JP2001257243A - Method for measurig fine particle on silicon wafer surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure fine particles that are less than the detection lower-limit value by a particle counter without nearly being affected by surface haze, and to measure only fine particles by the particle counter with a detection lower- limit value of 0.08 or 0.065 μm. SOLUTION: After a silicon single crystal layer of 1 μm or more is subjected to epitaxial growth on the surface of a mirror-surface silicon wafer or an epitaxial one for forming, the state of scattered defects on the surface of the mirror-surface silicon wafer or the epitaxial wafer is measured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for measuring fine particles present on the surface of a silicon wafer.

[0002]

2. Description of the Related Art As a method of reducing the influence of growth defects existing in a silicon single crystal formed by the Czochralski method (hereinafter referred to as CZ method) on device electrical characteristics, a pulling speed (in the crystal pulling process) is used. V) and a method of optimizing V / G defined by the crystal temperature gradient (G) in the pulling direction, a method of reforming the vicinity of the wafer surface by heat treatment in a hydrogen gas atmosphere or an argon gas atmosphere in a wafer state, Alternatively, there is a method in which a silicon single crystal layer is grown on the wafer surface to form an epitaxial wafer (hereinafter, referred to as epi-wafer). This epitaxial wafer has a grown-in defect (C) existing in a silicon single crystal formed by the CZ method as a substrate.
The effect of OPs and dislocation clusters on epitaxial growth has been reported (Kimura et al., Japan Society of Applied Physics 30p-L-1)
0,11 (1997) .2, Furukawa et al., Autumn Society of Applied Physics 2p-S-8 (1999).
3). Here, COPs (crystal-originated particles) refer to shallow etch pits that appear on the wafer surface. The COP is a kind of defect caused by a crystal grown from the silicon melt. In addition, stacking faults and the like are listed as surface defects peculiar to epiwafers, and it has been reported that the cause of these defects is related to fine particles such as organic substances attached to the substrate surface (Iwabuchi et al., Spring Applied Physics) Society 28a-PB-1 (1998)).

Conventionally, C existing on the wafer surface
The position, size, number, density, etc. of defects such as OPs and fine particles are mainly measured by a particle counter. Particle counter (light scattering automatic particle
The counter) is for recognizing the position, size and number of particles or defects by scanning the wafer surface with a strong light beam such as a laser and measuring the light scattering intensity from the particles or defects. Previous particle counters used polystyrene latex particles (pol
ystyrene latex particles, hereinafter referred to as PSL particles. )
Although the lower limit of detection was 0.10 μm in the conversion size according to the above, a particle counter using 0.08 μm and 0.065 μm as the lower limit of detection has recently been developed. When the surface haze is low, such as a polished wafer, the lower limit of detection of the particle counter can be relied upon.However, when the surface haze is generally high, such as a heat-treated wafer or an epiwafer, the haze is low. When the effect of (1) is removed, the lower limit of detection becomes about 0.12 μm.

[0004]

However, the influence on the manufacturing yield, device characteristics, and reliability due to the stacking faults of the epi-wafer is increasing more and more, and in a particle counter having a lower detection limit of 0.12 μm,
There has been a problem that it is not possible to sufficiently measure the fine particles that cause stacking faults. In addition, 0.08 μm, 0.0
In the case of a particle counter having a detection lower limit of 65 μm, when a defect is present on the wafer surface, it is not possible to distinguish whether the defect is a COP or a particle, so that the number of particles cannot be measured accurately. .

It is an object of the present invention to provide a method for measuring fine particles on a silicon wafer surface which can measure fine particles less than a lower limit of detection by a particle counter almost without being affected by surface haze. Another object of the invention is
It is an object of the present invention to provide a method for measuring fine particles on the surface of a silicon wafer capable of measuring only fine particles using a particle counter having a detection lower limit of 0.08 μm or 0.065 μm.

[0006]

The invention according to claim 1 is
After forming a silicon single crystal layer by epitaxial growth of 1 μm or more on the surface of a mirror-finished silicon wafer or an epi-wafer, measuring the state of scattering defects on the mirror-finished silicon wafer surface or the epi-wafer surface by a particle counter. This is a method for measuring fine particles. In the invention according to the first aspect, when fine particles are present on the surface, stacking faults caused by the fine particles are generated by forming an epitaxial layer of silicon single crystal on the surface of the mirror-finished silicon wafer or the epi-wafer. Since this stacking fault appears on the surface of the epitaxial layer in proportion to the size of the fine particles, by measuring the surface of the epitaxial layer with a particle counter, fine particles having a size that cannot be measured conventionally can be indirectly measured. As a result, the state of the fine particles such as the position, size, number, and density of the fine particles on the wafer surface can be measured. In addition, when an epitaxial layer is formed on the surface of a wafer having a COP, the silicon single crystal fills the COP, so that the particle counter does not detect the COP and only the surface defects due to the fine particles can be detected.

[0007]

Next, an embodiment of the present invention will be described. The thickness of the silicon single crystal layer epitaxially grown on the mirror-finished silicon wafer surface or the epi-wafer surface of the present invention is 1 μm or more. Preferably 3-5 μm
It is. If it is less than 1 μm, C existing on the wafer surface
OP is not filled, detection lower limit is 0.08 μm, 0.06
The 5 μm particle counter detects COP. In addition, since the formation of stacking faults caused by the fine particles is insufficient, a defect that cannot be detected by the particle counter occurs. The thickness may exceed 5 μm, but no further effect can be obtained by unnecessary epitaxial growth. The size of the fine particles on the wafer surface can also be estimated according to the thickness of the epitaxial layer.

The method for measuring fine particles according to the present invention is characterized in that an epitaxial layer is formed on a mirror-finished silicon wafer surface or an epi-wafer surface, and the surface of the epitaxial layer is measured by a particle counter. Note that when epitaxially grown on a mirror-polished silicon wafer surface, particles adhering to the wafer surface cause stacking faults in the epitaxial layer, and the stacking faults caused by these particles have a light scattering size larger than the particle size of the particles. did. By forming an epitaxial layer on the wafer surface by this method and measuring stacking faults appearing in the epitaxial layer, fine particles having a small particle size that cannot be measured by a conventional particle counter can be indirectly measured. Also,
Even when epitaxially grown on the epiwafer surface,
The same effect as in the case of the mirror-surface silicon wafer is obtained. Furthermore, when a COP is present on the wafer surface, since the COP is filled with a silicon single crystal by forming an epitaxial layer on the wafer surface, only the fine particles are measured with a particle counter having a detection lower limit of 0.08 μm and 0.065 μm. it can.

[0009]

Next, embodiments of the present invention will be described. <Example 1> Diameter 150m after normal mirror polishing process
5 μm silicon single crystal layer on a mirror-polished silicon wafer
An epitaxially grown epitaxial wafer was prepared. PSL particles having an average particle size of 0.08 μm were forcibly adhered to the surface of the epi-wafer by spin coating. Next, a silicon single crystal layer was further epitaxially grown to a thickness of 5 μm on the epiwafer surface by a CVD method. The number of PSL particles within a circle having a diameter of 146 mm on the surface of the epiwafer was examined using a laser particle counter (SS6200, manufactured by KLA-Tencor) having a lower detection limit of 0.10 μm. <Comparative Example 1> The same epiwafer as in Example 1 was prepared. The same PSL particles as in Example 1 were forcibly attached to this epiwafer in the same manner as in Example 1, and the same apparatus as in Example 1 was used without epitaxially growing a silicon single crystal layer on the epiwafer surface. The measurement was performed in the same manner as described above. <Comparative Evaluation 1> Scattering defects in Example 1 and Comparative Example 1
FIG. 1 shows the number and size of Light Point Defects (hereinafter referred to as LPDs). Comparative Example 1 as is clear from FIG.
Could not measure the number of LPD due to PSL particles. On the other hand, in Example 1, the number of LPDs corresponding to the PSL particles subjected to compulsory contamination was measured.

<Example 2> A mirror-finished silicon wafer having a diameter of 150 mm, in which it was previously found that a COP having a size of about 0.1 μm was present, was prepared by the method disclosed in Japanese Patent No. 2520316. This patent number 2520316
The method of No. 1 is to wash the wafer surface several times under a certain condition using an ammonia-based cleaning solution until the number of pits on the silicon wafer surface can be measured using a particle counter, The number of pits is measured using this particle counter, the wafer surface is re-cleaned under the same conditions, and the number of pits on the wafer surface after re-cleaning is measured using this particle counter. This is a method for detecting the size and the number of minute pits on the wafer surface after one-time cleaning based on the difference and the number of times of cleaning until the measurement becomes possible. The same PSL particles as in Example 1 were forcibly attached to this wafer in the same manner as in Example 1. Next, a silicon single crystal layer was formed on the wafer surface in the same manner as in Example 1 to a thickness of 5 μm.
An epitaxial wafer was obtained by epitaxial growth. PSL within a circle of 146 mm in diameter on the surface of this epiwafer
Laser particle counter (KLA-Tencor, SP-1) with a lower detection limit of 0.08 μm for detecting the number of particles
It investigated using.

Example 3 The same mirror-finished silicon wafer as in Example 2 was prepared. Without attaching PSL particles to this wafer, a silicon single crystal layer was epitaxially grown by 5 μm in the same manner as in Example 1 to obtain an epi-wafer. The measurement was performed in the same manner as in Example 1 using the same apparatus as in Example 2. Comparative Example 2 The same mirror-surface silicon wafer as in Example 2 was prepared. The same PSL particles as in Example 1 were forcibly attached to this wafer in the same manner as in Example 1, and the same apparatus as in Example 2 was used, without epitaxially growing a silicon single crystal layer on the mirror-polished silicon wafer surface. The measurement was performed in the same manner as in Example 1. Comparative Example 3 The same mirror-surface silicon wafer as in Example 2 was prepared. This wafer was measured in the same manner as in Example 1 using the same apparatus as in Example 2.

<Comparative Evaluation 2> The number and size of LPDs on the wafer surface are shown in FIG. 2 for Example 2, FIG. 3 for Example 3, FIG. 4 for Comparative Example 2, and FIG. 5 for Comparative Example 3. As is clear from FIG. 4, in Comparative Example 2, the number of LPDs equal to or greater than the PSL particles subjected to forced contamination was measured. It is considered that not only PSL particles but also COP was measured as LPD,
It cannot be determined whether it is due to PSL particles or PSL particles. On the other hand, in Example 2 shown in FIG. 2, the number of scattering defects of 0.1 μm or less greatly increased due to the influence of the surface haze caused by the epitaxial growth, but the L corresponding to the PSL particles forcibly contaminated was reduced.
The PD number was measured when the LPD size was 0.12 μm or more. In FIG. 5, the number of LPDs caused by the COP of Comparative Example 3 was measured. On the other hand, in Example 3, the number of LPDs caused by the COP was not measured as is clear from FIG.
Note that the peak appearing in the LPD size of 0.1 μm or less is due to the influence of surface haze.

[0013]

As described above, according to the present invention, after a silicon single crystal layer is epitaxially grown to a thickness of 1 μm or more on a mirror-finished silicon wafer surface or an epitaxial wafer surface, a particle counter is used on the mirror-finished silicon wafer surface or the epitaxial wafer surface. By measuring the state of the scattering defects caused by the fine particles, it is possible to measure the fine particles less than the lower limit of detection. Further, since the silicon single crystal formed by the epitaxial growth plays a role of covering the COP existing on the wafer surface, a particle counter having a detection lower limit of 0.08 μm or 0.065 μm can measure only fine particles.
By using this measurement method, it is possible to inspect non-defective products and optimize the manufacturing process in the epiwafer manufacturing process.

[Brief description of the drawings]

FIG. 1 is a diagram showing the number of LPDs according to an LPD size in Example 1 and Comparative Example 1.

FIG. 2 is a diagram illustrating the number of LPDs according to the LPD size according to the second embodiment.

FIG. 3 is a diagram illustrating the number of LPDs according to the LPD size according to a third embodiment.

FIG. 4 is a diagram showing the number of LPDs according to the LPD size in Comparative Example 2.

FIG. 5 is a diagram showing the number of LPDs according to the LPD size in Comparative Example 3.

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Claims (1)

[Claims] After a silicon single crystal layer is epitaxially grown on the surface of a specular silicon wafer or an epitaxial wafer by 1 μm or more, the state of scattering defects on the surface of the specular silicon wafer or the epitaxial wafer is measured by a particle counter. A method for measuring fine particles on a silicon wafer surface, the method comprising: