface of the upper part of the collector deep well region of the second conductivity type and the base deep well region of the first conductivity type. Active region photolithography is performed, and STI etching is performed to form STI trenches. SiO2 or other filling materials are deposited in the STI trenches to ensure electrode isolation. Then, chemical mechanical polishing is performed to form a shallow STI trench isolation structure.

[0014] Step 4: Photolithography and doped ion implantation are performed on the upper part of the collector deep well region of the second conductivity type and the base deep well region of the first conductivity type, followed by annealing to form the collector deep well region of the second conductivity type, the collector implantation region of the second conductivity type, the base deep well region of the first conductivity type, the base implantation region of the first conductivity type, the emitter deep well region of the second conductivity type, and the emitter implantation region of the second conductivity type, thus forming a complete radiation-hardened bipolar device structure.

[0015] Compared with existing technologies, the significant advantages of this invention are as follows: This invention forms a higher concentration of the first conductivity type base buried layer well region within the first conductivity type deep well region of a traditional bipolar device. This causes the base current path to change from being directly adjacent to the lower surface of the shallow trench isolation structure to having a certain distance from the shallow trench isolation structure. The current tends to flow along the lower resistance of the first conductivity type base buried layer well region towards the second conductivity type emitter well region, thereby moving away from SiO2-Si surface defects, weakening surface recombination, and reducing the generation of excess base current. Therefore, this invention can effectively reduce the excess base current after total dose radiation of bipolar devices, reduce the degree of current gain damage, and improve the radiation resistance of bipolar devices. Attached Figure Description

[0016] Figures 1-4 This is a schematic diagram of the process steps of the present invention;

[0017] Figure 5 This is a schematic diagram of the current path of the bipolar device (taking NPN as an example) formed by the present invention;

[0018] Figure 6 This is a schematic cross-sectional view of a bipolar device structure formed using traditional methods.

[0019] Figure 7 This is a schematic diagram of the current path of a bipolar device (taking NPN as an example) formed by traditional methods.

[0020] Explanation of the reference numerals: 1 is the substrate of the first conductivity type, 2 is the buried layer of the second conductivity type, 3 is the collector deep well region of the second conductivity type, 4 is the collector well region of the second conductivity type, 5 is the collector injection region of the second conductivity type, 6 is the base deep well region of the first conductivity type, 7 is the base buried well region of the first conductivity type, 6-1 is the lower half of the base deep well region 6 of the first conductivity type separated by the base buried well region 7 of the first conductivity type, 6-2 is the upper half of the base deep well region 6 of the first conductivity type separated by the base buried well region 7 of the first conductivity type, 8 is the base well region of the first conductivity type, 9 is the base injection region of the first conductivity type, 10 is the emitter well region of the second conductivity type, 11 is the emitter injection region of the second conductivity type, and 12 is the STI shallow trench isolation structure. Detailed Implementation

[0021] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a method for improving the total dose radiation effect of bipolar devices according to the present invention. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0022] A device for improving the total dose radiation effect of a bipolar device includes a first conductivity type substrate 1, a second conductivity type buried layer 2, a second conductivity type collector deep well region 3, a second conductivity type collector well region 4, a second conductivity type collector injection region 5, a first conductivity type base deep well region 6, a first conductivity type base buried layer well region 7, a first conductivity type base well region 8, a first conductivity type base injection region 9, a second conductivity type emitter well region 10, a second conductivity type emitter injection region 11, and a shallow trench isolation structure 12.

[0023] A second conductivity type buried layer 2 is provided on a first conductivity type substrate 1.

[0024] On the second conductivity type buried layer 2, there is a second conductivity type collector deep well region 3.

[0025] The second conductivity type collector deep well region 3 is led out through the second conductivity type collector well region 4 and the second conductivity type collector injection region 5, and serves as the collector of the bipolar device.

[0026] The collector deep well region 3 of the second conductivity type includes the base deep well region 6 of the first conductivity type.

[0027] The first conductivity type base deep well region 6 includes the first conductivity type base buried layer well region 7.

[0028] The first conductivity type base buried layer well region 7 divides the first conductivity type base deep well region 6 into a lower part 6-1 and an upper part 6-2.

[0029] The two ends of the first conductivity type buried well region 7 are led out through the first conductivity type base well region 8 and the first conductivity type base injection region 9, which are the bases of the bipolar device.

[0030] The center of the first conductivity type buried well region 7 is in contact with the second conductivity type emitter well region 10.

[0031] The second conductivity type emitter well region 10 is led out through the second conductivity type emitter injection region 11 and serves as the emitter of the bipolar device.

[0032] The second conductivity type emitter injection region 11 and the first conductivity type base injection region 9 are isolated by a shallow trench isolation structure 12.

[0033] The base injection region 9 of the first conductivity type and the collector injection region 5 of the second conductivity type are isolated by a shallow trench isolation structure 12.

[0034] The second conductivity type collector injection region 5 is electrode isolated from the outside of the device by a shallow trench isolation structure 12.

[0035] Furthermore, the doping concentration of the first conductivity type base buried well region 7 is higher than that of the first conductivity type base deep well region 6; the doping concentration of the second conductivity type collector implantation region 5 is higher than that of the second conductivity type collector well region 4; the doping concentration of the first conductivity type base implantation region 9 is higher than that of the first conductivity type base well region 8; and the doping concentration of the second conductivity type emitter implantation region 11 is higher than that of the second conductivity type emitter well region 10.

[0036] Furthermore, the upper surfaces at both ends of the first conductivity type base buried layer well region 7 form electrical contact with the lower surface of the first conductivity type base well region 8; the upper surface inside the first conductivity type base buried layer well region 7 forms electrical contact with the lower surface of the second conductivity type emitter well region 10.

[0037] The first conductivity type base buried layer well region 7 and the shallow trench isolation structure 12 are separated by the upper part 6-2 of the first conductivity type base deep well region 6, and are not in direct contact.

[0038] Furthermore, the edge of the second conductivity type collector injection region 5 is tangent to the STI shallow trench isolation structure 12, the edge of the first conductivity type base injection region 9 is tangent to the STI shallow trench isolation structure 12, and the edge of the second conductivity type emitter injection region 11 is tangent to the STI shallow trench isolation structure 12.

[0039] Furthermore, the second conductivity type collector deep well region 3, the second conductivity type collector well region 4, and the second conductivity type collector injection region 5 together constitute the collector structure.

[0040] The base deep well region 6, the base buried layer well region 7, the base well region 8, and the base injection region 9 of the first conductivity type together constitute the base structure.

[0041] The second conductivity type emitter well region 10 and the second conductivity type emitter injection region 11 together constitute the emitter structure;

[0042] Furthermore, the second conductivity type collector well region 4 and the first conductivity type base buried layer well region 7 cannot be in direct contact;

[0043] The collector well region 4 of the second conductivity type and the base well region 8 of the first conductivity type cannot be in direct contact.

[0044] The base well region 8 of the first conductivity type and the emitter well region 10 of the second conductivity type must not be in direct contact;

[0045] Furthermore, when the first conductivity type doped impurity in the device is acceptor type, the second conductivity type doped impurity is donor type; when the first conductivity type doped impurity is donor type, the second conductivity type doped impurity is acceptor type.

[0046] Furthermore, the first conductivity type base well region 8 can be omitted as needed. In this case, the upper surfaces of both ends of the first conductivity type base buried layer well region 7 need to form electrical contact with the lower surface of the first conductivity type base injection region 9.

[0047] Furthermore, depending on the requirements, the second conductivity type emitter well region 10 can be omitted. In this case, the inner upper surface of the first conductivity type base buried layer well region 7 needs to form an electrical contact with the lower surface of the second conductivity type emitter injection region 11.

[0048] Furthermore, the lower surface of the first conductivity type base buried layer well region 7 can coincide with the lower surface of the first conductivity type base deep well region 6.

[0049] This invention also provides a method for improving the total dose radiation effect of bipolar devices, comprising the following steps:

[0050] Step 1: Provide a silicon substrate 1 of the first conductivity type, perform photolithography and doping ion implantation on its surface, and anneal to form a buried layer 2 of the second conductivity type; perform photolithography and doping ion implantation on the upper surface of the buried layer 2 of the second conductivity type, and anneal to form a collector deep well region 3 of the second conductivity type; perform photolithography and doping ion implantation on the upper surface of the collector deep well region 3 of the second conductivity type to form a base deep well region 6 of the first conductivity type, such as... Figure 1 As shown;

[0051] Step 2: Photolithography is performed on the surface of the first conductivity type base deep well region 6 to expose the area window for buried layer implantation. High-energy doped ion implantation is then performed, followed by annealing to form the first conductivity type base buried well region 7. The first conductivity type base buried well region 7 divides the first conductivity type base deep well region 6 into two parts: lower 6-1 and upper 6-2. The concentration of the first conductivity type base buried well region 7 is higher than that of the first conductivity type base deep well region 6. Figure 2 As shown;

[0052] Step 3: On the surface of the upper portion 6-2 of the second conductivity type collector deep well region 3 and the first conductivity type base deep well region 6, an oxide layer is grown and a SiN layer is deposited. Active region photolithography is performed, followed by STI etching to form STI trenches. SiO2 or other filling materials are deposited within the STI trenches to ensure electrode isolation. Then, chemical mechanical polishing is performed to form the STI shallow trench isolation region 12. Figure 3 As shown;

[0053] Step 4: Photolithography and doped ion implantation are performed on the surface of the upper portion 6-2 of the second conductivity type collector deep well region 3 and the first conductivity type base deep well region 6, followed by annealing to form the second conductivity type collector well region 4, the second conductivity type collector implantation region 5, the first conductivity type base well region 8, the first conductivity type base implantation region 9, the second conductivity type emitter well region 10, and the second conductivity type emitter implantation region 11, thus forming a complete radiation-hardened bipolar device structure, such as... Figure 4 As shown.

[0054] Bipolar devices formed using traditional methods, such as Figure 6 As shown. Figure 4 and Figure 6 The main difference is Figure 4 A first conductivity type base buried layer well region 7 was added, and its concentration is higher than that of the first conductivity type base deep well region 6.

[0055] Taking an NPN transistor as an example, Figure 4 The current flow direction of the device is as follows Figure 5 As shown, Figure 6 The current flow direction of the device is as follows Figure 7 As shown.

[0056] Figure 7 In the middle, the base current I B The current is injected from the base injection region 9 of the first conductivity type, and after passing through the base well region 8 of the first conductivity type, it flows to the emitter well region 10 of the second conductivity type, i.e., close to the lower surface of the shallow trench isolation structure 12, via the shortest path. In this case, after total dose irradiation, the base current is most affected by the fixed charge and interface states of the oxide layer in the shallow trench isolation structure, which can easily lead to a decrease in current gain.

[0057] And in Figure 5 In this process, a higher concentration of the first conductivity type base buried layer well region 7 is added inside the first conductivity type base deep well region 6. This results in the base current I... B The path changes, and the surface current density decreases: Injected from the first conductivity type base injection region 9, after passing through the first conductivity type base well region 8, it tends to flow along the lower-resistance first conductivity type base buried layer well region 7 to the second conductivity type emitter well region 10. There is a certain distance between the base current flow direction and the shallow trench isolation structure 12, approximately the thickness of the upper portion 6-2 of the first conductivity type base deep well region 6. In this case, after total dose irradiation, the base current is minimally affected by the oxide layer fixed charge and interface states in the shallow trench isolation structure, reducing the recombination of base carriers and emitter carriers at the emitter-base junction surface. Therefore, it can effectively reduce the excess base current of the bipolar device and decrease the degree of current gain impairment.

[0058] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A device for improving the total dose radiation effect of a bipolar device, characterized in that, The structure includes a first conductivity type substrate (1), a second conductivity type buried layer (2), and a second conductivity type collector deep well region (3) arranged sequentially from bottom to top. A first conductivity type base deep well region (6) is arranged above the second conductivity type collector deep well region (3). A first conductivity type base buried layer well region (7) is arranged inside the first conductivity type base deep well region (6). The first conductivity type base buried layer well region (7) divides the first conductivity type base deep well region (6) into upper and lower parts. A second conductive type collector well region (4) is provided above the four edges of the second conductive type collector well region (3), and a second conductive type collector injection region (5) is provided above the second conductive type collector well region (4). The area of ​​the second conductive type collector injection region (5) is smaller than that of the second conductive type collector well region (4). A first conductive type base well region (8) is provided above the periphery of the first conductive type base deep well region (6). The lower surface of the first conductive type base well region (8) forms an electrical contact with the upper surface of the first conductive type base buried layer well region (7). A first conductive type base injection region (9) is provided above the first conductive type base well region (8). The area of ​​the first conductive type base injection region (9) is smaller than that of the first conductive type base well region (8). A second conductive type emitter well region (10) is provided above the base deep well region (6) of the first conductive type. The lower surface of the emitter well region (10) of the second conductive type forms an electrical contact with the upper surface of the base buried layer well region (7) of the first conductive type. A second conductive type emitter injection region (11) is provided above the emitter well region (10). The area of ​​the emitter injection region (11) of the second conductive type is smaller than that of the emitter well region (10). The emitter injection region (11) of the second conductivity type and the base injection region (9) of the first conductivity type are electrically isolated from each other by an STI shallow trench isolation structure (12), and the base injection region (9) of the first conductivity type and the collector injection region (5) of the second conductivity type are electrically isolated from other devices by an STI shallow trench isolation structure.

2. The device for improving the total dose radiation effect of a bipolar device according to claim 1, characterized in that, The concentration of the first conductivity type base buried layer well region (7) is higher than that of the first conductivity type base deep well region (6); the concentration of the second conductivity type collector injection region (5) is higher than that of the second conductivity type collector well region (4); the concentration of the first conductivity type base injection region (9) is higher than that of the first conductivity type base well region (8); and the concentration of the second conductivity type emitter injection region (11) is higher than that of the second conductivity type emitter well region (10).

3. The device for improving the total dose radiation effect of a bipolar device according to claim 1, characterized in that, The upper surfaces at both ends of the first type of base buried layer well region (7) form an electrical contact with the lower surface of the first type of base buried layer well region (8); the upper surface inside the first type of base buried layer well region (7) forms an electrical contact with the lower surface of the second type of emitter well region (10). The first conductivity type base buried layer well region (7) and the STI shallow trench isolation structure (12) are separated by the upper part (6-2) of the first conductivity type base deep well region (6) and do not directly contact each other.

4. The device for improving the total dose radiation effect of a bipolar device according to claim 1, characterized in that, The edge of the collector injection region (5) of the second conductivity type is tangent to the STI shallow trench isolation structure (12), the edge of the base injection region (9) of the first conductivity type is tangent to the STI shallow trench isolation structure (12), and the edge of the emitter injection region (11) of the second conductivity type is tangent to the STI shallow trench isolation structure (12).

5. The device for improving the total dose radiation effect of a bipolar device according to claim 1, characterized in that, The second type of collector deep well region (3), the second type of collector well region (4), and the second type of collector injection region (5) together constitute the collector structure. The base deep well region (6), the base buried layer well region (7), the base well region (8), and the base injection region (9) of the first conductivity type together constitute the base structure. The second conductivity type emitter well region (10) and the second conductivity type emitter injection region (11) together constitute the emitter structure.

6. The device for improving the total dose radiation effect of a bipolar device according to claim 1, characterized in that, The collector well region (4) of the second conductivity type and the base buried layer well region (7) of the first conductivity type cannot be in direct contact; The collector well region (4) of the second conductivity type and the base well region (8) of the first conductivity type cannot be in direct contact; The base well region (8) of the first conductivity type and the emitter well region (10) of the second conductivity type cannot be in direct contact.

7. The device for improving the total dose radiation effect of a bipolar device according to claim 1, characterized in that, When the first conductivity type doped impurity in the device is acceptor type, the second conductivity type doped impurity is donor type; when the first conductivity type doped impurity is donor type, the second conductivity type doped impurity is acceptor type.

8. The device for improving the total dose radiation effect of a bipolar device according to claim 1, characterized in that, The first conductivity type base well region (8) is omitted. The upper surfaces of both ends of the first conductivity type base buried layer well region (7) form electrical contact with the lower surface of the first conductivity type base injection region (9).

9. The device for improving the total dose radiation effect of a bipolar device according to claim 1, characterized in that, The second conductivity type emitter well region (10) is omitted, and the inner upper surface of the first conductivity type base buried layer well region (7) forms an electrical contact with the lower surface of the second conductivity type emitter injection region (11).

10. A method for fabricating a device for improving the total dose radiation effect of a bipolar device as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Step 1: Provide a first conductivity type substrate silicon wafer (1), perform photolithography and doping ion implantation on its surface, and anneal to form a second conductivity type buried layer (2); perform photolithography and doping ion implantation on the upper surface of the second conductivity type buried layer (2), and anneal to form a second conductivity type collector deep well region (3); perform photolithography and doping ion implantation on the upper surface of the second conductivity type collector deep well region (3) to form a first conductivity type base deep well region (6); Step 2: Photolithography is performed on the surface of the first conductivity type base deep well region (6) to expose the area window for buried layer implantation, high-energy doped ion implantation is performed, and annealing is performed to form the first conductivity type base buried well region (7); the first conductivity type base buried well region (7) divides the first conductivity type base deep well region (6) into upper and lower parts. Step 3: On the surface of the upper part (6-2) of the collector deep well region (3) of the second conductivity type and the base deep well region (6) of the first conductivity type, an oxide layer is grown and a SiN layer is deposited. Active region photolithography is performed, STI etching is performed to form STI trenches, SiO2 or other filling materials are deposited in the STI trenches to ensure electrode isolation, and then chemical mechanical polishing is performed to form an STI shallow trench isolation structure (12). Step 4: Photolithography and doped ion implantation are performed on the surface of the upper part (6-2) of the second conductivity type collector deep well region (3) and the first conductivity type base deep well region (6), and annealing is performed to form the second conductivity type collector well region (4), the second conductivity type collector implantation region (5), the first conductivity type base well region (8), the first conductivity type base implantation region (9), the second conductivity type emitter well region (10), and the second conductivity type emitter implantation region (11), forming a complete radiation-hardened bipolar device structure.

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