JP2559030B2 - Method for manufacturing metal thin film - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a metal thin film, and more particularly to a method for producing an aluminum thin film, which is widely used as an electrode wiring of a semiconductor integrated circuit.

[Conventional technology]

Conventionally, aluminum or aluminum alloy has been exclusively used as an electrode or wiring material in a general semiconductor integrated circuit device, and it is extremely rare to use other metal materials. The reason for this is that aluminum is one of the metals with the highest conductivity, and that it is available in large quantities and at low cost, and that alumina is chemically stable on the surface even in an oxidizing atmosphere,
It is considered that this is due to the fact that it has a high adhesiveness with silicon or a silicon oxide film.

On the other hand, with the increase in speed and capacity of semiconductor integrated circuit devices, there has been a strong demand for multilayer wiring and miniaturization of wiring, and some problems have arisen with respect to aluminum thin films as wiring materials. One of them is so-called through hole coating.

A physical vapor deposition method such as a vapor deposition method or an asputtering method has been generally used as a wiring forming method including coating of a through hole portion. FIG. 7 is a cross-sectional view showing a state in which a through-hole portion is covered with aluminum wiring according to a conventional technique. In the figure, 11 is a silicon substrate, 12 is a silicon oxide film, 13 is a through hole, and 14 is an aluminum wiring. As can be seen from this figure, the film thickness of aluminum is considerably thin at the stage. This is because, in the physical vapor deposition method, most of the deposited particles enter the substrate in a straight line from a direction close to vertical. That is, such a behavior of the deposited particles, as the simplest and most difficult effect, reduces the amount of the particles adhering to the portion vertical to the substrate smaller than that on the horizontal plane. In addition to such a cause, a shadow region may be generated at the lower part of the step (the lower part of the through hole 13) with respect to an obliquely incident component, and this may be amplified to generate a groove called a microcrack. .

One method for solving such a problem is to utilize selective growth of tungsten. Recently, a phenomenon has been found that tungsten is selectively deposited only on silicon or aluminum and not on a silicon oxide film. Therefore, an attempt is made to flatten the through hole by applying this. In a normal semiconductor integrated circuit, a silicon oxide film is used as an interlayer insulating film, and a base material for a through hole opened in this silicon oxide film is any one of a silicon substrate, polycrystalline silicon and aluminum. Therefore, a flat shape can be obtained by selectively growing tungsten after forming the through hole and burying tungsten having the same thickness as the interlayer insulating film only in the through hole. As described above, if the aluminum film is deposited on the entire surface by the sputtering method or the like after the flattening and the patterning is performed, the disconnection does not occur in the through hole portion.

[Problems to be solved by the invention]

However, when the tungsten selective growth technique as described above is used to fill the through hole, a dissimilar metal is inserted between the lower layer wiring made of aluminum and the wiring, and contact resistance, reaction, etc. It is not preferable in terms. Further, in the conventional tungsten selective growth, if the deposited film thickness is increased, the selectivity is deteriorated and the deposited film is also deposited on the silicon oxide film. Therefore, flattening may not be possible when the thickness of the through hole is large.

[Means for solving problems]

The method for producing a metal thin film according to the present invention has been made in view of the above problems, and by selectively removing the insulator formed on the metal or semiconductor on the substrate, the surface of the metal or semiconductor is A first step of forming the opening so as to be exposed, and then a second step of forming a barrier layer for protecting the surface on the surface of the metal or semiconductor exposed at the bottom of the opening And the third step of removing the natural oxide film layer formed on the surface of the barrier layer, and then introducing a gas containing an organic compound of aluminum to the vicinity of the substrate to heat the substrate and to remove the gas. Is heated in the vicinity of the surface of the substrate to selectively grow aluminum only on the barrier layer and fill the openings, and then the insulator and the openings are filled in the openings. And it has a fifth step of forming a aluminum film by depositing aluminum over the entire surface of Minyuumu.

[Action]

The organic compound of aluminum adhering to the substrate surface
A reduction reaction occurs only on the surface of the metal or semiconductor to form a stable nucleus of aluminum, and aluminum grows around the stable nucleus, and these are united to form an aluminum film.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to Examples. FIG. 2 shows the chemical vapor deposition (CV) used in the examples described below.
D) It is a schematic configuration diagram showing the device, and details of the device, an exhaust system, and a control system are omitted.

The vacuum chamber of this apparatus is roughly divided into a deposition chamber 21, a wafer loading / unloading chamber 22 and a raw material chamber 23, which can be evacuated independently. The ultimate pressure is preferably a high vacuum of about 10 ⁻⁶ Torr in all vacuum chambers, but a low vacuum exhausted using only a rotary pump does not have a fundamental effect in the practice of the present invention.

The deposition chamber 21 is connected to a wafer loading / unloading chamber 22 via a valve 24, and is connected to a raw material chamber 23 via a valve 25.
Further, in the deposition chamber 21, a substrate holder 27 capable of heating up to 500 ° C. is grounded. The substrate holder 27 can closely fix and fix the deposited substrate wafer 28 introduced from the wafer loading / unloading chamber 22.

A heater 29 is wound on the outer wall of the raw material chamber 23, and the liquid temperature of the raw material can be controlled to be a predetermined temperature. At this time, a stirring motor 30 for keeping the liquid temperature uniform is installed above the raw material chamber 23. A cylindrical pipe 31 that horizontally protrudes from the upper part of the raw material chamber 23 is connected to the inside of the deposition chamber 21 via a valve 25, and the raw material gas generated in the raw material chamber 23 is introduced into the deposition chamber 21 where there is almost no decrease in pressure. can do. The path of the raw material gas from the raw material chamber 23 to the deposition chamber 21 is structured to be heated to the same temperature as the raw material chamber 23 so that the once vaporized raw material is not liquefied again.

FIG. 1 is a process sectional view showing an embodiment of the method for producing a metal thin film of the present invention using such a CVD apparatus.

First, a silicon oxide film 2 is formed on a silicon substrate 1 as shown in FIG. The silicon substrate 1 used here is a p-type (100) 5 Ωcm, but there is no substantial difference in the plane orientation and the specific resistance even if other ones are used. Although the silicon oxide film 2 is formed by thermally oxidizing silicon in this embodiment, it may be deposited by another forming method such as a vapor phase growth method or a sputtering method. Further, even if other materials such as a silicon oxide film or a silicon nitride film to which phosphorus or boron is added are used as long as they are so-called insulating thin films,
There is no fundamental difference in the effect of this embodiment.

Next, as shown in FIG. 2B, a resist mask pattern is formed by using a known lithography technique,
Then, the through hole 3 is formed by using a known etching technique. Several methods are known for the lithography technology and the etching technology of the silicon oxide film 2 in this step, and any method may be used. But,
When so-called dry etching using glass plasma is performed as the etching of the silicon oxide film 2, an extremely slight polymerized film or an altered layer that is difficult to observe may be formed on the opened silicon surface. Since such a slight change in the surface state has a great influence on the subsequent aluminum deposition step, it is necessary to remove such a polymerized film and an altered layer without fail. Even when a clean silicon surface is obtained by using wet etching with a normal buffered hydrofluoric acid solution instead of dry etching, the silicon surface may be removed by the process of removing the resist pattern used as an etching mask or a simple lapse of time. Thin native oxide and other contaminants are produced. The natural oxide film 4 shown in FIG.
It is a generic term for the natural oxide film and the altered contamination layer described above.

In order to remove such a natural oxide film 4, a pretreatment for cleaning the silicon surface is required immediately before the aluminum deposition, as shown in FIG. The main purpose of this step is to remove the natural oxide film layer 4 formed on the surface of the silicon substrate 1 to ensure the reproducibility of selective aluminum deposition in the next step, and at the same time, to obtain a continuous, smooth and high-quality aluminum film. To get.

To obtain a clean silicon surface using wet etching, for example, it is usually necessary to immerse the silicon oxide film in 1.5% dilute hydrofluoric acid solution for about 10 seconds to several minutes to lightly etch the silicon oxide film. After confirming the hydrophobicity, it is sufficient to wash with pure water for several to ten or more minutes and dry.

The higher the concentration of hydrofluoric acid is, the higher the etching rate of the natural oxide film is. Therefore, when the concentration is high, the time taken to obtain hydrophobicity becomes short. However, since the silicon oxide film 2 other than the opening 3 is also etched, it is necessary to appropriately select the etching conditions depending on each case.

Further, when the water washing time becomes long, an oxide film is formed again on the surface of the silicon substrate 1 to show the water-immersive property. Therefore, the water washing is finished before such a case.

When hydrophobicity is not obtained even by etching with dilute hydrofluoric acid solution, or even when hydrophobicity is obtained, it is difficult to form a smooth and continuous film under normal deposition conditions when aluminum is deposited in a later step. There is. This is observed when the silicon surface is contaminated or damaged by the above-described dry etching or the like. In this case, after opening the through hole,
For example, a silicon oxide film of several tens of liters to several hundred liters is formed in the opening 3 by a method such as oxidizing the silicon surface in an oxygen atmosphere at about 900 ° C. Then, this oxide film is formed by using a dilute hydrofluoric acid solution or the like. By removing it to obtain hydrophobicity, a good aluminum film can be formed.

As a method of removing the natural oxide film, other than the above method, a method of setting the deposition substrate wafer in the deposition chamber and then performing etching with low energy using argon or Freon ions is also effective. For example, ECR (Electron Cyclotron
Resonance) method, acceleration voltage is 500V in Freon gas
It was possible to deposit a good aluminum film by performing the treatment for several minutes at a certain level.

The wafer substrate thus processed is set in the CVD apparatus shown in FIG. 2 to deposit aluminum. Before the wafer substrate is set, the CVD apparatus needs the following preparations.

First, the raw material chamber 23, the deposition chamber 21, and the wafer loading / unloading chamber
22 is sufficiently evacuated in advance, and the liquid of triisobutylariminium in the raw material chamber 23 is heated to a predetermined temperature by the stirring motor 30 while keeping the temperature uniform. Triisobutylaluminum has a sufficient vapor pressure even at room temperature without heating, but by heating the raw material chamber 23, vapor can be generated more efficiently. However, when the heating temperature exceeds 50 ° C., it is known that diisobutylaluminium hydride having a low vapor pressure is likely to change, and it is not possible to raise the temperature so high. here
It was set to 45 ° C.

Regarding the supply capacity of the raw material gas, the shape of the raw material chamber 23 is a cylindrical shape having a diameter of about 10 cm and a height of about 22 cm, and the evaporation rate of the raw material gas is sufficiently high if the liquid temperature and the surface area are at such a level, therefore, The vapor pressure of the raw material gas can be almost maintained even when the gas is normally used at several tens of cc / min. Further, since the raw material chamber 23 is cylindrical, the surface area of the liquid does not change even if the amount of the raw material gas changes, and the evaporation rate is always constant.
Therefore, the flow rate of the source gas can be changed while keeping the pressure substantially constant by operating the variable valve 26 provided between the deposition chamber 21 and the exhaust pump (not shown). In parallel with the heating of the raw material chamber 23 described above, the temperature of the substrate holder 27 in the deposition chamber 21 is also raised and controlled so as to be a constant temperature.

After the above preparatory work, the preprocessed wafer 28 shown in FIG. 1 (c) is set in the wafer loading / unloading chamber 22 and exhausted sufficiently. Subsequently, the wafer 28 is moved to the deposition chamber 21,
The temperature of the wafer 28 is made substantially the same as the temperature of the substrate holder 27 by holding the substrate 28 in close contact with the substrate holder 27 for several minutes.

Next, the valve 25 between the raw material chamber 23 and the deposition chamber 21 is opened to introduce the raw material gas into the deposition chamber 21, and the deposition of aluminum is started. It is desirable that the raw material chamber 23 be evacuated at the same flow rate as during deposition for an appropriate time until the valve 25 is opened so that the pressure in the deposition chamber 21 does not fluctuate immediately after opening the valve 25.

After a predetermined deposition time has elapsed, the valve 25 is closed and the deposition is completed.

By performing the above processing, the selectively grown aluminum 5 can be deposited only in the opening 3 of the silicon substrate 1 as shown in FIG.

As described above, in order to selectively deposit the aluminum only on the silicon substrate 1 without depositing it on the silicon oxide film 2, it is necessary to carefully select the film deposition conditions. In particular, the substrate temperature is an important parameter, and the range of the substrate temperature for carrying out selective growth in a good state is approximately 250 to 280 ° C, but 220 to 290 ° C is sufficient for selective growth. Aluminum is hardly deposited even on silicon below this temperature range, and aluminum nuclei are also generated on the silicon oxide film 2 above the above temperature range. At higher temperatures, there is no distinction between silicon and silicon oxide film. Deposited on choice. That is, in order to obtain good selectivity, a lower substrate temperature is desirable even within the above temperature range.

The state of aluminum deposition changes depending on deposition conditions other than the substrate temperature, that is, the pressure of the source gas, the velocity of the source gas on the wafer surface, and the like. The gas pressure can be controlled by changing the temperature of the raw material chamber 23 within the range from room temperature to about 50 ° C. as described above. In the case of the present embodiment, the selective growth was possible in any of the pressure control range of the raw material chamber 23 in the above temperature range and about 0.2 to 2 Torr. When the pressure was less than 0.2 Torr, the deposition hardly progressed, and when the pressure was more than 0.2 Torr, the deposition rate tended to increase as the resultant force increased.

The velocity of the raw material gas on the wafer surface is greatly affected by the structure of the deposition chamber 21 even if the flow rate is the same, and therefore it is generally difficult to handle. However, the velocity change of the source gas on the wafer surface can be obtained by the flow rate change when the apparatus is fixed.
The standard flow rate used in this example was about 20 to 30 cc / min, but if the flow rate was about 50 cc / min or less, no significant effect was observed on the film deposition state.

However, when the flow rate increased, the surface temperature of the wafer 28 or the temperature of the gas on the surface of the wafer 28 decreased, and it was observed that aluminum deposition was unlikely to occur. For example, when the flow rate is increased, the substrate temperature may be increased by 20 to 30 ° C. as compared with the case of the standard flow rate to cause deposition. Even at the same gas flow rate, the wafer
When 28 was installed near the gas outlet, a phenomenon was observed in which aluminum was not deposited only near the outlet on the wafer 28.

It is considered that these phenomena are due to the fact that the low temperature source gas is introduced to the surface of the wafer 28 and the temperature in the vicinity of the wafer 28 is lowered because the CVD method used in this embodiment is a cold wall type. Therefore, it is important not to increase the gas flow rate beyond the required consumption. The temperature range in which the selective growth is possible is for the case where the gas flow rate is not set higher than necessary. The standard of the required consumption is
This is the flow rate at which the deposition rate does not increase even if the gas flow rate is increased by fixing the device structure and increasing the gas flow rate. When the gas flow rate is small, such a phenomenon is not observed. In an extreme case, even if the exhaust chamber is stopped and the deposition chamber 21 connected to the raw material chamber 23 is sealed, aluminum deposition with a sufficient film thickness is possible. Met. However, in this case, the pressure in the deposition chamber 21 increases with time due to isobutylene and hydrogen gas generated by the decomposition reaction of triisobutylaluminum.

Now, let us consider the mechanism of selective growth, that is, the reason why aluminum is deposited only on the silicon substrate and not on the silicon oxide film.

It is said that the raw material gas, triisobutylaluminum, decomposes into diisobutylaluminium hydride and isobutylene at about 50 ° C or higher.

About 220 ° C for diisobutylaluminium halide
The above changes to aluminum.

As a total reaction, Becomes

It is considered that a part of the triisobutylaluminium introduced into the vacuum is heated in the vapor phase near the heating substrate and decomposes into diisobutylaluminium hydride and isobutylene. In the gas phase, in addition to these organic aluminum gases, hydrocarbons and hydrogen generated by the aluminum deposition reaction are contained. All of these gases are constantly exhausted by a vacuum pump, and in a steady state, the partial pressures of these gases have a constant ratio.

The process of film deposition by CVD is generally described as follows. Various gas molecules incident on the substrate surface are partially elastically reflected and the other gas molecules are adsorbed. The adsorbed gas molecules diffuse on the surface of the substrate and are then re-evaporated or reacted to decompose into aluminum. The aluminum atoms stochastically generated on the substrate in this manner form clusters due to collision of atoms while surface-diffusing on the substrate. These clusters repeatedly grow or disappear due to collision between clusters and absorption of aluminum atoms into the clusters. The total free energy of one cluster is the sum of the free energy change during condensation and the interfacial energy of the cluster, and becomes maximum when the cluster has a certain size. The clusters at this time are called critical nuclei, and the radius of the clusters is called critical radius. Clusters smaller than the critical nuclei disappear as an average, but those that once become stable nuclei beyond the critical radius continue to grow without disappearing. The grown nuclei eventually coalesce with each other to form a continuous film.

In the above thin film growth process, it is considered that the three processes of adsorption, reaction and formation of critical nuclei are different depending on the substrate material as a cause of the selectivity of film growth depending on the substrate material.

First, we focus on the adsorption process of the source gas. The residence time of atoms on the substrate surface is determined by the adsorption energy, and if the adsorption energy exceeds 20 kcal, the adsorption time is 10 ^-13.
It is known to approach infinity rapidly from the order of seconds. On a substrate with a small adsorption energy, re-evaporation occurs before a decomposition reaction into aluminum occurs, whereas in the case of a large adsorption energy, the staying time is long and the decomposition reaction into aluminum proceeds during this time. It is considered that a part of triisobutylaluminium has changed to diisoble aluminum hydride near the surface of the substrate. That affects the film formation
It is expected that this is the adsorption process of diisobutylaluminium hydride. The adsorption energy of this diisobutylaluminium hydride molecule on the silicon oxide film is
If the size is smaller than that on silicon, it is fully conceivable that selective growth will occur.

Next, when attention is paid to the reaction process, the silicon reduction reaction of triisobutylaluminum or diisobutylaluminium hydride or the catalytic action of silicon in the decomposition reaction of these gases is considered.
In this case, no reaction occurs on the silicon oxide film. In the case of the present invention, the result is that the film thickness increases linearly with the deposition time even when the film thickness of aluminum exceeds 1 μm, and the silicon reduction reaction proceeds in such a thick film state. In order to do so, it is necessary that the diffusion rate of silicon in aluminum is quite high. However, when the deposited aluminum was wet etched and the underlying silicon substrate was observed, it was revealed that part of the silicon was eroded, and a reaction with silicon is considered to be sufficient at the initial stage of film deposition. .

Finally, we consider the cause of selectivity in the critical nucleation process. The total free energy of one critical nucleus formed on the substrate increases sharply as the contact angle of the nucleus with the substrate increases. Then, this contact angle tends to be larger as the interface energy of the substrate is smaller than the interface energy of the nucleus. The interface energy of aluminum is as large as 1140 erg cm ^-2, and that of silicon is about the same. However, the surface energy of the silicon oxide film is 605e.
Small as rg cm ^-2 . Therefore, the free energy of the critical nucleus in the growth of the aluminum film is small on the silicon substrate and large on the silicon oxide film. The free energy of the critical nuclei can be regarded as the activation energy for stable nucleation. In the case of a silicon substrate with a small activation energy, stable nuclei are easily formed. To grow into a continuous film. On the other hand, on the silicon oxide film, the activation energy for stable nucleation is large, and nuclei are hardly formed. The interfacial energy is generally large for metals and semiconductors and small for insulators. This enables selective growth by depositing aluminum only on the conductive material.

The above three points can be considered as the mechanism of selective growth, but it is considered that which of these mechanisms is the main control factor actually depends on the deposition conditions. Need to be set.

Figure 3 shows a substrate temperature of 270 ° C, a pressure of 0.5 Torr, and a deposition time of 20.
3 is a scanning electron microscope (SEM) photograph showing the metallographic structure of aluminum deposited in a fine opening to be a through hole under a typical deposition condition of minute. It can be seen that the grain boundaries of aluminum tend to be slightly concave, but they are not islands, but a continuous film. Further, it can be seen that aluminum is not deposited on the silicon oxide film at all, but is selectively deposited only on the silicon openings. At this time, the thickness of the silicon oxide film is 5000Å,
Aluminum having the same thickness as this film is deposited on silicon. This aluminum film has a resistivity of 3.3.
It was about μmΩcm, and impurities in the film were as good as the detection limit of Auger analysis or less.

It should be noted that the surface shape of the aluminum deposited in a wide range according to the present example has a slightly larger surface unevenness as compared with other forming methods such as the sputtering method, but this is formed by the generally reported CVD method. This phenomenon is common to aluminum films. It is considered that the cause of the unevenness is that island formation occurs in the initial stage of film growth and these islands are connected to form a film. The unevenness of the film surface is greatly affected by the substrate heating temperature during deposition, and the unevenness tends to be reduced by lowering the substrate temperature. Therefore, it is desirable that the substrate temperature is low in order to reduce unevenness on the film surface.

FIG. 1 (e) shows the through hole portion 3 as described above.
In the figure, after selectively depositing aluminum having the same thickness as that of the silicon oxide film 2, the aluminum film 6 is deposited on the entire surface by the usual sputtering method. The figure also shows the cross-sectional shape of the through hole 3 in a state where the aluminum film 6 is further patterned to form an aluminum wiring pattern. By utilizing the selective growth of aluminum in this way, it is possible to obtain a flat aluminum wiring having no step in the silicon opening 3 which is a through hole.

Compared with the case of using selective growth of tungsten,
Since it is an aluminum of the same kind as the wiring material, there is no reaction at the contact interface or increase in resistance, the contact resistance with the silicon substrate 1 is sufficiently small, and it is possible to fill deep through holes with good selectivity. It has the following features. In particular, regarding the deposited film thickness, in the case of tungsten, there are problems that the film thickness is saturated with respect to the deposition time, and when the film thickness becomes thick, nuclei are generated on the silicon oxide film. It was difficult to fill the through holes. On the other hand, in the case of selective growth of aluminum, it is possible to deposit it even if the film thickness exceeds 1 μm.

In the present embodiment, the example in which the through hole 3 on the substrate silicon opened in the silicon oxide film 2 is filled with aluminum is shown, but the same can be done with other materials other than the combination of the silicon oxide film and the silicon substrate. is there. In many cases, the aluminum wiring of the semiconductor integrated circuit is connected to the element portion or the wiring of the lower layer through the opening of the insulating film. At this time, the base material in the opening is usually short crystal or polycrystalline silicon containing various impurities or aluminum. In addition, metals such as titanium, molybdenum, tungsten and platinum, or titanium silicide,
Silicide materials such as tungsten silicide, molybdenum silicide, tantalum silicide, platinum silicide,
Compound semiconductors such as GaAs, and compounds such as titanium nitride and molybdenum nitride may also be used.

In particular, when the base is silicon, the interface is likely to deteriorate due to reaction with aluminum or the like. Therefore, as shown in FIG. 4, for example, titanium, titanium nitride, or titanium silicide is formed on the silicon substrate 1 in the through holes. In some cases, it is better to selectively grow the aluminum film 5 after forming the barrier layer 50 made of a titanium-based metal, molybdenum or tungsten, or a silicide thereof, or platinum silicide.

Any of the above-mentioned materials is a conductive metal or semiconductor, and aluminum can be selectively grown on these materials. In particular, regarding silicon, it is possible to deposit aluminum on impurities containing arsenic, phosphorus, boron, etc. as impurities to the extent of solid solubility and high-resistance single-crystal silicon and polycrystalline silicon having low concentrations of these impurities. It was confirmed experimentally. Also, if the base is aluminum or an aluminum alloy such as aluminum containing silicon, it is needless to say that aluminum can be deposited because it is the same material, but a thick alumina layer of several tens of liters or more may be formed on the surface. Since it often occurs, in such a case, it is necessary to perform light etching using dilute hydrofluoric acid or the like as in the case of silicon.

On the other hand, as the material of the insulating film used in the semiconductor integrated circuit,
A silicon oxide film is most often used, but a silicon nitride film or the like is also used. The silicon oxide film includes a silicon oxide film formed by thermally oxidizing silicon,
Other forming methods, for example, those deposited by the vapor phase growth method or the sputtering method, and a silicon oxide film to which phosphorus or boron is added may be used. Under the conditions for selective growth of aluminum according to the present embodiment, aluminum is not deposited on these insulating films.

Although triisobutylaluminum has been described as an example of the organic compound of aluminum, triethylaluminum or trimethylaluminum may be used.

From the above, the formation of the flat aluminum wiring having no step in the opening as shown in FIG. 1E can be applied to all through holes in the semiconductor integrated circuit. In the conventional deposition method that does not use selective growth, such as sputtering or vapor deposition, a step is formed on the surface of the aluminum film in the opening that is a through hole, and microcracks are generated under the step, resulting in a yield due to disconnection. It was a cause of deterioration of reliability and reliability. According to the present invention, by selectively depositing aluminum having substantially the same thickness as the step of the through hole, the through hole portion of the semiconductor integrated circuit is flat and has no disconnection, and the aluminum wiring excellent in yield and reliability is provided. Can be formed.

FIG. 5 is a process sectional view showing a second embodiment of the present invention, which is an example in which aluminum is selectively deposited on the gate electrode, the source and the drain of a MOS LSI to reduce the resistance. (A) to (j) of the same figure show the flow of main manufacturing steps, and the parts that do not directly affect the present invention are omitted.

First, as shown in FIG. 5 (a), a p-type silicon substrate 61 having an element isolation region 62 formed by using a silicon oxide film is prepared, and a gate oxide film is formed in a region to be an active element. Forming 63.

Next, as shown in FIGS. 3B and 3C, a polycrystalline silicon thin film 64 doped with phosphorus is deposited, and the thin film 64 is processed by using a lithography technique and an etching technique.
The gate electrode 65 is formed. The impurities of polycrystalline silicon are
Other than phosphorus, arsenic, boron or the like may be used depending on the application.

Then, as shown in FIG. 3D, the periphery of the gate electrode 65 is oxidized to form a polycrystalline silicon oxide film 66, and the gate electrode 65 is used as a mask to form a region 67 which becomes a source and a drain.
Ion implantation is performed to form the. As ion species,
Normally, arsenic or phosphorus is used for n-channel devices, and boron is used for p-channel devices.

After that, a heat treatment for activating the implanted ions is performed, and a silicon oxide film 68 is deposited by the low pressure CVD method as shown in FIG. This silicon oxide film 68 is a gate electrode 65.
Since it is formed thickly on the side surface of the gate electrode 65, the side wall 69 can be formed on the side surface of the gate electrode 65 by using dry etching having directionality, as shown in FIG. The silicon oxide film 68 may be essentially anything as long as it is an insulating film thickly formed on the side surface of the gate electrode 65.
It may be a reflowed phosphosilicate glass (PSG), a borosilicate-phosphorus silicate glass (BPSG), a so-called bias sputtered silicon oxide film sputtered by applying a light bias, or a silicon nitride film.

Next, as shown in FIG. 3G, an aluminum 70 is selectively grown on the gate electrode 65 and the source / drain region 67 where the silicon surface is exposed. Prior to the deposition of the aluminum 70, a pretreatment for removing the native oxide film layer is performed. Since this pretreatment is after dry etching, once a silicon oxide film of about 100 Å is formed at about 800 to 900 ° C, and then etched with dilute hydrofluoric acid solution to expose a clean silicon surface. Is good. Aluminum 70 is deposited at a substrate temperature of 270 ° C and a source gas pressure of 0.5To.
It is performed under standard conditions of rr, and the film thickness is about 1000 when the deposition time is about 5 minutes.
Å formed aluminum.

Next, as shown in FIG. 3H, an interlayer insulating film 71 is deposited and a through hole 72 is formed by using a known lithography technique and etching technique (for example, plasma etching using CF ₄ ).

After that, generally, an aluminum film is deposited by using a sputtering method or the like to form a wiring, but here, as shown in FIG. 7I, the selective growth aluminum film 73 according to the present invention is used to form a through hole. Fill 72. As a pretreatment for depositing the aluminum 73, only etching with a dilute hydrofluoric acid solution is performed, and the aluminum 73 is deposited using the same method as in the case of FIG. The deposited film thickness is 50, which is the same as the depth of the through hole 72.
By setting it as 00Å, the inside of the through hole 72 can be surely filled and a flat surface can be obtained. After that, an aluminum film is deposited on the entire surface by using a sputtering method or the like, and an aluminum wiring 74 as shown in FIG. 1J is completed by using a known lithography technique and etching technique.

As described above, in this embodiment, the selectively grown aluminum is attached to the polycrystalline silicon to reduce the resistance of the electrode wiring, and further, it is used for filling the through hole to realize the flattening. We are using. In particular, when applied to the attachment technology, the resistivity of aluminum is 3.3 μΩcm, which is close to that of bulk, and it is possible to reduce the resistance by one to two digits compared to the case of attaching tungsten or silicide. is there. Also the source,
In the case of sticking to the drain, if the aluminum film thickness is large, the aluminum reacts with the substrate silicon and causes problems such as junction leak, but when the aluminum film thickness is 1000 Å or less as in this example. Is
Almost no problem. Also, if needed,
As shown in FIG. 4, a barrier layer may be attached on the source / drain or on the polycrystalline silicon gate electrode, and then selective growth of aluminum may be performed. The thickness of this barrier layer may be, for example, on the order of 100Å. The resistance of the barrier layer having such a thickness is several times to one digit higher than the resistance of the selectively grown aluminum, and the resistance can be made sufficiently low only by adhering the aluminum.

FIG. 6 is a process sectional view showing a third embodiment of the present invention, which is an example applied to electrode extraction of a bipolar LSI and formation of a resistor using polycrystalline silicon.

FIG. 3A shows a state in which an npn transistor is formed in the silicon substrate 101, and a polycrystalline silicon electrode pattern is further formed thereon. That is, 102 is an element isolation oxide film, 103 is an n ⁺ buried layer, 104 is a collector, 105 is a base, and 106 is an emitter. The surface of the silicon substrate 101 in this state is composed of a polycrystalline silicon electrode pattern 107, a silicon oxide film 108 for separating them, and a resistor-forming mask 109 formed on the polycrystalline silicon region where the resistance should be low. Has been done. As a material of the master 109, an insulator such as a silicon oxide film or a silicon nitride film is used.

In this state, aluminum 110 is selectively grown on the exposed polycrystalline silicon, as shown in FIG.
Prior to the deposition of the aluminum 110, a pretreatment for removing the natural oxide film layer is performed. In this case as well, since the dry etching is performed as in the second embodiment, the It is better to form a silicon oxide film of about 100 Å at about 900 ℃, and then etch with dilute hydrofluoric acid solution to expose a clean silicon surface. Aluminum 11
Deposition of 0 was performed under standard conditions of a substrate temperature of 270 ° C. and a source gas pressure of 0.5 Torr, and an aluminum film 110 having a film thickness of about 1000 Å was formed in a deposition time of about 5 minutes. The aluminum at this time reduces the resistance of the polycrystalline silicon electrode pattern 107, and at the same time, the polycrystalline silicon under the resistor formation mask 109 becomes a polycrystalline silicon resistor 111 whose dimensions are determined in a self-aligned manner. Become.

Next, as shown in FIG. 3C, an interlayer insulating film 112 is deposited, and a through hole 113 is opened by using a known lithography technique and, for example, an etching technique using CF ₄ gas plasma. After that, generally, an aluminum film is deposited by a sputtering method or the like to form a wiring,
Here, as shown in FIG. 3D, the through hole 113 is filled with the second selective growth aluminum film 114 according to the present embodiment. As the pretreatment before the deposition of the aluminum 114, only etching with a dilute hydrofluoric acid solution is performed, and the aluminum 114 is deposited using the same method as in the case of FIG. At this time, by setting the deposited film thickness to the same film thickness as the depth of the through hole 113, the inside of the through hole 113 can be surely filled and a flat surface can be obtained. After that, an aluminum film is deposited on the entire surface by using a sputtering method or the like, and an aluminum wiring 115 as shown in FIG. 8E is completed by using a known lithography technique and etching technique.

As described above, in this embodiment, the selectively grown aluminum is attached to the polycrystalline silicon electrode to reduce the resistance, and at the same time, it is used for forming the resistor. Further, flattening is achieved by using selective growth aluminum to fill the through hole 113. In particular, when applied to the attachment technology, the resistivity of aluminum is 3.3
Since μΩcm is close to a bulk, it is possible to reduce the resistance by about one to two digits compared to the case of attaching tungsten or silicide. When the film thickness of aluminum is large, the aluminum reacts with the substrate silicon and the element characteristics are deteriorated. However, when the film thickness of aluminum is about 1000 Å or less as in this embodiment, there is almost no problem. Further, if necessary, a barrier may be attached on the polycrystalline silicon electrode as shown in FIG. 4 and then selective growth of aluminum may be performed. The thickness of this barrier layer may be, for example, on the order of 100Å. The resistance of the barrier layer having such a thickness is several times to one digit higher than the resistance of the selectively grown aluminum, and the resistance can be made sufficiently low only by adhering the aluminum.

In addition, in all the above-mentioned examples, the selective growth of aluminum is shown in FIG.
Although it is done with D equipment, it is possible with hot wall type CVD equipment. In the case of a hot wall, the entire atmosphere is heated, so if the gas flow rate is insufficient, the source gas temperature rises to the same level as the wafer substrate temperature,
Aluminum nuclei are also easily generated on the silicon oxide film. Therefore, in the case of a hot wall, it is necessary to increase the gas flow rate and suppress the temperature rise of the gas. At this time, argon gas may be used as the carrier gas.

〔The invention's effect〕

As described above, according to the method for manufacturing a metal thin film of the present invention, aluminum can be selectively deposited only on a conductive material such as silicon or aluminum. Therefore, the through hole can be reliably filled with aluminum, and the flattening of the through hole, which has been conventionally performed by selective growth of tungsten, can be performed with aluminum. If the flattening of the through hole is performed by using aluminum, the contact resistance can be lowered and the through hole film thickness can be increased as compared with the case of using tungsten.

Further, conventionally, the resistance was further reduced by selectively attaching tungsten to the diffusion layer region of the silicon substrate, polycrystalline silicon, etc., but it is possible to further reduce the resistance by attaching aluminum according to the present invention instead of tungsten. Become.

Thus, the ability to selectively deposit aluminum, which is the main wiring material of a semiconductor integrated circuit, is extremely useful in terms of the wiring structure, and the present invention can realize a high-performance semiconductor device.

[Brief description of drawings]

FIG. 1 is a process sectional view showing an embodiment of the present invention, FIG. 2 is a schematic configuration diagram of a CVD apparatus used in this embodiment, and FIG. 3 is a scan showing a metal structure of aluminum deposited in a through hole. Electron micrograph, FIG. 4 is a sectional view showing a through hole portion when a barrier layer is used, FIG. 5 is a sectional view showing steps of a second embodiment of the present invention, and FIG. 6 is a sectional view of the present invention. FIG. 7 is a sectional view showing a process of showing the third embodiment, and FIG. 7 is a sectional view showing a covering shape of a conventional aluminum wiring in a through hole. 1,61,101 …… Silicon substrate, 2,71,112 …… Silicon oxide film, 3,72,113 …… Through hole, 4 …… Natural oxide film layer,
5,70,73,110,114 …… Selective growth aluminum, 6,74,11
5: Sputtered aluminum film.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H01L 21/3205 H01L 21/88 K

Claims (1)

(57) [Claims] 1. A first step of selectively removing an insulator formed on a metal or a semiconductor on a substrate to form an opening so that a surface of the metal or the semiconductor is exposed, After the first step, a second step of forming a barrier layer for protecting the surface on the surface of the metal or semiconductor exposed at the bottom of the opening, and the second step. After the step, a third step of removing the natural oxide film layer formed on the surface of the barrier layer; and, after the third step, introducing a gas containing an organic compound of aluminum into the vicinity of the substrate, A fourth step of heating the substrate and heating the gas in the vicinity of the surface of the substrate to selectively grow aluminum only on the barrier layer and fill the opening. After the insulator And a fifth step of depositing aluminum on the entire surface of the aluminum filled in the opening to form an aluminum film.