CN110828560A - A kind of base region ring doped radiation-resistant lateral PNP transistor and preparation method - Google Patents

Abstract

The invention discloses a base region ring doped radiation-resistant lateral PNP transistor and a preparation method. After the lateral PNP transistor structure is conventionally formed, an N-type N-type base region surface of the lateral PNP transistor is masked and implanted by means of photoresist. Type impurity implantation forms a ring-shaped N+ doped region on the surface of the N-type base region, and pushes the position of the base region width W _b of the lateral PNP transistor from the surface of the N-type epitaxial layer to the body of the N-type epitaxial layer. When the lateral PNP transistor of the base ring structure is in the total dose irradiation environment, although the accumulation of positive charges in the oxide layer will lead to the depletion and inversion of the P-type collector and the depletion and inversion of the surface of the P-type emitter, However, since the base region width W _b has moved down to the depletion and inversion of the P-type collector region and the depletion and inversion of the surface of the P-type emitter region, it does not affect the base region width of the lateral PNP transistor, Therefore, the lateral PNP transistor with the base ring structure has a strong resistance to total dose radiation.

Description

A kind of base region ring doped radiation-resistant lateral PNP transistor and preparation method

technical field

The invention belongs to the technical field of PNP transistors, and in particular relates to a base region ring doped radiation-resistant lateral PNP transistor and a preparation method.

Background technique

Lateral PNP transistor is a transistor structure often used in bipolar integrated circuits. In the production of traditional bipolar integrated circuits, diffusion process or ion implantation process is used to do P-type impurity doping in the collector and emitter regions of the lateral PNP transistor, namely Selective doping of P-type impurities on the N-type epitaxial layer forms the P-type collector region and P-type emitter region of the lateral PNP transistor. The epitaxial layer serves as the N-type base region of the lateral PNP transistor, and the lateral PNP is finally realized through the wires. In the transistor structure, a layer of silicon dioxide is covered on the surface of the transistor as an insulating layer between the metal leads and the doped regions of the transistor, so as to avoid short circuits between different doped regions of the transistor through metal connections.

Lateral PNP transistors have poor resistance to total dose radiation: total dose radiation will cause positive charges to be induced and accumulated in the silicon dioxide layer covering the surface of the transistor, and negative charges will be induced on the surface of the transistor, resulting in P-type collector/emission of the lateral PNP transistor. The surface of the PNP transistor is depleted/inverted, and the holes injected into the base region are pushed to the substrate, the hole diffusion distance increases, the width _WB of the base region of the PNP transistor increases, the transport coefficient α _T decreases, and β decreases.

SUMMARY OF THE INVENTION

Aiming at the influence mechanism of total dose radiation on lateral PNP transistors, the present invention proposes a new type of lateral PNP transistor with improved resistance to total dose radiation through base ring doping and a preparation method thereof. The lateral PNP transistor of this structure has higher resistance to total dose radiation.

In order to achieve the above purpose, the base ring-doped radiation-resistant lateral PNP transistor of the present invention includes an N-type epitaxial layer, and a P-type collector region and a P-type emitter region are concentrically arranged on the upper part of the N-type epitaxial layer. The depth of the electric region and the P-type emitter region is the same, an N-type base region ring is arranged between the P-type collector region and the P-type emitter region, and the N-type base region ring is doped with phosphorus.

Further, the junction depth of the N-type base region ring is 10% to 30% of the junction depth of the P-type collector region.

Further, the width of the N-type base region ring is 30%-80% of the width of the base region of the lateral PNP transistor.

Further, the distance d1 between the N-type base region ring and the P-type collector region is equal to the distance d2 between the N-type base region ring and the P-type emitter region.

Further, the upper end face of the N-type epitaxial layer is provided with a silicon dioxide insulating layer.

Further, the N-type base ring is a sector ring with a central angle of 30°˜360°.

A preparation method of the above-mentioned base region ring doped radiation-resistant lateral PNP transistor, comprising the following steps:

Step 1, using the traditional bipolar process to complete the selective doping of impurities in different regions, forming a lateral PNP transistor structure and forming a silicon dioxide insulating layer;

Step 2: Coating photoresist on the surface of the silicon dioxide insulating layer, and forming an N-type base ring window through exposure and development;

Step 3: Doping the region where the N-type base ring is located by ion implantation, and implanting impurities ³¹ P ⁺ ;

Step 4, remove the photoresist coated in step 2;

Step 5, thermal annealing, to form a base region ring lateral PNP transistor structure.

Compared with the prior art, the present invention has at least the following beneficial technical effects:

Aiming at the influence mechanism of total dose radiation on lateral PNP transistors, a novel bipolar transistor structure is proposed to improve the transistor's resistance to total dose radiation by doping the base region ring. An N-type base region ring is added between the emitter region and the collector region, and the position of the base region width W _b of the lateral PNP transistor is pushed from the surface of the N-type epitaxial layer to the body of the N-type epitaxial layer. Under the condition of total dose radiation of the transistor , although the accumulation of positive charges in the oxide layer will lead to the depletion and inversion of the P-type collector and the depletion and inversion of the surface of the P-type emitter, the base width W _b and the depletion or inversion are no longer in the same plane, Therefore, the width W _b of the base region will not change, thereby suppressing the decrease of the transport coefficient α _T , reducing the decrease of β caused by radiation, and improving the ability of the lateral PNP transistor to resist total dose radiation.

Further, the junction depth of the N-type base region ring is 10% to 30% of the junction depth of the P-type collector region. Under the premise of achieving the effect of the base region ring, the impurity concentration of the base region of the lateral PNP transistor by the doping of the base region ring is reduced. The effect of the base ring on the performance of the lateral PNP transistor is reduced.

Further, the width of the N-type base ring is 30% to 80% of the width of the base region of the lateral PNP transistor. Under the requirements of the distance between the N-type base ring and the collector region and the emitter region of the lateral PNP transistor, try to achieve a wider width. The base ring to ensure the effect of the base ring.

Further, the distance d1 between the N-type base region ring and the P-type collector region is equal to the distance d2 between the N-type base region ring and the P-type emitter region. On the premise of ensuring the width of the N-type base region ring, avoid The breakdown voltage of the base-emitter junction and the base-collector PN junction of the lateral PNP transistor varies due to the doping of the base ring.

Further, the upper end surface of the N-type epitaxial layer is covered with a silicon dioxide insulating layer to avoid short circuits between different doped regions of the transistor through metal connections.

The transistor of the above structure is formed by selective ion implantation: after the selective doping of impurities in different regions is completed by the traditional bipolar process to form the lateral PNP transistor structure, the surface of the N-type base region of the lateral PNP transistor is masked and implanted by photoresist. An N-type impurity implantation is performed to form a ring-shaped N+ doped region on the surface of the N-type base region, and the position of the base region width W _b of the lateral PNP transistor is pushed from the surface of the N-type epitaxial layer to the body of the N-type epitaxial layer. When the lateral PNP transistor of the base ring structure is in the total dose irradiation environment, although the accumulation of positive charges in the oxide layer will lead to the depletion and inversion of the P-type collector and the depletion or inversion of the surface of the P-type emitter, However, since the position of the base width W _b has moved down to the depletion and inversion of the P-type collector region and the depletion or inversion region of the surface of the P-type emitter region, it does not affect the base region width of the lateral PNP transistor. , so the lateral PNP transistor with the base ring structure has a strong ability to resist total dose radiation.

Description of drawings

Figure 1a: Top view of a conventional lateral PNP transistor;

Figure 1b: Top view of a conventional lateral PNP transistor;

Figure 2: Longitudinal sectional view of a traditional structure lateral PNP transistor;

Figure 3: Longitudinal cross-sectional view after total dose irradiation of a conventional lateral PNP transistor

Figure 4a: Top view 1 of a lateral PNP transistor with a base ring structure;

Figure 4b: Top view 2 of a lateral PNP transistor with a base ring structure;

Figure 5: Longitudinal cross-sectional view of a lateral PNP transistor with a base ring structure;

Figure 6: Longitudinal cross-sectional view after total dose radiation of a lateral PNP transistor with a base ring structure;

Figure 7: Schematic diagram of completing the selective doping of impurities in different regions, forming a lateral PNP transistor structure and forming a silicon dioxide insulating layer;

Figure 8: Schematic diagram of the N-type base ring doping window formed by photolithography;

Figure 9: Schematic diagram of N-type base ring doping by ion implantation;

Figure 10: Schematic diagram of removing photoresist on the surface of the silicon wafer as an implantation shielding layer;

Figure 11: Schematic diagram of the formation of an N-type base ring.

In the accompanying drawings: 1—N-type epitaxial layer; 21—P-type collector region of lateral PNP transistor; 22-P-type emitter region of lateral PNP transistor; 3-Silicon dioxide insulating layer; 41-P-type collector area surface depletion or inversion layer; 42 - surface depletion or inversion layer of P-type emission area after total dose irradiation; 5 - N-type base area ring; 7 - photoresist; 8 - N-type base area ring window; 9—implanted impurity ³¹ P ⁺ .

Detailed ways

In order to make the purpose and technical solutions of the present invention clearer and easier to understand. The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

In the description of the present invention, it should be understood that the terms "center", "portrait", "horizontal", "top", "bottom", "front", "rear", "left", "right", " The orientation or positional relationship indicated by vertical, horizontal, top, bottom, inner, outer, etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and The description is simplified rather than indicating or implying that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, unless otherwise specified, "plurality" means two or more. In the description of the present invention, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense, unless otherwise expressly specified and limited, for example, it may be a fixed connection or a detachable connection Connection, or integral connection; can be mechanical connection, can also be electrical connection; can be directly connected, can also be indirectly connected through an intermediate medium, can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood in specific situations.

Aiming at the influence mechanism of the total dose radiation on the silicon-based lateral PNP transistor, the present invention adopts a novel lateral PNP transistor structure to improve the resistance of the transistor to the total dose radiation by doping the base region ring. The bipolar transistor of this new structure is formed by selective ion implantation: after the selective doping of impurities in different regions is completed by the traditional bipolar process to form the lateral PNP transistor structure, the photoresist masking and implantation method is used in the lateral PNP transistor N. An N-type impurity implantation is performed on the surface of the N-type base region to form a ring-shaped N+ doped region on the surface of the N-type base region, and the position of the base region width W _b of the lateral PNP transistor is pushed from the surface of the N-type epitaxial layer to the N-type epitaxial layer. in vivo. When the lateral PNP transistor of the base ring structure is in the total dose irradiation environment, although the accumulation of positive charges in the oxide layer will lead to the depletion or inversion of the P-type collector region 21, the formation on both sides of the upper part of the P-type collector region 21 The surface depletion or inversion layer 41 of the P-type collector region leads to the depletion or inversion of the surface of the P-type emitter region 22, and the surface depletion or inversion layer of the P-type collector region is formed on both sides of the upper part of the P-type emitter region 22 42, but since the base region width W _b has moved down to the depletion and inversion of the P-type collector region 21 and the depletion and inversion of the surface of the P-type emitter region 22, it will not affect the lateral PNP transistor. The width of the base region, so the lateral PNP transistor of the base region ring structure has a strong ability to resist total dose radiation.

A lateral PNP transistor structure, including an N-type epitaxial layer 1 and a silicon dioxide insulating layer 3 arranged in sequence from bottom to top, a P-type collector region 21 and a P-type emitter region 22 are arranged on the upper part of the N-type epitaxial layer 1, and the P-type The collector region 21 and the P-type emitter region 22 are arranged concentrically, the depth of the P-type collector region 21 and the P-type emitter region 22 are the same, and an N-type base region ring is arranged between the P-type collector region 21 and the P-type emitter region 22 5. The junction depth of the N-type base ring 5 is 10% to 30% of the junction depth of the P-type collector region 21 .

Now in conjunction with embodiment, the present invention is further described:

Example 1

The N-type base ring lateral PNP transistor structure of the present invention includes an N-type epitaxial layer 1 and a silicon dioxide insulating layer 3 arranged in sequence from bottom to top, and a P-type collector region 21 and a P-type collector region 21 and a P-type collector region 21 and a P-type collector region 21 and a P-type collector region 21 and a Type emitter region 22, P-type collector region 21 and P-type emitter region 22 are arranged concentrically, P-type collector region 21 and P-type emitter region 22 have the same depth, and between P-type collector region 21 and P-type emitter region 22 An N-type base ring 5 is provided.

Among them, the junction depth of the emitter region 22 of the lateral PNP transistor is 2.5 μm, the N-type base region ring 5 is doped with phosphorus as impurities, the junction depth of the N-type base region ring 5 is 0.25 μm to 0.75 μm, and the junction depth of the N-type base region ring 5 is the emitter region. 10% to 30% of the junction depth of 22, the peak impurity concentration is 5E16cm ^-3 .

The lateral PNP transistor adopts a square emitter region with a side length of 10 μm, a square ring-shaped collector region with an inner side length of 30 μm and an outer side length of 50 μm, which is limited by the junction depth and breakdown voltage index of the collector region of the lateral PNP transistor. The distance between the side and the emitter of the lateral PNP transistor is 2μm to 3μm, which is controlled by the junction depth of the emitter of the lateral PNP transistor and the forward voltage drop of the BE junction. The width of the zone ring 5 is 4 μm˜6 μm. Compared with the traditional lateral PNP transistor, the lateral PNP transistor using the base ring structure, after 100krad (Si) total dose radiation, the transistor magnification attenuation is reduced from 29% to 18%, using the base ring structure lateral PNP transistor Transistors have higher resistance to total dose radiation.

The preparation method of the above-mentioned N-type base ring lateral PNP transistor comprises the following steps:

Step 1. Referring to FIG. 7, the traditional bipolar process completes the selective doping of impurities in different regions to form a lateral PNP transistor structure and form a silicon dioxide insulating layer. At this time, the lateral PNP transistor has an N-type epitaxial layer 1 and a silicon dioxide insulating layer. Layer 3, the upper part of the N-type epitaxial layer 1 has a P-type collector region 21 and a P-type emitter region 22;

Step 2. Referring to FIG. 8 , a photoresist 7 of 2.4 μm is coated on the surface of the silicon dioxide insulating layer, and an N-type base ring window 8 is formed by exposing and developing;

Step 3. Referring to FIG. 9 , the region where the N-type base ring 5 is located is doped by ion implantation, and the implantation impurity ³¹ P ⁺ implantation energy is 400keV, and the implantation dose is 3E12cm ⁻² ;

Step 4. Referring to FIG. 10 , after the implantation is completed, the photoresist 7 coated in Step 2 is removed by plasma etching and H ₂ SO ₄ +H ₂ O ₂ solution;

Step 5. Referring to FIG. 11 , thermal annealing is performed at 950° C. for 30 minutes to complete the activation of implanted impurities to form a base-ring lateral PNP transistor structure.

Example 2

The P-type guard ring bipolar transistor structure of the present invention is adopted, including an N-type epitaxial layer 1 and a silicon dioxide insulating layer 3 arranged in sequence from bottom to top, and a P-type collector region 21 and a P-type collector region 21 and a P-type collector region are arranged on the upper part of the N-type epitaxial layer 1 The emitter region 22, the P-type collector region 21 and the P-type emitter region 22 are arranged concentrically, the P-type collector region 21 and the P-type emitter region 22 have the same depth, and are arranged between the P-type collector region 21 and the P-type emitter region 22 There is an N-type base ring 5.

Among them, the lateral PNP transistor adopts a circular emitter with a diameter of 6 μm and a 30°~360° circular collector region with an inner diameter of 15 μm and an outer diameter of 27 μm. If it is less than 30°, the efficiency of the lateral PNP transistor is too low and not practical. ; The width of the base ring is 2.5 μm, the distance between the inner edge of the base ring and the emitter region of the lateral PNP transistor is 1 μm, and the distance between the outer edge of the base ring and the edge of the collector region is 1 μm; the N-type base ring 5 of the lateral PNP transistor is doped with phosphorus, The N-type base ring 5 has a junction depth of 0.3 μm and a peak impurity concentration of 7E16cm ⁻³ .

Compared with the traditional lateral PNP transistor, the lateral PNP transistor using the base ring structure, after 100krad (Si) total dose radiation, the transistor magnification attenuation is reduced from 29% to 18%, using the base ring structure lateral PNP transistor Transistors have higher resistance to total dose radiation.

The preparation method of the above-mentioned N-type base ring lateral PNP transistor comprises the following steps:

Step 1. Referring to FIG. 7, the traditional bipolar process completes the selective doping of impurities in different regions, forms a PNP transistor structure and forms a silicon dioxide insulating layer 3 on the surface of the PNP transistor;

Step 2. Referring to FIG. 8, a photoresist 7 of 1.3 μm is coated on the surface of the silicon dioxide insulating layer 3, and an N-type base ring window 8 is formed by exposing and developing;

Step 3. Referring to FIG. 9 , by ion implantation, the region where the N-type base ring is located is doped, and the impurity ³¹ P ⁺ is implanted, the implantation energy is 100keV, and the implantation dose is 5E12cm ⁻² ;

Step 4. Referring to FIG. 10 , after the implantation is completed, the photoresist 7 coated in Step 2 is removed by plasma etching and H ₂ SO ₄ +H ₂ O ₂ solution;

Step 5. Referring to FIG. 11 , thermal annealing is performed at 800° C. for 10 minutes to form a base-ring lateral PNP transistor structure.

The total dose radiation test evaluation was carried out on the new base ring structure lateral PNP transistor and the traditional structure lateral PNP transistor proposed in Example 1 of the present invention: after 100krad (Si) total dose radiation, the new base ring structure lateral PNP transistor amplification factor decays 18.85%, the amplification factor of the traditional structure lateral PNP transistor is attenuated by 29.68%, and the total dose radiation resistance of the base ring structure transistor is higher than that of the traditional structure bipolar transistor.

The above content is only to illustrate the technical idea of the present invention, and cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention all fall within the scope of the claims of the present invention. within the scope of protection.

Claims (7)

1. The base-ring-doped anti-radiation transverse PNP transistor is characterized by comprising an N-type epitaxial layer (1), wherein a P-type collector region (21) and a P-type emitter region (22) are concentrically arranged at the upper part of the N-type epitaxial layer (1), the depths of the P-type collector region (21) and the P-type emitter region (22) are the same, an N-type base ring (5) is arranged between the P-type collector region (21) and the P-type emitter region (22), and impurities doped in the N-type base ring (5) are phosphorus.

2. The base-ring-doped radiation-resistant lateral PNP transistor according to claim 1 characterized in that the junction depth of the N-type base ring (5) is 10% to 30% of the junction depth of the P-type collector region (21).

3. The base ring doped radiation resistant lateral PNP transistor of claim 1 wherein the width of the N-type base ring (5) is 30% to 80% of the base width of the lateral PNP transistor.

4. A base ring doped radiation resistant lateral PNP transistor according to claim 1 characterized in that the distance d1 between the N-type base ring (5) and the P-type collector region (21) is equal to the distance d2 between the N-type base ring (5) and the P-type emitter region (22).

5. A lateral PNP transistor with base ring doped radiation protection according to claim 1 characterized in that the upper end face of the N-type epitaxial layer (1) is provided with an insulating layer (3) of silicon dioxide.

6. The base-ring-doped radiation-resistant lateral PNP transistor of claim 1 characterized in that the N-type base ring (5) is a sector ring with a central angle of 30 ° to 360 °.

7. A method of making a base ring doped radiation resistant lateral PNP transistor of claim 1 comprising the steps of:

step 1, completing selective doping of impurities in different regions by using a traditional bipolar process to form a transverse PNP transistor structure and a silicon dioxide insulating layer (3);

step 2, coating photoresist (7) on the surface of the silicon dioxide insulating layer (3), and forming an N-type base region ring window (8) through exposure and development;

step 3, doping the region where the N-type base region ring (5) is located through ion implantation, and implanting impurities³¹P⁺(9)；

Step 4, removing the photoresist (7) coated in the step 2;

and 5, thermally annealing to form the base region ring transverse PNP transistor structure.

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