JPH05206421A - Manufacture of soi-type semiconductor device - Google Patents

Abstract

PURPOSE:To realize high integration and easy designing operation of the subject semiconductor device and to enhance the yield of the semiconductor device. CONSTITUTION:An SOI-type semiconductor device is manufactured by the following: a process wherein a groove having a prescribed width and a prescribed depth is formed in a silicon layer on a semiconductor substrate in which a silicon oxide film 22 is buried in a silicon substrate 21 and which is provided with the silicon layer on the silicon oxide layer 22 is formed and respectively independent semiconductor regions are formed; a process wherein the groove in the silicon layer and a region to be used as a silicon active layer 23' for a semiconductor device are covered with a silicon nitride film 28'; a process wherein the main face of the semiconductor substrate is exposed to an oxidizing atmosphere and one part of the silicon layer not covered with the silicon nitride film is changed to a silicon oxide film 29; and a process wherein the silicon nitride film 28' is left only at the inside of the groove and other parts are removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an SOI which operates at high speed.
The present invention relates to a method for manufacturing a semiconductor device.

[0002]

2. Description of the Related Art FIG. 8 shows a conventional SOI (Silicon-
It is a sectional view showing composition of an On-Insulator type semiconductor device. In the figure, 1 is a silicon substrate, 2 is a silicon oxide film, 3 is a p-type silicon active layer of the first conductivity type, 4 is a gate insulating film made of, for example, a silicon oxide film, 5 is a gate electrode, and 6 is a For example, n is a source region of 2 conductivity type, 7 is an n type drain region of second conductivity type, 8 is an insulating film for electrically insulating between wirings, 9 is a source electrode, and 10 is a drain electrode. is there.

In the SOI type semiconductor device having such a structure, the impurity concentration of the silicon active layer 3 is designed so that the thickness of the depletion layer which can spread from the gate electrode 5 side is thicker than the thickness of the silicon active layer 3. However, the entire region of the silicon active layer 3 is depleted during the operation of the semiconductor device.

The reason for such a configuration is to suppress the mobility deterioration of the inversion layer carrier just below the gate insulating film by reducing the effective electric field strength in the active layer, thereby increasing the drain current, and the active layer. This is because it is possible to increase the drain current by increasing the inversion layer carriers corresponding to the decrease in the charge amount of the depletion layer in the inside.

Further, in the SOI type semiconductor device having such a structure, since the inside of the active layer is depleted by the gate electric field, the penetration of the drain electric field from the drain junction into the active layer can be suppressed, and the threshold voltage is short. The channel effect can be suppressed. Therefore, this type of semiconductor device can be expected to have both high integration and high-speed operation of the semiconductor device due to the miniaturization of dimensions, and its future prospect has attracted attention in recent years.

9 to 12 are sectional views of steps for explaining a method of manufacturing the semiconductor device shown in FIG. First, FIG.
As shown in, a silicon semiconductor substrate having a silicon oxide film 11 embedded in a silicon substrate 1 and having a silicon layer 12 on the silicon oxide film 11 is prepared. Then, the surface of the silicon layer 12 is oxidized to form a silicon oxide film 13, and subsequently, for example, a silicon nitride film 14 is deposited as an oxidation resistant insulating film on the silicon oxide film 13.

Next, as shown in FIG. 10, the silicon nitride film 14 is processed into a predetermined size by, for example, an anisotropic plasma etching method, and then the silicon oxide film 13 is processed into the same size to form a part of the silicon layer 12. Expose.

Next, as shown in FIG. 11, this silicon semiconductor substrate is exposed to an oxidizing atmosphere to oxidize only the exposed region of the silicon layer 12. At this time, the silicon oxide film 2 already exists in the silicon substrate 1
Oxidize the silicon semiconductor substrate until it merges with 1. In this way, the silicon active layer 12 'is electrically isolated from the other active layers simultaneously formed in other regions.

Next, as shown in FIG. 12, a silicon nitride film 1 is formed.
4'is removed, for example with phosphoric acid. For example, by ion implantation, a predetermined impurity such as boron is introduced into the silicon active layer 12 'to make the silicon active layer 12' the first conductivity type. Subsequently, the silicon oxide film immediately below the silicon nitride film 14 'is removed by, for example, hydrofluoric acid, and the silicon semiconductor substrate is again exposed to an oxidizing atmosphere to form the silicon oxide film 4 as a gate insulating film. Then, the gate electrode 5 is formed.

After that, for example, by an ion implantation method,
A source region 6 and a drain region 7 of the second conductivity type are formed, and then an insulating film 8 such as a silicon oxide film is deposited on the main surface side of the silicon semiconductor substrate, and then the source region 6 is formed.
A contact hole is formed on the drain region 7 and a metal layer for electrode wiring is deposited. After that, the metal layer is processed to form the source electrode 9 and the drain electrode 10 to manufacture a semiconductor device.

A cross section taken along line X ₁ -X ₂ of the semiconductor device of this type shown in FIG. 8 which has been actually manufactured by such a method has the structure shown in FIG. In this case, the well-known bird's beak lateral growth of an oxide film occurs. Here, it extends to the region shown by the width l _B. By this lateral oxidation, the portion of the silicon active layer 12 'indicated by A is oxidized from the bottom of the silicon layer and pushed upward. On the other hand, in the portion indicated by B, the silicon layer is oxidized from the upper side.

[0012]

However, the semiconductor device formed by such a manufacturing method has the following problems. By generating the gate width of the bird's beak of the semiconductor device designed by the width l _A as shown in FIG. 12, it decreases to the gate width l _A '. This causes a problem that the gain of the semiconductor device is reduced. When the design is performed in consideration of the reduction of the gate width, the designed gate width lA relatively increases, which causes a problem that it is against the miniaturization of the semiconductor device. From the viewpoint of electrical characteristics, the thickness of the end portion C of the silicon active layer 12 'is equal to the thickness t _S of the other portion of the silicon active layer 12'.
It becomes thinner than. That is, if the impurity concentration in the silicon active layer 12 'is uniform over the entire region, the threshold voltage of this region is lower than the threshold voltages of other regions. The characteristic phenomenon observed in this case is shown in FIG.

FIG. 13 shows the relationship between the gate voltage and the drain current. In the figure, for example, normal n
In the channel-type semiconductor device, when the gate voltage is swept from a negative value to a positive value, the drain current first increases as shown by the broken line indicated by a and then changes as shown by b. At this time, assuming that the gate voltage at which the drain current flows by 10 ⁻⁷ A is the threshold voltage, the value becomes V _T1 .

On the other hand, in the semiconductor device shown in FIG. 8, when the gate voltage is similarly swept, the current initially flows in the region C shown in FIG. 12 and increases like a ', and then changes like b. In this case, the threshold voltage becomes V _T2 , which deviates significantly from the designed value V _T1 .

As described above, this type of semiconductor device has not been put into practical use because it has some of the great features but at the same time has the above problems.

Therefore, the present invention has been made in order to solve the above-mentioned conventional problems, and its purpose is to reduce the size of a semiconductor device due to a lateral oxidation phenomenon and to cause parasitic parasitics at the end of an active layer. It is possible to solve the difficulty of the threshold voltage design due to the influence of various semiconductor devices, and to realize large-scale integration of this type of semiconductor device and dramatically improve the yield.
It is to provide a method for manufacturing an OI type semiconductor device.

[0017]

In order to achieve such an object, the present invention provides a semiconductor substrate in which an insulating layer is embedded in a semiconductor and a surface having the semiconductor layer on the insulating layer is a main surface. A method of manufacturing an SOI type semiconductor device using the method of forming an SOI type semiconductor device, comprising: forming a groove having a predetermined width and depth in a semiconductor layer in a closed pattern, and forming independent semiconductor regions in the semiconductor layer. A step of covering the groove of the semiconductor layer and a region to be an active layer of the semiconductor device with an oxidation resistant insulating film, and a semiconductor layer exposed to an oxidizing atmosphere on the main surface side of the semiconductor substrate and not covered with the oxidation resistant insulating film Is partially converted into an oxide, and a step of leaving the oxidation-resistant insulating film only inside the groove and removing the others is performed.

[0018]

In the method of manufacturing a semiconductor device according to the present invention, not only the gate width of the semiconductor device can be realized as designed, but also the active layer can be prevented from becoming thin at the end of the active layer. ..

[0019]

Embodiments of the present invention will be described in detail below with reference to the drawings. 1 to 7 are sectional views of steps for explaining an embodiment of the method of manufacturing an SOI semiconductor device according to the present invention. First, as shown in FIG. 1, for example, a silicon substrate 21 is filled with a silicon oxide film 22 as an insulating layer, and a semiconductor substrate having a silicon layer 23 on the silicon oxide film 22 is prepared. Then, this silicon layer 23
A silicon oxide film 24 is formed thereon, and subsequently, for example, a silicon nitride film 25 is formed on the silicon oxide film 24 as an oxidation resistant insulating film.

Next, as shown in FIG. 2, a groove pattern having a predetermined size is formed in the silicon nitride film 25 by an anisotropic etching method such as a reactive ion etching method, and then the silicon oxide film 24 is subjected to, for example, hydrofluoric acid. By etching, followed by anisotropic etching such as reactive ion etching to form the silicon active layer 2 to be the active layer region.
A groove 26 surrounding 3'is formed. At this time, this groove 2
6 may be the depth to the bottom surface of the silicon layer 23, and
The depth to the bottom surface of the silicon oxide film 22 may be sufficient, and the depth reaching the inside of the silicon substrate 21 may be sufficient.

Next, as shown in FIG. 3, the silicon active layer 2 is formed by, for example, thermally oxidizing the surface of the semiconductor substrate.
3 ', a silicon oxide film 27 is formed in the region exposed in the groove 26, and subsequently, for example, a silicon nitride film 28 is formed as an oxidation resistant insulating film on the main surface side of the semiconductor substrate.
Deposit.

Next, as shown in FIG. 4, a silicon active layer 2 is formed.
The silicon nitride film 25 and the silicon nitride film 28 are processed by, for example, an anisotropic etching method to a size that can cover both 3'and the groove 26 surrounding the silicon nitride film 3'and the silicon nitride film 25 'and the silicon nitride film 28' are formed.

Next, as shown in FIG. 5, this semiconductor substrate is exposed to an oxidizing atmosphere to oxidize the main surface, and a silicon oxide film 29 is formed.
To form. At this time, the silicon oxide film 24 ′ may be removed to form the silicon oxide film 29, or the silicon oxide film 24 ′ may be left as it is and oxidized. Further, the bottom surface of the silicon oxide film 29 may be oxidized until it reaches the silicon substrate 21. Alternatively, the silicon oxide film 29
You may oxidize so that the bottom face of may not reach the silicon oxide film 22.

Next, as shown in FIG. 6, the silicon nitride film 2
8'is removed, for example using phosphoric acid. However, the groove 26
A silicon nitride film 28 ″ is left inside.

Next, as shown in FIG. 7, a silicon active layer 2 is formed.
Impurities are introduced into 3'by, for example, an ion implantation method to make the silicon active layer 23 'a first conductivity type. Next, after removing the silicon oxide film 24 ', the silicon active layer 23' is oxidized to form a gate oxide film 31, and subsequently a gate electrode 32 is formed on the main surface side of the semiconductor substrate. After that, a source region 33 and a drain region 34 of the second conductivity type are formed by, for example, an ion implantation method, and then an insulating film 35 is deposited on the main surface side of this semiconductor substrate, and then on the source region 33 and the drain region 34. A contact hole is formed in the semiconductor device, and finally a source electrode 36 and a drain electrode 37 are formed to manufacture a semiconductor device.

[0026]

As described above, according to the present invention,
The following excellent effects can be obtained. In the process of electrically insulating and isolating between semiconductor devices by oxidizing the periphery of the active layer, by covering the periphery of the silicon layer to be the active layer with an oxidation resistant insulating film, it is possible to prevent the reduction of the gate width due to lateral oxidation. The gain performance of the semiconductor device can be realized as designed. Due to the effects described above, it is not necessary to increase the gate width in advance when designing the semiconductor device, which is advantageous for downsizing the semiconductor device. In the manufacturing method according to the present invention, since the thickness of the active layer is uniform over the entire area, it is possible to prevent an abnormal drain current from being generated due to a parasitic semiconductor device that has been easily formed at the end. Yields are dramatically improved, facilitating higher integration.

[Brief description of drawings]

FIG. 1 is a sectional view of a step illustrating an embodiment of a method for manufacturing an SOI semiconductor device according to the present invention.

FIG. 2 is a sectional view of a step following the step of FIG.

FIG. 3 is a cross-sectional view of a step following the step of FIG.

FIG. 4 is a cross-sectional view of a step following the step of FIG.

5 is a sectional view of a step following the step of FIG. 4. FIG.

FIG. 6 is a sectional view of a step following the step of FIG. 5;

FIG. 7 is a sectional view of a step following the step of FIG. 6;

FIG. 8 is a cross-sectional view showing the structure of an SOI semiconductor device.

FIG. 9 is a cross-sectional view of a step illustrating a method for manufacturing the semiconductor device shown in FIG.

FIG. 10 is a sectional view of a step following the step of FIG. 9;

11 is a cross-sectional view of a step following the step of FIG.

12 is a cross-sectional view of a step following the step of FIG.

FIG. 13 is a diagram showing the results of measuring the relationship between the gate voltage and the drain current of the semiconductor device formed by the manufacturing method shown in FIGS. 9 to 12;

[Explanation of symbols]

 21 Silicon Substrate 22 Silicon Oxide Film 23 Silicon Layer 23 ′ Silicon Active Layer 24 Silicon Oxide Film 24 ′ Silicon Oxide Film 25 Silicon Nitride Film 25 ′ Silicon Nitride Film 26 Groove 27 Silicon Oxide Film 28 Silicon Nitride Film 28 ′ Silicon Nitride Film 28 ″ Silicon nitride film 29 Silicon oxide film 30 Silicon active layer 31 Gate oxide film 32 Gate electrode 33 Source region 34 Drain region 35 Insulating film 36 Source electrode 37 Drain electrode

Claims (1)

[Claims] 1. A method for manufacturing an SOI type semiconductor device, comprising forming an SOI type semiconductor device using a semiconductor substrate having an insulating layer embedded in a semiconductor and having a surface having a semiconductor layer on the insulating layer as a main surface. Forming a groove having a predetermined width and depth in the semiconductor layer in a closed pattern and forming independent semiconductor regions in the semiconductor layer, and forming the groove in the semiconductor layer and an active layer of a semiconductor device. Covering a region with an oxidation resistant insulating film, exposing the main surface side of the semiconductor substrate to an oxidizing atmosphere, and converting a part of the semiconductor layer not covered with the oxidation resistant insulating film into an oxide. A step of leaving the oxidation-resistant insulating film only inside the groove and removing the others, the method for manufacturing an SOI semiconductor device.