JP2003007709A - Silicon single crystal wafer having gettering capability and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon single crystal wafer that can have gettering capability even in a very small amount of contamination, and to provide a method for manufacturing the silicon single crystal wafer. SOLUTION: A silicon single crystal wafer has gettering capability. An aluminum-containing layer having impurity gettering capability is formed on the back face of silicon single crystal wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of a gettering method, which is a technology for removing heavy metal impurities that adversely affect device operation, and more specifically, a silicon single crystal wafer for semiconductors having a high gettering ability, and The manufacturing method is related.

[0002]

[Related technology] Higher density of devices such as semiconductor integrated circuits,
With high integration, stabilization of device operation has been eagerly desired. In particular, improvement of characteristic values such as leak current and oxide film breakdown voltage is an important issue.

However, the possibility of being contaminated by unwanted heavy metals, for example, impurities such as Cu, Fe, and Ni, in the manufacturing process of semiconductor integrated circuits cannot be denied at present. It is widely known that these heavy metal impurities, when solid-dissolved in a silicon single crystal, significantly deteriorate the leak current and the oxide film withstand voltage characteristic.

Therefore, various gettering techniques have been developed as a method for removing these heavy metal impurities to the outside of the device operating region. For example, IG (Internal G) that precipitates oxygen atoms contained in a silicon single crystal manufactured by the CZ method and traps heavy metals in the strain around the precipitate.
ettering) method, a method of forming a polycrystalline silicon film on the back surface of a silicon wafer, and capturing impurities in the strain of the polycrystalline grain boundaries. The latter is EG (External Getterin
g) A typical example of the method. Since these two types have different impurity trapping mechanisms, they are used properly depending on the application. Briefly, the former (IG method) is effective in the case of a large amount of pollution, but it may not be effective in the small amount of pollution, whereas the latter (a method using a polycrystalline silicon film) is effective even in the case of a small amount of pollution. .

However, with the high integration of devices, the concentration of impurities affecting the device operation has dropped considerably from the conventional level. Therefore, in order to cope with the further lowering of the impurity concentration, there is a possibility that even the case of a slight amount of contamination cannot be achieved by the conventional back surface polycrystalline silicon film which is effective.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and provides a silicon single crystal wafer capable of providing a gettering ability even in a trace amount of contamination and a method for manufacturing the same. To aim.

[0007]

In order to solve the above problems, a silicon single crystal wafer of the present invention is a silicon single crystal wafer having a gettering ability, and a getter of impurities on the back surface of the silicon single crystal wafer. A high-concentration aluminum-containing layer having ring ability is formed.

The aluminum concentration in the aluminum-containing layer is preferably 10 ¹⁵ cm ^-3 to 10 ¹⁹ cm ^-3 .

The method for producing a silicon single crystal wafer according to the present invention is a method for producing the above-described silicon single crystal wafer according to the present invention, wherein the back surface of the silicon single crystal wafer is ion-implanted with aluminum at a predetermined dose to obtain impurities. To form a high-concentration aluminum-containing layer having a gettering ability.

The dose of aluminum is 10
A range of ¹¹ cm ^-2 to 10 ¹⁵ cm ^-2 is suitable.

In order to cope with a trace amount of contamination, it is preferable to use a layer separate from single crystal silicon and having a large solubility of impurities due to its trapping mechanism. A typical example thereof is the above-mentioned polycrystalline silicon film, and recently, a high-concentration boron-doped substrate of a p / p ⁺ epitaxial wafer may be considered for that purpose.

[0012] In both of these examples, silicon with various ideas is used for another layer as a gettering layer. Each of these measures has the effect of improving the solubility of impurities. However, these methods cannot dramatically increase the solubility of impurities.

In view of this, considering a separate layer made of completely different substances, there are substances having high solubility of impurities. For example, a method using an aluminum film is known (SA McHu
go, H. Hieslmair, ER Weber; Appl. Phys. A 64 (1
997) 127-137). This aluminum film has an extremely high solubility for impurities, and its gettering ability utilizing the segregation effect is so strong that it cannot be compared with the back surface polycrystalline silicon. Specifically, while the back surface polycrystalline silicon is on the order of ppm, aluminum has a solubility of several tens of percent. However, the melting point of the aluminum film is as low as 660 ° C,
Because it melts during the heat treatment of the device manufacturing process,
Not practical.

Therefore, aluminum has a high gettering ability.
We devised a method to make full use of its power and put it into practical use. So
This is the method of the present invention.
In order to form a high-concentration aluminum-containing layer.
It Here, the aluminum containing
Layered aluminum concentration is 10¹⁵cm^-3Above 10 ¹⁹
cm^-3The following are preferred. 10¹⁵cm^-3More aluminum
The presence of aluminum improves the gettering ability and also improves the solid solubility.
The limit is 10¹⁹cm^-3With the addition of more than
This is because elution and precipitation become problems.

According to the method of the present invention, it is possible to manufacture a wafer having a high gettering ability without leaching during the device manufacturing process while utilizing the characteristics of aluminum. In addition, since it has a gettering ability even for damage in the silicon crystal formed by ion implantation of aluminum, the segregation effect was used even during heavy contamination of heavy metals and heavy metals that do not have the segregation effect on the aluminum-containing layer. A gettering effect due to a mechanism different from gettering can be expected.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION One embodiment of the present invention will be described below with reference to the accompanying drawings, but it will be understood that various modifications other than the illustrated examples are possible without departing from the technical idea of the present invention. There is no end.

FIG. 1 is a sectional view showing one embodiment of a silicon single crystal wafer of the present invention. In the figure,
On the back surface 10b of the silicon single crystal wafer W having the front surface 10a and the back surface 10b, the high-concentration aluminum-containing layer 1 is formed.
2 is formed. With such a structure, the silicon single crystal wafer W has a high gettering ability. The aluminum concentration in the high-concentration aluminum-containing layer 12 is preferably 10 ¹⁵ cm ^-3 to 10 ¹⁹ cm ^-3 . If the aluminum concentration is less than 10 ¹⁵ cm ^-3 , the gettering ability may decrease, while 10 ¹⁹ cm
^If it exceeds ^-3 , elution and precipitation of aluminum may be a problem.

The high-concentration aluminum-containing layer 12 is preferably formed by ion-implanting aluminum into the back surface of the silicon single crystal wafer W. Since damage in the silicon single crystal wafer W formed by ion implantation of aluminum also has gettering ability, a synergistic effect with high gettering ability of aluminum can be achieved.

The dose of aluminum at the time of ion implantation of aluminum is preferably in the range of 10 ¹¹ cm ^-2 to 10 ¹⁵ cm ^-2 . With such a dose amount, a high-concentration aluminum-containing layer having a sufficient gettering ability for impurities can be formed.

[0020]

The present invention will be described in more detail with reference to the following examples, but it goes without saying that these examples are shown by way of illustration and should not be construed as limiting.

(Example 1 and Comparative Examples 1 and 2) According to the CZ method, the diameter was 6 inches and the initial oxygen concentration was 14 ppma (JEI).
A silicon single crystal ingot of DA standard) and orientation <100> was pulled at a normal pulling rate (1.2 mm / min). This silicon single crystal ingot was processed into a silicon single crystal wafer, and aluminum was ion-implanted on the back surface thereof at a dose amount of 10 ¹³ cm ^-2 (implantation energy was 50 keV). As a result, an aluminum-containing layer having an aluminum concentration of about 10 ¹⁷ cm ^-3 was formed on the back surface of the wafer. JEIDA is an abbreviation for Japan Electronics Industry Promotion Association (currently renamed to JEITA: Japan Electronics and Information Technology Industries Association).

Fe on the surface of the wafer was 6 × 10 ¹¹ cm
^After coating at a concentration of ^-2 and uniformly distributing Fe atoms in the wafer depth direction at 1000 ° C for 1 hr, 600 ° C for 1 hour
Impurities were captured in the high-concentration aluminum implantation layer by a Fe capture heat treatment for 5 minutes. The Fe concentration in the vicinity of the wafer surface before and after the impurity capture was measured by DLTS (Deep Level
Transient Spectroscopy) method was used. In addition to the wafer with an aluminum-implanted layer according to the present invention (Example 1) produced by the above procedure, a wafer with a back surface polycrystalline silicon (Comparative Example 1) produced by a conventional method from the above-mentioned silicon single crystal wafer, and The Fe concentration in the vicinity of the wafer surface was also measured by the DLTS method for the wafer without a gettering layer (Comparative Example 2) using the silicon single crystal wafer as it was, and compared with each other.

As a result, in the wafer without any gettering layer (Comparative Example 2), the Fe concentration was 1 × 10 ¹³ c.
It was m ⁻³ , and the value was such that all the Fe applied on the surface was uniformly diffused and dissolved in the wafer. On the other hand, in the wafer with the back surface polycrystalline silicon film (Comparative Example 1), F
A value of 3 × 10 ¹¹ cm ⁻³ was obtained as the e concentration, indicating a high gettering ability. On the other hand, in the wafer with the high-concentration aluminum implantation layer (Example 1), the Fe concentration was D
The lower limit of detection by the LTS method was 1 × 10 ¹¹ cm ⁻³ or less, and it was revealed that the wafer had a stronger gettering ability than the wafer with the back surface polycrystalline silicon film (Comparative Example 1).

Therefore, by injecting a wafer having a high-concentration aluminum-containing layer on its back surface into a device process, even in a device process at a low temperature of 1000 ° C. or less, heavy metal impurities such as Fe are effectively gettered. It turned out to be possible.

The present invention is not limited to the above embodiment. The above embodiments are mere examples, and any of those having substantially the same configuration as the technical idea described in the scope of claims of the present invention and exhibiting the same operational effect It is included in the technical scope of.

For example, in the present invention, the method for forming the high-concentration aluminum-containing layer is not limited to ion implantation, and any method may be adopted as long as the high-concentration aluminum-containing layer is formed. Therefore, a method of forming the high-concentration aluminum-containing layer by thermal diffusion is also included in the scope of the present invention. When the high-concentration aluminum-containing layer is formed by thermal diffusion, unlike ion implantation, another type of gettering ability due to damage cannot be added, but there is an advantage that a thick aluminum-containing layer can be formed at low cost.

[0027]

As described above, the silicon single crystal wafer having the gettering ability of the present invention can effectively utilize the high gettering ability of aluminum, and is sufficient for the gettering even with a trace amount of contamination. You can exert your ability. Further, according to the method of the present invention, the silicon single crystal wafer having the gettering ability of the present invention can be efficiently manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one embodiment of a silicon single crystal wafer of the present invention.

[Explanation of symbols]

10a: front surface, 10b: back surface, 12: aluminum-containing layer, W: wafer.

Claims (4)

[Claims] 1. A silicon single crystal wafer having a gettering ability, wherein an aluminum-containing layer having an gettering ability of impurities is formed on the back surface of the silicon single crystal wafer. 2. Aluminum in the aluminum-containing layer
Mu concentration is 10¹⁵cm ^-3-10¹⁹cm^-3Characterized by
The silicon single crystal wafer according to claim 1. 3. The method for manufacturing a silicon single crystal wafer according to claim 1, wherein the back surface of the silicon single crystal wafer is ion-implanted with a predetermined dose amount of aluminum, and the aluminum has a gettering ability of impurities. A method for manufacturing a silicon single crystal wafer, which comprises forming a containing layer. 4. The dose amount of aluminum is 10 ¹¹ c.
The method for producing a silicon single crystal wafer according to claim 3, wherein m ⁻² to 10 ¹⁵ cm ⁻² .