JPH05315358A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To provide technique for efficiently modifying an active layer made of a polycrystalline Si layer or an amorphous Si layer deposited on an insulator in a method for manufacturing an SiMOS type semiconductor device including an ion implanting step. CONSTITUTION:The method for manufacturing a semiconductor device comprises the steps of depositing a polycrystalline Si layer or an amorphous Si layer as an active layer 2 on a substrate 1, forming a gate electrode 4 on the active layer through a gate insulating film 3, and ionizing source gas 5 containing a compound of an uncombined hand terminating element of Si and an impurity element and ion implanting the layer 2 by an acceleration energy of arriving a deep peak of the uncombined hand terminating element at the active layer under the electrode 4 without mass separation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for manufacturing a SiMOS type semiconductor device including an ion implantation step.

In recent years, rapid advances in Si technology have accelerated the speed, density and multifunction of integrated circuits. Among them, Si layer deposition technology on insulators,
So-called SOI has become a very important development target in connection with three-dimensional wiring technology.

[0003] In this technique, there is a tendency toward high functionality in which the active layer is made of Si single crystal, and the active layer is made of polycrystalline Si or amorphous Si.
Includes a trend toward lower prices that consists of The former aims at pursuing miniaturization technology and making it useful for VLSI manufacturing.
The latter is intended for application to solid-state image capturing, display, and printing devices called giant microelectronics.

In giant microelectronics, a thin film field effect transistor having polycrystalline Si or amorphous Si as an active layer is formed as a key device on a glass substrate having a relatively large area.

[0005]

2. Description of the Related Art A thin film transistor on a glass substrate is
Since the active layer is polycrystalline or amorphous, the carrier mobility is small and the leak current cannot be ignored. In the case of a large screen, many thin film transistors are formed in a large area, but it is not easy to form a thin film transistor having uniform characteristics over the entire screen.

One means for improving the characteristics of thin film transistors is
This is a termination process of Si dangling bonds (dangling bonds) in the active layer. That is, by introducing hydrogen, fluorine, or chlorine atoms called terminators into the active layer and chemically bonding with the dangling bonds of Si, the traps and recombination centers of signal transmission carriers are crushed, and the potential barrier at grain boundaries is reduced. Lower.

Since the signal transmission carrier travels in a channel formed in the vicinity of the surface of the active layer of a thin film transistor (TFT) which is a SiMOS type device, it is necessary to terminate the source, channel and drain of the TFT, especially in the surface region of the Si layer. It is important to do.

Conventionally, in the case of a polycrystalline SiTFT, after forming a gate electrode, ion implantation of impurities is performed in a self-aligned manner using the gate electrode as a mask to form source and drain regions of high impurity concentration.

Thereafter, the terminating treatment was performed for 6 to 7 hours or more by performing the treatment in hydrogen plasma at a temperature rising state or by hydrogen diffusion from the plasma SiN _x film. A method of implanting hydrogen ions after the impurity ions and performing heat treatment has also been proposed.

On the other hand, in the case of amorphous SiTFT, SiN _x
It is general that the gate insulating film and the amorphous Si active layer are continuously formed by the plasma CVD method. Plasma C
Although 5 to 8% of hydrogen is normally contained during film formation by VD, the quality of the SiN _x film is low (there are many defects), and S
It is also pointed out that there are many interface states between iN _x and Si, and the device characteristics are considerably lower than those of polycrystalline Si TFTs.

[0011]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Polycrystalline SiT
The FT crystallinity improving method has a problem that the throughput is small because it requires a long process and an extra process.

In the case of amorphous SiTFT, SiN _x
In addition to the problems of the film and interface, the hydrogen concentration in the Si film introduced by plasma CVD cannot be controlled, leaving problems in the homogeneity and reproducibility of film formation characteristics.

An object of the present invention is to provide a technique for efficiently modifying an active layer composed of a polycrystalline Si layer or an amorphous Si layer deposited on an insulator.

[0014]

A method of manufacturing a SiMOS type semiconductor device according to the present invention comprises a step of depositing a polycrystalline Si layer or an amorphous Si layer on a substrate as an active layer, and a gate insulation on the active layer. A step of forming a gate electrode through a film, and ionizing a source gas containing a compound of an unbonded hand terminating element of Si and an impurity element, a deep peak of the unbonded hand terminating element is generated without mass separation. Implanting ions into the active layer with acceleration energy reaching the lower active layer.

[0015]

When an ion having a large mass and an ion having a small mass are ion-implanted at the same acceleration voltage, the implantation depth of the large-mass ion is shallow, and the implantation depth of the small-mass ion is deep.

When a large mass of ions is composed of a compound of an impurity element and a dangling bond terminating element, these elements are separated after ion implantation. When the ion having a small mass is a dangling bond terminating element, two peaks appear in the distribution of the dangling bond terminating element in the depth direction.

When the acceleration energy is selected so that the deeper peak of the dangling bond terminating element reaches the active layer under the gate electrode, the dangling bond terminating element is ion-implanted into the channel region under the gate electrode, and the gate region is formed. Both the impurity element and the dangling bond termination element are ion-implanted into the source / drain regions on both sides of the electrode.

In this manner, the dangling bond termination element can be ion-implanted into the source region, the channel region and the drain region at the same time as the impurity element ion implantation into the source / drain region. Since dangling bonds in the active layer are terminated, Si characteristics of the active layer are improved.

[0019]

1 shows a basic embodiment of the present invention. Figure 1
(A) is a graph showing a concentration distribution of non-mass separated ion implantation into Si when PH ₃ is used as an impurity source gas. P in PH ₃ becomes an impurity element and H becomes Si
Becomes the dangling bond termination element of.

PH ₃ is diluted with H ₂ . H is also generated from this diluting H ₂ . Graph is P and H in Si
It is the result of having analyzed the density | concentration of a by SIMS. For comparison, the Si concentration analysis value is also shown.

The measurement conditions are: acceleration voltage 30 KeV,
The dose amount was 5E15 cm ^-2 , and PH ₃ / H ₂ gas was ion-implanted into Si without mass separation after ionization.

From FIG. 1 (A), only one peak of the impurity phosphorus (P) appears near the surface, but two peaks of hydrogen (H) appear near the surface and near the depth of 0.25 μm. ..
The peak near the surface is called the first peak, and the peak at a deeper position is called the second peak.

Of these, the first peak is the hydrogen phosphide compounds P ₁ H _x and P ₂ H in addition to P during the ionization process of PH ₃ gas.
It is considered that _{x and the} like were formed, and that it was caused by ion implantation as it was. Further, it is considered that the second peak is caused as a result of H and H ₂ separated from the PH ₃ gas and hydrogen of the diluent gas being ionized and directly injected.

In fact, when the PH ₃ / H ₂ gas is ionized, the mass is separated, and the material ion-implanted into Si under the same conditions is examined by SIMS, hydrogen as a light element is removed. It was confirmed that only the peak appeared.
This example utilizes these two peaks.

A method of manufacturing a SiMOS type semiconductor device according to an embodiment of the present invention will be described below with reference to FIG. An active layer 2 made of a polycrystalline Si layer or an amorphous Si layer is deposited on a substrate 1 such as glass or quartz. Subsequently, the gate electrode 4 is formed on the active layer 2 with the gate insulating film 3 made of SiO ₂ , SiN or the like interposed therebetween. The gate insulating film 3 other than under the gate electrode 4 may be left or removed.

As shown in FIG. 1B, in this state, a gas 5 of a compound of an impurity element and an element having a function of terminating dangling bonds of Si such as H and F is formed in the active layer 2 from above. Are ionized to perform ion implantation without mass separation.

When ions that do not undergo mass separation (ions containing P and ions containing only H generated from the PH ₃ gas 5) are implanted from above, the Si active layer 2 in the source / drain region where the gate electrode 4 does not exist above is implanted. The impurity element P is ion-implanted to form the source region 7 and the drain region 8.

At the same time, Si dangling bond termination element H contained in the compound of P and H is also ion-implanted into this region to form Si.
Terminate the unbound hand of. This H corresponds to the shallow first peak in FIG.

The Si dangling terminal element H corresponding to the deep second peak of FIG. 1A is ion-implanted into the Si active layer 2 of the channel region 9 on which the gate electrode 4 is formed. To terminate the dangling bonds of Si.

When the diluting H ₂ gas is used, the amount of H ion-implanted into the channel region increases. Although the case where PH ₃ and H ₂ gas are used has been described, other impurity elements such as B and As can be used as impurities in addition to P. Further, as the dangling bond terminating element, H
Alternatively, F or the like can be used.

However, in order to form two peaks in the distribution of the dangling bond terminating element, it is desirable that the dangling bond terminating element has a sufficiently smaller mass than the ion serving as the impurity source. Further, in order to ion-implant a sufficient amount of dangling bond terminating element into the channel region 9, it is desirable to dilute the gas serving as an impurity source with the gas of dangling bond terminating element.

After the ion implantation process is completed, ion-implanted S
In order to activate the dangling bond terminating element of i, it is desirable to perform heat treatment at a temperature of 450 ° C. or lower for an appropriate time. SiM
In the OS type semiconductor device, since the carrier transit region, so-called channel, is formed in the surface region of the active layer 2,
In particular, it is desired to suppress the density of Si dangling bonds in this region to a low level.

For this reason, the acceleration voltage of ion implantation and / or the acceleration voltage of ion implantation are set so that the concentration distribution of the dangling bond termination element of Si shows a second peak at the depth corresponding to the surface portion of the channel region 9 under the gate electrode 4. Alternatively, the gate insulating film 3 and the gate electrode 4
It is desirable to adjust the thickness of the.

Preferably, the dangling bond termination element of Si is hydrogen or fluorine, the impurity element is boron, phosphorus or arsenic, and the atomic weight of the impurity element is larger than hydrogen or fluorine.

In the process of manufacturing a SiMOS device, polycrystalline Si is obtained by ion-implanting dangling termination elements of Si at the same time as source and drain forming impurities.
The density of defect levels due to dangling bonds in the layer or the amorphous Si layer can be reduced in the active layer.

FIG. 2 shows a part of a TFT manufacturing process according to a more specific embodiment of the present invention. FIG. 2 shows the case of performing ion implantation through the gate oxide film. In FIG. 2, a polycrystalline Si active layer 12 having a thickness of about 100 is formed on a glass substrate 10.
nm, and a gate oxide film 13 thereon with a thickness of about 150 nm,
Furthermore, a gate metal electrode 14 having a thickness of about 750 nm is formed thereon.
Deposit and pattern gate metal electrode 14. Al, for example, is used as the gate metal.

Hydrogen is used as a dangling bond termination element of Si, and phosphorus is used as an impurity element for ion-implanting the polycrystalline Si active layer 12. PH ₃ is used as a source gas for ion implantation, and H ₂ is used as a diluting gas. The molar ratio is, for example, PH ₃ :
H ₂ = 1: 9.

PH ₃ / H ₂ source gas is simultaneously ionized in a bucket type ion implanter or an ion shower type ion implanter, and ions are implanted at an acceleration voltage of 90 KeV without mass separation.

The dose of impurities is, for example, about 5E15c.
m ^-2 . When ions are implanted under this condition, a peak of phosphorus impurities appears near a depth of about 100 nm. For this reason,
The source region 17 and the drain region 18 are formed in such a concentration distribution that the phosphorus concentration is highest in the surface region of the active layer 12 of polycrystalline Si under the gate oxide film 13. Hydrogen terminators are simultaneously introduced into these regions in the form of P ₁ H _x and P ₂ H _x .

On the other hand, under this condition, the second peak of ion-implanted hydrogen concentration appears near a depth of about 900 nm. In the source region 17 and the drain region 18, this hydrogen peak enters the glass substrate 10.

In a region of the gate metal electrode 14, the first peaks of impurity ions and hydrogen ions are consumed in the gate metal electrode 14, and the second peak of hydrogen concentration is polycrystalline S.
i Active layer 12, that is, channel region and gate oxide film 1
Appears near the interface with 3.

Therefore, it is possible to implant high-concentration impurity ions into the source region and the drain region and at the same time introduce hydrogen of the terminator, and further introduce high-concentration terminator into the channel region.

In this embodiment, the gate metal is Al.
However, other metals such as refractory gold such as Mo, W and Ti
It is also possible to use metal, silicide, polycrystalline Si, or the like.
it can. Further, as a gate insulating film, SiO₂Alone
SiN_x, SiON and Al₂O ₃, Ta₂O_FiveEtc.
It can also be used.

FIG. 3 shows an embodiment in which polycrystalline Si is used as the gate electrode, amorphous Si is used as the active layer, and ion implantation is performed after patterning the gate insulating film. As shown in FIG. 3, S having a thickness of about 300 nm is formed on the glass substrate 11.
iN _x film 33, amorphous Si active layer 22 having a thickness of about 50 nm, and gate oxide film 2 having a thickness of about 100 nm thereon.
3. A polycrystalline Si gate electrode 24 having a thickness of about 300 nm is deposited thereon, the gate oxide film 23 and the polycrystalline Si gate electrode 24 are patterned together, and then ion implantation is performed.

Hydrogen and PH ₃ are mixed as a source gas for ion implantation in a molar ratio of, for example, 95: 5,
After this is ionized, ions are implanted without mass separation. Accelerating voltage is 30 KeV and dose is about 1E16 cm.
^-2 .

The first peaks of the impurity ions P and hydrogen H are due to the polycrystalline gate electrode 24 and the amorphous Si on both sides thereof.
The n ⁺ -type polycrystalline Si gate electrode 24 and the n ⁺ -type source region 27 and the drain region 28 are formed by implanting in the active layer 22.

The second peak of hydrogen H is injected into the channel region 29 in the amorphous Si active layer 22 under the polycrystalline Si gate electrode 24, and terminates Si dangling bonds in this region. .. The second peak of hydrogen H in the source region 27 and the drain region 28 is absorbed in the glass substrate 11.

Thus, the ion implantation of the polycrystalline Si gate electrode and the termination of dangling bonds and the source region 27, the ion implantation of the drain region 28 and the dangling of dangling bonds, and the channel by a single ion implantation. The unbonded hands of the region 29 can be terminated at the same time.

The amorphous Si active layer 22 was formed.
The glass substrate 11 surface with SiN _xCovered with membrane 33
But this SiN_xThe membrane can be omitted. Also, non
Use a polycrystalline Si active layer instead of the crystalline Si active layer 22.
You can also stay. Also, a glass substrate is used as the substrate
However, it is not possible
A conductor substrate or the like can also be used.

After the ion implantation process as shown in FIGS. 2 and 3, the substrate is heat-treated at 400 ° C. for 1 hour to activate the ion-implanted impurities. In the above examples, PH ₃ was used as the compound consisting of the impurity element and the Si dangling termination element, and H ₂ was used as the dilution gas containing the dangling termination element. It is considered that a similar function can be realized when a compound of an impurity element and a dangling bond terminating element is used as an impurity gas and the dangling bond terminating element is lighter than the impurity element.

When forming a p-type region in the Si active layer,
Boron or the like can be used as an impurity. In this case, BF ₃ or B ₂ H ₆ can be used as the impurity gas and H ₂ can be used as the diluting gas.

When arsenic is selected as the n-type impurity element, AsH ₃ or AsF ₃ can be used as the impurity gas and H ₂ , He or the like can be used as the diluent gas. All of these are ionized and ion-implanted into the Si active layer without mass separation. Since H and F form two concentration peaks, it is considered that the channel region and the source / drain region can be terminated at the same time as described above.

Since the ionic radius of hydrogen is small, it has a large mobility in solid and may be desorbed from the Si active layer in the heat treatment step. On the other hand, fluorine has a large terminating effect of dangling bonds, has a large ionic radius, and is
It is easy to combine with arsenic impurities in the form of F _x and As ₂ F _x , and is more stable to the heat treatment process.

The present invention has been described above with reference to the embodiments.
The present invention is not limited to these. For example,
It will be apparent to those skilled in the art that various modifications, improvements, combinations and the like can be made.

[0055]

As described above, according to the present invention,
SiMO having an active layer of polycrystalline Si or amorphous Si
In the manufacturing process of an S-type device, the source and drain regions can be formed by impurity ion implantation and, at the same time, dangling bonds in the active layer can be terminated.

Therefore, the trap level can be reduced and the potential barrier at the grain boundary can be reduced, and the throughput can be improved. By modifying the Si active layer, the carrier mobility of the active layer can be increased and the off current of the MOS device can be reduced.

[Brief description of drawings]

FIG. 1 shows a basic embodiment of the present invention. FIG. 1A shows a doping profile of ion implantation without mass separation,
FIG. 1B is a sectional view showing a manufacturing process of the SiMOS semiconductor device.

FIG. 2 is a cross-sectional view showing a manufacturing process of a SiMOS device according to an example.

FIG. 3 is a cross-sectional view showing the manufacturing process of the SiMOS device according to the example.

[Explanation of symbols]

1 Substrate 2 Active layer 3 Gate insulating film 4 Gate electrode 5 Source gas for ion implantation 7 Source region 8 Drain region 9 Channel region 10 Glass substrate 11 Si substrate 12 Polycrystalline Si active layer 13 Gate oxide film 14 Gate metal electrode 17 Source region 18 Drain Region 19 Channel Region 22 Amorphous Si Active Layer 23 Gate Insulating Film 24 Polycrystalline Si Gate Electrode 27 Source Region 28 Drain Region 33 SiN _x Film

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location 8617-4M H01L 21/265 P

Claims (5)

[Claims] 1. A step of depositing a polycrystalline Si layer or an amorphous Si layer as an active layer (2) on a substrate (1), and a gate insulating film (3) on the active layer (2). The step of forming the gate electrode (4) and the ionization of the source gas (5) containing a compound of the dangling bond terminating element of Si and the impurity element, the deep peak of the dangling bond terminating element is generated without mass separation. And a step of implanting ions into the active layer (2) with acceleration energy reaching the active layer (2) below the gate electrode (4). 2. The method of manufacturing a SiMOS semiconductor device according to claim 1, wherein the source gas further contains a dangling bond termination element gas. 3. After the ion implantation step, 45
The method for manufacturing a SiMOS type semiconductor device according to claim 1, further comprising a step of performing heat treatment at a temperature of 0 ° C. or lower. 4. The gate electrode is formed of a polycrystalline Si layer, and in the ion implantation step, a dangling bond terminating element and an impurity element are ion-implanted into a gate electrode and an active layer not covered with the gate electrode. 4. The SiMOS according to claim 1, wherein at least one of the acceleration voltage and the total thickness of the gate insulating film and the gate electrode is selected so as to ion-implant a dangling bond terminating element into the active layer below the electrode. Type semiconductor device manufacturing method. 5. The dangling bond termination element of Si is hydrogen or fluorine, the impurity element is at least one selected from the group consisting of boron, phosphorus and arsenic, and the atomic weight of the impurity element is the above. The SiMOS according to any one of claims 1 to 4, which is an element larger than hydrogen or fluorine.
Type semiconductor device manufacturing method.