SU828057A1 - Method of dielectric film quality control - Google Patents

Description

one

The invention relates to the field of electronics and can be used to control the quality of thin dielectric films in integrated circuits.

Thin dielectric films are widely used in microelectronics as insulating and passivating coatings, dielectrics of thin-film capacitors, elements of MDM and MIS structures, and other devices.

Such defects in dielectric films as contaminants with foreign substances, microcracks, microcores, closed and through pores, degrade the electrophysical properties of the films and lead to catastrophic failures of devices made on their basis.

The quality control of dielectric films allows control methods based on the determination of the nature and magnitude of the electric current flowing through the film under study.

When such methods are carried out, the contact dielectric film deposited on the conductive substrate is created to make contact either mechanically (by probe) or by sputtering a metal film; the quality of the dielectric film is judged by the magnitude and nature of the current flowing through the obtained MDM n. MDP - structure

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When implementing such methods of control, the total defectness of the MDM and MIS structures is determined, to which both the defects of the dielectric film under study, and the metallization defects or imperfections of the probe-film contact can contribute.

The need to apply a metal film on the dielectric film under study makes the control method destructive, since the substrate with the film under study is eliminated from the process group of a specific instrument or integrated circuit.

In the manufacture and study of dielectric films, the task of non-destructive quality control,

direct detection of defects in the dielectric film.

It is known to detect capillary holes in a dielectric film, which implies that a dielectric film is applied to a conductive substrate, a moving probe is applied to the film and the probe and the substrate are connected through resistors to the power supply. Connect to the measuring resistor

low and high pass filters and measure the magnitude of high frequency and low frequency signals passing through a dielectric film. The ratio of these signals is the dielectric nonlinearity. The defectiveness of the film is judged by a well low frequency signal. The occurrence of the high frequency signal is explained by the discharge between the probe and the substrate.

This method, adopted as a prototype, permits the detection of defects causing leakage currents to flow through the dielectric film.

However, the accuracy of the assessment of defects is low due to the lack of contact “probe-film. The speed of the control process is limited by the speed of the mechanical movement of the probe. In addition, there is the possibility of mechanical damage to the film by an unshifting probe.

The purpose of the invention is to increase the accuracy and speed of the process of controlling the quality of dielectric films by implementing non-contact control of the current flowing through the film.

This is achieved by the fact that, before registering the current, the dielectric film is irradiated with a pulsed electron beam.

The parameters of the electron-beam effect are chosen based on the electrophysical properties and the thickness of the film under study.

For this, it is necessary that the electron path in the film material be much smaller than the thickness of the film, i.e.

.

where b is the depth of run of electro; L - thick film.

And the zero voltage in the dielectric, caused by the charge accumulating during the action of the irradiation pulse, was much less than the intrusive strength of the dielectric film, i.e.

etc,

where E is the field voltage in the dielectric;

pr - probippa dielectric filament.

The pulsed nature of the electron-beam effect is necessary so that the charge applied during the pulse action is neutralized during the pause between the pulses due to the injection of electrons from the conductive and the substrate.

Compliance with the irradiation condition bc is necessary so that there is no end-to-end shot through the electrons of the beam.

The observance of the condition Е С fnp is necessary to exclude the possibility of electrical breakdown of the filter. The intensity of the field E is determined by the potential difference D And

between the surface of the film and the substrate and the thickness of the dielectric.

The accuracy of modern methods for measuring the thickness of thin films suggests that subject to the conditions of

 ten

): 10 "through the chamber and

Electrical breakdown and h of thickness h will be excluded. Local reduced film thickness by 10 times or more (mk), respectively, will be identified as defects.

FIG. 1 shows a diagram of an apparatus for carrying out the method; in fig. 2 - thickness dependence of the defect thickness; in fig. 3 - dependence of the current through conduction on the film thickness.

The device contains an electronic nyushka 1 fed from a power source 2 through a filter of lower 3 frequencies, the dielectric 4 under study is installed on a conductive substrate 5. The signal passing through the dielectric film 4 is removed from measuring resistor 6 to which filters 7 and 8 are connected low and high frequencies. The output of the low-pass filter 7 through an adjustable attenuator 9 is connected to the speaker 10. The output of the filter 8 is upper frequencies through the selective amplifier 11 connected to the indicator 12.

By the detailed method, the dependence of the thickness of the GeO film on defects was determined. The GeO film was produced by thermal isolation in vacuum. An Al film deposited on a glass substrate was used as the conducting sublayer. The A1 and GeO films were sprayed on a UVN-2M-1 vacuum deposition unit.

The spray patterns are listed in the table.

T a b l and c a

The test specimen was as shown in FIG. 2. The sample was placed in a vacuum chamber and irradiated.

The source of electrons was an electron beam tube of type 8 L029I, which was powered and controlled from a C 1-5 pulsed synchroscope. The screen of the tube was cut off and the electron beam was directed to a controlled structure.

The following irradiation parameters were selected by calculation:

accelerating voltage 1 kV beam current / 5 μA

beam diameter in the plane

film 5 mm

pulse duration

pulse frequency / 40 Hz

With these electron-beam effect parameters, the conditions are met to ensure that for a defect-free film there is no "through chamber of the beam electrons and the possibility of electrical breakdown is excluded.

The application of the invention made it possible, by detecting the current flowing through the film, to determine the dielectric nonlinearity, and the through conduction current caused by conductive defects and through pairs in the dielectric film from the nonlinearity value.

The dependence of the current through conduction on the film thickness is shown in FIG. 3, curve 1.

To verify the objectivity of the proposed control method, the dependence of the density of through pores on the film thickness for the same sample was determined by poisoning the underlayer.

An etchant was applied to the dielectric film (3% pF solution), which, without destroying the dielectric, penetrated through through pores and strained the aluminum underlayer. The etching mode was chosen such that the aluminum was etched under the dielectric film and holes formed in the metamic film corresponding to the pores in the dielectric. After etching and washing, the samples were observed under a microscope.

MIM-8M. penetration density was determined. The dependence of the density of through pores / on the thickness of the dielectric film is shown in FIG. 3, curve 2. As can be seen, the curves are equidistant, which indicates the objectivity of the proposed control method.

Claims (2)

1. US patent jY 3967196, cl. 324-54, 1976. 2. Japanese patent No. 51-41074, cl. 112N02, 1976 (prototype). / Step./ w10 7yu0, 5 Weight Al about. s , x /, 5 Kff / Fig.d