JP2003037255A - Manufacturing method for simox wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an SIMOX wafer forming a highly reliable BOX, without introducing the process of an ITOX processing or epitaxial growth or the like, by implantation of for a low dose oxygen ions. SOLUTION: After implanting atomic oxygen ions into a silicon wafer by acceleration energy >=40 keV and <100 keV or implanting oxygen molecular ions by the acceleration energy >=80 keV and <200 keV, heat treatment is conducted in the atmosphere of an oxygen concentration >=1%, without having to apply heat treatment of the oxygen concentration <1%.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to SIMOX (Se).
partition by ImplantedOxyg
en) The present invention relates to a method for manufacturing a wafer, and particularly to a method for manufacturing a SIMOX wafer having high productivity and low manufacturing cost.

[0002]

2. Description of the Related Art SOI (Silicon on Ins)
SIMOX is one of the wafer manufacturing methods.
Method (K. Izumi et al .: Electro
n. Lett. 14 (1978) 593).

The concept at the beginning of the development of the SIMOX technology is that the acceleration energy is about 200 keV, and about 2 × 10 ¹⁸ ato.
After implanting oxygen atoms of ms / cm ² to form a stoichiometric buried oxide film (hereinafter, the buried oxide film is referred to as “BOX (Buried Oxide)”) by as-implantation, an SOI layer is formed. Heat treatment is performed to recover the crystallinity and modify the BOX layer. The SIMOX wafer produced by this manufacturing method is called a high-dose SIMOX wafer.

However, this high-dose SIMOX wafer has problems such as a large number of threading dislocations in the SOI layer and a long oxygen ion implantation time and high manufacturing cost.

Therefore, the threading dislocation in the SOI layer is reduced and the cost is reduced.
Many studies have been conducted on reduction, and low dose SIMOX
(S. Nakashima et al .: J. Mat.
er. Res. 8 (1993) 523) technology was developed
It was With this low dose SIMOX technology, the acceleration energy
4 × 10 for 180 keV¹⁷atoms / cm ^Two
After implanting oxygen atoms of
By performing heat treatment in the atmosphere,
To form a continuous BOX layer. Where less than 1% oxygen
Heat treatment in an atmosphere containing
Heat treatment of oxygen promotes outward diffusion of oxygen from the SOI layer.
This is to suppress defects such as oxygen precipitates, and
The oxygen content suppresses the roughness of the wafer surface.
is there. The formation of this continuous BOX layer requires an acceleration energy of 1
In case of 80 keV, the dose is 4 × 10¹⁷atoms
/ Cm^TwoSince this is possible only in the case of
This amount is called the dose window.

However, in the low-dose SIMOX wafer, the reliability of the BOX becomes a problem because the thickness of the BOX layer is thin, and the ITOX (Internal) was developed there.
Thermal Oxidation, S.M. Naka
Shima et al. : Proc. 1994 IE
EE International SOI Conf
erence (1994) 71; JP-A-7-26353.
No. 8 publication) technology.

The ITOX technique is a heat treatment in an atmosphere containing less than 1% oxygen to form a BOX layer having a thickness calculated from the dose of implanted oxygen ions, and then in an atmosphere containing 1% or more oxygen. In this technique, the BOX layer is thickened by heat treatment.

Low dose SI due to introduction of ITOX technology
Low dose SIMOX wafers having improved BOX reliability of MOX wafers and subjected to ITOX treatment are currently on the market. However, even with the low dose SIMOX method, the dose amount of oxygen ions is 4 × 10 ¹⁷ atoms / cm ^2.
Therefore, the ion implantation time is several hours per batch, and the high temperature heat treatment time is long due to the need for ITOX treatment, resulting in insufficient productivity and high manufacturing cost. There is.

If the acceleration energy of oxygen ions is lowered, the dose window is also shifted to the lower dose side, so that the dose amount can be reduced. Low dose SIMOX
In the case of the method, the peak value of oxygen concentration in as-implant is about 1.5 × 10 ²² atoms / cm ³ . Even if the acceleration energy is lowered, if the dose amount is set so that the peak value of oxygen concentration in as-implanted is the same, as in the case of high energy injection with a small dose amount,
It is possible to form a continuous BOX layer.

For example, when the acceleration energy is 65 keV, the peak value of the oxygen concentration is about 1.5 × 10 ²² atom.
The dose amount for s / cm ³ is 2 × 10 ¹⁷ atoms /
cm ² and 1 when acceleration energy is 180 keV
A continuous BOX layer can be formed with a dose amount of / 2.

If the oxygen ions to be implanted are changed from oxygen atom ions to oxygen molecule ions, the dose amount can be further halved. If oxygen molecular ions are implanted at an acceleration energy of 130 keV (this is the implantation depth equivalent to that of oxygen atom ion implantation at an acceleration energy of 65 keV), the oxygen concentration peak value becomes 1.5 × 10 ²² atoms / cm ^3. The dose amount is 1 × 10 ^{17 which is} 1/2 that in the case of atomic ion implantation.
Since it is molecules / cm ² , low dose SI
The dose amount can be reduced to 1/4 of the MOX method.

Japanese Patent Laid-Open No. 2001-110739 discloses that
By adopting low-energy ion implantation and oxygen molecular ion implantation, the dose of oxygen ions is greatly reduced, and BO
A method for manufacturing a SIMOX wafer with high X reliability has been proposed. In this SIMOX wafer manufacturing method, oxygen ions are implanted at an extremely low acceleration energy, specifically 40 keV or less for oxygen atom ions and 80 keV or less for oxygen molecule ions, and after epitaxial growth, oxidation is performed. Heat treatment is performed.

As described above, if the extremely low energy ion implantation is performed, the dose of oxygen ions can be made extremely low. For example, if oxygen atom ions are implanted with an acceleration energy of 30 keV, the dose amount is 1 × 10 ¹⁷ ato.
ms / cm can be in ^2, an acceleration energy 60keV in implanting oxygen molecular ion (which is the acceleration energy becomes an oxygen atom ion implantation comparable implantation depth at 30 keV) by if the dose amount 5 × ^{10 1} 6 molecules / cm Can be ² .

The dose amount in the case of this oxygen molecule ion implantation is 1 / of the low dose SIMOX method using oxygen atom ions.
The dose amount is 8, and it is expected that the ion implantation process will be significantly shortened in time. However, in such an extremely low energy ion implantation, the SOI layer disappears when heat treatment is performed in an atmosphere of high oxygen concentration in order to improve the reliability of the BOX. Therefore, an epitaxial growth step is introduced before the heat treatment step. Therefore, there is a problem that the manufacturing process becomes complicated and the manufacturing cost becomes high.

[0015]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and it is highly reliable with low dose oxygen ion implantation without introducing steps such as ITOX treatment and epitaxial growth. SI that can form BOX
Providing a method for manufacturing a MOX wafer, namely,
The purpose is to improve the productivity of SIMOX wafers and reduce the cost.

[0016]

In order to achieve the above-mentioned object, the present inventors diligently studied conditions under which oxygen in a heat treatment atmosphere can be effectively used for BOX formation of a SIMOX wafer. As a result, after implanting oxygen ions with a relatively low acceleration energy in the ion implantation step, without directly performing heat treatment in an atmosphere with an oxygen concentration of less than 1% as in the conventional case, an atmosphere with a high oxygen concentration of 1% or more is directly used. The present invention has been completed by discovering that a BOX layer can be efficiently formed by applying heat treatment.

The invention described in the first claim of the present application is a method for manufacturing a SIMOX wafer, which comprises a step of implanting oxygen ions into a silicon wafer and a step of subjecting it to heat treatment, and oxygen atom ions are generated at an acceleration energy of 40 keV or more and 100 keV or less. After the implantation, the heat treatment is performed in an atmosphere having an oxygen concentration of 1% or more without performing a heat treatment having an oxygen concentration of less than 1%.

In the low energy ion implantation of the present invention,
The implanted oxygen concentration distribution is very sharp, and the BOX layer can be easily formed from the implanted oxygen without performing heat treatment at a low oxygen concentration such as the ITOX method, and the process can be shortened accordingly. From this viewpoint, the lower the acceleration energy, the more desirable, but if the acceleration energy of the oxygen atom ions is too low, the SOI layer becomes too thin. Therefore, if heat treatment is performed in an atmosphere with a high oxygen concentration, the SOI layer disappears. Is preferably 40 keV or more. On the other hand, when the acceleration energy exceeds 100 keV, the distribution of the injected oxygen becomes broad and BOX is hard to be formed, and it is difficult to increase the thickness of the BOX layer due to inward diffusion of oxygen in the heat treatment atmosphere. It is preferably 100 keV or less. If the oxygen concentration in the heat treatment atmosphere is less than 1%, the effect of thickening the BOX layer is small, so the lower limit of the oxygen concentration is preferably 1% or more.

According to the second aspect of the present invention, in a method for manufacturing a SIMOX wafer, which comprises a step of implanting oxygen ions into a silicon wafer and a step of subjecting it to heat treatment, oxygen molecular ions are generated at an acceleration energy of 80 keV or more and 200 keV or less. After the implantation, the heat treatment is performed in an atmosphere having an oxygen concentration of 1% or more without performing a heat treatment having an oxygen concentration of less than 1%.

The difference between this item and the previous item is that the oxygen molecular ions are implanted and the acceleration energy is twice that of the previous item. The mass of oxygen molecular ion is twice that of oxygen atom ion, and when the acceleration voltage is doubled, the implantation depth becomes equal to that of oxygen atom ion. Other steps and oxygen concentration are the same as the previous section.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

1A and 1B show a SIM according to the present invention.
It is explanatory drawing which shows the flow of an OX wafer manufacturing process by the typical partial cross section of a wafer. First, in the step of implanting oxygen ions into the silicon wafer 1, if it is an oxygen atom ion, the acceleration energy is 40 keV or more 1
The oxygen high-concentration layer 2 is formed by implanting at an oxygen energy of not less than 00 keV and at an acceleration energy of not less than 80 keV and not more than 200 keV for oxygen molecular ions. After that, without performing heat treatment at an oxygen concentration of less than 1%, heat treatment is performed in an atmosphere having an oxygen concentration of 1% or more, so that the ion-implanted oxygen and the oxygen in the heat treatment atmosphere are both BOX.
The BOX layer 3 having high reliability is formed by utilizing the formation. By the heat treatment, the SOI layer 4 is formed on the BOX layer 3, and the oxide film 5 is also formed on the wafer surface.

In order to see the effect of the oxygen concentration of the heat treatment atmosphere on the SOI layer thickness and the BOX layer thickness, a silicon wafer is accelerated at an energy of 65 keV and a dose of 2 × 10.
After implanting oxygen atom ions of ¹⁷ atoms / cm ² , the wafer is divided into four and the heat treatment atmosphere is set to 1 in each of the oxygen concentrations of 0.25%, 0.5%, 1% and 2.5%.
Heat treatment was performed at 350 ° C. for 4 hours.

FIGS. 2A and 2B show SOI after heat treatment.
The layer thickness and the BOX layer thickness are shown respectively. It can be seen that by increasing the oxygen concentration in the heat treatment atmosphere, the SOI layer is made thinner and the BOX layer is made thicker.

Assuming that all of the ion-implanted oxygen was used for BOX formation, the BOX layer thickness is 2
It can be calculated by dividing × 10 ¹⁷ atoms / cm ² by the oxygen atom concentration in SiO ² 4.4 × 10 ²² / cm ³ , which is 45 nm. When the oxygen concentration is 0.25%, B
The OX layer thickness is almost the same as this theoretical film thickness,
By increasing the oxygen concentration, the BOX layer thickness can be made thicker than the theoretical film thickness, and especially when the oxygen concentration is 1% or more,
It was confirmed that the effect of thickening the X layer was great.

As a comparative example, a silicon wafer having an acceleration energy of 180 keV and a dose of 4 × 10 ¹⁷ ato.
After implanting oxygen atom ions of ms / cm ² , the wafer is divided into four and the oxygen concentration in the heat treatment atmosphere is 0.25%,
1350 ° C in each atmosphere of 0.5%, 1% and 2.5%, 4
Heat treatment was applied for an hour.

FIGS. 3A and 3B respectively show the SOI layer thickness and the BOX layer thickness after the heat treatment. By increasing the oxygen concentration of the heat treatment atmosphere, the SOI was
It can be seen that although the layer is thinned, the BOX layer is not thickened.

[0028]

According to the present invention, oxygen in the heat treatment atmosphere can be effectively used for BOX formation. Therefore, even if the dose amount of oxygen ions is reduced, it is possible to introduce steps such as ITOX treatment and epitaxial growth. Highly reliable B
OX can be formed, and a low cost SIMOX wafer with high productivity can be manufactured.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a flow of a SIMOX wafer manufacturing process according to the present invention by a schematic partial cross section of a wafer.

FIG. 2 Low energy (65 keV) and low dose amount
(2 x 10¹⁷atoms / cm ^Two) Oxygen atom ion
When the oxygen is injected, the oxygen concentration in the heat treatment atmosphere is (a) S
The figure which shows the influence which it has on OI layer thickness and (b) BOX layer thickness
Is.

FIG. 3 shows the oxygen concentration of (a) S in a heat treatment atmosphere when oxygen atom ions with high energy (180 keV) and low dose amount (4 × 10 ¹⁷ atoms / cm ² ) are implanted.
It is a figure which shows the influence which it has on OI layer thickness and (b) BOX layer thickness.

[Explanation of symbols]

1 Silicon wafer 2 High concentration layer of oxygen 3 BOX layer 4 SOI layer 5 Oxide film on wafer surface

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuhiro Yamamoto             2201 Kamioda, Oita, Kohoku-cho, Kishima-gun, Saga Prefecture             Sumitomo Metal Industries, Ltd. Sitix Business Division             Within (72) Inventor Seiichi Nakamura             2201 Kamioda, Oita, Kohoku-cho, Kishima-gun, Saga Prefecture             Sumitomo Metal Industries, Ltd. Sitix Business Division             Within (72) Inventor Masakazu Sano             2201 Kamioda, Oita, Kohoku-cho, Kishima-gun, Saga Prefecture             Sumitomo Metal Industries, Ltd. Sitix Business Division             Within F-term (reference) 5F032 AA91 DA53 DA60

Claims (2)

[Claims] 1. A method of manufacturing a SIMOX wafer, which comprises a step of implanting oxygen ions into a silicon wafer and a step of subjecting it to heat treatment. After implanting oxygen atom ions at an acceleration energy of 40 keV or more and 100 keV or less, the oxygen concentration is less than 1%. Oxygen concentration of 1% without heat treatment
SIMO characterized by heat treatment in the above atmosphere
X-wafer manufacturing method. 2. A method for manufacturing a SIMOX wafer, which comprises a step of implanting oxygen ions into a silicon wafer and a step of subjecting it to heat treatment. After implanting oxygen molecular ions at an acceleration energy of 80 keV or more and 200 keV or less, the oxygen concentration is less than 1%. Oxygen concentration of 1% without heat treatment
SIMO characterized by heat treatment in the above atmosphere
X-wafer manufacturing method.