JPS6311808A - Film thickness monitor - Google Patents

Abstract

PURPOSE:To enable application of the title monitor even under a high temperature along with an extended life, by providing a probe for detecting an ion current of a cluster reaching a substrate, a detector and an arithmetic control section. CONSTITUTION:A substrate S is mounted on a holder 23 arranged at an evaporation area C of a vacuum tank 10. A probe 1 in which is formed by fitting a leg 1b at the center of one side of a disc-shaped head 1a, both being made of conductive material, is mounted to a hole 23a cut close to the periphery of a holder 23 through an insulating material 1c and the position of the head 1a is so set that the head 1a almost is flush with the front surface of the substrate S. A ammeter 2 for small current is electrically connected between the leg 1b and the tank 10 grounded and detects current generated as a cluster 25 reaches the head 1a to send the detection value to an arithmetic control section 3, which 3 calculates an ion current density based on an ion current and the area of the head 1a to compute a thickness or the like of the surface of the substrate S according to a specified expression. This enables repeated use of the probe 1 to obtain a high measuring accuracy without being affected by atmospheric temperature.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides an ion cluster beam (ICB) vapor deposition device,
This invention relates to a film thickness monitoring device used in ion blating devices and the like.

[Technical background]

A closed crucible containing a substance to be evaporated is heated in a vacuum layer, and the vapor of the evaporation substance in the crucible is maintained in a thermal equilibrium state while being injected from an injection port into a low gas pressure region in a vacuum chamber. By using the supercooled state due to adiabatic expansion at that time and the condensation effect due to the supersaturated state based on this,
A cluster ion beam evaporation apparatus has been proposed, which forms a lumpy atomic group consisting of 1,000 atoms, a so-called cluster, ionizes the atomic mass, accelerates the collision toward the target substrate surface, and forms a film. Publication No. 54-9592).

This cluster ion beam evaporation apparatus is constructed as schematically shown in FIG. The first part is a schematic diagram of a cluster ion beam evaporation apparatus to which the film thickness monitoring device according to the present invention is applied, but the cluster ion beam evaporation apparatus itself has a conventionally known general configuration, so please refer to this. explain.

In the figure, numeral 10 indicates a vacuum chamber, which can be set to an appropriate degree of vacuum using an exhaust system (not shown). The interior of the vacuum chamber 10 includes a heating area A in which a crucible 14 containing a substance to be deposited is heated and steam is spouted out, and a heating zone A in which the spouted steam is condensed to form clusters 25, the clusters 25 are ionized, and the substrate S side is heated. The area is divided into an acceleration area B where the ionized clusters 25 are accelerated towards the substrate S, and a deposition area C where the ionized clusters 25 are made to collide with the substrate S to form a film.

A cylindrical electrode 1 is provided in the heating area A along the peripheral wall of the vacuum chamber 10.
A crucible 14 is disposed inside the crucible 14 containing a vapor deposition material with a small-diameter ejection port 14 a facing the opening 12 a of the electrode 12 . A bombarded filament 15 is provided for directly and indirectly heating.

A first DC power supply 17 for biasing is provided between the crucible 14 and the electrode 11 with the positive electrode facing the crucible 14, and an AC power supply 16 for heating the bombarded filament 15 to about 2000° C. is provided.

In the acceleration region B, there is an ionization filament 18 that emits electrons concentrically with the opening 12a inside the electrode 12, which has a cylindrical shape along the peripheral wall of the vacuum chamber IO and whose lower part is closed except for the central opening 12a. A grid 19 is provided that causes the generated electrons to collide with the cluster 25. The ionization filament 18 has an AC type i20 for heating it.
Further, a second bias DC power source 21 is provided between the electrode 12 and the grid 19.

The evaporation zone C is separated from the acceleration zone B by a disk-shaped electrode 13 with an opening 13a in the center, and a holder 23 is disposed above it, and the 'U +FtS can be attached and detached to this holder 23. is installed on.

Electrode 13, holder 23, grid 19, and crucible 14
A grid 19 and a crucible 1 are connected to the electrode 13 between
A third DC power supply 22 that positively biases the potential of No. 4 is provided. Both the electrode 13 and the holder 23 are grounded, and the electrode 13 accelerates the ionized clusters 25 to the electrode 13.

In the cluster ion beam evaporation apparatus as described above, an exhaust system (not shown) is operated to vacuum the inside of the vacuum chamber 10.
The degree of vacuum is set to about hTorr, and the bombarded filament 15 is heated with the AC power supply 16, and the crucible 14 is directly heated with the side radiation heat. The crucible 14 has electrons biased to a positive potential with respect to the bombarded filament 15 by a first DC power source 17.
The crucible 14 is indirectly heated by this collision.

The substance to be deposited housed in the crucible 14 is heated to evaporate so as to maintain a thermal equilibrium state, and is ejected from the ejection port 14a into the heating area A and further into the heating area B through the opening 12a. Adiabatic expansion due to the pressure difference between the inside and the inside of the vacuum chamber 10 results in a supercooled state, and due to the condensation action in the supersaturated state based on this, 200 to 100
A cluster 25 is formed in which about 0 atoms are condensed.

This cluster 25 is charged with a positive charge by colliding with electrons emitted from the ionized filament 8 whose potential is negatively biased with respect to the grid 19 by the second DC power supply 21 within the acceleration region B and accelerated by the grid 19. The cluster ions are converted into cluster ions having , are given kinetic energy toward the substrate S by the electrode 13, reach the surface of the substrate S, and are deposited thereon to form a thin film.

[Prior art]

When forming a thin film on a substrate, the thin film formation speed is closely related to the film quality, and the film formation speed or film thickness is an essential control item in order to improve the film quality. There is.

For this reason, conventionally, as shown in FIG. 5, a crystal oscillator type probe 31 is placed in the flying area of the cluster 25 immediately in front of the substrate S attached to the holder 23 by penetrating the vacuum chamber 10. The calculation control unit 32 calculates the change in vibration frequency due to the cluster 25 colliding and adhering to the probe 31.
, and calculates the film thickness for the substrate S (Japanese Unexamined Patent Publication No. 57-39171).

[Problem that the invention seeks to solve]

By the way, in the conventional device as mentioned above, the probe 3
1 itself is within the deposition area C, and naturally cluster 2 also exists here.
5 collides and adheres to it, so if it is used several times, errors will become large due to the clusters 25 deposited on it, and its function will be lost and it will have to be replaced. There were problems such as the inability to use it at high temperatures above ℃.

The present invention has been made in view of the above circumstances, and its object is to provide a film thickness monitoring device that has a long life span, can be used for a long period of time, and can be used without any inconvenience even at high temperatures.

[Means for deciding issues]

The present invention includes a probe and a detector that detect the ion current of ionized atoms or clusters thereof reaching the substrate, and an arithmetic control unit that calculates the film thickness based on the detected value.

[Effect]

This allows the present invention to be used continuously without being affected by the deposition of atoms or their clusters on the probe, and to determine the film thickness by detecting the ion current density, which is closely related to the deposition rate. .

〔Example〕

Hereinafter, a configuration in which the present invention is applied to a cluster ion beam evaporation apparatus as shown in FIG. 1 will be explained in detail. Second
The figure is a schematic diagram of a film thickness monitoring device according to the present invention (hereinafter referred to as the device of the present invention), and FIG. 3 is a partially enlarged sectional view showing the state in which the probe is attached.

A substrate S is removably attached to the center of a holder 23 disposed in the evaporation area C of the vacuum chamber 10, but the substrate S is located near the periphery of the holder 23 and is slightly spaced so that it does not come into contact with the base electrode S. A probe 1 constituting the device of the present invention is mounted across a gap, and a microcurrent meter 2 for detecting an ion current is attached to the probe 1, and a microcurrent meter 2 further detects the film of the substrate S based on the detected ion current. An arithmetic control section 3 that calculates and controls the thickness is provided.

The probe 1 is composed of a disk-shaped head 1a made of a conductive material, and a foot 1b provided at the center of one side of the head 1a. An insulating material I formed of ceramic or the like is placed in the hole 23a.
The head 1a is mounted in an insulated state from the holder 23 with a C interposed therebetween, and the head 1a is positioned on the lower surface side of the holder 23, and is set to be between the front surface of the substrate S fixed thereto and the road surface.

The microammeter 2 is electrically connected between the foot 1b of the probe 10 and the grounded vacuum chamber 10, and detects the current generated when the positively charged cluster reaches the head 1a. At the same time, the detected value is taken into the arithmetic control section 3.

The arithmetic control unit 3 calculates the ion current per unit area, that is, the ion current density, based on the ion current and the area of the head 1a of the probe 1, and based on this calculates the relational expression between the ion current density and the vapor deposition rate, etc., determined in advance. Accordingly, the deposition rate and film thickness of the cluster 25 on the substrate S are calculated, and the calculated film thickness is compared with a predetermined film-forming schedule.
The temperature of the heating bombarded filament 1-15 is controlled by adjusting the AC power source 16 to modify the deposition rate.

Figure 4 is a graph showing the relationship between ion current density (A/ms'') and material deposition rate (input/min), with the former plotted on the vertical axis and the latter plotted on the horizontal axis. shows the relationship when the accelerating voltage is set to 1 kV, 3 kV, and 5 kV, respectively.

As is clear from this graph, if the accelerating voltage is kept constant, the ion current density and the deposition rate, that is, the film thickness, have a substantially constant relationship.

Therefore, by providing the relational expression or proportionality coefficient for each acceleration voltage to the calculation control section 3 in advance, the deposition rate can be easily calculated based on the ion current density.

Therefore, in the device of the present invention configured as described above, the first
．． As shown in Figure 2.3, the steam ejected from the spout 14a of the crucible 14 expands adiabatically due to the difference in pressure and temperature between the inside and outside of the crucible 14 and becomes a supercooled state, and due to the supersaturated state based on this, atoms is condensed to form a cluster 25, which is ionized in the acceleration region B, accelerated by the electrode 13, and is made to collide and adhere to the surface of the substrate S, but some of it also collides and adheres to the surface of the head 1a of the probe 1. Therefore, an ionic current is generated in the probe 1 based on the positive charge charged on the cluster 25. This ion current is detected by the microammeter 2, and the detected value is taken into the calculation control section 33.

The arithmetic control unit 33 calculates the ion current density based on the area of the head 1a of the probe 1, etc., and then calculates the deposition rate (person/min) from the ion current density based on the relationship shown in FIG. The film thickness is calculated taking time into account, and the calculated film thickness is compared with a predetermined film formation schedule.
It is determined whether or not the film thickness is appropriate, and if the film thickness is small or large, the heating AC power source 16 of the crucible 14 is adjusted, for example, to adjust the film formation speed, and the film formation speed is automatically controlled.

In addition, in the above embodiment, the probe 31 is attached to the holder 23.
Although a configuration in which a single layer is installed has been described, a configuration may also be adopted in which a plurality of layers are installed along the peripheral edge of the substrate S and the film thickness is determined based on the average value. Furthermore, in the above embodiment, the probe 31 is fixed to the holder 23.
The configuration is not limited to this at all, and the configuration may be such that it is attached to an arm extending from the peripheral wall of the vacuum chamber 1 to the area where the clusters fly.

Furthermore, in the above-described embodiments, the configuration has been described as applied to a cluster ion beam evaporation apparatus, but it goes without saying that the present invention is not limited to this, and can also be applied to, for example, an ion blating apparatus.

〔effect〕

As described above, in the apparatus of the present invention, the ion current generated when ionized atoms or clusters thereof reach the conductive probe is detected, and the It
The present invention has excellent effects such as being able to be used repeatedly, having a long life, being almost unaffected by ambient temperature, and achieving high measurement accuracy.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the general configuration of a cluster ion beam evaporation apparatus to which the present invention is applied, and FIG. 2 is a schematic diagram showing the state in which the present invention apparatus is attached to the cluster ion beam evaporation apparatus shown in FIG. 1. , FIG. 3 is a partially enlarged sectional view showing how the probe is attached to the holder, FIG. 4 is a graph showing the relationship between ion current density and deposition rate, and FIG. 5 is similar to FIG. 1? FIG. 2 is a schematic diagram showing a state in which a conventional device is attached to the cluster ion beam evaporation device shown in FIG. 1... Probe 1a... Head 1b... Feet
1c...Insulator 2...Micro ammeter 3...Calculation control unit S...Substrate 10...Vacuum chamber 11,12.
13... Electrode 14... Crucible 15... Bombarded filament 16... AC power supply 17... First DC power supply 18... Ionization filament 19... Grid 20... AC power supply 21... -Second DC power supply 23...Holder In the drawings, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. In a device that ionizes atoms or clusters of a substance to be deposited on a substrate, allows them to reach the substrate, and monitors the thickness of a film formed on the substrate surface, the flying of the ionized atoms or clusters thereof A conductive probe arranged facing the direction, a detector that detects the ion current generated when ionized atoms or clusters thereof reach the probe, and 1. A film thickness monitoring device, comprising: an arithmetic control unit that determines the thickness of the film.