KR20080106463A - Vent groove modified sputter target assembly - Google Patents

Abstract

A sputter target assembly (105) including vent grooves (420) having a certain configuration so as to reduce target (110) arcing during the physical vapor deposition of a film. ® KIPO & WIPO 2009

Description

VENT GROOVE MODIFIED SPUTTER TARGET ASSEMBLY}

The present invention relates to a sputter target having a specific vent groove configuration and an apparatus comprising the same. In particular, the groove configuration of the present invention reduces the defect rate through arcing and subsequent deposition of particles on the substrate.

As in the semiconductor industry, in the manufacture of sputtering targets for use in devices, it is desirable to produce a target with a sputter surface that provides uniformity of the film during sputtering on a wafer. Physical vapor deposition is a widely used process in which targets are used for the deposition of thin layers of material on a desired substrate.

This process requires gas ion bombardment of the target with a surface formed of any material deposited as a thin film or thin layer on the substrate. The ion bombardment of the target not only causes the atoms or molecules of the target material to be sputtered, but also transfers significant thermal energy to the target. This heat is dissipated at or below the backing plate disposed in heat exchange relationship with the target. The target forms part of a cathode assembly, preferably located with the anode, in a vacuum chamber filled with an inert gas such as argon. High voltage electric fields are applied across the anode and cathode. Inert gases are ionized by collisions with electrons emitted from the cathode. Positively charged gas ions are attracted to the cathode and, upon impact with the target surface, these ions leave the target material. The released target material is deposited as a thin film on the required substrate across the vacuum enclosure and typically located proximate to the anode.

The deposited film is ideally very uniform and free of defects. However, undesirably significant blobs or splats of the target material are formed on the substrate in conventional sputtering chambers. These defects result from a phenomenon known as arcing (unfavorable effects such as pitting, flaking, cracking and local heating of the target material may occur on the target when arcing occurs). It is considered to be.

Conventional sputter deposition chambers typically use a sealing surface with a groove including a sealing member such as an o-ring disposed between the target assembly and the chamber wall to form a vacuum seal. In particular, the sealing member is generally disposed between the sputter target assembly (ie a so-called race or race track) and the side wall of the vacuum chamber in which the target assembly acts as the top or lid of the chamber. The gas may be trapped in the space created by the o-ring seal between mating surfaces of the groove, such as the sealing surface. Thus, during the sputtering process, the trapped gas flows from the sealing surface grooves into the vacuum chamber, causing arcing of the target.

Various attempts have been made to reduce, eliminate or control arcing phenomena resulting from the trapped gas. In US Pat. No. 6,416,634, Mostovoy et al. Disclose a plurality of vent grooves configured to restrict the flow of gas from an o-ring race through certain limited openings. In an attempt to reduce arcing, another redesign of the vent groove has been proposed. As shown in Figures 1A-1C, the shape of the vent groove was modified by an increase in the distance of the groove from the side wall, an increase in the width of the groove, and a combination of the two. However, none of these variations have been found to be suitable for minimizing defects in films deposited on substrates by minimizing arcing.

In order to overcome the drawbacks associated with the prior art, it is an object of the present invention to provide a construction of a new grooved vent that induces gas removal from the vacuum chamber upon pumping down.

Another object of the present invention is to provide a vent groove designed with a semi-circular cross section without sharp edges to minimize turbulence and not limit gas flow.

Other objects and aspects of the present invention will become apparent to those skilled in the art through the following specification, drawings and claims.

The sputter target assembly includes a vent groove having a particular configuration to reduce target arcing upon physical deposition of the film.

The objects and advantages of the present invention will be better understood from the following detailed description of the preferred embodiments, which is described below in connection with the accompanying drawings in which like features are designated by like reference numerals.

1A-1C are illustrations of sputter target assemblies of varying dimensions of grooved vents.

2 is a schematic diagram of a conventional magnetron sputtering system.

3 is a perspective view of a target backing plate having a race track for receiving the sealing member and a vent groove disposed therein;

4A is a schematic representation of a vent groove in accordance with the present invention.

4B is a perspective view of a sputter target assembly with eight semicircular conical grooves positioned in contact with the race track.

4C is an actual view of a sputter target made in accordance with the present invention.

5 shows the performance results of a target assembly with semicircular conical grooves compared to conventional grooves.

In the manufacture of thin films on substrates through physical vapor deposition processes, it is necessary to understand and minimize arc induced defects occurring during the process.

2 shows a conventional sputtering system 100 using a sputter target assembly 105. The sputter target assembly includes a target 100 and a target backing plate 115 extending beyond the periphery of the target 100, the target backing plate 115 forming a sealed processing chamber 125. A peripheral lip associated with the sidewall 120. Referring to Figure 3, the peripheral lip or in some cases the sputter target assembly 110 itself is a so-called "race", "race track" or groove 300 that receives a sealing member such as an o-ring. ). The sealing member need not have an o-ring configuration and can be made of any suitable material that functions as a sealing function.

The race track includes a number of vent grooves 310 that can be equally spaced on the inside of the processing chamber 125. When the treatment zone is pumped to vacuum pressure as described below, the vent grooves allow gas trapped between the o-ring and the race track of the inner wall to be pumped out of the treatment zone. Such trapped gas may be degassed, the permeation of air through the o-ring from the atmospheric environment around the sputtering system 100 to the vacuum environment within the sputtering system 100, the sputtering system 100 to atmospheric pressure. This may be due to a number of causes, including air trapped by the o-ring during aeration of the air. Without the aid of grooved vents, the trapped gas interferes with the mounting of the o-rings in the race track, and proper mounting of the o-rings in the grooves 300 allows the target backing plate 115 and the sidewalls ( It is essential for proper sealing between 120).

Referring again to FIG. 2, the sputter system 100 includes a magnet 130 disposed on the target backing plate 115, and a switch 135 connecting the target backing plate 115 to a direct current voltage source 140. . The substrate support 145 is disposed below the sputter target assembly 105 in the sealed processing chamber 125. The substrate support is configured to support the semiconductor substrate 150 during processing in the sputter system 100.

In operation, the first raising mechanism 155 raises the substrate 150, and the sealed processing chamber 125 is about 2 to 5 milliTorr of pressure (ie, through a vacuum pump (not shown)). Vacuum). The switch 135 is closed and a large negative voltage (eg, about 500 volts) occurs on the target assembly 105 relative to the substrate support 145. A corresponding electric field is formed between the target assembly 105 and the substrate support 145. Thereafter, an inert gas such as argon (Ar) is introduced into the chamber. Thus, argon ions Ar + charged in the same amount as argon ions 160 are formed between the target assembly 105 and the semiconductor substrate 150. These positively charged argon ions are accelerated toward and collide with the surface of the negatively charged target 110. As a result of this collision, electrons are emitted from the target 110.

Due to the electric field formed between the target assembly 105 and the substrate support 145 and the magnetic field formed by the magnet 130, each electron is accelerated toward the substrate support 145 and moves in a spiral trajectory. Spiral electrons eventually impinge on the argon atoms above the substrate, creating additional positively charged argon ions that accelerate and collide towards the target 110. Thus, additional electrons are allowed from the target 100, which forms additional positively charged argon ions, forming additional electrons and the like. This feedback process continues until a steady state plasma is generated over the substrate support 145.

When the plasma reaches a steady state, a region essentially free of charged particles is formed between the surface of the target 110 and the upper boundary of the plasma, and the individual electrons emitted from the target 110 maintain this large voltage difference. Is considered to be tunneled (eg, in wave form rather than particle form). As will be described further below, sometimes the plasma is broken and a large flux of charged particles (similar to current flow) moves through the plasma (ie, an arc is generated).

In addition to the electrons, due to the momentum movement between the argon ions and the target 110, the target atoms are released or “sputtered” from the target 110. The sputtered target atoms travel to and condense on the semiconductor substrate 150 to form a thin film of target material. Such thin films are ideally very uniform and free of defects. However, many blobs or splats of target material (i.e., splat defects or splats) are in thin films formed by sputter deposition in sputtering systems using conventional target backing plates with grooved vents therein. May appear.

Without being bound to any particular theory, it is believed that such splat defects are formed as a result of local arc induced local heating of the target 110, which dissolves and liberates a portion of the target material. The liberated target material migrates to the substrate 150 and splatters, cools, and regenerates due to the surface tension, which is the splat defect of the deposited thin film. The splats are very large (eg 500 μm) compared to conventional metal line widths (eg 1 μm or less), and shortening the metal wires affects device yield. Currently, up to 50% of in-film defects generated by interconnect metallization tools are considered to be splat type defects.

Conventional vent grooves have been found to contribute to splat formation by initiating target arcing. In particular, the use of multiple grooves with a particular configuration has been found to lead a dense flow of trapped gas from the o-ring to the treatment zone. Dense capture gas flow creates high partial pressure of the capture gas towards the plasma formed. Due to the high voltage present across the space between the target and the substrate at the time of processing, the high partial pressure of the trapping gas in each vent groove causes the target surface to exit when the trapped gas exits the slotted vent and enters the treatment zone. Increase the likelihood of arcing between and the upper boundary of the plasma. For example, the trapped gas may enter the plasma with a density that leaves the grooved vent by sufficient pressure leading to the electrical decomposition of the trapped gas atoms. Thus, the probability of splat formation is increased.

4A is a schematic diagram of a vent groove configuration in accordance with the present invention. As described for a conventional sputter target assembly, the sputter target assembly includes a backing plate with a lipped periphery. However, the invention is equally applicable to a target assembly without a lip, as described above. 4A and 4B, the target assembly includes a race track 400 for receiving therein a sealing member, such as an o-ring. Unlike the conventional target backing plate 115 of FIG. 2, the groove of the target backing plate of the present invention has an inner wall 410 having a specific configuration and having a plurality of vent grooves 420 disposed therein. Any number of equally spaced vent grooves may be used, but to balance out gas degassing from the vent grooves while applying a vacuum to the process chamber (ie, also referred to as “pump-down”). The vent groove 420 is preferably even. More preferably eight restrictive vent grooves are used. Preferred shapes and dimensions of the vent grooves are described below with reference to FIG. 4C.

The present invention may include any number of vent grooves whose construction is designed to reduce arcing by promoting rapid and complete pump down operation. More specifically, the geometric change of the vent groove ensures that the vacuum side of the o-ring allows for full flow of trapped air or gas upon pump down. As a result, the vent grooves of the present invention substantially reduce the density of trapped air discharged by each vent groove and reduce the partial pressure of trapped gas discharged to the treatment zone, thereby reducing the possibility of arcing.

Referring to FIG. 4C, the vent groove is disposed around the o-ring race in a configuration that maintains the integrity of the o-ring seal under high vacuum but discharges gas on the vacuum side of the o-ring to the chamber. The vent groove preferably has a hemispherical or semicircular shape with a variable cross section for both the vertical plane or the horizontal plane. The absence of sharp edges promotes unrestricted gas flow to minimize turbulence.

As shown in Figure 4C, the vent groove is disposed on the periphery of the target assembly. The vent groove is located on the race track with an opening towards the treatment zone. The size of the vent grooves may be adapted to suit the various sizes of the target assembly and each chamber in which the vent grooves are used. In a preferred embodiment, the eight semicircular conical grooves are spaced at approximately equal intervals around the periphery of the race track. Vent groove dimensions can be configured for groove tracks of various sizes, and in preferred embodiments are dimensioned to dimensions of 0.200 inch (about 0.508 cm) in diameter and about 0.080 inch (about 0.203 cm) in depth. It is natural that the depth of the vent groove does not reach, for example, the bottom height of the race track. The vent groove is disposed at a 45 degree angle between the inner diameter of the o-ring groove and the target sidewall.

example

As shown in Figure 5, the vent grooves formed in accordance with the present invention show reduced arcing as shown by the analyzed substrate. Lots of 25 wafers with a layer of aluminum alloy material deposited thereon were processed. One lot was processed using the target of the present invention with vent grooves of hemispherical or semicircular shape, and three lots were prepared as targets with vent grooves of standard rectangular shape. All wafers were processed at a power of 13 kW at a pressure of 2.1 Torr in the chamber for a life of 950 kWh (ie, until the target was used at full potential). As shown in the table below, aluminum alloys were deposited to 4,000 mm thick and defects were measured.

Vent groove type on target tool Processed Lot Lot defect Defect rate The present invention (semi-spherical shape) TSP 143 48 2 4% Prior Art (Rectangular Shape) TBM 150 54 7 13% TBM 144 92 17 18% TSP 145 63 9 14% Average Avg. 209 33 15% Difference 11%

Thus, as shown in the table above, the target of the invention with hemispherical grooves shows an 11% improvement in the removal of defects resulting from arcing. Similarly, these results are shown graphically in FIG.

Although the invention has been described in detail with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications are possible and equivalents may be used within the scope of the appended claims.

Claims (14)

Sealing structure of physical vapor deposition system, A track for receiving the sealing member, The tracks are formed in a hemispherical or semi-circular manner allowing removal of substantially all gas trapped in the tracks when pumping down the physical deposition system to create a vacuum therein and to reduce or eliminate arcing of the target during subsequent plasma processing. Sealing structure provided with the vent groove of the. The sealing structure according to claim 1, wherein the vent groove has a variable shape in both the vertical plane and the horizontal plane. The sealing structure as claimed in claim 1, further comprising at least four vent grooves disposed at approximately equal intervals from each other on the periphery of the track. The sealing structure of claim 1, wherein the sealing member is an o-ring. The sealing structure of claim 1, wherein the sealing member provides a suitable seal between the target backing plate of the physical deposition system and the sidewall of the processing chamber. The sealing structure of claim 1, wherein the vent grooves are standardized to dimensions of 0.200 inch (0.508 cm) in diameter and about 0.080 inch (0.203 cm) in depth. The sealing structure of claim 1, wherein the vent groove is disposed at a 45 degree angle between the inner diameter of the track and the sidewall of the target. Sputter target assembly of a physical deposition system, A target backing plate comprising a sealing surface, and a sputter target connected to the backing plate, The sealing surface includes a track that receives the sealing member, the track being substantially trapped in the grooves upon pumping down of the physical deposition system to create a vacuum therein and to reduce or eliminate arcing of the target during subsequent plasma processing. A sputter target assembly having a plurality of openings formed in a hemispherical or semicircular manner to allow removal of all gases. The sputter target assembly of claim 8, wherein the opening has a variable shape in both the vertical plane and the horizontal plane. 9. The sputter target assembly of claim 8, further comprising at least four openings disposed on the periphery of the track at substantially equal intervals from each other. The sputter target assembly of claim 8, wherein the sealing member is an o-ring. The sputter target assembly of claim 8, wherein the sealing member provides a suitable seal between the target backing plate of the physical deposition system and the sidewall of the processing chamber. The sputter target assembly of claim 8, wherein the opening is sized to a dimension of 0.200 inch (0.508 cm) in diameter and about 0.080 inch (0.203 cm) in depth. The sputter target assembly of claim 8, wherein the opening is disposed at a 45 degree angle between the inner diameter of the track and the sidewall of the target.

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