JP2002363739A - Method of thin film deposition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of thin film deposition, by which a target is hardly cracked even if sputtering voltage is increased and the improvement of the productivity of a thin film is easily attained by increasing the film deposition speed in the thin film deposition by a sputtering method using a ceramic target. SOLUTION: In the thin film deposition by the sputtering method using the ceramic target, the temperature T of cooling water for circulating near the target to suppress temperature rise due to the heat generation of the target is set to 300 K<=T<=360 K and >=4 W/cm<2> sputtering power is applied in this condition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for forming a thin film by a sputtering method using a ceramic target.

[0002]

2. Description of the Related Art A sputtering method is known and widely applied as a method capable of forming a thin film uniformly and with good controllability over a large area as compared with other physical vapor deposition methods such as a vacuum evaporation method. However, there is a problem that the film forming speed is low and the productivity is low. In particular, a ceramic target represented by a metal oxide has a lower sputtering rate and a film formation rate than a metal target represented by silver, gold, and aluminum, which is 1/2 or less of that of a metal target. Is 1/10 or less.

[0003] The deposition rate increases almost in proportion to the sputtering power. For this reason, in order to form a thin film with high productivity, it is sufficient to increase the power, and it is desired to apply a larger power to a ceramic target.

By the way, at the time of sputtering, since the temperature of the target rises due to heat generation, cooling water is circulated near the target to suppress the temperature rise. Until now, in the case of metal targets, by increasing the cooling power by increasing the flow rate of cooling water in response to the increase in sputtering power, the target temperature has been suppressed, and changes in the quality of the formed thin film have been avoided. In addition, problems such as melting of a metal target having a low melting point such as indium or the like are avoided.

However, in the case of a ceramic target, if an attempt is made to suppress the temperature rise of the target in the same manner as described above in response to an increase in the sputtering power, a crack is generated in the ceramic target. It has come off from the plate and the sputtering operation cannot be continued. For this reason, the sputtering power cannot be increased so much, and as a result, the productivity of the thin film cannot be improved by increasing the film forming rate at present.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and when forming a thin film by a sputtering method using a ceramic target, even if the sputtering power is increased, the target is hardly cracked. It is another object of the present invention to provide a method for forming a thin film which can easily improve the productivity of the thin film by increasing the film forming rate.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies on the above objects, and as a result, when a large sputtering power is applied to increase the film forming rate, the ceramic target is partially Cracks occur, and if you continue to use it as it is, the cracks will grow, causing problems such as the generation of nodules from that part. In the cooling water circulating system, the cracks tended to be generated on the source (entrance) side of the cooling water and the frequency of occurrence of the cracks on the drain (outlet) side was low.

[0008] From this, it is considered that the cause of the crack in the ceramic target is caused by thermal strain due to the temperature difference between the cooling water and the target. Based on this idea, the temperature of the cooling water is set to a certain degree. When a high temperature was set, the occurrence of cracks in the target was clearly reduced.

[0009] Based on this fact, the inventors of the present invention have repeated experiments and studies on the temperature of the circulating cooling water. As a result, when the temperature T of the cooling water is set in the range of 300K ≦ T ≦ 360K. Even when a large sputtering power of 4 W / cm ² or more per area of the ceramic target is applied, the generation of cracks in the target can be reduced while maintaining the initial cooling effect. It has been found that the productivity of the thin film can be reliably improved.

The present inventors have also proposed that the ceramic target is usually bonded on a backing plate. However, when the temperature of the cooling water is set to a relatively high value as described above and a large sputtering power is applied, Was divided into two or more members, and bonding was further reduced, and the generation of cracks in the target due to thermal strain was further reduced, and even if cracks were generated, it was found that further growth could be prevented. Furthermore, it was also found that the use of a material mainly composed of indium oxide, which is widely applied to a transparent electrode, a transparent conductive film for a touch panel, and the like, as a ceramic target, enables the above-described effects to be exhibited more effectively.

The present invention has been completed based on the above findings. That is, in the present invention, when a thin film is formed by a sputtering method using a ceramic target, the temperature T of the cooling water circulated in the vicinity of the target is set to 300K ≦ T ≦ 360K in order to suppress a temperature rise due to heat generation of the target. , And a sputtering power of 4 W / cm ² or more per area of the target is applied in this state.

Further, the present invention provides a method for forming a thin film having the above structure, wherein the ceramic target is divided into two or more parts on a backing plate and bonded, and the ceramic target is mainly composed of indium oxide. The present invention relates to a method for forming a thin film having the above-mentioned configuration made of a material to be formed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The ceramic target in the present invention includes indium oxide, tin oxide, titanium dioxide, cerium oxide, zirconium oxide, zinc oxide, tantalum oxide, niobium pentoxide, silicon dioxide, aluminum oxide, magnesium oxide and the like. A material made of a metal oxide is used, and other materials than a metal oxide such as silicon nitride and magnesium fluoride can also be used. Among these materials, a material mainly containing indium oxide and containing a small amount of titanium dioxide, tin oxide, cerium oxide, or the like is particularly preferably used.

In the present invention, the above ceramic target is bonded on a backing plate in a sputtering apparatus. At this time, the above-mentioned target may be bonded as one body, or may be divided into two or more bodies and bonded in order to further reduce cracks during sputtering. At a position facing the ceramic target, a substrate for sputtering the target to form a thin film is mounted. For example,
In a roll-to-roll type sputtering apparatus, a plastic film such as a polyethylene terephthalate film is used as a base material, and the plastic film is mounted on a roll so as to be able to run continuously.

In the sputtering apparatus, after evacuation, a sputtering gas such as an argon gas and a small amount of an active gas such as an oxygen gas are introduced as necessary, and the degree of vacuum is adjusted to a predetermined value. In this vacuum state, the target is sputtered by applying a sputtering power to the ceramic target to form a film on an opposing base material to form a desired ceramic thin film.

During the sputtering, the ceramic target generates heat, and the target is cooled by circulating cooling water near the target so that the temperature of the target does not excessively increase due to the generated heat. The method of circulating the cooling water is not particularly limited, and can be performed according to a known method.

In the present invention, the temperature T of the cooling water is set to 300
The gist is that K ≦ T ≦ 360K is set, and thus, even if the sputtering power applied to the target is increased to 4 W / cm ² or more, the target is not cracked and stable for a long time. Since the sputtering operation can be performed and the film formation rate can be increased by increasing the power, the productivity of the thin film can be dramatically improved. If the temperature of the cooling water is lower than 300K or higher than 360K, problems such as the above cracks being unable to be prevented and the deterioration of the cooling efficiency resulting in the deterioration of the thin film are likely to occur.

[0018]

The present invention will now be described more specifically with reference to examples.

Example 1 Using a roll-to-roll type sputtering apparatus,
On a roll in this device, as a substrate, a thickness of 125μ
m of polyethylene terephthalate film.
Also, on the backing plate facing this substrate, I
A material mainly composed of indium oxide having a composition of n ₂ O ₃ / SnO ₂ = 9/1 (weight ratio) (hereinafter, referred to as ITO) and having a length of 600 mm, a width of 150 mm, and a thickness of 6 mm. The ceramic target was bonded.

After evacuating the inside of the sputtering apparatus, argon gas was supplied at 100 SCCM (Standard Cub).
ic Centimeter per Minut
e) Oxygen gas was introduced at 3 SCCM and the degree of vacuum was increased to 0.4.
It was adjusted to Pa. In addition, in order to suppress heat generation during sputtering of the target, cooling water is circulated near the target, and the temperature of the cooling water is set to 330K.
Set to.

In such a state, a predetermined sputtering power is applied to the ceramic target for 30 minutes, and a sputtering operation is carried out.
An O thin film was continuously formed. As the sputtering power, 3 W / cm ² , 4
W / cm ² , 5 W / cm ² or 6 W / cm ^2, and each power was applied for 30 minutes.

Example 2 A ceramic target having a length of 150 mm, a width of 150 mm,
A sputtering operation was performed in the same manner as in Example 1 except that the thin film was divided into four bodies each having a size of 6 mm and bonded on a backing plate, and an ITO thin film was continuously formed on a base material. A film was formed.

Comparative Example 1 The procedure of Example 1 was repeated, except that the temperature of the cooling water circulated near the ceramic target was set to 280 K.
By performing a sputtering operation, an ITO thin film was continuously formed on the substrate.

In Examples 1 and 2 and Comparative Example 1, after performing a sputtering operation for 30 minutes at each sputtering power, the chamber was opened to the atmosphere, and the presence or absence of cracks in the ceramic target was visually observed. Further, while keeping the roll speed constant, the film thickness of the ITO thin film formed on the substrate was measured to calculate the dynamic film formation speed. The results are shown in Table 1.
(Presence or absence of cracks) and Table 2 (Dynamic film formation rate).

[0025]

[0026]

As is clear from the above results, in the method of Example 1 of the present invention, even if a large sputtering power of up to 5 W / cm ² was applied, no crack was generated in the ceramic target, and the film formation rate was reduced. , And increased almost in proportion to the applied power. In Example 2, the power was further increased by 6 W / cm.
^Even when increased to ² , no cracks occurred.

On the other hand, in the method of Comparative Example 1 different from the present invention, cracks occurred near the supply port of the target cooling water when a sputtering power of 4 W / cm ² was applied. When power was continuously applied at 6 W / cm ^{2 as} it was, the cracks grew greatly, and some of the intersections where the target chipped off occurred.

[0029]

As described above, according to the present invention, when a thin film is formed by a sputtering method using a ceramic target, the temperature of the cooling water of the target is set to a specific range by a simple method. Can suppress the frequency of occurrence of cracks and apply a higher sputtering power, thereby improving the productivity of thin films. Also, place a ceramic target on the backing plate.
The above effect can be further enhanced by dividing the body and bonding.

Continued on the front page F term (reference) 4F100 AA17B AA33 AD00B AK42 AT00A BA02 DC21B EA021 EC152 EH66B EH662 EJ502 EJ592 GB41 JL02 JL04 JM02B 4G030 AA34 AA39 BA01 4K029 AA11 AA25 BA45 DC09 DC05 DC05 DC05 DC05

Claims (3)

[Claims] In forming a thin film by a sputtering method using a ceramic target, the temperature T of cooling water circulated in the vicinity of the target is set to 300K ≦ T ≦ 3 in order to suppress a temperature rise due to heat generation of the target.
A method for forming a thin film, wherein the sputtering power is set to 60 K and a sputtering power of 4 W / cm ² or more per area of the target is applied in this state. 2. The method according to claim 1, wherein the ceramic target is divided into two or more parts on a backing plate and bonded. 3. The method according to claim 1, wherein the ceramic target is made of a material mainly composed of indium oxide.