JPH0867983A - Sputtering treatment - Google Patents

Abstract

PURPOSE: To prevent the deterioration in the quality of sputtered films by interrupting a sputtering treatment in a process of continuously forming the thin films of a target material on plural substrates by the sputtering treatment, then cleaning the target surface. CONSTITUTION: The inside of a vacuum vessel is exposed to the atm. and the target surface is oxidized and contaminated in the case of continuous formation of the thin films by the target material on the many substrates by a sputtering method in this vacuum vessel and, therefore, plasma to the extent of not generating sputtering with a low target voltage is generated prior to restarting of the sputtering treatment and an 'idle sputtering' operation to expose the clean surface of the target is executed after the removal of the oxidized films and deposits on the target surface is executed and thereafter, the normal sputtering treatment is executed. The 'idle sputtering' treatment is otherwise executed by turning electric power for starting the sputtering to be impressed on the target on and off at the time of restarting after the interruption time. The films formed on the substrate surfaces are not deteriorated even after the restart.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the quality of sputtered film when continuously performing sputtering using a sputtering apparatus.

A semiconductor device, which constitutes the main body of an information processing apparatus, is manufactured by making full use of a thin film forming technique, a photolithography technique (photolithography), an impurity ion implantation technique, and the like. A lot of technology is used.

That is, in vacuum vapor deposition, heat energy is applied to a material to be vapor-deposited such as a metal to melt it, and it is further heated to a boiling point to evaporate in an atomic state and deposited on a substrate to be processed, whereas sputtering is performed. Is a phenomenon in which when the cations generated by glow discharge collide with the material (target) placed on the cathode, the atoms that make up the target are knocked out by this kinetic energy. A high-quality film can be formed.

[0004]

2. Description of the Related Art In many cases, semiconductor device manufacturing processes are automated, and aluminum (Al) alloys are used for forming wirings and electrodes. Films are continuously formed on a substrate (wafer).

FIG. 3 is a principle sectional view showing the structure of a sputtering apparatus. A target 2 for sputtering is mounted on a target electrode 1 having a structure cooled by cooling water in a vacuum chamber. , This target electrode 1
There is an adhesion preventive plate 3 in front of this, and the target electrode 1 is circuit-connected to the negative electrode of the DC power supply 4 and the adhesion preventive plate 3 is connected to the positive electrode of the DC power supply 4 via a switch.

A magnet 5 is provided behind the target electrode 1.
Is installed and magnetron sputtering is performed. That is, the target 2 with the magnet 5
A closed annular magnetic field is created in the space near the surface of the target, while a vertical electric field is present on the surface of the target 2. Therefore, in this orthogonal electromagnetic field space, electrons generated by glow discharge make a swirling motion with a small diameter. As a result, high density plasma is generated.

A shutter plate 6 is provided in front of the deposition-inhibitory plate 3, and a wafer chuck unit 8 holding a wafer 7 is provided in front of the shutter plate 6, and the wafers are sequentially supplied by a transfer mechanism. ing.

That is, there is a mounting base of a cartridge capable of loading about 200 wafers in the sputter apparatus, and it is formed so that the wafer 7 is transferred from the cartridge to the wafer chuck unit 8 by the transfer mechanism to be adsorbed.

Then, when the shutter plate 6 is moved and the target 2 and the wafer 7 are opposed to each other, a voltage higher than that at which a spattering phenomenon is generated is applied between the deposition preventing plate 3 and the target electrode 1 to generate positive ions. The target constituent material that is ejected by the collision is deposited on the surface of the wafer 7 to form a film.

Then, when the time set in advance to reach the required film thickness is reached, the voltage of the DC power supply 4 drops or cuts off and the spattering phenomenon stops, and the shutter plate 6 is attached to the protection plate 3. The wafer 7 is moved to the upper position, and the wafer 7 on the wafer chuck unit 8 is stored in another cartridge by the transfer mechanism. On the other hand, a new wafer 7 is transferred from the cartridge to the wafer chuck unit 8 and fixed by suction. Is formed.

In this way, the wafer 7 stored in the cartridge is automatically sputtered to form a thin film having a required thickness. In this case, as a sputtering method, "Hi-LOW control" is performed. Method ”and“ ON-OFF control method ”, and they are used respectively.

That is, in order to perform sputtering, the chamber is first evacuated to a high vacuum of 10 ^-7 torr or less, and then evacuated while adding an inert gas such as argon (Ar) to 10 ^-3 torr.
It is maintained at a vacuum level of about rr that enables plasma discharge.

In the former control method, the LOW power (for example, 0.5 W) is always applied between the deposition preventive plate 3 and the target electrode 1.
However, when the wafer is fixed in a predetermined position, the power is switched to Hi power (for example, 1 KW) and sputtering is performed. Therefore, use of the shutter plate 6 is essential.

On the other hand, in the latter control method, the sputtering start power is turned on and off, and the shutter plate 6 may be omitted. By using any one of these methods, a thin film having a constant film thickness is automatically formed on a large number of wafers by a sputtering method.

[0015]

The wiring of a semiconductor device formed by using a silicon (Si) wafer is formed by using Al containing about 1% of Si, and by using such an Al alloy as a target, A thin film is formed by sputtering on a Si wafer, and photoetching technology is applied to this to perform selective etching to form a fine wiring pattern.

Here, the quality control of the Al film formed on the Si wafer by the sputtering method is performed by the grain size. That is, since the sputtered film is an aggregate of scattered atomic elements, the film quality should be amorphous,
Since the melting point of Al is as low as 660 ° C, the wafer is heated by the energy of collision of flying atoms, and as a result, crystallization progresses and the average grain size grows to about 4 μm.

Therefore, the inventors decided that the quality control target of the sputtered film of Al alloy is the average grain size, and if it is out of the set value, the spattering conditions such as vacuum degree and electric power are shifted.
We have performed quality control as defective products.

Here, when the average grain size of the sputtered film deviates from the set value, it is immediately after exchanging the target and immediately after opening the chamber to the atmosphere. That is, after the chamber was first evacuated to a high vacuum of 10 ^-7 torr or less, it was evacuated while adding Ar to a vacuum degree of about 10 ^-3 torr. Is small and the reflectance is low.

The reason for this is that moisture (H ₂
This is because O) adheres and is covered with an oxide film or the like. Therefore, when the target is replaced or when the chamber is opened to the atmosphere, multiple Si wafers are sacrificed (as dummy) until the deposits on the target surface are removed and a clean surface appears. This process is commonly called "flying away".

However, conventionally, it has been considered that after the "flying away" process, the growth of a good-quality Al alloy film will continue as long as no abnormality occurs in the chamber. However, it was found that if the sputtering was interrupted while the degree of vacuum was kept in the sputterable state, the film quality deteriorated in proportion to the interruption time.

That is, there is no problem if the sputter interruption time is about 10 to 20 minutes, but if the time exceeds 2 hours, the average grain size of the Al film becomes small, and if it exceeds 8 hours, the average particle size becomes too small to be measured. I understood.

Therefore, it is an issue to clarify the cause and take countermeasures.

[0023]

When the sputtering process is interrupted, the above-mentioned problem is to automatically measure the interrupt time, and the interrupt time exceeds the set time at which the effect of target oxidation becomes remarkable. In this case, the problem can be solved by taking a management method of cleaning the target before restarting the sputtering process.

[0024]

The inventors of the present invention have used the sputtering apparatus to continuously perform S
It was found that the reason why the quality of the sputtered film deteriorates due to interruption when forming the Al alloy film on the i-wafer is that water vapor or the like is adsorbed on the target to form an oxide film and contaminate it.

That is, the target is mounted in close contact with the target electrode having a water-cooled structure, and is heated by the continuous collision of Ar ⁺ constituting the plasma during the sputtering, but the "Hi-LOW control method" is used. If yes, L
In the OW state, plasma is only generated in the vicinity of the target, and when the "ON-OFF control method" is performed, there is no plasma in the OFF state, and in this state, the target has a water-cooled structure. Therefore, the surface state is cooled so that adsorption is likely to occur, and with time, adsorption of water vapor and the like progresses and oxidation progresses.

As a method for demonstrating this, the inventor measured the change in the average grain size of the sputtered film with respect to the standing time, and as a result, the average grain size was remarkably reduced, and after 8 hours, it became too small to be measured. .

Therefore, as a countermeasure against this, in the present invention, when the sputtering operation is interrupted, the interruption time is measured, and the interruption time is set to an average particle size for evaluation in quality control (for example, a set value).
After a time (for example, 2 hours) that is smaller than 3.5 μm), it is considered that a defect has occurred, and the target is replaced, or as in the case where the chamber is opened to the atmosphere, "spraying" processing is performed at the same time as restarting sputtering. Is.

If the interruption time does not exceed the set time (for example, 2 hours), the average grain size of the sputtered film is larger than a value (for example, 3.5 μm) which is considered to be defective, so that it is a good product, and it is continuous. Then, the sputtering may be performed, and in this process, the average particle size is restored to a normal value.

Further, the "flying away" process may use a dummy Si substrate as in the conventional case, but it is economical to use a shutter.

[0030]

【Example】

 Example 1: (When performing Hi-LOW control, see FIG. 1) The present invention was applied to the continuous sputtering apparatus shown in FIG.

Here, an Al alloy containing 1% Si (Al-1% Si) was used as a target, and 200 cartridges of Si wafers having a diameter of 5 inches were loaded in the cartridge and installed in a continuous sputtering apparatus. .

First, the exhaust system is operated to move the inside of the chamber.
After evacuating to a vacuum degree of 10 ^-7 torr or less, high-purity Ar was supplied at a flow rate of 40 sccm through a needle valve to keep the inside of the chamber at 1 × 10 ^-3 torr.

In this state, the shutter plate 6 is in front of the deposition preventive plate 3, and the wafer 7 is replaced in the wafer chuck unit 8. Then, in the continuous sputtering process, the average grain size of the Al alloy film was set to 3.5 μm as a reference value for quality judgment, and when the grain size was larger than this by microscopic observation, it was regarded as a non-defective product. Is 2 hours from the past results.

Then, an electric power of 0.5 W is applied between the deposition-inhibiting plate 3 and the target electrode 1 to cause discharge, plasma is generated and brought into a LOW state, and an electric power of 500 V and 20 A is applied for sputtering. In the Hi state, sputtering was automatically performed.

FIG. 1 shows the relationship between the power control of Hi-LOW and the elapsed time, which is synchronized with the wafer transfer mechanism.
-LOW power control is performed, but when the wafer transfer is interrupted, the timer operates, and this interrupt time is set to the set time (2
After the time, just like when inserting a cartridge, "skip" the shutter plate 6 for a specified time (10 minutes).
It was good to do.

As a result, it was possible to eliminate the occurrence of defects due to the interruption of the sputtering process. Example 2: (When performing ON-OFF control, refer to FIG. 2) In the continuous sputtering apparatus shown in FIG. 3, the wafer chuck unit 8 is set at a position facing the adhesion preventing plate 3 in synchronization with the transfer mechanism. The same as Example 1 except that the sputtering power (500 V, 20 A) is applied between the deposition preventing plate 3 and the target electrode 1 to perform sputtering.

Then, when the wafer transfer is interrupted, a timer operates, and when this interrupt time exceeds a set time (2 hours), the shutter plate 6 is "empty" for a prescribed time (10 minutes) as in the case of cartridge insertion. I decided to do "fly away".

As a result, it was possible to eliminate the occurrence of defects due to the interruption of the sputtering process.

[0039]

By implementing the present invention, it is possible to eliminate the occurrence of defects due to the interruption of the sputtering process, and it is possible to improve the quality of the sputtered film.

[Brief description of drawings]

FIG. 1 is a relationship diagram between applied power and elapsed time when performing Hi-LOW control.

FIG. 2 is a relationship diagram between applied power and elapsed time when ON-OFF control is performed.

FIG. 3 is a principle cross-sectional view showing the configuration of a sputtering apparatus.

[Explanation of symbols]

 1 Target Electrode 2 Target 3 Adhesion Prevention Plate 4 DC Power Supply 6 Shutter Plate 7 Wafer 8 Wafer Chuck Unit

Claims (3)

[Claims] 1. A target is mounted in an apparatus capable of evacuating, substrates are sequentially supplied into the apparatus, and plasma is generated on the target in the apparatus to form a target constituent material on the substrate. In the sputter processing method of depositing, when the interruption time of the sputter processing exceeds the time in which the sputtered film quality is worse than the set condition due to the alteration of the target surface, the sputtered film is formed after the target cleaning processing. A sputter treatment method characterized by performing. 2. The sputtering treatment method according to claim 1, wherein plasma is generated on the target as a cleaning treatment of the target. 3. In the plasma processing of the target,
The sputtering method according to claim 2, wherein the substrate surface is covered with a shutter.