JPH021914A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable an ultrathin film SOI substrate fit for producing a high speed device to be manufactured by a method wherein an impurity containing layer is formed at specified depth from the surface of a semiconductor substrate and after bonding the surface side of the semiconductor substrate onto a holding substrate, the rear side of the semiconductor substrate is wet-etched away using the impurity containing layer as an etching stopper. CONSTITUTION:An impurity is ion-implanted from the surface of a semiconductor substrate 11 to form an impurity containing layer 13 in the specified depth from the surface. Next, the surface side of the semiconductor substrate 11 is bonded onto a holding substrate 16 having a surface insulating layer and then the rear side of the semiconductor substrate 11 is wet-etched away using the impurity containing layer 13 as an etching stopper. Later, when the impurity containing layer 13 is removed to form a thin film semiconductor layer 11A on the holding substrate 16, an SOI substrate 17 can be formed. As for the impurity containing layer 13, an SiOx layer, an SiNx layer or an SiCx layer is formed. Finally, as for the wet-etching process, the solution etching or the vapor etching is applicable.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a semiconductor substrate in which a semiconductor layer is formed on a substrate through an insulating layer, that is, a so-called 5ol(:!, 1li
(con on 1 insulator) relating to a method of manufacturing a substrate.

[Summary of the invention]

In the method for manufacturing an SOI substrate, the present invention involves forming an impurity-containing layer at a predetermined depth from the surface of the semiconductor substrate, bonding the front side of the semiconductor substrate to a support substrate, and using the impurity-containing layer as an etching stopper to form the semiconductor substrate. By removing the back surface by wet etching and then removing the impurity-containing layer, a super 8f film Sol substrate can be easily manufactured.

[Conventional technology]

Recently, so-called SO1 substrates have been used to produce VLs such as CMO5.
Developments are underway to create SI (very large scale integrated circuits). Methods for manufacturing this Sol substrate include, for example, bonded wafer method, SIMOX (Heparati
Onby 13planted QJigen) method and the like are known. The Bonpunt wafer method is shown in Figure 6A-
5t027 on the surface as shown in C! (Prepare two silicon substrates (2) having
(21 is mutual CI) 5to2b# (They are bonded together so that the IJs are in contact with each other, and the silicon substrate (2) on one side is shaved to form a silicon thin film (2A) to create a Sol substrate (3).

The SIMOX method uses a silicon substrate (4) as shown in Figure 7.
Oxygen 02 (71) is ion-implanted into the 5i02 layer (5).
5i (h layer (5)) and silicon *I* (4
A) is formed to create a Sol substrate (6). Note that during oxygen ion implantation, the silicon thin film (4
In order to prevent A) from becoming amorphous and to make it easier to form the 5i02 layer (5), the substrate temperature was set to a high temperature (400°C).
Ions are implanted at a moderate temperature.

[Problem to be solved by the invention]

However, the difficulty in creating the Sol substrate (3) using the bonded wafer method described above is that after bonding both silicon substrates (2) together via the 5i02 layer (1), one silicon substrate (2) must be borated. The goal is to make the film thinner. Here, it is important to form a thin layer of silicon 11Jtl (2A) uniformly and with good reproducibility.Also, when creating, for example, a MOS transistor on the Sol substrate (3), the silicon "ilP! (2A) which will be the active layer ) The electrical characteristics will be better if the thickness of the thin film 3 is made thinner.
The 01 substrate can be said to be an important technology for device fabrication, but as shown in the manufacturing method shown in Figure 6, the silicon substrate on one side (2
) is difficult to produce uniformly and with good reproducibility by ordinary polishing.

On the other hand, the Sol substrate produced by the SIMOX method has the following problems.

(i) When ion-implanting oxygen into silicon base i (4), a large amount of oxygen of I x 10" to 5 x 10"ca-2 is ion-implanted, so many defects occur in the silicon thin film (4A). .

(ii) Silicon M film (4^) -5i02 layer (5)
Since there is a SiOx region at the interface, the 5iSift interface characteristics are poor and leakage occurs.

(iii) In order to obtain high-speed performance of the device fabricated on the 501 substrate (6), the substrate capacitance must be reduced, and for this reason, the insulating layer should be 5T with a thickness of 0.5 to 1.0μ.
(H layer is required. However, SO by SIMOX method
T substrate (61 (7) 5i (h layer (5) is 0.2 to 0.
Since it can only be formed to a thickness of 3 μm, it is difficult to create commercial speed devices.

(iv) An ultra-high current ion implanter is required.

In view of the above-mentioned points, the present invention provides a method for manufacturing a semiconductor substrate that can easily manufacture an ultra-thin SOt substrate.

Ion implantation is performed using

[Means to solve the problem]

The method for manufacturing a semiconductor substrate of the present invention includes a step of ion-implanting impurities from the surface of a semiconductor substrate (11) such as silicon to form an impurity-containing 1it (13) at a predetermined depth from the surface; A step of bonding the surface side of the semiconductor substrate (
11) includes a step of removing the back surface by wet etching.

Thereafter, the impurity-containing layer (13) is removed and the supporting substrate (1
6) Obtain a semiconductor substrate, ie, an SOI substrate (17), on which a thin film semiconductor layer (11^) is formed.

Oxygen, nitrogen, or carbon is used as the impurity to be ion-implanted, and the impurity-containing layer (13) is a SiOx layer, Si
A Nx layer or a 5iCx layer can be formed.

As the wet etching, solution etching or steam etching can be used.

According to the above manufacturing method, channeling is performed when impurity ions are implanted.
After forming an impurity-containing layer (13) serving as a wet etching stopper at a predetermined depth from the surface of 1) and bonding this semiconductor substrate (11) to a supporting substrate (16), the back surface of the semiconductor substrate (11) is formed. is removed by wet etching. During this wet etching, the etching of the semiconductor substrate (11) ends at the impurity-containing layer (13) which serves as an etching stopper.

Therefore, the uniform semiconductor layer II under the impurity-containing layer (13)
! (ie, the thin surface layer of the semiconductor substrate (11) separated by the impurity-containing layer (13)) (IIA) remains.

In other words, semiconductors can be processed uniformly and with good reproducibility! Membrane (IIA)
is formed, and then by removing the impurity-containing layer (13), a superstructure with a uniform semiconductor thin film (IIA) is formed.
1! ! A So1 substrate (17) is easily obtained.

In this Sol-based m(17), a semiconductor i film (IIA i
Since the lower insulating layer (15) is formed in advance on a separate support base Mi (16), it is possible to make it a sufficiently thick insulating layer, and when a device is created on this Sol substrate (17). The board capacitance becomes sufficiently small.

Semiconductor thin strip (11^) and support substrate, i.e. its insulation 1m
(15) Since no semi-insulating layer is interposed therebetween, the interface properties are good. Furthermore, when impurity ions are implanted, the ions are implanted using channeling, so that the semiconductor thin film (IIA) remaining on the surface can be a semiconductor thin film with few defects.

〔Example〕

Embodiments of the method for manufacturing an SO1 substrate according to the present invention will be described below with reference to the drawings.

In this example, a silicon single crystal substrate (11) is provided as shown in FIG. 12) is ion-implanted, i.e., for example (10
0) plane or (110) plane, ions are implanted from the direction perpendicular to the crystal plane), the substrate (110)
A SiOx layer (IIA), which acts as a wet etching stopper, is deposited at a predetermined depth from the surface so as to leave a thin surface layer (IIA) of
13). After ion implantation, annealing may be performed at a desired temperature. The dose of oxygen (12) is 5 at the peak concentration.
At% or more is allowed, and in this example, the peak concentration is 10%.
at% (dose amount 2X IQ" era-2 approximately) or more.

Figure 2 shows the oxygen concentration distribution in the depth direction from the surface of the silicon substrate (11) when oxygen ions are implanted into the silicon substrate (11). The curve (■) is a comparative example and shows the case of normal ion implantation.The implantation energy was about 70XeV.

Next, as shown in FIGS. 1B and C, a silicon substrate (14
), sufficiently thick on the surface, e.g., 0.5 to 1.0 μm thick.
A support substrate formed by forming a 5t021 complex (15) of about
16) is provided, and a silicon base i is provided on this support substrate (16).
(11) +71 surface Mt (11/1) IIJ is bonded to each other by thermocompression so as to be in contact with the 5irh layer (I5).

Next, the silicon substrate (11) into which oxygen ions have been implanted is wet-etched from the back side using, for example, a KOH solution. During this etching, the SiOx layer (13) acts as an etching stopper, and the etching ends at the SiOx layer (13). As a result, SiOx N
(13) Uniform single crystal silicon substrate film underneath (IIA)
remains (see first diagram).

Next, as shown in FIG. 1E, SiOx 11 (13)
The 5tCh layer (
15) Create a target SO1 substrate (17) having a single crystal silicon i film (IIA) thereon.

According to the above manufacturing method, SiO is implanted by ion implantation so that the silicon thin film (IIA) on the surface remains on the silicon substrate (11).
By forming an x layer (13), bonding this silicon substrate (11) and supporting substrate (16) together, and etching with a KOH solution from the back side of the silicon substrate (11),
5tyx Ii# (13) acts as an etching stopper, leaving a uniform silicon thin film (IIA) with a 0.1 μm difference with good reproducibility, making it easy to create the desired ultra-thin film 501 substrate (17). be able to.

Furthermore, when oxygen ions are implanted into the silicon substrate (11), channeling is used to implant the ions, so there is little damage to the surface side.
In step 7), a silicon thin film with fewer defects is formed.

Silicon substrate (1) on which SiOx In (13) is formed
1) and the support substrate (16) are bonded together, so the support substrate (I6) has a sufficient thickness of 5iOx.
1'1 (15) can be formed. therefore,
5 (Silicon on Jl substrate (17) 81!!1 (11Δ
) The lower 5i02 layer (15) can be made thick enough,
When devices are fabricated on silicon thin film (IIA), the substrate capacitance becomes sufficiently small that it becomes difficult to fabricate high-speed devices.
Becomes Noh.

Furthermore, silicon thin 1% (llA) is directly applied to the 5i02 layer (1
5), the 5i-3i(h interface is good and no leakage occurs.

FIG. 3 shows another embodiment of the invention.

In this example, oxygen (12) is ion-implanted into the silicon substrate (11) using channeling in the same manner as in FIG.
f& (see Figure 3A), silicon group 1 (11
) by oxidizing the very surface of the silicon\lil film (IIA) on the surface side of 5i0211! i! (21) (see Figure 3B) Next, as shown in Figure 3C, a supporting substrate (16) is formed by forming a 5tCh layer (15) on the surface of the silicon base 1 (14). A silicon substrate (11) is attached.

After that, as in the first drawing and E, the silicon substrate (11)
5iOxIel from the back side using, for example, KOHfa solution.
(13) Please refer to the 3rd diagram to remove the etching)
Then, the Si0g layer (13) is removed to create the desired Sol group 1 (18) shown in FIG. 3E.

In this example, in particular, after forming the SiOx layer (13), the silicon thin film (
IIA) was slightly oxidized to form a thin 5iOz film (21
) and bonded to the 5i02 layer (15) of the supporting substrate (16), the silicon thin film (118) and 5
i021'i! The interface with 5i-St(h) improves the interface characteristics and at the same time makes bonding easier.

FIG. 4 shows another embodiment of the invention.

In this example, as shown in FIGS. 4A to 4C, oxygen (12) is first ion-implanted into the silicon substrate (11) using the Naya ring as in the above example, and the silicon substrate (12) is ion-implanted to a predetermined depth from the surface.
An Ox layer (13) is formed and bonded to a support substrate (16), and then the silicon base 4i (11) is KOed from the back side to the SiOx I layer (13) which is an etching stopper.
Remove by etching with Hfa solution.

Next, 5tyx fat (13) has a high concentration of oxygen (5i
The SiOx layer (13) is changed into a 5i02 layer (13A) by annealing and oxidizing it in an oxygen atmosphere. (22) is the support substrate (16) at the same time.
) is the 5i02 layer formed on the back surface of the 5i02 layer. After that, this 5i02 layer (13A) was removed by etching with HF.
The desired Sol group 1 (19) is created. In this manufacturing method, 5iOx (13), which is an etching stopper,
Since the silicon substrate film (IIA) is annealed in an oxygen atmosphere to be oxidized and removed by etching, it can be removed without damaging the silicon substrate film (IIA). The etching stopper can be removed without causing damage due to ion bombardment that occurs during etching.

In the above example, when ion-implanting oxygen into the silicon substrate (11), the ions are implanted at a low substrate temperature (for example, 100K), and then the silicon substrate (11) is heated to 400°C.
Low temperature annealing at ~600°C is possible.

If ions are implanted at such a low temperature, lattice vibrations will be small and recharging will be more likely to occur. Therefore, 5iOx (13) can be formed while leaving an undamaged layer on the surface. Note that low-temperature annealing is performed using SiOx Ii
Simultaneously with the formation of i, the silicon thin film (IIA) which has been damaged on the surface side is also annealed. If sudden reannealing is performed at high temperature as annealing after ion implantation, defects will increase due to stress.

In addition, in the above example, after ion implantation of oxygen and low-temperature annealing, the oxygen concentration profile was changed to the broken line (111) in FIG.
100 in a nitrogen atmosphere to make the steepness as shown in
Annealing can also be performed at 0°C to 1100°C. In the above example, channeling is used to make the concentration profile steeper so that the peak is at a deeper position, but the solid line in Figure 5 (
As shown in 1), oxygen atoms also exist near the surface. By annealing at 1000°C to 1100°C, the f& element near the surface is released by out-diffusion, and the oxygen near the peak is absorbed on the high concentration side (the peak has the most defects). , oxygen is attracted to this defect).

Through such annealing, the silicon thin film (I
The oxygen concentration in IA) can be lowered, and the occurrence of defects can be further reduced.

In the above-described embodiment, SiOx Ha(13) formed by ion-implanting oxygen as an etching stopper/per.
However, it is also possible to use a SiNx layer or a 5iOx layer formed by ion-implanting nitrogen or carbon. The SiNx layer and the 5iOx layer can be removed by etching with CF4.

〔Effect of the invention〕

According to the present invention, an impurity-containing layer is formed at a predetermined depth from the surface of a semiconductor substrate, the front side of the semiconductor substrate is bonded to a support substrate, and then the back side of the semiconductor substrate is etched using the impurity-containing layer as an etching stopper. By including the step of removing by wet etching, the semiconductor thin film can be left uniformly and with good reproducibility. Then, by removing the impurity-containing layer, the ultra-thin 11!1lj layer was successfully fabricated for high-speed devices.
An sO1 substrate can be created.

[Brief explanation of the drawing]

Figures 1A-E are process diagrams showing an example of the SOI substrate manufacturing method according to the present invention, Figure 2 is an oxygen concentration distribution diagram by ion implantation, and Figures 3A-E are process diagrams showing an example of the SOI substrate manufacturing method of the present invention. 4A to 4E are process diagrams showing another example of the method for manufacturing the So1 substrate of the present invention, and FIG. 5 is an oxygen concentration distribution diagram for explaining still another example of the present invention. Figures 6A-C are process diagrams showing the conventional Sol substrate manufacturing method, and Figure 7 is the conventional SOI
FIG. 3 is a cross-sectional view showing another example of a method for manufacturing a crystal plate. (11) is a silicon substrate, (11^) is a silicon thin film,
(12) is oxygen ion implantation, (13) is SiOx layer,
(14) is a silicon substrate, (15) is a SiOx layer, (1
6) is a support substrate.

Claims (1)

[Claims] A step of forming an impurity-containing layer at a predetermined depth from the surface of a semiconductor substrate, a step of bonding the front side of the semiconductor substrate to a support substrate, and a step of forming the semiconductor substrate using the impurity-containing layer as an etching stopper. 1. A method for manufacturing a semiconductor substrate, comprising the step of removing the back surface of the semiconductor substrate by wet etching.