JP2013247272A - Method of manufacturing semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a semiconductor element capable of improving driving ability of the semiconductor element and suppressing deterioration in element characteristics.SOLUTION: There is provided a method of manufacturing a semiconductor element comprising: a step S1 of forming a layer on a surface of a substrate, the layer having a melting point higher than the substrate; a step S2 of heating the layer by irradiating the layer with laser and melting a part of the surface of the substrate, thereby making the part of the surface of the substrate in a wave pattern; a step S3 of removing the layer and exposing the part of the surface of the substrate; and a step S4 of forming a semiconductor element including the exposed part of the surface of the substrate.

Description

  The present invention relates to a method for manufacturing a semiconductor device.

  A semiconductor device in which a semiconductor element such as a transistor is formed on a substrate such as a silicon substrate is known. Conventionally, as a method for manufacturing a semiconductor device, a method capable of improving the driving capability of a semiconductor element has been proposed.

  As a method for manufacturing such a semiconductor device, for example, there is a method of increasing a channel region of a semiconductor element (increasing an effective channel width) by forming a rectangular groove or a V-shaped groove on a substrate. It is known (see, for example, Patent Document 1).

JP-A-5-75121

  In the method of manufacturing a semiconductor device disclosed in Patent Document 1, an electric field tends to concentrate on the corners of a rectangular groove or a V-shaped groove formed on a substrate. Therefore, there is a problem that a leak current is likely to be generated at the corner portion, and element characteristics are impaired.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for manufacturing a semiconductor element capable of improving the driving capability of the semiconductor element and suppressing the deterioration of the element characteristics. To do.

  In order to solve the above problems, a method of manufacturing a semiconductor device according to the present invention includes a step of forming a layer having a higher melting point than the substrate on one surface of the substrate, and heating the layer by irradiating the layer with a laser. Melting a portion on one side of the substrate to form a waveform on the one side of the substrate, exposing the portion on the one side of the substrate by removing the layer, and exposing the substrate Forming a semiconductor element including a portion on the one surface side.

  According to this method for manufacturing a semiconductor device, it is possible to selectively melt the portion on the one surface side of the substrate by appropriately adjusting the wavelength, intensity, etc. of the laser without directly heating the substrate. Also, evaporation of the substrate can be avoided by not heating the substrate directly. The corrugated shape formed by melting the portion on the one surface side of the substrate in this way is a smooth corrugated shape having no acute angle portion on the surface. Therefore, it is possible to suppress local concentration of the electric field on the corrugated portion of the substrate, and it is possible to suppress the occurrence of leakage current. Further, since the portion on the one surface side of the substrate has a corrugated shape, the channel region of the semiconductor element can be increased. Therefore, it is possible to improve the driving capability of the semiconductor element and suppress deterioration of the element characteristics.

  In the method for manufacturing a semiconductor device, the substrate is preferably a silicon substrate.

  In this way, in the step of forming the waveform on the one surface side of the silicon substrate, the portion on the one surface side of the silicon substrate can be melted, and the molten silicon can be deposited and expanded, and then recrystallized. Thereby, it can suppress that a crystal defect arises in the part of the one surface side of a silicon substrate, and generation | occurrence | production of junction leakage current can be suppressed.

  In the method for manufacturing a semiconductor device, the layer is preferably a carbon layer or a tantalum carbide layer.

  In this way, since the melting point of the layer can be markedly higher than the melting point of the substrate, it becomes easy to selectively melt the portion on the one surface side of the substrate. For example, when the substrate is a silicon substrate (melting point of about 1400 ° C.) and the layer is a carbon layer (melting point of 3000 ° C. or more), the difference between the melting point of the substrate and the melting point of the layer can be 1600 ° C. or more.

  In the semiconductor device manufacturing method, the laser is preferably an excimer laser.

  In this way, since it mainly has a wavelength in the ultraviolet region, most of the irradiation energy is absorbed by the layer and becomes heat. Thus, the layer can be heated to a sufficiently high temperature.

Also, in the method for manufacturing a semiconductor device, a portion of one surface of the silicon substrate in the step of the waveform shape, the energy density of the excimer laser, 0.2 J / cm ² or more 2.0 J / cm ² below It is desirable to do.

In this way, the portion on the one surface side of the substrate can be reliably melted, and the portion on the one surface side of the substrate can be formed into a regular corrugated shape. If the energy density of the excimer laser is less than 0.2 J / cm ² , it becomes difficult to melt the portion on the one surface side of the substrate. On the other hand, if it exceeds 2.0 J / cm ² , it may vaporize beyond the boiling point of silicon (2300 ° C. or higher), making it difficult to form a regular corrugated portion on one side of the substrate.

It is sectional drawing for demonstrating the manufacturing process of the manufacturing method of the semiconductor device of this invention. FIG. 2 is a cross-sectional view for explaining the manufacturing process following FIG. 1. It is a figure which shows the flowchart of the manufacturing method of the semiconductor device of this invention. It is a figure which shows the SEM (scanning electron microscope) photograph for demonstrating the manufacturing process of the manufacturing method of the semiconductor device of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. This embodiment shows one aspect of the present invention, and does not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, an actual structure and a scale, a number, and the like in each structure are different.

  1 and 2 are cross-sectional views for explaining a manufacturing process of a method for manufacturing a semiconductor device according to the present invention. FIG. 3 is a flowchart of the method for manufacturing a semiconductor device of the present invention. FIG. 4 is a view showing an SEM (scanning electron microscope) photograph for explaining a manufacturing process of the method for manufacturing a semiconductor device of the present invention.

  In the method of manufacturing a semiconductor device according to the present embodiment, first, a silicon single crystal substrate (hereinafter referred to as a silicon substrate) 1 is prepared as shown in FIG. Here, the silicon substrate 1 is a substrate of the present invention, and has a single crystal silicon film on one surface 1a thereof. The crystal plane of the single crystal silicon exposed on the one surface 1a of the silicon substrate 1 is, for example, a crystal plane represented by a Miller index (100) (hereinafter simply abbreviated as (100) plane). However, in addition to the (100) plane, a (111) plane inclined by 54.73 ° with respect to the (100) plane may be used.

Subsequently, the natural oxide film formed on the one surface 1a of the silicon substrate 1 is removed (cleaned).
For removal (cleaning) of the natural oxide film, for example, the silicon substrate 1 is placed in a vacuum chamber and annealing is performed in a reduced pressure atmosphere. Thereby, the natural oxide film (SiO ₂ ) adhering to the one surface 1a of the silicon substrate 1 is removed.

In the annealing process, hydrogen gas may be introduced into the vacuum chamber, the hydrogen gas may react with the natural oxide film, and the natural oxide film may be removed from the one surface 1a of the silicon substrate 1.
Instead of the annealing treatment, the natural oxide film may be removed by etching the one surface 1a of the silicon substrate 1 with an etchant such as hydrofluoric acid (HF).

  Next, as shown in FIG. 1B, a carbon layer 2 is formed on one surface 1a of the silicon substrate 1 by a sputtering method (step S1 shown in FIG. 3).

  The melting point of the carbon layer 2 is 3000 ° C. or higher, which is higher than the melting point of the silicon substrate 1 (about 1400 ° C.). The carbon layer 2 may contain a component other than carbon as an impurity as long as it contains carbon as a main component. Examples of the carbon layer 2 include a layer made of amorphous carbon, graphite, diamond-like carbon (DLC), or the like.

  The layer formed on the one surface 1a of the silicon substrate 1 is not limited to the carbon layer 2 as long as it has a higher melting point than the melting point of the silicon substrate 1, and various layers can be used. An example is a tantalum carbide layer.

  In this embodiment, the carbon layer 2 is formed by forming an amorphous carbon layer on the one surface 1a of the silicon substrate 1 by a sputtering method using a carbon target. For example, the silicon substrate 1 is introduced into the film formation chamber, the inside of the film formation chamber is brought into a high vacuum state of about 3 mtorr, xenon gas is injected, the temperature of the silicon substrate 1 (substrate temperature) is heated to about 400 ° C., and sputter output Is set to about 5 kW.

  The film thickness of the carbon layer 2 is preferably about 100 nm to 300 nm, for example. Such a film thickness is preferable because, when an excimer laser, which will be described later, is used as a laser for heating the carbon layer 2, a portion on the one surface 1a side of the silicon substrate 1 is selectively used without directly heating the silicon substrate 1. This is because it can be easily melted. In the present embodiment, as shown in FIG. 4A, the film thickness of the carbon layer 2 is set to about 230 nm.

  Next, as shown in FIG. 1 (c), the carbon layer 2 is irradiated with a laser to heat the carbon layer 2, thereby melting the portion on the one surface 1a side of the silicon substrate 1, as shown in FIG. 2 (a). As described above, the portion on the one surface 1a side of the silicon substrate 1 has a waveform shape (step S2 shown in FIG. 3).

Specifically, the silicon substrate 1 on which the carbon layer 2 is formed is introduced into a vacuum chamber, and the inside of the vacuum chamber is depressurized to about 1 × 10 ⁻⁴ Pa. Further, the silicon substrate 1 is heated to raise the substrate temperature to 400 ° C. And the carbon layer 2 is irradiated with a laser under the state, and the carbon layer 2 is heated.

  In heating the carbon layer 2 with such a laser, the silicon substrate 1 can be directly heated without adjusting the silicon substrate 1 by directly adjusting the intensity of the laser in accordance with the film thickness of the carbon layer 2 or the like. The portion on the one surface 1a side is selectively heated. Specifically, the silicon substrate 1 side at the interface between the carbon layer 2 and the one surface 1a of the silicon substrate 1 is intensively heated.

  Note that “without directly heating the silicon substrate 1” means that the silicon substrate 1 is indirectly heated. That is, since the silicon substrate 1 and the carbon layer 2 are in contact with each other, if the temperature of the carbon layer 2 is increased by heating the carbon layer 2, the temperature of the portion on the one surface 1a side of the silicon substrate 1 is increased due to heat conduction. Then, the portion on the one surface 1a side of the silicon substrate 1 is indirectly heated. Such indirect heating functions in order to make a portion on the one surface 1a side of the silicon substrate 1 described later into a corrugated shape.

  Here, an excimer laser having a wavelength in the ultraviolet region is particularly preferably used as the laser. Specifically, a XeCl excimer laser with a wavelength of 308 nm, a KrF excimer laser with a wavelength of 248 nm, or the like is preferably used.

  If the carbon layer 2 is amorphous carbon other than diamond, graphite, or diamond-like carbon (DLC), there is an absorption region in the ultraviolet region. Therefore, the carbon layer 2 can be heated satisfactorily by using such an excimer laser.

  In the present embodiment, as described above, the film thickness of the carbon layer 2 is set to about 230 nm, and a XeCl excimer laser having a wavelength of 308 nm is used as the laser.

The light irradiation time of the XeCl excimer laser is set to a sufficiently short time because excessive heating may cause melting of the entire silicon substrate 1. Specifically, it is about several nanoseconds (10 ⁻⁹ seconds) to several hundred nanoseconds. By setting such a light irradiation time, there is no possibility of melting the entire silicon substrate 1. In this embodiment, the light irradiation time of the XeCl excimer laser is set to about 180 nanoseconds.

  By performing laser irradiation for such a time, the silicon substrate 1 side at the interface between the carbon layer 2 and the silicon substrate 1 is selectively heated, and the portion on the one surface 1a side of the silicon substrate 1 is heated above the melting point of silicon. It becomes possible to do.

  When the carbon layer 2 is irradiated with the XeCl excimer laser under the above conditions, since the wavelength of the XeCl excimer laser is sufficiently short as 308 nm, most of the irradiation energy is absorbed by the carbon layer 2 made of amorphous carbon.

  Then, since the melting point of amorphous carbon is sufficiently high (melting point of graphite is 3550 ° C.), even if XeCl excimer laser is irradiated with high intensity, the carbon layer 2 is sufficiently heated without causing laser ablation. The The heating temperature of the carbon layer 2 by the XeCl excimer laser is preferably about 2000 ° C., for example.

In order to realize such a heating temperature, the energy density of the XeCl excimer laser, preferably below 0.2 J / cm ² or more 2.0 J / cm ^2. When the energy density is less than 0.2 J / cm ² , it becomes difficult to melt the portion on the one side 1a side of the silicon substrate 1. On the other hand, if it exceeds 2.0 J / cm ² , there is a possibility of vaporization exceeding the boiling point of silicon (2300 ° C. or higher), and it becomes difficult to form a regular corrugated portion on the one surface 1a side of the silicon substrate 1. Because. In this embodiment, the energy density of the XeCl excimer laser is set to about 1.0 J / cm ² .

  By irradiating the XeCl excimer laser with such an energy density, the portion on the one surface 1a side of the silicon substrate 1 is selectively melted, and the portion on the one surface 1a side of the silicon substrate 1 as shown in FIG. Can have a smooth corrugated shape with no sharp corners on the surface. The carbon layer 2 becomes a corrugated carbon layer 2 </ b> A following the corrugated portion 1 b of the silicon substrate 1.

  Next, as shown in FIG. 2B, the corrugated carbon layer 2A is removed to expose a portion of the silicon substrate 1 on the one surface 1a side (a portion 1b having a corrugated shape) (step S3 shown in FIG. 3). ).

  The removal of the carbon layer 2A is performed by, for example, an ashing process using oxygen plasma. As a result, as shown in FIG. 4C, the exposed portion of the silicon substrate 1 on the one surface 1a side has a smooth waveform with no acute angle portion on the surface.

  Next, as shown in FIG. 2C, a semiconductor element such as a transistor including the exposed portion of the silicon substrate 1 on the one surface 1a side (corrugated portion 1b) is formed (step S4 shown in FIG. 3). ).

  The semiconductor element is formed by a conventionally known method. For example, the gate insulating film 3 is formed on the corrugated portion 1 b of the silicon substrate 1, and then the gate electrode 4 is formed on the gate insulating film 3. Here, the bottom surface of the gate electrode 4 is formed along the corrugated portion 1 b of the silicon substrate 1 through the gate insulating film 3. Next, a source region and a drain region (region 6) are formed using the gate electrode 4 as a mask. Here, the lower portion of the gate electrode 4 becomes a channel region 7 having a smooth waveform surface.

Next, an interlayer insulating film 5 is formed on the gate electrode 4. Then, although not shown, contact holes that expose the source region and the drain region (region 6) are formed in the interlayer insulating film 5, and a source wiring and a drain wiring are formed in each contact hole.
Through the above steps, the semiconductor device according to the present embodiment is obtained.

  According to the method for manufacturing a semiconductor device described above, the portion on the one surface 1a side of the silicon substrate 1 is selectively adjusted by appropriately adjusting the wavelength, intensity, etc. of the laser without directly heating the silicon substrate 1. Can be melted. Moreover, evaporation of the silicon substrate 1 can be avoided by not directly heating the silicon substrate 1. The corrugated shape formed by melting the portion on the one surface 1a side of the silicon substrate 1 in this way is a smooth corrugated shape having no acute angle portion on the surface. Therefore, it is possible to suppress local concentration of the electric field on the corrugated portion 1b of the silicon substrate 1. Thereby, gate leakage current (current flowing from the silicon substrate side toward the gate electrode) can be suppressed. Further, since the portion on the one surface 1a side of the silicon substrate 1 has a wave shape, the channel region 7 of the semiconductor element can be increased. Therefore, it is possible to improve the driving capability of the semiconductor element and suppress deterioration of the element characteristics.

  In addition, since the photo process and the etching process are unnecessary in the step S2 in which the portion on the one surface 1a side of the silicon substrate 1 is corrugated, the manufacturing process can be shortened and the manufacturing cost can be kept low.

  Further, since the silicon substrate 1 is used as the substrate, the portion on the one surface 1a side of the silicon substrate 1 is melted and the molten silicon is deposited and expanded in step S2 in which the portion on one surface side of the silicon substrate is corrugated. Later, it can be recrystallized. Thereby, it can suppress that a crystal defect arises in the part by the side of the one surface 1a of the silicon substrate 1. FIG. Therefore, generation of leakage current (junction leakage current) generated between the source region and the silicon substrate or between the drain region and the silicon substrate can be suppressed.

  Further, since the carbon layer 2 is used as a layer, the melting point of the carbon layer 2 can be markedly higher than the melting point of the silicon substrate 1. For this reason, it becomes easy to selectively melt the portion on the one surface 1a side of the silicon substrate 1.

  Further, since a XeCl excimer laser is used as the laser, most of the irradiation energy is absorbed by the carbon layer 2 and becomes heat. Therefore, the carbon layer 2 can be heated to a sufficiently high temperature.

Further, in the step S2 in which the part on the one surface 1a side of the silicon substrate 1 is wave-shaped, the energy density of the XeCl excimer laser is set to about 1.0 J / cm ^2, so that the part on the one surface 1a side of the silicon substrate 1 is changed. It can be reliably melted. Therefore, the part on the one surface 1a side of the silicon substrate 1 can be formed into a regular corrugated shape.

  In this embodiment, a single crystal silicon substrate is used as the substrate of the present invention. However, a single crystal silicon film may be formed on a substrate made of, for example, quartz.

DESCRIPTION OF SYMBOLS 1 ... Silicon substrate (substrate), 1a ... One surface of silicon substrate (one surface of substrate), 1b ... Wave-shaped portion, 2 ... Carbon layer (layer), 2A ... Wave-shaped carbon layer (layer)

Claims (5)

Forming a layer having a higher melting point than the substrate on one surface of the substrate;
Irradiating the layer with a laser and heating the layer to melt a portion on one side of the substrate, and forming a portion on the one side of the substrate into a corrugated shape;
Removing the layer to expose a portion of one side of the substrate;
Forming a semiconductor element including a portion on one side of the exposed substrate;
A method of manufacturing a semiconductor device including:   The method for manufacturing a semiconductor device according to claim 1, wherein the substrate is a silicon substrate.   The method for manufacturing a semiconductor device according to claim 1, wherein the layer is a carbon layer or a tantalum carbide layer.   The method of manufacturing a semiconductor device according to claim 1, wherein the laser is an excimer laser. In the step of the waveform shape portion of the one surface of the silicon substrate, manufacturing a semiconductor device according to the energy density of the excimer laser, the 0.2 J / cm ² or more 2.0 J / cm ² according to claim 4, below Method.