JPH03120409A - Crystal oscillation type film thickness gauge - Google Patents

Abstract

PURPOSE:To stably measure film thickness with high accuracy by providing a film thickness measurement part, a crystal temperature control part, and a film thickness arithmetic part. CONSTITUTION:The film thickness measurement part 1 is installed in a vacuum vapor- deposition chamber and vapor-deposition metal powder are radiated from a vapor-deposition source. At such a time, a crystal plate 13 is raised in temperature by powering on a thermocou ple 15 controlled to set temperature by a crystal temperature control part 5 and its natural frequency is fixed corresponding to the set temperature. Variation in the natural frequency which is the difference between the natural frequency of the crystal plate 13 when a film 18 is not vapor-deposited and the natural frequency of the crystal plate 13 when the film 18 is vapor-deposited also varies gradually. The temperature rise of the crystal plate 13 due to the collision of vapor-deposition metal particles is detected by a temperature controller 17 which inputs a temperature detection signal ST outputted by a temperature sensor 16 to adjust the electric feeding quantity I is so adjusted that the temperature rise is eliminated. Consequently, the crystal plate 13 is held at the specific set temperature during formation of the vapor-deposited film 18 and the variation of natural frequency is set to that at the set temperature at all times. An electric signal SF indicating the variation of natural frequency is inputted to the film thickness arithmetic part 2 to calculate the film thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a crystal oscillation type film thickness meter used as a film thickness monitor in a film forming apparatus.

(Prior Art) In general, vacuum evaporation methods require monitoring and control of film thickness. This is because the directional distribution characteristics of the evaporation source, flight,
It is extremely difficult to achieve ideal adhesion. Therefore, the thickness of the film on the actual substrate that requires vapor deposition is controlled by monitoring on a monitor substrate. In this case, crystal is used as the monitor substrate. Then, the film thickness is measured based on the change in the natural frequency of the crystal when the vapor deposited film is attached to the monitor substrate.

(Problems to be Solved by the Invention) Incidentally, the change in the natural frequency of the crystal has temperature dependence, and is a cause of film thickness drift due to the influence of radiant heat during film formation. Therefore, in order to eliminate such radiant heat effects, in the past, the following methods were used: ■ Using crystal cut in a direction with a small temperature coefficient, ■ Installing a water cooling pipe around the crystal substrate to prevent the temperature of the crystal from rising, ■ Using silver A beryllia spacer baked with paste is provided on the back side of the crystal to suppress temperature changes in the crystal.

However, with respect to the above-mentioned 0 term, when forming a film of a high-melting point substance, a film thickness drift of the film thickness gauge occurs significantly due to the influence of high radiation heat. In addition, with respect to the above item 0, even if a water cooling pipe is provided, radiant heat irradiation to the crystal cannot be avoided structurally, so there is a limit to the prevention of temperature rise. Furthermore, with respect to the above-mentioned 0 term, there are restrictions on the temperature range in which temperature changes in the crystal can be effectively suppressed.

The present invention has been made in consideration of these various circumstances, and an object of the present invention is to provide a highly accurate crystal oscillation type film thickness meter that eliminates film thickness drift caused by temperature changes in the crystal oscillator. [Structure of the Invention] (Means and Effects for Solving the Problems) A film thickness measuring section having a crystal plate on which a thin film is applied, a crystal temperature control section heating the crystal plate and maintaining it at a predetermined temperature, The apparatus includes a film thickness measurement section that measures the thickness of a thin film, and is configured to perform film thickness measurement at a constant temperature to improve film thickness measurement accuracy.

(Example) Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a crystal oscillation type film thickness meter according to an embodiment of the present invention. This film thickness meter includes a cylindrical film thickness measurement part (1),
Natural frequency change Δf4C in the film thickness measurement part (1) with
a film thickness calculation unit (2) that calculates the film thickness d based on the film thickness calculation unit (2), a film thickness display unit (3) that displays the film thickness data calculated in the film thickness calculation unit (2), and a film thickness measurement unit t1). It consists of a crystal temperature control section (5) that controls the temperature of a crystal plate (13) to a constant temperature. (6) and this support (
A cylindrical heat shield cap (7) coaxially and removably connected to the opening of 6 and having a through hole (7) in the center.
8), a heat insulating member (9) that is attached to the inside of the heat shield cap (8) and has a through hole (7a) in the center that communicates with the through hole (7) K, and a heat shield cap (8).
A retaining ring having a flange part fixed near the part connected to the support body (6), and a cylindrical part αυ extending from the flange part coaxially with the heat shield cap (8). Q3
, the crystal plate α is removably glued to the tip of the retaining ring (130) and the cylindrical part (11), and the crystal plate α3 is inserted between the crystal plate a3 and the heat insulating member (9). (1
1) Consists of a plurality of leaf springs α that elastically suppress K. On the other hand, the crystal temperature control section (5) controls the crystal plate t.
A heating wire aS disposed close to the inner main surface of the hot water, a temperature sensor such as a thermocouple detachably attached to a part of the crystal plate C13, and temperature detection from this temperature sensor aQ. Based on signal ST, heating wire a! Temperature controller a? increases or decreases the current applied to crystal plate αJ to control the temperature of crystal plate αJ to, for example, 150°C ± 0.1°C. ). Furthermore, the film thickness calculation unit (2) applies a high frequency voltage to both sides of the crystal plate (13), calculates the natural frequency change Δf due to the adhesion of the deposited film α based on the resulting vibration, and further The film thickness d of the deposited film α barrel is determined based on this natural frequency change Δf.Furthermore, the film thickness display section (3) displays the film thickness data and the temperature sensor αe measured at this time. temperature data is displayed.

Next, the operation of the crystal oscillation type film thickness meter having the above configuration will be described.

First, the film thickness measuring section (1) is installed in a vacuum deposition chamber.

Next, the vapor-deposited metal particles are radiated from the vapor deposition source using, for example, electron beam heating. At this time, the temperature of the crystal plate α4 is raised in advance by energizing the heating wire a!9, which is controlled by the crystal temperature control section (5), at a set temperature T (lK) of, for example, 150°C. , the natural frequency fo of the crystal plate 0 is fixed at this set temperature.Thus, vapor deposited metal particles gradually adhere to the crystal plate 0, forming a vapor deposit tm-.

The natural frequency f changes as the deposited film α sand grows,
Natural frequency f of the crystal plate α when no vapor deposited film is applied
The natural frequency change Δf, which is the difference between the natural frequency f of the crystal plate a3 when the vapor deposited film (18) is applied, also gradually changes. As the collision occurs, the temperature gradually rises mainly due to the radiation heat effect of the vapor deposition source, but this temperature rise is detected by the temperature controller aη, which inputs the temperature detection signal 8T output from the temperature sensor αQ, and the temperature is set. The amount of electricity applied to the heating wire a!9 is adjusted so as to eliminate the temperature rise ΔT from the temperature T0.As a result, the crystal plate 0 is maintained at a predetermined set temperature during the formation of the end of the deposited film. Therefore, the natural frequency change Δf is always at the set temperature ToK.The electric signal SF indicating this natural frequency change Δf is sent to the film thickness calculating section (2).
K is input, and the film thickness d is calculated based on this natural frequency change ΔfK. This calculated film thickness d does not include an error caused by a temperature change of the crystal plate αj. This is because the crystal plate (13) is always maintained at the set temperature T.K, and the constant in the conversion formula from 1 natural frequency change Δf to film thickness d is This is because the obtained film thickness d and the temperature T of the crystal plate (13) are displayed in the film thickness display section (3). It shows the relationship between thickness, and the solid line is the measurement data by the film thickness meter of this example,
The broken line is the measurement data using the conventional technology, and the film thickness error Δ
It can be seen that d is occurring.

As described above, the crystal oscillation type film thickness meter of this embodiment measures the film thickness of the deposited film portion while maintaining the crystal plate (13) at the set temperature T.K using the heating wire αω. Film thickness measurement errors due to temperature changes of the crystal plate 0 are eliminated, and the film thickness d can be measured with high accuracy.

As a result, the film thickness can be reliably monitored during vacuum evaporation, so the film thickness can be controlled with high precision.

Note that although the above embodiments illustrate the formation of a single layer film, the crystal oscillation type film thickness meter of the present invention is noticeably applied to the formation of a multilayer film that forms an artificial lattice and acts as a diffraction grating. Effective.

Furthermore, the crystal oscillation type film thickness meter of the present invention is applicable not only to vacuum deposition but also to ion grating, ion beam sputtering, plasma sputtering, glass-r CVD (Ch
chemical vapor deposition
It can also be applied to various thin film formation processes such as (chemical vapor deposition).

〔Effect of the invention〕

Since the crystal oscillation type film thickness meter of the present invention maintains the crystal plate at a constant temperature during film formation, there is no film thickness measurement error caused by temperature changes of the crystal plate, which is a monitor plate, and the film thickness can be measured easily. High-precision measurements can be performed stably. As a result, the film thickness can be accurately monitored during film formation, and the film formation process can be controlled reliably.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a crystal oscillation type film thickness meter according to an embodiment of the present invention, and FIG. 2 is a graph for explaining the operation. (l): Film thickness measurement section. (2): Film thickness calculation section. (5): Crystal temperature control section. α3: Crystal plate.

Claims (1)

[Claims] a film thickness measurement unit having a crystal plate on which a thin film is deposited; a crystal temperature control unit that heats the crystal plate and maintains it at a predetermined temperature; A crystal oscillation type film thickness meter comprising: a film thickness measurement section that performs film thickness measurement based on changes in the natural frequency of a plate.