JPS6184512A - Measuring method of two-layer plating - Google Patents

Abstract

PURPOSE:To measure the thickness XB of intermediate plating by correcting adequately the change of the background of an intermediate metal B by the thickness XC of a surface metal C. CONSTITUTION:The primary X-ray 3 irradiated from an X-ray source 1 is irradiated through a collimator 2 to a sample 4. The secondary X-ray 6 generated from the sample 4 is detected by a radiation detector 7. The detected output is amplified by a preamplifier 8 and is then amplified to a linear output by a main amplifier 9. The output of the amplifier 9 is subjected to pulse height analysis by a pulse height discriminator 10 and is thereafter inputted to a CPU11 which calculates and measures the thickness XC of the surface plating from the fluorescent X-ray intensity from the intermediate metal B of an unknown two-layer plating sample by a conventional method and calculates and measures further the thickness XB of the intermediate plating. The results of the calculation are outputted to and displayed on a display part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a canopy meter using fluorescent X-rays, and in particular to measuring the intermediate plating thickness of a two-layer plating sample.

b. Prior art Conventionally, the intermediate plating thickness of a two-layer plating sample was measured using the following methods: A1 intermediate plating metal 't - B1 surface plating metal C
Then, the equation of the calibration curve (1
) expression is a shorthand.

From -((from oo-from 0)-(1-exp(-μ5
-Xs)))・exp(-μ′・XC)+1OCX O
) −・・・−・−・[11 Here, xo(xc) is a function indicating the background correction of the silicon element X-ray intensity in dB of gold due to the change in the thickness of the metal C) +21 It is shown by the formula.

0(XA)=(koooo-koo) (1-exp(
-tto 40 ) )+10 ・From 121' =(
From oo-techno) (1-6zp (-μ34g)) from 10 to O---i31 Here, XB in formula (1) is the thickness of the intermediate plating metal B, and 00 is the fluorescent X is the fluorescence X t9 intensity of metal B whose thickness is sufficient for the line to be saturated (hereinafter referred to as the saturated thickness), and then O is the total metal t-
It is the X-ray intensity (background) of metal B (7) at the time of measurement, and μB is the absorption coefficient of metal B for fluorescent X-rays, which is calculated using Equation (3) 1. Foot e work”0+
More O.

μB is a standard sample of metal B on metal A having five or more pure metals B with different thicknesses (hereinafter, Bm on A)
It is called a quasi-sample. ) is determined by measuring the x-ray intensity, substituting the intensity into equation (3), and solving the simultaneous equations.

μ' is the absorption coefficient O of metal C for fluorescent X-rays of metal B, and metal Ca quasi-sample (hereinafter referred to as B This can be determined by measuring the silicon element X-ray intensity of the above C standard sample) and substituting that intensity into equation (1). (1) In the formula, 0 (XO) is the metal B due to the change in the thickness of metal C.
It is the background of the fluorescent X-ray intensity of , and is a function of the plating thickness of metal C, XO. koooo, ko0 are the fluorescence X @ intensity of metal B corresponding to the thickness of the aSS sample on A is 0 and the saturated thickness, respectively, and μO is the coefficient representing the attenuation of the silicon element X-ray intensity of metal B. Then, measure the fluorescent X-ray intensity of metal B of three or more standard samples of C on A with different thicknesses, and check the intensity! 'k + Substituting into the formula 21, it is obtained by solving the simultaneous equations.

The fluorescence X@ intensity of metal B of the metal C double layer plating sample on metal B on gold MA was measured using the parameters determined in the above manner (Equation 11 and Equation (2)). The plating thickness of intermediate plating metal B was determined from equation (1).

C1 Problems to be Solved by the Present Invention Since the fluorescence Xi of the intermediate plating metal B is attenuated by the surface plating metal CK, the signal fraction becomes small. In order to obtain an accurate intermediate plating thickness, it is necessary to accurately determine the background corresponding to noise by using a conventional method, but the conventional method for correcting the background of the fluorescent X-ray intensity of metal B is XA) is an index function that shows a monotonous increase or decrease, but due to the combination of metals A, B, and C, the fluorescence X-ray intensity of metal B often does not show a monotonous increase or decrease. An example of this is shown in Table 1. (N on Cu
In the case of the C standard sample on A in the example of Au double-layer plating on i) Table 1. Changes in gold) I14B fluorescence Since it could not be corrected, it was not possible to measure the thickness of the intermediate plating (metal B), which had a high accumulation.

d1 Means for solving the problem In order to solve the conventional problem, measure the silica element x6 intensity (background) of metal B of four or more C standard samples on A each having different thickness, and The change t is expressed by the background correction formula l0(XO) of formula (4). Also, the equation (1) of the calibration curve is improved to equation (5).

Io'(Xc)=ko-e-μ+"'+Ioae・(1
-e-μ2°x0)-14) = [(11 than 0
)-41-exp(-uB-XB)):l'eXp(-
μ' Xa ) + 10' (XC) - (51 where, (
4) The 0 and 0 (1) in the formula are the same as the 0 and Qoo in the formula (2), and μ and μ are 0. This is a coefficient that indicates the change in the coefficient, and is obtained by substituting each data into equation (4) and solving simultaneous equations. If the background due to thickness change of metal C monotonically decreases or V′i increases, μm
= μ.

Accurately determine the background by improving the process of formula (4) to change the fluorescence X-ray intensity (background) of metal B due to the change in the thickness of metal C of the C standard sample on 00 action A. I can do things. From the data in Table 1, we selected four points: Au thickness Oμ, 1.6 μm, 4.0 μm, and saturated thickness.
Substitute into equation (4) and make it simultaneous μ7. Determine μwe and process the result for Ni corresponding to other Au thicknesses 7. Table 2 shows the results of calculating the line strength.

Table 2. (4) according to the present invention and the conventional (2
) formula for Ni-no plating (A on N1 plating on Cu)
Table 3 shows the intermediate plating thickness measurements during U plating).

Table 5 Intermediate plating thickness measurement accuracy (Au plating on N1 plating on Cu) Using the new formula (4) to calculate background changes due to changes in metal C thickness, two layers with high accuracy are shown in Table 5. Plating measurement is possible.

f, Details of the film thickness measurement method according to the present invention along with the drawings below
-Explain. The drawing shows a thickness measuring device i1 related to the present invention, and the reference numeral 1 in the drawing is an X-ray source, and the primary X-ray 5 irradiated from the X-ray source 1 passes through a collimator 2 and irradiates the sample 4. be done. Code 7 is the secondary X generated from the sample.
8 is an amplifier that amplifies the signal from the detector 7; 9 is a main amplifier for making the output of the amplifier 8 linear; 10 is a main amplifier for the purpose of linearizing the output of the amplifier 9; A pulse height discriminator 11 analyzes the pulse height from the output, and a CPU 112 that calculates the output from the pulse height discriminator 10 is a display unit for displaying the output of cpall.

Next, a case will be described in which the film thickness measuring device according to the invention having the above-mentioned construction is operated. 5 each with different thickness
From the silicon element X-ray intensity of metal B of B standard samples on A or more, ' is measured, and by substituting it into equation (3) and solving the simultaneous equations, O and μB are obtained from Elie 3on. By measuring the silicon element X-ray intensity o' (Xo) of metal B of C standard samples on four or more A with slightly different thicknesses, and substituting it into equation (4) and solving the simultaneous equations, , engineering 0. 0.2μm,
Find μt. Measure the silicon element X-ray intensity of metal B on five or more C standard samples on B with slightly different thicknesses, and (
5) Substitute into the equation to find the factor μ'.

From - [(engineering] 3ao-engineering no) (1-ecp (-μn
-Xa)l)-6zp(-4'Xc)+IO'(XO)
- (51) In this way, the factors in the above equation are determined, and the surface plating thickness xO is determined by measuring the fluorescent X-ray intensity from the intermediate metal B of the plated sample. After measuring with this method, the intermediate plating thickness XB can be measured with high precision.

g0 Effect of the present invention The method for measuring the thickness of Nino plating according to the present invention is as follows: sea urchin,
Since the change in the background of the intermediate metal B due to the thickness XOK of the surface metal C is appropriately corrected, it is possible to accurately measure the intermediate plating thickness XB.

[Brief explanation of drawings]

The drawing is a block diagram of an apparatus related to an embodiment of the present invention. 1... X-ray source 2... Collimator 6...-X# 4... Sample 5... Sample stage 6... Secondary X-ray 7... Radiation detector 8... Preamplifier 9... Main amplifier 10... Wave height discriminator 11... OF σ 12... Above the display section

Claims (1)

[Claims] By detecting the fluorescent X-rays generated from the sample excited by the primary X-rays from the X-ray source installed in the main body, A method for measuring the thickness of a film, including the step of detecting fluorescent X-ray intensity generated from an intermediate width with an X-ray detector, and a material having three or more pure intermediate metals each having a different thickness. measuring the fluorescent X-ray intensity of the intermediate metal above;
A step of measuring the fluorescent X-ray intensity of a surface metal on an intermediate metal having three or more pure surface metals each having a different thickness; The process of measuring the background fluorescent X-ray intensity (metal B fluorescent X-ray intensity) of the surface metal on a thick material and determining the equation of the calibration curve, and the process of determining the equation of the calibration curve, and the process of measuring the background fluorescent Measurement of double-layer plating characterized by performing calculation measurement through a process of correcting the background more accurately than the film thickness of the surface metal by measuring the optical X-ray intensity, and a process of calculating the intermediate film thickness. Method.