JPH0319218A - Formation process and device of soi substrate - Google Patents

Abstract

PURPOSE:To form a silicon single crystal in high quality on a silicon oxide film in precision thickness by a method wherein an electron gun type evaporator is provided while a substrate is injected with oxygen molecular beams from a plasma ion source under irradiation with silicon molecular beams to be heated later. CONSTITUTION:An MSE device provided with an electron gun type Si evaporator 12, ECR plasma ion sources 13, 14, 15 is used. An n type Si substrate 3 used as a specimen wafer is RCA cleaned up and then placed in a formation chamber 16; an alpha-Si deposited in 10Angstrom thick is cleaned up at 800 deg.C for one minute; the substrate temperature is lowered at 700 deg.C to form an SOI substrate to be irradiated with oxygen ion 6 in 1muA/cm<2> from an ion source and simultaneously irradiated with Si molecular beams 5 in 1.0Angstrom /S from an evaporator 12. After the film thickness of SiO2 reaches the specific value, the oxygen ion irradiation is stopped; Si is MBE deposited to perform the heat treatment in vacuum at 800 deg.C for 30 minutes so that an SOI substrate equal to that formed by using a thermal oxide film may be formed.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is an SOI (Silico
The present invention relates to a method of manufacturing a (onInsulator) substrate.

(Prior Art) SOI technology is a technology for forming a single crystal of Si on an insulating substrate, and has been actively researched in recent years. Methods for forming an SOI substrate include 1) melting and recrystallizing polysilicon formed on SiOZ with a laser beam or electron beam, and 2) growing polysilicon from a seed part onto SiO2 using vapor phase or liquid phase growth. Lateral growth method (ELO), 3) Oxygen ions are implanted into a silicon single crystal substrate to create a high oxygen concentration layer under the surface single crystal layer, and then heating changes the oxygen high concentration layer to a SiO2 layer. method (SI
MOX), etc. have been proposed. Each method has advantages and disadvantages, but SIMOX has high throughput and
Since it originally uses a single crystal substrate, it has excellent crystallinity and is a promising method for producing a single SOI layer. SIM
In OX, in order to ensure a sufficiently thick Si single crystal layer on the upper layer and a thick SiO2 layer on the lower layer, the 100ke
A large amount of high-velocity ions of V or higher must be implanted.

The oxygen profile immediately after implantation is as shown in Figure 3a). The oxygen distribution becomes close to a Gaussian distribution due to high-speed ion implantation.

After this, when high-temperature heat treatment is performed, SiO2 is formed and
As shown in Figure 3b), the oxygen distribution also becomes steep. However, the heat treatment temperature at this time is high because it is necessary to diffuse oxygen, and is 1400°C, which is close to the melting point of Si. At such high temperatures, all impurities in Si diffuse, so 8IMOX technology can only be used at the beginning of the device process. In addition, in order to diffuse and redistribute oxygen over long distances, Si single crystals contain SiO2 clusters, -Si
Clusters of Si are likely to form in the O, and this is the cause of defects.

(Problems to be Solved by the Invention) The purpose of the present invention is to eliminate such conventional drawbacks,
The object of the present invention is to provide a method for producing high-quality silicon single crystals with precisely controlled thickness on a silicon oxide film with precisely controlled thickness at low temperatures.

(Means for Solving the Problems) The present invention places a substrate having a silicon single crystal on its surface in a vacuum chamber, cleans the surface of the substrate, and then irradiates it with a silicon molecular beam while irradiating it with oxygen ions or A process of forming an oxygen-rich layer consisting of a silicon layer containing a high concentration of oxygen by simultaneously implanting an oxygen molecular beam containing oxygen ions, and forming a silicon layer by comparing the silicon molecular beam. and a step of changing the high oxygen concentration layer into a silicon oxide layer by heating. This SOI substrate manufacturing apparatus is characterized in that it is equipped with an electron gun type evaporation device for generating silicon molecular beams and a plasma ion source for generating oxygen ions.

(effect) First, the principle of the present invention will be explained.

SIMOX technology requires high-temperature, long-term heat treatment after ion implantation, as shown in Figure 3, which redistributes the wide profile of oxygen ions implanted at high speed and closes the interface between Si and 8102. This is thought to be due to the steepness.

Considering that normal thermal oxidation of Si is possible at 800 to 900°C, annealing at 800 to 900°C is considered to be sufficient to convert the implanted interstitial oxygen to SiO2. Therefore, in SIMOX technology,
If the oxygen profile after ion implantation is steep from the beginning as shown in Figure 2b), the S
It is thought that it is possible to form an SOI substrate without performing high temperature annealing close to the melting point of i.

Therefore, in order to reduce the spread of the oxygen profile after implantation, the inventor accelerated the oxygen ions by 1 to 5 keV.
When the oxygen ions were implanted into the surface of a Si single crystal cleaned in an ultra-high vacuum, the oxygen ions entered the crystal at several tens of amps and stopped.
It has been found that by irradiating the back surface with molecular beams and oxygen ions at the same time, it is possible to increase the thickness of the high-oxygen-concentration implanted layer while leaving the outermost layer in a single-crystal state. This is based on the following principle. Oxygen ions implanted into the solid lose kinetic energy through collision with substrate nuclei and interaction with valence electrons, and come to rest within the solid. These two speed reduction mechanisms can be treated as independent phenomena, and their respective stopping powers do not change as long as the incident energy is constant. Therefore, the average depth (P
The projected range does not change if the acceleration of oxygen ions is constant. Therefore, if we irradiate a Si molecular beam without implanting oxygen ions, since the outermost surface is a single crystal, the incoming Si molecules become ebitaxial and elongate, and the S of the uppermost layer becomes
i The thickness of the single crystal layer increases.

At this time, neutral oxygen molecules released from the ion source also fly to the Si surface, but if the growth temperature is 700'C or higher, they are not incorporated into the epitaxial layer.

Since the projected range of oxygen ions is constant, the oxygen-rich layer also grows toward the surface (Figure 1a).
) and b)). Even if the high oxygen concentration layer formed in this way becomes thicker, the spread of the oxygen profile at the interface with the Si single crystal layer is extremely steep, the same as when implanted at an acceleration of 1 to 5 keV. be. In addition, after the oxygen-rich layer reaches a predetermined thickness, if the supply of oxygen ions is stopped, the epitaxial information of the outermost single-crystal layer is inherited, and a Si single-crystal layer containing no oxygen is formed. MBE can be lengthened to some extent (Fig. 1e)). The substrate with the high oxygen concentration implanted layer formed as described above was heated to 800°C.
When heated, the oxygen-rich injection layer changes to SZO2, and an SOI substrate can be formed at an extremely low temperature compared to normal SIMOX technology (Fig. 1d)).

Next, the inventor devised a device for shaping an SOI substrate based on the above principle. As shown in FIG. 2, this device is equipped with an E-gun evaporator for elongating Si molecular beams and an ECR ion source for elongating oxygen ions in a vacuum chamber, and is characterized in that it can apply high pressure to the Si substrate.

The ECR ion source can generate plasma even in an oxygen atmosphere of 10 Torr, and has a large amount of ion current. In this way, ions can be generated even in high vacuum,
It became possible to simultaneously irradiate oxygen ions during the epitaxial growth of Si. Further, the ions are accelerated by applying a positive high voltage to the Si substrate. In this way, almost all the oxygen ions from the ECR ion source can be collected on the substrate, which is efficient. Further, near the surface, the electric lines of force are aligned perpendicular to the surface, and ions are incident perpendicularly to the surface. If a wafer whose surface plane orientation accurately matches the Channel-Nong orientation is used as the substrate, incident oxygen ions will channel within the substrate, reducing damage to the outermost single crystal layer.

(Example) Examples of the invention will be specifically described. The experiment is 40c
This was carried out using an MBE apparatus equipped with an electron gun type Si evaporator and an ECR plasma ion source. A 4-inch n-type Si (100) 0.01-0.02 Ωcm substrate was used as a sample wafer. After the sample wafer was cleaned by RCA, it was transported into the molding chamber, IOA a-Si was deposited thereon, and the sample wafer was cleaned for 800° 01 minutes to expose the clean surface. After lowering the substrate temperature to the SOI substrate temperature of 700°C, the substrate was irradiated with oxygen ions at a current density of 1 pA/cm from an ECR ion source, and at the same time, Si was irradiated at a current density of 1.0 A/s from an electron gun type Si evaporator. Irradiated with molecular beams.

At this time, a voltage of plus 5 keV was applied to the substrate.

The oxygen partial pressure inside the chamber was I x 10 Torr. When the film thickness of St02 reached a predetermined value, irradiation with oxygen ions was stopped, and Si molecular beam epitaxial growth was performed. Thereafter, the substrate temperature was raised to 8000C and heat treatment was performed in vacuum for 30 minutes.

Figure 4 shows the high oxygen concentration layer of IOOOA and the 100% oxygen concentration layer on top of it.
The depth distribution of oxygen concentration in a substrate with an elongated Si single crystal layer was investigated by SIMS. The profile is extremely steep even though no high-temperature heat treatment was performed. The width of the transition region was several tens of amps. The oxygen profile hardly changed after heat treatment at 800'C for 30 minutes. Figure 5 a) and b) show the leakage current between the upper silicon layer and the lower substrate of the sample shown in Figure 4 at 80%.
A comparison was made between those without and those subjected to heat treatment at 0°C. The leakage current was high in the case without heat treatment, but it was small in the case where it was done, and it was about the same level as in the case of using a thermal oxide film and recrystallizing the polysilicon formed thereon by laser annealing. From the above results, it was found that the oxygen-rich layer was converted to SiO2 by the subsequent heat treatment, and an SOI substrate comparable to that using a thermal oxide film was formed. Also, the heat treatment temperature is 6
If the temperature is 00°C or higher, the effects of the invention can be obtained. However, in consideration of reproducibility, it is desirable to perform heat treatment at 8006 C or higher, but if heat treatment is performed at the same time as light irradiation, results with good reproducibility can be obtained even with low-temperature heat treatment. The heat treatment atmosphere may be any normal heat treatment conditions such as hydrogen or nitrogen.

Note that in this example, silicon wafers were targeted;
The method of the present invention uses SOS (
Silicon on Sapphire) substrates and more generally SOI (Silicon on Insulat)
or) Of course, it can also be applied to substrates, etc.

(Effects of the Invention) As described above in detail, according to the present invention, the thickness of the injection layer, that is, the high oxygen concentration layer, can be adjusted to steepen the distribution of oxygen injected into Si for the purpose of forming an oxide film. You can do it regardless. Furthermore, the interface between the high oxygen concentration layer and the silicon formed thereon also becomes steep. Therefore, there is no need for a process to make the interface steep, which is required in the conventional heat treatment process.

Therefore, the heat treatment for changing the high oxygen concentration layer into an oxide film can be performed at a low temperature. High-quality silicon single crystals with precisely controlled thickness can be created at low temperatures on silicon oxide films with precisely controlled thickness.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of the principle of the present invention, FIG. 2 is a conceptual diagram of the apparatus of the present invention, FIG. 3 is a diagram showing a conventional example, and FIG.
FIG. 5 is a diagram showing the depth distribution of oxygen concentration in the SOI substrate grown in the example, and is a diagram showing the leakage current between the upper silicon layer and the lower substrate.

Claims (1)

[Claims] 1. A substrate having a silicon single crystal on its surface is placed in a vacuum chamber, and after cleaning the surface of the substrate, oxygen ions or oxygen molecules containing oxygen ions are irradiated with a silicon molecular beam. forming a high oxygen concentration layer consisting of a silicon layer containing high concentration of oxygen by simultaneously irradiating the
An SOI substrate comprising the steps of: forming a silicon layer by irradiating the high oxygen concentration layer with a silicon molecular beam; and converting the high oxygen concentration layer into a silicon oxide layer by heating. How to create. 2. A vacuum chamber capable of molecular beam growth, a means disposed in the vacuum chamber for applying a potential to a substrate, an electron gun type evaporation device for generating silicon molecular beams, and a plasma for generating oxygen ions, connected to the vacuum chamber. 1. An SOI substrate manufacturing apparatus, comprising: an ion source.