JPH0820317B2 - Stress measuring method and device - Google Patents

Description

The present invention relates to a method and an apparatus for measuring stress on a minute portion, and particularly to a case where a sample to be measured is extremely minute like an LSI element and the stress measurement is difficult. The present invention relates to a suitable stress measuring method and apparatus.

[Conventional technology]

For the conventional stress measurement method for minute parts, see Applied Physics Letters, Vol. 40, No. 10 (1982).
Pages 895 to 898 (Appl.Phys.Lett., Vol.40, No.10
(1982), pp895-898), the content of the method and apparatus for stress measurement by Raman spectroscopy is discussed.

In this conventional technique, stress measurement is performed as follows. When the sample to be measured is irradiated with a strong monochromatic light beam (in this device, Ar ion laser or Kr ion laser is used),
The incident light is frequency-shifted due to the molecular vibration of the sample, and Raman scattered light having a frequency different from that of the incident light is generated.
What measured the frequency-shifted Raman scattered light intensity is called a Raman spectrum, and qualitative analysis can be performed from the frequency position where this Raman spectrum shows a peak, and quantitative analysis can be performed from the scattered light intensity. When stress is applied, the frequency position where the Raman spectrum shows a peak shifts, and the amount of this shift is detected to quantitatively evaluate the stress.

[Problems to be Solved by the Invention]

The above conventional stress measuring method and apparatus use Ar as a light source.
Since an ion laser (wavelength 0.488 μm or 0.5145 μm) or a Kr ion laser (wavelength 0.6471 μm) is used, for example, in an area smaller than the spot size (0.8 to 1 μm) of the laser, such as an LSI device. However, in the case of a sample in which the stress value changes abruptly or a sample having a stress distribution, there is a drawback that the measurement accuracy deteriorates.

An object of the present invention is to provide a stress measuring method and apparatus for accurately obtaining stress and stress distribution in a minute portion (submicron order).

[Means for solving the problem]

The above object is achieved by using a UV laser in the stress measurement method by Raman spectroscopy and setting the spot diameter to a range of 1 to 2 times the wavelength of the UV laser light.

Further, the above-mentioned object is a device including an optical system such as a laser light source and a lens, a spectrometer and a detector, and a laser light source that oscillates an ultraviolet laser, and an optical system such as a lens that transmits ultraviolet light and the ultraviolet light is transmitted. And a detector with an entrance window to
This is achieved by configuring the optical system so that the spot diameter narrowed by the objective lens is in the range of 1 to 2 times the wavelength of the ultraviolet laser light. Furthermore, it is achieved by performing stress measurements in vacuum.

[Action]

As described above, by using an ultraviolet laser and setting the spot diameter in the range of 1 to 2 times the wavelength of the ultraviolet laser light,
It becomes possible to detect the stress value in the area of 0.1 μm,
It is possible to measure the stress or stress distribution in a minute portion, which was difficult in the past.

Further, as described above, by providing a laser light source that oscillates an ultraviolet laser, an optical system such as a lens that transmits ultraviolet light, and a detector that has an entrance window that transmits ultraviolet light, a minute portion (submicron) Since the (order) stress or the stress distribution can be grasped with high accuracy, it is possible to perform highly accurate measurement.

Further, by performing the stress measurement in vacuum, it is possible to reduce the attenuation of the intensity of the ultraviolet laser light, and it is possible to perform the stress measurement with high accuracy.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

The basic configuration of the present invention is shown in FIG. In this figure, the ultraviolet laser light 2 emitted from the laser light source 1 is focused by the objective lens 3 and irradiated onto the sample 4. Raman scattered light generated due to molecular vibration of the sample 4 passes through the objective lens 3, is guided to the spectrometer 6 by the half mirror 5, and is detected by the detection unit 7. The obtained Raman spectrum is read into the computer 8. The sample 4 is placed on the fine movement stage 9. By moving the stage 9, the laser beam 2 is scanned on the sample 4 and the Raman spectrum at each scanning position and the position sensor ( The computer 8 is made to read the positional information from a computer (not shown).
The stress value is obtained from the frequency shift value at each scanning point by the computer 8, and the stress distribution state is displayed by the image processing device 10.

When an H ₂ laser is used as an ultraviolet laser, its wavelength is short, and the spot diameter in the range of 1 to 2 times the wavelength of the laser light can be obtained by using the following material with good transparency for the objective lens as an optical system. Is possible. Therefore, the spot diameter of the stress-measured surface is about 0.1 μm, and the stress value of the region irradiated with the laser beam can be obtained from the frequency shift value of the scattered light in this region. Therefore, with the above configuration, it is possible to measure the stress of a minute portion of about 0.1 μm. At this time, an alkali halide, especially a LiF lens and an entrance window are preferably used as the entrance window of the objective lens and the detector, respectively. It may be used made of MgF _2.

In addition, as an ultraviolet laser, Ar ₂ laser, ArCl laser, ArF
When using excimer laser such as laser, KrCl laser, KrF laser, XeBr laser, XeCl laser or XeF laser,
It is possible to measure the stress in a minute portion of 0.13 μm to 0.35 μm. At this time, as the incident window of the objective lens and the detector, it is preferable to use a lens made of LiF, MgF ₂ or fluorite (CaF ₂ ) and an incident window, respectively. It may be made of synthetic quartz or fused quartz made of natural quartz. It may be made of sapphire glass (Al ₂ O ₃ ) or ultraviolet transparent glass.

The embodiment shown in FIG. 2 is an application example of the embodiment shown in FIG. 1, which is a laser light source 1, a laser light 2, an objective lens 3, a sample 4, a half mirror 5, a spectrometer 6, a detector 7, and a fine movement stage 9. Is provided in the vacuum chamber 11. As an ultraviolet laser, the oscillation wavelength is about
If the one having a thickness of 0.1 μm is used, the attenuation of the intensity of the laser light may be increased in the air, and therefore the attenuation can be reduced by performing the operation in a vacuum. Therefore, the stress value of the minute portion can be accurately measured.

〔The invention's effect〕

As described above, the method according to the present invention uses an ultraviolet laser and makes the spot diameter approximately the wavelength,
There is an effect that a stress value or a stress distribution state of a minute portion (submicron order), which has been difficult in the past, can be grasped.

Further, the apparatus according to the present invention is provided with a laser light source that oscillates an ultraviolet laser, an optical system such as a lens that transmits ultraviolet light, and a detector having an incident window that transmits ultraviolet light. This has the effect of accurately grasping the stress or stress distribution in a minute portion (submicron order).

Further, by performing the stress measurement in a vacuum, the attenuation of the intensity of the ultraviolet laser can be reduced, and the stress can be measured with high accuracy.

[Brief description of drawings]

FIG. 1 is a system diagram showing a configuration of a stress measuring device according to the present invention, and FIG. 2 is a system diagram showing a configuration of a stress measuring device according to another embodiment of the present invention. 1 ... Laser light source, 2 ... Laser light, 3 ... UV laser objective lens, 4 ... Sample, 5 ... Half mirror, 6 ...
… Spectrometer, 7 …… Detector, 8 …… Computer, 9 ……
Fine movement stage, 10 ... Image processing device, 11 ... Vacuum chamber.

Claims (5)

[Claims] 1. A Raman for irradiating a laser beam focused on the surface of an object to be stress-spotted through an objective lens in a spot shape, and guiding scattered light generated from the surface of the object-to-stress to be measured to a spectrometer by a half mirror. In the stress measurement method by spectroscopy, the measurement area of the surface of the object to be stress-stressed is a submicron-order minute portion, and an ultraviolet laser beam is used as the laser beam, and the spot diameter narrowed down by the objective lens is the ultraviolet laser beam. The stress measurement method is characterized by measuring the stress value and the stress distribution of the minute portion by setting the wavelength to be 1 to 2 times the wavelength. 2. A stress measuring device comprising a laser light source, an objective lens for focusing laser light in a spot shape on the surface of an object to be stressed, a half mirror for guiding scattered light to a spectrometer, and the spectrometer. The measurement area of the surface of the object to be stressed is a submicron-order minute portion, the laser light is an ultraviolet laser light, and the objective lens is one that transmits ultraviolet light, and is attached to the spectrometer. The entrance window of the container is also one that transmits ultraviolet laser light, and the optical system is configured so that the spot diameter narrowed down by the objective lens is in the range of 1 to 2 times the wavelength of the ultraviolet laser light. A stress measuring device characterized by: 3. The stress measuring method according to claim 1, wherein the stress measuring is performed in vacuum. 4. The stress measuring device according to claim 2, wherein at least the optical path of the ultraviolet laser light is evacuated. 5. The stress measuring device according to claim 2, wherein the ultraviolet laser light is H ₂ light, and the objective lens and the entrance window are made of LiF.