JPH09260621A - Manufacture of soi substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a high quality SOI substrate, having a high quality buried silicon oxide layer with extremely small Si islands and silicon pipe and an active Si layer on the surface of a substrate containing less silicon oxide deposit. SOLUTION: Oxygen ions in low dose are implanted in the inside of a silicon substrate 11, and then silicon ions are further implanted in a damaged region on the substrate side formed by the oxygen ion implantation from the ion implanted region inside the silicon substrate 11 implanted with the oxygen ions. Later, by burying, the silicon oxide layer 12 is formed in the region at a specific depth from the surface of the silicon substrate 11, so as to form an active Si layer 11a on the surface of the substrate 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an SOI (Silicon-On-Insulator) substrate in which a Si layer is formed on an insulating layer. More specifically, low dose SIMOX (Separa
The present invention relates to a method of manufacturing an SOI substrate by using the technology of Implanted Oxygen).

[0002]

2. Description of the Related Art SOI substrates are drawing attention as substrates to be used in future LSIs. This SOI substrate manufacturing method includes a bonding method in which silicon substrates are bonded to each other via an insulating film, a polycrystalline silicon thin film is deposited on an insulating substrate or a substrate having an insulating thin film on its surface, and polycrystalline silicon thin film is deposited. There are a method of recrystallizing a thin film, a SIMOX method, and the like. This SIMOX method is one of the methods of burying an insulating layer inside a silicon substrate, and specifically, high-concentration oxygen ions are implanted into the inside of the silicon substrate and then annealed at a high temperature. This is a method in which a buried silicon oxide layer is formed in a region having a predetermined depth from the surface and the Si layer on the surface side is used as an active region. The SIMOX method is a promising method that can obtain an active Si layer having a uniform thickness without grinding and polishing the Si layer on the surface unlike the above-mentioned bonding method.

In recent years, the amount of implantation of oxygen ions has been reduced,
Low-dose technology, which shortens the processing time of the ion implantation apparatus and reduces the manufacturing cost of the SOI substrate, has begun to be put into practical use. With this low dose technique, for example, an acceleration energy of 180
After oxygen ion implantation with keV and an implantation amount of 4 × 10 ¹⁷ / cm ² , annealing is performed at 1350 ° C. in a mixed gas atmosphere of argon and oxygen or a mixed gas atmosphere of nitrogen and oxygen. By this low-dose SIMOX method, the buried silicon oxide layer in the SOI substrate is made continuous, and the implantation conditions such as the oxygen ion implantation amount are strictly adhered to so as not to form island-shaped Si regions (Si islands) in this oxide layer. It is extremely important to optimize the annealing process.

[0004]

However, even if the oxygen ions are implanted under the conditions sufficiently controlled by the conventional low dose SIMOX method, as shown in FIG. 3 (a), the oxygen ion implantation region (oxygen ion peak position B ) From the surface side of the substrate 1 to the damaged area (damage peak position A) due to oxygen ion implantation
Exists. After the oxygen ion implantation, in a mixed gas atmosphere of argon and oxygen, or in a mixed gas atmosphere of nitrogen and oxygen, 1
In the intermediate stage of the annealing process at 300 ° C. or higher, oxygen molecules or oxygen atoms enter this damaged region and a silicon oxide precipitate is formed. In the low-dose SIMOX method, as shown by the reaction of the following equation (1), a silicon oxide precipitate is formed near the damaged region during the annealing process. (1 + x) Si + 2 [O] _i → SiO ₂ + x [Si] _i (1) However, most of the silicon oxide precipitates formed in the damaged region are shown in FIGS. As shown in c), in the subsequent annealing treatment, due to the agglomeration of the above-mentioned silicon oxide precipitate and the silicon oxide near the oxygen ion peak position B, the Si island C or the embedded silicon oxide C is embedded in the embedded silicon oxide layer. A silicon pipe D in which Si penetrates the silicon oxide layer is formed. In addition to Si islands and silicon pipes, in the conventional low-dose SIMOX method, some of the above-mentioned silicon oxide precipitates remain in the Si layer on the surface of the silicon substrate 1 without disappearing during the annealing treatment. I will end up. When the number of Si islands and silicon pipes of this type increases, the function of the buried silicon oxide layer 2 as an insulating layer becomes poor, and the devices cannot be sufficiently separated.

An object of the present invention is to provide a method for producing a high-quality SOI substrate having a high-quality buried silicon oxide layer with very few Si islands and silicon pipes and an active Si layer on the surface of a substrate with less silicon oxide deposits. To provide.

[0006]

The invention according to claim 1 is
As shown in FIGS. 1A to 1C, oxygen ions are implanted into the silicon substrate 11 at a low dose, and the oxygen ions are implanted on the substrate surface side of the oxygen ion implanted region inside the silicon substrate 11 into which the oxygen ions are implanted. After implanting silicon ions into the damaged region formed by, the silicon oxide layer 12 is formed in a region of a predetermined depth from the surface of the silicon substrate 11 by annealing, and the active Si layer 1 is formed on the surface of the substrate.
1a is a method for manufacturing an SOI substrate. As shown in FIG. 1A, an oxygen ion implantation region (oxygen ion peak position B) is formed by oxygen ion implantation,
A damaged region (damage peak position A) due to oxygen ion implantation is formed on the substrate surface side from this region. FIG. 1 (b)
As shown in, when silicon ions are implanted in this state, silicon atoms enter the damaged region and become interstitial silicon. If the annealing treatment is performed in this state, the reaction of the above-described formula (1) is less likely to occur in the damaged region, and the formation of silicon oxide precipitates is suppressed.

The invention according to claim 2 is based on FIG.
As shown in (c), silicon ions are implanted into the silicon substrate 11, and oxygen ions are implanted at a low dose into a predetermined region deeper than the silicon ion implanted region inside the silicon substrate 11 into which the silicon ions have been implanted, and then annealed. A method for manufacturing an SOI substrate is characterized in that a buried silicon oxide layer 12 is formed in the predetermined region from the surface of the silicon substrate 11 by processing, and an active Si layer 11a is formed on the surface of the substrate. As shown in FIG. 2A, silicon ions are implanted into a region closer to the substrate surface than a region having a predetermined depth from the substrate surface to be a buried silicon oxide layer. By this silicon ion implantation, silicon atoms are implanted between the silicon lattices in the region on the substrate surface side (peak position A ′). After that, when oxygen ions are implanted into a predetermined region deeper than the silicon ion implantation region (oxygen ion peak position B), a precipitate of silicon oxide is formed in this predetermined region, while a region on the substrate surface side from this region is formed. Since interstitial silicon already exists in, it becomes difficult for oxygen atoms to enter. This makes it difficult for the reaction of the above formula (1) to occur during the annealing treatment, and suppresses the formation of silicon oxide precipitates.

In the manufacturing method according to the first or second aspect, it becomes difficult to form a silicon oxide precipitate in the regions of the peak positions A and A ', and as a result, the precipitate and the silicon oxide in the region of the peak position B are formed. The number of Si islands in the buried silicon oxide layer due to the agglomeration with the precipitate is extremely small, and the growth of silicon oxide at the peak position B is increased, so that the number of silicon pipes is also extremely small. At the same time, the precipitate of silicon oxide in the active Si layer on the substrate surface is taken into the buried silicon oxide layer 12 by the annealing treatment, and this Si
Silicon oxide deposits are reduced in layer 11a.

[0009]

DETAILED DESCRIPTION OF THE INVENTION Oxygen ion implantation (dos) of the present invention
e) has a low dose. In both the inventions according to claims 1 and 2, the implantation of oxygen ions is at most 6 × 10 ¹⁷ / cm ^2.
Injection amount. Further, the implantation of silicon ions is performed with the implantation acceleration energy having the implantation peak position near the damage peak due to this implantation. For example, at most 6 × 10 ¹⁷
/ Cm ² injection amount. Oxygen ion implantation amount is 6 × 1
When it exceeds 0 ¹⁷ / cm ² , Si islands increase. It is preferably 4.5 × 10 ¹⁷ / cm ² or less. If the implantation amount of silicon ions exceeds 6 × 10 ¹⁷ / cm ² , defects due to implantation damage increase. It is preferably 2 × 10 ¹⁷ / cm ² or less. The annealing treatment is performed in a mixed gas atmosphere of argon and oxygen or a mixed gas atmosphere of nitrogen and oxygen for 1300
It is performed at a temperature in the range of ℃ or more and less than the melting point of silicon.

[0010]

Embodiments of the present invention will now be described in detail with reference to the drawings together with comparative examples. Example 1 Oxygen ions (O ⁺ ) were implanted into a predetermined region (for example, a region of about 0.46 μm from the substrate surface) of a 625 μm thick silicon substrate under the following conditions. Accelerating voltage: 185 keV Dose amount: 4 × 10 ¹⁷ / cm ² Substrate heating temperature: 600 ° C. Next, in the region on the substrate surface side from the above region of the silicon substrate (for example, a region of about 0.25 μm from the substrate surface), Silicon ions (Si ⁺ ) were implanted under the conditions. Accelerating voltage: 160 keV Dose amount: 8 × 10 ¹⁵ / cm ² Substrate heating temperature: 600 ° C. After the silicon ion implantation, the silicon substrate is subjected to argon (99)
%) And oxygen (1%) in a heat treatment furnace maintained at 800 ° C in a mixed gas atmosphere, and a temperature rising rate of 5 ° C / min for 1360
The temperature was raised to ° C. This temperature was maintained for 4 hours for annealing treatment.

Example 2 After implanting silicon ions into the same silicon substrate as in Example 1 under the same conditions as in Example 1, oxygen ions were subsequently implanted under the same conditions as in Example 1. After the oxygen ion implantation, the annealing treatment was performed in the same manner as in Example 1.

Comparative Example 1 After the same silicon substrate as in Example 1 was implanted with oxygen ions under the same conditions, the same annealing treatment as in Example 1 was performed without implanting silicon ions.

<Comparative Observation> The density of the silicon pipe in the buried silicon oxide layer of each SOI substrate of Examples 1 and 2 and Comparative Example 1 was measured. The density of this silicon pipe is SO
I was sandwiched between electrodes on both sides of the I substrate and immersed in a copper sulfate solution. Table 1 shows the results.
Shown in

[0014]

[Table 1]

As is apparent from Table 1, it was found that the silicon pipe densities of Examples 1 and 2 were significantly reduced as compared with the silicon pipe density of Comparative Example 1.

[0016]

As described above, according to the method for manufacturing an SOI substrate of the present invention, by implanting silicon ions before or after implanting oxygen ions, a high quality of silicon islands and silicon pipes is extremely small. A buried silicon oxide layer can be formed. In addition, silicon oxide precipitates can be reduced in the active Si layer on the substrate surface.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a cross section of a silicon substrate of the present invention according to claim 1 in the order of steps.

FIG. 2 is a view schematically showing the cross section of the silicon substrate of the present invention according to claim 2 in the order of steps.

FIG. 3 is a diagram schematically showing a cross section of a conventional silicon substrate in the order of steps.

[Explanation of symbols]

 11 Silicon Substrate 11a Si Layer on Substrate 12 Embedded Silicon Oxide Layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Nakai 1-297, Kitabukuro-cho, Omiya-shi, Saitama Mitsubishi Materials Corporation

Claims (2)

[Claims] 1. A silicon substrate in which oxygen ions are implanted into a silicon substrate (11) at a low dose, and the oxygen ions are implanted.
(11) After implanting silicon ions into the damaged region formed by oxygen ion implantation on the substrate surface side from the oxygen ion implantation region inside, annealing treatment is performed to a region of a predetermined depth from the silicon substrate (11) surface. A method for manufacturing an SOI substrate, which comprises forming an embedded silicon oxide layer (12) and forming an active Si layer (11a) on the substrate surface. 2. A silicon substrate (11) is implanted with silicon ions, and the silicon ions (1) are implanted.
1) After implanting oxygen ions into a predetermined region deeper than the internal silicon ion implantation region at a low dose, an annealing treatment is performed to form a buried silicon oxide layer (12) from the surface of the silicon substrate (11) to the predetermined region. The active S on the substrate surface.
A method for manufacturing an SOI substrate, which comprises forming an i layer (11a).