JPH02217468A - Compound thin film forming device - Google Patents

Abstract

PURPOSE:To easily build-up a thin film having the aimed composition on a base plate by discharging sputtering particles from an evaporating source of a plurality of elements and detecting the respective single elements stuck on the base plate and controlling sputtering. CONSTITUTION:Targets 16, 17, 18 made of a sintered body of e.g. PbO, ZrO2 and TiO2 are provided to a thin film forming device 28. The respective targets 16, 17, 18 are irradiated with Ar ions generated from the ion guns 10, 11, 12 respectively and sputtering particles are discharged. The respective sputtering particles are flown and collected on a base plate 19 and a thin film having required composition is formed. At this time, single elements correspondent to the respective targets 16, 17, 18 are stuck to the respective film thickness meters 25, 26, 27. Natural frequency of a crystal resonator is changed in accordance with membranaceoue amount and the build-up composition can be read. Therefore the ionic current densities of the correspondent ion guns are controlled in an ionic current controlling part and the thin film having the aimed composition is built-up on the base plate 19.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an apparatus for forming a compound thin film.

[Conventional technology]

In recent technological developments, thin film technology is being actively studied along with the development of new devices and new functional materials. The iI film formation technology is roughly divided into two types: physical methods and chemical methods.The physical methods include the vacuum evaporation method in which the thin film material is evaporated using a resistance heating element, an electron beam, etc. as a heating source, and the method using plasma gas, In addition to the sputtering method, in which ionized gas or the like collides with the target and uses this kinetic energy to knock out atoms or molecules from the target surface, there are also ion plating methods,
There are cluster ion beam methods, etc., and many chemical methods have been developed, including the general CVD method.

Among thin film materials, single metal thin films have been in practical use for a long time, but recently many compound thin films have been studied, such as superconducting thin films, semiconductor thin films for optoelectronics, and dielectric IIMs for optical ICs. In order to form these thin films, a uniform thin film is required in which the elemental composition ratio in the thin film is appropriate and the elements completely react with each other to form a single target compound.

In order to achieve this, various film forming parameters have been studied in thin film forming apparatuses, and many improvements have been proposed and put into practical use.

A typical practical device is a multi-source vacuum evaporation device, which performs atomic absorption analysis of each element in flight to quantify the composition, and manually sets each film-forming parameter such as the evaporation source heating temperature. An apparatus for controlling the composition of a deposited film is generally known.

However, among compound thin films, perovskite-based ferroelectric thin films such as PbTiOs and PZT (lead zirconate titanate), which contain components with high vapor pressure such as lead compounds, and La
g-xPbx Cu0a-v or YBatCusO? - Due to its characteristics, high-temperature superconductor thin films and the like require polycrystalline or single-crystalline films with a well-organized crystalline state. In order to promote crystallization, the substrate is also heated to a relatively high temperature (for example, 50
0°C to 800°C), reevaporation of some component elements such as lead, and reverse sputtering (particularly in magnetron sputtering) targets and groups are directly exposed to gas plasma at the same time. Furthermore, due to changes over time in the surface composition ratio caused by selective sputtering on the target surface, compositional distribution may occur in the formed thin film, and crystals may be formed due to compositional defects. There are problems with the non-generation of lattices and the induction of lattice defects, which can lead to problems such as the inability to exhibit the desired film characteristics, and it is necessary to set very strict film-forming conditions to obtain a stable thin film. Ta.

In all of the conventional examples mentioned above, this was done by analyzing and quantifying the components of elemental vapors flying from the target (evaporation source) toward the thin film formation substrate, but as in the case of When forming thin films of multi-component compounds such as It was not possible to obtain sufficient data to control the composition.

[Problem to be solved by the invention]

In view of the above-mentioned drawbacks, the present invention has been developed in order to obtain a thin film of a functional composite compound. A thin film with the target compound composition can always be stably obtained regardless of variations in numerous film formation parameters with respect to the thin film composition ratio, such as element re-evaporation, and structural defects in the film due to compositional deviations and deterioration of properties due to composition distribution. It is an object of the present invention to provide a means for easily obtaining a highly functional thin film having a composition that meets a desired composition ratio without deterioration over time or the like.

[Means and effects for solving the problem] This device has a plurality of elemental evaporation sources in a vacuum chamber, a substrate facing it, and a holding mechanism for holding the same. Alternatively, a composition ratio detection section that directly analyzes and quantifies the elemental composition ratio of a compound thin film being deposited on a reference substrate installed under the same conditions as the substrate, a phase compensation section for stably performing negative feedback control, and a composition ratio a comparison amplification section which compares the composition ratio signal output from the detection section with a preset target composition ratio and amplifies and outputs the difference between the two; The present invention is characterized in that it is equipped with a negative feedback control system composed of a control section that controls the amount of energy for element vaporization.

Before describing embodiments, the present invention will be described in detail using an example in which a film thickness meter using a crystal oscillator is installed in a state equivalent to a substrate on which a desired thin film is deposited, and composition control is performed in real time.

The principle of a film thickness meter using a crystal resonator is that the natural vibration of the crystal resonator changes depending on the change in its mass. ! II. When a thin film is attached to a crystal resonator, if the mass of the thin film is sufficiently small compared to the mass of the crystal resonator, the same effect as simply increasing the mass or thickness of the crystal resonator will occur, and the change in mass will be proportional to the change in mass. This method takes advantage of the fact that the natural frequency changes.

FIG. 1 shows a measurement circuit block diagram of a typical quartz crystal oscillator film thickness meter. Most commonly used quartz crystal oscillators have a natural frequency of several MHz, and here a 6 MHz oscillator is shown as an example.

The signal from the crystal oscillator 2 using this crystal resonator 1 is
Enter mixer 7. On the other hand, there is another crystal oscillator 3 using a standard 5,5) IHz crystal resonator. The standard signal from here is mixed with the signal from another oscillator 4 whose frequency is variable from 400 to 500 KHz in a mixer 5.The role of the 0 oscillator 4 is to combine crystal oscillators 1 and 3 The purpose is to adjust the difference in the frequency of the signals from the oscilloscope and appropriately change the zero point of the final output. By mixing the signals from the crystal oscillator 3 and the oscillator 4, the sum and difference frequencies of both frequencies are obtained. The lowest frequency is 5.0MHz when the difference is taken, which is too large a difference from 6M) Iz. Therefore, the signal is input to a mixer 7 through a bandpass filter 6 through which only the sum, that is, only signals with frequencies between the lowest frequency of 5.9 MHz and the highest frequency of 6.0 MHz are passed. A mixer 7 mixes the standard signal and a measurement signal to form a beat, which is sent to an amplifier 9 through a low-pass filter 8 and observed with a multimeter 10.

The following relational expression exists between the frequency change dv and the thin film thickness dx.

G ρ Here, ν is the natural frequency of the crystal resonator, G is the frequency constant (1670kHz・■), ρ is the density of the attached substance, and ρ is the density of the crystal. Calculate dx from this formula. The film thickness can be determined by

In this invention, since it is necessary to understand the composition, the above-mentioned general usage is not used, and the equation (1) is modified as shown in the following equation (2).

Here, S represents the effective area of the film thickness meter, and d- represents the change in mass. dw is calculated from dv using equation (2). If the molecular weight of the molecules forming one film is M, and the total number of molecules in the I film is N, then the relational expression d*=-N-M (K: constant of proportionality) (3) holds.Furthermore, the above molecules When composed of atoms A and B in a stoichiometric ratio ABg, the number n of atoms A,
is required for the following birch.

Now, if the atomic weights of atom A and atom B are a and b, respectively, the following relational expression holds true.

M-a+2b (4) (4
) is introduced into equation (3), and the mass change at this time is dl
Then, ds, = K-N(a+2b)
(5) Since N @ n, the number n^ of atoms A can be calculated using the above formula.

Similarly, the number of atoms C in a thin film formed of atoms C and molecules CtO consisting of atoms can be expressed as follows. here 8
is a proportionality constant, dl is the mass of a thin film made of C1D molecules, and C and d are the atomic weights of atoms C and D, respectively.

Now, taking the ratio of equations (6) and (7), we get La kl ds+ 2
c+dnCkg dJg a +
2b From the derivation process up to equation (6), it is kl-kW, so da,, dead are measured quantities, and a, b, c, and d are known quantities, so the atomic ratio can be found from equation (8). I can do it.

Since the composition of a desired thin film is determined not by the amount but by the relative ratio of each constituent atom, the composition ratio can be determined using a film thickness meter from the above explanation.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail using FIG. 2.

Independently controllable ion guns 10, 11.12 and respective drive devices 13, 14, 15 and targets 16, 17, 1 made of each element of the desired compound in positions opposite thereto.
Install 8. The target 16, 17, 18 is accelerated and ejected from the ion gun 10, 11, 12, and is hit by, for example, a meter ion to emit sputter particles from the surface. Make a geometric arrangement to concentrate on 19. However, here, the cross section 20 when the sputtered bundle is cut on the substrate surface,
21 and 22 are slightly shifted from each other so that they are not concentric. This creates a portion 23 where sputtered bundles from targets 16, 17, and 18 overlap and a portion 24 where they do not overlap.

The substrate 19 is placed at the center of the portion 23 where the sputtered bundles overlap, and film thickness gauges 25, 26, and 27 are individually installed corresponding to the positions of individual sputtered bundles from each target. All of these components are put together in one vacuum chamber (not shown).

A case where, for example, lead zirconate titanate [PZT:Pb(Zr+-wing Ti, es)] is formed into a film using the thin film forming apparatus 28 having the above configuration will be described in more detail. At this time, Targera) 16
．． For 17 and 18, sintered bodies of PbO5Zr01 and TiOx are used, respectively.

Ar ions generated from the ion guns 10, 11, and 12 are irradiated and collided with the targets to release sputtered particles from each target. Sputtered particles from each target gather on the substrate 19 to form the desired PZT. On the other hand, elemental elements corresponding to targets 16, 17, and 18 are adhered to the film thickness gauge 25.26°27, and as mentioned above, the fixed frequency loss of the crystal resonator is dνl according to the film mass.
change only.

By calculating this dv direct using equations (2) to (8), the mutual atomic ratio of Pb, Zr, and Z1, that is, the composition can be determined.

Furthermore, even more precise control can be achieved by appropriately installing a mask (not shown) between the film thickness gauge and the target to adjust the shape of the sputtered bundle so that only each single element is deposited on each film thickness gauge.

The output of the amplifier 30 which amplified the dv signal of the crystal resonator in FIG.

The arithmetic unit 31 calculates d-direction from each constant inputted in advance using equation (2).The 0th order arithmetic unit 32 calculates d-
Using the table, calculate each atomic number 1 using equation (7). Then, the comparator 33 compares it with a desired composition input in advance. At this time, a phase compensator 35 is provided before or after the comparator 33 to correct the time lag between measurement and control in order to stably feed back the measured data negatively to the ion current controller 34 below.

As a result, for example, the ratio of Zr and Tj is appropriate, but pb
If the amount is insufficient, control the ion current density of the ion gun. That is, the ion current control unit 26 increases the ion current density of the ion gun corresponding to the pb target. By controlling this negative feedback loop from time to time, a thin film having a desired composition can be deposited on the substrate.

Next, other embodiments will be described using the drawings from FIG. 3 onwards.

In FIG. 3, multiple elements are simultaneously vapor-deposited one by one on the substrates 37 on the rotating polyhedral substrate holder 36. The atomic or molecular beams evaporated from each evaporation source 38 are shifted from the same center as in the above-mentioned embodiment, and the detection section 39 consisting of a crystal oscillator or equivalent detector is arranged in the same manner. As the substrate holding table 36 rotates, no film is deposited on the substrate other than the one facing the evaporation source 38.
By providing 0** formation chamber 41 and thin film analysis chamber 42
It is possible to separate the elements, eliminate the influence of the incoming elemental vapors, provide a detector 43 of a different type, and use a plurality of analysis techniques in combination. The iI film formation chamber 41 and the thin film analysis chamber 42 are separated by a partition wall 40, and a separate chamber evacuation system can be provided to achieve different degrees of vacuum, making it easy to select usable detectors. Analytical techniques that require high vacuum, such as line microprobe analysis and photoelectron spectroscopy, can also be used. Furthermore, since a relatively large-sized device such as an X-ray diffraction device can be incorporated, it is possible to perform film formation without monitoring the crystallinity and orientation of the thin film being formed. Further, a reference substrate for analysis (not shown) can be separately provided in addition to the substrate 37, and highly accurate analysis methods such as secondary ion spectroscopy, which is destructive analysis, can also be applied. In this way, the effect can be further enhanced by using compositional determination methods based on different principles together and controlling while supplementing each other's data. This configuration can be used in most thin film forming methods such as vacuum evaporation, magnetron sputtering, etc. in addition to ion beam sputtering. Further, 44 is a phase compensation section, 45
4 is a comparison amplification section, and 46 is an evaporation source drive control section.

In addition, as an example of using another analysis method, an ion gun 47 arranged as shown in FIG.
Using a fluorescent X-ray analysis method, a detector 51 such as a scintillator counter detects the characteristic X-rays unique to each element excited by the X-rays incident on the thin film deposited on the substrate 49, and quantifies the elemental composition ratio of the thin film. Film deposition can also be controlled.

In this case, by replacing parts such as the slit of the X-ray source, this detector can be used as an X-ray diffraction device to observe the crystalline state of am, and based on this data, the temperature conditions of the substrate etc. can be controlled. You can also do it.

In FIG. 5, the quartz crystal resonator film thickness gauges 55, 56, and 57 are provided near the substrate 52 at equally spaced positions on the rotary support frame 53 on the same surface as the substrate 52, with the shielding plate 54 interposed therebetween.

The shielding plate 54 is arranged so that sputtered particles are attached only when any one of the film thickness gauges 55, 56, and 57 is located closest to the substrate 52. If the sputtered particles are at other positions, the shielding plate 54 blocks the sputtered particles. Film thickness gauge 55°56.57 is the target 58.
For example, the film thickness gauge 55 measures the amount of adhesion of only sputtered particles from the target 58, and the other film thickness gages similarly measure the amount of adhesion of individual elements.

The operation of this embodiment will be explained below. When the zero-rotation support frame 53 rotates and the film thickness meter 55 is exposed from the shielding plate 54, the ion gun 61 corresponding to the target 58 is operated in synchronization with this, and the ion gun 61 corresponding to the target 58 is activated. Sputtered particles, which are single elements, are emitted from 58 and adhere to the surface of the substrate 52 . At the same time, by similarly depositing on the surface of the film thickness meter 55, the number of atoms can be determined from the mass in the same manner as in the above embodiment. When it is detected that a certain mass has been deposited on the substrate 52, the ion gun 61 stops the sputtering operation and the emission of sputtered particles from the target 58 stops. is hidden behind the shielding plate 54, and the film thickness gauge 56 is exposed instead, and sputtering of a new corresponding target 59 begins. This operation is performed sequentially and continuously, and thin films of each element are laminated while feeding back the adhesion amount (number of atoms) of each element to the output of the ion gun. Like the embodiments described above, this configuration can also be applied to thin film forming methods other than ion beam sputtering, and exhibits sufficient effects in diode sputtering, magnetron sputtering, and other vacuum evaporation methods.

Alternatively, a configuration as shown in FIG. 6 may be adopted.

That is, the target 6 is made of each element or a composition of multiple elements (mixture or compound) corresponding to the target thin film composition.
2. 63, 64 are installed opposite to the substrates 66, 67, 68, 69 fixed to the side surface of the rotating substrate holder 65. Also, an ion gun that irradiates sputter ions to each target? Place 0.71.72. At this time, the ion gun 70, 71, 72 allows the atoms sputtered from the target 62, 63, 64 to be placed only on one side of the substrate holding table 65.
Geometrically arranged for concentrated deposition. Board holding stand 6
5 rotates at a constant speed or stops for a certain period of time when its side faces each target. Here, the thin film composition is measured using crystal oscillator film thickness gauges 73, 74, and 75 that are individually installed near the substrates 66, 67, and 68 in correspondence to each target 62, 63, and 64, respectively.
A detector 62 for the above-mentioned composition determination method or crystal state measurement is attached to the other surface other than the one on which the 2°63.64 is provided, if necessary.

When forming the thin film, the thickness of each crystal resonator was 73.74.
The frequency change due to mass change corresponding to the deposition rate output from ion gun 75 can be determined by the above-mentioned operation.
．． Control is performed so that the composition ratio of each element in the deposited thin film is always constant by being fed back to the sputter ion acceleration voltage and ion current value of 72.

In the above embodiments, the composition of the deposited thin film was controlled by changing the ion current density of the ion gun, but similar effects can also be obtained by controlling the sputtering time of each target.

Additionally, in addition to the above configuration, a detector 76 in the preliminary section is used to quantify low-molecular reaction gas components (e.g., oxygen, nitrogen, chlorine) necessary for forming a compound, and the flow rate of these introduced gases is controlled. You can also do that.

Note that the thickness of each single element thin film laminated on the substrate is preferably several tens of atomic layers, preferably ten atomic layers or less, in order to ultimately form a compound thin film in which these elements have reacted.
Further, in order to obtain a state in which each atom is likely to react, it is preferable to use techniques such as heating the substrate and ion mixing in combination.

Although the above embodiments have been described using three elemental evaporation fX (targets), the present invention is not limited to this.
It is of course possible to create a configuration in which the loss is increased or decreased depending on the composition of the target thin film, and the geometric arrangement of each member may be changed accordingly.

〔Effect of the invention〕

As is clear from the above, in a thin film forming apparatus that forms a compound thin film consisting of multiple elements on a substrate using multiple elemental evaporation sources provided in a vacuum layer, the device is installed on the substrate or under conditions equivalent to the substrate. a composition ratio detection section that directly analyzes and quantifies the elemental composition ratio of the thin film being deposited on the reference substrate, a phase compensation section that performs continuous and stable negative feedback control, and a composition ratio detection section that The thin film composition ratio is compared with the target thin film composition ratio input in advance based on the composition ratio data, and is equipped with a comparison amplification section and a control section that performs negative feedback control of the amount of evaporation of each element, thereby always maintaining a stable target composition. A highly functional thin film with excellent crystallinity and orientation can be obtained without any structural defects in the film due to compositional deviation, property deterioration due to composition distribution, or deterioration over time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram for explaining the invention in detail, FIG. 2 is a diagram for explaining one embodiment of the invention, and FIGS. 3 to 6 show other embodiments of the invention. FIG. 3 is a diagram for explaining an example. ! 0,11.12 Ion gun 16,17.1
8 Target 25.26.27
Membrane pressure gauge diagram Ax diagram Figure 6

Claims (1)

[Claims] 1) A vacuum chamber has a plurality of elemental evaporation sources, a substrate opposed to it, and a holding mechanism for holding the same, and a compound thin film consisting of a plurality of elements is kept under the substrate or under conditions equivalent to the substrate. A composition ratio detection section directly analyzes and quantifies the elemental composition ratio of the compound thin film being deposited on the installed reference substrate, a phase compensation section for stably performing negative feedback control, and an output from the composition ratio detection section. a comparison amplification section that compares the composition ratio signal with a preset target composition ratio and amplifies and outputs the difference between the two; and energy for elemental vaporization that is input to the evaporation source based on the difference signal output from the comparison amplification section. 1. A compound thin film forming apparatus comprising a negative feedback control system comprising a control section for controlling the amount. 2) The compound thin film forming apparatus according to claim 1, further comprising a film thickness detection section for measuring the thickness of the deposited film. 3) The compound thin film forming apparatus according to claim 1, further comprising a film state detection section for measuring the crystal structure and orientation state of the deposited film. 4) Multiple element evaporation sources include sputter deposition such as ion beam sputtering and magnetron sputtering, vacuum evaporation such as resistance heating evaporation, electron beam evaporation or laser heating evaporation, ion plating, physical vapor deposition such as cluster ion beam evaporation, or plasma CVD. 4. The compound thin film forming apparatus according to claim 1, 2 or 3, characterized in that the chemical vapor deposition method is used. 5) The composition ratio detection unit is a crystal oscillator, fluorescent X-ray detection, high-energy reflection electron beam diffraction, electron beam microprobe analysis,
4. The compound thin film forming apparatus according to claim 1, wherein the compound thin film forming apparatus is based on any one of secondary ion spectroscopy, ion microanalyzer, and photoelectron spectroscopy.