JPS6222003A - Method and instrument for measuring thickness of insulator film - Google Patents

Abstract

PURPOSE:To measure film thickness even at a small position and a curved- surface shape position with high precision by performing arithmetic operation on the basis of electrostatic capacity per unit length which is determined unequivocally from a dielectric constant, film thickness, width, and thickness, and measured electrostatic capacity, width, and thickness. CONSTITUTION:An electrostatic capacity characteristic data equation I corresponding to electrostatic capacity Ct0 per unit length when the film thickness D of an insulator and the width W and thickness T of the 2nd electrode 13 are varied variously while the dielectric constant epsilon of the insulator and an equation II based on the data are calculated previously. Then, the actual electrostatic capacity Ct per unit length of the insulator is measured. Then, contacts A, B, and C of the equations are calculated and those constants A, B, and C and the width W and thickness T of the electrode 13 are substituted in the equation II to obtain the unknown film thickness D.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an insulator film thickness measuring method and a measuring device therefor.

(Prior Art) Generally, as a method for measuring the film thickness of an insulator, an optical method using an interferometer or the like, a method using parallel plate electrodes, etc. are known. Among these measurement methods, the optical method cannot be used for opaque insulator films, so the parallel plate electrode method, which can measure even opaque insulator films, is often used.

As a conventional parallel plate electrode method, there is one as shown in FIG. 2, for example. The configuration will be explained below using figures.

In FIG. 2, l is an insulator to be measured, and parallel plate-shaped electrodes 2 and 3 are arranged on both sides of this insulator 1. A cable 4.5 is connected to the electrodes 2, 3, and a voltage V is applied between the electrodes 2, 3 via this cable 4.5. It is assumed that the insulator 1 has a dielectric constant ε and a film thickness d, and the electrodes 2 and 3 have an area A and a thickness t.

Now, when voltage V is applied between electrodes 2.3, both electrodes 2.3.
It is assumed that electric lines of force perpendicular to the electrode surface are generated between the electrodes and a uniform electric field is formed between the electrodes.

Then, the capacitance C becomes as shown in the following equation.

However, Q: electric charge of electrode 2.3.

Therefore, in the conventional measuring method, when the dielectric material ε and the area A are known, the film thickness d of the insulator I is measured based on the change in the charge Q with respect to the voltage ■.

(Problems to be Solved by the Invention) However, in the measurement method with the above configuration, the electrode 2.3 is Make the thickness t sufficiently thin, or
Alternatively, it is necessary to make the area A of the electrode 2.3 sufficiently large relative to the film thickness d, and to make the areas of both the electrodes 2 and 3 equal. When the film thickness d of the 1" insulation l becomes thinner, there is a limit to how thin the thickness t of the electrodes 2 and 3 can be made. Therefore, the area A of the electrodes 2.3 is made sufficiently large to obtain a uniform electric field.

Therefore, if the area of the insulator 1 is small, or if the insulator l is not flat but has a curved shape, it becomes difficult to obtain a uniform electric field, and there is a problem that highly accurate film thickness measurement cannot be performed. Ta.

The present invention provides an insulator film thickness measuring device and an insulator film thickness measuring device that solves the problem of the prior art that highly accurate film thickness measurement cannot be performed when the insulator has a small area or has a curved surface shape. The present invention provides a measuring device for the measurement.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a method for measuring the thickness of an insulator, in which the dielectric constant e is known and the film thickness is unknown on both sides of the insulator. A first electrode and a second electrode having a width W smaller than the widths of the first electrode and the insulator, a length L, and a thickness T are respectively disposed, 2
A predetermined voltage is applied between the electrodes, electric lines of force having a fringing effect are generated between the two electrodes, and the capacitance Ct per unit length of the length L between the two electrodes is measured. The unknown film thickness is calculated by calculating the capacitance per unit length Cto, which is uniquely determined from the above ε, D, W, and T, and the measured (t, w, T). be.

Further, in the insulator film thickness measuring device, a predetermined voltage is applied between the first and second electrodes and the first and second electrodes to measure the capacitance Ct per unit length of the length L. a measuring section that measures the above-mentioned ε, D, W, and T, a storage section that stores a plurality of data regarding the capacitance per unit length l1Cta uniquely determined from the above-mentioned ε, D, W, and T; and a calculation section that calculates the unknown film thickness based on Ct, W, and T.

(Function) According to the present invention, since the insulator film thickness measuring method and its measuring device are configured as described above, lines of electric force having a fringing effect are generated between the first and second electrodes. , the measured value of the capacitance Ct between both electrodes due to the lines of electric force, the preset ε of the insulator, W, T of the second electrode, ε, D, W
, T. By calculating the capacitance Cto which is uniquely determined from T, the unknown film thickness can be calculated. In this way, the use of electric lines of force with a fringing effect increases the degree of freedom in selecting the shapes of the first and second electrodes.In particular, by reducing the width W of the second electrode, the insulator can be made with a small area. Highly accurate film thickness measurements can be performed even on curved surfaces. Therefore, the above-mentioned problem can be eliminated.

(Example) FIG. 1 is a schematic diagram of a measuring device showing the insulator film thickness measuring method and measuring device of the present invention.

In FIG. 1, 11 is a PSG layer in a semiconductor element;
It is an insulator such as a silicon oxide layer, and this insulator 11 is
It has a relatively large area with a dielectric constant ε and film thickness. A first electrode 12 and a second electrode 13 are provided on both sides of the insulator 11.
and are provided. The first electrode 12 is made of a conductive metal layer, a semiconductor substrate, or the like, and, like the insulator 11, has a relatively large area. second electrode 1
3 is composed of a conductive metal layer such as A pattern, a semiconductor substrate, etc., and has a length of depth, a width of left and right sides W, and a thickness of T.
In consideration of the fringing effect, the width W is the insulator 11.
and is formed smaller than the width of the first electrode 12.

A cable 14.15 is connected to each of the first and second electrodes 12.13, and is connected to the measuring device main body 16 via this cable 14.15. Measuring device body 1
6 is a device for determining the film thickness of the insulator 11, and includes a measuring section 17, a storage section 18, and a calculation section 19. The measuring section 17 includes a power source that outputs a voltage (■) and a capacitance measuring device. The storage unit 18 has a memory device that stores various data, and the calculation unit 19 includes a control circuit that controls the measuring device main body 16 and a calculation circuit that performs various calculations, and is composed of, for example, a CPU. .

Using the above-described device, when voltage ■ is outputted from the measurement unit 17 and applied between the first and second electrodes 12.13, the second electrode r-electrode 13 due to the fringing effect.
Most of the lines of electric force from the first electrode 12 terminate at the surface of the first electrode 12, and most of the lines of electric force from the first electrode 12 terminate at the second side.
It terminates at the electrode 13 of.

Here, the second electrode 13 has a constant length L and various widths W and thickness T, and the insulator 11 has a dielectric constant ε
(: 3.9) is kept constant and the film thickness is varied, each total capacitance CO is measured by the measuring section 17, and then the measuring section 1
7 to calculate the capacitance Cto per unit length 1 (am) of the length. Then, a capacitance characteristic diagram as shown in FIG. 3 is obtained.

In Figure 3, the horizontal axis is %II/D, the vertical axis is Cto,
Each capacitance curve when T/D is 10.5.0.2.0.1.0.0.1 is shown by x1 to x5. Note that the straight line Y indicates the capacitance characteristic of the parallel plate electrodes.

From this FIG. 3, a first-order approximation equation for the capacitance Cto as shown in the following equation can be obtained.

Cto =A (W/D)+B (T/D)+C---
(1) Here, A, B, and C are constants, A is the slope, B is the correction value, and C is the vertical axis intercept. From formula (1), insulator 11
If we derive the film thickness of , we get the following.

AW+BT D=□ (2) The data shown in FIG. 3 including formula (2) for Ct- is stored in advance in the storage unit 18, and the film thickness of the insulator 11 is determined as follows. .

First, the width W = 4 (JLm), the thickness T = 1 (7 tm), and the length L = 1.8 (c++) are used as the second electrode 13, and the dielectric constant ε = 3.9 of the insulator 11 is used. When the capacitance C
o is measured by the measurement unit 17. Next, the measuring unit 17 calculates the capacitance Ct=2.5 (PF/c) per cm of the length L=1.8 (am).

Here, the film thickness to be determined is, for example, 1 (ILfl+
) to 10 (g, m). Then, the calculation unit 18 calculates a capacitance curve X4. of T/D = 0.1 to 1.0 within the range of horizontal axis W/D = 0.4 to 4.0 in FIG. From the average value at X5, constant A = 0.3
8 (PF/am), B = 0.15 (PF/cm)
, C = 0.8 (PF/cm), and further these constants A''C, Cto = 2.5 (PF/cm), W = 4
(JLll) and T=1 (JLI) are substituted into the above equation (2) to calculate the film thickness as follows.

D=0.98 (JLm) Since the actual value of the film thickness is 1 (JLm), this means that highly accurate film H measurement of ±2% can be performed.

Therefore, in the measurement method of this embodiment, the dielectric constant ε of the insulator 11 is kept constant and the film thickness, the width W of the second electrode 13,
Capacitance characteristic data for the capacitance Cto per unit length when the thickness T is varied variously, and equation (2) based on the data are obtained in advance. Then, the capacitance C per unit length of the insulator 11 to be actually measured
Next, constants A, B, and C of equation (2) are determined, and these constants A, B, and C, the measured capacitance Ct, and the width W and thickness T of the second electrode 13 are calculated using equation (2). ), the unknown film thickness can be obtained.

According to such a measurement method, by making the second electrode 13 small, not only can the insulator film thickness on a small surface be measured with high precision, but even when the insulator 11 has a curved shape, the curved surface can be measured. The film thickness can be measured with relatively high accuracy by regarding it as a substantially flat surface.

Further, in the measuring device of this embodiment, the capacitance characteristic data and the equation (2) based on the data are stored in the storage unit 18, and the insulator 11 to be actually measured is stored in the storage unit 18.
The measuring unit 17 measures the capacitance Ct of the measured capacitance Ct.
If the unknown film thickness is calculated in the calculating section 19 using t and the data in the storage section 18, the film thickness can be easily measured. In this device, not only does it have the advantages of the above method, but the first and second electrodes 12, 13 may be electrodes specially made for the measuring device, or they may be made of existing conductive members, semiconductor members, etc. It may also be used as an electrode. -For example,
When measuring the thickness of a paint film on a metal plate in a large device, use the metal plate as the first electrode 12, bring the small second electrode 13 into contact with the paint film, and measure the thickness of the paint film. becomes possible.

Note that the method and apparatus of the present invention are not limited to the illustrated embodiments, and can be modified in various ways. For example, in the above embodiment, a -order approximation formula is used as shown in equation (1), but when the -order approximation formula is used, the range in which accurate film thickness can be obtained is narrow, so a multidimensional approximation formula is used. If , the measurement accuracy is further improved. j (Effects of the Invention) As explained in detail above, according to the measuring method and the measuring device of the present invention, the film thickness is determined by actively utilizing the fringing effect. It is also possible to measure the film thickness at locations with high precision.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an insulator film thickness measuring device showing an embodiment of the method and device of the present invention, FIG. 2 is a diagram showing a conventional insulator film thickness measuring method, and FIG. FIG. 3 is a capacitance characteristic diagram for explaining the method and apparatus shown in the figure. 11... Insulator, 12... First electrode, 13... Second electrode, 14.15...
・Cable, 18... Measuring device body, 17...
...Measuring section, 18...Storage section, 19...
...Arithmetic section. Applicant's agent: Sei Kakinoki +18f! !
! Edge body Insulator film N measurement table of the present invention Fig. 1 Fig. 2

Claims (1)

[Claims] 1. A first electrode and a width W smaller than the width of the first electrode and the insulator are provided on both sides of an insulator whose dielectric constant ε is known and whose film thickness D is unknown. , and a second electrode having a length L and a thickness T, and applying a predetermined voltage between the first and second electrodes to create a fringing effect between the two electrodes. Generate electric lines of force, measure the capacitance Ct per unit length of the length L between the two electrodes, and uniquely calculate it from the dielectric constant ε, film thickness D, width W, and thickness T. Determined capacitance per unit length Ct
o, and the measured capacitance Ct, width W, and thickness T to calculate the unknown film thickness D. 2. A first electrode that contacts one surface of an insulator with a known dielectric constant ε and an unknown film thickness D, and a first electrode that contacts the other surface of the insulator and that insulator and the first electrode. A predetermined voltage is applied between a second electrode having a width W smaller than the width, a length L and a thickness T, and the first and second electrodes to create a fringing effect between the two electrodes. a measuring section that generates electric lines of force having a value of 1, and measures the capacitance Ct per unit length of the length L between the two electrodes; and the dielectric constant ε, film thickness D, width W, and thickness. a storage section that stores a plurality of data regarding capacitance Cto per unit length that is uniquely determined from T; and the data stored in this storage section, the measured capacitance Ct, width W, and thickness T. Based on, the unknown film thickness D
An insulator film thickness measuring device comprising: a calculation unit that calculates .