JP2004273664A - Standard sample for calibration - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the calibration of an inspecting device in a high accuracy by realizing standard samples for the calibration, in which recesses extremely similar to crystal defects are arranged, when the crystal defects are inspected. <P>SOLUTION: Quadrangular pyramidal-shape recesses 2 being similar to the crystal defect and having a different size, are arranged and formed by anisotropically etching on an Si wafer 1 having Miller indices (110). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a calibration standard sample suitable for calibrating an inspection device used for inspecting an unevenness existing on a semiconductor wafer, particularly a concave portion caused by a crystal defect.
[0002]
[Prior art]
In general, various irregularities are present on a semiconductor wafer, for example, a concave portion caused by a crystal defect, a scratch, a crack, and an attached impurity particle generated by a CMP (chemical mechanical polishing) method applied in a semiconductor device manufacturing process. And so on.
[0003]
At present, high integration and miniaturization of semiconductor devices are progressing, and the unevenness in the semiconductor wafer as described above damages the semiconductor device manufacturing process. It is necessary to improve the production yield of products by feeding back to the semiconductor device manufacturing process.
[0004]
2. Description of the Related Art Conventionally, irregularities on the surface of a semiconductor wafer are inspected using an inspection apparatus mainly including an Ar laser beam irradiator, a photodetector including a photomultiplier tube, and the like.
[0005]
That is, the surface of the semiconductor wafer is irradiated with an Ar laser beam, scattered light generated due to the presence of unevenness is received, and the presence or absence of unevenness is inspected based on the received scattered light intensity (pulse signal intensity).
[0006]
6A and 6B are explanatory diagrams showing a semiconductor wafer and scattered light intensities obtained by examining irregularities on the semiconductor wafer. FIG. 6A is a diagram, and FIG. Each wafer is shown.
[0007]
In the figure, 11 is a silicon wafer to be inspected, 12A and 12B are foreign matters (convex defects), 13A is a concave defect (scratch) generated by performing the CMP method, and 13B is a concave caused by an intracrystalline defect. Defects are shown, and in the diagram (A), the vertical axis shows the intensity of scattered light (pulse signal), the horizontal axis shows the position, and the horizontal axis shows the ground (GND) level. , And the threshold value indicates a boundary between a convex defect and a concave defect.
[0008]
As can be seen from the figure, the pulse signals from the foreign substances 12A and 12B exceed the threshold and are detected at a sufficient level, but the pulse signals from the concave defects 13A and 13B are below the threshold.
[0009]
The scattered light intensity, that is, the pulse signal, depends on whether it is scattered by the foreign matter 12A or 12B on the surface of the silicon wafer 1 or scattered by the concave defect 13A or 13B as described above. It is apparent that the laser beam is incident on the silicon wafer 11 at a low angle, that is, at a small (shallow) angle with respect to the surface of the silicon wafer 11, for example, about 20 °. Alternatively, the level differs depending on whether the light is incident at a high incidence, that is, at a large (deep) angle with respect to the surface of the silicon wafer 11, for example, at an angle of about 45 °.
[0010]
FIG. 7 is a diagram showing a comparison between the pulse signal heights when the laser beam is incident at a low incident angle and when the laser beam is incident at a high incident angle. The case of degree is represented by S-low, and the case of high incidence, that is, about 45 °, is represented by S-high.
[0011]
As is clear from the figure, the scattered light intensity, that is, the height of the pulse signal, is higher in the case of high incidence than in the case of low incidence and the case of high incidence.
[0012]
When the object to be inspected is a foreign substance (particle), the obtained pulse signal is S-low 、 S-high, and may be at a low incidence or at a high incidence. However, the inspection object is a crystal originated particle (COP). In the case of (1), the obtained pulse signal satisfies S-low <S-high and needs to have high incidence.
[0013]
The surface foreign matter inspection apparatus uses an Ar ion laser of a biaxial optical system, and the wavelength λ is 488 [nm] at low incidence and 514 [nm] at high incidence. The comparison is performed by comparing two signals, a scattered light detection signal due to a low incident beam and a scattered light detection signal due to a high incident beam, and in the separation algorithm, the comparison is performed using the peak value of the scattered light detection signal (pulse signal). .
As is apparent from the above description, when inspecting the unevenness of the semiconductor wafer, it is necessary to change the setting of the inspection apparatus depending on the type of the unevenness to be inspected, and therefore the calibration must be performed. Must.
[0015]
Conventionally, there is an invention that quantitatively inspects the depth and width of a scratch generated when a semiconductor wafer is polished by a CMP method and feeds it back to a semiconductor device manufacturing process to improve the product manufacturing yield. (For example, see Patent Document 1).
[0016]
In this case, an inspection device similar to the above-described inspection device is used. However, it is necessary to calibrate the inspection device, and the calibration is performed by using a focused ion beam (FIB). An inspection standard sample having a pseudo-processing mark (for example, see Patent Document 1) is used.
[0017]
However, calibrating an inspection apparatus using the above-mentioned known inspection standard sample cannot cope with calibration for inspecting a crystal defect.
[0018]
[Patent Document 1]
JP 2000-58606 A
[Problems to be solved by the invention]
According to the present invention, a calibration standard sample in which recesses very similar to crystal defects are arranged is realized, and the calibration of an inspection apparatus for inspecting crystal defects can be performed with high accuracy.
[0020]
[Means for Solving the Problems]
In the calibration standard sample according to the present invention, quadrangular pyramid-shaped recesses having a size different from that of a crystal defect are arranged and formed by anisotropic etching on a Si wafer having a plane index of (110). It is based on becoming.
[0021]
By adopting the above-described means, it is possible to carry out calibration with high accuracy when inspecting crystal defects with an inspection device for inspecting unevenness of a semiconductor wafer using a laser, and to perform crystal defect inspection which has not been conventionally performed. The inspection can be easily performed, which can contribute to improvement in the manufacturing yield of the semiconductor device.
[0022]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1
FIG. 1 is a plan view of a principal part showing a calibration standard sample according to a first embodiment of the present invention. In the drawing, 1 is a wafer made of Si whose plane index is (110), and 2 is a crystal. A quadrangular pyramid-shaped recess approximating a defect, a twin quadrangular pyramid-shaped recess closest to an existing crystal defect, and a groove-shaped recess approximating a scratch caused by CMP are shown.
[0023]
FIGS. 2A and 2B are main part explanatory views for explaining in detail each of the recesses described with reference to FIG. 1, wherein FIG. 2A shows a main part plane and FIG. Note that the same symbols as those used in FIG. 1 represent the same parts or have the same meanings.
[0024]
In the figure, 2A to 2E are quadrangular pyramidal depressions approximated to crystal defects, 3A to 3E are twin quadrangular pyramid depressions most similar to existing crystal defects, and 4A to 4D are approximate to scratches caused by CMP. The groove-shaped recess D indicates the depth in the quadrangular pyramid-shaped recess, respectively.
[0025]
The dimensions of one side of a square corresponding to the bottom surface in the quadrangular pyramid-shaped recesses 2A to 2E are exemplified as 2A = 0.10 [μm], 2B = 0.20 [μm], 2C = 0.30 [μm] 2D = 0.40 [μm], 2E = 0.50 [μm], and the depth is 0.10 [μm] to 0.50 [μm].
[0026]
One of the twin pyramidal recesses 3A to 3E in the twin quadrangular pyramidal recesses 3A to 3E has the same dimensions as the quadrangular pyramidal recesses 2A to 2E. The reason why the quadrangular pyramid-shaped recess is formed as a twin is that the crystal defects actually generated exist in a twin state, which is the calibration standard sample of the present invention. This is a great feature of
[0027]
To illustrate the dimensions of the groove-shaped recesses 4A to 4D, all widths are the same at 0.10 [μm], but lengths are 4A = 0.20 [μm] and 4B = 0.30 [μm]. 4C = 0.40 [μm], 4D = 0.50 [μm].
[0028]
One example of a process for producing the calibration standard sample described with reference to FIGS. 1 and 2 is as follows.
(1)
A Si wafer having a plane index of (110) and a thickness of 725 [μm] is prepared.
(2)
By applying the thermal oxidation method, an SiO ₂ film having a thickness of, for example, 10 [nm] is formed on the Si wafer.
(3)
By applying a resist process in lithography technology and a dry etching method using CHF ₃ + O ₂ or CF ₄ + H ₂ as an etching gas, the resist film is used as a mask to form a SiO ₂ film. An opening having a required dimension is formed by etching a portion where the pyramidal recess is to be formed.
(4)
After stripping the resist film, anisotropic etching of the Si wafer is performed using the SiO ₂ film as a mask to form a quadrangular pyramid-shaped recess by applying a wet etching method using an etchant of, for example, KOH.
(5)
The SiO ₂ film used as an etching mask is removed to realize a calibration standard sample having a pyramid-shaped recess.
[0029]
The addition of a groove-like recess approximating a scratch to the calibration standard sample thus prepared can be realized by excavating a Si wafer by a known means using an FIB (focused ion beam).
[0030]
In the calibration standard sample of the present invention, it is indispensable to have a quadrangular pyramid-shaped recess approximating a crystal defect or a twin quadrangular pyramid-shaped recess. If the groove-shaped recesses 4A to 4D are added, or if standard particles corresponding to foreign matter are added as in Embodiment 2 described below, a large number of calibration standard samples can be used. Inspection can be performed.
[0031]
Embodiment 2
FIG. 3 is a plan view of a main part showing a calibration standard sample according to a second embodiment of the present invention. The same symbols as those used in FIGS. 1 and 2 represent the same parts or have the same meanings. Shall have.
[0032]
The calibration standard sample according to the second embodiment is different from the calibration standard sample according to the first embodiment in that a quadrangular pyramid concave portion 2 similar to a crystal defect and a twin quadrangular pyramid concave portion most similar to an existing crystal defect are provided. The point 3 is that standard particle regions 5A to 5E corresponding to foreign matter are provided in addition to the groove-like concave portions 4 similar to scratches.
[0033]
The standard particles are polystyrene latex (PSL),
Standard particle area 5A: 5,000 standard particles having a diameter of 0.100 [μm] or less are spot-coated.
Standard particle area 5B: 5000 standard particles having a diameter of 0.100 to 0.200 [μm] φ are applied.
Standard particle area 5C: Spot application of 5000 standard particles of 0.200 to 0.300 [μm] φ.
Standard particle area 5D: 5000 standard particles having a diameter of 0.300 to 0.500 [μm] φ are applied.
Standard particle area 5E: 5000 standard particles having a size of 0.500 to 2.000 [μm] φ are applied by spotting.
It is formed as
[0034]
FIG. 4 is an explanatory view of a main part showing a spraying device or the like for explaining the formation of a standard particle region. The same symbols as those used in FIG. 3 represent the same portions or have the same meanings. .
[0035]
In the figure, the container 6, tank fed the N ₂ to the container 7, the nozzle 8, 9 heater, 10 have respectively a liquid obtained by dispersing the PSL, the tank 7 the pressure in the pump The PSL is sprayed by time control.
[0036]
FIG. 5 is a diagram showing the laser light scattering intensity of the standard particle region. In this case, the standard particle region is formed by applying 5000 spots of PSL having a diameter of 0.050 [μm].
[0037]
【The invention's effect】
In the calibration standard sample according to the present invention, quadrangular pyramid-shaped recesses having a size different from that of a crystal defect are arranged and formed by anisotropic etching on a Si wafer having a plane index of (110). It is based on becoming.
[0038]
By adopting the above configuration, it is possible to carry out calibration with high accuracy when inspecting a crystal defect with an inspection device that inspects the unevenness of a semiconductor wafer using a laser, and a crystal defect that has not been conventionally performed. The inspection can be easily performed, which can contribute to improvement in the manufacturing yield of the semiconductor device.
[Brief description of the drawings]
FIG. 1 is a main part plan view showing a calibration standard sample according to a first embodiment of the present invention.
FIG. 2 is a main part explanatory view for explaining in detail each recess described with reference to FIG. 1;
FIG. 3 is a plan view showing a main part of a calibration standard sample according to a second embodiment of the present invention.
FIG. 4 is an essential part explanatory view showing a spraying device and the like for explaining formation of a standard particle region.
FIG. 5 is a diagram showing laser light scattering intensity in a standard particle region.
FIG. 6 is an explanatory diagram showing a semiconductor wafer and scattered light intensities obtained by inspecting irregularities on the semiconductor wafer.
FIG. 7 is a diagram showing a comparison between pulse signal heights when a laser beam is incident at a low incident angle and when a laser beam is incident at a high incident angle.
[Explanation of symbols]
1 A wafer made of Si having a plane index of (110) 2 A quadrangular pyramid concave approximating a crystal defect 3 A twin quadrangular pyramid concave closest to an existing crystal defect 4 A groove similar to a scratch caused by CMP Recesses 2A to 2E Square pyramidal recesses 3A to 3E approximate to crystal defects Twin square pyramid recesses 4A to 4D most similar to existing crystal defects Groove-like recesses D approximate to scratches caused by CMP Square pyramid Depth in shape recess

Claims (3)

A calibration standard sample comprising a Si wafer having a plane index of (110) and quadrangular pyramid-shaped recesses having sizes different from each other which are similar to crystal defects and arranged by anisotropic etching. A quadrangular pyramid-shaped recess having a plane index of (110) and having a size different from that of a crystal defect is formed by anisotropic etching on a Si wafer,
Two quadrangular pyramid recesses of approximately the same size, which are similar to crystal defects on the same Si wafer, share one corner of a regular square on the surface and are located in an echelon shape to form a twin quadrangular pyramidal recess And a standard sample for calibration characterized in that the twin quadrangular pyramid-shaped recesses having different sizes are arranged and formed by anisotropic etching. 3. The standard sample for calibration according to claim 1, wherein a standard particle region corresponding to a foreign substance is sprayed and formed on an arbitrary portion of the same Si wafer.

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