JPS60215765A - Formation of thin film - Google Patents

Abstract

PURPOSE:To straighten camber of a substrate and to improve yield by controlling the compressive force and tension of the silicon nitride film deposited and formed on the substrate by a plasma CVD method by a plasma oscillation frequency. CONSTITUTION:An SiN film is deposited and formed by a plasma CVD method on the surface 11A part which is recessed and is not the effective part of a thin subsbrate 11 such as a filter substrate or driving element substrate of a color liquid crystal display or the like by setting plasma oscillation freqeuncy to about 50kHz if the substrate 11 is cambered downward. The stress of the SiN film is thereby provided with the tension toward the direction A by which the camber of the substrate 11 is corrected. The SiN film is deposited and formed by the plasma CVD method at about 13.56MHz frequency on the surface part 11A which projects and is not the effective part if the substrate is cambered up ward. The stress of the SiN film is then provided with the compressive force in the direction B by which the camber of the substrate 11 is straightened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming a thin film by depositing it on a substrate surface while controlling the stress of the thin film.

[Background technology and its problems]

For example, in the case of a color liquid crystal display, which requires sufficient uniformity in the spacing between two opposing substrates, if the thin substrate has scratches, it is necessary to maintain a uniform spacing between the substrates. Since it cannot be aligned, it is necessary to correct the anti-be of this substrate.

FIG. 1 schematically shows a cross section of this transmissive color liquid crystal display. To explain the structure of this color liquid crystal display, red, green, and blue color filters 2 corresponding to each pixel are attached to an upper substrate 1 made of a transparent thin plate such as glass, sandwiched between common electrodes 3. It is being Further, a lower substrate 5 made of a transparent thin plate such as glass is arranged with a distance p from the upper substrate 1 by a spacer 4.
A thin film transistor layer serving as the pixel electrode 6 is formed in the pixel electrode 6 . Further, a liquid crystal T is sealed between the upper substrate 1 and the lower substrate 5, and polarizing plates 8 and 9 are provided to sandwich these substrates 1 and 5. Light is then irradiated from the back side of the polarizing plate 9.

By the way, if the upper substrate 1, which is a filter substrate, or the lower substrate 5, which is a driving element substrate, has a warp, the uniformity of the spacing between the substrates 1 and 5 will be disrupted, causing local thickness unevenness in the liquid crystal 7. Furthermore, since the electric field strength changes, color unevenness occurs in the image on the liquid crystal display. Furthermore, the substrate 1,
If the damage is severe in 5, there will be areas where there is no liquid crystal and the image will no longer be displayed.

Therefore, if the upper substrate 1 or the lower substrate 5 has a warp, it is necessary to correct the warp and ensure sufficient flatness of the substrates 1 and 5.

By the way, when trying to correct the warpage of a very thin substrate that requires sufficient flatness, such as a filter substrate or drive element substrate of a liquid crystal display, it is necessary to correct the warping of a substrate made of glass, quartz glass, etc. If it is,
It is necessary to correct the warpage using a high temperature process.

Therefore, if a warp occurs on the drive element substrate after forming a thin film transistor array, a problem arises in that the characteristics of the transistor array deteriorate due to a high temperature process for correcting the warp.

Furthermore, in the final process of manufacturing, for example, a liquid crystal display, it is generally impossible to correct the warp.

[Object of the Invention] The present invention has been proposed in view of the above-mentioned circumstances. Straightening can be performed by forming, and straightening by this low-temperature process does not affect the characteristics of other elements attached to the substrate. Also, it is possible to straighten the edges in the final process of manufacturing the device, which improves yield. It is an object of the present invention to provide a method for forming a thin film that can be improved.

[Summary of the invention]

In order to achieve this objective, the method for forming a thin film of the present invention includes:
The plasma CVD method is characterized in that a silicon nitride film is deposited on a substrate surface while changing the plasma oscillation frequency, and the compressive force and tension of the silicon nitride film are controlled in accordance with the plasma oscillation frequency.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

As mentioned above, if there is a scratch on the filter substrate or drive element substrate of a color liquid crystal display, for example, the display will not display correctly and color unevenness will occur. Therefore, it is necessary to correct the warpage of these substrates and ensure sufficient flatness of the substrates.

The method for forming a thin film according to the present invention applies to the filter substrate, drive element substrate, etc. made of a thin film of glass, quartz glass, etc.
By plasma CVD method (plasma chemical vapor deposition method),
A silicon nitride film (hereinafter referred to as SiN film) is deposited,
This is to correct the warpage of the board.

FIG. 2 is a graph showing changes in the stress of the SiN film when the plasma oscillation frequency of the plasma CVD apparatus is changed. As shown in this graph, the stress of the SiN film changes as the plasma oscillation frequency changes, and the stress scale changes to
Tension is in the positive direction and compression is in the negative direction.

Therefore, for example, the plasma oscillation frequency may be changed on the surface of the filter substrate opposite to the effective surface on which the filter is attached, or on the surface of the drive element substrate on the opposite side to the effective surface on which the thin film transistor array is provided. By depositing and forming a SiN film by plasma CVD while controlling the stress of the film, it is possible to correct the warpage of these substrates.

Specifically, if a thin substrate 11 that requires flatness, such as the filter substrate or drive element substrate, is bent downward, as shown in FIG. In the surface portion 11A, which is a concave surface that is not an effective portion,
Set the plasma oscillation frequency to, for example, 50KHz and use the plasma CVD method! l) Depositing a SiN film. As a result, the stress in the SiN film becomes a tension in the direction of the arrow, and the warp of the substrate 11 is corrected. At this time,
The amount of correction of the warp can be controlled by the thickness of the SiN film to be deposited, the gas ratio in the reaction chamber of the plasma CVD apparatus, and the like.

Further, when the substrate 11 is curved upward as shown in FIG. 4, the plasma oscillation frequency is set to 13.56 MHz, for example, on the convex surface portion 118 of the substrate 11 that is not an effective portion. Selected by plasma CVD method!
A ysiN film is deposited. This results in p, ′ of the SiN film
The stress becomes a compressive force in the direction of arrow B, and the warp of the substrate 110 is corrected.

If the substrate 110 is not warped in one direction, a mask is attached to the surface portion 11A, a SiN film is partially deposited while controlling the stress, and the direction of warpage correction is changed. Try to correct the wrinkles.

Here, the plasma CVD method can form a SiN film on the surface of the substrate 11 at a relatively low temperature, and does not have any adverse effects such as deterioration of characteristics on the thin film transistor array provided on the drive element substrate, for example. .

As described above, in the thin film forming method according to the present invention, it is possible to correct the scratches on a filter substrate on which a filter is already attached or on a drive element substrate on which a thin film transistor layer is formed without affecting the scratch characteristics during a low-temperature process. Ru.

Therefore, the flatness of the substrate is ensured sufficiently, and the substrates can be assembled at a high yield.

Further, in the final process of manufacturing, for example, a liquid crystal display, the warpage of the substrate can be corrected, and the yield can further be improved.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a SiN film is deposited on a substrate surface by a plasma CVD method while controlling the tension and compression force of the SiN film by changing the plasma oscillation frequency. It is possible to correct the anti-shi.

Since the warpage of the substrate can be corrected by the low-temperature process of the plasma CVD method in this way, the characteristics of, for example, a thin film transistor array formed in advance on the substrate will not be deteriorated.

Furthermore, in the final process of producing, for example, a color liquid crystal display, the substrate can be corrected and the yield rate can be improved.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the configuration of a color liquid crystal display.
Fig. 2 is a glass showing the change in stress of the SiN film with respect to the plasma oscillation frequency when the SiN film is deposited on a substrate by plasma CVD method, and Fig. 3 is a glass of SiN film deposited by the thin film forming method according to the present invention. A schematic diagram illustrating how the tension of the film is controlled to correct the warpage of the substrate. Figure 4 shows how the SiN film deposited by the above thin film forming method is controlled to the compressive force and the warpage of the substrate is corrected. Schematic diagram. 11...Substrate 11A...Surface Patent applicant Kodo Koike, patent attorney representing Sony Corporation 1) Sakae Mura - Figure 1 Figure 2 AjvI Namimaki from Pusuma

Claims (1)

[Claims] A silicon nitride film is deposited on the upper surface of a substrate by a plasma CVD method while changing the psasma oscillation frequency, and the compressive force and tension of the upper chambered silicon film are adjusted to the psasma oscillation frequency. 1. A method for forming a thin film, which is controlled accordingly.