JP4067989B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device using a rare earth insulating film as a gate insulating film in a MIS (Metal Insulator Semiconductor) structure.
[0002]
[Prior art]
Along with the high integration of large scale integrated circuits (LSIs), field effect transistors (MISFETs) having metal / insulator / semiconductor junctions have also been miniaturized. According to the 2001 edition of ITRS (International Technology Roadmap for Semiconductors), after 2010, a gate insulating film with an equivalent physical oxide thickness (hereinafter referred to as EOT) of 1.0 nm or less is required. Yes. A silicon oxynitride film and a silicon nitride film, as well as a silicon oxide film, are insufficient for realizing a gate insulating film in which leakage current is suppressed with this film thickness. Therefore, an insulating film having a high dielectric constant, that is, a high dielectric metal insulating film such as an insulating film containing Al, Zr or Hf (Al ₂ O ₃ , ZrO ₂ , HfO ₂ and their silicate films) is required. Yes. In particular, research on HfO ₂ films has accelerated in recent years due to their thermal stability and high dielectric constant, but the thinning limit is estimated to be about 0.8 nm. A material with a high dielectric constant is required.
[0003]
In response to such demands, basic studies on rare earth insulating films such as Pr ₂ O ₃ and La ₂ O ₃ having a high dielectric constant of about 20 to about 30 have been actively conducted recently. According to the electrical characteristic evaluation, both EOT reduction and leakage current reduction are achieved (see Non-Patent Document 1).
[0004]
However, when these materials are applied to a normal semiconductor manufacturing process, the following problems are clarified. It is known that rare earth insulating films form volumetric expansion by forming hydroxides and carbonates by the adsorption, diffusion, and reaction of water vapor and carbon dioxide in the atmosphere when exposed to air after film formation (Non-patent Documents). 2).
[0005]
This causes film quality deterioration such as morphology deterioration, dielectric constant reduction, and leakage current increase. Similarly, in the solution treatment process including water, hydroxide is rapidly formed by the infiltration of water into the film, and the film quality is deteriorated in the resist stripping process and various cleaning processes that have not been a problem with the silicon oxide film so far. (See Non-Patent Document 3).
[0006]
In order to solve these problems, the transport process in which the rare earth insulating film is exposed to the atmosphere (for example, during the air transport until the gate polysilicon deposition after forming the insulating film) is replaced with a vacuum transport or a purge box transport filled with nitrogen. It is possible. In addition, a method of forming a cap such as a silicon nitride film on the surface of the rare earth insulating film before standing in the atmosphere or before the solution processing step can be considered.
[0007]
However, since the former method requires a large-scale device configuration and the latter causes an increase in the number of processes, a post-processing method after formation of a rare earth insulating film that is simple and applicable to general processes is essential. It is coming.
[0008]
[Non-Patent Document 1]
H. Iwai et al., International Electron Devices Meeting 2002, 26-04 (2002)
[Non-Patent Document 2]
Edited by Ginya Adachi "Science of rare earths" Chemistry (1999)
[Non-Patent Document 3]
A. Kikuchi et al., 202 ^nd Meeting of Electrochemical Society, Abst.No. 386 (2002)
[0009]
[Problems to be solved by the invention]
As described above, in the process after the formation of the rare earth insulating film, hydroxide and carbonate are formed along with adsorption / diffusion / reaction of water vapor and carbon dioxide gas due to exposure to the atmosphere, and morphological deterioration due to volume expansion of the film, There was a problem of a decrease in dielectric constant and an increase in leakage current. Also, in the solution treatment process, the rare earth insulating film has low water resistance, and hydroxide formation due to water soaking is a serious problem. The conventional proposal made to prevent these problems requires a large-scale change in the transportation system, the manufacturing process, and the like, which is a great obstacle to the application to a general semiconductor production line.
[0010]
The present invention has been made to solve these problems, and an object of the present invention is to realize a rare earth insulating film having a high dielectric constant and improved flatness by suppressing film quality deterioration in atmospheric exposure and solution processing. It is to provide a simple manufacturing method.
[0011]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is, La2 O3 film, LaSiO film on a semiconductor substrate on a semiconductor substrate, LaAlO film, LaON film, LaN film, Pr2O3 film, PrSiO film, PrAlO film, Pron film, PrN film, or forming an insulating film consisting of the multilayer film, before the atmospheric transfer or solution treated with at least partially exposed in the insulating film, in a helium or neon atmosphere, 200 ° C. or less 27 ° C. or higher And a pressure treatment process at a temperature exceeding 1 atm.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to a common structure through embodiment and an Example, and the overlapping description is abbreviate | omitted. Each figure is a schematic diagram for promoting explanation and understanding of the invention, and its shape, size, ratio, and the like are different from those of an actual apparatus. Such a specific configuration can be appropriately modified in consideration of the following description and a known technique.
[0013]
(First embodiment)
In the first embodiment, a MOSFET manufacturing method using a silicon oxide film as an insulating film will be described as an example of a MISFET. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5 and FIG. 6 are schematic cross-sectional views for explaining this manufacturing method.
[0014]
First, as shown in FIG. 1, a deep groove 12 for an element isolation region is formed on the surface of a general single crystal p-type silicon substrate 11, and this groove 12 is filled with a silicon oxide film by a CVD method to form an element isolation region. 13 is formed.
[0015]
Next, as shown in FIG. 2, a La ₂ O ₃ film 14 having a thickness of about 20 nm is formed on the surface of the silicon substrate 11 by vapor deposition. Next, as shown in FIG. 3, a polysilicon film 15 is formed on the La ₂ O ₃ film 14 by the CVD method.
[0016]
Next, as shown in FIG. 4, a photoresist pattern 16 is formed in the gate electrode planned region on the polysilicon 15. Next, as shown in FIG. 5, the polysilicon film 15 is subjected to reactive ion etching (RIE) using the photoresist pattern 16 as a mask. Thus, a strip-like polysilicon film 15 extending in the direction perpendicular to the paper surface of FIG. 5 is formed. Thereafter, the resist pattern 16 is peeled off. The step of removing the resist pattern 16 will be described in detail later.
[0017]
Next, arsenic (As) is ion-implanted into the surfaces of the polysilicon film 15 and the silicon substrate 11 under conditions of, for example, an acceleration voltage of about 40 keV and a dose amount of about 2 × 10 ¹⁵ cm ⁻² , followed by activation annealing of impurities (As). A high impurity concentration n ⁺ -type gate electrode (first gate electrode) 15, an n ⁺ -type source region 17 and an n ⁺ -type drain region 18 are formed.
[0018]
Next, as shown in FIG. 6, a silicon oxide film of about 300 nm is deposited on the entire surface of the silicon substrate 11 by the CVD method to form an interlayer insulating film 19. Thereafter, a photoresist pattern (not shown) for forming a contact hole is formed on the interlayer insulating film 19, and the interlayer insulating film 19 is etched by RIE using this as a mask to open a contact hole. Then, after a metal film such as Al is formed on the silicon substrate 11 by sputtering, this is patterned to form a source electrode 110, a drain electrode 111, and a second gate electrode 112 that fill the contact hole, and n Type MOS transistor is completed.
[0019]
The second gate electrode 112 is connected to the first gate electrode 15, the source electrode 110 is connected to the source region 17, and the drain electrode 111 is connected to the drain region 18 via contact holes.
[0020]
In the present embodiment, the manufacturing method of the n-type MOSFET has been described. However, the p-type MOSFET can be manufactured in the same manner except that the conductivity type is switched between the n-type and the p-type.
[0021]
(First embodiment)
Next, the resist stripping process will be described in the first embodiment.
[0022]
First, the photoresist pattern 16 on the gate electrode 15 is peeled off by oxygen plasma. Next, in order to remove the resist residue on the surface of the gate electrode 15, the sulfuric acid / hydrogen peroxide aqueous solution treatment (treatment: about 10 minutes + flowing water: about 10 minutes) and the choline / hydrogen peroxide solution treatment (treatment: about 10 minutes + flowing water: about 10 minutes) Min). Immediately before these solution treatments, the following pressure treatment is performed in order to improve the water resistance of the La ₂ O ₃ film 14 exposed to water.
・ He or N ₂ 2kg / cm ² sealed for 1 hour (room temperature)
Infiltration of water into the La ₂ O ₃ film 14 can be confirmed as a change in refractive index by spectroscopic ellipsometry.
[0023]
FIG. 7 shows the result of the change in the refractive index of the La ₂ O ₃ film after the pressure treatment during the water treatment time. The vertical axis represents the refractive index difference (Relative n) before and after water treatment. The horizontal axis in FIG. 7 indicates the water treatment time in units of time (H ₂ O dip time (hr)). Since the refractive index n before processing is about 3, it means that the refractive index decreases (film density decreases) as the negative value of the refractive index difference increases.
[0024]
For comparison, the result of a La ₂ O ₃ film not subjected to pressure treatment is also shown, but it can be seen that the refractive index decreases monotonously with increasing water treatment time. On the other hand, it can be seen that the decrease in the refractive index is suppressed up to 23 hours by the pressurized He and N ₂ treatment, and the water resistance is improved.
[0025]
It can also be confirmed from this figure that He is more effective in improving water resistance than N ₂ . The solution treatment for actual resist stripping is at least 40 minutes, and by applying this pressure N ₂ and He treatment immediately before, a decrease in the refractive index of the La ₂ O ₃ film 14 in the gate end region can be suppressed.
[0026]
Next, the difference in film quality of the La ₂ O ₃ film subjected to the pressurized N ₂ treatment was analyzed by X-ray photoelectron spectroscopy (hereinafter referred to as XPS). The result is shown in FIG. Here, changes in the N1s spectrum of the La ₂ O ₃ film before and after the substrate temperature is room temperature and the pressurized N ₂ treatment (2 kg / cm ² ) is performed for about 1 hour are shown. The X-ray source is MgKα, and the photoelectron escape angle is 45 °. From FIG. 8, it can be seen that the N1s spectrum intensity around the relative photoelectron binding energy (Relative binding energy) of about 400 eV is increased by the pressurized N ₂ treatment. That is, nitrogen is taken into the La ₂ O ₃ film by the pressurized N ₂ treatment despite the room temperature treatment, and this taken-in nitrogen suppresses the infiltration of water (water diffusion into the La ₂ O ₃ bulk). By doing so, it can be said that the water resistance was improved.
[0027]
Next, the temperature range applicable to the pressure treatment was also confirmed. FIG. 9 shows changes in the refractive index of the La ₂ O ₃ film (see the left vertical axis in FIG. 9) and changes in the interface silicon oxide film thickness (see the right vertical axis in FIG. 9) after 27 hours of water treatment. It can be seen that the lower the refractive index n due to the water treatment is suppressed, the higher the substrate temperature (the horizontal axis in FIG. 9) during the pressure treatment. That is, it can be said that the diffusion amount of the inert gas into the insulating film increases and the concentration of the inert gas in the film increases, thereby inhibiting the diffusion of water from the outside.
[0028]
In particular, helium gas has the highest diffusion rate and the highest solid solubility, and as is clear from FIG. 9, it is most excellent in terms of improving water resistance. However, it was also found that in the pressure treatment exceeding about 200 ° C., the oxidation reaction at the La ₂ O ₃ / Si interface proceeds due to residual oxygen and moisture in the gas, and the increase amount ΔT _int of the interfacial silicon oxide film thickness proceeds. Therefore, from the viewpoint of improving the water resistance while maintaining the initial interfacial oxide film thickness, the maximum effect was exhibited by performing the pressure treatment in the range of room temperature to 200 ° C.
[0029]
From the above, it can be said that the pressure treatment is most effective in water resistance in a process of heating at room temperature to 200 ° C. in a pressurized He atmosphere.
[0030]
The pressure treatment in this example is performed at about 2 kg / cm ² , but the treatment time can be shortened from about 1 hr to several minutes by performing a high pressure treatment of about 10 kg / cm ² or more. . Even in the case of normal pressure treatment, the same effect of improving water resistance can be obtained if the substrate temperature is higher than room temperature (up to about 200 ° C.).
[0031]
Next, the mechanism for improving the water resistance by the pressurized He treatment will be described with reference to the schematic cross-sectional view of FIG. In the conventional method, hydroxide (La ₂ (OH) ₃ ) is formed by water adsorption on the surface of the rare earth insulating film, grain boundary diffusion and reaction in the bulk, causing a decrease in dielectric constant accompanying volume expansion. It was.
[0032]
On the other hand, in the first embodiment in which the pressurized He treatment is performed in advance, the atomic radius and mass of He are small, so the solid solubility in the insulating film is large, and the water diffusing from the outside collides with He. It has the effect of physically suppressing water soaking. At the same time, since He is an inert gas, oxidation / reduction reactions of the insulating film due to the gas itself do not occur, so that the quality of the rare earth insulating film is not deteriorated.
[0033]
In the first embodiment, the results in the case of using He and nitrogen gas as the pressurizing treatment are mainly shown. However, the same improvement effect can be obtained with Ne, Ar, and their mixed gas having a smaller atomic radius than nitrogen gas. It was confirmed. Even if these inert gases are diluted with a rare gas (Kr, Xe, etc.) having a larger atomic radius than nitrogen gas, the effect is maintained.
[0034]
Furthermore, although the La ₂ O ₃ film has been mainly described in the first embodiment, the present invention is applicable to other rare earth insulating materials, in particular, Lu, Eu, Sm, Pr, La, Yb, Gd, Effective for oxide films containing Dy. Furthermore, the effectiveness of the silicate film, aluminate film, oxynitride film, nitride film, mixed film, and various multilayer films is maintained. In addition, the same effect can be obtained even with various rare earth insulating films formed by sputtering, ALCVD (Atomic Layer CVD), vapor deposition, plasma CVD, etc., regardless of the method of forming these rare earth insulating films.
[0035]
According to the first embodiment, in the process after the formation of the rare earth insulating film, it is possible to form a rare earth insulating film having a high dielectric constant and excellent flatness, suppressing film quality deterioration during atmospheric exposure and solution processing, and low consumption.・ High speed and high reliability MOSFETs can be provided.
[0036]
(Second embodiment)
Since the structure of the MOSFET according to the second embodiment of the present invention is the same as that of the first embodiment, its detailed description is omitted. In the present embodiment, not the La ₂ O ₃ film but the Pr ₂ O ₃ film is formed as the gate insulating film, and the subsequent transport process until the formation of the polysilicon film 15 is different from the first embodiment. Therefore, these steps will be described in detail with reference to FIG.
[0037]
First, a Pr ₂ O ₃ film 14 having a thickness of about 20 nm is formed on the Si substrate 11 by vapor deposition, and then the Si substrate 11 (wafer) is transferred into the CVD apparatus after being transported to the atmosphere to deposit the gate polysilicon film 15. Transport. Here, the following pressure reduction and pressurization processes are sequentially performed at room temperature before air transportation.
・ Ne atmosphere Pressure 10Torr About 10 minutes → Ne atmosphere Pressure 10kg / cm ² Ne gas can be diffused more efficiently in the insulating film by performing pressurized Ne treatment after sealed vacuum Ne treatment for 1 minute. By placing the insulating film in a reduced pressure Ne atmosphere of 1 atm (760 Torr) or less as in this embodiment, it is possible to replace Ne with sufficiently removing impurities such as oxygen and water contained in the insulating film. Further, the high pressure Ne gas can be easily diffused into the atomic bond network (network) of the insulating film by continuously performing the pressure Ne treatment.
[0038]
By this reduced pressure and pressurized Ne treatment, diffusion of water / carbon dioxide gas into the insulating film during atmospheric transportation is suppressed (the same action as explained in FIG. 10), and volume expansion due to hydroxide and carbonate formation Is suppressed.
[0039]
FIG. 11 shows changes in the actual film thickness of the Pr ₂ O ₃ film when left in the atmosphere in Ne treatment (Treatments). The atmospheric temperature was 23 ° C., the humidity was 90%, and the standing time was 24 hours. In FIG. 11, in addition to the membrane (c) by decompression and pressurization Ne treatment, for comparison, the data of the membrane (a) without any pressurization treatment and the membrane (b) with only pressurization Ne treatment are also shown. . From this, it was confirmed that the increase in the actual film thickness ΔT is minimized by the pressure Ne treatment, more preferably the pressure reduction and the pressure Ne treatment.
[0040]
The operation in these series of steps is the same as in the first embodiment. In accordance with the same idea as described in the first embodiment in all semiconductor manufacturing processes, particularly when a rare earth insulating film is exposed on the surface and exposed to the atmospheric transfer or solution processing process, N ₂ and Ar are added. However, addition of Ne and He is more effective. For example, the present invention can also be applied when a rare earth insulating film is used as an interlayer insulating film or a semiconductor sealing material.
[0041]
From the above, in order to improve the water resistance and hygroscopicity of the rare earth insulating film, decompression and pressurization treatment is performed in an inert gas atmosphere having an atomic radius equal to or less than that of nitrogen gas, and at the time of treatment It is effective to control the substrate temperature to room temperature (about 27 ° C.) or more and about 200 ° C. or less. Such treatment after the formation of the insulating film is particularly effective when the thickness of the rare earth insulating film is 20 nm or less.
[0042]
Note that the present invention is not limited to the above-described embodiments and examples as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.
[0043]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a semiconductor device including a rare earth insulating film that suppresses film quality deterioration of a rare earth insulating film in atmospheric exposure and solution processing and has a high dielectric constant and excellent flatness. .
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view for explaining a method of manufacturing a MOSFET according to a first embodiment of the invention.
FIG. 2 is a schematic cross-sectional view for explaining the MOSFET manufacturing process following FIG. 1;
3 is a schematic cross-sectional view for illustrating the manufacturing step of the MOSFET, following FIG. 2. FIG.
4 is a schematic cross-sectional view for explaining the MOSFET manufacturing process following FIG. 3. FIG.
FIG. 5 is a schematic cross-sectional view for explaining the MOSFET manufacturing process following FIG. 4;
6 is a schematic cross-sectional view for explaining the manufacturing step of the MOSFET subsequent to FIG. 5. FIG.
FIG. 7 is a view showing a change in refractive index of a La ₂ O ₃ film by water treatment after various pressure treatments according to the first embodiment of the present invention.
FIG. 8 is a diagram showing changes in the N1s photoelectron spectrum before and after the pressurized N ₂ treatment according to the first example.
FIG. 9 is a diagram showing a change in refractive index of La ₂ O ₃ film and a change in interfacial silicon oxide film thickness after water treatment according to a pressure treatment temperature according to the first embodiment.
FIG. 10 is a view for explaining a mechanism for improving water resistance by pressurized He treatment according to the first embodiment.
FIG. 11 is a diagram showing a change in actual film thickness due to standing in the atmosphere after the pressure Ne treatment according to the second embodiment of the present invention.
[Explanation of symbols]
11 ... p-type silicon substrate
12 ... Slot for element isolation region
13 ... Element isolation region
14 ... La ₂ O ₃ film (first embodiment), Pr ₂ O ₃ film (second embodiment)
15 ... Polysilicon film
16 ... Photoresist pattern
17 ... n ⁺ type source region
18 ... n ⁺ drain region
19 ... Silicon oxide film (interlayer insulating film)
110 ... Source electrode
111 ... Drain electrode
112 ・ ・ ・ Gate electrode

Claims (4)

Forming an insulating film composed of a La2O3 film , a LaSiO film , a LaAlO film , a LaON film , a LaN film , a Pr2O3 film , a PrSiO film , a PrAlO film , a PrON film , a PrN film , or a multilayer film thereof on a semiconductor substrate;
Performing a pressure treatment exceeding 1 atm at a temperature of 27 ° C. or higher and 200 ° C. or lower in a helium or neon gas atmosphere before performing atmospheric transfer or solution processing with at least a part of the insulating film exposed; A method for manufacturing a semiconductor device, comprising: Forming an insulating film composed of a La2O3 film , a LaSiO film , a LaAlO film , a LaON film , a LaN film , a Pr2O3 film , a PrSiO film , a PrAlO film , a PrON film , a PrN film , or a multilayer film thereof on a semiconductor substrate;
And carrying out atmospheric pressure treatment at a temperature higher than 27 ° C. and lower than 200 ° C. in a helium or neon gas atmosphere before performing atmospheric transfer or solution treatment with at least a part of the insulating film exposed. A method for manufacturing a semiconductor device.   3. The method of manufacturing a semiconductor device according to claim 2, further comprising a step of performing a decompression process in an inert gas atmosphere prior to the pressurization process.   The insulating film is a gate insulating film, and includes a step of forming a gate electrode on the gate insulating film and a step of forming source / drain regions on both sides of the gate insulating film. A method for manufacturing a semiconductor device according to claim 2.

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