Semiconductor devices and methods for manufacturing the same

Semiconductor devices and methods for manufacturing the same are disclosed. An example method includes loading a first substrate to be provided with an oxynitride layer along with a second substrate having a nitride layer in a boat, and forming the oxynitride layer on the first substrate by placing the boat into a furnace and thermally treating the boat under an oxygen atmosphere.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to semiconductor devices and semiconductor fabrication, and, more particularly, to semiconductor devices having a dual gate structure and methods for manufacturing the same.

BACKGROUND

As various semiconductor devices have been developed, their characteristics have evolved as well. For example, a logic circuit or a central processing unit (CPU) should have a dynamic random access memory (DRAM) and a static random access memory (SRAM) merged together.

When these memory devices are merged, gate oxide layers with different thicknesses must be formed on one chip so as to preserve the respective characteristics of the devices. Also, even when these devices are used without being merged together, gate oxide layers with different thicknesses must still be formed on one chip to enable operation at different operating voltages.

Such gate oxide layers are thermal oxide layers. Such layers have become thinner in accordance with the development of the design rules. However, when a gate insulating layer is formed by implanting boron as a P-type impurity into a SiO2substrate so as to form a P-type gate structure, boron penetration occurs due to the thinness of the gate oxide layer. The boron penetration degrades the characteristics of the thin film transistors (TFTs) by varying the threshold voltage.

In order to prevent the boron implanted into the SiO2substrate from penetrating a channel region, an oxynitride layer (also called a nitrided oxide layer) is provided. The oxynitride layer may be formed by a growing method performed in a furnace under a NO, N2O, or NH3gas atmosphere, or by a plasma enhanced chemical vapor deposition (PECVD) method.

The PECVD method is disadvantageous in that it increases production costs due to the need to purchase PECVD equipment. The growing method performed in a furnace is also disadvantageous in that it increases the process/fabrication time, because an oxide layer is formed and then an oxynitride layer is formed by thermally treating the oxide layer under a nitrogen gas atmosphere. Further, the method for growing the oxynitride layer in a furnace is disadvantageous in that it further increases production cost, since an apparatus for implanting nitrogen gas, an apparatus for neutralizing harmful gas, and a plurality of stabilization apparatus are required to grow the oxynitride layer in a furnace.

To clarify multiple layers and regions, the thickness of the layers are enlarged in the drawings. Wherever possible, the same reference numbers will be used throughout the drawing(s) and accompanying written description to refer to the same or like parts. As used in this patent, stating that any part (e.g., a layer, film, area, or plate) is in any way positioned on (e.g., positioned on, located on, disposed on, or formed on, etc.) another part, means that the referenced part is either in contact with the other part, or that the referenced part is above the other part with one or more intermediate part(s) located therebetween. Stating that any part is in contact with another part means that there is no intermediate part between the two parts.

DETAILED DESCRIPTION

In the example ofFIG. 1, an example semiconductor device1includes a Si substrate10, a plurality of active regions11formed in the Si substrate10, and a device isolation region12separating the active regions11.

The device isolation region12may be formed by a shallow trench isolation (STI) method or a local oxidation of silicon (LOCOS) method. In the illustrated example, the active region11is formed by implanting boron as a P-type impurity into the Si substrate10. In order for one substrate to realize multiple device characteristics, a first region A and a second region B are designated. Each of the first region A and the second region B has an insulating layer (e.g., an oxynitride layer). The insulating layer in region A is formed with a different thickness than the insulating layer in region B.

As a result, different operating voltages may be applied to the first region A and the second region B. For instance, the operating voltage of the first region A may be lower than that of the second region B. To this end, the first region A and the second region B respectively have a first oxynitride layer16and a second oxynitride layer16′ that are of different thicknesses. In the illustrated example, the first oxynitride16has a thinner thickness than the second oxynitride16′.

An example method for manufacturing a semiconductor device will now be described with reference to the accompanying drawings.

FIG. 2AtoFIG. 2Care cross-sectional views illustrating an example method of manufacturing a semiconductor device performed in accordance with the teachings of the present invention.FIG. 3is a schematic cross-sectional view of a boat loaded with substrates used in the method ofFIG. 2.

FIG. 2Ais a schematic, cross-sectional view of an example semiconductor device50without an oxynitride layer.

As shown inFIG. 2A, a device isolation region12is formed in a predetermined position of the Si substrate by an STI or LOCOS method to divide an active region11.

Then, ions for controlling a P-type threshold voltage (Vth), ions for fixing a channel, ions for forming a well, and ions for avoiding a punch-through are implanted into the active region(s). As a result, a PMOS is formed. The order of forming the active region(s)11and the device isolation region12can be varied, as will be evident to persons of ordinary skill in the art.

FIG. 2Bis a schematic, cross-sectional view of an example semiconductor device100with an oxynitride layer formed only on the first active area11aso as to form the first oxynitride layer and second oxynitride layer to have different thicknesses. It is to be understood that the semiconductor device100shows the semiconductor device50at a later production stage.

As noted above, when the insulating layers are formed to have different thicknesses on the same semiconductor device, the same semiconductor device can realize different device characteristics. With such a structure, for example, a P-type gate may have a dual gate characteristic.

As such, in order to form the insulating layers with different thicknesses, a first oxide layer14may be formed on the active region11by a thermal oxidation process. Herein, the first oxide layer14is defined to have a uniform crystalline structure and to be formed once.

The first oxide layer14is provided to enable formation of the different insulation layers in the first region A and the second region B. Since, due to the first oxide layer14, the first region A and the second region B respectively have the first oxynitride layer16and the second oxynitride16′ of different thicknesses, the first region A and the second region B may be operated at different operating voltages. The first oxide layer (see14′ defined by the dotted line inFIG. 2B) is removed from one active region11a(e.g., the first region A). The first oxide layer14remains on the other active region11b(e.g., on the second region B).

FIG. 2Cis a schematic cross-sectional view of an example semiconductor device1with the first oxynitride layer16and the second oxynitride layer16′. (It should be understood that the semiconductor device1illustrates the semiconductor device100at a later stage of fabrication). When semiconductor device substrate100(hereinafter called the first substrate) such as those shown inFIG. 2are loaded into the boat ofFIG. 3and oxidized in a furnace, the first oxynitride layer16and the second oxynitride layer16′ are formed to have different thicknesses, thereby completing the semiconductor device1. Since the semiconductor device1has the first region A and the second region B, different regions of the device1can be operated at different operating voltages.

An example method of manufacturing the first and the second oxynitride layers (16,16′) will now be described in detail with reference toFIG. 3. First, one or more first substrates100and one or more second substrates200are prepared. First oxide layers14are selectively formed on one active region11bof each of the first substrates100, and at the same time, nitride layers are formed on the surfaces of each of the second substrates200. The first and second substrates100and200are alternately loaded into the slots of a boat202to be mounted in the furnace.

When the boat202carrying the substrates100,200is mounted in the furnace, the first substrate100and the second substrate200are oxidized by a heat treatment under an oxygen atmosphere.

In this example, the first substrate may be differentially oxidized depending on the first oxide layer14.

The second substrate200may also be oxidized. In detail, when the Si is separated from the nitride layer (i.e., Si3N4film) and oxygen gas is injected into the furnace, the Si reacts with the oxygen gas to form an oxide layer on the second substrate200and nitrogen radicals are separated from the nitride layer.

The nitrogen radicals have good reactivity. Accordingly, the nitrogen radicals have an effect on the oxidation of the first substrate100. In more detail, since Si is fixed in the active region11a, the nitrogen radicals are subject to reaction with free oxygen. Accordingly, the nitrogen radicals are combined with the free oxygen to directly form the first oxynitride layer16on the active region11a. Also, the nitrogen radicals are attached to the first (or original) oxide layer14to form the second oxynitride layer16′. In this example, the first oxynitride layer16is formed on the active region11ato form the first region A and the second oxynitride layer16′ is formed on the first oxide layer14to form the second region B.

It has been experimentally determined that, when the first substrate100is loaded in the furnace and is oxidized along with the second substrate200having the nitride layer, the oxide layer (i.e., the first oxynitride16) is grown to be thinner. It is believed that the nitrogen radicals are separated from the nitride layer and, thus, have an effect on the oxidation of the first substrate.

Accordingly, the first oxynitride layer16has a thinner thickness and has a uniform crystalline structure. Meanwhile, the second oxynitride layer16′ has approximately the same thickness as the first oxide layer14regardless of the nitrogen radicals. The second oxynitride layer16′ has a high concentration of the nitrogen radicals at the surface thereof, and the concentration of the nitrogen radicals decreases along a depth direction proceeding away from the surface. Accordingly, the second oxynitride layer16′ has a non-uniform crystalline structure in comparison with the first oxynitride layer16.

The first oxide layer may not be formed on the active region11. As a result, only one oxynitride layer may be formed on the active region11without using the harmful nitrogen gas.

In some examples, when the first substrate100is oxidized along with the second substrate200having the nitride layer, the oxynitride layer can be easily formed without an additional process.

Since the example method does not use harmful NO, N2O gas and/or the like, the oxynitride layer can be safely formed.

From the foregoing, persons of ordinary skill in the art will appreciate that semiconductor devices and method of manufacturing the same have been provided wherein an oxynitride layer can be easily formed without reforming a conventional furnace or using harmful NO, N2O gas and/or the like.

An example method of manufacturing a semiconductor device disclosed herein includes loading first and second substrates together into a boat, wherein the first substrate is to be formed with an oxynitride layer and the second substrate has been formed with a nitride layer, and thereafter forming the oxynitride layer on the first substrate by placing the boat into a furnace and thermally treating the boat in an oxygen atmosphere.

The nitride layer may be formed on the surface of the first substrate.

The first and the second substrates may be alternately loaded in a plurality of slots of the boat.

An oxide layer may be selectively formed on only a predetermined area of the first substrate before loading the first and the second substrates. (In other words, one or more areas of the first substrate might not include the oxide layer).

An example semiconductor device disclosed herein includes a silicon substrate, a plurality of active regions formed in the silicon substrate and a device isolation region to separate the active regions, wherein the active regions contain a small amount of boron; and the active regions are divided into a first region and a second region, the first region having a first oxynitride layer and the second region having a secondary oxynitride layer.

The first oxynitride layer may have a thinner thickness than the second oxynitride layer.

The first oxynitride layer may have a more uniform crystalline structure than the second oxynitride layer.

The second oxynitride layer may have a decreased concentration of nitrogen along a depth direction of the second oxynitride layer.

The first and the second oxynitride layers may have no annealed fine crystalline structure.

The first oxynitride layer may have a thinner thickness and a more uniform crystalline structure than the second oxynitride layer.

The second oxynitride layer may have approximately the same thickness as that of the first oxide layer and a concentration of nitrogen decreased along a depth direction of the second oxynitride layer.

The first oxynitride layer may have a thinner thickness than the second oxynitride layer, and the second oxynitride layer may have approximately the same thickness as the first oxide layer.

The first oxynitride layer may have a uniform crystalline structure and the second oxynitride layer may have a concentration of nitrogen which decreases along a depth direction of the second oxynitride layer.

This application claims priority from Korean Patent Application 10-2004-0059206 which was filed in the Korean Intellectual Property Office on Jul. 28, 2004. The entire content of Korean Patent Application 10-2004-0059206 is incorporated herein by reference.