KR100496716B1 - Semiconductor device and its manufacturing method - Google Patents

Abstract

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

(a) forming a contact hole 32 in an interlayer insulating film (silicon oxide film 20 and BPSG film 30) formed on the semiconductor substrate 11 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 ° C. under reduced pressure;

(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 less,

(e) forming a 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) A step of 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 the present manufacturing method, a semiconductor device using aluminum or an aluminum alloy as a conductive material in a contact hole, having no contact or disconnection, and having a contact structure with excellent staff coverage is obtained.

Description

Semiconductor device and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly, to a semiconductor device having a contact structure using aluminum and having a contact structure using aluminum and a method for manufacturing the same.

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

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

According to this technique, the aluminum film of the first layer can be deposited relatively uniformly, and the coverage is considerably improved, but the problem of disconnection in the conductive portion in the contact hole due to the generation of voids or the like occurs. I can't say it's improved enough.

SUMMARY OF THE INVENTION An object of the present invention is to provide a semiconductor device that uses aluminum or an aluminum alloy as a conductive material in a contact hole, has no contact or voids, and has a contact structure with 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 an 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) Process of forming the 2nd aluminum film which consists of aluminum or the alloy which has aluminum as a main component on the said 1st aluminum film at the temperature of 300 degreeC or more.

One of the characteristics of the manufacturing method of this semiconductor device is the process (b) including the process (degassing process) which removes the gasification component contained in the said interlayer insulation film under specific conditions. By this degassing process, the gas generation, such as water, nitrogen, hydrogen, or oxygen contained in an interlayer insulation 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. have.

According to the inventors of the present invention, it is confirmed that the gas generated in such an interlayer insulating film is absorbed into the burry layer or not by the aluminum film in the contact hole. Therefore, by removing the gasification component contained in the interlayer insulating film in the step (b), the wettability of the barrier layer due to the presence of such a gas barrier layer and the first aluminum film is reduced. It can reliably suppress occurrence. As a result, a contact portion made of an aluminum film having good coverage and low resistance can be formed in the contact hole.

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. "Under reduced pressure" preferably refers to an air pressure of 2.6 Pa or less, more preferably 1.3 Pa or less.

Moreover, in this invention, in the said process (d), substrate temperature is cooled to 100 degrees C or less, Preferably it is normal temperature-50 degreeC. 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 temperature 300 degreeC or more in the degassing process of the said process (b), temperature control in a subsequent process (e) can be reliably performed by reliably lowering a substrate temperature in this process (d). have. 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 made extremely small. As a result, it is possible to prevent the influence of gases harmful to coverage and adhesion, adsorbed at the interface between the barrier layer and the first aluminum film.

In the step (e), gasifying a gasification component included in the interlayer insulating film and the barrier layer by forming a first aluminum film on the barrier layer at a temperature of 200 ° C. or lower, preferably 30 to 100 ° C. It can suppress and the fall of the wettability of a barrier layer by the gas which generate | occur | produces externally from a barrier layer can be prevented. As a result, the first aluminum film can be brought into close contact with the barrier layer satisfactorily, and favorable film formation of step coverage is possible.

Here, since there exists a 1st aluminum film, even if the temperature of a board | substrate rises, since gas generation from an interlayer insulation film and a barrier layer of a lower layer can be suppressed from a 1st aluminum film, in the film-forming process (f) of a 2nd aluminum film, Thus, the second aluminum film can be formed at a relatively high temperature, that is, at a high temperature such that aluminum or an aluminum alloy can flow-diffuse, specifically, at 300 ° C or higher, preferably 350 to 450 ° C.

Thus, by forming the first aluminum film at a relatively low temperature in step (e) and forming the second aluminum film at a relatively high temperature in step (f), there is no void generation and a contact hole with good step coverage. It is possible to bury the inside. 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 addition, it is preferable not to form a wetting layer on the surface of the barrier layer. The wetting layer is formed in order to increase the wettability of the conductive material on the surface of the barrier layer when, for example, the diameter of the contact hole is 0.5 µm or less and the aspect ratio is buried in the fine contact hole 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 tend to contain water or hydrogen relatively. Therefore, by not forming a wetting layer on the surface of a barrier layer, the quantity of gasification component can be reduced compared with the case where it has a wetting layer, and generation | occurrence | production of the gas which becomes a cause of a void can be suppressed more.

The sputtering method is preferable for film formation of the aluminum film in the said process (e) and (f), and it is preferable to perform a 1st aluminum film and a 2nd aluminum film continuously in the same chamber. By continuously forming the aluminum film in the same chamber as described above, the substrate temperature can be easily controlled, the atmosphere can be accurately controlled, and the inconvenience of forming an oxide film on the surface of the first aluminum film can be avoided. have.

In addition, it is preferable to perform the said fixing | fixed (d), (e), and (f) continuously in the same apparatus which has several chamber hold | maintained in reduced pressure state. This reduces the process of moving and installing the substrate, and as a result, the process can be simplified and the substrate can be prevented from being contaminated.

In addition, 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. It is desirable to. As a method of introducing oxygen into the barrier layer, a method of exposing a substrate in an oxygen plasma or performing a heat treatment in an oxygen atmosphere can be adopted.

The semiconductor device formed by the above manufacturing method,

A semiconductor substrate comprising an element,

An interlayer insulating film formed on the semiconductor substrate, wherein a gasification component is removed 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 containing aluminum as a main component is formed on the barrier layer.

The semiconductor device includes an interlayer insulating film from which a gasification component has been removed by heat treatment, and as described above, the contact portion is formed of an aluminum film having good staff coverage.

The contact structure of the present 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 thereto, and the impurity diffusion layer does not have other regions or silicide layers. The present invention can also be applied to a contact.

The contact hole in the present invention may be formed by appropriately tapering the upper end of the contact hole by combining isotropic wet etching and anisotropic dry etching in addition to being formed by anisotropic dry etching. For example, when the contact hole of this type is formed, and the diameter of the portion formed by the lower anisotropic dry etching is 0.5 to 0.8 mu m and the aspart ratio is 0.5 to 3, the second aluminum film is formed at 300 to 350 deg. Since it is possible to use a general sputtering device instead of the high temperature method, it is very useful practically.

Description of the Preferred Embodiments of the Invention

1A to 1C are schematic cross-sectional views for describing a method for manufacturing a semiconductor device and an 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 element is formed in the silicon substrate 11 by a method generally used. 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 pyrolysing monosilane (SiH ₄ ), and the silicon oxide film 18 is laminated and etched in a predetermined pattern to form a gate electrode. (14) is formed. At this time, if necessary, a wiring layer 37 made of a polysilicon film and a tungsten silicide film is formed on the field insulating film 12.

Next, a low concentration impurity layer 15 in the source region or the drain region is formed by ion implantation of phosphorus. Subsequently, after the sidewall spacers 13, which are 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 to thereby source or drain regions. High concentration impurity layer 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, by sputtering titanium at a film thickness of about 30 to 100 nm, and performing annealing for several seconds to about 60 seconds at a temperature of 650 to 750 ° C. in a nitrogen atmosphere in which oxygen is controlled to 50 ppm or less, A monosilicide layer of titanium is formed on the open silicon substrate surface, and a titanium-rich titanium nitride (TiN) layer rich in titanium is formed on the silicon oxide film 18. Subsequently, when immersed in a mixed aqueous 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 only on the silicon substrate surface. Further, lamp annealing at 750 to 850 ° C is performed, and the monosilicide layer is disilicided to form a titanium silicide layer 19 on the surface of the high concentration impurity layer 16 in a self-aligned manner.

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

The salicide 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 plasma-reacting teraethoxysilane (TEOS) with oxygen. The silicon oxide film 20 has no oxidation or casing of the titanium silicide layer 19, has a higher insulating property than the film grown from monosilane (SiH ₄ ), and has a slower etch rate for an aqueous solution of hydrogen fluoride. It becomes a film.

Here, the silicon oxide film 20 is directly formed on the titanium silicide 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 peels are formed. Since it is easy to generate | occur | produce, it is preferable to perform process temperature at 600 degrees C or less, More preferably, it is 250-400 degreeC. After the silicon oxide film is formed on the titanium silicide layer 19 at a relatively low temperature as described above at a film thickness of about 100 nm, when the annealing or gas phase oxidation process is performed in an oxidizing atmosphere other than water vapor, the temperature is about 900 ° C. It doesn't matter if you raise it up.

Next, as a part of the interlayer insulating film, a silane compound such as SiH ₄ or TEOS and a gas containing phosphorus and boron, such as oxygen or ozone, on the silicon oxide film 20 are subjected to vapor phase reaction, whereby the film thickness is several hundred nm. The BPSG film 30 of about -1 micrometer is formed. Thereafter, annealing at 800 to 900 ° C. is carried out in a nitrogen atmosphere, and planarization by high temperature flow is performed. 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, by anisotropically etching the BPSG film 30 and the silicon oxide film 20 constituting the interlayer insulating film by reactive ion etcher using CHT ₃ and CF ₄ as the main gas, the diameter is 0.2 to 0.5. A contact hole 32 of 탆 is formed.

(Degassing)

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

First, in the lamp chamber, lamp heating (heat treatment A) for 30 to 60 seconds is performed at a base pressure of 1 × 10 ⁻⁴ Pa or less and a temperature of 150 to 250 ° C. Next, argon gas is introduced in another 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 ° C.

In the present step, first, in the heat treatment A, mainly the entire wafer including the back and side surfaces of the wafer can be heat treated to remove moisture or the like adhering to the wafer.

In the heat treatment B, mainly, the interlayer insulating film can remove gasification components (oxygen, hydrogen, water, nitrogen) in the BPSG film 30 constituting it. As a result, generation of gasification components from the BPSG film can be prevented at the time of forming the barrier layer and the aluminum film which are the next steps.

In this embodiment, the barrier layer 33 is comprised by the barrier film which has a barrier function, and the multilayer film which consists only of electroconductivity. 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 cobalt can 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 be silicide.

The gasification component in the BPSG film 30 of the interlayer insulation film is formed by employing tens of atomic percent of gasification components (oxygen, hydrogen, water, nitrogen) in the barrier layer, such as a TiN film / TiN film, before forming these films. Is very effective because it can satisfactorily form the aluminum film in the contact hole. If the gasification component in the BPSG film below the barrier layer is not sufficiently removed, the gasification component in the BPSG film is released at a temperature (normally 300 ° C or more) at the time of barrier layer formation, and this gas is blown into the barrier layer. In addition, since this gas leaves the barrier layer at the time of film formation of the aluminum film and comes out at the interface between the barrier layer and the aluminum film, this adversely affects the adhesion or 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, and then, in another chamber, a TiN film is formed with a film thickness of 30 to 150 nm as a barrier film. The temperature which forms a barrier layer is selected in the range of 200-450 degreeC according to film thickness.

Next, the titanium oxide is island-shaped in the barrier layer by exposing for 10 to 100 seconds in an oxygen plasma at a pressure of 10 to 100 Pa and performing annealing for 10 to 60 minutes in a nitrogen or hydrogen atmosphere at 450 to 700 ° C. (islands) can be formed. It has been confirmed that the barrier property of the barrier layer can be improved by this treatment.

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

(Heat treatment before film formation of aluminum film)

First, prior to cooling the wafer, heat treatment (heat treatment C) for 30 to 60 seconds is performed at a base pressure of 1 × 10 ⁻⁴ Pa or less and a temperature of 150 to 250 ° C. in the lamp chamber, and then attached to the substrate. Remove substances such as water.

(Cooling of wafer)

Before depositing 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 temperature raised by the heat treatment C.

By cooling the wafer as described above, when the first aluminum film is formed, the amount of gas emitted from the BPSG film 30 and the barrier layer 33 and the entire surface of the wafer can be minimized. As a result, it is possible to prevent the influence of gases harmful to coverage or adhesion, adsorbed at the interface between the barrier layer 33 and the first aluminum film 34.

Such a cooling process is preferably performed by using a sputtering device having a plurality of chambers having the same configuration as the chamber for forming an aluminum film. For example, it is preferable to provide a substrate on a stage having a water cooling function provided in the chamber, and to lower the substrate temperature to a predetermined temperature. Below, this cooling process is explained in full detail.

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

The sputtering apparatus is provided with the plurality of chambers 50 of the same structure. The chamber 50 has a target 51 serving as an electrode and an electrode 52 serving as a stage, and is configured such that a substrate (wafer) W to be cooled is provided on the electrode 52. In the chamber 50, the exhaust means 60 for making a vacuum in a chamber, and the 1st gas supply path 53 for supplying in a gas chamber are provided. In the case where the substrate W is provided on the electrode 52, the electrode 52 is formed such that a predetermined space is formed between the electrode 52 and the substrate W. Specifically, as shown in FIG. 2B, the electrode ( A protruding support portion 52a is provided along the outer circumferential portion of the upper surface of 52. In addition, a second gas supply path 54 is connected to the electrode 52. The gas as the heat conductor, for example, argon gas, is supplied from the second gas supply path 54 to the space between the electrode 52 and the substrate W. As shown in FIG. The electrode 52 also serves as a cooling system for cooling the substrate W. As shown in FIG. The electrode 52 is adjusted to a constant temperature by reflux of a coolant supplied from the coolant supply path 56, for example, water. For example, as illustrated 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 supplies a second gas to a portion where the grooves cross. The blowing port 54a of the furnace 54 is provided.

The above chamber operates as follows to cool the wafer.

The inside of the chamber 50 is made into the pressure reduction state of 6x10 <^-6> Pa or less by the exhaust means 60, and the board | substrate W is provided on the support part 52a of the electrode 52. As shown in 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 from the second gas supply path 54, and the pressure of the space is applied. Is maintained at 600 to 1000 Pa, and the substrate W is cooled while exhausting the gas leaked from the space into the chamber to the exhaust means 60.

In the case of cooling the substrate W, some pressure is required in the space between the electrode 52 and the substrate W so as to maintain the cooling efficiency. That is, in order to improve the cooling efficiency of the board | substrate W, it is necessary to improve the thermal conductance between the board | substrate W of the electrode 52, and for this improvement, between the electrode 52 and the board | substrate W is required. It is necessary to raise the pressure of the gas (heat conduction medium) of space.

As a cooling method of a board | substrate, the method of installing and cooling a board | substrate in the vacuum chamber WHEREIN with the cooling mechanism in a chamber is considered. According to this cooling process, since the gas is not directly supplied to the space between the stage and the substrate, and the pressure in the space depends on the pressure in the chamber, in order to increase the pressure in the space between the stage and the substrate, the pressure in the chamber is increased. Need to increase However, in order to increase the cooling efficiency, increasing the pressure in the chamber increases the amount of gas molecules in the chamber, so that the upper surface of the substrate W tends to be contaminated by the gas molecules, thereby reflowing aluminum. ), There may be generation of voids and an increase in high resistance of the wiring. Conversely, in order to prevent contamination of the wafer, when the pressure in the chamber is lowered, the pressure in the space between the wafer and the stage is also lowered, whereby the thermal conductance between the wafer and the stage is lowered, and as a result, cooling efficiency This gets worse.

According to the cooling process of this embodiment mentioned above, gas is flowed in between the electrode 52 and the back surface of the board | substrate W, and thereby the pressure of the space between the electrode 52 and the board | substrate W is ensured. For this reason, the pressure in the space is controlled independently from the pressure in the chamber. 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 characteristic 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 reduced, raising the pressure of the space between the board | substrate W and the electrode 52, favorable cooling efficiency can be acquired, preventing contamination of a board | substrate. .

(Film formation of aluminum film)

First, the film formation is performed by sputtering at an aluminum film thickness of 150 to 300 nm containing 0.2 to 1.0% by weight of copper at a temperature of 200 ° C. or lower, more preferably 30 to 100 ° C., and the first aluminum film 34 is formed. do. Subsequently, in the same chamber, it heats to the substrate temperature of 350-460 degreeC, similarly the aluminum containing copper is formed into a film by the sputter | spatter at low speed, and the 2nd aluminum film 35 with a film thickness of 300-600 nm is formed. Here, in forming an aluminum film, "high speed" cannot be defined collectively depending on the film forming conditions or design details of the device to be manufactured, but generally means a sputtering speed of 10 nm / sec or more, and "low speed" is generally 3 nm / sec. The following sputtering speeds are meant.

Sputtering of aluminum is performed in the other chamber in the sputter apparatus used in the case of cooling of the wafer mentioned above. This chamber has the same structure as the chamber shown in FIG. 2A and FIG. 2B. In this way, by performing the cooling process and the film deposition process of aluminum in the same apparatus in which the reduced pressure state is maintained, the process of moving and installing the substrate can be reduced, thereby simplifying the process and preventing contamination of the substrate. can do.

Here, argon gas is supplied from the 1st gas supply path 53 and the 2nd gas supply path 54. 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 axis 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 the above 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. In the case of forming the first aluminum film, there is no gas supply from 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. In the case of forming the second aluminum film, the heated gas is supplied through the second gas supply passage 54 so that the substrate temperature rapidly rises and is controlled to be constant at a predetermined temperature as indicated by reference numeral b in FIG. 3. .

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

In the film formation of the aluminum film, control of the power applied to the sputtering device is important in addition to the film formation speed and substrate temperature control. That is, also related to the deposition rate, the deposition of the first aluminum film 34 is performed at a high power, the second aluminum film 35 is performed at a low power, and the power in the case of switching from a higher power to a lower power It is important not to zero. If the power is zero, even under pressure, an oxide film is formed on the surface of the first aluminum film, 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 always 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 | size of power cannot be prescribed | regulated by uniformity depending on a sputter apparatus or film-forming conditions, etc., for example, in the case of the temperature conditions shown in FIG. desirable.

In this way, by continuously forming the first aluminum film 34 and the second aluminum film 35 in the same chamber, it is possible to strictly control temperature and power, and to produce an aluminum film that is stable at a lower temperature than before. It becomes possible to form efficiently.

The film 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 from the aluminum film 34. Considering that the release of the gasification component from the ()) can be suppressed and the appropriate range is selected, for example, 200 to 400 nm is preferred. The second aluminum film 35 is determined by the size of the contact hole, its aspect ratio, and the like. For example, in order to fill a hole having an aspect ratio of about 0.5 μm or less, a film thickness of 300 to 1000 nm is required. .

(Film formation of antireflection film)

Further, in another sputter chamber, by depositing TiN by the sputter, an anti-radiation film 36 having a film thickness of 30 to 80 nm is formed. Thereafter, a deposition layer composed of the barrier layer 33, the first aluminum film 34, the second aluminum film 35, and the anti-reflection film 36 is selectively used as an anisotropic dry etcher mainly composed of gases of Cl ₂ and BCl ₃ . Is etched, and the metal wiring layer 40 is patterned.

In the metal wiring layer 40 thus formed, it was confirmed that good step coverage aluminum was buried without generating voids in contact holes having an aspect ratio of 0.5 to 3 and a diameter of 0.2 to 0.8 µm.

Experimental Example

(1) In FIG.4 and FIG.5, the experiment result performed in order to investigate the difference of the quantity (partial pressure) of the gas discharge | released from a wafer with or without a degassing process is shown.

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 the film formation thickness of the second aluminum film 35, and the vertical axis shows the partial pressure of residual gas in the chamber. Indicates. In FIG. 4 and FIG. 5, the line | wire A shows the case through a degassing process after formation of an interlayer insulation film, and the line shown by code | symbol B shows the case where a degassing process is not performed after formation of an interlayer insulation film. . In this experimental example, a degassing process is performed at 0.27 Pa of atmospheric pressure, the temperature of 460 degreeC, and time 120.

In each of the figures, reference numerals a and b on the horizontal axis indicate timing in the heat treatment C (first chamber) performed before film formation of the aluminum film, reference symbol a immediately after introducing the wafer into the first chamber, and symbol b Shows the wafer heated at 250 ° C. for 60 seconds by lamp heating. In the first chamber, the air pressure is set at 2.7 × 10 ⁻⁶ Pa.

Reference numerals c and d denote timings in the wafer cooling step (second chamber), reference numeral c denotes immediately after the introduction of the wafer into the second chamber, and reference numeral d denotes when the temperature of the wafer is cooled to 20 ° C. Indicates. In the second chamber, the air pressure 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 film forming process (third chamber) of the aluminum film, symbol e indicates immediately after the wafer is introduced into the third chamber, and symbol f indicates immediately after the film formation of the first aluminum film. Denotes immediately after forming the second aluminum film. In the third chamber, the air pressure is set at 0.27 Pa. And when measuring partial pressure, the atmospheric pressure of the chamber was reduced to 2.7x10 <^-6> Pa.

4 and 5, it was confirmed that degassing step after film formation of the interlayer insulating film and before film formation of the barrier layer, hardly generated water and nitrogen 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 mutually discharge | released in large quantities together with subsequent heat processing, especially heat processing C shown by the code | symbol b.

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

8A shows a view obtained from an electron micrograph of the cross section of the wafer in the case where aluminum is formed after cooling the wafer to a temperature of 120 ° C. of the heat treatment C, and FIG. 8B shows the heat treatment C without cooling the wafer. The figure calculated | required from the electron micrograph of the wafer in the case where aluminum is formed into a film at the temperature of 120 degreeC is shown.

In the case where the wafer is cooled and compared with the substrate having a film thickness of aluminum and when the wafer is not cooled, when cooling, as shown in FIG. 8A, the first and second aluminum films ( In the case where A1) is buried very satisfactorily, when cooling is not performed, as shown in FIG. 8B, the contact hole in which the aluminum film is not completely embedded in the bottom of the contact hole and a space (void) 100 is formed is About 30% of the number of contact holes on the wafer was generated.

(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 one aluminum film. 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 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). In addition, the sample of the experiment shown in FIG. 7 differs from the sample of the experiment shown in FIG. 6 in the same point that a Ti film is formed under an Al film.

6 and 7, it was confirmed that in the Al film, hydrogen, oxygen, and nitrogen were below the limit detection concentration in SIMS as the background level and hardly dissolved.

In addition, when there is a wetting layer (Ti film), as shown in FIG. 7, there is a big peak of hydrogen (H) represented by the symbol P _H in this film, and it turns out that a large amount of hydrogen is contained in a wetting layer. Can be.

In the above, when there is a wetting layer, when H or OH in the wetting layer is excited and released as water or hydrogen gas at the time of subsequent film formation of aluminum film, these gases are not dissolved in the aluminum film. At the interface between them, this causes a decrease in adhesiveness or voids.

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

In the case where there is a wetting layer, the titanium constituting the wetting layer reacts with aluminum at the time of forming the first aluminum to partially form a compound such as Al ₃ Ti, which is present when the second aluminum film is formed. Since the surface fluidity of aluminum is underground, the embedding of aluminum becomes complete and a void becomes easy to form. This phenomenon is particularly prone to occur at the entrance of the contact hole, so-called pin-off is likely to occur. And this pinch-off tends to occur in the embedding of the contact hole which has a diameter of 0.3 micrometer or less.

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

For this reason, it is preferable that the wet layer is not formed at least in the distribution layer of the first layer. And if a wetting layer is not formed, the process of that time will not be needed and a manufacturing process can be shortened.

In the present invention, as described above, the degassing treatment of the interlayer insulating film is performed after the formation of the contact hole, and the wafer layer is sufficiently cooled before the aluminum film is formed, so that the barrier layer and the wet layer are not formed. Even if it does not form sufficient adhesiveness with a 1st aluminum film, it has sufficient adhesiveness with a barrier layer and a 1st aluminum film. The gases such as hydrogen, nitrogen, and oxygen contained in the lower layer than the first aluminum film are sufficiently removed by the degassing process, and furthermore, since these gases cannot pass through the first aluminum film, the surface of the first aluminum film Will be very smooth. 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 the present invention, the following is considered as a reason why the first and second aluminum films 34 and 35 are well embedded in the compact hole.

(a) By performing a degassing step, the gas or water contained in the interlayer insulating film, in particular, the BPSG film is gasified and sufficiently discharged to thereby release the BPSG in the subsequent film formation of the first aluminum film 34 and the second aluminum 35. Since the generation of gas from the film 30 or the barrier layer 33 is suppressed, the adhesion between the barrier layer 33 and the first aluminum film 34 can be improved and the film formation of good step coverage can be achieved.

(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 lower so that moisture and nitrogen contained in the BPSG film 30 and the barrier layer 33 are not released. In addition to the effect of the degassing step, the adhesion of the first aluminum film 34 is enhanced.

(c) Further, since the first aluminum film 34 itself plays a role of suppressing 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 carry out at temperature, and can carry out the flow diffusion of a 2nd aluminum film favorably.

As described above, according to the present invention, a contact hole up to about 0.2 µm is filled only with aluminum or an aluminum alloy, including at least a degassing step and a cooling step before the sputtering of the aluminum film, and further forming an aluminum film in the same chamber. It is possible to do this, and improved in terms of reliability and yield. In addition, it was confirmed that there was no abnormal growth of segregation such as copper and crystal grains in the aluminum film constituting the contact portion, and also in terms of reliability including migration and the like.

Moreover, in the said embodiment, although demonstrated in the semiconductor device containing an N-channel MOS element, it can apply to the semiconductor device containing a P-channel type or CMOS type element.

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

1A to 1C are cross-sectional views schematically showing one example of a method for manufacturing a semiconductor device of the present invention in process order.

It is a figure which shows typically an example of the sputter apparatus used for embodiment which concerns on this invention.

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

FIG. 3 is a diagram illustrating a relationship between time and substrate temperature when the substrate temperature is controlled using the sputtering apparatus shown in FIGS. 2A and 2B.

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.

FIG. 7 shows data of SIMS in a layer structure having a 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 illustrating the cross section of the wafer in the case where aluminum is formed without cooling the wafer, based on an electron micrograph. FIG.

Explanation of symbols on main parts of drawing

11 silicon substrate 12 field insulating film

13 gate oxide film 14 gate electrode

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

Claims (8)

A semiconductor substrate comprising an element, An interlayer insulating film formed on the semiconductor substrate, wherein a gasification component is removed 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 containing aluminum as a main component, formed on the barrier layer; The barrier layer partially contains an oxide of a metal constituting the barrier layer. The semiconductor device according to claim 1, wherein there is no wetting layer between the barrier layer and the aluminum film to increase wettability with respect to the aluminum film. In the semiconductor device manufacturing method, (a) forming a contact hole in an 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 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 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 method according to claim 3, wherein in the step (e), a first aluminum film is directly formed on the barrier layer, without forming a wetting layer for enhancing wettability to the first aluminum film on the barrier layer. Semiconductor device manufacturing method. The method of manufacturing a semiconductor device according to claim 3 or 4, wherein the formation of the aluminum film in the steps (e) and (f) is performed by a sputtering method. The method of manufacturing a semiconductor device according to claim 3 or 4, wherein formation of the aluminum film in the steps (e) and (f) is performed continuously in the same chamber. The semiconductor device manufacturing method according to claim 3 or 4, 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 semiconductor device manufacturing method according to claim 3 or 4, further comprising a step of introducing oxygen into the barrier layer after the step (c).