JP2008108803A - Method of cleaning semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of cleaning a semiconductor device by which pollutant metal containing at least one of 3 group element (La, Ce, Pr, Nd, Th), 3A group element (Sc, Y), 4A group element (Zr, Hf), and 5A group element (Ta) can be removed at high speed and in high efficiency. <P>SOLUTION: The method of cleaning a semiconductor device is used to remove pollutant metal 11 that exists on a semiconductor substrate 10 and contains at least one selected from a group comprised of 3 group element (La, Ce, Pr, Nd, Th), 3A group element (Sc, Y), 4A group element (Zr, Hf), and 5A group element (Ta). It includes a step to oxidize the semiconductor substrate 10 by vapor phase so as to form a silicon oxide film 12 under the pollutant metal 11 and a step to remove the pollutant metal 11 together with the silicon oxide film 12 by chemical containing hydrofluoric acid or its salt. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for cleaning a semiconductor device, and in particular, a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y) on a silicon substrate, a silicon film, or a structure including silicon. The present invention relates to a method for removing a contaminating metal including at least one metal of a group 4A element (Zr, Hf) and a group 5A element (Ta).

  In the development of MOSFETs, investigations for thinning the gate insulating film have been actively conducted so far because of the demand for miniaturization and high integration of elements. According to the current technical level, the thickness of the gate insulating film has reached an extremely thin level of several nanometers, but forming an insulating film thinner than this makes the reliability of the element due to an increase in leakage current, etc. There is concern that it will be damaged.

Under these circumstances, in addition to the conventional SiO ₂ film or SiON film, application of a so-called high dielectric constant film (High-K) having a high dielectric constant is being studied. As the High-K material, for example, materials such as Zr _x O _y , Hf _x O _y , Hf _x Si _y O _z , and Hf _x La _y O _z have been studied. When a high dielectric constant film using such a material is applied to an insulating film of a transistor, gate capacitance can be increased and leakage current can be reduced. Therefore, a gate structure using a conventional SiO ₂ film or SiON film as a gate insulating film and a gate structure using a High-K material as a gate insulating film exist on the same substrate, that is, two or more types of gate structures are used. A semiconductor device in which gate insulating films having different materials and compositions are formed on the same substrate has been studied.

On the other hand, in a memory element such as a DRAM, a technique for forming a capacitive film with a material having a higher dielectric constant is desired. Currently, a material such as Ta _x O _y is being studied as a capacitive film.

  By the way, in general, an oxide of a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y), a group 4A element (Zr, Hf), or a group 5A element (Ta) is high. It is difficult to dissolve and remove with cleanliness. In particular, when contaminants made of these materials adhere to the surface of the silicon substrate, silicide or the like is formed by the reaction of these elements with silicon, making it extremely difficult to remove.

Further, as described above, the gate structure using the conventional SiO ₂ film or the SiON film as the gate insulating film and the gate structure using the High-K material as the gate insulating film exist on the same substrate, that is, In a semiconductor device in which two or more kinds of gate insulating films having different materials and compositions are formed on the same substrate, a contaminated metal generated during the formation of a gate insulating film made of a High-K material or the like is a conventional SiO ₂ film. Alternatively, there is a concern that the performance of the transistor may deteriorate due to cross contamination with the gate insulating film using the SiON film.

  Further, in a trench type DRAM in which cells are formed in the depth direction on a silicon substrate, there is a concern that the transistor performance is deteriorated due to cross contamination.

  Thus, the Group 3 element (La, Ce, Pr, Nd, Th), the 3A group element (Sc, Y), the 4A group element (Zr, Hf), and the 5A group element (Ta) used in the High-K film are used. It is necessary to remove the contaminating metal containing at least one metal) with a high degree of cleaning.

  On the other hand, generally, a method of removing a contaminating metal on a silicon substrate using hydrofluoric acid is employed (see, for example, Patent Document 1).

  10A and 10B are cross-sectional views showing a conventional method for removing contaminated metals in the order of steps.

A metal containing at least one of group 3 element (La, Ce, Pr, Nd, Th), group 3A element (Sc, Y), group 4A element (Zr, Hf), and group 5A element (Ta) When the contaminated metal 2 remains on the semiconductor substrate 1 as shown in FIG. 10A after the contained film is removed by cleaning treatment or dry etching, the thickness of the contaminated metal is reduced in the drawing. Although it is displayed in the state of the film provided, it is actually present to such an extent that it adheres to the surface.) As shown in FIG. 10 (b), hydrofluoric acid or a salt thereof is added. An etching cleaning process using a chemical solution is performed. If it does in this way, hydrofluoric acid will melt | dissolve a part of silicon substrate 1, and the contamination metal 2 will be removed by the lift-off effect.
JP 2003-229401 A

However, in the conventional method, at least one of the group 3 elements (La, Ce, Pr, Nd, Th), the group 3A element (Sc, Y), the group 4A element (Zr, Hf), and the group 5A element (Ta) is used. It is not easy to remove contaminating metals including one metal. That is, it is difficult to remove the contaminated metal at high speed and high efficiency. For example, the etching rate of the film to be removed with respect to an aqueous solution of 1% by mass of hydrofluoric acid is 0.5 nm / min or less in the case of LaO ₂ film or HfO ₂ film, and 4 nm / min in the case of SiO ₂ film. Compared with, the removal rate of contaminating metals is very slow and the efficiency is poor.

  In view of the above, the object of the present invention is to provide a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y), a group 4A element (Zr, Hf), at high speed and high efficiency. And a method for cleaning a semiconductor device that removes contaminating metals including at least one metal of Group 5A element (Ta).

  In order to achieve the above object, a semiconductor device cleaning method according to the first aspect of the present invention includes a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element present on a semiconductor substrate. (Sc, Y) A method for cleaning a semiconductor device for removing a contaminating metal including at least one metal selected from the group consisting of a group 4A element (Zr, Hf) and a group 5A element (Ta). A step of forming a silicon oxide film under the contaminated metal by vapor phase oxidation of the semiconductor substrate; and a step of removing the contaminated metal together with the silicon oxide film using a chemical solution containing hydrofluoric acid or a salt thereof. including.

  The method for cleaning a semiconductor device according to the second aspect of the present invention includes a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y), and a group 4A element present on a semiconductor substrate. (Zr, Hf) and a cleaning method of a semiconductor device for removing a contaminating metal containing at least one metal selected from the group consisting of 5A group elements (Ta), comprising: a gate insulating film on a semiconductor substrate; Forming a gate structure made of a metal-containing gate electrode, and forming a protective insulating film made of an oxidation-resistant insulating film on the top and side surfaces of the gate structure on the semiconductor substrate; After the step of forming the protective insulating film, a step of forming a silicon oxide film below the contaminated metal generated when forming the gate structure by vapor phase oxidation of the semiconductor substrate, and hydrofluoric acid or its A chemical solution containing salt There are, and removing the contaminant metals with silicon oxide film.

  The method for cleaning a semiconductor device according to the third aspect of the present invention includes a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y), and a group 4A element present on a semiconductor substrate. (Zr, Hf) and a method for cleaning a semiconductor device for removing a contaminating metal containing at least one metal selected from the group consisting of a group 5A element (Ta), including a metal on a semiconductor substrate When forming a gate structure by vapor phase oxidation of a semiconductor substrate after a step of forming a gate structure composed of a gate insulating film and a gate electrode not containing a metal and a step of forming a gate structure A step of forming a silicon oxide film under the generated contaminated metal and a step of removing the contaminated metal together with the silicon oxide film using a chemical solution containing hydrofluoric acid or a salt thereof are included.

  The method for cleaning a semiconductor device according to the fourth aspect of the present invention includes a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y), a group 4A element present on a semiconductor substrate. (Zr, Hf) and a method for cleaning a semiconductor device for removing a contaminating metal containing at least one metal selected from the group consisting of a group 5A element (Ta), including a metal on a semiconductor substrate A step of forming a metal film, a step of patterning the metal film into a desired shape, and a gas phase oxidation of the semiconductor substrate, thereby forming a silicon oxide film below the contaminated metal generated during the patterning and patterning. After the step of forming the metal oxide film by oxidizing the formed metal film, the step of forming the gate electrode not containing metal on the metal oxide film, and the step of forming the gate electrode, Acid or by using a chemical solution containing a salt thereof, and removing the contaminant metals with silicon oxide film.

  In the method for cleaning a semiconductor device according to the fourth aspect of the present invention, the metal film forming step uses a PVD (Physical Vapor Deposition) method, an ALD (Atomic Layer Deposition) method, or a CVD (Chemicla Vapor Deposition) method. Done.

  In the method for cleaning a semiconductor device according to the first to fourth aspects of the present invention, the step of performing vapor phase oxidation includes an oxidation method including at least one of thermal oxidation, radical oxidation, plasma oxidation, and UV oxidation. It is preferable to be carried out using.

  In the semiconductor device cleaning methods according to the first to fourth aspects of the present invention, the silicon oxide film preferably has a thickness of 0.3 nm or more.

  In the method for cleaning a semiconductor device according to the first to fourth aspects of the present invention, the contaminated metal further exists on the lower surface of the semiconductor substrate, and the step of performing vapor phase oxidation oxidizes the lower surface side of the semiconductor substrate. Preferably, the method includes a step of forming a silicon oxide film on the lower surface side of the semiconductor substrate.

  In the method for cleaning a semiconductor device according to the first to fourth aspects of the present invention, the step of performing vapor phase oxidation includes exposing a semiconductor substrate containing silicon and a structure containing silicon formed on the semiconductor substrate. A step of oxidizing the surface is preferred.

In the semiconductor device cleaning method according to the first to fourth aspects of the present invention, the contamination concentration of the contaminant is 1.0 × 10 ⁹ atoms / cm ² or more and 1.0 × 10 ¹⁶ atoms / cm 2. Preferably it is less than ² .

According to the method for cleaning a semiconductor device of the present invention, the time for reducing the residual concentration of the contaminating metal remaining on the semiconductor substrate to 1.0 × 10 ⁹ atoms / cm ² or less is greatly shortened, and the residual concentration is reduced. The level can be greatly reduced.

(First embodiment)
A method for cleaning a semiconductor device according to the first embodiment of the present invention will be described below with reference to the drawings.

  The method for cleaning a semiconductor device according to the first embodiment of the present invention includes a group 3 existing on the upper surface of a semiconductor substrate made of silicon, or the upper surface of a semiconductor substrate made of silicon and the surface of a structure containing silicon. At least one selected from the group consisting of an element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y), a group 4A element (Zr, Hf), and a group 5A element (Ta) Provided is a method for removing a contaminated metal including a metal. Specifically, a semiconductor substrate or a semiconductor substrate and a structure are vapor-phase oxidized to form a silicon oxide film under the contaminated metal. And a step of removing the contaminated metal together with the silicon oxide film using a chemical solution containing hydrofluoric acid or a salt thereof. Here, the case where the contaminating metal existing on the upper surface of the semiconductor substrate is removed is described as an example. However, the present invention is not limited to this, and the present invention is present on the lower surface of the semiconductor substrate including the following examples. Needless to say, the contaminated metal can be removed in the same manner as the case of removing the contaminated metal present on the upper surface of the semiconductor substrate.

  Hereinafter, first and second examples of the semiconductor device cleaning method according to the first embodiment of the present invention will be described.

-A first example according to the first embodiment-
1A to 1C are process cross-sectional views illustrating a first example relating to a semiconductor device cleaning method according to the first embodiment of the present invention.

First, as shown in FIG. 1A, on a semiconductor substrate 10 made of silicon, a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y), a group 4A element ( Contaminated metal 11 including at least one of Zr, Hf) and 5A group element (Ta) remains at 1.0 × 10 ¹⁶ atoms / cm ² or less.

  Next, as shown in FIG. 1B, by oxidizing the semiconductor substrate 10 using a method including any one of thermal oxidation, radical oxidation, plasma oxidation, and UV oxidation, the contamination metal 11 is removed. A silicon oxide film 12 having a thickness of 0.3 nm or more is formed below. Here, as an example of oxidation conditions, when pyrogenic heat treatment is performed at 1000 ° C. for 60 seconds, a silicon oxide film 12 having a thickness of 10 nm is formed.

Next, as shown in FIG. 1C, an etching cleaning process is performed using a chemical solution containing hydrofluoric acid or a salt thereof. Thereby, the silicon oxide film 12 is removed together with the contaminating metal 11. However, in this step, an etching cleaning process may be performed so that the silicon oxide film 12 is completely removed, or an etching cleaning process is performed so that the silicon oxide film 12 is etched by 0.3 nm or more and a part thereof remains. You may go. Thus, the contaminated metal 11 can be reduced to 1.0 × 10 ⁹ atoms / cm ² or less by etching away the silicon oxide film 12 by 0.3 nm or more.

  Here, FIG. 2 shows the relationship between the etching time and the residual concentration of the contaminating metal 11 in the first example relating to the semiconductor device cleaning method according to the first embodiment of the present invention.

As shown in FIG. 2, when the etching cleaning process of the present invention having an oxidation process (a1 to a3) is used, the comparison with the case of using a conventional etching cleaning process without an oxidation process (b1 to b3) is compared. went. In the figure, a1 and b1 use HF / HNO ₃ as a chemical solution, a2 and b2 use HF / HCl as a chemical solution, and a3 and b3 use HF as a chemical solution.

As apparent from FIG. 2, when the results using the same chemical solution are compared with each other, the residual concentration of the contaminating metal 11 remaining on the semiconductor substrate 10 after the etching cleaning process is reduced to 1.0 × 10 ⁹ atoms / cm ² or less. It can be seen that the time required to reduce the time is significantly reduced in the case of the present invention compared to the conventional case. It can also be seen that the residual concentration level of the contaminated metal 11 is significantly reduced in the present invention compared to the conventional case.

-Second Example of the First Embodiment-
FIGS. 3A to 3C are process cross-sectional views illustrating a second example of the semiconductor device cleaning method according to the first embodiment of the present invention.

First, as shown in FIG. 3A, a structure 21 exposing silicon on the surface is formed on a semiconductor substrate 20 made of silicon. On the upper surface of the semiconductor substrate 20, the upper surface and the side surface of the structure 21, a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y), a group 4A element (Zr, Hf), and Contaminated metal 23 containing at least one metal of group 5A element (Ta) remains at 1.0 × 10 ¹⁶ atoms / cm ² or less.

  Next, as illustrated in FIG. 3B, the top surface of the semiconductor substrate 20, the top surface and the side surface of the structure 21 are formed using a method including any one of thermal oxidation, radical oxidation, plasma oxidation, and UV oxidation. Is oxidized to form a silicon oxide film 24 having a thickness of 0.3 nm or more under the contaminated metal 23. Here, even if it is a complicated structure, the surface thereof can be oxidized relatively uniformly and with an oxidation rate lower than that of pyrogenic heat treatment and easy to control. When heat treatment is performed, a silicon oxide film 24 having a thickness of 2 nm is formed.

Next, as shown in FIG. 3C, an etching cleaning process is performed using a chemical solution containing hydrofluoric acid or a salt thereof as in the conventional case. Thereby, the silicon oxide film 24 is removed together with the contaminating metal 23. However, in this step, an etching cleaning process may be performed so that the silicon oxide film 24 is completely removed, or an etching cleaning process is performed so that the silicon oxide film 24 is etched by 0.3 nm or more and a part thereof remains. You may go. Thus, the contaminated metal 23 can be reduced to 1.0 × 10 ⁹ atoms / cm ² or less by etching away the silicon oxide film 24 by 0.3 nm or more.

  In the first embodiment described above, the oxidation method does not include chemical oxidation using a solution such as hydrogen peroxide water or ozone water. This is because chemical oxidation with a chemical solution has low film density, and more metal to be removed is taken into the chemical oxide film than the oxidation methods listed in the embodiments. That is, if a large amount of the metal to be removed is taken into the chemical oxide film, the removal target taken into the chemical oxide film in the subsequent etching cleaning process using the removal liquid containing hydrofluoric acid or a salt thereof is used. This is because it is difficult to remove the metal.

  On the other hand, the oxidation methods listed in the above embodiments are effective. This is because the element group that can be included in the contaminated metal has a larger bond with the oxygen atom than the silicon atom due to the formation enthalpy, and the diffusion length in the silicon film and the silicon oxide film is small. This is because these elements do not move and exist on the outermost surface of the semiconductor substrate and do not diffuse into the film.

  Note that the chemical solution used for the etching cleaning process performed after oxidation may include hydrogen peroxide water or ozone water in a chemical solution containing hydrofluoric acid or a salt thereof.

In the first embodiment described above, the concentration when the contaminating metal is generated is usually larger than 1.0 × 10 ⁹ atoms / cm ² and not larger than 1.0 × 10 ¹⁶ atoms / cm ² .

  In the above-described embodiment, the contaminated metal is displayed in a film state having a thickness in the drawing, but it actually exists to the extent that it adheres to the surface.

(Second Embodiment)
A semiconductor device cleaning method according to the second embodiment of the present invention will be described below with reference to the drawings.

The present embodiment is an application example of the semiconductor device cleaning method according to the first embodiment, and includes a gate structure using a conventional SiO ₂ film or SiON film as a gate insulating film, and High-K as a gate insulating film. In a semiconductor device in which a gate structure using a material is present on the same substrate, that is, a gate insulating film having two or more different materials and compositions is formed on the same substrate, gate insulation made of a High-K material It is an object of the present invention to provide a method for preventing the deterioration of the performance of a transistor by causing contaminated metal generated during the formation of a film or the like as a cross-contamination with a gate insulating film using a conventional SiO ₂ film or SiON film.

  The first to third examples of the semiconductor device cleaning method according to the second embodiment of the present invention will be described below.

-A first example according to the second embodiment-
FIGS. 4A to 4C and FIGS. 5A and 5B are process cross-sectional views illustrating a first example relating to a semiconductor device cleaning method according to the second embodiment of the present invention.

  First, as shown in FIG. 4A, an element isolation film 31 for partitioning an element formation region is formed on a semiconductor substrate 30 made of silicon. On the semiconductor substrate 30 and the element isolation film 31, respectively. At least one metal selected from Group 3 elements (La, Ce, Pr, Nd, Th), Group 3A elements (Sc, Y), Group 4A elements (Zr, Hf), and Group 5A elements (Ta). A gate insulating film forming film 32a and a gate electrode forming film 33a are sequentially formed from below. Here, the formation method of the gate insulating film formation film 32a and the gate electrode formation film 33a is not particularly limited. Can be used.

Next, as shown in FIG. 4B, the gate insulating film 32 and the gate electrode formed by patterning the gate insulating film forming film 32a by performing dry etching using a photoresist mask, a hard mask, or the like. A gate structure including the gate electrode 33 formed by patterning the formation film 33a is formed. In addition, by this step, the above group 3 elements are formed on the upper surface of the semiconductor substrate 30, the upper surface of the element isolation film 31, and the upper and side surfaces of the gate structure (the upper and side surfaces of the gate electrode 33 and the side surface of the gate insulating film 22). (La, Ce, Pr, Nd, Th), 3A group element (Sc, Y), 4A group element (Zr, Hf), and a contaminated metal comprising at least one metal of 5A group element (Ta) 34 remains at 1.0 × 10 ¹⁶ atoms / cm ² or less.

  Next, as shown in FIG. 4C, for example, a silicon nitride film or the like having oxidation resistance against an oxidation process described later is deposited on the entire surface of the semiconductor substrate 30, and then deposited on the upper surface of the semiconductor substrate 30. By removing the silicon nitride film and the like, sidewalls 35 are formed on the upper and side surfaces of the gate structure. Note that the contamination metal around the gate structure is sealed between the surface of the gate structure and the side wall, so that the display is omitted in the drawing.

  Next, as shown in FIG. 5A, a semiconductor substrate 30 and an element including a source / drain region (not shown) and the like using any one of thermal oxidation, radical oxidation, plasma oxidation, or UV oxidation. By oxidizing the upper surface of the separation film 31, a silicon oxide film 36 having a film thickness of 0.3 nm or more is formed below the contaminated metal 34. In addition, as an oxidation condition, an example in the 1st or 2nd Example of 1st Embodiment mentioned above can be used similarly.

Next, as shown in FIG. 5B, an etching cleaning process is performed using a chemical solution containing hydrofluoric acid or a salt thereof as in the conventional case. Thereby, the silicon oxide film 36 is removed together with the contaminated metal 34. However, in this step, the silicon oxide film 36 may be completely removed or the silicon oxide film 36 may be reduced to 0 as in the first or second example of the first embodiment. It is also possible to etch 3 nm or more and leave a part of it. Thereby, the contamination metal 34 can be reduced to 1.0 × 10 ⁹ atoms / cm ² or less.

Next, although not shown, a gate structure using a conventional SiO ₂ film or SiON film as a gate insulating film is formed on the same semiconductor substrate as the gate structure by a known method. In this case, since the contaminated metal 34 is washed and removed before the process, the contaminated metal generated when forming the gate insulating film 32 and the gate electrode 33 containing the above-mentioned metals which are High-K materials. 34 can prevent deterioration of the transistor performance due to cross contamination with the gate insulating film using the conventional SiO ₂ film or SiON film.

-Second Example according to Second Embodiment-
6 (a) and 6 (b) and FIGS. 7 (a) and 7 (b) are process cross-sectional views illustrating a second example relating to the semiconductor device cleaning method according to the second embodiment of the present invention.

  First, as illustrated in FIG. 6A, an element isolation film 41 that partitions an element formation region is formed on a semiconductor substrate 40 made of silicon. On the semiconductor substrate 40 and the element isolation film 41, 3 Gate insulation containing at least one metal of group elements (La, Ce, Pr, Nd, Th), group 3A elements (Sc, Y), group 4A elements (Zr, Hf), and group 5A elements (Ta) A film formation film 42a and a gate electrode formation film 43a that does not contain any of these metals are sequentially formed from below. As described above, in this example, unlike the first example in the second embodiment described above, only the gate insulating film formation film 42a contains the above-described metals, and the formation of the sidewalls is performed. Do not do. The method for forming the gate insulating film formation film 42a and the gate electrode formation film 43a is the same as that in the first example of the present embodiment described above.

Next, as shown in FIG. 6B, the gate insulating film 42 and the gate electrode formed by patterning the gate insulating film forming film 42a by performing dry etching using a photoresist mask, a hard mask, or the like. A gate structure including the gate electrode 43 formed by patterning the formation film 43a is formed. In addition, by this step, the above group 3 element (La, Ce, Pr, Nd, Th), 3A group element (Sc, Y), 4A group element is formed on the upper surface of the semiconductor substrate 40 and the upper surface of the element isolation film 41. Contaminated metal 44 containing at least one metal of (Zr, Hf) and Group 5A element (Ta) remains at 1.0 × 10 ¹⁶ atoms / cm ² or less.

  Next, as shown in FIG. 7A, a semiconductor substrate 40 and an element including a source / drain region (not shown) and the like using any one of thermal oxidation, radical oxidation, plasma oxidation, or UV oxidation. By oxidizing the upper surface of the separation film 41, a silicon oxide film 45 having a film thickness of 0.3 nm or more is formed below the contaminated metal 44. In addition, as an oxidation condition, an example in the 1st or 2nd Example of 1st Embodiment mentioned above can be used similarly.

Next, as shown in FIG. 7B, an etching cleaning process is performed using a chemical solution containing hydrofluoric acid or a salt thereof, as in the prior art. Thereby, the silicon oxide film 45 is removed together with the contaminating metal 44. However, in this step, the silicon oxide film 45 may be completely removed or the silicon oxide film 45 may be reduced to 0 as in the first or second example of the first embodiment described above. It is also possible to etch 3 nm or more and leave a part of it. Thereby, the contamination metal 44 can be reduced to 1.0 × 10 ⁹ atoms / cm ² or less.

Next, although not shown, a gate structure using a conventional SiO ₂ film or SiON film as a gate insulating film is formed on the same semiconductor substrate as the gate structure by a known method. In this case, since the contaminated metal 44 is cleaned and removed before the process, the contaminated metal 44 generated during the formation of the gate insulating film 42 containing the above-mentioned metals, which are High-K materials, is conventionally used. It is possible to prevent the transistor performance from being deteriorated due to cross contamination with the gate insulating film using the SiO ₂ film or the SiON film.

  In the first and second examples of the present embodiment, a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y), a group 4A element (Zr) is formed on the gate insulating film. , Hf), and the case where at least one metal of group 5A element (Ta) is included has been described, but when the gate electrode includes these metals, the gate insulating film includes these metals. There is no necessity. In this case, the influence of cross contamination can be prevented by removing the contaminated metal generated during the formation of the gate electrode in the same manner as described above.

-Third example according to the second embodiment-
FIGS. 8A to 8C and FIGS. 9A and 9B are process cross-sectional views illustrating a third example of the semiconductor device cleaning method according to the second embodiment of the present invention.

  First, as shown in FIG. 8A, an element isolation film 51 that partitions an element formation region is formed on a semiconductor substrate 50 made of silicon, and PVD is formed on the semiconductor substrate 50 and the element isolation film 51. Of group 3 elements (La, Ce, Pr, Nd, Th), 3A group elements (Sc, Y), 4A group elements (Zr, Hf), and 5A group elements (Ta) A metal film 52a containing at least one metal is formed. Here, the metal film 52a may contain an element that does not prevent the oxidation of the metal film itself, such as silicon, and does not contain an oxygen element. Further, the metal film 52a may be an oxide film of these metals formed by using an ALD method or a CVD method.

Next, as shown in FIG. 8B, dry etching is performed using a photoresist mask, a hard mask, or the like to form a metal film 52 in which the metal film 52a is patterned. In addition, by this step, the above group 3 element (La, Ce, Pr, Nd, Th), group 3A element (Sc, Y), group 4A element are formed on the upper surface of the semiconductor substrate 50 and the upper surface of the element isolation film 51. The contaminated metal 53 containing at least one metal of (Zr, Hf) and the group 5A element (Ta) remains at 1.0 × 10 ¹⁶ atoms / cm ² or less.

  Next, as shown in FIG. 8C, a patterned metal film 52, a source / drain region (not shown) using any one of thermal oxidation, radical oxidation, plasma oxidation, or UV oxidation. By oxidizing the upper surface of the semiconductor substrate 50 including the above and the upper surface of the element isolation film 51, the patterned metal film 52 is oxidized to form a gate insulating film 54 made of a High-K material, and contamination is caused. A silicon oxide film 55 having a thickness of 0.3 nm or more is formed below the metal 53. In addition, as an oxidation condition, an example in the 1st or 2nd Example of 1st Embodiment mentioned above can be used similarly.

  Next, as shown in FIG. 9A, a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y), a group 4A element (Zr, A gate electrode formation film 56a containing silicon, which does not contain any metal of Hf) and 5A group element (Ta), is formed. The formation method of the gate electrode formation film 56a is the same as that of the first example in the present embodiment described above.

  Next, as shown in FIG. 9B, the gate electrode 56 formed by patterning the gate electrode formation film 56a is formed by performing dry etching using a photoresist mask, a hard mask, or the like. In this step, the gate electrode formation film 56a is formed on the group 3 element (La, Ce, Pr, Nd, Th), the group 3A element (Sc, Y), the group 4A element (Zr, Hf), and Since any of the 5A group elements (Ta) is not included, a contaminated metal including these metals is not newly formed. In this step, the silicon oxide film 55 below the gate electrode formation film 56a is not etched.

Next, as shown in FIG. 9C, an etching cleaning process is performed using a chemical solution containing hydrofluoric acid or a salt thereof, as in the prior art. Thereby, although not shown, the silicon oxide film 55 is removed together with the contaminated metal 53 adhering to the surface. However, in this step, the silicon oxide film 55 may be completely removed or the silicon oxide film 55 may be reduced to 0 as in the first or second example of the first embodiment. It is also possible to etch 3 nm or more and leave a part of it. Thereby, the contamination metal 53 can be reduced to 1.0 × 10 ⁹ atoms / cm ² or less.

Next, although not shown, a gate structure using a conventional SiO ₂ film or SiON film as a gate insulating film is formed on the same semiconductor substrate as the gate structure by a known method. In this case, since the contaminated metal 55 is cleaned and removed before the process, the contaminated metal 55 generated during the formation of the gate insulating film 54 including the metal listed above as the High-K material is conventionally changed. It is possible to prevent the transistor performance from being deteriorated due to cross contamination with the gate insulating film using the SiO ₂ film or the SiON film.

  In the second embodiment described above, the oxidation method does not include chemical oxidation using a solution such as hydrogen peroxide water or ozone water. This is because chemical oxidation with a chemical solution has low film density, and more metal to be removed is taken into the chemical oxide film than the oxidation methods listed in the embodiments. That is, if a large amount of the metal to be removed is taken into the chemical oxide film, the removal target taken into the chemical oxide film in the subsequent etching cleaning process using the removal liquid containing hydrofluoric acid or a salt thereof is used. This is because it is difficult to remove the metal.

  On the other hand, the oxidation methods listed in the above embodiments are effective. This is because the element group that can be included in the contaminated metal has a larger bond with the oxygen atom than the silicon atom due to the formation enthalpy, and the diffusion length in the silicon film and the silicon oxide film is small. This is because these elements do not move and exist on the outermost surface of the semiconductor substrate and do not diffuse into the film.

  Note that the chemical solution used for the etching cleaning process performed after oxidation may include hydrogen peroxide water or ozone water in a chemical solution containing hydrofluoric acid or a salt thereof.

In the second embodiment described above, the concentration when the contaminating metal is generated is larger than 1.0 × 10 ⁹ atoms / cm ² and not larger than 1.0 × 10 ¹⁶ atoms / cm ² .

  In the above-described embodiment, the contaminated metal is displayed in a film state having a thickness in the drawing, but it actually exists to the extent that it adheres to the surface.

  As described above, the present invention provides a group 3 element (La, Ce, Pr, Nd, Th), a group 3A element (Sc, Y), a group 4A element (Zr, Hf), This is useful for a method of cleaning a semiconductor device that removes contaminating metals containing at least one of group 5A elements (Ta).

(A)-(c) is process sectional drawing which shows the 1st Example in the cleaning method of the semiconductor device which concerns on the 1st Embodiment of this invention. It is a graph which shows the relationship between the etching time and the density | concentration of a contamination metal about the 1st Example in the cleaning method of the semiconductor device which concerns on the 1st Embodiment of this invention. (A)-(c) is process sectional drawing which shows the 2nd Example in the cleaning method of the semiconductor device which concerns on the 1st Embodiment of this invention. (A)-(c) is process sectional drawing which shows the 1st Example in the cleaning method of the semiconductor device which concerns on the 2nd Embodiment of this invention. (A) And (b) is process sectional drawing which shows the 1st Example in the cleaning method of the semiconductor device which concerns on the 2nd Embodiment of this invention. (A) And (b) is process sectional drawing which shows the 2nd Example in the cleaning method of the semiconductor device which concerns on the 2nd Embodiment of this invention. (A) And (b) is process sectional drawing which shows the 2nd Example in the cleaning method of the semiconductor device which concerns on the 2nd Embodiment of this invention. (A)-(c) is process sectional drawing which shows the 3rd Example in the washing | cleaning method of the semiconductor device which concerns on the 2nd Embodiment of this invention. (A)-(c) is process sectional drawing which shows the 3rd Example in the washing | cleaning method of the semiconductor device which concerns on the 2nd Embodiment of this invention. It is process sectional drawing which shows the washing | cleaning method of the conventional semiconductor device.

Explanation of symbols

10, 20, 30, 40, 50 Semiconductor substrate 11, 23, 34, 44, 53 Contaminated metal 12, 24, 36, 45, 55 Silicon oxide film 21 Structure 31, 41, 51 Isolation insulating film 32, 42, 54 Gate insulating film 32a, 42a, 56a Gate insulating film forming film 33, 43, 56 Gate electrode 33a, 43a Gate electrode forming film 35 Side wall (protective insulating film)
52 Metal Film 52a Patterned Metal Film

Claims (10)

Group consisting of Group 3 elements (La, Ce, Pr, Nd, Th), Group 3A elements (Sc, Y), Group 4A elements (Zr, Hf), and Group 5A elements (Ta) existing on the semiconductor substrate A method for cleaning a semiconductor device for removing a contaminating metal including at least one metal selected from
Forming a silicon oxide film under the contaminated metal by vapor-phase oxidizing the semiconductor substrate;
And a step of removing the contaminating metal together with the silicon oxide film using a chemical solution containing hydrofluoric acid or a salt thereof. Group consisting of Group 3 elements (La, Ce, Pr, Nd, Th), Group 3A elements (Sc, Y), Group 4A elements (Zr, Hf), and Group 5A elements (Ta) existing on the semiconductor substrate A method for cleaning a semiconductor device for removing a contaminating metal including at least one metal selected from
Forming a gate structure comprising a gate insulating film and a gate electrode containing the metal on the semiconductor substrate;
Forming a protective insulating film made of the oxidation-resistant insulating film on the upper surface and side surfaces of the gate structure on the semiconductor substrate;
A step of forming a silicon oxide film under the contaminated metal generated when forming the gate structure by performing vapor phase oxidation of the semiconductor substrate after the step of forming the protective insulating film;
And a step of removing the contaminating metal together with the silicon oxide film using a chemical solution containing hydrofluoric acid or a salt thereof. Group consisting of Group 3 elements (La, Ce, Pr, Nd, Th), Group 3A elements (Sc, Y), Group 4A elements (Zr, Hf), and Group 5A elements (Ta) existing on the semiconductor substrate A method for cleaning a semiconductor device for removing a contaminating metal including at least one metal selected from
Forming a gate structure including a gate insulating film containing the metal and a gate electrode not containing the metal on the semiconductor substrate;
A step of forming a silicon oxide film under the contaminated metal generated when forming the gate structure by performing vapor phase oxidation of the semiconductor substrate after the step of forming the gate structure;
And a step of removing the contaminating metal together with the silicon oxide film using a chemical solution containing hydrofluoric acid or a salt thereof. Group consisting of Group 3 elements (La, Ce, Pr, Nd, Th), Group 3A elements (Sc, Y), Group 4A elements (Zr, Hf), and Group 5A elements (Ta) existing on the semiconductor substrate A method for cleaning a semiconductor device for removing a contaminating metal including at least one metal selected from
Forming a metal film containing the metal on the semiconductor substrate;
Patterning the metal film into a desired shape;
A vapor-phase oxidation of the semiconductor substrate forms a silicon oxide film below the contaminated metal generated during the patterning, and a metal oxide film is formed by oxidizing the patterned metal film. And a process of
Forming a gate electrode not containing the metal on the metal oxide film;
And a step of removing the contaminating metal together with the silicon oxide film by using a chemical solution containing hydrofluoric acid or a salt thereof after the step of forming the gate electrode.   5. The semiconductor according to claim 4, wherein the step of forming the metal film is performed using a PVD (Physical Vapor Deposition) method, an ALD (Atomic Layer Deposition) method, or a CVD (Chemicla Vapor Deposition) method. How to clean the device.   The step of performing the gas phase oxidation is performed using an oxidation method including at least one of thermal oxidation, radical oxidation, plasma oxidation, and UV oxidation. 2. A method for cleaning a semiconductor device according to item 1.   The method for cleaning a semiconductor device according to claim 1, wherein the silicon oxide film has a thickness of 0.3 nm or more. The contaminating metal is further present on a lower surface of the semiconductor substrate;
5. The step of performing vapor phase oxidation includes a step of oxidizing the lower surface side of the semiconductor substrate to form the silicon oxide film on the lower surface side of the semiconductor substrate. A method for cleaning a semiconductor device according to claim 1.   The step of performing the vapor phase oxidation is a step of oxidizing an exposed surface of the semiconductor substrate containing silicon and a structure containing silicon formed on the semiconductor substrate. 4. The method for cleaning a semiconductor device according to claim 1. The contamination concentration of the contaminant is 1.0 × 10 ⁹ atoms / cm ² or more and less than 1.0 × 10 ¹⁶ atoms / cm ² . 2. A method for cleaning a semiconductor device according to item 1.

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