Wafer with amorphous phase carbon film deposited on back surface and preparation method and application thereof

Abstract

The invention belongs to the field of semiconductors, and particularly relates to a wafer with an amorphous phase carbon film deposited on the back face and a preparation method and application of the wafer. An amorphous phase carbon film is deposited on the back surface of the wafer. According to the invention, the selectivity of depositing the film on the back of the traditional wafer can be improved. Compared with SiN, SiO and an amorphous phase carbon film, the stress and the warping of the amorphous phase carbon film are similar to those of the SiN under the condition of the same film thickness, and the stress neutralization (along with the accumulation of the film thickness and the increase of the process temperature, the requirements of higher stress and warping can be met) of a process sheet or a structure sheet with relatively large warping can be realized. The amorphous phase carbon film has good adhesive force at a high temperature, and deposition of a thin film with the thickness of # imgabs0 # or above can be achieved. SiN and SiO thin films deposited on the back surface of the wafer need to be removed through a (phosphoric acid or hydrofluoric acid) wet method, an amorphous phase carbon film can be removed in situ by reacting with oxygen ions under plasma excitation, and a byproduct is mainly carbon dioxide.

Description

Technical Field

[0001] The invention belongs to the field of semiconductors, and in particular relates to a wafer with an amorphous carbon film deposited on the back thereof, and a preparation method and application thereof. Background Art

[0002] In the existing semiconductor technology, thin films are deposited on the back of the wafer through processes such as CVD and ALD, and the stress of the back film is used to balance the warping problem caused by the front film formation. The existing films deposited on the back of the wafer include silicon nitride (SiN), silicon oxide (SiO), etc. Taking SiN as an example, it is usually necessary to deposit A thin film is used to offset the warping of the previous process or structural piece, and then it is removed by wet method (phosphoric acid or hydrofluoric acid). The film deposition time is long and the removal process is complicated.

[0003] In the above-mentioned wafer backside thin film deposition process, SiN is widely used, but a thicker film needs to be deposited to offset the greater stress and warpage, and the removal process is complicated. Therefore, there is an urgent need in the art to develop a new wafer preparation method that can overcome the warpage problem caused by film deposition on the front side of the wafer. Summary of the invention

[0004] The purpose of the present invention is to provide a wafer with an amorphous carbon film deposited on the back thereof, and a preparation method and application thereof.

[0005] According to a first aspect of the present invention, a wafer is provided, an amorphous carbon film being deposited on the back side of the wafer.

[0006] In one or more embodiments, the thickness of the crystalline carbon film is

[0007] In one or more embodiments, the amorphous carbon film has a stress of -900 to -1500 MPa.

[0008] In one or more embodiments, the amorphous carbon film has a wafer warpage value of -100 to -1500 μm.

[0009] In one or more embodiments, a thin film is deposited on the front side of the wafer, or a thin film is not deposited on the front side of the wafer.

[0010] The second aspect of the present invention provides a method for preparing the wafer described in the first aspect of the present invention, the method comprising the steps of: using acetylene or propylene as a deposition gas to deposit an amorphous carbon film on the back side of the wafer.

[0011] In one or more embodiments, the flow rate of acetylene is 50 to 500 sccm.

[0012] In one or more embodiments, the flow rate of propylene is 50 to 500 seem.

[0013] In one or more embodiments, the deposition pressure is 1 to 10 Torr.

[0014] In one or more embodiments, the deposition temperature is 275-660°C.

[0015] In one or more embodiments, the deposition time is 30 to 1000 seconds.

[0016] In one or more embodiments, the radio frequency is single frequency, and the radio frequency power is 2000-3000W; or the radio frequency is dual frequency, and the high frequency power is 100-150W, and the low frequency power is 300-400W.

[0017] A third aspect of the present invention provides a method for preparing a wafer, comprising the steps of:

[0018] (1) Providing the wafer according to the first aspect of the present invention, and performing film deposition on the front side of the wafer;

[0019] (2) Use argon and oxygen as cleaning gases to remove the amorphous carbon film on the back of the wafer.

[0020] In one or more embodiments, the flow rate of oxygen is 500 to 15,000 sccm.

[0021] In one or more embodiments, the flow rate of argon gas is 500 to 12,000 sccm.

[0022] In one or more embodiments, the radio frequency power is 500-3000W.

[0023] In one or more embodiments, the removal temperature is 275-660°C.

[0024] In one or more embodiments, the removal pressure is 2 to 10 Torr.

[0025] In one or more embodiments, the removal time is 120 to 1000 seconds.

[0026] A fourth aspect of the present invention provides the use of depositing an amorphous carbon film on the back side of a wafer to improve wafer warpage that occurs when film formation is performed on the front side of the wafer.

[0027] The present invention has the following beneficial effects:

[0028] Amorphous carbon films have good physical and chemical properties and high internal stress, and can be removed in situ by plasma-induced oxygen, with high mechanical production capacity and low energy consumption.

[0029] Amorphous carbon films have good mechanical properties and high internal stress, a wide deposition temperature range (275-660°C), controllable process, and can be removed in situ with high efficiency and low loss. The steps are simple and easy to control, which can reduce the problems and potential risks caused by wet removal of SiN films.

[0030] The present invention can increase the selectivity of the traditional wafer backside deposition film. Compared with SiN, SiO and amorphous carbon films, under the same film thickness conditions, the stress and warpage of amorphous carbon films are similar to those of SiN, which can achieve stress neutralization of process sheets or structural sheets with larger warpage (with the accumulation of film thickness and the increase of process temperature, it can meet the requirements of higher stress and warpage). In order to obtain greater stress and warpage, it is usually necessary to continue to increase the film thickness, but the SiN film thickness exceeds After that, it is easy to fall off, which reduces the stretching effect on the back of the wafer and affects the cavity state. The amorphous carbon film has good adhesion at high temperature and can achieve The SiN and SiO films deposited on the back of the wafer need to be removed by wet method (phosphoric acid or hydrofluoric acid), while the amorphous carbon film can be removed in situ by reacting with oxygen ions under plasma excitation, and the main by-product is carbon dioxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of flattening the wafer by depositing an amorphous carbon film on the back side of the wafer.

[0032] Figure 2 It is a schematic diagram of the process of in-situ removal of the amorphous carbon film deposited on the back side of the wafer. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0034] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0035] Herein, “comprising”, “including”, “containing” and similar terms encompass the meanings of “consisting essentially of” and “consisting of”. For example, when “A comprises B and C” is disclosed herein, “A consists essentially of B and C” and “A consists of B and C” should be deemed to be disclosed herein.

[0036] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0037] In this document, unless otherwise specified, percentage refers to mass percentage and ratio refers to mass ratio.

[0038] Herein, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all substitutes, improvements and equivalents of the methods and materials described in the present invention can be included in the scope limited by the claims.

[0039] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0040] The present invention provides a process for depositing a thin film on the back of a semiconductor, which is based on the design of a traditional device for depositing SiN and SiO thin films on the back of a wafer. Amorphous carbon films have high hardness and Young's modulus, high internal stress, good optical properties, excellent chemical inertness and wear resistance, etc. Compared with SiN films, amorphous carbon films of the same thickness can obtain stress and warpage similar to SiN (referring to the warpage or bending of amorphous carbon films due to large stress). With the accumulation of film thickness and the increase of process temperature, higher stress and warpage requirements can be met. The amorphous carbon film deposition temperature range is wide, the process is controllable, and it can be removed in situ. The overall process is efficient and low-loss, the steps are simple, and it is easy to control, which can reduce the problems and potential risks caused by the wet removal of SiN films.

[0041] The invention provides a wafer, on the back side of which an amorphous carbon film is deposited.

[0042] In the wafer of the present invention, the thickness of the amorphous carbon film is For example

[0043] In the wafer of the present invention, the stress of the amorphous carbon film is -900 to -1500 MPa, for example, -950 MPa, -980 MPa, -990 MPa, -1000 MPa, -1200 MPa, -1250 MPa, -1300 MPa, and -1450 MPa.

[0044] In the wafer of the present invention, the wafer warpage value of the amorphous carbon film is -100 to -1500μm, for example, -120μm, -135μm, -150μm, -180μm, -250μm, -350μm, -500μm, -800μm, -900μm, -1000μm, -1100μm, and -1350μm.

[0045] In some embodiments, a thin film is deposited on the front side of the wafer. In other embodiments, no thin film is deposited on the front side of the wafer. In practical applications, an amorphous carbon film can be deposited on the back side of the wafer in advance according to the process requirements to prevent warping caused by front deposition, or a back side thin film can be deposited in the middle of the front thin film deposition process to flatten the warping that may be caused by the previous process and prevent warping caused by the subsequent front thin film deposition process.

[0046] The present invention also provides a method for preparing a wafer, the method comprising the steps of: using acetylene or propylene as a deposition gas to deposit an amorphous carbon film on the back side of the wafer.

[0047] In some embodiments, the flow rate of acetylene is 50 to 500 sccm, for example, 50 sccm, 80 sccm, 100 sccm, 120 sccm, 150 sccm, 180 sccm, 250 sccm, 350 sccm, 400 sccm, or 500 sccm.

[0048] In some embodiments, the flow rate of propylene is 50 to 500 sccm, for example, 100 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm.

[0049] In some embodiments, the deposition pressure is 1 to 10 Torr, for example, 1 Torr, 2 Torr, 3 Torr, 4 Torr, 5 Torr, 6 Torr, 7 Torr, 8 Torr, 9 Torr, or 10 Torr.

[0050] In some embodiments, the deposition temperature is 275-660°C, for example 275°C, 280°C, 300°C, 350°C, 400°C, 450°C, 550°C, 600°C, 650°C.

[0051] In some embodiments, the deposition time is 30 to 1000 s, for example, 30 s, 50 s, 80 s, 100 s, 120 s, 150 s, 180 s, 250 s, 350 s, 450 s, 560 s, 600 s, 700 s, or 800 s.

[0052] In some embodiments, the radio frequency is single frequency, and the radio frequency power is 2000-3000 W, for example, 2000 W, 2300 W, 2500 W, 2700 W, 3000 W. The frequency of the single frequency is fixed, and a conventional frequency in the art can be used.

[0053] In other embodiments, the radio frequency is dual-frequency, the high frequency power is 100-150W, and the low frequency power is 300-400W. The high frequency power can be 100W, 110W, 120W, 130W, 140W, 150W. The low frequency power can be 300W, 310W, 320W, 330W, 340W, 350W, 360W, 370W, 380W, 390W, 400W. When the radio frequency is dual-frequency, the frequency is fixed, the high frequency frequency is 13.56MHz, and the low frequency frequency is 400KHz.

[0054] The present invention also provides a method for preparing a wafer, comprising the steps of:

[0055] (1) providing a wafer of the present invention, and performing film deposition on the front side of the wafer;

[0056] (2) Use argon and oxygen as cleaning gases to remove the amorphous carbon film on the back of the wafer.

[0057] In some embodiments, the flow rate of oxygen gas is 500 to 15,000 sccm, for example, 500 sccm, 1,000 sccm, 2,000 sccm, 3,000 sccm, 4,000 sccm, 5,000 sccm, 6,000 sccm, 7,000 sccm, 8,000 sccm, 10,000 sccm, or 12,000 sccm.

[0058] In some embodiments, the flow rate of argon gas is 500-12000 sccm, for example, 500 sccm, 1000 sccm, 2000 sccm, 3000 sccm, 4000 sccm, 5000 sccm, 6000 sccm, 7000 sccm, 8000 sccm, 10000 sccm, or 12000 sccm.

[0059] In some embodiments, the radio frequency power is 500-3000W, for example, 500W, 1000W, 1500W, 2000W, 2500W, 3000W.

[0060] In some embodiments, the removal temperature is 275-660°C, for example 275°C, 280°C, 300°C, 350°C, 400°C, 450°C, 550°C, 600°C, 650°C.

[0061] In some embodiments, the removal pressure is 2 to 10 Torr, for example, 2 Torr, 3 Torr, 4 Torr, 5 Torr, 6 Torr, 7 Torr, 8 Torr, 9 Torr, or 10 Torr.

[0062] In some embodiments, the removal time is 120 to 1000 s, for example, 120 s, 140 s, 180 s, 200 s, 300 s, 400 s, 500 s, 600 s, 700 s, 820 s, or 900 s.

[0063] The present invention also provides the use of depositing an amorphous carbon film on the back of a wafer to improve the wafer warpage that occurs when a film is formed on the front of the wafer. The deposition and amorphous carbon film are as described in any embodiment of the present invention.

[0064] Depositing amorphous carbon film on the back of the wafer can prevent the alarm of wafers with large warpage during measurement or film transmission. At the same time, large wafer warpage value will lead to uneven heating on the heating plate and poor uniformity of film deposition. Compared with SiN, SiO and amorphous carbon film, under the same film thickness conditions, amorphous carbon film has similar stress and warpage as SiN, which can meet the stress neutralization of process sheets or structural sheets with large warpage. With the accumulation of film thickness and the increase of process temperature, it can meet the requirements of higher stress and warpage. Amorphous carbon film has good physical and chemical properties and high internal stress, a wide deposition temperature range (275~660℃), and a controllable process.

[0065] The present invention can remove the amorphous carbon film deposited on the back of the wafer with high efficiency and low loss. The amorphous carbon film is deposited on the back of the wafer to neutralize the wafer stress. After the wafer front process deposition is completed, the back is in-situ removed by reacting with oxygen ions under plasma excitation, and finally the CO2 and other byproducts generated by the reaction are removed. The amorphous carbon film deposited on the back of the wafer can be removed in-situ by plasma-excited oxygen, which is efficient and low-loss, with simple steps and easy control, reducing the problems and potential risks caused by wet removal of SiN film (phosphoric acid or hydrofluoric acid).

[0066] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually based on conventional conditions or the conditions recommended by the manufacturer. Unless otherwise stated, percentages and parts are calculated by weight.

[0067] Both deposition and removal were performed using backside depo PECVD deposition equipment.

[0068] The film thickness, wafer thickness before film deposition on the back side, and wafer thickness after film removal on the back side were tested using a KLA film thickness instrument.

[0069] The pre-stress value is tested by the Zhongke Feice machine. The post-stress value requires the input of the film thickness to obtain the stress and warpage of the film.

[0070] Example 1

[0071] (1) Deposition of an amorphous carbon film on the back of the wafer

[0072] C2H2 was used as the deposition gas, with a flow rate of 120sccm, dual-frequency RF, 120W high frequency RF power, 400W low frequency RF power, 275°C deposition temperature, 2Torr deposition pressure, and 120s deposition time. The thickness of the deposition on the back of the wafer was of film.

[0073] (2) Removing the amorphous carbon film deposited in step (1)

[0074] A mixed gas of oxygen and argon was used as the cleaning gas, with an O2 flow rate of 8000 sccm, an Ar flow rate of 4000 sccm, a RF power of 1500 W, a removal temperature of 275° C., a removal pressure of 4 Torr, and a removal time of 120 s.

[0075] By observation, it can be seen that the color of the wafer surface is the color of the bare silicon wafer. After cleaning, the film thickness meter is used to test and it is found that the wafer has returned to the thickness before deposition, confirming that there is no residual amorphous carbon film.

[0076] Example 2

[0077] (1) Deposition of an amorphous carbon film on the back of the wafer

[0078] C3H6 was used as the deposition gas, with a flow rate of 300sccm, a single-frequency RF, a RF power of 2000W, a deposition temperature of 600°C, a deposition pressure of 5Torr, and a deposition time of 30s. The thickness of the deposition on the back of the wafer was of film.

[0079] (2) Removing the amorphous carbon film deposited in step (1)

[0080] A mixed gas of oxygen and argon was used as the cleaning gas, with an O2 flow rate of 8000 sccm, an Ar flow rate of 4000 sccm, a RF power of 1500 W, a removal temperature of 600° C., a removal pressure of 4 Torr, and a removal time of 140 s.

[0081] By observation, it can be seen that the color of the wafer surface is the color of the bare silicon wafer. After cleaning, the film thickness meter is used to test and it is found that the wafer has returned to the thickness before deposition, confirming that there is no residual amorphous carbon film.

[0082] Example 3

[0083] (1) Deposition of an amorphous carbon film on the back of the wafer

[0084] C3H6 was used as the deposition gas, with a flow rate of 300sccm, a single-frequency RF, a RF power of 2000W, a deposition temperature of 600°C, a deposition pressure of 5Torr, and a deposition time of 560s. The thickness of the deposition on the back of the wafer was of film.

[0085] (2) Removing the amorphous carbon film deposited in step (1)

[0086] A mixed gas of oxygen and argon was used as the cleaning gas, with an O2 flow rate of 8000 sccm, an Ar flow rate of 4000 sccm, a RF power of 1500 W, a removal temperature of 600° C., a removal pressure of 4 Torr, and a removal time of 820 s.

[0087] By observation, it can be seen that the color of the wafer surface is the color of the bare silicon wafer. After cleaning, the film thickness meter is used to test and it is found that the wafer has returned to the thickness before deposition, confirming that there is no residual amorphous carbon film.

[0088] Comparative Example 1

[0089] (1) Deposition of SiN on the back side of the wafer

[0090] SiH4 and NH3 were used as deposition gases to prepare SiN film. The SiH4 flow rate was 450sccm, the NH3 flow rate was 320sccm, the RF power was 1300W, the deposition temperature was 400℃, the deposition pressure was 4.5Torr, and the deposition time was 35s. The thickness of the film was deposited on the back of the wafer. of film.

[0091] (2) Removal

[0092] The SiN film is removed using the same removal method as in step (2) of Example 1.

[0093] By observation, it can be seen that the color of the wafer surface is not the color of the bare silicon wafer. After cleaning, the film thickness tester was used to test and found that there was a thin film layer remaining on the back of the wafer. Finally, the SiN film was completely removed by phosphoric acid wet method.

[0094] Comparative Example 2

[0095] (1) Deposition of SiO on the back side of the wafer

[0096] SiH4 and N2O were used as deposition gases to prepare SiO thin films. The SiH4 flow rate was 480sccm, the N2O flow rate was 7500sccm, the RF power was 600W, the deposition temperature was 400℃, the deposition pressure was 4.0Torr, and the deposition time was 12s. The thickness was deposited on the back of the wafer. of film.

[0097] (2) Removal

[0098] The SiO film was removed using the same removal method as in step (2) of Example 1.

[0099] By observation, it can be seen that the color of the wafer surface is not the color of the bare silicon wafer. After cleaning, the film thickness tester was used to test and found that there was a thin film layer remaining on the back of the wafer. Finally, the SiO film was completely removed by hydrofluoric acid wet method.

[0100] Test Case

[0101] The comparison of stress and wafer warpage of SiN and SiO films and amorphous carbon films is shown in Table 1.

[0102] Table 1

[0103]

[0104] The wafer warpage value refers to the warpage value caused by the film deposited on the back side of the wafer, that is, the warpage value measured after the film is deposited on the wafer minus the warpage value tested before deposition. The unit of the warpage value can be measured in microns (μm). The larger the warpage value, the greater the impact of the film deposited on the back side on the warpage deformation of the wafer, that is, the greater the deformation of the wafer deposited on the front side, thereby achieving wafer flattening.

[0105] In Table 1, the stress value and the wafer warpage value are both negative values, indicating that the directions of the stress value and the wafer warpage are both toward the back side of the wafer. The absolute values ​​of the stress value and the wafer warpage value in Table 1 represent the magnitude of the stress value and the amplitude of the wafer warpage.

[0106] The back-deposited film obtained in Example 1 is deposited at a relatively low temperature (275-300°C), and the back-deposited films obtained in Examples 2-3 are deposited at a relatively high temperature (600-660°C). Other preparation conditions and process parameters are different. The films deposited on the back side of Examples 2-3 have large stress and warpage values ​​due to the high process temperature. The amorphous carbon film deposited in Examples 1-3 can be removed in situ by reacting with oxygen, while the back-deposited SiN and SiO in the process are removed by wet etching. The advantage of the technical solution of the present invention is that no other removal steps need to be introduced, and the film can be removed on a thin film deposition machine.

[0107] SiN and SiO deposited film thickness exceeds Easy to fall off, so in the application of back deposition

[0108] SiN film thickness is The stress of SiO film is lower than that of SiN, and the thickness cannot reach the same level as that of SiN.

[0109] SiN and amorphous carbon films have equivalent stress.

Claims

1. A wafer, characterized in that: An amorphous carbon film is deposited on the back side of the wafer.

2. The wafer according to claim 1, characterized in that The amorphous carbon film has one or more of the following characteristics: The thickness of the amorphous carbon film is The stress of the amorphous carbon film is -900 to -1500 MPa; The wafer warpage value of the amorphous carbon film is -100 to -1500 μm.

3. The wafer according to claim 1, characterized in that A thin film is deposited on the front side of the wafer, or a thin film is not deposited on the front side of the wafer.

4. A method for preparing the wafer according to any one of claims 1 to 3, characterized in that: The method comprises the steps of: using acetylene or propylene as a deposition gas to deposit an amorphous carbon film on the back side of the wafer.

5. The method according to claim 4, characterized in that The flow rate of acetylene is 50 to 500 sccm; and / or the flow rate of propylene is 50 to 500 sccm.

6. The method according to claim 4, characterized in that The method has one or more of the following features: The deposition pressure is 1 to 10 Torr; The deposition temperature is 275-660°C; The deposition time is 30 to 1000 seconds; The radio frequency is single-frequency, and the radio frequency power is 2000-3000W; or the radio frequency is dual-frequency, the high-frequency power is 100-150W, and the low-frequency power is 300-400W.

7. A method for preparing a wafer, characterized in that: Includes steps: (1) Providing a wafer according to any one of claims 1 to 3, and performing film deposition on the front side of the wafer; (2) Use argon and oxygen as cleaning gases to remove the amorphous carbon film on the back of the wafer.

8. The method according to claim 7, characterized in that The flow rate of oxygen gas is 500 to 15000 sccm; and / or the flow rate of argon gas is 500 to 12000 sccm.

9. The method according to claim 7, characterized in that The method has one or more of the following features: RF power is 500~3000W; The removal temperature is 275-660°C; The removal pressure is 2 to 10 Torr; The removal time is 120 to 1000 seconds.

10. Application of amorphous carbon film deposited on the back side of wafer to improve wafer warpage that occurs when film is formed on the front side of wafer.

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