JPS6212122A - Controlling equipment for thick film - Google Patents

Abstract

PURPOSE:To make it possible to control with high precision the optical characteristics in the wavelength region near absorption band edge which is important to determine the optical features of film, by irradiating the light near the optical absorption band edge of the material to be deposited in the forming process of film, such as, the photoelectric conversion film which requires optical characteristics, and measuring the quantity of transmitted light during the deposition process. CONSTITUTION:The He-Ne laser (632.8nm wavelength) light source and the photo diode are used as the light emitting device 6 and the photo detector 7, respectively. The detected signal processing circuit 12 calculates the transmission coefficient T from the detected quantity of transmitted light, and calculates the film thickness (d) based on the absorption coefficient alpha obtained from the preliminary deposition material. When the calculated (d) reaches the desired film thickness previously input, the high frequency power source B, the driving power source for plasma discharge, is turned OFF. In this manner, the discharge automatically stops to half the deposition when the detected film thickness reaches the desired film thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is useful for forming photoelectric conversion films having a desired thickness or optical transmittance in film formation techniques that require methods such as plasma processes and vacuum evaporation. This invention relates to a film thickness control device that is homogeneous and can be produced in large quantities.

Conventional Technology Conventionally, when creating a photoelectric conversion film, the thickness of the film during deposition is monitored by electrical measuring means using a crystal oscillator or the like, or optical measuring means that detects the amount of transmitted light when irradiated with monochromatic light. Was. (For example, Japan Society for the Promotion of Science, edited by the 131st Thin Film Committee, published by Ohmsha, "Thin Film Handbook", Chapter 2 2.5.2 (p137), 2.5.3 (1) 140
)) Problems to be Solved by the Invention When monitoring film thickness using a crystal resonator in a film forming apparatus that requires a plasma discharge process, water cooling temperature correction is required as the temperature rises inside the vacuum container. In addition, since it is an electrical measurement, if it is installed near the plasma, the crystal oscillator output will be affected by strong noise interference, so the crystal oscillator must be installed in a position away from the plasma, and it is not possible to place the crystal oscillator in the same position as the board. However, there was a problem in that the film thickness could not be measured and could only be measured indirectly. This will cause a large error in the detection output if the plasma shape changes due to fluctuations in the flow rate of the introduced gas or fluctuations in the input power for discharge. Further, in a film forming apparatus using a vacuum evaporation method, although there is no influence of errors due to plasma, when a high temperature process is required, temperature correction is required, which causes errors.

In addition, it is thought that the optical film thickness monitoring method using monochromatic light to detect the amount of transmitted light does not cause the above-mentioned error.
Whether using electrical measurement means such as a crystal oscillator or optical measurement means using monochromatic light irradiation, it is possible to obtain information about characteristics near the optical absorption edge, which is important when used as an image sensor, during film deposition. I can't.

In view of this, the present invention makes it possible to create a large quantity of characteristics near the optical absorption edge of a material with good reproducibility by irradiating light having a wavelength near the optical absorption edge of the deposited material during deposition and measuring the amount of transmitted light. The purpose is to do so.

Means for Solving the Problems In order to solve the above problems, the present invention sets a substrate for film thickness detection, that is, for detecting the amount of transmitted light, on a sample support plate on which samples are arranged, and deposits the film on the substrate. irradiate light near the optical absorption edge of the material to be used. The film thickness is measured during deposition by detecting the amount of transmitted light, which changes depending on the thickness of the film deposited on the substrate, without being affected by electrical discharge plasma. Furthermore, by grasping the transmittance near the absorption edge, feedback is applied to the deposition control system, and film deposition can be automatically stopped at a desired film thickness or transmittance. At this time, before the actual deposition, a sample (preliminary deposition sample) is prepared that has been deposited on the substrate to an appropriate thickness under the same conditions as the actual deposition, and the film thickness d is determined by means such as spectral transmittance measurement. The optical absorption coefficient α is determined by the following formula.

α=-gn('r) Here, T is the transmittance obtained from spectral transmittance measurement.

During the main deposition, the film thickness d is calculated using α obtained by measuring the preliminary deposited sample and the transmittance T obtained during the main deposition. When the detected film thickness value obtained by this method reaches a desired film thickness value, the discharge is automatically stopped or the deposition is stopped via a shutter.

Effects of the present invention In the above-described configuration, the film thickness can be directly measured by irradiating the sample with light having a wavelength near the optical absorption edge of the material deposited during film deposition. It can be detected without being affected by electricity. When a rotating substrate is used, it is possible to produce a large quantity of films that are more homogeneous and have no variation in film thickness. Furthermore, it is possible to automatically control the creation of a film having a desired film thickness or transmittance based on the detected film thickness.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the film thickness detection portion of the film thickness control device of the first embodiment, and FIG. 1 (m) is a top view of the vacuum vessel. 1 is a vacuum container, 2 is a rotating substrate for fixing the sample, 3 is a glass substrate used for optically measuring the deposited film thickness, 4 is a sample substrate, and 6 is a plasma region in which deposition is performed and a device for optically measuring the film thickness. 6 is a light emitting element used as a light source; 7 is a light receiving element for detecting transmitted light; 8 and 9 are for generating plasma discharge; Regarding the electrodes, electrode 8 is provided with a heater, and electrode 9 is provided with a gas introduction hole. 1o indicates the rotation axis.

FIG. 1(B) shows the cross-sectional structure of FIG. 1(B). In this first embodiment, Hθ-NO is used as the light emitting element 6.
A laser (wavelength: e32.am) light source was used, and a photodiode was used as the light receiving element 7. First, an amorphous silicon photoconductive film was prepared by keeping the vacuum container 1 at a high vacuum, introducing silane gas, and applying a high-voltage AC voltage between the electrodes 7 and 8 to generate plasma discharge between the electrodes.

At this time, the sample substrate used was one in which metal molybdenum was deposited by vacuum evaporation on single crystal silicon. Quartz glass is used as a glass substrate for film thickness detection.

The film creation conditions were a rotating substrate temperature of 250°C and an input power of 20W.
Silane gas ~0.6 Torr, rotating board rotation speed 10
rp! The experiment was conducted at 1 m. In this example, the wavelength is 632.
1 refers to the creation of a photoelectric conversion film having a transmittance of 6 cm at 8 nm.

FIG. 2 is a block diagram of the film thickness control device in Example 1. 11 is a light source power supply circuit for driving the Ha-Ne laser, and 12 is a detection signal processing circuit for the amount of transmitted light by a photodiode, which calculates the transmittance T from the detected amount of transmitted light.
is calculated, and the film thickness d is calculated using the value of the absorption coefficient α determined from the preliminary deposited sample. When the desired film thickness value inputted in advance is reached, the high frequency power supply circuit 13, which is the drive power source for plasma discharge, It has the function of opening the circuit. circuit 12
The feedback circuit F is configured in step 113. As mentioned above, α=HAn(T).

FIG. 3 shows the signal waveform input to the detection signal processing circuit 12, and the transmittance when the desired film thickness d' is reached is T'.
When the time t' elapsed after the start of the deposition, the high frequency power supply circuit was opened and the deposition was automatically stopped.

Note that the wavelength of the preliminary deposited sample in the first example is 632.
According to the spectral transmittance measurement results at 8 nm, the transmittance T at the same wavelength was 5.7%, and the actual film thickness d measured using a surface profilometer was 1.28 μm.

Therefore, the absorption coefficient α at the same wavelength is as follows, and this value is input to the detection signal processing circuit 12.

FIG. 4 shows the spectral sensitivity characteristics of the amorphous silicon photoelectric conversion film deposited in this manner. The wavelength of this film is 63
Although the desired transmittance at 2.8 nH was 6 cm, it was possible to create a transmittance with an accuracy of 5 cm.

Further, in this example, 30 samples were prepared, and a high accuracy was obtained with a variation error of 2.4% in the film thickness.

Next, as a second embodiment, an example of a film thickness control device in a vacuum evaporation apparatus will be shown. FIG. 5 shows the film thickness detection part of the film thickness control device in this 20th embodiment, and the same figure (
Figure 1) is a top view of the vacuum vessel. Figure 5 (Bl shows the cross-sectional structure of Al in the same figure. In this example, a resistance heating method is used in which chalcogen material consisting of selenium, tellurium, and arsenic is evaporated from three evaporation sources under predetermined temperature conditions. In the figure, the first evaporation source 14 has a 5e67mm S.
, 5. The second evaporation source 15 has Sθ55ms 5Te46,
The third evaporation source 16 contains Seg5 MU S5. Each evaporation source is equipped with a crucible, a shroud, and an electric shutter 17.

The block diagram of the film thickness control circuit is the same as that shown in FIG. 2 in the first embodiment, and the output of the detection signal processing circuit is connected to the drive power source of each electric shutter 17, and as in the first embodiment, the desired When the film thickness is reached, the shutter is automatically fully closed and deposition is stopped. In this example, the wavelength JE e s
Although the transmittance at 2.8 nm was 6.6%, it was possible to create the transmittance with an accuracy of 4% error. Also, the film thickness variation error for 30 samples was 3.2%.
The film thickness could be controlled with high accuracy (desired film thickness: 3.20 μm).

In the embodiments of the present invention, examples of vacuum deposition using a resistance heating method and deposition using plasma discharge are shown, but it goes without saying that the present invention can also be applied to other thin film forming apparatuses such as electron beam evaporation. .

As described above, according to the present invention, in a film production technique that requires optical properties such as a photoelectric conversion film, light near the optical absorption edge of a material to be deposited is irradiated, and the amount of transmitted light is measured during deposition. By doing so, the optical properties near the absorption edge, which are important in determining the optical properties of the film, can be controlled with high precision. Furthermore, the reproducibility in producing photoelectric conversion films for image sensors and the like where spectral sensitivity characteristics are particularly important can be greatly improved.

Furthermore, according to the present invention, it is possible to automatically produce these films in a uniform manner in large quantities.

[Brief explanation of drawings]

Figure 1 (m) is a plan view of the main parts of a film thickness control device used for film formation by plasma discharge according to an embodiment of the present invention, figure (2) is a sectional view of the same device, and Figure 2 is a plan view of the same film thickness control device used for film formation by plasma discharge. A block diagram of the device, Fig. 3 is an input signal waveform diagram of the device, Fig. 4 is a spectral sensitivity characteristic diagram of an amorphous silicon photoelectric conversion film, and Fig. 5 (m) is a film thickness control device used for film formation by resistance heating. FIG. 2B is a plan view of the main parts of the device, and FIG. 2...Rotating substrate, 3...Glass substrate,
4...Sample substrate, 6...Light emitting element, 7
······Light receiving element. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure Feed Pa 177th Meiheizuka 13 Figure 4 Shiki Nagaku (nm) No. 5I21

Claims (3)

[Claims] (1) comprising means for irradiating light near the optical absorption edge of the material deposited on the substrate and means for detecting transmitted light that changes depending on the film thickness of the material deposited on the substrate; A film thickness control device configured to optically and directly monitor the film thickness during deposition based on the detection result of the means. (2) The film thickness control device according to claim 1, wherein the substrate on which the material is deposited is supported on a rotating substrate. (3) The film thickness control device according to claim 1, wherein the film thickness is calculated from the transmitted light detected by the detection means, and the deposition is automatically stopped when the desired film thickness is reached.