JP2000012547A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable enforcement of a single event upset immunity, by shortening a life time of carriers generated by incident charged particles. SOLUTION: A source region 5 and a drain region 6 are formed on a silicon substrate. Defects 8 and 9 having such a high density that a funneling phenomenon caused by incident charged particles can be suppressed are formed by a Ge-or Ar-ion implantation directly under a drain depletion layer 7 under the drain region 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a method for manufacturing the same.

[0002]

2. Description of the Related Art In a semiconductor device used in a radiation environment such as outer space, a single event upset (soft error) poses a problem. Here, first, a single event upset phenomenon in a normal MOS transistor will be described with reference to the drawings.

FIG. 3 shows a state in which charged particles are incident on a normal MOS transistor. A field insulating film 102, a gate insulating film 103, a gate electrode 104, a source region 105, and a drain region 106 are formed on a silicon substrate 101. Here, FIG. 3 shows a case where a reverse bias is applied to the drain region 106, and the depletion layer 107 extends below the drain region 106.

When charged particles enter this ordinary NMOS transistor, electron-hole pairs are generated along the track 108. At this time, at the bottom of the drain region 106 in the reverse bias state, the inside of the depletion layer becomes conductive due to the generated charges, and the electric field applied to the depletion layer extends in a columnar direction toward the substrate (well) with a low impurity concentration. Applied. This extended electric field region (= funneling region 10)
The minority carriers in 9) are collected by the electric field of the drain region 106, change the potential of the node connected to the drain region 106, and cause a soft error (single event upset) such as bit inversion.

In order to suppress the occurrence of the single event upset, various methods using the introduction of defects into a substrate have been devised.

For example, Japanese Patent Application Laid-Open No. 60-62111 discloses an example of a method for manufacturing a semiconductor substrate, and FIG. 4 illustrates this conventional technique. FIG.
As shown in FIG. 1, impurities of the conductivity type opposite to the dopant in the semiconductor substrate 110 are ion-implanted into the low-resistance semiconductor substrate 110, and heat treatment is performed to generate minute defects 111 in the entire semiconductor substrate 110. Then, a high resistance layer including the defect 111 is formed near the surface of the semiconductor substrate 110.

Next, a high-resistance, defect-free single crystal semiconductor layer 112 is formed on the surface of the semiconductor substrate 110 by, for example, epitaxial growth. When a MOS transistor is formed over a semiconductor substrate including the semiconductor substrate 110 and the single crystal semiconductor layer 112, the small defects 111 function as recombination centers, so that the recombination of minority carriers generated by radiation irradiation is promoted. Lifetime is shortened and occurrence of single event upset is suppressed.

Japanese Unexamined Patent Application Publication No. 60-54473 discloses another method of manufacturing a semiconductor memory device.
FIG. 5 illustrates this conventional technique. Referring to FIG. 5, a surface of the semiconductor substrate 113 containing oxygen of 10 ¹⁷ cm ⁻³ or more as an impurity is irradiated with a YAG laser while scanning, and supersaturated oxygen is deposited in the vicinity of the surface of the semiconductor substrate 113. A minute defect 114 of about ⁶ cm ^-3 is formed. At this time, the output of the laser beam is controlled so that 1 to 5 μm from the surface is in a defect-free state, and a high-density minute defect region is formed thereunder. As in the case of FIG. 4, this minute defect becomes a recombination center and suppresses the occurrence of a single event upset.

[0009]

These conventional methods have the following problems.

A first problem is that a defect-free layer is formed on the surface of the semiconductor substrate by epitaxial growth in the method shown in FIG. 4 and by laser irradiation in the method shown in FIG. That is, it is difficult to form the layer with good controllability.

A second problem is that all of the conventional methods distribute defects over the entire surface of a semiconductor substrate, and when a MOS transistor is actually formed on such a semiconductor substrate, the threshold voltage is reduced. Or a short channel effect, or the leakage current increases near the boundary of the well.

That is, in order to suppress the single event upset, the defects must be distributed in a sufficiently shallow region (immediately below the drain depletion layer at the time of reverse bias). If the region is formed shallow, defects will also exist below the channel region and under the element isolation insulating film. Therefore, if there is a defect near the channel, the defect may pile up the impurity implanted for controlling the channel profile and affect the threshold voltage, the short channel effect, and the like.
Further, if there is a defect in the vicinity of the element isolation region, for example, a leak current may increase near a boundary between wells.

As a method of improving the single event upset resistance by the substrate technology, there is an SOI technology. If an SOI substrate is used, the single event upset resistance can be improved without the above-mentioned problems. However, on the other hand, a new problem that the cost of the substrate is increased arises.

Accordingly, an object of the present invention is to shorten the lifetime of carriers generated by the incidence of charged particles,
It is an object of the present invention to provide a semiconductor device capable of enhancing single-event upset resistance and a method of manufacturing the same at a relatively low cost.

[0015]

According to the present invention, a high-density defect layer having a predetermined density is formed in a predetermined region inside the semiconductor substrate below a source region and a drain region formed on the semiconductor substrate. It is preferable that the predetermined region is a region directly below the drain depletion layer at the time of reverse bias, and the predetermined density is set to a density that can suppress funneling due to the incidence of charged particles.

In the present invention, the high-density defect layer may be formed by ion implantation of Ge or Ar.

Further, a method of manufacturing a semiconductor device according to the present invention
(A) forming a field insulating film on a substrate;
(B) a step of sequentially forming a gate insulating film, a gate electrode, a source region, and a drain region on the substrate, the method comprising the steps of: (a)
Forming a high-density defect layer in a predetermined region below the source / drain region by performing ion implantation and heat treatment only on the region serving as the source / drain under predetermined conditions before the step (b). It is preferable that the predetermined region is a region immediately below the drain depletion layer at the time of reverse bias.

[0018] In the present invention, the ion implantation may include 5
With implantation energy of 00 keV to 700 keV, 10
^The heat treatment may be performed by using Ge ions at a dose of ¹⁵ to 10 ¹⁶ cm ^-2 , and the heat treatment may be performed in a temperature range of 900 ° C. to 950 ° C .;
It may be an r ion.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment of the semiconductor device according to the present invention, a source region (5 in FIG. 1) and a drain region (5 in FIG. 1) formed on a silicon substrate are provided.
6) In the region directly below the lower drain depletion layer (7 in FIG. 1), high-density defects (8 and 9 in FIG. 1) that can suppress funneling due to the incidence of charged particles are formed by Ge ion implantation or Ar ion It is formed by injection.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention;

Embodiment 1 First, a semiconductor device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining a structure of a semiconductor device according to one embodiment of the present invention, and FIG. 2 is a diagram for schematically explaining a part of a method of manufacturing a semiconductor device.

First, a method of manufacturing a semiconductor device according to the present embodiment will be described with reference to FIGS. A field insulating film 2 is formed on a silicon substrate 1, and a photoresist pattern is formed by opening a portion where a source / drain region is to be formed by a known photolithography technique. Ions 11 are implanted. The implantation energy at this time is adjusted so that the range of the Ge ions 11 is slightly below the depth of the drain depletion layer at the time of reverse bias. For example, if the depth of the drain junction is 0.15 μm, the implantation energy of the Ge ions 11 may be set to 500 to 700 keV. The dose is preferably about 10 ¹⁵ to 10 ¹⁶ cm ^-2 .

Next, heat treatment is performed at a temperature of 900 to 950 ° C. to recrystallize the surface of the silicon substrate 1. At this time, the implanted Ge ions 11 are replaced with Si at lattice points, and the generated Si moves to the lattice gap. Then, the dislocation loop 9 is generated by the stress of the interstitial Si. The dislocation loop 9 is diffused by the heat treatment, and as shown in FIG.
Are unevenly distributed so as to surround the region where Thereafter, the gate insulating film 3, the gate electrode 4, the source region 5, the drain region 6, and the like are formed by a usual method, and the semiconductor device of FIG. 1 is obtained. In the process after the heat treatment after the Ge ion implantation, the temperature of the thermal process is set to 850 ° C. in order to prevent redistribution of Ge.
Do the following.

Next, the structure of the semiconductor device of this embodiment will be described. Referring to FIG. 1, on a silicon substrate 1,
By the same method as forming a normal MOS transistor,
Field insulating film 2, gate insulating film 3, gate electrode 4,
A source region 5 and a drain region 6 are formed. This embodiment shows a case where a reverse bias is applied to the drain region 6, and the depletion layer 7 extends below the drain region 6.

The feature of this embodiment is that the source
Ge8 and a dislocation loop 9 are introduced under the drain regions 5 and 6 and in regions other than the vicinity of the channel region and the vicinity of the element isolation region as defects that promote recombination of minority carriers. Here, Ge8 is distributed at a predetermined depth (slightly below the depth of the depletion layer when a reverse bias is applied between the drain region 6 and the silicon substrate 1), and the dislocation loop 9 is formed in the region where Ge8 exists. It exists to surround.

When a normal MOS transistor is used in a radiation environment such as outer space, several tens of p.
Between s and several hundred ps, the charges in the drain depletion layer and the charges in the funneling cylinder are collected by drift. Even after the charge collection by the drift ends, the charge collection by the diffusion continues for several ns to several tens ns. Among these charge collecting mechanisms, the funneling component contributes most to the change in the potential of the node. As described above, the malfunction due to the incidence of charged particles occurs when charges generated by the incidence of charged particles are collected by a mechanism such as a funneling phenomenon, and the potential of a node connected to the drain is changed.

On the other hand, the semiconductor device of this embodiment shown in FIG. 1 has Ge 8 and a dislocation loop 9 as defects just below the drain region 6. These Ges and defects generate energy levels in the band gap of the silicon substrate 1 and act as recombination centers. Therefore, even if charged particles enter the drain region in the reverse bias state and generate electron-hole pairs, the lifetime of minority carriers is shortened due to the presence of Ge8 and the dislocation loop 9, which are recombination centers. 6, the number of minority carriers collected is reduced, and the single event upset resistance is improved.

When charges are incident on the source region 5, the potential of the node does not change even if electrons are collected, so that a malfunction does not occur. Therefore, when the source and drain of the MOS transistor are fixed, it is unnecessary to implant Ge ions below the source region 5. Source·
In the case where the drain is not fixed, for example, when forming a transfer gate or forming the base of a gate array, it is necessary to implant Ge ions under both the source and drain regions as in this embodiment. .

In this embodiment, Ge is used as an ion to be implanted.
Although ions have been described as an example, the implanted ions only need to be recombination centers. For example, Ar ions may be used instead of Ge ions.
Ions and the like can also be used.

[0030]

As described above, according to the present invention, it is possible to effectively suppress the occurrence of a single event upset due to the incidence of radiation.

The reason is that, according to the present invention, recombination centers can be distributed with good controllability by adjusting the energy of ion implantation in the region where the funneling extends immediately below the drain region. It is because it can suppress efficiently.

Further, in the present invention, the Ge ion implantation region can be limited by photolithography, so that Ge is prevented from entering a region where no defect or the like is desired to exist, for example, near a channel or an element isolation region. be able to. Therefore, it is possible to suppress the influence on the device characteristics when the defect is distributed near the channel region and to suppress the increase in the leak current when the defect is distributed near the element isolation region.

Further, according to the present invention, compared with the case where a special substrate such as an SOI substrate is used, it is possible to improve the single event upset resistance at a relatively low cost.

[0034]

[Brief description of the drawings]

FIG. 1 is a sectional view schematically illustrating the structure of a semiconductor device according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view for schematically explaining a method for manufacturing a semiconductor device according to one embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a conventional semiconductor device.

FIG. 4 is a sectional view showing a conventional semiconductor device.

FIG. 5 is a sectional view showing a conventional semiconductor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Silicon substrate 2, 102 Field insulating film 3, 103 Gate insulating film 4, 104 Gate electrode 5, 105 Source region 6, 106 Drain region 7, 107 Depletion layer 8 Ge 9 Dislocation loop 10 Photoresist 11 Ge ions 108 Charged particles Track 109 funneling 111 defect 112 single crystal semiconductor layer 114 defect (oxygen precipitation)

Claims (10)

[Claims] 2. A semiconductor device according to claim 1, wherein a high-density defect layer having a predetermined density is formed in a predetermined region inside the semiconductor substrate below a source region and a drain region formed on the semiconductor substrate. 2. The semiconductor device according to claim 1, wherein said predetermined region is a region immediately below a drain depletion layer at the time of reverse bias. 3. The semiconductor device according to claim 1, wherein the predetermined density is set so as to suppress funneling due to incidence of charged particles. 4. The semiconductor device according to claim 1, wherein said high-density defect layer is formed by Ge ion implantation. 5. The semiconductor device according to claim 1, wherein said high-density defect layer is formed by Ar ion implantation. 6. A semiconductor comprising: (a) forming a field insulating film on a substrate; and (b) sequentially forming a gate insulating film, a gate electrode, a source region, and a drain region on the substrate. A method for manufacturing a device, comprising: after the step (a),
Prior to the step (b), a high-density defect layer is formed in a predetermined region below the source / drain region by performing ion implantation and heat treatment only on the source / drain region under predetermined conditions. A method for manufacturing a semiconductor device, comprising: 7. The method according to claim 6, wherein the predetermined region is a region immediately below a drain depletion layer at the time of reverse bias. 8. The method according to claim 1, wherein said ion implantation is performed at a temperature of 500 keV to 70 keV.
With an implantation energy of 0 keV, 10 ^Fifteen-10¹⁶cm^-2of
It is performed by a dose of Ge ions.
A method for manufacturing a semiconductor device according to claim 6. 9. The method according to claim 8, wherein the heat treatment is performed at a temperature in a range from 900 ° C. to 950 ° C. 10. The method according to claim 6, wherein the ions to be implanted are Ar ions.