JPH03286524A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce a contact resistance by a method wherein an insulating film is formed on a silicon substrate on which a prescribed region has been formed, a contact hole is made, a damage layer to be introduced into the surface of the substrate is removed, the edge of the contact hole is removed and an aluminum alloy electrode film containing silicon is formed on the surface of the substrate. CONSTITUTION:N-type regions 2, 3 constituting a source and a drain, a gate insulating film 4, a gate electrode 5 and an interlayer insulating film 6 are formed on the surface of a P-type silicon substrate 1. A photoresist 7 is deposited on the interlayer insulating film 6; after that, openings 7a, 7b are formed; a reactive etching operation is executed by making use of it as a mask; contact holes 6a, 6b are formed in the interlayer insulating film 6. Then, a prescribed aqueous solution of ammonia, hydrogen peroxide and water is made to act; a damage layer formed on the substrate 1 is removed; the smooth face of the silicon substrate is exposed; gentle tapers are made at edges of the contact holes. After a cleaning operation by pure water, an aluminum alloy electrode film 8 containing silicon is sputtered and vapor-deposited; it is patterned. Desired interconnections 8a, 8b are formed.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly, to a semiconductor device and a method for manufacturing the same, and in particular to an aluminum semiconductor device containing silicon that is in contact with a silicon substrate through a contact hole formed in an insulating film formed on the surface of the silicon substrate. The present invention relates to a semiconductor device including an electrode film made of an alloy and a method for manufacturing the same.

(Prior Art) As described above, semiconductor devices in which a region formed in a silicon substrate and an electrode film for wiring are interconnected through contact holes formed in an insulating film are known and widely used. ing. Aluminum is widely used as the electrode film for such semiconductor devices, but if pure aluminum is used, silicon will diffuse from the silicon substrate into the aluminum electrode film when heat treatment is performed after the electrode film is formed. Aluminum may diffuse into the silicon substrate and form an alloy bit that penetrates the region formed in the silicon substrate and reaches the substrate portion, impairing device characteristics. In order to prevent such interdiffusion between aluminum and silicon through contact holes, aluminum alloys containing silicon, such as AlS, are used as materials for electrode films for wiring.
i, AlCu5i.

It is known to use AlPdSi. in this case,
The solid solubility of silicon in aluminum is 350-400°
Aluminum alloys containing about 1% by weight of silicon are generally used to allow for a margin of about 0.25 to 0.5% by weight of silicon.

In this way, when using an aluminum alloy electrode film containing silicon, as the minimum width of the contact hole becomes smaller, the aspect ratio of the contact hole (the ratio of the width to the depth of the contact hole) increases, and the aluminum alloy electrode film becomes smaller. There is a problem in that the coverage is reduced and the electrode film is more likely to break. That is, as the aspect ratio of the contact hole increases, the electrode film is more likely to be cut at the edge of the contact hole.

Also, when forming a contact hole in an insulating film, it is important to know whether anisotropic etching such as reactive ion etching is used to avoid enlarging the size of the contact hole. During ion etching, accelerated ions collide with the surface of the silicon substrate, forming a damaged layer. If an aluminum alloy electrode film is formed on top of this damaged layer, ohmic contact cannot be made, resulting in contact failure. It has the disadvantage of increasing resistance.

Furthermore, when an aluminum electrode film containing silicon is deposited through a contact hole and heated in various subsequent steps, a phenomenon occurs in which silicon precipitates at the interface between the silicon substrate and the electrode film. It is known. As mentioned above, is it known to treat the surface of the silicon substrate with dilute hydrofluoric acid after forming contact holes by dry etching in order to remove the damaged layer formed on the surface of the silicon substrate? It was confirmed that when such a treatment is performed, silicon precipitation becomes severe and the contact resistance actually increases.

Such silicon precipitation is based on solid phase epitaxial growth that occurs during heat treatment after the formation of the aluminum alloy electrode film, and has the drawback of undesirably increasing contact resistance.

In a general wiring process, heat treatment is performed at a temperature of 350 to 450° C. for several hours, mainly during the interlayer insulating film formation process, so silicon precipitation is unavoidable. In this case, the minimum width of the contact hole, i.e. the length of one side if the contact hole is square, the length of the short side if it is rectangular, the diameter if it is circular, and the short axis if it is oval. If the length is too large, the silicon precipitate will not cover the entire minimum width of the contact area between the silicon substrate and the electrode film, so the increase in contact resistance will not be much of a problem, or the minimum width of the contact hole will be too large. , for example 1
When the contact resistance is as small as μm, the increase in contact resistance cannot be ignored. In particular, as devices have become increasingly finer and the minimum width of contact holes has become extremely small, the increase in contact resistance that occurs as a result of silicon precipitation due to solid-phase epitaxial growth at the interface between the silicon substrate and the electrode film is particularly important. I can no longer ignore it. For example, in the case of a contact hole or a square, its -side or 1.
If the thickness is larger than 5 μm, silicon precipitation is hardly a problem, but if it is smaller than 1.2 μm, the increase in contact resistance due to silicon precipitation can no longer be ignored. Therefore, in conventional semiconductor devices, when the minimum width of the contact hole is 1 μm or less, a barrier metal is formed between the silicon substrate and the electrode film, and silicon is removed during heat treatment after depositing the silicon-containing aluminum wiring electrode film. Precipitation is prevented from occurring. As such a barrier metal,
High-melting point metals such as tungsten, molybdenum, and titanium, or their silicides and nitrides are used. However, interposing such a barrier metal between the silicon substrate and the electrode film increases the number of manufacturing steps and has the drawback of lowering throughput. Furthermore, these high melting point metals are hard and have high stress, which causes them to peel off and deteriorate device characteristics. I wanted to,
A semiconductor device has been proposed in which a silicon-containing aluminum electrode film is brought into direct contact with a silicon substrate without using a barrier metal even when the minimum width of a contact hole is reduced to 1 μm or less.

For example, JP-A No. 6 published on December 16, 1986
1-285.762 discloses a semiconductor device in which an extremely thin insulating film is formed on the surface of a silicon substrate, and an aluminum electrode film containing silicon is formed on this insulating film. This insulating film is formed of silicon oxide or silicon nitride, and its thickness is on the order of 10 layers so that conduction between the silicon substrate and the electrode film is achieved by a tunnel effect.

Also, JP-A-62 published on November 12, 1987
-260 and 320 also disclose that 2
A semiconductor device is disclosed in which an extremely thin silicon oxide film of 0 Å or less is formed and an aluminum electrode film containing silicon is formed on the silicon oxide film. In this semiconductor device as well, conduction between the silicon substrate and the electrode film is achieved by the tunnel effect in which carriers penetrate the silicon oxide film.

(Problem to be solved by the invention) As described above, in a semiconductor device using an aluminum electrode film containing silicon as wiring, when the electrode film is brought into direct contact with the surface of a silicon substrate, silicon is formed in the contact hole by solid-phase epitaxial growth. The disadvantage is that it precipitates, leading to an increase in contact resistance. In particular, as miniaturization progresses, the minimum width of contact holes becomes smaller, 1μ
If it is less than m, the rate of increase in contact resistance becomes extremely high, and there is a problem that the yield is greatly reduced.

In an attempt to solve this problem, a barrier metal is interposed between the silicon substrate and the electrode film, but an extra step of depositing the barrier metal is required, resulting in a reduction in throughput. In addition, especially when using tungsten or molybdenum as a barrier metal, the contact resistance value differs depending on the conductivity type of the region formed on the silicon substrate, making it difficult to obtain an element with optimal electrical characteristics. . Furthermore, barrier metals have high hardness and high stress, so they tend to peel off and have the disadvantage of impairing device characteristics. In particular, reactive sputtering is used to deposit titanium or its nitride or silicide as a barrier metal, but it is extremely difficult to control nitrogen gas during this process, making it difficult to form a good barrier metal film. This has the disadvantage of causing peeling and increased contact resistance.

In addition, the above-mentioned Special Publication No. 61-285.762 and No. 62
In the semiconductor device disclosed in the -260 and 320 publications,
A silicon oxide film or a silicon nitride film is formed between the silicon substrate and the t-thickness film to prevent silicon precipitation, but the thickness of the film is minimized to the extent that it can be penetrated by carriers or the tunnel effect. Although it is intended to be thin, it is actually very difficult to stably form such a thin silicon oxide film or silicon nitride film. especially,
When an interlayer insulating film such as PSG or BPSG is formed on a silicon substrate, a resist pattern is formed on this insulating film by photolithography, and reactive ion etching is performed using this resist pattern as a mask to form a contact hole. In , accelerated ions collide with the surface of the silicon substrate, damaging the surface and forming a damaged layer, but it is possible to form an extremely thin stable silicon oxide film or silicon nitride film on this damaged layer. It is very difficult to do so. Therefore, it is not possible to reliably prevent the precipitation of silicon, or the silicon oxide film or silicon nitride film becomes too thick, resulting in an increase in contact resistance. Furthermore, since the silicon oxide film and silicon nitride film remain even in the completed final product device, conduction between the silicon substrate and the electrode film is realized by the tunnel effect. Since the film is an insulating film, the barrier for tunneling becomes high, making it impossible to obtain ohmic contact and increasing contact resistance.

Furthermore, in the conventional method of manufacturing a semiconductor device, a damaged layer is formed on the surface of the silicon substrate during tri-etching when forming a contact hole in an insulating film, resulting in an increase in contact resistance. If the surface of the silicon substrate is treated with dilute hydrofluoric acid after forming a contact hole to remove such a damaged layer, the above-mentioned silicon precipitation will be severe, and the contact resistance will increase.

In addition, when contact holes are formed in an insulating film by reactive ion etching, the opening edges of the contact holes form an angle of approximately 90°, which is a drawback in that step breaks are likely to occur when an aluminum alloy electrode film is formed. There is.

It is an object of the present invention to eliminate the above-mentioned conventional drawbacks, to prevent breakage of the aluminum alloy electrode film at the edge of the contact hole even if the aspect ratio of the contact hole becomes large, and to prevent breakage of the aluminum alloy electrode film at the edge of the contact hole. It is an object of the present invention to provide a method for manufacturing a semiconductor device that can avoid an increase in contact resistance due to a damaged layer.

Another object of the present invention is to eliminate silicon precipitation at the interface between a silicon substrate and an electrode film made of an aluminum alloy containing silicon without intervening a barrier metal at the interface;
Therefore, it is an object of the present invention to provide a method by which a semiconductor device having a predetermined low and stable contact resistance can be manufactured with high throughput.

(Means and Effects for Solving the Problems) A method for manufacturing a semiconductor device according to the present invention includes the steps of: forming an insulating film on a silicon substrate in which a predetermined region is formed; forming a contact hole in the insulating film; removing the damaged layer introduced into the surface portion of the silicon substrate during the formation of the contact hole to expose a smooth silicon substrate surface, and also removing the edge of the contact hole of the insulating film to form a gentle taper; , forming an aluminum alloy electrode film containing silicon on the insulating film and on the surface portion of the silicon substrate via the contact hole.

According to the manufacturing method of the present invention, after removing the damaged layer introduced when forming the contact hole,
Since an aluminum alloy electrode film containing silicon is formed on the surface of a silicon substrate with high flatness and crystallinity, it is possible to obtain an ohmic contact with low resistance and high uniformity. Furthermore, since the edge of the contact hole formed in the electrode film can be removed at the same time as the damaged layer to form a loose taper, the coverage of the electrode film is improved and breakage of the electrostatic film does not occur.

In a preferred embodiment of the present invention, after removing the damaged layer formed on the surface of the silicon substrate through the contact hole, a film with a thickness approximately the same as that of a natural oxide film is formed on the smooth silicon substrate surface. After forming a silicon oxide film having an aluminum alloy electrode film, a heat treatment is performed to reduce the silicon oxide film with aluminum.

According to the manufacturing method of the present invention, even if the surface of the silicon substrate is damaged by, for example, forming a contact hole in an insulating film by reactive ion etching, the damage layer is removed and then etched into the aluminum alloy. Either a silicon oxide film is formed to prevent the precipitation of silicon contained therein, or the thickness of this silicon oxide film can be formed to be extremely thin and uniform, thus effectively preventing the subsequent precipitation of silicon. As a result, an increase in contact resistance can be reliably avoided.

Further, after forming the silicon-containing aluminum alloy electrode film, heat treatment is performed to reduce the silicon oxide film, but since this heat treatment is generally performed in a wiring process, there is no need to perform any special heat treatment. However, if such heat treatment is not performed during the original manufacturing process, it goes without saying that a separate heat treatment may be performed. According to the method of the present invention, the silicon oxide film that prevents silicon precipitation is not present in the completed semiconductor device, and since the electrode film is in direct contact with the silicon substrate, the silicon oxide film is not present. Undesirable phenomena such as an increase in contact resistance due to residual contact resistance do not occur. In addition, when reducing silicon oxide, aluminum oxide (A1203) and silicon are generated, or these components diffuse into the aluminum electrode film and do not remain at the interface between the silicon substrate and the electrode film. This reduction step does not cause any increase in contact resistance.

In addition, after removing the damaged layer, a silicon oxide film is formed on the surface of the silicon substrate, or the process for forming this silicon oxide film is such that a silicon oxide film with a thickness similar to that of a natural oxide film is formed. It is suitable for The thickness of this natural oxide film is about 20 mm, or various methods can be used to form such an extremely thin silicon oxide film. For example, by applying an aqueous solution of hydrogen chloride and hydrogen peroxide, applying ultrasonic vibration in pure water, heating in hot water, or heating in an atmosphere containing oxygen gas, the film thickness can be increased to 20%. It is possible to form a silicon oxide film as thin as a human being.

The method of manufacturing a semiconductor device according to the present invention further includes a step of forming an insulating film on a silicon substrate on which a predetermined region is formed, a step of forming a contact hole in the insulating film by reactive ion etching, and a step of forming a contact hole through the contact hole. An aqueous solution of ammonia and hydrogen peroxide is applied to the exposed surface portion of the silicon substrate and the edge of the contact hole formed in the insulating film, and a contact hole is formed on the surface of the silicon substrate by the reactive ion etching. a step of removing a damaged layer introduced into the contact hole and a step of gently tapering the edge of the contact hole; and forming a natural oxide film on the surface portion of the silicon substrate exposed through the contact hole. forming a silicon oxide film having approximately the same thickness as the silicon oxide film; forming an aluminum alloy electrode film containing silicon on the silicon oxide film through the contact hole; and performing heat treatment to remove the silicon This method is characterized by comprising a step of reducing silicon oxide constituting the oxide film with aluminum constituting the electrode film to transform it into silicon.

In the semiconductor device manufactured by the method of the present invention, the edge of the contact hole is gently tapered, so that the aluminum alloy electrode film does not break, and the silicon substrate and the aluminum alloy containing silicon are separated. At the interface with the electrode film, there is not only no damaged layer but also substantially no silicon precipitates, so the contact resistance is a predetermined low value, and the device characteristics can be improved.

As mentioned above, the minimum width of the contact hole is approximately 1.
If the diameter is larger than 2 μm, even if silicon is deposited at the interface between the silicon substrate and the electrode film by solid-phase epitaxial method, the contact resistance will not increase undesirably. Preferably, the minimum width is approximately 1.2 μm or less.

According to the manufacturing method of the present invention, a contact hole is formed by reactive ion etching and then lightly etched with an aqueous solution of ammonia and hydrogen peroxide, thereby removing the damaged layer introduced by the ion etching and improving insulation. The film can be removed to form a gentle taper on the edge of the contact hole, and then, for example, treatment can be applied with an aqueous solution of hydrochloric acid and hydrogen peroxide, or treatment can be performed by immersing it in a hydrogen peroxide solution and applying ultrasonic waves. 2O by carrying out at least one of
An extremely thin silicon oxide film of A size can be stably formed. An aqueous solution of ammonia and hydrogen peroxide, which is an etchant for removing damaged layers and insulating films, is an etchant that is commonly used to remove organic substances in the manufacture of semiconductor devices.
It is something that can be easily done manually. Conventionally, in order to remove the damaged layer caused by reactive ion etching,
Is it known to treat the surface of a silicon substrate with a dilute hydrofluoric acid solution after ion etching?As will be explained in detail later, it is possible to treat the surface of a silicon substrate with a dilute hydrofluoric acid solution after ion etching, or to treat the surface of a silicon substrate with a dilute hydrofluoric acid solution as described above. If an aluminum electrode film containing silicon is deposited after treatment with an aqueous solution, further treatment with an aqueous solution of hydrochloric acid and hydrogen peroxide, and then treatment with a dilute hydrofluoric acid solution, the precipitation of silicon due to solid phase epitaxial formation will be severe and the contact resistance will increase. I confirmed that it increased in width. In the present invention, instead of immediately depositing and forming an aluminum electrode film containing silicon after removing the damaged layer using an aqueous solution of ammonia and hydrogen peroxide, it is treated with an aqueous solution of hydrochloric acid and hydrogen peroxide, and then By applying ultrasonic waves in an aqueous hydrogen solution to form an extremely thin and stable silicon oxide film on the surface of a silicon substrate, and then forming an aluminum electrode film containing silicon, silicon can also be deposited during subsequent heat treatment. I have confirmed that this is no longer the case, and that it is possible to maintain the contact resistance at a low value.

In such a method of the present invention, after treatment with an aqueous solution of ammonia and hydrogen peroxide, treatment with an aqueous solution of hydrochloric acid and hydrogen peroxide and/or treatment with an ultrasonic wave in pure water are performed. The mechanism by which an extremely thin silicon oxide film is stably formed by this process has not been clearly elucidated, and hydrogen chloride and hydrogen peroxide mainly contribute to the oxidation of silicon.
It is presumed from the experimental results that the ultrasonic waves physically remove the oxidation of silicon and the residue remaining on the surface of the silicon substrate.

Hereinafter, the present invention will be described in detail based on examples, but it goes without saying that the present invention is not limited to these examples, and can be modified and modified in many ways.

(Example) FIG. 1 is a cross-sectional view showing states in successive steps in an example of the method for manufacturing a semiconductor device according to the present invention. In this example, it is assumed that an N-channel MO3FET is manufactured. First, as shown in FIG. 1A, N-type regions 2 and 3 forming a source and a drain are formed on the surface of a P-type silicon substrate 1.
Further, a gate insulating film 4 is formed on the channel between the source and the drain, a gate electrode 5 is further formed on this gate insulating film, and an interlayer insulating film is formed on the gate electrode and the surface of the silicon substrate. A film 6 is formed.

In this example, this interlayer insulating film 6 is made of PSG (Phospho
5ilicate Glass) or
The present invention also uses other insulating materials, such as BPSG (Boro
Phosph.

It can also be formed from silicon oxide, silicon nitride, etc. Since the steps up to this point are the same as the conventional steps, they will not be described in further detail. Next, as shown in FIG. 1B, a photoresist 7 is deposited on the interlayer insulating film 6, and then the photoresist is selectively removed from the portion where contact holes for the regions 2 and 3 forming the source and drain are to be formed. to form open lowers a and 7b. Through this process, a contact hole for the gate electrode 5 is also formed at the same time, or in this example, since the contact between the gate electrode and the aluminum alloy electrode film is not a subject of the present invention, it is shown in the drawings, but its explanation will be omitted.

Reactive ion etching is performed using the photoresist with the openings formed as a mask to form contact holes 6a and 6b for the source and drain, respectively, in the interlayer insulating film 6 as shown in FIG. 1C. In this example, these contact holes 6a and 6b are square, and the length of the negative side is 1 μm. However, the shape of the contact hole is not limited to only a square, but can be any shape such as a circle, an ellipse, or a rectangle. In this case, an increase in contact resistance due to silicon precipitation becomes a problem when the minimum width of the contact hole is about 1.2 μm or less. Through this reactive ion etching process, the surface of the silicon substrate 1 is damaged by the collision of accelerated ions, and damaged layers 1a and tb are formed on the surface of the silicon substrate 1 exposed through the contact holes 6a and 6b. become. In reality, the damaged layers 1a and lb are extremely thin, or are shown thick in FIG. 1C for clarity. Is it known to treat the exposed surface of a silicon substrate l with dilute hydrofluoric acid to remove damaged layers 1a and 1b introduced by reactive ion etching to form such contact holes? It has been confirmed that if an aluminum electrode film containing silicon is formed after dilute hydrofluoric acid treatment, silicon will precipitate during the subsequent heat treatment, resulting in an extremely high contact resistance. In this example, in order to avoid such silicon precipitation, after contact holes 6a and 6b are formed in the interlayer insulating film 6, ammonia, hydrogen peroxide, and water are added in a volume ratio of 1:1:5. , the first aqueous solution heated to 85° C. is allowed to act for 10 minutes. Through this process, as shown in the first diagram, the damaged layers 1a and 1b formed on the silicon substrate 1 are removed, and the smooth surface of the silicon substrate is exposed through the contact holes 6a and 6b. The edge of the contact hole will have a gentle taper. That is, before this process, the edges of contact holes 6a and 6b formed an angle of 90 degrees, but after this process, the edges form an angle of about 120 degrees.

Next, after thorough cleaning with pure water, an aluminum alloy electrode film 8 containing silicon is sputter-deposited as shown in FIG.
As shown in FIG. F, desired wirings 8a and 8b are formed.

The contact resistance of a semiconductor device manufactured by such a method is sufficiently low, and no breakage occurs in the aluminum alloy electrode film. The reason is that the damaged layer on the surface of the silicon substrate exposed through the contact hole is removed, resulting in high flatness and crystallinity.
This is believed to be because when an aluminum alloy electrode film is deposited on top of the aluminum alloy electrode film, an ohmic contact with low resistance and high uniformity can be obtained.

In another embodiment of the present invention, after removing the damaged layers 1a and ib introduced when forming the contact hole and removing the edge of the contact hole to form a taper, that is, the step shown in the first diagram. After that, a second aqueous solution containing hydrochloric acid, hydrogen peroxide, and water in a volume ratio of 1:1:5 and heated to 70°C was applied for 7 minutes, and then immersed in pure water at room temperature. IMHz ultrasound 1
Let it act for 0 minutes. Although the effects of these first and second aqueous solutions and ultrasonic vibration are not completely understood, it is possible to etch the damaged layers 1a and 1b formed on the exposed surface of the silicon substrate 1 by the first aqueous solution. A silicon oxide film having an extremely thin or uniform thickness is formed on the clean silicon surface using a second aqueous solution, and the exposed surface of the silicon substrate is coated with ultrasonic cleaning. It is assumed that this removes any remaining dust. The thickness of the silicon oxide film formed on the surface of the silicon substrate by such treatment is approximately the same as the thickness of the natural oxide film, and is approximately 10% thick.
~50 people.

After performing the above-described processing, an aluminum alloy electrode film 8 containing silicon is deposited by sputtering in the same manner as in the previous example. Thereafter, treatments such as forming an interlayer insulating film are performed, and the heat treatment temperature at that time is about 400'C and the treatment time is about 3 hours. Conventionally, solid phase epitaxial growth occurred due to this heat treatment, and silicon precipitation occurred at the interface between the silicon substrate 1 and the aluminum alloy electrode film 8.
In the present invention, no silicon precipitation was observed. Silicon precipitation during heat treatment occurs intensively on silicon islands formed on the surface of the silicon substrate during aluminum alloy sputtering, or in the present invention, the aluminum alloy electrode film 8 is deposited by sputtering. During sputtering, a thin silicon oxide film is formed on the surface of the silicon substrate 1 exposed to the contact holes 6a and 6b, and the second silicon oxide film acts as a barrier against the generation of silicon nuclei. Since island-like silicon nuclei are not formed during the subsequent heat treatment, it is presumed that silicon will not precipitate during the subsequent heat treatment. As described above, according to the present invention, even if heat treatment is performed after forming the electrode film 8 made of an aluminum alloy containing silicon, silicon will not be deposited at the interface between the surface of the silicon substrate and the electrode film, and the contact resistance will be reduced. This will not lead to an increase in In this example, during the heat treatment after forming the electrode film 8 made of an aluminum alloy, the silicon oxide film that existed between the silicon and the aluminum electrode film is reduced by the aluminum electrode material, so that the completed device is In this case, this silicon oxide film hardly exists. That is, the following chemical reaction takes place and the silicon oxide film disappears.

4A]+3SiO□→2A1□03+3S iIn this case, aluminum oxide and silicon produced by reduction do not remain at the interface between the silicon substrate and the electrode film, but diffuse into the electrode film through the aluminum grain boundaries. I made sure to put it away. As shown in 2, in the semiconductor device manufactured by the method of the present invention, there is no silicon oxide film at the interface between the silicon substrate and the aluminum alloy electrode film, and furthermore, silicon precipitation due to solid phase epitaxial growth is observed. In addition, no precipitation of other insulators that would increase contact resistance was observed.

Next, in order to clarify the prevention of solicon precipitation in the present invention and the difference from the conventional example, light etching using a first aqueous solution containing ammonia and hydrogen peroxide was performed as in the above-mentioned embodiment of the present invention. By the method of the present invention, an electrode film made of an aluminum alloy containing silicon is formed by sputtering, followed by treatment with a second aqueous solution containing hydrochloric acid and hydrogen peroxide and ultrasonic treatment in pure water. The manufactured semiconductor device (hereinafter referred to as sample 1) and the semiconductor device (hereinafter referred to as sample 2) in which an electrode film made of an aluminum alloy was deposited by sputtering after etching with a dilute hydrofluoric acid aqueous solution as in the conventional method.
A semiconductor device was formed by lightly etching with an aqueous solution of ammonia and hydrogen peroxide and an aqueous solution of hydrochloric acid and hydrogen peroxide, and then etching with a dilute aqueous hydrofluoric acid solution, and then depositing an electrode film made of an aluminum alloy by sputtering. Three types of semiconductor devices (referred to as sample 3) were manufactured and their characteristics were investigated.

In these samples, the shape of the contact hole was square, and the length of the negative side was 1 μm. First, these samples 1 to 3 were subjected to SIMS (Secondary JonM
As a result of analysis using the ASSEM Spectrometry method, it was found that after the aluminum alloy electrode film was formed and before heat treatment, a silicon oxide film was formed on the surface of the silicon substrate in Sample 1 according to the present invention, whereas in Samples 2 and 2, a silicon oxide film was formed on the surface of the silicon substrate. 3
No formation of silicon oxide film was observed.

In addition, scanning electron micrographs of the interface between the silicon substrate and the electrode film of samples 1 and 2 after heat treatment were taken, and it was found that in the semiconductor device manufactured by the method of the present invention, the silicon substrate and the aluminum alloy electrode film No silicon precipitation was observed at the interface with the contact hole, or in the case of sample 2, a fairly large silicon precipitate was observed within the contact hole. Furthermore, in the semiconductor device manufactured by the method of the present invention, many silicon precipitates were observed on the interlayer insulating film, whereas in Sample 2, silicon precipitates were not observed on the interlayer insulating film, and most of the silicon precipitates were observed on the interlayer insulating film. It was confirmed that the metal was precipitated inside the contact hole.

Manufacture 56 chips from one silicon wafer,
When a histogram was created using the contact resistance value of each chip as a parameter, it was found that in sample 3, the contact resistance value varied, and many chips had high contact resistance of 1000Ω or more. In this way, it has been found that when a contact hole is formed by dry etching and then treated with dilute hydrofluoric acid as in the past, the contact resistance increases to the extent that more than half of the chips are not practical. In addition, the measurement results for Sample 1 and Sample 2 indicate that there is some difference in contact resistance depending on the time of light etching with an aqueous solution of ammonia and hydrogen peroxide in Sample 2, and there is a large variation in contact resistance. When the test was carried out for 10 minutes, it was observed that the contact resistance was concentrated from approximately 150Ω to 750Ω.

Furthermore, even when the light etching process was performed for 15 to 20 minutes, it was confirmed that the contact resistance was concentrated in the range of 100Ω to 400Ω. On the other hand, in all the samples according to the present invention, after the light etching treatment was performed for 7 minutes or more, the contact resistances were all 10Ω or less, and the average value was about 5Ω or less. Also, even when the light etching process is performed for 4 minutes, the contact resistance of most chips is approximately 80Ω or less, so it is possible to significantly improve the yield by tapering the edges of the contact holes. It was confirmed that in order to improve the coverage of the electrode film, it is appropriate to carry out the light etching treatment for 7 minutes or more.

In the experiment described above, Sample 1 according to the present invention was treated with an aqueous solution of ammonia and hydrogen peroxide, followed by an aqueous solution of hydrogen chloride and hydrogen peroxide after forming a contact hole, as in the example described above. After treatment, ultrasonic waves were applied in pure water, but after treatment with an aqueous solution of ammonia and hydrogen peroxide, treatment with an aqueous solution of hydrogen chloride and hydrogen peroxide, and ultrasonic treatment in pure water were No silicon precipitation was observed even when the order was reversed, and no silicon precipitation was observed when either one of the treatments was performed.

The present invention is not limited to the above-described embodiments, but can be modified in various ways.

For example, in the embodiments described above, an aluminum alloy containing silicon was used as the electrode film, but an aluminum alloy such as AlCu5i or AlPdSi containing copper or baradium may also be used. Furthermore, the aluminum alloy electrode film can be deposited by Al-CVD or electron beam evaporation in addition to sputtering. In addition, the removal of the damaged layer introduced by the formation of the contact hole and the formation of the natural oxide film were performed using the aqueous solution of ammonia and hydrogen peroxide used in the above-mentioned example, the treatment with the aqueous solution of hydrochloric acid and hydrogen peroxide, and the treatment with pure water. The present invention is not limited to ultrasonic cleaning treatment, and various etching solutions and cleaning treatments can also be used.

(Effects of the Invention) In the method for manufacturing a semiconductor device according to the present invention described above, after the damaged layer introduced when forming a contact hole is removed and the surface of the silicon substrate is smoothed, an aluminum alloy electrode film containing silicon is formed. Therefore, a good ohmic contact is obtained between the silicon substrate and the electrode film made of an aluminum alloy containing silicon, and the contact resistance is low. In addition, in the manufacturing method of the present invention in which a silicon oxide film is formed after smoothing the silicon substrate surface, the silicon oxide film acts as a barrier against the formation of silicon nuclei, so the silicon There is virtually no precipitation, especially when the minimum width of the contact hole is approximately 1.
Even if the contact resistance is as small as 2 μm or less, no increase in contact resistance occurs, and since there is no barrier metal at this interface, stable contact resistance can be obtained regardless of the conductivity type of the region formed on the silicon substrate. Since there is no need for troublesome control to form a , the manufacturing process becomes simple, costs can be reduced, and throughput has the advantage of being improved. In addition, during the process of forming contact holes in the insulating film, the edges of the contact holes are removed and a gentle taper is formed at the same time.
No breakage occurs in the aluminum alloy electrode film formed thereafter. Furthermore, the silicon oxide film that had been formed on the surface of the silicon substrate by the heat treatment after forming the aluminum alloy electrode film is reduced by the aluminum, and since the reduced silicon does not remain in the contact hole, the final product is a silicon oxide film. Therefore, it is not necessary to establish electrical conduction between the region formed on the silicon substrate and the electrode film by the tunnel effect via the silicon oxide film or silicon nitride film as in the conventional method, so the current density is stable and low. It is possible to obtain contact resistance. As described above, according to the manufacturing method of the present invention, the yield can be significantly improved and the throughput can be improved.

[Brief explanation of the drawing]

FIGS. 1A to 1F are cross-sectional views showing sequential steps in an embodiment of the method for manufacturing a semiconductor device according to the present invention. l...Silicon substrate la, lb...Damaged layer 2.3...N type region 4...Gate insulating film 5...Gate electrode 6...Interlayer insulating film 6a, 6b...Contact Hole 7... Photoresist 7a, 7b... Opening 8... Aluminum alloy electrode film 8a, 8b... Source, drain wiring Figure 1

Claims (1)

[Claims] 1. A step of forming an insulating film on a silicon substrate on which a predetermined region has been formed, a step of forming a contact hole in this insulating film, and a step of forming a contact hole on a surface portion of the silicon substrate during the formation of the contact hole. removing the introduced damaged layer to expose a smooth silicon substrate surface and removing the edge of the contact hole of the insulating film to form a gentle taper; 1. A method for manufacturing a semiconductor device, comprising the step of forming an aluminum alloy electrode film containing silicon on a surface portion of a silicon substrate. 2. After removing the damaged layer formed on the surface of the silicon substrate through the contact hole, forming a silicon oxide film having approximately the same thickness as the natural oxide film on the smooth silicon substrate surface. The method of manufacturing a semiconductor device according to claim 3 or claim 1, further comprising the steps of: after forming the silicon-containing aluminum alloy electrode film, performing heat treatment to reduce the silicon oxide film with aluminum. . A step of forming an insulating film on a silicon substrate on which a predetermined region has been formed, a step of forming a contact hole in this insulating film by reactive ion etching, and a step of forming a surface portion of the silicon substrate and the insulating film exposed through the contact hole. An aqueous solution of ammonia and hydrogen peroxide is applied to the edge of the contact hole formed in the silicon substrate to remove the damaged layer introduced to the surface of the silicon substrate during the formation of the contact hole by the reactive ion etching. A step of removing the edge of the contact hole to gently taper the edge of the contact hole, and applying silicon oxide to the surface portion of the silicon substrate exposed through the contact hole to have a film thickness that is approximately the same as that of the natural oxide film. a step of forming an aluminum alloy electrode film containing silicon on the silicon oxide film through the contact hole; and a step of heat-treating the silicon oxide constituting the silicon oxide film to form an electrode film. A method for manufacturing a semiconductor device, comprising the step of reducing constituent aluminum and transmuting it into silicon.