KR19980064489A - METHOD AND APPARATUS FOR MANUFACTURING A MIXED, HIGH-SPEED GATE AND CAPACITIVE INSUMER - Google Patents

Abstract

Using the grown first oxide film 3 to form a gate or capacitor insulator structure, depositing a high k dielectric 4 over the grown oxide film, and then depositing one oxide film 5 How the steps are organized. The deposited oxide film increases in density in the atmosphere of oxidation. A conductive film 6, such as a gate or capacitor plate, may be formed over the deposited oxide film. The final structure has a grown first oxide film 3, a dielectric 4 formed over the grown oxide film having a high k, and a deposited oxide film 5 over the dielectric oxide film having a high k. The conductive film 6 on the deposited oxide film is used as a gate or capacitor plate.

Description

METHOD AND APPARATUS FOR MANUFACTURING A MIXED, HIGH-SPEED GATE AND CAPACITIVE INSUMER

The present invention relates generally to integrated circuits and, more particularly, to gates or capacitors having a high dielectric constant (K).

As the sizes of integrated circuits become smaller, as in the case of memory storage capacitors, the capacity for a given circuit element is reduced and the operating voltage is also reduced.

In order for the transistors to operate reliably at low voltages, the threshold voltage of the transistors is lowered. One way to lower the threshold voltage is to thin the insulator (usually silicon dioxide) that separates the transistor channel from the transistor gate. However, at the thickness of very thin insulating layers (eg oxide films less than 3,5 nm thick), the oxide films are affected by pinholes and the leakage is too large. In addition, if the oxide is less than 2.5 nm, tunneling electrons from the transistor channel occurs, which degrades the transistor's performance. By incorporating materials with high dielectric constants (k) into the gate insulator between the gate and transistor channels, the gate is moved more efficiently to the channel. But. The use of high k materials (ferroelectric dielectrics) was not entirely satisfactory. The reason is that excessive gates cause substrate leakage due to defects in the dielectric and the silicon / dielectric interface caused by lattice mismatch.

Reduced size and lower operating voltages are particularly important for dynamic memory where capacitors are used to author information. Since many memory cells are added to a given memory array and the sizes are reduced so that extra cells can be added within a suitable chip size, the size of the storage capacitors is reduced accordingly. If the capacity of the storage capacitors is lowered and the voltage applied to the capacitors is reduced, more errors will occur in the memory. To compensate for the reduction in capacitor size and to maintain capacity, two methods can be used separately or in combination. That is, the dielectric constant is increased and the dielectric is thinned. However, the same problems arise in both methods.

In practical considerations, if leakage / defect problems can be satisfactorily solved, the use of high k materials is most desirable to solve these problems at sizes of 0.35 μm and below.

Therefore, in order to reduce defects and leakages generated in a method of manufacturing a device including high dielectric constant materials, it is necessary to include high dielectric materials in an integrated circuit.

The above features and other advantages of the present invention are obtained by a method of manufacturing an integrated circuit according to claim 1. In addition, the above features are obtained by an integrated circuit having the structure recited in claim 6.

1 is a cross-sectional view of a partially formed transistor having a gate oxide made in accordance with one embodiment of the present invention.

FIG. 2 shows a cross section of a partially formed polysilicon-polysilicon capacitor having a dielectric layer made in accordance with another embodiment of the present invention. FIG.

* Description of the symbols for the main parts of the drawings *

1: wafer 4: dielectric film

3: insulating film 5: oxide film

In general, the present invention is described with reference to FIG. According to one embodiment of the present invention, and as will be described in more detail below, here having a film 2 to be oxidized, the wafer 1 having a silicon substrate can be oxidized to some kind, such as a polysilicon film. It is just that. Then, it grows on the insulating film 3. The film 3 is an oxide of the substrate 92. On the film 3, a film of a material 4 having a high dielectric constant (hereafter referred to as a high k dielectric material) is deposited. An oxide film 5 is deposited on the film 4. The deposited oxide film 5 is increased in density.

In more detail, the wafer 1 includes a silicon substrate 2 on which an oxide film 3 is grown. Here, a silicon dioxide film is grown on the silicon substrate 2. The film 3 is grown in a conventional dry oxidation atmosphere having a temperature of 650 to 900 degrees and a pressure of 0.25 to 10 torr to form an oxide of 1 to 2 nm thickness. The thickness is not critical but sufficient enough to eliminate the formation of pinholes and to make a good substrate / oxide interface. While oxides grow in a dry atmosphere, they can also grow in wet atmosphere (steam).

The film 3 will reduce the strain between the later deposited high dielectric film 4 and the underlying silicon substrate 2. And in order to reduce unnecessary surface conditions in the silicon, it provides a good interface to the silicon. Without the film 3, lattice mismatch between the substrate 2 and the later deposited film 4 is known to cause defects at the interface between the films, thereby degrading the quality of the entire dielectric.

On the grown dielectric film 3, a high dielectric material, that is, a film or films 4 of ferroelectric material, is deposited. This material has a larger dielectric constant than silicon dioxide. These materials are a group of materials containing Ta ₂ O ₅ , TiO ₂ , SrO ₃ dioxide and perovskite material of MTiO ₃ . At this time, M is Sr, Ba, La, Pb, BA _x Sr _1-x, Pb _x La _1-x . It has been found that defects in these films can be used and that intercalated insulating films, such as silicon dioxide, can be added. Typical thicknesses of the membranes range from 2 to 20 nm, plasma is improved, ion beams are present, ozone low pressure chemical vapor deposition (LPCVD), or metalorganic chemical vapor deposition. deposition is formed by MOCVD). Examples of such treatments are the Preparation of (Ba, Sr) TiO ₃ Thin Films by Chemical Vapor Deposition using Liquid Sources, published in the Japanese Journal of Applied Physics, October 1994, vol. It is described in the Preparation of PbTiO ₃ Thin films by plasma Enhanced Metalorganic Chemical Vapor Deposition, pages 365-367.

After the film 4 is formed, the silicon dioxide film 5 is deposited. This film has a thickness of 1 to 3 nm and is formed in the LPCVD reactor in the same manner as the method used for depositing the film 4. Representative source gases for silicon include tetraethylorthosilicate (TEOS) or silane.

The film 5 is increased in density by exposing the wafer 1 to a conventional densification annealing process in an oxidizing ambient atmosphere. An example of this process is in an LPCVD reactor operating at temperatures between 650 and 900 degrees and pressures between 250 and 10 Torr for about 5 to 20 minutes. Oxidation atmosphere may comprise N ₂ O in order to add nitrogen to the membrane 5.

The densification process improves the overall quality of the membrane 5, removes traps in the membranes 3-5 and reduces all leakage in the membranes 3-5.

Representative conductive films 6, such as polysilicon, are shown on the film 5. The mirrored film 6 becomes one plate of the gate or capacitor (the other plate becomes the substrate or the top film not shown), and the combinations of the films 3-5 will be referred to as gate or capacitor insulators. If the above-described densification process is not protected, after the film 6 is formed, it is performed together with the oxidation process of the film 6.

Another embodiment of a representative polysilicon-polysilicon capacitor structure is shown in FIG. The wafer 10 has an insulating film 12 such as amorphous or polysilicon (amorphous silicon becomes conductive at a later stage) to separate the representative oxidizable conductive film 13. The films 14-16 correspond to the films 3-5 in FIG. 1 as described above. The film 17, which is a conductive film, forms the plates of the capacitor together with the film 13, and the films 14-16 form a capacitor insulating film.

Silicon has been described as a representative material for substrates and other films, and other materials such as GaAs, InP may also be used.

Claims (11)

A method of making an integrated circuit comprising the step of growing an oxide film (3) on an oxidizable surface, the method comprising: Depositing a high k dielectric film 4 on the grown oxide film, Depositing an oxide film (5) on the dielectric film having a high k. The method of claim 1 further comprising increasing the density of oxides deposited in the atmosphere of oxidation. The method of claim 2, wherein the high k dielectric film is selected from the group of materials such as Ta ₂ O ₅ , TiO _2, and perovskite. 3. The perovskite material of claim 2, wherein the perovskite material is in the form of MTiO ₃ and M is selected from the group of Sr, Ba, La, Ti, Pb, Ba _x Sr _1-x , and Pb _x La _1-x . Way. 3. The method of claim 2 wherein the oxide films are silicon oxide and the oxidizable film is a silicon substrate. 6. The method of claim 5, further comprising depositing a conductive film over the deposited oxide film. In an integrated circuit having an oxidizable film (2) on a surface having an oxide film (3) grown on an oxidizable surface, And a high k dielectric film (4) on the grown oxide film and an oxide film (5) deposited on the high k dielectric film. 8. The method of claim 7, wherein the deposited oxide film is a deposited oxide film of increased density. The method of claim 8, wherein the high k dielectric film is selected from the group of materials such as Ta ₂ O ₅ , TiO ₂ and perovskite. The method of claim 8, wherein the perovskite material is in the form of MTiO ₃ , M is selected from the group of Sr, Ba, La, Ti, Pb, Ba _x Sr _1-x , and Pb _x La _1-x Way. 9. The method of claim 8, wherein the oxide films are silicon oxide and the oxidizable film is a silicon substrate.