Manufacturing method of silicon device

Details Manufacturing method of silicon device Manufacturing method of silicon device

2000-09-08

2002-03-19

Fahmy, Wael (Department: 2823)

Semiconductor device manufacturing: process

Chemical etching

Liquid phase etching

C438S747000, C438S753000, C438S977000

Reexamination Certificate

active

06358861

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a method of manufacturing a silicon device fabricated by processing a silicon substrate, such as various sensors used for measuring inertial force caused by acceleration or angular velocity etc., pressure or other various physical quantities, or a fluid device having a passage through which fluid or the like flows, the passage being formed in the silicon substrate.
BACKGROUND ART
Conventionally, a cantilever or a mass of free standing structure formed on a silicon substrate, or a hollow structure formed in the silicon substrate etc., is broadly used for sensors for measuring various physical quantities, micro pumps and so on.
FIGS. 15A
to
15
F are views showing a conventional manufacturing process for fabricating a device having a movable portion on a silicon substrate. According to the manufacturing process, a plate-shaped silicon substrate
32
is prepared at first, as shown in FIG.
15
A. Next, as shown in
FIG. 15B
, a first oxide film
33
, which is to be used as a sacrificial layer, is formed on the silicon substrate
32
by means of the CVD technique or the like, and then a first polysilicon film
34
, which is to be used as a seed layer, is formed on the oxide film by means of the low pressure CVD technique or the like. After that, as shown in
FIG. 15C
, a second polysilicon film
35
, which is to become a structural part, is formed on the first polysilicon film
34
using an epitaxial reactor. Further, after the second polysilicon film
35
of a desired thickness has been obtained, as shown in
FIG. 15D
, a second oxide film
36
as the uppermost layer is formed on the second polysilicon film
35
by means of the CVD technique or the like, and then the second oxide film
36
is subjected to a patterning treatment so as to obtain the structural part of the desired shape. The patterned second oxide film
36
is used as a mask for etching the first and second polysilicon films
34
,
35
which are to become the structural part thereunder. Next, as shown in
FIG. 15E
, an etching treatment is performed to the first polysilicon film
34
and the second polysilicon film
35
by means of the reactive ion etching technique or the like till the etching reaches the first oxide film
33
. Further, as shown in
FIG. 15F
, a part of the first oxide film
33
, which is located under the first polysilicon film
34
, is removed by using hydrofluoric acid or the like. In consequence, there is obtained a movable portion which is substantially composed of the first polysilicon film
34
and the second polysilicon film
35
.
FIGS. 16A
to
16
E are views showing a conventional manufacturing process of a structural part having a movable portion, which is disclosed, for example, in pages 52 to 55 of the bulletin of “The 8th International Conference on Solid-State sensors and Actuators, and Eurosensors IX” held in Stockholm on June in 1995. According to this manufacturing process of the structural part, as shown in
FIG. 16A
, at first, a first oxide film
38
and a photoresist film
37
are formed on a silicon substrate
39
by turns. Next, as shown in
FIG. 16B
, the first oxide film
38
is patterned using the photolithography technique so that an oxide film mask is formed. Further, as shown in
FIG. 16C
, the silicon substrate
39
is etched using the oxide film mask, for example, by means of the reactive ion etching technique so that trenches or holes are formed. Following that, as shown in
FIG. 16D
, in order to protect side surfaces of the trenches or holes, a second oxide film
40
is formed, for example, by means of the CVD technique, and then portions of the second oxide film
40
, which exist on the bottoms of the trenches or holes, are removed by means of the reactive ion etching technique. Then, as shown in
FIG. 16E
, each neighboring trenches or holes are communicated with each other below the structural part by performing an isotropic reactive ion etching treatment to the silicon substrate
39
using another reactive gas. In consequence, the structural part having free standing structure may be obtained.
FIG. 17
is a view showing a conventional etching apparatus, which is disclosed, for example, in pages 653 to 659 of Number 2 in Volume 137 of “Journal of Electrochemical Society” published on February in 1990. As shown in
FIG. 17
, the etching apparatus is provided with a power source of constant voltage
41
, an amperemeter
42
, a counter electrode
43
, a reference electrode
44
and an etchant vessel
48
containing an etchant
47
. In the etching apparatus, after pits with inverted square pyramid shapes have been formed on a surface of a plate-shaped n-type silicon substrate
46
using KOH, a voltage is applied to the silicon substrate
46
while the silicon substrate
46
is immersed in the hydrofluoric acid aqueous solution, with the silicon substrate used a positive electrode. In addition, light
45
is applied to the silicon substrate
46
. In consequence, the silicon substrate
46
is etched in the direction depthwise of the substrate. Thus, regularly disposed pores may be formed by means of the etching process.
FIGS. 18A
to
18
F are views showing a conventional manufacturing process of a silicon device, which is disclosed, for example, in pages 189 to 197 of Volume 3223 of “Proceedings SPIE Micromachining and Microfabrication Process Technology III” published at Austin in Texas (U.S.A.) on September in 1997. According to the manufacturing process of the silicon device, as shown in
FIG. 18A
, at first, a plate-shaped n-type silicon substrate
49
is prepared. Further, as shown in
FIG. 18B
, a silicon nitride film
50
is formed on a surface of the silicon substrate
49
. Following that, as shown in
FIG. 18C
, the silicon nitride film
50
is patterned by means of the photolithography technique so that a pattern
51
is formed. Next, as shown in
FIG. 18D
, pits
52
with inverted triangle shapes are formed on the silicon substrate
49
using KOH. Moreover, the silicon nitride film
50
, which has been used as a mask for the etching using KOH, is removed so that the silicon substrate
49
having the pits
52
as shown in
FIG. 18E
is obtained. Then, as shown in
FIG. 18F
, a voltage is applied to the silicon substrate
49
while the silicon substrate
49
is immersed in a hydrofluoric acid aqueous solution, with the silicon substrate used a positive electrode. In addition, light is applied to the silicon substrate
49
so that the silicon substrate is etched in the direction depthwise of the substrate. Thus, trenches
54
are formed in the silicon substrate
49
.
Meanwhile,
FIG. 19
is a view showing a stepwise reaction mechanism when a conventional p-type silicon substrate is etched in the direction depthwise of the substrate by applying a voltage to the p-type silicon substrate while immersing the p-type silicon substrate in an organic solution including a hydrofluoric acid aqueous solution, with the substrate used as a positive electrode. The mechanism is disclosed, for example, in pages 1006 to 1013 of Number 4 in Volume 141 of “Journal of Electrochemical Society” published on April in 1994. At first, a hydrogen atom [H], which is combining with a silicon atom [Si] on the uppermost surface of the silicon substrate as indicated by (A) in
FIG. 19
, is changed to a hydrogen ion [H
+
] due to functions of a fluorine ion [F
−
] and a hole [h
+
] so that the bonding between the hydrogen ion and the silicon atom is ruptured while the silicon atom is changed to a silicon radical as indicated by (B). Further, the silicon radical combines with a fluorine atom due to supply of the fluorine ion and an electron [e
−
] as indicated by (C). Then, as indicated by (D) and (E), the same reaction occurs as to another remaining hydrogen atom, in consequence the silicon atom combines with two fluorine atoms. Moreover, as indicated by (F), the other two bonding hands, each of which has combined with another inner silicon atom, also combine w

Affiliated with

Also associated with

Rating

Manufacturing method of silicon device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Manufacturing method of silicon device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Manufacturing method of silicon device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2840828