Semiconductor device having a two-layer silicide structure and the ways of making /choices/

 

(57) Abstract:

The invention relates to a MOS semiconductor memory device, particularly to a semiconductor device that improves the high temperature stability of the titanium silicide used for the manufacture of gate lines policed in DRAM (random access memory). Essence: silicide layer is produced by deposition of a metal which forms a silicide at the predetermined first temperature, polycrystalline silicon for the formation of the first layer of metal silicide and the subsequent deposition of the metal, forming a silicide at a second temperature below the first temperature, to form the second layer of metal silicide; because the instability of the conventional semiconductor device, built on the titanium silicide, begins to occur at a higher temperature and subsequent annealing in a furnace, it is possible to avoid grain growth, plastic deformation and agglomeration. 3 C. and 15 C.p. f-crystals, 4 Il.

The invention relates to a MOS semiconductor memory device, particularly to a semiconductor device that improves socioterritorial stability of titanium silicide used for the manufacture of I & d of refractory metal, similar to titanium silicide, typically used to reduce the resistance of the internal wiring.

The titanium silicide is produced by compounds of titanium (Ti), which is a refractory metal with silicon (Si), this compound has a high electrical conductivity and excellent heat resistance. The titanium silicide is convenient for microstructural processing and therefore is widely used for building large-scale integrated semiconductor memory devices. The titanium silicide is applied on the self-leveling silicide (SALICIDE) because he has a small resistance (details can be found in IEDM 9-12, December, 1990, S. 249-262).

Fig. 1 illustrates an example of forming titanium silicide by a known method. In the step depicted in Fig. 1A is grown in a layer 2 of silicon dioxide with a thickness of about on the monocrystalline silicon substrate 1 whose specific resistance of 5 to 25 Ohm cm at a temperature of about 920oC, by thermal oxidation. Then thermally decomposing silane (SiH4) at a temperature of about 625oC at a pressure of 250 mtorr by vacuum deposition chemical vapor (LDCVD) for the deposition of polycrystalline silicon layer 3 on the upper part of layer 2 of the d is the layer 3 (layer 3) introducing phosphorus (P) in a known manner of introduction of ions. Jonah is an energy of about 30 Kev to implement with a density of about 51015ions/cm2. To prevent damage to the surface of the polycrystalline silicon layer 3 in the process of introduction of ions is annealed in a furnace at a temperature of 900oC for 30 minutes After completion of the annealing furnace on the upper surface of the polycrystalline silicon 3 is deposited titanium layer , the resulting structure is subjected to a short (about 20 s), annealing at a temperature of approximately 800oC in an atmosphere of argon (Ar). This short annealing furnace provides interaction polycrystalline silicon 3 and the Titan 4, resulting in the formation of the titanium silicide 5 as illustrated in Fig. 1B.

The melting point of titanium silicide is in the neighborhood 1540oC, i.e., 1813K in degrees absolute scale, and its high-temperature instability begins to occur at temperatures 814oC, numerically component to 0.6 of the absolute temperature. As is well known to experts in the art, silicide of refractory metal becomes unstable at a certain temperature, which can be calculated by multiplying the melting temperature in degrees absolute scale 0.6 which limits but, generally speaking, high-temperature instability begins to occur with temperature 900oC.

Therefore, during subsequent annealing in a furnace at a temperature of 900oC or higher in the titanium silicide develop plastic deformation and grain growth. At the same time, the phenomenon of agglomeration in a homogeneous thin film due to epitaxial growth of silicon, leading to the rupture of a thin film microstructure which is reminiscent of the Islands.

In other words, as illustrated by the position 6 in Fig. 1C, a titanium silicide is a discontinuous thin film in the form of separate Islands, and between them is a naked surface of the polycrystalline silicon 3. Because of stutter patterns of titanium silicide resistance of the internal wiring is significantly increased. As already mentioned, the increase of the wiring resistance adversely affects the operating characteristics of the semiconductor memory device and reduces its reliability.

Based on the foregoing, the purpose of the invention is to provide a semiconductor device that preserves the uniformity of the surface of the titanium silicide during high temperature Ognianovo device with improved high-temperature characteristics of instability in comparison with that achieved by known technologies and methods of its manufacture.

To achieve the mentioned objectives of the invention, the set of semiconductor device with a double layer of silicide structure having a silicon substrate predefined monocrystalline structure, the oxide layer formed on the entire surface of the monocrystalline silicon substrate, a polycrystalline silicon layer grown on the entire surface of the oxide layer, the first layer of the silicide of the metal, caused by the deposition of a metal which forms a silicide at the predetermined first temperature on the upper surface of the polycrystalline silicon layer and a second layer of metal silicide grown by deposition of a metal which forms a silicide with a predefined second temperature below the first temperature, the upper surface of the metal, forming a silicide at first named temperature.

To achieve another purpose of the invention, a method of manufacturing a semiconductor device with a double layer of silicide structure, comprising forming the oxide layer on the entire surface of the monocrystalline silicon substrate, growing a polycrystalline silicon layer on the entire surface of the oxide layer, the formation of the first silicide layer meta is definitely the first temperature, and the formation of the second layer of metal silicide on the top surface of the metal, forming a silicide at the first temperature, the deposition of the metal, forming a silicide at a second temperature which is below the first named temperature.

In Fig. 1 shows a sectional process of manufacturing a semiconductor device in a known manner, and Fig. 2 shows in section one variant of the method of manufacturing a semiconductor device corresponding to the invention; Fig. 3 shows in section another variant of the method of manufacturing a semiconductor device corresponding to the invention; Fig, 4 is the table that allows to compare the surface resistance of semiconductor devices made known and invented ways.

Fig. 2 illustrate a variant of the method of manufacturing a two-layer silicide corresponding to the invention.

In Fig. 2A depicts a layer of silicon dioxide (SiO2) 8 thick , deposited on a monocrystalline silicon substrate 7, the resistivity of which is from 5 to 25 OSM at a temperature of 920oC, by thermal oxidation. After thermal decomposition of silane (SiH4) at a temperature of about 62515ions/cm2. To prevent damage to the surface of the polycrystalline silicon layer 9 during the introduction of ions, etching is performed tebufelone HF solution obtained by dissolving hydrofluoride (HF) in water in a ratio of 1:100. After completion of the etching on the upper surface of the polycrystalline silicon layer 9 is covered with a layer of tantalum 10 thickness by a sputtering method, and then it is applied a layer of titanium 11 thickness by a sputtering method. After sputtering a layer of titanium 11 finished structure is subjected to intermittent heating annealing (about 20 C) at a temperature of 800oC in an atmosphere of argon (Ar). During short-term annealing in the furnace, as illustrated in Fig. 2B, polycrystalline silicon interacts with tantalum 10, forming the tantalum silicon (TaSi2) 12, and polycrystalline silicon 9 interacts with the titanium 11, forming a titanium silicide (TiSi2) 13.

Fig. 3 illustrates another variant of the method of manufacturing a two-layer silicide, sootvetstvujushej is on the monocrystalline silicon substrate 14, the resistivity of which is at a temperature of 920oC is from 5 to 25 Omsm, by thermal oxidation. After thermal decomposition of silane SiH4at a pressure of about 250 mtorr by vacuum deposition chemical vapor polycrystalline silicon layer 16 with a thickness of about is deposited on the upper surface of the layer of silicon dioxide 15. Then known method of introducing ions into the polycrystalline silicon layer 16 is embedded phosphorus. Introducing ions reported energy of about 30 Kev, the implementation is carried out with a density of about 51015ions/cm2. To prevent damage to the surface of the polycrystalline silicon layer 16 during the implementation of ions, etching is performed tebufelone HF solution obtained by dissolving hydrofluoride (HF) in water in a ratio of 1:100. As is shown in Fig. 3B, after etching the layer of tantalum silicide 17 thickness is applied on the upper surface of the polycrystalline silicon layer 16 by a sputtering method using a composite target of tantalum silicide. Then it (the layer 17) is covered with a layer of titanium silicide 18 thickness by a sputtering method using a composite target of titanium silicide. After completion of NAPA is the temperature 800oC in an atmosphere of argon (Ar). This short furnace annealing translates silicide layer from the amorphous into the crystalline state, is shown in Fig. 3B.

The melting point of tantalum silicide corresponds 2200oC, i.e., 2473K in degrees absolute scale. The multiplication of the temperature on the Kelvin scale by 0.6 gives 1483,8 K; (tantalum silicide) high-temperature instability begins to occur with temperature 1210,8oC, which, obviously, is much higher 814oC, which begins to show the instability of titanium silicide. Two-layer silicide structure composed of tantalum silicide and titanium silicide, is not affected by grain growth, plastic deformation and agglomeration, which is inherent to the method, even when the subsequent furnace annealing at a temperature of 900oC and even higher.

High temperature stability of two-layer silicide composed of tantalum silicide and titanium silicide in accordance with the invention, were measured and compared with that of titanium silicide, obtained in a known manner; the results are summarized in table depicted in Fig. 4. In the table are listed the data obtained in the measurements after the implementation of the known method, in nitrogen atmosphere (N2) for 30 min at temperatures of 850, 900, 950 and 1000oC, respectively. As can be seen in Fig. 4, when using the known method, the agglomeration of the titanium silicide begins at a temperature of 950oC, which leads to a significant increase in the surface resistance. More specifically, the surface resistance is 2.2 Ohms/sq at 850oC but reaches 5.3 Ohm/sq at 950oC, which means doubling. Moreover, the surface resistance at 1000oC becomes very large, reaching 2940 Ohm/sq. However, as you can see, the surface resistance of the double layer of silicide patterns of tantalum silicide and titanium increases slightly, because at 850oC it is equal to 3.8 Ohms/sq and 1000oC rises to 5.3 Ohms/sq.

Although the tantalum silicide is used as the lower silicide layer in one embodiment of the invention, in another embodiment, the invention can be used as the bottom layer of the silicide of molybdenum, tungsten silicide, and the like materials having a higher melting point than that of the titanium silicide used as an upper silicide layer.

state when 2438 and 2253K in degrees absolute scale. Multiplication of 0.6 at these temperatures, respectively, gives 1462,8 and 1351,8 K. Therefore, high-temperature instability begins to occur with temperature 1189,8oC of tungsten silicide and temperature 1078,8oC the silicide of molybdenum.

These temperatures are much higher 814oC, with which the titanium silicide begins to exhibit thermal instability. Therefore, there will be no agglomeration during subsequent furnace annealing at a temperature of 900oC and above.

As mentioned above, since the semiconductor device with two-layer silicide corresponding to the invention, it has improved high-temperature stability, manifested in the subsequent furnace annealing, prevents grain growth, plastic deformation and agglomeration, which significantly improves the operating characteristics of such semiconductor devices.

Although the invention is described and illustrated with reference to specific variations in its implementation, for the specialist in this area should be clear that it can be made a variety of modifications without going beyond its scope, while remaining within its essence, determined by the applied formula.

the spoon monocrystalline structure, the oxide layer formed on the entire surface of the mentioned single crystal silicon substrate, a polycrystalline silicon layer grown on the entire surface of the mentioned oxide layer, the first layer of metal silicide, a second layer of metal silicide, wherein the first layer of metal silicide obtained by deposition of a metal which forms a silicide at the first temperature, the upper surface of the polycrystalline silicon layer and a second layer of metal silicide obtained by deposition of a metal which forms a silicide at a second temperature below the first temperature, on the upper surface of the aforementioned metal, forming a silicide at the first temperature.

2. The semiconductor device according to p. 1, characterized in that the first metal silicide obtained by deposition of tantalum (Ta) or molybdenum (Mo).

3. The semiconductor device according to p. 2, characterized in that the second layer of metal silicide obtained by deposition of titanium (Ti).

4. The semiconductor device according to p. 1, characterized in that the thickness of the layer of deposited metal, forming a named silicide when the first temperature is

5. The semiconductor device according to p. 4, characterized in that the thickness of the planning unit under item 5, characterized in that the thickness of the grown polycrystalline silicon layer is equal to

7. A method of manufacturing a semiconductor device having a two-layer silicide structure, namely, that form the oxide layer on the entire surface of the monocrystalline silicon substrate, growing a polycrystalline silicon layer on the entire surface of the mentioned oxide layer, get the first layer of metal silicide, get the second layer of metal silicide, wherein the first layer of metal silicide is produced by deposition of a metal which forms a silicide at the first temperature, the upper surface of the polycrystalline silicon layer and a second layer of metal silicide is produced by deposition of a metal which forms a silicide at a second temperature below the first temperature, on the upper surface of the aforementioned metal, forming a silicide at the first temperature.

8. The method according to p. 7, characterized in that the first layer of metal silicide is produced by deposition of tantalum (Ta), molybdenum (Mo) or tungsten (W).

9. The method according to p. 8, characterized in that the second layer of metal silicide is produced by deposition of titanium (Ti).

10. The method according to p. 9, characterized
11. The method according to p. 10, characterized in that the layer thickness of these metal which forms a silicide at a second temperature is chosen within the

12. The method according to p. 11, characterized in that the polycrystalline silicon layer is grown by deposition of thermally decomposed silane (SiH4) to achieve the thickness of the layer named at 625oC at a pressure of 250 mtorr by a vacuum deposition chemical vapor.

13. A method of manufacturing a semiconductor device having a two-layer silicide structure, namely, that form the oxide layer on the entire surface of the monocrystalline silicon substrate, growing a polycrystalline silicon layer on the entire surface of the mentioned oxide layer, get the first layer of metal silicide, get the second layer of metal silicide, wherein receiving the first layer of metal silicide on the top surface of the polycrystalline silicon layer using a composite target, forming a silicide at the predetermined first temperature, and receive a second layer of metal silicide on the top surface of the first layer of metal silicide forming a silicide at the first temperature, using a composite target, different topics the first layer of metal silicide is produced by deposition using a composite target made of tantalum silicide, molybdenum silicide or tungsten silicide.

15. The method according to p. 14, characterized in that the second layer of metal silicide is produced by deposition using a composite target made of titanium silicide.

16. The method according to p. 15, characterized in that the layer thickness of the resulting metal silicide forming a silicide at the first temperature is chosen within the

17. The method according to p. 16, characterized in that the layer thickness of the resulting metal silicide forming a silicide on the second temperature is chosen within the

18. The method according to p. 17, characterized in that the polycrystalline silicon layer is grown thick by thermal decomposition of silane (SiH4) at a temperature of 625oC at a pressure of 250 mtorr with subsequent vacuum deposition, chemical vapor.

 

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