KR100431065B1 - Method of preventing bending of soi layer and semiconductor device formed by the same - Google Patents

Abstract

The present invention relates to a method capable of preventing bending of the soy layer when the trench elements are separated from the soy substrate, and a semiconductor device formed by the method. At least a portion of the interface between the soy layer and the buried silicon oxide layer is formed by forming a nitrogen-containing layer by ion implantation or by forming an isolation trench, and then laminating amorphous silicon and changing it using solid crystal growth. A method is used to prevent oxygen from diffusing through the layer and buried silicon oxide layer interface and oxidizing adjacent small layers.

Description

Soy-layer banding prevention method and a semiconductor device formed by the method {METHOD OF PREVENTING BENDING OF SOI LAYER AND SEMICONDUCTOR DEVICE FORMED BY THE SAME}

The present invention relates to a method of forming a semiconductor device on a SOI (Silicon On Insulator) substrate and a semiconductor device formed by the method, and more particularly to trench isolation in a small substrate. The present invention relates to a method of preventing bending of the soy layer around the active region and a semiconductor device formed by the method.

A junction type device region separation method in which semiconductor layers having different impurity types are in contact with each other is not suitable for semiconductor devices adopting high voltage elements due to the limitation of the breakdown voltage of the junction surface. In addition, in the device region separation method of the junction type, its use is inefficient in a high radiation environment because of the current generated in the depletion layer of the junction by radiation such as gamma rays. Therefore, as a high performance semiconductor device such as a central processing unit (CPU), many small semiconductor devices in which device regions are completely isolated by an insulating layer are used.

Mesa, LOCOS (LOCal Oxidation of Silicon), and Shallow Trench Isolation (STI) are the most widely used methods for isolation between devices in a soy substrate. In particular, the STI method has been widely employed in highly integrated semiconductor devices because it can substantially extend the device formation region by preventing a bird's beak phenomenon occurring in LOCOS.

However, when performing STI for device region separation on a soy substrate, there is a problem that bending occurs in the silicon layer constituting the active region due to the structural characteristics of the soy substrate.

Hereinafter, the problem will be described with reference to the accompanying drawings.

Referring to FIG. 1, a buried silicon oxide layer 11 is disposed on a lower silicon layer 10, and a soy layer 13 is formed on the buried silicon oxide layer 11 to form an active region. For the STI, a pad oxide film 15 and an etch-resistant silicon nitride film 17 are stacked on a soy layer of a soy substrate and patterned using a photoresist film 19 to form a pattern of a silicon nitride film. do.

Referring to FIG. 2, the trench is formed by sequentially removing the silicon oxide layer 17 pattern from the pad oxide layer 15 exposed through the etching mask and the lower layer 13 below. Thus, the bottom of the trench is made of a buried silicon oxide layer 11.

Referring to FIG. 3, the sidewall oxide layer 25 is formed through thermal oxidation on the cut surface of the small layer pattern 23 ′ forming the sidewalls of the trench. The sidewall oxide film 25 is produced as a result of a heat treatment to cure crystal damage resulting from etching. At this time, the interface between the small layer pattern 23 'constituting the active region and the buried silicon oxide layer 11 under the active region serves as a passage for oxygen diffusion, and the oxygen can be smoothly supplied from the exposed sidewalls according to the trench formation. Therefore, the oxide layer extends from the trench into the active region on the bottom of the soy layer pattern 23 'which is in contact with the lower buried silicon oxide layer 11. Therefore, although the position is different, a thermal oxidation layer having a shape such as Buzzvik is formed in a form in which the soy layer and the buried silicon oxide layer are infiltrated. The thermal oxidation layer formed at this time is thickly formed on the sidewall of the trench where oxygen is actively supplied. The silicon in the bottom portion of the soy layer pattern 23 'turns into a thermal oxide and causes volume expansion to lift up the soy layer pattern 23' from the trench side, thereby bending the soy layer. This is called.

When bending occurs, stress is applied to the soy layer by the lifting force on the trench sidewalls. In this state, when a subsequent ion implantation process or the like is performed, crystal phase defects are likely to occur in the soy layer, and the generated defects easily expand. Crystal defects increase junction leakage current. In addition, even when crystal defects do not occur at the time of ion implantation, the depth of the small layer is partially changed due to warpage and the depth of the ion implantation is changed, which may cause a functional problem in which the threshold voltage becomes unstable. Can be. (A comparison of oxidation induced stress and defectiveity in SIMOX and bonded SOI wafers: Proceedings 1997 IEEE International SOI Conference, Oct. 1997; Stress Induced Defect and Transistor Leakage for Shallow Trench Isolated SOI: IEEE ELECTRON DEVICE LETTERS, VOL. 20. NO. MAY 1999)

Under the condition that the oxide film on the sidewall is formed at 240Å, the soy layer can be lifted up to about 4000Å at the sidewall in the horizontal direction. Although it may vary depending on the degree and condition of sidewall oxidation, banding cannot be completely prevented.

Accordingly, an object of the present invention is to provide a method capable of preventing the problem of the small layer banding and a semiconductor device formed thereby.

More specifically, an object of the present invention is to provide a method capable of preventing a small layer banding caused by thickening of an oxide film at an interface between a small layer and a buried silicon oxide layer in trench isolation, and a semiconductor device formed thereby. .

It is also an object of the present invention to provide a method capable of preventing a phenomenon in which a stress is applied to a soy layer and damage occurs due to soy layer banding and an increase in leakage current, and a semiconductor device formed thereby.

1 to 3 are cross-sectional views for showing a problem of bending caused when trench isolation is performed on a conventional soy substrate.

4 to 6 are process cross-sectional views showing features in the first embodiment of the method of the present invention;

7 is a cross-sectional view showing features in accordance with a second embodiment of the method of the present invention;

8 and 9 are cross-sectional views showing features in accordance with a third embodiment of the method of the present invention;

10 is a cross-sectional view showing features in accordance with a fourth embodiment of the method of the present invention;

11 to 14 are process sectional views showing a process according to a fifth embodiment of the method of the present invention;

15 to 18 are process cross sectional views showing a process according to a sixth embodiment of the method of the present invention.

※ Explanation of code for main part of drawing

10,110: lower silicon layer 11,111: buried silicon oxide layer

13,113: soy layer 15,115: pad oxide film

17,117 silicon nitride film

19: photoresist film 119: photoresist pattern

23,23'123,123 ': soy layer pattern 25,125: sidewall oxide film

131: nitrogen-containing layer 132: CVD oxide film

133: oxygen barrier layer 151: amorphous silicon layer

153: residual silicon layer 161: surface oxide film

171: trench oxide film 173: device isolation film

According to the present invention for achieving the above object, a method for preventing the diffusion of oxygen in the trench sidewall at the buried silicon oxide layer and the soy layer interface to prevent the oxide film is formed, at least in the portion corresponding to the periphery of the active region and A nitrogen-containing layer is formed at the interface of the buried silicon oxide layer.

For this method, first, an example in which a nitrogen-containing layer is formed on the entire SOI layer and the buried silicon oxide layer interface in a soy substrate and a conventional trench element separation process can be considered. In this case, as a method of applying the nitrogen-containing layer to the entire soy substrate, a method of performing deposition or nitriding in a gas atmosphere containing nitrogen in the soy substrate forming step, and ion implantation containing nitrogen are performed. You can think of how to do it.

As another example, a trench is formed on the small-type substrate by a small-layer etching, and ion implantation containing nitrogen is rotated while tilting the substrate on which the trench is formed at a predetermined angle to limit the width of the active region to a predetermined width. A method of forming a nitrogen-containing layer at the interface between the soy layer and the buried silicon oxide layer can be considered.

According to another configuration of the method of the present invention, the present invention may be formed by etching the soy layer to form a trench and forming a single crystal silicon layer on the trench sidewalls.

Looking at a more specific method of such another configuration, the step of forming a pattern for stacking an etch stop layer on the soy substrate and exposing the trench region, forming a trench by etching the soy layer of the soy substrate using the pattern as an etching mask, Conformally stacking an amorphous silicon layer on the entire surface of the soy substrate including the trench, and performing annealing to solid-state crystal growth on the amorphous silicon layer in contact with the sidewall of the trench made of the soy layer. And the step of laminating the buried oxide film to fill the trench and removing the buried oxide film from the active region by performing a planarization etching. That is, the method may include conformally laminating an amorphous silicon layer with a temporary oxygen barrier in a state in which a trench is formed in the soy substrate, and solid phase crystal growth of the stacked amorphous silicon. In this case, the buried oxide film is mainly formed of a chemical vapor deposition (CVD) oxide film.

According to still another aspect of the present invention, a CVD oxide film is conformally formed on the entire surface of the substrate on which the trench is formed while the trench is formed by etching the soy layer for device isolation. At this time, an oxygen barrier liner may be stacked on the inner wall of the trench in a state where the CVD oxide film is stacked. The liner laminated to the trench inner wall usually uses a method of CVD deposition of a silicon nitride film.

According to yet another aspect of the present invention, rapid thermal oxidation (RTP) is performed in a state in which a device isolation trench is formed on a soy substrate. A silicon nitride film liner may be further formed on the oxide film formed by rapid thermal oxidation.

A device of the present invention for achieving the above object is a trench device isolation type semiconductor device having a substrate structure including a lower silicon layer, an embedded silicon oxide layer, and a soy layer in the active region, wherein at least the buried silicon oxide layer and soy around the active region are The nitrogen-containing layer is provided between the layers.

In the device of the present invention, an oxide film is formed on the side where the trench device isolation layer is in contact with the active region. The oxide film on the side is usually a thermal oxide film formed in a furnace, but may be a CVD oxide film or a rapid thermal oxide (RTO) oxide film. Most of the trench isolation film except for the side portion is usually formed of an oxide film filling a trench, such as a CVD oxide film.

In addition, the nitrogen containing layer of this invention is generally formed by nitrogen ion implantation. The silicon nitride film liner may be further provided on the opposite side of the substrate forming the active region based on the oxide film on the side of the trench isolation layer.

In another configuration of the device of the present invention, in a trench isolation device type semiconductor device having a substrate structure including a lower silicon layer, a buried silicon oxide layer, and a soy layer in the active region, the sidewalls of the active region in contact with the device isolation film of the trench are solid phase crystals. And a single crystal silicon layer formed by solid phase epitaxial growth (SPE). In this case, a thermal oxide film and a silicon nitride film liner may be further provided on the opposite side of the active region based on the single crystal silicon layer due to the solid crystal growth.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Example 1

4 to 6 show each process step of forming a nitrogen element-containing film at the boundary between the soy layer and the buried silicon oxide layer by one method of the present invention.

Referring to FIG. 4, a pad oxide layer 115 is formed on a surface of a soy substrate having a buried silicon oxide layer 111 on the lower silicon layer 110 and a soy layer 113 for forming elements on the buried silicon oxide layer 111. In the state where) is formed, ion implantation containing a nitrogen element is performed on the entire surface of the soy substrate. Therefore, the nitrogenous layer 131 is formed.

The energy of the ion implantation is determined such that a peak value of the concentration appears at the boundary between the soy layer 113 and the buried silicon oxide layer 111. The ion implantation energy varies depending on the thickness of the pad oxide film and the soy layer, but is usually performed in the range of 30 to 100 keV.

Referring to FIG. 5, a silicon nitride film 117 is stacked as an etch stop layer for forming trenches on a soy layer 113 on which a pad oxide film 115 is formed, and the device is separated by a conventional photolithography process on the silicon nitride film 117. A photoresist pattern 119 is formed to expose the trench region. Then, the silicon nitride layer 117 and the pad oxide layer 115 are etched using the photoresist pattern 119 as an etch mask, and then the trenches are etched to expose the buried silicon oxide layer to form the trench layer 123 to form trenches. do. The photoresist pattern 119 may be removed before the etching of the soy layer.

Referring to FIG. 6, thermal oxidation is performed on a trench-formed soy substrate to cure crystal damage of trench sidewalls that are damaged in a trench etching step. Thermal oxidation is performed for 15 minutes by a 900 ℃ dry oxidation in a furnace (furnace) similar to the conventional method, the thermal oxide film having a thickness of 200 to 300 Å is formed on the exposed surface of the soy layer pattern 123 forming the sidewalls of the trench. At this time, a nitrogen-containing layer 131 such as a silicon nitride film or a silicon oxynitride film is formed at the boundary between the soy layer pattern 123 and the buried silicon oxide layer 111 by the nitrogen injected in the step of FIG. The boundary between the silicon layer and the silicon oxide layer is eliminated, and oxygen does not diffuse well between the silicon layer and the silicon nitride layer or the silicon oxynitride layer, so that the bottom surface of the soy layer is oxidized and the banding phenomenon rising from the trench sidewall is suppressed. This may be a good comparison with the pad oxide film 115 being thickened on the sidewalls of the trench, but not shown in detail, but the upper silicon nitride film is lifted and a slight warp occurs in the silicon nitride film.

In the embodiment of the method of the present invention, the ion implantation containing the nitrogen element is performed in the state where the pad oxide film is present in the soy layer, but the presence of the pad oxide film is not essential. After the thermal oxidation, a silicon nitride film liner may be formed in the trench, and a buried oxide film such as a CVD oxide film fills the trench to form a device, and then a subsequent process is added to form an example of the semiconductor device of the present invention.

Example 2

FIG. 7 is a low ketone of about 10 keV in a state in which a trench is formed by etching a soy layer using an etch stop layer pattern as an etch mask for isolation of trench elements on a soy substrate having a lower silicon layer, an embedded silicon oxide layer, and a soy layer. The state of nitrogen ion implantation is shown. At this time, the arrow indicating the direction of ion implantation is inclined because the substrate on which the trench is formed is inclined by about 15 ° when the ion implantation is performed. On the other hand, since the ion implantation is performed while the substrate is rotated, ion implantation is performed on the exposed sidewalls of all the layers of the trench. What is important here is some area between the soy layer and the buried silicon oxide layer. Nitrogen containing layers are formed between the soy layer and the buried silicon oxide layer at the periphery of the active region in contact with the trench by the implanted nitrogen ions. Although a nitrogen-containing layer is formed only by a certain width, the nitrogen-containing layer serves to block oxygen from diffusing through the interface between the soy layer and the buried silicon oxide layer in a subsequent oxygen atmosphere thermal process to partially oxidize the soy layer below a certain thickness. Will be

Following the above method, the step of forming an oxide film or forming a nitride film on the sidewalls of the trench is selectively performed, and the semiconductor device of the present invention may be formed through a subsequent process by separating an element by filling an insulating film in the remaining trench.

Example 3

FIG. 8 illustrates a state in which a silicon oxide film is deposited by CVD on the entire surface of a soy substrate having trenches and a soy layer pattern 123 formed by etching a soy layer. The CVD deposition is performed at a temperature of 700 to 750 ° C. by low presure (LP) -CVD, and forms a thickness of 50 to 500 kPa using a siethylene (SiH ₄ ) gas and oxygen as the source gas. The LPCVD process is used, but the temperature of 700 ° C. or more may be used for the healing of crystal defects due to the etching of the etched cross section, and the CVD oxide layer 132 may serve as a protective layer for the trench sidewall formed of a soy layer in a subsequent process. However, due to low pressure and relative low temperature in the process, thermal oxide film is hardly generated, so there is no fear of banding.

More preferably in this embodiment, the step of further stacking the oxygen barrier layer 133 as shown in FIG. 9, a silicon nitride film (Si ₃ N ₄ ), a silicon oxynitride film (Si ₃ N ₄ ) as an oxygen barrier layer 133 on the CVD oxide film 132 in order to prevent soy layer banding when subsequent oxidation occurs in the state of FIG. 8. SiON) and aluminum oxide film (AlO ₃ ) are deposited at 30 to 300 Pa. Subsequent oxidation refers to a process of forming a screen oxide film, a gate oxide film, or oxidizing sidewalls of a gate poly to be formed on the soy layer pattern 123 forming the active region before ion implantation into the soy layer. The semiconductor device of the present invention is formed through the subsequent semiconductor device formation process.

Example 4

Referring to FIG. 10, rapid thermal oxidation (RTO) is performed on a soy substrate in which trenches are etched for device isolation. Unlike thermal oxidation in a general heating furnace, the silicon layer exposed to the substrate, that is, the sidewall of the soy layer pattern 123, is exposed at a short time of 30 to 200 seconds at a temperature of 950 to 1180 ° C. As a result, the sidewall oxide film 125 is formed. The diffusion of oxygen through the interface between the oxide film and the silicon layer and the oxidation of the silicon layer are proportional to the time with the process temperature, thereby shortening the time to suppress the expansion of the banding due to the bottom surface oxidation of the soy layer.

Example 5

11 to 14 are process sectional views showing respective process steps of this embodiment.

Referring to FIG. 11, the amorphous silicon layer 151 is formed on the entire surface of the soy layer by etching the soy layer, and the silicon nitride film 117 pattern formed to form the trench is present on the soy substrate on which the soy layer pattern 123 and the trench are formed. Conformally stacked 50-300 mm thick.

Referring to Fig. 12, a soy substrate on which an amorphous silicon layer is stacked is subjected to conventional trench sidewall oxidation but less than the amorphous silicon layer thickness. As a result, in the laminated amorphous silicon layer, the surface in contact with oxygen is oxidized to form a surface oxide film 161 and a residual silicon layer 153 of 30 to 250 kPa. The SOI layer, that is, the amorphous silicon layer in contact with the trench sidewalls, may be cured with crystal defects of the SOI layer at a high temperature applied to thermal oxidation, and some solid phase epitaxy (SPE) may occur.

Referring to FIG. 13, a trench oxide film 171 is deposited by CVD to fill a trench in a state where a surface oxide film 161 is formed on an amorphous silicon layer. The silicon nitride film liner may be first thinly stacked before the trench oxide film 171 is formed. And annealing is performed about 1 hour at the temperature of 750-1150 degreeC. Annealing may be performed at the same time as the annealing performed to strengthen the film quality of the trench oxide layer 171 and lower the wet etching ratio, and is preferably performed in a nitrogen atmosphere. Solid crystal growth occurs in the residual silicon layer 153 in contact with the soy layer during the annealing process to form an enlarged soy layer pattern 123 ', and the remaining portion that does not have solid phase growth becomes an oxide film in a subsequent process. There is no problem of insulation due to the amorphous silicon layer.

Referring to FIG. 14, the trench oxide layer except for the isolation layer 173 filling the trench in FIG. 13 is removed by CMP (Chemical Mechanical Polishing), and the silicon nitride layer and the pad oxide layer, which are anti-etching layers, are removed to remove the trench element. To complete. In addition, a semiconductor device having a structure for preventing soy layer banding is achieved through a necessary post process.

Example 6

15 to 17 are process sectional views showing respective process steps of this embodiment.

Referring to FIG. 15, the amorphous silicon layer 151 conforms to the entire surface in a state in which a silicon nitride film 117 pattern for forming a trench is present on a soy substrate in which a trench for etching a device is formed by etching the soy layer. It is laminated 300mm thick.

Referring to Fig. 16, annealing is performed at a temperature of 550 to 700 DEG C on a substrate on which the amorphous silicon layer 151 is laminated. Annealing is performed without oxygen in a general heating furnace or an ultra high vacuum system (UHV system), preferably in a nitrogen atmosphere. In this case, while the recrystallization work is performed on the amorphous silicon layer 151, the solid crystal growth (SPE) is performed in the portion adjacent to the small layer pattern 123 under the influence of the single crystal structure of the small layer pattern 123. As a result, an enlarged small layer pattern 123 'is formed.

Referring to FIG. 17, after the solid crystal growth is performed on the amorphous silicon layer of the trench sidewall, sidewall oxidation is performed to form the surface oxide film 161. The trench oxide film 171 is stacked to fill the trench. Afterwards, annealing of the trench oxide layer 171 is usually performed as in a conventional trench device isolation process. The portion of the amorphous silicon layer 151 that is not changed to the surface oxide film 161 becomes the remaining embodiment cone layer 153.

Referring to FIG. 18, the trench oxide film 171 on the small layer pattern 123 ′, which is an active region, is removed by planarization etching by CMP, leaving only the device isolation film 173. Then, the silicon nitride film and the pad oxide film, which serve as an etch mask in the trench patterning, are removed. The silicon nitride film liner may first be conformally stacked before stacking the trench oxide film.

On the other hand, since the crystal defect healing of the soy layer is performed in the annealing step for the solid crystal growth in the present embodiment, it is preferable that a separate sidewall thermal oxidation is omitted. The silicon layer which may be left without thermal oxidation, in particular, the residual silicon layer 153 on the bottom of the trench is oxidized in a subsequent thermal process exposed to oxygen after the CVD oxide layer is deposited, thereby causing no problem of insulation.

According to the present invention, it is possible to suppress or fundamentally prevent soy layer banding, which may occur when trench isolation is performed on a soy substrate.

Claims (13)

Forming a soy substrate having a lower silicon layer, a buried silicon oxide layer, and a soy silicon on insulator (SOI) layer; Directly injecting nitrogen (N) ions through the soy layer to form a nitrogen-containing layer between the buried silicon oxide layer and the soy layer; And And etching the soy layer of the soy substrate to form a device isolation trench. delete The method of claim 1, Said nitrogen ion implantation is a soy layer banding prevention method, characterized in that the pad oxide film is formed on the soy layer surface. Etching the soy layer of the soy substrate having a lower silicon layer, an buried silicon oxide layer, and a soy (silicon on insulator) layer to form a trench, And tilting the trench in which the trench is formed to perform nitrogen ion implantation to form a nitrogen-containing layer between the buried silicon oxide layer and the trench in the bottom edge of the trench. Etching the soy layer of the soy substrate including a lower silicon layer, an embedded silicon oxide layer, and a soy layer to form a trench; and And applying the LPCVD method on the entire surface of the soy substrate including the trench to conformally deposit an oxide film at a thickness of 50 to 500 kV at a temperature of 700 to 750 ° C. The method of claim 5, wherein Conformally stacking the CVD oxide film Forming a silicon nitride film liner And filling the trench with a buried oxide film. delete delete delete delete delete delete delete