JPS58167767A - Formation of thin film - Google Patents

Abstract

PURPOSE:To form a thin film with unifom film quality and excellent reproducibility on a substrate, by a method wherein the variation in the pressure of a reactant gas accompanying to metal evaporation is detected in a vacuum container and a metal evaporation amount is controlled corresponding to the detected result. CONSTITUTION:In the vacuum container 1 of a reactive RF plating apparatus provided with the power source 5 of an evaporation source, a high frequency discharge electrode 9 for glow discharge and a D.C. power source 8 for acceleration of generated ion, an evaporation metal 4 is evaporated in an atmosphere of a reactive gas introduced from an introducing port 10 to form a thin film comprising the reaction product of the reactive gas and the evaporation metal on the surface of a substrate 3. The variation in the pressure of the reaction gas accompanying to the evaporation of the above mentioned evaporation metal is detected by a vacuum gauge 17 and the detected output thereof is pref. converted to D.C. voltage by a D.C. converting part 18 while this D.C. voltage is further amplified by a D.C. amplifier 19 to be compared to a reference voltage value by a PID controller 20 and the power source 5 of the evaporation source is controlled to stabilize a metal evaporation amount.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a thin film configured so that a thin film having a constant composition can be obtained with good heat development property.

In the electrical field, chemical field, etc., various conductive thin films or insulating thin films are used.For example, in the field of electronic components, where technological progress has been remarkable in recent years, film quality is uniform for electronic devices. It is desired to realize thin films with excellent properties.

A reactive radio frequency (RF) ion blating method is known as a method for forming a thin film to satisfy such *yav. FIG. 1 is a schematic diagram showing an apparatus i used for carrying out such a conventional reactive 8F ion blating method, in which 1 is a vacuum vessel, 2 is a substrate holder,
3 is a substrate on which a thin film is to be formed, 4 is an evaporation source metal, 5 is an evaporation source power source, 6 is an Karasutaba power source, 7 is a matching circuit, 8 is a DC power source for acceleration, 9 is an electrode for frequency discharge, 10 is a 11 is a reaction gas inlet, 11 is a reaction scum exhaust port, 12 is pulp, and 13 is a crystal oscillator.

14 is a part of the film thickness monitor, and 15 is a part of the evaporation rate monitor.

16 is a part of the controller.

In the above, reactive Kl? The ion brating method is
Glow discharge is generated by the +1 Gjild wave discharge electrode 9 in the vacuum container 1, and the evaporation source metal 4 is evaporated in the atmosphere of the reaction gas introduced from the reaction gas inlet 10.
A thin compound film is deposited on the base &3 by combining the reactive gas component and the metal component. In this method, plasma is generated by the glow discharge, so the reaction gas and gold particles are radicalized or ionized and become chemically active, so the deposition rate is considerably lower than that of ordinary vacuum evaporation methods. Formation of a thin film with excellent crystallinity on a substrate at a temperature of 6J is possible.

Further, an accelerating DC power source 8 is applied between the evaporation source metal 4 and the substrate 3, or DC is applied by the accelerating DC power source 8 (substrate 3@
is θ and θ~several KV) By this, ion! By accelerating it and causing it to collide with the substrate 3, it is possible to make the upper effect more pronounced than in the case of red t. Furthermore, since this reactive F ion blating method utilizes the RP field, it is possible to maintain glow discharge even when the pressure inside the vacuum vessel 1 is quite low (~5X10 teorr). It is possible to form a smooth thin film without any cracks. In addition, the temperature of the substrate 3 can be easily controlled because there is little temperature rise due to ion bombardment or radiation.

Now, in order for M11'J[ to form a uniform thin film a with good reproducibility, the formation conditions for K must be kept constant throughout the entire process of thin film formation.

As mentioned above, when forming a thin film through a chemical reaction between a reactive gas and elements of class 211 or higher, such as metals, it is important to precisely control the amount of each element introduced to maintain the stoichiometry of the thin film. This is a plus in terms of keeping the composition constant.

In this context, parameters for forming a desirable thin film include substrate temperature, frequency power, accelerating voltage, gas pressure, and rust evaporation rate, but stably controlling the metal evaporation rate is the most important. This is the mold cost.

The means traditionally used to achieve this goal are:
This is a crystal oscillation type monitoring method in which a crystal oscillator 13 is placed in a vacuum vessel 1 as shown in FIG. 141, and the metal evaporation rate is detected by this crystal oscillator 13. In other words, depending on the amount of thin film attached to the crystal resonator 13, the resonance J
#1Utilizing the property that the number of rIi changes proportionally, the thickness of the deposited thin film is first measured by the film thickness monitor 514, and the resulting output signal is differentiated by the speed monitor part 15. A control method is adopted in which the rate of change in frequency, that is, the evaporation rate is detected, and the evaporation source power supply 5, which is an output signal to keep the evaporation rate stable at f', is turned on according to the detection result. .

However, in the crystal oscillation type monitoring method described above, when the temperature of the crystal resonator 13 rises due to radiant heat from the 11k source or plasma, the change in the number of resonances 8IjL becomes irregular, resulting in #1 constant error.

(2) There is an upper limit to the film thickness detected by the crystal resonator 13.

(3) Due to the long-term film formation, the high-frequency discharge voltage qh9 and the +1iIK thin film inside the container adhere, so the matching of the ^jIi1 wave power gradually breaks down and the discharge state changes, causing noise and making it difficult to monitor the film thickness. Part 14 K appears.

(4)! 1! The noise generated by the thickness monitor part 14Km is promoted by the differential action of the speed monitor part 15, and thus becomes a larger noise.

(5) Responsiveness is poor because it takes a relatively long processing time to detect a change in resonance frequency and reflect it in the control of evaporation rate from °C.

There were various gaps such as:

Therefore, the conventional method stabilizes the metal evaporation rate K i
iJ becomes difficult to control, and thin film wP+ with uniform film quality
It was impossible to make m-benign m-benign.

The present invention has been made in response to the above problems.

By utilizing the relationship between the chemical reaction between the reactive gas and the metal in the getter action, changes in the pressure of the reactive gas accompanying metal evaporation can be detected, and the amount of metal evaporated can be controlled according to the detection results. The purpose of this invention is to provide a method for forming lI# agricultural acid that is configured to stabilize the evaporation rate fY. Embodiments of the present invention will be described below with reference to the drawings.

When a highly active metal is evaporated in a vacuum vessel containing a reaction gas, the remaining gas is absorbed by the evaporated metal, thereby increasing the degree of vacuum in the vessel, a phenomenon known as getter action. The detailed mechanism of this getter action is complex, but in general.

The evaporated metal, that is, the metal vapor reacts with the residual gas in the gas phase and absorbs it, and even after the ETllK metal component in the container adheres to it, the pressure of the residual gas, so-called gas pressure, increases. It is thought that the degree of vacuum will improve as the pressure decreases. 1. Further, when plasma is generated by discharge, this tendency is accelerated, and the gettering effect is considered to become more pronounced. Therefore, this getter effect is % in the reactive RF ion blating method.
It can be caused by Km.

Here, if the flow rate of the reactant gas introduced after stabilizing the pumping speed in the vacuum container is constant, the gas pressure can be kept constant. The gas pressure at this time is t'Px, and when the metal is subsequently evaporated in the vacuum container 6, the gas pressure decreases to a value P2 lower than the above P1. The rate of decrease in P2 P1=ΔP depends on the amount of metal evaporation lj and the frequency power.

Since the formation of the desired thin film is achieved at the above gas pressure P2, there is a fee for stabilizing this Pzt, and the above Δ
It is desirable to stabilize P. Of the two upper parameters, it is relatively easy to control the high frequency power, but it is difficult to stably control the remaining metal evaporation rate.

However, by utilizing the relationship between the chemical reaction between the reactive gas and the metal in the getter action, the change in the gas pressure ΔPY can be stabilized by controlling KflAJ.

FIG. 2 is a schematic diagram showing a reactive RF brating device used in the thin film forming method according to an embodiment of the present invention. The same parts as in FIG. 1 are designated by the same numbers, and 1.17 is a vacuum gauge;
18 is a DC converter, 19 is a DCyC dump XJ is a PID
It is p4@@.

In the above configuration, after evacuating the inside of the vacuum container l to about 1 x 6 10 torr, oxygen gas is introduced as a reaction gas from the reaction gas inlet 10 to about 8 x 10 torr.
Maintain the gas pressure at rr.

Next, a glow discharge is generated in the vacuum container 1 by a high-frequency electric field, and after the discharge and the gas pressure have changed to a steady state, an evaporation source of gold @ 4° C., for example, zinc, is heated by the evaporation source power source 5 and evaporated. let As the metal evaporates, the gas pressure inside the vacuum container 1 decreases due to the getter action (the degree of vacuum is above normal), and the gas pressure assumes a certain value corresponding to the metal evaporation rate WIK.

The gas pressure value is detected by the vacuum gauge 17, and this detection output is converted to a DCC voltage by a DC converter 518K. Next, the DC voltage is amplified by the DC amplifier 19 and then applied to the PIDli1 moderator 20, where it is compared with a reference voltage value set in advance corresponding to the set gas pressure, and the output is adjusted to be equal to this reference voltage value. is PIDIllim I
is added to the evaporation source power supply 5 from above.

In response to this, the evaporation source power supply 5 controls the metal evaporation amount t's, and the evaporation amount fK corresponds to the DC voltage having a value equal to the reference setting value. Therefore, by detecting the change in gas pressure, the speed to Kimpo Island is controlled to be stable.

〔Example〕

Oxygen gas, which is the above-mentioned reaction gas, and zinc, which is Shimaen Gold #44, combine to form zinc oxide (ZnO).
The nO thin film is deposited on the substrate 3 surface a[IK]. This ZnO thin film has a constant composition and is formed with excellent reproducibility.

When the above evaporation rate changes, the change in gas pressure Δ
The evaporation rate will be controlled until this change ΔP is stabilized.

FIG. 3 shows the characteristics obtained by the present invention, in which the horizontal axis shows the deposition rate (■) and the vertical axis shows the gas pressure change ΔP. - As is clear from the figure, the two values show almost a correlation, indicating that the metal evaporation rate V can be controlled more than K by adjusting the gas pressure change ΔP. In the characteristic diagram, substrate 3 is (Ill) rkJ silicon, substrate temperature f: room temperature, ZnO film thickness: 4 μm, evaporation source boat: tantalum, RF
It shows the case obtained under each configuration condition: 100W, DC bias: OV.

the above! I! As a result of measuring the crystallinity and structure of the thin film '4r: It was confirmed that the method has a 71% accuracy.

As is clear from the above description, according to the present invention, by utilizing the relationship between the chemical reaction between the reactive gas and the metal in the getter action, changes in the pressure of the reactive gas due to metal evaporation can be detected. Adjust the amount of gold II4 evaporated according to the results.
Therefore, the gold-evaporation rate f1
Since the temperature can be stably controlled, a thin film with uniform quality and good development performance can be formed.

Therefore, according to the present invention, the conventional monitoring method using a set of quartz crystals becomes unnecessary, so there is no limit to the film thickness Kltl to be detected, and the detection results can be immediately reflected in the control of the evaporation rate. Therefore, advantages such as improved responsiveness can be obtained.

Furthermore, the cost of a complete crystal monitor device, which is 11bIII, is unnecessary, and the cost can be reduced by 1,000 yen.

Main text'5i! In the example, the case of forming a ZnO thin film was given as an example, but the method can be similarly applied to other cases where a thin film is formed using the chemical reaction between reaction residue and metal. For example, TiO2, Ir+! 03, A
J20m.

Examples include 8iU2, TiN, AjN, etc.

[Brief explanation of the drawing]

FIGS. 1 and 2 are schematic diagrams showing the conventional and E# embodiments, respectively, and FIG. 3 is a characteristic diagram obtained by the present invention. DESCRIPTION OF SYMBOLS 1... Vacuum container, 3... Substrate, 4... Evaporation source whole island, 5... Evaporation source power supply, 17... Vacuum gauge, 18...
...DC conversion section, 19...l) C amplifier, addition...P
li) Regulator. Patent Applicant: Clarion Co., Ltd. Representative: Yoshihiro Benkonshi 1) Takeshi Part 1 Figure 2 Figure 3 5L1 Tori (Door/hr) -

Claims (1)

[Claims] 1. Evaporating the metal in an atmosphere of a reaction gas introduced into a vacuum container, detecting a change in the pressure of the reaction scum accompanying the metal evaporation, and adjusting the metal evaporation according to the detection result. 5. A thin film forming method characterized in that the amount t111IIl is reduced. λ Controlling the amount of metal evaporation so that the amount of pressure change of the reaction gas is constant V% wA of the patent claim
v! The method for forming a thin film according to item M. 3. Depending on the detection result of the pressure change of the reaction gas, the PI
Controlling the amount of metal evaporation from DII[1IIKV
A method for forming a thin film according to claim 1 or 2.