JPH03291371A - Thin film formation - Google Patents

Abstract

PURPOSE:To stably produce a thin film having superior crystallinity hy measuring the state of excited particles in plumes and moving a substrate to the optimum position according to the result of the above measurement at the time of forming a thin film on a substrate by means of plumes by a laser ablation method. CONSTITUTION:A target 3 is disposed in a vacuum chamber 2, and the target 3 is irradiated with laser light from a laser generator 1 via a condenser lens 11 and a window material 12 to produce plumes, by which a thin film is formed on a substrate 5. At this time, the plumes in the vicinity of the substrate 5 are received via a window material 13 by an optical system device 6 and the resulting received light is sent via an optical fiber 14 a spectroscope 7 and a computer 8, where the state of excited particles in the plumes is measured. Signals according to the result of spectrometric measurement are sent to substrate holder driving devices 9, 10, by which the position of the substrate 5 is regulated by moving the substrate 5 vertically and horizontally so that the substrate 5 always shows a measurement result fitted to the result of the initial spectrometric measurement in the course of film formation. By this method, the thin films always having superior characteristics can be obtained even if thin film formation is continuously carried out for a long time.

Description

[Detailed description of the invention]

[0001]

[Industrial application field]

The present invention relates to a method for manufacturing thin films such as semiconductor integrated circuits, surface acoustic wave devices, drill tips, etc., and oxide superconducting thin films, and is particularly suitable for manufacturing continuous thin films and continuous thin film manufacturing on elongated bodies. This relates to a manufacturing method. [0002]

[Conventional technology]

In recent years, it has become clear that the laser ablation method has many advantages as a method for producing oxide superconducting thin films (Applied Physics Lett.
ers, 53, 6, 517-519 (1988) and Applied Physics Letters,
54.6.578-580 (1989), etc.). [0003] In addition, the laser ablation method has the following characteristics: (1) There is no compositional deviation between the target and the film, (2) It is possible to form a film at low temperature and at high speed, and the mechanism thereof has been investigated using spectroscopic methods. (Applied Phys.
ics Letters, 54, 2, 179-181
(1989) and Applied Physics
s Letters, 54, 3, 280-282
(1989) etc.). [0004] These studies have revealed that particles ejected from the target are photochemically excited, and the excited particles reach the substrate to form a film, making it possible to form films at low temperatures and at high speeds. It is being done. [0005]

[Problem to be solved by the invention]

In such laser ablation methods, when a thin film is repeatedly formed on a substrate or when a thin film is formed on a substrate over a long period of time, the crystallinity of the obtained thin film changes over time, making it difficult to maintain a stable and good quality film. There was a problem that a thin film with specific characteristics could not be obtained. [0006]An object of the present invention is to provide a method that can consistently produce a thin film with good properties even if the thin film is continuously formed for a long time in such a laser ablation method. [0007]

[Means to solve the problem]

In order to solve the problems of the conventional thin film manufacturing method according to the laser ablation method as described above, the present inventor conducted various studies and found that when thin films are manufactured continuously for a long time by the laser ablation method, good crystal properties can be obtained. The process of finding out that the position of the substrate that can be obtained changes with time, and the invention has been achieved. [0008] That is, the present invention irradiates a target with a laser to generate a plume according to a laser ablation method,
This method forms a thin film on a substrate using this plume, and includes the steps of measuring the state of excited particles within the plume and moving the substrate to an optimal position according to the measurement results. [0009] Here, the plume refers to plasma specific to the target, and refers to a state in which positive ions and electrons coexist. [0010] The reason why the substrate position, where good characteristics can be obtained when manufacturing a thin film continuously for a long time using the laser ablation method, changes over time is not clear, but it is due to changes in the target surface due to erosion, changes in the laser gas, etc. Possible causes include changes in beam shape and distribution due to deterioration, and deformation and movement of the lens and vacuum chamber due to vibration and thermal expansion. [0011] A step of discovering that the position of the substrate at which such good characteristics can be obtained changes with changes in the distribution of excited particles in the plume and the distribution of the ratio of excited particles to the description; The invention has been completed. [0012] The state of the excited particles within the plume can be measured, for example, by spectrometry. The described conditions within the plume can also be determined, for example, by laser spectroscopy and/or mass spectrometry. [0013] Although a thin film of an oxide superconductor can be produced by the production method of the present invention, the present invention is not limited to oxide superconductors and can be applied to other thin films. . [0014]

[Effect]

The manufacturing method of this invention keeps the temporality of the thin film constant by moving the substrate to a position equivalent to the initial state even if the state of the excited particles in the plume changes from its initial state. be. [0015] The state of excited particles within the plume can be measured by spectrometry. The emission intensity at a specific emission wavelength is approximately proportional to the concentration of particles exhibiting emission at that wavelength. For example, in the case of a Y-Ba-Cu-O-based oxide superconductor, excited particles such as Y, Cu, and Ba YO are observed as excited particles generated within the plume of laser ablation. [0016] In the present invention, it is not necessary to measure the described state, but in order to measure the described state, for example, by using a method such as laser spectroscopy or mass spectrometry, the described concentration or the sum of the described state and the excited particles can be measured. It can be measured as This stated concentration and the sum of the stated and excited particles can be measured separately for each particle. For this reason, for example, Y-Ba-
In the case of Cu-0 based oxide superconductor, YSBa, Cu
The concentration of each can be measured. [00i7] In the manufacturing method of the present invention, only the state of the excited particles may be measured by spectroscopic measurement, but it is more preferable to measure both the excited particles and the description since better results can be obtained. The reason for this is not clear, but it may be because the descriptions are distributed relatively evenly. [0018] The measurement results of the spectroscopic measurement indicate that the emission intensity of a specific emission wavelength is 1
It is good also as a signal of only a point, and good also as a signal of the measured value of multiple points. [0019] Further, for the description or the sum of the excited particles and the description, a signal corresponding to a specific element concentration may be used, or the sum of the concentrations of each element may be used. Note that as the sum of the concentrations of each element, a signal from a film thickness meter placed near the substrate may be used. [0020]

【Example】

FIG. 1 is a schematic configuration diagram showing an apparatus for explaining the present invention in detail. Referring to FIG. 1, a target 3 is installed within a vacuum chamber 2. A laser generator 1 is installed outside the vacuum chamber 2, and a laser beam from the laser generator 1 passes through a condenser lens 11 and a window member 12 provided in the vacuum chamber 2, and is irradiated onto the target 3. [0021] A substrate stand 4 is provided at a position facing the target 3, and a substrate 5 is placed on the substrate stand 4. The substrate stand 4 has a built-in heater for heating the substrate. The substrate stand 4 is held by a substrate stand driving device 10. This substrate stage driving device 10 is a driving mechanism for driving the substrate 5 in a direction parallel to the surface of the target 3. Further, this substrate stand driving device 10 is attached to a substrate stand driving device 9. The substrate stage driving device 9 is a driving mechanism for driving the substrate 5 in a direction perpendicular to the surface of the target 3. Board 5
An optical system device 6 for spectroscopically measuring a plume in the vicinity is provided outside the vacuum chamber 2.
The light passing through the window material 13 is received by the optical system device 6. The light received by the optical system device 6 is sent to the spectrometer 7 through the optical fiber 14. A computer 8 is connected to the spectrometer 7 , and sends a signal according to the result of spectroscopic measurement to a substrate table driving device 9 and a substrate table driving device 10 . The substrate stage driving device 9 drives the substrate 5 in a direction perpendicular to the surface of the target 3, and the substrate stage driving device 10 drives the substrate 5 in a direction parallel to the surface of the target 3. [0022] In the apparatus shown in FIG. 1, for example, in the initial stage, spectroscopic measurement of the plume near the substrate 5 is performed, and during film formation, the substrate 5 is always measured so that the substrate 5 shows the measurement result that matches or is closest to the initial spectroscopic measurement result. Move to adjust the position of 5. [0023] In addition to spectroscopic measurement, if a means that can also analyze descriptions in the ground state, such as laser spectroscopy and/or mass spectrometry, is used, the ratio of excited particles to descriptions can be measured, and even more precisely. control. Alternatively, spectroscopy and a simple film thickness meter may be used. [0024] Using an apparatus as shown in FIG. 1, a thin film of a Y-Ba-Cu-0 based oxide superconductor was manufactured on a substrate by a laser ablation method. The manufacturing conditions were as follows. [0025] Target: 100 mm diameter YIBa2Cu307-δ
Sintered laser: KrF excimer laser (248 nm) Energy density: 2 J/cm2 Repetition frequency: IHz Peak width: 15 ns Oxygen pressure: 100 mtorr Substrate temperature near 00°C Film forming time: 3000 angstroms/h Substrate: MgO
(100) Examples of the thin film manufacturing method according to the present invention are shown below. [Example 1] In this example, only the emission spectroscopy of Y Ba Cu in the excited state was performed, and the respective emission intensities in the initial state were expressed as ■Y'' (i) Ba (i)
. u(1)■ + and
+ and Y (x) Ba (x)
The position of the substrate was moved so that, when Cu(x), F expressed by the following formula was minimized. [0026]

[Equation 1] Measurement and control of the substrate position were performed every hour. The substrate was moved in the longitudinal direction and in the vertical direction with the same horizontal force by 1 mm each to determine the minimum value of F. [0027] [Example 2] In this example, the emission intensity of excited Y 2 by emission spectroscopy and the emission intensity of Y by laser spectroscopy were measured. The position of the substrate was moved so that the value of F determined by the same method as in Example 1 was minimized. [0028]

[Formula 2] is expressed by the following formula, where x' represents the intensity of light emitted by laser spectroscopy. [0029] [Comparative Example 1] For comparison, a thin film was manufactured without moving the substrate 1. [0030] In Examples 1 and 2 and Comparative Example 1, 77.0% was measured by the DC 4-terminal method every 10 times of thin film production.
The critical current density at 3° was measured. Note that when measurements were not performed, continuous film formation was performed for 9 hours using a dummy substrate. [00313 The obtained critical current density data is shown in FIG. 2. As is clear from FIG. 2, the thin films manufactured in Examples 1 and 2 according to the present invention exhibit high critical current densities as in the initial state even after time passes. On the other hand, in the thin film of Comparative Example 1 in which the substrate 1 was not controlled, the critical current density decreased significantly over time. [0032] [Example 3] Laser repetition frequency is 5 Hz, oxygen pressure is 200 mtor
A thin film of Y-Ba-Cu-0 based oxide superconductor was manufactured under the same conditions as in Example 1 except that the film forming time was 3000A715 minutes. The substrate was set to move on an axis perpendicular to the target passing through the laser irradiation portion of the target. [0033] The spectrum of plasma generated by the laser ablation method was collected and analyzed using a convex lens. A mechanism was provided to move the convex lens together with the substrate stand so that the focus of the convex lens was set at a position 10 mm directly above the center of the substrate. [0034] The sum of the spectral intensities of wavelengths 569.78 to 576.43 nm (emission spectra of YO and BaO) and 422
．． 04±0.1 nm (Y emission spectrum) ratio ■56
9.78 576, 43nm/■422.04 was determined.・[0035] ■569.78~5□6.43nm/■4°2. o4
> In the case of 15, move the board closer to the target.
■569.78~576, 43nm/■422.04〈
In the case of No. 10, the substrate was driven away from the target. [0036] When films were continuously formed on 10 substrates, the density of the distance between each substrate (representative value at the end of film formation on each substrate) was as shown in Table 1. [0037]

[Table 1] Target before and after continuous film formation of 0 sheets and critical current at 77.3 [Comparative Example 2] In Example 3, the first target-substrate distance was 63 mm.
The results were conducted for the 111th time. No movement of the substrate was performed. The critical current density decreased to 2.3×104 A/cm2. [0038] [Example 4] Using the apparatus shown in FIG. 1, B i -3r-Ca
A thin film of a -Cu-0 based oxide superconductor was fabricated on an MgO (110) surface by laser ablation. The manufacturing conditions are shown below. [0039] Target: Diameter 75 mrnB i2 S r 2
Ca 2 Cu 3 ox laser: KrF excimer laser (248 nm) Energy density = 3.2 J/Cm2 Repetition frequency: 5 Hz Oxygen pressure: 50 mtorr Substrate temperature near 00°C Film forming time: 5000 angstroms 720 minutes wavelength 55
The ratio of the sum of the spectral intensities from 0 to 580 nm (mainly the emission spectrum of oxide molecules) and 400 to 430 nm (mainly the emission spectrum of metal atoms or ions)
~ /■ ~ was sought. 550 580nm 400 430nm [004
0] I5. . ~580nm/I400~43onm>1.
In case of 5, move the board closer to the target.
~ /I ~ 1. In the case of O, the substrate was driven away from the target laser by 550 nm, 580 nm, 400 nm, and 430 nm. [0041] When film formation was performed on five substrates in succession, the target-substrate distance (representative value at the end of film formation for each substrate) and zero resistance temperature before and after continuous film formation on five substrates are shown in Table 2. The result was [0042]

[Table 2] [Comparative Example 3] In Example 4, the first target-substrate distance was 56 mm.
Then, the sixth film formation was performed. No substrate movement was performed. Zero resistance temperature decreased to 56K. [0043]

【Effect of the invention】

As is clear from the above, according to the thin film manufacturing method according to the present invention, a thin film having good crystallization time can be stably manufactured. This is particularly useful when manufacturing thin films many times or over a long period of time. Therefore, it is effective for manufacturing an oxide superconducting tape, etc., in which an oxide superconducting thin film is formed on a long body, for example, a tape-shaped substrate, and a copper stabilizing layer is formed thereon. [0044] In the example, the manufacturing of a superconducting thin film was explained as an example, but
The manufacturing method of the present invention is not limited to manufacturing superconducting thin films, but can also be applied to manufacturing other thin films. It is particularly useful for products that require low-temperature and high-speed film formation.

[Brief explanation of drawings]

[Figure 1] FIG. 1 is a schematic configuration diagram showing an apparatus for explaining the present invention.

FIG. 2 is a diagram showing temporal changes in critical current density of a Y-Ba-Cu-0 based oxide superconducting thin film produced according to the present invention.

[Explanation of symbols]

laser generator vacuum chamber target board stand substrate optical system equipment spectrometer Computer Board drive device O board stand drive device 1 Condensing lens 2.13 Window materials

[Document base]

drawing

[Figure 1]

[Figure 2]

Claims (6)

[Claims] 1. A method according to a laser ablation method, in which a target is irradiated with a laser to generate a plume, and the plume forms a thin film on a substrate, the method comprising: measuring the state of excited particles within the plume; and a step of moving the substrate to an optimal position according to the measurement result. 2. The thin film manufacturing method according to claim 1, wherein the state of non-excited particles as well as the state of excited particles within the plume are measured. 3. The thin film manufacturing method according to claim 1, wherein the state of excited particles within the plume is measured by spectrometry. 4. The thin film manufacturing method according to claim 2, wherein the state of unexcited particles within the plume is measured by laser spectroscopy and/or mass spectrometry. 5. The thin film manufacturing method according to claim 1, wherein the thin film is a superconducting thin film. 6. The thin film manufacturing method according to claim 1, wherein the substrate is a long body.