KR100431654B1 - Method of depositing aluminum film in semiconductor device - Google Patents

Abstract

A method of manufacturing a semiconductor device capable of preventing the occurrence of local peeling phenomenon at an interface between an aluminum film and an antireflection layer laminated thereon is disclosed. After the aluminum film is deposited on the substrate, the aluminum film is slowly cooled. After leaving the substrate for at least 3 minutes, an antireflection layer is deposited on the aluminum film. Regardless of the material of the cassette, the stress of the aluminum film is sufficiently alleviated due to the slow cooling time and the bending delay time of the aluminum film. The occurrence of ball defects due to shear stress can be prevented.

Description

Method of depositing aluminum film in semiconductor device

The present invention relates to a method for depositing a semiconductor device aluminum film, and more particularly, to a semiconductor device capable of preventing local delamination at an interface between an aluminum film and an anti-reflective layer stacked thereon. An aluminum film deposition method.

As semiconductor devices have been highly integrated, wiring has become smaller, and RC delay due to wiring has emerged as an important factor for determining the operation speed. Accordingly, the multilayer wiring structure has been put to practical use. The most common method for forming the multilayer wiring structure is by depositing an aluminum film containing a small amount of silicon (Si) or copper (Cu) by sputtering to fill a contact hole or via hole. To form metal wiring.

Since the aluminum film has a high reflectance, a desired pattern is not formed when a photosensitive resin film such as a photoresist is formed directly thereon and a pattern is formed by a projection exposure method. In particular, a so-called notching phenomenon in which a metal bridge is formed between wirings is caused by light reflected from the aluminum film in a stepped region. In order to solve such a problem, a method of minimizing the influence of reflected light by adding a dye or the like into the photoresist film is performed, but this method is difficult to be applied to fine wirings such as deteriorating the fine workability.

Therefore, a method of forming a film having a low reflectance on an aluminum film while using a conventional photoresist film excellent in fine workability has been used. Titanium nitride (TiN) is mainly used as such an anti-reflection layer, and an application thereof has been proposed in the Applied Physics Society of 1987, for example.

Hereinafter, an aluminum film deposition method by a multichamber physical vapor deposition (PVD) apparatus, which is mainly used to deposit an aluminum film, will be described with reference to FIG. 1.

Referring to FIG. 1, first, a lot of 25 or 26 silicon wafers is loaded into a cassette of a load lock chamber, and then the pressure in the load lock chamber is pumped and loaded. The interior of the lock chamber is kept in a vacuum. The wafer 10 in the load lock chamber is then moved to an RF-etch chamber to perform an etching process to remove impurities on the wafer.

After moving the wafer 10 to a reaction chamber, that is, a PVD chamber, a method of sputtering an aluminum film 14 on a wafer 10 covered with an interlayer insulating film 12 having a contact hole or via hole (not shown). To be deposited.

Then, after pumping the pressure in the PVD chamber, the wafer 10 is moved to the cooling chamber. Cooling water and argon (Ar) are injected into the cooling chamber to simultaneously perform water cooling with the cooling water and air cooling with the argon gas. The wafer 10 is then returned to the cassette of the load lock chamber.

After all the above steps are returned to the cassette in the load lock chamber, a venting process for unloading the wafers is performed. That is, the wafer is supplied with a vent gas such as nitrogen (N ₂ ) or argon (Ar) through a vent line connected to the load lock chamber until the pressure in the load lock chamber becomes 760torr. Remove them from the PVD device.

According to the aluminum film deposition method described above, the stress level of the aluminum film is changed according to the material of the cassette for storing the wafers. The cassette has 25 or 26 slots for loading wafers, and is generally referred to as polypropylene (hereinafter referred to as "PP") material and polybutylene terephtalate (hereinafter referred to as "PBT"). ) Are divided into materials.

FIG. 2 is a graph showing the difference in thermal conductivity according to the cassette material. The temperature of the cassette is measured by heating time in a state where the temperature of the hot plate is set to 100 ° C. and the cassette is placed thereon. That is, the result of measuring the slope) is shown.

Referring to FIG. 2, the PP cassette has a thermal conductivity of about 0.3 ° C./min, while the PBT cassette has a thermal conductivity of about 1.2 ° C./min, which is four times faster than that of the PP material.

When the PP cassette is used in the aluminum deposition process described above, as the wafer of the last slot is transferred to the load lock chamber, venting by argon (Ar) or nitrogen (N ₂ ) gas is performed immediately, so that the wafer of the last slot is used. Is fast cooled relative to the remaining wafers, resulting in higher stress levels. That is, the material formed of the thin film has an intrinsic stress according to the deposition conditions, for example, temperature or pressure, and thermal stress due to the difference in thermal expansion coefficient between the thin film and the underlying film during cooling after deposition. ) Will be received. Therefore, the aluminum film subjected to rapid cooling has its own stress level, so if the antireflection layer 16 made of titanium nitride (TiN) is deposited thereon and subjected to a thermal cycle in a subsequent process, the aluminum film At the interface between the 14 and the antireflection layer 16, shear stress due to stress relaxation occurs.

That is, as shown in FIG. 1, the aluminum film 14 is subjected to high thermal stress due to a difference in the coefficient of thermal expansion with the interlayer insulating film 12 thereunder, and is tensioned by the antireflection layer 16 thereon. Under stress (tensile stress). Under these stresses, the aluminum film 14, which is a soft material, causes plastic deformation to relieve stress, while the titanium nitride film, which is a hard material, causes elastic deformation. Therefore, in the wafer of the last slot where the stress level was increased by rapid cooling, the shear stress is generated at the interface between the aluminum film 14 and the TiN antireflection layer 16 by thermal cycling in a subsequent process, and this value is a threshold value. If exceeded, a so-called ball defect in which the TiN antireflection layer 16 is peeled from the aluminum film 14 will be generated (see A in FIG. 1).

When using a PBT material cassette having a thermal conductivity four times faster than that of the PP material, not only the wafer in the last slot but all wafers returned to the cassette are rapidly cooled by taking heat away from the cassette having high thermal conductivity. Their stress levels are high. Therefore, when the TiN anti-reflection layer is deposited on the aluminum film and subjected to thermal cycling in a subsequent process, as described above, ball defects occur in the entire wafer due to the generation of shear stress due to the stress relaxation of the aluminum film.

Accordingly, an object of the present invention is to provide a method of manufacturing a semiconductor device capable of preventing the occurrence of ball defects at an interface between an aluminum film and an antireflection layer laminated thereon.

1 is a cross-sectional view for explaining an aluminum film deposition method by a conventional method.

Figure 2 is a graph showing the thermal conductivity difference according to the cassette material.

3A to 3C are cross-sectional views illustrating a method of manufacturing a semiconductor device in accordance with a preferred embodiment of the present invention.

4 is a schematic diagram of a physical vapor deposition apparatus for carrying out a preferred embodiment of the present invention.

5 is an enlarged cross-sectional view of the cooling chamber of FIG. 4.

6 is a graph showing a comparison of temperature change with time in the deposition process of an aluminum film according to the conventional method and the present invention.

7 is a graph illustrating a comparison of hysteresis curves according to a conventional method and a method for cooling an aluminum film according to the present invention.

<Explanation of symbols for the main parts of the drawings>

100 semiconductor substrate 102 conductive region

104: interlayer insulating film 106: contact hole

108: barrier metal layer 110: aluminum film

112: antireflection layer 114: metal wiring

200: load lock chamber 210: buffer chamber

215: RF etching chamber 220: cleaning chamber

230: transfer chamber 240, 245, 265: reaction chamber

250: cooling chamber 255, 260: robot arm

270 finger 280 pedestal

In order to achieve the above object, the present invention comprises the steps of: depositing an aluminum film on a substrate on which an interlayer insulating film including a contact hole or a via hole is formed; Reflowing the aluminum film by heating the aluminum film; Slow cooling the reflowed aluminum film to about 100 ° C .; Leaving the aluminum film cooled to about 100 ° C. for at least 3 minutes to cool to room temperature; And depositing an anti-reflection layer on the aluminum film.

In addition, the object of the present invention is a method of depositing an aluminum film on a substrate by a physical vapor deposition (PVD) method, the method comprising the steps of: (a) loading a substrate having a contact hole or a via hole in the cassette of the load lock chamber; (b) transferring the substrate to the reaction chamber; (c) depositing an aluminum film on the substrate; (d) heating the substrate to reflow the aluminum film; (e) transferring the substrate to a cooling chamber; (f) slow cooling the reflowed aluminum film to about 100 ° C; (g) transferring the substrate to the load lock chamber; (h) leaving the aluminum film cooled to about 100 ° C. for at least 3 minutes to cool to room temperature; And (i) injecting a vent gas into the load lock chamber to unload the substrate.

According to the present invention, after the aluminum film is deposited, the cooling rate is slowed in the cooling chamber to slowly cool the aluminum film. Then, since the stress of the aluminum film is sufficiently relaxed regardless of the material of the cassette, it is possible to suppress the generation of the shear stress at the interface between the aluminum film and the anti-reflection layer when the anti-reflection layer is deposited on the aluminum film and then a subsequent heat cycling process is performed. can do.

In addition, when the wafer of the last slot is returned to the cassette of the load lock chamber, the substrate is left in the cassette for at least 3 minutes and then vented. Then, the wafer is sufficiently cooled during the venting delay time to reduce the supply of thermal energy required for oxidation, thereby preventing a decrease in adhesion between the aluminum film and the antireflection layer stacked thereon. In addition, since the stress of the aluminum film is sufficiently relaxed during the delay time, an aluminum film without ball defects can be obtained.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3A to 3C are cross-sectional views illustrating a method of manufacturing a semiconductor device in accordance with a preferred embodiment of the present invention. 4 is a schematic diagram of a physical vapor deposition apparatus for carrying out a preferred embodiment of the present invention.

Referring to FIG. 3A, an interlayer insulating layer 104 is formed by depositing silicon oxide on a semiconductor substrate 100 on which devices such as a transistor are formed. Subsequently, the interlayer insulating layer 104 is partially etched by a photolithography process to form a contact hole 106 or a via hole exposing a conductive region of the substrate 100, for example, an active region or a lower metal wiring.

3B and 4, after loading the substrate 100 into the cassette of the load lock chamber-A 200 of the physical vapor deposition (PVD) apparatus, the pressure in the load lock chamber-A 200 is reduced. The pumping is performed to keep the interior of the load lock chamber-A 200 in a vacuum state.

Subsequently, the substrate 100 in the load lock chamber-A 200 is moved to the buffer chamber 210 using the first robot arm 255, and then the substrate 100 is moved back to the RF etching chamber 215. Move to. The buffer chamber 210 serves to prevent vacuum loss that may occur during the movement of the wafer. In the RF etching chamber 215, an RF plasma etching of about 400 μs is performed to remove the native oxide layer existing at the bottom of the contact hole 106 or the via hole.

Subsequently, the first robot arm 255 moves the substrate 100 from the RF etching chamber 215 to the cleaning chamber 220, and the second robot arm 260 in the transfer chamber 230. The substrate 100 is transferred to the first reaction chamber 240 by using.

As the barrier metal layer 108 on the substrate 100 in the first reaction chamber 240, for example, a titanium (Ti) film is deposited to a thickness of about 300 kPa by a sputtering method at a deposition temperature of about 100 ° C. Subsequently, the substrate 100 on which the barrier metal layer 108 is formed is transferred to the second reaction chamber 245 by using the second robot arm 260, and then an aluminum film (not shown) is formed on the barrier metal layer 108. 110) is deposited to a thickness of about 8000 kPa by the sputtering method at room temperature. Preferably, the aluminum film 110 is formed of an aluminum alloy containing 0.2% silicon and 0.5% copper.

Subsequently, after the substrate 100 is transferred to the third reaction chamber 265, aluminum reflow is performed at a temperature of about 540 ° C. to completely fill the contact hole 106 or the via hole without voids. Proceed). At this time, titanium alumide (TiAl ₃ ) crystals are generated by the reaction of titanium (Ti) and aluminum (Al) of the barrier metal layer 108. The TiAl ₃ has excellent thermal stability because of its significantly higher hardness and higher melting temperature than aluminum.

When the above-described aluminum reflow process is completed, a slit valve (not shown) between the transfer chamber 230 and the third reaction chamber 265 is opened, and the second robot arm 260 of the transfer chamber 230 is moved to the substrate ( 100 is moved to the cooling chamber 250.

5 is an enlarged cross-sectional view of the cooling chamber 250. Here, reference numeral 270 denotes a finger for picking up the substrate 100, and reference numeral 280 denotes a pedestal for supporting the substrate 100.

Referring to FIG. 5, the substrate 100 having the aluminum reflow process completed is placed in the lift position H of the cooling chamber 250, and the substrate 100 is left as it is for about 110 seconds. Subsequently, cooling water and a cooling gas such as argon (Ar) are injected into the cooling chamber 250 to simultaneously perform water cooling and air cooling with respect to the aluminum film 110 for about 25 seconds. That is, the aluminum film 110 is slowly cooled for a cooling time of 135 seconds in total. When the aluminum film 110 is slowly cooled in this manner, an effect of sufficiently relieving thermal stress due to a difference in thermal expansion coefficient between the aluminum film 110 and the underlying layer can be obtained. Therefore, since the TiN anti-reflection layer is laminated in the state where the stress of the aluminum film is sufficiently relaxed, and the subsequent heat circulation process is performed, it is noted that ball defects are generated due to the shear stress caused by the stress relaxation of the aluminum film during the subsequent heat purification process. You can prevent it.

Here, the slow cooling condition may be adjusted according to the material of the cassette of the load lock chamber. That is, since the cooling rate of the wafer is determined by the thermal conductivity of the cassette, when using a cassette made of a material having a thermal conductivity of 0.3 ° C./min or more, such as a PBT material, the substrate 100 is returned to the cassette and then vented. Due to the high speed of cooling, the cooling rate should be reduced so that the stress of the aluminum film in the cooling chamber 250 can be sufficiently relaxed. For example, it is preferable that the substrate 100 having the aluminum reflow process completed is placed in the lift position H of the cooling chamber 250 and left as it is for at least 100 seconds, followed by water cooling and air cooling.

In contrast, in the case of using a cassette made of a material having a thermal conductivity of 0.3 ° C./minute or less, for example, a PB material, since the cassette has a low thermal conductivity and a low cooling rate of the wafer, the substrate 100 may be inserted into the cooling chamber 250. The aluminum film 110 may be cooled by supplying cold water and a cooling gas immediately after the transfer.

When the above-described cooling process is completed, the substrate 100 is moved to the load lock chamber-B 205 by using the first robot arm 255. After the above-described steps, when 25 or 26 wafers, ie, the substrates 100, which constitute one lot are returned to the cassette in the load lock chamber-B 205, the substrates 100 are left for at least 3 minutes. . Then, through a vent line (not shown) connected to the load lock chamber-B 205, such as nitrogen (N ₂ ) or argon (Ar), until the pressure in the load lock chamber-B 205 becomes 760torr. Supply vent gas. The load lock chamber-B 205 is then bent to unload the substrates 100 from the cassette.

Ball defects occur in the wafer of the last slot in both PP and PBT cassettes. The wafer is returned to the cassette at a temperature of about 100 ° C. In this state, venting is started by injecting nitrogen or argon gas immediately. Of wafers are cooled relatively rapidly compared to the remaining wafers. In addition, since the appropriate temperature conditions and atmosphere are formed during the venting, oxidation of the aluminum film 110 proceeds considerably, thereby lowering the adhesive strength with the titanium nitride (TiN) antireflection layer formed in a subsequent process.

However, according to the present invention which gives a delay time of 3 minutes or more before venting, the generation of shear stress can be suppressed in a subsequent thermal cycling process because the wafer in the last slot is cooled slowly to sufficiently relax the stress. In addition, since the wafer of the last slot is sufficiently cooled during the delay time, it is possible to reduce the supply of heat energy required for oxidation and to prevent a decrease in adhesion to the TiN antireflection layer formed in a subsequent process.

Referring to FIG. 3C, when the aluminum deposition process is completed as described above, another anti-reflection layer, such as titanium nitride (TiN), is deposited on the aluminum film 110 in another deposition facility. Subsequently, the metal layer 114 is completed by patterning the anti-reflection layer 112, the aluminum layer 110, and the barrier metal layer 108 by a photolithography process.

6 is a graph showing a comparison of temperature change with time in the deposition process of an aluminum film according to the conventional method and the present invention.

Referring to FIG. 6, according to the aluminum deposition process according to the conventional method, after the aluminum film is deposited at room temperature, the temperature is raised to about 540 ° C. to perform aluminum reflow (① region). Subsequently, water cooling and air cooling are simultaneously performed in the cooling chamber for about 70 seconds to cool the aluminum film to about 100 ° C (2 area). Then, immediately venting is performed to unload the substrate, i.e., the wafer (3 region).

In contrast, according to the aluminum deposition process of the present invention, after depositing an aluminum film at room temperature and reflowing aluminum at a temperature of about 540 ° C. (1 region), the substrate on which the aluminum film is deposited is lifted in the cooling chamber for about 110 seconds. After leaving it in position to reduce the cooling rate of the aluminum film, the water and air cooling are simultaneously performed for about 25 seconds to slowly cool the aluminum film to about 100 ° C. for 135 seconds in total (ⓐ region). Then, the effect of annealing the aluminum film for 110 seconds at a temperature of about 300 to 400 ° C. is obtained, so that a large amount of TiAl ₃ crystal is generated at the interface between the aluminum film and the titanium barrier metal layer thereunder. The TiAl ₃ is a median value of the silicon oxide constituting the interlayer insulating film with the aluminum coefficient of thermal expansion, and serves as a buffer layer to reduce the thermal stress caused by the difference in the coefficient of thermal expansion during cooling. In addition, since TiAl ₃ is harder than aluminum, it inhibits plastic deformation of the aluminum film, thereby reducing shear stress generated at the interface between aluminum and the TiN antireflection layer thereon.

Subsequently, the substrate is left in the load lock chamber for about 3 minutes and then the substrate is unloaded by venting. According to the conventional method, a lot of oxidation proceeds on the surface of the aluminum film of the last slot during the venting, and this causes a problem that the adhesion between the TiN anti-reflection layer and the aluminum film deposited in a subsequent process is reduced. In contrast, in the present invention, since a delay time of about 3 minutes is provided before the start of the venting, the wafer of the last slot is sufficiently cooled during the delay time, thereby reducing the supply of thermal energy required for oxidation, which is a diffusion reaction. Therefore, the surface of the aluminum film can be suppressed from being oxidized to prevent a decrease in adhesion between the TiN antireflection layer and the aluminum film, and stress relaxation sufficiently occurs in the wafer of the last slot. As a result, according to the present invention, since the aluminum film is slowly cooled to room temperature at an aluminum deposition temperature (about 540 ° C.), the stress of the aluminum film is sufficiently relaxed to prevent the occurrence of ball defects due to shear stress after deposition of the subsequent TiN antireflection layer. Can be.

FIG. 7 is a graph illustrating a comparison of hysteresis curves according to a conventional method and a method for cooling an aluminum film according to the present invention. After the deposition of an aluminum film at room temperature, the temperature is increased to 450 ° C. and is lowered again. The result of the stress measurement in (in-situ) is shown. Here, the dotted line shows the conventional method of cooling the aluminum film at the normal speed, and the solid line shows the present invention for slow cooling the aluminum film.

Referring to FIG. 7, according to the present invention, since the slow cooling is performed at a low cooling rate of the aluminum film, the compressive stress is considerably alleviated in the heating region of 200 to 350 ° C. It can be seen that the aspect. This is because, when the ball defect is generated due to the shear stress generated at the interface between the aluminum film and the TiN antireflection layer, the stress relaxation is sufficiently caused by reducing the cooling rate of the aluminum film.

As described above, according to the present invention, after the aluminum film is deposited, the cooling rate is slowed in the cooling chamber to slowly cool the aluminum film. Then, since the stress of the aluminum film is sufficiently relaxed regardless of the material of the cassette, it is possible to suppress the generation of the shear stress at the interface between the aluminum film and the anti-reflection layer when the anti-reflection layer is deposited on the aluminum film and then a subsequent heat cycling process is performed. can do.

In addition, when the wafer of the last slot is returned to the cassette of the load lock chamber, the substrate is left in the cassette for at least 3 minutes and then vented. Then, the wafer is sufficiently cooled during the venting delay time to reduce the supply of thermal energy required for oxidation, thereby preventing a decrease in adhesion between the aluminum film and the antireflection layer stacked thereon, and the stress of the aluminum film is sufficiently relaxed during the delay time. do.

Therefore, according to the present invention, an aluminum film in which ball defects do not occur can be obtained regardless of the material of the cassette.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified without departing from the spirit and scope of the invention described in the claims below. And can be changed.

Claims (14)

Depositing an aluminum film on a substrate having an interlayer insulating film including a contact hole or a via hole; Reflowing the aluminum film by heating the aluminum film; Slow cooling the reflowed aluminum film to about 100 ° C .; Leaving the aluminum film cooled to about 100 ° C. for at least 3 minutes to cool to room temperature; And And depositing an anti-reflection layer on the aluminum film. The method of manufacturing a semiconductor device according to claim 1, wherein the aluminum film is formed of aluminum or an alloy containing aluminum as a main component. delete delete The method of claim 1, wherein the anti-reflection layer is formed of titanium nitride (TiN). In the method of depositing an aluminum film on a substrate by a physical vapor deposition (PVD) method, (a) loading a substrate having a contact hole or a via hole into a cassette of a load lock chamber; (b) transferring the substrate to the reaction chamber; (c) depositing an aluminum film on the substrate; (d) heating the substrate to reflow the aluminum film; (e) transferring the substrate to a cooling chamber; (f) slow cooling the reflowed aluminum film to about 100 ° C; (g) transferring the substrate to the load lock chamber; (h) leaving the aluminum film cooled to about 100 ° C. for at least 3 minutes to cool to room temperature; And (i) injecting a vent gas into the load lock chamber to unload the substrate. The method of claim 6, wherein the cassette is made of a material having a thermal conductivity of 0.3 ° C./min or more. 8. The method of claim 7, wherein the cassette is made of polybutylene terephthalate (PBT). The method of claim 7, wherein the step (e) comprises: leaving the substrate at a lift position of the cooling chamber for at least 100 seconds, and injecting coolant and cooling gas into the cooling chamber to cool and air-cool the aluminum film. Aluminum film deposition method of a semiconductor device, characterized in that consisting of. The method of claim 6, wherein the cassette is made of a material having a thermal conductivity of 0.3 ° C./min or less. The method of claim 10, wherein the cassette is made of polypropylene (PP). The method of claim 10, wherein the step (e) comprises injecting coolant and cooling gas into the cooling chamber to cool and air-cool the aluminum film. delete The method of claim 6, wherein the vent gas is argon (Ar) or nitrogen (N ₂ ) gas.