US20010019156A1 - Semiconductor device and fabrication method thereof - Google Patents
Semiconductor device and fabrication method thereof Download PDFInfo
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- US20010019156A1 US20010019156A1 US09/761,176 US76117601A US2001019156A1 US 20010019156 A1 US20010019156 A1 US 20010019156A1 US 76117601 A US76117601 A US 76117601A US 2001019156 A1 US2001019156 A1 US 2001019156A1
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- 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
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
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- 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
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76801—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing
- H01L21/76802—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics
- H01L21/76805—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics characterised by the formation and the after-treatment of the dielectrics, e.g. smoothing by forming openings in dielectrics the opening being a via or contact hole penetrating the underlying conductor
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- H—ELECTRICITY
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- 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
- H01L21/768—Applying interconnections to be used for carrying current between separate components within a device comprising conductors and dielectrics
- H01L21/76897—Formation of self-aligned vias or contact plugs, i.e. involving a lithographically uncritical step
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- H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
- H01L23/482—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of lead-in layers inseparably applied to the semiconductor body
- H01L23/485—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of lead-in layers inseparably applied to the semiconductor body consisting of layered constructions comprising conductive layers and insulating layers, e.g. planar contacts
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B12/00—Dynamic random access memory [DRAM] devices
- H10B12/01—Manufacture or treatment
- H10B12/02—Manufacture or treatment for one transistor one-capacitor [1T-1C] memory cells
- H10B12/05—Making the transistor
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- H10B—ELECTRONIC MEMORY DEVICES
- H10B12/00—Dynamic random access memory [DRAM] devices
- H10B12/01—Manufacture or treatment
- H10B12/09—Manufacture or treatment with simultaneous manufacture of the peripheral circuit region and memory cells
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- H—ELECTRICITY
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
- H01L2924/0001—Technical content checked by a classifier
- H01L2924/0002—Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10B—ELECTRONIC MEMORY DEVICES
- H10B12/00—Dynamic random access memory [DRAM] devices
- H10B12/30—DRAM devices comprising one-transistor - one-capacitor [1T-1C] memory cells
- H10B12/48—Data lines or contacts therefor
- H10B12/485—Bit line contacts
Definitions
- the present invention relates to a semiconductor device and a method of fabricating a semiconductor device.
- the present invention relates to a semiconductor device and a fabrication method thereof employing a nitride stopper method applied to memory cells such as a DRAM (Dynamic Random Access Memory) and an SRAM (Static Random Access Memory).
- DRAM Dynamic Random Access Memory
- SRAM Static Random Access Memory
- FIG. 19 shows one example of a conventional semiconductor device employing the nitride stopper method.
- Gate electrode 2 has, for example, a doped polysilicon layer 2 a and a WSi layer 2 b.
- a hard mask insulating layer 3 formed of SiO 2 or the like is formed on gate electrode 2 .
- a thin SiO 2 layer 4 is formed to cover hard mask insulating layer 3 and gate electrode 2 .
- An SiO 2 sidewall spacer 15 is formed to cover side surfaces of gate electrode 2 and hard mask insulating layer 3 with the thin SiO 2 layer interposed.
- An SiN stopper layer 5 is formed to cover hard mask insulating layer 3 and SiO 2 sidewall spacer 15 .
- An interlayer insulating layer 6 formed of SiO 2 or the like is formed to cover SiN stopper layer 5 .
- a contact hole 7 is formed such that contact hole 7 penetrates interlayer insulating layer 6 , SiN stopper layer 5 and thin SiO 2 layer 6 to reach the main surface of silicon substrate 1 .
- Contact hole 7 is provided to reach one SiO 2 sidewall spacer 15 , and an SiN sidewall spacer 8 a is left on the surface of the one SiO 2 sidewall spacer 15 .
- Interconnection layer 9 is formed to extend from the inside of contact hole 7 onto interlayer insulating layer 6 .
- Interconnection layer 9 includes a doped polysilicon layer 9 a and a WSi layer 9 b formed thereon.
- An isolation width W 4 is defined by the thickness of the one SiO 2 sidewall spacer 15 and that of SiN sidewall spacer 8 a formed on the surface of spacer 15 . Insulation between gate electrode 2 and interconnection layer 9 can be obtained by setting a value of separation width W 4 at a prescribed value or more. In the case of FIG. 19, for example, if a width W 1 between electrodes adjacent to each other is 0.24 ⁇ m, an opening width W 2 of the bottom of contact hole 7 is approximately 0.06 ⁇ m.
- FIGS. 20 - 22 are cross sectional views showing the first to the third steps of a fabrication process of the semiconductor device shown in FIG. 19.
- gate electrode 2 and hard mask insulating layer 3 are formed on the main surface of silicon substrate 1 with a gate insulating layer interposed, and thin SiO 2 layer 4 is formed to cover those by the CVD (Chemical Vapor Deposition) or the like.
- a silicon oxide layer is deposited on thin SiO 2 layer 4 by the CVD or the like, and an anisotropic etching process is applied to the silicon oxide layer.
- SiO 2 sidewall spacer 15 is thus formed. Etching of SiO 2 sidewall spacer 15 uses plasma. Therefore, plasma is applied to the main surface of silicon substrate 1 .
- SiN stopper layer 5 is formed to cover SiO 2 sidewall spacer 15 and hard mask insulating layer 3 by the CVD or the like.
- Interlayer insulating layer 6 formed of SiO 2 or the like is formed on SiN stopper layer 5 by CVD or the like.
- a resist 10 patterned into a prescribed shape is provided on interlayer insulating layer 6 .
- interlayer insulating layer 6 is selectively etched using resist 10 as a mask. the etching is stopped by SiN stopper layer 5 and an opening 7 a is formed.
- SiN stopper layer 5 is next etched. As a result, contact hole 7 which selectively exposes the main surface of silicon substrate 1 is formed as shown in FIG. 22. An over etching process is applied to SiN stopper layer 5 so that SiN sidewall spacer 8 a having a small thickness is left on the surface of SiO 2 sidewall spacer 15 as shown in FIG. 22.
- Interconnection layer 9 is thereafter formed to extend from the inside of contact hole 7 onto interlayer insulating layer 6 by the CVD or the like. Accordingly, the semiconductor device shown in FIG. 19 is obtained through the processes described above.
- an element isolation oxide layer is formed to surround an element formation region where an MOS transistor or the like including gate electrode 2 is formed. Stress generated when the element isolation oxide layer is formed tends to remain in the vicinity of the periphery of the element isolation oxide layer.
- SiO 2 sidewall spacer 15 is generally extended over the element isolation oxide layer, and a pn junction may be formed about the periphery of the element isolation oxide layer where the stress remains.
- the plasma is applied to the portion where the pn junction is formed. Therefore, leakage current could be easily generated at the pn junction portion. The generated leakage current deteriorates the refresh characteristic of a capacitor if the semiconductor device is a DRAM.
- the opening width W 2 of the bottom of contact hole 7 becomes small as approximately 0.06 ⁇ m by forming SiO 2 sidewall spacer 15 as shown in FIG. 19 and as described above. As a result, an area of the opening at the bottom of contact hole 7 is decreased.
- An object of the invention is to provide a semiconductor device and a fabrication method thereof by which generation of leakage current resulted from the plasma applied to the main surface of the semiconductor substrate can be restricted, and the area of the opening at the bottom of the contact hole can be increased without increasing an interval between gate electrodes.
- a semiconductor device includes a gate electrode, a hard mask insulating layer, a thin insulating layer, a nitride stopper layer, a sidewall nitride layer, an interlayer insulating layer, and an interconnection layer.
- the gate electrode is formed on a main surface of a semiconductor substrate.
- the hard mask insulating layer is formed on a top surface of the gate electrode.
- the thin insulating layer is formed to cover a side surface of the gate electrode and the hard mask insulating layer.
- the thin insulating layer refers to an insulating layer having a thickness of approximately 5-20 nm, for example.
- the nitride stopper layer is directly formed on the thin insulating layer to extend from a portion on one side surface of the gate electrode onto a top surface of the hard mask insulating layer.
- the sidewall nitride layer is directly formed on the thin insulating layer to cover the other side surface of the gate electrode.
- the interlayer insulating layer is formed to cover the nitride stopper layer, and provided with a contact hole formed in a self alignment manner that reaches the main surface of the semiconductor substrate and the sidewall nitride layer.
- the interconnection layer is formed in the contact hole.
- the sidewall nitride layer may have its upper end on a side surface of the hard mask insulating layer or may cover the side surface of the hard mask insulating layer and be connected to the nitride stopper layer, provided that the sidewall nitride layer tapers as away from the semiconductor substrate.
- the nitride stopper layer is directly formed on the thin insulating layer, and SiO 2 sidewall spacer 15 is not provided between the thin insulating layer and the nitride stopper layer as in the conventional semiconductor device. Since SiO 2 sidewall spacer 15 which is formed with the plasma is not provided, application of the plasma to the main surface of the silicon substrate can be avoided. As a result, generation of leakage current which is a problem of the conventional semiconductor device can be effectively restricted.
- SiO 2 sidewall spacer 15 since SiO 2 sidewall spacer 15 is not formed, an area of the opening at the bottom of the contact hole formed in the self-aligned manner between gate electrodes can be increased without increasing an interval between gate electrodes adjacent to each other compared with the conventional semiconductor device. Since the sidewall nitride layer is provided between the gate electrode and the interconnection layer, insulation between the gate electrode and the interconnection layer can be obtained by the presence of the sidewall nitride layer.
- the thickness of the hard mask insulating layer is 120 nm or more.
- the value of the highest limit of the thickness of the hard mask insulating layer is the maximum value that allows the layer to be fabricated.
- the height of the sidewall nitride layer in the direction perpendicular to the main surface of the semiconductor substrate is larger than the thickness of the gate electrode in the perpendicular direction by 20 nm or more.
- the inventors of the present invention note the relation between generation of leakage current generated between the gate electrode and the interconnection layer in the structure shown in FIG. 1 of the present invention, and a value d(nm) of the difference between the thickness of the sidewall nitride layer and that of the gate electrode, and examine the relation.
- the result is shown in FIG. 4.
- the result shown in FIG. 4 proves that generation of leakage current can be almost restricted if the value of d is 20 nm or more.
- the inventors of the invention note the relation between a value of d and a thickness a (nm) of the hard mask insulating layer, and examine it. The result is shown in FIG. 3. As shown in FIG.
- the value of d becomes 20 nm or more when the value of the thickness a is 120 nm or more. Accordingly, by setting the value of the thickness a of the hard mask insulating layer at 120 nm or more, the value of d can be set at 20 nm or more, so that generation of leakage current between the gate electrode and the interconnection layer can be effectively restricted.
- a concave portion may be formed at the main surface of the semiconductor substrate in the vicinity of the sidewall nitride layer. Preferably, a part of the interconnection layer fills the inside of the concave portion.
- a layer which is changed in quality located at the bottom of the contact hole can be removed by providing the concave portion at the semiconductor substrate.
- the part of the interconnection layer which fills the inside of the concave portion reduces contact resistance between the interconnection layer and the semiconductor substrate.
- the upper portion of the other surface of the gate electrode may be recessed from the side surface of the hard mask insulating layer toward the inside of the gate electrode.
- the sidewall nitride layer has a shape which tapers towards the upper portion (in the direction away from the semiconductor substrate). Therefore, insulation between the upper corner portion of the gate electrode and the interconnection layer is necessary. If the upper portion of the other side surface of the gate electrode located on the side of the interconnection layer is recessed into the gate electrode, a distance between the upper corner portion of the gate electrode and the interconnection layer can be increased. As a result, withstand voltage between the gate electrode and the interconnection layer can be improved.
- the semiconductor device may have a memory cell portion and a peripheral circuit portion.
- the gate electrode is arranged within the memory cell portion.
- another gate electrode having a metal silicide part at its upper portion is formed.
- another hard mask insulating layer is formed on a top surface of the another gate electrode.
- Another thin insulating layer is formed to cover a side surface of the another gate electrode and the another hard mask insulating layer.
- a pair of another sidewall nitride layers is directly formed on the another thin insulating layer to cover both side surfaces of the another gate electrode.
- the interlayer insulating layer extends over the another hard mask insulating layer to be in contact with a top surface of the another hard mask insulating layer, and another contact hole which penetrates the interlayer insulating layer, the another hard mask insulating layer and the metal silicide part and has its bottom surface within the another gate electrode is formed.
- Another interconnection layer is formed in the another contact hole to be electrically connected to the another gate electrode.
- the nitride stopper layer does not cover the top surface of the another hard mask insulating layer located in the peripheral circuit portion. Therefore, using the same mask, the contact hole that reaches the main surface of the semiconductor substrate can be formed in the memory cell portion in the self alignment manner, and another contact hole which penetrates the metal silicide part and has its bottom surface in the gate electrode can be formed in the peripheral circuit portion. As a result, the fabrication process can be simplified and the cost can be reduced.
- a gate electrode is formed on a main surface of a semiconductor substrate.
- a hard mask insulating layer is provided on a top surface of the gate electrode.
- a thin insulating layer is formed to cover the gate electrode and the hard mask insulating layer.
- a nitride stopper layer is directly formed on the thin insulating layer.
- An interlayer insulating layer is formed to cover the nitride stopper layer.
- a contact hole formed in the self alignment manner which reaches the main surface of the semiconductor substrate, as well as a sidewall nitride layer formed on a side surface of the gate electrode are provided.
- An interconnection layer is formed in the contact hole.
- the nitride stopper layer is directly provided on the thin insulating layer, and SiO 2 sidewall spacer 15 is not formed between the thin insulating layer and the nitride stopper layer as in the conventional semiconductor device. Therefore, the plasma is not applied to the main surface of the semiconductor substrate, so that generation of leakage current can be effectively restricted.
- an area of an opening at the bottom of the contact hole can be increased compared with the conventional device when the contact hole is formed in the self alignment manner between gate electrodes adjacent to each other.
- SiO 2 sidewall spacer 15 since SiO 2 sidewall spacer 15 is not formed, the fabrication process can be simplified to reduce the cost. Insulation between the gate electrode and the interconnection layer can be obtained by the presence of the sidewall nitride layer.
- the step of forming the contact hole may include a step of forming a concave portion by isotropically etching the main surface of the exposed semiconductor substrate. Further, the step of forming the interconnection layer may include a step of forming an interconnection layer such that the layer fills the concave portion.
- the step of forming the hard mask insulating layer may include a step of forming a hard mask insulating layer such that it has a thickness of 120 nm or more.
- the step of forming the sidewall nitride layer may include a step of forming a sidewall nitride layer such that the height of the sidewall nitride layer in the direction perpendicular to the main surface of the semiconductor substrate is larger than the thickness of the gate electrode in the perpendicular direction by 20 nm or more.
- the thickness of the hard mask insulating layer By setting the thickness of the hard mask insulating layer at 120 nm or more, the difference between the height of the sidewall nitride layer in the direction perpendicular to the main surface of the semiconductor substrate and that of the gate electrode in the perpendicular direction d can be set at 20 nm or more. Generation of leakage current between the gate electrode and the interconnection layer can be effectively restricted by setting the value of d at 20 nm or more as shown in FIG. 4. As a result, a semiconductor device in which withstand voltage between the gate electrode and the interconnection layer is obtained can be provided.
- the method of fabricating a semiconductor device described above may include a step of recessing an upper portion of the side surface of the gate electrode into the gate electrode from the side surface of the hard mask insulating layer, by etching the upper portion of the side surface of the gate electrode after the hard mask insulating layer is formed.
- a distance between the upper corner portion of the gate electrode and the interconnection layer can be increased by recessing the upper portion of the side surface of the gate electrode into the gate electrode from the side surface of the hard mask insulating layer.
- the most important issue of the semiconductor device is the withstand voltage between the upper corner portion of the gate electrode and the interconnection layer as described above. Therefore, increase of the distance between the upper corner portion of the gate electrode and the interconnection layer allows a semiconductor device having an improved withstand voltage between the gate electrode and the interconnection layer to be provided.
- the method is for fabricating a semiconductor device having a memory cell portion and a peripheral circuit portion.
- the fabrication method of a semiconductor device according to this aspect includes the processes described below.
- a first hard mask insulating layer is formed on a main surface of a semiconductor substrate located in the memory cell portion with a first gate electrode interposed, and a second hard mask insulating layer is formed on a main surface located in the peripheral circuit portion with a second gate electrode interposed.
- a thin insulating layer is formed to cover the first and second hard mask insulating layers as well as side surfaces of the first and second gate electrodes.
- a nitride stopper layer is directly provided on the thin insulating layer.
- a first mask layer is formed to cover the nitride stopper layer located within the memory cell portion.
- the second hard mask insulating layer is exposed and a pair of sidewall nitride layers that covers the side surface of the second gate electrode is formed by etching the nitride stopper layer using the first mask layer.
- An interlayer insulating layer is provided to cover the nitride stopper layer and the second hard mask insulating layer.
- a second mask layer is formed on the interlayer insulating layer.
- a first contact hole that is formed in self alignment manner and selectively exposes the main surface of the semiconductor substrate is provided by etching the interlayer insulating layer, the nitride stopper layer, and the thin insulating layer located in the memory cell portion successively, and a second contact hole which reaches the second gate electrode is formed by successively etching the interlayer insulating layer and the second hard mask insulating layer located within the peripheral circuit portion.
- First and the second interconnection layers are respectively formed in the first and second contact holes.
- the nitride stopper layer on the second hard mask insulating layer is preliminary removed using the first mask layer. Therefore, using the second mask layer, the first contact hole formed in the self alignment manner can be formed in the memory cell portion and the second contact hole can be provided in the peripheral circuit portion. Since the first and second contact holes can be formed by using the same mask, the fabrication process can be simplified to decrease the fabrication cost.
- the second gate electrode may include a metal silicide part at its upper portion.
- the steps of forming the first and second contact holes may include a step of forming a concave portion at the main surface of the semiconductor substrate after the main surface is exposed and forming the second contact hole such that the hole penetrates the metal silicide part.
- the concave portion is formed at the main surface of the semiconductor substrate, an area where the interconnection layer and the semiconductor substrate are in contact with each other can be increased, resulting in reduction of contact resistance therebetween.
- the second contact hole is formed to penetrate the metal silicide part, so that a portion of the gate electrode other than the metal silicide part and the interconnection layer can be in contact with each other.
- the interconnection layer is formed of doped polysilicon, impurities from the interconnection layer are absorbed by the metal silicide part since the metal silicide part of the second gate electrode is in contact with the interconnection layer.
- FIG. 1 is a cross sectional view showing a semiconductor device according to the first embodiment of the invention.
- FIG. 2 shows a cross sectional view of a gate electrode and its environment in FIG. 1 by enlarging them.
- FIG. 3 shows a relation between a difference d between a height of an SiN sidewall spacer and a thickness of a gate electrode, and a thickness of a hard mask insulating layer.
- FIG. 4 shows a relation between leakage current between a gate electrode and an interconnection layer, and a difference d between a height of an SiN sidewall spacer and a thickness of a gate electrode.
- FIGS. 5 - 7 are cross sectional views respectively showing the first to the third steps of a fabrication process of the semiconductor device shown in FIG. 1.
- FIG. 8 is a cross sectional view showing a semiconductor device according to the second embodiment of the invention.
- FIG. 9 is a cross sectional view showing a characteristic fabrication process of the semiconductor device shown in FIG. 8.
- FIGS. 10 - 12 are cross sectional views respectively showing the characteristic first to the third steps of the fabrication process of a semiconductor device according to the third embodiment of the invention.
- FIGS. 13A and 13B are cross sectional views showing a semiconductor device according to the fourth embodiment of the invention.
- FIGS. 14A and 14B to 18 A and 18 B are cross sectional views showing the first to the fifth steps of the fabrication process of the semiconductor device shown in FIG. 13.
- FIG. 19 is a cross sectional view showing an example of a conventional semiconductor device.
- FIGS. 20 - 22 are cross sectional views respectively showing the first to the third steps of a fabrication process of the semiconductor device shown in FIG. 19.
- Embodiments of the present invention are hereinafter described referring to FIGS. 1 - 18 .
- FIG. 1 is a cross sectional view illustrating a semiconductor device according to the first embodiment of the invention.
- description is given on a case in which the invention is applied to a DRAM, the invention is applicable to another semiconductor memory device such as an SRAM.
- a pair of gate (transfer gate) electrodes 2 is formed on a main surface of a silicon substrate 1 with a gate insulating layer interposed.
- Gate electrode 2 includes a doped polysilicon layer 2 a and a WSi layer 2 b formed thereon.
- Doped polysilicon layer 2 a has, for example, a thickness of approximately 40-80 nm.
- WSi layer 2 b has a thickness of approximately 40-80 nm.
- WSi layer 2 b may be formed of a conductive layer with low resistance such as W.
- a hard mask insulating layer 3 formed of, for example, SiO 2 is formed on a top surface of gate electrode 2 .
- Hard mask insulating layer 3 has, for example, a thickness of approximately 100-250 nm.
- a thin SiO 2 layer 4 is formed to cover hard mask insulating layer 3 and a side surface of gate electrode 2 .
- Thin SiO 2 layer 4 has a flat surface and a thickness of approximately 5-20 nm.
- SiN (silicon nitride) stopper layer 5 is formed to extend from a portion on one side surface of gate electrode 2 onto a top surface of hard mask insulating layer 3 .
- SiN stopper layer 5 functions as a self alignment stopper layer, and has a thickness of approximately 40-100 nm.
- an SiN sidewall spacer 8 is formed on the other side surface of gate electrode 2 .
- SiN sidewall spacer 8 is directly formed on the thin SiO 2 layer 4 .
- SiN sidewall spacer 8 may have its upper end portion on the side surface of hard mask insulating layer 3 as shown in FIG. 1. However, SiN sidewall spacer 8 may cover the side surface of hard mask insulating layer 3 and be connected to SiN stopper layer 5 .
- silicon nitride may remain between SiN sidewall spacer 8 and SiN stopper layer that integrally connects them in FIG. 1.
- An interlayer insulating layer 6 formed of SiO 2 or the like is formed to cover SiN stopper layer 5 .
- a contact hole 7 formed in self alignment manner is provided to penetrate interlayer insulating layer 6 , SiN stopper layer 5 , and thin SiO 2 layer 4 to reach the main surface of silicon substrate 1 .
- SiN sidewall spacer 8 is formed around contact hole 7 to define an opening at a bottom of contact hole 7 .
- Interconnection layer 9 is formed to extend from the inside of contact hole 7 onto interlayer insulating layer 6 .
- Interconnection layer 9 is constituted of a doped polysilicon layer 9 a and a WSi layer 9 b formed thereon.
- SiO 2 sidewall spacer 15 in the conventional semiconductor device is not found between SiN sidewall spacer 8 and thin SiO 2 layer 4 . Therefore, an opening width W 2 at the bottom of contact hole 7 can be increased compared with that of the conventional device. Specifically, if an interval W 1 between gate electrodes 2 adjacent to each other is 0.24 ⁇ m, opening width W 2 is 0.14 ⁇ m. Since opening width W 2 is 0.06 ⁇ m in the conventional device, an area of an opening at the bottom of contact hole 7 can be dramatically increased compared with that of the conventional device. Accordingly, an area where interconnection layer 9 and silicon substrate 1 are in contact with each other can be increased, and contact resistance can be decreased.
- SiO 2 sidewall spacer 15 Since SiO 2 sidewall spacer 15 is not found, plasma used for forming SiO 2 sidewall spacer 15 is never applied to the main surface of silicon substrate 1 . Therefore, generation of leakage current caused by application of the plasma to the peripheral portion of an element isolation oxide film formed in an element isolation region of silicon substrate 1 can be effectively avoided. Accordingly, a semiconductor device which is reliable and has a high performance can be obtained.
- FIG. 2 shows a cross sectional view of gate electrode 2 and its vicinity of FIG. 1 by enlarging them.
- a represents a thickness of hard mask insulating layer 3
- b represents a thickness of WSi layer 2 b
- c represents a thickness of doped polysilicon layer 2 a
- d is obtained by subtracting thickness of gate electrode (b+c) from a height g of SiN sidewall spacer 8
- e represents an amount of etching of SiN sidewall spacer 8 generated by etching interlayer insulating 6
- f represents an amount of etching of SiN sidewall spacer 8 generated by etching SiN stopper layer 5
- h and i respectively represent a thickness of SiN stopper layer 5 and thin SiO 2 layer 4
- j represents a total height of thin SiO 2 layer 4 , gate electrode 2 , hard mask insulating layer 3 and SiN stopper layer 5 .
- FIG. 3 shows a relation between values of d and a.
- FIG. 4 shows a relation between leakage current between gate electrode 2 and interconnection layer 9 and the value of d.
- the data shown in FIGS. 3 and 4 are obtained when transistor voltage is 2 V.
- the inventors of the invention take various considerations for obtaining insulation between gate electrode 2 and interconnection layer 9 when SiO 2 sidewall spacer 15 used in the conventional device is not formed. As a result of the considerations, it is found that leakage current between gate electrode 2 and interconnection layer 9 depends on the value d. Specifically, as shown in FIG. 4, it is found that leakage current between gate electrode 2 and interconnection layer 9 can be restricted within the range that does not cause any problem if the value of d in FIG. 2 is 20 nm or more. In other words, insulation between gate electrode 2 and interconnection layer 9 can be obtained by setting the value of d in FIG. 2 at 20 nm or more. More preferably, the value of d is 30 nm or more.
- the inventors of the invention note that dependence of the value of d on the thickness a of hard mask insulating layer 3 . As shown in FIG. 3, if thickness a of hard mask insulating layer 3 is 120 nm or more, the value of d is found to be 20 nm or more. That is, by setting thickness a of hard mask insulating layer 3 at 120 nm or more, the value d can be set at 20 nm or more to restrict generation of leakage current between gate electrode 2 and interconnection layer 9 .
- FIGS. 5 - 7 are cross sectional views showing the first to the third steps of the fabrication process of the semiconductor device of FIG. 1.
- a gate insulating layer is formed on the main surface of silicon substrate 1 using thermal oxidation method or the like.
- a doped polysilicon layer having a thickness of approximately 4080 nm, a WSi layer having a thickness of approximately 4080 nm, and a silicon oxide layer having a thickness of approximately 100-250 nm are successively deposited on the gate insulating layer by the CVD, for example.
- Patterning the silicon oxide layer, hard mask insulating layer 3 is formed.
- Gate electrode 2 is formed by etching the WSi layer and the doped polysilicon layer successively using hard mask insulating layer 3 as a mask.
- SiO 2 layer 4 of approximately 5-20 nm is formed to cover a side surface of gate electrode 2 and hard mask insulating layer 3 by the CVD or the like.
- SiN stopper layer 5 having a thickness of about 40-100 nm is deposited on thin SiO 2 layer 4 by the CVD or the like.
- SiN stopper layer 5 is directly formed on thin SiO 2 layer 4 , and SiO 2 sidewall spacer 15 of the conventional semiconductor device is not provided between SiN stopper layer 5 and thin SiO 2 layer 4 . Therefore, the plasma is not applied to the main surface of silicon substrate 1 and generation of leakage current can be effectively avoided.
- interlayer insulating layer 6 formed of SiO 2 or the like is formed to cover SiN stopper layer 5 by the CVD or the like. Resist 10 is applied onto interlayer insulating layer 6 to be patterned into a prescribed shape.
- An opening 7 a that reaches SiN stopper layer 5 is formed by etching interlayer insulating layer 6 using the patterned resist 10 as a mask.
- the etching is carried out by an etching apparatus of a type such as ECR (Electron Cyclotron Resonance) or magnetron RIE (Reactive Ion Etching) using flon type gas and Ar type gas under a condition in which etching selectivity for the silicon nitride is high.
- Interlayer insulating layer 6 is etched in such a condition, and the etching is stopped at a surface of SiN stopper layer 5 . Accordingly, opening 7 a having a self-aligned shape is provided.
- SiN stopper layer 5 at the bottom of opening 7 a and thin SiO 2 layer 4 are successively etched by an etching apparatus of a type which is parallel and planar, using flon type gas containing hydrogen. As a result, the main surface of the silicon substrate is selectively exposed and SiN sidewall spacer 8 is formed.
- interconnection layer 9 is formed to extend from the inside of contact hole 7 onto interlayer insulating layer 6 by the CVD or the like. Accordingly, the semiconductor device shown in FIG. 1 is formed through the steps above.
- FIG. 8 is a cross sectional view illustrating a semiconductor device according to the second embodiment.
- a concave portion 11 is formed at the main surface of silicon substrate 1 according to the second embodiment. Concave portion 11 is formed to extend to a portion directly under SiN sidewall spacer 8 . Concave portion 11 is filled with a part of doped polysilicon layer 9 a.
- concave portion 11 By forming concave portion 11 at the main surface of silicon substrate 1 , a layer which is changed in quality at the bottom portion of contact hole 7 can be removed. Since a part of interconnection layer 9 fills concave portion 11 , contact resistance between interconnection layer 9 and silicon substrate 1 can be decreased.
- the depths of concave portion 11 is, for example, about 5-40 nm.
- FIG. 9 is a cross sectional view showing a characteristic fabrication process of the semiconductor device of FIG. 8.
- contact hole 7 is formed through the steps similar to those of the first embodiment.
- the main surface of silicon substrate 1 is etched by an isotropic polysilicon etching apparatus of down flow type using gas of CF 4 , O 2 type or the like.
- silicon substrate 1 is etched without etching most of SiN sidewall spacer 8 .
- concave portion 11 can be formed to extend to the portion under SiN sidewall spacer 8 while maintaining insulation between gate electrode 2 and interconnection layer 9 .
- the semiconductor device shown in FIG. 8 is thereafter formed through the steps similar to those of the first embodiment.
- FIGS. 10 - 12 are cross sectional views respectively showing the characteristic first to the third steps of a fabrication process of a semiconductor device according to the third embodiment.
- a wet etching process is applied to a side surface of WSi layer 2 b for approximately 25-50 minutes using aqueous ammonia.
- a wet etching process is applied to a side surface of WSi layer 2 b for approximately 25-50 minutes using aqueous ammonia.
- the side surface of WSi layer 2 b is recessed into WSi layer 2 b .
- An amount of recess W 3 is about 10 nm-20 nm. Accordingly, a concave portion 12 is formed at a side surface of an upper portion of gate electrode 2 .
- the semiconductor device according to the third embodiment is thus formed through the steps described above.
- the side surface of WSi layer 2 b is recessed inward, so that a separation width W 4 between the upper corner portion of gate electrode 2 and interconnection layer 9 can be increased compared with that of each embodiment described above. As a result, insulation between gate electrode 2 and interconnection layer 9 can be surely maintained.
- FIGS. 13A and B are cross sectional views showing a semiconductor device of the fourth embodiment. According to the fourth embodiment, not only a structure of a memory cell portion of DRAM, a structure of its peripheral circuit portion is illustrated.
- gate electrode 2 is formed on the main surface of silicon substrate 1 with the gate insulating layer interposed, and hard mask insulating layer 3 is formed thereon.
- An SiN sidewall spacer 13 is formed to cover both of a side surface of hard mask insulating layer 3 and a side surface of gate electrode 2 with thin SiO 2 layer 4 interposed.
- SiN sidewall spacer 13 is provided by etching SiN stopper layer 5 , and formed directly on thin SiO 2 layer 4 .
- Interlayer insulating layer 6 is extended on hard mask insulating layer 3 to be in contact with a top surface of hard mask insulating layer 3 .
- a contact hole 14 is formed to penetrate interlayer insulating layer 6 , hard mask insulating layer 3 and WSi layer 2 b .
- Interconnection layer 9 is formed to extend from the inside of contact hole 14 onto interlayer insulating layer 6 .
- doped polysilicon layer 9 a and doped polysilicon layer 2 a can be in direct contact with each other. If doped polysilicon layer 9 a is in contact with WSi layer 2 b , impurities from doped polysilicon layer 9 a are absorbed by WSi layer 2 b and a portion where concentration of impurities is low is formed between doped polysilicon layer 9 a and WSi layer 2 b . As a result, if doped polysilicon layer 9 a is in contact with only WSi layer 2 b , contact resistance between interconnection layer 9 and gate electrode 2 increases.
- FIGS. 14A and B to 18 A and B are cross sectional views showing the characteristic first step to the fifth step of a fabrication process of a semiconductor device according to the fourth embodiment.
- SiN stopper layer 5 is formed through the steps similar to those of the first embodiment.
- a resist 10 a is formed to cover SiN stopper layer 5 in the memory cell portion.
- resist 10 a is etched back.
- SiN sidewall spacer 13 is formed to expose a top surface of hard mask insulating layer 3 and cover both side surfaces of gate electrode 2 . Resist 10 a is thereafter removed.
- interlayer insulating layer 6 is formed by a method similar to that of the first embodiment, and a resist 10 b is formed thereon. Resist 10 b is provided with openings respectively in the memory cell portion and the peripheral circuit portion as shown in FIGS. 15A and B.
- interlayer insulating layer 6 is etched by a method similar to that of the first embodiment. A part of a surface of SiN stopper layer 5 in the memory cell portion is exposed, and a contact hole 14 a that penetrates interlayer insulating layer 6 and hard mask insulating layer 3 and reaches WSi layer 2 b is formed in the peripheral circuit portion. Since SiN stopper layer 5 is not formed on hard mask insulating layer 3 in the peripheral circuit portion, contact hole 14 a that reaches WSi layer 2 b can be provided.
- SiN stopper layer 5 and thin SiO 2 layer 4 at a bottom portion of opening 7 a are etched by an etching apparatus that is of a parallel and planar type using flon type gas containing hydrogen. As a result, the main surface of silicon substrate 1 is selectively exposed.
- WSi layer 2 b is overetched by D 1 .
- contact hole 7 formed in self alignment manner in the memory cell portion as well as contact hole 14 b formed on gate electrode 2 in the peripheral circuit portion are provided.
- a concave portion 11 is formed at the main surface of silicon substrate 1 located in the memory cell portion by a method similar to that of the second embodiment.
- the depth of concave portion 11 is approximately 5-100 nm.
- WSi layer 2 b is overetched by D 2 .
- D 2 is 20 nm or more, for example.
- Contact hole 14 that reaches doped polysilicon layer 2 a is thus formed in the peripheral circuit portion.
- Interconnection layer 9 is thereafter formed in each of contact holes 7 and 14 .
- the semiconductor device shown in FIG. 13 is accordingly obtained through the steps described above.
- the SiO 2 sidewall spacer is not formed so that application of plasma onto the main surface of the silicon substrate can be avoided, and the area of the opening at the bottom portion of the contact hole formed between the gate electrodes can be increased. As a result, generation of leakage current in the semiconductor device can be avoided and contact resistance between the interconnection layer formed in the contact hole and the semiconductor substrate can be decreased. A semiconductor device with high performance and high reliability can be obtained accordingly.
- the nitride stopper layer is directly formed on the thin insulating layer. Since the SiO 2 sidewall spacer is not formed, the effects as described above can be also obtained.
- the first contact hole that selectively exposes the main surface in the memory cell portion and the second contact hole that reaches the second gate electrode in the peripheral circuit portion are simultaneously formed using the second mask layer. Since the first and second contact holes are formed using the same mask, the fabrication process can be simplified and the fabrication cost can be decreased.
Abstract
A hard mask insulating layer is formed on a gate electrode which is formed on a main surface of a silicon substrate with a gate insulating layer interposed. An SiN sidewall spacer is directly formed on a thin SiO2 layer which is formed to cover a side surface of the gate electrode. A contact hole is formed to penetrate an interlayer insulating layer formed on an SiN stopper layer and reach the main surface of the silicon substrate.
Description
- 1. Field of the Invention
- The present invention relates to a semiconductor device and a method of fabricating a semiconductor device. In particular, the present invention relates to a semiconductor device and a fabrication method thereof employing a nitride stopper method applied to memory cells such as a DRAM (Dynamic Random Access Memory) and an SRAM (Static Random Access Memory).
- 2. Description of the Background Art
- A semiconductor device which employs the so called nitride stopper method using a nitride layer as a stopper layer has been known. FIG. 19 shows one example of a conventional semiconductor device employing the nitride stopper method.
- Referring to FIG. 19, on a main surface of a
silicon substrate 1, a pair ofgate electrodes 2 is formed with a gate insulating layer interposed.Gate electrode 2 has, for example, a dopedpolysilicon layer 2 a and aWSi layer 2 b. - A hard
mask insulating layer 3 formed of SiO2 or the like is formed ongate electrode 2. A thin SiO2 layer 4 is formed to cover hardmask insulating layer 3 andgate electrode 2. An SiO2 sidewall spacer 15 is formed to cover side surfaces ofgate electrode 2 and hardmask insulating layer 3 with the thin SiO2 layer interposed. - An
SiN stopper layer 5 is formed to cover hardmask insulating layer 3 and SiO2 sidewall spacer 15. Aninterlayer insulating layer 6 formed of SiO2 or the like is formed to coverSiN stopper layer 5. Acontact hole 7 is formed such thatcontact hole 7 penetratesinterlayer insulating layer 6,SiN stopper layer 5 and thin SiO2 layer 6 to reach the main surface ofsilicon substrate 1. Contacthole 7 is provided to reach one SiO2 sidewall spacer 15, and anSiN sidewall spacer 8 a is left on the surface of the one SiO2 sidewall spacer 15. - An
interconnection layer 9 is formed to extend from the inside ofcontact hole 7 ontointerlayer insulating layer 6.Interconnection layer 9 includes a dopedpolysilicon layer 9 a and aWSi layer 9 b formed thereon. - An isolation width W4 is defined by the thickness of the one SiO2 sidewall spacer 15 and that of
SiN sidewall spacer 8 a formed on the surface ofspacer 15. Insulation betweengate electrode 2 andinterconnection layer 9 can be obtained by setting a value of separation width W4 at a prescribed value or more. In the case of FIG. 19, for example, if a width W1 between electrodes adjacent to each other is 0.24 μm, an opening width W2 of the bottom ofcontact hole 7 is approximately 0.06 μm. - Referring to FIGS.20-22 next, a method of fabricating the semiconductor device shown in FIG. 19 is described. FIGS. 20-22 are cross sectional views showing the first to the third steps of a fabrication process of the semiconductor device shown in FIG. 19.
- First with reference to FIG. 20,
gate electrode 2 and hardmask insulating layer 3 are formed on the main surface ofsilicon substrate 1 with a gate insulating layer interposed, and thin SiO2 layer 4 is formed to cover those by the CVD (Chemical Vapor Deposition) or the like. A silicon oxide layer is deposited on thin SiO2 layer 4 by the CVD or the like, and an anisotropic etching process is applied to the silicon oxide layer. SiO2 sidewall spacer 15 is thus formed. Etching of SiO2 sidewall spacer 15 uses plasma. Therefore, plasma is applied to the main surface ofsilicon substrate 1. -
SiN stopper layer 5 is formed to cover SiO2 sidewall spacer 15 and hardmask insulating layer 3 by the CVD or the like.Interlayer insulating layer 6 formed of SiO2 or the like is formed onSiN stopper layer 5 by CVD or the like. Aresist 10 patterned into a prescribed shape is provided oninterlayer insulating layer 6. - Next with reference to FIG. 21,
interlayer insulating layer 6 is selectively etched using resist 10 as a mask. the etching is stopped by SiNstopper layer 5 and anopening 7 a is formed. -
SiN stopper layer 5 is next etched. As a result,contact hole 7 which selectively exposes the main surface ofsilicon substrate 1 is formed as shown in FIG. 22. An over etching process is applied toSiN stopper layer 5 so thatSiN sidewall spacer 8 a having a small thickness is left on the surface of SiO2 sidewall spacer 15 as shown in FIG. 22. -
Interconnection layer 9 is thereafter formed to extend from the inside ofcontact hole 7 ontointerlayer insulating layer 6 by the CVD or the like. Accordingly, the semiconductor device shown in FIG. 19 is obtained through the processes described above. - Because of the plasma applied to the main surface of
silicon substrate 1 exposed while SiO2 sidewall spacer 15 is formed, a problem as described below arises. - Although not shown in FIG. 19, an element isolation oxide layer is formed to surround an element formation region where an MOS transistor or the like including
gate electrode 2 is formed. Stress generated when the element isolation oxide layer is formed tends to remain in the vicinity of the periphery of the element isolation oxide layer. - SiO2 sidewall spacer 15 is generally extended over the element isolation oxide layer, and a pn junction may be formed about the periphery of the element isolation oxide layer where the stress remains. In this case, the plasma is applied to the portion where the pn junction is formed. Therefore, leakage current could be easily generated at the pn junction portion. The generated leakage current deteriorates the refresh characteristic of a capacitor if the semiconductor device is a DRAM.
- In addition, the opening width W2 of the bottom of
contact hole 7 becomes small as approximately 0.06 μm by forming SiO2 sidewall spacer 15 as shown in FIG. 19 and as described above. As a result, an area of the opening at the bottom ofcontact hole 7 is decreased. - The present invention is made to solve the problems above. An object of the invention is to provide a semiconductor device and a fabrication method thereof by which generation of leakage current resulted from the plasma applied to the main surface of the semiconductor substrate can be restricted, and the area of the opening at the bottom of the contact hole can be increased without increasing an interval between gate electrodes.
- A semiconductor device according to the present invention includes a gate electrode, a hard mask insulating layer, a thin insulating layer, a nitride stopper layer, a sidewall nitride layer, an interlayer insulating layer, and an interconnection layer. The gate electrode is formed on a main surface of a semiconductor substrate. The hard mask insulating layer is formed on a top surface of the gate electrode. The thin insulating layer is formed to cover a side surface of the gate electrode and the hard mask insulating layer. The thin insulating layer refers to an insulating layer having a thickness of approximately 5-20 nm, for example. The nitride stopper layer is directly formed on the thin insulating layer to extend from a portion on one side surface of the gate electrode onto a top surface of the hard mask insulating layer. The sidewall nitride layer is directly formed on the thin insulating layer to cover the other side surface of the gate electrode. The interlayer insulating layer is formed to cover the nitride stopper layer, and provided with a contact hole formed in a self alignment manner that reaches the main surface of the semiconductor substrate and the sidewall nitride layer. The interconnection layer is formed in the contact hole. The sidewall nitride layer may have its upper end on a side surface of the hard mask insulating layer or may cover the side surface of the hard mask insulating layer and be connected to the nitride stopper layer, provided that the sidewall nitride layer tapers as away from the semiconductor substrate.
- According to the semiconductor device of the present invention, the nitride stopper layer is directly formed on the thin insulating layer, and SiO2 sidewall spacer 15 is not provided between the thin insulating layer and the nitride stopper layer as in the conventional semiconductor device. Since SiO2 sidewall spacer 15 which is formed with the plasma is not provided, application of the plasma to the main surface of the silicon substrate can be avoided. As a result, generation of leakage current which is a problem of the conventional semiconductor device can be effectively restricted. Further, since SiO2 sidewall spacer 15 is not formed, an area of the opening at the bottom of the contact hole formed in the self-aligned manner between gate electrodes can be increased without increasing an interval between gate electrodes adjacent to each other compared with the conventional semiconductor device. Since the sidewall nitride layer is provided between the gate electrode and the interconnection layer, insulation between the gate electrode and the interconnection layer can be obtained by the presence of the sidewall nitride layer.
- Preferably, the thickness of the hard mask insulating layer is 120 nm or more. The value of the highest limit of the thickness of the hard mask insulating layer is the maximum value that allows the layer to be fabricated. Preferably, the height of the sidewall nitride layer in the direction perpendicular to the main surface of the semiconductor substrate is larger than the thickness of the gate electrode in the perpendicular direction by 20 nm or more.
- The inventors of the present invention note the relation between generation of leakage current generated between the gate electrode and the interconnection layer in the structure shown in FIG. 1 of the present invention, and a value d(nm) of the difference between the thickness of the sidewall nitride layer and that of the gate electrode, and examine the relation. The result is shown in FIG. 4. The result shown in FIG. 4 proves that generation of leakage current can be almost restricted if the value of d is 20 nm or more. In addition, the inventors of the invention note the relation between a value of d and a thickness a (nm) of the hard mask insulating layer, and examine it. The result is shown in FIG. 3. As shown in FIG. 3, the value of d becomes 20 nm or more when the value of the thickness a is 120 nm or more. Accordingly, by setting the value of the thickness a of the hard mask insulating layer at 120 nm or more, the value of d can be set at 20 nm or more, so that generation of leakage current between the gate electrode and the interconnection layer can be effectively restricted.
- A concave portion may be formed at the main surface of the semiconductor substrate in the vicinity of the sidewall nitride layer. Preferably, a part of the interconnection layer fills the inside of the concave portion.
- A layer which is changed in quality located at the bottom of the contact hole can be removed by providing the concave portion at the semiconductor substrate. The part of the interconnection layer which fills the inside of the concave portion reduces contact resistance between the interconnection layer and the semiconductor substrate.
- The upper portion of the other surface of the gate electrode may be recessed from the side surface of the hard mask insulating layer toward the inside of the gate electrode.
- As shown in FIG. 1, the sidewall nitride layer has a shape which tapers towards the upper portion (in the direction away from the semiconductor substrate). Therefore, insulation between the upper corner portion of the gate electrode and the interconnection layer is necessary. If the upper portion of the other side surface of the gate electrode located on the side of the interconnection layer is recessed into the gate electrode, a distance between the upper corner portion of the gate electrode and the interconnection layer can be increased. As a result, withstand voltage between the gate electrode and the interconnection layer can be improved.
- The semiconductor device may have a memory cell portion and a peripheral circuit portion. In this case, the gate electrode is arranged within the memory cell portion. Within the peripheral circuit portion, another gate electrode having a metal silicide part at its upper portion is formed. On a top surface of the another gate electrode, another hard mask insulating layer is formed. Another thin insulating layer is formed to cover a side surface of the another gate electrode and the another hard mask insulating layer. A pair of another sidewall nitride layers is directly formed on the another thin insulating layer to cover both side surfaces of the another gate electrode. The interlayer insulating layer extends over the another hard mask insulating layer to be in contact with a top surface of the another hard mask insulating layer, and another contact hole which penetrates the interlayer insulating layer, the another hard mask insulating layer and the metal silicide part and has its bottom surface within the another gate electrode is formed. Another interconnection layer is formed in the another contact hole to be electrically connected to the another gate electrode.
- The nitride stopper layer does not cover the top surface of the another hard mask insulating layer located in the peripheral circuit portion. Therefore, using the same mask, the contact hole that reaches the main surface of the semiconductor substrate can be formed in the memory cell portion in the self alignment manner, and another contact hole which penetrates the metal silicide part and has its bottom surface in the gate electrode can be formed in the peripheral circuit portion. As a result, the fabrication process can be simplified and the cost can be reduced.
- According to one aspect of a method of fabricating a semiconductor device according to the present invention, those steps as described below are provided. A gate electrode is formed on a main surface of a semiconductor substrate. A hard mask insulating layer is provided on a top surface of the gate electrode. A thin insulating layer is formed to cover the gate electrode and the hard mask insulating layer. A nitride stopper layer is directly formed on the thin insulating layer. An interlayer insulating layer is formed to cover the nitride stopper layer. By etching the interlayer insulating layer, the nitride stopper layer, and the thin insulating layer successively, a contact hole formed in the self alignment manner which reaches the main surface of the semiconductor substrate, as well as a sidewall nitride layer formed on a side surface of the gate electrode are provided. An interconnection layer is formed in the contact hole.
- According to the one aspect of the method of fabricating a semiconductor device according to the present invention as described above, the nitride stopper layer is directly provided on the thin insulating layer, and SiO2 sidewall spacer 15 is not formed between the thin insulating layer and the nitride stopper layer as in the conventional semiconductor device. Therefore, the plasma is not applied to the main surface of the semiconductor substrate, so that generation of leakage current can be effectively restricted. In addition, an area of an opening at the bottom of the contact hole can be increased compared with the conventional device when the contact hole is formed in the self alignment manner between gate electrodes adjacent to each other. Further, since SiO2 sidewall spacer 15 is not formed, the fabrication process can be simplified to reduce the cost. Insulation between the gate electrode and the interconnection layer can be obtained by the presence of the sidewall nitride layer.
- The step of forming the contact hole may include a step of forming a concave portion by isotropically etching the main surface of the exposed semiconductor substrate. Further, the step of forming the interconnection layer may include a step of forming an interconnection layer such that the layer fills the concave portion.
- By isotropically etching the main surface of the semiconductor substrate as described above, a layer which is changed in quality located at the bottom of the contact hole can be removed, and the concave portion can be formed. Contact resistance between the interconnection layer and the semiconductor substrate can be decreased by filling a part of the interconnection layer in the concave portion.
- The step of forming the hard mask insulating layer may include a step of forming a hard mask insulating layer such that it has a thickness of 120 nm or more. The step of forming the sidewall nitride layer may include a step of forming a sidewall nitride layer such that the height of the sidewall nitride layer in the direction perpendicular to the main surface of the semiconductor substrate is larger than the thickness of the gate electrode in the perpendicular direction by 20 nm or more.
- By setting the thickness of the hard mask insulating layer at 120 nm or more, the difference between the height of the sidewall nitride layer in the direction perpendicular to the main surface of the semiconductor substrate and that of the gate electrode in the perpendicular direction d can be set at 20 nm or more. Generation of leakage current between the gate electrode and the interconnection layer can be effectively restricted by setting the value of d at 20 nm or more as shown in FIG. 4. As a result, a semiconductor device in which withstand voltage between the gate electrode and the interconnection layer is obtained can be provided.
- The method of fabricating a semiconductor device described above may include a step of recessing an upper portion of the side surface of the gate electrode into the gate electrode from the side surface of the hard mask insulating layer, by etching the upper portion of the side surface of the gate electrode after the hard mask insulating layer is formed.
- A distance between the upper corner portion of the gate electrode and the interconnection layer can be increased by recessing the upper portion of the side surface of the gate electrode into the gate electrode from the side surface of the hard mask insulating layer. The most important issue of the semiconductor device is the withstand voltage between the upper corner portion of the gate electrode and the interconnection layer as described above. Therefore, increase of the distance between the upper corner portion of the gate electrode and the interconnection layer allows a semiconductor device having an improved withstand voltage between the gate electrode and the interconnection layer to be provided.
- According to another aspect of the method of fabricating a semiconductor device according to the present invention, the method is for fabricating a semiconductor device having a memory cell portion and a peripheral circuit portion. The fabrication method of a semiconductor device according to this aspect includes the processes described below. A first hard mask insulating layer is formed on a main surface of a semiconductor substrate located in the memory cell portion with a first gate electrode interposed, and a second hard mask insulating layer is formed on a main surface located in the peripheral circuit portion with a second gate electrode interposed. A thin insulating layer is formed to cover the first and second hard mask insulating layers as well as side surfaces of the first and second gate electrodes. A nitride stopper layer is directly provided on the thin insulating layer. A first mask layer is formed to cover the nitride stopper layer located within the memory cell portion. The second hard mask insulating layer is exposed and a pair of sidewall nitride layers that covers the side surface of the second gate electrode is formed by etching the nitride stopper layer using the first mask layer. An interlayer insulating layer is provided to cover the nitride stopper layer and the second hard mask insulating layer. A second mask layer is formed on the interlayer insulating layer. Using the second mask layer, a first contact hole that is formed in self alignment manner and selectively exposes the main surface of the semiconductor substrate is provided by etching the interlayer insulating layer, the nitride stopper layer, and the thin insulating layer located in the memory cell portion successively, and a second contact hole which reaches the second gate electrode is formed by successively etching the interlayer insulating layer and the second hard mask insulating layer located within the peripheral circuit portion. First and the second interconnection layers are respectively formed in the first and second contact holes.
- The nitride stopper layer on the second hard mask insulating layer is preliminary removed using the first mask layer. Therefore, using the second mask layer, the first contact hole formed in the self alignment manner can be formed in the memory cell portion and the second contact hole can be provided in the peripheral circuit portion. Since the first and second contact holes can be formed by using the same mask, the fabrication process can be simplified to decrease the fabrication cost.
- The second gate electrode may include a metal silicide part at its upper portion. In this case, the steps of forming the first and second contact holes may include a step of forming a concave portion at the main surface of the semiconductor substrate after the main surface is exposed and forming the second contact hole such that the hole penetrates the metal silicide part.
- Since the concave portion is formed at the main surface of the semiconductor substrate, an area where the interconnection layer and the semiconductor substrate are in contact with each other can be increased, resulting in reduction of contact resistance therebetween. Further, the second contact hole is formed to penetrate the metal silicide part, so that a portion of the gate electrode other than the metal silicide part and the interconnection layer can be in contact with each other. For example, if the interconnection layer is formed of doped polysilicon, impurities from the interconnection layer are absorbed by the metal silicide part since the metal silicide part of the second gate electrode is in contact with the interconnection layer. As a result, a portion where an impurity concentration is low is generated where the second gate electrode and the interconnection layer are connected to each other, and contact resistance between the second gate electrode and the interconnection layer increases. In particular, if the interconnection layer is in contact with only the metal silicide part, a problem is an increase of the contact resistance. If the interconnection layer is in contact with the portion other than the metal silicide part, generation of the portion where the impurity concentration is low can be limited to achieve reduction of the contact resistance.
- The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
- FIG. 1 is a cross sectional view showing a semiconductor device according to the first embodiment of the invention.
- FIG. 2 shows a cross sectional view of a gate electrode and its environment in FIG. 1 by enlarging them.
- FIG. 3 shows a relation between a difference d between a height of an SiN sidewall spacer and a thickness of a gate electrode, and a thickness of a hard mask insulating layer.
- FIG. 4 shows a relation between leakage current between a gate electrode and an interconnection layer, and a difference d between a height of an SiN sidewall spacer and a thickness of a gate electrode.
- FIGS.5-7 are cross sectional views respectively showing the first to the third steps of a fabrication process of the semiconductor device shown in FIG. 1.
- FIG. 8 is a cross sectional view showing a semiconductor device according to the second embodiment of the invention.
- FIG. 9 is a cross sectional view showing a characteristic fabrication process of the semiconductor device shown in FIG. 8.
- FIGS.10-12 are cross sectional views respectively showing the characteristic first to the third steps of the fabrication process of a semiconductor device according to the third embodiment of the invention.
- FIGS. 13A and 13B are cross sectional views showing a semiconductor device according to the fourth embodiment of the invention.
- FIGS. 14A and 14B to18A and 18B are cross sectional views showing the first to the fifth steps of the fabrication process of the semiconductor device shown in FIG. 13.
- FIG. 19 is a cross sectional view showing an example of a conventional semiconductor device.
- FIGS.20-22 are cross sectional views respectively showing the first to the third steps of a fabrication process of the semiconductor device shown in FIG. 19.
- Embodiments of the present invention are hereinafter described referring to FIGS.1-18.
- First Embodiment
- Referring to FIGS.1-7, the first embodiment of the invention is described. FIG. 1 is a cross sectional view illustrating a semiconductor device according to the first embodiment of the invention. Although description is given on a case in which the invention is applied to a DRAM, the invention is applicable to another semiconductor memory device such as an SRAM.
- Referring to FIG. 1, a pair of gate (transfer gate)
electrodes 2 is formed on a main surface of asilicon substrate 1 with a gate insulating layer interposed.Gate electrode 2 includes a dopedpolysilicon layer 2 a and aWSi layer 2 b formed thereon.Doped polysilicon layer 2 a has, for example, a thickness of approximately 40-80 nm.WSi layer 2 b has a thickness of approximately 40-80 nm.WSi layer 2 b may be formed of a conductive layer with low resistance such as W. - A hard
mask insulating layer 3 formed of, for example, SiO2 is formed on a top surface ofgate electrode 2. Hardmask insulating layer 3 has, for example, a thickness of approximately 100-250 nm. A thin SiO2 layer 4 is formed to cover hardmask insulating layer 3 and a side surface ofgate electrode 2. Thin SiO2 layer 4 has a flat surface and a thickness of approximately 5-20 nm. - An SiN (silicon nitride)
stopper layer 5 is formed to extend from a portion on one side surface ofgate electrode 2 onto a top surface of hardmask insulating layer 3.SiN stopper layer 5 functions as a self alignment stopper layer, and has a thickness of approximately 40-100 nm. On the other side surface ofgate electrode 2, anSiN sidewall spacer 8 is formed.SiN sidewall spacer 8 is directly formed on the thin SiO2 layer 4.SiN sidewall spacer 8 may have its upper end portion on the side surface of hardmask insulating layer 3 as shown in FIG. 1. However,SiN sidewall spacer 8 may cover the side surface of hardmask insulating layer 3 and be connected toSiN stopper layer 5. In other words, silicon nitride may remain betweenSiN sidewall spacer 8 and SiN stopper layer that integrally connects them in FIG. 1. - An
interlayer insulating layer 6 formed of SiO2 or the like is formed to coverSiN stopper layer 5. Acontact hole 7 formed in self alignment manner is provided to penetrate interlayer insulatinglayer 6,SiN stopper layer 5, and thin SiO2 layer 4 to reach the main surface ofsilicon substrate 1.SiN sidewall spacer 8 is formed aroundcontact hole 7 to define an opening at a bottom ofcontact hole 7. - An interconnection layer (bit line)9 is formed to extend from the inside of
contact hole 7 ontointerlayer insulating layer 6.Interconnection layer 9 is constituted of a dopedpolysilicon layer 9 a and aWSi layer 9 b formed thereon. - As shown in FIG. 1, SiO2 sidewall spacer 15 in the conventional semiconductor device is not found between
SiN sidewall spacer 8 and thin SiO2 layer 4. Therefore, an opening width W2 at the bottom ofcontact hole 7 can be increased compared with that of the conventional device. Specifically, if an interval W1 betweengate electrodes 2 adjacent to each other is 0.24 μm, opening width W2 is 0.14 μm. Since opening width W2 is 0.06 μm in the conventional device, an area of an opening at the bottom ofcontact hole 7 can be dramatically increased compared with that of the conventional device. Accordingly, an area whereinterconnection layer 9 andsilicon substrate 1 are in contact with each other can be increased, and contact resistance can be decreased. - Since SiO2 sidewall spacer 15 is not found, plasma used for forming SiO2 sidewall spacer 15 is never applied to the main surface of
silicon substrate 1. Therefore, generation of leakage current caused by application of the plasma to the peripheral portion of an element isolation oxide film formed in an element isolation region ofsilicon substrate 1 can be effectively avoided. Accordingly, a semiconductor device which is reliable and has a high performance can be obtained. - Next with reference to FIGS.2-4, a characteristic structure of the semiconductor device shown in FIG. 1 is described in detail. FIG. 2 shows a cross sectional view of
gate electrode 2 and its vicinity of FIG. 1 by enlarging them. - Referring to FIG. 2, a represents a thickness of hard
mask insulating layer 3, b represents a thickness ofWSi layer 2 b and c represents a thickness of dopedpolysilicon layer 2 a. d is obtained by subtracting thickness of gate electrode (b+c) from a height g ofSiN sidewall spacer 8, e represents an amount of etching ofSiN sidewall spacer 8 generated by etching interlayer insulating 6, and f represents an amount of etching ofSiN sidewall spacer 8 generated by etchingSiN stopper layer 5. h and i respectively represent a thickness ofSiN stopper layer 5 and thin SiO2 layer 4. j represents a total height of thin SiO2 layer 4,gate electrode 2, hardmask insulating layer 3 andSiN stopper layer 5. - FIG. 3 shows a relation between values of d and a. FIG. 4 shows a relation between leakage current between
gate electrode 2 andinterconnection layer 9 and the value of d. The data shown in FIGS. 3 and 4 are obtained when transistor voltage is 2 V. - The inventors of the invention take various considerations for obtaining insulation between
gate electrode 2 andinterconnection layer 9 when SiO2 sidewall spacer 15 used in the conventional device is not formed. As a result of the considerations, it is found that leakage current betweengate electrode 2 andinterconnection layer 9 depends on the value d. Specifically, as shown in FIG. 4, it is found that leakage current betweengate electrode 2 andinterconnection layer 9 can be restricted within the range that does not cause any problem if the value of d in FIG. 2 is 20 nm or more. In other words, insulation betweengate electrode 2 andinterconnection layer 9 can be obtained by setting the value of d in FIG. 2 at 20 nm or more. More preferably, the value of d is 30 nm or more. - The inventors of the invention note that dependence of the value of d on the thickness a of hard
mask insulating layer 3. As shown in FIG. 3, if thickness a of hardmask insulating layer 3 is 120 nm or more, the value of d is found to be 20 nm or more. That is, by setting thickness a of hardmask insulating layer 3 at 120 nm or more, the value d can be set at 20 nm or more to restrict generation of leakage current betweengate electrode 2 andinterconnection layer 9. - Next with reference to FIGS.5-7, a method of fabricating the semiconductor device shown in FIG. 1 is described. FIGS. 5-7 are cross sectional views showing the first to the third steps of the fabrication process of the semiconductor device of FIG. 1.
- First with reference to FIG. 5, a gate insulating layer is formed on the main surface of
silicon substrate 1 using thermal oxidation method or the like. A doped polysilicon layer having a thickness of approximately 4080 nm, a WSi layer having a thickness of approximately 4080 nm, and a silicon oxide layer having a thickness of approximately 100-250 nm are successively deposited on the gate insulating layer by the CVD, for example. Patterning the silicon oxide layer, hardmask insulating layer 3 is formed.Gate electrode 2 is formed by etching the WSi layer and the doped polysilicon layer successively using hardmask insulating layer 3 as a mask. - Next thin SiO2 layer 4 of approximately 5-20 nm is formed to cover a side surface of
gate electrode 2 and hardmask insulating layer 3 by the CVD or the like.SiN stopper layer 5 having a thickness of about 40-100 nm is deposited on thin SiO2 layer 4 by the CVD or the like. - As heretofore described,
SiN stopper layer 5 is directly formed on thin SiO2 layer 4, and SiO2 sidewall spacer 15 of the conventional semiconductor device is not provided betweenSiN stopper layer 5 and thin SiO2 layer 4. Therefore, the plasma is not applied to the main surface ofsilicon substrate 1 and generation of leakage current can be effectively avoided. - After
SiN stopper layer 5 is deposited as described above,interlayer insulating layer 6 formed of SiO2 or the like is formed to coverSiN stopper layer 5 by the CVD or the like. Resist 10 is applied onto interlayer insulatinglayer 6 to be patterned into a prescribed shape. - An
opening 7 a that reachesSiN stopper layer 5 is formed by etchinginterlayer insulating layer 6 using the patterned resist 10 as a mask. The etching is carried out by an etching apparatus of a type such as ECR (Electron Cyclotron Resonance) or magnetron RIE (Reactive Ion Etching) using flon type gas and Ar type gas under a condition in which etching selectivity for the silicon nitride is high.Interlayer insulating layer 6 is etched in such a condition, and the etching is stopped at a surface ofSiN stopper layer 5. Accordingly, opening 7 a having a self-aligned shape is provided. - Next with reference to FIG. 7,
SiN stopper layer 5 at the bottom of opening 7 a and thin SiO2 layer 4 are successively etched by an etching apparatus of a type which is parallel and planar, using flon type gas containing hydrogen. As a result, the main surface of the silicon substrate is selectively exposed andSiN sidewall spacer 8 is formed. - By providing
SiN sidewall spacer 8 such that the value of d in FIG. 2 is set at 20 nm or more, insulation betweeninterconnection layer 9 which is formed later andgate electrode 2 can be obtained. In addition, by setting the thickness of hardmask insulating layer 3 at 120 nm or more when the hardmask insulating layer 3 is formed, the value of d can be almost surely set at 20 nm or more. - After forming
contact hole 7 in self alignment manner as above,interconnection layer 9 is formed to extend from the inside ofcontact hole 7 ontointerlayer insulating layer 6 by the CVD or the like. Accordingly, the semiconductor device shown in FIG. 1 is formed through the steps above. - Second Embodiment
- Next with reference to FIGS. 8 and 9, the second embodiment of the invention is described. FIG. 8 is a cross sectional view illustrating a semiconductor device according to the second embodiment.
- Referring to FIG. 8, a
concave portion 11 is formed at the main surface ofsilicon substrate 1 according to the second embodiment.Concave portion 11 is formed to extend to a portion directly underSiN sidewall spacer 8.Concave portion 11 is filled with a part of dopedpolysilicon layer 9 a. - By forming
concave portion 11 at the main surface ofsilicon substrate 1, a layer which is changed in quality at the bottom portion ofcontact hole 7 can be removed. Since a part ofinterconnection layer 9 fillsconcave portion 11, contact resistance betweeninterconnection layer 9 andsilicon substrate 1 can be decreased. The depths ofconcave portion 11 is, for example, about 5-40 nm. - Next referring to FIG. 9, a method of fabricating the semiconductor device shown in FIG. 8 is described. FIG. 9 is a cross sectional view showing a characteristic fabrication process of the semiconductor device of FIG. 8.
- Referring to FIG. 9,
contact hole 7 is formed through the steps similar to those of the first embodiment. The main surface ofsilicon substrate 1 is etched by an isotropic polysilicon etching apparatus of down flow type using gas of CF4, O2 type or the like. At this time,silicon substrate 1 is etched without etching most ofSiN sidewall spacer 8. As a result,concave portion 11 can be formed to extend to the portion underSiN sidewall spacer 8 while maintaining insulation betweengate electrode 2 andinterconnection layer 9. The semiconductor device shown in FIG. 8 is thereafter formed through the steps similar to those of the first embodiment. - Third Embodiment
- Next, referring to FIGS.10-12, the third embodiment of the invention is described. FIGS. 10-12 are cross sectional views respectively showing the characteristic first to the third steps of a fabrication process of a semiconductor device according to the third embodiment.
- First, referring to FIG. 10, after hard mask insulating
layer 3 andgate electrode 2 are formed through the steps similar to those of the first embodiment, a wet etching process is applied to a side surface ofWSi layer 2 b for approximately 25-50 minutes using aqueous ammonia. As a result, the side surface ofWSi layer 2 b is recessed intoWSi layer 2 b. An amount of recess W3 is about 10 nm-20 nm. Accordingly, aconcave portion 12 is formed at a side surface of an upper portion ofgate electrode 2. - Using a method similar to that of the first embodiment, thin SiO2 layer 4 and
SiN stopper layer 5 are provided. Next, as shown in FIG. 12,interlayer insulating layer 6 andcontact hole 7 are formed by a method similar to that of the first embodiment.Interconnection layer 9 is thereafter formed incontact hole 7. - The semiconductor device according to the third embodiment is thus formed through the steps described above. In the semiconductor device of the third embodiment, the side surface of
WSi layer 2 b is recessed inward, so that a separation width W4 between the upper corner portion ofgate electrode 2 andinterconnection layer 9 can be increased compared with that of each embodiment described above. As a result, insulation betweengate electrode 2 andinterconnection layer 9 can be surely maintained. - Fourth Embodiment
- Next referring to FIGS. 13A and B to18A and B, the fourth embodiment of the invention is described. FIGS. 13A and B are cross sectional views showing a semiconductor device of the fourth embodiment. According to the fourth embodiment, not only a structure of a memory cell portion of DRAM, a structure of its peripheral circuit portion is illustrated.
- Referring to FIGS. 13A and B, the structure in the memory cell portion is similar to that shown in FIG. 8, and description thereof is not repeated here. In the peripheral circuit portion,
gate electrode 2 is formed on the main surface ofsilicon substrate 1 with the gate insulating layer interposed, and hard mask insulatinglayer 3 is formed thereon. AnSiN sidewall spacer 13 is formed to cover both of a side surface of hardmask insulating layer 3 and a side surface ofgate electrode 2 with thin SiO2 layer 4 interposed.SiN sidewall spacer 13 is provided by etchingSiN stopper layer 5, and formed directly on thin SiO2 layer 4. -
Interlayer insulating layer 6 is extended on hardmask insulating layer 3 to be in contact with a top surface of hardmask insulating layer 3. Acontact hole 14 is formed to penetrate interlayer insulatinglayer 6, hardmask insulating layer 3 andWSi layer 2 b.Interconnection layer 9 is formed to extend from the inside ofcontact hole 14 ontointerlayer insulating layer 6. - As shown in FIG. 13B, since
contact hole 14 is formed to penetrateWSi layer 2 b, dopedpolysilicon layer 9 a and dopedpolysilicon layer 2 a can be in direct contact with each other. If dopedpolysilicon layer 9 a is in contact withWSi layer 2 b, impurities from dopedpolysilicon layer 9 a are absorbed byWSi layer 2 b and a portion where concentration of impurities is low is formed between dopedpolysilicon layer 9 a andWSi layer 2 b. As a result, if dopedpolysilicon layer 9 a is in contact with onlyWSi layer 2 b, contact resistance betweeninterconnection layer 9 andgate electrode 2 increases. - On the other hand, if doped
polysilicon layer 9 a and dopedpolysilicon layer 2 a are in contact with each other, a portion where concentration of impurities is low is not formed entirely in a region whereinterconnection layer 9 andgate electrode 2 are in contact with each other. Accordingly, increase of contact resistance betweeninterconnection layer 9 andgate electrode 2 can be effectively avoided. - Next referring to FIGS. 14A and B to18A and B, a method of fabricating a semiconductor device according to the fourth embodiment is described. FIGS. 14A and B to 18A and B are cross sectional views showing the characteristic first step to the fifth step of a fabrication process of a semiconductor device according to the fourth embodiment.
- First referring to FIGS. 14A and B,
SiN stopper layer 5 is formed through the steps similar to those of the first embodiment. A resist 10 a is formed to coverSiN stopper layer 5 in the memory cell portion. Using resist 10 a as a mask,SiN stopper layer 5 in the peripheral circuit portion is etched back.SiN sidewall spacer 13 is formed to expose a top surface of hardmask insulating layer 3 and cover both side surfaces ofgate electrode 2. Resist 10 a is thereafter removed. - Next referring to FIGS. 15A and B,
interlayer insulating layer 6 is formed by a method similar to that of the first embodiment, and a resist 10 b is formed thereon. Resist 10 b is provided with openings respectively in the memory cell portion and the peripheral circuit portion as shown in FIGS. 15A and B. - Referring to FIGS. 16A and B next, using resist10 b as a mask,
interlayer insulating layer 6 is etched by a method similar to that of the first embodiment. A part of a surface ofSiN stopper layer 5 in the memory cell portion is exposed, and acontact hole 14 a that penetrates interlayer insulatinglayer 6 and hardmask insulating layer 3 and reachesWSi layer 2 b is formed in the peripheral circuit portion. SinceSiN stopper layer 5 is not formed on hardmask insulating layer 3 in the peripheral circuit portion,contact hole 14 a that reachesWSi layer 2 b can be provided. - Referring to FIGS. 17A and B,
SiN stopper layer 5 and thin SiO2 layer 4 at a bottom portion of opening 7 a are etched by an etching apparatus that is of a parallel and planar type using flon type gas containing hydrogen. As a result, the main surface ofsilicon substrate 1 is selectively exposed. In the peripheral circuit portion,WSi layer 2 b is overetched by D1. Using the same mask,contact hole 7 formed in self alignment manner in the memory cell portion as well ascontact hole 14 b formed ongate electrode 2 in the peripheral circuit portion are provided. - As shown in FIG. 18A and B, a
concave portion 11 is formed at the main surface ofsilicon substrate 1 located in the memory cell portion by a method similar to that of the second embodiment. The depth ofconcave portion 11 is approximately 5-100 nm. In the peripheral circuit portion,WSi layer 2 b is overetched by D2. D2 is 20 nm or more, for example.Contact hole 14 that reaches dopedpolysilicon layer 2 a is thus formed in the peripheral circuit portion. -
Interconnection layer 9 is thereafter formed in each ofcontact holes - In the semiconductor device according to the present invention, the SiO2 sidewall spacer is not formed so that application of plasma onto the main surface of the silicon substrate can be avoided, and the area of the opening at the bottom portion of the contact hole formed between the gate electrodes can be increased. As a result, generation of leakage current in the semiconductor device can be avoided and contact resistance between the interconnection layer formed in the contact hole and the semiconductor substrate can be decreased. A semiconductor device with high performance and high reliability can be obtained accordingly.
- According to one aspect of the fabrication method of a semiconductor device of the present invention, the nitride stopper layer is directly formed on the thin insulating layer. Since the SiO2 sidewall spacer is not formed, the effects as described above can be also obtained.
- According to another aspect of the fabrication method of a semiconductor device of the invention, the first contact hole that selectively exposes the main surface in the memory cell portion and the second contact hole that reaches the second gate electrode in the peripheral circuit portion are simultaneously formed using the second mask layer. Since the first and second contact holes are formed using the same mask, the fabrication process can be simplified and the fabrication cost can be decreased.
- Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
Claims (12)
1. A semiconductor device comprising:
a gate electrode formed on a main surface of a semiconductor substrate;
a hard mask insulating layer formed on a top surface of said gate electrode;
a thin insulating layer formed to cover a side surface of said gate electrode and said hard mask insulating layer;
a nitride stopper layer formed directly on said thin insulating layer to extend from a portion on one side surface of said gate electrode onto a top surface of said hard mask insulating layer;
a sidewall nitride layer formed directly on said thin insulating layer to cover the other side surface of said gate electrode;
an interlayer insulating layer formed to cover said nitride stopper layer, having a contact hole that reaches said main surface and said sidewall nitride layer; and
an interconnection layer formed in said contact hole.
2. The semiconductor device according to , wherein
claim 1
a thickness of said hard mask insulating layer is 120 nm or more.
3. The semiconductor device according to , wherein
claim 1
a height of said sidewall nitride layer in a direction perpendicular to said main surface is larger than a thickness of said gate electrode in said direction perpendicular to said main surface by 20 nm or more.
4. The semiconductor device according to , wherein
claim 1
a concave portion is formed at said main surface in the vicinity of said sidewall nitride layer, and
a part of said interconnection layer fills the inside of said concave portion.
5. The semiconductor device according to , wherein
claim 1
an upper part of the other side surface of said gate electrode is recessed from a side surface of said hard mask insulating layer into said gate electrode.
6. The semiconductor device according to , wherein
claim 1
said semiconductor device has a memory cell portion and a peripheral circuit portion,
said gate electrode is arranged in said memory cell portion,
another gate electrode having a metal silicide portion at its upper part is formed in said peripheral circuit portion,
another hard mask insulating layer is formed on a top surface of said another gate electrode,
another thin insulating layer is formed to cover a side surface of said another gate electrode and said another hard mask insulating layer,
a pair of another sidewall nitride layers is directly formed on said another thin insulating layer to cover both side surfaces of said another gate electrode,
said interlayer insulating layer extends on said another hard mask insulating layer to be in contact with a top surface of said another hard mask insulating layer,
another contact hole is formed to penetrate said interlayer insulating layer, said another hard mask insulating layer, and said metal silicide portion, and have its bottom surface in said another gate electrode, and
another interconnection layer is formed in said another contact hole to be electrically connected to said another gate electrode.
7. A method of fabricating a semiconductor device, comprising the steps of:
forming a gate electrode on a main surface of a semiconductor substrate;
forming a hard mask insulating layer on a top surface of said gate electrode;
forming a thin insulating layer to cover said gate electrode and said hard mask insulating layer;
forming a nitride stopper layer directly on said thin insulating layer;
forming an interlayer insulating layer to cover said nitride stopper layer;
forming a contact hole that reaches said main surface and forming a sidewall nitride layer on a side surface of said gate electrode by etching said interlayer insulating layer, said nitride stopper layer, and said thin insulating layer successively; and
forming an interconnection layer in said contact hole.
8. The method of fabricating a semiconductor device according to , wherein
claim 7
said step of forming said contact hole includes a step of forming a concave portion by isotropically etching said main surface which is exposed, and
said step of forming said interconnection layer includes a step of forming said interconnection layer to fill said concave portion.
9. The method of fabricating a semiconductor device according to , wherein
claim 7
said step of forming said hard mask insulating layer includes a step of forming said hard mask insulating layer to have a thickness of 120 nm or more, and
said step of forming said sidewall nitride layer includes a step of forming said sidewall nitride layer to have a height in a direction perpendicular to said main surface is larger than a thickness of said gate electrode in said direction perpendicular to said main surface by 20 nm or more.
10. The method of fabricating a semiconductor device according to , further comprising a step of recessing an upper part of a side surface of said gate electrode from a side surface of said hard mask insulating layer into said gate electrode by etching the upper part of the side surface of said gate electrode after said hard mask insulating layer is formed.
claim 7
11. A method of fabricating a semiconductor device having a memory cell portion and a peripheral circuit portion, comprising the steps of:
forming a first hard mask insulating layer on a main surface of a semiconductor substrate located in said memory cell portion with a first gate electrode interposed, and forming a second hard mask insulating layer on said main surface located in said peripheral circuit portion with a second gate electrode interposed;
forming a thin insulating layer to cover said first and second hard mask insulating layers and side surfaces of said first and second gate electrodes;
forming a nitride stopper layer directly on said thin insulating layer;
forming a first mask layer to cover said nitride stopper layer located in said memory cell portion;
exposing said second hard mask insulating layer and forming a pair of sidewall nitride layers that covers a side surface of said second gate electrode by etching said nitride stopper layer using said first mask layer;
forming an interlayer insulating layer to cover said nitride stopper layer and said second hard mask insulating layer;
forming a second mask layer on said interlayer insulating layer;
forming a first contact hole that selectively exposes said main surface by etching said interlayer insulating layer, said nitride stopper layer and said thin insulating layer located in said memory cell portion successively, and forming a second contact hole that reaches said second gate electrode by etching said interlayer insulating layer and said second hard mask insulating layer located in said peripheral circuit portion successively, using said second mask layer; and
forming first and second interconnection layers respectively in said first and second contact holes.
12. The method of fabricating a semiconductor device according to , wherein
claim 11
said second gate electrode includes a metal silicide portion at its upper part, and
said step of forming said first and second contact holes includes a step of forming a concave portion at said main surface after said main surface is exposed and forming said second contact hole to penetrate said metal silicide portion.
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US09/761,176 US6444515B2 (en) | 1997-12-24 | 2001-01-18 | Method of fabricating a semiconductor device |
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JP9355330A JPH11186389A (en) | 1997-12-24 | 1997-12-24 | Semiconductor device and manufacture thereof |
JP9-355330(P) | 1997-12-24 | ||
JP9-355330 | 1997-12-24 | ||
US09/115,514 US6249015B1 (en) | 1997-12-24 | 1998-07-15 | Semiconductor device and fabrication method thereof |
US09/761,176 US6444515B2 (en) | 1997-12-24 | 2001-01-18 | Method of fabricating a semiconductor device |
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US09/761,176 Expired - Fee Related US6444515B2 (en) | 1997-12-24 | 2001-01-18 | Method of fabricating a semiconductor device |
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Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
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US20050146942A1 (en) * | 2002-07-08 | 2005-07-07 | Madurawe Raminda U. | Semiconductor switching devices |
US20070166976A1 (en) * | 2005-12-29 | 2007-07-19 | Jung Hak Myung | Method of fabricating a semiconductor device |
US20070267707A1 (en) * | 2006-05-19 | 2007-11-22 | Masafumi Tsutsui | Semiconductor device and method for fabricating the same |
US20090134477A1 (en) * | 2007-11-26 | 2009-05-28 | Dae-Kyeun Kim | Semiconductor device and method of fabricating the same |
Families Citing this family (9)
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US6180494B1 (en) * | 1999-03-11 | 2001-01-30 | Micron Technology, Inc. | Integrated circuitry, methods of fabricating integrated circuitry, methods of forming local interconnects, and methods of forming conductive lines |
US6429124B1 (en) * | 1999-04-14 | 2002-08-06 | Micron Technology, Inc. | Local interconnect structures for integrated circuits and methods for making the same |
KR100383325B1 (en) * | 2001-01-19 | 2003-05-12 | 삼성전자주식회사 | Wiring of semiconductor device for forming a self-aligned contact and Method of manufacturing the same |
US6455406B1 (en) * | 2001-11-28 | 2002-09-24 | Micron Technology, Inc. | Semiconductor processing method of forming a conductive connection through WxSiyNz material with specific contact opening etching |
US7227234B2 (en) * | 2004-12-14 | 2007-06-05 | Tower Semiconductor Ltd. | Embedded non-volatile memory cell with charge-trapping sidewall spacers |
KR100724565B1 (en) | 2005-07-25 | 2007-06-04 | 삼성전자주식회사 | Shared contact structure having corner protection pattern, semiconductor devices, and methods of fabricating the same |
CN102456689A (en) * | 2010-10-21 | 2012-05-16 | 中国科学院微电子研究所 | Substrate structure, semiconductor device and manufacturing method thereof |
KR102301249B1 (en) | 2015-11-16 | 2021-09-10 | 삼성전자주식회사 | Semiconductor device |
CN112563208A (en) * | 2019-09-26 | 2021-03-26 | 长鑫存储技术有限公司 | Semiconductor memory and method of manufacturing the same |
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KR970003903B1 (en) * | 1987-04-24 | 1997-03-22 | Hitachi Mfg Kk | Semiconductor device and fabricating method thereof |
JPH06188385A (en) * | 1992-10-22 | 1994-07-08 | Mitsubishi Electric Corp | Semiconductor device and manufacture thereof |
US5605857A (en) * | 1993-02-12 | 1997-02-25 | Micron Technology, Inc. | Method of forming a bit line over capacitor array of memory cells and an array of bit line over capacitor array of memory cells |
JPH0964302A (en) | 1995-08-24 | 1997-03-07 | Matsushita Electron Corp | Manufacture of semiconductor device |
US5723381A (en) * | 1995-09-27 | 1998-03-03 | Siemens Aktiengesellschaft | Formation of self-aligned overlapping bitline contacts with sacrificial polysilicon fill-in stud |
JP3435943B2 (en) | 1995-11-24 | 2003-08-11 | ソニー株式会社 | Semiconductor device and manufacturing method thereof |
US5786249A (en) * | 1996-03-07 | 1998-07-28 | Micron Technology, Inc. | Method of forming dram circuitry on a semiconductor substrate |
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1997
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20050146942A1 (en) * | 2002-07-08 | 2005-07-07 | Madurawe Raminda U. | Semiconductor switching devices |
US20070166976A1 (en) * | 2005-12-29 | 2007-07-19 | Jung Hak Myung | Method of fabricating a semiconductor device |
US20090230484A1 (en) * | 2005-12-29 | 2009-09-17 | Jung-Hak Myung | Method of fabricating a semiconductor device |
US7638384B2 (en) * | 2005-12-29 | 2009-12-29 | Dongbu Hitek Co. Ltd. | Method of fabricating a semiconductor device |
US20070267707A1 (en) * | 2006-05-19 | 2007-11-22 | Masafumi Tsutsui | Semiconductor device and method for fabricating the same |
US8354726B2 (en) * | 2006-05-19 | 2013-01-15 | Panasonic Corporation | Semiconductor device and method for fabricating the same |
US20090134477A1 (en) * | 2007-11-26 | 2009-05-28 | Dae-Kyeun Kim | Semiconductor device and method of fabricating the same |
US7884399B2 (en) * | 2007-11-26 | 2011-02-08 | Dongbu Hitek Co., Ltd. | Semiconductor device and method of fabricating the same |
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TW407337B (en) | 2000-10-01 |
US6249015B1 (en) | 2001-06-19 |
JPH11186389A (en) | 1999-07-09 |
US6444515B2 (en) | 2002-09-03 |
KR19990062487A (en) | 1999-07-26 |
KR100274277B1 (en) | 2001-02-01 |
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Effective date: 20100903 |