FR2720855A1 - Method of manufacturing semiconductor devices with aluminum wiring by exposing the substrate to a reactive solution. - Google Patents

Abstract

According to the method of the invention, one begins by etching a conductive film and applying a pattern trace thereto using a gas based on chlorine, the conductive film being made of aluminum or aluminum alloy and being deposited on the surface of an insulating film formed on a substrate and this substrate provided with this conductive film is exposed to a reactive solution containing a metal which is able to react with chlorine and to form a metal chloride having a small product solubility. This improves the corrosion protection of the conductive film.

Description

The present invention relates to a method for manufacturing devices with

  semiconductor and, more particularly, a method of manufacturing semiconductor devices having AI wiring layers (aluminum or aluminum alloy). As materials for the wiring layers and electrodes of a semiconductor integrated circuit device, a thin conductive film of aluminum (AI), aluminum-copper alloy (AICu alloy), AICuSi alloy, etc. has been used. To form a pattern of thin conductive film of aluminum, aluminum alloy, or the like, on the surface of a substrate, a process is applied by which a mask of photosensitive agent of the reserve type is subjected to a drawing operation. pattern and the conductive thin film not covered by the

mask is engraved.

  As the reactive gas intended to carry out the dry etching of aluminum, a gas or a mixture of gases chosen from the group formed by chlorine (C12), boron trichloride (BCI3), carbon tetrachloride (CC14) was used. ), silicon tetrachloride (SiCI4), etc., due to their specific vapor pressures. Aluminum (or alloy) wiring is excellent in that it has

  low resistance. Low resistance and long service life are required

  for the wiring layers of a semiconductor device. The lifetime of aluminum (or alloy) wiring depends largely on the phenomena

  electromigration and corrosion.

  Figure 9A is a simplified diagram showing aluminum wiring in place on a semiconductor substrate. The surface of the semiconductor substrate 301 is a silicon surface or an insulating layer. A layer of AI 302 deposited on the surface of this underlying layer has a large number of grains

  303. A grain boundary 304 is formed between adjacent grains.

  Electromigration of AI atoms is more likely to occur at the grain boundaries and is a cause of wiring failure. It is known that an effective countermeasure making it possible to prevent the appearance of electromigration consists in increasing the size of the grains of AI. To increase the size of the grains of AI, the value is fixed at around 200 to 350 C

  substrate temperature when a layer of Ai is deposited by spraying

tion or by some other means.

  With the increase in the degree of integration of the integrated circuits and that of the number of wiring layers of these circuits, the thickness of a lower wiring layer decreases. When the thickness of an AI wiring layer decreases, the current density flowing in this AI wiring layer increases. Consequently, the electromigration of atoms pushed by electrons

  becomes more likely to happen.

  Electromigration causes an increase in the resistance of the wiring and, at worst, a break in the wiring layer. Conventional methods of depositing an Al wiring layer are not sufficient to remove

  electromigration in a thin layer of wiring.

  After the application of an etching operation and a pattern drawing operation to an aluminum film, a protective film containing a large amount of atoms is formed on the side wall of the aluminum pattern. chlorine. FIG. 9B is a simplified diagram showing, in section, a film

  aluminum (or alloy) having undergone an engraving and a pattern tracing.

  A side wall protective film (not shown) containing a large amount of chlorine atoms (C1) is formed on the side wall of an aluminum wiring film (AI) 302 itself formed on an insulating film 301 If a tablet with such a protective layer is exposed to air, the water (H20) contained in the air reacts with the residual chlorine on the AI 302 wiring film to form hydrochloric acid, which corrodes the wiring film in AI 302. This phenomenon does not occur

  only during the manufacturing process, but also after the end of manufacturing

  cation of the semiconductor device. More specifically, the water contained in the air can pass into a semiconductor device during its operation, for example from the interface between the output wires and the housing. If the water in the air reaches an aluminum wiring film and reacts with chlorine, hydrochloric acid is formed. Therefore, it is desirable to remove as much of the residual chlorine as possible to prevent corrosion of a wiring layer. Typical processes to prevent corrosion of aluminum wiring include a clean water wash process, an acid / alkaline process, a passivation process using fluorine-containing gases, as well as

other processes.

  As a washing process with pure water, there is a process which consists in mounting several tablets on a support and immersing them in pure water, and a method consisting in rotating each tablet maintained by

  a mandrel and dropping pure water on it.

  Under the acid / alkaline process, there is a process of immersing a pellet in a solution or dropping a solution on a spinning pellet. The solution is an acid solution or a solution

  alkaline. The acid solution is a solution obtained by mixing isopropyl alcohol

  lique (IPA) and nitric acid, or phosphoric acid, and the alkaline solution can be ammonium or choline. Another process is to expose a pellet in a sprayed acid / alkaline solution. In both cases, a rinsing process is then necessary, so that there is no remaining

chemical substances.

  As part of the passivation process using a fluorine-containing gas, there is a process of exposing a pellet in a gas made of carbon tetrafluoride (CF4) or a mixture of gases made of carbon tetrafluoride ( CF4) and fluoroform (CHF3) and to irradiate the pellet using a plasma. It is assumed that the improvement in corrosion resistance which is obtained by this process is due to the replacement of residual chlorine by fluorine or the existence of a hydrophobic surface of the tablet as a result of the formation of a fluorocarbon (CF) polymer by fluorine, which has the effect

  prevent contact of aluminum with atmospheric water.

  However, even if such a process is applied to prevent corrosion of an aluminum film having undergone etching and pattern-drawing operations, the removal of residual chlorine is insufficient. It is necessary

  to prevent corrosion to a much higher degree than is commonly done

  An alloy such as an aluminum-copper alloy in particular is liable to be corroded by a voltaic cell effect. By the voltaic cell effect of metals such as an aluminum alloy, the metals corrode due to the potential difference produced by the contact of different metals or by the potential difference produced by a fluctuation in composition (irregularity ) on the surface of the metal. Preventing corrosion is a very important factor from the point of view

  improving device performance.

  It is an object of the invention to produce a process for forming

  a layer of aluminum wiring, which is able to remove the electro-

  migration even in the case of a thin aluminum wiring layer.

  Another object of the invention is to provide a method of manufacturing a semiconductor device, which can prevent a layer of wiring from being

  aluminum is not broken (open circuit) by corrosion.

  Another object of the invention is to provide a method of manufacturing a semiconductor device, which can minimize the residual chlorine content in the vicinity of the side wall of an aluminum wiring pattern. According to one aspect of the invention, there is provided a method of manufacturing a semiconductor device which comprises the following operations: etching a conductive film and applying a pattern trace thereto using a gas based on chlorine , the conductive film being made of aluminum or aluminum alloy and being deposited on the surface of an insulating film formed on a substrate; and exposing the substrate having the conductive film to a reactive solution containing a metal which is able to react with chlorine and form a

  metal chloride having a low solubility product.

  The metal is for example silver or lead. The reactive solution is for example an aqueous solution of silver nitrate or an aqueous solution of

lead nitrate.

  The process may include, after the operation of exposing the substrate to the reactive solution, an operation consisting in exposing the substrate to a dissociation solution which is able to dissociate or cause the desorption of the silver chloride or the chloride of lead remaining on the substrate by transforming silver chloride or lead chloride into complex silver ions or ions

lead complexes.

  An engraved wiring pattern which is made of aluminum or aluminum alloy is subjected to further treatment with the reactive solution containing a metal which can react with chlorine and form a metal chloride having a low solubility product constant . The metal is for example silver or lead. The reactive solution is for example an aqueous nitrate solution

  silver or an aqueous solution of lead nitrate.

  The chlorine ions react with the metal ions contained in the reaction solution to form insoluble precipitates. As a result, the chlorine ions are made inactive so as to stop corrosion of a wiring pattern made of aluminum or aluminum alloy, which improves the reliability of the device.

  semiconductor having a similar wiring pattern.

  As described above, a pellet with a wiring pattern is subjected to further treatment with an aqueous solution containing a metal which forms a metal chloride having a low solubility product. Thus, it is possible to remove the residual chlorine found on the side wall of an aluminum (or alloy) wiring pattern using metal ions, to remove the

  corrosion of the wiring pattern and improve device performance.

  The following description, intended to illustrate the invention, aims

  to give a better understanding of its characteristics and advantages; it is based on the appended drawings, among which: - Figure 1 is a simplified diagram of a spraying system

  used to form a layer of aluminum wiring according to one embodiment

  tion of the invention; - Figures 2A and 2B are graphs showing the variation, over time, of the resistance values of the aluminum wiring layers formed by a conventional process and by a process constituting an embodiment of the invention; FIG. 3 is a cross-section view of a dynamic random access memory (DRAM) manufactured using the method of forming the aluminum wiring layer according to an embodiment of the invention; - Figure 4 is a simplified diagram showing a system used for dry etching of an aluminum film and the formation of an oxide film; - Figure 5 is a simplified diagram showing another system used for dry etching of an aluminum film and the formation of an oxide film; FIG. 6 is a simplified diagram showing another system used for the dry etching of an aluminum film and the formation of an oxide film; - Figures 7A to 7D are cross-section views explaining a

  method of manufacturing a semiconductor device according to one embodiment

  tion of the invention; - Figure 8 is a simplified diagram showing a system used for the manufacture of a semiconductor device according to the embodiment presented in Figures 7A to 7D; and - Figures 9A and 9B show the structure of an aluminum layer of a conventional semiconductor device and a cross-sectional view showing

the state of corrosion.

  We know that it becomes difficult for electromigration to occur when the grain size increases. We can assume that this is due to the fact that electromigration occurs mainly at the grain boundaries. We also know that it is difficult for electromigration to occur in aluminum if the aluminum crystals have a strong tendency to present the plane (1 1 1). An article by Vaidya, S. and Sinha, AK (Thin Solid Films, 15 <1981>, p. 253-259) reports that the mean time to failure (MITF) of an aluminum wiring layer is given by: ( s / o2) log (I (111) / 1 (200)) 3 os is the mean grain size, v2 is the variance of the grain sizes, and oi (111) and 1 (200) are the diffraction intensities respectively x-rays in

the plans (1 1 1) and (2 0 0).

  To extend the MTF of an aluminum wiring layer, the grain size is therefore increased and it is made to have a strong tendency to

present the plan (1 1 1).

  FIG. 1 is a simplified diagram of a spraying system used to form a layer of aluminum wiring according to an embodiment of the invention. A substrate holder 4 is mounted on a side wall of a chamber i placed under vacuum. To form a film, a substrate 3 is fixed on a substrate support surface of the substrate holder 4, on which a film is to be formed. In the substrate carrier 4, a cavity is formed with an inlet and an outlet, so that argon gas (Ar) can circulate in the cavity. For example, the substrate 3 maintained on the substrate holder 4 can be heated by circulating in the cavity heated argon gas. A target holder 5 is mounted on the side wall of the vacuum chamber 1 located opposite the substrate holder 4. To form a film, a spray target 2 is fixed on a target support plane of the target holder 5. To spray an aluminum wiring layer, an aluminum disc is used as target 2. To form a film, the spray gas, for example argon gas, is introduced into the vacuum chamber 1 via a spray gas guide tube 6 and it is taken out by a discharge tube 7 so as to

  maintain the interior of the vacuum chamber 1 at a predetermined pressure.

  When a DC voltage is applied between the substrate holder 4 and the target holder, an electric discharge occurs in the vacuum chamber. Since a negative potential is applied to the target carrier 5, argon ions Ar + enter

  collision with target 2 and aluminum is sprayed.

  We will now describe a process for forming a layer of

  aluminum wiring according to an embodiment of the invention.

  As the substrate 3, on which an aluminum wiring layer is formed, a silicon Si substrate is used comprising a metallic laminated film acting as a barrier, made of a layer of Ti and of a layer of TiN formed at the surface of it. It is generally difficult for a layer of AI lying on a layer of TiN to have a strong tendency to present the plane (1 1 1). We can firstly deposit a 200 nm thick layer of Ai by a spraying process on the surface of the laminated layer of Ti / TiN, without heating the substrate 3. After that, the substrate 3 is heated by circulating in the cavity of the substrate holder 4 of argon gas heated to 350 ° C. The substrate temperature rises to around 350C in around 5 s. We deposit a layer

  aluminum to a thickness of 300 nm during the heating of the substrate 3.

  In addition, during the temperature rise, the spraying is continued. It is sufficient that the temperature of the substrate reaches 350C upon completion of the deposit. While the total thickness of the aluminum film is 500 nm, it is possible to choose any total thickness. FIGS. 2A and 2B are graphs showing the variation of the resistance values of the aluminum wiring layers in function of time. The graph in FIG. 2A shows the variation in the resistance value of aluminum wiring patterns which have a thickness of 350 nm and which were formed by a conventional sputtering process, while the temperature of the substrate was set at 350 ' VS; while the graph in FIG. 2B shows the variation of the resistance values of aluminum wiring patterns formed by spraying aluminum to a thickness of approximately 150 nm without heating the substrate, then by spraying aluminum until at a thickness of about 200 nmn after the

  start of the heating of the substrate to lead it to the temperature of 350'C

  The abscissa represents the flow of time, the unit being the hour, from the start of the measurement, and the ordinate represents the resistance, the unit being the ohm (Q). The width of each aluminum wiring pattern is 2 man, its length is

  800, um, while the current density is 2 x 106 A / cm2.

  As can be seen in the graph in Figure 2A, the resistance value of each sample of aluminum wiring pattern formed by a conventional sputtering process increases sharply over time, even if there is a variation in resistance from one sample to another. If it is assumed that a sample which exhibits an increase in resistance of 10% or more compared to the initial value is defective, it is seen that approximately 40% of the samples become defective in 580 h. As can be seen in the graph of Figure 2B, the resistance value of each sample of aluminum wiring pattern formed by a method according to one embodiment hardly increases over time. There are no defective samples, even after 1200 hours have passed since the

start of measurement.

  The size of the grains present on the surfaces of aluminum wiring patterns formed respectively by a conventional method and by a method according to an embodiment of the invention are 2.76 / .m and 2.72 / .ni. Each aluminum wiring pattern formed by a conventional process has a relatively large grain size, since the substrate has been continuously heated throughout the duration of the process. The aluminum wiring patterns formed by a method according to one embodiment may each possibly have a small grain size, since the substrate was not heated during the initial stage of the process. However, since the substrate was heated from the middle of the treatment, the grain size becomes substantially as large as that

  of the wiring pattern formed by the conventional method.

  The crystalline planes (1 1 1) of aluminum wiring patterns formed by the conventional method and by the method according to the embodiment were measured by X-ray diffraction. Crests indicating the crystal planes (1 1 1) appeared at 1 510 cps in the case of the conventional method, and at 7 120 cps in the case of the method of the embodiment. It can therefore be understood that the aluminum wiring layer formed by the method of the embodiment has a

  tendency to present the plan (1 1 1) much greater than the conventional method.

  We can assume that the explanation for this phenomenon is as follows.

  If an aluminum layer is deposited during the heating of the substrate, the tendency to orient the plane (1 1 1) along the surface weakens although the grain size increases. On the other hand, if an aluminum layer is deposited without heating the substrate, an aluminum layer is formed which has a strong tendency to orientation along the plane (1 1 1), even if the size grains decreases. If the substrate is heated after the middle of the deposition operation, a large grain size can be obtained while retaining the strong tendency to orient along the plane (1 1 1). In this way, an aluminum wiring layer can be obtained which has a strong tendency to orient along the plane (1 1 1) together with a relatively large grain size. In this embodiment, the deposition can be carried out continuously without heating the substrate and the deposition with heating of the substrate in the same vacuum chamber, which makes it possible to maintain the same yield as for a

  conventional process, without increasing the number of operations.

  In the embodiment presented above, the temperature of the argon gas used to heat the substrate is fixed at 350 ° C. This temperature can be 300 ° C or more, and it is preferably 400 ° C or less, since aluminum

  melts at a temperature above 400C.

  It is preferable to set the thickness of the layer of aluminum wiring which is deposited before the heating of the substrate to a value of 20 to%, or, preferably, from 30 to 50%, of the total thickness of the layer of

final aluminum wiring.

  In the embodiment presented above, while using direct current spraying for the spraying process, it is possible to also use other spraying processes having expected effects.

  analogues, such as direct current magnetron sputtering,

  high frequency and high frequency magnetron sputtering.

  In the embodiment presented above, it has been indicated that the

  layer of aluminum wiring was deposited on a laminated layer of Ti / TN.

  The aluminum wiring layer can be deposited on other layers, for example a metal layer acting as a barrier and an insulating layer,

  while obtaining similar expected effects. The invention turns out to be particular-

  effective for depositing an aluminum wiring layer on a layer which can hardly give the aluminum wiring layer a strong tendency to present the plane (1 1 1) when the substrate is heated during the whole

duration of treatment.

  FIG. 3 is a partial cross-sectional view of a DRAM manufactured by a method of forming an aluminum layer according to a mode of

realization of the invention.

  A field oxide film 13 also known as thick oxide film, which is selectively formed on the surface of a p-type silicon substrate 10 surrounds and defines an active region. On the surface of the active region, a gate electrode 14 is formed, with a gate oxide film interposed therebetween. On both sides of the gate electrode 14, regions of

  source and drain type n +, 11 and 12.

  A bit line 16 is arranged on the source region 11. The bit line 16 is formed for example using a laminated structure comprising a

  layer of tungsten silicide on a layer of polycrystalline silicon.

  An electrode 17 of a storage capacitor is connected to the drain region 12. A counter-electrode 18 is formed opposite the electrode 17, with a thin insulating film interposed therebetween. These electrodes 17 and 18 are made for example of polycrystalline silicon. Instead of a structure of the so-called fin type in a single layer, it is also possible to use a structure with

  fin in two or more layers, or other condensing structures

  teurs. On the surface of the silicon substrate, an interlayer insulating film 15 of SiO2 is formed which buries the bit line 16, the gate electrode 15 and the storage capacitor. A contact hole (through hole) is formed in the interlayer insulating film 15 at the location which corresponds to the bit line 16. An aluminum wiring pattern forming a first layer is

  electrically connected to bit line 16.

  The aluminum wiring pattern of the first layer is made of a metallic laminated barrier film 19 comprising a layer of TiN placed on a layer of Ti and an layer of aluminum 20. The layer of Ti has a thickness of 20 nm for example, and the TiN layer has a thickness of 100 nm for example. The aluminum layer 20 is formed using the method of the embodiment described above and has a thickness of 500 nm for example. Interlayer insulating films 21 and 22 are formed which bury the aluminum wiring pattern 20 of the first layer. The aluminum wiring pattern 20 of the first layer is connected, via a contact hole formed in the interlayer insulating films 21 and 22, to a wiring pattern in

  aluminum 23 forming a second layer, of thickness 1 μm for example.

  The aluminum wiring pattern 20 of the first layer is thinner than the aluminum wiring pattern 23 of the second layer and, therefore, has a higher current density. However, the aluminum wiring pattern of the first layer which is formed by the method of the mode

  above described embodiment can suppress the appearance of electromigration.

  The underlying layer of the aluminum wiring pattern 23 forming the second layer is the interlayer insulating film or the aluminum wiring pattern forming the first layer, so that it is not necessarily necessary to form a layer of TiN intended to make barrier metal layer function. It is preferable to form, under the aluminum wiring pattern forming the second layer, a layer of Ti which has a thickness of around 30 nm for example. On the Ti layer, an aluminum layer can be formed which has a strong tendency to present the plane (1 1 1) even if the substrate is heated throughout the duration of the deposition operation. If a metallic laminate barrier layer comprising a Ti layer and a TiN layer is formed under the aluminum wiring pattern forming the second layer, the resistance to electromigration is improved. Without this, the aluminum wiring pattern of the second layer is preferably formed like the aluminum wiring pattern of the first layer, depositing from 30 to 50% of the thickness.

  total without heating, then having the rest deposited while heating the substrate.

  In this embodiment, aluminum is used for the

  wiring layers. A material consisting essentially of aluminum, i.e.

  say containing aluminum as its main composition and a small

  amount of another or more other metals and, or, of a semi-material

  conductive, can be used. For example, we can form a wiring layer in AI with 1% Si, in AI with 1% Si and 0.5% Cu, in AI with 1% Ti, or in AI with 1% Si and 0 , 5% Ti. The service life of an aluminum wiring layer depends on corrosion as well as electromigration. It is assumed that the corrosion comes mainly from the water which passes through the layer of

  aluminum wiring from outside the device during operation.

  Corrosion accelerates if chlorine or the like is permanently on the surface of an aluminum wiring layer, since chlorine,

  or others, reacts with water to form HCI or other compounds.

  We will now present a method for preventing corrosion of an aluminum wiring layer, according to an embodiment of the invention. FIG. 4 shows the structure of a system in which an operation for etching an aluminum film and an oxidation process are carried out in the same vacuum chamber. In FIG. 4, the number 101 represents a vacuum chamber, the reference number 102 represents an orifice for supplying etching gas, the reference number 103 represents a discharge orifice connected to a suction pump (not shown) , reference number 104 represents an oxygen supply orifice, reference number 105 represents a dehumidifier which contains silica gel, activated alumina, or the like, reference number 106 represents an electrode used to apply a high frequency electrical power produced by a high frequency electrical source 107, and the reference number 108 represents a fixing plate intended to carry a pellet. The fixing plate 108 has

  a passage for a gas, so that it can be heated or cooled.

  A tablet is mounted on the fixing plate 108 in the vacuum chamber 101. The tablet is prepared by forming an insulating film on a substrate, by forming an aluminum film on the insulating film, and by forming, by a lithographic process. , a sensitive agent dandruff pattern of the reserve type corresponding to a wiring pattern. After the chamber 101 has been evacuated via the evacuation orifice 103, a chlorine-based gas is introduced into the vacuum chamber 101 via the gas supply orifice 102. The gas based chlorine is for example a gaseous mixture of chlorine and boron chloride (BCI3), a gaseous mixture of chlorine and silicon chloride (SiC14), a gaseous mixture of chlorine and hydrogen bromide (HBr), or a mixture of chlorine and boron bromide (BBr). After that, the high frequency electrical power produced by the high frequency electrical source 107 is applied to the electrode 106 to form a plasma of the chlorine-based gas introduced. The aluminum film is etched by the plasma of the chlorine-based gas, so that it is

  formed an aluminum wiring pattern.

  After etching, the vacuum is maintained, the pellet is raised using rods mounted on the fixing plate 108, and the temperature of the fixing plate is raised to around 500C. Then, the pellet is returned to the fixing plate 108 heated to about 500 C and left there for a short time, about 1 s, so that it heats up. The chlorine attached to the surface of the tablet is therefore the object of desorption and is removed therefrom. The tablet is preferably heated to a

  temperature of approximately 180 to 650C and for a period of approximately 5 to 60 s.

  Then, the temperature of the fixing plate 108 is lowered by cooling it using a gas. The suction pump is stopped, and oxygen gas dehumidified by the dehumidifier 105 is introduced into the vacuum chamber 101, via the port 104 for oxygen supply, in order to form a film.

  oxide on the surface of the aluminum wiring pattern.

  In the embodiment presented above, the etching, heating and oxidation operations are carried out in the same chamber. At

  instead, two or more rooms could also be used.

  FIG. 5 represents a system in which an etching chamber placed under vacuum and an oxidation chamber placed under vacuum are provided separately. In FIG. 5, the elements identical to the elements represented in FIG. 4 are represented using identical reference numbers. In FIG. 5, the reference number 111 represents a vacuum etching chamber, the reference number 112 represents a vacuum oxidation chamber, and the

  Reference number 113 represents a valve acting as a door.

  After the etching carried out in the vacuum etching chamber 111, the valve 113 is opened and the tablet is transported in the vacuum oxidation chamber 112 in order to oxidize the surface of the aluminum wiring pattern. The heating operation to remove the chlorine that has attached to the surface of the aluminum wiring layer can be performed in the vacuum etching chamber

  111 or in the vacuum oxidation chamber 112.

  Figure 6 shows the structure of another system, in which the heating operation is carried out in an independent room. In FIG. 6, the elements which are identical to the elements presented in FIGS. 4

  and 5 are designated using identical reference numbers.

  Another vacuum chamber 116 is installed between a vacuum etching chamber 111 and a vacuum oxidation chamber 112, which are similar to those of FIG. 5. The vacuum chamber 116 has a hot plate 114 equipped with a heating means and a cold plate 115 equipped with cooling means. After the etching carried out in the vacuum etching chamber 111, the tablet is transported onto the hot plate 114, in order to heat it and remove the chlorine therefrom. Next, the plastic is transported to the cold plate 115 to cool it, after which the tablet is transported to the oxidation chamber 112 in order to form an oxide film on the surface of the

aluminum wiring pattern.

  The above embodiments use a wiring layer which contains 100% aluminum. Other aluminum wiring layers, consisting essentially of AI and having a small amount of other metal and, or, semiconductor material are widely used to improve resistance to stress migration and electromigration. For example, it may be AI with 1% silicon, AI with 1% silicon and 0.5% copper, and AI with 1% titanium (Ti). The above-presented embodiments are effective for these aluminum alloy wiring layers. If a metal, especially copper, has been placed in the aluminum alloy to improve resistance to migration, since there is a large difference in the tendency for ionization between copper and aluminum, a voltaic stack effect and

  corrosion is likely to occur.

  As the material placed under an aluminum wiring layer, a refractory metal, a refractory metal nitride, a refractory metal oxynitride, such as silicon nitride, is widely used, mainly to improve resistance to migration. In this case also, a voltaic cell effect appears and corrosion is likely to occur. The effects of the embodiments are expected to be more distinct in the case where the aluminum wiring layer forms a voltaic effect in conjunction with the adjacent layer.

located below or above.

  The above embodiments presented can be applied not only to an etching process using a chlorine-based gas, but

  also to an etching process using a halogen-based gas.

  Another embodiment will be described below, in which the residues remaining on a wiring layer or the like, which have been left for

  the engraving operation, can be removed reliably.

  Figs. 7A to 7D are cross-sectional views which explain a process of applying pattern plotting to aluminum foil or aluminum alloy film according to an embodiment of the invention. A motif made of aluminum or aluminum alloy is used as the motif

  wiring or as an electrode of a semiconductor device.

  In the following description, although only one film is used.

  aluminum alloy, walking and effects of the embodiment also applies

  generally with aluminum foil.

  First, an aluminum alloy film with a thickness of 0.5 to 1.2 / m is formed on the surface of an insulating film formed on a semiconductor wafer. The aluminum alloy film can be made of AI-Cu, Al-Cu-Si, or another alloy. A pattern of sensitive agent of the reserve type is formed on the aluminum alloy film to dry etch the aluminum alloy film and remove the part not covered by the agent pattern.

sensitive.

  To perform this dry etching, a gas mixture formed for example of BC13, C12 and SiCl4 is used as the etching gas, and an anisotropic etching with less lateral etching is used, for example reactive ion etching (RIE). The cross section obtained after this etching operation is presented in FIG. 7A. In FIG. 7A, we can see an insulating film 211, a film

  212 in aluminum alloy, and a pattern of sensitive agent 213, after engraving.

  During the etching operation of the aluminum alloy film 212, a side wall protective film 214 is fixed to the side wall, formed by the pattern line, of the aluminum alloy film 212, this side wall protection film 214 containing a large amount of AICl3, Cl2, etc., which were produced during the etching operation. The function of the side wall protection film 214 is to prevent lateral etching during the etching operation. The thickness of the side wall protection film 214 is approximately 20 nm. This thickness also varies with the

  process temperature, and it increases as the temperature decreases.

  After performing the pattern drawing operation on the aluminum alloy film 212, the pattern of sensitive agent 213 is abraded, for example using a plasma of 02, as shown in FIG. 16B . As shown in FIG. 8, an etching chamber 220 and an abrasion chamber 222 are coupled using a loading lock 224 which can maintain the vacuum inside the chambers 220 and 222. The etching process aimed at applying the pattern trace to the aluminum alloy film 212 is carried out in the etching chamber 220, for example by RIE. After etching, the etching gas contained in the etching chamber 220 is removed and the tablet is transported, via the loading airlock 224, to the abrasion chamber 220. Gas is introduced

  02 in the etching chamber 220 in order to abrade the pattern of sensitive agent 213.

  After the abrasion of the sensitive agent, the pellet provided with the insulating film 211 and the aluminum alloy film is removed from the abrasion chamber 220.

212.

  Then, as shown in FIG. 7C, the tablet carrying the insulating film 211 and the aluminum alloy film 212 is immersed in an aqueous solution of silver nitrate (AgNO3) 215.

  aqueous solution of silver nitrate 215 on the aluminum alloy film 212.

  When the aluminum alloy film 212 has been immersed in the aqueous silver nitrate solution 215, a reaction as indicated by the following equation (1) occurs, in which the chlorine ions ( CI-) located in the side wall of the aluminum alloy film 212 are

  captured by silver ions (Ag +). The reaction byproduct precipitates.

  Ag + + CI- - AgCl, ... (1) As shown in FIG. 7D, when the aluminum alloy film 12 containing residual chlorine is immersed in the aqueous solution of silver nitrate 215, the ions d (Ag +) react with ions of

  chlorine (Cl- ions) and a whitish precipitate of silver chloride (AgCI) is formed.

  The silver chloride (AgCl) obtained from the chlorine and silver ions is not active. In this way, using the aqueous silver nitrate solution (AgNO3) 215 as a solution containing silver (Ag), the residual chlorine can be made completely inactive. The use of the aqueous silver nitrate solution (AgNO3) 215 as a solution containing silver (Ag) appears

  also advantageous on the following points.

  More particularly, after the etching operation of the aluminum alloy film 212, a treatment is often carried out using nitric acid (HNO3). In this case, if the aqueous silver nitrate solution is used in place of nitric acid, the effects of nitric acid and the anticorrosive effects

  are both obtained, so operations can be simplified.

  A treatment using nitric acid (HNO3) carried out after an etching operation is intended to put the "polybrate" in floating state on the layer of aluminum alloy 212 and to eliminate it, as well as to prevent corrosion of the aluminum alloy film 212 by forming an oxide film. The "polybrat" is a composition associated with the side wall protective film which is formed by anisotropic etching, and it contains elements of

the sensitive agent of the reserve type.

  After treatment with the aqueous silver nitrate solution, washing is carried out with pure water. Only a small amount of silver chloride (AgCl) dissolves in pure water at room temperature, for example 1.5 x 10-3 g / l, and this product is chemically stable. Even if a very small amount of silver chloride remains on the side wall after washing with pure water or the rinsing operation, silver chloride is very little active in the form of a whitish precipitate, by comparison chlorine residual. This whitish precipitate of silver chloride rarely produces corrosion of the alloy film.

  212 aluminum and does not create any voltaic stack effect.

  As described above, in the method for manufacturing a semiconductor device according to this embodiment, the aluminum alloy film 212, after abrasion of the sensitive agent, is immersed in the aqueous silver nitrate solution. 215. It is therefore possible to react the residual chlorine (Cl) on the side wall of the aluminum alloy film 212 with silver ions (Ag +). We can therefore remove corrosion from the alloy film

  212 aluminum and improve the performance of the device.

  In the previous description, while the aqueous solution was used

  of silver nitrate 215 as a solution containing silver ions, it is obvious that a solution containing silver ions is not limited to the aqueous solution of silver nitrate 215. For example, if a alkaline to the aqueous silver nitrate solution, a dark brown silver oxide precipitates due to the reaction indicated in equation (2) below. This silver oxide dissolves in water and the water becomes strongly alkaline. Instead of the aqueous silver nitrate solution, an aqueous solution containing silver hydroxide (AgOH) can be used

  obtained from silver oxide.

  2 Ag + + 2 OH- 2 AgOH - Ag2O + H20 ... (2) In addition, instead of using a solution containing silver ions (Ag +) for which the solubility product [Ag +] [C1-] with Cl- ions is approximately 1.1 x 10-10 (at 18 C), an aqueous solution containing a metal which forms a metal chloride having a low solubility product can also be used. It is better that the solubility product is less than 1 x 10-1, and preferably 1 x 10-3, or less. For example, an aqueous solution of lead nitrate containing lead ions (Pb +), for which the solubility product [Pb2 +] [CI-] 2 with the CI- ions is approximately 2.4x 10-4 (at room temperature) can be used in place of silver ions (Ag +) to crystallize the residual chlorine (Cl) into a whitish precipitate of lead chloride (PbC12) and

  to prevent corrosion of the aluminum alloy film 212.

  It is possible to leave silver chlorine or lead chloride on the substrate (tablet). If, for some reason, it is not appropriate to leave these materials, they can be removed using one of the following two methods (i) and (ii). (i) AgCl reacts with a solution of ammonium hydroxide (NH4OH) according to equation (3) below and dissolves, forming complex ions. We can

  therefore eliminate AgCI from the substrate (tablet).

  AgCl + 2NH4OH - (Ag (NH3) 2) CI + 2 H2O ... (3)

o (Ag (NH3) 2) CI is achromatic.

  A pellet is treated with AgNO3 and an ammonium hydroxide solution to advance the reaction indicated by equation (3). Of this

  way, AgCI can dissolve in ammonium hydroxide solution.

  Likewise, lead chloride dissolves in an ammonium hydroxide solution, forming complex ions, which removes

  lead chloride from the substrate (tablet).

  To dissolve the silver chloride and the lead chloride in the form of complex ions, it is possible to use, instead of the ammonium hydroxide solution, a solution of Na2S203. The ammonium hydroxide solution is more effective because it does not contain sodium and the performance of the device

  semiconductor does not degrade unnecessarily.

  (ii) The tablet is treated with a 1% gelatin solution just before treating it with AgNO3, after which the tablet is treated with an AgNO3 solution added with 1% gelatin. . In this way, we can

  remove the residual silver chloride from the tablet.

  The pattern layout and the subsequent operations performed on the aluminum alloy film have been described previously. We can also wait

  a step and similar effects for aluminum foil.

  Of course, those skilled in the art will be able to imagine, from the

  processes whose description has just been given by way of illustration only and

  in no way limiting, various variants and modifications not departing from the scope of the invention.

Claims (5)

  1. A method of manufacturing a semiconductor device, characterized in that it comprises the following operations: etching a conductive film and applying to it a pattern trace using a chlorine-based gas, said conductive film being made of aluminum or an aluminum alloy and being deposited on the surface of an insulating film formed on a substrate; and exposing said substrate having said conductive film to a reactive solution containing a metal which is able to react with chlorine and   to form a metal chloride with a small solubility product.   2. Method according to claim 1, characterized in that said metal is silver or lead.   3. Method according to claim 1 or 2, characterized in that said reactive solution is an aqueous solution of silver nitrate or a solution aqueous lead nitrate.   4. Method according to any one of claims 1 to 3, characterized   in that it further comprises the step of exposing said substrate to a release solution which is capable of releasing the silver chloride or lead chloride remaining on said substrate by changing said silver chloride or said lead chloride into complex silver ions or complex ions of   lead, after said operation of exposing said substrate to said reactive solution.   5. Method according to claim 4, characterized in that said   release solution contains ammonium hydroxide or Na2S203.