JPH09326435A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove a damaged layer, without causing the irregularity on the surface of a semiconductor substrate by applying an accelerated oxygen ion beam on this surface through an opening of an insulation film on the sub strate surface. SOLUTION: Specified part of an insulation film 2 on the surface of a Si substrate 1 is selectively removed by photolithography and anisotropic dry etching using a gas of Cx Hy Fz +Ar to form contact holes with a damaged layer 3 on the surface of the openings of the substrate 1. Using an equilibrium flat plate type reactive ion etching apparatus, an oxygen plasma is produced in specified condition and accelerated oxygen ion beam 6 is applied on the damaged layer 3 to thereby utterly remove this layer 3. Thus a plane and smooth surface of the Si substrate 1 is formed, without causing a new damaged layer thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a semiconductor device capable of forming an electrical connection with an extremely highly reliable electrode.

[0002]

2. Description of the Related Art As is well known, a contact hole for electrically connecting an electrode to a diffusion layer or wiring formed on the surface of a semiconductor substrate is a predetermined portion of an insulating film formed on the semiconductor substrate. It is formed by forming an opening in. Such openings are usually formed selectively by using a technique called photolithography, but the dimensions of the openings have become finer as the integration density has increased in recent years. Dry etching, which has high etching anisotropy, such as reactive ion etching is generally used for forming the portions.

However, when an opening is formed in the insulating film by dry etching having high anisotropy such as reactive ion etching, the surface of the semiconductor substrate exposed through the opening is irradiated with ions or the like to form Si. A damage layer containing a large amount of —C, Si—O, etc. is formed, and the damage layer causes a failure in electrical connection between the semiconductor substrate and the electrode.

Therefore, conventionally, after forming the opening, downstream type plasma etching using a mixed gas of CF ₄ / O ₂ or CHF ₃ / O ₂ is performed to expose the surface of the semiconductor substrate in the opening. The damage layer had been removed.

[0005]

As described above, when the opening is formed in the insulating film 2 by dry etching having high anisotropy, the semiconductor substrate 1 is exposed as shown in FIG. 3 (a). The damage layer 3 is formed on the surface thus formed, and the damage layer 3 is formed by CxHyFz gas, CO gas or C gas.
This is particularly remarkable when the opening is formed by dry etching using a gas containing C as a component element such as O ₂ gas as an etching gas. When such a damage layer 3 is formed on the surface of the substrate 1, many adverse effects such as increase in contact resistance and destabilization of leak current occur, making it difficult to form a highly reliable semiconductor device. Become.

Conventionally, in order to remove the damaged layer 3, the downstream type plasma etching using the CF ₄ / O ₂ or CHF ₃ / O ₂ mixed gas as described above has been used. However, since this etching is performed using not only the O (oxygen) radicals 6 but also an etching gas containing F (fluorine), as shown in FIG. 3B, not only the damage layer 3 but also the Si substrate 1 is also etched at the same time to form a recess 5. Therefore, even after the damage layer 3 is completely removed, as shown in FIG. 3C, the recess 5 remains without being removed, and the surface of the Si substrate 1 is not smooth.

That is, in the process of removing the damage layer 2 by the downstream plasma etching, the removal of the damage layer 3 is already completed, and Si is removed.
The part where the surface of the substrate 1 is exposed and etched and the damage layer 3 still remain without being completely removed,
The surface of the Si substrate 1 is not exposed yet and a portion which is not etched coexists. The exposed and etched portion of the surface of the Si substrate 1 becomes a concave portion, and the portion that is not exposed and not etched becomes a convex portion, which causes unevenness on the surface of the Si substrate 1.

Therefore, in order to prevent the surface of the Si substrate 1 from becoming uneven, it is necessary to etch and remove only the damaged layer 2 without etching the surface of the Si substrate 1. However, such a method could not be performed by the method of. Further, since the damaged layer 3 is strong, it is impossible to completely remove the damaged layer 3 by the conventional downstream type plasma etching using the mixed gas or the downstream type plasma etching using oxygen. Is.

It is an object of the present invention to provide a method for manufacturing a semiconductor device, which can solve the problems of the above-mentioned conventional methods and can obtain good electrical connection between an electrode and a semiconductor substrate or the like.

Another object of the present invention is to remove a damaged layer on the surface of a Si substrate caused by dry etching having high anisotropy without etching the Si substrate to obtain a smooth Si substrate surface. A method of manufacturing a semiconductor device is provided.

[0011]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention comprises the steps of: after an insulating film formed on the surface of a semiconductor substrate is processed into a predetermined shape by dry etching; The method is characterized by including a step of irradiating the surface of the semiconductor substrate with oxygen ions accelerated through an opening of the insulating film to remove a damaged layer formed on the surface of the semiconductor substrate.

That is, according to the present invention, since the damaged layer is removed by the accelerated oxygen ions and fluorine is not used, the surface of the Si substrate is not etched, so that the surface of the Si substrate becomes uneven. There is no fear.

Oxygen ions are not accelerated in oxygen downstream plasma etching. With such unaccelerated oxygen ions, the reaction between oxygen ions and the damaged layer is only a chemical reaction, no physical reaction (sputtering reaction) is performed, and the strong damaged layer cannot be removed.
However, in the present invention, since accelerated oxygen ions are used for removing the damaged layer, a chemical reaction and a physical reaction occur at the same time, and a strong damaged layer can be easily removed.

However, even if accelerated oxygen ions are used, if the energy of oxygen ions is excessively high, a new damaged layer will be formed on the surface of the Si substrate due to ion bombardment after the damaged layer is removed. There is a fear.
On the other hand, if the energy of oxygen ions is too low, the physical reaction is significantly weakened and the removal rate of the damaged layer is reduced, making it difficult to obtain a sufficiently high throughput. For this reason, the energy of the oxygen ions is selected from the range of 0.3 to 1.5 keV, and the energy of 0.3 to 1.5 keV is selected.
More favorable results can be obtained with 1.0 keV,
The most preferable result can be obtained by setting 0.3 to 0.6 keV.

In order to stably perform the step of removing the damaged layer, the temperature of the semiconductor substrate is set to -60.
It is effective to carry out the treatment at a temperature of up to 300 ° C.

Furthermore, when an inert element is accelerated and irradiated to the semiconductor substrate together with the accelerated oxygen ions, the sputtering effect by the inert ions is added in addition to the effect by the oxygen ions, so that the processing efficiency is improved. Is effective for. The inert element is N
Elements having a large atomic weight such as e, Ar, and Kr are preferable.

In the step of removing the damaged layer, various ion etching devices such as a parallel plate type reactive ion etching device and a microwave ion etching device can be used.

The step of removing the damaged layer can be performed by adding oxygen to the etching gas at the final stage of the step of processing the insulating film into a predetermined shape by dry etching.

After removing the damaged layer, it is effective to add a step of wet etching the surface of the semiconductor substrate. By doing so, the silicon oxide layer generated by the reaction between the accelerated oxygen and the substrate surface is removed, and the connection with the electrode becomes extremely good. Various etchants can be used for this wet etching,
For example, if a mixed solution of hydrogen peroxide and hydrofluoric acid is used as an etchant, extremely favorable results can be obtained.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is characterized in that a damaged layer is removed by accelerated oxygen ions. Such accelerated oxygen ions are various ions such as parallel plate type or microwave type. It can be obtained using an etching device. These devices can independently change the energy of oxygen ions in a wide range and are appropriately selected depending on the damaged layer to be removed. The energy can remove the damaged layer within a range of 0.3 to 1.5 keV, but a more preferable result can be obtained within a range of 0.3 to 1.0 keV.
The most preferable result is obtained within the range of 0.6 keV.

In order to stably remove the damaged layer, it is effective to adjust the temperature of the processing table on which the Si substrate is placed to a desired temperature.
The optimum temperature is controlled in the range of 300 ° C.

Further, in order to improve the processing efficiency,
It is effective to increase the density of oxygen plasma, which is a source of oxygen ions, and a preferable result can be obtained when the density is 10 ¹¹ to 10 ¹³ / cm ³ . Adding an inert gas together with oxygen gas is also effective in improving treatment efficiency,
For example, it is effective to add an inert gas having a large atomic weight such as Ne, Ar or Kr. In this case, the amount of the inert gas added is appropriately 0 to 20 times that of the oxygen gas.

As the etching apparatus used for carrying out the present invention, an ordinary etching apparatus having only an etching chamber can be used, but an apparatus provided with a post-processing chamber in addition to the etching chamber is used. You can
If the damaged layer is removed with oxygen ions in the same etching chamber after the etching with the Freon-based gas, problems such as the generation of foreign matter may occur. By removing the damaged layer in the processing chamber, a clean surface can be obtained without causing such a problem, which is extremely preferable.

[0024]

【Example】

<Embodiment 1> As shown in FIG. 1A, a predetermined portion of a SiO ₂ film 2 having a thickness of 1 μm formed on the surface of a Si substrate 1 was subjected to a well-known photolithography and C _x H _y. An opening for contact was formed by selective removal by anisotropic dry etching using F _z + Ar or C _x H _y F _z + Ar + CO as an etching gas. By this treatment, the damage layer 3 is formed on the surface of the opening of the Si substrate 1.
Was formed.

Next, using a parallel plate type reactive ion etching apparatus, a reaction gas O ₂ and a gas pressure of 0.01 Tor were used.
Oxygen plasma was generated under the conditions of r and an applied voltage between electrodes of 600 V, and the damaged layer 3 was irradiated with accelerated oxygen ions 6 as shown in FIG.

As a result, as shown in FIG. 1C, the damage layer 3 is completely removed, and the Si substrate 1 is also removed.
No new damaged layer was generated on the surface, and an extremely smooth surface of the Si substrate 1 having no unevenness was obtained.

However, when the applied voltage is increased to 2400 V and the high energy oxygen ions 7 are irradiated as shown in FIG. 2B, the damaged layer 3 is removed.
As shown in (c), a new damaged layer 8 was formed by the irradiation of the high-energy oxygen ions 7, and good electrical connection was not obtained.

That is, the damaged layer 3 produced by anisotropic dry etching can be removed by irradiation with oxygen ions. However, if the energy of oxygen ions is too high, the Si substrate 1 is irradiated with high energy oxygen ions 7.
The surface of is damaged and a new damage layer 8 is generated.

After the damage layer 3 is removed, wet etching using a mixed solution of hydrogen peroxide (2%) and hydrofluoric acid (0.5%) as an etchant is performed to remove the surface of the substrate 1. The silicon oxide layer was removed.

Next, by a well-known wiring process, a conductive film was formed and patterned to form a wiring (not shown). On the surface of the Si substrate 1 in the contact portion formed in this example, the damage layer 3 was removed very well, and no unevenness was generated, so the connection with the wiring was very good.

[0031]

As is apparent from the above description, according to the present invention, the damage layer generated on the surface of the Si substrate at the time of forming the opening by anisotropic dry etching can be used without forming a new damage layer. Then, the surface of the Si substrate can be flattened. Therefore, good electrical connection can be obtained between the Si substrate and the electrodes, and a semiconductor device having extremely high reliability can be formed.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention,

FIG. 2 is a diagram showing a case where the energy of oxygen ions is high,

FIG. 3 is a diagram showing a conventional damage removal method.

[Explanation of symbols]

1 ... Si substrate, 2 ... Insulating film, 3 ... Damage layer, 4 ... Oxygen plasma, 5 ... Unevenness, 6 ... Oxygen ion, 7 ... High energy oxygen ion, 8 ... New damage layer.

Claims (9)

[Claims] 1. A step of processing an insulating film formed on a surface of a semiconductor substrate into a predetermined shape by dry etching using a predetermined etching gas, and acceleration through an opening of the insulating film. A method for manufacturing a semiconductor device, comprising at least a step of irradiating the surface of the semiconductor substrate with oxygen ions to remove a damaged layer formed on the surface of the semiconductor substrate. 2. The oxygen ions are 0.3 to 1.5 ke
2. The method for manufacturing a semiconductor device according to claim 1, having an energy selected from the range of V, preferably 0.3 to 1.0 keV, and more preferably 0.3 to 0.6 keV. . 3. The method for manufacturing a semiconductor device according to claim 1, wherein the step of removing the damaged layer is performed while maintaining the temperature of the semiconductor substrate at −60 to 300 ° C. 4. The semiconductor according to claim 1, wherein in the step of removing the damaged layer, an inert element is accelerated together with the oxygen ions to irradiate the semiconductor substrate. Device manufacturing method. 5. The inactive element is Ne, Ar or Kr.
The method for manufacturing a semiconductor device according to claim 4, wherein the method is selected from the group consisting of: 6. The step of removing the damaged layer is performed by using a parallel plate type reactive ion etching apparatus or a microwave ion etching apparatus. Manufacturing method of semiconductor device. 7. The step of removing the damage layer formed on the surface of the semiconductor substrate is the step of processing the insulating film into a predetermined shape by dry etching, in which oxygen is added to the etching gas. 7. The method for manufacturing a semiconductor device according to claim 1, wherein the method is performed as follows. 8. The manufacturing of a semiconductor device according to claim 1, further comprising a step of wet etching the surface of the semiconductor substrate after the step of removing the damaged layer. Method. 9. The semiconductor device according to claim 1, wherein the wet etching step is performed using an etchant composed of a mixed solution of hydrogen peroxide and hydrogen fluoride. Manufacturing method.