KR20040088172A - Methods of forming semiconductor device having capacitors - Google Patents

Abstract

PURPOSE: A method for forming a semiconductor device with a capacitor is provided to prevent degradation of a dielectric film by performing diffusion plasma annealing after depositing the dielectric film. CONSTITUTION: A lower electrode(112a) is formed on a semiconductor substrate(101). A pretreatment layer(114) is formed on the lower electrode by using a rapid thermal nitridation method, a rapid thermal oxidation method or chemical vapor deposition method. A dielectric film is deposited on the resultant structure. By performing diffusion plasma annealing, an annealed dielectric film(116a) is formed.

Description

Method of forming semiconductor device having capacitors

The present invention relates to a method of forming a semiconductor device, and more particularly, to a method of forming a semiconductor device having a capacitor.

In accordance with the trend toward higher integration of semiconductor devices, the size of capacitors among semiconductor devices is gradually decreasing. Accordingly, many studies are being actively conducted to increase the capacitance of the capacitor.

In general, a capacitor includes a lower electrode, an upper electrode, and a dielectric film interposed between the upper and lower electrodes. The capacitance of the capacitor may be increased by a method of increasing the overlapped area of the lower electrode and the upper electrode, or by reducing the thickness of the dielectric layer.

As a method of increasing the area, a cylindrical capacitor or a capacitor of a deep trench has been proposed. However, the method of increasing the area is gradually reaching its limit in a situation in which the tendency for high integration of semiconductor devices is further intensified. The method of reducing the thickness of the dielectric film can increase the capacitance, but on the other hand, its application is limited because it can degrade the leakage current characteristics between the upper and lower electrodes.

Meanwhile, a method of increasing the dielectric constant of the dielectric layer has been proposed as a method of increasing the capacitance of the capacitor. That is, the dielectric film is a method of increasing the capacitance of the capacitor by using a high-k dielectric having a high dielectric constant.

Briefly describing a method of forming a capacitor having the high dielectric film, first, a lower electrode is formed on a semiconductor substrate, and the high dielectric film is deposited on the lower electrode. Heat treatment of the oxygen atmosphere is performed on the deposited high dielectric film. The heat treatment of the oxygen atmosphere compensates for the oxygen deficiency in the deposited high dielectric film, and further densifies the deposited high dielectric film. A capacitor is formed by forming an upper electrode on the heat-treated high dielectric film.

In the heat treatment of the oxygen atmosphere, when only the activation energy of oxygen gases is used as heat energy, the process temperature of the heat treatment may be considerably high. Due to the high process temperature, characteristics of other semiconductor devices (eg, MOS transistors) under the capacitor may be degraded. In order to solve this problem, plasma heat treatment has been proposed. The plasma heat treatment is a method of reducing the required activation energy by plasma-forming the oxygen gases. Accordingly, the process temperature of the plasma heat treatment can be reduced.

In general, the plasma heat treatment uses RF plasma heat treatment. Briefly describing the RF plasma heat treatment, a first electrode is disposed on the back side of the wafer on which the high dielectric film is deposited, and a second electrode is disposed on the wafer. A reference voltage (eg, a ground voltage) is applied to the first electrode, and a radio frequency of several tens of MHz is applied to the second electrode. Accordingly, oxygen gases between the wafer and the second electrode are converted into a plasma state. Subsequently, oxygen ions of the plasma are injected into the high dielectric film anisotropically by an electric field applied between the first and second electrodes. In this case, when the high dielectric film is deposited on a three-dimensional structure, for example, a cylinder having a high height or a deep trench, the high dielectric film is non-uniformly supplemented with oxygen ions due to the anisotropic oxygen ions. . That is, the high dielectric film on the sidewall of the lower electrode may be replenished with less oxygen ions than the high dielectric film on the top surface of the lower electrode. In addition, the high dielectric film may be damaged by anisotropic oxygen ions accelerated by an electric field applied between the first and second electrodes. As a result, the dielectric film characteristics such as leakage current characteristics may be degraded due to oxygen deficiency or damage to the high dielectric film.

An object of the present invention is to provide a method of forming a semiconductor device having a capacitor capable of preventing the deterioration of characteristics of the dielectric film.

1 to 4 are cross-sectional views illustrating a method of forming a semiconductor device having a capacitor according to a preferred embodiment of the present invention.

5 is a schematic diagram of equipment used in the diffusion plasma heat treatment according to the present invention.

6 is a flow chart for explaining the diffusion plasma heat treatment method according to the present invention.

7 is a graph illustrating the leakage current characteristics of the dielectric film formed by the diffusion type plasma heat treatment according to the present invention.

To provide a method of forming a semiconductor device having a capacitor for solving the above technical problem. The method includes forming a bottom electrode on a semiconductor substrate and depositing a dielectric film on the bottom electrode. A diffusion plasma heat treatment using at least processing gases is performed on the semiconductor substrate having the dielectric film.

Specifically, the lower electrode may be formed of at least one selected from the group consisting of a doped polysilicon film and a conductive metal compound. Before depositing the dielectric film, the method may further include forming a pretreatment film on the surface of the lower electrode. The pretreatment layer may be formed of one selected from the group consisting of a rapid thermal nitridation method, a rapid thermal oxidation method, a chemical vapor deposition method, and an atomic layer deposition method. The dielectric layer may be formed of a high dielectric layer having a higher dielectric constant than that of the silicon oxide layer. Alternatively, the dielectric film may be formed of a ferroelectric film. The process gases preferably include at least one selected from oxygen source gases and nitrogen source gases. The diffusion plasma heat treatment is preferably microwave plasma heat treatment. In this case, the performing of the microwave plasma heat treatment may include introducing a semiconductor substrate having the dielectric film into a process chamber and supplying microwaves into the process chamber. At least the process gases are introduced into the process chamber supplied with the microwave to convert the process gases into a plasma state. The plasma-treated process gases are applied to the dielectric film by diffusion to heat the dielectric film. The heat treated dielectric film is withdrawn from the process chamber. Supplying the microwave may include generating microwaves from the microwave generator in communication with the waveguide through the waveguide. The microwave is guided to the waveguide and delivered into the process chamber, and the delivered microwave is uniformly supplied to the upper surface of the semiconductor substrate via a baffle plate in the process chamber. Depositing the dielectric film and performing the diffusion plasma heat treatment may be performed at least twice. The method may further include forming an upper electrode on the diffusion plasma heat-treated dielectric layer. The upper electrode may be formed of at least one selected from the group consisting of a doped polysilicon film and a conductive metal compound.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed subject matter is thorough and complete, and that the spirit of the present invention to those skilled in the art will fully convey. If it is mentioned that the layer is on another layer or substrate it may be formed directly on the other layer or substrate or a third layer may be interposed therebetween. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Portions denoted by like reference numerals denote like elements throughout the specification.

1 to 4 are cross-sectional views illustrating a method of forming a semiconductor device having a capacitor according to a preferred embodiment of the present invention.

Referring to FIG. 1, an isolation region 102 is formed on a semiconductor substrate 101 to define an active region. The device isolation layer 102 may be formed as a trench device isolation layer. Impurity diffusion layers 103 are formed by selectively implanting impurity ions into the active region. The impurity diffusion layer 103 may be a source / drain region of a MOS transistor. For example, the impurity diffusion layer 103 may be a source / drain region of a MOS transistor constituting a unit cell of a DRAM device. Alternatively, the impurity diffusion layer 103 may be a source / drain region of a MOS transistor constituting a unit cell of a ferroelectric memory device (FRAM device) that is a nonvolatile memory device.

An interlayer insulating film 104 is formed on the entire surface of the semiconductor substrate 101 having the impurity diffusion layer 103. The interlayer insulating film 104 may be formed of a silicon oxide film. A contact plug 105 is formed through the interlayer insulating film 104 and electrically connected to a predetermined region of the impurity diffusion layer 103. The contact plug 105 may be formed of a doped polysilicon film or a metal film such as tungsten as a conductive film.

An etch stop layer 107 and a mold layer 108 are sequentially formed on the entire surface of the semiconductor substrate 101 having the contact plug 105. The etch stop layer 107 is formed of an insulating layer having an etch selectivity with respect to the mold layer 108. For example, when the mold layer 108 is formed of a silicon oxide film, the etch stop layer 107 may be formed of a silicon nitride film.

The mold layer 108 and the etch stop layer 107 are successively patterned to form a lower electrode hole 110 exposing at least an upper surface of the contact plug 105. The lower electrode layer 112 is formed on the entire surface of the semiconductor substrate 101 having the lower electrode hole 110. The lower electrode layer 112 fills the inside of the lower electrode hole 110. The lower electrode film 112 is formed of a conductive film. For example, it is preferable to form at least one selected from the group consisting of a doped polysilicon film and a conductive metal compound. The conductive metal compound may be composed of a conductive metal oxide film such as ruthenium oxide film (RuO), a conductive metal oxynitride film, or a conductive metal nitride film (ex, TaN, TiN). Before forming the lower electrode layer 112, an anti-oxidation layer (not shown) may be further formed between the lower electrode layer 112 and the contact plug 105. The anti-oxidation film is a conductive film and serves to prevent the interface between the contact plug 105 and the lower electrode film 112 from being oxidized.

2, 3, and 4, the lower electrode layer 112 is planarized until the upper surface of the mold layer 108 is exposed to form the lower electrode 112a in the lower electrode hole 110. do. In the present embodiment, the lower electrode 112a is formed in a stack-shaped shape. Alternatively, the lower electrode 112a may be formed in a cylinder-shaped or concave-shaped shape. Alternatively, the lower electrode 112a may be a deep trench-shaped formed in the semiconductor substrate 101.

The mold layer 108 is removed by etching by wet etching. Accordingly, sidewalls of the lower electrode 112a and the etch stop layer 107 are exposed. In this case, the interlayer insulating film 104 is protected by the etch stop layer 107.

A pretreatment film 114 is formed on the entire surface of the semiconductor substrate 101 having the lower electrode 112a with the sidewalls exposed, and a dielectric film 116 is deposited on the pretreatment film 114. The pretreatment layer 114 prevents a reaction or diffusion between the lower electrode 112a and the dielectric layer 116. The pretreatment film 114 may be formed of an oxide film or a nitride film. The pretreatment layer 114 may be formed by a rapid thermal oxidation process (RTO process) or a rapid thermal nitridation process (RTN process). In this case, the pretreatment film 114 may be formed on the surface of the lower electrode 112a. Alternatively, the pretreatment film 114 may also be formed by chemical vapor deposition or atomic layer deposition. In some cases, the pretreatment film 114 may be omitted.

The dielectric film 116 is preferably formed of a high-k dielectric, which is an insulating film having a higher dielectric constant than a silicon oxide film. For example, it may be formed of a tantalum oxide film (TaxOy), a hafnium oxide film (HfxOy), a titanium oxide film (TixOy), an aluminum oxide film (AlxOy), or a lanthanum oxide film (LaxOy). Alternatively, the dielectric film 116 may be formed of a ferroelectric film. For example, SrTiO ₃ , BaTiO ₃ , BST, PZT, SBT (SrBi ₂ Ta ₂ O ₉ ), PLZT ((Pb, La) (Zr, Ti) O ₃ ), ((Pb, Ca) (Zr, Ti ) O ₃ ), Bi ₄ Ti ₃ O ₁₂ Or BLT (BiLaTiO ₃ ) It can be formed. The dielectric layer 116 may be formed by physical vapor deposition, chemical vapor deposition, or atomic layer deposition.

Diffusion plasma annealing using process gases is performed on the semiconductor substrate 101 having the dielectric layer 116.

Due to the diffusion type plasma heat treatment, impurities in the dielectric layer 116 are removed, and the dielectric layer 116 is further densified. In addition, the diffusion plasma heat treatment may cause phase transformation of the dielectric layer 116. The dielectric layer 116 exhibits various characteristics depending on the crystal state and the amorphous state. For example, when the dielectric layer 116 is in a crystalline state, the dielectric constant of the dielectric layer 116 increases while the leakage current characteristic of the dielectric layer 116 may deteriorate. When the dielectric layer 116 is in an amorphous state, while the dielectric constant of the dielectric layer 116 is reduced, the leakage current characteristic of the dielectric layer 116 may be improved. These characteristics can be adjusted according to the process conditions of the diffusion plasma heat treatment.

Another function of the diffusion plasma heat treatment is to inject the process gases into the dielectric film 116. The process gases are preferably at least one selected from oxygen source gases and nitrogen source gases. The oxygen source gases may use O ₂ or O ₃ . The nitrogen source gases may use N ₂ or NH ₃ and the like. Oxygen supplements insufficient oxygen in the dielectric film 116 to improve the characteristics of the acidic dielectric film 116. Alternatively, the nitrogen is injected into the dielectric film 116 to increase the crystallization temperature of the dielectric film 116. As a result, the leakage current characteristics of the dielectric layer 116 may be improved. In addition, in the diffusion type plasma heat treatment, argon (Ar), hydrogen (H ₂ ), or helium (He) gases may be used together with the processing gases.

The diffusion plasma heat treatment method first converts the process gases into a plasma state. In this case, the plasma may include ionic components in which the process gases are completely ionized and radical components sufficiently excited, although the process gases are not ionized. Subsequently, the ionic components or the radical components randomly move to the dielectric layer 116 by the diffusion motion due to the concentration difference. In other words, the ionic components or radical components move in a random direction, that is, isotropic to uniformly contact the entire dielectric layer 116. Accordingly, partial degradation of the dielectric film due to nonuniform injection of conventional ionic components can be prevented. In addition, the diffusion plasma heat treatment does not have ionic components that perform anisotropic motion according to a conventional electric field. Accordingly, it is possible to prevent damage to the dielectric film by conventional anisotropic ionic components. As a result, the deterioration of characteristics of the dielectric layer 116 may be prevented due to the diffusion type plasma heat treatment.

The process of depositing the dielectric film 116 and performing the diffusion plasma heat treatment may be performed once to form the diffusion plasma heat treated dielectric film 116a having a required thickness. Alternatively, the process of depositing the dielectric film 116 and performing the diffusion plasma heat treatment may be repeated at least twice to form at least two layers of the diffusion plasma heat treated dielectric films 116a. That is, a plurality of diffusion type plasma heat-treated dielectric layers 116a may be formed to form a capacitor dielectric layer having a required thickness. In FIGS. 3 and 4, two layers of the diffusion type plasma heat-treated dielectric layers 116a are illustrated, but three or more layers may be stacked.

An upper electrode 120 is formed on the semiconductor substrate 101 having the diffusion type plasma heat-treated dielectric layers 116a. The upper electrode 120 may be formed of one selected from the group consisting of a doped polysilicon film and a conductive metal compound. The upper electrode 120 may be formed of the same material as the lower electrode 112a. The lower electrode 112a, the diffusion plasma heat-treated dielectric layer 116a, and the upper electrode 120 constitute a capacitor. When the diffusion plasma heat-treated dielectric film 116a is the high dielectric film, the capacitor may constitute a unit cell of a DRAM element. When the diffusion plasma heat-treated dielectric film 116a is the ferroelectric film, the capacitor may be The unit cell of the ferroelectric memory element which is a nonvolatile memory element can be comprised. Of course, the capacitor may constitute another semiconductor device.

The diffusion plasma heat treatment is preferably performed by microwave plasma heat treatment. The microwave plasma heat treatment method will be described with reference to FIGS. 5 and 6.

5 is a schematic diagram of equipment used in the diffusion plasma heat treatment according to the present invention, Figure 6 is a flow chart for explaining the diffusion plasma heat treatment method performed by the equipment of FIG.

5 and 6, the equipment for performing the microwave plasma heat treatment of the equipment for performing the diffusion-type plasma heat treatment according to the present invention is shown in FIG. The equipment is arranged with a process chamber 150 having an interior space in which the diffusion plasma heat treatment process is performed. The microwave generator 160 communicating with the internal space of the process chamber 150 by the waveguide 158 is disposed. A wafer chuck 152 is disposed inside the process chamber 150 opposite the waveguide 158. The wafer chuck 152 is a place where the wafer W is loaded. The wafer W is used as the semiconductor substrate 101 shown in FIGS. 1 to 4. A baffle plate 154 is disposed in the process chamber 150. The baffle plate 154 is disposed adjacent to one side of the waveguide 158 in contact with the process chamber 150. At least one gas injection tube 156 is disposed in communication with the process chamber 150. The gas injection pipe 156 is disposed between the baffle plate 154 and the wafer chuck 152, and is disposed adjacent to the baffle plate 154.

A method of performing a microwave plasma heat treatment process using the above-described equipment will be described with reference to the flowchart of FIG. 6 and FIG. 2 or FIG. 3.

First, a wafer W having the deposited dielectric film 116 illustrated in FIG. 2 or 3 is introduced into the process chamber 150 (S200). The wafer W is loaded onto the wafer chuck 152. In this case, the wafer W may be fixed to the upper surface of the wafer chuck 152 by fixing means (not shown) using a vacuum pressure in the wafer chuck 152.

Microwaves are supplied to the process chamber 150 in which the wafer W is mounted (S210). In the method of supplying the microwave to the process chamber 150, first, the microwave is generated from the microwave generator 160. The microwave can have a frequency of several kilohertz. The microwave is delivered into the process chamber 150 via the waveguide 158. The microwaves delivered into the process chamber 150 are uniformly supplied to the entire upper portion of the wafer W via the baffle plate 154.

Subsequently, process gases are introduced into the process chamber 150 through the gas injection tube 156 (S220). In addition to the process gases, argon (Ar), hydrogen (H ₂ ) or helium (He) gases may be further introduced. At this time, the pressure in the process chamber 150 may be 100mtorr to 760torr. The process temperature of the process chamber 150 may be 20 ℃ to 600 ℃. The processing gases are introduced into the microwave which is uniformly supplied under the baffle plate 154. Accordingly, the process gases are converted into a plasma state composed of ionic or radical components by the microwave.

A diffusion plasma heat treatment is performed on the wafer W at the plasma and the process temperature (S230). The concentration of the plasma is highest at the place where the plasma is formed. In contrast, the concentration of the plasma on the upper surface of the wafer W is very low. Accordingly, the ionic or radical components in the plasma diffuse from the place where the plasma is formed to the wafer W and move randomly. Accordingly, even if the lower electrode 112a of FIG. 2 has a three-dimensional structure, the ion components or the radical components may be uniformly coated on the dielectric layer 116. In addition, the equipment does not apply an electric field between the waveguide 158 and the wafer chuck 152. Accordingly, the diffusion plasma heat treated dielectric layer 116a is not damaged. As a result, the characteristics of the diffusion type plasma heat treated dielectric layer 116a may be improved.

Subsequently, the wafer W is withdrawn from the process chamber 150 (S240).

The leakage current characteristics among the characteristics of the above-described diffusion type plasma heat-treated dielectric film will be described with reference to the graph of FIG. 7.

7 is a graph illustrating the leakage current characteristics of the dielectric film formed by the diffusion type plasma heat treatment according to the present invention. In the graph, the horizontal axis represents the voltage difference between the lower electrode and the upper electrode of the capacitor, and the vertical axis represents the amount of leakage current between the lower electrode and the upper electrode.

5 and 7, the curve 270 in the graph shows the leakage current according to the voltage of the dielectric film formed using the conventional RF plasma heat treatment, and the curve 275 shows the microwave plasma heat treatment according to the present invention. The leakage current according to the voltage of the dielectric film is shown. The dielectric layers of the curves 270 and 275 are formed to have the same thickness as 40 으로 with the hafnium oxide layer HfO ₂ , which is a high dielectric film. Process conditions for the RF plasma heat treatment performed on the dielectric film of the curve 270 is a process temperature of 200 ℃, the internal pressure of the process chamber 150 is 2.5torr, the flow rate of oxygen gas is 8 slm. Process conditions of the microwave plasma heat treatment performed on the dielectric film of the curve 275 is a process temperature of 250 ℃, the internal pressure of the process chamber 150 is 2.5torr, the concentration of oxygen gas is 8 slm.

As shown, it can be seen that the leakage current amount of the curve 275 is less than the leakage current amount of the curve 270. In particular, although the process temperature of the curve 275 is higher than that of the curve 270, the leakage current amount of the curve 275 is less than the leakage current amount of the curve 270.

As a result, it can be seen that a portion of the RF plasma heat-treated dielectric layer is damaged or oxygen is deficient in the portion. In contrast, it can be seen that the microwave plasma heat-treated dielectric film was provided with sufficient oxygen supplementation and was not damaged.

As described above, according to the present invention, after depositing the dielectric film constituting the capacitor, diffusion plasma heat treatment is performed. In the diffusion type plasma heat treatment, ion components or radical components are applied to the dielectric layer by diffusion using concentration differences. Accordingly, even if the lower electrode under the dielectric film has a three-dimensional structure, the dielectric film may be uniformly plasma-treated. In addition, it is possible to prevent dielectric film damage caused by conventional anisotropic ionic components. As a result, by performing the diffusion-type plasma heat treatment, it is possible to prevent the phenomenon in which the conventional dielectric film properties deteriorate.

Claims (17)

Forming a lower electrode on the semiconductor substrate; Depositing a dielectric film on the lower electrode; And And performing a diffusion type plasma heat treatment using at least process gases on the semiconductor substrate having the dielectric film. The method of claim 1, And forming the lower electrode at least one selected from the group consisting of a doped polysilicon film and a conductive metal compound. The method of claim 1, Before depositing the dielectric film, Forming a pretreatment film on the surface of the lower electrode further comprising the step of forming a semiconductor device having a capacitor. The method of claim 3, wherein The pretreatment film is formed of one selected from the group consisting of a rapid thermal nitriding method, a rapid thermal oxidation method, a chemical vapor deposition method, and an atomic layer deposition method. Method of formation. The method of claim 1, And the dielectric film is formed of a high dielectric film having a higher dielectric constant than a silicon oxide film. The method of claim 1, And the dielectric film is formed of a ferroelectric film. The method of claim 1, The process gas is a method of forming a semiconductor device having a capacitor, characterized in that at least one selected from oxygen source gas and nitrogen source gas. The method of claim 1, The diffusion plasma heat treatment is a method of forming a semiconductor device having a capacitor, characterized in that the microwave plasma heat treatment. The method of claim 8, Performing the microwave plasma heat treatment, Introducing a semiconductor substrate having the dielectric film into a process chamber; Supplying microwaves into the process chamber; Converting the process gas into a plasma state by introducing at least the process gases into the process chamber supplied with the microwaves; Heat treating the dielectric film by applying the plasmalized process gases to the dielectric film by diffusion; And And extracting the heat-treated dielectric film from the process chamber. The method of claim 9, Supplying the microwave, Generating microwaves from the microwave generator in communication with the process chamber through a waveguide; Directing the microwaves into the waveguide and delivering them into the process chamber; And And uniformly supplying the transferred microwaves to an upper portion of the front surface of the semiconductor substrate through a baffle plate in the process chamber. The method of claim 1, And depositing the dielectric film and performing the diffusion plasma heat treatment are performed at least twice. The method of claim 1, And forming an upper electrode on the diffusion type plasma heat-treated dielectric layer. The method of claim 12, And the upper electrode is formed at least one selected from the group consisting of a doped polysilicon film and a conductive metal compound. Forming a lower electrode on the semiconductor substrate; Depositing a high-k dielectric on the lower electrode; Performing a microwave plasma heat treatment using a processing gas on the semiconductor substrate having the high dielectric film; And And forming an upper electrode on the microwave plasma heat-treated high dielectric film. The method of claim 14, The process gas is a method of forming a semiconductor device having a capacitor, characterized in that at least one selected from oxygen source gases and nitrogen source gases. The method of claim 14, Performing the microwave plasma heat treatment, Introducing a semiconductor substrate having the high dielectric film into a process chamber; Applying a microwave inside the process chamber; Converting the process gas into a plasma state by introducing at least the process gases into the process chamber to which the microwave is applied; Heat-treating the dielectric film by applying the plasmalized process gases to the high dielectric film by diffusion; And And drawing out the heat-treated high dielectric film from the process chamber. The method of claim 14, And depositing the high dielectric film and performing the diffusion plasma heat treatment are performed at least twice.