阅读说明：本技术 PECVD制备硅片复合膜的方法和TOPCon电池的制备方法 (Method for preparing silicon wafer composite membrane by PECVD and preparation method of TOPCon battery ) 是由 李军阳 张勇 李学文 于 2021-07-12 设计创作，主要内容包括：本发明公开了一种管式PECVD设备制备硅片复合膜的方法和一种TOPCon太阳能电池的制备方法,管式PECVD设备制备硅片复合膜的方法包括将装载多个硅片的石墨舟置于PECVD设备的反应室内,设置射频频率为设置射频频率为40kHz-13.56MHz；通入笑气或氧气沉积氧化硅层,通入硅烷和氢气,或硅烷和氩气沉积第一本征ploy层,通入硅烷、氢气和掺杂源气体沉积第一掺杂ploy层,通入硅烷和笑气,或硅烷和氨气沉积mask层,再将装载多个硅片的石墨舟移出PECVD设备。本发明的硅片复合膜的制备方法能够在不出炉的情况下,成长多层复合膜,工艺流程简单,生产效率高,本发明TOPCon太阳能电池的制备方法生产效率高,太阳能电池的光线效率高,产品不良率低。(The invention discloses a method for preparing a silicon wafer composite film by using a tubular PECVD (plasma enhanced chemical vapor deposition) device and a method for preparing a TOPCon (top enhanced chemical vapor deposition) solar cell, wherein the method for preparing the silicon wafer composite film by using the tubular PECVD device comprises the steps of placing a graphite boat loaded with a plurality of silicon wafers in a reaction chamber of the PECVD device, and setting the radio frequency to be 40kHz-13.56 MHz; and introducing laughing gas or oxygen to deposit a silicon oxide layer, introducing silane and hydrogen or silane and argon to deposit a first intrinsic ploy layer, introducing silane, hydrogen and doping source gas to deposit a first doping ploy layer, introducing silane and laughing gas or silane and ammonia to deposit a mask layer, and then moving the graphite boat loaded with a plurality of silicon wafers out of the PECVD equipment. The preparation method of the TOPCon solar cell has the advantages that the multilayer composite film can be grown under the condition of not discharging from the furnace, the process flow is simple, the production efficiency is high, the production efficiency of the TOPCon solar cell is high, the light efficiency of the TOPCon solar cell is high, and the product reject ratio is low.)

1. The method for preparing the silicon wafer composite film by using the tubular PECVD equipment is characterized by comprising the following steps of:

placing a graphite boat loaded with a plurality of silicon wafers in a reaction chamber of the PECVD equipment;

setting the radio frequency to be 40kHz-13.56 MHz;

depositing a silicon oxide layer, wherein the reaction gas is laughing gas or oxygen, the flow of the laughing gas or oxygen is 1000-15000sccm, the pressure is 50-350Pa, the plasma power is 2-40kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 50-600s, and the reaction temperature is 200-600 ℃;

depositing a first intrinsic ploy layer, wherein the reaction gas is silane and hydrogen or silane and argon, the flow rate of silane is 300-5000sccm, the flow rate of hydrogen or argon is 1000-15000sccm, the pressure is 100-300Pa, the plasma power is 4-40kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-900s, and the reaction temperature is 200-600 ℃;

depositing a first doped ploy layer, wherein the reaction gases comprise silane, hydrogen and a doping source gas, the flow rate of the silane is 300-; the pressure is 100-300Pa, the plasma power is 4-40kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-3600s, and the reaction temperature is 200-600 ℃;

depositing a mask layer, wherein the reaction gas is silane and laughing gas or silane and ammonia gas, the flow rate of the silane is 300-5000sccm, the flow rate of the laughing gas or ammonia gas is 1000-15000sccm, the pressure is 100-300Pa, the plasma power is 4-40kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-300s, and the reaction temperature is 200-600 ℃;

and moving the graphite boat loaded with the plurality of silicon wafers out of the PECVD equipment.

2. The method for preparing a silicon wafer composite film by using a tubular PECVD apparatus as recited in claim 1,

depositing a silicon oxide layer by adopting laughing gas or oxygen, wherein the flow of the laughing gas or oxygen is 1000-5000sccm, the pressure is 50-350Pa, the plasma power is 4-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 50-600s, and the reaction temperature is 300-500 ℃;

depositing a first intrinsic ploy layer by adopting silane and hydrogen or silane and argon, wherein the flow rate of the silane is 1000-2000sccm, the flow rate of the hydrogen or argon is 3000-10000sccm, the pressure is 150-300Pa, the plasma power is 5-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-900s, and the reaction temperature is 300-500 ℃;

depositing a first doping ploy layer by adopting silane, hydrogen and doping source gas, wherein the flow rate of the silane is 1000-2000sccm, the flow rate of the hydrogen is 3000-10000sccm, the flow rate of the doping source gas is 1000-5000sccm, the pressure is 150-300Pa, the plasma power is 5-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-3600s, and the reaction temperature is 300-500 ℃;

silane and laughing gas or silane and ammonia gas are adopted to deposit the mask layer, the flow rate of the silane is 1000-10000 sccm, the flow rate of the laughing gas or ammonia gas is 3000-10000sccm, the pressure is 100-250Pa, the plasma power is 5-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-300s, and the reaction temperature is 300-500 ℃.

3. The method for preparing a silicon wafer composite film by using a tubular PECVD apparatus as recited in claim 1,

when depositing the first doped ploy layer, the reaction gas further comprises argon gas, wherein the flow rate of the argon gas is 1000-15000 sccm.

4. The method for preparing a silicon wafer composite film according to claim 1, wherein the flow rate of the reaction gas is adjusted with the deposition time during the deposition of the first intrinsic ploy layer or the deposition of the first doped ploy layer.

5. The method for preparing a silicon wafer composite film by using a tubular PECVD apparatus as recited in claim 4,

during the deposition of the first intrinsic ploy layer, the flow rate of silane gradually decreases, or the flow rate of silane gradually increases; or in the first deposition time period, the flow rate of the silane is Asccm, in the second deposition time period, the flow rate of the silane is Bsccm, and in the third deposition time period, the flow rate of the silane is Csccm; or the flow rate of the silane is Csccm in the first deposition time period, the flow rate of the silane is Bsccm in the second deposition time period, and the flow rate of the silane is Asccm in the third deposition time period; wherein A > B > C.

6. The method for preparing a silicon wafer composite film by using a tubular PECVD apparatus as recited in claim 4,

in the process of depositing the first doped ploy layer, the flow rate of the phosphane is gradually reduced, or the flow rate of the phosphane is gradually increased, or in the first time period of deposition, the flow rate of the phosphane is Esccm, in the second time period of deposition, the flow rate of the phosphane is Fsccm, and in the third time period of deposition, the flow rate of the phosphane is Gsccm; or in the first deposition time period, the flow rate of the phosphane is Gsccm, in the second deposition time period, the flow rate of the phosphane is Fsccm, and in the third deposition time period, the flow rate of the phosphane is Esccm; wherein E > F > G.

7. The method for preparing a silicon wafer composite film according to claim 1, further comprising depositing a second doped ploy layer before depositing the first intrinsic ploy layer, the second doped ploy layer being deposited with the same reaction gas as the first doped ploy layer, the second doped ploy layer being deposited for a period of 1-30 s.

8. The method for preparing a silicon wafer composite film by using a tubular PECVD apparatus as recited in claim 1,

the first intrinsic ploy layer and the first doped ploy layer are deposited the same number of times after the silicon oxide layer is deposited and before the mask layer is deposited, and the first intrinsic ploy layer and the first doped ploy layer are alternately deposited.

9. The method for preparing the silicon wafer composite film by using the tubular PECVD apparatus as recited in claim 1, further comprising in-situ cleaning, placing the empty graphite boat in a reaction chamber of the PECVD apparatus, and introducing a reaction gas NF₃、SF₆、CF₄、CHF₃Or C₂F₆And introducing the graphite boat into the reaction chamber to clean the graphite boat and the reaction chamber.

10. A preparation method of TOPCon solar battery is characterized in that,

(1) texturing a silicon wafer for one time;

(2) b diffusing the front side of the silicon wafer;

(3) removing BSG from the back of the silicon wafer, and performing secondary texturing;

(4) preparing a composite film on the back side of a silicon wafer by the method of any one of claims 1 to 9;

(5) annealing at 800-1000 deg.c;

(6) etching;

(7) depositing aluminum oxide and silicon nitride on the front surface of the silicon wafer;

(8) depositing silicon nitride on the back of the silicon wafer;

(9) printing and sintering.

Technical Field

The invention relates to the technical field of solar cell manufacturing, in particular to a method for preparing a silicon wafer composite film by PECVD (plasma enhanced chemical vapor deposition) and a method for preparing a TOPCon cell.

Background

The high-efficiency crystalline silicon solar cell is a Tunnel Oxide Passivated Contact solar cell (TOPCon), and the cell adopts a high-quality ultrathin silicon Oxide doped polycrystalline silicon layer to realize the high-efficiency passivation of the whole back of the cell and the selective collection of carriers.

In the related art, the LPCVD equipment (Low Pressure Chemical Vapor Deposition) is used to prepare the tunneling layer and the doping layer (ploy layer) in the TOPCon cell, and the Deposition rate is slow, which is not suitable for large-scale industrial production.

Disclosure of Invention

The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a method for preparing a silicon wafer composite film by using a tubular PECVD device, wherein a multilayer composite film can grow in the same reaction chamber without discharging, the process flow of the composite film is simplified, and the production efficiency is improved.

The invention also provides a preparation method of the TOPCon solar cell, and the method for preparing the silicon wafer composite film by using the tubular PECVD equipment is used for preparing the composite film on the back of the silicon wafer.

The method for preparing the silicon wafer composite film by using the tubular PECVD equipment comprises the following steps,

placing a graphite boat loaded with a plurality of silicon wafers in a reaction chamber of the PECVD equipment;

setting the radio frequency to be 40kHz-13.56 MHz;

depositing a silicon oxide layer, wherein the reaction gas is laughing gas or oxygen, the flow of the laughing gas or oxygen is 1000-15000sccm, the pressure is 50-350Pa, the plasma power is 2-40kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 50-600s, and the reaction temperature is 200-600 ℃;

depositing a first intrinsic ploy layer, wherein the reaction gas is silane and hydrogen or silane and argon, the flow rate of silane is 300-5000sccm, the flow rate of hydrogen or argon is 1000-15000sccm, the pressure is 100-300Pa, the plasma power is 4-40kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-900s, and the reaction temperature is 200-600 ℃;

depositing a first doped ploy layer, wherein the reaction gases comprise silane, hydrogen and a doping source gas, the flow rate of the silane is 300-; the pressure is 100-300Pa, the plasma power is 4-40kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-3600s, and the reaction temperature is 200-600 ℃;

depositing a mask layer, wherein the reaction gas is silane and laughing gas or silane and ammonia gas, the flow rate of the silane is 300-5000sccm, the flow rate of the laughing gas or ammonia gas is 1000-15000sccm, the pressure is 100-300Pa, the plasma power is 4-40kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-300s, and the reaction temperature is 200-600 ℃;

and moving the graphite boat loaded with the plurality of silicon wafers out of the PECVD equipment.

The method for preparing the silicon wafer composite film by using the tubular PECVD equipment disclosed by the embodiment of the invention at least has the following beneficial effects:

the multilayer film can be grown under the condition of not discharging from the furnace, the process flow is reduced, and the growth efficiency is improved.

According to some embodiments of the invention, laughing gas or oxygen is used for depositing the silicon oxide layer, the flow rate of the laughing gas or oxygen is 1000-5000sccm, the pressure is 50-350Pa, the plasma power is 4-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 50-600s, and the reaction temperature is 300-500 ℃;

depositing a first intrinsic ploy layer by adopting silane and hydrogen or silane and argon, wherein the flow rate of the silane is 1000-2000sccm, the flow rate of the hydrogen or argon is 3000-10000sccm, the pressure is 150-300Pa, the plasma power is 5-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-900s, and the reaction temperature is 300-500 ℃;

depositing a first doping ploy layer by adopting silane, hydrogen and doping source gas, wherein the flow rate of the silane is 1000-10000 sccm, the flow rate of the hydrogen is 3000-10000sccm, the flow rate of the doping source gas is 1000-5000sccm, the pressure is 150-300Pa, the plasma power is 5-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-3600s, and the reaction temperature is 300-500 ℃;

silane and laughing gas or silane and ammonia gas are adopted to deposit the mask layer, the flow rate of the silane is 1000-10000 sccm, the flow rate of the laughing gas or ammonia gas is 3000-10000sccm, the pressure is 100-250Pa, the plasma power is 5-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-300s, and the reaction temperature is 300-500 ℃.

According to some embodiments of the present invention, the reaction gas further comprises argon gas when depositing the first doped poly layer, wherein the flow rate of argon gas is 1000-.

According to some embodiments of the present invention, the flow rate of the reaction gas is adjusted with deposition time during deposition of the first intrinsic ploy layer or deposition of the first doped ploy layer.

According to some embodiments of the present invention, during deposition of the first intrinsic ploy layer, the silane flow rate is gradually decreased, or the silane flow rate is gradually increased; or in the first deposition time period, the flow rate of the silane is Asccm, in the second deposition time period, the flow rate of the silane is Bsccm, and in the third deposition time period, the flow rate of the silane is Csccm; or the flow rate of the silane is Csccm in the first deposition time period, the flow rate of the silane is Bsccm in the second deposition time period, and the flow rate of the silane is Asccm in the third deposition time period; wherein A > B > C.

According to some embodiments of the present invention, during the deposition of the first doped ploy layer, the flow rate of the phosphane is gradually decreased, or the flow rate of the phosphane is gradually increased, or during the first time period of the deposition, the flow rate of the phosphane is Esccm, during the second time period of the deposition, the flow rate of the phosphane is Fsccm, and during the third time period of the deposition, the flow rate of the phosphane is Gsccm; or in the first deposition time period, the flow rate of the phosphane is Gsccm, in the second deposition time period, the flow rate of the phosphane is Fsccm, and in the third deposition time period, the flow rate of the phosphane is Esccm; wherein E > F > G.

According to some embodiments of the present invention, there is further included depositing a second doped ploy layer prior to depositing the first intrinsic ploy layer, the second doped ploy layer being deposited with the same reaction gas as the first doped ploy layer, the second doped ploy layer being deposited for a time period of 1-30 s.

According to some embodiments of the present invention, the first intrinsic ply layer and the first doped ply layer are deposited the same number of times after depositing the silicon oxide layer and before depositing the mask layer, and the first intrinsic ply layer and the first doped ply layer are alternately deposited.

According to some embodiments of the invention, the method further comprises in-situ cleaning, placing the empty graphite boat in a reaction chamber of the PECVD equipment, and introducing reaction gases NF3, SF6, CF4, CHF3 or C2F6 into the reaction chamber to clean the graphite boat and the reaction chamber.

According to the preparation method of the TOPCon solar cell of the embodiment of the second aspect of the invention, a silicon wafer is subjected to primary texturing;

(1) b diffusing the front side of the silicon wafer;

(2) removing BSG from the back of the silicon wafer, and performing secondary texturing;

(3) preparing a composite film on the back side of a silicon wafer by the method of any one of claims 1 to 9;

(4) annealing at 800-1000 deg.c;

(5) etching;

(6) depositing aluminum oxide and silicon nitride on the front surface of the silicon wafer;

(7) depositing silicon nitride on the back of the silicon wafer;

(8) printing and sintering.

The preparation method of the TOPCon solar cell provided by the embodiment of the invention has at least the following beneficial effects: the production efficiency is high, the photoelectric efficiency of the solar cell is high, and the reject ratio of the product is low.

Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.

Detailed Description

In the description of the present invention, the meaning of a plurality is one or more, the meaning of a plurality is two or more, and the meaning of more, less, more, etc. is understood as excluding the number, and the meaning of more, less, more, etc. is understood as including the number. If there is a description of the first and second for the purpose of distinguishing technical features, it is not to be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of technical features indicated.

In the description of the present invention, unless otherwise explicitly defined, terms such as setting, installing, connecting and the like should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the terms in the present invention (utility model) by combining the specific contents of the technical solutions.

In the description of the present invention, reference to the description of the terms "one embodiment," "some embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The method for preparing the silicon wafer surface composite film by using the tubular PECVD equipment in the embodiment of the first aspect of the invention is described below.

In some embodiments, a method of preparing a silicon wafer composite film in a tubular PECVD apparatus includes placing a graphite boat, which is equipped with a plurality of silicon wafers, in a reaction chamber of the PECVD apparatus, depositing a silicon oxide layer, depositing a first intrinsic ploy layer, depositing a first doped ploy layer, and depositing a mask layer.

Specifically, pecvd (plasma Enhanced Chemical Vapor deposition) refers to a Vapor deposition method of plasma Enhanced Chemical. The graphite boat arranged on a plurality of silicon wafers is arranged in a reaction chamber of PECVD equipment, and the radio frequency is set to be 40kHz-13.56 MHz. Specifically, the method comprises the following steps of:

(1) vacuumizing a reaction chamber of PECVD equipment, introducing a certain amount of laughing gas or oxygen, wherein the flow rate of the laughing gas or oxygen is 1000-15000sccm, the pressure is 50-350Pa, the plasma power is 2-40kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 50-600s, the reaction temperature is 200-600 ℃, the PECVD equipment ionizes the laughing gas or oxygen to obtain plasma, and the plasma is deposited on the surface of a silicon wafer to form a silicon oxide layer;

(2) a first intrinsic ploy layer is deposited on the silicon oxide layer.

Vacuumizing a reaction chamber of PECVD equipment, introducing a certain amount of silane and hydrogen, wherein the flow rate of the silane is 300-5000sccm, the flow rate of the hydrogen is 1000-15000sccm, the pressure is 100-300Pa, the plasma power is 4-40kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-900s, the reaction temperature is 200-600 ℃, the PECVD equipment ionizes the silane and the hydrogen to obtain plasma, and the plasma is deposited on a silicon oxide layer to form a first intrinsic layer;

the reaction gas for forming the first intrinsic ploy layer can also be silane and argon, namely, the reaction gas hydrogen is replaced by the argon, the silane and the argon are ionized by PECVD equipment to obtain plasma, and the plasma is deposited on the silicon oxide layer to form the first intrinsic ploy layer;

(3) a first doped ploy layer is deposited on the first intrinsic ploy layer.

Introducing a certain amount of silane, hydrogen and a doping source gas into a reaction chamber of PECVD equipment, wherein the flow rate of the silane is 300-5000sccm, the flow rate of the hydrogen is 1000-15000sccm, and the flow rate of the doping source gas is 200-5000 sccm; the pressure is 100-.

The dopant source gas may be a phosphane, which means a mixed gas of phosphane and hydrogen (where PH3: H2 ═ 2:98) for improved safety. The doping source gas may also be B2H6, B2H6 refers to a mixed gas of B2H6 and H2.

After the deposition of the first intrinsic layer and before the deposition of the first doped layer, the reaction chamber may be further vacuumized to prevent the reaction gas of the first intrinsic layer from mixing with the reaction gas of the first doped layer, thereby improving the quality of the first doped layer.

(4) A mask layer was deposited on the first doped ploy layer.

After the reaction chamber of the PECVD equipment is vacuumized, a certain amount of silane and laughing gas are introduced into the reaction chamber of the PECVD equipment, the flow rate of the silane is 300-5000sccm, the flow rate of the laughing gas is 1000-15000sccm, the pressure is 100-300Pa, the plasma power is 4-40kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-300s, the reaction temperature is 200-600 ℃, the PECVD equipment ionizes the silane and the hydrogen to obtain plasma, and the plasma is deposited on the first doped ploy layer to form a mask layer.

The reaction gas for forming the mask layer can also be silane and ammonia gas, namely ammonia gas is adopted to replace laughing gas of the reaction gas, PECVD equipment ionizes the silane and the ammonia gas to obtain plasma, and the plasma is deposited on the first doped ploy layer to form the mask layer;

(5) and (4) moving the graphite boat loaded with the plurality of silicon wafers out of the PECVD equipment. And processing the silicon chip to prepare the TOPCon battery.

The method for preparing the silicon wafer composite film can be used for preparing the composite film on the back side of the silicon wafer and also can be used for preparing the composite film on the front side of the silicon wafer.

In some specific embodiments, in the process of depositing each layer of film, by adjusting corresponding parameters, each layer of film on the surface of the silicon wafer can be more uniform and have higher compactness, and the quality of the silicon wafer composite film is further improved.

Specifically, (1) carrying out vacuum-pumping treatment on a reaction chamber of PECVD equipment, then introducing a certain amount of laughing gas or oxygen, wherein the flow rate of the laughing gas or oxygen is 1000-5000sccm, the temperature in the reaction chamber is 50-350Pa, the plasma power is 4-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 50-600s, the reaction temperature is 300-500 ℃, the PECVD equipment ionizes the laughing gas or oxygen to obtain plasma, and the plasma is deposited on the surface of a silicon wafer to form a silicon oxide layer;

(2) a first intrinsic ploy layer is deposited on the silicon oxide layer.

Vacuumizing a reaction chamber of PECVD equipment, introducing a certain amount of silane and hydrogen, wherein the flow rate of the silane is 1000-10000 sccm, the flow rate of the hydrogen is 3000-10000sccm, the pressure is 150-300Pa, the plasma power is 5-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-900s, the reaction temperature is 300-500 ℃, the PECVD equipment ionizes the silane and the hydrogen to obtain plasma, and the plasma is deposited on a silicon oxide layer to form a first intrinsic ploy layer;

the reaction gas for forming the first intrinsic ploy layer can also be silane and argon, hydrogen is replaced by argon, Plasma Enhanced Chemical Vapor Deposition (PECVD) equipment ionizes the silane and the argon to obtain plasma, and the plasma is deposited on the silicon oxide layer to form the first intrinsic ploy layer;

(3) a first doped ploy layer is deposited on the first intrinsic ploy layer.

Introducing certain amount of silane, hydrogen and phosphane (or B2H6) into a reaction chamber of a PECVD device, wherein the flow rate of silane is 1000-2000sccm, the flow rate of hydrogen is 3000-10000sccm, the flow rate of phosphane (or B2H6) is 1000-5000sccm, the pressure is 150-300Pa, the plasma power is 5-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-3600s, the reaction temperature is 300-500 ℃, the PECVD device ionizes the silane, the hydrogen and the phosphane (or B2H6) to obtain plasma, and the plasma is deposited on the first intrinsic ply layer to form a first doped ply layer.

After the deposition of the first intrinsic ply layer and before the deposition of the first doped ply layer, the reaction chamber may be further vacuumized to make the reactive gas of the first doped ply layer approach the theoretical value (to avoid the mixing of the reactive gas of the first intrinsic ply layer and the reactive gas of the first doped ply layer), thereby improving the quality of the first doped ply layer.

(4) A mask layer was deposited on the first doped ploy layer.

After the reaction chamber of the PECVD equipment is vacuumized, a certain amount of silane and laughing gas (or ammonia gas) are introduced into the reaction chamber of the PECVD equipment, the flow rate of the silane is 1000-2000sccm, the flow rate of the laughing gas or ammonia gas is 3000-10000sccm, the pressure is 100-250Pa, the plasma power is 5-15kw, the radio frequency on-off ratio is 1:6-1:100, the deposition time is 30-300s, the reaction temperature is 300-500 ℃, the PECVD equipment ionizes the silane and laughing gas (or ammonia gas) to obtain plasma, and the plasma is deposited on the first doped ploy layer to form a mask layer.

(6) And (4) moving the graphite boat loaded with the plurality of silicon wafers out of the PECVD equipment. And processing the silicon chip to prepare the TOPCon battery.

In some embodiments, the reaction gas further comprises argon gas during the deposition of the first doped poly layer, wherein the flow rate of argon gas is 1000-.

When the first doped ploy layer is deposited, argon is added into the reaction gas, so that the deposition rate can be accelerated, the process time is saved, but the flow of the argon needs to be proper, and the film structure is loose due to too much or too little argon, so that the flow of the argon is set at 1000-15000sccm, and the first doped ploy layer can be more uniform and compact.

During the deposition of the first intrinsic ploy layer or the deposition of the first doped ploy layer, the flow rate of the reaction gas was adjusted with the deposition time. In some embodiments, the silane flow rate is gradually decreased, or the silane flow rate is gradually increased, during the deposition of the first intrinsic ploy layer; or in the first deposition time period, the flow rate of the silane is Asccm, in the second deposition time period, the flow rate of the silane is Bsccm, and in the third deposition time period, the flow rate of the silane is Csccm; or the flow rate of the silane is Csccm in the first deposition time period, the flow rate of the silane is Bsccm in the second deposition time period, and the flow rate of the silane is Asccm in the third deposition time period; wherein A > B > C.

Specifically, for example, during the deposition process, the flow rate of silane is gradually reduced from 5000sccm to 300sccm, or gradually increased from 300sccm to 5000 sccm; or the flow rate of the silane is reduced in a stepwise manner, the deposition is continued for a period of time at a flow rate of 3000ssm, the deposition is continued for a period of time at a flow rate of 2000sccm, and then the deposition is continued for a period of time at a flow rate of 1000 ssm; or the silane flow rate was increased in steps, with deposition continued for a period of time at a flow rate of 1000ssm, continued for a period of time at a flow rate of 2000sccm, and continued for a period of time at a flow rate of 3000 ssm.

The first time period, the second time period and the third time period may be the same or different times. In the present embodiment, the deposition time is divided into 3 stages, and it is understood that other stages (for example, 2 stages, 4 stages, etc.) of the deposition time atmosphere may be used according to the actual situation.

In other embodiments, during the deposition of the first doped ploy layer, the flow rate of the phosphane is gradually decreased, or the flow rate of the phosphane is gradually increased, or during the first time period of deposition, the flow rate of the phosphane is Esccm, during the second time period of deposition, the flow rate of the phosphane is fccm, and during the third time period of deposition, the flow rate of the phosphane is Gsccm; or in the first deposition time period, the flow rate of the phosphane is Gsccm, in the second deposition time period, the flow rate of the phosphane is Fsccm, and in the third deposition time period, the flow rate of the phosphane is Esccm; wherein E > F > G.

Specifically, in the deposition process, the flow rate of the silane is gradually reduced from 5000sccm to 300sccm, or gradually increased from 300sccm to 5000 sccm; or the flow rate of the silane is reduced in a stepwise manner, the deposition is continued for a period of time at a flow rate of 3000ssm, the deposition is continued for a period of time at a flow rate of 2000sccm, and then the deposition is continued for a period of time at a flow rate of 1000 ssm; or the silane flow rate is increased stepwise, with deposition continuing at 1000ssm for a period of time, continuing at 2000sccm for a period of time, and then continuing at 3000ssm for a period of time.

The first time period, the second time period and the third time period may be the same or different times. In the present embodiment, the deposition time is divided into 3 stages, and it is understood that other stages (for example, 2 stages, 4 stages, etc.) of the deposition time atmosphere may be used according to the actual situation.

Because the passivation effect and the deposition rate of the film are often difficult to achieve simultaneously, the staged deposition can achieve different stages with the passivation effect or the deposition rate being preferential; thereby optimizing the performance of the first intrinsic or first doped ploy layer.

In some embodiments, a second doped ploy layer is deposited prior to the deposition of the first intrinsic ploy layer, the second doped ploy layer being deposited with the same reactive gas as the first doped ploy layer, the second doped ploy layer being deposited for a time period of 1-30s, thereby forming the second doped ploy layer between the silicon oxide layer and the first intrinsic ploy layer. Since the deposition time of the second doped ploy layer is shorter than that of the first doped ploy layer, the thickness of the second doped ploy layer is smaller than that of the first doped ploy layer. After the silicon wafer is moved out of the PECVD equipment, in the subsequent annealing process, the doping sources in the first doping ploy layer and the second doping ploy layer can be infiltrated into the first intrinsic ploy layer, and a more reasonable doping concentration curve is obtained through the arrangement mode, so that the TOPCon cell has higher photoelectric conversion efficiency, the doping speed can be increased, and the production efficiency is improved.

In some embodiments, the first intrinsic layer and the first doped layer are deposited the same number of times and the first intrinsic layer and the first doped layer are alternately deposited before depositing the silicon oxide layer and depositing the mask layer.

Specifically, taking the example that the first intrinsic layer and the first doped layer are deposited twice respectively, the total number of the composite films on the surface of the silicon wafer is 6, and the following layers are sequentially deposited from the bottom layer to the surface layer: a silicon oxide layer, a first intrinsic layer, a first doped layer and a mask layer. It is understood that the number of times each of the first intrinsic ploy layer and the first doped ploy layer is deposited may be 3 times, 4 times … …. Through the arrangement, the deposition speed of the composite film on the surface of the silicon wafer is higher, and after the silicon wafer is moved out of the PECVD equipment, the doping source in the first doping ploy layer permeates into the adjacent first intrinsic ploy layer in the subsequent annealing treatment process. And a more reasonable doping concentration curve is obtained, so that the TOPCon battery is improved to have higher photoelectric conversion efficiency, and in addition, the doping speed can be improved, so that the production efficiency is improved.

In some embodiments, the method further comprises in-situ cleaning, placing the empty graphite boat in a reaction chamber of a PECVD apparatus, and introducing a reaction gas NF3, SF6, CF4, CHF3 or C2F6 into the reaction chamber to clean the graphite boat and the reaction chamber.

Specifically, in the process of preparing the silicon wafer surface composite film by the PECVD equipment, corresponding plasma is deposited on the surface of the silicon wafer, and is deposited on the surfaces of the reaction chamber and the graphite boat carrier, especially on the ceramic support ring of the graphite boat, and the ceramic support ring supports the two graphite boats with different polarities. Therefore, the reaction gases NF3, SF6, CF4, CHF3 or C2F6 (cleaning gases) are introduced into the reaction chamber, and the graphite boat and the reaction chamber are periodically cleaned in situ, so that the normal operation of the equipment is ensured, and the reliability of the work is improved. Compared with other wet cleaning and cleaning, the cleaning device does not need to be disassembled, transported and the like, and can effectively improve the production efficiency. It can be understood that in the cleaning process, stable gas such as argon can be introduced into the reaction chamber, so that the ratio of the cleaning gas to the stable gas is adjusted, the etching is more uniform, and the cleaning quality is improved.

In the process of preparing the TOPCon battery, taking the deposition of a multilayer composite film on the back surface of a silicon wafer as an example, residual substances such as PSG, polycrystalline silicon film, BSG and the like generated in the previous process of poly preparation or in the process of poly preparation exist on the front surface of the silicon wafer. In order to improve the quality of the silicon wafer, the front surface of the silicon wafer needs to be etched and cleaned, and the front surface of the silicon wafer is usually placed in a cleaning solution so as to etch and clean the residual substances. In the invention, the mask layer is deposited on the back surface of the silicon wafer, and in the process of etching and cleaning the front surface of the silicon wafer, the whole silicon wafer can be directly immersed into the etching liquid in most etching process links, the etching liquid does not etch the mask or the etching rate is very slow, and the mask plays a role in protecting the back poly layer. In the subsequent etching process link, the mask layer on the back of the silicon wafer is removed while the residual substances on the front of the silicon wafer are etched, and the effect of the mask is finished. Through the arrangement mode, in the process of etching and cleaning the front surface of the silicon wafer, the plurality of silicon wafers can be etched and cleaned simultaneously, accurate control on the contact between the silicon wafers and etching cleaning liquid is not needed in most etching process links, the cleaning efficiency is greatly improved, and the production efficiency is further improved.

According to the method for preparing the silicon wafer surface composite film, the growth temperature difference of each layer of film is small, so that the temperature suitable for the growth of the interlayer film can be adjusted under the condition that PECVD equipment is not withdrawn. Compared with other processes (after one layer of film is grown, the silicon wafer is moved out of the equipment and correspondingly treated, and then returned to the reaction chamber to grow the next layer of film), the method and the device for preparing the composite film on the surface of the silicon wafer by using the PECVD equipment can produce the multilayer film in situ in the reaction chamber of the PECVD, namely, the reaction chamber does not need to be withdrawn midway in the growth process of the composite film on the surface of the silicon wafer, after the growth of the composite film on the surface of the silicon wafer is finished, the silicon wafer is removed from the PECVD equipment, and the influence of environmental difference (such as temperature, air quality and the like) caused by repeatedly entering the reaction chamber on the quality of the silicon wafer and the composite film can be avoided. The preparation method can simplify the process flow, thereby improving the production efficiency and improving the quality of the silicon wafer back composite film.

The embodiment of the second aspect of the invention discloses a preparation method of a TOPCon solar cell, which comprises the following specific steps:

1. texturing a silicon wafer for one time;

2. b diffusing the front side of the silicon wafer;

3. removing BSG (borosilicate glass) on the back surface of the silicon wafer, and performing secondary texturing;

4. preparing a silicon wafer back composite film by using the method in the embodiment of the first aspect of the invention;

5. annealing at 800-1000 deg.c; doping atoms of the doped ploy layer are activated and diffused at high temperature, so that a proper doping concentration curve is obtained, and the photoelectric conversion efficiency is improved.

6. Etching; and in the etching process, removing impurities on the front side of the silicon wafer and the mask layer on the back side of the silicon wafer by using cleaning liquid.

7. Depositing aluminum oxide and silicon nitride on the front side of the silicon wafer;

8. depositing silicon nitride on the back of the silicon wafer;

9. printing and sintering.

Compared with the technical route of LPCVD (low pressure chemical vapor deposition), the technology of preparing the TOPCon solar cell by the PECVD route is simpler, the production speed can be improved, the monomer productivity can be greatly improved, and the reject ratio of the product is low.