US20040245574A1 - ESD protection device with thick poly film and method for forming the same - Google Patents
ESD protection device with thick poly film and method for forming the same Download PDFInfo
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- US20040245574A1 US20040245574A1 US10/829,983 US82998304A US2004245574A1 US 20040245574 A1 US20040245574 A1 US 20040245574A1 US 82998304 A US82998304 A US 82998304A US 2004245574 A1 US2004245574 A1 US 2004245574A1
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- 238000000034 method Methods 0.000 title claims abstract description 28
- 229910021420 polycrystalline silicon Inorganic materials 0.000 claims abstract description 106
- 229920005591 polysilicon Polymers 0.000 claims abstract description 106
- 239000000758 substrate Substances 0.000 claims abstract description 56
- 229920002120 photoresistant polymer Polymers 0.000 claims description 15
- 239000011521 glass Substances 0.000 claims description 6
- 239000010453 quartz Substances 0.000 claims description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 6
- 238000005530 etching Methods 0.000 claims description 4
- 238000000151 deposition Methods 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 239000010408 film Substances 0.000 description 72
- 230000015556 catabolic process Effects 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- 239000004973 liquid crystal related substance Substances 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- 230000008021 deposition Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000007943 implant Substances 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000000206 photolithography Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers
- H01L27/12—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being other than a semiconductor body, e.g. an insulating body
- H01L27/1214—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being other than a semiconductor body, e.g. an insulating body comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
- H01L27/1222—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being other than a semiconductor body, e.g. an insulating body comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs with a particular composition, shape or crystalline structure of the active layer
- H01L27/1233—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being other than a semiconductor body, e.g. an insulating body comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs with a particular composition, shape or crystalline structure of the active layer with different thicknesses of the active layer in different devices
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers
- H01L27/12—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being other than a semiconductor body, e.g. an insulating body
- H01L27/1214—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers the substrate being other than a semiconductor body, e.g. an insulating body comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
- H01L29/0657—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions characterised by the shape of the body
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers
- H01L27/0203—Particular design considerations for integrated circuits
- H01L27/0248—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection
- H01L27/0251—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection for MOS devices
- H01L27/0255—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection for MOS devices using diodes as protective elements
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having potential barriers; including integrated passive circuit elements having potential barriers
- H01L27/0203—Particular design considerations for integrated circuits
- H01L27/0248—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection
- H01L27/0251—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection for MOS devices
- H01L27/0266—Particular design considerations for integrated circuits for electrical or thermal protection, e.g. electrostatic discharge [ESD] protection for MOS devices using field effect transistors as protective elements
Definitions
- the present invention generally relates to an ESD protection device and, more particularly, to an ESD protection device with thicker polysilicon film in an electronic apparatus, and method for forming the same.
- the ESD protection device 10 when a positive discharge voltage is applied to the output pad (Drain) with the Vss pad (Source) relatively grounded, the ESD protection device 10 , such as a reverse diode at the drain, is stressed by the ESD voltage and breaks down, which results in the clamp of the overstress voltage on the pad. Furthermore, when the heat induced by the ESD is larger than that the ESD protection device can sustain, the ESD protection device will be damaged. There are therefore more and more researches investigating behavior of TFT devices in ESD events, most of which focus on the damage resulted and the mechanisms. For example, in order to sustain larger ESD currents, increasing the area of device is proposed to promote the breakdown voltage. However, as shown in FIG. 1B, when the channel length reaches a certain value, such as 10 ⁇ m, the breakdown voltage stays constant with an approximate value of 430V.
- the present invention provides an ESD protection device including a substrate and a polysilicon film in an ESD protection circuit to protect an electronic apparatus.
- the polysilicon film of a thickness in a range of about 100 to 500 nanometers is formed on the substrate.
- the ESD protection device can be a MOS transistor or a diode.
- the ESD protection device is a MOS transistor, which further includes source/drain regions, a gate dielectric layer, and a gate electrode. The source/drain regions are formed in the polysilicon film and separated by a channel.
- the ESD protection device is a diode, which further includes an n-type doped region and a p-type doped region in the polysilicon film. For example, the n-type doped region is adjacent to the p-type doped region to form a PN diode.
- the diode further includes an intrinsic region between the n-type doped and p-type doped regions so as to form a PIN diode.
- the substrate has a device area and an ESD protection circuit area.
- the first polysilicon film having a first thickness is formed on the device area so as to form an electronic device.
- the second polysilicon film having a second thickness is formed on the ESD protection circuit area so as to form the ESD protection device.
- the second thickness is larger than the first thickness and preferably in a range of about 100 to 500 nanometers.
- the electronic device can be a MOS transistor while the ESD protection device can be a diode or a MOS transistor.
- the method includes steps of providing a substrate having a device area and an ESD protection circuit area, forming a first polysilicon film of a first thick ness on the device area of the substrate so as to form an electronic device, and forming a second polysilicon film of a second thickness on the ESD protection circuit area of the substrate so as to form the ESD protection device.
- the second thickness is larger than the first thickness and preferably in a range of about 100 to 500 nanometers.
- the step of forming the first and second polysilicon films includes steps of forming the second polysilicon film on the substrate to cover the device area and the ESD protection circuit area, forming a patterned photoresist layer on the second polysilicon layer to expose a portion of the second polysilicon film corresponding to the device area, and etching the second polysilicon film to reach the first thickness by using the patterned photoresist layer as a mask.
- the step of forming the first and second polysilicon films includes steps of forming a polysilicon film of a third thickness on the substrate to cover the device area and the ESD protection circuit area, forming a patterned photoresist layer on the polysilicon film to expose a portion of the polysilicon film corresponding to the device area, etching the polysilicon film to expose the substrate by using the patterned photoresist layer as a mask, removing the patterned photoresist layer, and depositing the first polysilicon film on the substrate.
- the second thickness equals the third thickness plus the first thickness.
- the method further includes other steps of forming a diode or a MOS transistor as the ESD protection device.
- a diode or a MOS transistor as the ESD protection device.
- an n-type doped region and a p-type doped region are formed in the second polysilicon film so as to form a PN diode.
- an intrinsic region is formed between the n-type doped and p-type doped regions so as to form a PIN diode.
- FIG. 1A illustrates a conventional ESD protection circuit
- FIG. 1B illustrates a diagram showing relation between channel width and breakdown voltage of a conventional ESD protection device
- FIG. 2 illustrates an ESD protection circuit in one embodiment of the present invention
- FIG. 3A illustrates a cross-sectional view of an ESD protection device and an electronic device in a first embodiment of the present invention
- FIG. 3B illustrates a cross-sectional view of an ESD protection device and an electronic device in a second embodiment of the present invention
- FIG. 3C illustrates a cross-sectional view of an ESD protection device and an electronic device in a third embodiment of the present invention
- FIG. 4 illustrates a cross-sectional view of polysilicon films in one embodiment of the present invention
- FIGS. 5A and 5B illustrates a cross-sectional view of forming a first and second polysilicon films in one embodiment of the present invention.
- FIGS. 6A-6C illustrates a cross-sectional view of forming a first and second polysilicon films in another embodiment of the present invention.
- the present invention provides an electrostatic discharge (ESD) protection device, which has thicker polysilicon film to enhance the robustness so as to sustain higher currents or power heat.
- ESD electrostatic discharge
- FIG. 2 illustrates ESD protection devices having thick polysilicon films (such as 100 , 200 , and 300 ) in I/O pads of an electronic apparatus 400 so as to provide electrostatic discharge protection to the electronic apparatus 400 in one embodiment of the present invention.
- FIGS. 3A to 3 C illustrate cross-sectional views of exemplary embodiments of the present invention.
- the present invention provides an ESD protection device 100 , such as a MOS transistor, in an ESD circuit so as to protect the electronic apparatus 400 .
- the ESD protection device 100 includes a substrate 102 and a polysilicon film 104 .
- the substrate 102 can be selected from a group consisting of glass substrate, a quartz substrate, and the combination thereof.
- the polysilicon film 104 having a thickness in a range of about 100 to 500 nanometers is formed on the substrate 102 .
- Source/drain regions 106 are formed in the polysilicon film 104 and separated by a channel 104 A.
- the ESD protection device 100 further includes a gate dielectric layer 108 , such as gate oxide layer, and a gate electrode 110 , so as to be a MOS transistor used in an ESD protection circuit.
- the ESD protection device 200 is a diode, which includes a substrate 102 and a polysilicon film 104 .
- the substrate 102 can be selected from a group consisting of a glass substrate, a quartz substrate, and the combination thereof.
- the polysilicon film 104 which has a thickness in a range of about 100 to 500 nanometers, is formed on the substrate 102 .
- An n-type doped region 202 and a p-type doped region 204 are formed in the polysilicon film 104 .
- the ESD protection device 200 can be a PN diode when the n-type doped region 202 is adjacent to the p-type doped region 204 .
- ESD protection device 300 further includes an intrinsic region 302 , which is arranged between the n-type and p-type doped regions, 202 and 204 , to form a PIN diode as the ESD protection device 300 .
- the electronic apparatus 400 having the ESD protection device shown as 100 , 200 , or 300 includes a substrate 102 , a first polysilicon film 404 , and a second polysilicon film 104 .
- the substrate 102 can be selected from a group consisting of a glass substrate, a quartz substrate, and the combination thereof.
- the substrate 102 has a device area 400 A and an ESD protection circuit area 400 B.
- the device area 400 A can be an internal circuit region as shown in FIG. 2.
- the first polysilicon film 404 having a first thickness (H1) is formed on the device area 400 A of the substrate 102 , so as to form an electronic device 402 .
- the second polysilicon film 104 having a second thickness (H2) is formed on the ESD protection circuit area 400 B of the substrate 102 , so as to form an ESD protection device (such as 100 , 200 , or 300 ).
- the second thickness (H2) is larger than the first thickness (H1) and preferably in a range of about 100 to 500 nanometers.
- the electronic device 402 can be a p-type or n-type MOS transistor, and therefore, the electronic device 402 further includes first source/drain regions 406 formed in the first polysilicon film 402 and separated by a first channel 404 A.
- a gate dielectric layer 408 and gate electrode 410 are formed on the first polysilicon film 404 .
- the ESD protection device can be a diode (such as 200 or 300 ) or a MOS transistor 100 having a thicker polysilicon film 104 .
- the ESD protection device 100 further includes second source/drain regions 106 formed in the second polysilicon film 104 and separated by a second channel 104 A. Gate dielectric layer 108 and gate electrode 110 are formed on the second polysilicon layer 104 , as shown in FIG. 3A.
- the electronic apparatus 400 further includes an n-type doped region 202 and a p-type doped region 204 in the second polysilicon film 104 so as to form a PN diode as the ESD protection device 200 in FIG. 3B.
- an intrinsic region 302 can be formed between the n-type and p-type doped regions ( 202 and 204 ) to form a PIN diode as the ESD protection device 300 in FIG. 3C.
- a conventional ESD protection device has a polysilicon film of a thickness, preferably about 50 nanometers, which is the same as that of the active area of the electronic device in the internal circuit (such as 404 in FIGS. 3A-3C), so that the gate can have better controls over the channel.
- the application of thin polysilicon film is not suitable for ESD events. Therefore, the ESD protection device of the present invention, such as 100 , 200 , and 300 , having a thicker polysilicon film (preferably in a range between 100 to 500 nanometers) can efficiently disperse the ESD currents to the thick polysilicon film 104 and improve the robustness of the ESD protection device.
- the ESD protection device with thicker polysilicon film can sustain large currents to protect devices from damage.
- a method for forming an ESD protection device in an ESD protection circuit includes a step of providing a substrate 102 , which has a device area 400 A and an ESD protection circuit area 400 B.
- a first polysilicon film 404 of a first thickness (H1) is formed on the device area 400 A of the substrate 102 so as to form an electronic device 402 (as shown in FIGS. 3A to 3 C).
- a second polysilicon film 104 of a second thickness (H2) is formed on the ESD protection circuit area 400 B of the substrate 102 to form the ESD protection device (such as 100 , 200 , and 300 shown in FIGS. 3A to 3 C).
- the second thickness (H2) is larger than said first thickness (H1) and preferably in a range about 100 to 500 nanometers.
- the steps of forming the first and second polysilicon films include variety combinations of processes.
- the steps of forming the first and second polysilicon films include forming the second polysilicon film 104 over the entire substrate 102 .
- the second polysilicon film 104 having the second thickness (H2) covers the device area 400 A and the ESD protection circuit area 400 B.
- a pattern photoresist layer 412 is formed on the second polysilicon film 104 to expose a portion of the second polysilicon film 104 , which corresponds to the device area 400 A.
- the second polysilicon film 104 is etched to reach the first thickness (H1) by using the patterned photoresist layer 412 as a mask. Therefore, the first and second polysilicon films are formed.
- the step of forming the first and second polysilicon films includes forming a polysilicon film 414 of a third thickness (H3) on the entire substrate 102 to cover the device area 400 A and the ESD protection circuit area 400 B. Then, a patterned photoresist layer 416 is formed on the polysilicon film 414 to expose a portion of the polysilicon film 414 , which corresponds to the device area 400 A, as shown in FIG. 6A. The polysilicon film 414 is etched to expose a portion of the substrate 102 by using the patterned photoresist layer 416 as a mask. Then, the patterned photoresist layer 416 is removed, as shown in FIG.
- H3 third thickness
- the method may further include a step of defining active areas to accomplish the structure shown in FIG. 4.
- the method further includes steps of forming diodes or MOS transistors, which is compatible with current process flow of forming thin-film transistors.
- the method further includes forming first source/drain regions 406 of electronic device 402 .
- the source/drain regions 406 are separated by a fist channel 404 A in the first polysilicon film 404 .
- the method further includes a step of forming second source/drain regions 106 separated by a second channel 104 A in the second polysilicon film 104 . Therefore, the thicker polysilicon film 104 can sustain higher power heat to prevent the ESD protection device 100 from damage.
- the method further includes forming n-type and p-type doped regions 202 and 204 , so as to form the ESD protection device 200 (PN diode as shown in FIG. 3B). Moreover, the method further includes forming an intrinsic region 302 between the n-type doped region 202 and the p-type doped region 204 in the second polysilicon film 104 to form a PIN diode 300 as the ESD protection device.
- the polysilicon film 104 , 404 , or 414 can be formed by conventional technologies including deposition, photolithography, etch, and the like.
- the source/drain regions ( 106 and 406 ) or the n/p type doped regions ( 202 and 204 ) can be formed by conventional technologies such as diffusion or ion implant processes, which are not elaborated.
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Abstract
Description
- This application claims priority to Taiwan Patent Application No. 092109702 entitled “ESD Protection Device with Thick Poly Film, Electronic Device and Method for Forming the Same”, filed on Apr. 25, 2003.
- The present invention generally relates to an ESD protection device and, more particularly, to an ESD protection device with thicker polysilicon film in an electronic apparatus, and method for forming the same.
- Thin-film transistors (TFTs) are commonly used in most semiconductor electronic apparatus as switches in active matrix liquid crystal displays, image sensors or the like. However, applications of TFT devices have limitations. For example, in the process of manufacturing liquid crystal displays, when glass or quartz substrates are delivered or processed on the production line, TFT devices generally accumulate a large number of charges and introduce electrostatic discharge (ESD) damages because of their random grains and large resistance. It is therefore very important to provide ESD protection circuits around the input and output (I/O) pads to increase the production yield.
- However, as shown in FIG. 1A, when a positive discharge voltage is applied to the output pad (Drain) with the Vss pad (Source) relatively grounded, the
ESD protection device 10, such as a reverse diode at the drain, is stressed by the ESD voltage and breaks down, which results in the clamp of the overstress voltage on the pad. Furthermore, when the heat induced by the ESD is larger than that the ESD protection device can sustain, the ESD protection device will be damaged. There are therefore more and more researches investigating behavior of TFT devices in ESD events, most of which focus on the damage resulted and the mechanisms. For example, in order to sustain larger ESD currents, increasing the area of device is proposed to promote the breakdown voltage. However, as shown in FIG. 1B, when the channel length reaches a certain value, such as 10 μm, the breakdown voltage stays constant with an approximate value of 430V. - Therefore, there is a need to provide an ESD protection device with increased robustness to sustain higher ESD currents and prevent the electronic apparatus from damage.
- It is one aspect of the present invention to provide an ESD protection device which has a thicker polysilicon film than that of general semiconductor electronic devices, and therefore the robustness of the ESD protection device, such as a diode or a MOS transistor, is enhanced.
- It is another aspect of the present invention to provide an ESD protection device with a polysilicon film having a thickness in a range of about 100 to 500 nanometers, which can sustain higher currents so as to protect internal circuits from damage.
- The present invention provides an ESD protection device including a substrate and a polysilicon film in an ESD protection circuit to protect an electronic apparatus. The polysilicon film of a thickness in a range of about 100 to 500 nanometers is formed on the substrate. The ESD protection device can be a MOS transistor or a diode.
- In one embodiment, the ESD protection device is a MOS transistor, which further includes source/drain regions, a gate dielectric layer, and a gate electrode. The source/drain regions are formed in the polysilicon film and separated by a channel. In another embodiment, the ESD protection device is a diode, which further includes an n-type doped region and a p-type doped region in the polysilicon film. For example, the n-type doped region is adjacent to the p-type doped region to form a PN diode. In a further embodiment, the diode further includes an intrinsic region between the n-type doped and p-type doped regions so as to form a PIN diode.
- It is a further another aspect of the present invention to provide an electronic apparatus with an ESD protection device of thicker polysilicon film, which includes a substrate, a first polysilicon film, and a second polysilicon film. The substrate has a device area and an ESD protection circuit area. The first polysilicon film having a first thickness is formed on the device area so as to form an electronic device. The second polysilicon film having a second thickness is formed on the ESD protection circuit area so as to form the ESD protection device. The second thickness is larger than the first thickness and preferably in a range of about 100 to 500 nanometers. The electronic device can be a MOS transistor while the ESD protection device can be a diode or a MOS transistor.
- It is another aspect of the present invention to provide a method compatible with the current process flow to form an ESD protection device, which is capable of sustaining higher power heat so as to prevent electronic apparatus from damage.
- In one embodiment, the method includes steps of providing a substrate having a device area and an ESD protection circuit area, forming a first polysilicon film of a first thick ness on the device area of the substrate so as to form an electronic device, and forming a second polysilicon film of a second thickness on the ESD protection circuit area of the substrate so as to form the ESD protection device. The second thickness is larger than the first thickness and preferably in a range of about 100 to 500 nanometers.
- In an exemplary embodiment, the step of forming the first and second polysilicon films includes steps of forming the second polysilicon film on the substrate to cover the device area and the ESD protection circuit area, forming a patterned photoresist layer on the second polysilicon layer to expose a portion of the second polysilicon film corresponding to the device area, and etching the second polysilicon film to reach the first thickness by using the patterned photoresist layer as a mask.
- In another exemplary embodiment, the step of forming the first and second polysilicon films includes steps of forming a polysilicon film of a third thickness on the substrate to cover the device area and the ESD protection circuit area, forming a patterned photoresist layer on the polysilicon film to expose a portion of the polysilicon film corresponding to the device area, etching the polysilicon film to expose the substrate by using the patterned photoresist layer as a mask, removing the patterned photoresist layer, and depositing the first polysilicon film on the substrate. As a result, the second thickness equals the third thickness plus the first thickness.
- The method further includes other steps of forming a diode or a MOS transistor as the ESD protection device. For example, an n-type doped region and a p-type doped region are formed in the second polysilicon film so as to form a PN diode. Furthermore, an intrinsic region is formed between the n-type doped and p-type doped regions so as to form a PIN diode.
- The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:
- FIG. 1A illustrates a conventional ESD protection circuit;
- FIG. 1B illustrates a diagram showing relation between channel width and breakdown voltage of a conventional ESD protection device;
- FIG. 2 illustrates an ESD protection circuit in one embodiment of the present invention;
- FIG. 3A illustrates a cross-sectional view of an ESD protection device and an electronic device in a first embodiment of the present invention;
- FIG. 3B illustrates a cross-sectional view of an ESD protection device and an electronic device in a second embodiment of the present invention;
- FIG. 3C illustrates a cross-sectional view of an ESD protection device and an electronic device in a third embodiment of the present invention;
- FIG. 4 illustrates a cross-sectional view of polysilicon films in one embodiment of the present invention;
- FIGS. 5A and 5B illustrates a cross-sectional view of forming a first and second polysilicon films in one embodiment of the present invention; and
- FIGS. 6A-6C illustrates a cross-sectional view of forming a first and second polysilicon films in another embodiment of the present invention.
- The present invention provides an electrostatic discharge (ESD) protection device, which has thicker polysilicon film to enhance the robustness so as to sustain higher currents or power heat.
- FIG. 2 illustrates ESD protection devices having thick polysilicon films (such as100, 200, and 300) in I/O pads of an
electronic apparatus 400 so as to provide electrostatic discharge protection to theelectronic apparatus 400 in one embodiment of the present invention. FIGS. 3A to 3C illustrate cross-sectional views of exemplary embodiments of the present invention. - Referring to FIGS. 2 and 3A, in a first exemplary embodiment, the present invention provides an
ESD protection device 100, such as a MOS transistor, in an ESD circuit so as to protect theelectronic apparatus 400. TheESD protection device 100 includes asubstrate 102 and apolysilicon film 104. Thesubstrate 102 can be selected from a group consisting of glass substrate, a quartz substrate, and the combination thereof. Thepolysilicon film 104 having a thickness in a range of about 100 to 500 nanometers is formed on thesubstrate 102. Source/drain regions 106 are formed in thepolysilicon film 104 and separated by achannel 104A. TheESD protection device 100 further includes agate dielectric layer 108, such as gate oxide layer, and agate electrode 110, so as to be a MOS transistor used in an ESD protection circuit. - Referring to FIG. 3B, in a second exemplary embodiment, the
ESD protection device 200 is a diode, which includes asubstrate 102 and apolysilicon film 104. Similarly, thesubstrate 102 can be selected from a group consisting of a glass substrate, a quartz substrate, and the combination thereof. Thepolysilicon film 104, which has a thickness in a range of about 100 to 500 nanometers, is formed on thesubstrate 102. An n-type dopedregion 202 and a p-type dopedregion 204 are formed in thepolysilicon film 104. TheESD protection device 200 can be a PN diode when the n-type dopedregion 202 is adjacent to the p-type dopedregion 204. - Referring to FIG. 3C, in a third exemplary embodiment, the difference between he second and third embodiments is that
ESD protection device 300 further includes anintrinsic region 302, which is arranged between the n-type and p-type doped regions, 202 and 204, to form a PIN diode as theESD protection device 300. - Referring to FIGS. 2 and 3A to3C, the
electronic apparatus 400 having the ESD protection device shown as 100, 200, or 300, includes asubstrate 102, afirst polysilicon film 404, and asecond polysilicon film 104. As described above, thesubstrate 102 can be selected from a group consisting of a glass substrate, a quartz substrate, and the combination thereof. Thesubstrate 102 has adevice area 400A and an ESDprotection circuit area 400B. Thedevice area 400A can be an internal circuit region as shown in FIG. 2. Thefirst polysilicon film 404 having a first thickness (H1) is formed on thedevice area 400A of thesubstrate 102, so as to form anelectronic device 402. Thesecond polysilicon film 104 having a second thickness (H2) is formed on the ESDprotection circuit area 400B of thesubstrate 102, so as to form an ESD protection device (such as 100, 200, or 300). The second thickness (H2) is larger than the first thickness (H1) and preferably in a range of about 100 to 500 nanometers. - The
electronic device 402 can be a p-type or n-type MOS transistor, and therefore, theelectronic device 402 further includes first source/drain regions 406 formed in thefirst polysilicon film 402 and separated by afirst channel 404A. Agate dielectric layer 408 andgate electrode 410 are formed on thefirst polysilicon film 404. The ESD protection device can be a diode (such as 200 or 300) or aMOS transistor 100 having athicker polysilicon film 104. For example, as aMOS transistor 100, theESD protection device 100 further includes second source/drain regions 106 formed in thesecond polysilicon film 104 and separated by asecond channel 104A.Gate dielectric layer 108 andgate electrode 110 are formed on thesecond polysilicon layer 104, as shown in FIG. 3A. - Alternatively, the
electronic apparatus 400 further includes an n-type dopedregion 202 and a p-type dopedregion 204 in thesecond polysilicon film 104 so as to form a PN diode as theESD protection device 200 in FIG. 3B. Moreover, anintrinsic region 302 can be formed between the n-type and p-type doped regions (202 and 204) to form a PIN diode as theESD protection device 300 in FIG. 3C. - In general, a conventional ESD protection device has a polysilicon film of a thickness, preferably about 50 nanometers, which is the same as that of the active area of the electronic device in the internal circuit (such as404 in FIGS. 3A-3C), so that the gate can have better controls over the channel. However, the application of thin polysilicon film is not suitable for ESD events. Therefore, the ESD protection device of the present invention, such as 100, 200, and 300, having a thicker polysilicon film (preferably in a range between 100 to 500 nanometers) can efficiently disperse the ESD currents to the
thick polysilicon film 104 and improve the robustness of the ESD protection device. Moreover, as shown in FIG. 2, when ESD event happens in PS mode or ND mode, passing through the I/O pads, the ESD protection device with thicker polysilicon film can sustain large currents to protect devices from damage. - Referring to FIG. 4, in another embodiment, a method for forming an ESD protection device in an ESD protection circuit is provided. The method includes a step of providing a
substrate 102, which has adevice area 400A and an ESDprotection circuit area 400B. Afirst polysilicon film 404 of a first thickness (H1) is formed on thedevice area 400A of thesubstrate 102 so as to form an electronic device 402 (as shown in FIGS. 3A to 3C). Asecond polysilicon film 104 of a second thickness (H2) is formed on the ESDprotection circuit area 400B of thesubstrate 102 to form the ESD protection device (such as 100, 200, and 300 shown in FIGS. 3A to 3C). The second thickness (H2) is larger than said first thickness (H1) and preferably in a range about 100 to 500 nanometers. - It is noted that the steps of forming the first and second polysilicon films (404 and 104) include variety combinations of processes. For example, as shown in FIGS. 5A and 5B, the steps of forming the first and second polysilicon films include forming the
second polysilicon film 104 over theentire substrate 102. In other words, thesecond polysilicon film 104 having the second thickness (H2) covers thedevice area 400A and the ESDprotection circuit area 400B. Then, apattern photoresist layer 412 is formed on thesecond polysilicon film 104 to expose a portion of thesecond polysilicon film 104, which corresponds to thedevice area 400A. Thesecond polysilicon film 104 is etched to reach the first thickness (H1) by using the patternedphotoresist layer 412 as a mask. Therefore, the first and second polysilicon films are formed. - In another exemplary embodiment, as shown in FIGS. 6A to AB, the step of forming the first and second polysilicon films includes forming a
polysilicon film 414 of a third thickness (H3) on theentire substrate 102 to cover thedevice area 400A and the ESDprotection circuit area 400B. Then, a patternedphotoresist layer 416 is formed on thepolysilicon film 414 to expose a portion of thepolysilicon film 414, which corresponds to thedevice area 400A, as shown in FIG. 6A. Thepolysilicon film 414 is etched to expose a portion of thesubstrate 102 by using the patternedphotoresist layer 416 as a mask. Then, the patternedphotoresist layer 416 is removed, as shown in FIG. 6B. Thefirst polysilicon film 404 is deposited on thesubstrate 102. It is noted that the second thickness (H2) equals the third thickness (H3) plus said first thickness (H1), as shown in FIG. 6C. According to different design needs, the method may further include a step of defining active areas to accomplish the structure shown in FIG. 4. - The method further includes steps of forming diodes or MOS transistors, which is compatible with current process flow of forming thin-film transistors. As shown in FIG. 3A, the method further includes forming first source/
drain regions 406 ofelectronic device 402. The source/drain regions 406 are separated by afist channel 404A in thefirst polysilicon film 404. When the ESD protection device is aMOS transistor 100, the method further includes a step of forming second source/drain regions 106 separated by asecond channel 104A in thesecond polysilicon film 104. Therefore, thethicker polysilicon film 104 can sustain higher power heat to prevent theESD protection device 100 from damage. - Alternatively, the method further includes forming n-type and p-type doped
regions intrinsic region 302 between the n-type dopedregion 202 and the p-type dopedregion 204 in thesecond polysilicon film 104 to form aPIN diode 300 as the ESD protection device. - It is noted that the
polysilicon film - Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what is intended to be limited solely by the appended claims.
Claims (22)
Priority Applications (1)
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US11/451,344 US7632725B2 (en) | 2003-04-25 | 2006-06-13 | Method of forming ESD protection device with thick poly film |
Applications Claiming Priority (2)
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TW092109702A TW584953B (en) | 2003-04-25 | 2003-04-25 | ESD protection device with thick poly film, electronic device and method for forming the same |
TW092109702 | 2003-04-25 |
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US11/451,344 Division US7632725B2 (en) | 2003-04-25 | 2006-06-13 | Method of forming ESD protection device with thick poly film |
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US20040245574A1 true US20040245574A1 (en) | 2004-12-09 |
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US10/829,983 Abandoned US20040245574A1 (en) | 2003-04-25 | 2004-04-23 | ESD protection device with thick poly film and method for forming the same |
US11/451,344 Active 2025-12-16 US7632725B2 (en) | 2003-04-25 | 2006-06-13 | Method of forming ESD protection device with thick poly film |
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US11/451,344 Active 2025-12-16 US7632725B2 (en) | 2003-04-25 | 2006-06-13 | Method of forming ESD protection device with thick poly film |
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TWI424544B (en) * | 2011-03-31 | 2014-01-21 | Novatek Microelectronics Corp | Integral circuit device |
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Also Published As
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US7632725B2 (en) | 2009-12-15 |
TW200423368A (en) | 2004-11-01 |
US20060231896A1 (en) | 2006-10-19 |
TW584953B (en) | 2004-04-21 |
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