JP3412449B2 - Method for manufacturing SOI substrate - Google Patents

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 substrate having a single crystal thin film on a supporting substrate.

[0002]

2. Description of the Related Art This type of SOI substrate has been drawing attention as a future ultra high integrated circuit (ULSI) substrate. This S
The method of manufacturing an OI substrate includes a method of bonding silicon substrates to each other via an insulating film, a method of depositing a silicon thin film on an insulating substrate or a substrate having an insulating thin film on its surface, and a high concentration inside a silicon substrate. After the implantation of oxygen ions, an annealing process is performed at a high temperature to form a buried silicon oxide layer in a region of a predetermined depth from the surface of the silicon substrate, and a SIMOX method using the Si layer on the surface side as an active region is available. .

In addition, recently, after hydrogen ion implantation has been performed on a semiconductor substrate, this semiconductor substrate is superposed on a supporting substrate with the ion implantation surface as a superimposing surface, and this laminated body is heated to a temperature exceeding 500 ° C. A method of manufacturing a thin semiconductor material film having a thin film on the surface of the supporting substrate by separating the semiconductor substrate from the supporting substrate at the hydrogen ion-implanted portion has been proposed (JP-A-5-211128). In this method, if the ions can be uniformly injected into the inside of the semiconductor substrate from the surface, a semiconductor substrate having a thin film having a uniform thickness can be obtained. If an oxide layer is provided on the surface of the supporting substrate in advance, the SOI substrate can be manufactured by this method. The atmosphere for separating the semiconductor substrate from the supporting substrate at the hydrogen ion-implanted portion is usually the same nitrogen atmosphere as the atmospheric pressure.

On the other hand, in recent years, with the high integration of microelectronic devices and the reduction of the minimum device size, the cleanliness of the wafer surface and the micro-roughness of the wafer surface, that is, the micro-roughness, have been emphasized. There is. In particular, it is recognized that microroughness has a great influence on the electrical characteristics such as the breakdown voltage of the oxide film of the device ((M. Morita, et al., "Effect of Si Wa
fer surface micro-roughness on electrical properti
es of very-thin gate oxide films ", ULSI Science an
d Technology / 1991, pp.400-408, Electrochem, Society
(1991)). Here, the microroughness means a surface roughness on the order of 1 μm or less and several nm.

The average roughness of the surface of the thin film existing on the surface of the supporting substrate immediately after the semiconductor substrate is separated by the method disclosed in the above-mentioned Japanese Patent Laid-Open No. 511128/1 is the average roughness of the surface of the semiconductor substrate before separation. It is 10 times or more, the microroughness is relatively large, and there is a possibility that the electrical characteristics such as the oxide film withstand voltage described above are adversely affected. In particular, in this method, the surface of the thin film formed by separating the semiconductor substrate has a large microroughness because the shape of the fine bubbles due to the heat treatment remains, and is not suitable for device fabrication.

In order to solve this problem, the thin film surface on the supporting substrate after the semiconductor substrate is separated is touch-polished (to
The surface of this thin film is planarized by performing a light polishing called uch polishing (M.Bruel et a
l., "A Promising New SOI Material Technology" IEEE
International SOI Conference proceedings, pp.178-17
9 (1995)).

[0007]

However, when the current touch polishing technique is applied to an extremely thin thin film having a thickness of several hundreds nm or less produced by the above method, the thin film surface can be flattened. However, there is a problem that the thickness distribution of the thin film becomes large due to the variation in the polishing amount within the surface. Since the thickness distribution of this thin film is large, there is a problem that the device characteristics vary when the device is manufactured using the thin film semiconductor substrate after polishing.

The object of the present invention is to obtain a thin film which can minimize or eliminate the polishing of the surface of the thin film by touch polishing as much as possible, and has a uniform film thickness and a good surface roughness even if the film is extremely thin. It is to provide a manufacturing method of an SOI substrate that can be manufactured. Another object of the present invention is to provide a method for manufacturing an SOI substrate which can reduce the load of the manufacturing process by simultaneously flattening the surface of the thin film and bonding the thin film to a supporting substrate.

[0009]

The invention according to claim 1 is
As shown in FIGS. 1 and 2, a step of implanting hydrogen ions into a semiconductor substrate 11 having an insulating layer 11a formed on its surface to form a damaged region 11b parallel to the insulating layer 11a inside the semiconductor substrate 11, and The step of stacking the substrate 11 on the support substrate 12 to form the laminated body 13 and the laminated body 13 of 1 × 1
SOI including a step of raising the temperature to a range of 400 to 500 ° C. in a vacuum of 0 ⁻⁶ to 1 × 10 ⁻¹¹ torr and separating the semiconductor substrate 11 into a thick portion 11c and a thin film 11d at a damaged region 11b.
It is a method of manufacturing a substrate. SO described in claim 1
In the method of manufacturing the I substrate, the semiconductor substrate 11 has the thick portion 11c.
It is considered that the separation into the thin film 11d and the thin film 11d is caused by a sufficiently large difference between the internal pressure of the fine bubbles caused by the hydrogen ions implanted in the semiconductor substrate 11 and the pressure outside the semiconductor substrate 11. As a result, the smaller the pressure outside the semiconductor substrate 11 is, the smaller the internal pressure of the fine bubbles necessary for the separation of the thin film 11d is, so that the pressure is 1 × 10 ⁻⁶ to 1 × 10 ⁻¹¹ tor.
When heated in an atmosphere with a very high degree of vacuum of r, the thin film 11d can be separated in a state in which the growth of fine bubbles is relatively small. Therefore, it is considered that the surface roughness of the separation surface of the thin film 11d becomes small.

The invention according to claim 2 is the invention according to claim 1, further comprising a laminate 1 as shown in FIGS. 1 and 2.
After lowering the temperature of 3 to a predetermined temperature to remove the thick portion 11c of the semiconductor substrate 11, the laminated body 13 is set to 1 × 10 ⁻⁶ −1.
It is characterized in that the temperature is raised to a range of 900 to 1200 ° C. in a vacuum of × 10 ^-11 torr to flatten the surface of the thin film 11d and the thin film 11d is bonded to the support substrate 12. This claim 2
In the method for manufacturing an SOI substrate described in 1), 1 × 10 ⁻⁶
70 in an extremely high vacuum of 1 × 10 ^-11 torr
When the temperature is raised to 0 ° C., the desorption of hydrogen ions implanted in the semiconductor substrate 11 from the thin film 11d is completed, and the surface roughness of the thin film 11d is accordingly reduced. On the other hand, the thin film 11d
And the heat treatment for laminating the support substrate 12 are usually 900 to 120.
It is carried out in the range of 0 ° C. As a result, the above heat treatment is applied
Since the heat treatment for flattening the surface of 1d and the heat treatment for laminating the thin film 11d are combined, the number of manufacturing steps of the SOI substrate 14 can be reduced.

The invention according to claim 3 is the invention according to claim 1, further comprising a laminated body of 1 × 10 ⁻⁶ to 1 × 10 ⁻¹¹ while the thick portions separated in the damaged region are stacked on the thin film. It is characterized by further increasing the temperature in the range of 900 to 1200 ° C. in a torr vacuum to flatten the surface of the thin film and bonding the thin film to a supporting substrate, and then lowering the temperature to remove the thick portion. This claim 3
In the method of manufacturing an SOI substrate according to claim 1, since the temperature is further raised to a range of 900 to 1200 ° C. without lowering the temperature after the thin film of the semiconductor substrate is separated, the method for manufacturing an SOI substrate according to claim 2 is characterized by heat treatment. The number of steps and the loss of heat energy can be reduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2 (a),
In order to manufacture the SOI substrate of the present invention, first, a semiconductor substrate 11 made of a silicon wafer is thermally oxidized to form an oxide layer 11a (SiO ₂ layer) which is an insulating layer on the surface of the substrate 11, and then hydrogen ions are added to the substrate 11. 3.5 × 10 ¹⁶ H /
Ion implantation is performed with a dose amount of cm ² to 1 × 10 ¹⁷ H / cm ² (FIG. 1A). Reference numeral 11b is a damaged region formed inside the semiconductor substrate 11 by hydrogen ion implantation, and the damaged region 11b is formed parallel to the oxide layer 11a. Next, a supporting substrate 1 made of the same silicon wafer as above.
2 is prepared (FIG. 1B), and both substrates 11 and 12 are RCA.
After cleaning by the method, the semiconductor substrate 11 is formed on the supporting substrate 12.
Are laminated at room temperature to form a laminate 13 (see FIG. 1).
(C)). Next, the laminated body 13 is mixed with 1 × 10 ⁻⁶ to 1 × 10.
^-11 torr, preferably 1 × 10 ⁻⁷ to 1 × 10 ^{−9 in} a vacuum of 400 to 500 ° C. (FIG. 2), preferably 400 to 45
The temperature is raised to a range of 0 ° C., and the thin film separation heat treatment is performed by maintaining this temperature range for 0 to 10 minutes (FIG. 2), preferably 1 to 2 minutes. As a result, the semiconductor substrate 11 is cracked at the damaged region 11b and separated into an upper thick portion 11c and a lower thin film 11d (FIG. 1 (d)).

Here, the atmosphere for the thin film separation heat treatment is set to 1
The limit of the vacuum of × 10 ^-6 to 1 × 10 ^-11 torr is 1
This is because if it is less than × 10 ^-6 torr, the flattening of the separation surface becomes insufficient, and if it exceeds 1 × 10 ^-11 torr, it is difficult to realize the design of the device. In addition, the temperature of the heat treatment is 4
The reason why the temperature is limited to 00 to 500 ° C. is that if the temperature is lower than 400 ° C., the internal pressure of bubbles is not sufficiently increased by hydrogen.
This is because if the temperature exceeds 0 ° C., the growth of bubbles proceeds and the surface roughness increases.

Further, the semiconductor substrate 11 has a damaged region 11b.
The temperature of the laminated body 13 cracked in step 2 is lowered to 200 to 300 ° C. to remove the thick portion 11c of the semiconductor substrate 11, and the supporting substrate 1
In the state where the thin film 11d of single crystal silicon is laminated on the upper surface of 2 (FIG. 1 (e)), 1 × 10 ⁻⁶ to 1 × 10 ⁻¹¹ torr, preferably 1 × 10 ⁻⁷ to 1 × 10 ⁻⁹ torr. In the vacuum of 900
~ 1200 ° C (Fig. 2 (a)), preferably 1000-1
A heat treatment is performed by raising the temperature to a range of 100 ° C. and maintaining this temperature range for 30 to 120 minutes, preferably 40 to 60 minutes.
This heat treatment includes the heat treatment for flattening the surface of the thin film 11d and the thin film 11d.
This is a heat treatment that also serves as a heat treatment for laminating d on the support substrate 12.

That is, when the temperature is raised to 700 ° C. in an atmosphere having a very high degree of vacuum of 1 × 10 ^-6 to 1 × 10 ^-11 torr,
The desorption of hydrogen ions implanted in the semiconductor substrate 11 from the thin film 11d is completed, and the surface roughness of the thin film 11d is accordingly reduced. This is a thermal desorption gas analyzer (TDS)
It was found by measuring with. On the other hand, the heat treatment for laminating the thin film 11d and the supporting substrate 12 is usually performed in the range of 900 to 1200 ° C. As a result, in the above vacuum, 900 to 120
By raising the temperature in the range of 0 ° C., the surface of the thin film 11d can be flattened, and at the same time, the thin film 11d can be bonded to the supporting substrate 12, so that the manufacturing steps of the SOI substrate 14 can be reduced. Further, the temperature of the laminated body 13 is reduced to 200 to 300 ° C. to remove the thick portion 11c before the flattening heat treatment and the bonding heat treatment are performed. This is to improve its production efficiency.

In the above embodiment, an oxide layer (SiO ₂ layer), which is an insulating layer, is formed on the surface of the semiconductor substrate by thermal oxidation.
However, an insulating layer may be formed on the surface of the semiconductor substrate by nitriding treatment or the like. Further, in the above embodiment, the temperature of the laminated body is lowered to a predetermined temperature to remove the thick portion of the semiconductor substrate, and then the laminated body is subjected to 1 × 10 ⁻⁶ to 1 × 10 ⁻¹¹ tor.
In a vacuum of r, the temperature was raised to a range of 900 to 1200 ° C. to flatten the surface of the thin film and the thin film was attached to a supporting substrate. 900 to 12 in a vacuum of 1 × 10 ⁻⁶ to 1 × 10 ⁻¹¹ torr, preferably 1 × 10 ⁻⁷ to 1 × 10 ⁻⁹ torr.
00 ° C. (FIG. 2 (b)), preferably 1000 to 1100
By further raising the temperature to a range of ℃ and holding this temperature range for 30 to 120 minutes, preferably 40 to 60 minutes, the thin film surface is flattened and the thin film is attached to a supporting substrate, and then the temperature is lowered to obtain a thick wall. Parts may be removed. In this case, after the thin film of the semiconductor substrate is separated, the temperature is further lowered to 900 to 120 without lowering the temperature.
Since the temperature is raised to the range of 0 ° C., S according to the above-described embodiment
The number of heat treatment steps and the loss of heat energy can be reduced as compared with the OI substrate manufacturing method.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings. Example 1 A semiconductor substrate made of a silicon wafer having a thickness of 625 μm was thermally oxidized to form a thermal oxide film having a thickness of 400 nm on the surface. Hydrogen ions were implanted into this semiconductor substrate at 100 keV and a dose of 5 × 10 ¹⁶ H / cm ² . The semiconductor substrate was superposed on a supporting substrate made of the same silicon wafer as the above before thermal oxidation to form a laminated body. Both substrates were cleaned by the RCA method before stacking. This laminated body was heated to 400 ° C. in a vacuum of 1 × 10 ⁻⁸ torr and subjected to heat treatment for thin film separation (FIG. 3A). Due to the rearrangement of crystals in the semiconductor substrate and the pressure action of the minute bubbles by this heat treatment, the semiconductor substrate is broken and separated at the ion-implanted portion inside the semiconductor substrate, and a thin film of single-crystal silicon having a thickness of 120 nm is formed on the supporting substrate. An SOI substrate having
The variation in the thickness of the thin film at this time was ± 4 nm.
Further, the average roughness Ra of the thin film surface was measured with an atomic force microscope (hereinafter referred to as AFM), with the measurement regions being 10 μm square and 2 μm square. As a result, the average roughness R of the thin film surface when the measurement area is 10 μm square and 2 μm square
a is 6.26 nm (FIG. 4 (a)) and 5.11 n, respectively.
m (FIG. 4 (b)).

<Embodiment 2> In the same vacuum as in Embodiment 1, that is, in the same vacuum as in Embodiment 1, ie, 1 × 10 4, the supporting substrate with a thin film of single crystal silicon produced in the same manner as in Embodiment 1 is stacked on the thin film of the thick portion.
^The thin film was heated to 850 ° C. in a vacuum of ⁻⁸ torr to perform flattening heat treatment on the thin film (FIG. 3B). The thickness of the thin film at this time was 120 ± 4 nm, which was almost the same as in Example 1. The average roughness Ra of the thin film surface when the measurement area is 10 μm square and 2 μm square is 1.1 as a result of measurement by AFM.
It was 6 nm (FIG. 5 (a)) and 0.38 nm (FIG. 5 (b)). As a result, the average roughness Ra of the thin film surface was about ⅕ (measurement area 10 μm square) and about 1/13 (measurement area 2 μm square) of Example 1, which was extremely smaller than that of Example 1.

<Comparative Example 1> A laminated body of a semiconductor substrate and a supporting substrate manufactured in the same manner as in Example 1 was heated to 450 ° C. in a nitrogen atmosphere at atmospheric pressure and subjected to thin film separation heat treatment.
By this heat treatment, the semiconductor substrate is cracked and separated at the ion-implanted portion inside the semiconductor substrate, and the thickness of the semiconductor substrate is 120
An SOI substrate having a thin film of single crystal silicon of nm was obtained. The thickness of the thin film at this time was 120 ± 4 nm, which was almost the same as in Example 1. The average roughness Ra of the thin film surface when the measurement region is 10 μm square and 2 μm square is 12.7 nm (FIG. 6 (a)) and 1 respectively as a result of measurement by AFM.
It was 0.3 nm (FIG. 6 (b)). As a result, the average roughness Ra of the thin film surface was about twice as large as that in Example 1 in both cases where the measurement area was 10 μm square and 2 μm square.

<Comparative Example 2> A supporting substrate with a thin film of single crystal silicon produced in the same manner as in Comparative Example 1 was further heated in a nitrogen atmosphere at atmospheric pressure while being stacked on the thin film of the thick portion,
The film was held at 00 ° C. for 60 minutes, and heat treatment for laminating the thin film on the supporting substrate was performed. The thickness of the thin film at this time is 120 ± 4 nm
There was almost no difference from Example 2. The measurement area is 10μ
The average roughness Ra of the thin film surface at m-square and 2 μm-square is A
As a result of measurement by FM, each is 10.2 nm (Fig. 7).
(a)) and 9.69 nm (FIG. 7 (b)). As a result, the average roughness Ra of the thin film surface was slightly improved as compared with Comparative Example 1, but was about 9 times that of Example 2 (measurement area 10 μm).
m square) and about 25 times (measurement area 2 μm square), which is much larger than that in Example 2.

[0021]

As described above, according to the present invention, hydrogen ions are implanted into a semiconductor substrate having an insulating layer formed on the surface thereof to form a damaged region parallel to the insulating layer inside the semiconductor substrate. The substrate is superposed on the support substrate to form a laminated body, and the laminated body is further heated to a range of 400 to 500 ° C. in a vacuum of 1 × 10 ⁻⁶ to 1 × 10 ⁻¹¹ torr to damage the semiconductor substrate. Since it is separated into a thick portion and a thin film by, it is possible to obtain a thin film having a good surface roughness. This is because if the pressure outside the semiconductor substrate can be made small, the internal pressure of the hydrogen ion microbubbles required for thin film separation can be small, so that the thin film can be separated with relatively little growth of the microbubbles. This is because the surface roughness of the surface can be reduced. Further, since it is extremely unnecessary to polish the surface of the thin film by touch polishing, the thickness distribution of the thin film does not increase even if the thin film is extremely thin, and a device is manufactured using the SOI substrate of the present invention. However, the device characteristics do not vary.

After the temperature of the laminated body is lowered to a predetermined temperature to remove the thick portion of the semiconductor substrate, the laminated body is subjected to 1 × 10.
By performing a heat treatment in the range of 900 to 1200 ° C. in a vacuum of ⁻⁶ to 1 × 10 ⁻¹¹ torr, the thin film surface can be flattened and the thin film can be bonded to the supporting substrate at the same time. The load on the manufacturing process of the SOI substrate can be reduced. This is because when the temperature is raised to 700 ° C. in an atmosphere with a very high degree of vacuum, desorption of hydrogen ions implanted in the semiconductor substrate from the thin film is completed and the surface roughness of the thin film becomes small, so that the thin film and the supporting substrate are separated from each other. This is because the heat treatment for laminating is usually performed in the range of 900 to 1200 ° C. Further, the laminated body is 1 × 10 ⁻⁶ to 1 × 10 ⁻¹¹ t with the thick portion separated in the damaged region being stacked on the thin film.
After further raising the temperature in the range of 900 to 1200 ° C. in the vacuum of orr to flatten the thin film surface and bonding the thin film to the supporting substrate, the temperature is lowered to remove the thick portion, and once the thin film separation heat treatment is performed. The number of man-hours of heat treatment and loss of heat energy can be reduced as compared with the method of manufacturing an SOI substrate in which the temperature is lowered.

[Brief description of drawings]

FIG. 1 is a diagram showing a method of manufacturing an SOI substrate according to an embodiment of the present invention in process order.

FIG. 2A is a diagram showing heat treatment temperature conditions of the SOI substrate. (b) The figure which shows the heat processing temperature condition of the SOI substrate of another embodiment.

FIG. 3A is a diagram showing heat treatment temperature conditions for the SOI substrate of Example 1 of the present invention. FIG. 6B is a diagram showing heat treatment temperature conditions for the SOI substrate of Example 2 of the present invention.

FIG. 4A is a diagram showing Example 1 of the present invention, in which the thin film surface immediately after being heated to 400 ° C. to separate the semiconductor substrate in the damaged region shows a measurement region of 10 μm square by AFM.
(b) shows Example 1 of the present invention, in which the thin film surface immediately after the semiconductor substrate was separated at the damaged region by heating to 400 ° C.
The figure which shows the measurement area | region as 2 micrometers square by M.

FIG. 5 (a) shows Example 2 of the present invention, in which the thin film surface immediately after being heated to 400 ° C. to separate the semiconductor substrate in the damaged region and further heated to 850 ° C.
The figure shown as a 0-micrometer square. (b) shows Example 2 of the present invention, showing the thin film surface immediately after being heated to 400 ° C. to separate the semiconductor substrate at the damaged region and further heated to 850 ° C., with the measurement region being 2 μm square by AFM.

FIG. 6 (a) shows Comparative Example 1, in which the thin film surface immediately after the semiconductor substrate was separated at the damaged region by heating at 450 ° C.
The figure which shows the measurement area | region as 10 micrometers square by M. (b) shows Comparative Example 1, showing the thin film surface immediately after heating to 450 ° C. to separate the semiconductor substrate in the damaged region, and the measurement region measured by AFM as 2 μm square.

FIG. 7 (a) shows Comparative Example 2, in which the thin film surface immediately after being heated to 450 ° C. to separate the semiconductor substrate in the damaged region and further heated to 1000 ° C. was measured by AFM to have a measurement region of 10 μm.
Figure shown as a corner. (b) shows Comparative Example 2, and shows the thin film surface immediately after being heated to 450 ° C. to separate the semiconductor substrate at the damaged region and further heated to 1000 ° C., where the measurement region is 2 μm square by AFM.

[Explanation of symbols]

11 Semiconductor substrate 11a Oxide layer (insulating layer) 11b Damage area 11c thick part 11d thin film 12 Support substrate 13 laminate 14 SOI substrate

Continuation of the front page (56) Reference JP-A-5-212128 (JP, A) JP-A-9-162090 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 27 / 12 H01L 21/265

Claims (3)

(57) [Claims] 1. A damaged region (11b) parallel to the insulating layer (11a) inside the semiconductor substrate (11) by implanting hydrogen ions into the semiconductor substrate (11) having an insulating layer (11a) formed on the surface thereof. And a step of forming the semiconductor substrate (11) on the supporting substrate (12) to form a laminated body.
The step of forming (13); and heating the laminated body (13) to a temperature in the range of 400 to 500 ° C. in a vacuum of 1 × 10 ⁻⁶ to 1 × 10 ⁻¹¹ torr.
(11) in the damaged region (11b) thick part (11c) and thin film (11d)
A method of manufacturing an SOI substrate, the method comprising: 2. The laminated body (13) is cooled down to a predetermined temperature to remove the thick portion (11c) of the semiconductor substrate (11), and then the laminated body (13) is subjected to 1 × 10 ⁻⁶ -1. The SOI substrate according to claim 1, wherein the thin film (11d) is flattened by raising the temperature in the range of 900 to 1200 ° C. in a vacuum of × 10 ^-11 torr and bonding the thin film (11d) to the supporting substrate (12). Manufacturing method. 3. The laminated body is further heated to a temperature of 900 to 1200 ° C. in a vacuum of 1 × 10 ⁻⁶ to 1 × 10 ⁻¹¹ torr while the thick portions separated in the damaged region are stacked on the thin film. The SO according to claim 1, wherein after the thin film surface is flattened and the thin film is bonded to a supporting substrate, the temperature is lowered to remove the thick portion.
I substrate manufacturing method.