CN102108494B - Deposition method of microcrystalline silicon thin film and monitoring device for plasma-assisted deposition - Google Patents

Abstract

A method for depositing a microcrystalline silicon film comprises: performing plasma-assisted deposition in an open-loop manner; after the film crystallization rate reaches a stable level in the deposition process without adjusting the process parameters in the open-loop, plasma-assisted deposition is performed in a closed-loop manner with the process parameters adjusted, wherein the closed-loop manner is to monitor SiH ^* and Hα active species in the plasma and adjust the process parameters in the plasma-assisted deposition so that the component concentrations of the SiH ^* and Hα active species in the plasma are maintained within a stable range, thereby increasing the deposition rate of the coating film.

Description

Deposition method of microcrystalline silicon thin film and monitoring device for plasma-assisted deposition

technical field

The invention relates to a thin film deposition technology, in particular to a microcrystalline silicon thin film deposition method. the

Background technique

)常常造成应用上的重大瓶颈，尤其，薄膜太阳电池所需的微晶硅薄膜膜厚高达1-2μm，镀膜时间往往超过1个小时以上，特别是在大面积沉积制作工艺应用时，所使用的制作工艺参数是以能获得稳定的结晶品质为优先考虑，因此也造成产量低、电池每瓦发电成本高等不利影响，所以若能在获得稳定的结晶率的制作工艺条件下，发展增进沉积速率的制作工艺方法成为硅薄膜产业重要的研究课题。  A tandem silicon thin film solar cell generally uses a microcrystalline silicon (μc-Si) thin film, which has the advantage of improving the photoelectric conversion efficiency of the thin film solar cell. Microcrystalline silicon thin films are generally produced by plasma-assisted chemical vapor deposition (PECVD), but the deposition rate is too low (about

) often cause a major bottleneck in the application, especially, the thickness of the microcrystalline silicon film required for thin-film solar cells is as high as 1-2 μm, and the coating time is often more than 1 hour, especially in the application of large-area deposition manufacturing processes. The production process parameters are based on the priority of obtaining stable crystallization quality, which also causes adverse effects such as low output and high power generation cost per watt of the battery. The production process method of silicon thin film industry has become an important research topic.

Known technology Japanese Patent No. JP 2005183620 uses plasma with less energy in the initial stage of the deposition process to make microcrystalline silicon form an initial layer at a low deposition rate, and then uses plasma with higher energy to increase The film deposition rate completes the entire layer, and finally obtains a microcrystalline silicon film with a high deposition rate. Although the patent JP 20030421313 achieves the purpose of increasing the deposition rate and crystallization rate of the microcrystalline silicon film by selecting the segmented pulse plasma effect, however, it adopts the preset multi-stage manufacturing process condition method. For the user, It is easy to complicate the operation of the manufacturing process and make it difficult to adjust the manufacturing process. In addition, the technology of the patent JP 20030421313 is an open-loop manufacturing process. During the deposition process after the initial stage of the microcrystalline silicon thin film manufacturing process, the deposition rate cannot be adjusted in real time due to the inability to detect changes in the active species in the plasma field and adjust the manufacturing process conditions. Still limited by the concern that too much Hα would produce a large etch effect. the

Contents of the invention

According to the above, the present invention provides a method for depositing a microcrystalline silicon thin film, comprising: performing plasma-assisted deposition in an open-loop manner without modulating the manufacturing process parameters; after the open-loop deposition manufacturing process stabilizes the crystallization rate of the film , followed by plasma-assisted deposition in a closed-loop manner and modulating production process parameters, wherein the closed-loop method is to monitor the SiH* and Hα active species in the plasma, and adjust the production process parameters in the plasma-assisted deposition , so that the concentration of SiH* and Hα active species in the plasma is maintained in a stable range, and the deposition rate of the coating film is increased. the

The invention provides a monitoring device for plasma-assisted deposition, including a plasma-assisted deposition device, a plasma composition analysis device connected to the plasma-assisted deposition device, and a production process modulation system, connected to the plasma composition analyzer device and the Plasma-Assisted Deposition Apparatus. the

In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and understandable, the preferred embodiments are specifically cited below, together with the accompanying drawings, and are described in detail as follows:

Description of drawings

Fig. 1 is the relationship diagram of deposition time and spectral intensity of deposition microcrystalline silicon film in general plasma-assisted chemical vapor deposition (PECVD) manufacturing process;

Fig. 2 is the relationship figure between the deposition time and the spectral intensity of the deposition microcrystalline silicon film in the manufacturing process of the embodiment of the present invention;

3 is a schematic diagram of a plasma thin film deposition device including a manufacturing process modulation system according to an embodiment of the present invention;

Fig. 4 is the flowchart of the depositing method of microcrystalline silicon thin film of the embodiment of the present invention;

Figure 5 is a graph showing the relationship between crystallization rate and coating time. the

Explanation of reference signs

302～vacuum cavity;

304～upper electrode;

306～lower electrode;

308～the first gas mass flow controller;

310～Second gas mass flow controller;

312～substrate;

314～plasma composition spectrum analyzer;

316～Manufacturing process modulation system;

318～optical sensor head;

320～plasma spectrometer;

322~power generator. the

Detailed ways

First, look at the growth mechanism of microcrystalline silicon thin films from the perspective of thin film engineering, which includes SiH* active species, which generate adsorption on the substrate, diffuse to form cluster nucleation, nuclei growth, continuous crystalline film formation, and crystalline film growth. and so on, the Hα active species provide the necessary hydrogen etching to obtain the required crystallization rate. In the open-loop production process of microcrystalline silicon deposition using plasma-assisted vapor deposition, the active species of the process gas after dissociation in the plasma field are SiH* and Hα, of which SiH* is the source of film growth, and Hα mainly plays the role of The effect of hydrogen etching is to obtain the required crystallization rate, but excessive Hα will cause excessive dilution of SiH* and inhibit the growth rate of the film. Figure 1 shows the curves of detecting the variation of SiH* and Hα in the general open-loop unmodulated production process parameters using the compositional spectrometer (OES), please refer to Figure 1, through the plasma-assisted chemical vapor deposition (PECVD) production process When depositing microcrystalline silicon thin films, Hα will increase by more than 22% in the long-term microcrystalline silicon thin film manufacturing process, while SiH* is relatively stable to Hα, that is, after the initial stage of microcrystalline silicon thin film deposition, it will increase due to excessively increased Hα. The effect of excessive hydrogen etching is produced, thereby reducing the deposition rate of the microcrystalline silicon film. the

As shown in Figure 2, the present invention provides a plasma-assisted thin film deposition method for improving the deposition rate of microcrystalline silicon thin films. In the initial stage of the production process of microcrystalline silicon thin film deposition (in the crystallization deposition time T), the open loop is not adjusted. Depositing by changing the production process parameters to obtain the required crystal quality microcrystalline silicon film, and after the initial stage of the microcrystalline silicon film deposition process (crystal deposition time T), use the closed-loop modulation process parameters to use the plasma The monitoring device adjusts the production process, controls the plasma environment to maintain the plasma environment conditions and maintain stability when the microcrystalline silicon film deposition is completed in the early stage (that is, the concentration of SiH* and Hα components in the plasma remains fixed), so it can avoid The long-time coating process produces too many Hα active species in the plasma environment, which inhibits the growth of the microcrystalline silicon film in the process, thereby increasing the deposition rate of the microcrystalline silicon film. the

Fig. 3 shows the plasma thin film deposition device including the manufacturing process modulation system in the embodiment of the present invention, please refer to Fig. 3, this embodiment provides a plasma thin film deposition device, such as high frequency plasma assisted chemical vapor deposition (VHF PECVD) etc. , including a vacuum chamber 302, an upper electrode 304 connected to a high-frequency pulse power supply, a lower electrode 306 (which is also a heater that can heat the substrate), a set of production process gas pipelines, such as hydrogen (H ₂ ) And silane (Silane, SiH ₄ ) pipeline, each gas pipeline includes a gas mass flow controller (MFC) to control the flow of each gas, for example, the first gas mass flow controller 308 controls the flow of hydrogen, and the second gas mass flow control Device 310 controls the flow of silane. The plasma thin film deposition device is connected to a high-frequency pulse power supply to generate plasma to dissociate hydrogen and silane (Silane) into active species Hα and SiH*, so that the microcrystalline silicon thin film deposition process and plasma thin film deposition can be performed on the surface of the substrate 312 The residual gas in the device and the gas generated by the deposition reaction are extracted from the vacuum chamber by the vacuum system.

In addition, the present embodiment further includes a plasma monitoring device, which includes a plasma composition spectrum analyzer (OES) 314 and a computer-based production process modulation system 316, and the spectrum analyzer 314 includes an optical sensing head 318 and The plasma spectrometer 320 and the spectrum analyzer 314 are used to detect the spectral intensity belonging to SiH* at a wavelength of 414nm, and the spectral intensity belonging to Hα at a wavelength of 656nm. The computer-based manufacturing process modulation system 316 reads SiH* and Hα Spectral intensity, and the gas flow rate is controlled by the gas mass flow controller 310, and the power is adjusted by the power generator 322 to adjust the production process parameters, so that the controlled plasma environment remains stable (that is, the SiH* and Hα components in the plasma Concentration ratio remains constant). the

Please refer to Fig. 4 below, describe the deposition method of the microcrystalline silicon thin film of the embodiment of the present invention, at first, start microcrystalline silicon coating procedure in step S402, then carry out step S404, set the required time t of coating procedure, microcrystalline silicon thin film The crystallization deposition time T at the initial stage of the production process, the initial conditions of the production process, etc., the crystallization deposition time T at the initial stage of the microcrystalline silicon thin film production process, please refer to the graph of the relationship between the crystallization rate and the coating time in Figure 5, which is in an open loop And under the condition of not adjusting the production process parameters, using the same microcrystalline silicon film deposition process conditions, at different deposition times, the crystallization rate of the microcrystalline silicon film is measured, and the crystallization rate of the microcrystalline silicon film can be obtained from Figure 5 Therefore, within this crystal deposition time T, it is called the initial stage of the microcrystalline silicon film deposition process, and after this crystal deposition time T, it is called the microcrystalline silicon film deposition process. After the initial period. Next, proceed to step S406 to deposit the microcrystalline silicon thin film. In step S408, it is judged whether the crystallization deposition time T has been reached. Continue to step S406 to deposit the microcrystalline silicon film; if the deposition time T has been reached, then in step S410 it is judged whether the deposition has reached the coating program time t. If the deposition and coating program time t has not ended, it enters into a closed-loop manufacturing process control loop for modulating manufacturing process parameters, and starts from step S412 to detect SiH* and Hα in the plasma. Then, step S414 is performed to determine whether the target values of SiH* and Hα are determined. The volume spectral value is set as the control target value of the closed loop. Then in step S416 it is judged whether the SiH* and Hα spectral intensity values detected in real time are within the allowable range (such as 1% of the control target value, but it can be changed according to the requirements of the manufacturing process), if the SiH* and Hα plasma spectra If the value is within the allowable range of the set control target, it is not necessary to adjust the manufacturing process parameters and continue to deposit microcrystalline silicon film S406. However, if the SiH* and Hα plasma spectral values are not within the allowable range of the control target, you must Perform step S418 to adjust the production process parameters, such as adjusting gas flow, power, pressure and temperature, and then perform S406 microcrystalline silicon thin film deposition according to the adjusted production process conditions, and repeat the above-mentioned closed-loop modulation process. The crystalline silicon thin film is deposited until the coating program time t ends, that is, the coating is completed S422. It is worth noting that in this embodiment, the microcrystalline silicon thin film was deposited in an open-loop manner at the initial stage of the manufacturing process without adjusting the manufacturing process parameters to obtain the required crystal quality of the microcrystalline silicon thin film. After the initial stage of the thin film deposition process, use the plasma spectrum monitoring device to detect the spectral values of the active species SiH* and Hα in the plasma at that time (crystal deposition time T) in a closed-loop manner and adjust the process parameters as a control The benchmark of the plasma environment is to adjust the production process to keep the plasma composition stable. The plasma environment when the microcrystalline silicon thin film deposition process is completed in the early stage (that is, the concentration ratio of SiH* and Hα components in the plasma remains fixed), At the same time, it can avoid the phenomenon that the growth of the microcrystalline silicon film in the production process is inhibited due to the excessive Hα active species produced in the plasma environment due to the long-term coating process, thereby increasing the deposition rate of the microcrystalline silicon film . the

In addition to using the plasma spectrum monitoring device to adjust the manufacturing process, in another embodiment of the present invention, a residual gas analyzer (RGA) or an integrated residual gas analyzer and optical spectrum analyzer (OES) can also be used to monitor the plasma environment. To achieve the purpose of inhibiting the excessive concentration of Hα active species. the

According to the above, the present invention can improve the complex problem of the manufacturing process caused by the preset method of setting multi-stage manufacturing process conditions when performing the microcrystalline silicon thin film deposition manufacturing process in the known technology, and can provide the microcrystalline silicon thin film The long-term plasma stability after the initial stage of the deposition process can suppress the over-etching effect caused by the increase of the Hα concentration, and further increase the deposition rate in a plasma environment with a good film crystallization rate, which is suitable for mass production and for production High-efficiency silicon thin-film solar cells. the

Although the preferred embodiments of the present invention have been disclosed above, they are not intended to limit the present invention. Any person skilled in the art may make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall prevail as defined by the appended claims. the

Claims (17)

1. the deposition method of a microcrystalline silicon film comprises:

With open the loop and not the manufacture craft of modulation parameter carry out plasma ion assisted deposition; And

When this opens loop and when the deposition manufacture craft of modulation parameter does not reach default thin film crystallization rate, manufacture craft with loop circuit and modulation parameter is carried out plasma ion assisted deposition, wherein the manufacture craft of this loop circuit and modulation parameter is SiH* and H alpha active species in this plasma of monitoring, and adjust the manufacture craft parameter in this plasma assistant depositing, SiH* in this plasma and the plasma spectrometry intensity level of H alpha active species are maintained in desired value and allowed band thereof, to improve coated film deposition speed

Wherein reaching this default thin film crystallization rate is by the crystallization control depositing time, and this crystallization deposition time is determined by following methods:

With this open the loop and not the manufacture craft of modulation parameter carry out plasma ion assisted deposition; And

Measure the microcrystalline silicon film percent crystallization in massecuite of different depositing times, stablize necessary this crystallization deposition time to obtain the microcrystalline silicon film percent crystallization in massecuite.

2. the deposition method of microcrystalline silicon film as claimed in claim 1, wherein the manufacture craft of this loop circuit and modulation parameter is to continue after the time at this crystallization deposition to carry out.

3. the deposition method of microcrystalline silicon film as claimed in claim 1, wherein this manufacture craft parameter comprises: hydrogen flowing quantity, silane flow rate, power, pressure or temperature.

4. the deposition method of microcrystalline silicon film as claimed in claim 1, wherein this target value is this crystallization deposition in the time, the plasma spectrometry intensity level of its SiH* and H alpha active species.

5. the deposition method of microcrystalline silicon film as claimed in claim 1, wherein this allowed band is this crystallization deposition in the time, 1% of the plasma spectrometry intensity level of its SiH* and H alpha active species.

6. the deposition method of microcrystalline silicon film as claimed in claim 1, wherein the step of the SiH* in this plasma body of this monitoring and H alpha active species is using plasma composition spectrum analyzers, measures the plasma spectrometry intensity level of this SiH* and H alpha active species.

7. the deposition method of microcrystalline silicon film as claimed in claim 1, wherein the step of the SiH* in this plasma body of this monitoring and H alpha active species is to adopt residual gas analyzer.

8. the deposition method of microcrystalline silicon film as claimed in claim 1, wherein the step of the SiH* in this plasma body of this monitoring and H alpha active species is using plasma composition spectrum analyzer and residual gas analyzer.

9. the deposition method of microcrystalline silicon film as claimed in claim 1, wherein the deposition method of this microcrystalline silicon film is the microcrystalline silicon film that applies to make silicon film type solar cell.

10. the deposition method of microcrystalline silicon film as claimed in claim 1, wherein this deposition method improves the sedimentation velocity of this microcrystalline silicon film.

11. the monitoring device of a plasma ion assisted deposition comprises:

The plasma ion assisted deposition device;

The plasma composition analytical equipment connects this plasma body assistant depositing device; And

Manufacture craft modulation system connects this plasma body analytical instrument device and this plasma body assistant depositing device.

12. the monitoring device of plasma ion assisted deposition as claimed in claim 11, wherein this plasma body assistant depositing device comprises:

Vacuum cavity;

Top electrode and lower electrode are arranged in this vacuum cavity;

The power generator connects this top electrode and this lower electrode;

Hydrogen pipeline connects this vacuum cavity;

The silane pipeline connects this vacuum cavity;

The first gas mass flow controller connects this hydrogen pipeline; And

The second gas mass flow controller connects this silane pipeline.

13. the monitoring device of plasma ion assisted deposition as claimed in claim 11, wherein this plasma body composition analysis device is the plasma composition spectrum analyzer.

14. the monitoring device of plasma ion assisted deposition as claimed in claim 11, wherein this plasma body composition analysis device is residual gas analyzer.

15. the monitoring device of plasma ion assisted deposition as claimed in claim 11, wherein this this plasma body composition analysis device comprises plasma composition spectrum analyzer and residual gas analyzer.

16. the monitoring device of plasma ion assisted deposition as claimed in claim 11, wherein this manufacture craft modulation system is that computer is the system on basis, after be used for receiving and process the signal that this plasma body composition analysis device measures, this plasma body assistant depositing device is carried out the adjustment of manufacture craft parameter.

17. the monitoring device of plasma ion assisted deposition as claimed in claim 12, wherein power generator and the gas mass flow controller of this manufacture craft modulation system this plasma body assistant depositing device of capable of regulating.

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