A method for depositing a carbon film on a trench device and a trench device

Abstract

This invention relates to the field of semiconductor manufacturing and discloses a method for depositing carbon film on a trench device and the trench device itself. The method includes spin-coating a photoresist layer on the wafer surface of the trench device to form a first wafer; depositing a first carbon film of thickness T1 on the first wafer to form a second wafer; removing the photoresist layer and carbon film layer deposited on the surface of the second wafer to form a third wafer; and depositing a second carbon film of thickness T2 on the third wafer to form a target wafer, where c is the step coverage of the trench device. Through these two carbon film depositions, the carbon film thickness is made the same on the wafer surface, trench sidewalls, and trench bottom of the trench device, resulting in the same carbon protection capability and ensuring the consistency of carbon protection capability at different locations of the trench device.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing, and more particularly to a method for depositing carbon films in a trench device and the trench device itself. Background Technology

[0002] As a third-generation semiconductor material, SiC has many superior properties, such as high temperature resistance, high pressure resistance, and radiation resistance. As a result, SiC devices have significant advantages over traditional devices and are consistently regarded as the most promising semiconductor devices.

[0003] However, some unique properties of SiC materials also bring new requirements to its manufacturing process. Due to the low impurity diffusion coefficient of SiC, ion implantation is the best method for selective doping of SiC devices. However, the impurity ions implanted into the SiC material are mainly located in interstitial positions. To allow these impurity ions to substitute at lattice points, the ion-implanted SiC material needs to undergo high-temperature activation annealing. The annealing temperature is generally higher than 1400℃ for N-type impurities and 1600℃-1800℃ for P-type impurities. At such high annealing temperatures, silicon in SiC will volatilize and redeposit, resulting in step clusters on the wafer surface after annealing, which degrades the wafer surface morphology and severely affects device performance. To solve this problem, a protective layer is usually applied to the SiC wafer surface during high-temperature activation annealing to suppress silicon volatilization and deposition.

[0004] Currently, carbon protective films are the most widely used because carbon and SiC do not react at high temperatures. Furthermore, carbon protective films have a certain degree of hardness, effectively inhibiting silicon precipitation in SiC. Additionally, after high-temperature activation annealing, the carbon protective film can be effectively removed by oxidation or other methods without affecting device performance. Existing technologies using PVD magnetron sputtering provide effective protection for planar SiC devices. However, for SiC trench devices, the PVD sputtered carbon film only covers about 30% of the trench steps, and the thickness of the carbon film on the trench sidewalls, bottom, and SiC surface differs significantly, resulting in substantial differences in protective capabilities (the protective capability of the carbon film decreases with increasing thickness). Figure 1 As shown. Therefore, ensuring that the sidewalls, bottom, and surface of SiC trench devices have the same carbon protection capability has become an urgent technical problem to be solved. Summary of the Invention

[0005] The present invention aims to provide a method for depositing carbon film on trench devices. By performing carbon film deposition on the trench device twice, the carbon film thickness deposited on the trench sidewalls, trench bottom and surface of the trench device is the same, thereby having the same carbon protection capability and ensuring the consistency of the carbon film's protection capability at different locations of the trench device.

[0006] The above-mentioned objectives are mainly achieved through the following technical solutions:

[0007] In a first aspect, a method for depositing a carbon film on a trench device, the wafer of the trench device comprising a surface, trench sidewalls, and a trench bottom, the method comprising:

[0008] Step 1: Spin-coat a photoresist layer onto the wafer surface of the trench device to form a first wafer;

[0009] Step 2: The first wafer is subjected to a first carbon film deposition with a thickness of T1 to form a second wafer. The surface of the second wafer is deposited with a photoresist layer and a first carbon film layer with a thickness of T1. The trench sidewalls and the bottom of the trench of the second wafer are respectively deposited with a second carbon film layer and a third carbon film layer with a thickness of T1*c, where c is the step coverage of the trench device.

[0010] Step 3: Remove the photoresist layer and the first carbon film layer deposited on the surface of the second wafer to form a third wafer. The third wafer has a second carbon film layer and a third carbon film layer with a thickness of T1*c deposited only on the trench sidewall and the trench bottom, respectively.

[0011] Step 4: The third wafer is subjected to a second carbon film deposition with a thickness of T2 to form a target wafer. The surface of the target wafer is deposited with a fourth carbon film layer with a thickness of T2, while the trench sidewalls of the target wafer are respectively deposited with the second carbon film layer and a fifth carbon film layer with a thickness of T2*c. The bottom of the trench of the target wafer is respectively deposited with the third carbon film layer and a sixth carbon film layer with a thickness of T2*c.

[0012] in,

[0013] Therefore, it can be seen from the above that the thickness of the carbon film deposited on the trench sidewall of the target wafer is:

[0014] T1*c+T2*c···(2)

[0015] Substituting equation (1) into equation (2), we get:

[0016] T1*c + T2*c = T2···(3)

[0017] That is, the thickness of the carbon film deposited on the trench sidewall of the target wafer is T2.

[0018] Furthermore, according to formula (1), the thickness of the carbon film deposited at the bottom of the trench of the target wafer is also:

[0019] T1*c + T2*c = T2;

[0020] That is, the thickness of the carbon film deposited at the bottom of the trench of the target wafer is also T2.

[0021] Therefore, the target wafer undergoes two carbon film depositions, and the carbon film deposited on its surface, trench sidewalls, and trench bottom has the same thickness and the same carbon protection capability. This ensures the consistency of the carbon film's protection capability at different locations of the trench device. Furthermore, the process of this invention is simple, easy to implement, and low in cost, which is conducive to large-scale promotion and application.

[0022] Preferably, spin-coating a photoresist layer on the wafer surface of the trench device includes: spin-coating a negative photoresist layer on the wafer surface of the trench device; processing the negative photoresist using exposure and development technology to form a chamfered photoresist layer on the wafer surface of the trench device; and facilitating peeling and removal. Spin-coating a photoresist layer on the wafer surface of the trench device facilitates the subsequent peeling and removal of the carbon film deposited on the wafer surface by the first carbon film deposition. Based on the pre-coated photoresist layer, peeling and removing the photoresist layer and the first carbon film layer deposited on the surface of the second wafer only requires a lift-off process. The lift-off solution can peel off the photoresist layer and the first carbon film layer together, leaving only the carbon film on the trench sidewalls and the bottom of the trench. This is easy to implement and low in cost. The above-mentioned processing of the negative photoresist using exposure and development technology to form a chamfered photoresist layer on the wafer surface of the trench device further facilitates peeling and improves removal efficiency.

[0023] Preferably, similarly, the Lift-off process is used to remove the photoresist layer and carbon film layer deposited on the surface of the second wafer. This is easy to implement and low in cost. Combined with the above-mentioned chamfered photoresist layer, the removal of the photoresist layer and the first carbon film layer can be achieved using only the Lift-off solution.

[0024] Preferably, before the first carbon film deposition, the method further includes: using a lift-off process to remove the photoresist negative on the trench sidewalls and trench bottom of the first wafer. During the spin-coating of photoresist negative on the wafer surface of the trench device, some photoresist negative will inevitably remain on the trench sidewalls and trench bottom. If this is the case, when removing the photoresist layer and the first carbon film layer, the carbon film formed on the trench sidewalls and trench bottom during the first carbon film deposition will also be removed. Therefore, in this embodiment of the invention, before the first carbon film deposition, a lift-off process is used to remove the photoresist negative on the trench sidewalls and trench bottom of the first wafer, exposing the trench sidewalls and trench bottom for subsequent first carbon film deposition.

[0025] Preferably, both the first and second carbon film depositions are performed using room-temperature PVD carbon film sputtering technology. Utilizing the mature PVD carbon film sputtering technology for carbon film deposition is a simple and low-cost process that can deposit carbon films of the same thickness on the wafer surface, trench sidewalls, and trench bottom, providing consistent carbon protection capabilities and ensuring uniform protection for different locations on trench-type devices.

[0026] Secondly, a trench-type device includes:

[0027] The device comprises a wafer substrate, a wafer surface, trench sidewalls and trench bottoms formed on the wafer surface by an etching process, and carbon films deposited on the wafer surface, the trench sidewalls and the trench bottoms, wherein the carbon films are prepared using any of the trench device deposition methods described in the first aspect; such that the carbon films deposited on the wafer surface, trench sidewalls and trench bottoms of the trench device have the same thickness and the same carbon protection capability, ensuring the consistency of the protection capability of the carbon films for different locations of the trench device.

[0028] Advantages compared to existing technologies: Utilizing two carbon film deposition processes, with the first deposition thickness being T1 and the second deposition thickness being T2, the relationship between the two is as follows: The carbon film deposited for the first time on the wafer surface is stripped away, leaving only the thickness T2 of the second deposition on the surface. However, it is not stripped away on the trench sidewalls and bottom, thus forming two carbon films. Due to the step coverage, their final thicknesses are T1*c and T2*c, respectively. In summary, the total thickness of the carbon film finally deposited on the trench sidewalls and bottom is T2. Therefore, through the above two carbon film depositions, the carbon film thickness on the wafer surface, trench sidewalls, and trench bottom of the trench device is the same, providing the same carbon protection capability and ensuring the consistency of carbon protection capability of the carbon film at different locations of the trench device. Attached Figure Description

[0029] Figure 1 This diagram illustrates the significant differences in carbon film deposition thickness between the SiC surface, trench sidewalls, and trench bottom in existing SiC trench devices.

[0030] Figure 2 A schematic diagram of trenches formed on the surface of a SiC wafer using a SiC etching process is shown in this invention;

[0031] Figure 3 This diagram illustrates the spin-coating of a chamfered photoresist layer onto the surface of a SiC wafer in this invention.

[0032] Figure 4 A schematic diagram of the first carbon film deposition in this invention is shown;

[0033] Figure 5 This diagram illustrates the process of peeling off and removing the chamfered photoresist layer and the first carbon film layer in this invention.

[0034] Figure 6 A schematic diagram of the second carbon film deposition in this invention is shown. Detailed Implementation

[0035] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0036] Example 1

[0037] This invention provides a method for depositing carbon films on trench devices, using SiC trench devices as an example. This invention is applied to the carbon film deposition stage after cleaning a silicon carbide wafer and forming trenches on the SiC wafer surface using a SiC etching process. Figure 2 As shown, a SiC wafer surface A, trench sidewalls B, trench bottom C, and SiC substrate D are formed.

[0038] like Figures 3-6 As shown, the method for depositing carbon film on a trench device according to the present invention includes the following steps:

[0039] Step 1, as follows Figure 3 As shown, a chamfered photoresist layer E is spin-coated onto the SiC wafer surface A of the trench device to form a first wafer. Spin-coating a photoresist layer onto the SiC wafer surface A of the trench device facilitates the removal of the first carbon film layer F1 formed by the first carbon film deposition on the SiC wafer surface A in subsequent step 3. Based on the pre-coated photoresist layer, the photoresist layer and the first carbon film layer deposited on the surface of the second wafer (i.e., SiC wafer surface A) in step 2 can be removed by using a lift-off process. The lift-off solution can be used to remove the photoresist layer and the first carbon film layer together, leaving only the carbon film on the trench sidewalls and the bottom of the trench. This is easy to implement and has low cost.

[0040] Furthermore, a layer of photoresist is spin-coated onto the SiC wafer surface A of the trench device; the photoresist is then processed using exposure and development technology to form a chamfered photoresist layer on the SiC wafer surface A of the trench device; this facilitates peeling and increases removal efficiency.

[0041] Step 2, as follows Figure 4 As shown, the first wafer is subjected to a first carbon film deposition of thickness T1 to form a second wafer. The surface of the second wafer (i.e., the SiC wafer surface A) is deposited with a chamfered photoresist layer E and a first carbon film layer F1 of thickness T1. The trench sidewalls B and the trench bottom C of the second wafer are respectively deposited with a second carbon film layer F2 and a third carbon film layer F3 of thickness T1*c, where c is the step coverage of the trench device.

[0042] Step 3, as follows Figure 5 As shown, the chamfered photoresist layer E and the first carbon film layer F1 deposited on the surface of the second wafer (i.e., the SiC wafer surface A) are removed using a lift-off process to form a third wafer. The third wafer then has a second carbon film layer F2 and a third carbon film layer F3 with thicknesses T1*c deposited only on the trench sidewall B and trench bottom C, respectively. Based on step 1 above, the chamfered photoresist layer E and the first carbon film layer F1 can be removed using only a lift-off solution, resulting in low cost, simple process, and ease of implementation.

[0043] Step 4, as follows Figure 6 As shown, the third wafer is subjected to a second carbon film deposition with a thickness of T2 to form a target wafer. The surface of the target wafer (i.e., the SiC wafer surface A) is deposited with a fourth carbon film layer F4 with a thickness of T2, while the trench sidewalls B of the target wafer are respectively deposited with the second carbon film layer F2 and the fifth carbon film layer F5 with a thickness of T2*c. The bottom C of the trench of the target wafer is respectively deposited with the third carbon film layer F3 and the sixth carbon film layer F6 with a thickness of T2*c.

[0044] in,

[0045] Therefore, the total thickness of the carbon film deposited on the trench sidewall B of the target wafer (the sum of the thicknesses of F2 and F5) is:

[0046] T1*c+T2*c···(2)

[0047] Substituting equation (1) into equation (2), we get:

[0048] T1*c + T2*c = T2···(3)

[0049] That is, the total thickness of the carbon film deposited on the trench sidewall B of the target wafer is T2.

[0050] Furthermore, according to equation (1), the total thickness of the carbon film deposited at the bottom C of the trench of the target wafer (the sum of the thicknesses of F3 and F6) is:

[0051] T1*c + T2*C = T2;

[0052] That is, the total thickness of the carbon film deposited at the bottom of the trench of the target wafer is also T2.

[0053] Therefore, the target wafer undergoes two carbon film depositions, and the carbon film deposited on its surface, trench sidewalls, and trench bottom has the same thickness and the same carbon protection capability. This ensures the consistency of the carbon film's protection capability at different locations of the trench device. Furthermore, the process of this invention is simple, easy to implement, and low in cost, which is conducive to large-scale promotion and application.

[0054] In a preferred embodiment, prior to the first carbon film deposition, the method further includes:

[0055] The photoresist in the trench sidewalls and trench bottom of the first wafer is removed using a lift-off process. During the spin-coating of photoresist on the wafer surface of the trench device, some photoresist inevitably remains on the trench sidewalls and trench bottom. Therefore, when removing the photoresist layer and the first carbon film layer, the carbon film formed by the first carbon film deposition on the trench sidewalls and trench bottom is also removed. Therefore, in this embodiment of the invention, before the first carbon film deposition, the photoresist in the trench sidewalls and trench bottom of the first wafer is removed using a lift-off process to expose the trench sidewalls and trench bottom for subsequent first carbon film deposition.

[0056] In a preferred embodiment, both the first and second carbon film depositions are performed using room-temperature PVD carbon film sputtering technology. Utilizing the mature PVD carbon film sputtering technology for carbon film deposition is a simple and low-cost process that can deposit carbon films of the same thickness on the wafer surface, trench sidewalls, and trench bottom, providing consistent carbon protection capabilities and ensuring uniform protection for different locations on trench-type devices.

[0057] Advantages compared to existing technologies: Utilizing two carbon film deposition processes, with the first deposition thickness being T1 and the second deposition thickness being T2, the relationship between the two is as follows: The carbon film deposited for the first time on the wafer surface is stripped away, leaving only the thickness T2 of the second deposition on the surface. However, it is not stripped away on the trench sidewalls and bottom, thus forming two carbon films. Due to the step coverage, their final thicknesses are T1*c and T2*c, respectively. In summary, the total thickness of the carbon film finally deposited on the trench sidewalls and bottom is T2. Therefore, through the above two carbon film depositions, the carbon film thickness on the wafer surface, trench sidewalls, and trench bottom of the trench device is the same, providing the same carbon protection capability and ensuring the consistency of carbon protection capability of the carbon film at different locations of the trench device.

[0058] Example 2

[0059] This invention also provides a trench-type device, comprising:

[0060] The device comprises a wafer substrate, a wafer surface, trench sidewalls and trench bottoms formed on the wafer surface using an etching process, and carbon films deposited on the wafer surface, trench sidewalls and trench bottoms. The carbon films are prepared using any of the trench device carbon film deposition methods provided in the above embodiments. This ensures that the carbon films deposited on the wafer surface, trench sidewalls and trench bottoms of the trench device have the same thickness and the same carbon protection capability, thus ensuring the consistency of the carbon film's protection capability at different locations of the trench device.

[0061] The method for depositing carbon film on a trench device involved in this embodiment of the invention is described in the above embodiments and will not be repeated here.

[0062] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for depositing a carbon film on a trench device, wherein the wafer of the trench device includes a surface, trench sidewalls, and a trench bottom, characterized in that, include: A photoresist layer is spin-coated onto the wafer surface of the trench device to form a first wafer; The first wafer is subjected to a first carbon film deposition of thickness T1 to form a second wafer; The photoresist layer and carbon film layer deposited on the surface of the second wafer are removed to form a third wafer; The third wafer undergoes a second carbon film deposition with a thickness of T2 to form the target wafer, wherein... c represents the step coverage of the trench-type device.

2. The method for depositing carbon film on a trench device as described in claim 1, characterized in that, A photoresist layer is spin-coated onto the wafer surface of the trench device, comprising: A layer of photoresist is spin-coated onto the wafer surface of the trench device; The photoresist is processed using exposure and development techniques to form a chamfered photoresist layer on the wafer surface of the trench device.

3. The method for depositing carbon film on a trench device as described in claim 2, characterized in that, Prior to the first carbon film deposition, the method further includes: The photoresist negative in the trench sidewalls and trench bottom of the first wafer is removed using a lift-off process.

4. The method for depositing carbon film on a trench device as described in claim 1, characterized in that, The photoresist layer and carbon film layer deposited on the surface of the second wafer are removed using a lift-off process.

5. The method for depositing carbon film on a trench device as described in claim 1, characterized in that, Both the first and second carbon film depositions were performed using room-temperature PVD carbon film sputtering technology.

6. A trench-type device, characterized in that, include: The wafer substrate, the wafer surface, the trench sidewalls and the trench bottom formed on the wafer surface by an etching process, and the carbon film deposited on the wafer surface, the trench sidewalls and the trench bottom, wherein the carbon film is prepared by a method for depositing carbon film in a trench device as described in any one of claims 1 to 5.

Images