JPS6338234A - Manufacture of substrate for semiconductor element - Google Patents

Abstract

PURPOSE:To be able to form an SOI structure of high quality without an impurity mixed with excellent smoothness of its surface by using an oxygen ion- implanted layer as an etching stopper layer. CONSTITUTION:After oxygen atom ions are implanted from the front surface of an Si substrate 11, the substrate is heat treated. Monosilane gas diluted with hydrogen gas is used as material gas to form a single crystal Si thin film layer 13 by a vapor growth method on the substrate. An SiO2 film 14 is formed by a wet oxidizing method on the layer 13. Then, a transfer substrate 16 made of a 2-inch Si wafer having an SiO2 film 15 on the surface is prepared, the film 14 on the layer 13 and the film 15 on the substrate 16 are opposed, pressurized, the substrate is heated to 750 deg.C in a wet oxidizing furnace and held. The substrate 11 is polished form its rear side surface to be reduced in its thickness. The remaining substrate 11 is all removed in a polishing step with an etchant of ethylene diamine, water and pyrocatechol. At this time, an oxygen ion-implanted layer 12 acts as a stopper of etching.

Description

[Detailed description of the invention]
The single-crystal thin film rotation method is a type of method for forming the InsuIator (hereinafter referred to as 501) structure, which involves mixing impurity atoms into the thin film layer constituting the Sol structure,
This method prevents the unevenness phenomenon that occurs on the surface of a thin film.

That is, after bonding a silicon substrate on which a thin film layer of silicon 2 17 is formed to a transfer substrate, an oxygen ion implantation layer is used as an etching stopper during etching to remove the silicon substrate from the back side. In addition to preventing impurity atoms from being introduced into the thin film layer,
Using a mechanochemical polishing method using an etching solution with a high etching selectivity between the oxygen ion implanted layer and the thin Ili layer, the oxygen ion implanted layer is etched but the thin I layer is not etched. Removal of the ion implantation layer results in a Sol structure with a high quality and flat thin layer of silicon.

[Industrial application field]

The present invention relates to a Si single-crystal thin film rotation method, which is a type of method for forming a 501 structure, and particularly relates to the formation of a semiconductor element in which impurity atoms are not introduced into the thin film layer and the thin film layer is formed flat. The present invention relates to a method of manufacturing a substrate for use in a computer.

When a semiconductor element is formed in an SOI structure in which a thin single crystal layer of Si is formed on an insulating substrate, it is difficult to form a semiconductor element using the conventional LOCO8 method or P-N method when forming a semiconductor element on a Si crystal.
Unlike the junction formation method, there is no need to use element isolation methods that impede higher integration and higher speeds, and CMO3
Even when a semiconductor device is formed, the latch-up phenomenon that tends to occur when a CMO3 semiconductor device is formed on a Si substrate does not occur.

It also prevents soft error phenomena caused by radiation such as η and alpha rays when formed on a highly integrated DRA MfcSi substrate.
1-I can.

To realize such a 501 structure, -1 of the insulating substrate
- a laser annealing method in which a thin film layer of polycrystalline Si is formed on the substrate and then laser annealed to form a single crystal of Si;
There are methods such as forming an oxide film region partially inside the i di crystal and using the surface as an active region, but all of these methods require a large area of S.
There are problems in that an ol structure is not formed and the crystallinity is poor.

Therefore, after forming a layer to serve as an etch stopper on a Si substrate, a thin In crystal of Si is formed on top of the layer, which is then bonded to an insulating substrate, and then the Si substrate is removed from the back side. This method is seen as a promising method for obtaining an area-wide Sol structure.

[Conventional technology]

Regarding the conventional method using such thin film transfer method, Part 7
This will be explained using the figures up to FIG. 12.

As shown in FIG. 7, a high-concentration boron implanted layer 2 in which boron (B) atoms are ion-implanted at a high degree to serve as a stopper during the etching of 111 in the vicinity of the surface of a Si single-crystal substrate I. form.

Next, as shown in FIG. 8, a single crystal Si thin film layer 3 is formed on the high 1 degree boron t film 2.

Next, as shown in FIG. 9, a SiO2 layer 4 is formed on this Si thin film N3 by chemical vapor deposition (CVD).

Next, as shown in FIG. 10, adhesive 5 is applied to this SiO2 layer 4''2, and 5i02
Glue with N4 facing each other.

The method of adhering to this transfer substrate 6 is this Si02 layer 4.
After forming a phosphosilicate glass (PSG) film on the second layer, this SiO2
With the layer 4 and the transfer substrate 6 facing each other, psGI!
Bonding can also be achieved by melting t+.

Next, as shown in FIG. 11, the Si substrate 1 fixed to the transfer substrate 6 is polished from the back side to form a thin film.

Furthermore, by etching with a mixture of caustic potash (KOH), isopropyl alcohol, and water,
Etching is stopped when reaching the high concentration boron implanted layer 2 of 7-etching stonoper.

Here, when the above-mentioned etching solution is used, the rate at which a boron implanted layer with a high concentration of O boron atomic concentration of 10/cm' or more is etched is as follows:
This is about 1750 times the etching rate of a Si substrate with a diameter of less than 1,750 cm.

In other words, the etching selectivity between the 51 substrate and the high concentration boron implanted layer is 50.

Next, as shown in FIG. 12, the high concentration boron injection layer 2 is selectively etched using a mixed solution of hydrofluoric acid (liver), acetic acid (C83COO11) and nitric acid (11NOa) as an etching solution.

The rate at which the high-degree boron implanted layer is etched using this etching solution is about 70 times the rate at which the Si thin film layer is etched.

In other words, the etching selectivity between the high 1 degree boron implant layer and the Si thin film layer is 70.

[Problem that the invention seeks to solve]

However, in such conventional methods, a high-degree boron layer doped with boron atoms at a high degree is used as an etching stopper, and after forming the high-degree boron layer, these boron atoms are added to single crystal Si. Vapor phase growth process when forming the thin H-layer 3 and CV when forming the 5i02 layer 4 on top of it
There is a possibility that B atoms will diffuse into the Si substrate 1 or the formed Si thin film layer 3 due to the heating process in step D, and the concentration of B atoms in the high concentration boron implanted layer 2 will decrease, causing the etching stopper to deteriorate. There is a problem that the B atoms may stop working, or the B atoms may diffuse into the Si thin layer 3, changing the properties of the thin film.

In addition, in this method, the etching selectivity between the Si substrate and the high-concentration boron implantation layer, and between the high-1 degree boron implantation layer and the SiM film layer is not sufficient, so the high-1 degree boron implantation layer 2 is removed. There is a problem that the surface of the subsequent Si thin film layer 30 becomes rough or uneven, making it impossible to obtain a flat surface.

Therefore, the Sol formed by this thin film transfer method
Using the structure as a substrate for forming a semiconductor device is less practical.

The present invention aims to eliminate the above-mentioned problems and provide a method for forming an SOr structure in which impurity atoms are not introduced into the Si thin film layer and the surface of the thin film layer can be obtained as flat as a mirror surface. shall be.

[Means for solving problems]

The method for manufacturing a semiconductor device of the present invention includes a step of implanting oxygen ions into a semiconductor substrate, a step of forming a thin film layer of the same material as the substrate on the surface of the semiconductor substrate into which the oxygen ions have been implanted, and a step of transferring the surface of the thin film layer. A step of adhering the semiconductor substrate facing the substrate, a step of etching the substrate from the back side of the semiconductor substrate using the oxygen ion implanted layer as an etching stopper, an etching step in which the oxygen ion implanted layer is etched but the thin film layer is not etched or etched. The method includes a step of removing the oxygen ion-implanted layer by mechanochemical polishing using a liquid.

[Effect]

The method of the present invention uses SiN ion-implanted with oxygen atoms as an etching stopper in place of the conventional high-degree boron implanted layer, and when these oxygen atoms are implanted into the Si substrate, the oxygen atoms form a compound with Si. As a result, during the subsequent heat treatment process, they do not diffuse into the St thin film layer like boron atoms (and do not change the characteristics of the Si thin film layer).

Furthermore, when etching a Si substrate from the back side, the etching selectivity between the Si substrate and the oxygen ion implanted layer is 25.
The 31 substrate is etched using an etching solution of a mixed solution of ethylenediamine, water, and pyrocatechol, which exhibits a high value of 0.00.

Furthermore, when separating the Si thin film layer and the Si oxygen ion-implanted layer formed as an etching stopper by etching, if an etching solution of a mixture of hydrofluoric acid and water is used, the Si oxygen ion-implanted layer can be separated. Since it is possible to use an etching solution with a high selectivity that is quickly etched but hardly etches the SiO thin film layer, etching can be easily controlled and a Si thin film layer with a flat surface can be obtained.

Furthermore, since the mechanochemical polishing method can also remove the 5 in Xiff (0<x<2) region near the surface of the Si thin film layer, the final Sol structure obtained is of very high quality.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings.

As shown in FIG. 1, a Si wafer with a 2-inch target is used as a semiconductor substrate, and an acceleration voltage of 200 KeV is applied from the surface side of this Si substrate 11, and a dose of 2 XIO''/
Ion implantation of oxygen atoms was performed under cI112 conditions.

At this stage, the oxygen ion implantation layer I2 has a degree of 0 from the surface.
．． The peak state occurs at a location within 5 μm, and the concentration distribution exhibits a substantially Gaussian distribution.

Next, by performing heat treatment at a temperature of 950°C for 1 hour, the region 12^ where oxygen atoms are added at a high concentration becomes 5to
Two layers are formed, but the region 12B where oxygen atoms are added at a low concentration is SiO, (0<2), or S
SiO2 is scattered within i.

Next, as shown in FIG. 2, a single crystal Si thin film was grown on the substrate using a vapor phase growth method using monosilane (Silla) gas diluted with hydrogen gas as a raw material gas and a reaction temperature of 1050°C. Layer 13 is formed to a thickness of 1.2 μm.

Next, as shown in FIG. 3, two SiO layers 14 are formed on the single-crystal Si thin film layer 13 to a total thickness of 145 .mu.m by the Weno 1-oxidation method in which the substrate is heated to 950.degree.

Next, as shown in FIG. 4, a transfer substrate 16 made of a 2-inch Si wafer having a 5i02 film I5 with a thickness of 0.5 μm on its surface was prepared, and a single crystal Sr thin film 13 - an Sx02 film 14 of and 5i02Iil15 on the transfer substrate 16 are placed facing each other and pressurized, and the temperature of the substrate is raised to 7.
The temperature was kept at 50°C for 20 minutes.

By doing this, 5102M'J114 and 5iO
A siloxic acid bond is formed between 2H'A15 and the substrate 11
and the transfer substrate 16 are fixed.

Next, as shown in FIG. 5, the SI substrate 11 is polished from the back side to be thinned to a thickness of 30 μm.

Furthermore, all of the Si substrate 11 remaining in the polishing process is removed using an etching solution of ethylenediamine, water, and pyrocatechol.

At this time, the Si oxygen ion-implanted layer I2 acts as an etching stopper, but when this etching solution is used, the Si substrate is etched by 25% more than the Si oxygen ion-implanted layer.
Since etching is performed at an etching rate of 0 times, even if the thickness of the oxygen ion implanted layer 12 is several μm, it completely serves as an etching stopper.

Next, as shown in FIG. 6, the oxygen ion implantation layer 12 is completely removed by a mechanochemical etching method using a mixture of hydrofluoric acid and water and a tS mechanical polishing agent. .

A SiO2 film that satisfies stoichiometric bonding easily dissolves in a mixture of hydrofluoric acid and water, but Si does not dissolve at all. Further, in the region 12B of 5iOX (0< to <2), the microscopically existing 5i02 is dissolved, so that mechanical polishing becomes easier.

Furthermore, when the entire region 128 of 5iOy (0<x<2) is removed, the polishing speed is significantly reduced, and at this stage, the mechanochemical polishing is stopped.

Finally, the final product is S with a mirror finish and no impurities.
A single crystal thin film of i is formed on the 5i02 film to form an SOI structure.

Note that the conditions for ion implantation, single crystal Si thin film formation, etc. are not limited to those in the above embodiments.

In addition, if the thickness of the 5I02 film in the Sol structure needs to be thick, after forming the 5I02 film I4, CVD
There is also a method of depositing a 5i02 film using a method.

In addition to the above-mentioned examples, there are also methods for bonding to the transfer substrate.
A PSG film melt adhesion method, an anodic bonding method, and a method using a 5i02 coating agent are also applicable.

In addition, the etching solution for removing the Si substrate is 4-methyl ammonium hydroxide or 3-methyl-2
Ethyl ammonium hydroxide (80 to 90°C) and the like are also fully applicable.

In addition to the Si substrate, the substrate used in the present invention is GaA.
Other substrates such as s-substrates can also be used.

Further, as the transfer substrate, not only the Sr substrate as in this embodiment, but also other semiconductor substrates such as gallium-arsenide (GaAs), or insulating substrates such as sapphire substrates may be used.

Furthermore, a Freon-based etching gas such as trifluoromethane gas may be used to etch the oxygen ion-implanted layer.

〔Effect of the invention〕

As described above, according to the method of the present invention, the impurity atoms are diffused into the SrO thin layer as the etching layer, and the Si substrate and the thin Si film IfiFf are etched. An oxygen ion implantation layer with a high selectivity ratio is used, and in the final finishing, a mechanochemical polishing method is used in conjunction with an etching solution that dissolves the oxygen implantation layer, resulting in an extremely smooth surface. This makes it possible to form a high-quality Sol structure without contamination with impurities.

[Brief explanation of the drawing]

Figures 1 to 6 are cross-sectional views for explaining an embodiment of the method of the present invention in the order of steps, and Figures 7 to 12 are cross-sectional views for explaining the conventional method in the order of steps. It is. In the figure, 11 is a Si substrate, 12.12A, 12B are oxygen ion implantation layers, 13 is a Si thin film layer, 14.15 is a 5i02 film,
16 indicates a rotating board. Invention of λ and λ
Figure] 6 4-Tower / 1 side is l: Y pu shu tsu he hat T button i T chima sword 4th figure 41-m 4th life work 1 chin 7 □ I frog figure 5, 1-August/+pt Dou Io>j person ΔF7? Seten T purchase map 6th figure 7th table stingy 1-. Ena 3S,, -i = model included 1T Fig. 8 Jukuri - Gan, + j 3 Turn hook 9 Myoju 11 group diagram Fig. 10 Yurato Yuhoda ni O ◇tsu Si Kiyoko, 17 '°T profit diagram Figure 11

Claims (5)

[Claims] (1) A step of implanting oxygen ions into a semiconductor substrate (11) to form an oxygen ion implantation layer (12), a single crystal thin film made of the same material as the substrate (11) on the oxygen ion implantation layer (12). a step of forming a layer (13), a step of adhering the surface of the single crystal thin film layer (13) to the transfer substrate (16), using the oxygen ion implantation layer (12) as an etching stopper to form the semiconductor substrate; (11) from the back surface side, using an etching agent that dissolves the oxygen ion implantation layer (12) but does not dissolve the single crystal thin film layer (13),
A method for manufacturing a substrate for forming a semiconductor element, the method comprising the step of removing the oxygen ion implantation layer (12). (2) The method for manufacturing a substrate for forming a semiconductor element according to claim (1), further comprising the step of heat-treating the substrate (11) after implanting the oxygen ions. (3) After forming the single crystal thin film layer (13), a step of forming an oxide film (14) on the surface of the thin film layer (13) is provided. A method for manufacturing a substrate for forming a semiconductor element as described in 1. (4) The semiconductor element according to claim (1), characterized in that a step of mechanically polishing the semiconductor substrate (11) from the back side to the vicinity of the oxygen ion implantation layer (12) is applied in advance. A method for manufacturing a forming substrate. (5) The semiconductor according to claim (1), characterized in that when removing the oxygen ion implantation layer (12), etching is performed using a mechanochemical polishing method using the etching agent. A method for manufacturing a substrate for forming an element.