JPH0411729A - Forming method of insulating film for semiconductor element - Google Patents

Abstract

PURPOSE:To form an insulating film having an excellent interface level on a semiconductor layer by carrying a substrate into a sputtering chamber, in which a target material is arranged, making ions collide with the target material from a plasma ion source and discharging particles. CONSTITUTION:A target holder 11 holding a target 6 and a substrate holder 12 holding a substrate 1 with a semiconductor layer 3 are installed into a sputtering chamber 10. A plasma ion source 16 separated is mounted to the sputtering clamber 10, and a gas supply pipe 17 supplying a gas is set up to the ion source 16. When an ionized gas, etc., are introduced into a discharge chamber l6a in the ton source 16 from the pipe 17, the gas, etc., are plasma- ionized by the ionization by collisions of thermoelectrons discharged from filaments 16d, and plasma ions are discharged into the sputtering chamber 10 from the section of an accelerating electrode 16b. The ion beams collide with the target 6, constituent atoms or molecules thereof are ejected, and an insulating film is deposited on the layer 3. Accordingly, the insulating film having an excellent interface level can also be formed on the semiconductor layer formed on the substrate having the comparatively low melting point.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for forming an insulating film for semiconductor elements,
The present invention relates to a method of forming an insulating film for a semiconductor element suitable as a gate insulating film of a device.

(Prior Art and its Problems) Conventionally, gate insulating films and the like of MOS devices are generally formed by a thermal oxidation method in which a surface portion of bulk silicon is heated to 800° C. or higher to form a silicon oxide film.

However, when forming a gate insulating film on a semiconductor layer formed on a glass substrate or the like, thermal oxidation cannot be used due to the heat resistance of the glass substrate. Therefore, conventionally, there was no choice but to form a gate insulating film using a plasma CVD method or a high frequency sputter link method that can be formed at low temperatures.

Silicon oxide films formed by plasma CVD method have a density of 60 to 90% compared to films formed by thermal oxidation method.
The film is porous, and hydrogen, which is a component of the raw material gas used during the manufacturing process, exists in the film as residual hydrogen. For this reason, the film quality is structurally unstable, the withstand voltage is low, and there is also a large amount of fixed charge inside, so when a transistor is formed, the threshold voltage V 1
There was a problem in that h fluctuated greatly, making it impossible to form a homogeneous transistor.

Furthermore, although it is easy to form a dense silicon oxide film using the high-frequency sputtering method, high-energy particles such as ions accelerated by plasma and atoms ejected from the target may cause damage to the film adhesion surface or the film itself. There was also a problem with reproducibility due to the lack of independence among film-forming parameters such as atmospheric gas pressure, reactive gas pressure, input power, and plasma excitation state. .

The present invention was devised in view of the problems of the conventional technology, and it is possible to control the threshold voltage of a MOS device to a constant level, and to form a semiconductor element with good interface states with good reproducibility. The purpose of the present invention is to provide a method for forming a semiconductor element that can be manufactured using the following methods.

(Means for Solving the Problems) According to the present invention, a semiconductor substrate or a substrate having a semiconductor layer is carried into a sputtering chamber in which a target material is arranged, and the target material is exposed to a plasma separate from the sputtering chamber. Formation of an insulating film for semiconductor devices in which an insulating film made of constituent atoms or molecules of the target material is deposited on a semiconductor substrate or semiconductor layer by colliding ions from an ion source with a target material in a sputtering chamber and releasing particles. A method is provided by which the above objects are achieved.

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

In the method for forming an insulating film for a semiconductor element according to the present invention, an amorphous or polycrystalline semiconductor layer is formed by, for example, plasma CVD on a semiconductor substrate made of bulk silicon or a glass substrate. Alternatively, a semiconductor layer crystallized by irradiating such a semiconductor layer with a high energy beam such as a laser beam or an electron beam is used.

For convenience of explanation, FIG. 1 shows a staggered thin film transistor as an example. For example, AI, Ti, Ni, Cr, Ta, Mo, W, etc. are deposited on an insulating substrate 1 made of glass or the like.
A source electrode 2a and a drain electrode 2b are formed, and then an amorphous or polycrystalline semiconductor layer 3 containing a donor or acceptor is formed, for example, by plasma CVD. This semiconductor layer 3 is provided with an insulating layer M which becomes a gate insulating film made of silicon oxide or silicon nitride.
form 4. Note that on the gate insulating film 4, AI-T
i=A gate electrode 5 made of Ni-Cr, Ta, Mo-W, etc. is formed.

FIG. 2 schematically shows an apparatus for forming the gate insulating film 4. This apparatus includes a target holder 11 holding a target 6 and a semiconductor layer 3 in a sputtering chamber 10.
and a substrate holder 12 that holds the substrate 1 having a structure. The sputtering chamber 10 is provided with a gas supply pipe 13 for supplying a reactive gas into the sputtering chamber 10, a gas exhaust pipe 14 for exhausting the gas, and an exhaust pipe 15 for maintaining a high degree of vacuum in the sputtering chamber 10. There is. t, sputtering chamber 1
0 is provided with an ion source 13 separated from the sputtering chamber 10, and this ion source 13 is provided with a gas supply pipe 14 for supplying gas.

As the target 6, bulk silicon or bulk silicon oxide is used when forming a silicon oxide film, and bulk silicon or bulk silicon nitride is used when forming a silicon nitride film.

In addition, when forming a silicon oxide film, ~ sputtering chamber 1
The pressure inside the sputtering chamber 10 is reduced to about 10-1 to 10-' Torr, and the pressure inside the sputtering chamber 10 is reduced to about 10-' to 10-'' Torr.
A reactive gas (assist gas) such as 02 gas or N2 gas is introduced to achieve the following. This assist gas is supplied to modify the insulating film deposited on the substrate.

FIG. 3 is a sectional view showing the ion source 16 portion of the apparatus shown in FIG. The ion source 16 includes a discharge chamber 16a that generates plasma ions and a sputtering chamber 10 that generates ions.
An electrode system 16b having at least two grid electrodes for drawing out and accelerating the discharge, a magnet coil 16c for forming a magnetic field in the discharge chamber 16a, and an anode 16d and a filament 16e for causing arc discharge are provided. When ionizing gas or the like is introduced into the discharge chamber 16a from the gas supply pipe 17, the filament 16d
Plasma ionization is caused by the collision of thermoelectrons emitted from the accelerating electrode 13b, and plasma ions are emitted into the sputtering chamber 10 from the accelerating electrode 13b.

In this case, the ion energy of the ion beam is controlled by controlling the voltage applied to the accelerating electrode 13b.

Argon gas is preferably used as the sputtering gas, and the temperature inside the discharge chamber 13 is 10-4 to 10-'T.

Argon gas is introduced so that the ion current is 100 mA or less and the ion energy is 200 to 1.
The ion beam is extracted at a low energy of 500 eV.

This ion beam collides with the target 6 to eject constituent atoms or molecules of the target 6, thereby depositing an insulating film 4 on the semiconductor layer 3.

In such an apparatus, since the ion source 16 is independent of the sputtering chamber 10, it is possible to reduce
The insulating film 4 can be formed under a vacuum that is ~2 orders of magnitude higher, and the purity of the film is high. Film-forming parameters such as ion beam energy, beam amount, atmospheric gas pressure, and reactive gas pressure can be controlled independently (beam energy control is especially important), and the insulating film 4 can be formed with good reproducibility and low energy. Therefore, the insulating film 4 can be formed without damaging the semiconductor film 3. Further, by providing a plurality of ion sources, ion irradiation can be performed during the formation of the insulating film 4.

(Experimental Example 1) A 20 mm silicon substrate containing n-type impurities was carried into a chamber in which the sputtering chamber and the ion source were separated, and the space inside the chamber was 2.5 x 10-s.
The gas was brought in, the substrate temperature was set at 200°C, 9999% SiO2 was used as a target, and Arcon gas was introduced into the ion generation chamber to generate a 5.0X10-
An insulating film with a thickness of 1080 nm was formed on the semiconductor substrate by sputtering at 5 Torr, ion energy of 700 eV, and ion current of 5 OmA for 10 minutes. When Q, 5/elementary charge q) was examined, the refractive index was 1491, the relative dielectric constant was 3.57, and Q, , /q was 4°84X10"cm
-2, and it was confirmed that the film was similar to a thermal oxide film. In other words, the silicon oxide film formed by thermal oxidation has a refractive index l of about 46, a dielectric constant of about 3.82, and a Q
, , /q is on the order of 100 cm'', whereas the silicon oxide film formed by plasma CVD has a refractive index of about 1.
5, relative permittivity is about 5.01, Q, , /q is 1.3
It is about 4×1012 cm−2.

In addition, FIG. 4 shows the C-V characteristic diagram. As is clear from FIG. 4, the flat band voltage is near O■,
It can be seen that there are few interface states.

(Experimental Example 2) Sputtering was performed for 11 minutes under the same conditions as Experimental Example 1 except that the ion energy of Experimental Example 1 was set to 1000 eV and the substrate temperature was set to room temperature.
When a silicon oxide film was formed to a thickness of 0.0 and the refractive index, dielectric constant, and interface state (surface charge density Q5./elementary charge q) were examined, the refractive index was 1.491. The dielectric constant is 3.98, and Q, , /q is 3.48X10”cm-2
It was confirmed that f: a silicon oxide film, which approximates the silicon oxide film formed by the thermal oxidation method as in Experimental Example 1.

FIG. 5 shows its CV characteristic diagram. As is clear from FIG. 5, the flat hand voltage is near OV, indicating that there are few interface states.

(Effects of the Invention) As described above, according to the method for forming an insulating film for a semiconductor element according to the present invention, a semiconductor substrate or a substrate having a semiconductor layer is carried into a sputtering chamber in which a target material is arranged, and the target material is An insulating film made of constituent atoms of the target material is deposited on a semiconductor substrate or semiconductor layer by bombarding the target material in the sputtering chamber with ions from a plasma ion source that is separated from the sputtering chamber and releasing particles. As a result, insulating films with good interface states can be formed even on semiconductor layers formed on substrates with relatively low melting points, such as glass substrates, leading to a breakthrough in the semiconductor industry. be able to.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a semiconductor element, FIG. 2 is a schematic configuration diagram showing an apparatus for explaining the method of forming an insulating film for a semiconductor element according to the present invention, and FIG. 3 is an ion source portion of the apparatus. The enlarged views, FIGS. 4 and 5, are diagrams showing the C-■ characteristics of the insulating film formed by the method according to the present invention. 1: Substrate 4: Insulating film 6: Target 10 Varnish batter chamber 16: Plasma ion source

Claims (1)

[Claims] A semiconductor substrate or a substrate having a semiconductor layer is carried into a sputtering chamber where a target material is placed, and particles are generated by bombarding the target material with ions from a plasma ion source separated from the sputtering chamber. A method for forming an insulating film for a semiconductor device, in which an insulating film made of constituent atoms or molecules of a target material is deposited on a semiconductor substrate or a semiconductor layer by emitting it.