(19)
(11)EP 1 419 990 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
11.05.2011 Bulletin 2011/19

(21)Application number: 03256961.8

(22)Date of filing:  04.11.2003
(51)International Patent Classification (IPC): 
B81B 1/00(2006.01)

(54)

Method of forming a via hole through a glass wafer

Verfahren zur Herstellung eines Durchgangsloches in einem Wafer aus Glas

Procédé de formation d'un trou traversant dans une plaquette de verre


(84)Designated Contracting States:
DE FR GB

(30)Priority: 12.11.2002 KR 2002070121

(43)Date of publication of application:
19.05.2004 Bulletin 2004/21

(73)Proprietor: SAMSUNG ELECTRONICS CO., LTD.
Suwon-City, Kyungki-do (KR)

(72)Inventors:
  • Lee, Moon-chul
    Sungnam-city Gyunggi-do (KR)
  • Choi, Hyung
    Bundang-gu Sungnam-city Gyunggi-do (KR)
  • Jung, Kyu-dong
    Suwon-city Gyunggi-do (KR)
  • Jang, Mi
    Suwon-city Gyunggi-do (KR)

(74)Representative: Ertl, Nicholas Justin 
Elkington and Fife LLP Prospect House 8 Pembroke Road
Sevenoaks Kent TN13 1XR
Sevenoaks Kent TN13 1XR (GB)


(56)References cited: : 
  
  • OBERHAMMER J ET AL: "Incrementally etched electrical feedthroughs for wafer-level transfer of glass lid packages" TRANSDUCERS, SOLID-STATE SENSORS, ACTUATORS AND MICROSYSTEMS, 12TH INTERNATIONAL CONFERENCE, 2003, vol. 2, 9 June 2003 (2003-06-09), pages 1832-1835, XP010647406 PISCATAWAY, NJ, USA, IEEE ISBN: 0-7803-7731-1
  • PATENT ABSTRACTS OF JAPAN vol. 2002, no. 04, 4 August 2002 (2002-08-04) -& JP 2001 341314 A (RICOH CO LTD), 11 December 2001 (2001-12-11)
  • GRETILLAT M-A ET AL: "A new fabrication method for borosilicate glass capillary tubes with lateral inlets and outlets" SENSORS AND ACTUATORS A, vol. 60, no. 1-3, May 1997 (1997-05), pages 219-222, XP004134625 ELSEVIER SEQUOIA S.A., LAUSANNE, CH ISSN: 0924-4247
  • DIEPOLD T ET AL: "Smoothing of ultrasonically drilled holes in borosilicate glass by wet chemical etching" JOURNAL OF MICROMECHANICS AND MICROENGINEERING, vol. 6, no. 1, March 1996 (1996-03), pages 29-32, XP002346952 IOP PUBLISHING, UK ISSN: 0960-1317
  • SCHLAUTMANN S ET AL: "Powder-blasting technology as an alternative tool for microfabrication of capillary electrophoresis chips with integrated conductivity sensors" JOURNAL OF MICROMECHANICS AND MICROENGINEERING, vol. 11, no. 4, 1 October 2000 (2000-10-01), pages 386-389, XP002221383 IOP PUBLISHING, UK ISSN: 0960-1317
  • BELLOY E ET AL: "Micromachining of glass inertial sensors" JOURNAL OF MICROELECTROMECHANICAL SYSTEMS, vol. 11, no. 1, February 2002 (2002-02), pages 85-90, XP001124520 IEEE, USA ISSN: 1057-7157
  • WENSINK H ET AL: "Fine tuning the roughness of powder blasted surfaces" JOURNAL OF MICROMECHANICS AND MICROENGINEERING, vol. 12, no. 5, September 2002 (2002-09), pages 616-620, XP002346953 IOP PUBLISHING, UK ISSN: 0960-1317
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

BACKGROUND OF THE INVENTION



[0001] The present invention relates to a method of forming a via hole through a glass wafer. More particularly, the present invention relates to a method of forming a via hole through a glass wafer without producing an undercut.

[0002] It is generally known in the art that a via hole (or simply a "via") necessarily should be formed in a wafer level of a micro-electromechanical system (MEMS) packaging utilizing glass to permit the electrical processing of elements in the MEMS. In a conventional method of forming a via hole in a wafer level, however, since the via hole is formed by sandblasting after being patterned on a surface of the glass wafer, it is problematic in that the formed via hole may have an undercut portion and a rough surface. This undercut problem is especially pronounced in the formation of a via hole having a small diameter. In this case, not only is it difficult to etch the via hole, but the formed via hole may also have an undercut portion that causes a severe problem.

[0003] FIG. 1 illustrates a sectional view of a via hole formed through a glass wafer 100 using a conventional process, in which the via hole has an undercut portion 10 formed at a lower end thereof and a rough surface 20. FIGS. 2A and 2B are photographs showing enlarged views of a via hole, which is formed in an actual glass wafer using a conventional process, and an undercut portion formed at a lower end of the via hole, respectively.

[0004] In order to reduce formation of the undercut portion at the lower end of a via hole as described above, conventional methods of forming a via hole have employed a chemical mechanical polishing (CMP) step or a thick deposition of a metal film that enables electrical connection. In the case of the method employing the CMP step, however, since a portion of the glass surface is completely eliminated, characteristics of elements may be damaged in a packaging in which the delicate glass surface plays an important role. Further, the method employing the deposition of a metal film requires increased manufacturing steps and manufacturing cost.

[0005] Moreover, when the via hole is formed by sandblasting, the via hole may not only have a rough surface, but may also have minute cracks formed therein.

[0006] JP 2001 341314 discloses a sandblasting process using different grain sizes.

[0007] The article "A new fabrication method for borosilicate glass capillary tubes with lateral inlets and outlets", Sensors and Actuators A, vol. 60, no. 1-3, May 1997, pp 219-222 (XP004134625) discloses that HF etching can be used for processing a glass wafer.

[0008] The article "Smoothing of ultrasonically drilled holes in borosilicate glass by wet chemical etching", Journal of Micromechanics and Microengineering, vol. 6, no. 1 , March 1996, pp 29-32 (XP002346952) discloses that sandblasting, ultrasonic drilling or laser machining can be used to form holes.

SUMMARY OF THE INVENTION



[0009] According to the invention, there is provided a method of forming a via hole through a glass wafer as claimed in claim 1.

[0010] This method of forming a via hole through a glass wafer in an MEMS packaging is capable of preventing formation of an undercut and minute cracks at the via hole and enables the via hole to have a smooth surface.

[0011] The formation of the via-patterned portion may include laminating a film resistor on an upper surface of the material layer, and exposing and developing the film resistor to form the via-patterned portion on one side of the material layer. Preferably, the film resistor comprises a material having a large resistance to sandblast etching to permit the film resistor to function as a protection film during subsequent sandblasting of the glass wafer.

[0012] More preferably, the wet etching uses a hydrofluoric acid (HF) solution.

[0013] In the method of forming a via hole through a glass wafer according to the embodiment of the present invention as described above, a rough preliminary via hole is formed by a first etching and is then subjected to a second etching, so that a via hole is formed without an undercut or minute cracks.

BRIEF DESCRIPTION OF THE DRAWINGS



[0014] The above and other features and advantages of the present invention will become more apparent to those of ordinary skill in the art by describing in detail preferred embodiments thereof with reference to the attached drawings in which:

FIG. 1 illustrates a sectional view of a via hole formed through a glass wafer using a conventional process;

FIGS. 2A and 2B are photographs showing enlarged views of a via hole, which is formed in an actual glass wafer using a conventional process, and an undercut portion formed at a lower end of the via hole, respectively;

FIGS. 3A to 3E illustrate sectional views of sequential stages in a method of forming a via hole through a glass wafer according to a preferred embodiment of the present invention; and

FIGS. 4A and 4B are photographs showing enlarged views of a via hole, which is formed in an actual glass wafer by a method according to an embodiment of the present invention, and a lower end of the via hole, respectively.


DETAILED DESCRIPTION OF THE INVENTION



[0015] The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which a preferred embodiment of the invention is shown. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the thickness of layers and regions are exaggerated for clarity. It will also be understood that when a layer is referred to as being "on" another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Like numbers refer to like elements throughout.

[0016] FIGS. 3A to 3E illustrate sectional views of sequential stages in a method of forming a via hole through a glass wafer according to a preferred embodiment of the present invention.

[0017] Referring to FIG. 3A, a material layer 110 is deposited on an outer surface of a glass wafer 200. The material layer has a selection ratio higher than that of the glass wafer 200. The material layer is formed of polysilicon.

[0018] Referring to FIG. 3B, a film resistor 120 is laminated on an upper surface of the polysilicon layer 110 deposited on the glass wafer 200, and a via-patterned portion is formed thereon by exposure and development. The film resistor 120 is a material having a large resistance to sandblast etching, thus functioning as a protection film against subsequent sandblasting of the glass wafer 200. In an embodiment of the present invention, the formation of the via-patterned portion on the polysilicon layer 110 does not necessarily require the film resistor 120. The via-patterned portion may be formed using various photosensitive means.

[0019] Referring to FIG. 3C, the via-patterned portion is thereafter subjected to a first etching to form a preliminary via hole 130. During the first etching, the preliminary via hole 130 is etched to a sufficient depth so that the preliminary via hole 130 has a bottom adjacent to another side of the polysilicon layer opposite to the via-patterned portion. More specifically, the preliminary via hole 130 is formed to have a bottom adjacent to the polysilicon layer 110 formed on a lower surface of the glass wafer 200. The first etching is performed by sandblasting.

[0020] Referring now to FIG. 3D, subsequently, the film resistor 120 is eliminated, and the preliminary via hole 130 is etched a second time so that a via hole 130' having a smooth surface and extending completely to the polysilicon layer 110 through the glass wafer 200 is formed. The second etching is a wet etching. The second etching, which is a wet etching, may employ various etching solutions capable of making a chemical reaction with the glass wafer. Preferably, the wet etching uses a hydrofluoric acid (HF) solution.

[0021] Referring to FIG. 3E, the polysilicon layer 110 is eliminated to complete the formation of the via hole 130' through the glass wafer 200.

[0022] In the process described above, after the preliminary via hole 130 having a bottom adjacent to the polysilicon layer 110 has been formed by sandblasting, as shown in FIG. 3C, the preliminary via hole 130 still has a rough surface. However, since the preliminary via hole 130 is not a through hole extending through the glass wafer 200, the preliminary via hole 130 has no undercut portion, which is usually formed at a lower end thereof due to the characteristic of the glass. Thereafter, the preliminary via hole 130 is subjected to the second etching, which is a wet etching preferably utilizing the hydrofluoric acid (HF) solution. Then, the hydrofluoric acid (HF) solution chemically reacts with the rough glass surface of the preliminary via hole 130 formed by the sandblasting, thereby smoothing the rough surface. As a result, a via hole 130' having smooth surfaces and extending through the glass wafer, without an undercut portion formed at the lower end thereof, is completely formed.

[0023] FIGS. 4A and 4B are photographs showing enlarged views of a via hole, which is formed in an actual glass wafer by a method according to an embodiment of the present invention, and a lower end of the via hole, respectively. As shown in FIG. 4A, the via hole formed through the glass wafer by a method according to the present invention has a surface which is much smoother than the surface of the via hole shown in FIG. 2A formed by the conventional method. Further, a lower end of the via hole shown in FIG. 4B has no undercut portion.

[0024] The method of forming a via hole through a glass wafer according to the present invention as described above is able to overcome problems of the prior art, such as cut-off, which may be caused by the undercut portion formed during the formation of the via hole, thereby increasing a yield of MEMS elements.

[0025] Further, since the present invention employs a wet etching process that is capable of preventing the formation of minute cracks, the present invention improves reliability of the MEMS elements.

[0026] A preferred embodiment of the present invention has been disclosed herein and, although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. Accordingly, it will be understood by those of ordinary skill in the art that various changes in form and details may be made without departing from the scope of the present invention as set forth in the following claims.


Claims

1. A method of forming a via hole through a glass wafer, comprising:

depositing a material layer (110) on an entire surface of the glass wafer (200), the material layer being formed of polysilicon;

forming a patterned portion on one side of the material layer to define the via position;

performing a first etching in which the patterned portion is etched to form a preliminary via hole (130) which has a bottom adjacent to the material layer (110) on the opposite side of the wafer (200) to the patterned portion but not extending completely through the wafer (200), wherein the first etching is performed by sandblasting;

removing any remaining patterning material (120) used in the formation of the patterned portion;

performing a second etching in which the preliminary via hole (130) is etched to form a via hole (130') having a smooth surface and extending through the glass wafer (200) thereby extending completely to the material layer (110), wherein the second etching is a wet etching; and

removing the material layer (110).


 
2. The method as claimed in any preceding claim, wherein forming a patterned portion on one side of the material layer (110) comprises:

laminating a film resistor (120) on an upper surface of the material layer (110); and

exposing and developing the film resistor (120) to form the patterned portion on one side of the material layer (110).


 
3. The method as claimed in claim 2, wherein the film resistor (120) comprises a material having a large resistance to sandblast etching to permit the film resistor to function as a protection film during subsequent sandblasting of the glass wafer (200).
 
4. The method as claimed in claim 1, wherein the wet etching uses a hydrofluoric acid (HF) solution.
 


Ansprüche

1. Verfahren zum Bilden eines Kontaktlochs durch einen Glaswafer, das Folgendes beinhaltet:

Aufbringen einer Materialschicht (110) auf eine gesamte Oberfläche des Glaswafers (200), wobei die Materialschicht aus Polysilicium gebildet ist;

Ausbilden eines strukturierten Abschnitts auf einer Seite der Materialschicht, um die Kontaktierungsposition zu definieren;

Durchführen einer ersten Ätzung, bei der der strukturierte Abschnitt geätzt wird, um ein vorläufiges Durchkontaktierungsloch (130) mit einem Boden neben der Materialschicht (110) auf der gegenüberliegenden Seite des Wafers (200) bis zu dem strukturierten Abschnitt, aber nicht ganz durch den Wafer (200) zu bilden, wobei das erste Ätzen durch Sandstrahlen erfolgt;

Entfernen von verbleibendem Strukturierungsmaterial (120), das bei der Bildung des strukturierten Abschnitts verwendet wird;

Durchführen einer zweiten Ätzung, bei der das vorläufige Durchkontaktierungsloch (130) geätzt wird, um ein Durchkontaktierungsloch (130') mit einer glatten Oberfläche zu bilden, das durch den Glaswafer (200) und dadurch ganz bis zu der Materialschicht (110) verläuft, wobei das zweite Ätzen ein Nassätzen ist; und

Entfernen der Materialschicht (110).


 
2. Verfahren nach dem vorherigen Anspruch, wobei das Bilden eines strukturierten Abschnitts auf einer Seite der Materialschicht (110) Folgendes beinhaltet:

Laminieren eines Schichtwiderstands (120) auf eine Oberseite der Materialschicht (110); und

Belichten und Entwickeln des Schichtwiderstands (120) zum Bilden des strukturierten Abschnitts auf einer Seite der Materialschicht (110).


 
3. Verfahren nach Anspruch 2, wobei der Schichtwiderstand (120) ein Material mit einem hohen Widerstand gegenüber Sandstrahlätzen umfasst, so dass der Schichtwiderstand als Schutzfilm beim nachfolgenden Sandstrahlen des Glaswafers (200) dienen kann.
 
4. Verfahren nach Anspruch 1, wobei beim Nassätzen eine Fluorwasserstoff-(HF)-Lösung verwendet wird.
 


Revendications

1. Procédé de formation d'un trou de raccordement dans une plaquette de verre, comprenant :

le dépôt d'une couche de matériau (110) sur une surface entière de la plaquette de verre (200), la couche de matériau étant constituée de silicium polycristallin ;

la formation d'une partie à motif sur un côté de la couche de matériau pour définir la position de la connexion ;

l'exécution d'une première gravure dans laquelle la partie à motif est gravée pour former un trou de connexion préliminaire (130) qui a un fond adjacent à la couche de matériau (110) du côté de la plaquette (200) opposé à la partie à motif mais ne traversant pas complètement la plaquette (200), la première gravure étant exécutée par jet de sable ;

l'enlèvement de tout matériau de motif restant (120) utilisé dans la formation de la partie à motif ;

l'exécution d'une deuxième gravure dans laquelle le trou de connexion préliminaire (130) est gravé pour former un trou de connexion (130') ayant une surface lisse et traversant la plaquette de verre (200), pour se prolonger ainsi jusqu'à la couche de matériau (110), la deuxième gravure étant une gravure humide ; et

l'enlèvement de la couche de matériau (110).


 
2. Procédé selon la revendication précédente, dans lequel la formation d'une partie à motif d'un côté de la couche de matériau (110) comprend :

la lamination d'une résistance à couche (120) sur la surface supérieure de la couche de matériau (110) ; et

l'exposition et le développement de la résistance à couche (120) pour former la partie à motif sur un côté de la couche de matériau (110).


 
3. Procédé selon la revendication 2, dans lequel la résistance à couche (120) comprend un matériau ayant une grande résistance à la gravure par jet de sable pour permettre à la résistance à couche de servir de film protecteur pendant le sablage ultérieur de la plaquette de verre (200).
 
4. Procédé selon la revendication 1, dans lequel la gravure humide utilise une solution d'acide fluorhydrique (HF).
 




Drawing




















Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description




Non-patent literature cited in the description