JP4562751B2 - Formation method of insulating film - Google Patents

Description

  The present invention relates to a method for forming an insulating film. More specifically, the present invention modifies the insulating film by irradiating the insulating film formed by CVD (Chemical Vapor Deposition) or the like with plasma based on a processing gas containing at least a rare gas. The present invention relates to a method for forming an insulating film that involves a step of performing the following. The modification method of the present invention can be used particularly preferably when the film obtained by this modification is used for a gate insulating film of a so-called transistor or an inter-electrode insulating film of a memory device.

  The present invention is generally widely applicable to the manufacture of electronic device materials such as semiconductors, semiconductor devices, and liquid crystal devices. Here, for convenience of explanation, a gate insulating film forming technique for transistors in semiconductor devices is described here. The background will be described as an example.

  Various treatments such as formation of an insulating film including an oxide film, film formation by CVD, etching, and the like are performed on a base material for a semiconductor or electronic device material including silicon.

  It is no exaggeration to say that the recent high performance of semiconductor devices has developed on the miniaturization technology of the devices including transistors. At present, transistor miniaturization technology is being improved with the aim of achieving higher performance. With the recent demand for miniaturization and higher performance of semiconductor devices, the need for higher performance insulating films (for example, in terms of leakage current) has increased remarkably. This is because even in the case of a leakage current of a level that was not practically a problem in a conventional relatively low integration device, a large amount of power is required in a recent miniaturized and / or high performance device. It is because there is a possibility of consuming. In particular, low power consumption devices are essential for the development of portable electronic devices in the so-called ubiquitous society that has started in recent years (information society using electronic devices connected to networks anytime and anywhere). This is a very important issue.

Typically, for example, in developing a next-generation MOS transistor, as the miniaturization technology as described above progresses, the thinning of the gate insulating film is approaching the limit, and a big problem to be overcome has appeared. . That is, as a process technology, it is possible to reduce the silicon oxide film (SiO ₂ ) currently used as a gate insulating film to the limit (1-2 atomic layer level), but the film thickness is 2 nm or less. In the case of the conversion, the leakage current due to the direct tunnel due to the quantum effect increases exponentially, and the power consumption increases.

  Currently, the IT (information technology) market is moving from fixed electronic devices (devices that supply power from outlets) represented by desktop personal computers and home phones to a “ubiquitous network society” that allows access to the Internet, etc. anytime and anywhere. Is trying to achieve the transformation. Accordingly, in the very near future, mobile terminals such as mobile phones and car navigation systems will become mainstream. Such a portable terminal is required to be a high-performance device itself, but at the same time, it is long even when driven by a small, lightweight battery, battery, or the like that is not so necessary for the above-mentioned fixed device. It is assumed that it has a function that can withstand the use of time. Therefore, in mobile terminals, it is extremely important to reduce power consumption while achieving higher performance.

  Typically, for example, when developing a next-generation MOS transistor, if the miniaturization of a high-performance silicon LSI is pursued, there is a problem that leakage current increases and power consumption also increases. Therefore, in order to reduce power consumption while pursuing performance, it is necessary to improve the transistor characteristics without increasing the gate leakage current of the MOS transistor.

Various methods (for example, modification of silicon oxide film, use of silicon oxynitride film SiON) have been proposed to meet the demand for realizing such a high-performance and low-power-consumption transistor. One of the promising methods is the development of a gate insulating film using a high-k (high dielectric constant) material, that is, a material having a dielectric constant higher than that of the SiO ₂ film. By using such a high-k material, it is possible to make EOT (Equivalent Oxide Thickness) which is a SiO2 equivalent film thickness thinner than the physical film thickness. That is, even with the same EOT as SiO2, it is possible to use a physically thick film, and a significant reduction in power consumption can be expected. As such a High-k material, various materials or substances having a dielectric constant higher than that of the SiO ₂ film are listed as candidates.

  A silicon oxide film (SiO 2) formed using an oxidation method has been used as a gate insulating film of a conventional transistor. The Si / SiO2 interface formed by this method has good characteristics and has characteristics such as fast carrier mobility during transistor operation. However, the leakage current increases as the film thickness decreases. And problems such as variations in threshold voltage due to boron penetration in PMOS have come to arise.

The aforementioned high-k material, which is a promising candidate for the gate insulating film of the next-generation transistor, cannot be formed using the same oxidation method as conventional oxide film formation. The film is formed by the method. In the conventional film formation technique, when a high-k material is formed on a large area (for example, a silicon wafer having a diameter of 200 mm), the film formation is performed at a low temperature of 500 degrees or less in order to maintain the uniformity of the film thickness and film quality. In this case, a large number of dangling bonds of atoms in the film due to the low-temperature process are generated, and the film characteristics may be deteriorated. In the case of high-k film formation by thermal CVD, an organic metal source such as Zr (OC (CH ₃ ) ₃ ) ₄ or Hf (OC ₂ H ₅ ) ₄ containing carbon atoms is often used as a film forming material. However, in this case, since carbon atoms are contained in the film, characteristic deterioration such as a decrease in dielectric constant and an increase in traps in the film is observed (Non-patent Document 1). In addition, when the film is formed directly on the silicon substrate by the CVD method, there is a significant deterioration of the interface characteristics. Therefore, when a high-k material is used for the gate insulating film, a laminated structure in which a thin (-10 A) oxide film (underlying oxide film) is formed at the interface is used to improve the interface characteristics between the insulating film and the Si substrate. ing.

Since the target film thickness of the gate insulating film using the high-k material is 12 A or less, a thin insulating film of 10 A or less is required as the base oxide film. However, when a thin oxide film of 10 A or less is directly formed on a Si substrate by a conventional thermal oxidation or plasma oxidation technique, it is necessary to perform processing at a low temperature in order to control the film thickness. Leakage current increases and interface characteristics deteriorate, and it becomes difficult to use this oxide film as a base oxide film. In addition, the oxide film formed by the CVD method, whose film thickness is relatively easy to control, has more silicon dangling bonds due to oxygen deficiency than the oxide film formed by thermal oxidation or plasma oxidation. It is inferior in terms of leak characteristics, reliability, and interface characteristics.
In addition, with the demand for miniaturization and low power consumption in the interelectrode insulating film of DRAMs and flash memories, the same problems as transistors such as high dielectric constant, high reliability, and reduction of leakage current have arisen. (Non-Patent Document 2).

ZrO2 film growth by chemical vapor deposition using zirconium tetra-tert-butoxide, M.A. Cameron, S.M. George, Thin Solid Films, 348 (1999), pp. 90-98 Ta2O5 capacitor formation technology for DRAM, Satoshi Kamiyama, Applied Physics, Vol. 69, No. 9, pp. 1067-1073 (2000)

  An object of the present invention is to provide a method for forming an insulating film capable of providing an insulating film which has solved the above-mentioned drawbacks of the prior art.

  Another object of the present invention is to provide a method for forming an insulating film capable of providing an insulating film having excellent film quality for an electronic device having excellent characteristics such as high performance and / or low power consumption. There is.

  As a result of earnest research, the inventor used a laminated structure composed of a plurality of materials for an insulating film based on vapor deposition, and further irradiated the plasma based on a processing gas containing at least a rare gas on the insulating film, It has been found that modifying the insulating film is extremely effective for achieving the above object.

  The insulating film forming method of the present invention is based on the above knowledge. More specifically, an insulating film formed by a method based on vapor deposition on a substrate for an electronic device is laminated with a plurality of layers. The film is formed so as to have a structure, and the above-described plasma treatment is performed to improve the characteristics by modifying the insulating film. The plasma treatment can be devised as necessary, for example, after each layer is formed or after all layers are formed, so that an optimum reforming effect can be easily obtained and the degree of freedom in process management is large. In addition, materials used for the plurality of layers can be widely selected as necessary, for example, when they are all made of the same substance, when they are made of different substances, or when they are partially the same. By changing the method of introducing the plasma modification treatment and the combination of the insulating materials, it is possible to expect the formation of an insulating film having suitable insulating characteristics under any process control.

  As described above, according to the present invention, a method for modifying an insulating film capable of providing an insulating film having excellent film quality for an electronic device having excellent characteristics such as high performance and / or low power consumption. Is provided.

  The present invention includes, for example, the following aspects.

  [1] When forming an insulating film including at least two layers on the surface of a substrate for electronic devices, one or more of these insulating film layers are modified by plasma irradiation based on a processing gas including at least a rare gas. A method for forming an insulating film, comprising:

  [2] The method for forming an insulating film according to [1], wherein the electronic device base material includes any one of a semiconductor material, a metal material, and an insulating material as a main component.

  [3] The method for forming an insulating film according to [1] or [2], wherein the plasma is formed by irradiating a planar antenna member (Slot Plane Antenna) with microwaves.

  [4] The insulating film is any one of a thermal oxidation (nitridation) method, a plasma oxidation (nitridation) method, a catalytic oxidation (nitridation) method, a CVD method (chemical vapor deposition method), and a PVD method (physical vapor deposition method). The method for forming an insulating film according to any one of [1] to [3], which is a film formed by the method.

  [5] The insulating film has two or more layers including at least a first layer immediately above the substrate surface and a second layer formed on the first layer, and these The method for forming an insulating film according to any one of [1] to [4], wherein the presence / absence of the modification treatment by the plasma irradiation and / or the modification conditions differ for each layer formation.

  [6] The insulating film has two or more layers including at least a first layer immediately above the substrate surface and a second layer formed on the first layer, and each layer is formed. The method for forming an insulating film according to any one of [1] to [4], wherein the modification treatment by plasma irradiation is performed every time.

  [7] The insulating film has two or more layers including at least a first layer immediately above the substrate surface and a second layer formed on the first layer, and these The method for forming an insulating film according to any one of [1] to [4], wherein after all the layers are formed, the modification treatment by the plasma irradiation is performed.

  [8] Any one of [1] to [7], wherein at least two layers constituting the insulating film are made of any one of an insulating material, a high-k (high dielectric constant) material, and a compound of these materials. The insulating film formation method as described.

[9] The method for forming an insulating film according to [8], wherein the insulating material is any one of SiO ₂ , Si ₃ N ₄ , and SiON.

[10] The High-k (high dielectric constant) _{material, Ta 2 O 5, ZrO 2} , HfO 2, Al 2 O 3, La2O 3, TiO 2, Y 2 O 3, BST, STO, PZT, Pr2O 3 , Cd2O _3, consists either of CeO ₂ [8] or [9] the method of forming a dielectric film according to.

  [11] The method for forming an insulating film according to any one of [1] to [10], wherein at least two layers constituting the insulating film are formed by CVD and / or PVD.

[12] The first layer of the insulating film is formed by any one of a thermal oxidation (nitridation) method, a plasma oxidation (nitridation) method, and a catalytic oxidation (nitridation) method, SiO ₂ , Si ₃ N ₄ , SiON And the method for forming an insulating film according to any one of [1] to [11], which is a layer selected from compounds of these substances.

  [13] The method for forming an insulating film according to any one of [1] to [12], wherein the kind of material forming each of at least two layers constituting the insulating film is one or more.

  [14] The method for forming an insulating film according to any one of [1] to [12], wherein the substances forming each of at least two layers constituting the insulating film are different from each other.

  [15] The method for forming an insulating film according to any one of [1] to [12], wherein the substances forming each of at least two layers constituting the insulating film are all the same substance.

  [16] The method for forming an insulating film according to any one of [1] to [15], wherein the insulating film is used as a gate insulating film of a transistor.

[17] The first layer immediately above the substrate constituting the insulating film is a silicon oxide film (SiO ₂ ) or a silicon oxynitride film (SiON), and the second layer is a high-k material [1] to [ The method for forming an insulating film according to any one of [16].

  [18] The method for forming an insulating film according to any one of [1] to [15], wherein the insulating film is used as a capacitive insulating film on a storage node electrode in a DRAM (Dynamic Random Access Memory).

  [19] The method for forming an insulating film according to any one of [1] to [15], wherein the insulating film is used as an interpoly insulating film on a floating gate electrode in a flash memory.

  [20] The insulating film according to any one of [1] to [19], wherein the plasma includes at least a rare gas and is formed of a processing gas including one or more of oxygen atoms, nitrogen atoms, and hydrogen atoms. Forming method.

  Hereinafter, the present invention will be described more specifically with reference to the drawings as necessary. In the following description, “parts” and “%” representing the quantity ratio are based on mass unless otherwise specified.

(Modification method)
In the present invention, the insulating film based on vapor deposition deposited on the substrate for electronic devices is irradiated with plasma based on a processing gas containing at least an oxygen atom-containing gas to modify the insulating film. .

(Electronic device substrate)
The substrate for electronic devices that can be used in the present invention is not particularly limited, and can be appropriately selected from one or a combination of two or more known substrates for electronic devices. Examples of such electronic device base materials include semiconductor materials and liquid crystal device materials. Examples of the semiconductor material include a material mainly composed of single crystal silicon, a material mainly composed of metal, and a material mainly composed of quartz.

(Insulating film based on oxidation and nitridation)
When the present invention is applied to a gate insulating film of a transistor, the first layer immediately above the substrate is formed by a thermal oxidation (nitriding) method, a plasma oxidation (nitriding) method, or a catalytic oxidation (nitriding) method. (SiO 2), silicon oxynitride film (SiON), and silicon nitride film (Si 3 N 4) can be used.

(Insulating film based on vapor deposition)
As long as the insulating film is based on vapor deposition, a film formed by known vapor deposition such as PVD or CVD can be used without particular limitation. When this insulating film contains a high-k material, the high-k film can be formed by PVD typified by techniques such as electron beam evaporation and sputtering, hot wire CVD utilizing a catalytic reaction, plasma. Although plasma CVD using a radical formation reaction by the above can be used, it is preferable to use a thermal CVD method from the viewpoint of uniformity and film quality.

(Insulating film modification by plasma)
The insulating film is modified by plasma. The type of gas used at this time can be selected as follows according to the purpose.
The plasma reforming process can be broadly divided into two cases: an oxygen plasma made of a gas containing a rare gas and oxygen atoms, and a nitrogen plasma made of a gas containing a rare gas and nitrogen atoms.
When a gas containing a rare gas and oxygen atoms is used, a large amount of oxygen radicals are generated and an oxidation reaction occurs. Therefore, when an oxidation process according to the present invention is performed on an insulating film formed by CVD using an organometallic source, organic substances (carbon atoms) contained in the insulating film in a large amount are burned by oxidation to improve the film quality. The effect to improve is expected. In addition, when applied to a CVD oxide film, improvement of characteristics can be expected by terminating the dangling bonds of Si existing in the film with oxygen.
When a gas containing a rare gas and a nitrogen atom is used, a large amount of nitrogen radicals are generated and a nitriding reaction occurs. Since the dielectric constant of the film increases when nitrogen atoms are contained in the insulating film, it can be suitably applied to miniaturization of capacitors. Further, since the oxidation resistance of the insulating film is improved by nitriding, when the metal electrode is formed on the insulating film between the electrodes of the capacitor, the oxidation of the upper metal electrode is suppressed, and the electrode It is possible to avoid problems such as peeling off and lowering of the dielectric constant. Moreover, since the effect of preventing boron penetration in the PMOS device is improved by performing nitriding, it is possible to suppress characteristic deterioration such as variation in threshold voltage of the PMOS device.
When applied to a laminated structure, plasma modification can be introduced arbitrarily during the formation of each layer. For example, the following various introduction methods are conceivable.
First layer formation → plasma oxidation → second layer formation → plasma nitridation → third layer formation → plasma oxidation → electrode formation first layer formation → second layer formation → third layer formation → plasma nitridation → electrode formation 1st layer formation → 2nd layer formation → plasma oxidation → 3rd layer formation → plasma nitridation → electrode generation 1st layer formation → plasma oxidation → 2nd layer formation → plasma nitridation → plasma oxidation → electrode formation 1st layer formation → plasma oxidation → Second layer formation → Plasma nitridation → Electrode formation By combining the conventional film formation method as described above and a modification process using plasma, an insulating film having suitable characteristics can be formed.

  The plasma to be used for the insulating film modification is not particularly limited. That is, currently used parallel plate RF plasma, induction coil (ICP) plasma, ECR plasma, or the following SPA plasma can be used.

These plasma characteristics have the following characteristics. In general, parallel plate RF plasma has an electron density of 1E9 to 11 / cm ³ and an electron temperature of ³ to 4 eV. This is a plasma with a low electron density and a high electron temperature. Due to the low density, sufficient reactive species cannot be formed, and due to the high electron temperature, charge injection into the film and plasma damage to the substrate are caused. It tends to occur.

In ICP plasma, the density is sufficient as 1E10-12 / cm ³ , but the electron temperature is as high as 3-4 eV, and damage tends to occur. Furthermore, the electron density of the ECR plasma can be controlled in a wide range of 1E9 to 13 / cm ³ , but the electron temperature is as high as 2 to 7 eV, and the electron density and temperature are trade-off, high and low. It is relatively difficult to form an electron temperature plasma. In addition, since each plasma has a common problem that it is difficult to increase the area, it is extremely difficult to apply it to a 300 mm wafer process, which is expected to be greatly developed in terms of mass productivity (Improvement of Electrical Properties for High-k Dielectrics Grown by MOCVD via Cyclic Remote Plasma Oxidation, Sadayoshi Horii et al. Extended Abstracts of the SSDM, Nagoya, 2002, pp.172-173).

  It is preferable to use the following SPA plasma from the viewpoint that it is easy to form a high-density and low-electron temperature plasma and that it is easy to cope with a large area (Characterization of Ultra Thin Oxynitride Formed by Radical Nitridation). with Slot Plane Antenna Plasma, Takuya Sugawara et al. Extended Abstracts of the SSDM, Nagoya, 2002, pp.714-715).

(Flat antenna member)
In the method for manufacturing an electronic device material according to the present invention, plasma with a low electron temperature and high density is formed by irradiating microwaves through a planar antenna member (SPA) having a plurality of slots. In the present invention, since the insulating film is modified by using plasma having such excellent characteristics, a process with low plasma damage and high reactivity can be achieved.

(Processing gas conditions)
In the modification of the insulating film of the present invention, the following conditions can be preferably used from the viewpoint of the characteristics of the insulating film to be formed by the modification.

  Noble gas (for example, Kr, Ar, He or Xe): 500 to 3000 sccm, more preferably 1000 to 2000 sccm,

O ₂ : 10 to 500 sccm, more preferably 10 to 300 sccm,

  Temperature: Room temperature (25 ° C.) to 600 ° C., more preferably 250 to 500 ° C., particularly preferably 250 to 400 ° C.

  Pressure: 3 to 400 Pa, more preferably 67 to 270 Pa, particularly preferably 67 to 130 Pa

Microwave: 0.7 to 4.5 W / cm ² , more preferably 1.4 to 3.6 W / cm ² , particularly preferably 1.4 to 2.8 W / cm ²

  According to the present invention, a high-quality insulating film can be formed. Therefore, it is easy to form a semiconductor device structure with excellent characteristics by forming another layer (for example, an electrode layer) on the insulating film and performing a subsequent process.

(One aspect of manufacturing apparatus)
Hereinafter, an aspect of a semiconductor manufacturing apparatus suitably used in the manufacturing method of the present invention will be described.

(One aspect of semiconductor device)
First, as an example of the structure of a semiconductor device that can be manufactured by the method for manufacturing an electronic device material of the present invention, a semiconductor device having a MOS structure having a gate insulating film as an insulating film will be described with reference to FIG.

  Referring to FIG. 1A, in FIG. 1A, reference numeral 1 is a silicon substrate, 11 is a field oxide film, 2 is a gate insulating film, and 13 is a gate electrode. As described above, according to the manufacturing method of the present invention, it is possible to form the gate insulating film 2 which is extremely thin and has a good quality. As shown in FIG. 1B, the gate insulating film 2 is made of a high quality insulating film formed at the interface with the silicon substrate 1.

In this example, the high quality insulating film 2 is formed by modifying a silicon oxide film (High Temperature Oxide: HTO) formed by thermal CVD with oxygen plasma using a rare gas and an oxygen gas as a processing gas. The first layer (21 in FIG. 1 (b)) and the second layer (22 in FIG. 1 (b)) formed by modifying HfSiO formed by thermal CVD with nitrogen plasma and oxygen plasma. And a laminated structure.
The example of a specific process is shown below. SiH.sub.2Cl.sub.2 and N.sub.2O were flowed at 200 sccm and 400 sccm respectively on a silicon substrate heated to 780.degree. C., and the pressure was maintained at 60 Pa for 5 minutes to form a 10A CVD silicon oxide film (HTO). The silicon substrate on which the HTO film is formed is plasma-modified by the following method. The silicon substrate on which the HTO film is formed is heated to 400 ° C., and a rare gas and oxygen are flowed over the wafer by 2000 sccm and 200 sccm, respectively, and the pressure is maintained at 130 Pa. A plasma containing oxygen and a rare gas is formed by irradiating a microwave of 3 W / cm 2 for 10 seconds through a planar antenna member (SPA) having a plurality of slots in the atmosphere. The film is modified to improve the film properties by terminating many Si dangling bonds existing in the film with oxygen atoms. Further, an HfSiO film is formed on the modified HTO film. Tertiary butoxyhafnium (HTB: Hf (OC2H5) 4) and silane gas (SiH4) are introduced at 1 sccm and 400 sccm, respectively, and the pressure is maintained at 50 Pa. The flow rate of HTB is the flow rate of the liquid mass flow controller, and the flow rate of silane gas is the flow rate of the gas mass flow controller. In this atmosphere, the silicon substrate on which the HTO is formed is heated at 350 ° C., and a reactive species of Hf, Si, and O is reacted on the substrate to form an HfSiO film. A 4 nm HfSiO film is formed by adjusting process conditions including processing time. This HTO / HfSiO laminated structure is further modified as follows using nitrogen plasma and oxygen plasma. The substrate is heated to 400 ° C., and a rare gas and nitrogen are flowed over the wafer at 2000 sccm and 150 sccm, respectively, and the pressure is maintained at 130 Pa. A plasma containing nitrogen and a rare gas is formed by irradiating a microwave of 3 W / cm 2 for 10 seconds through a planar antenna member (SPA) having a plurality of slots in the atmosphere. Nitriding treatment of the HfSiO laminated structure is performed to improve the dielectric constant and the oxidation resistance. Furthermore, oxygen plasma treatment similar to HTO reforming is performed to burn organic substances (carbon atoms) contained in a large amount in the film to improve the film characteristics. Since the nitriding treatment is performed before the final oxidation, an excessive increase in film thickness due to the oxidation is suppressed, and the formation of a gate insulating film having good characteristics with an electrical thickness of about 2 nm can be expected in the end.

  On the surface of the insulating film 2, a gate electrode 13 mainly composed of silicon (polysilicon or amorphous silicon) or metal is formed.

  Next, a semiconductor manufacturing apparatus for forming the above-described gate insulating film 2 will be described as one aspect of the manufacturing method.

  FIG. 2 is a schematic view (schematic plan view) showing an example of the entire configuration of a semiconductor manufacturing apparatus 30 for forming a gate insulating film according to the present invention. The semiconductor manufacturing apparatus 30 mainly includes a CVD processing unit 33 for forming an insulating film, a plasma processing unit 32 for modifying the insulating film formed in the CVD processing unit 33, and a transport system necessary for performing the processing. It is configured. Here, only the structure of each apparatus will be described in detail, and the description of the process including the wafer flow in the actual processing will be described in one aspect of logic device manufacturing described later.

  As shown in FIG. 2, a transfer chamber 31 for transferring the wafer W (FIG. 3) is disposed almost at the center of the semiconductor manufacturing apparatus 30, and surrounds the periphery of the transfer chamber 31. A plasma processing unit 32, a CVD processing unit 33, two load lock units 34 and 35 for performing communication / blocking operations between the processing chambers, and a heating unit 36 for performing various heating operations are provided. ing.

  Next to the load lock units 34 and 35, a preliminary cooling unit 45 and a cooling unit 46 for performing various preliminary cooling or cooling operations are respectively arranged.

  Inside the transfer chamber 31, transfer arms 37 and 38 are disposed, and the wafer W (FIG. 2) can be transferred between the units 32 to 36.

  Loader arms 41 and 42 are disposed on the front side of the load lock units 34 and 35 in the drawing. These loader arms 41 and 42 can further load / unload wafers W with four cassettes 44 set on a cassette stage 43 disposed on the front side thereof.

(One aspect of green membrane reformer)
FIG. 3 is a schematic cross-sectional view in the vertical direction of a plasma processing unit 32 that can be used for modifying the gate green film 2.

Referring to FIG. 3, reference numeral 50 is a vacuum vessel made of, for example, aluminum. An opening 51 larger than the substrate (for example, the wafer W) is formed on the upper surface of the vacuum vessel 50, and a flat made of a dielectric material such as quartz or aluminum oxide so as to close the opening 51. A cylindrical top plate 54 is provided. On the side wall on the upper side of the vacuum vessel 50, which is the lower surface of the top plate 54, for example, gas supply pipes 72 are provided at 16 positions arranged uniformly along the circumferential direction. A processing gas containing at least one selected from O ₂ , rare gas, N _2, H _{2, and the} like is supplied uniformly in the vicinity of the plasma region P of the vacuum vessel 50.

  On the outside of the top plate 54, a high frequency power supply unit is formed via a planar antenna member having a plurality of slots, for example, a slot plane antenna (SPA) 60 formed of a copper plate, for example, 2.45 GHz micro A waveguide 63 connected to a microwave power source 61 that generates a wave is provided. The waveguide 63 includes a flat plate-shaped waveguide 63A having a lower edge connected to the SPA 60, a cylindrical waveguide 63B having one end connected to the upper surface of the circular waveguide 63A, and the cylindrical waveguide. A coaxial waveguide converter 63C connected to the upper surface of the tube 63B, and a rectangular waveguide having one end connected perpendicularly to the side surface of the coaxial waveguide converter 63C and the other end connected to the microwave power source 61. 63D is combined.

  Here, in the present invention, UHF and microwaves are referred to as a high frequency region. That is, the high-frequency power supplied from the high-frequency power supply unit is 300 MHz to 2500 MHz including UHF of 300 MHz or higher and microwaves of 1 GHz or higher, and the plasma generated by these high-frequency power is called high-frequency plasma. .

  Inside the cylindrical waveguide 63B, one end side of the shaft portion 62 made of a conductive material is connected to substantially the center of the upper surface of the SPA 60, and the other end side is connected to the upper surface of the cylindrical waveguide 63B. Thus, the waveguide 63B is configured as a coaxial waveguide.

  A mounting table 52 for the wafer W is provided in the vacuum container 50 so as to face the top plate 54. The mounting table 52 incorporates a temperature control unit (not shown) so that the mounting table 52 functions as a heat plate. Further, one end side of the exhaust pipe 53 is connected to the bottom of the vacuum vessel 50, and the other end side of the exhaust pipe 53 is connected to the vacuum pump 55.

(One aspect of SPA)
FIG. 4 is a schematic plan view showing an example of SPA 60 that can be used in the electronic device material manufacturing apparatus of the present invention.

  As shown in FIG. 4, in the SPA 60, a plurality of slots 60a, 60a,... Are formed concentrically on the surface. Each slot 60a is a substantially rectangular through groove, and adjacent slots are arranged so as to be orthogonal to each other to form the letter “T” of the alphabet. The length and arrangement interval of the slots 60 a are determined according to the wavelength of the microwave generated from the microwave power supply unit 61.

(One aspect of CVD processing unit)
FIG. 5 is a schematic cross-sectional view in the vertical direction showing an example of a CVD processing unit 33 that can be used in the electronic device material manufacturing apparatus of the present invention.

  As shown in FIG. 5, the processing chamber 82 of the CVD processing unit 33 is formed in an airtight structure with aluminum or the like, for example. Although omitted in FIG. 5, the processing chamber 82 includes a heating mechanism and a cooling mechanism.

As shown in FIG. 5, the processing chamber 82 is connected to a gas introduction pipe 83 that introduces gas into the upper center, and the inside of the processing chamber 82 and the inside of the gas introduction pipe 83 are communicated with each other. The gas introduction pipe 83 is connected to a gas supply source 84. A gas is supplied from the gas supply source 84 to the gas introduction pipe 83, and the gas is introduced into the processing chamber 82 via the gas introduction pipe 83. Examples of the gas include silane and dichlorosilane, which are raw materials for forming a gate insulating film, and organic metal substances (for example, Hf (OC ₂ H ₅ ) ₄ , Ta (OC ₂ ) vaporized from a liquid through a vaporizer (heating evaporator). H ₅ ) ₅ ) or the like can be used, and an inert gas can also be used as a carrier gas if necessary.

  A gas exhaust pipe 85 for exhausting the gas in the process chamber 82 is connected to the lower part of the process chamber 82, and the gas exhaust pipe 85 is connected to an exhaust means (not shown) such as a vacuum pump. By this exhaust means, the gas in the processing chamber 82 is exhausted from the gas exhaust pipe 85, and the processing chamber 82 is set to a desired pressure.

  In addition, a mounting table 87 on which the wafer W is mounted is disposed below the processing chamber 82.

  In the embodiment shown in FIG. 5, the wafer W is mounted on the mounting table 87 by an electrostatic chuck (not shown) having the same diameter as that of the wafer W. The mounting table 87 is provided with a heat source means (not shown), and has a structure capable of adjusting the processing surface of the wafer W mounted on the mounting table 87 to a desired temperature.

  The mounting table 87 has a mechanism capable of rotating the mounted wafer W as necessary.

  In FIG. 5, an opening 82a for taking in and out the wafer W is provided on the wall surface of the processing chamber 82 on the right side of the mounting table 87. The opening and closing of the opening 82a moves the gate valve 98 in the vertical direction in the drawing. Is done. In FIG. 5, a transfer arm (not shown) for transferring the wafer W is provided adjacent to the right side of the gate valve 98, and the transfer arm enters and exits the processing chamber 82 through the opening 82a. The wafer W is placed on the substrate 87, and the processed wafer W is unloaded from the processing chamber 82.

  A shower head 88 as a shower member is disposed above the mounting table 87. The shower head 88 is formed so as to partition a space between the mounting table 87 and the gas introduction pipe 83, and is made of, for example, aluminum.

The shower head 88 is formed so that the gas outlet 83a of the gas introduction pipe 83 is located at the upper center of the shower head 88, and the gas is introduced into the processing chamber 82 through the gas supply hole 89 provided at the lower part of the shower head 88. Yes.
(One aspect of logic device manufacturing)
One mode in which the present invention is applied to the manufacture of a logic device will be described. Such a mode is roughly divided into element isolation, MOS transistor fabrication, capacitor fabrication, interlayer insulating film formation, and wiring. FIG. 6 is a flowchart of a logic device manufacturing process using the present invention.

  In the following, the fabrication of a MOS structure particularly deeply related to the present invention will be described among the pre-process for fabricating a MOS transistor including the process of the present invention.

(substrate)
A P-type or N-type silicon substrate is used as the substrate, and one having a specific resistance of 1 to 30 Ωcm and a plane orientation (100) is used.

  Depending on the purpose, element isolation processes such as STI and LOCOS and channel implantation are performed on the silicon substrate, and a sacrificial oxide film is formed on the surface of the silicon substrate on which the gate oxide film and gate insulating film are formed. (FIG. 6A).

(Cleaning before forming the gate insulation film)
In general, by RCA cleaning combining APM (mixture of ammonia, hydrogen peroxide, and pure water), HPM (mixture of hydrochloric acid, hydrogen peroxide, and pure water) and DHF (mixture of hydrofluoric acid and pure water). Remove sacrificial oxide film and contaminating elements (metal, organic matter, particles). SPM (mixed solution of sulfuric acid and hydrogen peroxide solution), ozone water, FPM (mixed solution of hydrofluoric acid, hydrogen peroxide solution and pure water), hydrochloric acid solution (mixed solution of hydrochloric acid and pure water), organic as required Sometimes alkali or the like is used.

(Formation of underlying oxide film)
Following the cleaning, a CVD oxide film (HTO: High Temperature Oxide) is formed in a thermal CVD apparatus (not shown) (FIG. 6B).

  Next, a gate valve (not shown) provided on the side wall of the vacuum vessel 50 in the plasma processing unit 32 (FIG. 2) is opened, and a CVD oxide film (HTO, 21) is formed on the surface of the silicon substrate 1 by the transfer arms 37 and 38. The wafer W on which (FIG. 1B) is formed is mounted on the mounting table 52 (FIG. 3), and the HTO is modified by plasma oxidation (FIG. 6B).

  After the gate valve is closed and the inside is sealed, the internal atmosphere is evacuated by the vacuum pump 55 through the exhaust pipe 53 and evacuated to a predetermined degree of vacuum, and maintained at a predetermined pressure. On the other hand, a microwave of 2.45 GHz (2200 W), for example, is generated from the microwave power source 61, and this microwave is guided by a waveguide and introduced into the vacuum vessel 50 via the SPA 60 and the top plate 54, whereby a vacuum is generated. High-frequency plasma is generated in the upper plasma region P in the container 50.

  Here, the microwave is transmitted through the rectangular waveguide 63D in the rectangular mode, converted from the rectangular mode to the circular mode by the coaxial waveguide converter 63C, and transmitted through the cylindrical coaxial waveguide 63B in the circular mode. The flat waveguide 63A is transmitted in the radial direction, is radiated from the slot 60a of the SPA 60, passes through the top plate 54, and is introduced into the vacuum vessel 50. At this time, since microwaves are used, high-density and low-electron temperature plasma is generated, and since microwaves are radiated from a number of slots 60a of the SPA 60, the plasma has a uniform distribution.

Next, while adjusting the temperature of the mounting table 52 and heating the wafer W to, for example, 400 ° C., a rare gas such as krypton or argon and O ₂ gas are introduced from the gas supply pipe 72 at a flow rate of 2000 sccm and 200 sccm, respectively. Then, oxygen plasma is generated to modify the CVD oxide film (HTO). FIG. 6 (B)
(Formation of High-k Gate insulating film)
Next, the gate valve (not shown) is opened, the transfer arms 37 and 38 (FIG. 2) are moved into the vacuum vessel 50, and the wafer W on the mounting table 52 is received. The transfer arms 37 and 38 take out the wafer W from the plasma processing unit 32, set it on a mounting table in the adjacent CVD processing unit 33, and form a high-k insulating film (step 2). FIG. 6 (C)

In the CVD processing unit 33, a high-k insulating film 22 is formed by introducing a source gas used for forming a High-k insulating film under predetermined conditions and appropriately heating the wafer W (FIG. 1). (E)). For example, an HfSiO film is formed as the high-k material. Tertiary butoxyhafnium (HTB: Hf (OC 2 H 5) 4) and silane gas (SiH 4) are introduced into the processing chamber 82 by 1 sccm and 400 sccm, respectively, through the gas introduction pipe 83, and the pressure in the processing chamber 82 is maintained at 50 Pa. The flow rate of HTB is the flow rate of the liquid mass flow controller, and the flow rate of silane gas is the flow rate of the gas mass flow controller. In this atmosphere, the silicon substrate W on which the HTO is formed is heated at 350 ° C., and the HfSiO film is formed by reacting the reactive species of Hf, Si, and O on the substrate. A 4 nm HfSiO film is formed by adjusting process conditions including processing time. (Fig. 6 (e), Fig. 10)
Next, nitriding was performed on the surface of the HTO / HfSiO laminated structure (2 in FIG. 1A) formed in the plasma processing unit 32 (FIG. 6D).

In this surface nitriding treatment, for example, in the vacuum vessel 50, the wafer temperature is, for example, 400 ° C., and the process pressure is, for example, 66.7 Pa (500 mTorr). N ₂ gas is introduced at a flow rate of 2000 sccm and 150 sccm, respectively.

On the other hand, for example, a microwave of ² W / cm ² is generated from the microwave power source 61, and this microwave is guided by the waveguide and introduced into the vacuum vessel 50 through the SPA 60 b and the top plate 54, thereby High-frequency plasma is generated in the upper plasma region P in the vacuum vessel 50.

  In this step (surface nitridation), the introduced gas is turned into plasma and nitrogen radicals are formed. The nitrogen radicals react on the insulating film on the upper surface of the wafer W, and nitride the surface of the insulating film in a relatively short time.

  By performing this nitriding treatment for 20 seconds, for example, the dielectric constant of the HTO / HfSiO multilayer structure is increased, and a reduction in storage capacity caused by miniaturization can be prevented. In addition, since the oxidation resistance and the boron penetration resistance are improved, it is possible to suppress deterioration of device characteristics when an electrode is formed on the upper portion. Subsequently, a plasma oxidation process is performed in the plasma processing unit 32 under the same conditions as those used for the above-described HTO reforming, and organic substances (carbon atoms) contained in the HfSiO film are burned to improve the film characteristics. Thereafter, the wafer W on which the HTO / HfSiO laminated structure was formed was taken out from the plasma processing unit 32 by the transfer arms 37 and 38, and set on the cassette stage 43 installed in front of the apparatus via the load lock units 34 and 35. The wafer cassette is transported by loader arms 41 and 42.

(Polysilicon film formation for gate electrodes)
Polysilicon (including amorphous silicon) is formed by CVD as a gate electrode of the MOS transistor on the high-k gate insulating film (including the base film) formed as described above. Gate insulation is achieved by heating a silicon substrate on which a gate insulating film is formed within a range of 500 ° C. to 650 ° C. and introducing a gas containing silicon (such as silane or disilane) onto the substrate under a pressure of 10 to 100 Pa. A polysilicon film for an electrode having a thickness of 50 nm to 500 nm is formed on the film. As the gate electrode, silicon germanium or metal (W, Ru, TiN, Ta, Mo, etc.) may be used in place of polysilicon (FIG. 6E).

(Gate patterning, source / drain formation, metal electrode formation)
Thereafter, gate patterning and selective etching are performed to form a MOS capacitor (FIG. 6F), and ion implantation (implantation) is performed to form a source and a drain (FIG. 6G). Thereafter, the dopant (phosphorus (P), arsenic (As), boron (B), etc. implanted into the channel, source, and drain) is activated by annealing. Subsequently, a MOS transistor according to this embodiment is obtained through a wiring process that combines film formation of an interlayer insulating film, patterning, selective etching, and metal film formation, which are subsequent processes (FIG. 6H). Finally, a logic device is completed by performing a wiring process on the transistor in various patterns and making a circuit.

In this embodiment, the application of the present invention to logic device manufacturing is taken as an example, and an HTO / HfSiO laminated structure is formed as a gate insulating film. However, it is also possible to form insulating films having other compositions. As the gate insulating film, insulating materials typified by SiO2, Si3N4, SiON, and High--typified by Ta2O5, ZrO2, HfO2, Al2O3, La2O3, TiO2, Y2O3, BST, STO, PZT, Pr2O3, Cd2O3, and CeO2. Examples thereof include one or more selected from the group consisting of k (high dielectric constant) substances and compounds of these substances.
In this embodiment, only the application of the present invention to logic device manufacturing is taken as an example. However, the method for forming an insulating film according to the present invention is applied to a capacitor insulating film on a storage node electrode in a DRAM or a floating gate electrode in a flash memory. It is also possible to apply to an interpoly insulating film.

  Further, in this embodiment, only thermal CVD is taken up as a method for forming an insulating film, but the film forming method is arbitrary. For example, film formation can be performed by a plasma CVD method or a PVD method.

  Hereinafter, the present invention will be described more specifically with reference to examples.

  7 and 8 show the evaluation results of the electrical characteristics of the MOS capacitor using the present invention for forming the insulating film. In the present invention, a laminated structure is used. Here, the effect of the invention was verified by modifying the HTO single layer.

  FIG. 7 shows leakage characteristics when the plasma treatment is performed after the HTO film formation and when the plasma treatment is not performed. The horizontal axis represents the electrical film thickness, and the vertical axis represents the leakage current value of the HTO oxide film at a gate voltage of −5V. FIG. 8 shows the evaluation results of the reliability evaluation results (TDDB: Time Dependent Dielectric Breakdown) of the same film. The horizontal axis of this graph represents the Qbd value (insulating film breakdown charge), and the vertical axis represents the failure rate. The device structure in this measurement was created by the following methods 1-7.

1: Substrate 2: Gate pre-oxidation cleaning 3: HTO film formation An HTO film was formed by CVD. SiH2Cl2 and N2O were allowed to flow 200 sccm and 400 sccm respectively on the substrate heated to 780 ° C., and the treatment was performed for 30 minutes while maintaining the pressure at 60 Pa to form a 60 A CVD oxide film (High Temperature Oxide: HTO).

4: Plasma oxidation process The silicon substrate on which the HTO film of 3 was formed was modified by the following method. 3 was transferred to a reaction chamber in a vacuum (back pressure 1 × 10 ^ -4 Pa or less), the substrate was kept at a temperature of 400 ° C., and noble gas and oxygen were each 1000 sccm, The pressure was maintained at 130 Pa (1 Torr) at a flow rate of 20 sccm. A plasma containing oxygen and a rare gas is formed by irradiating a microwave of 3 W / cm 2 through a planar antenna member (SPA) having a plurality of slots in the atmosphere, and 3 HTO films are formed using this plasma. Was reformed.

5: Polysilicon film formation for gate electrode Polysilicon film was formed by CVD as a gate electrode on the silicon substrate on which the HTO film formed in 1-4 was formed. The silicon substrate on which the HTO film was formed was heated at 630 ° C., 250 sccm of silane gas was introduced onto the substrate under a pressure of 33 Pa, and held for 30 minutes, thereby forming a polysilicon film for an electrode having a thickness of 3000 A on the HTO film. .

6: P (phosphorus) doping into polysilicon The silicon substrate on which the electrode polysilicon produced in 5 is formed is heated to 850 ° C., and PO ₂ Cl ₃ gas, oxygen, and nitrogen are added to the substrate at 350 sccm and 200 sccm, respectively. Phosphorus was doped into polysilicon by introducing 20,000 sccm at normal pressure and holding for 24 minutes.

7: Patterning, gate etching A portion that is not patterned by performing lithography patterning on the silicon substrate produced in Step 6 and immersing the silicon substrate in a chemical solution with a ratio of HF: HNO3: H2O = 1: 60: 60 for 3 minutes. The polysilicon capacitor was melted to fabricate a MOS capacitor.

  The measurement was performed by the following method. First, CV and IV characteristics of a capacitor having a gate electrode area of 10,000 um 2 were evaluated. The CV characteristic was obtained by sweeping the gate voltage from 0 V to -5 V with a frequency of 100 KHz and evaluating the capacitance at each voltage. The electrical film thickness was determined from the capacitance value at -5V. Further, the IV characteristic was obtained by sweeping the gate voltage from 0 V to −5 V and evaluating the current value (leakage current value) flowing at each voltage. Subsequently, a constant current stress of −0.1 A / cm 2 was applied to a capacitor having a gate electrode area of 10,000 μm 2, and the time until dielectric breakdown occurred (Break Down Time: Tbd) was measured. The absolute value of the product of current stress−0.1 A / cm 2 and Tbd was taken, and the dielectric breakdown charge (Qbd) was calculated.

  FIG. 7 shows the leakage characteristics of an HTO film formed by the above method and an HTO film not subjected to plasma treatment for comparison. The horizontal axis represents the electrical film thickness, and the vertical axis represents the leakage current value of the HTO oxide film at a gate voltage of −5V. As shown in FIG. 7, even when the plasma treatment is performed, the distribution of the electrical film thickness does not change, and the leakage current value is reduced to about half.

  FIG. 8 shows the evaluation results of the reliability evaluation results (TDDB: Time Dependent Dielectric Breakdown) of the same film. The horizontal axis of this graph represents the Qbd value (insulating film breakdown charge), and the vertical axis represents the failure rate. As shown in FIG. 8, the reliability (Qbd value) has been improved by about two orders of magnitude by performing plasma treatment on the HTO film.

  As described above, by using the process including the present invention, it is possible to form an HTO film having good leak characteristics and reliability. By using this HTO film as a base oxide film of a high-k gate insulating film, it can be expected to form a gate insulating film having good electrical characteristics.

  In the above example, only the result of applying the HTO film manufactured using the present invention to a MOS capacitor is mentioned. However, the present invention is used to form a laminated structure of an insulating film, and the insulating film is used as a transistor. The same effect can be realized by applying it to the gate insulating film and the inter-electrode insulating film of the memory device.

It is a typical vertical sectional view which shows an example of the semiconductor device which can be manufactured with the formation method of the base insulating film of this invention. It is a schematic plan view which shows an example of the semiconductor manufacturing apparatus for enforcing the formation method of the base insulating film of this invention. It is a typical vertical sectional view which shows an example of the slot plane antenna (SPA) plasma processing unit which can be used for the formation method of the base insulating film of this invention. It is a typical top view which shows an example of SPA which can be used for the formation method apparatus of the base insulating film of this invention. It is a typical vertical sectional view which shows an example of the CVD processing unit which can be used for the formation method of the base insulating film of this invention. It is a flowchart which shows an example of the transistor preparation process using the manufacturing method of this invention. It is a leak characteristic of the HTO film | membrane formed using this invention. It is a reliability evaluation result of the HTO film | membrane formed using this invention.

Claims (8)

A method for forming an insulating film , comprising:
On a substrate, forming a divorced oxide film,
Modifying the silicon oxide film by exposing it to a first plasma;
Forming a HfSiO film on the modified silicon oxide film;
Modifying the HfSiO film by exposing it to a second plasma,
The second plasma is a plasma containing a rare gas and a nitrogen gas,
A method further comprising exposing the HfSiO film treated with the second plasma to a plasma containing a rare gas and an oxygen gas. The method of claim 1 , wherein the first plasma is a rare gas and oxygen gas plasma. The HfSiO film The method of claim 1 or 2 formed by the silane and tertiary over Butokishiha off hexafluorophosphate (HTB). The insulating layer, the method according to any one of claims 1 to 3 which is a gate insulating film. The plasma, ICP plasma or method according to any one of claims 1 to 4, which is a microwave plasma through a planar antenna having a plurality of slots. _2. The method according to claim 1 , wherein the rare gas is selected from Kr, Ar, He, or Xe, and has a flow rate of 500 to 3000 sccm and a flow rate of O ₂ of 10 to 500 sccm. The method according to claim 1 or 6 , wherein the temperature of the substrate is room temperature (25 ° C) to 600 ° C. The pressure in the first plasma treatment, claim 1 is 3～400Pa, method of any one of 6,7.

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