JP2010003843A - Formation method of insulation film, and manufacturing method of semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an insulation film reduced in mixture of carbon and variations in composition. <P>SOLUTION: In this formation method of an insulation film, a two-layer structure of silicon and metal is formed by sequentially forming a silicon layer and a metal layer on a substrate; a reaction temperature at which the silicon and the metal produce a metal silicide in targeted composition is selected; and a metal silicide layer is formed by heating the two-layer structure. A part within the metal remaining in an unreacted state is removed. The insulation layer is formed by oxidizing or nitriding the metal silicide layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for forming an insulating film on a substrate and a method for manufacturing a semiconductor device to which such an insulating film is applied.

  Conventionally, a silicon oxide film (SiO 2) has been used for many years as a gate insulating film in a semiconductor element such as a MOSFET from the viewpoint of thermal stability, interface characteristics, and the like. In the future, in order to promote higher performance of semiconductor devices, further miniaturization of MOSFETs is being planned, and the thickness of the gate insulating film is expected to be less than 1 nm.

  However, when the physical film thickness of the SiO2 gate insulating film is about 2 nm or less, an increase in gate leakage current due to the direct tunnel effect becomes a serious problem. Therefore, as a gate insulating film material, a high-k material having a high dielectric constant is actively researched as an alternative to SiO2. With a high-k material, it is possible to increase the physical film thickness while suppressing the effective film thickness in terms of silicon oxide film to less than 1 nm, so that a reduction in gate leakage current is expected.

  When selecting a high-k material, it is desirable that the dielectric constant is sufficiently high in order to sufficiently increase the film thickness. In addition, the crystallization temperature needs to be sufficiently high so as not to cause crystallization of the gate insulating film which causes an increase in leakage current. Furthermore, the band gap is also required to be sufficiently large. In these respects, metal silicates such as zirconium silicate, hafnium silicate, lanthanum silicate, yttrium silicate, and metal silicate nitride obtained by nitriding the same are considered promising as next-generation gate insulating film materials.

  As a method for producing metal silicates and metal silicate nitrides, CVD (chemical vapor deposition) is the mainstream, but this method often uses carbon as a raw material because organic materials are used as raw materials. Probability is high. It has been reported that the incorporation of carbon may contribute to the formation of defect levels and cause an increase in leakage current (see, for example, Non-Patent Document 1).

  Further, in the case of the CVD method, the composition of the metal element in the metal silicate or metal silicon nitride and silicon varies between wafers or within the wafer, which may affect the variation in device characteristics.

  Instead of the CVD method, a metal hafnium (Hf) layer is formed on a silicon substrate by a PVD method (sputtering or the like), and the metal Hf layer is oxidized to form an Hf-containing silicon oxide film as a gate insulating film. A method has been proposed (see, for example, Patent Document 1).

  FIG. 1 shows the method of Patent Document 1. As shown in FIGS. 1A to 1C, a metal Hf layer 112 is formed on a silicon substrate 110, and the metal Hf layer 112 is oxidized to form a Hf-containing silicon oxide film 114. In this process, however, contaminants (such as carbon) 111 remaining on the cleaned silicon substrate 110 and defects 113 on the surface layer of the substrate caused by sputtering are taken into the Hf-containing silicon oxide film 114, and contaminants and Defects can be reduced. As the oxidation method, rapid heating oxidation or plasma oxidation containing oxygen radicals is used. Thereafter, as shown in FIG. 1D, a conductor film 115 to be a gate electrode film is formed on the Hf-containing silicon oxide film 114.

2 also shows a method for forming a gate insulating film by a sputtering method (see, for example, Patent Document 2). In this method, a metal target 210 is used to sputter metal ions (for example, Hf ions) 211 on a silicon substrate 201 in an oxygen-free atmosphere to form a metal Hf film 212 (FIG. 2A). Thereafter, an oxidation treatment is performed in an atmosphere containing oxygen radicals 213 in a temperature range of 300 to 500 ° C. (FIG. 2B) to form a metal oxide film (HfO 2 film) 202 (FIG. 2C) . A silicon oxide film 203 is formed at the interface between the metal oxide film 202 and the silicon substrate 201. Note that there are oxygen atoms (or oxygen molecules) 214 that are not activated in the oxidation treatment of FIG.
JP 2003-179049 A JP 2005-79563 A “High-k gate dielectrics: Current status and materials properties considerations”, GD Wilk, RM Wallace, JM Anthony, J. Appl. Phys., 89, 5243 (2001).

  In an embodiment of the present invention, a method of forming an insulating film made of metal silicide oxide or metal silicate nitride having a uniform composition within a wafer surface and between wafers is provided. In addition, a method for manufacturing a semiconductor device to which such an insulating film is applied is provided.

As a first aspect of the present invention, a method for forming an insulating film is provided. The method of forming the insulating film is as follows:
A silicon layer and a metal layer are sequentially formed on the substrate to form a two-layer structure of silicon and metal,
Select a reaction temperature at which the silicon and the metal produce a metal silicide with a target composition, heat the two-layer structure to form a metal silicide layer,
Removing the unreacted portion of the metal,
A step of oxidizing or nitriding the metal silicide layer to form an insulating film;

As a second aspect, a method for manufacturing a semiconductor device to which the above-described insulating film is applied is provided. The manufacturing method of the semiconductor device is as follows:
Forming a first insulating film on the semiconductor substrate;
A silicon layer and a metal layer are sequentially formed on the first insulating film to form a two-layer structure of silicon and metal,
Select a reaction temperature at which the silicon and the metal produce a metal silicide with a target composition, heat the two-layer structure to form a metal silicide layer,
Removing the unreacted portion of the metal,
Oxidizing or nitriding the metal silicide layer to form a second insulating film;
Forming an electrode film on the first and second insulating films;

  Metal silicate and metal silicate nitride with reduced mixing of carbon and composition variation can be formed as an insulating film. The electrical characteristics and reliability of a device to which such an insulating film is applied can be improved, and the manufacturing yield can be improved.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 3 is a diagram showing an insulating film forming process according to the first embodiment of the present invention. As described above, in the conventional method for forming an insulating film by a chemical vapor deposition (CVD) method using an organic raw material, (1) the composition ratio of metal and silicon in the insulating film varies between wafers and within the wafer. 2) There is a problem that carbon is mixed into the insulating film.

  The problem (1) is considered to be mainly due to variations in gas flow rate, gas pressure, and temperature. Regarding (2), when an organic source gas containing carbon (such as TEMAH) is used, carbon remains in the insulating film.

Therefore, in the embodiment, a metal silicide whose composition is determined by temperature (M _x Si _1-x : M is a metal element) is produced using a sputtering method with very little carbon contamination, and then oxidized or nitrided, A metal silicate or a metal silicate nitride is produced to form an insulating film.

  In FIG. 3A, a first insulating film 12 is formed on the silicon substrate 11. The first insulating film is silicon oxide, silicon nitride, silicon oxynitride, or the like. In this example, a silicon oxide film 12 having a thickness of 0.5 to 1.0 nm is formed on a silicon substrate 11. Specifically, the silicon substrate 11 is pretreated to be hydrogen-terminated, and heated while supplying an oxidizing gas such as O 2 to form a silicon oxide film. In the pretreatment, for example, the surface is washed with a 0.5% hydrofluoric acid solution after the treatment in an aqueous sulfuric acid solution (H2SO4: H2O2 = 4: 1). In the case of forming a silicon nitride film, any method such as a plasma nitridation method or a thermal nitridation method can be used. In the case of forming a silicon oxynitride film, any method such as plasma nitriding after forming a silicon oxide film can be used. Use of silicon nitride or silicon oxynitride for the first insulating film 12 is advantageous because the capacity of the entire insulating film can be increased.

Next, as shown in FIG. 3B, a composition and a film of a metal silicate (M _x Si _1-x O: M is a metal element) to be formed in a later process on the first insulating film 12. A silicon layer 13 corresponding to the thickness is deposited by sputtering. For example, to form hafnium silicate with x = 0.333, that is, hafnium silicate having a composition ratio of hafnium and silicon of approximately 1: 2 (Hf: Si = 1: 2) of 6 nm, silicon is deposited to 2.1 nm. To do. Next, a sufficient amount of metal hafnium (1.2 nm or more) is deposited by sputtering. The sputtering conditions are an output of 100 to 120 W, a total pressure of 10 mTorr (1.33 Pa), and an argon atmosphere.

  As a result, as shown in FIG. 3C, a sufficiently thick metal hafnium layer 14 is deposited on the silicon layer 13, and a two-layer structure 19 of silicon and metal is obtained.

Next, as shown in FIG. 3D, annealing is performed by RTA (rapid heat treatment) at 800 to 900 ° C. in a non-oxidizing atmosphere containing nitrogen 10 Torr (1333 Pa), and the composition of hafnium x = 0. 333 hafnium silicide (Hf _x Si _1-x ) 15 is formed. On the hafnium silicide 15, unreacted metal hafnium 14 remains.

  Next, as shown in FIG. 3E, the unreacted metal hafnium 14 is removed with sulfuric acid / hydrogen peroxide (H 2 SO 4: H 2 O 2 = 9: 1).

  Next, as shown in FIG. 3F, the hafnium silicide 15 is plasma-oxidized to form a hafnium silicate 17. For example, plasma oxidation is performed in an oxygen atmosphere with an output of 100 W, a total pressure of 10 mTorr (1.33 Pa). After the plasma oxidation, a deficient amount of oxygen may be compensated by heating in a nitrogen atmosphere containing a small amount of oxygen. In this case, for example, heating at 1000 ° C. is performed in a nitrogen atmosphere containing a total pressure of 5 Torr (667 Pa) and 0.2% oxygen.

  By this method, hafnium silicate 17 containing little variation in composition and containing no carbon can be formed.

  FIG. 4 is a diagram showing the relationship between the substrate heating temperature and the composition of hafnium silicide. Metal silicides are known to have a defined composition at a constant temperature (see, for example, J. F. Ziegler et al. J. Appl. Phys, 44, 3851 (1973)). In the example of FIG. 3, the substrate heating temperature was set to 800 to 900 ° C. in order to set the composition ratio of hafnium and silicon to 1: 2. When the hafnium composition x is set to x = 0.5, that is, when it is desired to form hafnium silicide having a hafnium / silicon composition ratio of 1: 1, the substrate heating temperature is heated to 700 to 750.degree. By setting the substrate heating temperature to less than 700 ° C., it is expected that the composition ratio of hafnium and silicon can be made 2: 1.

  Specifically, when the hafnium silicate 17 of Hf: Si = 1: 1 is formed with a film thickness of 6 nm, the silicon layer 13 is deposited by 1.6 nm in the process of FIG. Thereafter, a sufficient amount of metal hafnium layer 14 (1.8 nm or more) is deposited in the step of FIG. 3C, and RTA treatment is performed at 700 to 750 ° C. in a non-oxidizing atmosphere containing 10 Torr (1333 Pa) of nitrogen. A hafnium silicide 15 having a hafnium composition x = 0.5 is formed. Subsequent processing methods are the same as those in FIGS. 3E and 3F.

  FIG. 5 is a flowchart of forming the insulating film according to the embodiment. First, a first insulating film is formed on a silicon substrate (S1). The first insulating film is selected from a silicon oxide film, a silicon nitride film, and a silicon oxynitride film. Next, a silicon layer and a metal layer are deposited in this order on the first insulating film to produce a metal / silicon two-layer structure (S2). In addition to hafnium, scandium, yttrium, lanthanum, titanium, zirconium, tantalum, aluminum, or the like may be used as the metal.

  Next, the substrate heating temperature is set so that a metal silicide having a desired composition is obtained (S3). The metal / silicon bilayer structure is heated at a set temperature in a non-oxidizing atmosphere to form a metal silicide (S4). Then, unreacted remaining metal is removed (S5). Thereafter, the metal silicide is oxidized to form a metal silicate film (S6).

Instead of forming the metal silicate film, the metal silicide may be nitrided to form a metal silicate film (M _x Si _1-x N) (S7). In this case, the obtained metal silicate film is further oxidized to form a metal silicate nitride film (M _x Si _1-x ON) (S8). This metal silicon nitride film becomes the second insulating film.

  FIG. 6 is a process diagram for forming an insulating film according to the second embodiment of the present invention. In the second embodiment, the process proceeds to steps S7 and S8 in the flowchart of FIG. 5 to form a metal silicate nitride film. FIG. 6A is the same as FIG. 3C and is a schematic cross-sectional view showing a state in which a two-layer structure 19 of silicon 13 and metal hafnium 14 is formed on the first insulating film 12.

  Next, as shown in FIG. 6B, similarly to FIG. 3D, annealing is performed by RTA (rapid heat treatment) at 800 to 900 ° C. in a non-oxidizing atmosphere containing nitrogen 10 Torr (1333 Pa). A hafnium silicide 15 having a hafnium composition x = 0.333 is formed. On the hafnium silicide 15, unreacted metal hafnium 14 remains.

  Next, as shown in FIG. 6 (c), unreacted metal hafnium 14 is removed with sulfuric acid / hydrogen peroxide (H2SO4: H2O2 = 9: 1) as in FIG. 3 (e).

  Next, as shown in FIG. 6D, the hafnium silicide 15 is nitrided to form a hafnium silicate film 21. The nitriding conditions at this time are, for example, in the case of plasma nitriding, an output of 500 W, a total pressure of 20 mTorr (2.67 Pa), and a nitrogen atmosphere.

  Next, as shown in FIG. 6E, the hafnium silicate nitride film 21 is oxidized to form a hafnium silicate nitride film 23. For example, in the case of plasma oxidation, the oxidation conditions are an output of 100 W, a total pressure of 10 mTorr (1.33 Pa), and an oxygen atmosphere. After the plasma oxidation, a deficient amount of oxygen may be compensated by heating in a nitrogen atmosphere containing a small amount of oxygen. In this case, for example, heating is performed at 1000 ° C. for 10 seconds in a nitrogen atmosphere containing a total pressure of 5 Torr (667 Pa) and 0.2% oxygen. This hafnium silicate nitride film 23 becomes the second insulating film. The hafnium silicate nitride film 23 is a stable insulating film with little composition variation because the temperature is selected so that silicon and hafnium have a desired composition in the heating step of FIG. 6B. In addition, since no organic source gas is used for film formation, carbon is hardly mixed.

  FIG. 7 is a schematic cross-sectional view illustrating a configuration example of a semiconductor device to which the insulating film of the embodiment is applied. The semiconductor device 50 is, for example, a field effect transistor. The semiconductor device 50 includes a gate electrode 36 disposed on a silicon substrate 11 via a gate insulating film 41, an extension (low concentration impurity diffusion layer) 37, and a source / drain impurity diffusion layer (high concentration impurity diffusion layer). 39. Sidewall spacers 38 are disposed on the side walls of the gate electrode 36 and the gate insulating film 41. The source / drain impurity diffusion layer 39 is electrically connected to an upper layer wiring or element by a plug electrode (not shown).

The gate insulating film 41 includes a first insulating film 12 and a second insulating film 35 on the first insulating film 12. The second insulating film is a metal silicate film (M _x Si _1-x O) or a metal silicate nitride film (M _x Si _1-x ON), and has a high dielectric constant. In addition, since the two-layer structure of silicon and metal formed by sputtering is subjected to heat treatment by selecting a temperature at a predetermined composition, variation in composition between wafers and within wafers is suppressed.

  In the example of FIG. 7, the insulating film of the embodiment is applied to the gate insulating film 41 of the field effect transistor, but may be applied to a dielectric film of a capacitor. The insulating film of the embodiment may be applied to a capacitor structure on a silicon substrate.

The following notes are presented for the above explanation.
(Appendix 1)
A silicon layer and a metal layer are sequentially formed on the substrate to form a two-layer structure of silicon and metal,
Select a reaction temperature at which the silicon and the metal produce a metal silicide with a target composition, heat the two-layer structure to form a metal silicide layer,
Removing the unreacted portion of the metal,
A method for forming an insulating film, comprising oxidizing or nitriding the metal silicide layer to form an insulating film.
(Appendix 2)
2. The method for forming an insulating film according to claim 1, further comprising a step of oxidizing the obtained metal silicate film to form a metal silicate nitride film when the metal silicide layer is nitrided.
(Appendix 3)
The heating temperature is set higher when the composition of silicon is larger than the composition of the metal in the metal silicide, compared to the case where the composition of the metal is increased. 3. A method for forming an insulating film as described in 2.
(Appendix 4)
The silicon layer and the metal layer are formed by a sputtering method.
The method for forming an insulating film according to any one of appendices 1 to 3, wherein:
(Appendix 5)
The method for forming an insulating film according to any one of appendices 1 to 4, wherein the forming step of the two-layer structure and the heating step are performed in a non-oxidizing atmosphere.
(Appendix 6)
6. The method for forming an insulating film according to any one of appendices 1 to 5, wherein the first insulating film is selected from a silicon oxide film, a silicon nitride film, and a silicon oxynitride film.
(Appendix 7)
7. The method for forming an insulating film according to any one of appendices 1 to 6, wherein the metal layer is selected from scandium, yttrium, lanthanum, titanium, hafnium, zirconium, tantalum, and aluminum.
(Appendix 8)
Forming a first insulating film on the semiconductor substrate;
A silicon layer and a metal layer are sequentially formed on the first insulating film to form a two-layer structure of silicon and metal,
Select a reaction temperature at which the silicon and the metal produce a metal silicide with a target composition, heat the two-layer structure to form a metal silicide layer,
Removing the unreacted portion of the metal,
Oxidizing or nitriding the metal silicide layer to form a second insulating film;
A method of manufacturing a semiconductor device, comprising the step of forming an electrode film on the first and second insulating films.

It is a figure which shows the well-known gate insulating film formation method. It is a figure which shows the well-known gate insulating film formation method. It is a formation process figure of the insulating film of a 1st embodiment of the present invention. It is a figure which shows a substrate heating temperature and a composition of hafnium and silicon. It is a flowchart of the insulating film formation which concerns on embodiment of this invention. The formation process figure of the insulating film of 2nd Embodiment of this invention. 1 is a schematic diagram of a semiconductor device to which an insulating film according to an embodiment of the present invention is applied.

Explanation of symbols

11 Substrate (silicon substrate)
12 First insulating film 13 Silicon layer 14 Metal layer (hafnium layer)
15 Metal silicide layer 17 Metal silicate film (M _x Si _1-x O; second insulating film)
19 Metal / silicon two-layer structure 21 Metal silicate nitride layer 23 Metal silicate nitride film (M _x Si _1-x ON; second insulating film)
35 Second insulating film 36 Gate electrode 37 Source / drain extension 38 Side wall spacer 39 Source / drain impurity diffusion layer 41 Gate insulating film 50 Semiconductor device

Claims (5)

A silicon layer and a metal layer are sequentially formed on the substrate to form a two-layer structure of silicon and metal,
Select a reaction temperature at which the silicon and the metal produce a metal silicide with a target composition, heat the two-layer structure to form a metal silicide layer,
Removing the unreacted portion of the metal,
A method for forming an insulating film, comprising oxidizing or nitriding the metal silicide layer to form an insulating film. 2. The insulating film according to claim 1, further comprising a step of oxidizing the obtained metal silicon nitride layer to form a metal silicon nitride layer when the metal silicide layer is nitrided. Forming method.   The heating temperature is set to be higher when the composition of silicon is larger than the composition of the metal in the metal silicide than when the composition of the metal is increased. The insulating film formation method as described. The silicon layer and the metal layer are formed by a sputtering method.
The method for forming an insulating film according to claim 1, wherein: Forming a first insulating film on the semiconductor substrate;
A silicon layer and a metal layer are sequentially formed on the first insulating film to form a two-layer structure of silicon and metal,
Select a reaction temperature at which the silicon and the metal produce a metal silicide with a target composition, heat the two-layer structure to form a metal silicide layer,
Removing the unreacted portion of the metal,
Oxidizing or nitriding the metal silicide layer to form a second insulating film;
A method of manufacturing a semiconductor device, comprising the step of forming an electrode film on the first and second insulating films.

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