CN1975989B - Preparation method of polycrystalline silicon thin film, polycrystalline silicon prepared by method and thin film transistor - Google Patents

Abstract

Amorphous silicon can form device-level polysilicon after metal-induced lateral crystallization. The present invention describes a technology for preparing semiconductor devices using metal-induced crystallized polysilicon thin films (including longitudinal and lateral crystallization directions) annealed by solid laser. Metal-induced polysilicon thin films are formed by furnace annealing of amorphous silicon thin films into which metal nickel is introduced. In order to improve the quality of such polysilicon thin films, solid lasers are used to anneal the above-mentioned polysilicon thin films to reduce the structural defects of the thin films and the influence of the metal nickel element on the properties of the thin films. However, during the annealing process, the main grain structure of the metal-induced polysilicon is not changed. Solid lasers are also used for doping activation in the device. Compared with excimer lasers, solid lasers are relatively cheap and simple to operate, and are suitable for industrial production. Such polysilicon materials have a wide range of applications, such as sensors, electronic devices, flat panel displays, and three-dimensional circuits.

Description

Preparation method of polysilicon thin film, polysilicon and thin film transistor prepared by the method

technical field

What the present invention tells is the technique of preparing semiconductor devices by using solid laser annealing metal-induced crystallization polysilicon film (including vertical and lateral crystallization directions). The metal-induced polysilicon film is formed by annealing the amorphous silicon film with metal nickel through the furnace tube. In order to improve the quality of this kind of polysilicon film, solid-state laser is used to anneal the above polysilicon film to reduce the film structure defects and the influence of metal nickel elements on the properties of the film, but the main grain structure of the metal-induced polysilicon will not be changed during the annealing process. . Doping activation in the device also uses a solid-state laser. Compared with excimer lasers, solid-state lasers are relatively cheap and easy to operate, and are suitable for industrial production.

The polysilicon material has a wide range of applications, such as sensors, electronic devices, flat panel displays and three-dimensional circuits.

Background technique

Thin-film transistors (TFTs) have been widely used in the fabrication of active liquid crystal displays, active organic light-emitting diode displays, active electronic books, and active image sensors.

TFTs based on amorphous silicon are difficult to implement peripheral circuits due to their slow switching speed and the inability to prepare P-type devices. This has led to a shift to polysilicon, which is obtained by heating amorphous silicon through furnaces or lasers.

Conventional low-pressure chemical vapor deposition to prepare polysilicon requires high processing temperature (620-650°C) and low material quality. Quality can be improved by high temperature annealing (above 1000°C), however this can only be used for substrates which are expensive quartz substrates and not for cheaper glass substrates.

Another technique for preparing polysilicon is metal-induced crystallization (US patents 5275851, 5879977, 2001018224 and 6737674). The material grains produced are larger and have continuous grain boundaries, and the uniformity and repeatability of materials and devices are better. However, if the micro-defects in materials can be reduced, materials and devices with better performance can be obtained.

Another technique is to perform excimer laser crystallization on amorphous silicon to obtain higher quality polysilicon (US patents 535229, 6071796 and 2004087116). However, it has the disadvantages of poor uniformity and repeatability, and the cost is high.

In US patents (5705829, 58937730, 5869362 and 2003129853), a method combining metal-induced crystallization and excimer laser annealing has been proposed. However, the excimer lasers used are expensive and complex.

Polysilicon can be obtained by adding Nd:YAG laser and heat conduction layer on amorphous silicon (US Patent No. 6,537,864). The lasers are relatively cheap, but the technology is processed at higher temperatures and the quality of the resulting materials is not as good.

However, the present invention is a technique for preparing polysilicon film by combining the induced crystallization of amorphous silicon metal and the annealing of solid laser. The resulting films are of high quality, uniform and reproducible. Semiconductor devices can be fabricated on this thin film, and the maximum processing temperature does not exceed 590°C. Solid-state lasers are also very low cost.

Contents of the invention

The invention is a technique for preparing polysilicon film by combining amorphous silicon metal induced crystallization and solid laser annealing. The resulting films are of high quality, uniform and reproducible. Semiconductor devices can be fabricated on this thin film, and the maximum processing temperature does not exceed 590°C. Solid-state lasers are also very low cost.

The first innovative point of the present invention is to use a cheaper solid-state laser to reduce the number of material micro-defects in polysilicon formed by metal-induced crystallization.

The second innovative point of the present invention is to use a higher frequency multiplied laser of a solid-state laser. For Nd:YAG lasers, the tripled laser at 335nm is easily absorbed by silicon, while the doubled laser at 532nm is preferentially absorbed by microdefects. The former can be used to reduce bulk defects and the latter can be used to reduce local grain boundary defects.

The polysilicon material has a wide range of applications, such as sensors, electronic devices, flat panel displays and three-dimensional circuits.

A method for preparing a polysilicon film according to the present invention is characterized in that it comprises the following steps:

1) forming a layer of amorphous silicon film;

2) depositing a thin layer of nickel on the amorphous silicon film;

3) annealing the amorphous silicon and nickel films together at a temperature of 420°C-620°C for 0.5-5 hours;

4) The generated thin film is simultaneously irradiated with double-frequency and triple-frequency pulsed lasers, and the wavelength of the pulsed lasers is between 0.9 microns and 1.2 microns.

The amorphous silicon thin film is formed by but not limited to a low-pressure chemical vapor deposition process.

The thickness of the amorphous silicon film is 10-100 nanometers;

The nickel thin film is 0.1-0.01% of the amount of silicon in amorphous silicon;

The thickness of the nickel film is 1-10 nanometers;

Described pulse laser can be Nd:YAG laser;

Described pulse laser can be Nd:Glass laser;

Described pulse laser can be Alexandrite laser;

The duration of the pulsed laser is 5-30 nanoseconds;

The substrate of the polysilicon thin film device can be glass, polymer, insulating stainless steel, polysilicon or single crystal silicon containing prefabricated conventional integrated circuits.

The thin film transistor made of polysilicon made by the method is characterized in that the thin film transistor is of top gate type, or bottom gate type, or double gate type with top gate and bottom gate at the same time, or a top gate type A DC bottom-gate type and a dual-gate type.

The polysilicon prepared by the method is characterized in that the polysilicon is used to prepare a temperature sensor.

The polysilicon produced by the method is characterized in that the polysilicon can be used to prepare micromechanical systems.

The polysilicon produced by the method is characterized in that the polysilicon is used to prepare an image sensor.

The polysilicon prepared by the method is characterized in that the polysilicon is used to prepare an infrared sensor.

The polysilicon produced by the technology is characterized in that the polysilicon is used to prepare pixel electrodes in displays.

The thin film transistor is used to prepare the active substrate and peripheral driving circuit of the flat panel display.

The thin film transistor is used to prepare the active substrate and peripheral driving circuit of the image sensor.

The thin film transistor is used to prepare digital circuits, analog circuits and storage units.

The above detailed description is a specific description of the present invention, and any equivalent implementation or modification that does not deviate from the spirit of the present invention falls within the scope of the present invention.

Description of drawings

Figure 1: Schematic cross-sectional view of a thin film of amorphous silicon deposited on top of a substrate covered with an insulating layer and a mask defining selected and non-selected regions.

Figure 2: Schematic cross-sectional view of depositing trace amounts of nickel on the surface of amorphous silicon.

Figure 3: Schematic cross-sectional view of metal-induced crystallization in vertical and lateral directions.

Figure 4: Schematic cross-sectional view of an active island formed on a substrate by metal-induced crystallization and metal-induced lateral crystallization.

Figure 5: A cross-sectional schematic diagram of metal-induced crystallization of polysilicon irradiated by solid-state laser tripled frequency or a combination of tripled frequency and doubled frequency laser.

Figure 6: Schematic diagram of mixed irradiation of "n" frequency-doubled and "m" frequency-doubled lasers of solid-state lasers.

Fig. 7: A schematic cross-sectional view of ion implantation for forming a gate electrode and a source-drain region of a thin film transistor.

Figure 8: Schematic cross-sectional view of doping and activating a thin film transistor by thermal annealing or Nd:YAG frequency tripled laser.

Figure 9: Schematic cross-sectional view of a thin film transistor fabricated by metal-induced crystallization and solid-state laser annealing.

Detailed ways

The present invention is described in detail as follows with reference to accompanying drawing:

The method of fabricating a semiconductor device using metal-induced crystallization of polysilicon annealed by a solid-state laser is described below, see FIGS. 1-9.

FIG. 1 : A schematic cross-sectional view of an amorphous silicon film 103 and a mask layer 104 deposited on a substrate 101 covered with an insulating layer 102 .

The substrate can be one of high temperature polymer, glass, stainless steel, polycrystalline silicon or single crystal silicon containing prefabricated conventional integrated circuits.

The transition layer can withstand processing at a processing temperature higher than 650° C. for a long time, including but not limited to silicon oxide, silicon oxynitride, and silicon nitride.

An amorphous silicon film 103 with a thickness of 10 nanometers to 3 micrometers is formed at a low temperature of 150°C-600°C. Techniques employed include but are not limited to sputtering, evaporation or low pressure and plasma enhanced chemical vapor deposition.

After the amorphous silicon film 103 is formed, a mask layer 104 (including but not limited to silicon oxide, silicon oxynitride, and silicon nitride) is formed with a thickness of 100-200 nanometers. This layer can withstand processing at a processing temperature higher than 650° C. for a long time.

FIG. 2 : Schematic cross-sectional view of nickel 201 deposited on the exposed area of the amorphous silicon film 103 . Methods of introducing nickel include, but are not limited to, electron beam evaporation, sputtering, chemical vapor deposition, ion implantation, or immersion of the substrate in a solution containing nickel ions.

Figure 3: Schematic cross-sectional view of amorphous silicon polysilicon formed at 420°C to 620°C in a conventional annealing furnace under a nitrogen atmosphere. The area 301 directly under the nickel layer is "vertical" crystallization, and the area 302 covered by the mask layer 104 is lateral crystallization.

After the crystallization is complete, the residual nickel and masking layer will be removed. Active islands are defined by conventional photolithographic etching techniques.

FIG. 4 : Schematic cross-sectional view of polysilicon active islands 401 and 402 formed in regions 301 and 302, respectively.

Fig. 5: A schematic diagram of an insulating layer 501 (including but not limited to silicon oxide). Through layer 501, the active island 401 or 402 is irradiated by a single-mode or multi-mode solid-state laser.

Figure 6: Alternate irradiation of two single-mode lasers. The irradiation time, wavelength, and energy of each mode are optimized.

FIG. 7 : Schematic cross-sectional view of thin film transistors implemented on active islands 401 and 402 . 703 is a gate electrode. The source and drain electrodes on the active islands 401 and 402 are marked with 701 and 702, respectively.

Figure 8: Thermal activation of source and drain regions using solid-state laser radiation. Or use the method of annealing at a temperature of 420°C to 620°C in the conventional annealing record.

Figure 9: Schematic cross-sectional view of two thin film transistors. An insulating layer 901 is deposited. Contact holes open to the gate, source and drain electrodes. Metal connection lines 902 are deposited and shaped.

Concrete implementation preparation method is:

1: On Corning 1737F glass 101 with a thickness of 1.1 mm, 200 nanometers of low-temperature silicon nitride and 100 nanometers of low-temperature silicon oxide (LTO) 102 were deposited by PECVD, and then LPCVD was used. For example, 50 nanometers of amorphous silicon 103 is deposited on the upper substrate.

2: Deposit a 150nm LTO layer 104 on the surface of the amorphous silicon, and form a selective area (amorphous silicon exposed area) and a non-selective area (LTO masked area) by photolithography.

3: For the above sample, a small amount of nickel is deposited on the surface by sputtering in an argon-oxygen atmosphere through a nickel-silicon mixed target. The amount of nickel is 0.1-0.01% of the amount of silicon in amorphous silicon.

4: An amorphous silicon sample with a small amount of nickel attached is annealed in a conventional annealing furnace under a nitrogen atmosphere at a temperature of 590° C. for 3 hours to form a metal-induced region 301 and a metal-induced lateral crystallization region 302 .

5: After the crystallization is completed, use diluted hydrofluoric acid (5%) to remove the residual nickel and the mask layer.

6: In different crystallization intervals, photolithography forms TFT active islands.

7: Depositing a 100nm LTO layer by LPCVD to cover the active silicon islands 401 and 402 .

8: Simultaneously irradiating the sample surface with YAG triple frequency and double frequency lasers 502 and 503 (energy ratio 10:1). The pulse width is 30 nanoseconds, the laser energy is 120 mJ/square, and the scanning speed is 0.5 cm/s.

9: Prepare TFT with the above-mentioned polysilicon, the gate insulating layer is a 100 nm thick LTO layer 501 deposited by LPCVD, a 280 nm polysilicon gate electrode 703 , and ion-implanted source and drain electrodes 701 and 702 .

10: Irradiate with TAG double frequency (532 nm) laser 801 to heat and activate doped polysilicon source, gate and drain electrodes.

11. 500nm LTO electrode insulating layer 901 was deposited by LPCVD, contact holes were opened, and metal lead-out electrodes 902 were formed. After alloying, the preparation of the device was completed.

Claims (18)

1. method for preparing polysilicon membrane is characterized in that comprising the following step:

1) forms one deck amorphous silicon membrane;

2) deposition skim nickel on described amorphous silicon membrane;

3) described amorphous silicon and nickel film are annealed under 420 ℃ of-620 ℃ of temperature together, the duration is 0.5-5 hour;

4) film of Sheng Chenging shines simultaneously through two frequencys multiplication and frequency tripling pulse laser, and the wavelength of pulse laser is between 0.9 micron to 1.2 microns.

2. the method described in the claim 1, described amorphous silicon membrane forms by the low-pressure chemical vapor deposition process.

3. the method described in the claim 1, described amorphous silicon membrane thickness is the 10-100 nanometer.

4. the method described in the claim 1, described nickel film thickness is the 1-10 nanometer.

5. the method described in the claim 1, described pulse laser is a Nd:YAG laser.

6. the method described in the claim 1, described pulse laser is a Nd:Glass laser.

7. the method described in the claim 1, described pulse laser is an Alexandrite laser.

8. the method described in the claim 1, the described pulse laser duration is 5-30 nanosecond.

9. the method described in the claim 1, the substrate of the device that described polysilicon membrane constitutes is glass, polymer, insulation stainless steel, polysilicon or the monocrystalline silicon that contains prefabricated custom integrated circuit.

10. the thin-film transistor that the polysilicon that adopts the method described in one of claim 1-8 to make prepares, it is characterized in that thin-film transistor is a top gate type, or bottom gate type, or have the double grid type of top grid and bottom gate simultaneously, or the double grid type of top grid and a direct current bottom gate.

11. the thin-film transistor according to described in the claim 10 is characterized in that, described thin-film transistor is used for preparing the active base plate and the peripheral drive circuit of flat-panel monitor.

12. the thin-film transistor according to described in the claim 10 is characterized in that, described thin-film transistor is used for preparing the active base plate and the peripheral drive circuit of imageing sensor.

13. the thin-film transistor according to described in the claim 10 is characterized in that, described thin-film transistor is used for preparing digital circuit, analog circuit and memory cell.

14. the polysilicon that adopts the method described in one of claim 1-8 to make is characterized in that, described polysilicon is used for the preparation temperature transducer.

15. the polysilicon that adopts the method described in one of claim 1-8 to make is characterized in that, described polysilicon can be used for preparing micro mechanical system.

16. the polysilicon that adopts the method described in one of claim 1-8 to make is characterized in that described polysilicon is used for preparing imageing sensor.

17. the polysilicon that adopts the method described in one of claim 1-8 to make is characterized in that described polysilicon is used for preparing infrared sensor.

18. the polysilicon that adopts the method described in one of claim 1-8 to make is characterized in that described polysilicon is used for preparing the pixel capacitors in the display.

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