JPS60166834A - Internal stress measuring apparatus for tabular object - Google Patents

Abstract

PURPOSE:To measure internal stress accurately while simplifying the measuring route by memorizing various data on an object to be measured into a memory means and the number of interference fringes detected to perform an automatic measurement based on the data therefrom. CONSTITUTION:Values of elastic constant, Poisson's ratio, substrate diameter and thickness are inputted into a data input means 11. These data are memorized as intact into a memory means 14 composed of a microcomputer such as RAM. Then, interference fringes are detected with a interference fringe detection means 12 by uniform-thickness interference fringe method. Light reflected from the substrate 1 reaches a camera 24 through a lens 22 and a mirror 23 to take interference fringes. Then, a means 13 of detecting the number of interference fringes detects the number thereof utilizing the existing method enabling the recognition of the image of interference fringes. The data thus obtained are inputted and memorized into the memory means 14. Then, a means 15 of detecting the level of curve detects the level of curve of the substrate based on the data on the number of interference fringes among those outputted data from the memory means 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring device designed to accurately obtain internal stress values of a plate-shaped object such as a semiconductor substrate.

Various films such as a protective film are often provided on the surface of the semiconductor substrate constituting each pillow semiconductor device.

Figure 1 1a) shows this situation, and Si (silicon)
A film 2 of 5i02 (silicon dioxide) or the like is formed on the surface of a semiconductor substrate such as the like, and this film 2 is then subjected to various treatments depending on the purpose.

By the way, when a film is formed on a plate-shaped object such as a semiconductor substrate, stress is applied to the plate-shaped object (hereinafter referred to as a substrate) by the film. This stress can generally be broadly classified into external stress as thermal stress and intrinsic internal stress due to dislocations, defects, etc. in the crystal of the substrate.

When the substrate is made of a hard material, there is no noticeable deformation in appearance, but if you closely observe it, you will notice slight deformation due to the film, as shown in Figure 1. It is observed that the substrate 1 is curved due to the film 2 formed on the substrate 1.

At this time, the moment generated within the base &l and the moment generated within the membrane 2 are considered to be balanced.

In particular, the term "can internal stress" which is caused by a moment in the membrane 2 is a general term for so-called stress.

Understanding the value of this internal stress is a crucial step in designing semiconductor devices, etc., and several methods are known for its measurement, such as the cantilever dyeing method, the disk method, and the diffraction method. I'm here.

Below - as an example, when discussing the disk method, the curved part formed on the two-board work is considered to be a part of a sphere, and its radius of curvature w
When R is the above internal stress σ.

You can wear it with clothes.

However, E: elastic constant of the substrate 10 t8: thickness of the substrate l tf thickness of the two-layer film 2 In particular, the radius of curvature R can be determined by interferometry using the Newton ring method as shown in FIG. Second
In the figure, 3 is a light source, 4 and 9 are lenses, 5 is a filter, 6 is an optical surface plate, 7 is a mirror, and 8 is a half mirror.
is a camera.

In the above arrangement, from the light source 3 to the lens 4. Filter 5.
When the surface of the substrate 1 is irradiated with nine beams through the half mirror 8,
From the surface of the substrate 1, interference fringes consisting of regular bright and dark fringes drawn centered around the apexes of the curved portions formed thereon are observed.

The radius of curvature R can be determined by photographing this interference fringe using the camera 0 and using the following formula based on this image.

(r/l)+1 R= □ ...(2) Also, r: Distance along the plane from the center of the light and dark stripes (medium diameter) l: Gap at that point When the stress t611 is constant, the substrate 1 is
A device for detecting the amount of warpage of the curved portion of the surface χ based on interference fringes and a camera or display device for observing the interference fringes are required. Furthermore, it was necessary to manually process the data obtained from these devices and perform calculations using a total of xBA. For this reason, it was inevitable that the measurement strategy would be sloppy, and it was difficult to incorporate it into internal stress calculation means.

The present study was made from the above points of view, and in particular, the amount of warpage, the radius of curvature, and the internal stress of the curved portion of the substrate are fll11.
Internal stress d111 that is determined manually
Its purpose is to provide a fixed device, and its characteristics are as follows: (A means to manually generate various data regarding Al plate-shaped objects.)

[F]) means for detecting interference fringes of the plate-like object;
C) means for detecting the number of interference fringes on the plate-shaped object; - means for storing output data from the human-powered means and the interference fringe number detection means; means for calculating the amount of warpage of the curved portion formed on the plate surface of the plate-shaped object based on the output data from the amount calculation means of the said curved portion; , fGl means for outputting the internal stress of the plate-like object based on the output data from the storage means and the radius of curvature calculation means, and a-υ means for outputting the output data from the internal stress calculation means to the outside. and.

This is a device used to measure the internal stress of a plate-like object.

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

FIG. 3 is a block diagram showing an apparatus for measuring internal stress of a plate-shaped object according to an embodiment of the present invention, in which 11 is a data manual means, 12 is an interference fringe detection means, 13 is an interference pattern number detection bow/stage, and 14 is a data storage. Means, 15 is a sled gong calculation means.

16 is a radius of curvature calculation means, and 17 is an internal stress calculation means.

18 is a data output means.

In the above configuration, the data manual means 11 includes various data regarding the substrate which is the traveling object to be measured, namely the elastic storage number E,
Six values are manually entered: Poisson's ratio ν, substrate diameter, substrate thickness ts, and n-plate thickness t. These data are stored as they are in a storage means 14 constituted by a microcomputer such as a RAM.

Next, in the interference fringe detection means 12, interference fringes are detected by the @float fringe method as shown in FIG. 4, for example.

In FIG. 4, 19 is a light source, 20 is an incident angle adjusting prism, 21 is a prism, 22 is a lens, 23 is a mirror, and Sae is a camera. The light emitted from the light source 19 is adjusted to parallel light beams (originally) by adding a prism with an angle of incidence of 14, and then is irradiated onto the substrate l via the prisms 21.

The original reflected by the substrate 5 is transmitted through the lens ρ and the mirror 23 to the camera, and interference fringes are photographed.

FIG. 5 shows an image of interference fringes obtained by Cameras, in which a pattern of bright and dark fringes arranged concentrically can be observed.

FIG. 6 shows an enlarged view of the opposing portion of the prism 21 and the substrate 1, where X, , X2 are optical paths, a and b are optical path lengths,
A, B, C, and D are the nine passing points, and h is the distance between them. Wave number after 2 days of optical path excursion and optical path length “2 a e m
Each of b can be expressed as follows.

a m2a = 7 (light path A→C→B) −+3128
．． 2 mb = -5 illy (optical path p-e13) -
(4)λ Here, the conditions for the appearance of bright and dark stripes as shown in Figure 5 are [1n2
Since a-mb is an integer value + r/2Jvc, 1
It will look like this:

rn2a rnb ``'W'' Δh - . . .) Therefore, when Δh changes by λ/2 cozy, the stripe changes by one line. Conversely, this means that the amount of warpage of the substrate can be measured by multiplying the number of stripes by the known ΔhlC. Such measurement principles can be applied as they are known.

Next, the interference fringe number detection means 13 can easily detect the number of interference fringes by using a known method that can recognize the image of interference fringes as shown in FIG. For example, by projecting the interference fringes mentioned above as an image on a general CRT (cathode ray tube), and then binarizing the brightness of the screen (by making the black and white contrast sharp), you can determine the number of fringes. can be counted. The data obtained thereby is manually stored in the storage means 14.

Next, the warpage value detection means 15 detects the warpage amount of the plate based on the data regarding the number of interfering manuscripts among the data outputted from the storage means 14.

In this first step, the detection means 15 is a CPU, a ROM.

It is constructed of EPROM, FROM, etc., and is programmed in advance to calculate the warpage value based on human data.

Subsequently, the radius of curvature calculation means 16 calculates the radius of curvature based on the output data from the upward value detection means 15. For this purpose, a calculation formula as shown below can be used.

First, when an arc Li is drawn with a radius of curvature R as shown in FIG.

(First example formula) It can be expressed by the % formula %(6). However, L': arc length can be substituted by the diameter of the board) (Second example formula) % formula % (Third example formula) f(R)=Rsin(L/2R) ZJR+j! ! −
(8) Here, since the above equations (7) and (8) are transcendental functions, it is necessary to perform approximate calculations. Since the following general formula can be expressed by Newton's successive approximation method, the curvature RY can be determined using this formula.

Rn+2 = RH' (Rn) / ”(Rn)
...(3 calculation formulas over 91 + 61. f7L (
When comparing the 81 formulas, formulas (7) and (8) are more advantageous than formula (6) in terms of accuracy. Also, the calculation speed is faster than the Newton method.
son) law is larger.

Next, the internal stress 3+L output means 17 calculates the target internal stress value n. For this purpose, the above-mentioned il1 formula is used based on the output data from the above-mentioned storage means 14 and the curvature radius calculation means 16. The programs necessary for calculation are C1'U, ROM, EPROM, FROM as mentioned above.
etc., in advance. This also applies to the radius of curvature calculation means.

The internal stress value determined in this way is supplied as data to the data output means, and is output from the device to an external device such as a display or a line printer.

FIG. 8 is a flowchart showing the software of the microcomputer constituting the measuring device of the present invention, in which the measuring thread is controlled and detected by the block A and the ROM, etc. into which various data regarding the substrate that is the object to be measured is input. The data of block B from which the number of interference fringes has been obtained is stored in block C.

Next, the amount of warpage of the substrate is calculated in block D based on the data from block C, and then the approximate calculation of the radius of curvature is performed in block E based on the amount of warpage. Further, the internal stress is divided in block F based on the radius of curvature and output to block G.

In the above, the calculation of the shell, the radius of curvature, and the internal stress are automatically performed.

The software can be modified in various ways in response to an increase in the number of data to be processed.

As is clear from the above explanation, according to the present invention.

Various data regarding the object to be measured and detected interference documents &
iv) The measurement path is simplified because the measurement method is configured to be stored in the storage means and to automatically measure the amount of warpage, radius of curvature, and internal stress of the object to be measured based on the data from the storage means. This allows for accurate measurement of internal pressure. In other words, since the measuring device can be configured with a single unit and does not require additional equipment as in the past, it also eliminates the need for data processing by human means using dedicated or dual-purpose equipment. Simplification 1 - It is possible to do this easily.

Particularly compact by incorporating a microcomputer,
Since it is possible to measure the shape of the stem lid, it is effective when applied to the field of beef specialty confectionery.

Although the embodiment has been described using the equal float fringe method γ as the interference fringe detection means, other means such as the Newton ring method may also be used. If the substrate is plate-shaped or disc-shaped, it can be applied to a wide range of fields without being limited to specific objects.

[Brief explanation of the drawing]

FIG. 1(a) is a cross-sectional view for explaining the present invention, FIG. 2 is a configuration diagram showing a conventional example, and FIG. 3 is a block diagram of a conventional example. FIG. 4 shows the optical fiber structure according to the present invention, FIG. 5 shows an interference fringe pattern for explaining the present invention, and FIG. 6 and FIG. figure. The MJJs diagram is a flowchart for explaining the present invention. L...Plate-shaped object (substrate), 2...Membrane, 11...Data manual means, 12...Interference fringe detection means, 13...
・Detection of the number of interference fringes + stage, 14... Storage means, 15.
... Warpage amount calculation means, 16゛°゛curved cow diameter calculation means, 1
7-°゛Internal stress dance, output means, 18...output means. Patent Applicant Clarion Co., Ltd. Figure 1 (a) (b) Academic Year 2 Figure 3 Figure 4

Claims (1)

[Claims] (5) A means for manually collecting various data regarding a plate-like object. IBI means for detecting interference fringes of the plate-like object. (Q A means for detecting the number of interference fringes of the plate-shaped object. (DJ A means for storing output data from the input means and the interference fringe number detection means. (El Number of interference fringes output from the storage means) (F) Calculating the radius of curvature of the curved portion based on the output data from the warp amount calculation means; A means for calculating the internal stress of the plate-like object based on the output data from the storage means and the curvature medium diameter calculation means.0 A means for outputting the output data from the internal stress calculation means to the outside. .An internal stress measuring device for a plate-like object characterized by χ.