JP2001308025A - Method for manufacturing soi substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent formation of unnecessary recessed grooves on the surface of the body of a substrate or unnecessary cavities in an embedded oxide film by preventing the exposure of the edge area of the oxide film on the surface of the main body of the substrate. SOLUTION: A surface oxide film 14 is formed on the surface of the body 12 of the substrate, composed of single-crystal silicon, and a resist layer 16 is formed on the surface of the oxide film 14 in a prescribed pattern. Then the oxide film 14 is etched through anisotropic etching perpendicularly to the surface of the main body 12 by using the resist layer 16 as a mask, and the body 12 is cleaned, after removing the resist layer 16. Thereafter, the embedded oxide film 13 is formed in the main body 12 by implanting oxygen ions 22 into the body 12 perpendicular to surface of the main body 12 by using the oxide film 14 as a mask and annealing the body at 1,300 deg.C or higher. In addition, the surface oxide film 14 is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a SIMOX (Sepa
ration by IMplanted OXygen)
The present invention relates to a method for manufacturing an SOI substrate in which an OI (Silicon-On-Insulator) structure element and a bulk structure element are mixed.

[0002]

2. Description of the Related Art Conventionally, as a method of manufacturing this type of SOI substrate, a mask is formed on a first portion of a substrate, and a buried oxide film is formed below the surface of the second portion of the substrate. Forming an isolation region at a boundary between the first portion and the first portion, forming a first element to be located on the first portion, and further having a supply voltage of less than 3.3 volts on a second portion of the substrate. A method for forming a thin film and a bulk mixed semiconductor substrate for forming a second element has been disclosed (JP-A-8-17694).
In this method of forming a semiconductor substrate, a semiconductor substrate in which a thin film and a bulk are mixed can be manufactured, and both the thin film SOI element and the thick field ESD protection element or the high voltage I / O buffer circuit can be arranged on the same substrate. .

In the conventional method of forming a semiconductor substrate disclosed in Japanese Patent Application Laid-Open No. H8-17694, the implantation angle of oxygen ions to the substrate surface for forming a buried oxide film is not specified. However, the formation of the buried oxide film is usually performed as follows. As shown in FIG. 5, first, the surface oxide film 3 is formed on the surface of the substrate body 2 (the substrate body 2 is cut out at a plane perpendicular to the axis of the silicon single crystal rod).
(FIG. 5A), and a resist layer 6 patterned on the surface of the surface oxide film 4 by photolithography.
Is formed (FIGS. 5B and 5C). Next, the surface oxide film 4 is patterned by anisotropic etching (FIG. 5).
(D) and (e)), after removing the resist layer 6 (FIG. 5 (f)), the substrate body 2 is washed. Next, oxygen ions 7 are implanted into the substrate body 2 from a direction inclined at 7 degrees with respect to a perpendicular to the surface of the substrate body 2 (FIG. 5G), and a mixed gas of argon and oxygen or a mixed gas of nitrogen and oxygen is injected. Then, the buried oxide film 3 is formed by annealing at 1300 ° C. or higher for a predetermined time in the above atmosphere (FIG. 5H). Further, the substrate body 2 is immersed in a mixed solution (etching solution) of an aqueous solution of ammonium fluoride and hydrofluoric acid to remove the surface oxide film 4 (FIG. 5 (i)). The inclination of 7 degrees during the implantation of the oxygen ions 7 into the substrate body 2 is to prevent channeling and to make the implantation depth of the oxygen ions 7 uniform. Channeling means that when ions, electrons, and the like are incident on the crystal substantially parallel to the crystal axis and the crystal plane, there is a gap (channel) surrounded by constituent atoms in the traveling direction. A phenomenon that proceeds deeply in a channel.

[0004]

However, in the above-mentioned conventional method for forming a buried oxide film, the edge region of the buried oxide film 3 is exposed on the surface of the substrate body 2 as shown in FIGS. Therefore, when the surface oxide film 4 is removed, the edge region is etched, and a groove 8 is formed on the surface of the substrate body 2 along the edge region, or a cavity is formed in the buried oxide film 3. There was a case. An object of the present invention is to prevent the edge region of the patterned buried oxide film from being exposed on the surface of the substrate, thereby forming an unnecessary concave groove on the surface of the substrate body or forming an unnecessary cavity in the buried oxide film. SOI that can prevent
An object of the present invention is to provide a method for manufacturing a substrate.

[0005]

The invention according to claim 1 is
As shown in FIG. 1, a substrate body 1 made of silicon single crystal
Forming a surface oxide film 14 on the surface of the substrate 2, forming a resist layer 16 having a predetermined pattern on the surface of the surface oxide film 14, and applying the surface oxide film 16 to the substrate body 12 using the resist layer 16 as a mask. A step of performing anisotropic etching in a direction perpendicular to the surface, a step of removing the resist layer 16 and cleaning the substrate body 12, and a step of removing oxygen ions perpendicular to the surface of the substrate body 12 using the surface oxide film 14 as a mask. And a step of removing the surface oxide film 14 after forming the buried oxide film 13 inside the substrate body 12 by annealing the substrate body 12 at a temperature of 1300 ° C. or higher.
This is a method for manufacturing a substrate. SO according to claim 1
In the method of manufacturing the I-substrate, the surface oxide film 14 is
Is anisotropically etched perpendicularly to the surface of the substrate body 12, and oxygen ions 2
2, the edge region of the buried oxide film 13 is not exposed on the surface. As a result, even if the substrate main body 12 is immersed in the etching solution to remove the surface oxide film 14,
Since the edge region of the buried oxide film 13 is not removed, it is possible to prevent unnecessary grooves from being formed on the surface of the substrate body 12 or to prevent unnecessary cavities from being formed in the buried oxide film 13.

The invention according to claim 2 is the invention according to claim 1, wherein the substrate body is further cut at an angle of 7 to 10 with respect to the (100) plane or the (111) plane of the crystal structure of silicon single crystal. It is characterized by being issued. In the method of manufacturing an SOI substrate according to the second aspect, channeling at the time of implanting oxygen ions can be prevented, and thereby the implantation depth of oxygen ions can be made uniform.

According to a third aspect of the present invention, as shown in FIG.
A step of cutting out the 0) plane or the (111) plane;
Forming a surface oxide film 44 on the surface of the substrate, forming a resist pattern 46 having a predetermined pattern on the surface of the surface oxide film 44, and using the resist layer 46 as a mask.
4 is a step of performing anisotropic etching from a direction inclined by 7 to 10 degrees with respect to a perpendicular to the surface of the substrate main body 42, a step of removing the resist layer 46 and cleaning the substrate main body 42, A step of implanting oxygen ions 62 into the surface of the substrate main body 42 as a mask from a direction inclined at 7 to 10 degrees with respect to a vertical line thereof, and annealing the substrate main body 42 at 1300 ° C. or more to bury the substrate main body 42 inside Removing the surface oxide film 44 after forming the oxide film 43
This is a method for manufacturing an I substrate. S described in claim 3
In the method of manufacturing the OI substrate, the surface oxide film 44 is
2 is anisotropically etched at a predetermined angle with respect to the surface of the substrate 2, and oxygen ions 62 are tilted at a predetermined angle with respect to the surface of the substrate body 42 in the same manner as described above.
, The buried oxide film 4 is formed as in the first embodiment.
In addition to the edge region of No. 3 not being exposed on the surface, channeling at the time of implanting oxygen ions 62 can be prevented. As a result, the implantation depth of the oxygen ions 62 can be made uniform. Also, anisotropic etching of the surface oxide film 44 is performed by ECR.
It is preferable to use a plasma etching apparatus 51.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a first embodiment of the present invention will be described with reference to the drawings. As shown in FIG.
The OI substrate 11 has a substrate body 12 and a buried oxide film 13 formed inside the substrate body 12. The substrate body 12 is cut into a thin plate along a plane perpendicular to the axis of the silicon single crystal rod grown by the Czochralski (CZ) method (the (100) plane of the silicon single crystal crystal structure).
The buried oxide film 13 is formed as follows. The substrate body may be cut from a silicon single crystal rod or a silicon single crystal plate grown by a floating zone (FZ) method, an epitaxial growth method, or the like, instead of the CZ method.

First, a surface oxide film 14 is formed on the surface of the substrate body 12.
Is formed (FIG. 1A). The surface oxide film 14 is a silicon oxide film (SiO ₂ film) and is formed by thermally oxidizing the substrate body 12 or by a chemical vapor deposition (CVD) method. The thickness of the surface oxide film 14 is 200 nm.
It is formed within a range of １０００1000 nm. Surface oxide film 14
Is limited to the range of 200 nm to 1000 nm. If the thickness is less than 200 nm, oxygen ions 22 described below may pass through the surface oxide film 14 and be implanted into the substrate body 12. This is because it can be cut off. Next, a resist layer 16 having a predetermined pattern is formed on the surface of the surface oxide film 14 by photolithography (FIGS. 1B and 1C). This resist layer 16 is exposed using a photomask 18 (FIG. 1).
(B)), through development and rinsing, a predetermined pattern is formed on the resist layer 16 (FIG. 1 (c)).

Using the resist layer 16 as a mask, the surface oxide film 14 is anisotropically etched in a direction perpendicular to the surface of the substrate body 12 (FIGS. 1D and 1E). The anisotropic etching is a reactive ion etching in this embodiment. In the reactive ion etching, although not shown, the substrate main body is placed on the lower electrode of two counter electrodes provided in the reaction chamber, and a high-frequency voltage is applied to these electrodes to induce plasma, whereby CF ₄ is induced. Alternatively, a radical ion nuclide having a higher reactivity than an etching gas such as SF ₆ is formed, and the above-described radical ions of several tens to several hundreds eV enter the substrate main body 12 due to a self-bias potential difference generated between the plasma and the substrate main body 12. The surface oxide film 14 is formed by both the sputtering action and the chemical reaction by the radical ions.
Etching proceeds. Therefore, the inner peripheral edge of the surface oxide film 14 has a vertical etching shape without undercut (FIG. 1E). Note that ECR plasma etching described later may be used as the anisotropic etching. After the completion of the etching, the resist layer 16 is removed with a sulfuric acid-hydrogen peroxide mixture or the like (FIG. 1F), and thereafter, the substrate is washed.

Next, oxygen ions 22 are implanted vertically into the surface of the substrate body 12 using the surface oxide film 14 as a mask (FIG. 1).
(G)). At this time, the implantation conditions of the oxygen ions 22 are such that the implantation amount is 1 × 10 ¹⁷ / cm ² to 2 × 10 ¹⁸ / cm ² , preferably 1.5 × 10 ¹⁷ / cm ^{2 to} 1.8 × 10 ¹⁸ / cm ^2. And the implantation energy is 50 keV to 300 keV, preferably 50 keV to 220 keV. Oxygen ion 22
After the implantation, the substrate body 12 is placed in a mixed gas atmosphere of argon and oxygen, or in a mixed gas atmosphere of nitrogen and oxygen,
After holding at 1300 ° C. or more, preferably in the range of 1310 to 1380 ° C. for 2 to 100 hours, annealing treatment for slow cooling is performed (FIG. 1 (h)). This promotes oxidation of the portion of the substrate main body 12 into which the oxygen ions 22 have been implanted, so that the buried oxide film 13 is formed inside the substrate main body 12. Further, the substrate body 12 is immersed in a mixed solution (etching solution) of an ammonium hydrofluoric acid aqueous solution and hydrofluoric acid to form a surface oxide film 1.
4 is removed (FIG. 1 (i)). On the other hand, as shown in FIG. 2, a substrate body 12 having a buried oxide film 13 formed therein is formed.
After forming an isolation region 23 made of a field oxide film (FOX), a dopant is implanted to form a source region 24 and a drain region 26, and an SOI structure element 27 and a bulk structure element 28 are integrally formed on the substrate body 12. Form. Reference numeral 29 in FIG. 2 denotes a gate of an internal MOSFET or the like.

In the SOI substrate 11 manufactured as described above, the surface oxide film 14 is subjected to anisotropic etching perpendicular to the surface of the substrate main body 12, and further, oxygen is applied from the direction perpendicular to the surface of the substrate main body 12. Since the ions 22 are implanted, the edge region of the buried oxide film 13 is not exposed on the surface. As a result, even if the substrate body 12 is immersed in the etching solution to remove the surface oxide film 14, the buried oxide film 13
Of the substrate body 1 is not removed.
2 can be prevented from being formed on the surface of the substrate 2 or unnecessary cavities can be prevented from being formed in the buried oxide film 13. In the first embodiment, the substrate body is cut out along a plane perpendicular to the axis of the silicon single crystal rod [the (100) plane of the crystal structure of silicon single crystal]. [Single crystal single crystal (10
0) plane]. In this case, channeling when implanting oxygen ions can be prevented, and the implantation depth of oxygen ions can be made uniform. Even if the silicon single crystal is cut at an angle of 7 to 10 degrees with respect to the (111) plane of the crystal structure, channeling when oxygen ions are implanted can be prevented in the same manner as described above.

FIGS. 3 and 4 show a second embodiment of the present invention. In this embodiment, first, as in the first embodiment, the substrate main body 42 is cut out on a plane perpendicular to the axis of the silicon single crystal rod (the (100) plane of the silicon single crystal crystal structure). After the surface oxide film 44 is formed on the surface of the substrate (FIG. 3A), a resist pattern 46 having a predetermined pattern is formed on the surface of the surface oxide film 44 (FIGS. 3B and 3C). Next, using the resist layer 46 as a mask, the surface oxide film 44 is
Perform anisotropic etching from the direction inclined at an angle (FIG. 3D)
And (e)). This anisotropic etching is preferably performed using the ECR plasma etching apparatus 51 (FIG. 4), whereby the undercut of the surface oxide film 44 can be more reliably prevented than in the first embodiment. The etching apparatus 51 includes a diffusion magnetic field method, a source plasma method, and the like. In this embodiment, a diffusion magnetic field method apparatus is used.

As shown in FIG. 4, a diffused magnetic field type apparatus 51 includes a chamber 52 for accommodating a substrate body 42, a plasma chamber 54 provided on an upper surface of the chamber 52 and partitioned by an extraction electrode 53, and a plasma chamber 54. A waveguide 56 for guiding microwaves (2.45 GHz) to the plasma chamber 5;
4 surrounding the coil 57. Substrate body 4
2 is placed on the base 58 in a state of being inclined by the predetermined angle. As an etching gas, halogenated carbon, halogenated sulfur or the like is used. This device 51
In the Electron Cyclotron Resonance (Electron Cyclotron r
esonance), the plasma can be efficiently heated by accelerating electrons in a direct current manner, and the electrons make a swirling motion (Larmor motion) around the lines of magnetic force. It can be longer than. For this reason, high-density plasma is generated under a low pressure with a long mean free path, and the etching gas is ionized and passes through the extraction electrode 53 (a voltage of 400 V to 2 kV is applied). Then, the surface oxide film 44 is etched. As a result, the degree of anisotropy can be improved in pattern formation by etching, so that the inner peripheral edge of the surface oxide film 44 is etched while being inclined by the predetermined angle. In addition,
Reference numeral 61 in FIG. 4 is a quartz plate.

After completion of the etching, the resist layer 46 is removed with sulfuric acid and hydrogen peroxide as in the first embodiment (FIG. 3).
(F)) Then, washing is performed. Next, using the surface oxide film 44 as a mask, the surface of the substrate
Oxygen ions 62 are implanted from a direction inclined by 10 degrees (the same direction as the etching direction of the surface oxide film 44) (FIG. 3).
(G)). At this time, the implantation condition of the oxygen ions 62 is such that the implantation amount is 1 × 10 ¹⁷ / cm ² to 2 × 10 ¹⁸ / cm ² , preferably 1.5 × 10 ¹⁷ / cm ^{2 to} 1.8 × 10 ¹⁸ / cm ^2. And the implantation energy is 50 keV to 300 keV, preferably 50 keV to 220 keV. Oxygen ion 62
After the implantation, the substrate main body 42 is placed in a mixed gas atmosphere of argon and oxygen or a mixed gas atmosphere of nitrogen and oxygen at a temperature of 1300 ° C. or higher, preferably 1310 to 1380 ° C., as in the first embodiment. After that, an annealing process of gradually cooling is performed after holding for 2 to 100 hours (FIG. 3 (h)).
Thereby, oxidation of the portion of the substrate main body 42 into which the oxygen ions 62 have been implanted is promoted, and a buried oxide film 43 is formed inside the substrate main body 42. Further, the substrate body 42 is immersed in a mixed solution (etching solution) of an aqueous solution of ammonium fluoride and hydrofluoric acid to remove the surface oxide film 44 (FIG. 3).
(I)).

In the SOI substrate 41 manufactured as described above, the surface oxide film 44 is anisotropically etched with the surface oxide film 44 inclined at a predetermined angle with respect to the surface of the substrate main body 42, and further, the surface oxide film 44 is As described above, since the oxygen ions 62 are implanted from a direction inclined by a predetermined angle as described above,
As in the first embodiment, in addition to the edge region of the buried oxide film 43 not being exposed on the surface, channeling at the time of implanting the oxygen ions 62 can be prevented. As a result, the implantation depth of the oxygen ions 62 can be made uniform. In addition,
In the second embodiment, the substrate body is cut along the (100) plane of the silicon single crystal crystal structure, but may be cut along the (111) plane of the silicon single crystal crystal structure. This is because, after cutting along the (111) plane of the crystal structure of silicon single crystal, the direction of anisotropic etching of the surface oxide film and the direction of implantation of oxygen ions are 7 to 10 degrees with respect to the normal to the surface of the substrate body. This is because channeling can be prevented by performing the tilting in the same manner as described above.

[0017]

As described above, according to the present invention, a resist layer having a predetermined pattern is formed on a surface of a substrate body made of silicon single crystal via a surface oxide film, and the surface is formed using the resist layer as a mask. The oxide film is anisotropically etched in a direction perpendicular to the surface of the substrate body, and after removing the resist layer, oxygen ions are implanted vertically into the surface of the substrate body using the surface oxide film as a mask. Since the surface oxide film is removed after the buried oxide film is formed inside the substrate body by annealing, the edge region of the buried oxide film is not exposed on the surface. As a result, even if the substrate body is immersed in the etching solution to remove the surface oxide film, the edge region of the buried oxide film is not removed, so that unnecessary concave grooves are formed on the surface of the substrate body. Alternatively, formation of unnecessary cavities in the buried oxide film can be prevented. In addition, the substrate body may be made of (100) plane or (11)
1) If cutting is performed at an angle of 7 to 10 with respect to the plane, channeling at the time of oxygen ion implantation can be prevented, so that the oxygen ion implantation depth can be made uniform.

The crystal structure of the silicon single crystal (10
A resist layer having a predetermined pattern is formed on the surface of the substrate body cut out by the (0) plane or the (111) plane via a surface oxide film, and the surface oxide film is formed with respect to a perpendicular to the surface of the substrate body using the resist layer as a mask. Anisotropic etching is performed from a direction inclined by 7 to 10 degrees, and after removing the resist layer, the surface oxide film is used as a mask and the surface of the substrate main body is deflected by 7 to 10 with respect to the perpendicular.
Oxygen ions are implanted from the direction inclined by 10 degrees, the substrate body is annealed to form a buried oxide film inside the substrate body, and then the surface oxide film is removed. Can be prevented from being exposed to the surface, and channeling during the implantation of oxygen ions can be prevented.
As a result, the implantation depth of oxygen ions can be made uniform. Further, if the anisotropic etching of the surface oxide film is performed by using an ECR plasma etching apparatus, the inner peripheral edge of the surface oxide film is accurately etched at the predetermined angle, so that the buried oxide film is exposed to the surface of the edge region. Can be more reliably prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a method of manufacturing an SOI structure element on an SOI substrate in a first embodiment of the present invention in the order of steps.

FIG. 2 is a cross-sectional view of an SOI substrate including the SOI structure element and the bulk structure element.

FIG. 3 is a cross-sectional view corresponding to FIG. 1, showing a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a state in which an anisotropic etching is performed on a surface oxide film of the SOI substrate using an ECR plasma etching apparatus.

FIG. 5 is a sectional view showing a conventional example and corresponding to FIG.

[Explanation of symbols]

 11, 41 SOI substrate 12, 42 Substrate body 13, 43 Buried oxide film 14, 44 Surface oxide film 16, 46 Resist layer 22, 62 Oxygen ion 51 ECR plasma etching apparatus

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 27/12 H01L 29/78 613Z 29/786

Claims (4)

[Claims] A step of forming a surface oxide film on a surface of a substrate body made of silicon single crystal; and forming a resist pattern having a predetermined pattern on a surface of the surface oxide film. Forming and the surface oxide film (14) using the resist layer (16) as a mask
Performing anisotropic etching in a direction perpendicular to the surface of the substrate body (12); removing the resist layer (16) to wash the substrate body (12); and (14) using a mask as a mask to implant oxygen ions (22) perpendicular to the surface of the substrate body (12); and annealing the substrate body (12) at 1300 ° C. or higher to obtain the substrate body (12). Forming a buried oxide film (13) inside the substrate and then removing the surface oxide film (14).
Substrate manufacturing method. 2. The method for manufacturing an SOI substrate according to claim 1, wherein the substrate body is cut out at an angle of 7 to 10 with respect to a (100) plane or a (111) plane of a silicon single crystal structure. 3. A step of cutting the substrate body (42) at a (100) plane or a (111) plane of a silicon single crystal, and forming a surface oxide film (44) on the surface of the substrate body (42). Performing a step of forming a resist pattern (46) having a predetermined pattern on the surface of the surface oxide film (44); and using the resist layer (46) as a mask to form the surface oxide film (44).
Performing anisotropic etching from a direction inclined by 7 to 10 degrees with respect to a perpendicular to the surface of the substrate main body (42); and removing the resist layer (46) and cleaning the substrate main body (42). A step of implanting oxygen ions (62) into the surface of the substrate body (42) from a direction inclined at 7 to 10 degrees with respect to a perpendicular to the surface of the substrate body (42) using the surface oxide film (44) as a mask; (42) annealing at 1300 ° C. or higher to form a buried oxide film (43) inside the substrate body (42), and then removing the surface oxide film (44).
Substrate manufacturing method. 4. Anisotropic etching of the surface oxide film (44) is performed by E
4. The method according to claim 3, wherein the etching is performed using a CR plasma etching apparatus.
The manufacturing method of the SOI substrate described in the above.