阅读说明：本技术 检验板式pecvd微波能力的方法 (Method for testing plate type PECVD microwave capability ) 是由 朱少杰 王贵梅 赵江雷 于 2020-05-12 设计创作，主要内容包括：本发明公开一种检验板式PECVD微波能力的方法,包括步骤：S1、设计镀膜参数；S2、选取待测石英管,仅开启待测石英管的单一端微波系统,同时通入反应气,采用镀膜参数对硅片进行镀膜,获取测试片样本；S3、逐一对每根石英管每端的微波系统循环操作S2；S4、分别选取各组测试片样本上平行于微波传导方向的同一列测试片作为测试列,检测各测试列中各个测试片的膜厚,若测试列中膜厚最大值与最小值的差值不大于20nm,则与之对应的待测石英管测试端微波能力正常；若否,则与之对应的待测石英管的测试端微波能力异常。本发明提供的方法可以精准锁定微波传导异常的石英管,以及发生异常的微波端,排查出镀膜不均匀、产能降低的原因。(The invention discloses a method for testing plate type PECVD microwave capacity, which comprises the following steps: s1, designing coating parameters; s2, selecting a quartz tube to be tested, only starting a single-end microwave system of the quartz tube to be tested, simultaneously introducing reaction gas, and coating a silicon wafer by adopting coating parameters to obtain a test wafer sample; s3, circulating the microwave system at each end of each quartz tube one by one S2; s4, respectively selecting the same row of test pieces parallel to the microwave conduction direction on each group of test piece samples as test rows, detecting the film thickness of each test piece in each test row, and if the difference value between the maximum value and the minimum value of the film thickness in each test row is not more than 20nm, enabling the microwave capability of the test end of the corresponding to-be-tested quartz tube to be normal; if not, the microwave capability of the corresponding test end of the quartz tube to be tested is abnormal. The method provided by the invention can accurately lock the quartz tube with abnormal microwave conduction and the abnormal microwave end, and find out the reasons of uneven coating and reduced productivity.)

1. A method for testing plate type PECVD microwave capability is characterized by comprising the following steps:

s1, designing coating parameters under the condition that a single-end microwave system of a single normal quartz tube provides the microwave power required by coating, so that the thickness of the generated coating is 50-100 nm;

s2, selecting one quartz tube as a quartz tube to be tested, closing the microwave systems on the other quartz tubes, only opening the microwave system at the single end of the quartz tube to be tested, simultaneously introducing reaction gas into the quartz tube to be tested, and adopting the film coating parameters in S1 to coat the silicon wafer to obtain a test piece sample;

s3, circularly operating the microwave system at each end of each quartz tube one by one S2 to respectively obtain test piece samples corresponding to one;

s4, respectively selecting the same row of test pieces parallel to the microwave conduction direction on each group of test piece samples as test rows, detecting the film thickness of each test piece in each group of test rows, longitudinally comparing the film thicknesses, and if the difference value between the maximum value and the minimum value of the film thickness in each test row is not more than 20nm, enabling the microwave capability of the test end of the corresponding to-be-tested quartz tube to be normal; if not, the microwave capability of the corresponding test end of the quartz tube to be tested is abnormal.

2. The method according to claim 1, wherein S4 further comprises detecting the refractive index of each test strip in each group of the test columns, and finding out the test columns with the significant abnormality of the film thickness and/or refractive index and other groups by transversely comparing the film thickness and the refractive index of the test strips in each group of the test columns, thereby correspondingly judging the quartz tubes with the abnormality of the special gas flow meter.

Wherein the apparent anomaly comprises: the film thickness and the refractive index of the test piece in the test column are in positive correlation; or the film thickness and the refractive index of each test piece in the test columns are in negative correlation, but the film thickness of each test piece in one test column is different from the film thickness of other test columns by more than 10 nm.

3. The method of claim 1, wherein the coating parameters include microwave power, flow rate of the reaction gas, phase, belt speed, ratio of microwave on-time to microwave off-time pulses; wherein the microwave power is 3000-4000W; the reaction gas comprises NH₃And SiH₄NH of said₃The flow rate of the SiH is 500-700sccm₄The flow rate of the (C) is 200-300 sccm; the phase is 30-80 degrees; the belt speedIs 40-60 cm/min; the ratio is 8: 8.

4. The method of claim 3, wherein the microwave power is 3500W; the reaction gas comprises NH₃And SiH₄NH of said₃At a flow rate of 600sccm, the SiH₄The flow rate of (2) is 250 sccm; the phase is 50 degrees; the belt speed is 50 cm/min; the ratio is 8: 8.

5. The method of claim 1, wherein the silicon wafer in S2 is a single crystal silicon wafer or a polycrystalline silicon wafer.

6. The method of claim 1, wherein the silicon wafer is subjected to at least the steps of texturing, diffusing, removing back and surrounding PN junctions, and removing PSG and/or BSG before plating in S2.

7. The method of claim 6, wherein the silicon wafer in S2 is further superimposed with one or more of an alumina deposition, thermal oxidation or SE laser step prior to coating.

Technical Field

The invention relates to the technical field of silicon cell manufacturing, in particular to a method for testing plate type PECVD microwave capacity.

Background

The principle of plate PECVD deposition of silicon nitride films is to ionize a gas containing film-forming atoms by microwaves to form a plasma to react, thereby depositing a desired thin film on a substrate. The microwave capability determines whether the deposition of the silicon nitride film can reach the standard or not on the basis of a large factor.

The microwave refers to electromagnetic wave with the frequency of 300 MHz-300 GHz, and the capacity of the microwave shows a decreasing trend along with the increase of the transmission distance. Under normal conditions, the linear microwave power gradually declines along the direction of the quartz tube from the input end; however, when the hardware such as the quartz tube is abnormal, the decline trend of the microwave power is suddenly changed, thereby affecting the microwave capability and causing the coating effect of the substrate to be different.

The existing plate-type PECVD reaction chamber usually uses six quartz tubes and a copper antenna to form a coaxial system, when in work, reaction gas is introduced into the six quartz tubes simultaneously, and microwaves at two ends of each quartz tube are started to form a high-frequency electric field, so that the reaction gas in each quartz tube is ionized into plasma which is attached to the surface of a silicon wafer to form a silicon nitride film. At present, when industrialized PECVD enterprises perform obstacle elimination on quartz tubes, a relative judgment method is mostly adopted, and the method comprises the following steps: (1) firstly, designing proper technological parameters, independently opening an extra-gas input channel of each quartz tube, simultaneously opening microwaves at two ends of each quartz tube, and testing the film thickness and the refractive index of each quartz tube; circulating in this way, and collecting the film thickness and the refractive index of each quartz tube through 6 times of detection; (2) transversely comparing the film thicknesses and the refractive indexes of the six groups of quartz tubes, and if the data of one quartz tube is obviously different from the data of the other quartz tubes, preliminarily judging that the special gas flowmeter of the quartz tube is possibly abnormal; (3) measures are taken to solve the abnormal quartz tube.

According to the method, the phenomenon that the special gas flow meter of the quartz tube is seriously too high or too low is judged through mismatching of the film thickness and the refractive index data of a certain quartz tube, so that the reason that the conversion efficiency of a PECVD device for producing the cell is low is checked; but the problems of uneven coating and color difference in the production process cannot be solved, because when the data of each group of quartz tubes are transversely compared by adopting the method, obvious data abnormity does not occur, it is impossible to find out which quartz tube is out of order and affects the microwave capability of the whole equipment, meanwhile, the microwave capability of accurately locking which end of the quartz tube is weakened, and no corresponding troubleshooting method exists at present, so that, when the microwave conduction is abnormal during the deposition of the silicon nitride film, it is generally adopted in such a manner that all the quartz tubes are blindly replaced, which undoubtedly increases the production cost, even if the quartz tube is replaced, the problem of uneven color difference of the coating film caused by abnormal microwave conduction cannot be fundamentally solved, so that a method for accurately checking and verifying the microwave capacity is urgently needed.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides a method for inspecting the microwave capacity of a plate type PECVD (plasma enhanced chemical vapor deposition), which can accurately lock a quartz tube with abnormal microwave conduction and a microwave end with abnormal microwave, and find out the reasons of uneven coating and reduced productivity.

In order to achieve the above purpose, the invention provides the following technical scheme:

a method for testing plate type PECVD microwave capability comprises the following steps:

s1, designing coating parameters under the condition that a single-end microwave system of a single normal quartz tube provides the microwave power required by coating, so that the thickness of the generated coating is 50-100 nm;

s2, selecting one quartz tube as a quartz tube to be tested, closing the microwave systems on the other quartz tubes, only opening the microwave system at the single end of the quartz tube to be tested, simultaneously introducing reaction gas into the quartz tube to be tested, and adopting the film coating parameters in S1 to coat the silicon wafer to obtain a test piece sample;

s3, circularly operating the microwave system at each end of each quartz tube one by one S2 to respectively obtain test piece samples corresponding to one;

s4, respectively selecting the same row of test pieces parallel to the microwave conduction direction on each group of test piece samples as test rows, detecting the film thickness of each test piece in each group of test rows, longitudinally comparing the film thicknesses, and if the difference value between the maximum value and the minimum value of the film thickness in each test row is not more than 20nm, enabling the microwave capability of the test end of the corresponding to-be-tested quartz tube to be normal; if not, the microwave capability of the corresponding test end of the quartz tube to be tested is abnormal.

Of course, in addition to the microwave capability of the quartz tube determined by measuring the film thickness and longitudinally comparing, in practical application, the microwave capability may also be determined by transversely comparing the variation trends of the colors of the coating films on the test columns, specifically: if the color change trend of each test row in the S4 gradually becomes lighter from dark to light, the microwave capability of the corresponding test end of the quartz tube to be tested is normal; if there is sudden change, the corresponding quartz tube to be tested is abnormal. The method can be used as an auxiliary means for visually screening and rapidly and roughly locking the abnormal quartz tube, and the final judgment result is judged by a longitudinal comparison result of the test column film thickness.

As an optional embodiment, S4 further includes detecting the refractive index of each test strip in each group of test columns, and by transversely comparing the film thickness and the refractive index of the test strips in each group of test columns, finding out a test column in which the film thickness and/or the refractive index are obviously abnormal with those of other groups, and further correspondingly judging the quartz tube in which the special gas flow meter is abnormal;

the significant anomalies include: the film thickness and the refractive index of the test piece in the test column are in positive correlation; or the film thickness and the refractive index of each test piece in the test columns are in negative correlation, but the film thickness of each test piece in one test column is different from the film thickness of other test columns by more than 10 nm.

As an optional embodiment, the coating data includes microwave power, flow rate of the reaction gas, phase, belt speed, ratio of microwave on-time to microwave off-time pulse;

wherein the microwave power is 3000-4000W; the reaction gas comprises NH₃And SiH₄NH of said₃The flow rate of the SiH is 500-700sccm₄The flow rate of the (C) is 200-300 sccm; the phase is 30-80 degrees; the ratio is 8: 8; the belt speed is 40-60 cm/min.

As an alternative implementationFor example, the microwave power is 3500W; the reaction gas comprises NH₃And SiH₄NH of said₃At a flow rate of 600sccm, the SiH₄The flow rate of (2) is 250 sccm; the phase is 50 degrees; the belt speed is 50 cm/min; the ratio is 8: 8.

SCCM (Standard Cubic centrimeter per minute) is expressed in standard milliliters per minute.

As an alternative example, the silicon wafer in S2 is a single crystal silicon wafer or a polycrystalline silicon wafer.

As an alternative embodiment, the silicon wafer in S2 is subjected to at least the steps of texturing, diffusing, removing PN junctions on the back and around, and removing PSG and/or BSG before plating.

As an alternative embodiment, the silicon wafer in S2 is further stacked with one or more steps of alumina deposition, thermal oxidation or SE laser step before plating.

Compared with the prior art, the invention has the following beneficial effects:

the plate-type PECVD microwave capability inspection method provided by the invention can accurately lock the quartz tube with abnormal microwave conduction and the abnormal microwave end, can be used as a method for checking uneven coating and low productivity, and the reason of the problem can be determined by adopting the detection result obtained by the invention, so that the problem part can be maintained in a targeted manner, the problems of poor quality caused by color difference due to uneven PECVD coating caused by abnormal microwave conduction and the problem of influence on productivity caused by low belt speed due to abnormal microwave are effectively solved, the performance of the silicon nitride antireflection passivation film is improved, and the productivity is improved.

When the method is adopted for detection, the design idea is as follows: firstly, setting coating parameters required by detection, wherein the setting basis of the coating parameters is to provide the microwave power required by coating for a single-end microwave system of a single normal quartz tube, so that the coating parameters can be used as standard parameters for subsequently detecting the microwave capacity of each end of each quartz tube, and a coating with the thickness of 50-100nm can be generated when the microwave capacity of the single end of the single quartz tube is detected by adopting the coating parameters, and the coating with the thickness can meet the identification of a subsequent detection tool, so that the accuracy of basic data is improved, and the comparison precision is further improved;

then only opening reaction gas corresponding to a certain quartz tube to be detected during detection, and coating the silicon wafer by using the microwave system at the single end of the quartz tube to be detected, namely closing the microwave systems of other quartz tubes except the quartz tube to be detected, providing microwave power required by coating by using the microwave system at one end of the quartz tube to be detected only, and then obtaining a test piece with the film thickness of 50-100nm according to set coating parameters, such as temperature, gas flow, belt speed, phase and other process parameters; circulating the steps, detecting each end of all the quartz tubes one by one, and obtaining test piece samples corresponding to one by one; then, respectively selecting the same row of test pieces parallel to the microwave conduction direction on each group of test piece samples as test columns, detecting the film thickness of each test piece in each group of test columns, and longitudinally comparing the film thicknesses, wherein if the difference value between the maximum value and the minimum value of the film thickness in each test column is not more than 20nm, the microwave capability of the test end of the corresponding to-be-tested quartz tube is normal; if not, the microwave capability of the test end of the quartz tube to be tested corresponding to the quartz tube to be tested is abnormal, and naturally, before the film thickness is detected, the change trend of the color of the coating film on each test line can be transversely compared for judgment, specifically: if the color change trend of each test row in the S4 gradually becomes lighter from dark to light, the microwave capability of the corresponding test end of the quartz tube to be tested is normal; if there is sudden change, the corresponding quartz tube to be tested is abnormal. The judging method can be used as an auxiliary means, the abnormal quartz tube can be visually screened and rapidly and roughly locked, then the film thickness of the test column corresponding to the quartz tube roughly locked is detected, longitudinal comparison is carried out, and finally the abnormal end of the abnormal quartz tube is precisely locked, so that the judging time can be saved.

Compared with the prior art, the method judges the microwave capability by longitudinally comparing the thickness of the coating film at each end of each quartz tube when the microwave system is started, not only can find out an abnormal quartz tube, but also can accurately lock the abnormal end of the abnormal quartz tube; in addition, the method can also simultaneously check the abnormal quartz tube of the special gas flow meter, and the method comprises the steps of detecting the refractive index of each test piece in each group of test columns, transversely comparing the film thickness and the refractive index of the test piece in each group of test columns, and if the film thickness and the refractive index of the test piece in each group of test columns are in positive correlation; or the film thickness and the refractive index of each test piece in the test column are in negative correlation, but the film thickness of each test piece in a certain test column is obviously larger or smaller than that of other test columns, the abnormality of the quartz tube special gas flow meter corresponding to the test column can be judged, so that the abnormality of the special gas flow meter caused by the reasons of efficiency reduction, belt speed reduction, capacity reduction and the like is found, and further, targeted measures can be taken to improve the capacity and the conversion efficiency.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic view of a coating process according to an embodiment of the present invention.

Description of reference numerals:

1. a first quartz tube; 2. a second quartz tube; 3. a third quartz tube; 4. a fourth quartz tube; 5. a fifth quartz tube; 6. a sixth quartz tube; 7. a microwave system; 8. testing the sheet sample; 81. test columns.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.

In addition, the technical features involved in the different embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.