Thin film forming apparatus and thin film forming method

A thin film forming apparatus includes a substrate holding portion and a target portion. The target portion has a plurality of targets arranged at predetermined intervals and parallel to a substrate held by the substrate holding portion. The substrate holding portion is configured to move the substrate parallel to the target portion. A shield portion configured to block sputtered particles flying from the target portion is placed on the target portion side of the substrate so as to face a gap between adjoining ones of the targets.

TECHNICAL FIELD

The present invention relates to thin film forming apparatuses and thin film forming methods.

BACKGROUND ART

A sputtering method is commonly known as a method of forming a thin film on a substrate surface. The sputtering method is widely known as a dry process technique that is essential for a film deposition technique. The sputtering method is a method of depositing a film by introducing a rare gas such as Ar gas into a vacuum container and supplying direct current (DC) power or high frequency (RF) power to a cathode including a target to cause a glow discharge.

The sputtering method includes a magnetron sputtering method capable of depositing a film at a high speed by increasing plasma density near the surface of a target by placing a magnet on the back side of the target in an electrically grounded chamber. Such a sputtering method is used by a process of forming a predetermined thin film on, e.g., a processing substrate having a large area such as a glass substrate forming a liquid crystal display panel etc.

For example, Patent Document 1 discloses that in a magnetron sputtering apparatus having a plurality of targets arranged at predetermined intervals and parallel to a substrate to be processed, an alternating current (AC) voltage that alternates in polarity at a predetermined frequency is applied to each target to cause a glow discharge with anode and cathode electrodes being alternately switched between each pair of adjoining targets, whereby a plasma atmosphere is produced.

On the other hand, Patent Document 2 discloses that in a magnetron sputtering apparatus having a plurality of targets to which a voltage of the same polarity is applied, the substrate is moved parallel to the targets.

CITATION LIST

Patent Document

PATENT DOCUMENT 1: Japanese Patent Publication No. 2003-96561

PATENT DOCUMENT 2: Japanese Translation of PCT International Application No. WO/2008-108185

SUMMARY OF THE INVENTION

Technical Problem

In the sputtering apparatus of Patent Document 1, since the predetermined interval is provided between adjoining ones of the targets, quality of the sputtered thin film may vary between the region facing the target and the region facing the gap between the targets. One solution to this problem is to move the substrate with respect to the targets to achieve uniform quality of the thin film formed on the substrate, as in Patent Document 2.

However, in the sputtering apparatus described in Patent Document 1, not only sputtered particles traveling straight from the target in a direction perpendicular to the substrate but also sputtered particles flying obliquely from other targets are deposited on the region facing the target on the substrate.

Since the sputtered particles flying in different directions with respect to the substrate surface are deposited on the substrate, the quality of the thin film formed on the substrate is not uniform, and it is difficult to form a thin film having desired quality with high controllability.

The present invention was developed in view of the above problems, and it is an object of the present invention to form a thin film having desired quality with high controllability.

Solution to the Problem

In order to achieve the above object, a thin film forming apparatus according to the present invention is a thin film forming apparatus including: a substrate holding portion configured to hold a substrate; and a target portion placed so as to face a substrate held by the substrate holding portion.

The target portion has a plurality of targets arranged at predetermined intervals and parallel to the substrate held by the substrate holding portion. The substrate holding portion is configured to move the substrate held by the substrate holding portion, parallel to the target portion. A shield portion configured to block sputtered particles flying from the target portion is placed on the target portion side of the substrate held by the substrate holding portion, so as to face a gap between adjoining ones of the targets.

According to the above thin film forming apparatus, the substrate held by the substrate holding portion is moved parallel to the target portion, and plasma is generated on the substrate side of the target portion. Thus, the sputtered particles as constituent particles of the targets fly from the target portion toward the substrate. Since the shield portion is placed on the target portion side of the substrate so as to face the gap between adjoining ones of the targets, the sputtered particles flying from the targets perpendicularly to the substrate are deposited as they are on the substrate, while the sputtered particles flying from the targets obliquely to the substrate are blocked by the shield portion. That is, since the shield portion can suppress deposition of the sputtered particles flying obliquely to the substrate surface on the substrate, a thin film having desired quality can be formed on the substrate with high controllability.

Advantages of the Invention

According to the present invention, since the shield portion facing the gap between adjoining ones of the targets is placed on the target portion side of the substrate, deposition of the sputtered particles flying obliquely to the substrate surface on the substrate can be suppressed, whereby a thin film having desired quality can be formed on the substrate with high controllability.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The present invention is not limited to the following embodiments.

First Embodiment

FIGS. 1-4show a first embodiment of the present invention.

FIG. 1is a sectional view showing the general configuration of a thin film forming apparatus1according to the first embodiment.FIG. 2is a plan view showing a target portion20according to the first embodiment.FIG. 3is a bottom view showing shield portions according to the first embodiment.FIG. 4is an enlarged sectional view of a target21and a magnet41.

As shown inFIG. 1, a magnetron sputtering apparatus1as the thin film forming apparatus of the first embodiment includes a substrate holding portion11configured to hold a substrate10, a target portion20placed so as to face the substrate10that is held by the substrate holding portion11, a power source30configured to supply electric power to the target portion20, a magnet portion40placed on the back side of the target portion20as the side of the target portion20facing opposite the substrate10, and a chamber50configured to accommodate the substrate holding portion11, the target portion20, and the magnet portion40.

The chamber50is a vacuum chamber with its sidewall electrically grounded. The apparatus main body including the chamber50is comprised of, e.g., aluminum, stainless steel, etc. A vacuum pump, not shown, is connected to the chamber50so that the chamber50is decompressed by the vacuum pump. The chamber50is provided with a gas supply portion (not shown). The gas supply portion is configured to introduce an Ar gas and, as necessary, an O2gas into the chamber50in a vacuum state.

The substrate10is a substrate such as a glass substrate that forms, e.g., a liquid crystal display panel (not shown). The substrate10has a size of, e.g., 730 mm by 920 mm. The substrate holding portion11holds the substrate10on its lower surface, and has a heater (not shown) configured to heat the substrate10when depositing a film. A substrate mask24that covers the outer edge portion of the lower surface of the substrate10is provided in the chamber50. The substrate mask24serves to prevent unnecessary adhesion of sputtered particles to the substrate10and the chamber50, and has a rectangular opening24ain the center thereof.

As shown inFIGS. 1 and 2, the target portion20has a plurality of targets21arranged at predetermined intervals and parallel to the substrate10held by the substrate holding portion11. Each target21is formed in the shape of, e.g., a rectangular plate, and the targets21are arranged in a predetermined direction (the lateral direction inFIGS. 1 and 2) and parallel to each other so that their longer sides adjoin each other. The targets21are arranged at predetermined intervals in the direction in which the magnet portion40is moved.

The targets21are comprised of, e.g., a material containing IGZO (In—Ga—ZnO4; amorphous oxide semiconductor). The targets21may be comprised of other semiconducting material. Each target21is formed in the shape of, e.g., a 200 mm by 3,400 mm rectangular plate.

Each target21is supported by a target support portion22via a backing plate26. Each backing plate26is comprised of a conductive material such as a metal material, and serves to cool the target21during a sputtering process. The target21is bonded to the backing plate26via a bonding material such as indium or tin.

The target support portion22is comprised of an insulating material, and is fixedly attached to the chamber50. The target support portion22has a plurality of openings22acorresponding to the targets21. As shown inFIG. 1, the targets21and the backing plates26are arranged so as to correspond to the openings22a.

One AC power source30is connected to every pair of adjoining targets21. The frequency of a drive voltage (cathode voltage) of the power source30is, e.g., about 19 kHz to 20 kHz. Drive power is about 10-90 kW.

The magnet portion40is configured to reciprocate along the back surface of the target portion20by a drive mechanism, not shown. As shown inFIG. 1, the magnet portion40has a plurality of magnets41arranged at predetermined intervals in the direction in which the magnet portion40is moved (the lateral direction inFIG. 1). The magnets41are provided so as to correspond to the targets21, and are comprised of permanent magnets. Each magnet41is formed in the shape of, e.g., a 100 mm by 3,350 mm rectangular plate. The width of the magnet41in the direction in which the magnet41is moved is smaller than that of the target21in this direction.

The magnets41swing in synchronization with each other. The magnets41swing at a speed of, e.g., 10 mm/s to 30 mm/s. As shown inFIG. 4, each magnet41swings along a corresponding one of the targets21, with its swing ends being located about 1 cm inside both ends of this target21.

The substrate holding portion11is configured so that the substrate10held by the substrate holding portion11is moved parallel to the target portion20by, e.g., a roller mechanism etc. The substrate holding portion11reciprocates the substrate10in the lateral direction as shown by arrow A inFIG. 1.

Moreover, as shown inFIG. 1, a shield portion28configured to block sputtered particles flying from the target portion20is placed on the target portion20side of the substrate10held by the substrate holding portion11, so as to face a gap29between adjoining ones of the targets21.

As shown inFIGS. 1 and 3, the shield portion28is formed in the shape of, e.g., a 100 mm by 3,500 mm rectangular plate, and a plurality of the shield portions28are provided so as to correspond to the respective gaps29between the targets21. The shield portions28are comprised of, e.g., titanium, stainless steel, etc. Both ends of each shield portion28are fixedly attached to the substrate mask24. The width of the shield portion28in the direction A (i.e., the direction in which the plurality of targets21are arranged) is larger than that of the gap29in the direction A. For example, the shield portion28overlaps the entire gap29, and overlaps side portions of the targets21by a width of about 4 cm.

According to the magnetron sputtering apparatus1, an AC voltage that alternates in polarity at a predetermined frequency is applied from the power sources30to the targets21to cause a glow discharge with anode and cathode electrodes being alternately switched between each pair of adjoining targets21, whereby a plasma atmosphere is produced in the chamber50. The plasma causes Ar ions to bombard the targets21, causing sputtered particles to fly from the targets21toward the substrate10. A film is thus deposited on the surface of the substrate10.

Thin Film Forming Method

A method of forming a thin film on the substrate10by the magnetron sputtering apparatus1will be described below.

In the case of depositing a film on the substrate10by the magnetron sputtering apparatus1, the substrate10as a glass substrate is first carried into the chamber50, and is held by the substrate holding portion11. Next, the chamber50is decompressed by the vacuum pump (not shown), and the substrate10is heated with the heater (not shown) of the substrate holding portion11. The targets21are comprised of, e.g., a material containing IGZO (In—Ga—ZnO4; amorphous oxide semiconductor).

Then, an Ar gas, and as necessary, an O2gas are introduced into the chamber50by the gas supply portion (not shown) while maintaining high vacuum. Subsequently, a predetermined AC voltage is applied from the power sources30to supply electric power to the target portion20and to swing the magnet portion40. The magnet portion40swings at a speed of, e.g., about 10 mm/s to 30 mm/s. Moreover, the substrate10held by the substrate holding portion11is reciprocated in the direction A inFIG. 1.

The thin film can be efficiently deposited with higher quality by swinging the magnets41in such a range that the magnets41do not overlap the shield portions28in the direction perpendicular to the surface of the substrate10.

A glow discharge is thus caused between the target portion20and the wall surface of the chamber50, whereby plasma is generated on the substrate10side of the target portion20. Positive Ar ions produced by this plasma are attracted toward the target portion20. The Ar ions bombard the targets21, and sputtered particles as constituent particles of the targets21are ejected from the targets21and fly toward the substrate10.

The sputtered particles flying from the targets21perpendicularly to the surface of substrate10adhere to and deposited on the surface of the substrate10which is located between the shield portions28and faces the targets21. On the other hand, part of the sputtered particles flying from the targets21obliquely to the surface of the substrate10is blocked by the shield portions28and adheres to the shield portions28.

In this manner, the shield portions28are placed on the target portion20side of the substrate10so as to face the gaps29between the targets21, and the substrate10is moved parallel to the target portion20, whereby a thin IGZO film is formed on the substrate10.

Advantages of First Embodiment

As described above, according to the first embodiment, the substrate10is reciprocated parallel to the target portion20, and the shield portions28facing the gaps29between adjoining ones of the targets21are placed on the target portion20side of the substrate10. Thus, the sputtered particles flying from the targets21perpendicularly to the substrate10can be deposited as they are on the substrate10, while the sputtered particles flying from the targets21obliquely to the substrate10can be blocked by the shield portions28.

That is, since the shield portions28can suppress deposition of the sputtered particles flying from the targets21obliquely to the surface of the substrate10on the substrate10, a thin film having desired quality can be formed on the substrate10with high controllability without adding a complicated mechanism configuration to the magnetron sputtering apparatus.

Second Embodiment

FIG. 5shows a second embodiment of the present invention.

FIG. 5is an enlarged sectional view showing a part of a magnetron sputtering apparatus1according to the second embodiment. In the following embodiments, the same portions as those ofFIGS. 1-4are denoted by the same reference characters, and detailed description thereof will be omitted.

In the second embodiment, the magnetron sputtering apparatus1described in the first embodiment is improved in a manner in which the substrate holding portion11holding the substrate10is moved.

That is, as shown inFIG. 5, the substrate holding portion11in the second embodiment is configured to reciprocate by a width D corresponding to a region facing one target21and at least a part of the gap29located on each of both right and left sides of this target21.

In the case of forming a thin film on the substrate10by the magnetron sputtering apparatus1of the second embodiment, in the thin film forming method of the first embodiment, the substrate holding portion11reciprocates by a width corresponding to a region facing one target21and at least a part of the gap29located on each of both right and left sides of this target21.

Thus, according to the second embodiment, the substrate10that reciprocates faces all of the targets21and the gaps29therebetween (the gaps29where the power source30is placed and the gaps29where the power source30is not placed), whereby the quality of the thin film formed on the substrate10can further be improved.

Third Embodiment

FIG. 6shows a third embodiment of the present invention.

FIG. 6is an enlarged sectional view of the target21and the magnet41.

In the third embodiment, when forming a thin film by using the magnetron sputtering apparatus1of the first embodiment, movement of the magnets41is restricted at the start of film deposition on the substrate10.

That is, in a thin film forming method of the third embodiment, as shown inFIG. 6, each magnet41is made stationary at the central position of a corresponding one of the targets21during a predetermined period from the start of film deposition. In particular, the predetermined period is a period from the start of film deposition until the substrate holding portion11initially moves to the outermost position in the reciprocating direction A (i.e., the swing end in the lateral direction inFIG. 1). After the predetermined period, the magnets41are swung in a manner similar to that of the first embodiment.

Moving the magnet portion40at the start of film deposition on the substrate10makes the plasma state in the chamber50uneven, which tends to reduce the quality of a thin film formed at the start of film deposition. In the third embodiment, each magnet41is made stationary at the central position of a corresponding one of the targets21during the predetermined period from the start of film deposition on the substrate10. Thus, the magnets41can be moved to deposit a thin film after the plasma state is stabilized, whereby the quality of the thin film can further be enhanced. In this case, the thin film formed on the substrate10is a film comprised of two layers having different qualities.

Fourth Embodiment

FIGS. 7 to 9show a fourth embodiment of the present invention.

FIG. 7is a sectional view showing the general configuration of the magnetron sputtering apparatus1according to the third embodiment.FIG. 8is a plan view showing the target portion20and partition wall portions35according to the third embodiment.FIG. 9is an enlarged sectional view showing a region around the targets21and the partition wall portions35according to the third embodiment.

In the fourth embodiment, the partition wall portions35are provided in the gaps29between the targets21in the magnetron sputtering apparatus1described in the first embodiment.

That is, as shown inFIGS. 7 and 8, the magnetron sputtering apparatus1of the third embodiment has the partition wall portions35each provided between adjoining ones of the targets21and configured to block sputtered particles flying from the targets21. As shown inFIG. 9, each partition wall portion35has a flange portion (protrusion portion)36that faces a portion on the gap29side of the surface on the substrate holding portion11side of the target21(i.e., a portion of the end along the longer side of the target21). That is, as shown inFIG. 9, each partition wall portion35has a T-shaped or L-shaped section.

The flange portion36of the partition wall portion35overlaps the target21by a width of, e.g., larger than about 0 mm and equal to or less than about 5 mm A gap of about 5 mm is provided between the flange portion36and the surface of the target21facing the flange portion36.

Thus, in the case of forming a thin film on the substrate10by the magnetron sputtering apparatus1, film deposition on the substrate10is performed with each partition wall portion35being provided between adjoining ones of the targets21.

In this case, the thin film can be efficiently deposited with higher quality by swinging the magnets41in such a range that the magnets41do not overlap the partition wall portions35in the direction perpendicular to the surface of the substrate10.

As described above, according to the fourth embodiment, each partition wall portion35is provided between adjoining ones of the targets21. Thus, sputtered particles flying from the target portion20obliquely to the substrate10can be blocked not only on the part of the substrate10but also on the part of the target portion20by the partition wall portions35. This further reduces arrival of the obliquely flying sputtered particles at the substrate10, whereby the quality of the thin film formed on the substrate10can further be enhanced.

OTHER EMBODIMENTS

Although the first embodiment is described with respect to an example in which the shield portions38are arranged so as to extend parallel to the targets21, the shield portion28may further be provided so as to surround the opening24ain the substrate mask24inFIG. 3. Although the fourth embodiment is described with respect to an example in which the partition walls35are arranged so as to extend parallel to the targets21, the partition wall portion35may further be provided so as to surround the targets21inFIG. 8. This can further improve the quality of the thin film formed on the substrate10.

Although each of the above embodiments is described with respect to an example in which the magnets41are moved in the same direction as the direction A in which the substrate10is moved (that is, the direction of the shorter side of the target21), the magnets41may be moved in a direction perpendicular to the direction A in which the substrate10is moved (that is, the direction of the longer side of the target21), or may be moved in a direction perpendicular to the surface of the substrate10.

The present invention is not limited to the first to fourth embodiments, and includes a configuration obtained by combining the first to fourth embodiments as appropriate.

INDUSTRIAL APPLICABILITY

As described above, the present invention is useful for thin film forming apparatuses and thin film forming methods.

DESCRIPTION OF REFERENCE CHARACTERS