JP2008294156A - Method of manufacturing substrate for semiconductor film deposition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method which can improve true manufacturing efficiency of a substrate for semiconductor film deposition with formed with concavo-convex portions installed on the surface. <P>SOLUTION: By conducting a process of partially forming a mask on the surface of a substrate and a process of forming concave portions by etch-removing a portion of the surface of the substrate which is not covered with the mask by a dry etching method in this order, concave-convex portions are formed on the surface of the substrate. In the process of forming the concave portions, etching is conducted, in such a manner that deposition is suppressed by making the etch rate of the substrate from half to twice the etching rate of the mask in a final stage of etching and then etching is finished. Since the occurrence of defective substrates which are not suitable for semiconductor film deposition can be suppressed, true manufacturing efficiency of substrates can be improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a method for manufacturing a semiconductor film forming substrate, and more particularly, to a method for manufacturing a semiconductor film forming substrate having an uneven portion on the surface.

When a semiconductor film made of a Group 3-5 compound such as AlGaInN is grown on a substrate such as sapphire, silicon carbide, or spinel, the semiconductor film is caused by a difference in lattice constant or thermal expansion coefficient between the substrate and the semiconductor film. There was a problem that the crystallinity of the remarkably decreased. In order to solve this problem, a high-quality semiconductor film with a reduced dislocation density is obtained by providing uneven portions on the substrate surface, thereby generating lateral growth of crystals (Patent Document 1).

In addition, in a light-emitting element such as an LED formed by forming a semiconductor film made of a Group 3-5 compound such as AlGaInN on a substrate such as sapphire, a substrate and a semiconductor film It is known that the effect of improving the light extraction efficiency of the light emitting element can be obtained by forming a concavo-convex refractive index interface at the interface (Patent Document 2, Patent Document 3, and Patent Document 4). In this case, when the film is formed so that the semiconductor crystal starts growing from the surface of the concave portion in the concave and convex portion, a structure in which the concave portion is filled with the semiconductor crystal is formed, so that the effect of improving the light extraction efficiency becomes higher. .

As a method for forming the concavo-convex portion on the substrate surface, a step of partially forming a mask on the substrate surface and a dry etching method such as RIE (Reactive Ion Etching) are used to form the mask on the substrate surface. In general, the step of forming the recesses by etching away the portions not covered by the coating is performed in this order.
JP 2000-331947 A JP 2002-280611 A JP 2003-318441 A JP 2005-101656 A

When the concave portion is formed on the substrate surface by using the dry etching method, the concave portion can be formed more efficiently as the selection ratio [(substrate etching speed) / (mask etching speed)] is increased. However, as a result of studies by the present inventors, it has been found that when a semiconductor film is grown on a substrate in which a recess is formed under the condition where the selectivity is increased, abnormal crystal growth is likely to occur on the surface of the recess. In other words, if this selection ratio is increased, the recesses can be formed quickly, so that it seems that the manufacturing efficiency is increased, but in reality, many defective substrates are not suitable for film formation of semiconductors. Manufacturing efficiency is reduced.

The present invention has been made to solve the above-mentioned problems, and its main object is to provide a manufacturing method for improving the true manufacturing efficiency of a semiconductor film forming substrate having an uneven portion on the surface. That is.

The following invention is disclosed as a suitable means for achieving the above object.
(1) A step of partially forming a mask on the surface of the substrate, and a step of etching and removing a portion of the surface of the substrate that is not covered with the mask by using a dry etching method. A method for manufacturing a substrate for semiconductor film formation, in which an uneven portion is provided on the surface of the substrate by performing in order, and in the step of forming the recess, at least the etching rate of the substrate is at least half the etching rate of the mask. A method of manufacturing a substrate for semiconductor film formation, characterized in that the etching is terminated when etching is performed while suppressing deposition by setting it to double.
(2) In the step of forming the recess, etching is performed while suppressing deposition by setting the etching rate of the substrate to be half to twice the etching rate of the mask from the beginning to the end. Manufacturing method.
(3) The manufacturing method according to (1), wherein in the step of forming the concave portion, the etching is terminated at least when the etching rate of the substrate and the etching rate of the mask are finally made substantially the same.

According to the method for manufacturing a semiconductor film forming substrate of the present invention, there is provided a semiconductor film forming substrate in which abnormal growth of crystals on the surface of the concave portion does not occur when the semiconductor film is grown on the surface provided with the concave and convex portions. Obtainable. Although the efficiency of forming the recesses decreases and the manufacturing efficiency of the substrate seems to decrease, the generation of defective substrates that are not suitable for semiconductor film formation can be suppressed, and the true manufacturing efficiency of the substrate is improved.

Next, a method for manufacturing a semiconductor film forming substrate according to an embodiment of the present invention will be described with reference to FIG.

In this manufacturing method, first, a mask 2 is partially formed on the surface of the substrate 1 as shown in FIG. The substrate 1 is, for example, a C-plane sapphire substrate. The mask 2 is, for example, a photoresist film formed using a spin coater and patterned by a photolithography technique.

Next, the substrate 1 is mounted in an etching container of a general RIE apparatus, and the portion of the surface of the substrate 1 not covered with the mask 2 is removed by etching as shown in FIG. A recess 11 is formed. The depth of the recess 11 is, for example, 0.1 μm to 3 μm. The cross-sectional view shown in FIG. 1B shows a state in which the formation of the recess 11 is completed, but the change Δt in the thickness of the mask 2 before and after the formation of the recess 11 and the depth D of the recess 11 are approximately. It is the same. To do this, for example, the first etching step until the last, of the substrate 1 of the etching rate R _1, selection ratio, which is the ratio of the etching rate R ₂ of the mask 2 (R 1 _{/ R 2)} is about 1 Etching is performed under the following conditions. The selection ratio can be adjusted by the antenna power, the bias voltage, the gas atmosphere in the etching container, and the like. As an etching gas, Cl ₂ , SiCl ₄ , BCl ₃ , HBr, SF ₆ , CHF ₃ , C ₄ F ₈ , CF ₄ , Ar, or the like can be used.

After the formation of the recess 11, the mask 2 is removed as shown in FIG. 1C to complete a semiconductor film forming substrate having an uneven portion. When the mask 2 is a photoresist film, it can be removed using a commercially available registry mover.

In the manufacture of a semiconductor film formation substrate provided with a concavo-convex part, it can be obtained by increasing the selectivity ratio [(substrate etching speed) / (mask etching speed)] when forming a concave part using a dry etching method. Regarding the reason why abnormal growth of crystals is likely to occur on the surface of the recess when a semiconductor is formed on the formed substrate, and the abnormal growth can be prevented by lowering this selection ratio, the inventors have as follows. I am thinking about:
(A) Dry etching (especially RIE) has a chemical etching side and a physical etching side. The condition with a high selectivity in dry etching is a condition in which the etching rate differs greatly between the substrate and the mask made of different materials. Since the difference in material strongly affects the etching rate, it can be said that the etching under such conditions has a strong aspect of chemical etching. On the other hand, it can be said that etching under conditions where the selectivity is close to 1, that is, under conditions where the etching rate is not very different between different materials, has a strong aspect of physical etching.
(B) In the dry etching process, the etching gas and / or a part of the workpiece (substrate and mask) cause a chemical reaction by the energy supplied in the form of plasma, and the product of the reaction is deposited on the substrate. There are things to do. This phenomenon is called deposition. The material constituting the material deposited on the substrate surface by deposition is usually not the same as the material of the substrate. Therefore, under conditions where the side surface of chemical etching is strong, a difference occurs in the etching rate between the substrate and the deposited material. Under conditions with a high selectivity (which is set so that the etching rate of the substrate is increased), the etching rate of the substrate is usually much higher than the etching rate of the deposit, so that the deposit is like an etching mask. As a result, a fine structure is formed on the surface of the recess. This fine structure is considered to cause abnormal growth of crystals on the surface of the recess when a semiconductor is deposited on the substrate.
(C) After forming the recess by dry etching, the mask is removed. In this step, a method and conditions for removing the used mask as completely as possible are usually selected. However, the material constituting the deposited material on the substrate caused by deposition is not the same as the material of the mask. Therefore, even if a method and conditions that can remove the mask almost completely are used, the deposited material may not be completely removed. The remaining deposited material may cause abnormal growth of crystals on the surface of the recess when a semiconductor film is grown on the obtained substrate.
(D) Under the etching conditions where the side of physical etching is strong, the difference in etching rate due to the difference in materials is small, so that it is difficult for deposition to occur. This is because the substance deposited on the surface of the substrate is also removed by etching together with the substrate (this makes it difficult to form a fine structure due to the deposited substance acting as an etching mask). For this reason, in a substrate in which a recess is formed while suppressing deposition using etching conditions with strong physical etching side surfaces, abnormal growth of crystals on the surface of the recess is less likely to occur when a semiconductor film is grown. Conceivable.

In the method for manufacturing a semiconductor film forming substrate according to the present invention, the recess formed by etching may be a hole-like recess or a groove-like recess. Moreover, the convex part complementarily formed by forming a recessed part may be a recessed part which exhibits columnar shape (a cylinder, a prism, etc.) or frustum shape (a truncated cone, a truncated pyramid, etc.). The cross-sectional shape of the recess is not limited to a rectangular shape, and may be trapezoidal, inverted trapezoidal, V-shaped, U-shaped, or the like. The etching rate of the substrate mentioned above is defined as the rate of increase of the depth of the concave portion per hour regardless of whether or not the concave portion formed by etching has a shape having a clear bottom surface. The depth of the recess here is the depth at the deepest portion of the recess. The etching rate of the mask is defined as the rate of decrease of the mask height per time. The height of the mask here may be referred to as the thickness at the thickest portion of the mask.

The method for manufacturing a semiconductor film forming substrate according to the present invention includes various semiconductors including a film forming substrate for a Group 3-5 compound semiconductor such as an AlGaInN-based semiconductor (for example, GaN, AlN, GaAlN, GaInN, AlGaInN). The present invention can be applied to the manufacture of a film formation substrate.

When the present invention is applied to the production of an AlGaInN-based semiconductor film-forming substrate, sapphire (C-plane, A-plane, R-plane) substrate, SiC (6H, 4H) can be used as a usable starting substrate (substrate before unevenness is provided). 3C) Substrate, GaN substrate, AlN substrate, Si substrate, spinel substrate, ZnO substrate, GaAs substrate, NGO substrate, LGO substrate, LAO substrate, ZrB ₂ substrate, TiB ₂ substrate and the like are preferably exemplified. A multilayer structure substrate having a single crystal layer made of sapphire, SiC, GaN, AlN, Si, spinel, ZnO, GaAs, NGO, LGO, LAO, ZrB ₂ , TiB ₂ or the like as a surface layer can also be preferably used.

In the manufacturing method of the present invention, the mask formed on the surface of the substrate includes a photoresist film, an inorganic film made of SiO ₂ , Si ₃ N ₄ , nickel (Ni), chromium (Cr), aluminum (Al). A metal film made of titanium (Ti), platinum (Pt), or the like can be used.

In the manufacturing method of the present invention, the formation of the concave portion using the dry etching method can be performed using a known RIE apparatus. As the etching gas, a gas containing a halogen element such as chlorine and fluorine is preferably exemplified, and chlorine gas (Cl ₂ ), silicon tetrachloride (SiCl ₄ ), boron trichloride (BCl ₃ ), hydrogen bromide (HBr), Gases such as sulfur hexafluoride (SF ₆ ), trifluoromethane (CHF ₃ ), and tetrafluoromethane (CF ₄ ) can be used alone or in combination. These gases can be mixed with an inert gas such as argon (Ar). It is also possible to use an inert gas alone.

In one of the preferred embodiments, in order to sufficiently suppress the deposition in the step of forming the recesses in the substrate, the selection ratio is 0.5 to 2 from the beginning to the end (the substrate etching rate is half the mask etching rate). Etching can be performed under the condition of (twice), but is not limited. In this step, at least lastly, etching is performed at a selection ratio of 0.5 to 2, and at the end of the etching, at least a part of the deposits deposited on the substrate can be removed. Obtainable. In particular, when the concave portion is formed deeply (for example, a depth of 1 μm or more), the first 1/2 to 3/4 are etched under a condition where the selectivity is larger than 2, and the remaining portion is etched with a selectivity of 0.5. Etching at ~ 2 is preferred. Specifically, in the case of forming a recess having a depth of 1.2 μm, etching is performed with a selection ratio larger than 2 until the depth reaches 0.6 μm to 0.9 μm, and then the etching conditions are changed. Etching is performed until the selection ratio is lowered to 0.5 to 2 and the depth is 1.2 μm. This is because if etching is performed from the first to the last with a selection ratio of 0.5 to 2, not only does the time required for forming the recesses increase, the manufacturing efficiency decreases, but also the mask needs to be formed thicker. Therefore, there is a problem that the consumption of the mask material increases, a problem that the time required for mask formation becomes long, a problem that accurate patterning of the mask becomes difficult, a problem that the mask pattern is easily broken, and a time that it takes to remove the mask after etching is long. This is because various problems may occur, such as a problem that the consumption of chemicals and cleaning liquid necessary for mask removal increases.

In a preferred embodiment of the present invention, a selection ratio close to 1 is used as the selection ratio when dry etching is performed at a selection ratio of 0.5-2. As described above, it is considered that the closer the selection ratio is to 1, the stronger the side surface of physical etching, and the more effective the deposition is suppressed.

The mask removal after the etching can be performed using a conventionally known method. When the mask is an inorganic film or a metal film, it can be removed using acid or alkali.

It is sectional drawing for demonstrating the manufacturing method of the board | substrate for semiconductor film-forming concerning embodiment of this invention.

Explanation of symbols

1 Substrate 2 Mask

Claims (3)

A step of partially forming a mask on the surface of the substrate, and a step of forming a recess by etching away a portion of the surface of the substrate that is not covered with the mask using a dry etching method are performed in this order. A method for manufacturing a semiconductor film-forming substrate, wherein an uneven portion is provided on the surface of the substrate,
In the step of forming the recess, at least the etching rate of the substrate is set to half to twice the etching rate of the mask, and the etching is terminated when the etching is performed while suppressing deposition. , A method of manufacturing a semiconductor film forming substrate. 2. The manufacturing method according to claim 1, wherein in the step of forming the recess, etching is performed while suppressing deposition by setting the etching rate of the substrate from half to two times the etching rate of the mask from the beginning to the end. 2. The manufacturing method according to claim 1, wherein in the step of forming the concave portion, the etching is terminated when the etching is performed at least last with the etching rate of the substrate and the etching rate of the mask being substantially the same.

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