JP2007116069A - Method for forming metal silicate film and method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a high dielectric film that is flattened on the surface of a silicon substrate. <P>SOLUTION: The method for forming the silicate film repeatedly performs a first process and a second process. A metal silicate film is formed onto the silicon substrate 40 by organic metal CVD process. The first process supplies a first gaseous raw material comprising an organic metal compound containing a metal element consisting of the metal silicate film 43, and a second gaseous raw material consisting of the organic silicon compound. The second process decomposes the first gaseous raw material and the second gaseous raw material on the surface of the silicon substrate 40, to form the metal silicate film 43. The metal silicate film 43 is formed in film thickness of 0.5 nm or more and 2 nm or less by repeating. It is preferable that the first raw material is tetratertiarybutoxyhafnium and the second raw material is TEOS. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention generally relates to a film forming technique, and more particularly, to a method for forming a metal silicate film and a method for manufacturing a semiconductor device using such a metal silicate film.

  With the advancement of miniaturization technology, it is now possible to manufacture ultra-miniaturized and ultra-high-speed semiconductor devices with a gate length of less than 0.1 μm.

  In such ultra-miniaturized / ultra-high-speed semiconductor devices, the gate oxide film thickness needs to be reduced according to the scaling law as the gate length is reduced. However, in a semiconductor device in which the gate length is less than 0.1 μm. When the conventional thermal oxide film is used, the thickness of the gate oxide film needs to be set to 1 nm or less. However, in such a very thin gate insulating film, the tunnel current increases, and as a result, the problem that the gate leakage current increases cannot be avoided.

Under such circumstances, Ta ₂ O ₅ or Al having a relative dielectric constant much larger than that of a thermal oxide film and having a small film thickness when converted to a SiO ₂ film even if the actual film thickness is large. It has been proposed to apply a high dielectric (so-called high-K dielectric) material such as ₂ O ₃ , ZrO ₂ , HfO ₂ , ZrSiO ₄ or HfSiO ₄ to the gate insulating film. By using such a high dielectric material, it is possible to use a gate insulating film having a physical film thickness of about 5 nm even in a very short ultrahigh-speed semiconductor device having a gate length of 0.1 μm or less. Gate leakage current can be suppressed.

  In particular, when a high dielectric film is formed directly on the silicon substrate surface, large interdiffusion of Si atoms and metal atoms occurs between the silicon substrate and the high dielectric film. Generally, it is formed through a very thin silicon oxide film formed on the surface of the silicon substrate.

  On the other hand, in such a highly miniaturized semiconductor device, when the gate insulating film is formed of a high dielectric film made of a high-K material, the high dielectric film is formed on a flat silicon oxide film. Even in this case, it has been found that the surface roughness of the gate insulating film increases and the amplitude of the unevenness may reach, for example, 1 nm.

  When the gate electrode is formed of polysilicon or the like on the gate insulating film having such a rough surface, a local leakage current is generated in the form of a tunnel current or other leakage current in the thin portion, and as a result, the gate Even in the entire insulating film, the leakage current increases.

  As described above, in the ultra-miniaturized and ultra-high-speed transistor having a gate length of 0.1 μm or less, even when a high dielectric film is used, the thickness of the gate insulating film is at most several nanometers, and the power consumption has stable characteristics. In order to manufacture a small number of semiconductor devices, the morphology control of the surface of the high dielectric gate insulating film becomes a very important issue.

  As an effective method for improving the surface roughness (roughness) of a film, an atomic layer deposition method (so-called ALD method) in which film formation is performed by one atomic layer or molecular layer is known. According to this ALD method, an extremely smooth film can be formed.

  However, in the ALD method, a plurality of raw materials are adsorbed on the substrate surface below the decomposition temperature, so that undecomposed products and reaction products are likely to remain in the film, and it is difficult to obtain good film quality. In addition, if an ALD method is used to form a film having a practical thickness of, for example, 2 to 4 nm, a very long processing time is required, and important productivity is sacrificed in the manufacture of a semiconductor device. .

  Under such circumstances, there is a demand for a technique capable of improving the surface roughness to the level of a thermal oxide film by film formation by a CVD method.

The present invention solves the above problems.
As described in claim 1,
A method for forming a metal silicate film on a silicon substrate,
A first vapor phase material composed of an organometallic compound containing a metal element constituting the metal silicate film and a second vapor phase material composed of an organic silicon compound are supplied to the silicon substrate surface, and the metal is deposited on the silicon substrate. A first step of forming a silicate film;
Repeating the second step of interrupting the supply of the first vapor phase raw material and interrupting the formation of the metal silicate film,
In the first step, the temperature of the silicon substrate is kept equal to or higher than the decomposition temperature of the first vapor phase raw material, and the metal silicate film is formed with a film thickness corresponding to at least one molecular layer. According to the method for forming a metal silicate film, or as described in claim 2,
The method of forming a metal silicate film according to claim 1, wherein in the second step, the temperature of the silicon substrate is maintained at a temperature equal to or lower than a decomposition temperature of the second vapor phase raw material. As described in
The metal silicate film forming method according to claim 1 or 2, wherein the first raw material is HTB (tetratertiarybutoxyhafnium), or as described in claim 4.
The metal silicate film forming method according to claim 3, wherein the second raw material is TEOS (tetraethoxysilane), or as described in claim 5,
7. The metal silicate film forming method according to claim 3, wherein the first step is performed while maintaining the silicon substrate temperature at 300 ° C. or higher, or as described in claim 6. ,
5. The metal silicate film forming method according to claim 4, wherein the first step is performed such that the metal silicate film is formed to a thickness of 0.5 to 2 nm. As described in Section 7,
The metal silicate film forming method according to claim 1, wherein the second step is performed while supplying oxygen gas to the silicon substrate, or as described in claim 8.
The metal silicate film forming method according to claim 7, wherein the second step is performed while supplying ozone gas to the silicon substrate, or as described in claim 9.
A method for manufacturing a semiconductor device comprising a method for forming a metal silicate film according to any one of claims 1 to 8, or as described in claim 10.
A computer-readable recording medium that records software that, when executed, causes a general-purpose computer to control a film forming apparatus,
The software is solved by a computer-readable recording medium that causes the film forming apparatus to execute the metal silicate film forming method according to claim 1.

  According to the present invention, the metal silicate film is formed on the surface of the silicon substrate by a plurality of processes and in each process so as to have a film thickness of 0.5 nm or more and 2 nm or less. The surface roughness can be suppressed to the same level as that of the silicon oxide film interposed between the silicon substrate and the metal silicate film, and the surface of the metal silicate film has an extremely small surface roughness equivalent to that of the silicon oxide film. Can be realized. Therefore, by forming a gate electrode on such a flat metal silicate film, it becomes possible to effectively suppress the gate leakage current of the transistor. In addition, since such a metal silicate film is formed at a substrate temperature of 480 ± 50 ° C., it has a characteristic that the film quality is superior to that of a metal silicate film formed by the ALD method, and further suppresses gate leakage current. Is done.

  Further, the formation of the metal silicate film is divided into a plurality of processes, and in the film formation interruption process between the processes, oxygen gas or ozone gas is supplied to the surface of the formed metal silicate film, thereby Flat film formation in the process is guaranteed.

[First Embodiment]
FIG. 1 shows the configuration of an MOCVD apparatus 20 used in the present invention.

  Referring to FIG. 1, the MOCVD apparatus 20 includes a processing container 22 that is evacuated by a pump 21, and a holding table 22 </ b> A that holds a substrate W to be processed is provided in the processing container 22.

  Further, a shower head 22S is provided in the processing container 22 so as to face the substrate W to be processed, and a line 22a for supplying oxygen gas is not shown in the shower head 22S. And is connected via a valve V1.

  The MOCVD apparatus 20 includes a container 23B for holding an organometallic compound material such as HTB, and the organometallic compound material in the container 23B is vaporized via a fluid flow rate controller 22d by a pumping gas such as He gas. The organometallic compound raw material gas supplied to the vaporizer 22e and vaporized with the aid of a carrier gas such as Ar in the vaporizer 22e is supplied to the shower head 22S via the valve V3.

  Further, the MOCVD apparatus 20 is provided with a heating vessel 23A for holding an organic silicon compound material such as TEOS, and the organic silicon compound material gas evaporated in the heating vessel 23A is supplied to the shower head through the MFC 22b and the valve V2. 22S.

  In the shower head 22S, the oxygen gas, the organic silicon compound source gas, and the organometallic compound source gas pass through their respective paths, and through an opening 22s formed on the surface of the shower head 22S that faces the silicon substrate W. , And discharged into the process space in the processing vessel 22.

FIG. 2 shows the relationship between the surface roughness and film thickness of a hafnium silicate (HfSiO ₄ ) film formed on the silicon substrate by the MOCVD apparatus 20 of FIG. 1 in various film thicknesses, and FIG. The relationship between Hf density | concentration in the made hafnium silicate film | membrane and film-forming time is shown. In FIG. 2, the surface roughness is measured by an atomic force microscope, and the film thickness is measured by ellipsometry, and is displayed including the film thickness of the silicon oxide film formed between the hafnium silicate film and the silicon substrate. ing. In FIG. 3, the Hf concentration in the film is measured by XRF.

Referring to FIG. 2, the hafnium silicate film is formed on a silicon substrate via a SiO ₂ film having a thickness of 0.5 nm. The hafnium silicate film is formed under a process pressure of 40 Pa at a temperature of 480 ± 50 ° C. while supplying HTB at a flow rate of 0.2 sccm and TEOS at a flow rate of 0.2 sccm. .

  Referring to FIG. 2, from the time when film formation is started (0 sec) until the film thickness of the hafnium silicate film reaches about 0.3 nm (5 sec: 5 seconds after film formation starts), the surface roughness is abrupt. As shown in FIG. 4A, the island-shaped growth of hafnium silicate 42 occurs on the silicon oxide film 41 covering the silicon substrate 40 immediately after the start of film formation. It shows that. The surface roughness value of 0.18 nm at the start of film formation (0 sec) corresponds to the surface roughness of the silicon oxide film 41.

  On the other hand, with the start of film formation, the hafnium silicate island 42 grows as shown in FIG. 4B, and the surface roughness rapidly increases with this, but the film thickness of the island reaches about 0.3 nm. If the film formation is further continued beyond the time point (5 sec), the surface roughness decreases rapidly, and after 10 seconds (10 sec) after the start of film formation, when the film thickness of the hafnium silicate island 42 reaches 0.5 nm. It was discovered that the surface roughness of the film 42 returned to the original value of 0.18 nm.

  This means that, as shown in FIG. 4C, the hafnium silicate island 42 in the state of FIG. 4B has collapsed and a phenomenon of changing to a flat hafnium silicate film 43 occurs. The film thickness is an optical measurement value by ellipsometry, and corresponds to the film thickness when the islands are averaged.

  This state continues for a while, and when the thickness of the flat hafnium silicate film 43 exceeds about 2 nm, the surface roughness of the film 43 begins to increase again. This is due to the occurrence of grain growth in the hafnium silicate film 43. Is interpreted as indicating.

  The result of FIG. 2 shows that the surface roughness equivalent to the surface roughness of the underlying silicon oxide film 41 is realized when the net film thickness of the hafnium silicate film exceeds 0.5 nm. This is because the balance between the surface tension (surface free energy) of the island 42 and the thermal energy of the molecules constituting the island 42 is lost in the film thickness range of 0.3 to 0.5 nm of the hafnium silicate film, and the flat film structure 43 Suggests that is more stable.

  FIG. 3 shows the result of measuring the Hf concentration by ICPMS (inductively coupled plasma mass spectrometry) for a sample having a film formation time of 0 seconds (zero residual gas adsorption amount), 5 seconds, and 10 seconds. Indicates. However, the samples with a film formation time of 5 seconds and 10 seconds correspond to the 5 sec and 10 sec samples in FIG. 2, respectively.

In the ICPMS measurement, the average Hf concentration on the surface of the silicon substrate is detected. From the relationship shown in FIG. 3, the hafnium concentration on the silicon oxide film 41 increases linearly with the deposition time, and hafnium silicate. It is shown that the film is growing with the feed. In particular, in a sample formed for 10 seconds, that is, a sample corresponding to the structure of FIG. 4C, the Hf concentration reaches 5 × 10 ¹⁴ cm ⁻³ . This Hf concentration value corresponds to the Hf concentration of one molecular layer of HfSiO _4. Therefore, in the structure of FIG. 4C, a hafnium silicate film having a thickness of one molecular layer is actually obtained as the film 43. It is thought that.

  Therefore, in this embodiment, in order to obtain a flat hafnium silicate film having a desired film thickness, a film forming method is proposed in which the steps of FIGS. 4A to 4C are repeated with a growth interruption interposed therebetween.

  FIG. 5 is a flowchart showing a method of forming a hafnium silicate film according to the first embodiment of the present invention.

  Referring to FIG. 5, in step 1, the flat hafnium silicate film 43 is formed on the silicon substrate 40 by supplying HTB and TEOS materials from the showerhead 22S using the MOCVD apparatus 20 of FIG. A film having a thickness of 0.5 nm or more and 2 nm or less is formed on 41.

  Next, in step 2, the supply of the HTB and TEOS raw materials is stopped, and further growth of the hafnium silicate film 43 is stopped.

  Further, returning to Step 1, by repeating Steps 1 and 2, a flat hafnium silicate film 43 is repeatedly formed on the silicon substrate 40 until a desired film thickness is reached.

  As described above, in this embodiment, by repeatedly forming the flat hafnium silicate film 43, it is possible to form a flat hafnium silicate film having a small surface roughness to a desired thickness.

  In this embodiment, the substrate temperature is set to 480 ° C. However, since HTB is decomposed at 250 to 300 ° C., it may be 300 ° C. or higher in order to realize film formation by the CVD method.

  In this embodiment, the supply of TEOS is stopped at the same time as the HTB in the step 2. However, if the substrate temperature is equal to or lower than the decomposition temperature of TEOS, even if the supply of TEOS is continued, the film is substantially removed. Growth stops.

In this embodiment, N ₂ gas or inert gas is supplied to the processing container 22 in Step 2, but oxygen gas may be supplied. By supplying oxygen gas, the undecomposed TEOS remaining on the surface of the hafnium silicate film 43 formed in Step 1 can be oxidized, and the surface of the hafnium silicate film 43 can be brought into an excess SiO ₂ state.

  Further, ozone gas having a stronger oxidizing power can be supplied instead of oxygen gas or in addition to oxygen gas, so that the surface of the hafnium silicate film 43 can be made to be in an excessive SiO 2 state.

  As described above, when the surface of the hafnium silicate film formed in each step is oxidized to form a hafnium silicate film thereon, the steps shown in FIGS. 4 (A) to (C) are performed. Formation of a flat film by the mechanism can be more reliably performed.

The flattening of the metal silicate film by the same mechanism is not limited to the hafnium silicate film, but other metal silicate films such as a zirconium silicate film, and also so-called high-K dielectric such as hafnium oxide and zirconium oxide. It is considered that this also occurs in metal oxide films used as body films.

[Second Embodiment]
FIG. 7 shows a configuration of a semiconductor device 60 according to the second embodiment of the present invention.

  Referring to FIG. 7, the semiconductor device 60 is formed in a device region 61 </ b> A defined by a device isolation structure 61 </ b> I on a silicon substrate 61, and a gate electrode 63 corresponding to the channel region in the silicon substrate 61. Is formed through a gate insulating film 63 having a stacked structure of a silicon oxide film 62ox and a hafnium silicate film 62hk. In the silicon substrate 61, source and drain extension regions 61a are formed on both sides of the gate electrode 63. , 61b are formed.

  Further, sidewall insulating films 63A and 63B are formed on both side wall surfaces of the gate electrode 63, respectively, and source and drain diffusion regions are formed outside the sidewall insulating films 63A and 63B in the silicon substrate 61, respectively. 61c and 61d are formed.

In this configuration, the hafnium silicate film 62hk is formed by the process shown in FIG. 5 to obtain a flat high-K gate insulating film 62, and a gate leakage current due to a local film thickness reduction of the gate insulating film. Is effectively suppressed.

[Third Embodiment]
FIG. 8 shows a configuration of a control device 80 that controls the MOCVD apparatus 20 shown in FIG. 1 or 6 to execute the film forming process of the present invention shown in FIG.

  The control device 80 is a general-purpose computer, and includes a system bus 81, a CPU 82, a memory 83, a graphic card 84, a disk drive 85 such as a hard disk and an optical disk, an input / output interface 86 for a keyboard and pointing device, and an interface. The MOCVD apparatus 20 is controlled via the interface card 87.

  The disk drive 85 holds a control program code corresponding to the flowchart of FIG. 5. When the computer 80 is started, the control program code is read by the CPU 82 and stored in the memory 83 and the disk drive 85. Expanded on the hard disk.

  Such a control program is recorded on an information recording medium such as a magnetic disk or an optical disk, and is written on a hard disk in the disk drive 85 via the input / output interface 86.

  The computer 80 is connected to the network 89 via a network interface 88, and the control program can be written into the hard disk device 85 from the network.

  Although the present invention has been described with reference to the preferred embodiments, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made within the scope of the claims.

It is a figure which shows the structure of the MOCVD apparatus used by this invention. It is a figure explaining the principle of this invention. It is another figure explaining the principle of this invention. (A)-(C) is a figure explaining the film-forming method by the 1st Embodiment of this invention. It is a flowchart explaining the 1st Embodiment of this invention. It is a figure which shows the structure of the semiconductor device by the 2nd Embodiment of this invention. It is a figure which shows the structure of the computer by the 3rd Embodiment of this invention.

Explanation of symbols

20 MOCVD equipment 21 Exhaust system 22 Processing vessel 22A Substrate holder 22a Oxygen gas line 22b, 22d MFC
22c raw material gas line 22e vaporizer 22S shower head 22U ultraviolet light source 22s opening 23A, 23B raw material container 40 silicon substrate 41 interface silicon oxide film 42, 43 hafnium silicate film 60 semiconductor device 61 silicon substrate 61A element region 61I element isolation region 61a source Extension region 61b Drain extension region 61c Source region 61d Drain region 62 Gate insulating film 62ox Interfacial oxide film 62hk Hafnium silicate film 63 Gate electrode 63A Source region 63B Drain region 80 Computer

Claims (10)

A method for forming a metal silicate film on a silicon substrate,
A first vapor phase material composed of an organometallic compound containing a metal element constituting the metal silicate film and a second vapor phase material composed of an organic silicon compound are supplied to the silicon substrate surface, and the metal is deposited on the silicon substrate. A first step of forming a silicate film;
Repeating the second step of interrupting the supply of the first vapor phase raw material and interrupting the formation of the metal silicate film,
In the first step, the temperature of the silicon substrate is kept equal to or higher than the decomposition temperature of the first vapor phase raw material, and the metal silicate film is formed with a film thickness corresponding to at least one molecular layer. A method for forming a metal silicate film.   2. The method of forming a metal silicate film according to claim 1, wherein, in the second step, the temperature of the silicon substrate is maintained at a temperature equal to or lower than a decomposition temperature of the second vapor phase raw material.   3. The method of forming a metal silicate film according to claim 1, wherein the first raw material is HTB (tetratertiary oxyhafnium).   4. The method of forming a metal silicate film according to claim 3, wherein the second raw material is TEOS (tetraethoxysilane).   5. The method of forming a metal silicate film according to claim 3, wherein the first step is performed while maintaining the silicon substrate temperature at 300 ° C. or higher.   5. The method of forming a metal silicate film according to claim 4, wherein the first step is performed such that the metal silicate film is formed with a thickness of 0.5 to 2 nm.   2. The method of forming a metal silicate film according to claim 1, wherein the second step is performed while supplying oxygen gas to the silicon substrate.   8. The method of forming a metal silicate film according to claim 7, wherein the second step is performed while supplying ozone gas to the silicon substrate.   A method for manufacturing a semiconductor device, comprising a method for forming a metal silicate film according to claim 1. A computer-readable recording medium that records software that, when executed, causes a general-purpose computer to control a film forming apparatus,
A computer-readable recording medium, wherein the software causes the film forming apparatus to execute the metal silicate film forming method according to claim 1.

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