JP4035141B2 - Annealing method - Google Patents

Description

The present invention relates to an annealing method for annealing a thin film formed on a semiconductor substrate, and more particularly to an annealing method suitably used for annealing a low dielectric constant film having micropores formed on a semiconductor substrate. .

  In recent years, in the field of semiconductor materials, research on a low dielectric constant film (low-k film) used as an interlayer insulating material for multilayer wiring has been actively conducted (for example, see Patent Document 1). Examples of the method for forming the low dielectric constant film include CVD (Chemical Vapor Deposition) and SOD (Spin on dielectric coating).

  The low dielectric constant film described above generally has a large number of voids called micropores. Therefore, maintaining the micropore structure and completing the wiring without sacrificing other physical characteristics of the low dielectric constant film is important in the manufacture of semiconductor devices using the low dielectric constant film as an interlayer insulating material. Technology.

When the low dielectric constant film is formed, problems regarding the following items 1 to 4 usually occur. Therefore, in order to solve these problems, a special annealing technique is required.
1. Removal of organic substances and moisture taken in the film.
2. Volatilization of solvent during film growth and molding of micropore structure.
3. Strengthening film quality by annealing after film growth.
4). Prevents oxidation of copper and other metal wiring.

  2. Description of the Related Art Conventionally, there is an apparatus in which a coater and an annealing apparatus are integrated as a low dielectric constant film forming apparatus by the SOD method. In this film forming apparatus, annealing is performed in a multi-stage manner using a plurality of hot plate type hot plates heated to a constant temperature by an electric heater after coating of a low dielectric constant film. Specifically, for example, film coating → drying at 100 ° C. or lower → primary annealing at 200 ° C. or lower → secondary annealing at 400 ° C. or lower is performed in this order.

  Conventionally, an apparatus for annealing a low dielectric constant film by a CVD method irradiates the low dielectric constant film with ultraviolet rays while heating the low dielectric constant film using a hot plate in a vacuum (for example, Patent Documents). 1).

JP 2004-356508 A

  However, in the above-described low dielectric constant film deposition apparatus using the SOD method, the substrate is heated by a hot plate type hot plate using an electric heater. Micropore structure and other physical properties could change. Furthermore, in this apparatus, since the low dielectric constant film is heated at atmospheric pressure, it is necessary to control the atmosphere in all steps to prevent oxidation, and heating the film to a high temperature is a problem of oxidation. It was not desirable.

  In addition, the above-described CVD apparatus for annealing a low dielectric constant film heats the substrate with a hot plate in a vacuum, so the temperature of the hot plate does not necessarily match the temperature of the substrate, for example, when the degree of vacuum decreases. The substrate temperature rises rapidly, the micropore structure of the low dielectric constant film and other physical characteristics change, and the substrate temperature becomes unstable due to changes in the degree of vacuum. It was very difficult to manage.

The present invention has been made in view of the above-described circumstances, and provides excellent annealing of the low dielectric constant film without changing the micropore structure and other physical characteristics of the low dielectric constant film formed on the semiconductor substrate. An object of the present invention is to provide an annealing method that can be performed safely.

The present invention, in order to achieve the above object, a precure section for heating the semiconductor substrate in a low vacuum by the hot plate temperature is controlled by the supply of temperature control liquid, the semiconductor substrate in a high vacuum by an electric furnace A thin film made of a low dielectric constant film having micropores formed on a semiconductor substrate, using an annealing apparatus comprising a main cure section to be heated and a transfer means for transporting the semiconductor substrate from the pre-curing section to the main cure section In the annealing, the following steps (a) to (f) are performed, and an annealing method is provided.
(A) In the precure portion, the film is precure by heating the semiconductor substrate under a low vacuum with a hot plate.
(B) The semiconductor substrate that has been pre-cured is transferred from the pre-curing portion to the main curing portion by a transfer means under a low vacuum.
(C) In the main cure part, the film is fully cured by heating the semiconductor substrate in a high vacuum with an electric furnace.
(D) The pressure inside the cure unit is set to a low vacuum.
(E) The semiconductor substrate that has been subjected to the main curing is transferred from the main curing unit to the pre-curing unit by a transfer unit.
(F) The semiconductor substrate is cooled by a hot plate in the precure portion.

The annealing apparatus used in the present invention performs pre-curing under a low vacuum in a pre-curing section and performs this curing under a high vacuum in the main curing section. In this case, the low vacuum and the high vacuum are relative concepts, and the low vacuum in the precuring part means that the degree of vacuum is lower than the high vacuum in the main curing part. Under high vacuum means that the degree of vacuum is higher than under low vacuum in the precure part.

The main purpose of the precure in the present invention is to remove unnecessary components in the film, and in the precure part of the apparatus used in the present invention , by using a hot plate whose temperature is controlled by supplying a temperature control liquid, Unlike the conventional hot plate type hot plate (multistage, temperature fixed), by changing the heating rate, cooling rate, etc. according to the material and thickness of the film, without changing the structure of the film and other physical properties, A predetermined precure can be performed. That is, in the apparatus used in the present invention , by using liquid heating and liquid cooling for heating and cooling the hot plate, heating and cooling are performed at a high speed, and overheating and cooling rate on the high temperature side, which is likely to occur in vacuum, are reduced. A reduction is prevented, and precure can be safely performed at a predetermined temperature. In the apparatus used in the present invention , a plurality of precure units may be provided, and the precure may be performed in a multistage manner by the plurality of precure units.

Further, in the present curing portion of the apparatus used in the present invention , the semiconductor substrate is heated by an electric furnace, so that the semiconductor substrate can be heated at a constant temperature (isothermal heating), and the influence of the degree of vacuum is minimized. be able to. That is, since the apparatus used in the present invention uses an electric furnace in which the semiconductor substrate does not contact the heating element, unlike the heating by the hot plate in the vacuum described above, the temperature of the substrate rapidly increases when the degree of vacuum decreases. There is no inconvenience that the film structure and other physical characteristics are increased and the temperature of the substrate becomes unstable due to a change in the degree of vacuum. In the apparatus used in the present invention , a plurality of main curing units may be provided, and the main curing may be performed in a multistage manner by the plurality of main curing units.

  In the present invention, it is preferable to heat the semiconductor substrate to 50 to 300 ° C., particularly 50 to 250 ° C., particularly 100 to 200 ° C. under a low vacuum of 100 to 1000 Pa, particularly 100 to 400 Pa in the precure part. Precure can be performed safely. In this case, it is appropriate to heat the semiconductor substrate by continuously increasing the temperature of the hot plate at a predetermined temperature increase rate by supplying the temperature control liquid.

  In the present invention, it is preferable to heat the semiconductor substrate to 200 to 800 ° C., particularly 300 to 500 ° C. under a high vacuum of 0.001 to 1 Pa, particularly 0.001 to 0.01 Pa, in this cure portion. This cure can be performed well and safely.

  In the present invention, a light irradiating means for irradiating light (ultraviolet light, visible light, etc.) to the thin film can be provided in the present curing portion, and this curing can be performed more satisfactorily and safely depending on the material of the film. Is possible.

Furthermore, the annealing apparatus used in the present invention can be connected to a film forming apparatus for forming a thin film on a semiconductor substrate by a CVD method or an SOD method.

The annealing apparatus used in the present invention can be suitably used for annealing a low dielectric constant film having micropores formed on a semiconductor substrate. Specific examples of such a low dielectric constant film include SiLK (trade name) manufactured by Dow Chemical Company .

In addition, the annealing apparatus used in the present invention has an excess of the film after cleaning of the low dielectric constant film having a micropore structure formed on the semiconductor substrate and other films (cleaning after CMP, cleaning after resist removal, etc.). It is also suitable as a drying and curing device for removing water and chemicals.

Furthermore, in the manufacturing process of semiconductor elements, it is not possible to immediately move to the next process, and there are frequent waiting for processes, temporary storage of elements, etc., in order to remove element contamination, moisture adsorption, etc. that occur at this time In many cases, it is necessary to clean and dry the element. The annealing apparatus used in the present invention is effective as a device for drying and curing an element in the manufacturing process of a semiconductor element having a micropore structure film after waiting for the process or temporarily storing the element. The reason for this is that the film with micropores easily absorbs moisture, chemicals, organic matter, etc. after the cleaning process and long-term storage, and if these are not completely removed, wiring corrosion and dielectric constant increase are easily caused. This is because it is necessary to remove these adsorbents by drying the liquid. In the two-stage curing system of the present invention, it is possible to easily remove moisture, chemicals, organic substances and the like adsorbed on the membrane without destroying the micropore structure of the membrane.

According to the annealing method of the present invention, the low dielectric constant film can be annealed satisfactorily and safely without changing the micropore structure and other physical characteristics of the low dielectric constant film formed on the semiconductor substrate. it can.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples. FIG. 1 is a schematic view showing an example of an annealing apparatus used in the present invention. In the figure, 10 is a substrate transfer device, 12 is a pre-cure unit, 14 is a substrate transfer device (transfer means), and 16 is a main cure unit.

  The substrate transfer apparatus 10 carries in the semiconductor substrate into the precure unit 12 and carries out the semiconductor substrate from the precure unit 12. The precure unit 12 heats the semiconductor substrate with a hot plate 18 under a low vacuum, and supplies liquid for temperature control (two liquids of high temperature liquid and low temperature liquid in this example) from the liquid supply means 20 to the hot plate 18. To control the temperature of the hot plate 18. The substrate transfer device 14 is for transferring a semiconductor substrate from the precure unit 12 to the main cure unit 16 under a low vacuum. The curing unit 16 heats the semiconductor substrate in a high vacuum by an electric furnace 22 and uniformly applies light such as ultraviolet light and visible light to the thin film on the semiconductor substrate using an optical fiber or the like by the light irradiation means 24. Can be irradiated. The electric furnace 22 heats the semiconductor substrate without bringing the heating element into contact with the semiconductor substrate. For example, the electric furnace 22 is provided with a heater wire around a cylindrical body made of a heat-resistant material such as a quartz tube, and the inside of the cylindrical body. For example, a semiconductor substrate is disposed.

Next, an example of an annealing method using the apparatus of this example will be shown.
(1) A low dielectric constant film is formed on a semiconductor substrate using a film forming apparatus (not shown) by a CVD method or an SOD method.
(2) The semiconductor substrate is carried into the precure unit 12 by the substrate carrying device 10 and placed on the hot plate 18.
(3) In the precure section 12, the semiconductor substrate is heated by a hot plate 18 under a low vacuum, thereby precuring the film. Specifically, for example, the semiconductor substrate is heated at about 200 ° C. for a predetermined time under a low vacuum of about 100 Pa. In this case, by supplying a high temperature liquid of about 200 ° C. from the liquid supply means 20 to the hot plate 18 at a predetermined supply rate, the hot plate 18 is continuously heated from room temperature to about 200 ° C. at a predetermined temperature increase rate. Let Thereby, unnecessary components such as organic components in the film are removed without changing the structure of the film and other physical characteristics.
(4) The semiconductor substrate that has been pre-cured is transferred from the pre-curing unit 12 to the main curing unit 16 by a substrate transfer device 14 under a low vacuum, and is placed in the electric furnace 22.
(5) In the main curing unit 16, the semiconductor substrate is heated in a high vacuum by the electric furnace 22, and light is irradiated on the film by the light irradiation unit 24, thereby performing the main curing of the film. Specifically, for example, the semiconductor substrate is heated at about 500 ° C. for a predetermined time under a high vacuum of about 0.01 Pa. Thereby, the water | moisture content and organic component which are taken in in the micropore are removed. Note that light irradiation may be omitted depending on the material of the film.
(6) The pressure in the cure unit 16 is set to a low vacuum (for example, about 100 Pa). This pressure reduction process can be realized by using an electric furnace. When a hot plate is used, a change in the temperature of the substrate occurs when the degree of vacuum changes. For example, in a hot plate, when the pressure is changed from 0.01 Pa to 100 Pa, the temperature of the substrate instantaneously increases from 500 ° C. to 750 ° C., and the structure of the film and other physical characteristics are changed to damage the film. .
(7) The semiconductor substrate that has been subjected to the main curing is transferred from the main curing unit 16 to the pre-curing unit 12 by the substrate transfer device 14 and placed on the hot plate 18.
(8) The semiconductor substrate is cooled by the hot plate 18. Specifically, for example, a low-temperature liquid of about room temperature is supplied from the liquid supply unit 20 to the hot plate 18 at a predetermined supply rate, and the hot plate 18 is continuously cooled to a room temperature at a predetermined temperature decrease rate. Cool the substrate. In this case, the temperature lowering speed is set so as not to damage the film.
(9) The semiconductor substrate is unloaded from the precure unit 12 by the substrate transfer device 10.

It is the schematic which shows an example of the annealing apparatus used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Substrate conveyance apparatus 12 Precure part 14 Substrate transfer apparatus (transfer means)
16 Cure unit 18 Hot plate 20 Liquid supply means 22 Electric furnace 24 Light irradiation means

Claims (5)

A precure section for heating the semiconductor substrate in a low vacuum by the hot plate temperature is controlled by the supply of temperature control fluid, and the cure unit for heating the semiconductor substrate in a high vacuum by an electric furnace, from the pre-cured part When annealing a thin film made of a low dielectric constant film having a micropore formed on a semiconductor substrate using an annealing apparatus having a transfer means for transferring the semiconductor substrate to the cure unit, the following step (a) An annealing method characterized by performing (f).
(A) In the precure portion, the film is precure by heating the semiconductor substrate under a low vacuum with a hot plate.
(B) The semiconductor substrate that has been pre-cured is transferred from the pre-curing portion to the main curing portion by a transfer means under a low vacuum.
(C) In the main cure part, the film is fully cured by heating the semiconductor substrate in a high vacuum with an electric furnace.
(D) The pressure inside the cure unit is set to a low vacuum.
(E) The semiconductor substrate that has been subjected to the main curing is transferred from the main curing unit to the pre-curing unit by a transfer unit.
(F) The semiconductor substrate is cooled by a hot plate in the precure portion. 2. The annealing method according to claim 1, wherein in the precure portion, the semiconductor substrate is heated to 50 to 300 ° C. under a low vacuum of 100 to 1000 Pa. 3. The annealing method according to claim 1 or 2, wherein in the precure portion, the semiconductor substrate is heated by continuously raising the temperature of the hot plate at a predetermined temperature rise rate by supplying a temperature control liquid. The annealing method according to any one of claims 1 to 3, wherein in the main cure portion, the semiconductor substrate is heated to 200 to 800 ° C under a high vacuum of 0.001 to 1 Pa. Annealing method according to claim 1, wherein the benzalkonium be irradiated light to the thin film in the main cure unit.

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