JPH02301554A - Production of thin tantalum film - Google Patents

Abstract

PURPOSE:To uniformize etching distribution and to arbitrarily control etching speed by carrying out sputtering by the use of a Ta cathode while regulating the mixing ratio of nitrogen gas in a gaseous mixture consisting of argon, oxygen, and nitrogen to <=5%. CONSTITUTION:As a sputter gas for a magnetron sputtering device, a gaseous mixture of argon, oxygen, and nitrogen is used. The mixing ratio of nitrogen in the above gaseous mixture is regulated to <=5%. Then, sputtering is carried out by the use of tantalum as a cathode. By this method, etching distribution can be uniformized and etching speed can be arbitrarily controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a transparent tantalum thin film used in liquid crystal displays and the like.

[Summary of the Invention] The present invention is a method for manufacturing a tantalum thin film for liquid crystal displays, etc., in which active sputtering is performed using a mixed gas of argon, oxygen, and nitrogen with the mixing ratio of the nitrogen gas being 5% or less. This is a means of obtaining a transparent insulating film that allows the etching rate to be arbitrarily made uniform within the substrate.

[Prior Art] Conventionally, as a means of obtaining a transparent tantalum insulating film, sputtering was performed using a mixed gas of oxygen and argon.

Furthermore, Japanese Patent Application Laid-Open No. 55-107774 describes a tantalum thin film used in a passive element of a hybrid IC, but it is unclear whether oxygen was used as a mixed gas and the mixing ratio of nitrogen is 5% or more.

[Problem to be Solved by the Invention 1] However, as the size of the substrate increases, the amount of Kuntal thin film (TaOx) formed by sputtering with a mixed gas of oxygen and argon increases.
However, depending on the film forming equipment, it not only causes non-uniform etching distribution, but also requires controlling the etching rate regardless of the equipment.On the other hand, in tantalum thin films using a mixed gas of oxygen, argon, and nitrogen, When the mixing ratio of nitrogen is 5% or more, the etching rate becomes extremely slow.

The present invention is intended to solve these problems, and its purpose is to improve tantalum thin films (
An object of the present invention is to provide a method for manufacturing a tantalum thin film in which the etching distribution is uniform and the etching speed can be arbitrarily controlled by doping a small amount of nitrogen (5% or less) into TaOx.

[Means for Solving the Problems] The method for producing a Kuntal thin film of the present invention uses a magnetron sputtering device and uses argon (A) as the sputtering gas.
r), using a mixed gas of oxygen (O□), and nitrogen (N, .

Even if the mixing ratio of nitrogen is increased to 5% or more, the etching rate of the resulting tantalum thin film does not change, and the only drawback is that the sputtering rate is small.

``Example'' An example of the present invention will be described below based on the drawings. FIG. 1 shows a spacing device used in this example.

A rotating substrate holder 2 is provided in a vacuum chamber 1, and a target 4 (tantalum) is provided at a position opposite to the rotating substrate holder 2 and offset from the rotation axis of the substrate holder 2. The size of the glass substrate 14 is 25 cm x 30 cm. Inside this chamber argon 72sccm oxygen 40sccm
M, glass substrate 1 when sputtering was performed by introducing a mixed gas in which the nitrogen doping flow rate was varied from 0 to IO3CCM.
FIG. 2 shows the sputter rate distribution at the center and end portions of No. 4.

As is clear from FIG. 2, as the nitrogen doping flow rate increases, the sputtering rate decreases. Furthermore, the distribution at the center and edges of the glass substrate 14 is uniform regardless of the nitrogen doping flow rate.

This tendency also appears when the flow rate of oxygen is increased while keeping the flow rates of argon and nitrogen constant. In other words, increasing the partial pressure of the reactive gas lowers the sputtering rate, -M
It is said that this tendency is λ.

As mentioned above, when looking only at the sputtering rate, there is no special nitrogen doping effect.

In Figure 3, argon 72SCCM and oxygen 40SCCM are similarly shown.
The etching rate of tantalum and 1IPN sputtered by introducing a mixed gas in which CM and nitrogen were varied from 0 to IO3ccM is shown.

Etching is a general dry etching method using a mixed gas of freon (CF4) and oxygen, and it has already been confirmed that there is no etching distribution caused by the device itself.

As can be seen from FIG. 3, a sputtered thin film obtained using only argon and oxygen at a nitrogen doping flow rate of 0 causes a significant difference in etching rate between the center and the edges of the glass substrate 14. Here, even if the flow rate of oxygen is increased, although there is a slight decrease in the etching rate at both the center and the edges of the glass substrate I4, the difference is not improved.

It is believed that the cause of such an etching distribution is largely due to the film forming conditions, particularly the structure and configuration of the film forming apparatus. FIG. 4 shows a glass substrate 1 in the spacing device used in this example.
4 shows the state of deposition at the center and edges,
While there is always a constant amount of deposition at the center of the glass substrate 14, at the edges the film is formed in an alternating current manner with the same period as the rotation of the substrate holder 26.Then, the total film thickness at the edges is It will be the same as that in the center. However, the membrane quality is different. The two differ in particular in the way oxygen is taken into the film. It seems that the edges of the glass substrate 14 take in less oxygen than the center, and there are many dangling spots or voids. Therefore, it is considered that the etching rate is larger than that in the center. Furthermore, even if the oxygen partial pressure (flow rate) during sputtering is increased, there may be a limit to the amount of oxygen taken into the film depending on the method of film formation, and therefore the etching rate distribution will not be improved. .

Returning to Figure 3, add nitrogen at 2.5SCCM (mixing ratio 2.2
%) The etching rate distribution of doped and sputtered tantalum thin films is significantly improved. This is thought to be due to nitrogen filling in the dangling bonds that are common at the edges of the glass substrate 14 or due to a reduction in the number of bonds. Then, up to the nitrogen doping flow rate of 6SCCM (in combined ratio 5%),
The etching rate gradually decreases.

A similar experiment was conducted on a tantalum thin film deposited using an in-line spacing device that passes through the target and front substrate.

At this time, there was no etching rate distribution even when the nitrogen doping flow rate was 0. This is for the reason mentioned above. In other words, it is thought that this is because the film formation method is the same at the center and at the edges of the glass substrate 14. Further, the etching rate gradually decreased until the nitrogen mixing ratio reached 3%, and then became saturated.

What can be said from these experiments is that even if there are differences in film formation methods depending on the equipment, the etching rate distribution can be made uniform by sputtering with a small amount of nitrogen doped. By increasing the maximum mixing ratio to 5%, the etching rate can be gradually lowered, that is, controlled.

Next, we will explain the advantages of being able to control the etching rate.

5, 6, and 7 (a) show that the tantalum thin film 13 of this embodiment is formed on a glass substrate 14, and then a metal film 12 (an insulating film is also acceptable) is further formed. (b) shows the profile when dry etching is performed after patterning with the resist 11. (b) shows the profile when the resist is then peeled off and a metal film 15 (an insulating film is also acceptable) is further formed. Show profile.

FIG. 5 shows a profile when the tantalum thin film 11113 and the metal film 12 have approximately the same etching rate. At this time, disconnection of the metal film 15 does not occur.

FIG. 6 shows a profile when the etching rate of tantalum thin film 11i13 is larger than that of metal l112. At this time, the edge portion of the tantalum thin film 13 is etched more than that of the metal film 12. Therefore, the metal film 15 thereon is disconnected.

Conversely, FIG. 7 shows a profile when the etching rate of the tantalum thin film 13 is smaller than that of the metal film 12. At this time, the edge portion of the metal film 12 is overetched. At this time, the metal 11115 is similarly disconnected.

As described above, by controlling the etching rate of the tantalum thin film 13 and making it comparable to the etching rate of the metal blade 112, it is possible to prevent disconnection of the metal film 15, which is the upper layer film. This is one of the advantages of being able to control the etching rate.

〔Effect of the invention〕

As described above, by sputtering using argon, oxygen, and nitrogen at a mixing ratio of 5% or less of the nitrogen gas, it is possible to fill the dangling bonds in the resulting tantalum thin film or reduce the voids and nitride it. This has the effect that the etching rate can be adjusted to make the distribution of the etching rate uniform, and the etching rate itself can be controlled.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the sputtering apparatus used in the example. FIG. 2 is a diagram showing the relationship between nitrogen doping flow rate and sputtering rate during tantalum thin film formation. FIG. 3 is a diagram showing the relationship between the amount of 7M nitrogen doped during the formation of a tankle thin film and the etching rate of the thin film. FIG. 4 is a diagram illustrating the deposition process of the spackle device used in the example. FIGS. 5, 6, and 7 are diagrams showing the etching profile of a tantalum thin film. 1...Vacuum chamber 2...Substrate handling holder 4...Target 11...Resist 12...Metal film 13...Tantalum thin film 14...Glass substrate 15...Metal film and above Applicant Seiko Epson Co., Ltd. Representative Patent Attorney Kisanbe Suzuki (and 1 other person) No. 1 Nitrogen tofu Ota amount αcc) Me No. 3 4 g ca) cb) Hayabusa B Hiroshi] mouth

Claims (1)

[Claims] 1. Using a magnetron sputtering device, the sputtering gas is argon (Ar), oxygen (O_2), nitrogen (N
A method for producing a tantalum thin film, using the mixed gas of _2), further setting the mixing ratio of nitrogen to 5% or less, and performing sputtering using tantalum (Ta) as a cathode.