Device for improving total dose radiation effect of bipolar device and preparation method thereof

Abstract

The invention discloses a device for improving the total dose radiation effect of a bipolar device and a preparation method thereof, and belongs to the technical field of radiation hardening of semiconductor devices. A first conductive type base buried layer well region with higher concentration is formed in a first conductive type base deep well region of a traditional bipolar device, so that a current path of the base region is changed from being tightly attached to the lower surface of a shallow trench isolation structure to be a certain distance away from the shallow trench isolation structure; when the resistance of the first conductive type is smaller than that of the second conductive type, the first conductive type is more inclined to flow to the second conductive type emitter well region along the first conductive type base buried layer well region with smaller resistance, thereby being far away from the SiO2-Si surface defect, weakening the surface recombination and reducing the generation of excessive base current. According to the invention, the excess base current after the total dose radiation of the bipolar device can be effectively reduced, the degree of current gain damage is reduced, and the anti-radiation capability of the bipolar device is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of radiation resistance reinforcement of semiconductor devices, and in particular to a device for improving the total dose radiation effect of a bipolar device and a preparation method thereof. Background Art

[0002] In bipolar devices, the SiO2 oxide layer covering the emitter-base region of bipolar devices is very thick and relatively low in quality, and the hydrogen content is usually high, so it contains various types of neutral oxygen vacancy defects and hydrogenation defects. When the device is irradiated with a total dose, the radiation generates electron-hole pairs in the SiO2 oxide layer through ionizing radiation loss energy. Since the mobility of electrons is much greater than the mobility of holes, electrons will leave the oxide layer, while holes are concentrated in the oxide layer: holes are transported to the vicinity of the Si-SiO2 interface and captured by the trap region concentrated in the interface of about 100nm, thereby forming oxide trap charges; ionizing radiation also breaks some silicon-hydrogen bonds, forming interface states (traps) at the Si-SiO2 interface on the base-emitter junction. These traps do not contribute to the surface current when they are on the undepleted surface, but when the positive charge in the oxide layer increases, the surface depletion region increases, exposing more interface traps. When the interface traps are on the depleted surface, they become effective recombination centers, increasing the surface recombination rate at the interface. These two damage mechanisms act together on the surface space charge region of the emitter-base junction. As a result, although the oxide layer charge and interface traps only increase sublinearly or linearly with the total dose, the base current increases superlinearly with the increase of the total dose, reducing the base region transport coefficient, increasing the excess base current, and reducing the current gain. At present, the main idea in the industry to improve the total dose radiation effect of bipolar devices is to strengthen the masking oxide layer on the emitter-base junction surface, which is a sensitive position for the total dose radiation of bipolar devices, and weaken the influence of the total dose radiation effect from the source. For example, thinning the thickness of the masking oxide layer, or changing the composition of the masking oxide layer material. However, changing the oxide layer will cause large changes in the process, which seriously affects the normal performance of other devices.

[0003] Through extensive research, we have discovered another way to improve the total dose radiation effect of bipolar devices: optimize the base current path, reduce the surface current density of the emitter-base junction, and let the base current flow mainly from the bottom of the emitter-base junction to the emitter, thereby staying away from surface defects, weakening surface recombination, and reducing the generation of excess base current. This cleverly bypasses the large process changes caused by directly reinforcing the Si-SiO2 interface area. Summary of the invention

[0004] The object of the present invention is to provide a device for improving the total dose radiation effect of a bipolar device and a preparation method thereof, so as to reduce the excess base current of the bipolar device after the total dose radiation.

[0005] The technical solution to achieve the purpose of the present invention is: a device for improving the total dose radiation effect of a bipolar device, comprising a first conductive type substrate, a second conductive type buried layer, and a second conductive type collector deep well region arranged in sequence from bottom to top, a first conductive type base deep well region is arranged above the second conductive type collector deep well region, a first conductive type base buried layer well region is arranged inside the first conductive type base deep well region, and the first conductive type base buried layer well region divides the first conductive type base deep well region into two upper and lower parts;

[0006] A second conductive type collector well region is arranged above the edges of the second conductive type collector well region, a second conductive type collector injection region is arranged above the second conductive type collector well region, and the area of ​​the second conductive type collector injection region is smaller than that of the second conductive type collector well region;

[0007] A first conductive type base well region is arranged above the edges of the first conductive type base deep well region, the lower surface of the first conductive type base well region forms electrical contact with the upper surface of the first conductive type base buried layer well region, and a first conductive type base injection region is arranged above the first conductive type base well region, and the area of ​​the first conductive type base injection region is smaller than the first conductive type base well region;

[0008] A second conductive type emitter well region is provided above the first conductive type base deep well region, a lower surface of the second conductive type emitter well region forms electrical contact with an upper surface of the first conductive type base buried well region, a second conductive type emitter injection region is provided above the second conductive type emitter well region, and an area of ​​the second conductive type emitter injection region is smaller than that of the second conductive type emitter well region;

[0009] The second conductive type emitter injection region and the first conductive type base injection region, and the first conductive type base injection region and the second conductive type collector injection region are electrically isolated by STI shallow trench isolation structures, and the outer side of the second conductive type collector injection region is electrically isolated from other devices by STI shallow trench isolation structures.

[0010] A method for preparing a device for improving the total dose radiation effect of a bipolar device comprises the following steps:

[0011] The first step: providing a first conductive type substrate silicon wafer, performing photolithography and doping ion implantation on the surface thereof, and annealing to form a second conductive type buried layer; performing photolithography and doping ion implantation on the upper surface of the second conductive type buried layer, and annealing to form a second conductive type collector deep well region; performing photolithography and doping ion implantation on the upper surface of the second conductive type collector deep well region to form a first conductive type base deep well region;

[0012] Step 2: Photolithography is performed on the surface of the first conductive type base deep well region to expose a window of the region where buried layer injection is required, and high energy doping ion injection is performed, followed by annealing to form a first conductive type base buried well region; the first conductive type base buried well region divides the first conductive type base deep well region into two upper and lower parts;

[0013] Step 3: growing an oxide layer and depositing a SiN layer on the surface of the second conductive type collector deep well region and the upper part of the first conductive type base deep well region, performing active area photolithography, performing STI etching, forming an STI groove, depositing SiO2 or other filling materials in the STI groove, performing electrode isolation, and then performing chemical mechanical polishing to form an STI shallow trench isolation structure;

[0014] Step 4: Perform photolithography and doping ion implantation on the surface of the second conductivity type collector deep well region and the upper part of the first conductivity type base deep well region, and anneal to form a second conductivity type collector well region, a second conductivity type collector injection region, a first conductivity type base well region, a first conductivity type base injection region, a second conductivity type emitter well region, and a second conductivity type emitter injection region to form a complete radiation-resistant reinforced bipolar device structure.

[0015] Compared with the prior art, the significant advantages of the present invention are as follows: the present invention forms a first conductivity type base buried well region with a higher concentration in the first conductivity type base deep well region of the traditional bipolar device, so that the base region current path changes from being close to the lower surface of the shallow trench isolation structure to having a certain distance from the shallow trench isolation structure, and is more inclined to flow along the first conductivity type base buried well region with smaller resistance to the second conductivity type emitter well region, thereby staying away from SiO2-Si surface defects, weakening surface recombination, and reducing the generation of excess base current. Therefore, the present invention can effectively reduce the excess base current of the bipolar device after total dose radiation, reduce the degree of current gain damage, and improve the radiation resistance of the bipolar device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 to Figure 4 It is a schematic diagram of the process steps of the present invention;

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

[0018] Figure 6 is a schematic cross-sectional view of a bipolar device structure formed by a conventional method;

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

[0020] Explanation of the accompanying drawings: 1 is a first conductive type substrate, 2 is a second conductive type buried layer, 3 is a second conductive type collector deep well region, 4 is a second conductive type collector well region, 5 is a second conductive type collector injection region, 6 is a first conductive type base deep well region, 7 is a first conductive type base buried well region, 6-1 is a lower half of the first conductive type base deep well region 6 separated by the first conductive type base buried well region 7, 6-2 is an upper half of the first conductive type base deep well region 6 separated by the first conductive type base buried well region 7, 8 is a first conductive type base well region, 9 is a first conductive type base injection region, 10 is a second conductive type emitter well region, 11 is a second conductive type emitter injection region, and 12 is an STI shallow trench isolation structure. DETAILED DESCRIPTION

[0021] The following is a further detailed description of a method for improving the total dose radiation effect of a bipolar device proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims. It should be noted that the accompanying drawings are in a very simplified form and are not in precise proportions, and are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention.

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

[0023] On the first conductive type substrate 1, there is a second conductive type buried layer 2.

[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 a bipolar device collector.

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

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

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

[0029] Two ends of the first conductive type buried well region 7 are led out through the first conductive type base well region 8 and the first conductive type base injection region 9 to form the base 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 is the emitter of the bipolar device.

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

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

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

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

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

[0037] The first conductive type base buried well region 7 and the shallow trench isolation structure 12 are separated by the upper portion 6 - 2 of the first conductive type base deep well region 6 and are not in direct contact with each other.

[0038] Furthermore, the edge of the second conductive type collector injection region 5 is tangent to the STI shallow trench isolation structure 12 , the edge of the first conductive type base injection region 9 is tangent to the STI shallow trench isolation structure 12 , and the edge of the second conductive 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 a collector structure;

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

[0041] A second conductive type emitter well region 10 and a second conductive type emitter injection region 11, which together constitute an emitter structure;

[0042] Furthermore, the second conductivity type collector well region 4 cannot directly contact the first conductivity type base buried well region 7;

[0043] The second conductivity type collector well region 4 cannot directly contact the first conductivity type base well region 8;

[0044] The first conductivity type base well region 8 and the second conductivity type emitter well region 10 cannot be in direct contact with each other;

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

[0046] Furthermore, the first conductive type base well region 8 can be omitted as required, and in this case, the upper surfaces of both ends of the first conductive type base buried well region 7 need to form electrical contact with the lower surface of the first conductive type base injection region 9;

[0047] Furthermore, the second conductive type emitter well region 10 can be omitted as required, and in this case, the inner upper surface of the first conductive type base buried well region 7 needs to form an electrical contact with the lower surface of the second conductive type emitter injection region 11;

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

[0049] The present invention also provides a preparation method for improving the total dose radiation effect of a bipolar device, comprising the following steps:

[0050] The first step is to provide a first conductive type substrate silicon wafer 1, perform photolithography and doping ion implantation on the surface thereof, and anneal to form a second conductive type buried layer 2; perform photolithography and doping ion implantation on the upper surface of the second conductive type buried layer 2, and anneal to form a second conductive type collector deep well region 3; perform photolithography and doping ion implantation on the upper surface of the second conductive type collector deep well region 3 to form a first conductive type base deep well region 6, such as Figure 1 As shown;

[0051] Step 2: Photolithography is performed on the surface of the first conductive type base deep well region 6 to expose the area window where buried layer injection is required, and high energy doping ion injection is performed, followed by annealing to form the first conductive type base buried well region 7; the first conductive type base buried well region 7 divides the first conductive type base deep well region 6 into two parts, a lower part 6-1 and an upper part 6-2; the concentration of the first conductive type base buried well region 7 is higher than that of the first conductive type base deep well region 6; Figure 2 As shown;

[0052] Step 3: grow an oxide layer on the surface of the second conductive type collector deep well region 3 and the upper part 6-2 of the first conductive type base deep well region 6, deposit a SiN layer, perform active area photolithography, perform STI etching, form STI grooves, deposit SiO2 or other filling materials in the STI grooves, perform electrode isolation, and then perform chemical mechanical polishing to form STI shallow trench isolation regions 12, such as Figure 3 As shown;

[0053] Step 4: Photolithography and doping ion implantation are performed on the surface of the second conductive type collector deep well region 3 and the upper portion 6-2 of the first conductive type base deep well region 6, and annealing is performed to form a second conductive type collector well region 4, a second conductive type collector injection region 5, a first conductive type base well region 8, a first conductive type base injection region 9, a second conductive type emitter well region 10, and a second conductive type emitter injection region 11, so as to form a complete anti-irradiation reinforced bipolar device structure, such as Figure 4 shown.

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

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

[0056] Figure 7 In the case of B It is injected from the first conductivity type base injection region 9, passes through the first conductivity type base well region 8, and then chooses the shortest path to flow to the second conductivity type emitter well region 10, that is, close to the lower surface of the shallow trench isolation structure 12. In this case, after the total dose irradiation, the base current is most affected by the fixed charge of the oxide layer and the interface state in the shallow trench isolation structure, which is very likely to cause a reduction in current gain.

[0057] And in Figure 5 In the embodiment, a first conductive type base buried well region 7 with a higher concentration is added inside the first conductive type base deep well region 6. This results in a base current I B The path changes and the surface current density decreases: the current is injected from the first conductive type base injection region 9, and after passing through the first conductive type base well region 8, it tends to flow along the first conductive type base buried well region 7 with smaller resistance to the second conductive type emitter well region 10. There is a certain distance between the base current flow direction and the shallow trench isolation structure 12, which is roughly the thickness of the upper part 6-2 of the first conductive type base deep well region 6. In this case, after the total dose irradiation, the base current is little affected by the fixed charge and interface state of the oxide layer in the shallow trench isolation structure, which reduces the recombination of base carriers and emitter carriers on the emitter-base junction surface, thereby effectively reducing the excess base current of the bipolar device and reducing the degree of current gain damage.

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

Claims

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

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

3. A 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 conductive type base buried layer well region (7) form electrical contact with the lower surface of the first conductive type base well region (8); the upper surface inside the first conductive type base buried layer well region (7) forms electrical contact with the lower surface of the second conductive type emitter well region (10); The first conductive type base buried layer well region (7) and the STI shallow trench isolation structure (12) are separated by the upper portion (6-2) of the first conductive type base deep well region (6) and are not in direct contact.

4. A device for improving the total dose radiation effect of a bipolar device according to claim 1, characterized in that: The edge of the second conductive type collector injection region (5) is tangent to the STI shallow trench isolation structure (12), the edge of the first conductive type base injection region (9) is tangent to the STI shallow trench isolation structure (12), and the edge of the second conductive type emitter injection region (11) 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: A second conductive type collector deep well region (3), a second conductive type collector well region (4), and a second conductive type collector injection region (5), which together constitute a collector structure; A first conductive type base deep well region (6), a first conductive type base buried layer well region (7), a first conductive type base well region (8), and a first conductive type base injection region (9), the four together constitute a base structure; The second conductive type emitter well region (10) and the second conductive type emitter injection region (11) together form an emitter structure.

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

7. A 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 an acceptor type, the second conductivity type doped impurity is a donor type; when the first conductivity type doped impurity is a donor type, the second conductivity type doped impurity is an 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 conductive type base well region (8) is omitted, and the upper surfaces at both ends of the first conductive type base buried layer well region (7) are in electrical contact with the lower surface of the first conductive 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 conductive type emitter well region (10) is omitted, and the inner upper surface of the first conductive type base buried layer well region (7) forms electrical contact with the lower surface of the second conductive type emitter injection region (11).

10. A method for preparing a device for improving the total dose radiation effect of a bipolar device as claimed in any one of claims 1 to 7, characterized in that: The steps include: The first step is to provide a first conductive type substrate silicon wafer (1), perform photolithography and doping ion implantation on the surface of the substrate, and perform annealing to form a second conductive type buried layer (2); perform photolithography and doping ion implantation on the upper surface of the second conductive type buried layer (2), and perform annealing to form a second conductive type collector deep well region (3); perform photolithography and doping ion implantation on the upper surface of the second conductive type collector deep well region (3), and form a first conductive type base deep well region (6); Step 2: performing photolithography on the surface of the first conductive type base deep well region (6) to expose a window in the region where buried layer implantation is required, performing high energy doping ion implantation, and performing annealing to form a first conductive type base buried layer well region (7); the first conductive type base buried layer well region (7) divides the first conductive type base deep well region (6) into two upper and lower parts; Step 3: growing an oxide layer and depositing a SiN layer on the surface of the second conductive type collector deep well region (3) and the upper portion (6-2) of the first conductive type base deep well region (6), performing active area photolithography, performing STI etching, forming an STI trench, depositing SiO2 or other filling materials in the STI trench, performing electrode isolation, and then performing chemical mechanical polishing to form an STI shallow trench isolation structure (12); Step 4: Photolithography and doping ion implantation are performed on the surface of the second conductive type collector deep well region (3) and the upper portion (6-2) of the first conductive type base deep well region (6), and annealing is performed to form a second conductive type collector well region (4), a second conductive type collector injection region (5), a first conductive type base well region (8), a first conductive type base injection region (9), a second conductive type emitter well region (10), and a second conductive type emitter injection region (11), thereby forming a complete radiation-resistant reinforced bipolar device structure.

Images