JP3456521B2 - 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 (Silicon On Insulator) substrate having a semiconductor layer provided on an insulating film.

[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. . Also, recently, after implanting hydrogen ions or the like into a semiconductor substrate, this semiconductor substrate is stacked on a support substrate with the ion implantation surface as a stacking surface, and this stack is formed into a stack of 500
By raising the temperature to a temperature exceeding ℃ to generate bubbles in the ion-implanted region, the semiconductor substrate is separated from the support substrate in the ion-implanted region, and a thin semiconductor material film having a semiconductor thin film on the surface of the support substrate is formed. A manufacturing method has been proposed (Japanese Patent Laid-Open No. 5-211128). In this method, if ions can be uniformly injected into the semiconductor substrate from the surface, a semiconductor substrate having a thin semiconductor layer with a uniform thickness can be obtained. Further, if an oxide film is provided on the surface of the supporting substrate in advance, the supporting substrate, the oxide film formed on this substrate and acting as a buried oxide film, and the semiconductor layer formed on this oxide film are provided by this method. An SOI substrate can be manufactured.

[0003]

However, in the above-described conventional method for manufacturing a thin semiconductor material film, a relatively large amount of 3.5 × 10 5 is implanted when hydrogen ions are implanted into the semiconductor substrate.
Ion implantation must be performed at a dose of ¹⁶ to 10 × 10 ¹⁶ / cm ² , and a relatively long time is required for ion implantation, resulting in a problem that the productivity of the SOI substrate decreases. An object of the present invention is to efficiently generate bubbles in the ion implantation region with a small amount of ion implantation and separate the semiconductor substrate in the ion implantation region, thereby improving the productivity of the SOI substrate.
It is to provide a method for manufacturing a substrate.

[0004]

The invention according to claim 1 is
As shown in FIG. 1, a step of forming an oxide film 12 on the surface of the first silicon substrate 11 and a step of selecting hydrogen gas ions, hydrogen molecule ions, helium ions and silicon ions from the surface of the first silicon substrate 11 are selected. 1 or 2
A step of implanting seed ions to form an ion-implanted region 11a parallel to the oxide film 12 inside the first substrate 11, and a step of heat-treating the first silicon substrate 11 at a temperature of 400 ° C. or lower in a hydrogen atmosphere, A step of superimposing the first silicon substrate 11 on the second silicon substrate 13 serving as a support substrate through the oxide film 12 so as to be in close contact with the second silicon substrate 13, and the first silicon substrate 11
500 to 80 with the second silicon substrate 13 in close contact with
The first silicon substrate 11 is separated from the second silicon substrate 13 in the ion-implanted region 11a by heat treatment at a temperature of 0 ° C., so that the silicon layer 11 is formed on the surface of the second silicon substrate 13.
S including the step of forming b and the step of further heat-treating the second silicon substrate 13 having the silicon layer 11b on its surface.
It is a method of manufacturing an OI substrate. As a result of the ion implantation, dangling bonds (bonding hands in which silicon (Si) in which hydrogen atoms are not bound are released) are formed in the ion implantation region 11a. This dangling bond is terminated by being combined with hydrogen supplied by heat treatment at 400 ° C. or lower in a hydrogen atmosphere performed after the ion implantation step.
Later, when the first silicon substrate 11 is brought into close contact with the second silicon substrate 13 for heat treatment, hydrogen bonded to the dangling bonds generates hydrogen gas as the temperature rises. This hydrogen gas generates bubbles in the ion-implanted region 11a, and the first silicon substrate 11 is easily cracked in the ion-implanted region 11a starting from the bubbles and separated from the second silicon substrate 13, whereby the second silicon substrate is formed. A silicon layer 11b is formed on the surface of 13. In this specification, the “hydrogen atmosphere” means a hydrogen gas atmosphere or a hydrogen plasma atmosphere. Hydrogen becomes more active in the hydrogen plasma atmosphere.

The invention according to claim 2 is the invention according to claim 1, which is selected from the group consisting of hydrogen gas ions, hydrogen molecule ions, helium ions and silicon ions.
Implantation amount of one or two kinds of ions is 0.5 × 10 ^{16 to} 3.5
It is a method for manufacturing an SOI substrate having a density of × 10 ¹⁶ / cm ² .
The invention according to claim 3 is the invention according to claim 1 or 2, wherein when the ions to be implanted are hydrogen gas ions or hydrogen molecule ions and helium ions, the order of implanting the ions is after implanting the helium ions. It is a method of manufacturing an SOI substrate in which the hydrogen gas ions or hydrogen molecular ions are implanted. In the method of manufacturing an SOI substrate according to claim 2 or 3, the ion implantation amount of 3.5 × 10 ¹⁶ to 10 × 10 ¹⁶ / c when the conventional hydrogen gas ions are individually implanted.
Bubbles can be generated in the ion implantation region 11a with a smaller total ion implantation amount than m ² .

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the SOI of the present invention
In order to manufacture a substrate, first, a first silicon substrate 11 made of a silicon wafer is thermally oxidized to form an oxide film 12 on the surface (FIG. 1A). Next, one or both of hydrogen ions and helium ions are ion-implanted into the first substrate 11 at a dose amount of 0.5 × 10 ^{16 to} 3.5 × 10 ¹⁶ / cm ² , and the first substrate 11 An ion implantation region 11a is formed inside in parallel with the oxide film 12 (see FIG. 1).
(B)). That is, for this ion implantation, a method of implanting any one of hydrogen gas ions, hydrogen molecule ions, helium ions or silicon ions, and a method of implanting helium ions and then hydrogen gas ions, hydrogen molecule ions or silicon ions There is a way to inject. In the method here, one of the above-mentioned ions is added at 0.5 × 10 ^{16 to} 3.
With the method of implanting at a dose of 5 × 10 ¹⁶ / cm ² , helium ions are added in an amount of 0.5 × 10 ^{16 to} 3.5 × 10 ¹⁶ / c.
After implanting at a dose of m ² , hydrogen gas ions, hydrogen molecule ions or silicon ions are added at 0.5 × 10 ^{16 to} 3.5.
It is preferable to implant at a dose of × 10 ¹⁶ / cm ² .

Next, the first substrate 11 is heat-treated in a hydrogen atmosphere at a temperature of 400 ° C. or lower, preferably 300 to 400 ° C. (FIG. 1 (c)). The reason why the heat treatment is performed at 400 ° C. or lower is that if the temperature exceeds 400 ° C., the first substrate 11 may be cracked at the ion implantation region 11 a before being superposed on the second substrate 13. Then, the first substrate 1
A second silicon substrate 13 having the same surface area as that of No. 1 and made of a silicon wafer to be a supporting substrate is prepared (see FIG.
(D)) After cleaning both substrates 11 and 13 by the RCA method, the first substrate 11 is placed on the second substrate 13 at room temperature so as to be in close contact with each other (FIG. 1E).

Next, the first substrate 11 is kept in close contact with the second substrate 13 and heated in a nitrogen atmosphere to a temperature range of 500 to 800 ° C., preferably 500 to 600 ° C., and kept in this temperature range for 5 to 30 minutes. Then, thin film separation heat treatment is performed. As a result, the first substrate 11 is broken at the ion-implanted region 11a, and the thick portion 11c at the upper portion and the thin silicon layer 11b at the lower portion are broken.
(Fig. 1 (f)). Here, the reason for limiting the temperature of the heat treatment to 500 to 800 ° C. is that when the temperature is less than 500 ° C., the bubbles due to hydrogen supplied into the first substrate 11 by the heat treatment in the hydrogen atmosphere shown in FIG. This is because there is a problem that the internal pressure does not rise sufficiently, and when the temperature exceeds 800 ° C., there is a problem that bubble growth progresses and the surface roughness increases. Next, the temperature is lowered to remove the thick portion 11c (see FIG.
(G)), the second substrate 1 having the silicon layer 11b on its surface
3 is heated in an oxygen or nitrogen atmosphere to a temperature range of 900 to 1200 ° C. and is kept in this temperature range for 30 to 120 minutes (FIG. 1 (h)). This heat treatment is performed on the silicon layer 11
This is a heat treatment for strengthening the bonding of b to the second substrate 13. Finally, the separation surface of the silicon layer 11b and the thick portion 11c
The separation surfaces of (1) and (2) are each smoothed by polishing (touch polishing) (FIGS. 1 (i) and 1 (j)). As a result, the second substrate 13 becomes an SOI substrate, and the thick portion 11c can be used again as a new silicon substrate for manufacturing the SOI substrate.

[0009]

EXAMPLES Next, examples of the present invention will be described together with comparative examples in order to show specific embodiments of the present invention. <Example 1> As shown in FIG. 1A, the thickness was 625 μm.
The silicon substrate 11 made of the above silicon wafer was thermally oxidized to form an oxide film 12 having a thickness of 400 nm on the surface. A voltage of 70 keV was applied to the silicon substrate 11 to implant hydrogen gas ions (H ⁺ ) at 1 × 10 ¹⁶ / cm ² (FIG. 1).
(B)). Next, this silicon substrate 11 was heat-treated in a hydrogen gas atmosphere at a temperature of 350 ° C. for 60 minutes (FIG. 1C). This heat-treated silicon substrate 11 was used as the silicon substrate of Example 1.

Example 2 Example 2 was repeated by substantially repeating the method of Example 1 except that helium ions (He ⁺ ) were injected at 1 × 10 ¹⁶ / cm ² instead of hydrogen gas ions.
A silicon substrate was manufactured.

Example 3 Substantially except that helium ions were implanted into the silicon substrate 11 at 0.5 × 10 ¹⁶ / cm ² and then hydrogen gas ions were implanted at 0.5 × 10 ¹⁶ / cm ^2. Then, the method of Example 1 was repeated to manufacture the silicon substrate of Example 3.

Comparative Example 1 Substantially the method of Example 1 except that the heat treatment was not carried out in a hydrogen gas atmosphere, and that hydrogen gas ions were implanted at a dose of 1 × 10 ¹⁶ / cm ^2. Then, the silicon substrate of Comparative Example 1 was manufactured.

<Comparative Test and Evaluation> The silicon substrates of Examples 1 to 3 and Comparative Example 1 were subjected to the same heat treatment as the thin film separation heat treatment, that is, after being held at 600 ° C. for 30 minutes in a nitrogen atmosphere, the oxide film of each silicon substrate It was examined whether blisters (fire blisters) had occurred on the surface. The results are shown in Table 1. The reason why the occurrence of blisters on the oxide film surface was examined after the above heat treatment is described below.
In order to manufacture the substrate, the first substrate 11 and the second substrate 13
This is because when heat treatment is performed by closely contacting with each other, bubbles need to be generated in the ion implantation region 11b of the first substrate 11, and when the bubbles are generated, blisters are generated on the surface of the oxide film 12. That is, it is possible to determine whether or not bubbles are generated in the ion implantation region 11b depending on whether or not blister is generated.

[0014]

[Table 1]

As is clear from Table 1, blisters were generated in Examples 1 to 3, whereas no blisters were generated in Comparative Example 1. In Examples 1 to 3, hydrogen is supplied by heat treatment in a hydrogen gas atmosphere after ion implantation even if the ion implantation amount is small, and this hydrogen is a dangling bond of silicon (Si) in the ion implantation region 11a. This is because hydrogen gas bubbles are generated when the first substrate 11 and the second substrate are brought into close contact with each other and heat-treated, and blisters are generated. On the other hand, in Comparative Example 1, since the heat treatment in the hydrogen atmosphere after the ion implantation is not performed, the blisters do not occur when the ion implantation amount is small in this way. Particularly, in the third embodiment, by implanting the helium ions having a large mass first, the ion implantation region 11a is formed more effectively than the relatively light hydrogen gas ions, and the implantation of the hydrogen gas ions implanted thereafter is performed. To make the distribution width sharper, the total ion implantation amount is smaller than in Examples 1 and 2, but blister is generated.

[0016]

As described above, according to the present invention, an oxide film is formed on the surface of the first silicon substrate, and hydrogen gas ions, hydrogen molecule ions, helium ions and silicon ions are formed from the surface of the first silicon substrate. 1 type or 2 types of ions selected from the group consisting of are implanted to form an ion implantation region inside the first silicon substrate, and the first silicon substrate is heat-treated at a temperature of 400 ° C. or lower in a hydrogen atmosphere, Since the first silicon substrate is superposed and adhered to the second silicon substrate via the oxide film, and the first silicon substrate is heat-treated while being adhered to the second silicon substrate, the ion implantation amount is small and efficient. Bubbles are generated in the ion implantation region. That is, in the present invention, the first silicon substrate can be efficiently separated into a thick portion and a thin silicon layer in the ion implantation region.
As a result, since ion implantation can be performed in a short time, the productivity of the SOI substrate can be improved.

[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.

[Explanation of symbols]

11 First silicon substrate 11a ion implantation region 11b Silicon layer 12 Oxide film 13 Second silicon substrate

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-11-233449 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 21/265 H01L 21/02 H01L 27 / 12

Claims (3)

(57) [Claims] 1. An oxide film (1) is formed on the surface of a first silicon substrate (11).
2) forming hydrogen gas ions from the surface of the first silicon substrate (11),
An ion implantation region (11a) parallel to the oxide film (12) is implanted into the first substrate (11) by implanting one or two ions selected from the group consisting of hydrogen molecule ions, helium ions and silicon ions. ) Is formed on the first silicon substrate (11) in a hydrogen atmosphere.
A step of heat-treating at a temperature of 0 ° C. or lower; a step of superimposing the first silicon substrate (11) on the second silicon substrate (13) serving as a support substrate through the oxide film (12) and closely adhering the same. The first silicon substrate (11) is replaced with the second silicon substrate (13)
The first silicon substrate (11) is heat-treated at a temperature of 500 to 800 ° C. while being in close contact with the first silicon substrate (11) and the ion implantation region (11a).
Separating the second silicon substrate (13) from the second silicon substrate (13), thereby forming a silicon layer (11b) on the surface of the second silicon substrate (13), and the second step having the silicon layer (11b) on the surface. A method of manufacturing an SOI substrate, further comprising the step of further heat treating the silicon substrate (13). 2. An implantation amount of one or two ions selected from the group consisting of hydrogen gas ions, hydrogen molecule ions, helium ions and silicon ions is 0.5 × 10 ^{16 to} 3.
The method for manufacturing an SOI substrate according to claim 1, wherein the SOI substrate has a density of 5 × 10 ¹⁶ / cm ² . 3. When the ions to be implanted are hydrogen gas ions or hydrogen molecule ions and helium ions, the order of implanting the ions is to implant the helium ions and then implant the hydrogen gas ions or the hydrogen molecule ions. 2. The method for manufacturing an SOI substrate according to 2.