JPH11274021A - Manufacture of wafer and <111> wafer manufactured thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize the in-plane resistivity distribution of a wafer obtained from a single crystal, having a specified crystal orientation (just angle) by reinclining a single crystal grown from a seed crystal, having the specified crystal orientation reinclined by a specified angle from the just angle by the floating zone method to the just angle and slicing it. SOLUTION: Using (S11) a seed crystal which is inclined at about 4 deg. from the just angle of the crystal orientation <111> to the crystal orientation <112>, an Si single-crystal ingot of the crystal orientation <111> according to desired wafer diameter is produced (S12). After forming an orientation flat on the ingot (S13), it is reinclined to the just angle made corresponding to the inclination angle of about 4 deg. (S14) and sliced to produce a slice wafer (S15), and the circularizing S16, lapping S17, etching S18 and polishing S19 steps are conducted to complete a mirror surface finish wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a wafer from a silicon ingot having a crystal orientation of <111> by the FZ method and a <111> wafer produced by the production method. <1
11> Wafer manufacturing method and <
111> wafer.

[0002]

2. Description of the Related Art Semiconductor single crystal production methods include a Czochralski method (CZ method) and a floating zone method (hereinafter referred to as FZ method).
Method), and the FZ method is advantageous in that a higher purity single crystal can be obtained as compared with the CZ method.

Next, a method for producing a Si single crystal by the FZ method will be schematically described with reference to FIG. 3. A polycrystalline raw material having a conical tip processed in a metal chamber 2 held in an argon atmosphere or a vacuum atmosphere. The rod 3 is held vertically, and the tip of a prismatic seed crystal 8 having a side of 5 mm, for example, is disposed coaxially near the lower end thereof, and the lower end of the polycrystalline raw material rod 3 is heated and melted by the high-frequency induction heating coil 4. The upper end of the seed single crystal 8 is melted or heated to the vicinity thereof by the radiant heat, and is welded to the polycrystalline raw material rod 3.
Is gradually melted, and after thermal equilibrium is reached, crystal growth from seed single crystal 8 begins.

In the initial stage of crystal growth, the diameter is, for example, 2-3 mm.
After this state is continued until the length becomes, for example, 20 mm or more, the diameter is increased. From the point when the crystal growth of the seed single crystal 8 starts to increase in diameter until the target diameter (diameter) is reached, the single crystal grows in an inverted conical shape (hereinafter referred to as a cone). After that, the process enters into a process of controlling to a constant diameter (hereinafter referred to as a straight body manufacturing process). Thereafter, the polycrystalline raw material rod 3 and the single crystal rod 7 move in the axial direction relatively to the heating coil 4, and when the effective length of the polycrystalline raw material rod 3 is reached, the polycrystalline raw material and the single crystal part are cut off. The production of the crystal ingot ends.

In the conventional FZ method, the main growth axis is <
When manufacturing a wafer with a <111> just angle, a single crystal seed crystal of a <111> just angle is used to manufacture a single crystal ingot of a <111> just angle corresponding to a target wafer diameter. Wafer processing such as slicing is added. (First prior art)

[0006]

The uniformity of the in-plane resistivity distribution on a wafer has a great effect on the device yield, and it is necessary to make the in-plane resistivity distribution uniform in order to improve the device yield. There is. However, when a <111> silicon single crystal is manufactured by a conventional method, the temperature outside a facet (off-facet region) formed near the center of the single crystal is almost the same at each position, and this region is overcooled. Then, step growth occurs from this region toward the center, and the (111) facet is easily formed. That is, the moving speed of the step increases.

This tendency is particularly remarkable when the melt convection at the center of the FZ method is weak. That is, since the impurity concentration increases in proportion to the moving speed of the step, the dopant is easily taken in during facet growth. Therefore, when the <111> silicon single crystal is manufactured by the first conventional technique, there is a problem that the resistivity at the central portion of the wafer decreases and the in-plane resistivity distribution becomes non-uniform.

Further, since the convection of the melt at the outer peripheral portion in the FZ method is weak, when a silicon single crystal having a <111> just angle is produced by a conventional method,
The growth of the interface facet formed in the crystal peripheral portion is delayed and supercooled, so that the melt tends to protrude into an overhang state, and the diameter increases. This overhang state of the crystal outline is called bump. When the bumps grow, there is also a problem that a dripping trouble in which the melt is dripped from the outer wall of the crystal or a disorder trouble in which the single crystal is polycrystallized easily occurs.

According to the present invention, the crystal orientation <111 is determined by the FZ method.
It is an object of the present invention to provide a method for producing a wafer capable of making the in-plane resistivity distribution uniform when producing a wafer from the silicon ingot of <1> and a wafer produced by the producing method. Another object of the present invention is to provide an orientation <111> by the FZ method.
It is an object of the present invention to provide a wafer manufacturing method capable of preventing the occurrence of bumps on the surface of the single crystal when the single crystal is manufactured, thereby reducing the drip trouble and the disorder trouble.

[0010]

According to the first aspect of the present invention, a single crystal is grown by using a seed crystal whose orientation is slightly inclined from a just angle of the crystal orientation <111>. The second feature is that the single crystal obtained by the first feature is subjected to slice cutting after reorienting the crystal orientation <111> to a just angle when performing slice cutting. <111
> To manufacture just-angled wafers.

In this case, when a single crystal is manufactured, <111
> If the angle of inclination from the just angle is too small, the effect of improving the in-plane resistivity distribution and the effect of reducing the hump are too small, and if the angle is too large, it is wasteful to return the obtained single crystal to the just angle for slicing. Too many parts. Therefore, considering these points, the tilt angle is 1 °
Is desirably in the range of 30 ° to 30 °.

That is, according to the first aspect of the present invention, an ingot obtained by growing a single crystal by the FZ method using a seed crystal whose orientation is inclined by a predetermined angle from the just angle of the crystal orientation <111> is adjusted to correspond to the inclination angle. Then, the wafer is tilted back to a just angle, and then sliced to produce a sliced wafer. In this case, since the slice wafer is slightly elliptical,
The invention described in (1) is characterized in that chamfering is performed after the slice cutting, and rounding of the slice wafer is performed. In the invention according to claim 3, the inclination angle from the <111> just angle is set to 1 ° to 30 °.

According to a fourth aspect of the present invention, the <111> wafer manufactured by the FZ method is specified, and the in-plane resistivity of the wafer takes a local maximum value at a central portion and a maximum value at an outermost peripheral portion. It is characterized by being larger than the maximum value.

[0014]

When the FZ growth is performed using the seed single crystal tilted from the <111> just angle, the temperature of each part outside the facet (off facet region) formed near the center of the single crystal is different. Therefore, overcooling in the entire region is reduced. Therefore, step growth from this region toward the center is unlikely to occur, and facet growth at the center of the melt can be suppressed, so that the dopant is not excessively taken in. As a result, the resistivity at the center increases, and the in-plane resistivity distribution is made uniform.

That is, <11 manufactured by the conventional FZ method.
1> With respect to the wafer, the resistivity on the outer peripheral side of the wafer was the highest and tended to gradually decrease as it proceeded toward the center. However, according to the present invention, the resistivity of the wafer has a maximum value at the center. Therefore, the variation range of the in-plane resistivity becomes smaller than in the past.

Further, when zoning is performed using a seed single crystal tilted from the <111> just angle, facet growth is also suppressed at the outer peripheral portion of the melt, and supercooling due to delay in growth of interface facets is caused. The occurrence of bumps can be suppressed, thereby preventing the occurrence of bumps. As a result, dripping troubles and turbulence troubles are reduced.

As a technique similar to the present invention by the present applicant, as a method of obtaining a single crystal inclined at 3 ° from the <111> orientation with good yield, the seed crystal itself is inclined at a required angle from the main crystal orientation to grow a single crystal. Technology to perform
No. 242983. (Second conventional technology)

However, such a technique is mainly applied to the CZ method, and is less than <11
1> When cutting a crystal wafer, 4 ° or 3 ° from the main axis
The slice cutting must be performed at an angle, and the loss of a single crystal due to the inclined cutting increases as the diameter of the wafer increases. For this reason, the second prior art eliminates the inclined cutting at the time of wafer slice cutting by performing the single crystal growth by tilting the seed crystal itself by 3 to 4 ° in advance, and enables the slice cutting in the direction orthogonal to the main axis. I have to.

However, even if the seed crystal itself is inclined at a required angle from the main crystal orientation and the ingot on which the single crystal is grown is sliced in a direction perpendicular to the main axis, the in-plane resistivity cannot be made uniform. Therefore, in this prior art, the ingot is sliced in a direction perpendicular to the main axis in order to prevent the loss of the single crystal from increasing with the increase in the diameter of the wafer. After re-tilting to a just angle corresponding to the angle, by cutting the slice to produce a slice wafer,
Uniformity of the in-plane resistivity is achieved. Therefore,
The present invention is different from the conventional art in any of the objects, configurations, and effects, and is a similar and different technology.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. However, unless otherwise specified, dimensions, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the invention, but are merely illustrative examples.

First, a flow from the production of a single crystal based on the FZ method to the fabrication of a wafer according to the conventional technique for producing a <111> wafer will be described with reference to FIG. In FIG. 2, a <111> just-angled silicon single crystal seed crystal is used (S1), and a <111> just-angled silicon single crystal ingot corresponding to an intended wafer diameter is manufactured based on the FZ apparatus in FIG. Then, after the ingot is cylindrically polished to form a notch or orientation flat (S3), the ingot is sliced in a direction orthogonal to the main axis of the ingot using an inner peripheral blade or a wire saw. (S4)

Thereafter, as is well known, a slice wafer chamfering step (S5), a lapping step (S6) for flattening the cut surface, an etching step (S7) for removing the processing strain in each of the above steps, and a mirror polishing of the main surface of the wafer. Polishing process (S
Through 8), the target mirror surface wafer is manufactured.

FIG. 1 is a flow chart showing a flow from a single crystal production based on the FZ method to a wafer processing according to an embodiment of the present invention. In the present embodiment, the crystal orientation <11
4 ° from <1> just angle to <112> plane
Using a tilted seed crystal (hereinafter referred to as a 4 ° off-angle seed) (S11), <1 depending on the target wafer diameter
11> A silicon single crystal ingot is manufactured based on the FZ apparatus of FIG. 3 (S12), and the ingot is cylindrically polished and processed into a notch or orientation flat (S13), and is then tilted to a just angle corresponding to the above-mentioned tilt angle. After that (S14), slice cutting is performed using an inner peripheral blade or a wire saw to produce a slice wafer. (S15)

In this case, since the slice wafer is slightly elliptical, the outer periphery is ground during the chamfering grinding after the slice cutting, and the slice wafer slightly elliptical due to the 4 ° inclination is rounded. Perform processing.
(S16) Then, similarly to the known technique, a lapping step (S17) for flattening the cut surface, an etching step (S18) for removing the processing strain in each step, and a polishing step for mirror-polishing the main surface of the wafer are performed. The target mirror surface wafer is manufactured.
(S19)

FIG. 4 shows that from <111> just angle <
The in-plane resistivity distribution of a <111> silicon single crystal wafer manufactured using a seed crystal tilted 4 ° in the direction of the 112> plane (hereinafter referred to as a 4 ° off-angle seed) and the <100> just-angle seed 5 <φ <1 manufactured under the same conditions
00> In-plane resistivity distribution of silicon single crystal wafer and <
111><111 when using just-angled species
The comparison of the in-plane resistivity distribution of the silicon single crystal wafer is shown below. The diameter of the single crystal wafer is 125 mmφ.
It is.

As is apparent from FIG. 2, in the case of the conventional wafer of the <111> just-angle single crystal manufactured according to the flow shown in FIG. 2, the resistivity decreases from the outer peripheral side toward the center, and the center decreases. It can be seen that the resistivity of the portion is very low. However, the resistivity of the wafer according to the present embodiment manufactured from the <111> 4 ° off-angle type decreases as it goes from the outer peripheral side to the center, but the resistivity increases in a region 20 mm outside the center and the center increases. It can be seen that the resistivity of the portion increases to the same level as the <100> silicon single crystal.

Incidentally, in the ingot using the <111> just angle type of the prior art, a large bump is generated on the surface over the entire straight body from the start of the cone. However, when the <111> 4 ° off-angle type of the present embodiment was used, although bumps occurred at the initial stage of the cone (around 30 mmφ), no bumps were observed thereafter.

Next, the following Table 1 shows that the diameter of the single crystal is 125 m.
A comparison table of the trouble occurrence rate in the case of the prior art using the <111> just angle type and the trouble occurrence rate in the case of the present embodiment using the <111> 4 ° off angle type at mφ is shown. It can be seen that when the <111> 4 ° off-angle type is used, the trouble occurrence rate is reduced to １ ／ compared to when the <111> just-angle type is used.

[0029]

[Table 1]

[0030]

As described above, according to the present invention, it is possible to make the in-plane resistivity distribution uniform by preventing the resistivity from decreasing in the central portion, and to prevent the occurrence of bumps on the single crystal surface. This has the effect of reducing dripping troubles and turbulence troubles.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a flow from a single crystal production based on an FZ method to a wafer processing according to an embodiment of the present invention.

FIG. 2 is a flow chart showing a flow from a single crystal production based on the FZ method to a wafer processing according to a conventional technique.

FIG. 3 is a schematic explanatory view of an apparatus for producing a Si single crystal by the FZ method.

FIG. 4 shows the in-plane resistivity distribution of the <111> single crystal wafer of the present embodiment manufactured using the 4 ° off-angle seed and the 5 ″ φ manufactured under the same conditions using the <100> just-angle seed. FIG. 3 is a comparison diagram showing an in-plane resistivity distribution of a <100> single crystal wafer and an in-plane resistivity distribution of a conventional <111> single crystal wafer, respectively.

[Explanation of symbols]

 Reference Signs List 1 upper shaft 2 metal chamber 3 polycrystalline raw material rod 4 induction heating coil 5 melting zone 6 solid-liquid interface 7 single crystal rod 8 seed single crystal 9 lower shaft

Claims (4)

[Claims] 1. A floating zone method (FZ method)
<11 by a semiconductor single crystal ingot manufactured by
1> In a method of manufacturing a wafer, an ingot obtained by growing a single crystal using a seed crystal whose orientation is tilted by a predetermined angle from a just angle of a crystal orientation <111> is tilted to a just angle corresponding to the tilt angle. A wafer manufacturing method, which comprises cutting a slice, cutting the slice, and manufacturing a slice wafer. 2. The wafer manufacturing method according to claim 1, wherein a chamfering process is performed after the slice cutting to round the slice wafer. 3. The wafer manufacturing method according to claim 1, wherein seeds having an inclination angle from 1 ° to 30 ° from the <111> just angle are used. 4. In a <111> wafer manufactured by slicing a semiconductor ingot manufactured by the FZ method, the in-plane resistivity of the wafer takes a local maximum value at a central portion and a local maximum value at an outermost peripheral portion. Characterized by being greater than
111> wafer.