JP3639812B2 - Etching method and etching apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an etching method and an etching apparatus for selectively etching a thin film (such as a gate insulating film) containing a high dielectric constant material formed on a substrate surface. Substrates to be processed include semiconductor wafers, glass substrates for liquid crystal display devices, glass substrates for plasma displays, and the like.
[0002]
[Prior art]
With the high integration and miniaturization of semiconductor integrated circuit elements, the gate length has been shortened, and the gate insulating film has been made thinner accordingly. However, the thinning of the gate insulating film and the increase in leakage current from the gate are in a trade-off relationship, and the thinning of the gate insulating film has reached its limit.
Therefore, a thick gate insulating film is formed using a high dielectric constant material (so-called high-k material) having a dielectric constant higher than that of silicon oxide instead of silicon oxide which has been conventionally used as a material for the gate insulating film. It has been proposed. Examples of such a high dielectric constant material include hafnia (HfO ₂ ), alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), and the like.
[0003]
[Problems to be solved by the invention]
However, these high dielectric constant materials do not have selectivity for polysilicon and silicon oxide, which can be said to be basic constituent materials of silicon semiconductor elements, in conventional etching using a chemical solution. Therefore, it is impossible to pattern a thin film of a high dielectric constant material on the substrate. Therefore, there is no practical method for manufacturing a semiconductor integrated circuit device using such a high dielectric constant material as a gate insulating film or a capacitor.
[0004]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an etching method and an etching apparatus that can selectively etch a thin film containing a high dielectric constant material on a substrate, solving the above technical problem.
[0005]
[Means for Solving the Problems and Effects of the Invention]
In order to achieve the above object, the invention according to claim 1 is characterized in that a thin film (1) containing hafnia or alumina as a high dielectric constant material is formed from the surface of a substrate (W) on which a silicon oxide film or a polysilicon film is formed. An etching method for etching and removing a substrate by heating a substrate to a predetermined temperature and supplying a vapor containing hydrofluoric acid to the surface of the substrate in parallel with the substrate heating step. A vapor supply step of selectively removing the thin film containing hafnia or alumina on the surface of the silicon oxide film or the polysilicon film on the substrate by etching. The alphanumeric characters in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.
[0006]
The vapor containing hydrofluoric acid may be a vapor of a hydrofluoric acid aqueous solution (hydrofluoric acid vapor), or may be a mixture of this hydrofluoric acid vapor in a carrier gas such as an inert gas. In addition, the vapor containing hydrofluoric acid may be a vapor of a mixed solution obtained by adding an oxidizing agent such as hydrogen peroxide water or ozone, or an organic solvent such as methanol to hydrofluoric acid .
[0007]
Further, the steam containing the hydrofluoric acid may be a vapor containing anhydrous hydrofluoric acid gas. Note that the vapor containing anhydrous hydrofluoric acid gas, may be one which is mixed with hydrofluoric acid gas and water vapor anhydride, in which a vapor of an organic solvent such as hydrofluoric acid gas and anhydrous methanol is mixed They may also be mixed with a carrier gas such as an inert gas.
[0008]
In etching using such a vapor of a hydrofluoric acid solution or a vapor containing anhydrous hydrofluoric acid gas, the temperature dependence of the etching rate is extremely large. Therefore, a high dielectric constant increases the etching rate of the hafnia or alumina as the material, while heating the substrate to a predetermined temperature such that the etch rate of the silicon oxide film or a polysilicon film formed on the substrate surface is reduced, fluoride By introducing the vapor containing the acid to the substrate surface, the thin film containing hafnia or alumina can be selectively etched away with respect to the silicon oxide film or the polysilicon film .
[0009]
Thereby, a practical manufacturing method of a device such as a semiconductor integrated circuit element using a thin film containing hafnia or alumina as a high dielectric constant material can be realized, and mass production of such a device becomes possible.
The invention according to claim 2 is the etching method according to claim 1, wherein the predetermined temperature in the substrate heating step is 50 ° C. or more and 160 ° C. or less.
By setting such temperature conditions, a thin film containing hafnia or alumina as a high dielectric constant material can be etched away with good selectivity.
[0010]
The invention described in claim 3 further includes a depressurizing step of depressurizing the space in which the substrate is placed to a predetermined atmospheric pressure (for example, 100 to 300 Torr) in parallel with the vapor supplying step. The etching method according to 1 or 2.
The etching rate in etching with vapor containing hydrofluoric acid is not only highly temperature-dependent, but also highly dependent on the pressure of the space in which the substrate is placed. Therefore, when performing etching using vapor containing hydrofluoric acid , the etching selectivity can be further increased by reducing the space in which the substrate is placed to a predetermined pressure.
[0012]
The invention according to claim 4 is the etching method according to any one of claims 1 to 3 , wherein the thin film is a gate insulating film or a capacitor.
[0013]
The high dielectric constant material that can be applied to the gate insulating film, there are etc. hafnia (HfO ₂₎ or alumina (Al ₂ O _3).
As a metal film for wiring such as a gate electrode, copper, aluminum, tungsten or the like can be used.
The invention described in claim 5 is an etching apparatus for etching and removing a thin film (1) containing hafnia or alumina as a high dielectric constant material from the surface of a substrate (W) on which a silicon oxide film or a polysilicon film is formed. The substrate heating means (45) for heating the substrate at a predetermined temperature and the thin film containing hafnia or alumina on the surface of the substrate are selectively removed by etching with respect to the silicon oxide film or the polysilicon film on the substrate. In order to do so, vapor supply means (31-34, 36, 37, 43, 52-54) for supplying vapor containing hydrofluoric acid to the surface of the substrate heated to a predetermined temperature by the substrate heating means An etching apparatus including the etching apparatus.
[0014]
With this configuration, it is possible to achieve an effect similar to the effect described with respect to the invention of claim 1.
According to a sixth aspect of the invention further comprises a decompression means to decompress the said substrate is placed space to a predetermined pressure, the steam supply means is placed in the vacuum spaces to a predetermined pressure by the pressure reducing means 6. The etching apparatus according to claim 5 , wherein vapor containing hydrofluoric acid is supplied to the surface of the substrate heated to a predetermined temperature by the substrate heating means .
[0015]
With this configuration, it is possible to achieve the same operation and effect as described for the invention of claim 3 .
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a cross-sectional view showing a state in which a semiconductor wafer (hereinafter simply referred to as “wafer”) W, which is an example of a substrate, is processed by a vapor phase etching apparatus according to an embodiment of the present invention. As shown in FIG. 1A, a gate insulating film 1 is formed on the wafer W, and a gate electrode 2 is formed on the gate insulating film 1. In addition, although not shown, a pattern of a polysilicon film or a silicon oxide film is formed on the surface of the wafer W.
[0017]
By performing the vapor phase etching process on the wafer W in this state, the gate insulating film 1 in a region other than the region immediately below the gate electrode 2 is selectively removed, and the gate insulating film 1 is patterned. .
A so-called High-k (high dielectric constant) insulating film is applied to the gate insulating film 1, and the gate electrode 2 is made of a metal film such as copper, aluminum or tungsten.
[0018]
The high-k insulating film is an insulating film made of a material having a dielectric constant higher than that of a silicon oxide film conventionally used as a gate insulating film, and is made of hafnia (HfO ₂ ) or alumina (Al ₂ O ₃ ). Applicable to membranes.
In one embodiment of the present invention, the gate insulating film 1 on the wafer W is selectively removed by vapor phase etching while minimizing damage to the silicon oxide film or the polysilicon film on the wafer W.
[0019]
FIG. 2 is a schematic cross-sectional view for explaining the configuration of a vapor phase etching apparatus according to an embodiment of the present invention. This apparatus is an apparatus for selectively removing the High-k insulating film from the surface of the wafer W by etching.
This device, in a housing 41, a acid vapor generating vessel 43 hydrofluoric storing aqueous acid 42 Tsu Fu in a sealed state. Below the hydrofluoric acid vapor generating container 43, a punching plate 44 having a number of through-holes for releasing the hydrofluoric acid vapor downward is provided.
[0020]
A hot plate 45 that holds the wafer W to be processed horizontally with the punching plate 44 facing the punching plate 44 is disposed below the punching plate 44. The hot plate 45 is fixed to the upper end of a rotary shaft 47 that is rotated around a vertical axis by a rotary drive mechanism 46 including a motor and the like.
A bellows 48 that contracts up and down with respect to the bottom surface 41 a of the housing 41 is provided on the outer side of the hot plate 45 in plan view. The bellows 48 has a sealed position (a position indicated by a solid line in FIG. 2) in which a processing chamber is formed by sealing the peripheral space of the hot plate 45 with an upper end edge abutting the periphery of the punching plate 44, and an upper end thereof. The edge is driven to extend / shrink by a drive mechanism (not shown) between a retracted position (a position indicated by a broken line in FIG. 2) retracted downward from the upper surface 45a of the hot plate 45.
[0021]
The internal space of the bellows 48 is exhausted by the exhaust means 55 via the exhaust pipe 49 connected to the bottom surface 41 a of the housing 41. The exhaust means 55 may be a forced exhaust mechanism such as an exhaust blower or an ejector, or may be exhaust equipment provided in a clean room where the substrate surface treatment apparatus is installed.
On the side of the hot plate 45, a loading opening 21 for loading the wafer W and a loading opening 22 for discharging the wafer W are formed on the side wall of the housing 41. Shutters 38 and 39 are disposed in these openings 21 and 22, respectively. When the wafer W is loaded, the bellows 48 is lowered to the retracted position (the position indicated by the broken line in FIG. 2), the shutter 38 is opened, and the wafer W is delivered to the hot plate 45 by a transfer robot (not shown). Further, when the wafer W is unloaded, the bellows 48 is set to the retracted position, and the shutter 39 is opened, and the wafer W on the hot plate 45 is transferred to another transfer robot (not shown) and unloaded. .
[0022]
A nitrogen gas supply pipe 54 for supplying nitrogen gas as a carrier gas is connected to the hydrofluoric acid vapor generating container 43 in a space 35 above the liquid surface of the hydrofluoric acid aqueous solution 42. The space 35 can be connected to a hydrofluoric acid vapor supply path 36 for guiding the hydrofluoric acid vapor to the punching plate 44 via the valve 37. Nitrogen gas from a nitrogen gas supply source 31 is supplied to the hydrofluoric acid vapor supply path 36 via a flow rate controller (MFC) 32, a valve 33, and a nitrogen gas supply pipe 34.
[0023]
The nitrogen gas from the nitrogen gas supply source 31 is supplied to the nitrogen gas supply pipe 54 via the flow rate controller 52 and the valve 53.
The hydrofluoric acid aqueous solution 42 stored in the hydrofluoric acid vapor generating container 43 is prepared to a concentration (for example, about 39.6% under 1 atm and room temperature (20 ° C.)) so as to have a so-called pseudo eutectic composition. ing. In the hydrofluoric acid aqueous solution 42 having the pseudo-zeotropic composition, water and hydrogen fluoride have the same evaporation rate. Therefore, the hydrofluoric acid vapor is guided from the valve 37 to the punching plate 44 through the hydrofluoric acid vapor supply path 36. Even if the hydrofluoric acid aqueous solution 42 in the hydrofluoric acid vapor generating container 43 decreases, the concentration of the hydrofluoric acid vapor led to the hydrofluoric acid vapor supply path 36 is maintained unchanged.
[0024]
When the high-k insulating film on the surface of the wafer W is selectively removed, the bellows 48 is raised to a close contact position (solid line position in FIG. 2) in close contact with the peripheral edge of the punching plate 44, and the valves 33, 53, and 37 are be opened. Thus, the hydrofluoric acid vapor generated in the space 35 in the hydrofluoric acid vapor generating container 43 is pushed out by the nitrogen gas from the nitrogen gas supply pipe 54 to the hydrofluoric acid vapor supply path 36 through the valve 37. The hydrofluoric acid vapor is further carried to the punching plate 44 by the nitrogen gas from the nitrogen gas supply pipe 34. Then, it is supplied to the surface of the wafer W through a through hole formed in the punching plate 44.
[0025]
FIG. 3 shows the temperature dependence of the etching rate of a silicon oxide (SiO ₂ : thermal silicon oxide) film, a hafnia (HfO ₂ ) film, and an alumina (Al ₂ O ₃ ) film in vapor phase etching using a vapor of an aqueous hydrofluoric acid solution. It is a characteristic view which shows property. The etching rate of silicon oxide decreases rapidly as the temperature of the wafer W is increased, whereas the etching rates of hafnia and alumina increase as the temperature of the wafer W increases, and the temperature of the wafer W further increases. It turns out that it descends slowly according to.
[0026]
In particular, in the region where the temperature of the wafer W is 45 ° C. or higher, the etching rate of silicon oxide and the etching rates of hafnia and alumina are reversed. In the region where the temperature of the wafer W is 50 ° C. or more, there is a significant difference in the etching rates of silicon oxide, hafnia and alumina. If vapor phase etching is performed in this temperature region, the hafnia and alumina on the wafer W are good. It will be understood that the etch can be removed with great selectivity. The upper limit of the temperature range is determined by the specifications of the hot plate 45, but is approximately 160 ° C.
[0027]
On the other hand, the etching rate in the vapor phase etching process also depends on the atmospheric pressure of the space where the wafer W is placed. Specifically, the High-k insulating film on the wafer W can be selectively removed under a reduced pressure atmosphere of about 200 Torr.
Therefore, in this embodiment, the hot plate 45 is controlled so that the temperature of the wafer W can be maintained at about 60 ° C., for example. Further, the exhaust means 55 is controlled so that the atmospheric pressure around the wafer W in the space on the hot plate 45 becomes a reduced pressure atmosphere of about 200 Torr. In this state, the vapor of the hydrofluoric acid aqueous solution is guided to the surface of the wafer W. Thereby, the gate insulating film 1 made of the High-k insulating film on the wafer W can be selectively removed while minimizing damage to the silicon oxide film and the polysilicon film on the wafer W. As a result, it is possible to provide a practical means for producing a device such as a semiconductor integrated circuit element using a high-k insulating film as a gate insulating film, and mass production of such a device becomes possible.
[0028]
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form. For example, in the above-described embodiment, the step of selectively removing the High-k insulating film on the wafer W by the vapor phase etching process using the hydrofluoric acid aqueous solution has been described. However, the chemical solution used for the vapor phase etching process is as follows. Further, it may be a mixed solution obtained by adding an oxidizing agent such as hydrogen peroxide, ozone, or an organic solvent such as methanol to hydrofluoric acid .
[0029]
In the above embodiments have been described vapor-phase etching process using a vapor of hydrofluoric acid aqueous solution, rather it may also be used vapor containing anhydrous hydrofluoric acid gas, and anhydrous hydrofluoric acid gas, ammonia gas, hydrogen chloride gas, it may be used vapor containing nitrogen dioxide gas, and SO ₃ any one of gas, or a mixed gas of two or more gases of these. Note that the vapor containing anhydrous hydrofluoric acid gas, may be one which is mixed with hydrofluoric acid gas and water vapor anhydride, in which a vapor of an organic solvent such as hydrofluoric acid gas and anhydrous methanol is mixed They may also be mixed with a carrier gas such as an inert gas.
[0030]
Instead of using a chemical solution (containing hydrofluoric acid) or chemical gas (containing hydrofluoric acid gas) with a mixed composition, a vapor source is provided for each component of such chemical solution or chemical gas. A plurality of vapors may be mixed in the vicinity of the wafer W such that the vapor from the wafer W is guided to the surface of the wafer W.
The vapor source is preferably provided with a chemical solution or chemical gas supply mechanism in order to replenish the chemical solution or chemical gas or maintain the concentration of the chemical solution or chemical gas.
[0031]
In addition, various design changes can be made within the scope of matters described in the claims.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view for explaining an example of processing by a vapor phase etching apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic sectional view showing a configuration of a vapor phase etching apparatus according to an embodiment of the present invention.
FIG. 3 is a characteristic diagram showing the temperature dependence of the etch rate of various films in a vapor phase etching process using vapor of a hydrofluoric acid aqueous solution.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Gate insulating film 2 Gate electrode 31 Nitrogen gas supply source 36 Hydrofluoric acid vapor supply path 41 Housing 42 Hydrofluoric acid aqueous solution 43 Hydrofluoric acid vapor generation container 44 Punching plate 45 Hot plate 46 Rotation drive mechanism 48 Bellows 49 Exhaust piping 55 Exhaust means W Wafer

Claims (6)

An etching method for etching and removing a thin film containing hafnia or alumina as a high dielectric constant material from the surface of a substrate on which a silicon oxide film or a polysilicon film is formed ,
A substrate heating step of heating the substrate to a predetermined temperature;
In parallel with this substrate heating step, by supplying a vapor containing hydrofluoric acid to the surface of the substrate, a thin film containing hafnia or alumina on the surface of the substrate is made to a silicon oxide film or a polysilicon film on the substrate. And a vapor supplying step of selectively removing the etching.   The etching method according to claim 1, wherein the predetermined temperature in the substrate heating step is 50 ° C. or higher and 160 ° C. or lower.   3. The etching method according to claim 1, further comprising a depressurizing step of depressurizing a space in which the substrate is placed to a predetermined pressure in parallel with the vapor supplying step. The thin film is etching method according to any one of claims 1 to 3, characterized in that a gate insulating film or a capacitor. An etching apparatus for etching and removing a thin film containing hafnia or alumina as a high dielectric constant material from the surface of a substrate on which a silicon oxide film or a polysilicon film is formed ,
A substrate heating means for heating the substrate at a predetermined temperature;
The substrate heated to a predetermined temperature by the substrate heating means in order to selectively remove the thin film containing hafnia or alumina on the surface of the substrate with respect to the silicon oxide film or the polysilicon film on the substrate. And a vapor supply means for supplying a vapor containing hydrofluoric acid to the surface of the etching apparatus. Further comprising a vacuum means to vacuum the substrate is placed space to a predetermined pressure,
The vapor supply means supplies vapor containing hydrofluoric acid to the surface of the substrate which is placed in a space whose pressure is reduced to a predetermined pressure by the pressure reduction means and which is heated to a predetermined temperature by the substrate heating means. 6. The etching apparatus according to claim 5, wherein the etching apparatus is a thing.

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