KR20030002352A - Method for Self-Aligned Shallow Trench Isolation and Method of manufacturing Non-Volatile Memory Device comprising the same - Google Patents

Abstract

PURPOSE: A method for isolating a self-aligned shallow trench and a method for fabricating a non-volatile memory device by using the same are provided to form simultaneously a gate and an active region by using a self-aligned shallow trench isolation method. CONSTITUTION: An oxide layer is formed on a semiconductor substrate(100). The first conductive layer is formed on the oxide layer. A stopping layer is formed on the first conductive layer. A hard mask layer and an anti-reflective layer are formed on the stopping layer. A mask pattern is formed by etching the anti-reflective layer and the hard mask layer. A gate oxide layer(102), the first floating gate pattern(104), and a stopping layer pattern are formed by patterning the stopping layer, the first conductive layer, and the oxide layer. A trench(110) is formed by etching the substrate(100) neighboring to the first floating gate pattern(104). A sidewall of the first floating gate pattern(104) is rounded. A trench oxide layer is formed on an inner face of the trench(110). A field oxide layer is formed in the inside of the trench(110). The second floating gate pattern(118) is formed by removing a conductive layer of the field oxide layer. An ONO dielectric layer(120) is formed on the whole surface of the above structure. A control gate layer(122) is formed on the dielectric layer(120). A stack type gate structure is formed by etching the control gate layer(122), the dielectric layer(120), and the second floating gate pattern(118) and the first floating gate pattern.

Description

Method for Self-Aligned Shallow Trench Isolation and Method of manufacturing Non-Volatile Memory Device comprising the same}

The present invention relates to a device isolation method and a method of fabricating a semiconductor device using the same, and more particularly, self-aligned shallow trench isolation (SA-STI) for simultaneously forming a gate and an active region. ) And a method of manufacturing a nonvolatile memory device using the same.

In the manufacture of highly integrated memory devices, the degree of integration of the cells is mainly determined by the layout of the memory cells and the scalability of the layout as the critical dimension shrinks. As the critical dimension shrinks below the sub-micron region, the scalability of the layout is limited by the resolution of the manufacturing process and the alignment tolerance by the design mask. The alignment of the mask is limited by the mechanical technique of placing the mask on top of the wafer during processing and the technique of consistently printing the pattern on top of the mask. Accumulation of alignment tolerances causes misalignment errors in the layout of the array, so it is desirable to use fewer alignment threshold masks to control the alignment tolerances in chip design. Thus, so-called "self-aligned" process steps have been developed.

Since most highly integrated memory designs require device isolation structures between cells in the column direction within the array, it is desirable to minimize the size of device isolation structures to increase the density of the memory array. However, the size of the device isolation structure is limited by the process for forming the device isolation structure and by the alignment of the structures in the memory array.

Typically, device isolation structures are formed using thermal field oxidation processes such as LOCal Oxidation of Silicon (LOCOS). According to LOCOS device isolation, first, an oxide film and a nitride film are sequentially formed on a silicon substrate, and then the nitride film is patterned. Next, the silicon substrate is selectively oxidized using the patterned nitride film as an oxidation mask to form a field oxide film. According to the LOCOS device isolation, a bird's beak is generated at the end of the field oxide film as oxygen penetrates to the side of the oxide film under the nitride film used as a mask for selective oxidation of the silicon substrate. Since the field oxide film is extended to the active area by the length of the buzz beak by such a buzz beak, the width of the active area is reduced to deteriorate the electrical characteristics of the device.

Accordingly, a shallow trench isolation (STI) structure is in the spotlight in the ultra-high density semiconductor device. According to the STI process, after the silicon substrate is etched to form a trench, an oxide film is deposited to fill the trench. Next, the oxide film is etched by etch back or chemical mechanical polishing (CMP) to form a field oxide film in the trench.

The above-described LOCOS method or STI method commonly includes a mask step for defining a device isolation region and a field oxide film formed in the region. After forming the device isolation structure, mask steps for forming memory cells are performed. Therefore, the alignment tolerance accompanying the formation of the device isolation structure and the alignment tolerance associated with the layout of the memory cell are combined to cause misalignment that has a fatal effect on the operation of the device.

As one method for solving the alignment problem, a method of self-aligning and forming a LOCOS device isolation structure in a floating gate in a nonvolatile memory device is proposed. Further, a method of self-aligning and forming an STI structure in a floating gate is disclosed in US Pat. No. 6,013,551 issued to Jong Chen and the like. According to these methods, the floating gate and the active region used for the storage of the charge are defined at the same time using one mask, thereby providing self-alignment between the active region and the floating gate.

Non-volatile memory devices have characteristics that can maintain their state over time once data is input. Recently, there is an increasing demand for a flash memory that can electrically input and output data. A memory cell for storing data in a flash memory device has a floating gate structure formed of a floating gate formed on top of a silicon substrate via a tunnel oxide film and a control gate formed of a control gate formed on top of the floating gate through a dielectric film. In flash memory cells having such a structure, data is stored by applying an appropriate voltage to the control gate and the substrate to insert or draw electrons into the floating gate. In this case, the dielectric layer maintains charge characteristics charged in the floating gate and transfers the voltage of the control gate to the floating gate.

1A to 1D are cross-sectional views illustrating a method of manufacturing a flash memory device having a conventional self-aligned shallow trench device isolation.

Referring to FIG. 1A, an oxide film, a first polysilicon layer, and a nitride film (not shown) are sequentially deposited on a semiconductor substrate 10 made of a semiconductor material such as silicon. The oxide film is provided as a tunnel oxide film, that is, a gate oxide film of a flash memory cell, and the first polysilicon layer is provided as a floating gate. The nitride film serves as an abrasive stopper film in a subsequent chemical mechanical polishing (CMP) process.

Subsequently, the nitride layer, the first polysilicon layer, and the oxide layer are sequentially dry-etched through a photolithography process using one mask to form the gate oxide layer 12, the first floating gate pattern 14, and the nitride layer pattern 18. do. Subsequently, the trench 20 is formed by etching the upper portion of the substrate 10 adjacent to the first floating gate pattern 14 using the mask. That is, the active region and the floating gate are simultaneously defined by a trench process using one mask.

Referring to FIG. 1B, the exposed portion of trench 20 is heat treated in an oxidizing atmosphere to cure silicon damage caused by high energy ion bombardment during the trench etching process and to suppress the generation of leakage currents. Then, the trench inner wall oxide film 22 is formed on the inner surface including the bottom surface and the sidewall of the trench 20 by an oxidation reaction between the exposed silicon and the oxidant.

During the oxidation process, an oxidant penetrates into the side surface of the gate oxide layer 12 under the first floating gate pattern 14 to form a burj beek b as shown in FIG. 2. In addition, during the oxidation, the volume expansion of the oxide film occurs continuously. Since the oxidation proceeds only on the surfaces of the silicon substrate 10 and the first floating gate pattern 14, the gap between the first floating gate pattern 14 and the gate oxide film 12 is increased. At the interface edge and at the interface edge between the silicon substrate 10 and the gate oxide film 12, volume expansion due to oxidation is limited. Therefore, at these interfacial edges, stress due to volume expansion is concentrated to slow the diffusion of the oxidant, thereby inhibiting oxidation (see FIG. 2C). In Fig. 2, reference numeral a denotes a profile before an oxidation process for forming the trench inner wall oxide film 22.

As a result, the bottom edge portion of the first floating gate pattern 14 is bent to the outside, and the sidewall of the first floating gate pattern 14 has a positive slope. Here, the sidewall having a positive slope means that the sidewall has an inclination with respect to the etchant. That is, as shown, the penetration of the oxidant is suppressed by the presence of the nitride film pattern 18 immediately below the nitride film pattern 18, so that the upper portion of the sidewall of the first floating gate pattern 14 has a negative slope, The bottom of the sidewall has a positive slope where the bottom edge portion is bent outward and erodes or acts as a barrier of the lower film quality with respect to the etchant introduced from the upper direction of the substrate, such as the sidewall of the mesa structure.

Referring to FIG. 1C, after a gap-fill oxide layer 23 is formed by chemical vapor deposition (CVD) to fill the trench 20, the upper surface of the nitride layer pattern 18 is formed. The gap buried oxide film 23 is removed by chemical mechanical polishing (CMP) until it is exposed. As a result, the field oxide film 24 is formed inside the trench 20.

Referring to FIG. 1D, the nitride film pattern 18 is removed by a phosphoric acid strip process to expose a surface of the first floating gate pattern 14. Subsequently, a second polysilicon layer to be used as a floating gate is deposited on the first floating gate pattern 14 and the field oxide layer 24. The second polysilicon layer is in electrical contact with the first floating gate pattern 14, and serves to increase the area of the dielectric film to be formed in a subsequent process.

Subsequently, the second polysilicon layer on the field oxide film 24 is partially removed by a photolithography process to form a second floating gate pattern 26, and then an ONO (oxide / nitride / oxide) dielectric film is formed on the entire surface of the resultant. 28 and the control gate layer 30 are sequentially formed. The control gate layer 30 is typically formed of a polyside structure in which a doped polysilicon layer and a tungsten silicide layer are stacked.

Then, the control gate layer 30, the dielectric layer 28, and the second and first floating gate patterns 26 and 14 are sequentially dry-etched by a self-aligned gate etching process to stack the nonvolatile memory device. Complete the gate structure.

In this case, as shown in FIG. 1B, since the lower portion of the sidewall of the first floating gate pattern 14 has a positive slope, the first floating is performed by the anisotropic etching characteristic of the dry etching process (that is, the etching proceeds only in the vertical direction). The portion masked by the field oxide film 24 of the gate pattern 14 remains unetched. Thus, a line-shaped polysilicon residue 14a is left along the surface boundary between the field oxide film 24 and the active region. This polysilicon residue 14a forms a bridge between adjacent floating gates, causing electrical failure of the device.

Accordingly, a first object of the present invention is to provide a self-aligned shallow trench device isolation method capable of preventing electrical failure of the device.

It is a second object of the present invention to provide a method of manufacturing a nonvolatile memory device capable of preventing the positive slope of the floating gate sidewall.

1A to 1D are cross-sectional views illustrating a method of manufacturing a flash memory device to which a conventional self-aligned shallow trench device isolation process is applied.

FIG. 2 is an enlarged cross-sectional view of portion A of FIG. 1B.

3A to 3H are cross-sectional views illustrating a method of manufacturing a nonvolatile memory device to which a self-aligned shallow trench device isolation process according to a first embodiment of the present invention is applied.

4A to 4E are cross-sectional views illustrating a method of manufacturing a nonvolatile memory device to which a self-aligned shallow trench device isolation process according to a second embodiment of the present invention is applied.

<Explanation of symbols for the main parts of the drawings>

100, 200: semiconductor substrate 102, 202: gate oxide film

104, 204: First floating gate pattern

206: buffer film pattern 108, 208: low film pattern

109, 209: mask pattern 110, 210: trench

112, 212: trench inner wall oxide film 114: gap buried oxide film

116 and 216: Field oxide film 118: Second floating gate pattern

120 dielectric film 122 control gate layer

In order to achieve the first object of the present invention described above, the present invention comprises the steps of forming an oxide film on a semiconductor substrate; Forming a first conductive layer on the oxide film; Forming a stop layer on the first conductive layer; Etching the barrier layer, the first conductive layer, and the oxide layer using one mask to form an oxide layer pattern, a first conductive layer pattern, and a barrier layer pattern; Etching the upper portion of the substrate adjacent to the first conductive layer pattern using the mask to form a trench; Performing annealing to round sidewalls of the first conductive layer pattern; Oxidizing an inner surface of the trench to form a trench inner wall oxide layer on the inner surface of the trench; And forming a field oxide film inside the trench.

In order to achieve the second object of the present invention, the present invention comprises the steps of forming a gate oxide film on a semiconductor substrate; Forming a first conductive layer for floating gate on the oxide film; Forming a stop layer on the first conductive layer; Patterning the stop layer, the first conductive layer, and the gate oxide layer using one mask to form a first floating gate pattern from the first conductive layer; Defining an active region on the substrate by etching the upper portion of the substrate adjacent the first floating gate pattern using the mask to form a trench aligned with the first floating gate pattern; Performing annealing to round sidewalls of the first floating gate pattern; Oxidizing an inner surface of the trench to form a trench inner wall oxide layer on the inner surface of the trench; Forming a field oxide film inside the trench; And sequentially forming a dielectric film and a control gate layer on the first floating gate pattern.

According to the present invention, annealing using hydrogen (H ₂ ) or argon (Ar) gas is performed before the sidewall oxidation of the trench to round the sidewalls of the first conductive layer pattern (ie, the first floating gate pattern). Then, when the sidewalls of the trench are oxidized, the sidewalls from the middle portion to the bottom portion of the first floating gate pattern may be compensated for inclination with a positive slope. In addition, since both an upper edge and a lower edge of the first floating gate pattern are rounded by the annealing, stress due to volume expansion during sidewall oxidation of the trench is reduced, thereby suppressing buzz beak. Accordingly, the sidewall of the first floating gate pattern may be prevented from having a positive slope, thereby preventing an electrical failure of the device caused by the gate residue during subsequent gate etching.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1

3A to 3H are cross-sectional views illustrating a method of manufacturing a nonvolatile memory device to which a self-aligned shallow trench device isolation process according to a first embodiment of the present invention is applied.

Referring to FIG. 3A, an oxide film or an oxynitride film is thinly grown on a semiconductor substrate 100 such as silicon to a thickness of about 50 to 100 microseconds to be used as a gate oxide film (or tunnel oxide film) of a cell transistor ( 101). Subsequently, polysilicon or amorphous silicon to be used as a floating gate on the oxide film 101 is formed by a low pressure chemical vapor deposition (LPCVD) method to a thickness of about 300 to 1000 GPa, and a conventional doping method such as POCl ₃ diffusion and ion The first conductive layer 103 is formed by doping with a high concentration of N-type impurities by implantation or in-situ doping.

Here, in-situ doping while depositing the first conductive layer 103 in an amorphous phase may deteriorate the gate oxide film thereunder due to the change of crystal grains from the amorphous phase to the crystalline phase by a thermal budget of a subsequent process. have. Therefore, depositing the first conductive layer 103 while in-situ doping the crystal phase at a temperature of 600 ° C. or more is stable in terms of stress due to a small phase change.

Subsequently, a nitride film is deposited on the first conductive layer 103 by a low pressure chemical vapor deposition method to a thickness of about 1000 to 2000 GPa to form a blocking film 107 which serves as an abrasive stop film in a subsequent chemical mechanical polishing process. .

Subsequently, a hard mask layer made of an oxide and an antireflection layer made of SiON (not shown) are sequentially formed on the blocking film 107. The anti-reflection layer serves to prevent diffuse reflection of light in a subsequent photographic process and is removed in a subsequent trench formation process.

The mask pattern 109 is formed by dry etching the anti-reflection layer and the hard mask layer by a photolithography process for defining a floating gate.

Referring to FIG. 3B, the blocking layer 107, the first conductive layer 103, and the oxide layer 101 are sequentially dry-etched using the mask pattern 109 as an etching mask to sequentially gate gate oxide layer 102 and first gate. The floating gate pattern 104 and the blocking layer pattern 108 are formed.

Subsequently, the trench 110 is formed by etching the upper portion of the substrate 100 adjacent to the first floating gate pattern 104 to a depth of about 2000 to 5000 microns using the mask pattern 109. At this time, the anti-reflective layer arbitrarily formed above is removed and the mask pattern 109 is also etched by a predetermined thickness.

As a result, the first floating gate patterns 109 are separated by the trench 110. According to the process of forming the trench 110, since the active region and the floating gate are simultaneously defined using one mask, self-alignment is obtained between the active region and the floating gate.

Referring to FIG. 3C, annealing using hydrogen (H ₂ ) gas or argon (Ar) gas is performed to round the sidewalls of the first floating gate pattern 104. Preferably, the annealing using the hydrogen (H ₂ ) gas is performed using about 1 to 30 liters of hydrogen gas at a temperature of about 750 to 950 ° C. and a pressure of about 10 to 40 torr.

As described above, when annealing is performed at a temperature of about 750 ° C. to 950 ° C., silicon existing in an edge portion of the first floating gate pattern 104 flows to a side portion or an upper surface thereof, and the first floating gate pattern is flowed. The sidewall of 104 is rounded (see B).

Referring to FIG. 3D, after the annealing described above, the inner surface of the trench 110 is treated in an oxidizing atmosphere to remove silicon damage caused by high energy ion bombardment during the trench etching process and to prevent leakage current. do. Then, the trench inner wall oxide layer 112 is formed along the inner surface of the trench 110, that is, about 10 to about 500 kPa, preferably about 30 to about 40 kPa, along the inner surface of the trench 110.

When annealing is performed to form curvatures on the sidewalls of the first floating gate pattern 104 and then trench sidewall oxidation, the sidewalls from the middle portion to the lower end of the first floating gate pattern 104 are inclined positively. Can compensate for inclination. In addition, since both the upper and lower edges of the first floating gate pattern 104 are rounded by the above-described high temperature annealing, stress due to volume expansion during trench sidewall oxidation is reduced, so that the lower portion of the first floating gate pattern 104 is reduced. Burj Beek is suppressed. Therefore, according to the present invention, since the bottom edge portion of the first floating gate pattern 104 is not bent outwardly, the floating gate finally obtained has a good profile.

Referring to FIG. 3E, an oxide film having excellent gap filling properties such as USG, O ₃ -TEOS USG, or high density plasma (HDP) oxide film is deposited to a thickness of about 5000 kPa by a chemical vapor deposition method to fill the trench 110. A gap buried oxide film 112 is formed. Preferably, a high density plasma oxide film is formed by generating a high density plasma using SiH ₄ , O ₂ and Ar gases as the plasma source. At this time, the trench 110 is embedded by improving the gap filling capability of the high density plasma oxide film so that cracks or voids are not formed in the trench 110.

A capping oxide film (not shown) made of PE-TEOS may be deposited on the gap buried oxide film 112 by a plasma method using Si (OC ₂ H ₅ ) ₄ as a source. Further, if necessary, annealing may be performed under a high temperature and inert gas atmosphere of about 800 to 1050 ° C. in order to densify the gap filling oxide film 112 to lower the wet etch rate for the subsequent cleaning process.

Subsequently, the gap buried oxide layer 112 is removed to the upper surface of the blocking layer pattern 108 by an etch back or chemical mechanical polishing (CMP) method to form a field oxide layer 114 in the trench 110. .

Referring to FIG. 3F, after the blocking layer pattern 108 is removed by a phosphate strip process, the exposed buffer layer pattern 106 is removed by dry etching to expose the first floating gate pattern 104. Subsequently, the substrate is cleaned with an etchant containing hydrofluoric acid for about 30 seconds in advance. As a result of the above-described process, the field oxide film 114 is wet etched by a predetermined thickness.

Referring to FIG. 3G, polysilicon or amorphous silicon is deposited on the floating gate pattern 104 and the field oxide film 114 to a thickness of about 1000 to 3000 kPa by a low pressure chemical vapor deposition method, and high concentration by a conventional doping method. By doping with an N-type impurity, a second conductive layer in electrical contact with the first floating gate pattern 104 is formed. The second conductive layer is formed to increase the area of the dielectric film to be formed in a subsequent step, and is preferably formed as thick as possible. According to the flash memory cell of the SA-STI structure, since the area of the first floating gate pattern 104 formed by self-alignment in the active region is smaller than the existing floating gate area, the second conductive layer is used to maintain a high coupling coefficient. Is deposited to increase the sidewall height of the floating gate to increase the area of the dielectric film.

Subsequently, the second conductive layer on the field oxide layer 114 is partially removed by a conventional photolithography process to form a second floating gate pattern 118. Then, floating gates of neighboring cells are separated from each other along the word line direction.

Referring to FIG. 3H, an ONO dielectric layer 120 is formed on the front of the resultant to maintain charge characteristics charged in the floating gate and to transfer a voltage of the control gate to the floating gate. The dielectric film 120 may be formed by a thermal oxidation process or may be formed by a low pressure chemical vapor deposition method. When the dielectric film 120 is formed by a low pressure chemical vapor deposition process, annealing is performed in an NO or N ₂ O atmosphere in order to obtain the same characteristics as the thermal oxide film.

Subsequently, the control gate layer 122 in which a polysilicon layer doped with N ⁺ type and a metal silicide layer such as tungsten silicide (WSix), titanium silicide (TiSix), and tantalum silicide (TaSix) are stacked on the dielectric layer 120. To form. Preferably, the polysilicon layer of the control gate layer 122 is formed to a thickness of about 1000 kPa, and the metal silicide layer is formed to a thickness of about 1000 to 1500 kPa.

Then, the control gate layer 122, the dielectric layer 120, and the second and first floating gate patterns 118 and 114 are sequentially dry-etched by a self-aligned gate etching process to stack the nonvolatile memory device. Complete the gate structure.

Since the sidewalls of the first floating gate pattern 104 do not have a positive slope during the dry etching process, the exposed portion of the first floating gate pattern 104 is completely removed, thereby providing a surface between the field oxide layer 116 and the active region. No silicon residue is formed at the boundary.

Example 2

4A to 4E are cross-sectional views illustrating a method of manufacturing a nonvolatile memory device to which a self-aligned shallow trench device isolation process according to a second embodiment of the present invention is applied.

Referring to FIG. 4A, an oxide film to be used as a gate oxide film (or a tunnel oxide film) of a cell transistor and a first conductive layer (not shown) to be used as a floating gate are sequentially formed on a semiconductor substrate 200 such as silicon.

Subsequently, a buffer film (not shown) is formed on the first conductive layer to have a thickness substantially the same as that of the oxide film. Preferably, the buffer film is formed by depositing an oxide film by low pressure chemical vapor deposition (LPCVD) or plasma-enhanced chemical vapor deposition (PE-CVD).

After forming a blocking film (not shown) made of nitride on the buffer film, a mask pattern 209 defining an active region is formed on the blocking film. Subsequently, the blocking layer, the buffer layer, the first conductive layer, and the oxide layer are sequentially dry-etched using the mask pattern 209 as an etching mask to form a gate oxide layer 202, a first floating gate pattern 204, and a buffer layer pattern. 206 and a blocking film pattern 208 are formed.

Subsequently, the trench 210 is formed by etching the upper portion of the substrate 200 adjacent to the first floating gate pattern 204 to a predetermined depth using the mask pattern 209. At this time, the anti-reflective layer arbitrarily formed above is removed and the mask pattern 209 is also etched by a predetermined thickness. According to the process of forming the trench 210, since the active region and the floating gate are simultaneously defined using one mask, self-alignment is obtained between the active region and the floating gate.

Referring to FIG. 4B, the sidewall of the first floating gate pattern 204 is rounded by annealing using hydrogen (H ₂ ) gas or argon (Ar) gas. Preferably, the annealing using the hydrogen (H ₂ ) gas is performed using about 1 to 30 liters of hydrogen gas at a temperature of about 750 to 950 ° C. and a pressure of about 10 to 40 torr.

As described above, when annealing is performed at a temperature of about 750 ° C. to 950 ° C., silicon existing in an edge portion of the first floating gate pattern 204 flows to a side surface or an upper surface thereof, and the first floating gate pattern is formed. The sidewall of 204 is rounded.

Referring to FIG. 4C, after the annealing described above, the inner surface of the trench 210 is treated in an oxidizing atmosphere to remove silicon damage caused by high energy ion bombardment during the trench etching process and to prevent leakage current. do. Then, the trench inner wall oxide layer 212 is formed along the bottom surface and sidewalls of the trench 210.

When the high temperature annealing is performed to form curvatures on the sidewalls of the first floating gate pattern 204 and the trench sidewall oxidation is performed, the sidewalls from the middle portion to the lower end of the first floating gate pattern 204 are positive. Inclination can be compensated for by inclination.

In addition, since both the upper and lower edges of the first floating gate pattern 204 are rounded by the above-described high temperature annealing, stress due to volume expansion during trench sidewall oxidation is reduced, so that the lower portion of the first floating gate pattern 204 is reduced. In this case, an oxidant (or an oxidizing gas) penetrates into the side surface of the gate oxide film 202, thereby suppressing a first buzz beneath the first floating gate pattern 204. At the same time, the second buzz beak that is generated in the upper portion of the first floating gate pattern 204 by the oxidant penetrating into the side of the buffer film pattern 206 under the blocking film pattern 208 is also suppressed. Thus, the sidewall of the first floating gate pattern 204 has an almost flat slope.

Referring to FIG. 4D, for example, a high density plasma (HDP) oxide film (not shown) is deposited by a chemical vapor deposition method to fill the trench 210, and then, to the upper surface of the stop layer pattern 208. The high density plasma oxide film is planarized by etching back or chemical mechanical polishing (CMP) to form a field oxide film 216 inside the trench 210.

Referring to FIG. 4E, after the blocking layer pattern 208 is removed by a phosphate strip process, the exposed buffer layer pattern 206 is removed by dry etching to expose the first floating gate pattern 204. In this case, the field oxide layer 216 may also be wet-etched by a predetermined thickness. Then, the field oxide layer 216 may be removed to prevent gate patterning defects that may be caused by a second buzz be formed on the first floating gate pattern 204 by the buffer layer pattern 206. Wet etching by a predetermined thickness. Then, the height of the field oxide layer 216 is lower than the height of the first floating gate pattern 204.

Subsequently, although not shown, the second floating gate pattern, the dielectric layer, and the control gate layer which are in contact with the first floating gate pattern 204 are sequentially formed in the same manner as the second embodiment of the present invention. An alignment gate etching process sequentially dry-etchs the control gate layer, the dielectric layer, and the second and first floating gate patterns to complete the stacked gate structure of the nonvolatile memory device.

Since the sidewalls of the first floating gate pattern 204 do not have a positive slope during the dry etching process, the exposed portions of the first floating gate pattern 204 are completely removed, thereby providing a surface between the field oxide layer 216 and the active region. No silicon residue is formed at the boundary.

Table 1 below shows data obtained by measuring the radius of curvature of each silicon pattern immediately after hydrogen annealing was performed on silicon patterns having a critical dimension (CD) of 0.15 μm.

Radius of curvature Application film quality (flow rate ratio of doping gas) Annealing temperature Undoped Polysilicon Low concentration doped polysilicon (SiH ₄ : PH ₃ = 1000: 8) Floating Gate of the Invention (SiH ₄ : PH ₃ = 1000: 19) Highly Doped Polysilicon (SiH ₄ : PH ₃ = 500: 50) Undoped Silicon Substrate 800 ℃ 300 to 350 Å 350-400 yen 200 to 250 Å 20-50 Å 100 to 140 Å 850 ℃ Overflow Overflow Overflow 250 to 300 Å 700 to 800 Å 900 ℃ Overflow Overflow Overflow Overflow Overflow

Referring to [Table 1], as the doping level of the polysilicon film is lowered, the increase in the radius of curvature due to hydrogen annealing increases, and the increase in the radius of curvature of the polysilicon film is greater than that of the silicon substrate. In addition, if the annealing temperature is too high, the sidewall rounding of the polysilicon film becomes excessive and the radius of curvature is over-flowed. Therefore, if the doping level of the polysilicon film used as the floating gate is adjusted, the desired curvature radius can be obtained by annealing performed at a temperature of about 800 ° C., so that the sidewalls of the floating gate are inclined positively without degrading the electrical characteristics of the device. It can be prevented to have.

As described above, according to the present invention, the sidewalls of the first conductive layer pattern (ie, the first floating gate pattern) are rounded by annealing using hydrogen (H ₂ ) or argon (Ar) gas before the sidewalls of the trench are oxidized. . Then, when the sidewalls of the trench are oxidized, the sidewalls from the middle portion to the bottom portion of the first floating gate pattern may be compensated for inclination with a positive slope. In addition, since both the upper and lower edges of the first floating gate pattern are rounded by the annealing, stress due to volume expansion during sidewall oxidation of the trench is reduced, thereby suppressing the burj beak. Accordingly, the sidewall of the first floating gate pattern may be prevented from having a positive slope, thereby preventing an electrical failure of the device caused by the gate residue during subsequent gate etching.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified without departing from the spirit and scope of the invention described in the claims below. And can be changed.

Claims (15)

Forming an oxide film on the semiconductor substrate; Forming a first conductive layer on the oxide film; Forming a stop layer on the first conductive layer; Etching the barrier layer, the first conductive layer, and the oxide layer using one mask to form an oxide layer pattern, a first conductive layer pattern, and a barrier layer pattern; Etching the upper portion of the substrate adjacent to the first conductive layer pattern using the mask to form a trench; Performing annealing to round sidewalls of the first conductive layer pattern; Oxidizing an inner surface of the trench to form a trench inner wall oxide layer on the inner surface of the trench; And And forming a field oxide layer in the trench. The method of claim 1, wherein the annealing is performed using hydrogen (H ₂ ) gas. The method of claim 2, wherein the hydrogen gas is used in an amount of about 1 to 30 liters. The method of claim 2, wherein the annealing is carried out at a temperature of about 750 ~ 950 ℃ self-aligned shallow trench device isolation method. The method of claim 2, wherein the annealing is carried out at a pressure of about 10 to 40 torr. The method of claim 1, wherein the annealing is performed using argon (Ar) gas. The method of claim 1, further comprising forming a buffer film of an oxide on the first conductive layer before forming the nitride film. Forming a gate oxide film on the semiconductor substrate; Forming a first conductive layer for floating gate on the oxide film; Forming a stop layer on the first conductive layer; Patterning the stop layer, the first conductive layer, and the gate oxide layer using one mask to form a first floating gate pattern from the first conductive layer; Defining an active region on the substrate by etching the upper portion of the substrate adjacent the first floating gate pattern using the mask to form a trench aligned with the first floating gate pattern; Performing annealing to round sidewalls of the first floating gate pattern; Oxidizing an inner surface of the trench to form a trench inner wall oxide layer on the inner surface of the trench; Forming a field oxide film inside the trench; And And sequentially forming a dielectric film and a control gate layer on the first floating gate pattern. The method of claim 8, wherein the annealing is performed using hydrogen (H ₂ ) gas. 10. The method of claim 9, wherein the hydrogen gas is used in an amount of about 1 to 30 liters. The method of claim 9, wherein the annealing is performed at a temperature of about 750 ° C. to 950 ° C. 10. 10. The method of claim 9, wherein the annealing is performed at a pressure of about 10 to 40 torr. The method of claim 8, wherein the annealing is performed using argon (Ar) gas. The method of claim 8, further comprising forming a buffer film made of an oxide on the first conductive layer before forming the nitride film. The method of claim 8, wherein before the forming of the dielectric layer, Forming a second conductive layer for the floating gate on the first floating gate pattern and the field oxide layer; And And partially removing the second conductive layer on the field oxide layer to form a second floating gate pattern.