JP2000306915A - Manufacture of silicon wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a gettering effect enough for repeated heat treatment, avoiding recrystallization of polysilicon, by stacking polycrystalline silicon on it after forming a silicon carbide film layer on a single crystalline silicon face prior to stacking the polycrystalline silicon. SOLUTION: A silicon carbide(SIC) film layer 2 is made on the rear side of a single crystalline silicon wafer 1, and a polycrystalline silicon (polysilicon) layer 3 is made on the SIC film layer 2. When applying gettering to the rear side (the opposite side of a device process face) of this silicon wafer 1, in the first place an SIC film layer 5-40 nm thick is made on this rear face. A polycrystalline silicon layer 0.5-2 nm thick is made on this SIC film. Hereby, the polycrystalline silicon layer is made in equal thickness with excellent adhesive force. The single crystallization by the epitaxial recrystallization of the polysilicon layer does not occur even by heat treatment, and the gettering performance of the layer does not drop.

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 a silicon wafer, and more particularly, to forming a gettering site by depositing polycrystalline silicon (polysilicon) on the back surface of a single crystal silicon wafer in a silicon wafer manufacturing process. The present invention relates to a method for manufacturing a silicon wafer.

[0002]

2. Description of the Related Art In the manufacture of silicon wafers for semiconductors, gettering treatment is performed to remove and capture impurities such as heavy metals and sodium which deteriorate device characteristics. There are various methods for this gettering, one of which is the PBS method (Polysilicon Ba).
ck Sealing method). This method is one of the so-called “extriding gettering method”, in which polysilicon is deposited on the back surface of a single-crystal silicon wafer (opposite to the device process surface of a semiconductor wafer) to have a thickness of about 1 to several μm. Is formed. The grain boundaries in the formed polysilicon layer and the interface between the single crystal silicon wafer and the polysilicon layer are used as gettering sites for capturing impurities such as heavy metals and sodium which migrate during the wafer heat treatment in the process. . The formation of the polysilicon film layer in the PBS method is as follows.
It is carried out at the beginning of the wafer manufacturing process or at an appropriate time during the process. Conventionally, this polysilicon film layer is usually formed by slicing a silicon ingot, wrapping it, removing the distortion by etching, and then depositing polysilicon directly on the back surface of the wafer single crystal silicon by, for example, a low pressure CVD method. Was formed.

[0003]

However, in the conventional method in which a polysilicon film layer is formed directly on the back surface of a single crystal silicon wafer, the polysilicon at the formation interface is formed on the silicon wafer by a solid reaction due to a heat treatment in a subsequent process. To recrystallize. In addition, at this time, since the silicon wafer of the substrate is single crystal, crystal growth of the polysilicon from the interface with the surface of the silicon single crystal substrate occurs in an epitaxial manner, leading to single crystallization of polysilicon from the portion. However, there is a technical problem that the number of gettering sites decreases accordingly. Furthermore, as the heat treatment of the wafers in the process overlaps, single crystallization by recrystallization solid phase growth of the polysilicon layer progresses, the polysilicon phase decreases and becomes thinner, and in extreme cases, the polysilicon disappears. Leads to. Therefore, there has been a problem that the number of gettering sites is extremely reduced and the gettering ability is reduced.

Some proposals have already been made regarding a method for improving the gettering ability of the polysilicon layer and a method for avoiding the disadvantage of recrystallization of polysilicon.
For example, Japanese Patent Application Laid-Open No. 1-253242 discloses that when polysilicon is deposited on the back surface of a silicon wafer to form a gettering site, the polysilicon on the single crystal silicon is monocrystalline before the deposition of the polysilicon. A method for manufacturing a semiconductor wafer, characterized by ion-implanting impurities that suppress solid phase growth into the back surface of the wafer, is disclosed in the specification, as a suitable ion-implanted impurity,
Nitrogen, oxygen or argon are mentioned. Japanese Patent Application Laid-Open No. 5-206144 discloses a method of forming a strained layer due to mechanical damage on the back surface of a silicon wafer and then forming a polysilicon film layer on the strained layer to improve the gettering ability. In addition, Japanese Patent Application Laid-Open No. 1-315144 discloses that one surface of a single crystal silicon substrate is oxidized to form a silicon oxide film having a thickness of 1 to 8 °, and this silicon oxide film is heated with gaseous silanes. There is disclosed a method of manufacturing a silicon wafer in which a polysilicon layer is formed on the silicon oxide film by making contact therewith.

However, Japanese Patent Application Laid-Open No. Hei.
The method disclosed in Japanese Patent Publication No. 2 requires complicated steps such as an ion implantation step, and requires appropriate control of an ion implantation dose amount, implantation energy, and the like. Other methods require gettering for repeated heat treatment. It is not always sufficient to be adopted in an industrial-scale production process as a simple and effective method, for example, the effect is not long-lasting and it is difficult to uniformly adjust the thickness to an appropriate silicon oxide layer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and avoids the inconvenience of recrystallization of polysilicon and forms a large number of gettering sites at the layer or at the interface between the layers. This provides a simple and effective method of manufacturing a silicon wafer capable of forming a gettering site of a semiconductor silicon wafer that can maintain a sufficient gettering effect even with repeated heat treatments and can be easily applied to an industrial-scale manufacturing process. The purpose is to provide.

[0007]

According to the present invention, in forming a gettering site by depositing a polycrystalline silicon layer on the back surface of a single crystal silicon wafer, prior to depositing the polycrystalline silicon, A method for manufacturing a silicon wafer is provided, wherein a silicon carbide thin film layer is formed on a crystalline silicon surface, and then polycrystalline silicon is deposited on the silicon carbide thin film layer.

In the production of a silicon wafer for a semiconductor, a so-called gettering process for forming a site for trapping an impurity (atom) that enters due to thermal diffusion or mixing during a device process is performed. According to the present invention, during the gettering process, polysilicon is deposited on the back surface of a single crystal silicon wafer to form a polysilicon film layer having a thickness of about 1 to several μm, and grain boundaries in the formed polysilicon layer are formed. The so-called PBS method is improved in that the interface between the single crystal wafer and the polysilicon layer is a gettering site for capturing impurities such as heavy metals and sodium that migrate during the wafer heat treatment in the process.

When polysilicon is directly formed on the back surface of a silicon wafer by the conventional PBS method, the subsequent heat treatment causes the polysilicon at the formation interface to be recrystallized by a solid phase reaction. At this time, since the silicon wafer of the substrate is a single crystal, the crystal growth by recrystallization starting from the interfacial polysilicon occurs in an epitaxial state and becomes a single crystal.
Naturally, the portion of the polysilicon that has grown in the epitaxial single crystal state has fewer defects and dislocations than the polysilicon phase (polycrystalline silicon phase), so that the number of gettering sites is reduced. Then, when the heat treatment is repeatedly performed on the wafer after the gettering site is formed by the polysilicon layer, the polysilicon phase of the layer decreases due to the progress of single crystallization by recrystallization solid phase growth of the polysilicon layer. It becomes thinner and, in extreme cases, the polysilicon disappears. As described above, the gettering site of the silicon wafer is extremely reduced, and the gettering ability is reduced.

In order to prevent this inconvenience, the method for manufacturing a silicon wafer according to the present invention requires a step of forming a silicon carbide (Si) layer before forming a polysilicon layer on the back surface of the wafer substrate.
C) A feature is that a thin film is formed in advance on the substrate surface, and then a polysilicon film layer is formed.

That is, due to the difference in crystal lattice constant between SiC and Si (there is a lattice mismatch of about 20% between Si and SiC), single crystal of polysilicon is prevented. In general, the rate of epitaxial growth is greatly affected by temperature conditions (epitaxy temperature), the state of a single crystal on a substrate surface, its structure, especially the difference between the crystal lattice size of the substrate and the lattice size of the crystal to be epitaxially grown, and the like. . Usually, polycrystalline silicon (polysilicon) directly grown and formed on a silicon single crystal substrate is silicon (S).
i) recrystallization (single crystallization) in a solid state when subjected to a heat history due to a heat treatment at a temperature of about の of the melting point,
It has a tendency to exhibit the so-called solid phase epitaxial growth phenomenon, but this growth is almost completely suppressed by inserting an SiC film layer having a different crystal lattice constant from Si.

An SiC thin film layer manufactured by the method of manufacturing a silicon wafer according to the present invention, that is, a thermally and chemically stable substance, is inserted as an intermediate layer, and a polysilicon layer is formed on the surface of this layer. The deposited silicon wafer can trap impurity metal atoms at the interface between the silicon substrate single crystal and the SiC interface and between the SiC and the polysilicon interface, so that the gettering effect is further enhanced. Also,
In the method of manufacturing a silicon wafer according to the present invention, when the SiC phase to be formed is a polycrystalline SiC phase, this effect is particularly remarkable, and the polycrystalline SiC is deposited on the polycrystalline silicon (poly). Since a large number of nuclei required for silicon (Si) crystal growth are supplied, there is also an advantage that formation of a polysilicon crystal phase can be achieved uniformly and at high speed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a method of manufacturing a silicon wafer according to the present invention, as shown in FIG. 1, a silicon carbide (SiC) thin film layer 2 is formed on the back side surface of a single crystal silicon wafer 1.
A polycrystalline silicon (polysilicon) layer 3 is formed on the SiC thin film layer 2. The single crystal silicon wafer used in the present invention is subjected to a process usually performed in a general manufacturing process of a silicon wafer for semiconductors, that is, slicing of a silicon single crystal ingot, surface lapping of the sliced wafer, and subsequent chemical etching. Thickness of 300 to 2000 μm, which has been polished through a process such as surface layer etching removal of several tens μm or less by
m is used.

In the method of manufacturing a silicon wafer according to the present invention, as described above, when performing the gettering process on the back side (the side opposite to the device process surface) of the silicon wafer, first, an SiC thin film layer is formed on the back side. Let it form. In the present invention, the thickness of the SiC film formed on the single crystal silicon substrate is usually 5 to 40 nm, more preferably 5 to 20 nm. If the film thickness is less than 5 nm, the thickness of the polysilicon layer formed thereon tends to be non-uniform, the adhesion is not sufficient, and the crystal grains of the formed polysilicon layer are large. Therefore, it is not preferable. On the other hand, when the thickness exceeds 40 nm, when impurities in the single crystal silicon substrate migrate to the polysilicon layer, the thickness of the SiC layer is too large, which becomes an obstacle, and lowers the gettering ability.

An SiC film is formed on the surface of a single crystal silicon wafer.
Before forming, first attach to the surface of the single crystal silicon substrate.
Oxides and contaminants, such as dilute hydrofluoric acid
And then rinsed with pure water etc. and dried
Is preferred. In particular, as a method of forming a SiC thin film layer,
Although not limited, for example, C _Three H₈ , C_Two H
_Four , C_Two H_Two Using hydrocarbons such as
To form SiC layer by carbonization of wafer surface Si
Method, SiH_Four , SiHCl_Three , SiCl_Four Si
Source, C_Three H₈ , C_Two H_Four , C_Two H_Two C source, carrier, etc.
H as gas_Two Reaction at 1300 to 1800 ° C using
By a gas phase reaction method (CVD method)_Three Si
Cl_Three For thermal decomposition of compounds containing the same number of atoms as Si and C
In addition to the so-called pyrolysis method, graphite, C
_Two H_Two Molecular beam epitaxy using a carbon source such as
BE method) can be used.

The formed SiC film layer may be a single crystal layer,
A polycrystalline layer may be used, and cubic 3C-SiC or hexagonal 6H-SiC may be used. However, when a polysilicon film layer (polycrystalline silicon film layer) is subsequently deposited, a large number of crystal growth nuclei are formed. From the point that crystal grain size of 0.
More preferably, the polycrystalline phase has a thickness of about 05 to 0.5 μm.

In the present invention, on this SiC film,
A polycrystalline silicon (polysilicon) layer is formed. The thickness of the polycrystalline silicon layer is 0.5 to 2 μm, preferably 0.1 to 2 μm.
5 to 1 μm, and the crystal grains thereof are not amorphous but 2 μm or less, preferably 0.05 to 0.5 μm.

In order to form a polycrystalline silicon layer on the SiC film, the single crystal substrate is formed in an atmosphere of gaseous silanes diluted with nitrogen gas, argon gas or the like.
800 ° C., preferably at a temperature of 600-700 ° C.
It is carried out by heating under reduced pressure or normal pressure for up to 7 hours, preferably 1 to 2 hours. An example of a preferable method for forming the polycrystalline silicon layer is a thin film formation by a low pressure CVD method. The silanes used include monosilane (SiH ₄ ), dichlorosilane (Si
H ₂ Cl ₂ ), monochlorosilane (SiH ₃ CI) and the like.

In the silicon wafer manufactured by the method for manufacturing a silicon wafer according to the present invention, since the SiC layer having a specific thickness is formed on the surface of the single crystal silicon substrate, the polycrystalline silicon layer has excellent adhesion. A uniform thickness is formed by force. In addition, the SiC film layer provides a growth nucleus necessary for growing the polycrystalline silicon layer. If the SiC film is not formed, the polycrystalline silicon layer grows in an island shape with dirt and the like as nuclei, so that uniformity of the growth rate cannot be ensured. On the other hand, when the SiC film layer is formed as in the silicon wafer manufactured by the method for manufacturing a silicon wafer according to the present invention, the polycrystalline silicon is uniformly and rapidly grown.

In the method of manufacturing a silicon wafer according to the present invention, the SiC film is formed on the back surface of the silicon single crystal substrate, and the polycrystalline silicon layer (polysilicon layer) is formed thereon. Not only is performed uniformly and at high speed, but also the formed polysilicon layer does not undergo single crystallization due to epitaxial recrystallization of the polysilicon layer even after multiple heat treatments in the subsequent semiconductor wafer processing step, Gettering performance does not decrease.

[0021]

EXAMPLE 1 A single-crystal silicon wafer having a thickness of 700 μm was immersed in a 1% hydrofluoric acid aqueous solution to remove impurities such as a natural acid film adhered to the back surface, and then rinsed with pure water. And further dried with a spin dryer. The device process surface of the silicon single crystal substrate after the drying is sealed, and SiH ₄ and CH
_According to a well-known method of reacting at 1100 ° C. using ₄ ,
SiC films having thicknesses of 5, 20 and 40 nm were formed. Next, a silane gas (Si
H ₄ ) was thermally decomposed at 650 ° C. using hydrogen gas as a carrier to deposit about 1.5 μm of a polysilicon layer in the form of a SiC film. The size of the crystal grains in these polysilicon layers was measured. Next, the obtained polysilicon film layer forming wafer is set in a heat treatment furnace, and the wafer is placed in an argon atmosphere for 12 hours.
The crystal grain size of the polysilicon film formed by heat treatment at 00 ° C. for 60 minutes and 120 minutes was measured. Table 1 shows the results.

"Comparative Example 1" A single-crystal silicon wafer substrate similar to that of Example 1 was subjected to impurity removal, pure water rinsing and drying in the same manner as in Example 1, and a polysilicon layer was directly formed on the back surface of this wafer substrate under reduced pressure. It was deposited to a thickness of about 1.5 μm by the CVD method. The gettering performance of the obtained polysilicon film layer-formed wafer substrate was evaluated in the same manner as in Example 1.

As can be seen from Table 1, the Si of the present invention
It is understood that the growth of the crystal forming the polysilicon layer is suppressed in the silicon wafer on which the polysilicon layer is formed via the C film even if the heat treatment is performed. Thereby, the gettering performance can be maintained for a long time.

[0024]

[Table 1]

[0025]

As described above, a silicon wafer manufactured by the method for manufacturing a silicon wafer according to the present invention is provided on a single-crystal silicon substrate through a silicon carbide film layer formed to a specific thickness. Due to the difference in the lattice constant between the SiC crystal and the Si crystal, single-crystallization due to epitaxial recrystallization of the polysilicon layer occurs even in the subsequent heat treatment in the semiconductor wafer processing step. And the gettering performance of the layer does not decrease. Further, the adhesiveness and the homogeneity with the polysilicon layer are also excellent, and therefore, it is suitably used as a material having a high yield as a device of a high-density integrated circuit.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining a layer configuration of a silicon wafer manufactured by a method of manufacturing a silicon wafer according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Single crystal silicon wafer 2 Silicon carbide (SiC) thin film layer 3 Polycrystalline silicon (polysilicon) layer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K030 AA05 AA06 AA09 AA17 BA29 BA37 BB03 CA12 DA03 HA01 JA01 JA09 5F045 AA03 AA05 AA06 AB03 AB06 AC01 AC03 AC05 AC07 AC15 AC16 AD10 AD11 AD16 AD17 AD18 AF03 BB09 BB70 BB18 DA61 5F058 BA10 BC20 BE10 BF02 BF23 BF24 BF26 BH20 BJ01 BJ10

Claims (5)

[Claims] In forming a gettering site by depositing a polycrystalline silicon layer on the back surface of a single crystal silicon wafer, a silicon carbide thin film layer is formed on the single crystal silicon surface prior to depositing the polycrystalline silicon. A method for manufacturing a silicon wafer, comprising forming polycrystalline silicon on a silicon carbide thin film layer after forming. 2. The silicon carbide thin film layer has a thickness of 5 to 40.
2. The method for manufacturing a silicon wafer according to claim 1, wherein 3. The method according to claim 1, wherein the silicon carbide thin film layer is a polycrystalline silicon carbide thin film layer formed by a CVD method. 4. The polycrystalline silicon film layer has a thickness of 0.5
4. The method for manufacturing a silicon wafer according to claim 1, wherein the thickness is from 2.0 μm to 2.0 μm. 5. 5. The method according to claim 1, wherein the polycrystalline silicon film layer is formed by low pressure CVD.
5. The method for manufacturing a silicon wafer according to claim 1, wherein the silicon wafer is formed by deposition.