JP2011049248A - Method for inspecting etching - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inspecting the etching that facilitates obtaining the size of a reverse taper in the etching by a reverse-taper condition. <P>SOLUTION: In the method for inspecting the etching, a plurality of dummy pillars 30 as columnar structures having different widths or diameters are formed to part of a substrate to be etched upon etching. In the method, parts forming the dummy pillars in the substrate to be etched are observed after the completion of etching. In the method, when at least a part in a plurality of the dummy pillars is lost, trenches formed to the substrate to be etched by etching are decided to have reverse pillar-shaped sidewall shapes. In the method, 1/2 or more of the largest width or diameter of the dummy pillars lost by etching and 1/2 less than having the smallest width or the diameter in the residual dummy pillars are used as the quantities of overhangs in the trenches. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an etching inspection method, and more particularly to an etching inspection method that can easily determine the size of an overhang generated in a trench when etching is performed under a reverse taper condition.

  When manufacturing a semiconductor device, a semiconductor wafer is dry-etched or wet-etched under predetermined conditions to form a trench. Depending on the etching conditions, a forward tapered structure in which the side wall of the trench is narrowed toward the bottom, or An inverted taper structure in which the side wall extends toward the bottom surface may be formed.

  When etching is performed under a forward taper condition, which is an etching condition for forming a forward taper structure, the size of the side wall taper can be measured by observing the trench with an optical microscope. On the other hand, when etching is performed under a reverse taper condition, which is an etching condition for forming a reverse taper structure, the size of the reverse taper is not known even when the trench is observed with an optical microscope. Therefore, the monitor wafer, which is the same material and the same thickness as the semiconductor wafer on which the semiconductor device is to be formed, is etched under the same conditions, and a reverse taper is obtained by observing the cross section of the monitor wafer after etching. In general, a cross-sectional analysis for obtaining the size of the surface has been performed.

  However, cross-sectional analysis is burdensome for the operator. Further, in the cross-sectional analysis, it is necessary to prepare a monitor wafer in addition to the semiconductor wafer for the semiconductor device. Furthermore, since there is no guarantee that etching is progressing at the same speed in both the monitor wafer and the semiconductor device wafer, the reverse taper shape obtained by observing the cross section of the monitor wafer is the wafer for the semiconductor device. There is no guarantee that the wall shape of the trench is the same.

  As a method for monitoring the taper shape of the trench, for example, a step of forming an etching mask having a plurality of windows having different shapes and sizes and different intervals (window pattern intervals) on a semiconductor wafer, and a window of the etching mask The step of etching the semiconductor wafer exposed in the region to form a recess, and after removing the etching mask, the smallest width from the top width of the protrusion of the semiconductor wafer remaining between the recesses There is a semiconductor device manufacturing method including a step of knowing a pattern width and inspecting an etching depth from a window pattern interval of an etching mask corresponding to the minimum pattern width (Patent Document 1).

  In addition, a resist pattern for measuring overhangs having different width dimensions is formed on a substrate through resist coating, exposure, and development processes, and the amount of overhang is measured from the advantageous situation of the plurality of patterns with respect to the substrate. In this overhang measurement method, there is a resist overhang measurement method in which, when a resist pattern for measurement is formed, a fixing resist pattern that is thicker than twice the overhang amount is formed integrally at both ends thereof (Patent Document 2).

  Furthermore, in the semiconductor device in which the trench for element isolation is formed in the semiconductor substrate, the trench includes at least two types of first and second trenches having different depths by etching the semiconductor substrate, The trench has a V shape with a cross-sectional shape in the width direction having a predetermined taper angle, and the second trench has a cross-sectional shape in the width direction with the predetermined taper angle, and the bottom surface of the semiconductor substrate has a predetermined taper angle. Some have a plane parallel to the surface (Patent Document 3).

JP 09-191038 A JP-A-64-061030 JP 2007-158107 A

  According to the method for manufacturing a semiconductor device described in Patent Document 1, the etching depth is used by using the fact that the etching amount is directly proportional to the side etching amount, which is the size along the surface direction of the taper under the forward taper condition. Can do. However, when etching is performed under a reverse taper condition, the window portion of the etching mask in the semiconductor wafer is etched in a reverse taper shape, so that the amount of overhang, which is the size of the surface direction of the reverse taper, is directly measured by optical observation. I can't ask for it.

  In the overhang measuring method described in Patent Document 2, half of the maximum width of the resist pattern floating from the substrate is used as the overhang amount, and whether or not the resist is floating from the substrate is determined by the resist pattern. Judgment from the interference color. Therefore, the overhang amount cannot be obtained unless the interference color is different between when the resist is floating from the substrate and when the resist is in close contact. Therefore, the overhang measuring method of Patent Document 2 cannot be applied to obtain the overhang amount formed in the trench under the reverse taper condition.

  In the invention of Patent Document 3, two types of trenches having different depths are formed in a single etching process on the semiconductor wafer by utilizing the fact that the etching stops when the width of the bottom surface becomes 0 under the forward taper condition. Therefore, it cannot be applied to the reverse taper condition.

  The present invention has been made to solve the above problem, and an object of the present invention is to provide an etching inspection method capable of easily obtaining the size of the reverse taper in the etching under the reverse taper condition.

  The invention according to claim 1 is an etching inspection method for inspecting a trench structure formed by etching a substrate to be etched under a predetermined condition, wherein a width or a diameter of a part of the substrate to be etched is formed in the etching. A plurality of dummy pillars that are different columnar structures are formed, and after etching is completed, the portion where the dummy pillars are formed in the substrate to be etched is observed, and when at least a part of the plurality of dummy pillars has disappeared, It is determined that the trench formed in the substrate to be etched in etching has a reverse pillar-shaped side wall shape, and more than half of the dummy pillars that have disappeared by the etching and have the largest width or diameter remain. Less than 1/2 of the smallest of the width or diameter It relates etching inspection method characterized by the overhang amount in the trench.

  In the etching inspection method, the dummy pillar whose width or diameter is not more than twice the overhang amount is separated from the substrate to be etched after the etching is finished and disappears, but the width or diameter is twice the overhang amount. In a larger dummy pillar, the state connected to the substrate to be etched is maintained even after the etching is completed.

  Therefore, the overhang amount caused by the etching is equal to or more than ½ of the largest dummy pillar having the largest width or diameter among the dummy pillars disappeared by the etching and less than half of the smallest dummy pillar having the smallest width or diameter. can do.

  A second aspect of the present invention relates to the etching inspection method according to the first aspect, wherein dummy pillars having rectangular or oval planar shapes having different widths are formed during the etching.

  In the etching inspection method, since the dummy pillar has a rectangular or oval planar shape, the dummy pillar whose width is not more than twice the overhang amount is separated from the substrate to be etched and disappears after the etching is completed. . On the other hand, in the dummy pillar whose width is larger than twice the overhang amount, the connected state with the substrate to be etched is maintained even after the etching is completed.

  Therefore, the overhang amount generated by the etching can be set to 1/2 or more of the largest dummy pillar disappeared by the etching and less than 1/2 of the smallest dummy pillar remaining. .

  A third aspect of the present invention relates to the etching inspection method according to the first aspect, wherein a dummy pillar having a circular planar shape having a different diameter is formed during the etching.

  In the etching inspection method, since the dummy pillar has a circular plane shape, the dummy pillar whose diameter is not more than twice the overhang amount is separated from the substrate to be etched and disappears after the etching is completed. On the other hand, in the dummy pillar whose diameter is larger than twice the overhang amount, the state connected to the substrate to be etched is maintained even after the etching is completed.

  Therefore, the overhang amount generated by the etching can be set to 1/2 or more of the largest dummy pillar disappeared by the etching and less than 1/2 of the smallest dummy pillar remaining. .

  According to a fourth aspect of the present invention, in the etching inspection method according to any one of the first to third aspects, a mask pattern corresponding to the dummy pillar is formed on a surface of the substrate to be etched, and then the predetermined condition is satisfied. It is related with what forms a dummy pillar by etching.

  In the etching inspection method, a trench structure and a dummy pillar are formed on the surface of the substrate to be etched by etching the substrate to be etched having a mask pattern corresponding to the trench and the dummy pillar formed on the surface.

  The invention according to claim 5 is the etching inspection method according to any one of claims 1 to 4, wherein the substrate to be etched is selected from a group III-V compound material substrate, a silicon substrate, and a SiC substrate. Relates to a semiconductor substrate.

  A sixth aspect of the present invention relates to the etching inspection method according to any one of the first to fifth aspects, wherein the etching is dry etching.

  In the etching inspection method, etching is performed by spraying an etching gas onto the surface of the substrate to be etched at a predetermined flow rate. Therefore, dummy pillars having a width or a diameter that is twice or less the overhang amount are not etched until the etching is completed. It is blown away by the air current and disappears.

  A seventh aspect of the present invention relates to the etching inspection method according to any one of the first to fifth aspects, wherein the etching is wet etching.

  In the etching inspection method, etching is performed by immersing the substrate to be etched in an etching solution. Therefore, the dummy pillar whose width or diameter is not more than twice the overhang amount dissolves in the etching solution and disappears before the etching is completed.

  According to the first aspect of the present invention, the burden on the operator can be greatly reduced as compared with the case of performing the cross-sectional analysis. In addition, as described above, a plurality of dummy pillars having different widths or diameters are formed on the same substrate to be etched together with the trench structure, and the overhang amount of the reverse taper shape is obtained by determining which dummy pillar has disappeared. Thus, it is guaranteed that the overhang amount obtained based on the disappearance result of the dummy pillar is substantially the same as the overhang amount of the trench in the wafer for semiconductor devices.

  According to the invention of claim 2, since the dummy pillar having a rectangular or oval planar shape is formed, there is provided an etching inspection method capable of easily confirming with an optical microscope or the like which dummy pillar remains after completion of etching. Provided.

  According to the invention of claim 3, since the dummy pillar having a circular planar shape is formed, the present invention can be applied even when there is no room for forming a rectangular or oval dummy pillar on the substrate to be etched. Easy to apply.

  According to the fourth aspect of the present invention, there is provided an etching inspection method in which a mask pattern is formed on the surface of a substrate to be etched, and then the amount of overhang of the trench can be easily obtained in a normal etching process of etching.

  According to the invention of claim 5, there is provided an etching inspection method capable of easily determining the overhang amount of a trench when a III-V group compound material substrate, a silicon substrate, or a SiC substrate is used as a substrate to be etched. The

  According to the sixth aspect of the present invention, there is provided an etching inspection method capable of easily determining the amount of trench overhang when performing a dry etching process.

  According to the seventh aspect of the present invention, there is provided an etching inspection method capable of easily obtaining an overhang amount of a trench when performing a wet etching process.

FIG. 1 is a flowchart showing a procedure for manufacturing an LED array in the first embodiment. FIG. 2 is a cross-sectional view showing a state after etching in the first embodiment. 3A and 3B show an example of a dummy pillar pattern formed in the first embodiment, where FIG. 3A is a plan view and FIG. 3B is a cross-sectional view. 4A and 4B show another example of the dummy pillar pattern formed in the first embodiment, where FIG. 4A is a plan view and FIG. 4B is a cross-sectional view. FIG. 5 shows still another example of the dummy pillar pattern formed in the first embodiment, in which (A) is a plan view and (B) is a cross-sectional view. 6 shows a state after etching of the N-type GaAs substrate on which the dummy pillar pattern shown in FIG. 3 is formed. FIG. 6A is a plan view and FIG. 6B is a cross-sectional view. 7 shows a state after etching of the N-type GaAs substrate on which the dummy pillar pattern shown in FIG. 4 is formed. FIG. 7A is a plan view and FIG. 7B is a cross-sectional view. 8 shows a state after etching of the N-type GaAs substrate on which the dummy pillar pattern shown in FIG. 5 is formed. FIG. 8A is a plan view and FIG. 8B is a cross-sectional view. FIG. 9 is a schematic cross-sectional view showing the relationship between the width or diameter of the dummy pillar after etching and the formation of the dummy pillar.

1. Embodiment 1
Hereinafter, an example in which the etching inspection method of the present invention is applied when manufacturing an LED array by wet etching a GaAs substrate which is an example of a III-V group compound material will be described.

  In the first embodiment, an N-type GaAs substrate 10 which is a semiconductor substrate made of a III-V group compound material is used as an example of a substrate to be etched in the present invention. As shown in FIG. 1A, an N-type GaAsP layer 10A is formed in advance on the surface of an N-type GaAs substrate 10 by a method such as epitaxial growth.

  Next, as shown in FIG. 1A, the area of the surface of the N-type GaAs substrate 10 is divided into an LED array forming area 11 and an inspection area 13 for forming a dummy pillar 30 described later, and the LED array forming area. 11 is formed with a diffusion prevention film 12 having a window, and a diffusion control film 14 is formed on the entire surface region of the N-type GaAs substrate 10 including the diffusion prevention film 12.

  Then, as shown in FIG. 1B, for example, zinc (Zn) is diffused from above the diffusion control film 14 to form a P-type GaAsP region 16 in the window region of the diffusion prevention film 12.

  After the P-type GaAsP region 16 is formed on the N-type GaAs substrate 10, an insulating film 18 having a window is formed as shown in FIG.

  When the insulating film 18 is formed, as shown in FIG. 1D, a P electrode 20 is formed so as to cover the insulating film 18 and the P-type GaAsP region 16, and at the same time, an N electrode 22 is formed on the back surface of the N-type GaAs substrate 10. Form.

  When the P electrode 20 and the N electrode 22 are formed on the N-type GaAs substrate 10, the entire surface of the N-type GaAs substrate 10 is covered with a masking film 24 as shown in FIG. A trench pattern 26 for forming a trench structure is formed in a portion corresponding to the LED formation region 11 in the masking film 24, and a dummy pillar pattern 28 for forming a dummy pillar 30 in a portion corresponding to the inspection region 13. Form.

  After the trench pattern 26 and the dummy pillar pattern 28 are formed, the N-type GaAs substrate 10 is etched. For the etching, a citric acid-based etching solution (a mixed solution of a 50% by mass citric acid aqueous solution and a 30% by weight hydrogen peroxide aqueous solution) can be used.

  As shown in FIG. 2, the trench 32 is formed in the LED formation region 11 and the dummy pillar 30 is formed in the inspection region 13 by the etching, but a part of the dummy pillar 30 is dissolved in the etching solution and disappears, and is inversely tapered. A recessed portion 31 having a shaped side wall is formed.

  Hereinafter, the dummy pillar pattern 28 and the dummy pillar 30 will be described in detail. As shown in FIGS. 3 to 5, for example, four dummy pillar patterns 28 are formed in the inspection region 13 of the N-type GaAs substrate 10. Hereinafter, the four dummy pillar patterns 28 are referred to as dummy pillar patterns 28A, 28B, 28C, and 28D from the left side to the right side in FIGS.

  The dummy pillar patterns 28A, 28B, 28C, and 28D have masking regions 24A, 24B, 24C, and 24D in which portions where the dummy pillars 30 are to be formed are covered with the masking film 24, and N around the masking regions 24A to 24D. The substrate GaAs substrate 10 comprises a substrate exposed region 25 that is exposed in a ring shape with a predetermined width.

  The shape of the masking regions 24A, 24B, 24C, 24D, in other words, the planar shape of the dummy pillar 30 may be rectangular as shown in FIG. 3, may be oval as shown in FIG. It may be circular as shown in FIG.

  The width or diameter of the masking regions 24A, 24B, 24C, 24D, in other words, the width or diameter of the dummy pillar 30 is set to 0.10 μm, 0.15 μm, 0.20 μm, and 0.25 μm, respectively.

  When the N-type GaAs substrate 10 is etched, as shown in FIGS. 6 to 9, portions of the substrate exposed region 25 in the dummy pillar patterns 28A, 28B, 28C, and 28D are etched to form the recessed portions 31, and masking is performed. The regions 24A, 24B, 24C, and 24D remain, and the dummy pillar 30 that is a columnar structure is formed. However, when the etching is performed under a reverse taper condition, the side walls of the dummy pillar 30 and the recessed portion 31 become a reverse taper shape spreading toward the bottom surface as shown in FIG. Here, if the amount of protrusion of the dummy pillar 30 and the top surface of the recessed portion 31 protruding toward the bottom surface is h, the amount of protrusion h of the dummy pillar 30 and the recessed portion 31 is equal. Here, the overhang amount h can be rephrased as a conversion difference.

  When the width w or diameter d of the dummy pillar 30 is not more than twice the overhang h, the dummy pillar 30 disappears at the end of etching as shown in FIG. On the other hand, when the width w or the diameter d of the dummy pillar 30 is larger than twice the protruding amount h, the bottom of the dummy pillar 30 is N-type GaAs substrate even at the end of etching as shown in FIG. The state connected to 10 is maintained.

  Therefore, when the presence or absence of the dummy pillar 30 formed in the inspection region 13 is observed with an optical microscope or the like after the etching is completed, the overhang amount h, that is, the conversion difference can be evaluated. For example, in the examples shown in FIGS. 6 to 8, the dummy pillars 30 having a width (diameter) of 0.10 μm and a width (diameter) of 0.15 μm have disappeared. Since those with a diameter (0.20 μm) and those with a width (diameter) of 0.25 μm remain, the conversion width is the width (diameter) of the largest dummy pillar 30 that has disappeared (diameter). Which is larger than 0.075 μm which is 1/2 of 0.15 μm which is 0.15 μm and which is 1/2 of 0.20 μm which is the width (diameter) of the smallest dummy pillar 30 among the remaining dummy pillars 30. It can be estimated that it is 10 μm or less.

Hereinafter, the etching inspection method when manufacturing an LED array by wet-etching a GaAs substrate has been described. It can also be applied to GaAlAs and InGaAsP.
The present invention can also be applied to the manufacture of semiconductor devices by dry etching or wet etching of silicon substrates, and the manufacture of semiconductor devices by dry etching of SiC substrates.
Furthermore, the method of Embodiment 1 can also be applied to the manufacture of micromachines by etching silicon.

DESCRIPTION OF SYMBOLS 10 N type GaAs board | substrate 10A N type GaAsP layer 11 LED array formation area 11 Formation area 12 Diffusion prevention film 13 Inspection area 14 Diffusion control film 16 P type GaAsP area 18 Insulating film 20 Electrode 22 Electrode 24 Masking film 24A Masking area 25 Substrate exposure Region 26 Trench pattern 28 Dummy pillar pattern 28A Dummy pillar pattern 30 Dummy pillar 31 Recessed portion 32 Trench

Claims (7)

An etching inspection method for inspecting a trench structure formed by etching a substrate to be etched under a predetermined condition, wherein a plurality of dummy pillars are columnar structures having different widths or diameters at a part of the substrate to be etched during the etching. Form the
After the etching is completed, observe the portion where the dummy pillar is formed in the substrate to be etched,
When at least some of the plurality of dummy pillars have disappeared, it is determined that the trench formed in the substrate to be etched in the etching has a reverse pillar-shaped sidewall shape,
Further, the overhang amount in the trench is defined as 1/2 or more of the largest dummy pillar having the largest width or diameter among the dummy pillars disappeared by the etching and less than half of the smallest dummy pillar having the smallest width or diameter. Etching inspection method. The etching inspection method according to claim 1, wherein dummy pillars having rectangular or oval planar shapes having different widths are formed during the etching. The etching inspection method according to claim 1, wherein a dummy pillar having a circular planar shape having a different diameter is formed during the etching. The etching inspection method according to any one of claims 1 to 3, wherein a mask pattern corresponding to a dummy pillar is formed on a surface of the substrate to be etched, and thereafter, etching is performed under the predetermined condition to form a dummy pillar. The etching inspection method according to claim 1, wherein the substrate to be etched is a semiconductor substrate selected from a III-V group compound material substrate, a silicon substrate, and a SiC substrate. The etching inspection method according to claim 1, wherein the etching is dry etching. The etching inspection method according to claim 1, wherein the etching is wet etching.

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