KR20040100766A - Method of forming composite dielectric layer by atomic layer deposition and method of manufacturing capacitor using the same - Google Patents

Abstract

PURPOSE: A method of forming composite dielectric films and a method of manufacturing a capacitor using the same are provided to form sequentially thin films with different decomposition temperature in one chamber by performing an ALD(Atomic Layer Deposition) using a reaction material with a large temperature window. CONSTITUTION: A substrate is loaded in a reaction chamber(S10). A first metal(S20) is adsorbed on the substrate by providing a first metal compound to the reaction chamber(S20). A first dielectric film is formed by oxidizing the adsorbed first metal by providing oxidizing gas to the reaction chamber(S30). A second metal is adsorbed on the first dielectric film by providing a second metal compound to the reaction chamber(S40). The second metal compound is a metal alkoxide compound with electron withdrawing group substituted for at least one hydrogen. A second dielectric film is formed by oxidizing the adsorbed second metal by providing oxidizing gas to the reaction chamber(S50).

Description

METHODS OF FORMING COMPOSITE DIELECTRIC LAYER BY ATOMIC LAYER DEPOSITION AND METHOD OF MANUFACTURING CAPACITOR USING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a composite dielectric film used in a semiconductor device and a method of manufacturing a capacitor using the same, and more particularly, using an atomic layer deposition (ALD) method, which shows remarkably improved processability and economy. An in-situ formation method of a composite dielectric film and a method of manufacturing a capacitor of a semiconductor device using the same.

The ALD method is a thin film deposition technique using chemical adsorption and desorption of monoatomic layers. Each reactant is individually separated and supplied to the chamber in a pulse form. Adsorption and desorption are used.

1A-1D are cross-sectional views illustrating the reaction mechanism of a typical ALD. Referring to FIG. 1A, a gaseous reactant AXn (g) is transferred to the wafer 10. The delivered reactant AXn (g) is adsorbed to the surface by chemisorption and is deposited by physical adsorption on the chemical adsorbate.

Referring to FIG. 1B, when the physically adsorbed AXn is removed by a purging process, only the chemically adsorbed solid state AXn (s) remains. Therefore, the monoatomic layer has a thickness. Here, Xn means a chemical ligand formed of n groups.

Referring to FIG. 1C, when water vapor such as H20 is delivered to the surface of the material coated with AXn (s), A is oxidized to generate AO on the surface, and the Xn group reacts with the H group to remove HXn (g). Referring to FIG. 1D, when residual impurities are removed by a purging process, only an oxide layer having a thickness of a monoatomic layer of AO (s) in a chemically adsorbed solid state remains.

Unlike the conventional chemical vapor deposition (CVD), the ALD reacts with the reaction gas only on the substrate surface and does not react between the gas and the gas by a self-limiting reaction. Therefore, it is easy to precisely control the composition of the thin film, there is no particle generation, it is excellent in uniformity when depositing a large area of the thin film, it is easy to precisely control the thickness of the thin film, contains less impurities in the thin film, and has excellent step coverage. . In addition, the ALD thin film deposition process is expected to emerge as a more important process as the design rule of the semiconductor device is reduced in the future.

On the other hand, the dielectric film used for the semiconductor capacitor and the like must have both dielectric properties to ensure large capacitance in a thin film state and insulating properties to be small in current leakage. In order to satisfy these characteristics, recent studies on composite dielectric films have been conducted.

For example, Korean Patent Laid-Open Publication No. 10-2001-0088207 discloses a tantalum oxide film-titanium which can improve the stable leakage current characteristics and the dielectric constant of the tantalum oxide film by forming a titanium oxide film on the tantalum oxide film formed by the CVD method by the ALD method. A method of forming an oxide composite dielectric film is disclosed. However, in this method, since the tantalum oxide film is laminated by the CVD method, precise thickness control is not easy, and there is a problem in fairness because different lamination methods such as CVD and ALD are used simultaneously.

In addition, Korean Patent Publication No. 10-2001-0056446 discloses a continuous deposition method of aluminum oxide and tantalum oxide by the ALD method. According to the present invention, aluminum oxide and tantalum oxide are continuously deposited in the temperature range of 200 to 600 ° C. In this case, since decomposition temperature is different between different reaction sources, the decomposition of some source materials before the ALD reaction results in the ALD method. There is a possibility that the lamination by means may not be easy.

In other words, since the composite dielectric film uses different heterogeneous compounds as reactants, the temperature window of the process is important. This will be described by taking an aluminum oxide film (Al 2 O 3) and a hafnium oxide film (HfO 2) as an example of continuous deposition using ozone as an oxidizing gas.

The reaction temperature of the process of forming aluminum oxide film (Al2O3) by ALD method using trimethyl aluminum (TMA) as a precursor and ozone (O3) as an oxidizing gas is about 450 ° C.

The ALD deposition temperature of the hafnium oxide film using hafnium alkoxide (Hf (OtBu) 4) as a precursor and ozone as an oxidizing gas on the formed aluminum oxide film is about 300 ° C., in which case a reaction as in Scheme 1 below occurs. However, in the following reaction formula, M represents a metal.

However, the hafnium alkoxide precursor causes decomposition as shown in Scheme 2 at about 450 ° C., which is the formation temperature of the aluminum oxide film.

That is, when the aluminum oxide film and the hafnium oxide film are continuously reacted in an in-situ environment in a reactor having the same temperature range, atomic layer deposition of the hafnium oxide film becomes difficult due to decomposition of the hafnium alkoxide.

Therefore, when the composite oxide film is formed, it may be reacted in a separate reactor according to the type of dielectric film, or one dielectric film is formed and the temperature of the reactor is lowered before forming another dielectric film. This results in reduced throughput per unit time of the semiconductor manufacturing process and lowered economics.

Therefore, research has been conducted to select suitable reactants for the reaction. For example, U.S. Patent No. 6486080 puts a semiconductor substrate in a reaction chamber and halogen such as metal alkoxide, M (OCH2CF3) 4, M (OCH (CF3) 2) 4, M (OC (CH3) 2CCl3) 4, A method of producing a metal oxide film having a high dielectric constant is disclosed by manufacturing an insulating film using an included metal alkoxide precursor and an oxidizing gas.

However, the present invention aims at the formation of a dielectric film having excellent dielectric constant for basically deposition by CVD. Therefore, there is no suitable method for continuously forming heterogeneous dielectric films by the ALD method under the same process environment (in-situ). Therefore, a method of forming a composite dielectric film using a reactant having a wide temperature margin for continuous formation of the composite dielectric film by an ALD method has been requested.

Accordingly, a first object of the present invention is to provide a method for forming a composite dielectric film using a reactant suitable for in-situ ALD process as a precursor.

A second object of the present invention is to provide a method of manufacturing a semiconductor capacitor using the method of forming a composite dielectric film.

1A to 1D are cross-sectional views illustrating an atomic layer deposition method.

2 is a flowchart illustrating a method of forming a composite dielectric film according to an embodiment of the present invention.

3 is a flowchart illustrating a method of forming a capacitor according to an embodiment of the present invention.

4 is a cross-sectional view illustrating an example of a lower structure of the capacitor illustrated in FIG. 3.

Brief description of the main parts of the drawing

20: substrate 22: device isolation layer

24: gate oxide film 26: polysilicon layer

28 tungsten silicide layer 30 sidewall spacer

32 mask layer 34 drain contact plug

36 source contact plug 38 first insulating film

40: bit line 42: spacer

44 mask layer 46 second insulating film

48: lower electrode 50: first dielectric film

50: second dielectric layer 52: upper electrode

According to the method of forming a composite dielectric film according to an embodiment of the present invention for achieving the first object of the present invention described above, the substrate is first placed in a reactor, the first metal compound is introduced into the reactor and 1 After the metal is adsorbed, oxidizing gas is introduced into the reactor to oxidize the adsorbed first metal to form a first dielectric film. Subsequently, a second metal compound, which is a metal alkoxide compound substituted with an electron withdrawing group, is adsorbed to the reactor to adsorb a second metal on the first dielectric layer, and then an oxidizing gas is introduced into the reactor. The adsorbed second metal is oxidized to form a second dielectric layer.

Here, the electron withdrawing group is F, Cl, NO, CO, or CN, and the decomposition temperature of the second metal compound is controlled by controlling the number of substituted electron withdrawing groups. In addition, the first dielectric film and the second dielectric film are continuously formed by the ALD reaction in the same temperature range.

According to the method of manufacturing a capacitor according to an embodiment of the present invention for achieving the second object of the present invention described above, first, a substrate on which a lower structure including a lower electrode is formed is placed in a reactor. Subsequently, a first metal compound is added to the reactor to adsorb the first metal on the lower electrode, and then an oxidizing gas is added to the reactor to oxidize the adsorbed first metal to form a first dielectric film. Subsequently, a second metal compound, which is a metal alkoxide compound substituted with at least one electron withdrawing group, is introduced into the reactor to adsorb the second metal on the first dielectric layer, and an oxidizing gas is introduced into the reactor to oxidize the adsorbed second metal. To form a second dielectric layer to form a composite dielectric layer. Finally, an upper electrode is formed on the formed composite dielectric film to manufacture a capacitor.

According to the present invention, by using a reactant having a large temperature margin, thin films having a different decomposition temperature in a deposition process using an ALD method can be continuously formed in one chamber. In addition, when such a reactant is used to form a composite dielectric film of a capacitor, it is possible to simultaneously form a composite dielectric film having excellent reliability in one chamber, and consequently, contribute to the improvement of reliability and yield of a semiconductor device.

Hereinafter, a method of continuously forming a composite dielectric film and a method of manufacturing a capacitor using the same will be described in detail with reference to the accompanying drawings.

2 is a flowchart illustrating a method of forming a composite dielectric film according to an embodiment of the present invention. Referring to FIG. 2, the substrate is placed in a reactor (S10), the first metal is adsorbed (S20), and a first dielectric layer is formed (S30). Subsequently, a second metal precursor is introduced to adsorb the second metal (S40), and finally, a second dielectric film is formed to form a composite dielectric film (S50).

First, in this embodiment, the substrate is placed in the reactor (S10).

The substrate may be, for example, a conventional silicon wafer, and the silicon wafer may include a substructure on which various active devices and the like are formed. The reactor is an ALD reactor, and the substrate is introduced into the reactor by a substrate transfer device such as a robot arm.

Subsequently, a first metal compound is introduced into the reactor to adsorb the first metal on the substrate (S20).

The first metal compound depends on the type of film to be deposited. For example, when the aluminum oxide film is to be formed as a dielectric film, the first metal compound may use TMA, triethyl aluminum (TEA), or the like as a precursor thereof, and TMA is suitable. A case where TMA is used as a precursor will be described in detail below. A gaseous TMA is introduced into the reactor and the TMA is adsorbed onto the substrate surface by chemical adsorption and deposited by physical adsorption on the chemical adsorbate. When a purge gas such as nitrogen (N 2) gas is added thereto to remove the portion formed by physical adsorption, only the chemically adsorbed solid metal remains.

Subsequently, an oxidizing gas is introduced into the reactor to oxidize the adsorbed first metal to form a first dielectric layer (S30).

As the oxidizing gas, H 2 O, O 3, or the like may be used, but O 3 is preferable in view of the reliability of the film formed. That is, when H 2 O is used, the reaction temperature can be lowered, but problems such as OH groups remain in the film formed. In addition, the first dielectric film formed when TMA is used as the reactant is an aluminum oxide film. Taking the TMA as an example, an oxidizing gas such as ozone is added to the formed chemically adsorbed metal layer to oxidize the first metal. Subsequently, a purge gas is introduced to remove residual impurities, thereby forming a first dielectric film, which is a chemically adsorbed solid aluminum oxide film. The deposition of the aluminum oxide film by the ALD method described above is performed at about 450 ° C.

Thereafter, a second metal compound, which is a metal alkoxide compound substituted with an electron withdrawing group, is introduced into the reactor to adsorb a second metal on the first dielectric layer (S40).

When hafnium alkoxide, titanium alkoxide, or zirconium alkoxide is used as the second metal compound, the decomposition temperature of the second metal compound is about 300 to 350 ° C. When the second metal compound is introduced in an in-situ environment after depositing the aluminum oxide film, the second metal compound is decomposed as shown in Scheme 3 below at about 450 ° C., which is the deposition temperature of the aluminum oxide film. Deposition becomes difficult.

Therefore, in the present invention, a compound in which hydrogen of the metal alkoxide is substituted with one or more electron withdrawing groups F, Cl, NO, CO, or CN is used. When the second metal compound is used as a precursor, the energy barrier is large due to the instability of the carbocation generated in Scheme 3, and thus the temperature at which the decomposition reaction occurs is increased. Therefore, the temperature margin of the process may be increased, and the second dielectric layer may be formed in an in-situ environment after depositing the aluminum oxide layer. As a result, the problem of forming the composite dielectric film in a separate reactor or adjusting the temperature of the reactor can be overcome.

In this case, the decomposition temperature may be adjusted by controlling the number of electron withdrawing groups to be substituted. In the case of replacing hydrogen with F in the hafnium alkoxide, for example, two substitutions have a decomposition temperature of about 400 ° C, four of which are about 450 ° C, and six of which are about 500 ° C. Therefore, when forming a hafnium oxide film after depositing a dielectric film that reacts at a higher temperature when forming the aluminum oxide film, an optimal precursor may be used by controlling the number of electron withdrawing groups to be substituted.

This step may also include removing the physical adsorbate with a purge gas such as N2 as described above.

Finally, an oxidizing gas is introduced into the reactor to oxidize the adsorbed second metal to form a second dielectric layer (S50).

As the oxidizing gas, H 2 O, O 3, or the like may be used, but O 3 is preferable in view of the reliability of the film formed. In addition, the second dielectric layer formed may be a hafnium oxide film, a zirconium oxide film, or a titanium oxide film depending on the type of reaction material used.

Specifically, an oxidizing gas such as ozone is injected onto the formed chemically adsorbed second metal layer to oxidize the second metal. Subsequently, a purge gas such as N 2 is introduced to remove residual impurities to form a chemically adsorbed solid state second dielectric film.

According to the above method, the first dielectric film and the second dielectric film can be formed in the same temperature range, so that the yield of the semiconductor device can be remarkably improved. In addition, when using ozone as the oxidizing gas, the problem caused by the reaction temperature rise can be overcome by using a reactant having a large temperature margin, thereby contributing to improving the reliability of the device.

In addition, the present invention provides a method of manufacturing a capacitor using the continuous formation method of the composite dielectric film. Hereinafter, a dielectric film formation of a semiconductor capacitor will be described. However, the same principle may be applied to a dielectric film of a metal oxide semiconductor (MOS) transistor in which a gate electrode is formed on a semiconductor substrate through a dielectric film.

3 is a flowchart illustrating a method of forming a capacitor according to an embodiment of the present invention. Referring to FIG. 3, first, a substrate on which a lower electrode is formed is placed in a reactor (S100). Subsequently, a first metal compound is introduced into the reactor to adsorb the first metal on the lower electrode (S200), and an oxidizing gas is introduced into the reactor to oxidize the adsorbed first metal to form a first dielectric layer. (S300).

Subsequently, a second metal compound, which is a metal alkoxide compound substituted with at least one electron withdrawing group, is introduced into the reactor to adsorb a second metal on the first dielectric layer (S400), and an oxidizing gas is introduced into the reactor. The adsorbed second metal is oxidized to form a second dielectric layer (S500). Finally, a capacitor having a composite dielectric film is manufactured by forming an upper electrode on the second dielectric film (S600).

First, in this embodiment, the substrate on which the lower structure including the lower electrode is formed is placed in the reactor (S100).

The lower electrode includes a conductive material such as metal, metal oxide, metal nitride, metal oxynitride, or conductive silicon, and the lower structure includes various active elements. 4 is a cross-sectional view illustrating an example of a lower structure of the capacitor illustrated in FIG. 3. 4 illustrates a substructure of a cell capacitor of a DRAM (Dynamic Random Access Memory (DRAM)).

The DRAM forms a trench type isolation layer 22 in the silicon substrate 20 and forms an active device in the active region. Typically, the active element is composed of MOS transistors. The MOS transistor includes a gate electrode layer having a stacked structure of polysilicon 26 and tungsten silicide 28 on the gate oxide film 24. The gate electrode layer is protected by an insulating material sidewall spacer 30 and a mask layer 32. Using the gate electrode layer as an ion implantation mask, impurities are implanted into the surface of the substrate in the active region to form source and drain regions.

The contact plugs 34 and 36 are formed by forming a contact by a self-aligned contact technique for contacting the drain region and the source region, and filling the formed contact with a conductive material such as polysilicon. The contact plugs may be separated independently from each other by a CMP process. The MOS transistor configured as described above is covered with the first insulating film 38 and the surface of the first insulating film 38 is processed to be flat by the CMP process.

The bit line contact is formed on the first insulating layer 38, the drain contact plug 34 is exposed, and the bit line 40 is formed. The bit line 40 is protected by an insulating material sidewall spacer 42 and a mask layer 44. Similarly, the second insulating film 46 is covered on the surface on which the bit line 40 is formed, and the surface of the second insulating film 46 is similarly processed by the CMP process.

The cell capacitor is formed on the second insulating film 46. A buried contact is formed in the second insulating film 46, and the source contact plug 36 is exposed. A lower electrode 48 made of a conductive material such as polysilicon is formed on the second insulating layer 46 where the source contact plug is exposed. The lower electrode 48 may have a cylindrical shape having a high height of about 5,000 to 15,000 위하여 in order to increase the surface area, and may have a concave-convex structure such as HSG on the surface thereof.

Subsequently, the first metal compound is introduced into the reactor to adsorb the first metal on the lower electrode 48 (S200).

The first metal compound depends on the type of film to be deposited. For example, when the aluminum oxide film is to be formed as a dielectric film, the first metal compound may use TMA, TEA, or the like as its precursor, of which TMA is suitable. A case where TMA is used as a precursor will be described in detail below. A gaseous TMA is introduced into the reactor and the TMA is adsorbed on the lower electrode surface by chemical adsorption and deposited by physical adsorption on the chemical adsorbate. If a purge gas such as N2 gas is added thereto to remove the portion formed by physical adsorption, only chemically adsorbed solid metal remains.

Subsequently, an oxidizing gas is introduced into the reactor to oxidize the adsorbed first metal to form a first dielectric layer 50 (S300).

As the oxidizing gas, H 2 O, O 3, or the like may be used, but O 3 is preferable in view of the reliability of the film formed. In addition, when TMA is used as the reactant, the first dielectric layer is an aluminum oxide layer. Taking the TMA as an example, an oxidizing gas such as ozone is added to the formed chemically adsorbed metal layer to oxidize the first metal. Subsequently, a purge gas is introduced to remove residual impurities, thereby forming a first dielectric film, which is a chemically adsorbed solid aluminum oxide film. The deposition of the aluminum oxide film by the ALD method described above is performed at about 450 ° C.

In addition, a second metal compound, which is a metal alkoxide compound substituted with at least one electron withdrawing group, is introduced into the reactor to adsorb a second metal on the first dielectric layer (S400).

When hafnium alkoxide, titanium alkoxide, or zirconium alkoxide is used as the second metal compound, the decomposition temperature of the second metal compound is about 300 to 350 ° C. When the second metal compound is introduced in an in-situ environment after the deposition of the aluminum oxide film, the second metal compound is decomposed as shown in Scheme 3 at about 450 ° C., which is the deposition temperature of the aluminum oxide film. Deposition becomes difficult.

Therefore, the present invention uses a compound in which hydrogen of the metal alkoxide is substituted with one or more electron withdrawing groups, that is, F, Cl, NO, CO, or CN. When the second metal compound is used as a precursor, a temperature at which a decomposition reaction shown in Scheme 3 occurs is increased to deposit an aluminum oxide layer, and then to form a second dielectric layer in an in-situ environment. Therefore, it is possible to overcome the problem of forming the composite dielectric film in a separate reactor or after adjusting the temperature of the reactor.

In this case, the decomposition temperature may be adjusted by controlling the number of electron withdrawing groups to be substituted. In the case of replacing hydrogen with F in the hafnium alkoxide, for example, two substitutions have a decomposition temperature of about 400 ° C, four of which are about 450 ° C, and six of which are about 500 ° C. Therefore, when forming a hafnium oxide film after depositing a dielectric film that reacts at a higher temperature when forming the aluminum oxide film, an optimal precursor may be used by controlling the number of electron withdrawing groups to be substituted.

This step may also include removing the physical adsorbate with a purge gas such as N2 as described above.

Thereafter, an oxidizing gas is introduced into the reactor to oxidize the adsorbed second metal to form a second dielectric layer 51 (S500). As the oxidizing gas, O 3 is preferable. In addition, the second dielectric layer formed may be a hafnium oxide film, a zirconium oxide film, or a titanium oxide film depending on the type of reaction material used.

Specifically, an oxidizing gas such as ozone is injected onto the formed chemically adsorbed second metal layer to oxidize the second metal. Subsequently, a purge gas such as N 2 is introduced to remove residual impurities to form a chemically adsorbed solid state second dielectric film.

Finally, a capacitor is manufactured by forming an upper electrode 52 on the second dielectric layer (S600). The lower electrode includes a conductive material such as metal, metal oxide, metal nitride, metal oxynitride, or conductive silicon, and is formed by a conventional conductive material deposition method.

According to the present invention, by using a reactant having a large temperature margin, thin films having a different decomposition temperature in a deposition process using an ALD method can be continuously formed in one chamber. In addition, when such a reactant is used for forming a composite dielectric film of a capacitor, it is possible to simultaneously form a composite dielectric film having excellent reliability in one chamber and consequently contribute to the improvement of reliability and yield of a semiconductor device.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (11)

Positioning the substrate in the reactor; Injecting a first metal compound into the reactor to adsorb the first metal on the substrate; Injecting an oxidizing gas into the reactor to oxidize the adsorbed first metal to form a first dielectric layer; Adsorbing a second metal compound on the first dielectric layer by introducing a second metal compound, which is a metal alkoxide compound substituted with at least one hydrogen with an electron withdrawing group, to the reactor; And And injecting oxidizing gas into the reactor to oxidize the adsorbed second metal to form a second dielectric layer. The method of claim 1, wherein the first metal compound comprises TMA, and the first dielectric layer is an aluminum oxide layer. The method of continuously forming a composite dielectric film according to claim 1, wherein the oxidizing gas comprises ozone gas. The method of claim 1, wherein the electron withdrawing group is at least one selected from the group consisting of F, Cl, NO, CO, and CN. The method of claim 1, wherein the decomposition temperature of the second metal compound is controlled by controlling the number of substituted electron withdrawing groups. The method of claim 1, wherein the second metal is selected from the group consisting of Hf, Zr, and Ti. The method of claim 1, wherein the second dielectric film is selected from the group consisting of a hafnium oxide film, a zirconium oxide film, and a titanium oxide film. The method of claim 1, wherein the first dielectric layer and the second dielectric layer are formed at the same temperature range. The method of claim 1, wherein the first dielectric layer and the second dielectric layer are formed by an ALD method. Positioning a substrate having a lower structure including a lower electrode in a reactor; Injecting a first metal compound into the reactor to adsorb a first metal on the lower electrode; Injecting an oxidizing gas into the reactor to oxidize the adsorbed first metal to form a first dielectric layer; Adsorbing a second metal compound on the first dielectric layer by introducing a second metal compound, which is a metal alkoxide compound substituted with at least one electron withdrawing group, to the reactor; Injecting an oxidizing gas into the reactor to oxidize the adsorbed second metal to form a second dielectric layer; And And forming an upper electrode on the second dielectric layer. The method of claim 10, wherein the lower electrode and the upper electrode include at least one conductive material selected from the group consisting of metal, metal oxide, metal nitride, metal oxynitride, and conductive silicon.