Semiconductor device manufacturing: process – Formation of electrically isolated lateral semiconductive... – Total dielectric isolation
Reexamination Certificate
2000-04-11
2001-04-24
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Formation of electrically isolated lateral semiconductive...
Total dielectric isolation
C438S452000
Reexamination Certificate
active
06221732
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to Japanese application No. HEI 11(1999)-172472 filed on Jun. 18, 1999, whose priority is claimed under 35 USC § 119, the disclosure of which is incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a production technology of semiconductor devices both on an SOI (Semiconductor On Insulator) structure portion and on a semiconductor substrate not having the SOI structure portion of a partial SOI substrate. More particularly, this invention relates to a method of producing semiconductor devices which includes a step of making the thickness of an insulation film for device isolation different between an SOI structure portion and an exposed portion of a semiconductor substrate not having the SOI structure portion, when the insulation film (oxide film) is used for device isolation in order to electrically isolate devices from one another.
2. Description of the Relate Art
The following methods are possible measures for forming device isolation regions both in SOI structure portion comprising an insulation layer and a semiconductor layer, and in an exposed substrate portion of a semiconductor substrate (hereinafter referred to as the “bulk substrate portion”) in a substrate comprising the SOI structure portion and the bulk substrate portion (which substrate will be hereinafter referred to as a “partial SOI substrate”). The first method is the one that simultaneously forms both of them. When a production method is directed to fabricate complete depletion type transistors in the SOI structure portion by forming a semiconductor layer to a thin film in the SOI structure portion, the thickness of a device isolation oxide film of a field transistor of the bulk substrate portion becomes small if this device isolation oxide film is fabricated under the formation condition of the device isolation region of the SOI structure portion. Therefore, the insulation resistance of the field transistor cannot be secured sufficiently.
When the formation of the device isolation region is conducted under the formation condition of the device isolation oxide film of the bulk substrate portion, on the other hand, oxidation becomes excessive in the SOI structure portion. In consequence, a semiconductor layer (Si layer) at the ends of an active region of the SOI structure portion is oxidized, too. Thus the film thickness of the semiconductor layer becomes locally thin (i.e. the semiconductor layer at the end of the active region is thin) and the device isolation oxide film creates a stress with the result that transistor characteristics get deteriorated.
When the thickness of the device isolation oxide film of the SOI structure portion is different from the thickness of the device isolation oxide film of the bulk substrate portion, the device isolation region and a well region are generally formed by the following second method (see FIGS.
5
(
a
) to
7
(
c
)).
FIG.
5
(
a
) shows a partial SOI substrate. In the drawing, reference numeral
10
denotes a semiconductor layer. Reference numeral
20
denotes an insulation layer and reference numeral
30
denotes a semiconductor substrate. The following method is known as a fabrication method of this partial SOI substrate, by way of example. An oxygen ion, or the like, is implanted into a suitable depth of a semiconductor substrate (silicon substrate), and a silicon oxide layer (buried insulation layer) is formed in the silicon substrate. As a result of this process step, the silicon layer is formed on the silicon oxide layer. Next, the silicon oxide layer and the silicon layer on the former are selectively etched away, giving the structure shown in FIG.
5
(
a
). Alternatively, the partial SOI substrate having the structure shown in FIG.
5
(
a
) can be acquired by laminating selectively and serially the insulation layer (silicon oxide film) and the semiconductor layer (silicon layer) on a semiconductor substrate (silicon substrate).
Next, as shown in FIG.
5
(
b
), a pad oxide film
40
and a nitride film
50
are deposited over the entire surface of the substrate by thermal oxidation and by vacuum CVD, respectively.
A photolithography step (resist patterning step), an etching step, and an oxidation step for forming a device isolation region, are carried out for forming an active region and a device isolation region in the SOI structure portion as shown in FIGS.
5
(
c
) to (
e
). Incidentally, reference numeral
60
′ in FIG.
5
(
c
) denotes a patterned photoresist mask, and reference numeral
70
-
1
in FIG.
5
(
e
) denotes a device isolation oxide film in the SOI structure portion.
Next, a nitride film
80
is deposited by vacuum CVD as shown in FIG.
6
(
a
). A photolithography step (resist patterning step), an etching step and an oxidation step for forming a device isolation region are carried out for forming an active region and a device isolation region subsequently for the bulk substrate portion as shown in FIGS.
6
(
b
) to (
d
). Incidentally, reference numeral
60
′-
1
in FIG.
6
(
b
) denotes a patterned resist mask, and reference numeral
70
-
3
in FIG.
6
(
d
) denotes a device isolation oxide film in the bulk substrate portion. Thereafter, the nitride films
50
and
80
are etched away. Resist masks
60
′-
2
and
60
′-
3
for forming the well are formed in the SOI structure portion and the bulk substrate portion, respectively, as shown in FIGS.
7
(
a
) to (
c
). Next, an impurity ion is implanted (
90
and
100
) into each region, and annealing treatment is carried out for activation, thereby giving the well.
In the production method of a semiconductor device using a partial SOI substrate, the second method described above is generally used in order to acquire reliably the desired device characteristics. According to this method, however, the photolithography step, the etching step and the oxidation step for forming the device isolation region must be carried out for both SOI structural portion and bulk substrate portion. Furthermore, the photolithography step for forming the wells must also be carried out for the SOI structure portion and the bulk substrate portion (see FIGS.
5
(
c
),
6
(
b
),
7
(
b
) and
7
(
c
)). In other words, the photolithography step must be conducted four times in total. The number of the photolithography steps must be decreased in order to decrease the production time and the production cost.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, there is provided a first method of producing a semiconductor device, which method comprises the steps of:
(a) forming partially an SOI structure portion comprising an insulation layer and a semiconductor layer on a semiconductor substrate;
(b) forming selectively a first oxidation-resistant film on a region other than device isolation region-forming portions of the SOI structure portion and of an exposed portion of the semiconductor substrate;
c) forming an oxide film in the device isolation region-forming portions of the semiconductor substrate and of the SOI structure portion under such condition that the semiconductor layer of the SOI structure portion is oxidized up to the bottom of the semiconductor layer;
(d) depositing a second oxidation-resistant film over the entire surface of the resultant obtained by the above steps (a) to (c);
(e) etching away selectively the second oxidation-resistant film on the exposed portion of the semiconductor substrate using a resist mask so patterned as to cover the SOI structure portion;
(f1) implanting an impurity ion into the semiconductor substrate using the resist mask; and
(g1) removing the resist mask, and conducting heat-treatment to activate the implanted impurity ion and increase the thickness of the oxide film in the device isolation region-forming portion of the exposed portion of the semiconductor substrate to a predetermined film thickness.
According to another aspect of the present invention, there is provided a second method of producing a
Fourson George
Garcia Joannie A.
Nixon & Vanderhye P.C.
Sharp Kabushiki Kaisha
LandOfFree
Method of producing semiconductor 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 Method of producing semiconductor device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of producing semiconductor device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2467910