JPH01161650A - Secondary ion mass analyzer - Google Patents

Abstract

PURPOSE:To enable measurement and indication, together with its mass analysis, of the etching depth of a sample to be inspected which changes continuously by arranging a crystal oscillator near a sample holding part. CONSTITUTION:A crystal oscillator 6 is arranged near a sample holding part 3, and a film thickness meter is composed of this crystal oscillator 6, an oscillator 7 and a signal processing means 8. Since the oscillation number of this crystal oscillator 6 is reversely proportional to square root of the weight, even if it is small change it is measured accurately in electrical meaning. Though a sputtering phenomenon also changes delicately by impurity and grid defect, since there is an approximate bulk phenomenon in the first place, if mass of the bulk and sputter area are known in advance, it is easy to convert mass change into etching amount. Hereby, the etching depth of a sample to be inspected which changes continuously can be measured and indicated as well as its mass analysis.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for measuring and displaying the etching depth of a test sample simultaneously with mass spectrometry of the measured element when measuring the depth distribution of impurity concentration. This invention relates to a secondary ion mass spectrometer that can perform

[Prior Art] In general, a secondary ion mass spectrometer irradiates a sample with primary ions such as oxygen or cesium, and performs mass analysis of the secondary ions generated from the sample to identify elements or perform in-plane depth analysis. This device measures the distribution in the horizontal direction, and its detection accuracy is the highest among surface analysis instruments, and it has the excellent advantage of being applicable to all elements, including hydrogen.

In particular, it detects the secondary ions emitted from the surface layer of the sample to be inspected without etching it with primary ions, so it is a very effective analytical instrument for compositional analysis in the depth direction. It is effectively used to evaluate the concentration profile of impurities and the interface of epitaxial layers.

[Problems to be Solved by the Invention] In depth direction analysis, it is essential to measure the etching depth, and in particular, it is important to know the depth at the time of measurement at the same time as elemental analysis. However, none of the conventional secondary ion mass spectrometers could meet this demand. Normally, after the analysis is completed, the etching depth is measured using an optical interferometer or surface roughness meter, and the etching rate is calculated from the etching time. However, when evaluating multilayer epitaxial crystals of different materials or interfaces between semiconductors and metals or oxides, the etching rate of each layer is naturally different, so even if the overall etching depth is measured, the thickness of each layer cannot be measured. Currently, it is impossible to evaluate the thickness of each layer, and the etching rate of each layer is estimated by separately measuring the thickness of each layer by diagonal polishing or the like. This is a major obstacle to obtaining quick measurement results.

The present invention was devised in view of these problems, and an object of the present invention is to provide a secondary ion mass spectrometer that can simultaneously measure and display the continuously changing etching depth of a sample to be inspected. With the goal.

[Means for Solving the Problems] The present invention irradiates a sample with an ion beam from a primary ion generator and analyzes the mass of secondary ions emitted at that time to determine the elemental distribution on the sample surface. A mass spectrometer for measuring the state is characterized in that a crystal oscillator is disposed near the sample holder and is equipped with a film thickness δ1 for measuring, recording and displaying the etching depth of the sample at the same time as mass analysis of the sample. This is a secondary ion mass spectrometer.

[Function] The film thickness meter of the present invention has a crystal oscillator disposed near the sample holder, so that the quartz crystal oscillator can measure the changes in the deposited material from the sample sputter-deposited on the quartz crystal oscillator. If we refer to the changes in the quality spectrum of the test sample being measured moment by moment and the data on the area where sputtering is being performed, we can detect changes in frequency, that is, changes in the frequency of sputtering. It is possible to trace the depth of the crater. Either display the signal on the external recording side, or convert the measurement time to crater depth using the data processing system after measurement and display the etching depth along with the number of detected counts for each element in the depth direction analysis mode. Bye.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of a mass spectrometer according to the present invention. In the figure, 1 is a part of the ion generating part, and 2 is a sample. The primary ion generating section 1 is a part of a known ion generating mechanism, and includes a duo plasmatron, an electrostatic condenser lens, an electrostatic deflector, etc. (not shown). Some of the ions generated by the duoplasmatron are narrowed down to a beam diameter of several microns by an electrostatic condenser V lens, roughly electrically scanned by an electrostatic deflector, and held in the sample holder 3. The sample 2 is irradiated, and the sample 2 is etched into a rectangle of arbitrary size. The applied voltage at this time is stored and used as data on the crater area. The primary ion beam is directed diagonally to the sample 2 at a predetermined angle.
The secondary ions and neutral atoms generated are extracted perpendicularly to the etched surface. In the figure, 4 is an electrode to which an accelerating electric field is applied to extract secondary ions;
Secondary ions are guided to the mass spectrometer 5 by an accelerating electric field of about 0 kV. The mass spectrometer 5 may have a conventional configuration such as a fan-shaped electromagnetic field or an electron multiplier.

In the figure, reference numeral 6 denotes a crystal oscillator, which is disposed in the space between the surface of the sample 2 near the sample holder 3 and the extraction electrode 4 so as to allow a predetermined solid angle to be observed. 7 constitutes a part of the resonant circuit. The resonance imaging number measured by the resonance circuit is converted into a depth corresponding to the sputter area and mass number data in the signal processing means 8, and then recorded and displayed on the recorder 9. The above-mentioned crystal oscillator 6, camera 7, and signal processing means 8 constitute the film thickness meter of the present invention.

In order to realize the above functions, from the surface of sample 2,
It is necessary to arrange the crystal resonator 6 in the space up to the extraction electrode 4 in a direction that does not interfere with secondary ion extraction. Since the extraction electrode 4 is normally placed at ground potential, the crystal oscillator 6 is also set at the same potential. Most of the sputtered atoms from the surface of the sample 2 are neutral atoms, and the ratio of the neutral atomic state to the ionic state is determined by the primary ion irradiation conditions. The weight of material is proportional to the weight of total material sputtered from Sample 2. Since the frequency of the crystal oscillator 6 is inversely proportional to the square root of the weight,
Even minute changes can be accurately measured electrically. The sputtering phenomenon changes slightly depending on impurities and lattice defects, but in the first approximation it is a bulk phenomenon, so if the mass of the bulk and the sputtering area are known in advance, the change in mass can be converted to etching ω. It's easy to do.

The present invention particularly improves the depth direction analysis function of a secondary ion mass spectrometer.

That is, when analyzing the depth profile of several multilayer films made of several materials, it is possible to apply the actual thickness of each layer to the horizontal axis instead of simply using a scale based on measurement time. The accumulation of such data is considered useful for understanding the fundamental physical property constant of each material, such as the sputtering rate. The method of the present invention can be applied not only to the above-mentioned mass spectrometers, but also to devices that have a mechanism for physically etching the surface with ions, such as electron microscope sample preparation devices, Auger electron spectrometers, etc. Needless to say, this method is quite useful in that the etching depth can be observed on the spot.

[Effects of the Invention] As explained above, according to the present invention, there is provided a secondary ion mass spectrometer capable of measuring and displaying h'1 of the continuously changing etching depth of a sample to be inspected at the same time as mass spectrometry. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention. 1...Primary ion generating section 2...Sample 3...Sample holding section 4...Secondary ion extraction electrode 5...Quality is analysis means 6...Crystal oscillator 7.
...Oscillator 8...Signal processing means 9...
・Record ＾1

Claims (1)

[Claims] (1) A sample is held in a mass spectrometer that measures the elemental distribution state on the sample surface by irradiating the sample with an ion beam from the primary ion generator and analyzing the mass of the secondary ions released at that time. 1. A secondary ion mass spectrometer, characterized in that a crystal oscillator is disposed near the sample, and a film thickness meter is provided for simultaneously measuring, recording and displaying the etching depth of the sample while performing mass analysis of the sample.