Etching method and etching device

Abstract

Provided is technology that enables faster formation of a plurality of through holes in an insulating substrate. A plasma reactor (5) faces a conductive first mask (31) that is disposed on a first main surface (Wa) of an insulating substrate (W) and that has a plurality of first openings (31a) with a first gaseous space (G1) interposed between the plasma reactor (5) and the conductive first mask (31). The plasma reactor (5) converts gas inside the first gaseous space (G1) into plasma, causes the plasma to act on the first mask (31) to generate an electric field between the first mask (31) and an electrode plate (4) which is provided on the opposite side of the insulating substrate (W) from the first mask (31), and generates plasma between the electrode plate (4) and the first mask (31).

Description

Etching method and etching apparatus

[0001] The present disclosure relates to an etching method and an etching apparatus.

[0002] Conventionally, in the field of fan-out panel level packaging, an interposer is provided between a chip and a substrate. The interposer is a glass-based substrate. A plurality of through holes are formed in the glass-based substrate, and the through holes are filled with a conductive member. The interposer achieves electrical connection between the chip and the substrate.

[0003] In manufacturing such an interposer, a technique for forming through holes in a glass-based substrate by laser processing and wet etching has been proposed (Patent Documents 1 to 3).

[0004] Japanese National Publication of International Patent Application No. 2019-530629, Japanese Unexamined Patent Application Publication No. 2020-66551, Japanese Unexamined Patent Application Publication No. 2017-61401

[0005] In laser processing, microcracks may occur in the glass-based substrate. For this reason, it is desirable to process the glass-based substrate at a low speed, or process the glass-based substrate using a pulsed laser. However, such a method requires a relatively long time to form a plurality of through holes. In particular, when the number of through holes reaches several millions or more, the throughput of laser processing is low.

[0006] Accordingly, an object of the present disclosure is to provide a technique capable of more quickly forming a plurality of through holes in an insulating substrate.

[0007] In the etching method, a plasma reactor facing a conductive first mask having a plurality of first openings arranged on a first main surface of an insulating substrate with a first gas space interposed therebetween plasmarizes gas in the first gas space, causes plasma to act on the first mask, generates an electric field between an electrode plate provided on a side opposite to the first mask with respect to the insulating substrate and the first mask, and generates plasma between the electrode plate and the first mask.

[0008] The etching apparatus comprises a substrate placement section that supports or holds an insulating substrate on which a conductive first mask having a plurality of first openings is arranged on a first main surface; an electrode plate provided on the opposite side of the insulating substrate arranged by the substrate placement section from the first mask, to which a potential is applied; and a plasma reactor that faces the first mask across a first gas space, and which plasmaizes the gas in the first gas space and applies the plasma to the first mask.

[0009] Multiple through-holes can be formed in the insulating substrate more quickly.

[0010] Figure 1 is a schematic side view showing an example of the configuration of an etching apparatus according to the first embodiment. Figure 2 is a schematic plan view showing an example of a part of the configuration of the first mask. Figure 3 is a schematic plan view showing an example of the configuration of a plasma reactor. Figure 4 is a schematic diagram showing an example of the internal configuration of the control unit. Figure 5 is a flowchart showing an example of the operation of the etching apparatus. Figure 6 is a schematic diagram showing another example of the configuration of the etching apparatus. Figure 7 is a schematic side view showing an example of the configuration of an etching apparatus according to the second embodiment. Figure 8 is a schematic cross-sectional view showing an example of the configuration of an insulating substrate in which through holes have been formed by the etching apparatus according to the second embodiment. Figure 9 is a schematic side view showing a first example of the configuration of an etching apparatus according to the third embodiment. Figure 10 is a schematic plan view showing an example of the configuration of a plasma reactor according to the third embodiment. Figure 11 is a schematic side view showing a second example of the configuration of an etching apparatus according to the third embodiment.

[0011] The embodiments will be described in detail below with reference to the drawings. Note that, for the purpose of ease of understanding, the dimensions and number of parts in the drawings are exaggerated or simplified as needed. Also, parts with similar configurations and functions are denoted by the same reference numerals, and redundant explanations are omitted in the following description.

[0012] Furthermore, in the following explanations, similar components will be denoted by the same symbols, and their names and functions will also be the same. Therefore, detailed explanations of them may be omitted to avoid redundancy.

[0013] Furthermore, even if ordinal numbers such as "first" or "second" are used in the following descriptions, these terms are used for convenience to facilitate understanding of the embodiments and are not limited to the order that may result from these ordinal numbers.

[0014] When expressions indicating relative or absolute positional relationships are used (e.g., "in one direction," "along one direction," "parallel," "orthogonal," "center," "concentric," "coaxial," etc.), unless otherwise specified, such expressions shall not only strictly represent the positional relationship but also represent a state in which there is a relative displacement in terms of angle or distance within a tolerance or a range in which equivalent functionality is obtained. When expressions indicating equality are used (e.g., "identical," "equal," "homogeneous," etc.), unless otherwise specified, such expressions shall not only strictly represent a state in which there is a quantitatively exact equality but also represent a state in which there is a difference within a tolerance or a range in which equivalent functionality is obtained. When expressions indicating shape are used (e.g., "quadrilateral" or "cylindrical"), unless otherwise specified, such expressions shall not only strictly represent the geometrically exact shape but also represent a shape with features such as concavities or chamfers within a range in which equivalent effects are obtained. When expressions such as "equipped with," "possess," "possess," "include," or "have" a single component are used, such expressions are not exclusive expressions that exclude the existence of other components. When the expression "at least one of A, B, and C" is used, it includes A only, B only, C only, any two of A, B, and C, and all of A, B, and C.

[0015] <First Embodiment> <Etching Apparatus> Figure 1 is a schematic side view showing an example of the configuration of an etching apparatus 1 according to the first embodiment. The etching apparatus 1 is a dry-type etching apparatus that forms a plurality of through holes in an insulating substrate W. The insulating substrate W is, for example, a glass substrate and has a plate-like shape. The insulating substrate W has a first main surface Wa and a second main surface Wb. The first main surface Wa and the second main surface Wb are surfaces that face each other in the thickness direction of the insulating substrate W. The first main surface Wa and the second main surface Wb may be, for example, flat surfaces. The etching apparatus 1 dry-etches the insulating substrate W to form a plurality of through holes in the insulating substrate W. The etching apparatus 1 can also be said to be a through-hole forming apparatus. In a process after the etching apparatus 1, for example, conductive members (through electrodes) are provided in the through holes of the insulating substrate W to produce an interposer.

[0016] As shown in Figure 1, the etching apparatus 1 includes a substrate placement section 2, a first mask 31, an electrode plate 4, and a plasma reactor 5.

[0017] The substrate placement section 2 supports or holds the insulating substrate W in a horizontal position. Here, "horizontal position" means that the thickness direction of the insulating substrate W is aligned with the vertical direction. In the example shown in Figure 1, the first main surface Wa of the insulating substrate W corresponds to the top surface. The substrate placement section 2 may also be a mounting platform that supports the second main surface Wb of the insulating substrate W. The substrate placement section 2 may also be called a stage or susceptor. The substrate placement section 2 may be formed of a dielectric material. The dielectric material is not particularly limited, but may include, for example, at least one of synthetic resin, quartz glass, and ceramics.

[0018] As shown in Figure 1, a conductive first mask 31 is placed on the first main surface Wa of the insulating substrate W. The first mask 31 is formed of a conductive material. The conductive material is not particularly limited, but includes, for example, metals. As a specific example, the conductive material may include at least one of copper, aluminum, molybdenum, yttrium, and tungsten.

[0019] The first mask 31 has a plate-like shape and is positioned so that its thickness direction is aligned with the thickness direction of the insulating substrate W. The first mask 31 has a plurality of first openings 31a. The first openings 31a penetrate the first mask 31 in its thickness direction. The plurality of first openings 31a are arranged two-dimensionally in a plan view. Figure 2 is a schematic plan view showing an example of a part of the configuration of the first mask 31. As shown in Figure 2, the plurality of first openings 31a may be arranged in a matrix in a plan view. As shown in Figure 2, each first opening 31a may have a circular shape in a plan view. The diameter of the first openings 31a can be set to several tens of μm (for example, 30 μm) or less. In the example of Figure 1, the number of first openings 31a is small, but in reality, there may be, for example, more than a million. In the example of Figure 1, one main surface (for example, the bottom surface) of the first mask 31 is in contact with the first main surface Wa of the insulating substrate W. The main surface of the first mask 31 may be a flat surface.

[0020] The first mask 31 may be placed, for example, on the first main surface Wa of the insulating substrate W before it is brought into the etching apparatus 1. A transport robot (not shown) may then transport the insulating substrate W on which the first mask 31 is placed to the substrate placement section 2.

[0021] The electrode plate 4 is provided on the side of the insulating substrate W opposite to the first mask 31. In the example of Figure 1, the electrode plate 4 is provided on the side of the substrate placement area 2 opposite to the insulating substrate W. Here, the electrode plate 4 is provided below the substrate placement area 2. In other words, the first mask 31, insulating substrate W, substrate placement area 2, and electrode plate 4 are provided in this order in the vertical direction. In the example of Figure 1, the electrode plate 4 is provided in a position where its thickness direction is aligned with the thickness direction of the insulating substrate W. The electrode plate 4 may be larger than the insulating substrate W in a plan view. That is, in a plan view, the contour of the insulating substrate W may be located inside the contour of the electrode plate 4.

[0022] The electrode plate 4 is formed of a conductive material. The conductive material is not particularly limited, but may be any of the materials exemplified as the material for the first mask 31. A potential is applied to the electrode plate 4. For example, a ground potential is applied to the electrode plate 4.

[0023] The plasma reactor 5 faces the first mask 31 across a first gas space G1. In other words, the first gas space G1 is the space between the plasma reactor 5 and the first mask 31. The plasma reactor 5 is in contact with the first gas space G1, and the first mask 31 is also in contact with the first gas space G1. The portions of the first main surface Wa of the insulating substrate W within each first opening 31a are also in contact with the first gas space G1. In the example of Figure 1, the plasma reactor 5 is positioned above the insulating substrate W and the first mask 31, which are placed in the substrate placement section 2. The plasma reactor 5 plasmaizes the gas in the first gas space G1. For example, the plasma reactor 5 plasmaizes the gas under atmospheric pressure. More specifically, the plasma reactor 5 plasmaizes the gas under a pressure of 0.1 Pa or more and 10 Pa or less.

[0024] The plasma generated in the first gas space G1 acts on the first main surface Wa of the insulating substrate W within each first opening 31a of the first mask 31, and also acts on the conductive first mask 31. In other words, the distance between the plasma reactor 5 and the first mask 31 is set to a value such that the plasma acts on the first mask 31. The effects of the plasma will be described in detail later.

[0025] In the example shown in Figure 1, the plasma reactor 5 is a planar plasma reactor. The plasma reactor 5 has a plate-like shape overall and is installed in a position where its thickness direction is aligned with the thickness direction of the insulating substrate W. As a specific example, the plasma reactor 5 includes a plurality of first electrodes 51 and a plurality of second electrodes 52. Figure 3 is a schematic plan view showing an example of the configuration of the plasma reactor 5. The first electrodes 51 have a rod-like shape. As a more specific example, the first electrodes 51 have a cylindrical shape. Each first electrode 51 is installed in a position where its longitudinal direction is aligned with the horizontal extension direction D1. A plurality of first electrodes 51 can be arranged parallel to each other. A plurality of first electrodes 51 are arranged at intervals in the arrangement direction D2. The arrangement direction D2 is along the horizontal direction and perpendicular to the extension direction D1.

[0026] The second electrode 52 also has a rod-like shape. As a more specific example, the second electrode 52 has a cylindrical shape. Each second electrode 52 is positioned so that its longitudinal direction is along the extension direction D1. Multiple second electrodes 52 can be arranged parallel to each other. Multiple second electrodes 52 are arranged at intervals in the arrangement direction D2.

[0027] In the example shown in Figure 3, in a plan view, the first electrode 51 and the second electrode 52 are arranged alternately in the arrangement direction D2. The size of the first electrode 51 in the extending direction D1 may be greater than or equal to the size of the insulating substrate W in the extending direction D1. The same applies to the size of the second electrode 52 in the extending direction D1.

[0028] Multiple first electrodes 51 are connected to the first output terminal 50a of the high-frequency power supply 50, and multiple second electrodes 52 are connected to the second output terminal 50b of the high-frequency power supply 50. The second output terminal 50b of the high-frequency power supply 50 can be grounded.

[0029] As shown in Figures 1 and 3, the plasma reactor 5 may include a dielectric 53. The dielectric 53 has, for example, a plate shape and is positioned so that its thickness direction is aligned with the thickness direction of the insulating substrate W. The dielectric 53 is formed of a dielectric material such as quartz glass. In the example of Figure 1, the vertical size of the dielectric 53 is larger than the vertical size of the first electrode 51 and the second electrode 52, respectively. For example, the vertical size of the dielectric 53 is larger than the diameter of the first electrode 51 and the second electrode 52, respectively. Referring to Figure 3, at least the portion of each first electrode 51 facing the second electrode 52 in the alignment direction D2 is covered by the dielectric 53. Similarly, at least the portion of each second electrode 52 facing the first electrode 51 in the alignment direction D2 is covered by the dielectric 53. In other words, the portions of the first electrode 51 and the second electrode 52 are embedded in the dielectric 53.

[0030] In the example shown in Figure 3, a portion of each first electrode 51 protrudes from the side surface 53c of the dielectric 53. Side surface 53c is one side surface of the dielectric 53 in the extending direction D1. This portion of each first electrode 51 is connected to the first output terminal 50a of the high-frequency power supply 50 via wiring. Similarly, in the example shown in Figure 3, a portion of each second electrode 52 protrudes from the side surface 53d of the dielectric 53. Side surface 53d is the other side surface of the dielectric 53 in the extending direction D1. This portion of each second electrode 52 is connected to the second output terminal 50b of the high-frequency power supply 50 via wiring.

[0031] In the example shown in Figure 1, the multiple first electrodes 51 and the multiple second electrodes 52 are positioned at approximately the same height. In the example shown in Figure 1, the multiple first electrodes 51 and the multiple second electrodes 52 are positioned closer to the lower surface 53b of the dielectric 53 than to the upper surface 53a. That is, the distance between the first electrode 51 and the lower surface 53b is narrower than the distance between the first electrode 51 and the upper surface 53a, and the distance between the second electrode 52 and the lower surface 53b is narrower than the distance between the second electrode 52 and the upper surface 53a.

[0032] The lower surface 53b of the dielectric 53 faces the first gas space G1. The lower surface 53b may be a flat surface parallel to the first main surface Wa of the insulating substrate W.

[0033] The high-frequency power supply 50 includes, for example, a switching power supply circuit. The high-frequency power supply 50 is controlled by the control unit 9 and outputs a high-frequency voltage between the first electrode 51 and the second electrode 52. This high-frequency voltage generates a high-frequency electric field between the first electrode 51 and the second electrode 52, and a portion of this electric field acts on the first gas space G1, causing the gas in the first gas space G1 to become plasma. In other words, the effective value and frequency of the high-frequency voltage output by the high-frequency power supply 50 are set to values ​​such that the electric field generated between the first electrode 51 and the second electrode 52 can cause the gas to become plasma. For example, the voltage may be 9kV to 15kV and the frequency may be 12kHz to 30kHz. The gas in the first gas space G1 may be air. For example, oxygen gas in the first gas space G1 becomes plasma.

[0034] The plasma can act on the first main surface Wa of the insulating substrate W at each first opening 31a of the first mask 31. As a result, the portion of the first main surface Wa of the insulating substrate W within the first opening 31a can be etched.

[0035] Furthermore, the plasma also acts on the conductive first mask 31. This electrical action of the plasma on the first mask 31 generates an electric field between the first mask 31 and the electrode plate 4. In other words, due to the action of the plasma on the first mask 31, the first mask 31 and the electrode plate 4 function as capacitively coupled plasma electrodes. This electric field generates plasma between the first mask 31 and the electrode plate 4. To put it another way, the effective value and frequency of the high-frequency voltage output by the high-frequency power supply 50 are set to a value sufficient to plasmaize the gas between the first mask 31 and the electrode plate 4. A specific example is as described above.

[0036] The plasma generated by the electric field between the first mask 31 and the electrode plate 4 occurs, in a plan view, particularly in the contour region R1 along the contour of each first aperture 31a of the first mask 31. In other words, a plasma with high plasma density is generated in the contour region R1. Plasma density is, for example, electron density or ion density. In short, the plasma density in the contour region R1 of the first aperture 31a is higher than the plasma density at the center of the first aperture 31a. The reason why such a high-density plasma is generated in the contour region R1 is thought to be because the contour of the first aperture 31a of the first mask 31 is in contact with the gas in the space between the first mask 31 and the electrode plate 4 where plasma can be generated. This reason can also be explained as follows: The path from the contour of the first aperture 31a along the contour region R1 to the electrode plate 4 is shorter than the path from the contour of the first aperture 31a through the center of the first aperture 31a to the electrode plate 4. Therefore, the gradient of the electric field strength in the contour region R1 becomes steeper, and it is thought that a high-density plasma is generated in the contour region R1.

[0037] Incidentally, when the high-frequency power supply 50 applies a high-frequency voltage between the first electrode 51 and the second electrode 52, not only a high-frequency electric field but also a high-frequency magnetic field can be generated between the first electrode 51 and the second electrode 52. The distance between the plasma reactor 5 and the first mask 31 may be set to a value such that the high-frequency magnetic field acts on the first mask 31. When the high-frequency magnetic field acts on the first mask 31, induced power can be generated in the first mask 31. This induced power can also contribute to the generation of an electric field between the first mask 31 and the electrode plate 4. In other words, the induced power can contribute to the generation of plasma between the first mask 31 and the electrode plate 4.

[0038] Figure 4 is a schematic diagram showing an example of the internal configuration of the control unit 9. The control unit 9 comprehensively controls the etching apparatus 1. The control unit 9 is an electronic circuit and includes, for example, an arithmetic processing unit 91 and a storage unit 92. The arithmetic processing unit 91 and the storage unit 92 can be interconnected via a bus 93. The arithmetic processing unit 91 may be, for example, an arithmetic processing unit such as a CPU (Central Processor Unit). The storage unit 92 may include a non-temporary storage unit (e.g., ROM (Read Only Memory)) 921 and a temporary storage unit (e.g., RAM (Random Access Memory)) 922. The non-temporary storage unit 921 may store, for example, a program that defines the processing to be executed by the control unit 9. By executing this program, the arithmetic processing unit 91 enables the control unit 9 to execute the processing defined in the program. Of course, some or all of the processing executed by the control unit 9 may be executed by hardware such as dedicated logic circuits. In the example of Figure 4, the control unit 9 is also connected to a non-temporary auxiliary storage device 94 (e.g., memory such as flash memory or a hard disk).

[0039] Figure 5 is a flowchart illustrating an example of the operation of the etching apparatus 1. First, the first mask 31 is placed on the first main surface Wa of the insulating substrate W (step S1). For example, a transport robot (not shown) holds the first mask 31 in a horizontal position. This transport robot is controlled by the control unit 9 and holds the first mask 31 using, for example, a mechanical chuck, a suction method, or an electrostatic chuck method. Under the control of the control unit 9, the transport robot moves the held first mask 31 and places it on the first main surface Wa of the insulating substrate W. Then, under the control of the control unit 9, the transport robot transports the insulating substrate W with the first mask 31 placed on it to the substrate placement section 2. The substrate placement section 2 supports or holds the insulating substrate W with the first mask 31 placed on it in a horizontal position.

[0040] Next, the etching apparatus 1 performs plasma etching (step S2). Specifically, the control unit 9 causes the high-frequency power supply 50 to output a high-frequency voltage. This generates an electric field between the first electrode 51 and the second electrode 52, causing the gas in the first gas space G1 to become plasma. In the above example, since the first electrode 51 and the second electrode 52 are covered with a dielectric 53, the plasma reactor 5 can turn the gas into plasma by a so-called dielectric barrier discharge.

[0041] The plasma acts on the insulating substrate W at the first opening 31a of the first mask 31, potentially etching the insulating substrate W. This plasma also acts on the conductive first mask 31. The action of this plasma on the first mask 31 generates a high-frequency electric field between the first mask 31 and the electrode plate 4, generating plasma between the first mask 31 and the electrode plate 4. A plasma with high plasma density is generated between the first mask 31 and the electrode plate 4, particularly in the contour region R1. The plasma in the contour region R1 acts on the first main surface Wa of the insulating substrate W, causing the insulating substrate W to be etched, especially in the contour region R1.

[0042] This etching process removes the portion of the first main surface Wa of the insulating substrate W that is within the first opening 31a of the first mask 31, forming a hole. This hole deepens over time and eventually becomes a through hole connecting the first main surface Wa and the second main surface Wb.

[0043] When a plurality of through holes are formed in the insulating substrate W, the control unit 9 causes the high-frequency power supply 50 to stop outputting high-frequency voltage. As a specific example, the control unit 9 stops the high-frequency power supply 50 when a predetermined processing time has elapsed from the start of output of the high-frequency voltage. The processing time is set in advance and stored in, for example, the auxiliary storage device 94. The time measurement is performed using, for example, a timer circuit (not shown) built into the control unit 9. Note that the method by which the control unit 9 stops the high-frequency power supply 50 is not limited to this. For example, when a ground potential is applied to the electrode plate 4, the control unit 9 may acquire the value of current flowing through the electrode plate 4 and stop the high-frequency power supply 50 based on a change in the current value. This is because there is a large difference in the value of current flowing through the electrode plate 4 before and after the through holes are formed in the insulating substrate W.

[0044] As described above, in the etching apparatus 1, the plasma generated by the plasma reactor 5 not only contributes to the etching of the insulating substrate W, but also enables the first mask 31 and the electrode plate 4 to function as capacitively coupled plasma electrodes. The plasma caused by the electric field between the first mask 31 and the electrode plate 4 also contributes to the etching of the insulating substrate W. Therefore, the etching apparatus 1 can form a plurality of through holes in the insulating substrate W more rapidly. In particular, the plasma caused by the electric field between the first mask 31 and the electrode plate 4 is generated at a higher density in the contour region R1. Accordingly, the etching apparatus 1 can form a plurality of through holes in the insulating substrate W even more rapidly.

[0045] In the above example, the lower surface 53b of the plasma reactor 5 is a flat surface, and plasma is generated along the lower surface 53b. Therefore, the plasma reactor 5 can generate plasma more uniformly in a plan view, and can make the plasma act on the first mask 31 and the insulating substrate W more uniformly. Accordingly, the etching apparatus 1 can uniformly form a plurality of through holes in the insulating substrate W.

[0046] Incidentally, in the example of Fig. 1, the etching apparatus 1 includes a gas supply unit 6. The gas supply unit 6 supplies a gas for plasma to a first gas space G1. The gas may contain, for example, an inert gas. The inert gas contains, for example, at least one of nitrogen gas and a rare gas. The rare gas contains, for example, argon gas. The gas may contain a reactive gas. The reactive gas is a gas that chemically reacts with the insulating substrate W, and includes, for example, a fluorine-containing gas having a fluorine element. The fluorine-containing gas includes, for example, at least one of a carbon fluoride gas (CxFy) and a sulfur fluoride gas (SFx).

[0047] In the example of Fig. 1, the gas supply unit 6 includes an air supply pipe 61 and a valve 62. In the example of Fig. 1, a downstream outlet of the air supply pipe 61 is provided on a side of the first gas space G1. An upstream end of the air supply pipe 61 is connected to a gas supply source (not shown). The valve 62 is provided on the air supply pipe 61. The valve 62 is controlled by a control unit 9 to switch opening and closing of the air supply pipe 61. When the control unit 9 opens the valve 62, the gas is supplied into the first gas space G1 through the air supply pipe 61. The gas is turned into plasma by the plasma reactor 5.

[0048] The control unit 9 may open the valve 62 in step S2, for example. Accordingly, the gas supply unit 6 can supply gas to the first gas space G1 during etching. When the gas supply unit 6 supplies a reactive gas to the first gas space G1, the etching apparatus 1 can etch the insulating substrate W accompanied by a chemical reaction. Therefore, the etching apparatus 1 can more rapidly form a plurality of through holes in the insulating substrate W.

[0049] Also, in the example of Fig. 1, the substrate arrangement portion 2 includes a first dielectric portion 21 and a second dielectric portion 22. The first dielectric portion 21 and the second dielectric portion 22 are formed of a dielectric material. Although the dielectric material is not particularly limited, it includes, for example, at least one of synthetic resin, quartz glass and ceramics.

[0050] The first dielectric portion 21 faces the second main surface Wb of the insulating substrate W, which is held or supported by the substrate placement portion 2, across the second gas space G2. In the example of Figure 1, the first dielectric portion 21 is located between the insulating substrate W and the electrode plate 4. The first dielectric portion 21 has, for example, a plate-like shape and is provided in a position where its thickness direction is aligned with the thickness direction of the insulating substrate W. The main surface of the first dielectric portion 21 that faces the second main surface Wb of the insulating substrate W (here, the top surface) may be a flat surface parallel to the second main surface Wb. The second main surface Wb of the insulating substrate W is in contact with the second gas space G2.

[0051] The second dielectric portion 22 can be formed from a dielectric material. The dielectric material includes, for example, at least one of synthetic resin, quartz glass, and ceramics. The second dielectric portion 22 protrudes from the main surface (here, the top surface) of the first dielectric portion 21 toward the insulating substrate W. The second dielectric portion 22 supports or holds at least a portion of the peripheral edge of the insulating substrate W. In the cross-section illustrated in Figure 1, two second dielectric portions 22 are shown. One second dielectric portion 22 supports the peripheral edge of the insulating substrate W on one side in the arrangement direction D2, and the other second dielectric portion 22 supports the peripheral edge of the insulating substrate W on the other side in the arrangement direction D2. The space enclosed by the insulating substrate W, the first dielectric portion 21, and the second dielectric portion 22 corresponds to the second gas space G2. In other words, the substrate portion 2 including the first dielectric portion 21 and the second dielectric portion 22 contributes to the formation of the second gas space G2.

[0052] In this structure, the high-frequency electric field between the first mask 31 and the electrode plate 4 also acts on the gas in the second gas space G2. As a result, the gas in the second gas space G2 is also plasma-generated. Therefore, the second gas space G2 can effectively function as a conductor. Hereafter, the plasma in the second gas space G2 will also be referred to as the plasma conductor. The insulation distance between the first mask 31 and the plasma conductor is shorter than the insulation distance between the first mask 31 and the electrode plate 4. Therefore, the plasma density of the plasma generated in multiple contour regions R1 can be further improved.

[0053] Furthermore, since the plasma in the second gas space G2 is in uniform contact with the second main surface Wb of the insulating substrate W, the electrical contact between the first mask 31 and the plasma conductor is relatively high. Therefore, variations in plasma density among the multiple first apertures 31a can be reduced. Consequently, the etching rate on the insulating substrate W can be made more uniform among the multiple first apertures 31a. In other words, the etching apparatus 1 can carry out etching on the insulating substrate W more uniformly among the multiple first apertures 31a.

[0054] Here, as an alternative example of the etching apparatus 1, a structure in which the electrode plate 4 is in contact with the second main surface Wb of the insulating substrate W will also be described. Figure 6 is a schematic diagram showing an alternative configuration of the etching apparatus 1. In the example of Figure 6, the second dielectric portion 22 is not provided, and the electrode plate 4 is provided on the first dielectric portion 21. The insulating substrate W is then placed on the electrode plate 4. In this structure, since the electrode plate 4 can support the insulating substrate W, the electrode plate 4 can also function as the substrate placement portion 2. In this structure as well, plasma is generated in the contour region R1 of each first opening 31a due to the high-frequency electric field between the first mask 31 and the electrode plate 4. Moreover, since the insulation distance between the first mask 31 and the electrode plate 4 is short, the etching apparatus 1 can generate plasma with a relatively high plasma density.

[0055] On the other hand, since the insulating substrate W and the electrode plate 4 are solid, minute gaps may occur between the insulating substrate W and the electrode plate 4. As a result, variations in the distribution of electrical contact between the first mask 31 and the electrode plate 4 occur in a plan view. Consequently, variations in the etching rate of the insulating substrate W may occur among the multiple first openings 31a.

[0056] In contrast, if a second gas space G2 is formed as shown in Figure 1, the etching apparatus 1 can etch the insulating substrate W more uniformly between the multiple first openings 31a.

[0057] Furthermore, as described above, if the substrate placement area 2 is made of a dielectric material, the substrate placement area 2 has almost no effect on the generation of plasma using the first mask 31 and electrode plate 4 as plasma electrodes. Conversely, the etching apparatus 1 can generate plasma in the second gas space G2 with little influence from the substrate placement area 2.

[0058] Incidentally, the gas supply unit 6 supplies gas to the first gas space G1 during etching. At this time, the gas supply unit 6 does not need to supply much reactive gas to the second gas space G2. For example, the second dielectric portion 22 of the substrate placement portion 2 may have an annular shape in plan view, and may be in contact with the peripheral edge of the insulating substrate W around its entire circumference. As a result, the entire second gas space G2 is surrounded by the insulating substrate W, the second dielectric portion 22, and the first dielectric portion 21, so the second gas space G2 is separated from the first gas space G1. Therefore, the inflow of reactive gas from the gas supply unit 6 into the second gas space G2 is reduced or avoided. This reduces the possibility that the second main surface Wb of the insulating substrate W will be unnecessarily etched.

[0059] In the example described above, the electrode plate 4 is subjected to ground potential, but this is not necessarily the only example. A high-frequency potential opposite in phase to the high-frequency voltage between the first electrode 51 and the second electrode 52 may also be applied to the electrode plate 4.

[0060] <Second Embodiment> Figure 7 is a schematic side view showing an example of the configuration of the etching apparatus 1 according to the second embodiment. The etching apparatus 1 according to the second embodiment differs from the etching apparatus 1 according to the first embodiment in that it has a second mask 32 or not.

[0061] The second mask 32 has a plate-like shape. The second mask 32 is positioned on the second main surface Wb of the insulating substrate W with its thickness direction aligned with the thickness direction of the insulating substrate W. In the example shown in Figure 7, the second mask 32 is supported by the substrate placement portion 2, the insulating substrate W is placed on the second mask 32, and the first mask 31 is placed on the insulating substrate W. In other words, the insulating substrate W is located between the first mask 31 and the second mask 32.

[0062] The second mask 32 has a plurality of second openings 32a. Each second opening 32a penetrates the second mask 32 in its thickness direction. The plurality of second openings 32a are arranged two-dimensionally in a plan view. The first mask 31 and the second mask 32 are aligned with respect to the insulating substrate W such that each of the plurality of second openings 32a is aligned vertically with each of the plurality of first openings 31a. For example, in a plan view, the relative positional relationship of the plurality of second openings 32a is the same as the relative positional relationship of the plurality of first openings 31a. Also, as a specific example, the shape of each second opening 32a in a plan view is the same as the shape of the first opening 31a in a plan view (here, circular). The second mask 32 may have the same shape as the first mask 31 in a plan view. The first mask 31 and the second mask 32 are positioned on the first main surface Wa and the second main surface Wb of the insulating substrate W, respectively, in a positional relationship where the plurality of first openings 31a and the plurality of second openings 32a are coaxial.

[0063] In the example shown in Figure 7, the second dielectric portion 22 of the substrate placement area 2 supports the peripheral edge of the second mask 32. The main surface (in this case, the top surface) of the second mask 32 is in contact with the second main surface Wb of the insulating substrate W. The second mask 32 is also in contact with the second gas space G2.

[0064] The second mask 32 may be formed of a conductive material or a dielectric material. Here, as an example, the second mask 32 is formed of a dielectric material.

[0065] An example of the operation of the etching apparatus 1 according to the second embodiment is the same as in Figure 5. However, in step S1, the first mask 31 is placed on the first main surface Wa of the insulating substrate W, and the second mask 32 is placed on the second main surface Wb of the insulating substrate W. For example, a transport robot (not shown) holds the insulating substrate W under the control of the control unit 9 and moves the insulating substrate W to place the insulating substrate W on the second mask 32. Next, the transport robot holds the first mask 31 under the control of the control unit 9 and moves the first mask 31 to place the first mask on the insulating substrate W. Next, the transport robot transports the first mask 31, the insulating substrate W, and the second mask 32 together to the substrate placement section 2. The substrate placement section 2 supports or holds the first mask 31, the insulating substrate W, and the second mask 32 together.

[0066] Next, in step S2, with the first mask 31 positioned on the first main surface Wa of the insulating substrate W and the second mask 32 positioned on the second main surface Wb of the insulating substrate W, the plasma reactor 5 applies plasma to the insulating substrate W and the first mask 31. Specifically, the control unit 9 outputs a high-frequency voltage to the high-frequency power supply 50. As a result, the gas in the first gas space G1 is converted into plasma, and the plasma acts on the insulating substrate W within the first opening 31a of the first mask 31, as well as on the first mask 31. The plasma acting on the first mask 31 generates a high-frequency electric field between the first mask 31 and the electrode plate 4. This electric field causes a plasma with high plasma density to form in the contour region R1, and also converts the gas in the second gas space G2 into plasma. The plasma in the second gas space G2 etches the second main surface Wb of the insulating substrate W within each second opening 32a of the second mask 32.

[0067] As described above, in the second embodiment, through holes are formed by etching both the first main surface Wa and the second main surface Wb of the insulating substrate W. Therefore, the etching apparatus 1 can form through holes even more quickly.

[0068] Figure 8 is a schematic cross-sectional view showing an example of the configuration of an insulating substrate W in which a through-hole H1 is formed by an etching apparatus 1 according to the second embodiment. According to the second embodiment, as shown in Figure 8, the through-hole H1 tends to be hourglass-shaped. That is, in the second embodiment, since the insulating substrate W is etched from both the first main surface Wa and the second main surface Wb, the shape of the through-hole H1 tends to be hourglass-shaped. In the example of Figure 8, the through-hole H1 includes a first diameter-reducing portion that decreases in diameter as it moves away from the first main surface Wa, a second diameter-reducing portion that decreases in diameter as it moves away from the second main surface Wb, and a cylindrical portion between the first and second diameter-reducing portions. The first and second diameter-reducing portions may have a frustoconical shape. In an interposer in which a through-electrode is formed inside the through-hole H1, an hourglass-shaped through-hole H1 can reduce poor contact between the semiconductor chip and the wiring substrate through the through-electrode.

[0069] Incidentally, in the second embodiment as well, the etching apparatus 1 may include a gas supply unit 6. The gas supply unit 6 may supply gas to both the first gas space G1 and the second gas space G2 during etching. In other words, the second gas space G2 may be in communication with the first gas space G1. For example, the second dielectric portion 22 does not need to be provided on both peripheral edges of the insulating substrate W in the extending direction D1.

[0070] The control unit 9 may, for example, open the valve 62 in step S2. This allows the gas supply unit 6 to supply gas to the first gas space G1 and the second gas space G2 during etching. When the gas supply unit 6 supplies reactive gas to the first gas space G1 and the second gas space G2, the etching apparatus 1 can etch the insulating substrate W with a chemical reaction. As a result, the etching apparatus 1 can more quickly form multiple through holes H1 in the insulating substrate W.

[0071] Furthermore, if the second mask 32 is formed of a dielectric material, the second mask 32 does not electrically interact with the plasma. Therefore, the etching apparatus 1 can generate plasma in the second gas space G2 using the first mask 31 and electrode plate 4 as plasma electrodes, with minimal influence from the second mask 32.

[0072] <Third Embodiment> In the third embodiment, another example of the plasma reactor 5 will be described. Figure 9 is a schematic side view showing a first example of the configuration of the etching apparatus 1 according to the third embodiment. The etching apparatus 1 according to the third embodiment differs from the etching apparatus 1 according to the first and second embodiments in terms of the configuration of the plasma reactor 5. Figure 10 is a schematic plan view showing an example of the configuration of the plasma reactor 5 according to the third embodiment.

[0073] The plasma reactor 5 is a planar plasma reactor and includes a plurality of first electrodes 51, a plurality of second electrodes 52, a plurality of dielectric members 54, a plurality of dielectric members 55, and a dielectric plate 56. The dielectric plate 56 has a plate-like shape and is positioned so that its thickness direction is aligned with the thickness direction of the insulating substrate W. The dielectric plate 56 is formed of a dielectric material such as quartz glass.

[0074] Multiple first electrodes 51 are positioned above the dielectric plate 56, and multiple second electrodes 52 are positioned below the dielectric plate 56. In other words, the dielectric plate 56 is positioned between the first electrodes 51 and the second electrodes 52.

[0075] As shown in Figure 10, the positional relationship between the first electrode 51 and the second electrode 52 in a plan view is the same as in the first embodiment. Of each first electrode 51, at least the portion facing the second electrode 52 is covered by a dielectric member 54. The dielectric member 54 has a cylindrical shape with a closed tip. Each first electrode 51 is inserted into the dielectric member 54 from its tip. The dielectric member 54 may have a cylindrical shape, and its inner circumferential surface may be in contact with the side surface of the first electrode 51. Of each second electrode 52, at least the portion facing the first electrode 51 is covered by a dielectric member 55. The dielectric member 55 has a cylindrical shape with a closed tip. Each second electrode 52 is inserted into the dielectric member 55 from its tip. The dielectric member 55 may have a cylindrical shape, and its inner circumferential surface may be in contact with the side surface of the second electrode 52. The dielectric member 54 and the dielectric member 55 are formed from a dielectric material such as quartz glass.

[0076] Multiple dielectric members 54 are in contact with the upper surface of the dielectric plate 56, and multiple dielectric members 55 are in contact with the lower surface of the dielectric plate 56. The multiple dielectric members 55 and the lower surface of the dielectric plate 56 are in contact with the first gas space G1.

[0077] In the third embodiment as well, the control unit 9 causes the high-frequency power supply 50 to output a high-frequency voltage. This generates a high-frequency electric field between the first electrode 51 and the second electrode 52. This electric field causes the gas in the first gas space G1 to become plasma. Similar to the first and second embodiments, the plasma acts on the insulating substrate W at the first opening 31a of the first mask 31, as well as on the conductive first mask 31. Therefore, a high-frequency electric field is also generated between the first mask 31 and the electrode plate 4, generating a high-density plasma, particularly in the contour region R1.

[0078] In the first example of the third embodiment, since the plasma reactor 5 is a planar plasma reactor, multiple through holes can be formed more uniformly in the insulating substrate.

[0079] Figure 11 is a schematic side view showing a second example of the configuration of the etching apparatus 1 according to the third embodiment. In the second example, the plasma reactor 5 is a pen-type plasma reactor. The plasma reactor 5 includes a housing 57, a first electrode 58, and a second electrode 59. The housing 57 is provided above the insulating substrate W placed on the substrate placement section 2. The housing 57 has a cylindrical shape, and in the example of Figure 11, it is provided in a position where its longitudinal direction is aligned with the vertical direction. An outlet 57a is formed at the lower end of the housing 57. The outlet 57a may have a circular shape in plan view. Gas is supplied into the housing 57. In the example of Figure 11, the downstream end of the air supply pipe 61 is connected to the upper part of the housing 57. When the valve 62 is opened, gas from the gas supply source flows into the housing 57 through the air supply pipe 61. Inside the housing 57, the gas is plasma-generated by the electric field between the first electrode 58 and the second electrode 59, and the plasma flows out from the outlet 57a. In the example of Figure 11, the first electrode 58 has a rod shape and is positioned so that its longitudinal direction is aligned with the vertical direction. Part of the first electrode 58 is located inside the housing 57, and the upper part of the first electrode 58 protrudes through the upper part of the housing 57. In the example of Figure 11, at least the portion of the first electrode 58 located inside the housing 57 is covered by a dielectric member 581. The dielectric member 581 has a cylindrical shape with a closed tip. Each first electrode 58 is inserted into the dielectric member 581 from its tip. The second electrode 59 has a cylindrical shape that surrounds the housing 57 from the outside. The second electrode 59 surrounds a portion of the first electrode 58 in the vertical direction. The first electrode 58 is connected to the first output terminal 50a of the high-frequency power supply 50, and the second electrode 59 is connected to the second output terminal 50b of the high-frequency power supply 50. The gas is converted into plasma as it passes between the first electrode 58 and the second electrode 59.

[0080] The plasma reactor 5 is moved by a moving drive unit 500. The moving drive unit 500 is controlled by a control unit 9 and moves the plasma reactor 5 along a horizontal movement direction D4. The moving drive unit 500 may be a two-axis moving drive unit that moves the plasma reactor 5 in two mutually orthogonal horizontal directions. The moving drive unit 500 includes, for example, a drive source such as a motor and a power transmission unit that transmits the driving force of the drive source to the plasma reactor 5. The power transmission unit includes, for example, a ball screw mechanism.

[0081] The control unit 9 opens the valve 62 and outputs a high-frequency voltage to the high-frequency power supply 50, and controls the moving drive unit 500 to move the plasma reactor 5 along the moving direction D4. As a result, the plasma reactor 5 moves along the moving direction D4 while releasing plasma from the outlet 57a toward the first mask 31 and the insulating substrate W. By causing the control unit 9 to scan the plasma reactor 5 in two dimensions, the plasma reactor 5 can apply plasma to the entire surface of the first mask 31 and the insulating substrate W.

[0082] As described above, the etching method and etching apparatus 1 have been explained in detail, but the above description is illustrative in all respects, and this disclosure is not limited thereto. Furthermore, the various modifications described above can be applied in combination as long as they do not contradict each other. And it is understood that many modifications not illustrated can be conceivable without falling outside the scope of this disclosure.

[0083] This disclosure includes the following aspects:

[0084] A first embodiment is an etching method, wherein a plasma reactor facing a conductive first mask having a plurality of first openings arranged on a first main surface of an insulating substrate, across a first gas space, causes the gas in the first gas space to become plasma, and the plasma acts on the first mask to generate an electric field between the first mask and an electrode plate provided on the opposite side of the insulating substrate from the first mask, thereby generating plasma between the electrode plate and the first mask.

[0085] A second embodiment is an etching method according to the first embodiment, wherein the electric field between the first mask and the electrode plate generates plasma in the second gas space facing the second main surface of the insulating substrate.

[0086] A third embodiment is an etching method according to the second embodiment, wherein the plasma reactor applies the plasma to the first mask while a second mask having a plurality of second openings coaxially positioned with the plurality of first openings of the first mask is placed on the second main surface of the insulating substrate.

[0087] A fourth embodiment is an etching method according to the third embodiment, wherein the second mask, formed of a dielectric material, is placed on the second main surface of the insulating substrate, and the plasma reactor acts the plasma on the first mask.

[0088] A fifth embodiment is an etching method according to any one of the first to fourth embodiments, wherein a planar plasma reactor applies the plasma to the first mask.

[0089] A sixth embodiment is an etching apparatus comprising: a substrate placement section that supports or holds an insulating substrate on which a conductive first mask having a plurality of first openings is disposed on a first main surface; an electrode plate provided on the opposite side from the first mask to the insulating substrate disposed by the substrate placement section, to which a potential is applied; and a plasma reactor facing the first mask across a first gas space, which plasmaizes the gas in the first gas space and acts the plasma on the first mask.

[0090] The seventh embodiment is an etching apparatus according to the sixth embodiment, wherein the electrode plate is provided in a position facing the second main surface of the insulating substrate, separated by a second gas space that faces the second main surface of the insulating substrate.

[0091] The eighth aspect is an etching apparatus according to the seventh aspect, wherein the substrate placement portion includes a first dielectric portion provided between the second main surface of the insulating substrate and the electrode plate, and a second dielectric portion connected to the first dielectric portion and supporting or holding at least a part of the peripheral edge of the insulating substrate.

[0092] The ninth aspect is an etching apparatus according to the seventh or eighth aspect, wherein the substrate placement portion supports or holds the insulating substrate on which the first mask is placed on the first main surface and a second mask having a plurality of second openings is placed on the second main surface.

[0093] The tenth embodiment is an etching apparatus according to the ninth embodiment, wherein the second mask is formed of a dielectric material.

[0094] The eleventh embodiment is an etching apparatus according to any one of the sixth to tenth embodiments, wherein the plasma reactor is a planar plasma reactor.

[0095] According to the first and sixth embodiments, the conductive first mask and electrode plate can function as capacitively coupled electrodes, and plasma is generated between the first mask and the electrode plate. This plasma is generated particularly along the contours of each opening in the first mask. In other words, a plasma with a higher plasma density can be generated along the contours of each opening in the first mask. Therefore, multiple through holes can be formed in the insulating substrate more quickly.

[0096] According to the second and seventh embodiments, the plasma in the second gas space allows the second gas space to function as an equivalent conductor. The plasma in the second gas space is in more uniform contact with the second main surface of the insulating substrate. As a result, variations in plasma density among the multiple first apertures can be reduced, and the etching rate on the insulating substrate can be made more uniform among the multiple first apertures.

[0097] According to the third and ninth embodiments, multiple through-holes are formed by etching from both the first and second main surfaces of the insulating substrate. Therefore, multiple through-holes can be formed more quickly.

[0098] According to the fourth and tenth embodiments, plasma can be generated in the second gas space with minimal influence from the second mask.

[0099] According to the fifth and eleventh embodiments, multiple through holes can be formed more uniformly in the insulating substrate.

[0100] According to the eighth aspect, a second gas space can be formed.

[0101] 1 Etching apparatus 2 Substrate placement area 21 First dielectric portion 22 Second dielectric portion 31 First mask 31a First opening 32 Second mask 32a Second opening 4 Electrode plate 5 Plasma reactor G1 First gas space G2 Second gas space W Insulating substrate Wa First main surface Wb Second main surface

Claims

1. An etching method comprising: a plasma reactor facing a conductive first mask having a plurality of first openings arranged on a first main surface of an insulating substrate, separated by a first gas space, which plasmaizes the gas in the first gas space, and acts the plasma on the first mask to generate an electric field between the first mask and an electrode plate provided on the opposite side of the insulating substrate from the first mask, thereby generating plasma between the electrode plate and the first mask.

2. An etching method according to claim 1, wherein the electric field between the first mask and the electrode plate generates plasma in the second gas space facing the second main surface of the insulating substrate.

3. An etching method according to claim 2, wherein the plasma reactor applies the plasma to the first mask while a second mask having a plurality of second apertures coaxially positioned with the plurality of first apertures of the first mask is placed on the second main surface of the insulating substrate.

4. An etching method according to claim 3, wherein the plasma reactor acts the plasma on the first mask while the second mask, formed of a dielectric material, is placed on the second main surface of the insulating substrate.

5. An etching method according to any one of claims 1 to 4, wherein a planar plasma reactor applies the plasma to the first mask.

6. An etching apparatus comprising: a substrate placement section that supports or holds an insulating substrate on which a conductive first mask having a plurality of first openings is disposed on a first main surface; an electrode plate provided on the opposite side from the first mask to the insulating substrate disposed by the substrate placement section, to which a potential is applied; and a plasma reactor facing the first mask across a first gas space, which plasmaizes the gas in the first gas space and applies the plasma to the first mask.

7. Etching apparatus according to claim 6, wherein the electrode plate is provided at a position facing the second main surface, separated by a second gas space that faces the second main surface of the insulating substrate.

8. An etching apparatus according to claim 7, wherein the substrate placement portion includes a first dielectric portion provided between the second main surface of the insulating substrate and the electrode plate, and a second dielectric portion connected to the first dielectric portion and supporting or holding at least a part of the peripheral edge of the insulating substrate.

9. Etching apparatus according to claim 7 or claim 8, wherein the substrate placement portion supports or holds the insulating substrate on which the first mask is placed on the first main surface and a second mask having a plurality of second openings is placed on the second main surface.

10. Etching apparatus according to claim 9, wherein the second mask is formed of a dielectric material.

11. An etching apparatus according to any one of claims 6 to 8, wherein the plasma reactor is a planar plasma reactor.

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