KR19990023960A - Semiconductor device and manufacturing method thereof - Google Patents

Abstract

The manufacturing method of a semiconductor device includes the following processes (a)-(f).

(a) forming a contact hole 32 in the interlayer insulating film (silicon oxide film 20 and BPSG film 30) formed on the semiconductor substrate 11 including the element, (b) 300 to 550 under reduced pressure A degassing step of removing gasification components contained in the interlayer insulating film by heat treatment at a substrate temperature of 占 폚, (c) forming a barrier layer 33 on the surfaces of the interlayer insulating film and the contact hole 32, (d) Cooling the substrate temperature to 100 ° C. or lower, (e) forming the first aluminum film 34 made of aluminum or an alloy containing aluminum as a main component at a temperature of 200 ° C. or lower on the barrier layer 33. And (f) forming a second aluminum film (35) made of aluminum or an alloy containing aluminum as a main component at a temperature of 300 ° C or higher on the first aluminum film (34).

According to this manufacturing method, a semiconductor device using aluminum or an aluminum alloy as a conductive material in the contact hole, and having a contact structure with excellent staff coverage without generating voids or disconnection, is obtained.

Description

Semiconductor device and manufacturing method thereof

The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device and a method of manufacturing the same, which can be particularly miniaturized and has a contact structure using aluminum.

In semiconductor devices such as LSIs, contact holes having a large aspect ratio are required as the device becomes smaller, denser, and multilayered. The embedding of wiring material into such contact holes is difficult and has become an important technical problem in recent years. And it has been attempted to bury in contact holes with aluminum or aluminum alloy useful as wiring material.

Therefore, as a technique, there exists a technique disclosed by Unexamined-Japanese-Patent No. 64-76736, for example. In this technique, first, a manufacturing method is disclosed in which aluminum or an aluminum alloy is deposited by a bias sputter at a temperature of 150 ° C. or lower, and an aluminum film is embedded in a contact hole in the step.

According to this technique, the aluminum film of the first layer can be deposited relatively uniformly and the coverage is considerably improved, but it cannot be said that the problem of disconnection in the conductive portion in the contact hole due to the generation of voids or the like has been sufficiently improved.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor device using aluminum or an aluminum alloy as a conductive material in a contact hole, and having a contact structure having no step or disconnection and excellent step coverage.

Another object of the present invention is to provide a method of manufacturing the semiconductor device.

The manufacturing method of the semiconductor device of this invention includes the following processes (a)-(f).

(a) forming a contact hole in the interlayer insulating film formed on the semiconductor substrate including the element,

(b) a degassing step of removing gasification components contained in the interlayer insulating film by heat treatment at a substrate temperature of 300 to 550 캜 under reduced pressure;

(c) forming a barrier layer on surfaces of the interlayer insulating film and the contact hole,

(d) cooling the substrate temperature to 100 ° C. or less,

(e) forming a first aluminum film of aluminum or an alloy containing aluminum as a main component at a temperature of 200 ° C. or lower on the barrier layer, and

(f) forming a second aluminum film containing aluminum or an alloy containing aluminum as a main component at a temperature of 300 ° C. or higher on the first aluminum film.

One of the features of this semiconductor device manufacturing method includes a step (degassing step) of removing gasification components contained in the interlayer insulating film under specific conditions in step (b). Since this degassing process is carried out, gas generation such as water, nitrogen, hydrogen or oxygen contained in the interlayer insulating film can be suppressed in a subsequent step, for example, a step of forming a second aluminum film performed under a high temperature condition of 300 ° C. or higher. .

According to the present inventors, it is confirmed that the gas generated in such an interlayer insulating film is absorbed into the burry layer or not in the aluminum film in the contact hole. Therefore, by removing the gasification component contained in the interlayer insulating film by the step (b), the degradation of the noise resistance and the generation of voids due to the existence of such gas barrier layer and the first aluminum film are assured. Can be suppressed. As a result, it is possible to form a contact portion in the contact hole which is made of an aluminum film having good keyage and low resistance.

Here, a "gasification component" means the gas component, such as water, hydrogen, oxygen, or nitrogen which generate | occur | produces in a deposited layer, ie, an interlayer insulation film or a barrier layer, when a substrate temperature is 300 degreeC or more under reduced pressure, for example. Moreover, "under reduced pressure" is preferably 2.6 Pa or less, more preferably 1.3 Pa or less.

In the present invention, the substrate temperature in the step (d) is preferably 100 ° C or lower, and preferably cooled to room temperature to 50 ° C. By cooling the substrate temperature in this step (d), the substrate temperature can be sufficiently lowered before forming the first aluminum film. In order to make a board | substrate temperature high in 300 degreeC or more in a degassing process to the said process (b), temperature control in a subsequent process (e) can be performed reliably, by reliably lowering a substrate temperature in this process (d). . In addition, through this step (d), when the first aluminum film is formed, the amount of gas emitted from the interlayer insulating film, the barrier layer, and the entire surface of the wafer can be extremely reduced. As a result, it is possible to prevent the influence of gases harmful to the coverage and adhesion adsorbed at the interface between the barrier layer and the first aluminum film.

In the step (e), gasification of components contained in the interlayer insulating film and the barrier layer can be suppressed by forming the first aluminum film on the barrier layer at a temperature of 200 ° C. or lower, preferably 30 to 100 ° C. In addition, the wettability of the barrier layer due to the gas generated externally in the barrier layer can be prevented. As a result, even if the temperature of the substrate increases due to the presence of the first aluminum film, gas generation in the lower interlayer insulating film and the barrier layer can be suppressed from the first aluminum film. ), The second aluminum film can be formed at a relatively high temperature, specifically 300 ° C or more, preferably 350 to 450 ° C.

Thus, in the step (e), the first aluminum film is formed at a relatively low temperature, and in the step (f), the second aluminum film is formed at a relatively high temperature, whereby no voids are generated and a good step coverage contact hole is formed. Landfilling becomes possible. In addition, it has been confirmed that the manufacturing method of the present invention can be applied to a contact hole of 0.2 mu m.

In order to increase the wettability of the conductive material on the surface of the barrier layer when the conductive material is embedded in the surface of the barrier layer with, for example, a contact hole having a diameter of 0.5 µm or less and an aspect ratio of 1-4. It is usually formed by a film of high melting point metal such as titanium. However, according to the inventors of the present application, it has been confirmed that metal films such as titanium are relatively easy to contain water and hydrogen. Therefore, the amount of gasification component can be reduced compared with the case of having a wetting layer, and the generation | occurrence | production of the gas which becomes a cause of a void can be suppressed more, without forming a wet layer on the surface.

The sputtering method is preferable for forming the aluminum film in the steps (e) and (f), and it is hoped that the first aluminum film and the second aluminum film are continuously performed in the same chamber. In this way, by forming the aluminum film continuously in the same chamber, the substrate temperature can be easily controlled, the atmosphere can be precisely controlled, and the inconvenience of forming an oxide film on the surface of the first aluminum film can be avoided.

In addition, it is hoped that the fixings (d), (e) and (f) will be carried out continuously in the same apparatus having a plurality of chambers kept in a reduced pressure state. This makes it possible to reduce the process of moving and installing the substrate, thereby simplifying the process and preventing contamination of the substrate.

Further, after the step of forming the barrier layer in the step (c), oxygen is introduced into the barrier layer to partially form an oxide of a metal constituting the barrier layer in the barrier layer, thereby improving barrier properties. As a method of introducing oxygen into the barrier layer, a method of exposing the substrate in a coral plasma or performing heat treatment in an oxygen atmosphere may be employed.

The semiconductor device formed by the above manufacturing method includes a semiconductor substrate including an element,

An interlayer insulating film formed on the semiconductor substrate and removed from the gasification component by heat treatment;

A contact hole formed in the interlayer insulating film,

A barrier layer formed on a surface of the interlayer insulating film and the contact hole, and

An aluminum film made of aluminum or an alloy mainly composed of aluminum formed on the barrier layer is included.

The semiconductor device is characterized by having an interlayer insulating film from which a gasification component has been removed by heat treatment, and having a contact portion which is an aluminum film of a good step cover as described above.

Further, the contact structure of the invention is suitably applied to the silicide layer formed on the surface of the impurity diffusion layer constituting the source region or the drain region of the MOS device, but is not limited to this, but the contact in the impurity diffusion layer having no other region or silicide layer. Applicable to

In addition, the contact hole in this invention may be formed by anisotropic dry etching, and may form the upper end part of a contact hole suitably on a wafer by combining isotropic wet etching and anisotropic dry etching. For example, when the diameter of the contact hole of this type and the portion formed by the dry anisotropy of the lower part is 0.5 to 0.8 m and the aspart ratio is 0.5 to 3, the second aluminum film can be formed at 300 to 350 ° C. It is very useful in practical use because it can use a general sputtering device rather than a high temperature specification.

1A to 1E are sectional views showing, implicitly, one example of a method for manufacturing a semiconductor device of the present invention in the order of steps.

2A implicitly shows an example of a sputtering apparatus used in the embodiment according to the present invention.

2B is a plan view of one example of a stage.

FIG. 3 is a diagram showing a relationship between time and substrate temperature when the substrate temperature is pied up using the sputtering apparatus shown in FIG. 2; FIG.

4 is a diagram showing a relationship between processing timing and partial pressure of residual gas (water) in a chamber in the method of manufacturing a semiconductor device according to the present invention.

Fig. 5 is a diagram showing a relationship between processing timing and partial pressure of residual gas (nitrogen) in a chamber in the method of manufacturing a semiconductor device according to the present invention.

Fig. 6 is a diagram showing data of SIMS in a layer structure having no wetting layer.

FIG. 7 is a diagram showing data of SIMS in a layer structure having no wetting layer. FIG.

8A is a view based on an electron micrograph of a cross section of a wafer in the case where aluminum is formed after cooling the wafer.

Fig. 8B is a diagram based on an electron micrograph on the cross section of the wafer when aluminum is formed without cooling the wafer.

Explanation of symbols for main parts of drawings

11 silicon substrate 12 field insulating film

13 gate oxide film 14 gate electrode

15: low concentration impurity layer 16: high concentration impurity layer

Description of the preferred implementation of the invention

1A to 1C are schematic cross-sectional views for explaining a method for manufacturing a semiconductor device and one embodiment of a semiconductor device according to the present invention.

An example of the manufacturing method of a semiconductor device is shown below.

(Formation of elements)

First, a MOS device is formed on the silicon substrate 11 by a commonly used method. Specifically, for example, the field insulating film 12 is formed on the silicon substrate 11 by selective oxidation, and the gate oxide film 13 is formed in the active region. After adjusting the threshold voltage by channel injection, tungsten silicide is sputtered on the polysilicon film grown by pyrolysis of monosilane (SiH ₄ ), and the silicon oxide film 18 is stacked and etched in a predetermined pattern to form the gate electrode 14. Is formed. At this time, if necessary, a wiring layer 37 which is a polysilicon film and a tungsten silicide film is formed on the field insulating film 12.

Thus, by implanting phosphorus ion, a low concentration impurity layer 15 in the source region or the drain region is formed. Subsequently, after the sidewall spacers 13 made of silicon oxide films are formed on the side of the gate electrode 14, arsenic is ion-implanted and impurities are activated by annealing using a halogen lamp, so that a high concentration impurity layer in the source region or the drain region is formed. 16 is formed.

Next, a silicon oxide film of 100 nm or less is vapor-grown and selectively etched with a mixed aqueous solution of hydrogen fluoride (HF) and NH ₄ F to expose a predetermined silicon substrate region. Subsequently, for example, in a nitrogen atmosphere in which titanium is sputtered to a film thickness of about 30 to 100 nm and oxygen is controlled to 50 ppm or less, an instant anneal of several seconds to 60 seconds is performed at a temperature of 650 to 750 ° C. to the surface of the silicon substrate to be opened. A monosilicide layer of titanium is formed, and a titanium rich titanium nitride (TiN) layer is formed on the silicon oxide film 18. Subsequently, when immersed in a mixed solution of ammonium hydroxide (NH ₄ OH) and hydrogen peroxide (H ₂ O ₂ ), the TiN layer is etched to leave a monosilicide layer of titanium on only the silicon substrate surface. Further, a lamp annealing at 750 to 850 ° C. is carried out to disillate the monosilicide layer, so that the titanium silicide layer 19 is formed on the surface of the high concentration impurity layer 10 in a self-aligned manner.

In addition, when the gate electrode 14 is formed of only polysilicon and exposed by selective etching, the gate electrode 14 has a titanium sariside structure in which both the gate electrode, the source, and the drain region are separated by sidewall spacers.

The polyside structure may be composed of tungsten silicide and molybten silicide instead of titanium silicide.

(Formation of Interlayer Insulating Film)

Next, as part of the interlayer insulating film, first, a silicon oxide film 20 having a thickness of 100 to 200 nm is formed by performing plasma reaction between tetraethoxysilane (TEOS) and oxygen. The silicon oxide film 20 has higher insulating properties than the film grown on the titanium silicide layer 19 and the filming grown on the molybdenum (SiH ₄ ), and the etching rate of the hydrogen fluoride solution is slow and dense.

In this case, the silicon oxide film 20 is directly formed on the titanium sidside layer 19. If the film formation temperature is high, the oxidizing gas and titanium silicide react easily at the beginning of film formation, so that cracks or peeling are likely to occur. Preferably it is 600 degrees C or less, More preferably, it is performed at 250-400 degreeC. After the silicon oxide film is formed on the titanium silicide layer 19 at a relatively low temperature as described above with a thickness of about 100 nm, it is not a problem even if the temperature is raised to about 900 ° C. if the annealing or vapor phase oxidation treatment is exposed to an oxidizing atmosphere other than water vapor. .

Next, as a part of the interlayer insulating film, BPSG having a thickness of several hundred nm to 1 탆 after vapor-phase reaction of a silane compound such as SiH ₄ or TEOS with a gas containing oxygen, oron, and this and boron on the silicon oxide film 20. The film 30 is formed. Thereafter, annealing at 800 to 900 ° C. is carried out in a nitrogen atmosphere and planarization is performed by high temperature flow. Instead of performing the high temperature flow of the BPSG film 30, planarization may be performed using chemical mechanical polishing (CMP) or a commonly used SOG film.

(Formation of contact hole)

Subsequently, the contact hole 32 having a diameter of 0.2 to 0.5 µm is formed by selectively anisotropically etching the BPSG film 30 and the silicon oxide film 20 constituting the interlayer insulating film with a reactive ion edger having CHT ₃ and CF ₄ as main gases. Is formed.

(Degassing)

Next, the heat treatment including the degassing process characterized by the present invention will be described.

First, lamp heating (heat treatment A) for 30 to 60 seconds is performed at a base arm force of 1 × 10 ⁻⁴ Pa or less and a temperature of 150 to 250 ° C. in the lamp chamber. Subsequently, argon gas is introduced into the other chamber at a pressure of 0.1 to 1.0 Pa, and degassing is performed by performing heat treatment (degassing step; heat treatment B) for 30 to 120 seconds at a temperature of 300 to 550 占 폚.

In this step, the barrier layer 33 is composed of a barrier film having a barrier function and a multilayer film serving as a conductive film. The conductive film is constituted by a high-resistance barrier film and a multilayer film that is a conductive film. The conductive film is formed between the barrier film and the impurity diffusion layer in order to increase the conductivity between the high resistance barrier film and the impurity diffusion layer formed on the silicon substrate, that is, the source region or the drain region. As the barrier film, generally a material such as titanium, cobalt, or the like can be preferably used.

In this step, first, in the heat treatment A, the entire wafer including mainly the back and side surfaces of the wafer is heat-treated to remove moisture and the like attached to the wafer.

In the processing B, the interlayer insulating film can mainly remove gasification components (oxygen, hydrogen, water, nitrogen) in the BPSG film 30 constituting it. As a result, generation | occurrence | production of the gasification component in a BPSG film | membrane at the time of formation of a barrier layer and an aluminum film which are the next process can be prevented.

In this embodiment, the barrier layer 33 is comprised by the barrier film which has a barrier function, and the multilayer film which only becomes a conductive. The conductive film is formed between the barrier film and the impurity diffusion layer in order to increase the conductivity between the high resistance barrier film and the impurity diffusion layer formed on the silicon substrate, that is, the source region or the drain region. As the barrier film, a general material such as nitride such as titanium or coalt may be preferably used. As the conductive film, a high melting point metal such as titanium or cobalt can be used. These titanium and cobalt react with the silicon constituting the substrate to form silicide.

In employing a barrier layer, such as a TiN film / TiN film, by employing dozens of atomic percent of gasification components (oxygen, hydrogen, water, nitrogen), removing the gasification component in the BPSG film 30 of the interlayer insulating film before forming these films is a contact. It is very effective in performing the film formation of the aluminum film in the hole satisfactorily. If the gasification component in the BPSG film below the barrier layer is not sufficiently removed, the gasification component of the BPSG film layer is released at the temperature (normally 300 ° C. or more) at the time of barrier layer formation, and this gas is introduced into the barrier layer. In addition, this gas is released from the barrier layer during film formation of the aluminum film and comes out at the interface between the barrier layer and the aluminum film, which adversely affects the adhesion and fluidity of the aluminum film.

(Barrier Deposition)

As a conductive film constituting the barrier layer 33 by the sputtering method, a titanium film is formed with a film thickness of 20 to 70 nm, followed by a TiN film with a film thickness of 30 to 150 nm as a barrier film in another chamber. The temperature at which the barrier layer is formed is selected in the range of 200 to 450 ° C. depending on the thickness.

Next, the oxide plasma layer is exposed to the oxygen plasma layer at a pressure of 10 to 100 Pa for 10 to 100 seconds, and annealing is performed for 10 to 60 minutes in a nitrogen or hydrogen atmosphere at 450 to 700 ° C., thereby forming titanium oxide in a stripe pattern. have. It has been confirmed that the barrier property of the barrier layer can be improved by this treatment.

Moreover, this annealing process can also be performed by 400-800 degreeC heat processing in the lamp annealing furnace containing at least several hundred ppm-several% of oxygen, and can also improve the barrier property of a barrier layer similarly.

(Heat treatment before film formation of aluminum film)

First, before cooling the wafer, a material such as water attached to the substrate by performing a heat treatment (heat treatment C) for 30 to 60 seconds at a base pressure of 1 × 10 ^-4 Pa or less and a temperature of 150 to 250 ° C. in the lamp chamber. Remove it.

(Cooling of wafer)

Before forming the aluminum film, the substrate temperature is lowered to 100 ° C or lower, preferably from room temperature to 50 ° C. This cooling process is important for lowering the substrate misconductivity raised by the heat treatment C.

By cooling the wafer in this manner, when the first aluminum film is formed, the amount of gas emitted from the BPSG film 30, the barrier layer 33, and the entire surface of the wafer can be minimized. As a result, the influence of the gas harmful to the cover blocking property and the adhesiveness which adsorb | sucks at the interface of the barrier layer 33 and the 1st aluminum film 34 can be prevented.

It is hoped that this cooling step will be performed by combining a sputtering device having a plurality of chambers having the same configuration as the chamber for forming an aluminum film. For example, it is desired to place a substrate on a stage having a cooling function provided in the chamber and to lower the substrate temperature to a predetermined temperature. This cooling process is explained in full detail below.

FIG. 2A is a schematic diagram of one example of a chamber including a stage having a water cooling function, and FIG. 2A is a plan view of one example of a stage.

The sputtering apparatus is provided with the some chamber 50 of the same structure. In the chamber 50, a target 51 serving as an electrode and an electrode 52 serving as a stage are provided, and a substrate (wafer) W to be cooled is provided on the electrode 52. In the chamber 50, an exhaust means 60 for evacuating the chamber and a first gas supply passage 53 for supplying the gas chamber are provided. When the substrate 52 is placed on the electrode 52, a predetermined space is formed between the electrode 52 and the substrate W. Specifically, as shown in FIG. 2B, an outer peripheral portion of the upper surface of the electrode 52 is formed. Therefore, the projection support part 52a is provided. A second gas supply path 54 is connected to the electrode 52. The gas as a heat conductor, such as argon gas, is supplied to the space between the electrode 52 and the substrate W in the second gas supply path 54. In addition, the electrode 52 is adjusted to a constant temperature by reflux of a refrigerant, for example, water, supplied from the refrigerant supply passage 56. As shown in FIG. 2B, the upper surface of the electrode 52 is provided with a groove 58 in a predetermined pattern so as to uniformly supply gas to the space, and the second gas supply path 54 at a portion where the grooves intersect. The spout 54a of is provided.

The chamber operates as follows to cool the wafer.

The board | substrate W is mounted on the support part 52a of the electrode 52 by setting the inside of the chamber 50 to the pressure reduction state of 6x10 <^-6> Pa or less by the exhaust means 60. FIG. A gas serving as a heat conducting medium between the electrode 52 and the substrate W is introduced into the space between the electrode 52 and the substrate W in the second gas supply path 54 and the pressure of the space is maintained at 600 to 1000 Pa. In addition, the substrate W is cooled while exhausting the gas exported from the chamber to the exhaust means 60.

When cooling the substrate W, some pressure is required in the space between the electrode 52 and the substrate W in order to maintain the cooling efficiency. In other words, in order to increase the cooling efficiency of the substrate W, it is necessary to improve the thermal conductance between the substrate W of the electrode 52 and to improve the gas, the gas in the space between the electrode 52 and the substrate W (heat conductor). It is necessary to increase the pressure.

As a cooling method of a board | substrate, the method of mounting and cooling a board | substrate on the spage which has a cooling mechanism in a chamber in a vacuum chamber is abbreviate | omitted. This cooling process does not supply gas directly to the space between the stage and the substrate, but depends on the pressure in the chamber. Therefore, in order to increase the pressure in the space between the stage and the substrate, it is necessary to increase the pressure in the chamber. have. However, if the pressure in the chamber is increased to increase the cooling efficiency, the gas molecules in the chamber increase accordingly, and the upper surface of the substrate W tends to be easily introduced by the gas molecules, thereby preventing the reflow of aluminum and generating voids and This can lead to higher resistance of the wiring. Conversely, in order to prevent contamination of the wafer, lowering the pressure in the chamber also lowers the pressure in the space between the wafer and the stage, thereby lowering the thermal conductance between the wafer and the stage, resulting in poor cooling efficiency.

According to the cooling process of this embodiment described above, in order to introduce a gas between the electrode 52 and the back side of the substrate W, the pressure in the space is applied to the chamber so as to secure the pressure in the space between the electrode 52 and the substrate W. Independently controlled in pressure. From the standpoint of securing the thermally conductive medium between the substrate and the stage, the pressure in the chamber can be suppressed to a pressure of 1 × 10 ^{−3 to} 0.1 Pa independently of the pressure in the space. As a result, contamination of the upper surface of the substrate by the gas molecules can be reliably prevented, and as a result, the reflow property of aluminum is improved and the resistance is reduced. In addition, since the pressure in the space can be set within the range of 600 to 1300 Pa without increasing the pressure in the chamber, the thermal conductance can be improved and the cooling efficiency can be increased. Thus, according to this cooling process, since the pressure in a chamber can be lowered, raising the pressure of the space between the board | substrate W and the electrode 52, favorable cooling efficiency can be obtained, preventing contamination of a board | substrate.

(Film formation of aluminum film)

First, the first aluminum film 34 is formed by highway forming by 150-300 nm sputtering after aluminum film containing 0.2-1.0 weight% copper at 200 degrees C or less, More preferably, it is 30-100 degreeC temperature. Subsequently, the substrate temperature 350-460 degreeC is heated in the same chamber, and similarly aluminum containing copper is formed into a film by sputter | spatter at low speed, and the 2nd aluminum film 35 of 300-600 nm thick is formed. Here, in the film formation of an aluminum film, "high speed" means the sputtering speed of 10 nm / sec or more, although it cannot be defined by the uniformity according to the film forming conditions or the design of the device to be manufactured.

Sputtering of aluminum is performed in another chamber in the sputter apparatus used at the time of cooling of the above-mentioned wafer. This chamber has the same configuration as the chamber shown in Figs. 2A and 2B. In this manner, the cooling process and the aluminum film forming process are performed in the same apparatus in which the reduced pressure state is maintained, thereby reducing the process of moving and installing the substrate, thereby simplifying the process and preventing the substrate from being contaminated.

The argon gas is supplied from the 1st gas supply path 53 and the 2nd gas supply path 54 here. The temperature of the wafer W is controlled by the gas supplied from the second gas supply path 54.

3 shows an example in which the substrate temperature is controlled using such a sputtering device. In FIG. 3, the horizontal side represents elapsed time and the new axis represents the substrate (wafer) temperature. In addition, in FIG. 3, the line | symbol a shows the board | substrate temperature change when the temperature of the stage 52 of a sputter apparatus is set to 350 degreeC, and the line | symbol b shows the 2nd gas supply path 54. In addition, in FIG. The change of the substrate temperature at the time of raising the temperature of the stage 52 by supplying argon gas into a chamber through this is shown.

For example, temperature control of a board | substrate is performed as follows. First, the temperature of the stage 52 is previously set to the temperature (350-500 degreeC) for forming a 2nd aluminum film. When forming the first aluminum film, there is no gas supply in the second gas supply path 54 and the substrate temperature gradually rises as indicated by a symbol a in FIG. 3 by heating by the stage 52. When the second aluminum film is formed, the heated gas is supplied through the second gas supply passage 54, so that the substrate temperature is rapidly raised and controlled to be constant at a predetermined temperature as indicated by the symbol b in FIG. .

In the example shown in FIG. 3, the first aluminum film 34 is formed while the stage temperature is set at 350 ° C. and the substrate temperature is set at 125 to 150 ° C., and soon after that, the second aluminum film 35 is formed. Film formation is performed.

In the film formation of the aluminum film, control of the power applied to the sputtering device is important, as well as the film formation speed and substrate temperature control.

In other words, it is also related to the deposition rate. The deposition of the first aluminum film 34 is performed at a high power, and the second aluminum film 35 is performed at a low power, and power is changed when switching from a higher power to a lower power. It is important not to zero. If power is used as ash, an oxide film is formed on the surface of the first aluminum film even under pressure, and the wettability of the second aluminum film to the first aluminum film is lowered and the adhesion between the two is deteriorated. In other words, by constantly applying power, active aluminum can be continuously supplied to the surface of the aluminum film during film formation, and formation of an oxide film can be suppressed. In addition, although the magnitude of power cannot be defined by the uniformity depending on the sputtering apparatus or the film forming conditions, for example, in the case of the temperature conditions shown in FIG. 3, high power is set to 5 to 10 kW and low power is set to 300 W to 1 kW. .

As described above, when the first aluminum film 34 and the second aluminum film 35 are continuously formed in the same chamber, the temperature and power can be strictly controlled. It is possible to form.

The thickness of the first aluminum film 34 is that the continuous layer can be formed with good step coverage, and the BPSG film 30 constituting the barrier layer 33 and the interlayer insulating film which are lower layers of the aluminum film 34. In consideration of being able to suppress the release of the gasification component in the ()), an appropriate range is selected, for example 200 to 400 nm. The second aluminum film 35 is determined by the size of the contact hole and its aspect ratio. For example, in order to fill a hole having an aspect ratio of about 0.5 μm or less, a thickness of 300 to 1000 nm is required.

(Film formation of antireflection film)

Further, the TiN is deposited by sputtering in another sputtering chamber to form an anti-radiation film 36 having a thickness of 30 to 80 nm. Subsequently, a deposition layer comprising the barrier layer 33, the first aluminum film 30, the second aluminum film 35, and the anti-reflection film 36, using an anisotropic dry edge mainly composed of gases of Cl ₂ and BCl ₃ . Is selectively etched and the metal wiring layer 40 is patterned.

It was confirmed that the metal wiring layer 40 thus formed was buried in stepless aluminum without generating voids in a contact hole having an aspect ratio of 0.5 to 3 and a diameter of 0.2 to 0.8 µm.

Experimental Example

(1) FIG. 4 and FIG. 5 show experimental results conducted to investigate the difference in the amount (partial pressure) of gas discharged from the wafer with or without a degassing step.

4 and 5, the horizontal axis shows the timing of the processing from the heat treatment (heat treatment C) performed before the aluminum film is formed to after the deposition of the second aluminum film 35, and the new axis shows the partial pressure of the residual gas in the chamber. It is shown. 4 and 5 show a case in which the degassing step is performed after the formation of the interlayer insulating film in the line indicated by symbol A, and the line shown in B is not subjected to the degassing step after the interlayer insulating film is formed. In this experimental example, a degassing process is performed with air pressure 0.27 Pa, temperature 460 degreeC, and time 120.

In each figure, the symbols a and b on the horizontal axis indicate the timing in the heat treatment C (the first chamber) performed before the deposition of the aluminum film, and the symbol a is immediately after the wiper is inserted into the first chamber, and the symbol b is the lamp heating. Indicates a case where the wafer is heated at 250 ° C. for 60 seconds. In the first chamber, the air pressure is set at 2.7 × 10 ⁻⁶ Pa.

Symbols C and V denote timings in the wafer cooling process (second chamber), and symbol C denotes when the wafer is cooled to 20 ° C just after the wafer is placed in the second chamber. . The air pressure in the second chamber is set at 0.27 Pa. And when measuring partial pressure, the atmospheric pressure of the chamber was reduced to 2.7x10 <^-6> Pa.

Reference numerals e, f and g 'show the timings in the aluminum film deposition process (third chamber), and symbol e indicates immediately after the wafer is placed in the third chamber, symbol f indicates immediately after the first aluminum film is deposited. And symbol g 'denote a time immediately after forming the second aluminum film. In the third chamber, the air pressure is set at 0.27 Pa. And when measuring an installment, the atmospheric pressure of the chamber was reduced to 2.7x10 <^-6> Pa.

4 and 5, it was confirmed that degassing was performed after the interlayer insulating film was formed and before the barrier layer was formed, so that water and nitrogen were hardly generated during the subsequent heat treatment and film formation of the aluminum film. On the other hand, when it does not go through the said degassing process, it turns out that water and nitrogen are released in large quantities at the time of subsequent heat processing, especially the heat processing C shown by the code | symbol b.

(2) An experiment was conducted to investigate what effect the aluminum film formation would have caused by the presence or absence of the cooling step of the wafer before the aluminum film formation. The following findings were obtained. In addition, film-forming of aluminum was performed on the conditions of aspect ratio 3.18 of a contact hole, and the film thickness of 1148 nm of an interlayer insulation film.

Fig. 8A shows a drawing obtained from an electron micrograph of a cross section of a wafer in the case where aluminum is formed after cooling the wafer to a temperature of 120 ° C of heat treatment C. Fig. 8B shows a temperature of 120 ° C of heat treatment C without cooling the wafer. The figure is shown by the electron microscope photograph of the wafer in the case where aluminum is formed into a film.

When the wafer is cooled, the substrate after the film formation of aluminum is compared with that of the non-cooled film. In the case of cooling, as shown in FIG. 8A, the first and second aluminum films A1 are formed in the contact holes. In the case where the cooling is not performed with respect to the very good filling, the contact hole in which the aluminum film is not completely buried at the bottom of the contact hole and a space (void) 100 is formed as shown in FIG. 8B is the number of contact holes on the wafer. It happened enough.

(3) FIG. 6 and FIG. 7 show measurement results by secondary ion mass spectrometry (SIMS) by irradiation of cesium primary ions.

FIG. 6 shows data of a laminate having a film structure (TiN film / Al film / TiN film / Ti film) when there is no wetting layer between the barrier layer and the first aluminum film, and FIG. 7 shows the barrier layer and the first film. Data of a laminate having a film structure (TiN film / Al film / Ti film / TiN film / Ti film) in the case of having a wetting layer made of titanium between the aluminum films of 1. 6 and 7, the new axis on the left shows quantitatively hydrogen, nitrogen and oxygen in the Al film, and the new axis on the right shows the secondary ionic strength of layers other than the Al film.

In addition, the test sample shown in FIG. 6 is formed by the method mentioned above except not performing the degassing process of said (C). The sample of the experiment shown in FIG. 7 differs from the sample of the experiment shown in FIG. 6 in that the Ti film is under the Al film.

In FIGS. 6 and 7, hydrogen, oxygen, and nitrogen are in the background of the Al film. It was confirmed that the level is below the limit detection concentration in SIMS and is hardly employed.

In addition, when there is a wetting layer (Ti film), as shown in FIG. 7, there is a large pig of hydrogen (H) represented by code pH in this film, and it turns out that a large amount of hydrogen is contained in a wetting layer.

In the above case, when there is a wet layer, when H or OH in the wet layer is excited and released as water or hydrogen gas by the plasma heat radiation during the film formation of the aluminum film, these gases are not dissolved in the aluminum film. This is caused at the interface of and causes a decrease in adhesiveness and voids.

As described above, the wetting layer (Ti film) is generally formed in order to improve the wettability of the aluminum film, and it has been clarified that it causes the above-mentioned problems in the subsequent heating step. In particular, it has been confirmed that the wafer after contact hole formation partially absorbs moisture, and contact defects or electromigration defects due to voids in the moisture absorption portion are likely to occur due to the presence of the wetting layer.

In addition, when there is a wetting layer, titanium constituting the wetting layer reacts with aluminum at the time of forming the first aluminum to partially form a fertilizer such as Al ₃ Ti, which is present during the deposition of the second aluminum film. When the surface fluid of aluminum is made underground, the filling of aluminum becomes perfect and voids are formed easily. This phenomenon is particularly prone to occur at the inlet of the contact hole and so-called pin-off is likely to occur. This value off is likely to occur in the filling of contact holes having a diameter of 0.3 µm or less.

In addition, when there is a wetting layer, titanium constituting the wetting layer can reduce the titanium oxide present in the barrier and lower the barrier property of the barrier layer.

For this reason, it is hoped that the wetting layer is not formed at least in the distribution layer of the first layer. And if the wetting layer is not formed, then the process of the door is not required, so the manufacturing process can be shortened.

In the present invention, the degassing treatment of the interlayer insulating film is performed after the formation of the contact hole as described above, and the wafer is sufficiently cooled before the aluminum film is formed. Thus, the barrier layer and the first aluminum film do not need to be formed. Even if it does not form sufficient adhesiveness, it has sufficient adhesiveness with a barrier layer and a 1st aluminum film. In the first aluminum film, gases such as hydrogen, nitrogen, and oxygen contained in the lower layer are sufficiently removed by the degassing process. Furthermore, since these gases cannot pass through the first aluminum film, the surface of the first aluminum film is removed. Very calm Therefore, when the second aluminum film is formed, aluminum smoothly flows on the surface of the first aluminum film to form a good buried layer.

In this invention, the following is considered for the reason that the 1st and 2nd aluminum films 34 and 35 were filled well in the compact hole.

(a) BPSG in the subsequent film formation of the first aluminum film 34 and the second aluminum 35 by gasifying the interlayer insulating film, in particular, the water or nitrogen contained in the BPSG film and releasing it sufficiently by performing the degassing step. By suppressing generation of gas in the film 30 or the barrier layer 33, the adhesion between the barrier layer 33 and the first aluminum film 34 was improved, and the formation of good step coverage was possible.

(b) In the film formation of the first aluminum film 34, the substrate temperature is set at a relatively low temperature of 200 ° C. or less so that moisture and nitrogen contained in the BPSG film 30 and the barrier layer 33 are not released. The adhesiveness of the 1st aluminum film 34 was improved in addition to the effect of a degassing process.

(c) In addition, since the first aluminum film 34 itself serves to suppress the generation of gas in the lower layer when the substrate temperature rises, the film formation of the next second aluminum film 35 is relatively high. It can be carried out at a temperature, and the flow diffusion of the second aluminum film can be performed satisfactorily.

As described above, according to the present invention, it is possible to bury contact holes up to about 0.2 μm only with aluminum or aluminum alloy, including at least a degassing step and a cooling step before the aluminum film is sputtered, and subsequently forming an aluminum film in the same chamber. It is possible to bury only reliability and yield or aluminum alloy, and the improvement was aimed at reliability and yield point. Moreover, it was confirmed that there was no abnormal growth of segregation and crystal grains, such as copper in the aluminum film which comprises a contact part, and also the point of reliability including migration etc. was favorable.

In the above embodiment, the semiconductor device including the N-channel MOS device has been described, but the present invention can be applied to a semiconductor device including a P-channel or CMOS device.

Moreover, although the said embodiment demonstrated the embedding of the aluminum film in the contact hole of the 1st layer, it is the same about embedding of the aluminum film in the wiring layer of 2nd or more layers (2nd layer, 3rd layer, and 4th layer). The effect is spreading.

Claims (9)

A semiconductor substrate comprising an element, An interlayer insulating film formed on the semiconductor substrate and having gaseous components removed therefrom by heat treatment; A contact hole formed in the interlayer insulating film, A barrier layer formed on a surface of the interlayer insulating film and the contact hole, and And an aluminum film made of aluminum or an alloy containing aluminum as a main component formed on the barrier layer. 2. The semiconductor device according to claim 1, wherein no semiconductor layer is provided between the barrier layer and the aluminum film to increase wettability of the aluminum film. The semiconductor device according to claim 1 or 2, wherein the barrier layer partially contains an oxide of a metal constituting the barrier layer. (a) forming a contact hole in the interlayer insulating film formed on the semiconductor substrate including the element, (b) a degassing step of removing gasification components contained in the interlayer insulating film by performing heat treatment at a substrate temperature of 300 to 500 ° C. under reduced pressure; (c) forming a barrier layer on surfaces of the interlayer insulating film and the contact hole, (d) cooling the substrate temperature to 100 ° C. or lower, (e) forming a first aluminum film of aluminum or an alloy containing aluminum as a main component at a temperature of 200 ° C. or lower on the barrier layer, and and (f) forming a second aluminum film of aluminum or an alloy containing aluminum as a main component at a temperature of 300 ° C or higher on the first aluminum film. The semiconductor device according to claim 4, wherein in the step (e), a first aluminum film is directly formed on the barrier layer without forming a wetting layer for enhancing wettability with respect to the first aluminum film on the barrier layer. Method of preparation. The method for manufacturing a semiconductor device according to claim 4 or 5, wherein the aluminum film is formed in the steps (e) and (f) by a sputtering method. The method for manufacturing a semiconductor device according to claim 4 or 5, wherein the aluminum film is formed in the steps (e) and (f) continuously in the same chamber. The method of manufacturing a semiconductor device according to claim 4 or 5, wherein the steps (d), (e), and (f) are continuously performed in the same device having a plurality of chambers in which a reduced pressure state is maintained. The method of manufacturing a semiconductor device according to claim 4 or 5, further comprising a step of introducing oxygen into the barrier layer after the step (c).