JP5109269B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method of manufacturing a semiconductor device using a high dielectric constant material for a gate insulating film, and in particular, a semiconductor device having a gate insulating film formed by laminating a silicon oxide film, a silicon nitride film, and a high dielectric constant material film. It relates to the manufacturing method.

  In recent years, higher functionality and higher integration of semiconductor devices have been promoted, and accordingly, further miniaturization of MOS transistors constituting the semiconductor devices is required. In order to miniaturize a MOS transistor, it is indispensable to reduce the thickness of a gate insulating film. Therefore, a gate insulating film having a thickness of 2 nm or less is currently required. However, in the silicon oxide film generally used as the gate insulating film of the MOS transistor, when the film thickness is 2 nm or less, the leakage current due to the tunnel effect increases remarkably, and the power consumption increases and cannot be practically used. Is known.

For this reason, it has been proposed to form the gate insulating film with a high dielectric constant material (so-called high-k material) having a relative dielectric constant several times to several tens of times that of the silicon oxide film. Examples of the high dielectric constant material used for this type of application include HfO ₂ , ZrO ₂ , Ta ₂ O _5, and La ₂ O ₃ . When the gate insulating film is formed of such a high dielectric constant material, the effective film thickness (thickness converted to a SiO ₂ film) can be reduced while the physical film thickness is increased. Thereby, the leakage current can be suppressed, and the MOS transistor can be further miniaturized.

  Incidentally, the gate insulating film is required to have not only a small leakage current but also a small number of defects that trap electrons. However, when the above-described high dielectric constant material is directly formed on a silicon substrate, a large number of interface states and defect levels (defects) are generated at the interface between the silicon substrate and the high dielectric constant material film. Then, electrons are trapped in these levels, causing variations in the electrical characteristics of the gate insulating film. As a result, the characteristics of the MOS transistor become extremely unstable.

  In order to solve this problem, for example, Patent Document 1 proposes forming a silicon oxide film between a silicon substrate and a high dielectric constant material film. Thus, when the silicon oxide film is interposed between the silicon substrate and the high dielectric constant material film, the interface between the silicon substrate and the gate insulating film (that is, the interface between the silicon substrate and the silicon oxide film) becomes flat, The number of defects that trap electrons is reduced. In this case, in order to avoid a decrease in the relative dielectric constant of the gate insulating film (high dielectric constant material film + silicon oxide film), it is necessary to form the silicon oxide film with a thickness of 1 nm or less.

In addition, there exists patent document 2 as another prior art document considered to be related to this invention. In Patent Document 2, after a silicon oxide film is formed on a semiconductor substrate, a smoothing nitridation process using nitrogen radical ion active species is performed to form a silicon nitride film between the semiconductor substrate and the silicon oxide film. It is described to form and reduce crystal defects and interface states.
Japanese Patent No. 3513018 JP 2005-86023 A

  However, in a semiconductor device in which a silicon oxide film is simply disposed between a silicon substrate and a high dielectric constant material film, the silicon oxide and atoms in the high dielectric constant material film are oxidized in various heat treatment steps performed after the gate insulating film is formed. Interdiffuse with atoms in the film. The interdiffusion of atoms deteriorates the interface characteristics between the high dielectric constant material film and the silicon oxide film, and the metal atoms in the high dielectric constant material film reach the silicon substrate, generating metal silicide on the substrate surface. Problems occur.

  As described above, an object of the present invention is to provide a method for manufacturing a semiconductor device that has a gate insulating film having an extremely thin effective film thickness and that does not cause defects due to the gate insulating film, and can be further miniaturized as compared with the prior art. Is to provide.

According to one aspect of the present invention, a step of forming a silicon oxide film on a first silicon substrate, a step of forming a silicon nitride film on a second silicon substrate having a surface of (111), A step of bringing the silicon oxide film and the silicon nitride film into contact with each other, superimposing the second silicon substrate on the first silicon substrate, and bonding the silicon oxide film and the silicon nitride film; A step of removing the silicon substrate, and laminating a high dielectric constant material film on the silicon nitride film to form a gate insulating film composed of the silicon oxide film, the silicon nitride film, and the high dielectric constant material film. forming, to form a step of forming a gate electrode on the gate insulating layer, source and drain by introducing impurities into both surfaces of the first silicon substrate of the gate electrode The method of manufacturing a semiconductor device having a degree is provided.

In general, even if an attempt is made to form a silicon nitride film having an atomic layer thickness on a silicon oxide film, it is extremely difficult to form a silicon nitride film having a uniform thickness. However, if the surface is on a (111) silicon substrate, a uniform silicon nitride film having a thickness of one to several atomic layers can be formed relatively easily by, for example, plasma nitriding. Therefore, in the present invention, a silicon nitride film having a thickness of, for example, one to several atomic layers is formed using a silicon substrate (second silicon substrate) having a (111) surface.

On the other hand, a silicon oxide film is previously formed on the first silicon substrate. Then, on the second silicon substrate of a first silicon substrate, superposed as the first silicon substrate a silicon oxide film and a silicon nitride film of the second silicon substrate are in contact, then for example heat treatment In practice, the silicon oxide film and the silicon nitride film are physically coupled. Next, the second silicon substrate is removed by polishing or etching. Thereafter, when a high dielectric constant material film is formed on the silicon nitride film, a gate insulating film composed of the silicon oxide film, the silicon nitride film, and the high dielectric constant material film is obtained. Next, a gate electrode is formed on the gate insulating film, and impurities are introduced into the surface of the first silicon substrate to form a source / drain.

In the method of the present invention, as described above, since the silicon nitride film is formed on the silicon substrate having the (111) surface, an extremely thin silicon nitride film on the atomic layer order can be formed with a uniform thickness. Further, since the silicon nitride film thus formed is disposed between the silicon oxide film and the high dielectric constant material film, interdiffusion of atoms between the silicon oxide film and the high dielectric constant material film is prevented. .

Furthermore, in the method of the present invention, as described above, the gate insulating film is composed of a silicon oxide film, a silicon nitride film, and a high dielectric constant material film, and the lowermost silicon oxide film is in contact with the silicon substrate. When the silicon oxide film is formed on a silicon substrate by, for example, a sputtering method, a flat and defect-free interface that traps electrons is obtained between the silicon oxide film and the silicon substrate. Thereby, a MOS transistor with stable characteristics can be formed.

  Furthermore, in the method of the present invention, since the gate insulating film is formed using a high dielectric constant material, the effective film thickness can be reduced while the physical film thickness remains large. As a result, the MOS transistor can be further miniaturized.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  1 to 10 are cross-sectional views showing a method of manufacturing a semiconductor device according to an embodiment of the present invention in the order of steps.

  First, as shown in FIG. 1, a silicon substrate (first semiconductor substrate) 11 having a (100) surface is prepared. Then, an amorphous silicon oxide film 12 is formed on the silicon substrate 11 to a thickness of 0.5 to 1 nm, for example, by sputtering. The amorphous silicon oxide film 12 is formed at room temperature. The silicon oxide film 12 is formed in order to prevent the occurrence of defects (surface levels and defect levels) that trap electrons. When the thickness of the silicon oxide film 12 is less than 0.5 nm, the effect of preventing the occurrence of defects cannot be sufficiently obtained. On the other hand, if the thickness of the silicon oxide film 12 exceeds 1 nm, the effective thickness of the gate insulating film increases, and it becomes difficult to miniaturize the MOS transistor. Accordingly, the thickness of the silicon oxide film 12 is preferably 0.5 to 1 nm as described above.

  On the other hand, as shown in FIG. 2, a (111) silicon substrate (second semiconductor substrate) 13 is prepared. Then, a silicon nitride film 14 is formed on the silicon substrate 13 to a thickness of 10 atomic layers or less (1 to several atomic layers) by plasma nitriding. The silicon nitride film 14 is formed at a relatively low temperature of, for example, 500 ° C. or lower. Thus, by using the silicon substrate 13 having the (111) surface and the plasma nitriding method, an extremely thin silicon nitride film 14 can be formed on the silicon substrate 13 with a uniform thickness. As the thickness of the silicon nitride film 14 increases, it becomes difficult to obtain a uniform film quality. Therefore, as described above, the thickness of the silicon nitride film 14 is 10 atomic layers or less (more preferably 1 to 3 atomic layers). ).

  Dangling bonds (unbonded hands) of nitrogen atoms exist on the outermost surface of the silicon nitride film 14 thus formed. In order to prevent this dangling bond from bonding with foreign atoms, the silicon substrate 13 after the formation of the silicon nitride film 14 is exposed to a hydrogen gas atmosphere at room temperature, and termination treatment with hydrogen atoms is performed.

  Next, as shown in FIG. 3, the silicon substrates 11 and 13 are overlapped so that the amorphous silicon oxide film 12 and the silicon nitride film 14 are in contact with each other. And in this state, it heat-processes at the temperature of 800-900 degreeC. Then, hydrogen atoms bonded to the nitrogen atoms on the outermost surface of the silicon nitride film 14 are released in the initial stage of the heat treatment by the termination process, and then the nitrogen atoms on the outermost surface of the silicon nitride film 14 and the amorphous silicon oxide film 12 are released. Bonds with the silicon atom on the outermost surface. As a result, the silicon oxide film 12 and the silicon nitride film 14 are physically joined to form a uniform and stable interface.

Next, as shown in FIG. 4, the silicon substrate 13 is polished from the back surface side (the surface side opposite to the surface on which the silicon nitride film 14 is formed) by chemical mechanical polishing (CMP). Then, the polishing is finished when the silicon substrate 13 remains slightly, for example, when the thickness of the silicon substrate 13 becomes about 2 nm. Thereafter, the remaining silicon substrate 13 is removed as shown in FIG. 5 by dry etching using CF ₄ as an etching gas, for example, and the silicon nitride film 14 is exposed.

  In this way, the silicon substrate 11 is obtained in which the silicon oxide film 12 having a film thickness of 0.5 to 1 nm and the silicon nitride film 14 having a film thickness of one to several atomic layers are stacked.

Next, as shown in FIG. 6, a silicate film 15 made of a high dielectric constant material such as HfO ₂ , ZrO ₂ , Ta ₂ O ₅ or La ₂ O ₃ is formed on the silicon nitride film 14 by a sputtering method. To a thickness of 5 nm. The silicate film 15 is formed at room temperature. Note that an aluminate film made of a high dielectric constant material may be formed instead of the silicate film 15 made of a high dielectric constant material.

Next, a high dielectric constant material film 16 such as HfO ₂ , ZrO ₂ , Ta ₂ O ₅ or La ₂ O ₃ is formed to a thickness of 1 to 1.5 nm on the silicate film 15 by sputtering. In this manner, the gate insulating film 17 formed by laminating the silicon oxide film 12, the silicon nitride film 14, the silicate film 15, and the high dielectric constant material film 16 is formed on the silicon substrate 11.

  In the present embodiment, as described above, the silicate film 15 (or aluminate film) of the high dielectric constant material and the high dielectric constant material film 16 are formed on the silicon nitride film 14. As shown in FIG. 3, a high dielectric constant material film 16 having a thickness of 2 to 3 nm may be directly formed on the silicon nitride film 14. However, as shown in FIG. 6, by forming a silicate film 15 (or aluminate film) of a high dielectric constant material between the silicon nitride film 14 and the high dielectric constant material film 16, the gate insulating film 17 Insulation characteristics are improved. Further, when a high dielectric constant material in which nitrogen atoms are added to the silicate film 15 (or aluminate film) and the high dielectric constant material film 16 is used, the insulating characteristics of the gate insulating film 17 are further improved.

  When the total thickness of the high dielectric constant material film 16 and the silicate film 15 (the thickness of only the high dielectric constant material film 16 when there is no silicate film 15) exceeds 3 nm, the effective film thickness of the gate insulating film increases. This makes it difficult to miniaturize the MOS transistor. For this reason, it is preferable that the total thickness of the high dielectric constant material film 16 and the silicate film 15 (the thickness of the high dielectric constant material film 16 alone when there is no silicate film 15) be 3 nm or less.

  Next, as shown in FIG. 7, a polysilicon film 18 imparted with conductivity by introducing impurities is formed on the gate insulating film 17 to a thickness of, for example, 80 to 100 m.

  Next, the polysilicon film 18 is patterned by photolithography to form a gate electrode 19 as shown in FIG. Then, the gate insulating film 17 (silicon oxide film 12, silicon nitride film 14, silicate film 15, and high dielectric constant material film 16) exposed on both sides of the gate electrode 19 is sequentially removed by etching. Thereafter, impurities are introduced into the surface of the silicon substrate 11 at a low concentration using the gate electrode 19 as a mask to form a low concentration impurity region 20 to be an LDD (Lightly Doped Drain).

  Next, a silicon oxide film is formed on the entire upper surface of the silicon substrate 11, and this silicon oxide film is etched back, so that the side walls 21 covering the side surfaces of the gate electrode 19 and the gate insulating film 17 are formed as shown in FIG. Form. Then, impurities are introduced into the surface of the silicon substrate 11 at a high concentration using the gate electrode 19 and the sidewalls 21 as a mask to form a high concentration impurity region 22.

  Next, for example, heat treatment is performed at a temperature of 950 to 1000 ° C. for 10 seconds to activate the impurities in the low-concentration impurity region 20 and the high-concentration impurity region 22 to form the source / drain 23 as shown in FIG. . In this way, a semiconductor device having a MOS transistor is completed.

  In the present embodiment, as described above, the silicon nitride film 14 is formed on the (111) surface silicon substrate 13 by plasma nitriding. When a silicon nitride film is directly formed on a silicon oxide film, it is extremely difficult to form a silicon nitride film having a uniform thickness corresponding to one to several atomic layers. However, in the present embodiment, as described above, the silicon nitride film 14 is formed on the (111) silicon substrate 13 using the plasma nitriding method. The silicon nitride film 14 can be formed relatively easily.

  In this embodiment, the silicon nitride film 14 formed as described above is bonded to the silicon oxide film 12 formed on the (100) silicon substrate 11 to thereby form the silicon oxide films 12 and 1. A laminated structure is formed with the silicon nitride film 14 having a thickness of up to several atomic layers. Then, after the silicon substrate 13 used for forming the silicon nitride film 14 is removed by chemical mechanical polishing and etching, a silicate film 15 of a high dielectric constant material is formed on the laminated structure of the silicon oxide film 12 and the silicon nitride film 14. The gate insulating film 17 is formed by laminating the high dielectric constant material film 16. As described above, the semiconductor device manufactured according to the present embodiment has the gate insulating film 17 formed by laminating the silicon oxide film 12, the silicon nitride film 14, the silicate film 15, and the high dielectric constant material film 16. The interface between the silicon substrate 11 and the gate insulating film 17 (that is, the interface between the silicon substrate 11 and the silicon oxide film 12) becomes flat, and the occurrence of defects that trap electrons is prevented. Therefore, the characteristics of the MOS transistor are stabilized, and the reliability of the semiconductor device is improved.

  Further, in the semiconductor device manufactured according to the present embodiment, since the silicon nitride film 14 is interposed between the high dielectric constant material film 16 and the silicon oxide film 12, the high dielectric constant material film 16 and the silicon oxide film 12 are provided. Interdiffusion of atoms between the two is prevented. As a result, good insulating characteristics of the gate insulating film 17 are maintained.

  Furthermore, in this embodiment, since the gate insulating film 17 is formed using the high dielectric constant material film 16, the effective film thickness is reduced while the physical film thickness of the gate insulating film 17 is increased. Can do. Thereby, there is an effect that further miniaturization of the MOS transistor is realized while suppressing the leakage current.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1) A step of forming a silicon oxide film on a first semiconductor substrate;
Forming a silicon nitride film on a second semiconductor substrate having a surface of (111);
Bringing the silicon oxide film and the silicon nitride film into contact with each other, overlaying the second substrate on the first substrate, and bonding the silicon oxide film and the silicon nitride film;
Removing the second semiconductor substrate;
Stacking a high dielectric constant material film on the silicon nitride film to form a gate insulating film composed of the silicon oxide film, the silicon nitride film, and the high dielectric constant material film;
Forming a gate electrode on the gate insulating film;
And a step of forming a source / drain by introducing impurities into the surface of the first semiconductor substrate on both sides of the gate electrode.

  (Supplementary note 2) The semiconductor device according to supplementary note 1, further comprising a step of terminating the surface of the silicon nitride film with hydrogen after forming the silicon nitride film on the second semiconductor substrate. Production method.

  (Supplementary note 3) The method of manufacturing a semiconductor device according to Supplementary note 1 or 2, wherein the step of bonding the silicon oxide film and the silicon nitride film is performed by a heat treatment at a temperature of 800 to 900 ° C.

  (Appendix 4) Prior to the step of forming the high dielectric constant material film, a silicate film or aluminate film of a high dielectric constant material is formed on the silicon nitride film, and the silicate film or aluminate film is formed on the silicate film or aluminate film. 4. The method of manufacturing a semiconductor device according to any one of appendices 1 to 3, wherein a high dielectric constant material film is formed.

  (Appendix 5) At least one of the high dielectric constant material film and the silicate film or aluminate film of the high dielectric constant material is formed of a high dielectric constant material to which nitrogen atoms are added. A manufacturing method of a semiconductor device given in any 1 paragraph.

  (Supplementary note 6) The method for manufacturing a semiconductor device according to any one of supplementary notes 1 to 5, wherein a surface of the first semiconductor substrate is a (100) plane.

  (Additional remark 7) The said silicon nitride film is formed by the plasma nitriding method, The manufacturing method of the semiconductor device of any one of Additional remark 1 thru | or 6 characterized by the above-mentioned.

  (Additional remark 8) The said silicon nitride film is formed in the thickness below 10 atomic layers, The manufacturing method of the semiconductor device of any one of Additional remark 1 thru | or 7 characterized by the above-mentioned.

  (Supplementary note 9) The semiconductor device according to any one of supplementary notes 1 to 8, wherein the silicon oxide film is formed to a thickness of 0.5 nm or more and 1.0 nm or less. Production method.

  (Supplementary note 10) The method of manufacturing a semiconductor device according to any one of supplementary notes 1 to 9, wherein the high dielectric constant material film is formed to a thickness of 3 nm or less.

(Supplementary Note 11) The high dielectric constant material film _is characterized in that a main component _{HfO 2, ZrO 2, Ta 2} O 5 and any one compound selected from the group consisting of La ₂ O ₃ The method for manufacturing a semiconductor device according to any one of appendices 1 to 10.

FIG. 1 is a cross-sectional view (No. 1) showing a method for manufacturing a semiconductor device according to an embodiment of the present invention. FIG. 2 is a sectional view (No. 2) showing the method for manufacturing a semiconductor device according to the embodiment of the invention. FIG. 3 is a sectional view (No. 3) showing the method for manufacturing a semiconductor device according to the embodiment of the invention. FIG. 4 is a sectional view (No. 4) showing the method for manufacturing a semiconductor device according to the embodiment of the invention. FIG. 5 is a sectional view (No. 5) showing the method for manufacturing a semiconductor device according to the embodiment of the invention. FIG. 6 is a sectional view (No. 6) showing the method for manufacturing a semiconductor device according to the embodiment of the invention. FIG. 7 is a sectional view (No. 7) showing the method for manufacturing a semiconductor device according to the embodiment of the invention. FIG. 8 is a sectional view (No. 8) showing the method for manufacturing a semiconductor device according to the embodiment of the invention. FIG. 9 is a sectional view (No. 9) showing the method for manufacturing a semiconductor device according to the embodiment of the invention. FIG. 10 is a sectional view (No. 10) showing the method for manufacturing a semiconductor device according to the embodiment of the invention. FIG. 11 is a cross-sectional view showing an example in which a high dielectric constant material film is directly formed on a silicon nitride film in the method for manufacturing a semiconductor device according to the embodiment of the present invention.

Explanation of symbols

11 ... Silicon substrate (first semiconductor substrate),
12 ... Silicon oxide film,
13 ... Silicon substrate (second semiconductor substrate)
14 ... Silicon nitride film,
15 ... silicate film,
16 ... high dielectric constant material film,
17 ... Gate insulating film,
18 ... polysilicon film,
19 ... Gate electrode,
20 ... low concentration impurity region,
21 ... Sidewall,
22 ... High concentration impurity region 23 ... Source / drain.

Claims (5)

Forming a silicon oxide film on the first silicon substrate;
Forming a silicon nitride film on a second silicon substrate having a surface of (111);
Contacting the silicon oxide film and the silicon nitride film to superimpose the second silicon substrate on the first silicon substrate, and bonding the silicon oxide film and the silicon nitride film;
Removing the second silicon substrate;
Stacking a high dielectric constant material film on the silicon nitride film to form a gate insulating film composed of the silicon oxide film, the silicon nitride film, and the high dielectric constant material film;
Forming a gate electrode on the gate insulating film;
Forming a source / drain by introducing impurities into the surface of the first silicon substrate on both sides of the gate electrode. 2. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of terminating the surface of the silicon nitride film with hydrogen after forming the silicon nitride film on the second silicon substrate.   3. The method of manufacturing a semiconductor device according to claim 1, wherein the step of bonding the silicon oxide film and the silicon nitride film is performed by heat treatment at a temperature of 800 to 900.degree. 4. The method of manufacturing a semiconductor device according to claim 1, wherein a surface of the first silicon substrate is a (100) plane. 5. 2. The high dielectric constant material film comprising, as a main component, any one compound selected from the group consisting of HfO ₂ , ZrO ₂ , Ta ₂ O ₅ and La ₂ O _3. 5. The method for manufacturing a semiconductor device according to claim 4.

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