Electrostatic discharge protection structure

Abstract

An electrostatic discharge (ESD) protection structure includes a substrate, a well region, a first doped region, a second doped region, and a voltage extraction structure. The substrate has a first conductivity type. The well region is disposed within the substrate and has a second conductivity type. The first doped region is disposed within the well region, electrically connected to a first power line, and has the first conductivity type. The second doped region is disposed within the substrate, electrically connected to a second power line, and has the second conductivity type. The voltage extraction structure includes a complex number of oxide-defined regions. The total area of ​​the oxide-defined regions disposed in the well region mapped onto the substrate is smaller than the area of ​​the first doped region mapped onto the substrate. The total area of ​​the oxide-defined regions disposed in the substrate mapped onto the substrate is smaller than the area of ​​the second doped region mapped onto the substrate.

Description

Technical Field

[0001] This invention relates to a semiconductor structure, and more particularly to an electrostatic discharge protection structure. Prior Technology

[0002] Electrostatic discharge (ESD) has become one of the most significant reliability issues for integrated circuit products. Especially as dimensions continue to shrink to sub-micron levels, the gate oxide layer of metal-oxide-semiconductors (MOSFETs) is becoming increasingly thin, making integrated circuits more susceptible to damage from ESD. Summary of the Invention

[0003] This invention provides an electrostatic discharge (ESD) protection structure, including a substrate, a well region, a first doped region, a second doped region, and a voltage extraction structure. The substrate has a first conductivity type. The well region is disposed within the substrate and has a second conductivity type. The first doped region is disposed within the well region, electrically connected to a first power line, and has the first conductivity type. The second doped region is disposed within the substrate, electrically connected to a second power line, and has the second conductivity type. The voltage extraction structure includes a plurality of oxide-defined regions. The oxide-defined regions are disposed in at least one of the well region and the substrate. The total area of ​​the oxide-defined regions disposed in the well region mapped onto the substrate is less than the area of ​​the first doped region mapped onto the substrate. The total area of ​​the oxide-defined regions disposed on the substrate mapped onto the substrate is less than the area of ​​the second doped region mapped onto the substrate. When an ESD event occurs on the first power line and the second power line receives a ground voltage, an ESD current flows from the first power line, through the first doped region, the well region, the substrate, and the second doped region, into the second power line. Simple Explanation of the Diagram

[0004] Figure 1 is a top view of the electrostatic discharge protection structure of the present invention. Figure 2 is another schematic diagram of the electrostatic discharge protection structure of the present invention. Figure 3 is another schematic diagram of the electrostatic discharge protection structure of the present invention. Figure 4 is a cross-sectional view of line A-A' in Figure 3. Figure 5 is a schematic diagram of the electrostatic discharge protection structure shown in Figure 3. Implementation

[0005] To make the objectives, features, and advantages of this invention more apparent and understandable, embodiments are provided below, along with detailed descriptions in conjunction with the accompanying drawings. This specification provides different embodiments to illustrate the technical features of different implementations of the invention. The configuration of elements in the embodiments is for illustrative purposes only and is not intended to limit the invention. Furthermore, the repetition of some reference numerals in the embodiments is for simplification and does not imply any correlation between different embodiments.

[0006] Figure 1 is a top view schematic diagram of the electrostatic discharge protection structure of the present invention. The electrostatic discharge protection structure 100 includes a substrate 110, a well region 121, doped regions 131 and 132, and a voltage extraction structure 140. The substrate 110 has a first conductivity type. The well region 121 is disposed in the substrate 110 and has a second conductivity type. The second conductivity type is relative to the first conductivity type. In one possible embodiment, the first conductivity type is P-type and the second conductivity type is N-type. In another possible embodiment, the first conductivity type is N-type and the second conductivity type is P-type.

[0007] Doped region 131 is disposed within well region 121 and has a first conductivity type. In this embodiment, the doping concentration of doped region 131 is greater than the doping concentration of substrate 110. Doped region 132 is disposed within substrate 110 and has a second conductivity type. In this embodiment, the doping concentration of doped region 132 is greater than the doping concentration of well region 121.

[0008] Doped region 131, well region 121, substrate 110, and doped region 132 constitute a silicon controlled rectifier (SCR). When an electrostatic discharge (ESD) event occurs in doped region 131 and doped region 132 is grounded, an ESD current flows through doped region 131, well region 121, substrate 110, and doped region 132, and is released to ground. When no ESD event occurs, the SCR is not conducting.

[0009] In some embodiments, the electrostatic discharge protection structure 100 further includes a well region 122. The well region 122 is disposed in the substrate 110 and has a first conductivity type. The doping concentration of the well region 122 is greater than the doping concentration of the substrate 110 but lower than the doping concentration of the doped region 131. In this example, the doped region 132 is disposed within the well region 122. When an electrostatic discharge event occurs in the doped region 131 and the doped region 132 is grounded, an electrostatic discharge current flows through the doped region 131, well regions 121 and 122, and doped region 132, and is released to ground.

[0010] The voltage extraction structure 140 is located in well region 121 and includes oxide definition regions 141 and 142. Oxide definition regions 141 and 142 have a second conductivity type. In some embodiments, the doping concentration of oxide definition regions 141 and 142 is greater than the doping concentration of well region 121. Additionally, the doping concentration of oxide definition regions 141 and 142 is similar to the doping concentration of doped region 132. In this embodiment, the total area of ​​oxide definition regions 141 and 142 mapped to substrate 110 is smaller than the area of ​​doped region 131 mapped to substrate 110. In a possible embodiment, the area of ​​oxide definition region 141 mapped to substrate 110 is the same as the area of ​​oxide definition region 142 mapped to substrate 110.

[0011] This invention does not limit the positions of oxide defining regions 141 and 142. In one possible embodiment, oxide defining regions 141 and 142 are respectively disposed on both sides of doped region 131, but this is not intended to limit the invention. In another embodiment, oxide defining regions 141 and 142 may be located on the same side of doped region 131. Furthermore, the distance D1 between oxide defining region 141 and doped region 131 may be the same as or different from the distance D2 between oxide defining region 142 and doped region 131.

[0012] This invention does not limit the number of oxide-defined regions. By adjusting the number of oxide-defined regions, the trigger current and holding voltage of the electrostatic discharge protection structure 100 can be increased, making the electrostatic discharge protection structure 100 applicable to high-voltage fields, such as automotive high-voltage systems.

[0013] In some embodiments, the voltage extraction structure 140 further includes oxide defining regions 142 and 144. Oxide defining regions 142-144 are located to the left of the doped region 131. A distance D3 exists between oxide defining region 143 and the doped region 131. A distance D4 exists between oxide defining region 144 and the doped region 131. Distance D3 may be the same as or different from distance D4. Additionally, at least one of distances D3 and D4 may be the same as or different from distance D2. Furthermore, the distance S1 between oxide defining regions 142 and 143 may be the same as or different from the distance S2 between oxide defining regions 142 and 144.

[0014] In other embodiments, the voltage extraction structure 140 further includes oxide defining regions 145 and 146. Oxide defining regions 141, 145, and 146 are located to the right of the doped region 131. A distance D5 exists between oxide defining region 145 and the doped region 131. A distance D6 exists between oxide defining region 146 and the doped region 131. Distance D5 may be the same as or different from distance D6. Additionally, at least one of distances D5 and D6 may be the same as or different from distance D1. Furthermore, the distance S3 between oxide defining regions 141 and 145 may be the same as or different from the distance S4 between oxide defining regions 141 and 146.

[0015] In this embodiment, the positions of oxide definition regions 141, 145, and 146 are symmetrical to oxide definition regions 142-144. In this example, distances D1-D6 are all the same, and distances S1-S4 are all the same. Furthermore, the total area of ​​oxide definition regions 141-146 mapped onto the substrate 110 is smaller than the area of ​​the doped region 131 mapped onto the substrate 110. In some embodiments, oxide definition regions 141-146 are used to enhance the voltage level of well region 121; therefore, oxide definition regions 141-146 can be referred to as voltage pickup regions.

[0016] Figure 2 is another schematic diagram of the electrostatic discharge protection structure of the present invention. The electrostatic discharge protection structure 200 includes a substrate 210, well regions 221, 222, doped regions 231, 232, and a voltage extraction structure 240. Since the characteristics of the substrate 210, well regions 221, 222, and doped regions 231, 232 are similar to those of the substrate 110, well regions 121, 122, and doped regions 131, 132 in Figure 1, they will not be described in detail again.

[0017] In this embodiment, the voltage extraction structure 240 is located in the substrate 210. In some embodiments, the voltage extraction structure 240 is located in the well region 122. In this embodiment, the voltage extraction structure 240 includes oxide definition regions 241 and 242. The oxide definition regions 241 and 242 have a first conductivity type. In some embodiments, the doping concentration of the oxide definition regions 241 and 242 is greater than the doping concentration of the well region 122. In addition, the doping concentration of the oxide definition regions 241 and 242 is similar to the doping concentration of the doped region 131. In this embodiment, the total area of ​​the oxide definition regions 241 and 242 mapped onto the substrate 110 is smaller than the area of ​​the doped region 132 mapped onto the substrate 110. In one possible embodiment, the area of ​​the oxide definition region 241 mapped onto the substrate 110 is the same as the area of ​​the oxide definition region 242 mapped onto the substrate 110. The present invention does not limit the number of oxide definition regions. In one possible embodiment, the voltage extraction structure 240 has more oxide definition regions, such as 243 to 246. Since the voltage extraction structure 240 is similar to the voltage extraction structure 140 in Figure 1, it will not be described again.

[0018] Figure 3 is another schematic diagram of the electrostatic discharge protection structure of the present invention. The electrostatic discharge protection structure 300 includes a substrate 310, well regions 321, 322, doped regions 331, 332, and a voltage extraction structure 340. Since the characteristics of the substrate 310, well regions 321, 322, and doped regions 331, 332 are similar to those of the substrate 110, well regions 121, 122, and doped regions 131, 132 in Figure 1, they will not be described in detail again.

[0019] The voltage extraction structure 340 includes a first structure 340A and a second structure 340B. The first structure 340A is located in the well region 121 and includes oxide definition regions 341_A to 346_A. The oxide definition regions 341_A to 346_A have a second conductivity type. The doping concentration of each of the oxide definition regions 341_A to 346_A is similar to the doping concentration of the doped region 332. The oxide definition regions 341_A to 346_A are uniformly and symmetrically disposed around the doped region 331. The total area of ​​the oxide definition regions 341_A to 346_A mapped onto the substrate 310 is smaller than the area of ​​the doped region 331 mapped onto the substrate 310. In one possible embodiment, the areas of each of the oxide definition regions 341_A to 346_A mapped onto the substrate 310 are equal, but this is not intended to limit the invention. In other embodiments, the area of ​​one of the oxide definition regions 341_A to 346_A mapped onto the substrate 310 is different from the area of ​​the other oxide definition region 341_A to 346_A mapped onto the substrate 310. The present invention does not limit the number of oxide definition regions. In other embodiments, the first structure 340A has other numbers of oxide definition regions. Since the characteristics of the first structure 340A are similar to those of the voltage extraction structure 140 in Figure 1, further details are omitted.

[0020] The second structure 340B is located in well region 122 and includes oxide definition regions 341_B to 346_B. Oxide definition regions 341_B to 346_B have a first conductivity type. In this embodiment, the doping concentration of each of the oxide definition regions 341_B to 346_B is similar to the doping concentration of the doped region 331. The oxide definition regions 341_B to 346_B are uniformly and symmetrically disposed around the doped region 332. The total area of ​​the oxide definition regions 341_B to 346_B mapped onto the substrate 310 is smaller than the area of ​​the doped region 332 mapped onto the substrate 310. In one possible embodiment, the area of ​​each of the oxide definition regions 341_B to 346_B mapped onto the substrate 310 is equal, but this is not intended to limit the invention. In other embodiments, the area of ​​one of the oxide definition regions 341_B to 346_B mapped onto the substrate 310 is different from the area of ​​the other of the oxide definition regions 341_B to 346_B mapped onto the substrate 310. The present invention does not limit the number of oxide-defined regions. In other embodiments, the second structure 340B has other numbers of oxide-defined regions. Since the characteristics of the second structure 340B are similar to those of the voltage extraction structure 140 in Figure 1, they will not be described further.

[0021] In this embodiment, the number of oxide-defined regions in the first structure 340A is the same as the number of oxide-defined regions in the second structure 340B, but this is not intended to limit the invention. In other embodiments, the number of oxide-defined regions in the first structure 340A may be less or more than the number of oxide-defined regions in the second structure 340B. Furthermore, the arrangement of the first structure 340A and the doped region 331 is symmetrical to the arrangement of the second structure 340B and the doped region 332. For example, oxide-defined regions 341_A to 346_A are uniformly disposed around the doped region 331, and oxide-defined regions 341_B to 346_B are uniformly disposed around the doped region 332. In other embodiments, the arrangement of oxide-defined regions 341_A to 346_A differs from the arrangement of oxide-defined regions 341_B to 346_B.

[0022] Figure 4 is a cross-sectional view along line A-A' in Figure 3. As shown, well regions 321 and 322 are disposed within the substrate 310. For ease of explanation, it is assumed that the conductivity type of well region 321 is N-type and the conductivity type of well region 322 is P-type. Doped regions 331, oxide definition regions 341_A and 342_A are disposed in well region 321. Doped regions 332, oxide definition regions 341_B and 342_B are disposed in well region 322. In this embodiment, the doping concentration of doped regions 331, oxide definition regions 341_B and 342_B is higher than the doping concentration of well region 322. The doping concentration of doped regions 332, oxide definition regions 341_A and 342_A is higher than the doping concentration of well region 321. In some embodiments, doped regions 331, well regions 321 and 322, and doped region 332 constitute a silicon controlled rectifier 350. In other embodiments, well region 322 may be omitted. The doped region 332 and the second structure 340B are disposed within the substrate 310. In this example, the doped region 331, the well region 321, the substrate 310, and the doped region 332 constitute a silicon controlled rectifier.

[0023] Doped region 331, oxide definition regions 341_A and 342_A are electrically connected to a power line 351 to receive an operating voltage HV. In this embodiment, all oxide definition regions 341_A to 346_A of the first structure 340A located in well region 321 are electrically connected to the power line 351.

[0024] Doped region 332, oxide definition regions 341_B and 342_B are electrically connected to a power line 352 to receive an operating voltage GND. In this embodiment, all oxide definition regions 341_B to 346_B of the second structure 340B located in well region 322 are electrically connected to the power line 352.

[0025] In some embodiments, the electrostatic discharge protection structure 300 further includes isolation structures 361-367. An oxide defining region 341_B is located between isolation structures 361 and 362. Isolation structure 362 separates the oxide defining region 341_B from the doped region 332. Isolation structure 363 separates the doped region 332 from the oxide defining region 342_B. Isolation structure 364 separates the oxide defining regions 342_B and 342_A. Isolation structure 365 separates the oxide defining region 342_A from the doped region 331. Isolation structure 366 separates the doped region 331 from the oxide defining region 341_A. The oxide defining region 341_A is located between isolation structures 366 and 367. In one possible embodiment, isolation structures 361-367 are the same insulating layer and are interconnected.

[0026] Under normal operation (without electrostatic discharge events), the operating voltage HV may be 12V or higher, and the operating voltage GND is a ground voltage, such as 0V. Since oxide defining regions 341_A and 342_A receive the operating voltage HV, the voltage of well region 321 is close to the voltage of doped region 331. Therefore, the PN junction between doped region 331 and well region 321 is not easily conductive, thus the silicon controlled rectifier 350 does not conduct. Furthermore, oxide defining regions 341_B and 342_B receive the operating voltage GND, so the voltage of well region 322 is close to the voltage of doped region 332. Therefore, the PN junction between well region 322 and doped region 332 is also not easily conductive, further ensuring that the silicon controlled rectifier 350 does not conduct. Therefore, even if power lines 351 and 352 are automotive high-voltage power lines, malfunction of the silicon controlled rectifier 350 can still be avoided.

[0027] However, when an electrostatic discharge (ESD) event occurs on power line 351 and power line 352 receives a ground voltage, the silicon-controlled rectifier 350 turns on. Therefore, an ESD current flows from power line 351, through doped regions 331, well regions 321, 322, and doped region 332, into power line 352. The voltage extraction structure 340 increases the sustaining voltage of the silicon-controlled rectifier 350, preventing latch-up.

[0028] Figure 5 is an electrical schematic diagram of the electrostatic discharge protection structure 300 in Figure 3. Assume the distance between oxide definition regions on the same side and adjacent oxide definition regions is S. Taking oxide definition regions 342_A~344_A to the left of doped region 331 as an example, the distance between oxide definition regions 341_A and 343_A is S, and the distance between oxide definition regions 341_A and 344_A is S. Similarly, the distance between oxide definition regions 341_B and 345_B to the left of doped region 332 is S, and the distance between oxide definition regions 341_B and 346_B is S.

[0029] The area ratio in Figure 5 refers to the percentage of the total area of ​​the oxide definition region of the voltage extraction structure 340 mapped onto the substrate 310, relative to the total area of ​​well regions 321 and 322 mapped onto the substrate 310. When the distance S is smaller, more oxide definition regions can be placed in well regions 321 and 322. Therefore, the percentage of the oxide definition region area is higher. When the distance S is larger, fewer oxide definition regions are placed in well regions 321 and 322. Therefore, the percentage of the oxide definition region area is lower. For example, when the distance S is 11 μm, the total area of ​​the oxide definition region mapped onto the substrate 310 is 5.56% of the total area of ​​well regions 321 and 322 mapped onto the substrate 310.

[0030] As shown in Figure 5, the smaller the distance S (i.e., the greater the number of oxide-defined regions), the higher the trigger voltage and trigger current of the electrostatic discharge protection structure 300. Therefore, under normal operation (without electrostatic discharge events), the electrostatic discharge protection structure 300 is less likely to be falsely triggered. Furthermore, the smaller the distance S, the higher the sustaining voltage of the electrostatic discharge protection structure 300, thus preventing latch-up of the electrostatic discharge protection structure 300.

[0031] Unless otherwise defined, all terms herein (including technical and scientific terms) are as commonly understood by one of ordinary skill in the art to which this invention pertains. Furthermore, unless expressly stated otherwise, the definitions of terms in a general dictionary should be interpreted as consistent with their meaning in writings of the relevant technical field, and not as idealized or overly formal expressions. While terms such as “first” and “second” can be used to describe various elements, these elements should not be limited by these terms. These terms are merely used to distinguish one element from another. Within the claims, terms such as “first” and “second” are used as designations and are not intended to impose numerical requirements on their objects.

[0032] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make modifications and refinements without departing from the spirit and scope of the invention. For example, the systems, apparatus, or methods described in the embodiments of the present invention can be implemented in physical embodiments using hardware, software, or a combination of hardware and software. Therefore, the scope of protection of the present invention should be determined by the appended claims.

[0033] 100, 200, 300: Electrostatic discharge protection structure 110, 210, 310: Base 121, 122, 221, 222, 321, 322: Well areas 131, 132, 231, 232, 331, 332: Doped regions 140, 240, 340: Voltage extraction structure 141~146, 241~246, 341_A~346_A, 341_B~346_B: Oxide definition region D1~D6, S1~S4, S: Distance 351, 352: Power cord

Claims

1. An electrostatic discharge protection structure, comprising: A substrate having a first conductivity type; A well zone is disposed within the substrate and has a second conductivity type; A first doped region is disposed in the well region, electrically connected to a first power line, and has the first conductivity type; a second doped region is disposed in the substrate, electrically connected to a second power line, and has the second conductivity type; and a voltage extraction structure includes a plurality of oxide-defined regions disposed in at least one of the well region and the substrate, wherein: the total area of ​​the oxide-defined regions disposed in the well region mapped onto the substrate is smaller than the area of ​​the first doped region mapped onto the substrate; the total area of ​​the oxide-defined regions disposed in the substrate mapped onto the substrate is smaller than the area of ​​the second doped region mapped onto the substrate; when an electrostatic discharge event occurs on the first power line and the second power line receives a ground voltage, an electrostatic discharge current flows from the first power line, through the first doped region, the well region, the substrate, and the second doped region, into the second power line; each of the oxide-defined regions disposed in the well region has the second conductivity type.

2. The electrostatic discharge protection structure as claimed in claim 1, wherein each of the oxide definition regions disposed on the substrate has the first conductivity type.

3. The electrostatic discharge protection structure as described in claim 1, wherein: The oxide definition area includes a first extraction area, a second extraction area, a third extraction area and a fourth extraction area, the first and second extraction areas are disposed in the well area, and the third and fourth extraction areas are disposed in the substrate.

4. The electrostatic discharge protection structure as described in claim 3, wherein the first and second extraction regions are symmetrically disposed around the first doped region, and the third and fourth extraction regions are symmetrically disposed around the second doped region.

5. The electrostatic discharge protection structure as described in claim 3, wherein the doping concentration of the first and second extraction regions is the same as the doping concentration of the second doped region, and the doping concentration of the third and fourth extraction regions is the same as the doping concentration of the first doped region.

6. The electrostatic discharge protection structure as described in claim 3, wherein the distance between the first and second extraction regions is the same as the distance between the third and fourth extraction regions.

7. The electrostatic discharge protection structure as described in claim 6, wherein the oxide definition area further includes a fifth extraction area disposed in the well area, and the distance between the first and fifth extraction areas is the same as the distance between the first and second extraction areas.

8. The electrostatic discharge protection structure as claimed in claim 7, wherein the oxide definition region further includes a sixth extraction region disposed in the substrate, and the distance between the third and sixth extraction regions is the same as the distance between the third and fourth extraction regions.

9. The electrostatic discharge protection structure as claimed in claim 8, wherein the area of ​​the first extraction region mapped onto the substrate is the same as the area of ​​the second extraction region mapped onto the substrate and the area of ​​the third extraction region mapped onto the substrate.

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