JP6007002B2 - Through-hole forming method and glass substrate with through-hole - Google Patents

Description

  The present invention relates to a through hole forming method and a glass substrate with a through hole.

  In the biochip manufacturing process, it is known that a through-hole penetrating in the thickness direction is formed in a glass substrate, and biomolecules such as DNA and protein and cells having this biomolecule are fixed inside the through-hole. ing.

  In addition, in a semiconductor device manufacturing process, it is known to dispose an interposer between a semiconductor chip and a mounting substrate in order to electrically connect the semiconductor chip and the mounting substrate (for example, see Patent Document 1). ). Here, the interposer is provided with a through hole penetrating in the thickness direction, and a via contact is formed by filling the through hole with a metal material or forming a metal film on the inner surface of the through hole. The semiconductor chip and the mounting substrate are electrically connected through the via contact. In this case, the above conventional example discloses that a glass substrate is used as a substrate constituting the interposer. The glass substrate is preferably used for a specific application or for miniaturization of devices.

  A method of forming the through hole in the glass substrate is known from Patent Document 2. In this case, a glass substrate is formed by forming a resist pattern on one surface of the glass substrate, forming a protective film on the other surface of the glass substrate, and wet-etching the glass substrate from the one surface side through the resist pattern. A tapered hole that tapers from one surface side of the substrate to a substantially intermediate position is formed. Then, using a similar method, a tapered hole that tapers from the other surface side of the glass substrate to a substantially intermediate position is formed. In this way, the holes formed from both sides of the glass substrate communicate with each other to form a through hole. However, the diameter of the through hole gradually decreases from the upper surface to the intermediate position of the glass substrate, and the through hole extends from the intermediate position to the lower surface. Since the diameter of the hole gradually increases, a flange extending inward is formed at an intermediate position of the through hole. This flange remains even if another substrate that has been subjected to predetermined processing is bonded to the lower surface of the glass substrate after the formation of the through-hole. Become.

  Therefore, a protective film is formed on the lower surface of the glass substrate, a resist pattern is formed on the upper surface of the glass substrate, the glass substrate is wet-etched only from the upper surface, and a through hole having a tapered surface that tapers from the upper surface to the lower surface of the glass substrate. It is conceivable that the flange portion is not formed at the intermediate position of the through hole.

  However, as described in Patent Document 2, the protective film is generally made of rubber or resin, and the protective film made of rubber or resin has low adhesion to the glass substrate. For this reason, as shown in FIG. 6, when the protective film 12 is exposed at the bottom of the through hole 10, the etching solution penetrates between the exposed protective film 12 and the lower surface 1 b of the glass substrate 1. Etching is performed in the surface direction (direction perpendicular to the thickness direction). Thereby, the line | wire which makes the surrounding wall part 10b of the through-hole 10 formed in the glass substrate 1 has the inflection point 11, and becomes a reverse taper shape by which the hole diameter is gradually expanded below the inflection point 11. . And when the said another board | substrate is joined to the lower surface 1b of the glass substrate 1 in which the through-hole 10 was formed, the part of the inflection point 11 will become a wrinkle. This collar portion is also chipped due to a small impact at the time of joining, for example, and causes particles. In addition, after bonding another substrate to the lower surface of the glass substrate, when forming a metal film for wiring on the inner surface of the through-hole, the metal film is formed in a portion that is shaded by the flange (the reverse tapered portion) with good coverage It cannot be done, causing disconnection.

JP 2011-258654 A JP 2010-70415 A

  In view of the above points, the present invention provides a through-hole forming method and a glass substrate with a through-hole that can form a through-hole in which a flange does not occur even if another substrate is bonded to the glass substrate. Let it be an issue.

  In order to solve the above-mentioned problem, the through hole forming method of the present invention for forming a through hole penetrating in the thickness direction in a glass substrate is a first method of forming a metal film on one surface and the other surface of the glass substrate. A second step of patterning the metal film formed on the one surface to form a metal mask, and wet etching the glass substrate from the upper surface side through the metal mask with the metal mask side up. And a third step of forming a through hole having a tapered peripheral wall portion tapered from the upper surface to the lower surface of the glass substrate.

  Further, in the glass substrate with a through hole of the present invention in which at least one through hole penetrating in the thickness direction is formed in the glass substrate, the through hole is directed from one surface of the glass substrate to the other surface. It has a tapered tapered peripheral wall portion, and a line forming the peripheral wall portion reaches the other surface without having an inflection point.

  According to the above, in the first step, for example, a chromium film is formed as a metal film on one surface and the other surface of the glass substrate by a sputtering method. Next, in the second step, for example, a resist pattern is formed on the metal film formed on one surface of the glass substrate, and the metal film is patterned by wet etching over the resist pattern to form a metal mask. Next, in a third step, the glass substrate is wet-etched from the upper surface side through the metal mask, thereby forming a through hole having a tapered peripheral wall portion that tapers from the upper surface to the lower surface of the glass substrate. When the through hole is formed in this way, the metal film is exposed in the lower part, but the exposed metal film has good adhesion to the glass substrate, so that the etchant hardly penetrates between the metal film and the glass substrate, The lower surface of the glass substrate is not etched in the surface direction. For this reason, the line | wire which makes the surrounding wall part of a through-hole will reach a glass substrate lower surface, without having an inflection point. Therefore, the through hole can be formed in the glass substrate without generating a flange in the middle of the cross section of the through hole. And even if it joins to the other board | substrate by which the predetermined process was given to the lower surface of the glass substrate with such a through-hole, a collar part does not arise. Furthermore, since a metal film for wiring can be formed with good coverage on the peripheral wall portion (inner surface) of the through hole after substrate bonding, disconnection does not occur.

  In the present invention, it is preferable to provide a protective member for protecting the metal film below the glass substrate. According to this, even when the hole diameter of the through hole on the lower surface of the glass substrate is large, it is possible to prevent the metal film exposed at the lower portion of the through hole from breaking and etching the lower surface of the glass substrate in the surface direction.

1A to 1C are schematic cross-sectional views illustrating a through hole forming method according to an embodiment of the present invention. The photograph which expands and shows the cross section of the through-hole formed in the glass substrate. The schematic cross section which expands and shows the state which mounted | wore the mounting substrate to the glass substrate in which the through-hole was formed. The schematic cross section which shows the state which the metal film of the glass substrate lower side fractured | ruptured. The schematic cross section which shows the state which provided the protection member which protects the metal film of the glass substrate lower side. The schematic cross section which shows the state by which the glass substrate lower surface was etched by the surface direction.

  Hereinafter, with reference to the drawings, in a through hole forming method according to an embodiment of the present invention, one surface of a glass substrate is used as an upper surface, a metal mask is formed on the upper surface, and the glass substrate is placed on the upper surface side through the metal mask. A case where through-holes are formed by wet etching will be described as an example.

  As shown in FIG. 1A, chrome films 2 and 3 are formed on the upper surface 1a and the lower surface 1b of the glass substrate 1 to a thickness of 100 to 300 nm, for example (first step). The material of the glass substrate 1 is not particularly limited, and examples thereof include soda glass, alkali-free glass, borosilicate glass (Tempax float manufactured by Schott), and glass for low temperature anodic bonding (SW series manufactured by Asahi Glass Co., Ltd.). It is done. As a method of forming the chromium films 2 and 3, it is preferable to use a sputtering method in consideration of mass productivity. In this case, it is preferable to use a mixed gas of argon gas, nitrogen gas, and carbon dioxide gas as the sputtering gas, and the flow rate ratio can be set so that desired stress and reflectance can be obtained. In addition, since the thing which has a well-known structure can be used as a sputtering apparatus, detailed description about an apparatus structure and conditions is abbreviate | omitted here.

  Next, a resist 4 is applied to the surface of the chromium film 2 by a spin coat method with a thickness of, for example, 1 to 3 μm, and a pattern for forming a through hole is exposed on the applied resist 4 and developed with a developer, A resist pattern 4a is formed. Then, the chromium film 2 is wet-etched through the resist pattern 4a and patterned to form a chromium mask 2a (second step). As an etching solution for the chromium film 2, for example, a solution containing cerium ammonium nitrate can be used, and an acid such as nitric acid or perchloric acid may be added.

  Next, as shown in FIG. 1B, the glass substrate 1 is wet etched through the chrome mask 2a. As the etching solution, a hydrofluoric acid-based one can be used, and a mixed solution of diluted hydrofluoric acid, buffered hydrofluoric acid (BHF) and inorganic acid is used according to the material of the glass substrate 1 and a desired etching rate. be able to. When wet etching is performed for a predetermined time, a through-hole 10 that penetrates in the thickness direction of the glass substrate 1 is formed as shown in FIG. By adjusting the etching time, the hole diameter d of the through hole 10 on the lower surface 1b of the glass substrate can be controlled. When the through hole 10 is formed, the chromium film 3 is exposed in the lower part. Here, since the chromium film 3 has good adhesion to the glass substrate 1, it is difficult for the etching solution to penetrate between the exposed chromium film 3 and the glass substrate 1, and the lower surface 1 b of the glass substrate 1 has its surface direction (in the drawing). Not etched in the lateral direction). Therefore, the through-hole 10 has a tapered peripheral wall portion 10a that tapers from the upper surface 1a to the lower surface 1b of the glass substrate 1, and the line forming the peripheral wall portion 10a reaches the lower surface 1b without having an inflection point. . That is, it is possible to prevent the flange from being generated in the middle of the cross section of the through hole 10 of the glass substrate 1.

  Thereafter, the resist pattern 4a is peeled, and the chrome mask 2a and the chrome film 3 are dissolved and removed in an etching solution, whereby the glass substrate 1 with the through holes 10 as shown in FIGS. 2 and 3 is obtained. As the resist stripping solution, a known alkali-based one can be used, and as the etching solution, the above cerium ammonium nitrate can be used.

  As shown in FIG. 3, predetermined processing (for example, precision polishing, groove processing, hole processing, wiring pattern formation not shown) is performed on the lower surface of the glass substrate 1 in which the through holes 10 are formed in this way. Even if another substrate 5 is bonded, no gap is formed between the lower surface 1b of the glass substrate and the other substrate 5, so that no ridge is generated. For this reason, when a metal film is formed on the peripheral wall portion (inner surface) 10a of the through-hole 10 after the substrate is bonded, a metal film for wiring can be formed on the peripheral wall portion 10a with good coverage and adhesiveness. Can be prevented. For example, a glass substrate or a silicon substrate can be used as the other substrate 5. When the other substrate 5 is made of glass, the glass substrate 1 and the other substrate 5 are aligned, the aligned substrates are temporarily bonded, and the temporarily bonded substrate is softened at a softening point or less. The glass substrate 1 and the other substrate 5 can be joined by baking at a temperature of 500 ° C. (for example, 500 to 600 ° C. when both substrates are made of Schott Tempax float).

  By the way, the film forming speed of the chromium film 3 by the sputtering method is not so high, and the thickness of the chromium film 3 is set within the above range in consideration that the productivity decreases when the thickness of the chromium film 3 is increased. Is done. In this case, when the hole diameter d of the through hole 10 on the lower surface 1b of the glass substrate is large (for example, 3 mm or more), the etching of the glass substrate 1 proceeds and chromium is formed below the through hole 10 as shown in FIG. When the film 3 is exposed, the chromium film 3 is broken, and the chromium film 3 is peeled off from the lower surface 1b of the glass substrate. At this time, a gap is formed between the chromium film 3 and the glass substrate lower surface 1 b, the etchant penetrates into the gap, the glass substrate lower surface 1 b is etched in the surface direction, and the flange 11 is formed on the peripheral wall portion 10 b of the through hole 10. Will be formed.

  Therefore, as shown in FIG. 5, it is preferable to provide a protective member (protective film) 6 that protects the chromium film 3 on the lower side of the glass substrate 1 prior to wet etching of the glass substrate 1. As the protective member 6, a laminated film of a resist 6a and a protective film 6b can be used. If the resist 6a is formed by applying the same material immediately after the application of the resist 4 and is peeled off together with the resist pattern 4a, the production efficiency is good. As the protective film 6b, a resinous adhesive protective film can be used, and a known alkaline stripping solution can be used for peeling after the through hole 10 is formed. By providing such a protective member 6, it is possible to prevent the chrome film 3 from being broken when the through hole 10 is formed, and to surely form the flange 11 by etching the glass substrate lower surface 1 b in the surface direction. Can be prevented.

  The present invention is not limited to the above embodiment. For example, prior to the formation of the metal film 2, the upper surface 1a and the lower surface 1b of the glass substrate 1 may be polished or dipped. Moreover, you may comprise the protection member 6 only with 1 layer of a resist or a protective film. Further, as the metal films 2 and 3, a metal film having high adhesion to the glass substrate 1 or a laminated film in which at least two kinds of metal films are laminated can be used. For example, a Cr film, a Si film, a Ni film, a Cr film A laminated film of one kind of film selected from the films and an Au film, or a laminated film of a Cr film, a Ni film, and an Au film can be used. Moreover, naturally the glass substrate 1 with the through-hole 10 can be used also for uses other than a biochip and an interposer.

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 1a ... One side (upper surface), 1b ... The other side (lower side), 2 ... Chromium film (metal film), 2a ... Chromium mask (metal mask), 3 ... Chromium film (metal film), 6 ... protective member, 10 ... through hole, 10a ... peripheral wall, 11 ... inflection point.

Claims (3)

In a through hole forming method for forming a through hole penetrating in the thickness direction in a glass substrate,
A first step of forming a metal film on one side and the other side of the glass substrate;
A second step of patterning the metal film formed on the one surface to form a metal mask;
A third through hole having a tapered peripheral wall portion tapered from the upper surface side to the lower surface of the glass substrate is wet-etched from the upper surface side of the glass substrate with the metal mask side facing up. and the process, only including,
Prior to wet etching of the glass substrate, the method further includes a step of covering a metal film formed on the lower side of the glass substrate with a protective member, and the metal film exposed to the lower portion of the through hole during wet etching by the protective member is broken. A method for forming a through-hole, characterized in that The method for forming a through hole in a glass substrate according to claim 1 , wherein the protective member includes a resinous adhesive protective film . In the glass substrate with a through hole in which at least one through hole penetrating in the thickness direction is formed in the glass substrate,
A patterned metal film is formed on one surface of the glass substrate, a metal film and a protective member covering the metal film are laminated on the other surface of the glass substrate,
The through hole has a tapered peripheral wall portion that tapers from one surface of the glass substrate to the other surface, and a line forming the peripheral wall portion reaches the other surface without having an inflection point. A glass substrate with a through hole.