JP4454883B2 - Manufacturing method of semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a silicon nitride film or a silicon oxynitride film and an annealing method thereof.
[0002]
[Prior art]
The thermal oxide film of silicon is used as a gate insulating film of a memory MOSFET, a capacitor insulating film of a DRAM, or the like. In recent years, as the degree of integration of semiconductor devices increases, it is necessary to reduce the area occupied by MOSFETs, etc. In order to do so, the thickness of the silicon thermal oxide film must be reduced to maintain a certain capacitance. In recent years, the thermal oxide film has been required to be thinned to about several tens of kilometers due to the demand for scaling associated with the miniaturization of elements. The same applies when a thermal oxynitride film is formed instead of the thermal oxide film.
[0003]
Such thinning of the thermal oxide film or thermal oxynitride film of silicon directly increases the tunnel current, thereby causing a leakage current when the gate is turned off, and the circuit of the semiconductor device does not operate normally or is consumed. Problems such as an increase in power have occurred.
[0004]
For this reason, for example, a silicon nitride film or an oxynitride film having a dense structure has been studied as a good insulating film instead of a silicon thermal oxide film or a thermal oxynitride film.
[0005]
The silicon nitride film or oxynitride film is formed by nitriding or oxynitriding a silicon thermal oxide film or thermal oxynitride film. By using a relatively large dielectric constant of the nitride film or oxynitride film, the capacitance of the nitride film or oxynitride film having the same capacitance as that of the silicon thermal oxide film that maintains a constant capacitance is obtained. The film thickness (physical film thickness) can be increased, thereby reducing the leakage current. Hereinafter, in this specification, the thickness of a silicon nitride film or oxynitride film converted to the thickness of a silicon thermal oxide film that provides an equivalent capacitance is referred to as an electrical film thickness.
[0006]
As described above, it is difficult to sufficiently reduce the leakage current of silicon nitride film or oxynitride film. On the other hand, in the case of a MOS capacitor having an oxynitride film as an insulating film, the flat band voltage shifts. This causes the phenomenon that the absolute value increases.
[0007]
The phenomenon that the absolute value of the flat band voltage increases is due to an increase in positive fixed charges in the film, and the threshold value of the operating voltage changes, causing a malfunction of the device.
[0008]
Further, even when a silicon nitride film or an oxynitride film is formed, further reduction in leakage current is required.
[0009]
Therefore, it has been studied to further anneal the silicon nitride film or oxynitride film to improve the film quality.
[0010]
For example, as an annealing method, it has been proposed to treat the silicon nitride film or oxynitride film at a high temperature of about 1000 ° C. in an atmosphere of ammonia gas or nitric oxide gas.
[0011]
[Problems to be solved by the invention]
However, the annealing method using ammonia gas or nitric oxide gas described above is not so effective in reducing the leakage current. Further, the phenomenon that the absolute value of the flat band voltage increases is not solved.
[0012]
The present invention has been made in view of the above problems, and a method for manufacturing a semiconductor device including an annealing method that can further reduce a leakage current and reduce an increase in the absolute value of a flat band voltage. The purpose is to provide.
[0013]
[Means for Solving the Problems]
The method for manufacturing a semiconductor device according to the present invention includes a step of forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate, and a silicon nitride film or a silicon oxynitride film on the first film. A step of forming a second film comprising: a step of treating the second film with nitrogen plasma, and a step of treating the second film with oxygen plasma .
[0015]
As a result, the portion of the second film where the nitriding treatment is insufficient is sufficiently nitrided to reduce the leakage current, and react with oxygen plasma to react with the positive fixed charge of the silicon oxide film or silicon oxynitride film. Decreases and the increase in the absolute value of the flat band voltage is mitigated.
[0016]
The method for manufacturing a semiconductor device according to the present invention includes a step of forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate, and a silicon nitride film or silicon oxide on the first film. The method includes a step of forming a second film made of a nitride film, and a step of treating the second film with oxygen plasma generated by a planar antenna member having a plurality of slits .
[0017]
Thereby, the plasma damage given to a film | membrane can be reduced significantly by setting it as a low plasma sheath voltage.
[0018]
The method for manufacturing a semiconductor device according to the present invention includes a step of forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate, and a silicon nitride film or silicon oxide on the first film. The method includes a step of forming a second film made of a nitride film, and a step of treating the second film with hydrogen plasma generated by a planar antenna member having a plurality of slits .
[0019]
As a result, dangling bonds (unbonded hands), that is, irregularities at the film interface and crystal defects in the film can be reduced, and an increase in the absolute value of the flat band voltage is mitigated. In addition, the leakage current is reduced. In addition, since the plasma sheath voltage is low, plasma damage to the film can be greatly reduced.
[0020]
The method for manufacturing a semiconductor device according to the present invention includes a step of forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate, and a silicon nitride film or silicon oxide on the first film. The method includes a step of forming a second film made of a nitride film, and a step of treating the second film with nitrogen plasma generated by a planar antenna member having a plurality of slits .
[0021]
As a result, the portion of the second film where the nitriding treatment is insufficient is sufficiently nitrided to reduce the leakage current. In addition, since the plasma sheath voltage is low, plasma damage to the film can be greatly reduced.
[0026]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment (hereinafter referred to as this embodiment) of a method for manufacturing a semiconductor device according to the present invention will be described below with reference to the drawings.
[0027]
First, a semiconductor device manufacturing apparatus according to this embodiment will be described with reference to FIG.
[0028]
A manufacturing apparatus 10 shown in FIG. 1 is a kind of a rapid thermal processing system (FTPS).
[0029]
The production apparatus 10 includes a reaction tube 12 made of, for example, quartz, which is formed in a cylindrical shape with a ceiling whose longitudinal direction is directed in the vertical direction. Below the reaction tube 12, a manifold 14 made of a stainless steel tube formed in a cylindrical shape is disposed so as to be airtight with the lower end of the reaction tube 12. A lid body 16 is arranged below the manifold 14 so as to be movable up and down, and is configured so that the lower side of the manifold 14 is closed when the lid body 16 is raised.
[0030]
The reaction chamber 12, the manifold 14 and the lid 16 constitute a processing chamber.
[0031]
A shelf-like wafer port 18 made of quartz is disposed on the lid 16. A plurality of silicon substrates 20 are accommodated in the wafer port 18 at predetermined intervals in the vertical direction.
[0032]
Surrounding the reaction tube 12 is provided a heater 22 for raising temperature made of, for example, a resistance heating element.
[0033]
A process gas supply pipe 24 is inserted into the side surface of the manifold 14. The process gas supply pipe 24 is bent so that the tip end portion 24a faces upward. Therefore, the process gas supplied from the process gas supply pipe 24 is ejected above the reaction pipe 12. Reference numeral 26 indicates an exhaust pipe.
[0034]
Since the manufacturing apparatus 10 described above is configured so that the process gas reaches above the reaction tube, it is supplied at a high speed and a large flow rate. In addition, the process gas is configured to reach the ceiling of the reaction tube, and a predetermined gap is provided in the reaction tube, so that the process gas is uniformly supplied to the processing region and the silicon substrate is evenly distributed. It is processed.
[0035]
A method for manufacturing a semiconductor device according to this embodiment using the manufacturing apparatus 10 will be described below.
[0036]
A method of manufacturing a semiconductor device includes a step of forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate, and a second step made of a silicon nitride film or a silicon oxynitride film on the first film. A step of forming a film, and a step of annealing the second film in an ozone gas atmosphere.
[0037]
In the method of manufacturing a semiconductor device according to the present embodiment, both the first film formed of the silicon oxide film or the silicon oxynitride film and the second film formed of the silicon nitride film or the silicon oxynitride film are used. There is no particular limitation, and for example, a thermal oxidation method may be used, or a deposition method such as CVD may be used. In this case, when using the CVD method, it can be appropriately selected from each CVD method such as thermal CVD, plasma CVD, or photo-CVD.
[0038]
Here, the following method is preferable from the viewpoint of the leakage current reduction effect.
[0039]
That is, a silicon oxide film as a first film is formed on a silicon substrate by a thermal oxidation method. Next, this silicon oxide film is heat-treated in an ammonia gas atmosphere. Further, a silicon nitride film as a second film is deposited. In the thermal oxide film formation stage, a silicon oxynitride film may be formed instead of the silicon oxide film.
[0040]
In the stage of forming the thermal oxide film, using a mixed gas having a flow rate ratio of about O ₂ / N ₂ = 8/2 (slm ratio) as a process gas, at a temperature of about 850 ° C. under a pressure of about 1.3 kPa, Processing is performed for about 60 seconds (seconds). Thereby, a silicon oxide film (SiO ₂ film) having a thickness of, for example, about 1.0 nm is formed on the silicon substrate.
[0041]
In the heat treatment stage, ammonia gas (NH ₃ ) having a flow rate of about 2 (slm) is used as a process gas, and a pressure of about 1.1 kPa and a temperature of about 850 to 900 ° C. for a time of about 10 min (minutes). To do. This stage of heat treatment is an in-situ cleaning (ISC) step, whereby the silicon oxide film surface is nitrided in preparation for the next nitride film formation process.
[0042]
In the step of forming a silicon nitride film, a mixed gas having a flow rate ratio of about TCS / NH ₃ = 50/50 (sccm ratio) is used as a process gas at a pressure of about 35 Pa at a temperature of about 550 to 650 ° C. for 120 s. Process for about time. Thereby, for example, a silicon nitride film (SiN film) having a thickness of about 1.0 to 1.5 nm is formed on the silicon oxide film. Here, TCS refers to tetrachlorosilane.
[0043]
The silicon nitride film formed as described above can obtain a leakage current reducing effect more than other conventional methods. However, the phenomenon that the positive fixed charge in the film increases occurs to the same extent as other conventional methods.
[0044]
For this reason, in the semiconductor device manufacturing method of the present embodiment, the formed silicon nitride film is further annealed in an ozone gas atmosphere.
[0045]
As the ozone gas, a gas having a volume ratio of about O ₃ / O ₂ = 10/90 (volume% ratio) is used, and is processed at a temperature of about 850 ° C. for about 60 seconds under a pressure of about 18 Pa.
[0046]
FIG. 2 and FIG. 3 show the characteristic evaluation results when the silicon nitride film formed by the above method is used as an insulating film of an nMOS capacitor.
[0047]
FIG. 2 shows the gate leakage current evaluation results. Here, the vertical axis (Ig) represents the leakage current when the flat band voltage is accumulated at −0.6 V, and the horizontal axis (Teq) represents the electrical film thickness.
[0048]
In the figure, POA-C indicates the case of this embodiment. In the figure, Ref. Pure SiO ₂ indicates a case of a silicon oxide film, None-POA indicates a case where only the above silicon nitride film formation process is performed, and no annealing process is performed, and POA-A indicates a temperature of 900 ° C. in an oxygen gas atmosphere. And POA-B indicates a case where annealing is performed at a temperature of 850 ° C. in a nitrogen monoxide gas atmosphere.
[0049]
As is clear from FIG. 2, the effect of reducing the leakage current is not observed in the case where the conventional annealing process using oxygen gas or nitric oxide gas is performed, compared with the case where the annealing process is not performed. In the case of the embodiment, in addition to the leakage current reduction effect (with respect to the silicon oxide film) by the silicon nitride film formation process, a further leakage current reduction effect can be obtained.
[0050]
FIG. 3 shows the evaluation result of the flat band voltage. Here, the vertical axis (Vfb) indicates the flat band voltage, and the horizontal axis (Teq) indicates the electrical film thickness. Reference numerals such as POA-A in the figure indicate the same as those in FIG.
[0051]
As is apparent from FIG. 3, when only the silicon nitride film forming process is performed and the annealing process is not performed, the absolute value of the flat band voltage is greatly increased as compared with the silicon oxide film. On the other hand, in the case of the present embodiment, an increase in the absolute value of the flat band voltage is largely suppressed.
[0052]
As described above, according to the method for manufacturing a semiconductor device according to the present embodiment, the leakage current can be further reduced and the increase in the absolute value of the flat band voltage is mitigated.
[0053]
In addition, although the manufacturing method of the semiconductor device according to the present embodiment uses ozone gas in the annealing process of the second film, oxygen plasma, nitrogen plasma, or hydrogen plasma may be used instead. Further, nitrogen plasma and oxygen plasma may be used sequentially.
[0054]
In addition, as a manufacturing apparatus used in the method of manufacturing a semiconductor device according to the present embodiment, a vertical rapid thermal processing apparatus capable of processing a large number of silicon substrates as described above is used. A leaf-shaped device may be used.
[0055]
In addition, the manufacturing apparatus used the vertical rapid thermal processing apparatus in the process of forming the silicon oxide film and the silicon nitride film and in the process of annealing the silicon nitride film in an ozone gas atmosphere. When the film is processed with plasma, a plasma processing apparatus is used.
[0056]
As the plasma processing apparatus, a plasma processing apparatus described below is preferably used.
[0057]
A plasma processing apparatus 28 shown in FIG. 4 includes a processing container 30 and a microwave generator 32.
[0058]
The processing container 30 has a shape in which, for example, a side wall and a bottom portion are made of a conductor such as aluminum, the whole is formed into a cylindrical shape, and an upper portion is reduced in diameter to a stepped shape. Inside the processing container 30, a mounting table 33 on which a silicon substrate is mounted is provided, and a sealed processing space S is formed. A plasma generation space S1 is formed above the processing space S. Further, a gas supply nozzle 34 for supplying a process gas whose flow rate is controlled is provided on the side wall of the processing container 30. An exhaust port 36 is provided at the bottom of the processing container 30.
[0059]
A microwave transmission window 38 is provided on the ceiling of the processing container 30. A disk-shaped planar antenna member 40 having a plurality of slits (not shown) formed on the upper surface side of the microwave transmitting window 38 is disposed. A slow wave material 42 is disposed on the upper surface of the planar antenna member 40.
[0060]
The microwave generator 32 generates microwaves of 2.45 GHz, for example, and is connected to the planar antenna member 40 via a rectangular waveguide 48 or the like.
[0061]
In the processing apparatus 28 configured as described above, the microwave generated by the microwave generator 32 propagates through the waveguide 48 and reaches the planar antenna member 40. Furthermore, an electrostatic field is generated between a plurality of concentrically formed slits in the planar antenna member 40 during the microwave propagation radially from the central portion of the planar antenna member 40 to the peripheral portion. An electrostatic field is formed. The process gas excited by the electrostatic field is turned into plasma, and the surface of the silicon substrate is processed.
[0062]
When the plasma processing apparatus 28 is used, the electron temperature is about 1 eV or less, and the plasma sheath voltage is also several volts or less, so that plasma damage can be greatly reduced with respect to conventional plasma having a plasma sheath voltage of about 50 V. .
[0063]
【The invention's effect】
According to the method of manufacturing a semiconductor device according to the present invention, since the second film made of the silicon nitride film or the silicon oxynitride film has the step of annealing in an ozone gas atmosphere, the increase in the absolute value of the flat band voltage is alleviated. In addition, the leakage current is reduced.
[0064]
Further, the same effect as described above can be obtained by using any one of oxygen plasma, nitrogen plasma, and hydrogen plasma instead of ozone gas, or by sequentially using nitrogen plasma and oxygen plasma.
[0065]
In addition, according to the method for manufacturing a semiconductor device of the present invention, plasma is generated by a planar antenna member having a plurality of slits, so that plasma damage to the film can be greatly reduced.
[Brief description of the drawings]
FIG. 1 is a schematic view of a semiconductor device manufacturing apparatus according to an embodiment of the present invention.
FIG. 2 is a graph for explaining a characteristic evaluation result when a silicon nitride film formed by the method for manufacturing a semiconductor device according to the present embodiment is used as an insulating film of an nMOS capacitor; Results are shown.
FIG. 3 is a graph for explaining a characteristic evaluation result when a silicon nitride film formed by the method for manufacturing a semiconductor device according to the present embodiment is used as an insulating film of an nMOS capacitor; An evaluation result is shown.
FIG. 4 is a schematic view of a plasma processing apparatus as another example of a semiconductor device manufacturing apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Manufacturing apparatus 12 Reaction tube 14 Manifold 16 Lid 18 Wafer port 20 Silicon substrate 22 Heating heater 24 Process gas supply pipe 26 Exhaust pipe 28 Plasma processing apparatus 30 Processing vessel 32 Microwave generator 33 Mounting table 34 Gas supply nozzle 36 Exhaust port 40 Planar antenna member 42 Slow wave material

Claims (6)

Forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate;
Forming a second film made of a silicon nitride film or a silicon oxynitride film on the first film;
Treating the second film with nitrogen plasma;
And subsequently, a process of treating the second film with oxygen plasma. Forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate;
Forming a second film made of a silicon nitride film or a silicon oxynitride film on the first film;
The second membrane, method for producing a semi-conductor device you; and a step of treating with oxygen plasma generated by the planar antenna member having a plurality of slits. Forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate;
Forming a second film made of a silicon nitride film or a silicon oxynitride film on the first film;
The second membrane, method for producing a semi-conductor device you; and a step of treating with hydrogen plasma generated by the plane antenna member having a plurality of slits. Forming a first film made of a silicon oxide film or a silicon oxynitride film on a silicon substrate;
Forming a second film made of a silicon nitride film or a silicon oxynitride film on the first film;
The second membrane, method for producing a semi-conductor device you; and a step of treating with nitrogen plasma generated by the plane antenna member having a plurality of slits. The method of manufacturing a semiconductor device according to claim 1, wherein the nitrogen plasma and the oxygen plasma are generated by a planar antenna member having a plurality of slits. Claims 1 to 5, further comprising the the first film during the step of forming the the process the second film forming a heat-treating the first film in an ammonia gas atmosphere The manufacturing method of the semiconductor device of any one of these.

Images