An NPN device based on a non-polar isolation zone and a preparation method thereof

Abstract

The present invention relates to an NPN device based on a non-polar isolation strip, which includes a P-type substrate, an N-type buried layer, and an N-type epitaxial layer. First isolation strips are respectively provided at both ends of the N-type epitaxial layer; between the two first isolation strips, a P-type deep well region, a second isolation strip, and a first diffusion region are sequentially formed; a second diffusion region and a third diffusion region are respectively formed in the P-type deep well region; a first insulating layer is formed on the N-type epitaxial layer, and a second insulating layer is formed on the first insulating layer; a first metal, a second metal, and a third metal are sequentially and spacedly provided on the second insulating layer; the first metal penetrates into the second diffusion region; the second metal penetrates into the third diffusion region; the third metal penetrates into the first diffusion region. The present invention can be applied to circuits with relatively high integration, and can meet medium and high operating voltages and operating frequencies.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and particularly relates to an NPN device based on a non-polar isolation strip and a preparation method thereof. Background Art

[0002] At present, the NPN structures in relatively mature integrated circuit processes all adopt bipolar doping isolation. The characteristics of this structure are low operating voltage and low operating frequency. In the field of low voltage and low operating frequency, this structure is widely used due to its low cost. However, when the application scenario requires higher operating voltage and operating frequency, the products of this structure can no longer meet the requirements. For example, in the case of medium voltage, when the voltage reaches 80V and higher voltage application occasions, NPN basically appears in the form of discrete devices rather than in the form of integrated circuits, which limits the circuit architecture and circuit integration that must use NPN devices.

[0003] In traditional bipolar integrated circuit processes, the operating voltage is mainly related to the breakdown voltage VCEO between the collector and the emitter. At the same time, after VCEO meets the requirements, the lateral breakdown voltage VCBO between the collector and the base also needs to be greater than VCEO. The breakdown voltage of this structure is improved by controlling the distance between N+ and P+ of CB in the process. And there is a parasitic capacitance between N+ and P+ in the traditional structure before breakdown. The continuous charging and discharging of this capacitance in the switching characteristics will restrict the operating frequency of the device. Therefore, the breakdown voltage resistance and operating frequency of the NPN structure in traditional bipolar integrated circuit processes are restricted by the structural characteristics, making this structure unable to meet high operating voltage and operating frequency. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the present invention provides an NPN device based on a non-polar isolation strip and a preparation method thereof. This NPN structure can be applied to circuits with higher integration, and can meet medium and high operating voltage and operating frequency.

[0005] In order to achieve the above object, the technical solution of the present invention is:

[0006] An NPN device based on a non-polar isolation strip, comprising a P-type substrate; an N-type buried layer is formed on the P-type substrate, an N-type epitaxial layer is formed on the N-type buried layer, and two ends of the N-type epitaxial layer are respectively provided with a first isolation strip that extends downward through the N-type buried layer and penetrates into the P-type substrate and is filled with a non-polar material;

[0007] Between the two first isolation strips, a P-type deep well region, a second isolation strip, and a first diffusion region are sequentially formed from left to right; wherein, both the second isolation strip and the first diffusion region extend downward into the N-type buried layer;

[0008] A second diffusion region and a third diffusion region are respectively formed in the P-type deep well region; a first insulating layer is formed on the N-type epitaxial layer, and a second insulating layer is formed on the first insulating layer;

[0009] On the second insulating layer, a first metal, a second metal, and a third metal are sequentially arranged at intervals from left to right; the first metal extends downward through the first insulating layer and penetrates into the second diffusion region; the second metal extends downward through the first insulating layer and penetrates into the third diffusion region; the third metal extends downward through the first insulating layer and penetrates into the first diffusion region.

[0010] In the above NPN device based on a non-polar isolation strip, the third diffusion region is the base region of the NPN structure device, the second diffusion region is the emitter region of the NPN device, and the N-type epitaxial layer is the collector region of the NPN device.

[0011] In the above NPN device based on a non-polar isolation strip, both the first diffusion region and the second diffusion region are N-type diffusion regions, and the third diffusion region is a P-type diffusion region; the first diffusion region, the second diffusion region, and the third diffusion region form an NPN device;

[0012] The second diffusion region is connected to the first metal to form the emitter of the NPN structure device; the third diffusion region is connected to the second metal to form the base of the NPN device; the first diffusion region, the N-type buried layer, and the N-type epitaxial layer are connected to the third metal to form the collector of the NPN device.

[0013] In the above NPN device based on a non-polar isolation strip, both the first isolation strip and the second isolation strip are composed of non-polar material polysilicon, which is used to protect the NPN device to achieve electrical isolation.

[0014] The preparation method of the above NPN device based on a non-polar isolation strip includes the following steps:

[0015] Step 1) Provide a P-type substrate, form an N-type buried layer on the P-type substrate, and perform photolithography and diffusion on the N-type buried layer;

[0016] Step 2) Form an N-type epitaxial layer on the N-type buried layer;

[0017] Step 3) Etch a first diffusion region in the N-type epitaxial layer, and the first diffusion region extends downward and penetrates into the N-type buried layer;

[0018] Step 4) Form a P-type deep well region in the N-type epitaxial layer and on the left side of the first diffusion region, perform photolithography and diffusion on the P-type deep well region, and form a third diffusion region in the P-type deep well region, and perform photolithography and diffusion on the third diffusion region;

[0019] Step 5) A second diffusion region is formed within the P-type deep well region and to the left of the third diffusion region, and photolithography and diffusion are performed on the second diffusion region;

[0020] Step 6) A first grooving is performed at both ends of the N-type epitaxial layer. The grooving at the left end is located to the left of the P-type deep well region, and the grooving at the right end is located to the right of the first diffusion region. Both groovings at both ends extend downward, passing through the N-type buried layer and deep into the P-type substrate;

[0021] Step 7) A second grooving is performed within the N-type epitaxial layer between the P-type deep well region and the first diffusion region, and the second grooving extends downward and deep into the N-type buried layer;

[0022] Step 8) A non-polar material is deposited in both the first grooving and the second grooving; the non-polar material deposited in the first grooving forms a first isolation band, and the non-polar material deposited in the second grooving forms a second isolation band;

[0023] Step 9) Contact holes are respectively photolithographed in the second diffusion region, the third diffusion region, and the first diffusion region, and a first metal, a second metal, and a third metal are sequentially deposited and etched back in the contact holes; then a first insulating layer is deposited on the N-type epitaxial layer, and a second insulating layer is deposited on the first insulating layer.

[0024] In the above preparation method of an NPN device based on a non-polar isolation band, the thickness of the N-type epitaxial layer is greater than the sum of the base region diffusion junction depth + the collector junction depletion width + the buried layer upward push distance.

[0025] In the above preparation method of an NPN device based on a non-polar isolation band, the non-polar material includes polysilicon.

[0026] In the above preparation method of an NPN device based on a non-polar isolation band, the first metal, the second metal, and the third metal are all aluminum alloy materials.

[0027] In the above preparation method of an NPN device based on a non-polar isolation band, the first grooving and the second grooving are both completed by lithography and etching through a deep trench etching machine.

[0028] Technical effects and advantages of the present invention:

[0029] An NPN device based on a non-polar isolation band provided by the present invention can convert the breakdown voltage of the collector's isolation of the PN junction into the breakdown voltage of the non-polar material isolation band by grooving on the N-type epitaxial layer and depositing a non-polar material in the grooving to form an isolation band, so that the voltage withstand capacity of the NPN device becomes higher under the same conditions; the parasitic capacitance generated by the collector region and the N / P-type isolation band can be eliminated through the isolation band, and the junction capacitance becomes smaller, making the frequency characteristics of the device better; the isolation band can effectively shorten the distance between the isolation band and the base, thereby improving the area utilization rate and reducing the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic structural diagram of the present invention;

[0031] Figure 2 is a schematic structural diagram of the NPN device and the circuit symbol diagram of the NPN device of the present invention;

[0032] Figure 3 is a schematic structural diagram of step 1) of the preparation of the present invention;

[0033] Figure 4 is a schematic structural diagram of step 2) of the preparation of the present invention;

[0034] Figure 5 is a schematic structural diagram of step 3) of the preparation of the present invention;

[0035] Figure 6 is a schematic structural diagram of step 4) of the preparation of the present invention;

[0036] Figure 7 is a schematic structural diagram of step 5) of the preparation of the present invention;

[0037] Figure 8 is a schematic structural diagram of step 6) of the preparation of the present invention;

[0038] Figure 9 is a schematic structural diagram of step 7) of the preparation of the present invention;

[0039] Figure 10 is a schematic structural diagram of step 8) of the preparation of the present invention;

[0040] Figure 11 is a schematic structural diagram of step 9) of the preparation of the present invention.

[0041] Reference numerals in the figures: 1, P-type substrate; 2, N-type buried layer; 3, N-type epitaxial layer; 4, P-type deep well region; 5, second diffusion region; 6, first diffusion region; 7, second isolation strip; 8, first isolation strip; 9, third diffusion region; 10, first insulating layer; 11, second insulating layer; 12, first metal; 13, second metal; 14, third metal. DETAILED DESCRIPTION OF THE INVENTION

[0042] The following examples given in conjunction with the drawings further illustrate the present invention in detail.

[0043] Example 1

[0044] See Figure 1As shown in the figure, an NPN device based on a non-polar isolation strip according to the present invention is composed of a P-type substrate 1, an N-type buried layer 2, an N-type epitaxial layer 3, a P-type deep well region 4, a second diffusion region 5, a first diffusion region 6, a second isolation strip 7, two first isolation strips 8, a third diffusion region 9, a first insulating layer 10, a second insulating layer 11, a first metal 12, a second metal 13, and a third metal 14.

[0045] During specific implementation, refer to Figure 1 As shown in the figure, the N-type buried layer 2 is formed on the P-type substrate 1, the N-type epitaxial layer 3 is formed on the N-type buried layer 2, and the two first isolation strips 8 are respectively vertically arranged at both ends of the N-type epitaxial layer 3. Their upper ends are flush with the bottom of the N-type epitaxial layer 3, and their lower ends respectively extend downward and pass through the N-type buried layer 2 and penetrate into the P-type substrate 1.

[0046] During specific implementation, refer to Figure 1 As shown in the figure, between the two first isolation strips 8, a P-type deep well region 4, a second isolation strip 7, and a first diffusion region 6 are also formed; among them, the P-type deep well region 4, the second isolation strip 7, and the first diffusion region 6 are arranged at intervals from left to right in sequence.

[0047] During specific implementation, refer to Figure 1 As shown in the figure, the upper ends of the P-type deep well region 4, the second isolation strip 7, and the first diffusion region 6 are all flush with the top of the N-type epitaxial layer 3, and the lower ends of the second isolation strip 7 and the first diffusion region 6 both extend downward into the N-type buried layer 2.

[0048] During specific implementation, the first isolation strip 8 and the second isolation strip 7 are both composed of non-polar material polysilicon, which is used to protect the NPN structure device to achieve electrical isolation.

[0049] During specific implementation, refer to Figure 1 As shown in the figure, a second diffusion region 5 and a third diffusion region 9 are respectively formed in the P-type deep well region 4; a first insulating layer 10 is formed on the N-type epitaxial layer 3, and a second insulating layer 11 is formed on the first insulating layer 10.

[0050] During specific implementation, refer to Figure 1 As shown in the figure, a first metal 12, a second metal 13, and a third metal 14 are sequentially arranged at intervals from left to right on the second insulating layer 11; the first metal 12 extends downward through the first insulating layer 10 and penetrates into the second diffusion region 5; the second metal 13 extends downward through the first insulating layer 10 and penetrates into the third diffusion region 9; the third metal 14 extends downward through the first insulating layer 10 and penetrates into the first diffusion region 6.

[0051] In this embodiment, the third diffusion region 9 is the base region of the NPN structure device, the second diffusion region 5 is the emitter region of the NPN structure device, and the N-type epitaxial layer 3 is the collector region of the NPN device.

[0052] In this embodiment, by providing the first isolation strip 8 and the second isolation strip 7, the breakdown voltage resistance of the NPN device is improved. Not only is the breakdown voltage increased, but the junction capacitance is also reduced; the breakdown voltage of the PN junction isolation in the original process for the collector is converted into the breakdown voltage of the non-polar material isolation strip, so that under the same conditions, the NPN device not only has improved breakdown voltage resistance, but also reduces the area of the NPN device and lowers the cost. At the same time, the junction capacitance is reduced and the operating frequency is increased.

[0053] By grooving on the N-type epitaxial layer 3 and depositing non-polar materials in the grooves to form the first isolation strip 8 and the second isolation strip 7, the breakdown voltage of the PN junction isolation for the collector can be converted into the breakdown voltage of the non-polar material isolation strip, so that the breakdown voltage resistance of the NPN device becomes higher under the same conditions; through the isolation strip, the parasitic capacitance generated by the collector region and the N / P type isolation strip can be eliminated, and the junction capacitance becomes smaller, making the frequency characteristics of the device better; through the isolation strip, the distance between the isolation strip and the base can be effectively shortened, thereby improving the area utilization rate and reducing the cost.

[0054] The operating voltage of the NPN device is mainly related to the breakdown voltage VCEO between the collector and the emitter. At the same time, after VCEO meets the requirements, the lateral breakdown voltage VCBO between the collector and the base needs to be greater than VCEO. The lateral breakdown voltage VCBO is positively correlated with the lateral distance between the base region and the collector region. Adding an isolation strip of non-polar isolation material can effectively reduce the positive correlation coefficient. And using a non-polar material as the isolation strip, converting the breakdown voltage into the breakdown voltage of the non-polar material isolation strip, improving the breakdown voltage resistance of the NPN structure device, can eliminate the parasitic capacitance Csub generated by the collector region and the isolation ring, making the frequency characteristics of the device better, improving the insulation isolation performance between NPN devices, and eliminating leakage current. The breakdown voltage resistance of the device can also be improved by setting different distances between the non-polar material isolation ring and the base and different numbers of non-polar material isolation rings.

[0055] In this embodiment, referring to Figure 2 as shown, the conduction types of the first diffusion region 6 and the second diffusion region 5 are both N-type, and the conduction type of the third diffusion region 9 is P-type; that is, the conduction types of the emitter region and the collector region of the NPN device are both N-type, and the conduction type of the base region is P-type. Thus, the structure formed by the first diffusion region 6, the second diffusion region 5, and the third diffusion region 9 is an NPN device.

[0056] In this embodiment, the second diffusion region 5 is connected to the first metal 12 to form the emitter of the NPN device; the third diffusion region 9 is connected to the second metal 13 to form the base of the NPN structure device; the first diffusion region 6, the N-type buried layer 2, and the N-type epitaxial layer 3 are connected to the third metal 14 to form the collector of the NPN device.

[0057] Embodiment 2

[0058] See Figures 3 to 11 As shown, a method for fabricating an NPN device based on a non-polar isolation strip according to the present application includes the following steps:

[0059] Step 1) Provide a P-type substrate 1, form an N-type buried layer 2 on the P-type substrate 1, and perform photolithography and diffusion on the N-type buried layer 2;

[0060] Step 2) Form an N-type epitaxial layer 3 on the N-type buried layer 2; the thickness of the N-type epitaxial layer 3 is greater than the sum of the base region diffusion junction depth + the collector junction depletion width + the buried layer upward push distance.

[0061] Step 3) Etch a first diffusion region 6 in the N-type epitaxial layer 3, and the first diffusion region 6 extends downward and penetrates into the N-type buried layer 2;

[0062] Step 4) Form a P-type deep well region 4 in the N-type epitaxial layer 3 and on the left side of the first diffusion region 6, perform photolithography and diffusion on the P-type deep well region 4, and form a third diffusion region 9 in the P-type deep well region 4, and perform photolithography and diffusion on the third diffusion region 9;

[0063] Step 5) Form a second diffusion region 5 in the P-type deep well region 4 and on the left side of the third diffusion region 9, and perform photolithography and diffusion on the second diffusion region 5;

[0064] Step 6) Perform a first grooving at both ends of the N-type epitaxial layer 3. The grooving at the left end is located on the left side of the P-type deep well region 4, and the grooving at the right end is located on the right side of the first diffusion region 6, and both groovings at both ends extend downward, penetrate through the N-type buried layer 2, and penetrate into the P-type substrate 1; the first grooving is completed after photolithography by a deep groove etching machine;

[0065] Step 7) Perform a second grooving in the N-type epitaxial layer 3 between the P-type deep well region 4 and the first diffusion region 6, and the second grooving extends downward and penetrates into the N-type buried layer 2; the second grooving is completed after photolithography by a deep groove etching machine;

[0066] Step 8) Deposit a non-polar material in both the first grooving and the second grooving; deposit a non-polar material in the first grooving to form a first isolation strip 8, and deposit a non-polar material in the second grooving to form a second isolation strip 7; the non-polar material includes polysilicon.

[0067] Step 9) Lithographically define contact holes in the second diffusion region 5, the third diffusion region 9, and the first diffusion region 6 respectively, and sequentially deposit and etch back the first metal 12, the second metal 13, and the third metal 14 in the contact holes; then deposit a first insulating layer 10 on the N-type epitaxial layer 3, and deposit a second insulating layer 11 on the first insulating layer 10; the first metal (12), the second metal (13), and the third metal (14) are all made of aluminum alloy material.

[0068] In this embodiment, compared with the traditional bipolar integrated circuit process, using a non-polar material as the isolation strip is a new process structure. Two grooves are dug on the silicon wafer, and non-polar polycrystalline material is deposited. The breakdown voltage of the PN junction isolation in the original process for the collector is converted into the breakdown voltage of the non-polar material isolation strip, making the withstand voltage higher under the same conditions. It not only eliminates the parasitic capacitance between the collector region and the isolation strip, but also can reduce the area of a single device. It is a new structure with high withstand voltage, small area, and low cost.

[0069] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the inventive concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. An NPN device based on a non-polar isolation band, characterized in that: It includes a P-type substrate (1), on which an N-type buried layer (2) is formed. An N-type epitaxial layer (3) is formed on the N-type buried layer (2). At both ends of the N-type epitaxial layer (3), first isolation bands (8) that extend downward, pass through the N-type buried layer (2) and penetrate into the P-type substrate (1) and are filled with non-polar materials are provided respectively. Between the two first isolation bands (8), a P-type deep well region (4), a second isolation band (7) filled with non-polar materials, and a first diffusion region (6) are formed in sequence from left to right. Among them, both the second isolation band (7) and the first diffusion region (6) extend downward into the N-type buried layer (2). A second diffusion region (5) and a third diffusion region (9) are respectively formed in the P-type deep well region (4). A first insulating layer (10) is formed on the N-type epitaxial layer (3), and a second insulating layer (11) is formed on the first insulating layer (10). A first metal, a second metal, and a third metal are sequentially arranged at intervals from left to right on the second insulating layer (11). The first metal (12) extends downward through the first insulating layer (10) and penetrates into the second diffusion region (5). The second metal (13) extends downward through the first insulating layer (10) and penetrates into the third diffusion region (9). The third metal (14) extends downward through the first insulating layer (10) and penetrates into the first diffusion region (6). Both the first diffusion region (6) and the second diffusion region (5) are N-type diffusion regions, and the third diffusion region (9) is a P-type diffusion region. The structure formed by the first diffusion region (6), the second diffusion region (5), and the third diffusion region (9) is an NPN device.

2. The NPN device based on a non-polar isolation strip according to claim 1, wherein: The third diffusion region (9) is the base region of the NPN device, the second diffusion region (5) is the emitter region of the NPN device, and the N-type epitaxial layer (3) is the collector region of the NPN device.

3. An NPN device based on a non-polar isolation strip according to claim 2, characterized in that: The second diffusion region (5) is connected to the first metal (12) to form the emitter of the NPN device. The third diffusion region (9) is connected to the second metal (13) to form the base of the NPN device. The first diffusion region (6), the N-type buried layer (2), the N-type epitaxial layer (3) are connected to the third metal (14) to form the collector of the NPN device.

4. The NPN device based on a non-polar isolation strip according to claim 1, characterized in that: Both the first isolation band (8) and the second isolation band (7) are composed of non-polar material polysilicon, which is used to protect the NPN device to achieve electrical isolation.

5. A method for preparing an NPN device based on a non-polar isolation zone, characterized in that, It includes the following steps: Step 1) Perform photolithography and diffusion on the P-type substrate (1) to form the N-type buried layer (2). Step 2) Form the N-type epitaxial layer (3) on the N-type buried layer (2). Step 3) Form the first diffusion region (6) in the N-type epitaxial layer (3), and the first diffusion region (6) extends downward and penetrates into the N-type buried layer (2). Step 4) Perform photolithography and diffusion in the N-type epitaxial layer (3) and on the left side of the first diffusion region (6) to form the P-type deep well region (4), and perform photolithography and diffusion in the P-type deep well region (4) to form the third diffusion region (9). Step 5) Perform photolithography and diffusion in the P-type deep well region (4) and on the left side of the third diffusion region (9) to form the second diffusion region (5). Step 6) Conduct the first grooving at both ends of the N-type epitaxial layer (3). The grooving at the left end is located on the left side of the P-type deep well region (4), and the grooving at the right end is located on the right side of the first diffusion region (6). Moreover, the grooving at both ends extends downward, passing through the N-type buried layer (2) and penetrating into the P-type substrate (1). Step 7) Conduct the second grooving within the N-type epitaxial layer (3) between the P-type deep well region (4) and the first diffusion region (6). And the second grooving extends downward and penetrates into the N-type buried layer (2). Step 8) Deposit non-polar materials in both the first grooving and the second grooving; depositing non-polar materials in the first grooving forms the first isolation band (8), and depositing non-polar materials in the second grooving forms the second isolation band (7). Step 9) Deposit the first insulating layer (10) on the N-type epitaxial layer (3), and deposit the second insulating layer (11) on the first insulating layer (10); lithograph contact holes in the second diffusion region (5), the third diffusion region (9), and the first diffusion region (6) respectively, and sequentially deposit and etch back to form the first metal (12), the second metal (13), and the third metal (14) in the contact holes. Both the first diffusion region (6) and the second diffusion region (5) are N-type diffusion regions, and the third diffusion region (9) is a P-type diffusion region; the structure formed by the first diffusion region (6), the second diffusion region (5), and the third diffusion region (9) is an NPN device.

6. The manufacturing method of an NPN device based on a non-polar isolation strip according to claim 5, characterized in that: The non-polar material includes polysilicon.

7. The manufacturing method of an NPN device based on a non-polar isolation strip according to claim 5, characterized in that: The first metal (12), the second metal (13), and the third metal (14) are all made of aluminum alloy material.

8. The manufacturing method of an NPN device based on a non-polar isolation strip according to claim 5, characterized in that: Both the first grooving and the second grooving are completed by etching through a deep groove etching machine after lithography.

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