Method for growing low-temperature silicon nitride thin film by utilizing AMAT Center DxZ CVD (Chemical Vapor Deposition) equipment

Abstract

The invention provides a method for growing a low-temperature silicon nitride film by utilizing AMAT Center DxZ CVD (Chemical Vapor Deposition) equipment. The method comprises the following steps: providing a substrate; the cavity temperature of the equipment is controlled to be 150-200 DEG C, and the pressure of the cavity is controlled to be first pressure; transferring the substrate into the cavity, and controlling the distance between the substrate and the upper part of the cavity to be a first distance; the pressure of the cavity is controlled to be 2-5 Torr, reaction gas and N2 are introduced and stabilized for a first preset duration, and the silicon nitride film grows. Deposition of the low-temperature silicon nitride film and regulation and control of stress can be achieved under the condition that original equipment for high-temperature silicon nitride deposition is not transformed.

Description

Technical Field

[0001] The present application relates to the field of semiconductor manufacturing, and in particular to a method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device. Background Art

[0002] Plasma, also known as plasma, is an ionized gaseous substance composed of positive and negative ions generated by the ionization of atoms and atomic groups that have been deprived of some electrons. It has strong chemical activity and can enable chemical reactions to proceed at lower temperatures. Based on this, plasma enhanced chemical vapor deposition (PECVD) technology is widely used in semiconductor manufacturing processes. PECVD is a technology that uses radio frequency to ionize the reaction gas in the cavity into plasma and deposits a thin film on the substrate under appropriate temperature, pressure and other conditions.

[0003] PECVD technology has the characteristics of low temperature, fast film formation rate, controllable film thickness, good film uniformity, etc. It can be used to deposit thin film materials commonly used in various semiconductor devices such as silicon oxide, silicon nitride, silicon carbide, etc. It is widely used in semiconductor production fields such as IC (integrated circuit) and MEMS (Micro-Electro-Mechanical System). Among these thin film materials, silicon nitride materials are widely used in semiconductor devices due to their excellent anti-oxidation and anti-corrosion properties, excellent barrier properties and controllable film stress. In the actual production process, it is often necessary to adjust the growth conditions of silicon nitride thin film materials to meet the device design requirements.

[0004] In the current wafer manufacturing industry, PECVD equipment mainly comes from companies such as Applied Materials (AMAT) and Lam Research (LAM). AMAT Centura DxZ chamber is a commonly used PECVD deposition equipment. The reaction gases silane (SiH4) and ammonia (NH3) are introduced into the equipment chamber to generate a silicon nitride film on the wafer surface under appropriate pressure and temperature conditions. The reaction equation can be expressed as: SiH4+NH3+N2→SiN x:H. However, the mature process of the AMAT Centura DxZ chamber is to deposit silicon nitride film at 400°C. However, due to special design requirements, some devices require silicon nitride deposition process at low temperature. In addition, due to device design requirements, the grown low-temperature silicon nitride film needs to be able to adjust different stress conditions. At this time, the AMAT Centura DxZ chamber lacks relevant supporting processes. In this case, you can choose to purchase other specialized low-temperature silicon nitride deposition equipment for the process, but this will bring additional cost investment. If such low-temperature silicon nitride process can be developed on the existing AMATCentura DxZ chamber, the cost investment and development speed can be greatly reduced.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of the present application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section of the present application. Summary of the invention

[0006] The object of the present invention is to provide a new process for realizing the deposition of low-temperature silicon nitride film without modifying the original AMATCentura DxZ CVD equipment for high-temperature silicon nitride deposition.

[0007] In order to solve the above problems, a method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device is provided below, comprising the following steps:

[0008] S1. providing a substrate;

[0009] S2, controlling the cavity temperature of the device to be between 150-200° C., and controlling the cavity pressure to be a first pressure;

[0010] S3, introducing the substrate into the cavity, and controlling the distance between the substrate and the upper part of the cavity to be a first distance;

[0011] S4, controlling the pressure of the chamber to be between 2-5 Torr, introducing reaction gas and N2 and stabilizing them for a first preset time, and growing a silicon nitride film.

[0012] Before step S2, the interior of the cavity is cleaned.

[0013] The first pressure is less than 0.02 Torr.

[0014] The first distance is 250-1000 mils.

[0015] After step S3, a preheating process is also included, during which N2 is introduced as a preheating gas and stabilized for a second preset time.

[0016] The reaction gas includes SiH 4 and NH 3 , and the flow ratio of SiH 4 to NH 3 is between 1:1 and 4:1.

[0017] In step S4, the radio frequency is turned on after being stabilized for a first preset time, and the power of the radio frequency is between 300-1200W.

[0018] The N2 flow rate during the preheating process is consistent with the N2 flow rate in step S4; the first preset time length is 5-15s, and the second preset time length is 20-40s.

[0019] The substrate is a silicon wafer, which is cleaned before being introduced into the cavity.

[0020] The average pressure of the silicon nitride film ranges from -500 to 200 MPa.

[0021] Compared with the prior art, the beneficial effects of the present invention mainly include the following: low-temperature silicon nitride film deposition can be achieved without modifying the original AMAT Centura DxZ CVD equipment for high-temperature silicon nitride deposition. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 Schematic diagram of the preparation process of low-temperature silicon nitride film provided in this application.

[0024] Figure 2 The silicon nitride film thickness and uniformity repeatability data provided in Example 1.

[0025] Figure 3 The stress repeatability data of silicon nitride film provided in Example 1. DETAILED DESCRIPTION

[0026] The above and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of a preferred embodiment with reference to the drawings. The directional terms mentioned in the following embodiments, such as up, down, left, right, front or back, etc., are only referenced to the directions of the attached drawings. Therefore, the directional terms used are used to illustrate and not to limit the present invention.

[0027] The following will describe the various embodiments of the present application in detail with reference to the accompanying drawings. However, it will be appreciated by those skilled in the art that in the various embodiments of the present application, many technical details are provided in order to enable the reader to better understand the present application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solution claimed in the present application can be implemented.

[0028] The steps in the following embodiments do not correspond one to one with the summary of the invention.

[0029] Due to special design requirements, some devices require a silicon nitride deposition process at low temperature, and due to device design requirements, there are also requirements for the stress conditions of the formed low-temperature silicon nitride film. Among the current silicon nitride film deposition equipment, most are high-temperature deposition equipment. Taking the AMAT Centura DxZ chamber as an example, its mature process is to deposit silicon nitride films at 400°C. At this time, the AMAT Centura DxZ chamber lacks relevant supporting processes, and other specialized low-temperature silicon nitride deposition equipment is required for the process, but this will bring additional cost investment. Therefore, this application develops such a low-temperature silicon nitride process based on the existing AMAT Centura DxZ chamber, which can greatly reduce cost investment and development speed.

[0030] This application provides a new process that can achieve the deposition of low-temperature silicon nitride films without modifying the original AMATCentura DxZ CVD equipment for high-temperature silicon nitride deposition. In this case, silicon nitride films can be deposited at conditions below 400°C, and by adjusting the process parameters, the various properties of the silicon nitride film can be adjusted to meet the design requirements of different devices. Through this solution, the coexistence of high and low temperature silicon nitride deposition processes on the AMAT Centra CVD equipment can be achieved, reducing cost investment.

[0031] It is understandable that at low temperatures, especially below 350°C, the reactivity of silane decreases severely, and the parameter adjustment direction becomes difficult to predict compared to normal high-temperature reaction conditions, and film formation is even more impossible by directly using the parameters under high-temperature processes. This application takes the AMAT Centra CVD equipment as an example to provide a preferred parameter range for generating stress-adjustable low-temperature silicon nitride films below 350°C, especially at 150-200°C.

[0032] Specifically, the optimal parameter range of the achievable process program is as follows:

[0033] The process temperature is set between 150 and 200°C;

[0034] The chamber pressure is set to 2 to 5 Torr;

[0035] The flow ratio of the reaction gases silane (SiH4) and ammonia (NH3) ranges from 1:1 to 4:1, with nitrogen as the diluent gas;

[0036] The RF power was set between 300W and 1200W;

[0037] During the reaction, the distance between the wafer and the upper part of the chamber (ie, the first distance) is set to be between 250-1000 mils.

[0038] Among them, Torr is millimeters of mercury and mils is milliinches.

[0039] The following is a detailed description with specific embodiments.

[0040] Embodiment 1

[0041] The present invention provides a method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device, wherein the method comprises: Figure 1 The flowchart shown includes the following steps:

[0042] Step 1: Provide a PECVD chamber and clean the inside of the chamber.

[0043] In this embodiment, the thin film deposition equipment used is an AMAT Centra DxZ CVD equipment, and the inside of the cavity is first cleaned. There are many ways to complete the cavity cleaning. For example, the prior art generally uses the cleaning process of the PECVD equipment, that is, by inputting a cleaning gas to generate plasma to etch the cavity to remove possible residual particles and silicon-containing compounds.

[0044] Step 2: After the temperature inside the cavity is raised to a predetermined process temperature, the inside of the cavity is evacuated until a first pressure is reached.

[0045] In this embodiment, the process temperature is 200°C, that is, the temperature is first raised to 200°C and kept stable, and then the chamber is evacuated to a first pressure (<0.02torr). In this embodiment, the first pressure can be 1mTorr-10mTorr to ensure that the clean gas in the chamber is completely exhausted.

[0046] Step 3: Provide a substrate, introduce the substrate into the process chamber and place it on a susceptor, and then perform a preheating treatment.

[0047] In this embodiment, the substrate is a silicon wafer. In this embodiment, the AMAT Centra DxZ CVD equipment is a common equipment for 8-inch wafers, and the substrate used is an 8-inch silicon wafer. It can be understood that in other embodiments, the wafer can be an intrinsic wafer or a doped wafer; it can be a semiconductor wafer such as a germanium wafer, a germanium silicon wafer or an SOI wafer; and the substrate can be a bare wafer or a wafer with other semiconductor structure layers formed on the surface. Before using the substrate, it is usually cleaned to remove surface particles.

[0048] After the substrate is introduced into the chamber and reaches the reaction position (in this embodiment, the distance between the substrate and the upper part of the chamber is controlled to be 400 mils), a preheating treatment is performed. Generally speaking, the temperature of the preheating treatment is the same as or close to the process temperature during the thin film deposition. For example, in this embodiment, the preheating temperature and the process temperature are both 200°C.

[0049] When the substrate is placed in the chamber for preheating, the preheating gas is introduced and stabilized for a second preset time. The preheating gas here is nitrogen (N2) with a flow rate of 1200 sccm (sccm is standard cubic centimeters per minute), so that the chamber pressure is 2.5 torr. Stabilization for a certain period of time here is to ensure the stability of the gas flow rate, because the gas usually fluctuates when it is first introduced and cannot reach the proportion we actually set. After a period of continuous flow, a relatively accurate value can be maintained. It can be understood that the second preset time here is equal to the preheating time, and the specific length of this time can be confirmed according to the temperature of the process. For example, in this embodiment, the second preset time is 30s; in other embodiments, the second preset time is 20-40s.

[0050] In this embodiment, nitrogen is used as the preheating gas, which is also the reaction source gas in the subsequent reaction process. The introduction of the preheating gas first can further remove the previous cleaning gas and help stabilize the subsequent reaction atmosphere.

[0051] Step 4: Introduce reaction gas and perform thin film deposition.

[0052] In this embodiment, the reaction gases used are silane (SiH4) and ammonia (NH3). First, the reaction gases are introduced, and the flow rates of the two gases are 150 sccm for silane and 40 sccm for ammonia, respectively. After stabilization for 10 seconds, the RF is turned on to start growth. In this embodiment, the RF power is 500 W and the growth time is 9 seconds.

[0053] It can be understood that during the reaction process, nitrogen also maintains the original flow rate, that is, the gases actually introduced at this time include nitrogen, silane and ammonia, and the corresponding flow rates are 1200sccm, 150sccm and 40sccm. The reaction gas and nitrogen are introduced and stabilized for the first preset time before turning on the radio frequency for growth, mainly to ensure the stability of the proportion of each gas during the reaction. This stabilization time can be adjusted according to actual conditions. For example, in other embodiments, the first preset time is 5-15s; similarly, the growth time of the film can also be adaptively adjusted according to the actual required thickness. In this embodiment, the target film thickness is 80nm, so the corresponding growth time is 9s.

[0054] The above is the preparation process of the low temperature silicon nitride film in this embodiment. The prepared silicon nitride film was analyzed. For repeatability testing, a total of 10 wafers were selected. The results are as follows: Figure 2 and Figure 3 The results of film thickness and uniformity are shown in Figure 2 As shown, the average stress data of the film is Figure 3 shown.

[0055] It can be seen that in the repeatability test results, the thickness of the silicon nitride film is close to the target value of 80nm, and the uniformity is <3%, and the stress is stable at 100±20MPa, which meets the general IC, MEMS and other industry specifications.

[0056] Further, based on Example 1, when the thickness and uniformity are basically the same, by adjusting the RF power, gas ratio and other parameters, silicon nitride films with different stresses can be obtained to meet the stress requirements of different design structures. The process provided in this application can obtain a low-temperature silicon nitride film with an average stress range of -500 to 200Mpa.

[0057] Embodiment 2

[0058] In the second embodiment, the basic steps are the same as those in the first embodiment, except that the RF power during the thin film growth is 600 W, and the corresponding test results are: film thickness 79.3 nm, film thickness uniformity 2.19%, and average stress -290 MPa.

[0059] Embodiment 3

[0060] In the third embodiment, the basic steps are the same as those in the first embodiment, except that the RF power during the thin film growth is 400 W, and the corresponding test results are: film thickness 79.4 nm, film thickness uniformity 1.84%, and average stress 98 MPa.

[0061] Embodiment 4

[0062] In this embodiment 4, the basic steps are the same as those in embodiment 1, with the difference being that the RF power during thin film growth is 400 W, the silane flow rate is 120 sccm, the ammonia flow rate is 80 sccm, and the corresponding test results are: film thickness 80.4 nm, film thickness uniformity 1.65%, and average stress 204 MPa.

[0063] Embodiment 5

[0064] In this embodiment five, the basic steps are the same as those in embodiment one, with the difference being that the RF power during thin film growth is 375 W, the silane flow rate is 120 sccm, the ammonia flow rate is 110 sccm, and the nitrogen flow rate is 1600 sccm. The corresponding test results are: film thickness 80.3 nm, film thickness uniformity 1.65%, and average stress 204 MPa.

[0065] Embodiment 6

[0066] This embodiment provides process parameters at another temperature. The basic steps are the same as those in Embodiment 1, with the following differences: the process temperature is 150°C, the chamber pressure during deposition is 2.3 Torr, the silane flow rate is 120 sccm, the ammonia flow rate is 110 sccm, the nitrogen flow rate is 1500 sccm, the RF power is 375 W, and the first distance is 350 mils.

[0067] In order to facilitate the description, some common English nouns or letters used in the present invention are only used for exemplary reference rather than restrictive interpretation or specific usage, and the protection scope of the present invention should not be limited by their possible Chinese translations or specific letters.

[0068] It should also be noted that, in this document, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

Claims

1. A method for growing low-temperature silicon nitride thin films using an AMAT Centra DxZ CVD device, characterized in that: The steps include: S1. providing a substrate; S2, controlling the cavity temperature of the device to be between 150-200° C., and controlling the cavity pressure to be a first pressure; S3, introducing the substrate into the cavity, and controlling the distance between the substrate and the upper part of the cavity to be a first distance; S4, controlling the pressure of the chamber to be between 2-5 Torr, introducing reaction gas and N2 and stabilizing them for a first preset time, and growing a silicon nitride film.

2. The method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device according to claim 1, characterized in that: Before step S2, the interior of the cavity is cleaned.

3. The method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device according to claim 1, characterized in that: The first pressure is less than 0.02 Torr.

4. The method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device according to claim 1, characterized in that: The first distance is 250-1000 mils.

5. The method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device according to claim 1, characterized in that: After step S3, a preheating process is also included, during which N2 is introduced as a preheating gas and stabilized for a second preset time.

6. The method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device according to claim 1, characterized in that: The reaction gas includes SiH 4 and NH 3 , and the flow ratio of SiH 4 to NH 3 is between 1:1 and 4:

1.

7. The method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device according to claim 1, characterized in that: In step S4, the radio frequency is turned on after being stabilized for a first preset time, and the power of the radio frequency is between 300-1200W.

8. The method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device according to claim 5, characterized in that: The N2 flow rate during the preheating process is consistent with the N2 flow rate in step S4; the first preset time length is 5-15s, and the second preset time length is 20-40s.

9. The method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device according to claim 1, characterized in that: The substrate is a silicon wafer, which is cleaned before being introduced into the cavity.

10. The method for growing a low-temperature silicon nitride film using an AMAT Centra DxZ CVD device according to claim 1, characterized in that: The average pressure of the silicon nitride film ranges from -500 to 200 MPa.

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