# Patent

## Title
Method for manufacturing semiconductor device

## Abstract

According to one embodiment, a method for manufacturing a semiconductor device includes forming a mask layer on a layer to be etched, the mask layer containing tungsten and boron, a composition ratio of the tungsten being not less than 30%, patterning the mask layer, and performing a dry etching to the layer to be etched using the mask layer being patterned, and forming a hole or a slit in the layer to be etched.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from Japanese Patent Application No.2015-119821, filed on Jun. 12, 2015; and U.S. patent application Ser. No. 15/179,387, filed on Jun. 10, 2016; the entire contents of all of which are incorporated herein by reference.
FIELD
Embodiments described herein relate generally to a method for manufacturing a semiconductor device.
BACKGROUND
For example, a technology for making a hole in a stacked body in which different types of materials are stacked repeatedly is required in a method for manufacturing a memory cell array having a three dimensional structure. As increasing a number of stacks for increasing bit density, a thickness of the stacked body increases, then, it is required to make a hole having a high aspect ratio. Because etching amount for mask increases in the etching for making a hole having a high aspect ratio, a mask configuration easily degrades. Degradation of the mask configuration affects configuration and size of the hole made in the stacked body.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic perspective view of a semiconductor device of an embodiment;
FIG. 2 is a schematic cross-sectional view of the semiconductor device of the embodiment;
FIG. 3 is an enlarged cross-sectional view of one portion of FIG. 2;
FIG. 4 to FIG. 20 are schematic cross-sectional views showing a method for manufacturing the semiconductor device of the embodiment;
FIG. 21 is a schematic cross-sectional view showing one example of a degradation in a mask configuration;
FIG. 22 is a graph showing measurement results of an etching rate of a film containing tungsten as a main component in a direction of 80° by argon ion;
FIG. 23 is a graph showing the relationship between the etching rate in the direction of 80° by argon ion and a bond number ratio of atoms in a film;
FIG. 24 is a graph showing the relationship between a crystal peak FWHM measured by 2θ/θ method of XRD analysis to a mask layer and circularity of a hole configuration of the mask layer;
FIG. 25 is a schematic view showing an incident angle of argon ion to a substrate;
FIG. 26 is a schematic view for describing a shoulder dropping of the mask;
FIG. 27 is a schematic view showing an example of a planar shape of the hole of the mask layer; and
FIG. 28 is a graph showing the relationship between a Young's modulus of the mask layer and a sputtering rate.



DETAILED DESCRIPTION
According to one embodiment, a method for manufacturing a semiconductor device includes forming a mask layer on a layer to be etched, the mask layer containing tungsten and boron, a composition ratio of the tungsten being not less than 30%, patterning the mask layer, and performing a dry etching to the layer to be etched using the mask layer being patterned, and forming a hole or a slit in the layer to be etched.
Embodiments will now be described with reference to the drawings. The same components are marked with the same reference numerals in the drawings.
The semiconductor device of the embodiment is a semiconductor memory device. FIG. 1 is a schematic perspective view of a memory cell array 1 in the semiconductor memory device of the embodiment.
In FIG. 1, two mutually-orthogonal directions parallel to a major surface of a substrate 10 are taken as an X-direction and a Y-direction; and a direction orthogonal to both the X-direction and the Y-direction is taken as a Z-direction (a stacking direction).
The memory cell array 1 includes the substrate 10, a stacked body 100 provided on the major surface of the substrate 10, multiple columnar portions CL, a conductive material LI, and upper layer interconnects provided above the stacked body 100. For example, bit lines BL and a source line SL are shown as the upper layer interconnects in FIG. 1.
The columnar portions CL are formed in circular columnar or elliptical columnar configurations extending in the stacking direction (the Z-direction) through the stacked body 100. The conductive material LI spreads in the X-direction and the stacking direction of the stacked body 100 (the Z-direction) between the upper layer interconnect and the substrate 10, and divide the stacked body 100 in the Y-direction.
The multiple columnar portions CL have, for example, a staggered arrangement. Or, the multiple columnar portions CL may have a square lattice arrangement along the X-direction and the Y-direction.
The multiple bit lines (e.g., metal film) BL are provided above the stacked body 100. The multiple bit lines BL are separated from each other in the X-direction, and each of the bit lines extends in the Y-direction.
The upper end of the columnar portion CL is connected to the bit line BL via a contact portion Cb. The multiple columnar portions CL, each of which is selected from each of regions (blocks) divided in the Y-direction by the conductive material LI, are connected to one common bit line BL.
FIG. 2 is a schematic cross-sectional view of the stacked body 100, the columnar portions CL, and the conductive material LI. FIG. 2 shows a cross-section parallel to the Y-Z plane in FIG. 1.
The stacked body 100 includes multiple conductive layers 70 and multiple insulating layers 40 stacked on the major surface of the substrate 10. The multiple conductive layers 70 are stacked in the Z-direction at a predetermined period with the insulating layer 40 interposed.
The conductive layer 70 is a metal layer containing at least one of tungsten (W) and molybdenum (Mo). The conductive layer 70 is a tungsten layer containing tungsten as a major component, or a molybdenum layer containing molybdenum as a major component. The insulating layer 40 contains, for example silicon oxide (SiO2) as a major component.
FIG. 3 is an enlarged cross-sectional view of one portion of FIG. 2.
The columnar portion CL includes a memory film 30, a semiconductor film 20, and an insulative core film 50. The semiconductor film 20 extends in a pipe-like configuration in the stacking direction (the Z-direction) through the stacked body 100. The memory film 30 is provided between the conductive layer 70 and the semiconductor film 20, and surrounds the semiconductor film 20 from an outer circumferential side. The core film 50 is provided on the inner side of the semiconductor film 20 having the pipe-like configuration.
The upper end of the semiconductor film 20 is electrically connected to the bit line BL via the contact portion Cb shown in FIG. 1.
The memory film 30 includes a tunneling insulating film 31 as a first insulating film, a charge storage film 32, and a blocking insulating film 34 as a second insulating film. The charge storage film 32, the tunneling insulating film 31, and the semiconductor film 20 extend to be continuous in the stacking direction of the stacked body 100. The blocking insulating film 34, the charge storage film 32, and the tunneling insulating film 31 are provided between the conductive layer 70 and the semiconductor film 20 in order from the conductive layer 70 side.
The tunneling insulating film 31 contacts the semiconductor film 20. The charge storage film 32 is provided between the blocking insulating film 34 and the tunneling insulating film 31.
The semiconductor film 20, the memory film 30, and the conductive layer 70 are included in a memory cell MC. The memory cell MC has a vertical transistor structure in which the conductive layer 70 surrounds the periphery of the semiconductor film 20 with the memory film 30 interposed.
In the memory cell MC having the vertical transistor structure, the semiconductor film 20 functions as a channel;
and the conductive layer 70 functions as a control gate (control electrode). The charge storage film 32 functions as a data storage layer that stores charge injected from the semiconductor film 20.
The semiconductor memory device of the embodiment is a nonvolatile semiconductor memory device that can freely and electrically erase/program data and can retain the memory content even when the power supply is OFF.
The memory cell MC is, for example, a charge trap memory cell. The charge storage film 32 has many trap sites that trap charge inside an insulative film. The charge storage film 32 includes, for example, a silicon nitride film.
The tunneling insulating film 31 works as a potential barrier when charge is injected from the semiconductor film 20 into the charge storage film 32, or when the charge stored in the charge storage film 32 is released into the semiconductor film 20. The tunneling insulating film 31 includes, for example, a silicon oxide film.
The blocking insulating film 34 prevents the charge stored in the charge storage film 32 from being released into the conductive layer 70. The blocking insulating film 34 includes, for example, a silicon oxide film. The blocking insulating film 34 prevents back-tunneling of electrons from the conductive layer 70 in an erasing operation.
The blocking insulating film 34 is provided also between the conductive layer 70 and the insulating layer 40. The blocking insulating film 34 contacts the lower surface of the insulating layer 40 immediately above the conductive layer 70, and the upper surface of the insulating layer 40 immediately below the conductive layer 70.
A blocking insulating film 34 between the conductive layer 70 and the charge storage film 32, and a blocking insulating film 34 between the conductive layer 70 and the insulating layer 40 are provided to be continuous as one body.
A nitride film 60 is provided between the conductive layer 70 and the blocking insulating film 34. The nitride film 60 includes, for example, a titanium nitride film. The nitride film 60 increases adhesion between the conductive layer 70 and the blocking insulating film 34. Also, the nitride film 60 prevents a diffusion of metal contained in the conductive layer 70 into the blocking insulating film 34 side. The nitride film 60 contacts the conductive layer 70 and the blocking insulating film 34. The nitride film 60 is provided continuously along the upper surface, lower surface and side surface of the conductive layer
The nitride film 60 and the blocking insulating film 34 are not provided between the side surface of the insulating layer 40 and the charge storage film 32. A cover insulating film 33 is provided between the side surface of the insulating layer 40 and the charge storage film 32. The cover insulating film 33 is, for example, a silicon oxide film.
As shown in FIG. 1, a drain-side selection transistor STD is provided at the upper end portion of the columnar portion CL, and a source-side selection transistor STS is provided at the lower end portion of the columnar portion CL. For example, the conductive layer 70 of the lowermost layer among the multiple conductive layers 70 functions as a control gate (control electrode) of the source-side selection transistor STS. For example, the conductive layer 70 of the uppermost layer among the multiple conductive layers 70 functions as a control gate (control electrode) of the drain-side selection transistor STD. Similarly to the memory cell MC, the drain-side selection transistor STD and the source-side selection transistor STS are the vertical transistors in which current flows in the stacking direction of the stacked body 100 (the Z direction).
The memory cells MC are provided between the drain-side selection transistor STD and the source-side selection transistor STS. The memory cells MC, the drain-side selection transistor STD, and the source-side selection transistor STS are connected in series via the semiconductor film 20, and are included in one memory string. For example, the memory strings have a staggered arrangement in a surface direction parallel to the X-Y plane; and the memory cells MC are provided three-dimensionally in the X-direction, the Y-direction, and the Z-direction.
As shown in FIG. 2, an insulating film 42 is provided on both side walls of the conductive material LI dividing the stacked body 100 in the Y-direction. The insulating film 42 is provided between the stacked body 100 and the conductive material LI. The insulating film 42 is not shown in FIG. 1.
The conductive material LI is a metal material containing, for example, tungsten as a main component. The upper end of the conductive material LI is connected to the source layer SL provided above the stacked body 100 shown in FIG. 1. As shown in FIG. 2, the lower end of the conductive material LI contacts the substrate 10. Also, the lower end of the semiconductor film 20 contacts the substrate 10. The substrate 10 is, for example, a conductive silicon substrate doped with an impurity. Accordingly, the lower end of the semiconductor film 20 is electrically connected to the source layer SL via the substrate 10 and the conductive material LI.
The films included in the columnar portion CL are formed inside the memory hole made in the stacked body 100. The memory hole is, for example, made by reactive ion etching (RIE). For increasing a storage capacity, it is required to form the memory cells in high density. For example, a diameter of the memory hole is required to be 100 nm or less, and a stacked number of the conductive layers 70 is required to be about several tens, and thus, the memory hole is to be a fine hole having extremely high aspect ratio.
As shown in FIG. 21, as etching for a layer 100 to be etched progresses, a corner portion (shoulder portion) adjacent to an opening portion of a mask layer 200 is sputtered by ion and is easily to be a tapered shape, generally in the RIE technology. Also, the sputtered mask material may be deposited on a side surface of the opening portion.
As increasing the thickness of the layer 100 to be etched due to further increase of the capacity, the aspect ratio of a hole H increases, and it is expected that making a hole having an appropriated configuration will be more difficult.
A method for making the memory hole will now be described with reference to FIG. 4 to FIG. 10.
As shown in FIG. 4, the stacked body 100 is formed on the substrate 10 as a layer to be etched. The substrate 10 is, for example, a monocrystalline silicon substrate.
The insulating layer (a second layer) 40 is formed on a major surface of the substrate 10; and a sacrificial layer (a first layer) 41 is formed on the insulating layer 40. The sacrificial layer 41 is a layer of a different type of material from the insulating layer 40. The processes of repeatedly stacking the insulating layer 40 and the sacrificial layer 41 are repeated multiple times, and the stacked body 100 including a plurality of insulating layers 40 and a plurality of sacrificial layers 41 are formed on the substrate 10.
For example, a silicon oxide film (SiO2 film) is formed as the insulating layer 40 by CVD (Chemical Vapor Deposition), and a silicon nitride film (SiN film) is formed as the sacrificial layer 41 by CVD. The sacrificial layer 41 is removed in a subsequent process, and the blocking insulating film 34, a nitride film 60 and the conductive layer 70 are formed in the gap (space) where the sacrificial layer 41 was removed.
The sacrificial layer 41 may be a layer having high etching selectivity with respect to the insulating layer 40 and is not limited to a silicon nitride film. For Example, a polycrystalline silicon film may be formed as the sacrificial layer 41 by CVD.
As shown in FIG. 5, a mask layer 81 is formed on the stacked body 100. A first intermediate layer 82 is formed on the mask layer 81. A resist 83 is formed on the first intermediate layer 82.
The mask layer 81 is a layer of a different type of material from the stacked body 100 (the insulating layer 40 and the sacrificial layer 41). The mask layer 81 contains tungsten (W), boron (B) and carbon (C). A composition ratio of tungsten is higher than the composition ratio of boron and the composition ratio of carbon in the mask layer 81. The composition ratio here is represented by an atomic percent.
The composition ratio of tungsten is higher than 50 atomic percent. For example, the composition ratio of tungsten is 60 atomic percent, the composition ratio of boron is 20 atomic percent, and the composition ratio of carbon is 20 atomic percent.
The mask layer 81 is formed, for example, by plasma CVD (Chemical Vapor Deposition). For example, inorganic based gas such as tungsten hexafluoride (WF6), tungsten hexachloride (WCl6), and tungsten hexacarbonyl (W(CO)6) is used as a tungsten source gas in the CVD.
Or, an organic based gas can be used as a tungsten source gas. For example, Bis (cyclopentadienyl) tungsten(IV) dihydride (C10H12W), Cyclopentadienyl tungsten (II) tricarbonyl hydride (C8H6O3W), Bis (tert-butylimino) bis (tert-butylamino) tungsten ((C4H9NH)2W(C4H9N)2), Tetracarbonyl (1,5-cyclooctadiene) tungsten (0)(C12H12O4W), Triamminetungsten (IV) tricarbonyl ((NH3)3W(CO)3), Tungsten (0) pentacarbonyl-N-pentylisonitrile ((CO)5WCN(CH2)4CH3), Bis (isopropylcyclopentadienyl) tungsten (IV) dihydride ((C5H4CH(CH3)2)2WH2), Bis (tert-butylimino) bis(dimethylamino) tungsten (VI)(((CH3)3CN)2W(N(CH3)2)2), Bis (butylcyclopentadienyl) tungsten(IV) diiodide (C18H26I2W), or Bis (cyclopentadienyl) tungsten (IV) dichloride (C10H10Cl2W) can be used as the organic based gas.
For example, diborane (B2H6), boron trifluoride (BF3), or pentaborane (B5H9) can be used as a boron source gas in CVD for forming the mask layer 81.
For example, propylene (C3H6), acetylene (C2H2), ethylene (C2H4), or methane (CH4) can be used as a carbon source gas in CVD for forming the mask layer 81.
The first intermediate layer 82 is a layer of different types of materials from the mask layer 81. The first intermediate layer 82 is, for example, an amorphous carbon layer containing amorphous carbon as a main component, a boron carbide layer containing boron carbide (BC) as a main component, a boron nitride layer containing boron nitride (BN) as a main component, a silicon oxide layer containing silicon oxide (SiO) as a main component, a silicon nitride layer containing silicon nitride (SiN) as a main component, or an amorphous silicon layer containing amorphous silicon as a main component. The first intermediate layer 82 is formed, for example, by plasma CVD.
A resist 83 is formed, for example, by a coating method. As shown in FIG. 6, multiple hoes 83a are made in the resist 83 by exposing and developing to the resist 83.
As shown in FIG. 7, the first intermediate layer 82 is patterned by RIE using the resist 83 having the holes 83a as a mask. Multiple holes 82a are made in the first intermediate layer 82. In case where the first intermediate layer 82 is a silicon oxide layer, the first intermediate layer 82 is etched using a gas containing fluorocarbon and a gas containing oxygen.
Further, as shown in FIG. 8, the mask layer 81 is patterned by RIE using the resist 83 and the first intermediate layer 82 as masks. Multiple holes 81a are formed in the mask layer 81. For example, a gas containing fluorine is used as an etching gas at this time. The resist 83 may be disappeared in the etching of the mask layer 81.
Then, as shown in FIG. 9, the stacked body 100 is patterned by RIE using the mask layer 81 as a mask. Multiple memory holes MH are made in the stacked body 100.
The stacked body 100 is etched by RIE using a gas containing fluorine (for example, a gas containing fluorocarbon or hydrofluorocarbon). The sacrificial layer 42 and the insulating layer 40 are etched continuously using the same etching gas without changing gases for etching the sacrificial layer 42 and the insulating layer 40. The first intermediate layer 82 may be disappeared in the etching of the stacked body 100.
According to the embodiment, the mask layer 81 is used as an etching mask for etching the stacked body 100. The mask layer 81 contains tungsten, boron and carbon. And the composition ratio of tungsten is higher than the composition ratio of boron and the composition ratio of carbon. A shoulder dropping (taper) at an opening end of the hole 81a hardly occurs in the etching of the stacked body 100 using such a mask layer 81.
Table 1 shows measurement results of etching rates of an argon ion with respect to films of various materials.



























WBC
WBC
WBC



W
B
C
WB
WC
BC
(W main)
(B main)
(C main)

























 0° etching rate
0.52
0.35
0.16
0.65
0.74
0.15
0.36
0.39
0.05


45° etching rate
0.48
0.74
0.75
0.97
1.04
0.69
0.37
1.35
1.21





[nm/min.]






In evaluation of Table 1, a 0°-etching rate and a 45°-etching rate were measured with respect to each of a W film, a B film, a C film, a WB film, a WC film, a BC film, a WBC film containing W as a main component, a WBC film containing B as a main component, and a WBC film containing C as a main component.
The W film is a single layer film of tungsten. The B film is a single layer film of boron. The C film is a single layer film of carbon. The WB film contains tungsten boride as a main component and does not substantially contain carbon. The WC film contains tungsten carbide as a main component and does not substantially contain boron. The BC film contains boron carbide as a main component and does not substantially contain tungsten. The WBC film containing W as a main component corresponds to the mask layer 81 of the embodiment described above, and is a film containing tungsten, boron and carbon in which the composition ratio of tungsten is higher than the composition ratio of boron and the composition ratio of carbon. The WBC film containing B as a main component is a film containing tungsten, boron and carbon in which the composition ratio of boron is higher than the composition ratio of tungsten and the composition ratio of carbon. The WBC film containing C as a main component is a film containing tungsten, boron and carbon in which the composition ratio of carbon is higher than the composition ratio of tungsten and the composition ratio of boron.
The 0°-etching rate shows a measurement result of the etching rate when the argon ion enters perpendicularly to surfaces of the films. The 45°-etching rate, as shown in FIG. 25, shows a measurement result of the etching rate when the argon ion enters from a direction inclined by 45 degree (45 degree direction) from a direction perpendicular to the surfaces of the films (0 degree direction).
In RIE, the etching rate depends on the incident direction (angle) of an ion. For example, the etching by the ion entering from the 45 degree direction tends to show a higher etching rate than the etching by the ion entering perpendicularly, and easily causes the shoulder dropping (taper) in the mask layer as shown in FIG. 21. Accordingly, the mask layer having a high etching resistance to the ion entering from 45 degree direction is effective for suppressing the shoulder dropping (taper) in the mask layer and the degradation of the hole configuration caused by the shoulder dropping.
The measurement results in Table 1 show that the etching rate of the WBC film containing W as a main component is the lowest among the measurement results of the 45°-etching rate.
This means that the shoulder dropping (taper) in the mask layer 81 can be suppressed by using the mask layer 81 that contains tungsten, born, and carbon, and in which the composition ratio of tungsten is higher than the composition ratio of boron and the composition ratio of carbon.
Therefore, according to the embodiment, such as plugging the hole 81a can be suppressed; the etching of the stacked body 100 in the substantially perpendicular direction to the major surface of the substrate 10 can progress. And it is easy to make the memory hole MH in which the fluctuation of the diameter in the depth direction is suppressed and a side wall has a straight configuration. The memory hole MH having an appropriate configuration can suppress, for example, the fluctuation in the characteristics of the memory cell in the stacking direction.
Also, the single layer film of tungsten (W film) is easily crystallized. The crystallized film has many crystal grain boundaries. In case where such a W film is used as the mask layer 81, there may be a possibility that the etching progresses along the crystal grain boundary and that fluctuation of the etching occurs due to the differences of the etching rate that depends on the direction of crystal. Therefore, micro unevenness that reflects the crystal grain boundary configuration is easily occurs in the side surface of the hole 81a. This may disturb to realize a fine patterning.
The mask layer 81 of the embodiment described above is substantially amorphous. Here, substantially amorphous layer is a layer of non-crystalline or micro-crystalline in which crystal grain size is less than 100 nm. Also, substantially amorphous layer may be a layer in which a broad diffraction intensity, or, halo peak can be observed in a diffraction measurement represented by an electron beam diffraction such as RHEED (Reflection High Energy Electron Diffraction), or an X-Ray diffraction, or a layer in which diffraction ray from intermetallic compound micro-crystalline due to imperfection of amorphous can be occurred. Further, the mask layer 81 may not be amorphous in it entirely, and the mask layer 81 may have a structure in which part of the crystalline thin film is amorphized.
The mask layer 81 is formed by CVD in a state that a wafer is heated; the temperature of the wafer at that time is 1000° C. or less, and the mask layer 81 is not substantially crystallized at that temperature. After the film formation, the film may be reformed by performing general heat and electromagnetic wave process such as furnace annealing, RTA (rapid thermal anneal), FLA (flash lamp anneal), microwaves annealing, UV (ultraviolet) radiation, EB (electron beam) radiation to the mask layer 81.
The mask layer 81 can be formed by sputtering method. The CVD having film forming speed faster than sputtering method is excellent in mass productivity as a method for forming the mask layer 81.
Tungsten that is a metal contained as a main component in the mask layer 81 belongs to a group having a lower sputtering rate due to ion among metals commonly used in semiconductor process. From the same view point, in addition to tungsten, tantalum, zirconium, hafnium, molybdenum, niobium, ruthenium, osmium, rhenium, or iridium can be a metal contained as a main component in the mask layer 81.
In other words, the mask layer 81 contains boron, carbon and at least one type of metal selected from a group including tungsten, tantalum, zirconium, hafnium, molybdenum, niobium, ruthenium, osmium, rhenium, and iridium. Also, the composition ratio of the metal is higher than the composition ratio of boron and the composition ratio of carbon in the mask layer 81.
The mask layer 81 containing the above metal other than tungsten with higher in composition ratio than boron and carbon shows the same result as shown in Table 1. In other words, the mask layer 81 that contains boron, carbon and at least one type of metal selected from a group including tungsten, tantalum, zirconium, hafnium, molybdenum, niobium, ruthenium, osmium, rhenium, and iridium, and the composition ratio of the metal is higher than the composition ratio of boron and the composition ratio of carbon has low 45° etching rate so that shoulder dropping is hardly occurs.
Tungsten, tantalum, zirconium, hafnium, molybdenum, and niobium are desirable among these metals, due to experiences applying to the semiconductor process, and low possibility of fatal contamination risk.
Among them, in particular, tungsten is used for the conductive layer (control electrode) 70 and the conductive material LI in the memory cell MC due to low resistance and high melting point. Therefore, process control and management become easier and mass productivity is expected to be improved by selecting tungsten as a metal contained in the mask layer 81 similarly.
If elements due to the source gas used at CVD for forming the mask layer 81 are contained in the mask layer 81 other than those metals, boron, and carbon, the elements may be trace amount and do not affect to the characteristics of the mask layer 81.
In case where consumption amount of resist 83 is large with respect to etching gas used for patterning the mask layer 81, it may be considered to increase film thickness of the resist 83. However, increasing the thickness of the resist 83 is limited by a resolution limit of lithography. Therefore, as shown in the embodiment above, it is desirable that the first intermediate layer 82 is formed between the mask layer 81 and the resist 83, and the first intermediate layer 82 is used for the process mask for mask layer 82.
Also, as shown in FIG. 20, by forming a film 85 containing metal nitride between the stacked body 100 and the mask layer 81, adhesion between the stacked body 100 and the mask layer 81 can be increased. A nitride film of the same metal (for example, tungsten) as the metal (for example, tungsten) contained in the mask layer 81 can be used for the film 85.
Or, adhesion between the mask layer 81 and the stacked body 100 can be increased by further containing nitrogen in the mask layer 81 itself.
Or, the insulating layer 40 of the stacked body 100 is a silicon oxide film and the sacrificial layer 41 is a silicon nitride film; both are chemical compounds containing silicon. Therefore, adhesion between the mask layer 81 and the stacked body 100 can be increased by further containing silicon in the mask layer 81.
As shown in FIG. 18, a second intermediate layer 84 can be formed between the stacked body 100 and the mask layer 81. The second intermediate layer 84 is a layer of a material different from the stacked body 100 (the insulating layer 40 and the sacrificial layer 41) and the mask layer 81. The second intermediate layer 84 is, for example, an amorphous carbon layer containing amorphous carbon as a main component, a boron carbide layer containing boron carbide (BC) as a main component, a boron nitride layer containing boron nitride (BN) as a main component, or an amorphous silicon layer containing amorphous silicon as a main component. The second intermediate layer 84 is formed, for example, by plasma CVD.
The second intermediate layer 84 functions as a mask for processing the stacked body 100 in case where the mask layer 81 does not have an enough thickness as an etching mask for etching the stacked body 100. In case where there is a possibility of increasing film stress due to increasing the film thickness of the mask layer 81 containing metal, there may be a possibility that it is difficult to increase the film thickness of the mask layer 81. The second intermediate layer 84 not containing the metal can compensate insufficiency of the thickness of the mask layer 81 as a mask for processing the stacked body 100 without increasing the film thickness of the mask layer 81 itself.
Also, if the second intermediate layer 84 formed between the stacked body 100 and the mask layer 81 can be easily peeled off from the stacked body 100, the mask layer 81 on the second intermediate layer 84 may be lifted off and can be easily removed from a surface of the stacked body 100.
As shown in FIG. 19, the second intermediate layer 84 is formed between the stacked body 100 and the mask layer 81, and also, the first intermediate layer 82 is formed between the mask layer 81 and the resist 83.
As shown in FIG. 10, multiple memory holes MH are made in the stacked body 100 by dry etching (RIE) using the mask layer 81 described above. The memory hole MH extends in the stacking direction of the stacked body 100 (the Z-direction), pierces the stacked body 100 and reaches the substrate 10.
As shown in FIG. 11 and FIG. 12 that shows an enlarged view of one portion of FIG. 11, a stacked film 80, the semiconductor film 20, and the core film 50 are formed inside the memory hole MH. As shown in FIG. 12, the stacked film 80 includes the cover insulating film 33, the charge storage film 32, and the tunneling insulating film 31.
First, for example, a silicon oxide film (SiO2 film) is formed on the side surface of the memory hole MH as the cover insulating film 33 by ALD (Atomic Layer Deposition). The cover insulating film 33 is also formed on a bottom of the memory hole MH.
For example, a silicon nitride film (SiN film) is formed on the inner side of the cover insulating film 33 as the charge storage film 32 by ALD. The charge storage film 32 may be a film which can trap charge, and for example, hafnium oxide film (HfOx film), aluminum oxide film (AlOx film), or aluminum nitride film (AlN film) can be used for the charge storage film 32. Or, the charge storage film 32 may be a stacked film including at least two of a silicon nitride film, a hafnium oxide film, an aluminum oxide film, and an aluminum nitride film.
For example, a silicon oxide film (SiO2 film) is formed on the inner side of the charge storage film 32 as tunneling insulating film 31 by ALD.
Cavity remains on the inner side of the stacked film 80, and a portion of the stacked film 80 deposited on the bottom of the memory hole MH below the cavity is removed, for example, by RIE. Then, the semiconductor film 20 is formed on the side surface of the tunneling insulating film 31.
As shown in FIG. 11, the semiconductor film 20 is also formed on the bottom of the memory hole MH and contacts to the substrate 10. For example, a silicon film is formed as the semiconductor film 20 by CVD.
Cavity remains on the inner side of the semiconductor film 20, and for example, a silicon oxide film (SiO2 film) is buried in the cavity as the core film 50.
Then, as shown in FIG. 13, a slit 91 is made in the stacked body 100. The slit 91 is also made by the similar RIE using the similar mask layer 81 used for making the memory hole MH. The slit can be formed in the stacked body 100 by the RIE using the mask layer 81 having not a hole but a slit. Also at this time, the shoulder dropping in the mask layer 81 can be suppressed.
The slit 91 extends in the stacking direction of the stacked body 100 (the Z-direction), pierces the stacked body 100 and reaches the substrate 10. Also, the slit 91 extends into the page surface (the X-direction) and divides the stacked body 100 in the Y-direction.
Then, the sacrificial layer 41 is removed by wet etching using, for example, a hot phosphoric acid supplied through the slit 91. As shown in FIG. 14, a gap (or a space) 92 is made between the insulating layers 40 by the removal of the sacrificial layer 41. The cover insulating film 33 protects the charge storage film 32 during the etching.
Further, a portion of the cover insulating film 33 is also removed by the wet etching. The cover insulating film 33 facing the gap 92 is removed as shown in the enlarged view of FIG. 15, and the charge storage film 32 is exposed in the gap 92.
By controlling the etching rate for removing the cover insulating film 33 lower than the etching rate for removing the sacrificial layer 41, etching damage to the charge storage film 32 can be suppressed.
Then, the blocking insulating film 34 is formed on an inner wall of the gap 92 as shown in FIG. 16. For example, the silicon oxide film (SiO2 film) is formed as the blocking insulating film 34 by ALD. Or, the blocking insulating film 34 may be a stacked film of a silicon oxide film and a silicon nitride film. Or, the blocking insulating film 34 may be a high-k film such as an aluminum oxide film (AlOx film), a hafnium oxide film (HfOx film), a lanthanum aluminum oxide film (LaAlOx film). Further, the blocking insulating film 34 may be a stacked film of the high-k film recited above and a silicon oxide film. The high-k film recited above can be used for the tunneling insulating film 31.
The blocking insulating film 34 is formed conformally along the upper surface and lower surface of the insulating layer 40 and the charge storage film 32, exposed in the gap 92.
Then, as shown in FIG. 17, a titanium nitride film (TiN film) 60 is formed on the inner side of the blocking insulating film 34, for example, by CVD. The titanium nitride film 60 is formed conformally along the blocking insulating film 34.
The gap 92 remains on the inner side of the titanium nitride film 60. The conductive layer 70 is formed inside the gap 92 as shown in FIG. 3.
A tungsten layer is buried in the gap 92 as the conductive layer 70, for example, by CVD using tungsten fluoride (WF6) gas. Or, a molybdenum layer is buried in the gap 92 as the conductive layer 70, for example, by CVD using molybdenum fluoride (WMo6) gas.
By interposing the titanium nitride film 60 between the blocking insulating film 34 and the conductive layer 70, adhesion between the conductive layer 70 and the titanium nitride film 60 can be increased compared to a case where the conductive layer 70 is formed on the blocking insulating film 34 directly.
Also, the titanium nitride film 60 functions as a barrier layer for preventing the diffusion into the memory film 30 side of the metal (tungsten or molybdenum) contained in the conductive layer 70.
For example, a nitride film such as tantalum nitride film (TaN film), tantalum aluminum nitride film (TaAlN film), titanium silicon nitride film (TiSiN film) or the like other than the titanium nitride film can be interposed between the blocking insulating film 34 and the conductive layer 70.
The source gas for the conductive layer 70 enters the gap 92 through the slit 91 shown in FIG. 14. At that time, a material film (a metal film) of the conductive layer 70 is deposited on the side surface 40a of the insulating layer 40 exposed in the slit 91. Then, the metal film on the side surface 40a of the insulating layer 40 is removed, and a short through the metal film between the conductive layers 70 of different layers can be blocked.
The titanium nitride film 60 formed conformally along the inner wall of the gap 92 before forming the conductive layer 70 is also formed on the side surface 40a of the insulating layer 40, and the titanium nitride films 60 of the different layers continue via a portion of the titanium nitride film 60 formed on the side surface 40a of the insulating layer 40. Because the conductive layer 70 formed after forming the titanium nitride film 60 contacts the titanium nitride film 60, between the conductive layers 70 of the different layers are shorted through the titanium nitride film 60 that is conductive. Therefore, the titanium nitride film 60 formed on the side surface 40a of the insulating layer 40 is also removed so as to divide the connection of the titanium nitride films 60 in the vertical direction (the stacking direction). Thereby, the short between the conductive layers 70 of the different layers through the titanium nitride film 60 are blocked.
Then, the conductive material LI is formed inside the slit 91 with the insulating film 42 interposed. The insulating film 42 is formed conformally on a side surface and a bottom of the slit 91. The insulating film 42 at the bottom of the slit 91 is removed, for example, by RIE, and the substrate 10 is exposed at the bottom of the slit 91. Then, the conductive material LI is formed on the inner side of the insulating film 42 in the slit 91, and the lower end of the conductive material LI contacts the substrate 10. Further, subsequently, the bit lines BL and the source line SL shown in FIG. 1 and the like are formed.
Other embodiments of the mask layer 81 will now be described.
The mask layer 81 containing tungsten as a main component described below is also formed, for example, on the stacked body 100 as the layer to be etched. As shown in FIG. 5, a first intermediate layer 82 is formed on the mask layer 81.
As shown in FIG. 8, the mask layer 81 is patterned. As shown in FIG. 9 and FIG. 10, the hole MH or the slit is formed in the staked body 100 by RIE using the patterned mask layer 81 as a mask.
As shown in FIG. 18, a second intermediate layer 84 may be formed between the stacked body 100 and the mask layer 81.
As shown in FIG. 19, the second intermediate layer 84 is formed between the stacked body 100 and the mask layer 81, and a first intermediate layer 82 may be formed between the mask layer 81 and the resist 83.
As shown in FIG. 20, a film 85 containing a metal nitride may be formed between the stacked body 100 and the mask layer 81.
FIG. 22 shows the measurement results of the etching rate of the film by argon ion.
As shown in FIG. 25, an argon ion is incident on the film formed on the substrate 10 in a direction inclined by 80° from a normal line of the substrate 10. A sputtering rate of the film in this case is represented by 80° sputtering rate.
A graph of a triangular in FIG. 22 shows composition ratios (atomic percent) of tungsten (W), boron (B), and carbon (C) in the film. The composition ratio (percent) is represented by an atomic percent below. A vertex W of the triangle represents a tungsten single layer film with a W composition ratio of 100%, a vertex B represents a boron single layer film of a B composition ratio of 100%, and a vertex C represents a carbon single layer film of a C composition ratio of 100%.
Points on a line WB represent a WB film containing tungsten and boron and not substantially containing carbon. A line BC represents a BC film containing boron and carbon and not substantially containing tungsten. A line WC represents a WC film containing tungsten and carbon and not substantially containing boron.
A region on the inner side of the triangle represents a WC film containing tungsten, boron, and carbon.
It has been found by the inventors that, as shown in FIG. 26, if a film 181 containing tungsten as a main component is etched for a long time by RIE method, a corner between an upper surface of the film 181 and a side surface of an opening (or hole) 181a shoulder-drops, and the side surface of the opening 181a tends to be formed in a tapered configuration inclined with about 80° from a horizontal direction to the substrate. The hard mask, which is a rectangle at the beginning, gradually shoulder drops, thereby forming a taper as shown by a dotted line in FIG. 23. For the taper having this angle, in the RIE method, most of the ions are incident in a direction perpendicular to the substrate (stacking direction of the stacked body 100). Thus, etching by ions incident at an angle as shown in FIG. 25 occurs on the tapered surface.
In this way, the etching rate of this tapered portion correlates to an etching resistance by an incident ion from the above angle (direction) of 80°. If the etching rate of the tapered portion is high, shoulder-drop of the mask proceeds and for example, a process selection ratio to the stacked body which is the layer to be etched results in being small. Furthermore, a distance a between adjacent openings 181a (mask back alignment) becomes small. This increases the incident ion in the inclined direction to the stacking direction of the stacked body 100, and can decrease configuration controllability of the hole MH formed in the stacked body 100.
Therefore, the mask layer is desired to have a high etching resistance to the incident ion in 80° direction.
Seeing the measurement results in FIG. 22, it is found that the WB film having the W composition ratio of not less than 30%, the WC film having the C composition ratio of less than 50%, and the WBC film having the W composition ratio of not less than 30% and having the C composition ratio of less than 50% have the etching resistance in 80° direction equal to or greater than the tungsten single layer film.
That is, a film having a composition ratio of a region having a higher W composition ratio than the curve “a” is desired. The curve “a” connects a point of the C composition ratio of 50% on the WC line to a point of the W composition ratio of 30% on the WB line.
It has been found that the WB film having the W composition ratio of not less than 40%, the WC film having the C composition ratio of less than 40%, and the WBC film having the W composition ratio of not less than 40% and the C composition ratio of less than 40% have the higher etching resistance in 80° direction than the tungsten single layer film.
Therefore, a film having a composition ratio of a region having a higher W composition ratio than the curve b is more desired for the mask layer 81. The curve b connects a point of the C composition ratio of 40% on the WC line to a point of the W composition ratio of 40% on the WB line.
An etching selection ratio of the tungsten single layer film to the stacked body having alternately stacked silicon nitride film and silicon oxide film is higher than an etching selection ratio of a carbon hard mask to the above stacked body by approximately 3 to 4 times.
In the case of the film having the higher etching resistance in 80° direction than the tungsten single layer film, the process selection ratio can be further improved and reduction of the back alignment can be suppressed.
By using the WB film having the W composition ratio of not less than 30%, the WC film having the C composition ratio of less than 50%, and the WBC film having the W composition ratio of not less than 30% and having the C composition ratio of less than 50% as the mask layer 81, the shoulder-drop (taper) of the mask layer 81 can be more suppressed than the mask layer of the tungsten single layer film to form an adequate configuration hole MH.
FIG. 23 shows the relationship between a 80°-etching rate of the above argon ion and a bond number ratio of atoms in a film.
Tungsten-tungsten (W—W) bond, tungsten-born (W—B) bond, and tungsten-carbon (W—C) bond are detected by XPS (X-ray photoelectron spectroscopy) of the film.
The triangle of FIG. 23 shows a ratio of W—W bond number, a ratio of W—B bond number, and a ratio of W—C bond number to a total of the W—W bond number, the W—B bond number, and the W—C bond number.
In the triangle of FIG. 23, vertexes marked with W—W, W—B, W—C show a film of the W—W bond number ratio of 100%, a film of the W—B bond number ratio of 100%, and a film of the W—C bond number ratio of 100%, respectively. The film of the W—W bond number ratio of 100% is the tungsten single layer film.
A point connecting W—W and W—B on the straight line represents the WB film. A point connecting W—W and W—C on the straight line represents the WC film.
A region on the inner side of the triangle represents a film including W—W bond, W—B bond, and W—C bond.
The film is etched by approximately 5 nm by sputtering using argon ion in vacuum and impurities in a film surface layer are removed, and thereafter in-situ XPS analysis is performed.
The bond number ratio is calculated as follows.
The W composition ratio is calculated from an integrated value in a signal profile near a bond energy corresponding to 4f orbital of tungsten (W) obtained from the XPS analysis. The B composition ratio is calculated from an integrated value of a bond energy peak corresponding to 1s orbital of born (B). The C composition ratio is calculated from an integrated value in a signal profile near a bond energy corresponding to 1s orbital of carbon (C) obtained from the XPS analysis.
The details of the calculation will be described below.
The composition ratio of tungsten included in W—W bond, W—B bond, or W—C bond is calculated from an integrated value of the signal profile of the bond energy corresponding to W—W bond, W—B bond, or W—C bond existing near bond energy of 31 eV, 34 eV in the bond energy signal profile of 4f orbital of tungsten.
With respect to W—W bond, W—B bond, W—C bond in the bond energy signal profile of 4f orbital, separation of bond energy is difficult and is hard to discuss each bond.
Next, the bond energy of boron and the bond energy of carbon are confirmed.
With respect to boron, B—B bond near the bond energy 187 eV of the bond energy signal profile of 1s orbital, W—B bond near the bond energy 188 eV of is orbital, and B—C bond near the bond energy 189 eV of 1s orbital exist. The integrated value is separated by fitting, and the composition ratio of boron included in W—B bond is calculated from an integrated value of the signal profile of the bond energy corresponding to W—B bond.
With respect to carbon, the composition ratio of carbon included in W—C bond is calculated from a signal profile integrated value near the bond energy of about 283.3 to 283.5 eV corresponding to W—C bond in the bond energy signal profile of 1s orbital.
A W═W bond amount is determined by subtracting a W—B bond amount and a W—C bond amount from a compound peak of 4f orbital of tungsten initially determined.
Next, the ratio of W—W bond number, the ratio of W—B bond number, and the ratio of W—C bond number are calculated using the W composition ratio belonging to the W—W bond, the W—B bond or the W—C bond, the B composition ratio (atomic percent) belonging to the W—B bond, and the C composition ratio belonging to the W—C bond, W—W bond, W—B determined initially.
At this time, it is assumed that one W atom and one W atom, one W atom and one B atom, one W atom and one C atom are bonded by 1:1 to form one bond.
(W composition ratio belonging to the W—W bond) is calculated as “(Composition ratio of W belonging to W—W bond)=(W composition ratio belonging to W—W bond or W—B bond or W—C bond)−(B composition ratio belonging to W—B bond)−(C composition ratio belonging to W—C bond)”.
Approximate the proportion of the number of bonds of the W—W bond, the W—B bond, and the W—C bond so as to be a positive value as [Number of W—B bonds]: [Number of W—B bonds]:[W—C bond number]=[(W composition ratio belonging to W—W bond)/2]:[B composition ratio belonging to W—B bond]:[C composition ratio].
In this definition, it is assumed that two atoms combine to form one bond, such as W—W, W—B, and W—C, and three. It is assumed that it does not include a state in which three or more atoms are bonded like W—W—W, W—B—W, B—W—B, W—C—W, C—W—C. Actually, there are states where three or more atoms are bonded. However, in the XPS analysis, it is impossible to distinguish between W—W and W—W—W, W—C and W—C—W, W—B and W—B—W. Thus, we make assumptions as described above and uniquely determine the calculation method.
FIG. 23 is a plot of the etching rate of each film for the ratio of the number of bonds for the W—W bond, the W—B bond, and the W—C bond determined in this way.
In FIG. 23, the total value of the number of W—W bonds, the number of W—B bonds, and the number of W—C bonds is taken as 100%. In FIG. 23, the number of B—B bonds and the number of B—C bonds are not included.
It is known that for those having a composition ratio of W of 40% or more, it is almost composed only of W—W bond, W—B bond, and W—C bond.
Incidentally, it was found that the B—C bond was included in the one having the W composition ratio of 30%. However, it is confirmed that there is no contradiction in the conclusion even if discussion is made focusing only on W—W bond, W—B bond, and W—C bond as shown in FIG. 23.
Seeing the measurement results in FIG. 23, it is found that a WB film, a WBC film having a ratio of W—W bond number of not less than 20% and a ratio of W—C bond number of not more than 50%, and a WC film having a ratio of W—W bond number of not less than 20% and a ratio of W—C bond number of not more than 50% have the etching resistance in 80° direction equal to or greater than the tungsten single layer film.
In the film included in all ranges of the above region of FIG. 23, the composition ratio of tungsten is 30% or more, and the composition ratio of carbon is less than 50%.
Therefore, a WB film having the tungsten composition ratio of not less than 30% and the carbon composition ratio of less than 50% is desired for the mask layer 81.
Alternatively, a WBC film having the tungsten composition ratio of not less than 30%, the carbon composition ratio of less than 50%, the ratio of W—W bond number of not less than 20% and the ratio of W—C bond number of not more than 50% is desired for the mask layer 81.
Alternatively, a WC film having the tungsten composition ratio of not less than 30%, the carbon composition ratio of less than 50%, the ratio of W—W bond number of not less than 20% and the ratio of W—C bond number of not more than 50% is desired for the mask layer 81.
Among the peaks of the crystal observed at 2θ being 30° or more and 50° or less, as measured by the 2θ/θ method of XRD (X-ray diffraction) analysis on the mask layer 81, it is defined as a representative full width at half value maximum (FWHM) of the evaluation material. FIG. 24 shows the relationship between a crystal peak full width at half maximum (FWHM) and circularity of the hole configuration of the mask layer 81.
The mask layer 81 is a WB layer containing tungsten and boron and not containing substantially carbon, a WC layer containing tungsten and carbon and not containing substantially boron, or a WBC layer containing tungsten, boron and carbon.
The circularity is represented by 4 nS/L2.
FIG. 27 is a schematic view showing an example of a planar shape of the hole 81a of the mask layer 81.
S represents an area of the hole 81a, and L represents a circumference of the hole 81a. 
As the circularity approaches 1, the planar shape of the hole 81a is close to a perfect circle.
Increase of the crystal peal FWHM shows approach from microcrystals to amorphous.
When no peak is observed and the crystal peak FWHM is infinite, or the crystal FWHM is in a level of background, it is considered to be amorphous.
Seeing the results of FIG. 24, it is found that as the crystal peak FWHM becomes large, the mask hole approaches a perfect circle.
It is considered that, from the inventor's experience, if the circularity of the memory hole is not less than 0.8, influence to characteristics of the memory cell is small.
When the crystal peak FWHM is 0.5°, the circularity of about 0.8 is obtained.
Therefore, a material having the crystal peak FWHM of not less than 0.5° is desired for a material of the mask layer 81.
When the crystal peak FWHM is 0.5°, a crystal grain diameter is calculated to be about 20 nm by using Scheller's formula [D=(Kλ)/(β cos θ)]. Therefore, if the grain diameter of the crystal of the mask layer 81 is not more than 20 nm, the hole having high circularity can be formed.
D is a crystal grain diameter, K is a Scheller constant, λ is measured X-ray wavelength, β is a peak FWHM (rad), and θ is a Bragg angle of a diffraction line. The calculation is performed assuming that K=1, a characteristic X-ray wavelength of Kα of cu used at XRD measurement is λ=1.54 angstroms, and 2θ is not less than 30° and not more than 50°.
When the crystal peak FWHM is 0.8°, the crystal grain diameter is about 10 nm, and when the crystal peak FWHM is 3°, the crystal grain diameter is about 3 nm.
The circularity is saturated when the crystal peak FWHM is not less than 3°.
If the mask layer 81 is made of microcrystals, HER (hole edge roughness) of the hole side surface can be reduced as well.
FIG. 28 is a graph showing the relationship between a Young's modulus (lateral axis) of the mask layer 81 containing tungsten as a main component and a sputtering rate (vertical axis).
Argon ion is incident on the mask layer 81 formed on the substrate at an incident angle θ shown in FIG. 25. The incident angle θ is set to be 0°, 30°, 45°, 60°, 70°, 80°.
The mask layer 81 is formed by PVD (physical vapor deposition) or PECVD plasma enhanced chemical vapor deposition). The Young's modulus of the mask layer 81 is measured by a nano-indentation method.
A Berkovich type trigonal pyramid indenter (Berkovich indenter) made of diamond tip is pressed into a material surface, and a load applied to the indenter and a projected area A under the indenter are measured. A load-variation curve is obtained by the continuous stiffness measurement method like this. The load-variation curve is formed of a load curve when the indenter is pressed into the sample and a load removal curve when drawing up. In order to calculate the Young's modulus, firstly, a stiffness modulus Er of the indenter and the sample is determined from contact stiffness S corresponding to a slope of the load removal curve of the load-variation curve, the projected area A, and the following formula.

S=2/π1/2×Er×A1/2 

The modulus (Young's modulus) Es of the sample is calculated using this formula.

Er=[(1−vs2)/Es+(1−vi2)/Ei]−1 

Ei is the modules of the indenter, vi is a Poisson ratio of the indenter, and vs is a Poisson ratio of the sample. The calculation is performed assuming that the maximum value of the Poisson ratio is 0.5. Poisson's ratio has a defined maximum of 0.5. The Poisson's ratio of industrial materials lies between approximately 0.15 and 0.35. The error given to the Young's modulus even if the numerical value of 0.15-0.35 is changed is the influence degree of the measurement error range (±5%). Here, it is calculated by adopting 0.25 which is the average value of Poisson's ratio of industrial material.
As shown in FIG. 28, it has been found that the sputtering rate gradually decreases to near 170 GPa in Young's modulus, has a bottom when the Young's modulus is around 180 GPa, and if the Young's modules is greater than 180 GPa, the sputtering rate tends to increase somewhat from the bottom.
A film having a low sputtering rate is desired for the mask layer 81 having a high resistance to the shoulder-drop. It can be said from FIG. 28 that the film like this is a film having a Young's modulus greater than 170 GPa.
It has been known that, among films containing tungsten as a main component, the tungsten single layer film has the maximum Young's modulus, and the selection ratio to the stacked body 100 at RIE is good. However, as described previously, micro irregularity reflecting the shape of crystal grain boundary is easy to appear on the side surface of the mask hole.
The Young's modulus is expressed by E=σ/ε (ε: strain, σ: stress), and represents a change rate of elasticity of a crystal. The Young's modulus can be considered to be a resistance to a change of an atomic distance microscopically. The sputtering can be considered to be a non-elastic state occurring over the resistance, and the Young's modulus is effective as one index of the sputtering.
Like the mask layer 81 of the embodiment, the Young's modulus of a film formed of microcrystals in which born or carbon is added to main component tungsten, or boron and carbon are added, and W—W bond, W0B bond, W—C bond or the like are mixed is not the Young's modulus determined by the specific lattice structure. However, it is possible to considered the Young's modules as the index showing an average bond strength of the whole film which is composed of microcrystalline or amorphous material, and the Young's modulus like this is reasonable as one index showing characteristics of physical sputtering included in a film.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modification as would fall within the scope and spirit of the inventions.

## Claims

1. A method for manufacturing a semiconductor device, comprising:
forming a mask layer on a layer to be etched, the mask layer containing tungsten and boron, a composition ratio of the tungsten being not less than 30%;
patterning the mask layer; and
performing a dry etching to the layer to be etched using the mask layer being patterned, and forming a hole or a slit in the layer to be etched.

2. The method according to claim 1, wherein
a ratio of tungsten-tungsten (W—W) bond number in the mask layer is not less than 20%.

3. The method according to claim 1, wherein
the mask layer further contains carbon, and
a ratio of tungsten-carbon (W—C) bond number in the mask layer is not more than 50%.

4. The method according to claim 1, wherein
the mask layer further contains carbon, and
a composition ratio of the carbon in the mask layer is less than 50%.

5. The method according to claim 1, wherein
a Young's modulus of the mask layer is not less than 170 GPa.

6. The method according to claim 1, wherein
the layer to be etched contains silicon, and
the layer to be etched is etched using a gas containing fluorine.

7. The method according to claim 1, wherein
the layer to be etched is a stacked body including a plurality of first layers and a plurality of second layers alternately stacked, the second layers being layers of a different type of material from the first layers.

8. The method according to claim 1, further comprising:
forming a film containing a metal nitride provided between the layer to be etched and the mask layer.

9. A method for manufacturing a semiconductor device, comprising:
forming a mask layer on a layer to be etched, the mask layer containing tungsten and carbon, a composition ratio of the carbon being less than 50%;
patterning the mask layer; and
performing a dry etching to the layer to be etched using the mask layer being patterned, and forming a hole or a slit in the layer to be etched.

10. The method according to claim 9, wherein a ratio of tungsten-tungsten (W—W) bond number in the mask layer is not less than 20%.

11. The method according to claim 9, wherein
a ratio of tungsten-carbon (W—C) bond number in the mask layer is not more than 50%.

12. The method according to claim 9, wherein
a Young's modulus of the mask layer is not less than 170 GPa.

13. The method according to claim 9, wherein
the layer to be etched contains silicon, and
the layer to be etched is etched using a gas containing fluorine.

14. The method according to claim 9, wherein
the layer to be etched is a stacked body including a plurality of first layers and a plurality of second layers alternately stacked, the second layers being layers of a different type of material from the first layers.

15. The method according to claim 9, further comprising:
forming a film containing a metal nitride provided between the layer to be etched and the mask layer.

16. A method for manufacturing a semiconductor device, comprising:
forming a mask layer on a layer to be etched, the mask layer containing tungsten and boron, containing tungsten and carbon, or containing tungsten, boron and carbon, the mask layer having a full width at half maximum being not less than 0.5° in XRD (X-ray diffraction) peaks measured by 2θ/θ method of XRD analysis in which 2θ is between 30° and 50°;
patterning the mask layer; and
performing a dry etching to the layer to be etched using the mask layer being patterned, and forming a hole or a slit in the layer to be etched.

17. The method according to claim 16, wherein
a Young's modulus of the mask layer is not less than 170 GPa.

18. The method according to claim 16, wherein
the layer to be etched contains silicon, and
the layer to be etched is etched using a gas containing fluorine.

19. The method according to claim 16, wherein
the layer to be etched is a stacked body including a plurality of first layers and a plurality of second layers alternately stacked, the second layers being layers of a different type of material from the first layers.

20. The method according to claim 16, further comprising:
forming a film containing a metal nitride provided between the layer to be etched and the mask layer.