CN110943030A - Field oxide layer structure and manufacturing method thereof - Google Patents
Field oxide layer structure and manufacturing method thereof Download PDFInfo
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- CN110943030A CN110943030A CN201811105192.7A CN201811105192A CN110943030A CN 110943030 A CN110943030 A CN 110943030A CN 201811105192 A CN201811105192 A CN 201811105192A CN 110943030 A CN110943030 A CN 110943030A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
- H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
- H01L21/76—Making of isolation regions between components
- H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
- H01L21/76202—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using a local oxidation of silicon, e.g. LOCOS, SWAMI, SILO
- H01L21/76205—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using a local oxidation of silicon, e.g. LOCOS, SWAMI, SILO in a region being recessed from the surface, e.g. in a recess, groove, tub or trench region
Abstract
The invention provides a field oxide layer structure and a manufacturing method thereof, wherein the field oxide layer structure comprises a substrate and a field oxide layer, wherein the field oxide layer is formed in the substrate and isolates a plurality of active regions in the substrate; wherein, the field oxide both sides have the beak, and the length of beak and the thickness ratio of field oxide is between 0.2:1 to 0.4: 1. According to the invention, after the liner oxide layer is removed by etching and before the field oxide layer is grown by thermal oxidation, the limit side wall is formed by depositing and etching silicon oxynitride, and the limit side wall can ensure that the growth of the bird's beak is limited by the limit side wall when the field oxide layer is grown, so that the length of the bird's beak can be obviously reduced. According to the invention, the length of the bird's beak can be strictly controlled by limiting the adjustment of the width of the side wall, so that the area of the active region and the integration level of devices are improved, and the electrical performance of the devices in the active region is effectively improved.
Description
Technical Field
The invention belongs to the field of semiconductor manufacturing, and particularly relates to a field oxide layer structure and a manufacturing method thereof.
Background
As is well known, a semiconductor integrated chip may include a plurality of various components such as capacitors and resistors, and when the semiconductor integrated chip is manufactured, different components need to be formed on a silicon wafer, and in order to avoid mutual interference or short circuit between adjacent components, isolation regions are usually required to be disposed between different components so that the components do not affect each other.
One conventional method of forming isolation regions between components is a local oxidation isolation (LOCOS) method. The manufacturing steps of the local field oxide isolation comprise: growing a thin liner oxide layer on the surface of a bare silicon substrate in a furnace tube mode, depositing and growing a layer of silicon nitride on the liner oxide layer, removing the thermal oxide layer and the silicon nitride on a field region through photoetching and etching, forming an opening in the field region to expose the silicon substrate, performing thermal oxidation on the exposed silicon substrate to grow a field oxide layer, removing all the silicon nitride and the liner oxide layer on the surface of the silicon wafer, and forming an active region (a region where a device is located) and the field region (an isolation region) on the surface of the silicon wafer.
With the large scale of integrated circuits, the integration level of the semiconductor process is higher and higher, the whole semiconductor manufacturing process is more and more complex, various wet etches, such as forming gate oxide layers with different thicknesses by using the wet etches, etc., are used in a large amount in the whole process, and the etches are not selective usually, so the thickness of field oxide is reduced continuously, and finally, the field opening is insufficient, the field tube leaks electricity, the isolation function is lost, and the circuit loses the function. The method of solving the continuous reduction of field oxygen thickness can improve initial field oxide's thickness, nevertheless in traditional field oxidation isolation technology, can produce the beak phenomenon when forming field oxide, the effective length of beak and the thickness of field oxygen are directly proportional in addition, if increase the thickness of field oxygen, then the length of beak also can lengthen, can occupy the area in active area, make the effective area in active area reduce, lead to original circuit design rule can't realize.
In addition, when forming the field oxide layer, the consumption of bulk silicon and the generation of oxide layer are about 1:2, i.e. half of the field oxide layer is located on the bulk silicon, as shown in fig. 1. Thus, a step difference may be formed between the active region and the field region. The thicker the field oxide layer is, the more obvious the step difference is, which will cause great influence on the subsequent process steps. For example, after fabricating a poly (poly) resistor on a field oxide layer, a poly-dielectric-poly (PIP) capacitor, an inter-layer dielectric (ILD) layer is deposited, followed by Chemical Mechanical Planarization (CMP), and then a via is etched. In order to prevent CMP from damaging a device structure, an ILD is required to have a certain thickness, if the step difference between a field region and an active region is increased, the ILD is required to be thickened, so that the difficulty of subsequent through hole etching is increased, meanwhile, the step difference between the field region and the active region is large, the depth difference of corresponding through holes is also large, and the requirement on the etching selection ratio is also improved in order to ensure that the through hole leading-out regions of the field region and the active region are not damaged.
Based on the above, it is necessary to provide a field oxide layer structure and a method for manufacturing the same, which can effectively reduce the length of the bird's beak and improve the step difference between the source region and the field region.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a field oxide structure and a method for fabricating the same, which are used to solve the problem of the prior art that the bird's beak length is too large, which results in the reduction of the active area.
To achieve the above and other related objects, the present invention provides a method for fabricating a field oxide structure, the method comprising: 1) providing a substrate, and sequentially forming a pad oxide layer and a sacrificial dielectric layer on the substrate; 2) the sacrificial dielectric layer and the pad oxide layer are etched in a patterning mode to form a field area window exposing the substrate; 3) forming a limiting side wall in the field area window; 4) thermally oxidizing and growing a field oxide layer in the substrate based on the field area window and the limiting side wall, wherein the limiting side wall is used for limiting the length of a bird's beak part of the field oxide layer; and 5) removing the limiting side wall, the sacrificial structure layer and the pad oxide layer so as to form a field oxide layer and an active region isolated by the field oxide layer in the substrate.
Optionally, the length of the beak part of the field oxide layer is controlled by adjusting the width of the limiting sidewall.
Optionally, the method for growing the field oxide layer in the substrate by thermal oxidation in the step 4) includes a wet oxygen oxidation process, wherein a reaction temperature of the wet oxygen oxidation process is between 900 ℃ and 1100 ℃, a reaction gas includes oxygen and hydrogen, and a flow ratio of the oxygen to the hydrogen is between 4:9 and 5: 7.
Optionally, in step 5), an etching selection ratio of the sacrificial dielectric layer to the field oxide layer is not less than 5:1, and an etching selection ratio of the limiting sidewall to the field oxide layer is not less than 5: 1.
Furthermore, the sacrificial dielectric layer is made of silicon nitride, the limiting side wall is made of silicon oxynitride, and the field oxide layer is made of silicon dioxide.
Optionally, the thickness of the pad oxide layer ranges from 200 angstroms to 500 angstroms, and the thickness of the sacrificial dielectric layer ranges from 1000 angstroms to 2000 angstroms.
Optionally, step 3) comprises: 3-1) depositing a side wall material on the bottom and the side wall of the window of the field region and the surface of the sacrificial dielectric layer; and 3-2) etching to remove the side wall materials positioned at the bottom of the field window and on the surface of the sacrificial medium layer, and reserving the side wall materials positioned on the side wall of the field window so as to form a limiting side wall in the field window.
Optionally, step 3) comprises: 3-1) thermally oxidizing the substrate within the field region window to form a thermal oxide layer in the substrate, the thermal oxide layer extending toward both sides of the field region window to form an extension between the substrate and the sacrificial dielectric layer; 3-2) removing the thermal oxidation layer to form a groove body in the substrate, wherein side grooves are formed in two sides of the groove body and are positioned between the substrate and the sacrificial medium layer; 3-3) depositing a side wall material on the window of the field region and the surface of the sacrifice medium layer, wherein the side wall material is filled into the side groove; and 3-4) etching to remove the side wall materials positioned at the bottom of the field window and on the surface of the sacrificial medium layer, and reserving the side wall materials positioned in the side groove so as to form the limiting side wall in the side groove.
Optionally, the thickness of the thermal oxide layer ranges from 1000 angstroms to 5000 angstroms, the width of the extension portion ranges from 500 angstroms to 4000 angstroms, and the width of the limiting sidewall ranges from 500 angstroms to 4000 angstroms.
Optionally, the field oxide layer includes an isolation portion located below the top surface of the substrate and a protruding portion protruding above the top surface of the substrate, and a ratio of a thickness of the isolation portion to a thickness of the protruding portion is between 4:1 and 3: 2.
Further, the thickness of the isolation part is 4000-6000 angstroms, and the thickness of the protruding part is 1500-3000 angstroms.
Optionally, the field oxide layer includes a main body portion and a beak portion, the beak portion is located on both sides of the main body portion, and the thickness of the beak portion is from the main body portion extends towards the outside and gradually decreases.
Optionally, a ratio of a length of the beak portion to a thickness of the field oxide layer is between 0.2:1 and 0.4: 1.
Further, the thickness of the field oxide layer ranges from 2500 angstroms to 15000 angstroms, and the length of the beak portion ranges from 500 angstroms to 6000 angstroms.
The present invention also provides a method for manufacturing a semiconductor device, comprising the steps of: forming a field oxide layer and an active region in a substrate by adopting the manufacturing method of the field oxide layer structure in any scheme; and manufacturing a semiconductor device in the active region.
The present invention also provides a field oxide structure, including: a substrate; the field oxide layer is formed in the substrate and isolates a plurality of active regions in the substrate; wherein, the field oxide both sides have the beak, and the length of beak and the thickness ratio of field oxide is between 0.2:1 to 0.4: 1.
Optionally, the thickness of the field oxide layer ranges from 2500 a to 15000 a, and the length of the beak portion ranges from 500 a to 6000 a.
Optionally, the field oxide layer includes a main body portion and a beak portion, the beak portion is located on both sides of the main body portion, and the thickness of the beak portion is from the main body portion extends towards the outside and gradually decreases.
Optionally, the substrate includes a silicon substrate, and the material of the field oxide layer includes silicon dioxide.
Optionally, the field oxide layer includes an isolation portion located below the top surface of the substrate and a protruding portion protruding above the top surface of the substrate, and a ratio of a thickness of the isolation portion to a thickness of the protruding portion is between 4:1 and 3: 2.
Further, the thickness of the isolation part is 4000-6000 angstroms, and the thickness of the protruding part is 1500-3000 angstroms.
The present invention also provides a semiconductor device comprising: a field oxide structure as in any of the above aspects; and a semiconductor device formed in the active region.
The field oxide layer structure and the manufacturing method thereof have the following beneficial effects:
according to the invention, after the liner oxide layer is removed by etching and before the field oxide layer is grown by thermal oxidation, the limit side wall is formed by depositing and etching silicon oxynitride, and the limit side wall can ensure that the growth of the bird's beak is limited by the limit side wall when the field oxide layer is grown, so that the length of the bird's beak can be obviously reduced. The invention can strictly control the length of the beak by limiting the adjustment of the width of the side wall.
The field oxide layer with the smaller beak length can be obtained, the area of the active region can be effectively increased, the integration level of the device can be improved, and meanwhile, the electrical performance of the device in the active region can be effectively improved.
In the embodiment, the depth of the groove body on the substrate can be correspondingly increased by increasing the thickness of the thermal oxide layer and removing the thermal oxide layer by etching, so that the height of the protruding part of the field oxide layer formed subsequently, which is exposed out of the top surface of the substrate, is reduced, and the step difference between the active region and the field region is effectively reduced.
The invention has wide application prospect in the field of large-scale integrated circuit design and manufacture.
Drawings
Fig. 1 is a schematic flow chart illustrating a method for fabricating a field oxide structure according to the present invention.
Fig. 2 to 9 are schematic structural diagrams showing steps of a method for manufacturing a field oxide layer structure according to embodiment 1 of the present invention.
Fig. 10 to 19 are schematic structural diagrams showing steps of a method for manufacturing a field oxide layer structure according to embodiment 2 of the present invention.
Description of the element reference numerals
101 substrate
102 pad oxide layer
103 sacrificial dielectric layer
104 photoresist layer
105 field area window
106 side wall material
107 limit sidewall
108 field oxide layer
109 bird's beak part
110 thermal oxidation layer
111 side groove
112 trough body
113 limit sidewall
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Please refer to fig. 1 to 19. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the drawings only show the components related to the present invention rather than being drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of each component in actual implementation may be changed arbitrarily, and the layout of the components may be more complicated.
Example 1
As shown in fig. 1 to fig. 9, the present embodiment provides a method for manufacturing a field oxide layer 108 structure, the method includes the following steps:
as shown in fig. 1 and fig. 2 to fig. 3, step 1) S11 is performed first, a substrate 101 is provided, and a pad oxide layer 102 and a sacrificial dielectric layer 103 are sequentially formed on the substrate 101.
The substrate 101 may be a substrate 101 suitable for fabricating a field oxide layer 108 structure, for example, the substrate 101 may be a silicon substrate 101 or the like.
Firstly, a thermal oxidation process may be adopted to form a pad oxide layer 102 on the substrate 101, a thickness range of the pad oxide layer 102 may be between 200 angstroms and 500 angstroms, for example, 300 angstroms, 400 angstroms, and the pad oxide layer 102 may protect a surface of the substrate 101 on one hand, and on the other hand, may be used as a buffer layer between the substrate 101 and the sacrificial medium layer 103, so as to reduce a stress of the sacrificial medium layer 103 and improve a growth quality thereof.
Then, a sacrificial dielectric layer 103 may be deposited on the surface of the pad oxide layer 102 by using a method such as Chemical Vapor Deposition (CVD) or Atomic Layer Deposition (ALD), the sacrificial layer may be made of silicon nitride, and is preferably made of silicon nitride, and the thickness of the sacrificial dielectric layer 103 ranges from 1000 angstroms to 2000 angstroms, such as 1500 angstroms.
As shown in fig. 1 and 4-5, step 2) S12 is then performed to pattern the sacrificial dielectric layer 103 and the pad oxide layer 102 to form a field region window 105 exposing the substrate 101.
As shown in fig. 4, a photoresist layer 104 is spin-coated on the surface of the sacrificial dielectric layer 103, and then a field pattern is formed in the photoresist layer 104 by exposure and development processes.
As shown in fig. 5, the sacrificial dielectric layer 103 in the field region pattern is removed by etching using a dry etching process, and then the pad oxide layer 102 in the field region pattern is removed by etching, so as to form a field region window 105 exposing the substrate 101 in the sacrificial dielectric layer 103 and the pad oxide layer 102.
As shown in fig. 1 and fig. 6 to 7, step 3) S13 is performed to form sidewall spacers 107 in the field window 105.
Further, the sacrificial dielectric layer 103 is made of silicon nitride, the limiting sidewall 107 is made of silicon oxynitride, and the field oxide layer 108 is made of silicon dioxide.
Specifically, step 3) includes:
as shown in fig. 6, step 3-1) is first performed to deposit a sidewall material 106 on the bottom and the sidewall of the field region window 105 and the surface of the sacrificial dielectric layer 103, for example, a sidewall material 106 may be deposited on the bottom and the sidewall of the field region window 105 and the surface of the sacrificial dielectric layer 103 by using a Chemical Vapor Deposition (CVD) method or an Atomic Layer Deposition (ALD) method, and the sidewall material 106 may be silicon oxynitride.
As shown in fig. 7, then, step 3-2) is performed, in a mask-free condition, the sidewall material 106 located at the bottom of the field region window 105 and the surface of the sacrificial dielectric layer 103 is etched and removed, the sidewall material 106 located at the sidewall of the field region window 105 may remain during the etching process, so as to form a limiting sidewall 107 in the field region window 105, and the bottom of the limiting sidewall 107 is tightly attached to the top surface of the substrate 101, so as to improve the subsequent limiting effect on the bird's beak of the field oxide layer 108.
Meanwhile, because the sacrificial dielectric layer 103 made of silicon nitride and the sidewall material 106 made of silicon oxynitride have a certain selection ratio, when the sidewall material 106 on the surface of the substrate 101 in the field window 105 is removed, the sacrificial dielectric layer 103 can maintain a sufficient thickness.
As shown in fig. 1 and 8, step 4) S14 is then performed, a field oxide layer 108 is thermally oxidized and grown in the substrate 101 based on the field window 105 and the limiting sidewall 107, and the limiting sidewall 107 is used to limit the length of the beak portion 109 of the field oxide layer 108.
For example, the method for growing the field oxide layer 108 by thermal oxidation in the substrate 101 may be a wet oxidation process, first, placing the substrate 101 in a furnace tube reaction furnace, setting the initial temperature of the furnace tube reaction furnace to about 800 ℃, then gradually heating the temperature in the furnace tube to a reaction temperature, where the reaction temperature of the wet oxidation process is between 900 ℃ and 1100 ℃, preferably 1100 ℃, and when the reaction temperature is reached, maintaining the temperature for about 1.5 hours, during which, introducing a reaction gas into the furnace tube for wet oxidation to form the field oxide layer 108, where the reaction gas may be oxygen and hydrogen, and a flow ratio of the oxygen to the hydrogen is between 4:9 and 5: 7.
The field oxide layer 108 includes a main body portion and a beak portion 109, the beak portion 109 is located on both sides of the main body portion, and the thickness of the beak portion 109 is from the main body portion extends toward the outside and gradually decreases.
In the process of forming the field oxide layer 108 through the above reaction, the limiting sidewall 107 is used for limiting the length of the beak portion 109 of the field oxide layer 108, and the width of the limiting sidewall 107 can be controlled to control the length of the beak portion 109 of the field oxide layer 108.
For example, the ratio of the length D2 of the bird's mouth 109 to the thickness D1 of the field oxide layer 108 is between 0.2:1 and 0.4: 1. Specifically, the thickness of the field oxide layer 108 may range from 2500 a to 15000 a, and the length of the beak portion 109 may range from 500 a to 6000 a. The field oxide layer 108 with the smaller bird's beak length can be obtained, the area of the active region can be effectively increased, the integration level of the device can be improved, and meanwhile, the electrical performance of the device in the active region can be effectively improved.
As shown in fig. 1 and 9, step 5) S15 is finally performed to remove the limiting sidewall 107, the sacrificial structure layer, and the pad oxide layer 102, so as to form a field oxide layer 108 and an active region isolated by the field oxide layer 108 in the substrate 101.
In this step, the sacrificial dielectric layer 103 is made of silicon nitride, the limiting sidewall 107 is made of silicon oxynitride, and the field oxide layer 108 is made of silicon dioxide, so that the etching selection ratio of the sacrificial dielectric layer 103 to the field oxide layer 108 is not less than 5:1, and the etching selection ratio of the limiting sidewall 107 to the field oxide layer 108 is not less than 5:1, so as to reduce the damage to the field oxide layer 108 in the process of limiting the sidewall and the sacrificial structure layer, and improve the isolation effect.
The present embodiment also provides a method for manufacturing a semiconductor device, including the steps of: forming a field oxide layer 108 and an active region in a substrate 101 by using the method for manufacturing the field oxide layer 108 structure of the present embodiment; and manufacturing a semiconductor device in the active region.
The semiconductor device may be an integrated circuit composed of one or more of the group consisting of a field effect transistor, a diode, a transistor, a semiconductor capacitor or inductor, a photoelectric device, a sensor, a memory, and the like, and is not limited to the examples listed herein.
As shown in fig. 9, the present embodiment further provides a field oxide layer 108 structure, which includes: a substrate 101 and a field oxide layer 108.
As shown in fig. 9, the substrate 101 may be a substrate 101 suitable for fabricating a field oxide layer 108 structure, for example, the substrate 101 may be a silicon substrate 101 or the like.
As shown in fig. 9, the field oxide layer 108 is formed in the substrate 101, and the field oxide layer 108 isolates a plurality of active regions in the substrate 101; wherein, the field oxide layer 108 has bird-shaped beaks 109 on two sides, and the ratio of the length D2 of the bird-shaped beaks 109 to the thickness D1 of the field oxide layer 108 is between 0.2:1 and 0.4:1, and the material of the field oxide layer 108 may be silicon dioxide.
As shown in fig. 9, the field oxide layer 108 includes a main body portion and a beak portion 109, the beak portion 109 is located at two sides of the main body portion, and the thickness of the beak portion 109 gradually decreases from the main body portion toward the outside. In this embodiment, the thickness of the field oxide layer 108 ranges from 2500 a to 15000 a, and the length of the beak portion 109 ranges from 500 a to 6000 a.
The present embodiment also provides a semiconductor device including: a field oxide layer 108 structure as described in any of the above aspects; and a semiconductor device formed in the active region. The semiconductor device may be an integrated circuit composed of one or more of the group consisting of a field effect transistor, a diode, a transistor, a semiconductor capacitor or inductor, a photoelectric device, a sensor, a memory, and the like, and is not limited to the examples listed herein.
Example 2
As shown in fig. 10 to 19, the present embodiment provides a method for manufacturing a field oxide layer 108 structure, which includes the following steps:
as shown in fig. 10 to 11, step 1) is performed first, a substrate 101 is provided, and a pad oxide layer 102 and a sacrificial dielectric layer 103 are sequentially formed on the substrate 101.
The substrate 101 may be a substrate 101 suitable for fabricating a field oxide layer 108 structure, for example, the substrate 101 may be a silicon substrate 101 or the like.
Firstly, a thermal oxidation process may be adopted to form a pad oxide layer 102 on the substrate 101, a thickness range of the pad oxide layer 102 may be between 200 angstroms and 500 angstroms, for example, 300 angstroms, 400 angstroms, and the pad oxide layer 102 may protect a surface of the substrate 101 on one hand, and on the other hand, may be used as a buffer layer between the substrate 101 and the sacrificial medium layer 103, so as to reduce a stress of the sacrificial medium layer 103 and improve a growth quality thereof.
Then, a sacrificial dielectric layer 103 may be deposited on the surface of the pad oxide layer 102 by using a method such as Chemical Vapor Deposition (CVD) or Atomic Layer Deposition (ALD), the sacrificial layer may be made of silicon nitride, and is preferably made of silicon nitride, and the thickness of the sacrificial dielectric layer 103 ranges from 1000 angstroms to 2000 angstroms, such as 1500 angstroms.
As shown in fig. 12 to 13, step 2) S12 is then performed to pattern the sacrificial dielectric layer 103 and the pad oxide layer 102 to form a field region window 105 exposing the substrate 101.
As shown in fig. 12, a photoresist layer 104 is spin-coated on the surface of the sacrificial dielectric layer 103, and then a field pattern is formed in the photoresist layer 104 by exposure and development processes.
As shown in fig. 13, the sacrificial dielectric layer 103 in the field region pattern is removed by etching using a dry etching process, and then the pad oxide layer 102 in the field region pattern is removed by etching, so as to form a field region window 105 exposing the substrate 101 in the sacrificial dielectric layer 103 and the pad oxide layer 102.
As shown in fig. 14 to 17, step 3) S13 is performed to form a sidewall spacer 113 in the field window 105.
Further, the sacrificial dielectric layer 103 is made of silicon nitride, the limiting sidewall 113 is made of silicon oxynitride, and the field oxide layer 108 is made of silicon dioxide.
Specifically, step 3) includes:
as shown in fig. 14, step 3-1) is performed first, the substrate 101 in the field region window 105 is thermally oxidized to form a thermal oxide layer 110 in the substrate 101, and the thermal oxide layer 110 extends toward both sides of the field region window 105 to form an extension between the substrate 101 and the sacrificial dielectric layer 103.
For example, the thickness of the thermal oxide layer 110 may range from 1000 to 5000 angstroms, and the width of the extension may range from 500 to 4000 angstroms. The increase of the thickness of the thermal oxide layer 110 may reduce the step difference between the subsequent field oxide layer 108 and the active region, but may increase the width of the extension, and if the width of the extension is too large, the area of the active region may be reduced, so the thickness of the thermal oxide layer 110 is preferably controlled to be one quarter to one half of the growth thickness of the subsequent field oxide layer 108.
As shown in fig. 15, step 3-2) is then performed to remove the thermal oxide layer 110, so as to form a trench 112 in the substrate 101, where two sides of the trench 112 have side trenches 111 located between the substrate 101 and the sacrificial medium layer 103.
As shown in fig. 16, step 3-3) is performed to deposit a sidewall material 106 on the field region window 105 and the surface of the sacrificial dielectric layer 103, wherein the sidewall material 106 fills the side trench 111. For example, a sidewall material 106 may be deposited on the field region window 105 and the surface of the sacrificial dielectric layer 103 by using a Chemical Vapor Deposition (CVD) method or an Atomic Layer Deposition (ALD) method, the sidewall material 106 fills the side trench 111, and the sidewall material 106 may be silicon oxynitride.
As shown in fig. 17, finally, step 3-4) is performed, in a mask-free condition, the sidewall material 106 located at the bottom of the field region window 105 and on the surface of the sacrificial medium layer 103 is etched and removed, and the sidewall material 106 in the side trench 111 is shielded by the sacrificial medium layer 103 and can be completely retained in the side trench 111, so as to form the limit sidewall 113. The width D4 of the limiting sidewall 113 is substantially the same as the width of the extension, and is between 500 angstroms and 4000 angstroms. Meanwhile, because the sacrificial dielectric layer 103 made of silicon nitride and the sidewall material 106 made of silicon oxynitride have a certain selection ratio, when the sidewall material 106 on the surface of the substrate 101 in the field window 105 is removed, the sacrificial dielectric layer 103 can maintain a sufficient thickness.
The limiting side wall 113 of the embodiment is located in the beak formation region of the field oxide layer 108, so that the effect of limiting the beak by the limiting side wall can be greatly improved, and the length of the beak can be remarkably reduced.
In addition, in the present embodiment, by increasing the thickness of the thermal oxide layer 110 and removing the thermal oxide layer by etching, the depth of the slot 112 on the substrate 101 can be correspondingly increased, and further, the height of the protrusion of the field oxide layer 108 formed subsequently exposed on the top surface of the substrate 101 is reduced, thereby effectively reducing the step difference between the active region and the field region.
As shown in fig. 18, step 4) S14 is then performed, a field oxide layer 108 is thermally oxidized and grown in the substrate 101 based on the field window 105 and the limiting sidewall 113, wherein the limiting sidewall 113 is used to limit the length of the bird' S beak 109 of the field oxide layer 108.
For example, the method for growing the field oxide layer 108 by thermal oxidation in the substrate 101 may be a wet oxidation process, first, placing the substrate 101 in a furnace tube reaction furnace, setting the initial temperature of the furnace tube reaction furnace to about 800 ℃, then gradually heating the temperature in the furnace tube to a reaction temperature, where the reaction temperature of the wet oxidation process is between 900 ℃ and 1100 ℃, preferably 1100 ℃, and when the reaction temperature is reached, maintaining the temperature for about 1.5 hours, during which, introducing a reaction gas into the furnace tube for wet oxidation to form the field oxide layer 108, where the reaction gas may be oxygen and hydrogen, and a flow ratio of the oxygen to the hydrogen is between 4:9 and 5: 7.
The field oxide layer 108 includes a main body portion and a beak portion 109, the beak portion 109 is located on both sides of the main body portion, and the thickness of the beak portion 109 is from the main body portion extends toward the outside and gradually decreases.
In the process of forming the field oxide layer 108 through the above reaction, the limiting sidewall 113 is used to limit the length of the beak portion 109 of the field oxide layer 108, and the width of the limiting sidewall 113 can be controlled to control the length of the beak portion 109 of the field oxide layer 108.
For example, the ratio of the length of the beak portion 109 to the thickness of the field oxide layer 108 is between 0.2:1 and 0.4: 1. Specifically, the thickness of the field oxide layer 108 may range from 2500 a to 15000 a, and the length of the beak portion 109 may range from 500 a to 6000 a. The field oxide layer 108 with the smaller bird's beak length can be obtained, the area of the active region can be effectively increased, the integration level of the device can be improved, and meanwhile, the electrical performance of the device in the active region can be effectively improved.
Since the substrate 101 is formed with the groove 112 in advance, the height of the protruding portion of the field oxide layer 108 exposed on the top surface of the substrate 101 can be effectively reduced, thereby effectively reducing the step difference between the active region and the field region. In this embodiment, the field oxide layer 108 includes an isolation portion located below the top surface of the substrate 101 and a protrusion portion protruding above the top surface of the substrate 101, and a ratio of a thickness of the isolation portion to a thickness of the protrusion portion is between 4:1 and 3: 2. Further, the thickness of the isolation part is 4000-6000 angstroms, and the thickness of the protruding part is 1500-3000 angstroms.
As shown in fig. 19, step 5) S15 is finally performed to remove the limiting sidewall 113, the sacrificial structure layer, and the pad oxide layer 102, so as to form a field oxide layer 108 and an active region isolated by the field oxide layer 108 in the substrate 101.
In this step, the sacrificial dielectric layer 103 is made of silicon nitride, the limiting sidewall 113 is made of silicon oxynitride, and the field oxide layer 108 is made of silicon dioxide, so that the etching selection ratio of the sacrificial dielectric layer 103 to the field oxide layer 108 is not less than 5:1, and the etching selection ratio of the limiting sidewall 113 to the field oxide layer 108 is not less than 5:1, so as to reduce the damage to the field oxide layer 108 caused by the process of limiting the sidewall 113 and the sacrificial structure layer, and improve the isolation effect.
As shown in fig. 19, the present embodiment further provides a field oxide layer 108 structure, which includes: a substrate 101 and a field oxide layer 108.
As shown in fig. 19, the substrate 101 may be a substrate 101 suitable for fabricating a field oxide layer 108 structure, for example, the substrate 101 may be a silicon substrate 101 or the like.
As shown in fig. 19, the field oxide layer 108 is formed in the substrate 101, and the field oxide layer 108 isolates a plurality of active regions in the substrate 101; wherein, the field oxide layer 108 has bird-shaped beaks 109 on two sides, and the ratio of the length D2 of the bird-shaped beaks 109 to the thickness D1 of the field oxide layer 108 is between 0.2:1 and 0.4:1, and the material of the field oxide layer 108 may be silicon dioxide.
As shown in fig. 19, the field oxide layer 108 includes a main body portion and a beak portion 109, the beak portion 109 is located at two sides of the main body portion, and the thickness of the beak portion 109 gradually decreases from the main body portion toward the outside. In this embodiment, the thickness of the field oxide layer 108 ranges from 2500 a to 15000 a, and the length of the beak portion 109 ranges from 500 a to 6000 a.
The field oxide layer 108 comprises an isolation portion located below the top surface of the substrate 101 and a protrusion portion protruding above the top surface of the substrate 101, and the ratio of the thickness D6 of the isolation portion to the thickness D5 of the protrusion portion is between 4:1 and 3: 2. Further, the thickness of the isolation part is 4000-6000 angstroms, and the thickness of the protruding part is 1500-3000 angstroms. The invention effectively reduces the height of the projecting part of the field oxide layer 108 exposed on the top surface of the substrate 101, thereby effectively reducing the step difference between the active region and the field region.
The field oxide layer 108 structure and the manufacturing method thereof of the invention have the following beneficial effects:
according to the invention, after the liner oxide layer 102 is removed by etching and before the field oxide layer 108 is grown by thermal oxidation, the limit side wall 113 is formed by depositing and etching silicon oxynitride, and the limit side wall 113 can ensure that the growth of the bird's beak is limited by the limit side wall 113 when the field oxide layer 108 is grown, so that the length of the bird's beak can be obviously reduced. The invention can strictly control the length of the beak by limiting the adjustment of the width of the side wall 113.
The field oxide layer 108 with the smaller bird's beak length can be obtained, the area of the active region can be effectively increased, the integration level of the device can be improved, and meanwhile, the electrical performance of the device in the active region can be effectively improved.
In the present embodiment, by increasing the thickness of the thermal oxide layer 110 and removing the thermal oxide layer by etching, the depth of the slot 112 on the substrate 101 can be correspondingly increased, and further, the height of the protrusion of the field oxide layer 108 formed subsequently exposed on the top surface of the substrate 101 is reduced, thereby effectively reducing the step difference between the active region and the field region.
The invention has wide application prospect in the field of large-scale integrated circuit design and manufacture.
Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (22)
1. A method for fabricating a field oxide structure, the method comprising:
1) providing a substrate, and sequentially forming a pad oxide layer and a sacrificial dielectric layer on the substrate;
2) the sacrificial dielectric layer and the pad oxide layer are etched in a patterning mode to form a field area window exposing the substrate;
3) forming a limiting side wall in the field area window;
4) thermally oxidizing and growing a field oxide layer in the substrate based on the field area window and the limiting side wall, wherein the limiting side wall is used for limiting the length of a bird's beak part of the field oxide layer; and
5) and removing the limiting side wall, the sacrificial structure layer and the pad oxide layer so as to form a field oxide layer and an active region isolated by the field oxide layer in the substrate.
2. The method of claim 1, wherein: and controlling the length of the beak part of the field oxide layer by adjusting the width of the limiting side wall.
3. The method of claim 1, wherein: and 4) the method for growing the field oxide layer in the substrate by thermal oxidation comprises a wet oxygen oxidation process, wherein the reaction temperature of the wet oxygen oxidation process is 900-1100 ℃, the reaction gas comprises oxygen and hydrogen, and the flow ratio of the oxygen to the hydrogen is 4: 9-5: 7.
4. The method of claim 1, wherein: in the step 5), the etching selection ratio of the sacrificial dielectric layer to the field oxide layer is not less than 5:1, and the etching selection ratio of the limiting side wall to the field oxide layer is not less than 5: 1.
5. The method of claim 4, wherein: the sacrificial dielectric layer is made of silicon nitride, the limiting side wall is made of silicon oxynitride, and the field oxide layer is made of silicon dioxide.
6. The method of claim 1, wherein: the thickness range of the pad oxide layer is 200-500 angstroms, and the thickness range of the sacrificial dielectric layer is 1000-2000 angstroms.
7. The method of claim 1, wherein: the step 3) comprises the following steps:
3-1) depositing a side wall material on the bottom and the side wall of the window of the field region and the surface of the sacrificial dielectric layer; and
and 3-2) etching to remove the side wall materials at the bottom of the field window and on the surface of the sacrificial medium layer, and reserving the side wall materials at the side wall of the field window so as to form a limiting side wall in the field window.
8. The method of claim 1, wherein: the step 3) comprises the following steps:
3-1) thermally oxidizing the substrate within the field region window to form a thermal oxide layer in the substrate, the thermal oxide layer extending toward both sides of the field region window to form an extension between the substrate and the sacrificial dielectric layer;
3-2) removing the thermal oxidation layer to form a groove body in the substrate, wherein side grooves are formed in two sides of the groove body and are positioned between the substrate and the sacrificial medium layer;
3-3) depositing a side wall material on the window of the field region and the surface of the sacrifice medium layer, wherein the side wall material is filled into the side groove; and
and 3-4) etching to remove the side wall materials at the bottom of the field window and on the surface of the sacrificial medium layer, and reserving the side wall materials in the side groove so as to form the limiting side wall in the side groove.
9. The method of claim 8, wherein: the thickness range of the thermal oxidation layer is between 1000 angstroms and 5000 angstroms, the width range of the expansion part is between 500 angstroms and 4000 angstroms, and the width range of the limiting side wall is between 500 angstroms and 4000 angstroms.
10. The method of claim 8, wherein: the field oxide layer comprises an isolation part located below the top surface of the substrate and a protruding part protruding above the top surface of the substrate, and the ratio of the thickness of the isolation part to the thickness of the protruding part is 4: 1-3: 2.
11. The method of claim 10, wherein: the thickness of the isolation part is 4000-6000 angstroms, and the thickness of the protruding part is 1500-3000 angstroms.
12. The method of claim 1, wherein: the field oxide layer includes main part and beak portion, the beak position in the both sides of main part, just the thickness of beak portion certainly the main part extends towards the outside and reduces gradually.
13. The method for manufacturing a field oxide layer structure according to any one of claims 1 to 12, wherein: the ratio of the length of the beak part to the thickness of the field oxide layer is between 0.2:1 and 0.4: 1.
14. The method of claim 13, wherein: the thickness of the field oxide layer ranges from 2500 angstroms to 15000 angstroms, and the length of the beak portion ranges from 500 angstroms to 6000 angstroms.
15. A method for manufacturing a semiconductor device, comprising:
forming a field oxide layer and an active region in a substrate by using the method of fabricating a field oxide layer according to any one of claims 1 to 14; and
and manufacturing a semiconductor device in the active region.
16. A field oxide structure, comprising:
a substrate; and
the field oxide layer is formed in the substrate and isolates a plurality of active regions in the substrate;
wherein, the field oxide both sides have the beak, and the length of beak and the thickness ratio of field oxide is between 0.2:1 to 0.4: 1.
17. The field oxide structure of claim 16, wherein: the thickness of the field oxide layer ranges from 2500 angstroms to 15000 angstroms, and the length of the beak portion ranges from 500 angstroms to 6000 angstroms.
18. The field oxide structure of claim 16, wherein: the field oxide layer includes main part and beak portion, the beak position in the both sides of main part, just the thickness of beak portion certainly the main part extends towards the outside and reduces gradually.
19. The field oxide structure of claim 16, wherein: the substrate comprises a silicon substrate, and the material of the field oxide layer comprises silicon dioxide.
20. The field oxide structure of claim 16, wherein: the field oxide layer comprises an isolation part located below the top surface of the substrate and a protruding part protruding above the top surface of the substrate, and the ratio of the thickness of the isolation part to the thickness of the protruding part is 4: 1-3: 2.
21. The field oxide structure of claim 20, wherein: the thickness of the isolation part is 4000-6000 angstroms, and the thickness of the protruding part is 1500-3000 angstroms.
22. A semiconductor device, comprising:
the field oxide structure of any of claims 16-21; and
a semiconductor device formed in the active region.
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