JP6842841B2 - Ion implantation mask forming method and semiconductor device manufacturing method - Google Patents

Description

The present invention relates to a method for forming an ion implantation mask and a method for manufacturing a semiconductor device.

Most of the current power semiconductor devices are manufactured using semiconductor Si. In power semiconductor devices using Si, the performance limit due to the material properties of Si is approaching. When semiconductor SiC is used as the semiconductor material, it has withstand voltage characteristics, high saturated electron mobility, and high thermal conductivity that greatly exceed those of semiconductor Si. Therefore, the performance of power semiconductor devices is improved, the loss is reduced, and the device cooling mechanism is used. Since it is possible to reduce the size of the system by simplifying the above, it is promising as a next-generation power semiconductor material.

For the manufacture of SiC power devices, it is necessary to inject ions into desired portions of SiC to dope carriers. In ion doping to SiC, the diffusion coefficient of the dopant of SiC is small and it is difficult to apply the thermal diffusion method. Therefore, the doping method by ion implantation is widely used.

In the step of reducing the resistance of SiC by ion implantation, it is necessary to perform high-dose ion implantation. However, when high-concentration ion implantation is performed at room temperature, SiC is amorphized, so that the expected device performance cannot be obtained. Further, it is difficult to restore the once amorphized SiC to the same polymorphic structure having the same crystallinity as before ion implantation by heat firing or the like.

Therefore, by keeping the base material at a high temperature of 200 ° C. or higher in the ion implantation step into SiC, the crystallinity of the base material is restored at the same time as the ion implantation, and the deterioration of the electrical characteristics of the device is prevented. The law is known.

In the above high-temperature ion implantation method, since ion implantation is performed at a high temperature of 200 ° C. or higher, a photoresist material used for ion implantation at room temperature, such as ion implantation into silicon, as a mask layer for ion implantation, for example, a chemically amplified type. Photoresist cannot be used.

Therefore, in the above-mentioned high-temperature ion implantation method, as a mask for ion implantation, _{an inorganic film such as SiO 2} having sufficient heat resistance at the substrate temperature of the ion implantation step, for example, Chemical Vapor Deposition (CVD). ) And the like, it has been proposed to use an inorganic film such as _{SiO 2 (for example, Patent Document 1).} By pre-patterning such a heat-resistant ion implantation mask on the semiconductor SiC, carrier doping can be performed on a desired region in the semiconductor SiC through the opening of the ion implantation mask.

A dry process such as a wet etching method or a reactive ion etching method (RIE) using a photoresist as a mask is used for patterning such a heat-resistant ion implantation mask.

An example of the above-mentioned ion implantation mask forming step and ion implantation step will be described with reference to FIG.

First, a SiC base material (2) having a SiC epitaxial film (1) is provided (FIG. 2 (a)), and a SiO ₂ film (3) is deposited on the SiC epitaxial film (1) by a CVD method or the like. (Fig. 2 (b)). Next, a _{photosensitive resist (4) is formed on the SiO 2} film (3) (FIG. 2 (c)). After that, patterning exposure and development, which are normal photolithography steps, are performed to form a pattern of the photosensitive resist (FIG. 2 (d)). _{Then, the SiO 2} film is removed with hydrofluoric acid or the like _{to obtain a desired SiO 2} film pattern having the mask pattern opening (12) (FIG. 2 (e)). Next, the _{photosensitive resist is peeled off by O 2} ashing (FIG. 2 (f)). Then, using a beam of dopant ions (7), ion implantation is performed at a high temperature of 200 ° C. or higher to form an ion implantation region (6) (FIG. 2 (g)), and hydrofluoric acid or the like is used. _{The SiO 2} film is peeled off by the wet process (FIG. 2 (h)).

Since this ion implantation process has a large number of steps, is complicated and is a high-cost process, simplification of the process is required.

In order to simplify the process, a method of ion implantation at room temperature using a chemically amplified photoresist as an ion implantation mask has been proposed (for example, Patent Document 2).

Further, in order to simplify the process, a siloxane-containing photoresist firing pattern formed by patterning a siloxane-containing photoresist and then firing it is used as an ion implantation mask to generate ions at a high temperature such as 400 ° C. A method of implanting has been proposed (for example, Patent Document 3).

Further, as a method of simply forming the ion implantation mask layer by omitting the vacuum process and the step of patterning exposure on the substrate or the substrate, a solution in which the ion implantation mask material is dissolved is used by an inkjet method. A method of obtaining a mask pattern for ion implantation by patterning on a substrate or a substrate has been proposed (for example, Patent Document 4).

In order to solve the problem of charge-up generated in the substrate and the ion implantation mask, a low-energy secondary ion shower having a polarity opposite to that of the implanted ion is supplied to the substrate surface to supply the substrate. (For example, Patent Document 5), a method of pre-coating an insulating ion implantation mask with a conductive antistatic film such as a metal film or a doped semiconductor film when ion implantation is performed. A method to be used (for example, Patent Document 6) is known.

Further, for the purpose of improving the performance of the ion implantation mask as an ion blocking layer, a method of using a metal thin film such as titanium or molybdenum, which has a high density and high ion shielding performance, as an ion implantation mask has been proposed (for example). Patent Document 7).

Japanese Unexamined Patent Publication No. 2006-324585 Japanese Unexamined Patent Publication No. 2008-108869 International Publication No. 2013/0997785 International Publication No. 2001/011426 Japanese Unexamined Patent Publication No. 6-295700 Japanese Unexamined Patent Publication No. 7-58053 Japanese Unexamined Patent Publication No. 2007-42803

The method described in Patent Document 1 in which a SiO ₂ film grown by a CVD method is used as an ion implantation mask has excellent heat resistance and allows ion implantation at a high temperature, but the formation of the _{SiO 2 film is complicated.} It is expensive because it uses a flexible CVD method. Further, since the photolithography method is used for a complicated process for patterning the SiO ₂ film, a complicated process such as patterning exposure and a developing process is required, which is costly.

The method of using a chemically amplified photoresist as an ion implantation mask described in Patent Document 2 has a problem that a high temperature ion implantation process cannot be applied because of its low heat resistance. In addition, it is expensive because it requires complicated processes such as patterning exposure and development process.

The method described in Patent Document 3 in which a patterned siloxane-containing photoresist is used as an ion implantation mask has high heat resistance, so that a high-temperature ion implantation process can be applied. It is expensive because it requires a complicated process such as a firing process.

The method of forming an ion implantation mask layer on a substrate or a substrate by an inkjet method described in Patent Document 4 is a process-saving process because it does not include a vacuum process or a step of patterning exposure on the substrate or the substrate. However, the pattern resolution that can be reached by the inkjet method is 50 μm to 100 μm at the highest, which is insufficient for forming a SiC power device.

The present invention has been made in view of the above background, and in particular, it has high temperature heat resistance and conductivity, and there is no concern that metal impurities are generated in the semiconductor substrate, and the resolution is as high as 1 μm. Provided is a semiconductor device manufacturing method capable of forming a mask pattern for ion implantation and being applicable to a high temperature ion implantation process at low cost.

In response to the above problems, the inventors of the present invention came up with the following invention.

<1> A method for forming an ion implantation mask having an opening on a semiconductor layer or a base material, which comprises at least the following steps:
(A) A particle film is formed by applying particles and a particle dispersion containing at least a dispersion medium to the entire surface or a part of the semiconductor layer or the base material directly or via a transfer base material. Steps; and (b) A step of forming the opening by irradiating a part of the particle film with light and removing the light-irradiated portion of the particle film.
<2> The method according to the above item <1>, wherein the light irradiation is laser irradiation.
<3> The method according to the above <1> or <2>, wherein the ion implantation mask contains particles and a heat-resistant binder.
<4> The method according to any one of the above items <1> to <3>, wherein the sheet resistance of the ion implantation mask is 10 ^{12 Ω / □ or less.}
<5> The method according to any one of <1> to <4> above, wherein the particle dispersion contains a heat-resistant binder-forming component.
<6> The method according to item <5> above, wherein the heat-resistant binder-forming component is siloxane.
<7> The method according to any one of <1> to <6> above, wherein the particle dispersion further contains a temporary binder-forming component.
<8> The method according to <7> above, wherein the temporary binder forming component is a polymer.
<9> The particles are conductive and / or semiconductor particles, and / or the resistivity of the material of the conductive and / or semiconductor particles is 1 × 10 ³ Ωcm or less.
The method according to any one of the above items <1> to <8>.
<10> The method according to item <9> above, wherein the particles are silicon particles.
<11> The method according to <10> above, wherein the silicon particles contain boron or phosphorus as a dopant.
<12> The method according to any one of the above items <1> to <11>, wherein the proportion of the particles in the particle dispersion is in the range of 1% by weight to 90% by weight.
^{<13> When Al +} ions having a kinetic energy of 40 keV are incident on the particle film of the ion implantation mask at a number density of 1 × 10 ¹⁴ cm- ^{2 , Al +} ions passing through the particle film are incident. The method according to any one of the above items <1> to <12>, wherein the number of ions is 1% or less.
<14> A semiconductor device including a step of implanting ions into the semiconductor layer or a base material through an opening of an ion implantation mask formed by the method according to any one of the above items <1> to <13>. Manufacturing method.

The method of the present invention for forming an ion-implanted mask enables the formation of an ion-implanted mask layer having high heat resistance and conductivity. Further, in particular, since the method of the present invention for forming an ion implantation mask forms a pattern by light irradiation, the ion implantation mask can be formed with high productivity and low cost as compared with the conventional method.

FIG. 1 is a schematic diagram of the ion implantation process in the present invention. FIG. 2 is a schematic diagram of the ion implantation process in the prior art.

<< Dispersion for forming mask for ion implantation >>
The dispersion for forming a mask for ion implantation of the present invention contains a dispersion medium and particles dispersed in the dispersion medium.

<particle>
From the viewpoint of stabilizing the pattern shape in the ion implantation step, the particles used in the present invention are preferably particles of a material having a melting point exceeding the temperature of the semiconductor layer or the substrate in the ion implantation step.

Therefore, for example, as the particles used in the present invention, particles of a material having a melting point of, for example, 400 ° C. or higher, 600 ° C. or higher, 800 ° C. or higher, 1000 ° C. or higher, 1200 ° C. or higher, 1500 ° C. or higher can be used.

The average primary particle size of the particles used in the present invention can be 500 nm or less, 200 nm or less, 100 nm or less, 50 nm or less, 20 nm or less, or 5 nm or less. Further, the primary particle size of the particles used in the present invention can be 0.1 nm or more, or 1 nm or more.

The average primary particle size of the particles used in the present invention is preferably 200 nm or less, 100 nm or less, 50 nm or less, 20 nm or less, or 5 nm or less in order to reduce pattern distortion due to the particle size of the particles. ..

Here, in the present invention, the average primary particle diameter of the particles is the diameter equivalent to the projected area circle directly based on the image taken by observation with a scanning electron microscope (SEM), a transmission electron microscope (TEM), or the like. By measuring and analyzing a particle group consisting of 100 or more aggregates, it can be obtained as a number average primary particle diameter.

As the particles used in the present invention, a single type of particles may be used, or two or more types of particles may be used in combination.

When high-density ion implantation is performed on a semiconductor covered with an insulator film such as an ion implantation mask, the charge-up generated in the substrate and the ion implantation mask becomes a problem. When the substrate and the ion implantation mask are charged during the ion implantation process, a potential difference occurs between the ion-implanted region in the semiconductor, the insulator such as the ion implantation mask, and the semiconductor substrate, and a discharge phenomenon occurs. Sometimes. In addition, the spatial electric field generated by charging may cause non-uniformity of the injected ion density. Due to such a cause, it is known that when high-density ion implantation is performed into a semiconductor covered with an insulator film, the performance and yield of the semiconductor device are deteriorated. This charging phenomenon is particularly remarkable when the semiconductor surface is covered with an insulator film such as _{SiO 2.}

Therefore, from the viewpoint of imparting conductivity to the ion implantation mask and solving the problem of charging, it is preferable to use particles of conductive and / or semiconductor material as the particles used in the present invention.

The conductive and / or semiconductor material forms an ion-implanted mask by the method of the present invention, and when ion-implanted, the semiconductor layer or substrate and the ion-implanted mask are charged (charge-up). The mask can be selected to have sufficient conductivity to suppress.

Specifically, the conductive and / or semiconductor material includes, for example, 1 × 10 ¹² Ωm or less, 1 × 10 ⁹ Ωm or less, 1 × 10 ⁶ Ωm or less, 1 × 10 ³ Ωm or less, 1 Ωm or less, 1 ×. Materials having a resistivity of 10 ^-3 Ωm or less or 1 × 10 ^-6 Ωm or less can be selected.

Of these, from the viewpoint of preventing charge even in a high-throughput ion implantation step performed at a high beam density of 100 mA class, the conductive and / or semiconductor material is preferably 1 × 10 ³ Ωm or less, more preferably. Can be selected from materials having a resistivity of 1 Ωm or less, more preferably 1 × 10 ^-3 Ωm or less, and particularly preferably 1 × 10 ^{-6 Ωm or less.}

Further, in the conductive and / or semiconductor material, when an ion implantation mask layer formed of a particle film having a thickness of 0.5 μm is obtained, the sheet resistance of the ion implantation mask layer is 10 ¹² Ω / □. Hereinafter, it can be selected to be ^{10 11} Ω / □ or less, or 10 ^{10 Ω / □ or less.}

As the particles used in the present invention, particles of metal, metalloid, or a combination thereof may be used. Here, examples of the metalloid include silicon and germanium.

In the step of heating the semiconductor layer or the base material to a high temperature and performing ion implantation, it is more preferable to use particles of the semiconductor material in order to prevent contamination of the semiconductor layer or the base material by metal impurities.

Therefore, for example, the particles used in the present invention are silicon (Si), germanium (Ge), diamond (C), silicon carbide (SiC), silicon germanium (SiGe), gallium arsenide (GaN), indium phosphate (InP). , Gallium arsenide (GaAs), cadmium sulfide (CdS), zinc selenium (ZnSe), zinc oxide (ZnO) and other semiconductor material particles.

The particles of the semiconductor material, especially the silicon particles, may be pre-doped with an impurity dopant and thereby have favorable conductivity.

The particles of the semiconductor material in this case, particularly silicon particles, may contain at least one element of Group 13 and Group 15 elements as a dopant. That is, the dopant may be p-type or n-type, and for example, boron (B), aluminum (Al), gallium (Ga), indium (In), titanium (Ti), iron (Fe), and the like. The dopant may contain a dopant selected from the group consisting of phosphorus (P), arsenic (As), antimony (Sb), or a combination thereof, such as boron or phosphorus.

In particular, when the silicon particles contain boron as a dopant, boron provides preferable conductivity to the silicon particles, but in the ion implantation step, boron is difficult to move from the silicon particles to the semiconductor substrate. preferable.

The concentration of the dopant in the semiconductor particles, particularly the silicon particles, may be 10 ¹⁸ atoms / cm ³ or more, 10 ¹⁹ atoms / cm ³ or more, or 10 ²⁰ atoms / cm ³ or more.

In the step of heating the semiconductor layer or the base material to a high temperature and performing ion implantation, in order to prevent the semiconductor layer or the base material from being contaminated by metal impurities, the concentrations of the metal impurities contained in the semiconductor particles are 100 ppb or less and 50 ppb or less, respectively. Semiconductor particles of 20 ppb or 10 ppb or less can be used. Here, when the semiconductor is a compound semiconductor containing a metal as a constituent element, the "metal impurity" means a metal other than the metal constituting the semiconductor.

The particles used in the present invention can be used at any concentration within a range in which an ion implantation mask can be formed. For example, the particles used in the present invention may be 5% by weight or more, 10% by weight or more, 15% by weight or more, or 20% by weight or more with respect to the dispersion. Further, the particles used in the present invention are 95% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less with respect to the dispersion. , Or 30% by weight or less.

By setting the density of the particles to the above-mentioned concentration, it is possible to provide a dispersion having a viscosity suitable for patterning by a printing method. Further, within the above concentration range, it is possible to form an ion implantation mask pattern having sufficient ion implantation ability in the ion implantation step by printing the dispersion.

<Dispersion medium>
The dispersion of the present invention contains a dispersion medium. The type of dispersion medium is not particularly limited, but it is preferable to select a dispersion medium capable of uniformly dispersing the particles used in the present invention. Further, it is preferable that the dispersion medium dissolves other optional components contained in the dispersion, for example, a heat-resistant binder-forming component.

The boiling point of the dispersion medium contained in the dispersion of the present invention under atmospheric pressure is preferably 100 ° C. to 400 ° C. By selecting a dispersion medium having a boiling point of 100 ° C. or higher, the dispersion medium evaporates at an appropriate rate during film formation of the dispersion, and a uniform film can be obtained. Further, by selecting a dispersion medium having a boiling point of 400 ° C. or lower, it is possible to reduce the amount of the dispersion medium remaining in the dispersion film after the dispersion film is formed, so that cracks and surfaces due to film shrinkage during firing can be reduced. It is possible to suppress a decrease in flatness.

As a specific dispersion medium, an organic dispersion medium that does not react with the particles used in the present invention can be used. Specifically, this dispersion medium is a non-aqueous dispersion medium such as alcohol, alkane, alkene, alkyne, ketone, ether, ester, aromatic compound, or nitrogen-containing ring compound, particularly isopropyl alcohol (IPA), N-methyl-. It may be 2-pyrrolidone (NMP), terpineol or the like. Further, as the alcohol, glycol (divalent alcohol) such as propylene glycol and ethylene glycol can also be used. When the particles used in the present invention are metal and / or semiconductor particles, a dehydration dispersion medium is preferable in order to suppress the oxidation of these particles.

<Heat-resistant binder forming component>
The dispersion of the present invention may further contain a heat-resistant binder-forming component for the purpose of binding particles to each other to form a stable ion implantation mask.

Here, with respect to the present invention, the heat-resistant binder forming component means a component capable of forming a stable binder in an atmosphere where ion implantation is performed using an ion implantation mask, for example, a reduced pressure atmosphere at a temperature of 400 ° C. The heat-resistant binder-forming component is preferably dissolved in the dispersion medium of the dispersion of the present invention in terms of uniformity, but may be dispersed without being dissolved. Further, this heat-resistant binder-forming component chemically changes during drying and / or firing of the film of the dispersion of the present invention to form a heat-resistant binder, but also chemically changes. Instead, only the shape may be changed to form a heat-resistant binder.

Such a heat-resistant binder-forming component is an organic binder-forming component that forms an organic binder such as a fluoropolymer, even if it is an inorganic binder-forming component that forms an inorganic binder such as silica, sodium phosphate, or sodium silicate. There may be. Examples of the inorganic binder forming component include a siloxane compound, sodium phosphate, sodium silicate and the like, and examples of the organic binder forming component include a fluoropolymer and the like.

When the heat-resistant binder-forming component is used, it is preferable to perform firing for the purpose of firing the heat-resistant binder-forming component after forming the layer of the dispersion. By firing, the particles constituting the ion implantation mask layer can be bound to each other to form a stable ion implantation mask. Further, by performing the firing, it is possible to prevent contamination in the ion implantation apparatus and a decrease in the degree of vacuum due to the gas released from the ion implantation mask in the ion implantation step.

When the heat-resistant binder is a material that is dissolved by an acid or the like, for example, when the heat-resistant binder forming component is siloxane and a vitreous material as a heat-resistant binder is formed by firing the heat-resistant binder, ions are ion-implanted. By treating the implantation mask with an acid or the like, the removability of the ion implantation mask can be improved. Further, when the heat-resistant binder is a material that melts or decomposes by heating at a temperature higher than that of ion implantation, for example, when the heat-resistant binder is a fluoropolymer, the ion implantation mask is further heat-treated after ion implantation. Thereby, the removability of the ion implantation mask can be improved.

<Temporary binder forming component>
The dispersion of the present invention may further contain a temporary binder-forming component for the purpose of stably forming the pattern of the film of the dispersion to be formed.

Here, with respect to the present invention, the temporary binder forming component is for stably forming the particle film formed in the process of forming the ion implantation mask, and when forming the final ion implantation mask. It is removed by heating or the like. The temporary binder-forming component is preferably dissolved in the dispersion medium of the dispersion of the present invention in terms of uniformity, but may be dispersed without being dissolved. Further, even if this temporary binder forming component chemically changes when the film of the dispersion of the present invention is dried to form a temporary binder, the shape does not change chemically. Only may change to form a temporary binder.

Such a temporary binder-forming component may be an organic binder-forming component that forms an organic binder such as a polymer. Examples of the organic binder forming component include polymers such as ethyl cellulose.

When a temporary binder forming component is used, it is preferable to perform firing for the purpose of removing the temporary binder after the role of the temporary binder for stably forming and / or maintaining the particle film is completed. .. By temporarily removing the binder, it is possible to prevent contamination in the ion implantation apparatus and a decrease in the degree of vacuum due to the gas released from the ion implantation mask in the ion implantation step.

《Ion implantation mask》
The ion implantation mask of the present invention contains particles and an optional heat-resistant binder.

Examples of the particles contained in the ion implantation mask of the present invention and the optional heat-resistant binder include those described with respect to the dispersion of the present invention.

In the ion implantation mask of the present invention, when Al ⁺ ions having a kinetic energy of 40 keV are incident at a number density of 1 × 10 ¹⁴ cm- ^{2 , the Al +} ions passing through the dispersion film are the particles of the incident ions. It may be 1% or less of the number. Further, the sheet resistance of the ion implantation mask of the present invention may be 10 ¹² Ω / □ or less, 10 ¹¹ Ω / □ or less, or 10 ¹⁰ Ω / □ or less.

<< Method of forming a mask for ion implantation and method of manufacturing a semiconductor device >>
The method of the present invention for forming a mask for ion implantation applies a particle dispersion to a semiconductor layer or substrate by, for example, a coating method, directly or via a transfer substrate, and the particle film contained in the dispersion. After obtaining the particle film, the particle film is irradiated with light, particularly laser irradiation, to remove a part of the particle film, thereby forming a pattern of the particle film on the semiconductor layer or the base material. This method can further include a step of drying and / or firing the particle film formed on the semiconductor layer or the substrate and / or the particle film formed on the transfer substrate.

In addition, the method of the present invention for manufacturing a semiconductor device includes the following steps:
Forming an Ion Implantation Mask A step of forming an ion implantation mask on a semiconductor layer or a substrate by the method of the present invention, or a step of providing an ion implantation mask of the present invention on a semiconductor layer or a substrate.
A step of injecting ions into the semiconductor layer or the base material through the pattern opening of the ion implantation mask, and a step of removing the ion implantation mask.

An example of the method of the present invention for manufacturing a semiconductor device will be described below with reference to FIG.

First, as shown in FIG. 1 (a), a SiC substrate (2) having a SiC epitaxial film (1) is provided, and as shown in FIG. 1 (b), with particles contained in the particle dispersion. The formed particle film (11) is formed on the epitaxial film (1) of the SiC substrate by an arbitrary method. By performing light irradiation (5) on an arbitrary portion of the particle film, the particle film of the portion irradiated with light is removed and the particle film is patterned to obtain a mask for ion implantation. According to this, as shown in FIG. 1 (c), an ion implantation mask having a mask pattern opening (12) is formed on the SiC substrate (2) having the SiC epitaxial film (1).

Then, after an optional step of drying and firing the particle film, as shown in FIG. 1 (d), a dopant is passed through the mask pattern opening (12) of the ion implantation mask (11) using an ion implantation device. The ion implantation region (6) is formed by implanting ions into the SiC epitaxial film (1) on the surface of the SiC substrate (2) with the ion beam (7). At this time, the ion-implanted semiconductor layer or substrate can be heated to a temperature of 200 ° C. or higher to perform the ion implantation step.

Then, as shown in FIG. 1 (e), the ion implantation mask (11) can be removed by means such as immersion in a soluble chemical solution.

<Semiconductor layer or base material>
As the semiconductor layer or base material, any semiconductor layer or base material intended to diffuse the dopant can be used.

Therefore, as the semiconductor layer or the base material, silicon (Si), germanium (Ge), diamond (C), silicon carbide (SiC), silicon germanium (SiGe), gallium arsenide (GaN), indium phosphate (InP), Examples include, but are not limited to, gallium arsenide (GaAs), cadmium sulfide (CdS), zinc selenium (ZnSe), zinc oxide (ZnO), and in particular silicon carbide (SiC).

Further, the semiconductor layer or the base material may be composed of a single layer, or may be a laminate composed of two or more types of layers including one or more semiconductor layers.

The semiconductor layer or base material may be a semiconductor layer or base material having an impurity dopant of 10 ¹⁶ cm ^-3 or less, and may be pre-doped with ^{an impurity dopant to a concentration of more than 10 16} cm ^-3.

A metal film or a metal wiring pattern may be formed in advance on the semiconductor layer or the base material.

<Method of forming a mask for ion implantation>
In the method of the present invention for forming an ion implantation mask, the particle dispersion is applied to the semiconductor layer or the substrate by, for example, a coating method, directly or via a transfer substrate, and then light irradiation is performed on the particle membrane. This includes a step of removing the dispersion particles and forming a pattern of the particle film on the semiconductor layer or the base material.

<Particle film formation process>
The step of forming the particle film composed of the particles contained in the dispersion on the semiconductor layer or the base material shall be performed by any means capable of forming the film on the semiconductor layer or the base material. Can be done. Examples of such means include spin coating method, gravure offset coating method, inkjet method, screen-in printing method, slit die coating method, screen printing method, gravure printing method, gravure offset printing, flat plate offset printing, and flat plate printing method. Examples include a resin offset printing method, a flexo printing method, and a microcontact printing method. Further, as such a means, a laminating method or the like in which a particle film formed in advance on another base material by an arbitrary method is transferred onto a semiconductor base material can be mentioned. However, as such a means, any method not limited to these can be selected.

Among the above methods, from the viewpoint of efficiently manufacturing the semiconductor device, it is preferable to use a method capable of forming the particle film at an arbitrary position on the semiconductor layer or the base material. Examples of such means include a screen printing method, a gravure printing method, a gravure offset printing, a flat plate offset printing, a lithographic printing method, a resin letterpress printing method, a flexo printing method, a microcontact printing method, and the like. Any method that is not limited can be selected.

According to the method of forming the particle film at an arbitrary position on the semiconductor layer or the base material, the area to be irradiated with light can be reduced in the step of forming the pattern of the particle film by light irradiation, so that the semiconductor device can be used. There is an advantage that manufacturing can be performed efficiently.

A transfer substrate, a semiconductor substrate, or a semiconductor layer having a patterned particle film or a particle film before patterning can be heated for the purpose of removing the dispersion medium contained in the particle film. As a method for removing the dispersion medium by heating, an oven, a hot plate, an infrared ray, or any other method capable of heating can be used.

When the particle dispersion contains a heat-resistant or temporary binder-forming material, the binder-forming material forms a binder at the heating temperature of the transfer base material, the semiconductor substrate, or the semiconductor layer, and exhibits its binding performance. It can be a temperature that can be achieved.

When the particle dispersion contains a heat-resistant binder-forming material, the step of heating the semiconductor layer or the base material to a temperature at which the above-mentioned heat-resistant binder-forming material forms a binder and exhibits its binding performance is performed. , The particle film may be formed after the step of forming the particle film on the semiconductor layer or the base material, or may be carried out after the patterning step of irradiating the dispersion particles with light.

<Process of forming a mask for ion implantation by patterning a particle film>
Then, by irradiating an arbitrary portion of the particle film with light, the particle film of the portion irradiated with light is removed. According to this, the ion implantation mask forming step does not have to contain a difficult-to-handle component such as a photosensitive resin that has been used for conventional patterning, and has been used for conventional patterning. It is not necessary to include a complicated and expensive process such as a photolithography method.

By irradiating an arbitrary part of the particle film with light, the light-irradiated part of the film is removed to pattern the semiconductor particle film and form an ion implantation mask. Examples of the light irradiation means at this time include, but are not limited to, laser processing, flash lamp processing through a photomask, maser processing, and the like, and any method can be selected.

Among these means, from the viewpoint of performing high-resolution patterning used in the production of power semiconductors, it is preferable to use a method capable of patterning at a resolution of 10 μm or less, such as laser processing.

The laser light source used for laser processing is not particularly limited, but a laser light source that emits a wavelength in which the particles constituting the ion implantation mask have absorption can be preferably used. When, for example, silicon particles are used as the particles contained in the dispersion, the wavelength of the laser light source may be, for example, 1500 nm or less, 1200 nm or less, 600 nm or less, or 550 nm or less, and 100 nm or more, 200 nm or more. , Or 350 nm or more.

The focusing diameter of the laser light source used for laser processing can be 10,000 μm or less, 1000 μm or less, 100 μm or less, 50 μm or less, 20 μm or less, 10 μm or less, 5 μm or less, 2 μm or less, and 1 μm or less. Further, from the viewpoint of improving the efficiency of the semiconductor manufacturing process, a plurality of laser light sources having different focusing diameters can be used in combination.

The energy density of the laser light used for laser processing is, for example, 1 mJ / cm ² or more, 10 mJ / cm ² or more, 50 mJ / cm ² or more, or 100 mJ / cm ² or more when a laser light having a wavelength of 532 nm is used as a laser light source. It may be 100 J / cm ² or less, 10 J / cm ² or less, 1 J / cm ² or less, 500 mJ / cm ² or less, 300 mJ / cm ² or less, but preferably 0.1 to 10 J / cm. It can be in the range of ^2. Within the above range, there is an advantage that a particle film composed of semiconductor particles or the like can be patterned to form an ion implantation mask while minimizing damage to the semiconductor layer or the base material.

(Film thickness of ion implantation mask)
Any thickness can be selected for the film thickness of the particle film constituting the ion implantation mask. The film thickness varies depending on the composition of the dispersion, printing conditions, printing method, and the like, but for example, the film can be applied so that the film thickness of the particle film is 0.1 μm to 100 μm.

From the viewpoint of using the patterned particle film as a mask layer for ion implantation, it is preferable that the film thickness is sufficient as a mask layer for ion implantation. Therefore, for example, considering factors that affect the penetration length of ion implantation, such as the temperature of the SiC substrate, the acceleration voltage of ions, and the dopant ion species during ion implantation, the obtained ion implantation mask is sufficient for ions. The film thickness of the particle film can be selected so that the film thickness has a stopping power.

<Baking for the purpose of temporarily removing the binder>
When the particle composition contains a temporary binder, the semiconductor substrate or the semiconductor layer can be heated to a temperature at which the temporary binder can be removed for the purpose of removing the temporary binder.

<Ion implantation process>
In the method of the present invention, ions are then implanted into the semiconductor layer or substrate through the pattern opening of the ion implantation mask.

The ion implantation mask is preferably applied to the manufacturing process of a semiconductor device including ion implantation into a SiC layer or a substrate having an ion implantation temperature of 200 to 1000 ° C. The ion implantation temperature is 200 ° C. or higher, 250 ° C. or higher, 300 ° C. or higher, or 350 ° C. or higher, and the temperature is 1000 ° C. or lower, 800 ° C. or lower, 700 ° C. or lower, 600 ° C. or lower, or 500 ° C. or lower. is there.

When the semiconductor layer or the base material is a SiC layer or a base material, when the ion implantation temperature is lower than 200 ° C., the implantation layer becomes continuously amorphous, and good recrystallization proceeds even if high temperature annealing is performed. However, there is a concern that a low resistance layer cannot be formed. Further, in this case, if the ion implantation temperature is higher than 1000 ° C., thermal oxidation of SiC and step bunching occur, so that it is necessary to remove those portions after the ion implantation.

The resolution when forming the ion implantation mask by the method of the present invention is preferably 7 μm or less, more preferably 5 μm or less, still more preferably 3 μm or less, and particularly preferably 1 μm or less.

<Ion implantation mask removal process>
The ion implantation mask is removed after the ion implantation step. Examples of the removing method include, but are not limited to, a wet process using hydrofluoric acid, buffered hydrofluoric acid, hydrofluoric acid, TMAH, or the like, and a dry process such as plasma treatment. The wet process is preferred from the standpoint of low cost.

<< Examples 1 to 5 >>
In Examples 1 to 5 below, a dispersion medium and a particle dispersion containing particles dispersed in the dispersion medium are prepared, and a particle film is formed on the SiC substrate by using a screen printing method. After removing the dispersion medium by heating, a pattern of an ion implantation mask was formed by irradiating a part of the particle film with light. In addition, regarding these Examples and Comparative Examples, the possibility of pattern formation of the particle film, the presence or absence of problems due to charging during ion implantation, and the ion shielding performance of the particle film were evaluated.

<Example 1>
(Preparation of boron (B) -doped silicon particles)
Silicon nanoparticles were produced by a laser pyrolysis (LP: Laser pyrolysis) method using a carbon dioxide laser using monosilane gas as a raw material. At this time, diborane (B ₂ H ₆ ) gas was introduced together with monosilane gas to obtain boron-doped silicon particles. The doping concentration of the obtained boron-doped silicon particles was 1 × 10 ²¹ atom / cm ³ . Moreover, when the metal impurity content of the obtained boron-doped silicon particles was measured using an inductively coupled plasma mass spectrometer (ICP-MS), the Fe content was 15 ppb, the Cu content was 18 ppb, and the Ni content. The amount was 10 ppb, the Cr content was 21 ppb, the Co content was 13 ppb, the Na content was 20 ppb, and the Ca content was 10 ppb.

(Preparation of boron-doped silicon particle-containing dispersion)
A boron-doped silicon particle-containing dispersion was prepared by mixing 90% by weight of propylene glycol and 10% by weight of silicon nanoparticles prepared by the above method.

(Formation of boron-doped silicon particle film)
The boron-doped silicon particle-containing dispersion was printed on a SiC substrate by a screen printing method to obtain a boron-doped silicon particle film having a thickness of 1.5 μm.

Then, the dispersion medium remaining on the boron-doped silicon particle film was removed by firing at 600 ° C.

(Formation of boron-doped silicon particle film pattern)
As a light source for light irradiation, the boron-doped silicon particle film is irradiated with laser light having ^{a wavelength of 532 nm, an energy density of 4.0 J / cm 2, and a pulse width of 100 ns.} The portion was removed to obtain a pattern of a boron-doped silicon particle film.

(Observation with an optical microscope)
The mask pattern for ion implantation was observed using an optical microscope to confirm whether or not a 5 μm line-and-space pattern could be formed.

(Ion implantation)
Ion implantation was performed on the SiC substrate through the mask pattern opening of the ion implantation mask under the following conditions:
Ion species: Al,
Energy amount: 40 keV,
Injection temperature: 400 ° C,
Amount of dose: 1 × 10 ¹⁴ Ions / cm ²

After the Al ion implantation, the substrate was immersed in a mixed solution of buffered hydrofluoric acid and concentrated nitric acid to remove the ion implantation mask. Then, the depth dependence of the Al concentration from the surface of the SiC substrate was measured using a secondary ion mass spectrometry (SIMS) apparatus.

SIMS measurement was performed on the surface of the SiC substrate in which the ion-implanted SiC substrate was covered with the particle film pattern at the time of Al ion implantation and the region was the opening of the ion-implanted mask. It was.

In the depth-dependent profile of Al ion concentration obtained by SIMS measurement, the Al ion concentration at a depth of 50 nm from the surface of the region covered with the particle film pattern at the time of Al ion implantation is ion implantation. The particle film pattern has the performance as an ion implantation mask layer when it is 1/100 times or less of the Al ion concentration at a depth of 50 nm from the surface of the SiC substrate in the region that was the opening of the mask. I decided.

<Example 2>
Instead of mixing 90% by weight of propylene glycol and 10% by weight of silicon nanoparticles as the dispersion, 90% by weight of propylene glycol, 5% by weight of silicon particles, and 5% by weight of an organic siloxane compound as a heat-resistant binder forming component were mixed. Except for this, a dispersion was prepared in the same manner as in Example 1 to obtain a particle film pattern. Further, as in Example 1, the possibility of forming the particle film pattern, the presence or absence of problems due to charging during ion implantation, and the ion shielding performance of the particle film pattern were evaluated.

<Example 3>
Instead of mixing 90% by weight of propylene glycol and 10% by weight of silicon nanoparticles as the dispersion, 90% by weight of propylene glycol, 5% by weight of silicon particles, and 5% by weight of ethyl cellulose as a temporary binder forming component were mixed.
The heating temperature for the purpose of removing the dispersion medium from the particle dispersion after the step of forming the dispersion particle film was set to 250 ° C.
Further, after patterning the dispersion particle film by laser light irradiation, a dispersion was prepared in the same manner as in Example 1 except that firing was performed in the air at 600 ° C. for the purpose of temporarily removing the binder. A particle film pattern was obtained.

Further, as in Example 1, the possibility of forming the particle film pattern, the presence or absence of problems due to charging during ion implantation, and the ion shielding performance of the particle film pattern were evaluated.

<Example 4>
A solution obtained by diluting spin-on glass (12000-T manufactured by Tokyo Ohka Co., Ltd.) with isopropyl alcohol is spin-coated on a SiC substrate, and the mixture is fired at 800 ° C. A particle film pattern was obtained in the same manner as in Example 1 except that the glass film was formed in advance. Further, as in Example 1, the possibility of forming the particle film pattern, the presence or absence of problems due to charging during ion implantation, and the ion shielding performance of the particle film pattern were evaluated.

<Example 5>
As a light source for light irradiation, instead of using laser light having a wavelength of 532 nm and an energy density of ^{4.0 J / cm 2 , the wavelength is 532 nm, the energy density is 0.5 J / cm 2} , and the pulse width is A dispersion was prepared in the same manner as in Example 1 except that 1.0 ns of laser light was used to obtain a particle film pattern. Further, as in Example 1, the possibility of forming the particle film pattern, the presence or absence of problems due to charging during ion implantation, and the ion shielding performance of the particle film pattern were evaluated.

<Example 6>
In Example 6, a dispersion medium and a particle dispersion containing particles dispersed in the dispersion medium are prepared, a particle film is formed on a glass substrate by a screen printing method, and the particles are heated. After removing the dispersion medium, a particle film pattern was formed by irradiating a part of the particle film with light, and the sheet resistance of the particle film pattern was measured.

Specifically, a dispersion was prepared in the same manner as in Example 1 except that a glass substrate was used instead of the SiC substrate as the substrate, and a particle film pattern was obtained. Therefore, the obtained particle film itself is substantially the same as the particle film obtained in Examples 1, 4 and 5 (the base materials are different). Then, through a shadow mask, an aluminum electrode for measuring the resistivity of the particle film pattern was formed on the pattern of the mask layer by a vacuum vapor deposition method.

As the pattern of the aluminum electrode for the purpose of measuring the resistivity, an electrode pattern in which the 1000 μm sides of a set of rectangular electrodes having a size of 1000 μm × 200 μm are arranged so as to face each other at an interval of 200 μm is used. There was.

After that, the sheet resistance of the mask layer was determined by measuring the potential drop between the aluminum electrodes when a constant current of 1 μA was applied between the vapor-deposited aluminum electrodes, and it was 20 GΩ / □.

The experimental conditions and results for Examples 1 to 5 are summarized in Table 1 below.

<Evaluation results>
From the results of Examples 1 to 5, it can be understood that the formed particle film pattern can be used as a mask layer for ion implantation without a problem of charging.

From the results of Examples 1 to 3, these binder-forming components are not used even by adding the heat-resistant binder-forming component (Example 2) or the temporary binder-forming component (Example 3) to the dispersion. As in the case of Example 1, it can be understood that the dispersion has preferable printability and the formed particle film pattern can be used as a mask layer for ion implantation without a problem of charging.

From the comparison of Examples 1 and 2, the shape stability of the finally obtained mask layer for ion implantation is improved by adding the heat-resistant binder forming component (Example 2) to the dispersion. Was observed. Further, from the comparison of Examples 1 and 3, by adding a temporary binder forming component (Example 3) to the dispersion, the shape stability of the particle layer in the patterning step of the particle film by laser irradiation is performed. Was observed to be improved.

From the results of Examples 1 and 4, the film of the dispersion is formed even when the peelability after ion implantation is improved by forming the release layer (Example 4) on the substrate in advance. It can be understood that the particle film pattern having preferable patterning property and formed can be used as a mask layer for ion implantation without a problem of charging.

From the comparison of Examples 1 and 4, it was observed that the removal of the ion implantation mask after Al ion implantation was promoted by forming the release layer (Example 4) on the substrate in advance. ..

From the results of Example 6, it can be understood that the formed particle film pattern has a sheet resistance that can be used as a mask layer for ion implantation without a problem of charging.

1 SiC epitaxial film 2 SiC base material 3 SiO ₂ film 4 photosensitive resist 5 laser light 6 ion implantation area 7 dopant ion beam 11 ion implantation mask / particle film 12 mask pattern opening

Claims (8)

A method of forming an ion implantation mask having an opening on a semiconductor layer or a base material, which comprises at least the following steps:
(A) Particles composed of only particles by applying the particles and a particle dispersion containing at least a dispersion medium to the entire surface or a part of the semiconductor layer or the base material directly or via a transfer base material. A step of forming the film; and (b) a step of forming the opening by irradiating a part of the particle film with a laser and removing the light-irradiated portion of the particle film by laser processing .
Here, the particles are silicon particles, and the silicon particles contain boron or phosphorus as a dopant . The method according to claim 1, wherein the sheet resistance of the ion implantation mask is 10 ¹² Ω / □ or less. The method according to claim 1 or 2 , wherein the particle dispersion further contains a temporary binder-forming component. The method according to claim 3 , wherein the temporary binder-forming component is a polymer. Resistivity of the particle element is 1 × 10 ³ Ωcm or less, The method according to any one of claims 1-4. The method according to any one of claims 1 to 5 , wherein the proportion of the particles in the particle dispersion is in the range of 1% by weight to 90% by weight. ^{When Al +} ions having a kinetic energy of 40 keV are incident on the particle membrane of the ion implantation mask at a number density of 1 × 10 ¹⁴ cm- ^{2 , the Al +} ions passing through the particle membrane are the particles of the incident ions. The method according to any one of claims 1 to 6 , which is 1% or less of the number. A method for manufacturing a semiconductor device, which comprises a step of implanting ions into the semiconductor layer or a base material through an opening of an ion implantation mask formed by the method according to any one of claims 1 to 7.

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