JP3097827B2 - Method for manufacturing SOI substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an SOI (Silicon-On-Insulator) substrate in which a silicon layer is formed on an insulating layer. See SIMOX (Separation by
(Implanted Oxygen) technology.

[0002]

2. Description of the Related Art SOI substrates are used in future ultra-high integrated circuits (UL).
SI) It has attracted attention as a substrate. The method of manufacturing the SOI substrate includes a method of bonding silicon substrates together via an insulating film, a method of depositing a silicon thin film on an insulating substrate or a substrate having an insulating thin film on its surface,
OX method and the like. The SIMOX method is one of the methods of embedding an insulating layer inside a silicon substrate. Specifically, after implanting high-concentration oxygen ions into the silicon substrate,
In this method, a buried silicon oxide layer is formed at a predetermined depth from the surface of the silicon substrate by annealing at a high temperature, and the Si layer on the surface side is used as an active region. This SIM
In the OX method, oxygen is excessively ion-implanted into a silicon substrate at a time to release silicon atoms at lattice positions to form interstitial silicon atoms and form vacancies at lattice positions. Subsequently, high-temperature annealing is performed to expand the volume of the silicon substrate, thereby rearranging the implanted oxygen ions and interstitial silicon atoms, thereby depositing a silicon oxide layer in the ion implantation damaged region in a very short time. .

[0003]

However, the conventional S
In the IMOX method, a minute defect is generated by excessive interstitial silicon atoms, and the minute defect grows near the substrate surface during rearrangement by high-temperature annealing, and has a problem that a dislocation defect is easily formed. Further, in the above method, the atomic weight of oxygen to be ion-implanted is relatively large, which requires a high accelerating voltage. Therefore, the oxygen concentration is easily distributed widely in the depth direction from the surface of the implanted substrate, and the surface of the substrate becomes rough. However, the boundary between the buried silicon oxide layers tends not to be steep. In particular, when the buried silicon oxide layer is to be formed deep from the substrate surface, the tendency is remarkable. In other words, in the case of oxygen ion implantation, the surface roughness of the SOI substrate is large,
In addition, the ion implantation damage region is likely to be widened, and it is difficult to form a buried silicon oxide layer having a steep boundary in a predetermined depth region by annealing. Further, in the above method, when oxygen ions are implanted, F
Heavy metals such as e, Ni, Cu, Zn, and Cr easily enter the vicinity of the surface of the silicon substrate as impurities at a high concentration. When these heavy metals exist in the Si layer in the active region on the substrate surface, there is a problem that the electrical characteristics of the device are greatly affected.

[0004] It is an object of the present invention to provide a semiconductor device having an active region on a substrate surface.
An object of the present invention is to provide a method for manufacturing an SOI substrate in which dislocation defects are hardly formed in an i-layer. Another object of the present invention is to provide an SOI substrate capable of forming a buried silicon oxide layer having a steep boundary and a small thickness in a predetermined depth region with a relatively low acceleration voltage to reduce the substrate surface roughness. It is to provide a manufacturing method. Still another object of the present invention is to provide a method for manufacturing an SOI substrate capable of reducing heavy metals in the substrate.

[0005]

[0006]

[0007]

[0008]

The invention according to claim 1 is
As shown in FIG. 1 (a) ~ FIG 1 (e), a silicon substrate 2
1. At least He ion , H ion , Ar ion in vacuum
Forming an ion implantation damaged region 22 inside the silicon substrate 21 by implanting ON or Si ions ;
Silicon substrate 21 with ion implantation damaged region 22 formed
The 800 to 1400 ° C. temperature annealing to He atoms injected into the ion implantation damage region 22 of, H atom, Ar
Forming a vacancy region 23 by releasing atoms or Si atoms from the region 22; and implanting oxygen ions into the silicon substrate 21 to form a SiOx region 24 around the vacancy region 23.
And forming the silicon substrate 21 on which the SiOx region 24 is formed in an oxidizing atmosphere at 1000 ° C. to 1400 ° C.
Forming an embedded silicon oxide layer 26 in a region at a predetermined depth from the surface of the silicon substrate 21 by annealing at a temperature of ° C. to form a single-crystal Si layer 21a on the surface of the silicon substrate. Is the way. According to this method, He atoms , H atoms , Ar atoms or
(In the figure, it represented circled the h) Si atom (in the figure, indicated by marks ●) air oxygen atom in the hole region 23 caused by release for to form a SiOx invade by ion implantation, a buried silicon it is possible to stably form an oxide layer.

The invention according to claim 2 is the invention according to claim 1 , wherein the buried silicon oxide layer 26 is formed by annealing.
This is a method for manufacturing an SOI substrate, further comprising a step of polishing the surface of the silicon substrate 21 after forming the substrate. According to this method, the surface roughness of the substrate can be further reduced, and a single-crystal Si layer 21a having a smaller micro roughness can be obtained. The invention according to claim 3 is the invention according to claim 1 or 2 , wherein when the ions to be implanted are He ions or H ions, the dose at the time of the ion implantation is 1 × 10 ¹⁶ /.
cm ² -5 × 10 ¹⁷ / cm ² , and the accelerating voltage is 40 keV
This is a method for manufacturing an SOI substrate at 200 keV. The invention according to claim 4 is the invention according to any one of claims 1 to 3 , wherein the annealing for forming the buried silicon oxide layer 26 is performed in an oxidizing atmosphere at 10 to 100 atm. This is a method for manufacturing a substrate. According to this method,
The buried silicon oxide layer can be formed more stably.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, when the ions to be implanted are Ar ions or Si ions, Ar or Si ions are used.
Has a greater atomic weight than He, and the dose at the time of ion implantation is 1 × 10 ¹⁵ / cm ² to 1 × 10 ¹⁷ / cm ² depending on the depth from the surface of the buried silicon oxide layer.
The acceleration voltage at this time is 150 keV to 200 keV. The substrate temperature during the ion implantation according to the present invention is 500 ° C. to 70 ° C.
0 ° C is preferred, and 600 ° C is more preferred. The annealing treatment is performed in an oxidizing atmosphere at a temperature in the range of 1000C to 1400C for 1 to 8 hours. The processing temperature is 1300 ° C
To 1400 ° C is preferable, and 1350 ° C is more preferable.
The time is preferably 4 to 8 hours, more preferably about 6 hours. Examples of the oxidizing atmosphere include an oxygen atmosphere having a concentration of 10 to 100%, and an oxygen atmosphere having a high concentration close to 100% is preferable. The atmosphere of the annealing treatment for releasing the He atoms or H atoms implanted into the ion-implanted damaged region from the damaged region to form a void region is 0.5 to 3% O ₂ , and the remaining inert gas is mixed. A gas atmosphere is preferred. The reason for containing a small amount of oxygen is to prevent the substrate surface from being roughened. The surface of the silicon substrate is lightly polished by a silicon wafer polishing machine, a lens polishing machine or the like.
In this polishing, the substrate surface has a thickness of 50 Å to 5 Å.
It is desirable to wear down to a depth of about 100 Å, preferably about 100 Å.

In particular, when the implanted ions are He ions or H ions, since He and H have small atomic weights, dislocation defects in the Si layer near the surface of the substrate are less likely to occur as compared with conventional oxygen ion implantation, and An ion implantation damaged region can be formed at a predetermined depth with an acceleration voltage lower than that of oxygen ions. Due to the low accelerating voltage, a buried silicon oxide layer having a sharp boundary and a small layer thickness is easily formed in the ion implantation damaged region, and as a result, control of deposition of SiO ₂ is facilitated. Also, sputtering on the surface of the Si layer during ion implantation is reduced, and the surface roughness of the substrate is reduced. At the same time, the sputtering of the inner wall of the apparatus is greatly reduced, and the contamination of the substrate with heavy metals is reduced.

[0012]

Next, embodiments of the present invention will be described in detail with reference to the drawings together with comparative examples.

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019]

<Comparative Example 1> Oxygen ions (O ⁺ ) were implanted into a predetermined region (for example, a region approximately 0.4 μm from the substrate surface) of a 625 μm-thick silicon substrate under the following conditions. Accelerating voltage: 120 keV Dose amount: 0.4 × 10 ¹⁸ / cm ² Substrate heating temperature: 600 ° C. After oxygen ions are implanted into the silicon substrate 11, Ar 97%
The silicon substrate was annealed at 1325 ° C. for 6 hours in a mixed gas atmosphere of O ₂ 3% to obtain an SOI substrate.

[0021] <Example 1> As shown in FIG. 1 (a) and (b), was injected He ions (He ⁺⁾ under the following conditions in a predetermined region of the silicon substrate 21 with a thickness of 625 .mu.m. Acceleration voltage: 40 keV Dose: 1 × 10 ¹⁷ / cm ² Substrate heating temperature: 600 ° C. By this ion implantation, an ion implantation damaged region 22 of about 0.3 μm was formed from the surface of the silicon substrate 21. After the ion implantation, FIG. 1 (c) and 1325 ° C. in O ₂ 1% in the mixed gas atmosphere of the silicon substrate 21 as shown in (d) in Ar99%, subjected to 2 hours annealing, ion implantation damage region 22 He atoms implanted into the damaged region 2
2 to form a hole region 23.

Subsequently, oxygen ions (O ⁺ ) were implanted into the silicon substrate 21 under the following conditions. Accelerating voltage: 150 keV Dose amount: 4 × 10 ¹⁷ / cm ² Substrate heating temperature: 600 ° C. After oxygen ions are implanted into the silicon substrate 21, Ar 99%
The silicon substrate was annealed at 1360 ° C. for 4 hours in a mixed gas atmosphere of 1% O ₂ to obtain an SOI substrate.

Example 2 A silicon substrate 21 having an ion-implanted damaged region 22 formed thereon was prepared in a mixed gas atmosphere of 99% Ar and 1% O _{2 in an} atmosphere of 1000%.
A silicon substrate was treated in the same manner as in Example 1 except that annealing was performed at 2 ° C. for 2 hours to obtain an SOI substrate.

<Evaluation> (a) Defect Density The dislocation defect density in the Si layer on the substrate surface of each of the SOI substrates of Example 1 , Example 2 and Comparative Example 1 was measured. The dislocation defect density was determined by etching the SOI substrate surface with a solution containing chromium oxide and observing the dislocation defects enlarged by etching with an electron microscope. Table 1 shows the results.

[0025]

[Table 1]

As is clear from Table 1, after implanting He ions which do not react with Si compared with the dislocation defect density of Comparative Example 1 which was subjected to high-temperature annealing in a mixed gas atmosphere of Ar and O ₂ after oxygen ion implantation. dislocation defect density in example 1 and example 2 was high-temperature annealing in a mixed gas Kiri囲<br/> aerial of Ar and O ₂ are both small.

(B) Surface roughness of SOI substrate 2 μm × 2 of the surface of each SOI substrate of Example 1 and Comparative Example 1
The surface roughness in the region of μm was measured using an atomic force microscope. Table 2 shows the results. In Table 2, Ra
Is the average roughness of the surface roughness, Rmax is the maximum height, and Rz is the ten-point average roughness.

[0028]

[Table 2]

As is clear from Table 2, the SO of Comparative Example 1
Whereas the surface roughness of the I substrate was significantly greater, performed
The surface roughness of the SOI substrate of Example 1 was small, and was about the same as the initial silicon wafer.

[0030]

[0031]

[0032]

(C) Boundary of Embedded Silicon Oxide Layer The cross section of each SOI substrate of Example 1, Example 2, and Comparative Example 1 was observed with a transmission electron microscope, and the steepness of the boundary of the embedded silicon oxide layer was observed. As a result, the boundary between the buried silicon oxide layers in Comparative Example 1 was not so steep, whereas the boundary between the buried silicon oxide layers in Examples 1 and 2 was steep .

[0034]

As described above, according to the method for manufacturing an SOI substrate of the present invention, a He ion or the like which does not react with silicon is implanted into a silicon substrate in a vacuum to form an ion-implanted damaged region inside the substrate. After that , annealing treatment
A region is formed, oxygen ions are further implanted, and the substrate is oxidized.
Annealing at a high temperature in a neutral atmosphere diffuses oxygen atoms into the substrate by diffusion control, and preferentially forms a buried silicon oxide layer in the ion-implanted damaged region due to the presence of vacancies formed by ion implantation. be able to. Whereas conventional oxygen ion implantation forms a buried silicon oxide layer in a very short time and rapidly generates interstitial silicon atoms, this oxidation proceeds with diffusion control, so the rapid There is no occurrence, and dislocation defects can be suppressed. In particular, when the implanted ions are ions of an element having a small atomic weight such as He ions or H ions, dislocation defects in the Si layer near the surface of the substrate are more unlikely to occur, and the acceleration voltage is lower than that of oxygen ions. Thus, an ion implantation damaged region can be formed at a predetermined depth. In other words, even with the same acceleration voltage, the buried silicon oxide layer can be formed in a deeper region by the ion implantation of the present invention as compared with the oxygen ion implantation. This low accelerating voltage facilitates formation of a buried silicon oxide layer having a sharp boundary and a small thickness, and facilitates control of SiO ₂ deposition. Also, sputtering on the surface of the Si layer during ion implantation is reduced,
The surface roughness of the substrate is reduced. At the same time, the sputtering of the inner wall of the apparatus is greatly reduced, and the contamination of the substrate with heavy metals is reduced.

[Brief description of the drawings]

FIG. 1 is a view schematically showing a method for manufacturing an SOI substrate according to an embodiment of the present invention.

[Description of Signs] 20 SOI substrate 21 Silicon substrate 21a Si layer on substrate surface 22 Ion implantation damaged region 23 Vacancy region 24 SiOx region 25 Oxygen atom 26 Embedded silicon oxide layer

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-8-191140 (JP, A) JP-A-8-111453 (JP, A) JP-A-1-108764 (JP, A) JP-A 48-81 21979 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 27/12 H01L 21/265

Claims (4)

(57) [Claims] 1. A step of forming an ion-implanted damaged region (22) inside a silicon substrate (21) by implanting at least He ions , H ions , Ar ions or Si ions in a silicon substrate (21) in a vacuum. A silicon substrate on which the ion implantation damaged region (22) is formed
(21) is annealed at a temperature of 800 to 1400 ° C., and He atoms , H atoms , Ar atoms or
Forming a vacancy region (23) by releasing Si atoms from the region (22); and implanting oxygen ions into the silicon substrate (21) to form SiOx around the vacancy region (23). Forming a region (24); annealing the silicon substrate (21) on which the SiOx region (24) is formed at a temperature of 1000 ° C. to 1400 ° C. in an oxidizing atmosphere; Forming a buried silicon oxide layer (26) in a region having a predetermined depth from the substrate and forming a single-crystal Si layer (21a) on the surface of the substrate. 2. A buried silicon oxide layer (2)
Method of manufacturing a SOI substrate according to claim 1, further comprising a step of polishing the silicon substrate (21) surface after forming the 6). 3. When the ions to be implanted are He ions or H ions, the dose at the time of the ion implantation is 1 × 10 5.
¹⁶ / cm ² -5 × 10 ¹⁷ / cm ² and acceleration voltage of 40 ke
The method for manufacturing an SOI substrate according to claim 1 or 2 wherein the V～200keV. 4. A buried silicon oxide layer during the annealing treatment for forming (26) an oxidizing atmosphere, claims 1 to 3 SOI substrate manufacturing method according to any one carried out under 10 to 100 atm.