Formation method of semiconductor device
By adjusting the deposition rate of the silicon oxide layer and the deposition conditions of the tungsten material layer, the problem of aluminum liner falling off was solved, and high-yield and low-cost production of semiconductor devices was achieved.
Patent Information
- Application Number
- CN202410263406.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-07
- Publication Date
- 2025-09-12
AI Technical Summary
The aluminum pad easily falls off the substrate in back-illuminated CMOS image sensors, resulting in reduced product yield and increased process costs. The reason is that the stress difference between the tungsten material layer and the silicon oxide layer is too large, making it difficult for the silicon oxide layer to pull the tungsten material layer.
By adjusting the deposition rate of the silicon oxide layer to increase its compressive stress, and combining increasing the deposition temperature of the tungsten material layer and adjusting the flow rate of the tungsten-containing gas to reduce the tensile stress of the tungsten material layer, the stress difference between the silicon oxide layer and the tungsten material layer is reduced, thereby improving the adhesion of the aluminum liner.
The peeling defects of the aluminum liner are significantly reduced, the yield of semiconductor devices is improved, and the process cost is reduced.
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Figure CN120640796A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductors, and in particular to a method for forming a semiconductor device. Background Art
[0002] Aluminum pads (Al PADs) are often used in backside illumination (BSI) CMOS image sensors to connect the wafer to external circuits.
[0003] In some back-illuminated CMOS image sensor manufacturing processes, aluminum liners are typically formed on top of a tungsten (W) material layer during the final step. Using existing processes, aluminum liners are prone to detaching from the substrate, severely reducing product yield and increasing process costs. Summary of the Invention
[0004] The invention aims to solve the technical problem that an aluminum liner is easily fallen off from a substrate.
[0005] In order to achieve the above object, the present invention provides a method for forming a semiconductor device, comprising:
[0006] providing a substrate;
[0007] A silicon oxide layer is deposited on the substrate at a deposition rate of
[0008] depositing an adhesion layer on the silicon oxide layer;
[0009] depositing a tungsten material layer on the adhesion layer;
[0010] An aluminum liner is deposited on the tungsten material layer.
[0011] Optionally, the tungsten material layer includes a tungsten nucleation layer deposited on the adhesion layer, and a tungsten bulk layer deposited on the tungsten nucleation layer.
[0012] Optionally, the deposition temperature of the tungsten body layer is 400°C-430°C.
[0013] Optionally, a tungsten-containing gas is introduced into the substrate to form the tungsten material layer; the flow rate of the tungsten-containing gas is 150 sccm-300 sccm.
[0014] Optionally, when forming the tungsten body layer, the flow rate of the tungsten-containing gas is 150 sccm-180 sccm.
[0015] Optionally, the silicon oxide layer and the adhesion layer are in close contact with each other, and the adhesion layer and the tungsten material layer are in close contact with each other.
[0016] Optionally, the compressive stress in the silicon oxide layer is 300 MPa-350 MPa.
[0017] Optionally, the tensile stress in the tungsten material layer is 1200 MPa-1600 MPa.
[0018] Optionally, a stress difference between the silicon oxide layer and the tungsten material layer is no more than 1050 MPa.
[0019] Optionally, the substrate includes a trench structure, and the aluminum liner is deposited in the trench structure.
[0020] Optionally, the thickness of the silicon oxide layer is The thickness of the adhesion layer is The thickness of the tungsten material layer is
[0021] Optionally, the material of the adhesion layer includes tungsten nitride and / or titanium nitride.
[0022] Optionally, the semiconductor device is a back-illuminated image sensor.
[0023] The beneficial effects of the present invention are:
[0024] (1) The present invention first noticed the technical problem that the aluminum liner is easy to fall off from the substrate, which affects the product yield. The cause of this problem was explored and it was found that the aluminum liner fell off due to the peeling between the tungsten material layer and the silicon oxide layer, which caused the tungsten material layer to fall off along with the aluminum liner. It was further found that the reason for the peeling between the tungsten material layer and the silicon oxide layer was that the stress difference between the two film layers was too large, resulting in the silicon oxide layer being unable to properly pull the tungsten material layer located on its upper layer, and a crack was present between the tungsten material layer and the silicon oxide layer. Based on this reason, a method for forming a semiconductor device was proposed. By increasing the compressive stress in the silicon oxide layer and reducing the tensile stress of the tungsten material layer, the stress difference between the tungsten material layer and the silicon oxide layer was reduced, thereby improving the problem of the aluminum liner falling off defect.
[0025] (2) In order to increase the compressive stress in the silicon oxide layer, the present invention adjusts the deposition rate of the silicon oxide layer to The compressive stress of the silicon oxide layer was measured to be 300MPa-350MPa. Compared with the prior art, the semiconductor device obtained by adjusting the deposition rate has an order of magnitude reduction in aluminum liner peeling defects, and the aluminum liner peeling defect has been significantly improved.
[0026] (3) In order to reduce the tensile stress in the tungsten material layer, the present invention provides two adjustment methods. One is to increase the deposition temperature of the tungsten material layer to a limited extent to fully ensure that the deposition temperature will not have a negative impact on the overall performance of the device; the other is to reduce the deposition gas flow rate of the tungsten body layer within the mass saturation flow rate range. In addition, the present invention applies these two adjustment methods simultaneously to the formation process of the semiconductor device, achieving the technical effect of "1+1>2". The final substrate obtained not only has no aluminum liner falling off, but also has no defects in other film layers around the aluminum liner. The film layers are tightly fitted with each other, and the device yield is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 Schematic diagram of the structure of an existing back-illuminated CMOS image sensor.
[0028] Figure 2 The present invention provides a flow chart of a method for forming a semiconductor device.
[0029] Figure 3 A schematic structural diagram of a back-illuminated CMOS image sensor manufactured by the semiconductor device forming method provided by the present invention.
[0030] Figure 4 FIG2 is a schematic diagram of a machine used for depositing a tungsten material layer in the method for forming a semiconductor device of the present invention.
[0031] Figure 5 These are the various detection and analysis diagrams of substrate A obtained in Comparative Example 1.
[0032] Figure 6 These are the various detection and analysis diagrams of substrate B obtained in Example 1.
[0033] Figure 7 This is a statistical result diagram of the number of aluminum liner peeling defects in substrates manufactured according to the semiconductor device forming method provided in Example 1 and Comparative Example 1.
[0034] Figure 8 These are the various detection and analysis diagrams of substrate C obtained in Example 7.
[0035] In the figure, 100-second wafer, 200-first wafer, 300-first silicon oxide layer, 400-first silicon nitride layer, 500-second silicon oxide layer, 600-first tungsten material layer, 700-first aluminum liner, 800-first trench structure, 900-crack, 1-fourth wafer, 2-third wafer, 3-substrate silicon oxide layer, 4-silicon nitride layer, 5-silicon oxide layer, 6-adhesion layer, 7-tungsten material layer, 8-aluminum liner, 9-trench structure. DETAILED DESCRIPTION
[0036] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.
[0037] In the description of the present invention, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0038] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections; they may refer to direct connections, indirect connections through an intermediate medium, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.
[0039] A back-illuminated CMOS image sensor is formed by bonding a new blank wafer to the front side of a wafer that has undergone the frontside illumination process. The wafer is then flipped 180° so that the back side of the wafer that has undergone the frontside illumination process faces upward. The back side of the wafer that has undergone the frontside illumination process is then subjected to a series of back-illuminated processes.
[0040] The first wafer 200 is a wafer that has completed the front illumination process. A second wafer 100 is bonded to the front of the first wafer 200. The second wafer 100 is a blank wafer. The bonded first wafer 200 and the second wafer 100 are flipped 180° as a whole, so that the front of the first wafer 200 faces down and the back faces up. The second wafer 100 is located below the first wafer 200 and serves as a tray to support the first wafer 200. Afterwards, the back of the first wafer 200 is subjected to a back illumination process. The surface of the back of the first wafer 200 is a silicon material. First, a silicon material is processed to face the front of the first wafer 200 (i.e., facing the front of the first wafer 200). Figure 1A first trench structure 800 (backside shallow silicon trench) is formed on the back surface of the first wafer 200. A first silicon oxide layer 300, a first silicon nitride layer 400, a second silicon oxide layer 500, a first tungsten material layer 600, and a first aluminum liner 700 are then sequentially deposited on the back surface of the first wafer 200. The first aluminum liner 700 is located within the first trench structure 800, resulting in a back-illuminated CMOS image sensor. The first aluminum liner 700 is typically the last step in the back-illuminated process. To ensure adhesion of the first tungsten material layer 600 to the second silicon oxide layer 500, a thin adhesion layer (not shown) is deposited on the surface of the second silicon oxide layer 500. The first tungsten material layer 600 is deposited on the surface of this adhesion layer.
[0041] However, in the back-illuminated CMOS image sensor manufactured by the prior art, the first aluminum liner 700 located in the first trench structure 800 is often easily detached from the substrate, which seriously reduces the product yield and leads to an increase in process costs.
[0042] After investigation, the inventors found that although it appeared on the surface that the first aluminum liner 700 was falling off, it was actually peeling and falling off between the first tungsten material layer 600 and the second silicon oxide layer 500, causing the first tungsten material layer 600 and the first aluminum liner 700 deposited on the surface of the first tungsten material layer 600 to fall off from the substrate together.
[0043] After further investigation, the inventors found that the reason why the first tungsten material layer 600 falls off from the second silicon oxide layer 500 is that the stress difference between the two is too large. Figure 1 As shown, the second silicon oxide layer 500 is formed by a plasma enhanced chemical vapor deposition (PECVD) process using tetraethyl orthosilicate (TEOS) as a reaction gas. The stress within the second silicon oxide layer 500 is compressive stress, that is, the stress direction is along the cross-sectional direction of the layer, from both sides to the center ( Figure 1 The first tungsten material layer 600 is formed by chemical vapor deposition (CVD) using WF6 as the reaction gas. The stress within the first tungsten material layer 600 is tensile stress, that is, the stress direction is along the cross-section of the layer, from the center to the sides ( Figure 1(direction of the yellow arrow in the middle). The compressive stress within the second silicon oxide layer 500 causes the film layer to tend to be squeezed from both sides toward the center, while the tensile stress within the first tungsten material layer 600 causes the film layer to tend to be pulled and extended from the center toward both sides. The tensile stress within the first tungsten material layer 600 is typically much greater than the compressive stress within the second silicon oxide layer 500. Assuming the tensile stress within the first tungsten material layer 600 remains unchanged, the greater the compressive stress within the second silicon oxide layer 500, the greater the force exerted on the second silicon oxide layer 500 to squeeze and retract toward the center, the stronger the pulling effect on the first tungsten material layer 600, and the better the effect of preventing the first tungsten material layer 600 from being pulled toward both sides. If the compressive stress within the second silicon oxide layer 500 and the tensile stress within the first tungsten material layer 600 are of the same magnitude and there is no difference in their values, then the stresses within the two layers can be considered to cancel each other out. It is precisely because the difference in stress between the second silicon oxide layer 500 and the first tungsten material layer 600 is too large that the second silicon oxide layer 500 cannot pull the first tungsten material layer 600, and the first tungsten material layer 600 is easily pulled to both sides, which leads to the formation of a crack 900 between the second silicon oxide layer 500 and the first tungsten material layer 600. Figure 1 The red dotted circle is specifically the white gap between the second silicon oxide layer 500 and the first tungsten material layer 600. Figure 1 It can be seen that cracks 900 primarily originate in the first trench structure 800 formed by the recessing of the silicon oxide layer 500 and the first tungsten material layer 600. Due to the presence of cracks 900, the first tungsten material layer 600 easily peels off from the second silicon oxide layer 500, resulting in the detachment of the first aluminum liner 700. Although an adhesion layer exists between the second silicon oxide layer 500 and the first tungsten material layer 600, this adhesion layer is much thinner than the second silicon oxide layer 500 and the first tungsten material layer 600, and the thickness of the adhesion layer should not be increased. This adhesion layer alone is unable to overcome the stress difference between the second silicon oxide layer 500 and the first tungsten material layer 600, ensuring a tight fit between the two. Furthermore, the stress within the first aluminum liner 700 is also tensile.
[0044] To address the issue of first aluminum liner 700 detachment, the stress difference between the second silicon oxide layer 500 and the first tungsten material layer 600 should be reduced. In existing back-illuminated CMOS image sensors, the compressive stress of the second silicon oxide layer 500 is 70 MPa, and the tensile stress of the first tungsten material layer 600 is 1563 MPa. The compressive stress of the second silicon oxide layer 500 is too low, while the tensile stress of the first tungsten material layer 600 is too high. The internal stress of the material can be increased or decreased by optimizing the manufacturing process. For example, the process temperature used to manufacture the second silicon oxide layer 500 or the first tungsten material layer 600 can be changed. However, the internal stress of the second silicon oxide layer 500 or the first tungsten material layer 600 can only be significantly reduced if the process temperature is significantly changed. Reducing the stress difference by adjusting the process temperature has significant limitations. This is because changes in process temperature also require consideration of the compatibility of previous and subsequent processes and the potential impact of temperature on the device. Therefore, reducing the stress difference without significantly changing the process temperature, thereby improving the aluminum liner peeling defect, is of great significance to improving device performance and reducing costs.
[0045] Based on this, Figure 2 As shown, the present invention provides a method for forming a semiconductor device, comprising:
[0046] Step S1: providing a substrate.
[0047] In some embodiments, as Figure 3 As shown, the substrate includes from bottom to top: a fourth wafer 1, a third wafer 2, a substrate silicon oxide layer 3 and a silicon nitride layer 4. The third wafer 2 is a wafer that has completed the front-illuminated process. A fourth wafer 1 is bonded to the front of the third wafer 2. The fourth wafer 1 is a blank wafer. The bonded third wafer 2 and the fourth wafer 1 are flipped 180° as a whole, so that the front of the third wafer 2 faces down and the back faces up. The fourth wafer 1 is located below the third wafer 2 and serves as a tray to support the third wafer 2. Afterwards, the back of the third wafer 2 is subjected to a back-illuminated process. The surface on the back of the third wafer 2 is a silicon material. First, a portion facing the front of the third wafer 2 (i.e., facing the front) is processed on the silicon material. Figure 1 A recessed trench structure 9 is formed (below the third wafer 2), and then a substrate silicon oxide layer 3 and a silicon nitride layer 4 are sequentially deposited on the surface of the back side of the third wafer 2, and the structure including the fourth wafer 1, the third wafer 2, the substrate silicon oxide layer 3 and the silicon nitride layer 4 is used as a substrate.
[0048] Step S2: depositing a silicon oxide layer on the substrate at a deposition rate of
[0049] Using tetraethyl orthosilicate (TEOS) as the reaction gas, a silicon oxide layer 5 is formed on the surface of the substrate through a plasma enhanced chemical vapor deposition (PECVD) process. In some embodiments, the silicon oxide layer 5 is deposited on the surface of the silicon nitride layer 4. When a thin film layer is formed by chemical vapor deposition, the stress of the film is related to the deposition rate. The faster the deposition rate, the faster the growth rate of the film. The atoms in the film do not have sufficient time to rearrange, and the disordered matter increases, thereby increasing the stress in the film. The existing deposition rate of the silicon oxide layer is The compressive stress of the silicon oxide layer obtained is 70 MPa. The present invention adjusts the deposition rate of the silicon oxide layer 5 to The compressive stress of the silicon oxide layer 5 is measured to be 300 MPa-350 MPa.
[0050] In some embodiments, the thickness of the silicon oxide layer is
[0051] Step S3: depositing an adhesion layer on the silicon oxide layer.
[0052] In some embodiments, the thickness of the adhesion layer 6 is The material of the adhesion layer 6 includes tungsten nitride and / or titanium nitride.
[0053] Step S4: depositing a tungsten material layer on the adhesion layer.
[0054] A tungsten-containing gas is introduced into the substrate to deposit the tungsten material layer 7 on the surface of the adhesion layer 6. Optionally, the tungsten-containing gas includes WF6. The tungsten-containing gas also includes SiH4 and H2. The tungsten material layer 7 includes a tungsten nucleation layer deposited on the adhesion layer 6. The tungsten nucleation layer serves as a seed, and a tungsten bulk layer is then deposited on the tungsten nucleation layer, ultimately forming the tungsten material layer 7.
[0055] In some embodiments, using Figure 4 The tool shown forms a tungsten material layer 7 on the adhesion layer 6 via chemical vapor deposition. The tool comprises four pedestals. A substrate, already coated with the adhesion layer 6, is first placed on the first pedestal 101 for chemical vapor deposition. The substrate is then rotated and transported via a support puller, and then sequentially placed on the second pedestal 102, the third pedestal 103, and the fourth pedestal 104 for chemical vapor deposition. Deposition on the first pedestal 101 and the second pedestal 102 forms a tungsten nucleation layer. Deposition on the third pedestal 103 and the fourth pedestal 104 forms a tungsten bulk layer. Finally, the tungsten material layer 7 is obtained and then transported out of the tool.
[0056] In some embodiments, the thickness of the tungsten material layer 7 is
[0057] Step S5: depositing an aluminum liner on the tungsten material layer.
[0058] An aluminum liner 8 deposited on the surface of the tungsten material layer 7 is located within the trench structure 9 .
[0059] Example 1
[0060] Step S1.1: Provide Figure 3 The substrate shown includes, from bottom to top, a fourth wafer 1 , a third wafer 2 , a substrate silicon oxide layer 3 and a silicon nitride layer 4 .
[0061] Step S1.2: Depositing a silicon oxide layer 5 on the substrate. The silicon oxide layer 5 is deposited on the surface of the silicon nitride layer 4. The deposition rate of the silicon oxide layer 5 is The compressive stress of the silicon oxide layer 5 was measured to be 330 MPa. The thickness of the silicon oxide layer 5 is
[0062] Step S1.3: depositing an adhesion layer 6 on the silicon oxide layer 5. The material of the adhesion layer 6 is tungsten nitride (WN). The thickness of the adhesion layer 6 is
[0063] Step S1.4: Use Figure 4 In the machine shown, WF6 gas is introduced to form a tungsten material layer 7 on the adhesion layer 6 by chemical vapor deposition. When the substrate is subjected to a growth process on the first base 101 and the second base 102, the flow rate of the WF6 introduced is 300 sccm, and the temperature of the first base 101 and the second base 102 is 300°C, forming a tungsten nucleation layer. When the substrate is subjected to a growth process on the third base 103 and the fourth base 104, the flow rate of the WF6 introduced is 300 sccm, and the temperature of the third base 103 and the fourth base 104 is 395°C, forming a tungsten body layer; finally, a tungsten material layer 7 is obtained and then transferred out of the machine. The thickness of the tungsten material layer 7 is The tensile stress of the tungsten material layer 7 is 1563 MPa.
[0064] Step S1.5: Deposit an aluminum liner 8 on the tungsten material layer 7. The aluminum liner 8 is located in the trench structure 9. The thickness of the aluminum liner 8 is In Example 1, the difference between the compressive stress of the silicon oxide layer 5 and the tensile stress of the tungsten material layer 7 is 1233 MPa.
[0065] Comparative Example 1
[0066] In Comparative Example 1, the deposition rate of the silicon oxide layer is The compressive stress of the silicon oxide layer was measured to be 70 MPa. The remaining steps were the same as those in Example 1. In Comparative Example 1, the difference between the compressive stress of the silicon oxide layer and the tensile stress of the tungsten material layer was 1493 MPa.
[0067] The substrate A obtained in comparative example 1 and the substrate B obtained in example 1 were tested and analyzed respectively. Dark field defect inspection (DFI) was used to detect the detachment of the aluminum liner on the substrate surface. When a black spot appears on the circular substrate in the figure, it indicates that there is a defect there. Figure 5 As shown in (a), a large number of black spots appear in substrate A, and the distribution range of the black spots is relatively wide, indicating that a large area of defects appears in substrate A; Figure 6 As shown in (a), although black spots also appeared in substrate B, the number of black spots was significantly less than that in substrate A, and the black spots only existed in a small area in the center of the substrate. According to the method for forming a semiconductor device provided in Example 1 and Comparative Example 1, 25 substrates were again produced. The peeling of the aluminum liner on the substrate surface was detected by DFI, and the number of aluminum liner peeling defects on each substrate was counted. Figure 7 As shown in the figure, the horizontal axis is the substrate number, and the vertical axis is the number of aluminum liner peeling defects on each substrate. Figure 7 As shown in (a), in the 25 substrates prepared by the method provided in Comparative Example 1, the number of aluminum liner peeling defects ranges from 500 to 3100, while Figure 7 As shown in (b), in the 25 substrates manufactured by the method provided in Example 1, the number of aluminum liner peeling defects ranges from 0 to 30, indicating that compared with Comparative Example 1, the semiconductor device formation method of Example 1 reduces the number of aluminum liner peeling defects by an order of magnitude, and the aluminum liner peeling defects are significantly improved.
[0068] Substrate A and substrate B were observed by optical microscope (OM), and the Figure 5 (b) Figure 5 (c) and Figure 6 (b) Figure 6 (c); Substrate A and substrate B were observed by scanning electron microscopy (SEM), and the Figure 5 (d) Figure 5 (e) and Figure 6 (d) Figure 6 (e). In the optical microscope image, the aluminum liner is yellow. Figure 5 In (b), no yellow aluminum liner is observed, and combined with Figure 5 (d) shows that the aluminum liner on substrate A has fallen off in one piece. Figure 5 In (c), the yellow aluminum liner can be observed, but the aluminum liner is not complete, and there are defects on the right side and upper right corner. Figure 5(e) shows that the aluminum pad on substrate A has partially fallen off.
[0069] exist Figure 6 (b) and Figure 6 In (c), the whole aluminum liner can be observed, and the edges and corners of the aluminum liner are intact. The aluminum liner has neither fallen off as a whole nor has any defects. However, the film around the aluminum liner has peeling defects, such as Figure 6 In (c), there is a defect in the brown film above the yellow aluminum liner, which exposes a black area and combines Figure 6 (d) and Figure 6 In (e), it can be clearly observed that the film around the aluminum liner has defects.
[0070] Therefore, in the semiconductor device formation method provided by the present invention, the compressive stress in the silicon oxide layer is increased by accelerating the deposition rate of the silicon oxide layer. The silicon oxide layer with high compressive stress can pull the tungsten material layer with high tensile stress, thereby reducing the stress difference between the existing silicon oxide layer and the tungsten material layer from 1493 MPa to 1233 MPa, and the situation of aluminum pad falling off is effectively improved.
[0071] In order to further confirm the specific film layer of the film peeling in substrate B and explore the cause of the film peeling defect around the aluminum pad, substrate B was sliced along the direction perpendicular to its surface using a focused ion beam (FIB), and the cross section after the slice was used to confirm the specific film layer of the peeling. Figure 6 As shown in (f), there is no crack between the silicon oxide layer 5 and the tungsten material layer 7 at the edge of the substrate B at the corner of the trench structure (the area circled by the red dotted circle in the figure). In an ideal state, the gap between the silicon oxide layer 5 and the tungsten material layer 7 should be as follows. Figure 6 As shown in (f), the silicon oxide layer 5 and the tungsten material layer 7 are tightly attached to each other at any position where they are stacked. Figure 6 As shown in (g), there is an obvious crack between the silicon oxide layer 5 and the tungsten material layer 7 located at the center of the substrate B (the area circled by the red dotted circle in the figure, there is a small white crack between the silicon oxide layer 5 and the tungsten material layer 7 in this area), and the crack is located at the corner of the groove structure. This is because the stress of the thin film material is more concentrated at the corner of the groove structure, which makes it most difficult for the silicon oxide layer 5 to pull the tungsten material layer 7 at this location. Although the compressive stress in the silicon oxide layer 5 has been increased, the stress difference between the two thin films is still large, resulting in the existence of cracks at this location. When cracks exist, the aluminum liner and the film layer around the aluminum liner are still at risk of falling off. The method of accelerating the deposition rate of the silicon oxide layer 5 cannot completely solve the technical problem of the aluminum liner falling off.
[0072] The present invention further reduces the stress difference between the silicon oxide layer and the tungsten material layer by reducing the tensile stress of the tungsten material layer. Two methods for reducing the tensile stress in the tungsten material layer are provided below.
[0073] (1) Increase the deposition temperature of the tungsten layer
[0074] During the chemical vapor deposition process for tungsten layer deposition, increasing the deposition temperature reduces the impurity content of the tungsten lattice and reduces dislocations. Therefore, increasing the temperature can reduce the tensile stress in the tungsten layer. However, as mentioned above, considering the compatibility of the previous and subsequent process temperatures and the potential impact of temperature on the device, the adjustment range of the deposition temperature should not be too large.
[0075] In some embodiments, the deposition temperature of the tungsten bulk layer is increased to 400° C. to 430° C. Compared to a technical solution in which the tungsten bulk layer is deposited at 395° C., the deposition temperature of the tungsten bulk layer of the present invention is only increased by 5° C. to 35° C. Within this temperature increase range, no other negative impacts on the device are caused.
[0076] Example 2
[0077] In Example 2, when forming the tungsten bulk layer, the temperature of the third pedestal 103 and the fourth pedestal 104 was 405°C, and the remaining steps were the same as in Example 1. The tensile stress of the tungsten material layer 7 obtained in Example 2 was 1505 MPa. The difference between the compressive stress of the silicon oxide layer 5 and the tensile stress of the tungsten material layer 7 was 1175 MPa.
[0078] Example 3
[0079] In Example 3, when forming the tungsten bulk layer, the temperature of the third pedestal 103 and the fourth pedestal 104 was 415°C, and the remaining steps were the same as in Example 1. The tensile stress of the tungsten material layer 7 obtained in Example 3 was 1476 MPa. The difference between the compressive stress of the silicon oxide layer 5 and the tensile stress of the tungsten material layer 7 was 1146 MPa.
[0080] Considering the compatibility of the previous and subsequent process temperatures and the impact of temperature on the device, the deposition temperature of the tungsten bulk layer can only be increased by 5°C to 35°C. Compared with the tensile stress of the tungsten material layer in Example 1, the tensile stress of the tungsten material layer in Example 2 was reduced by 58 MPa, and the tensile stress of the tungsten material layer in Example 3 was reduced by 87 MPa.
[0081] (2) Adjust the flow rate of tungsten-containing gas
[0082] During the chemical vapor deposition process for forming a tungsten material layer, the flow rate of a tungsten-containing gas (e.g., WF6) can also affect the stress of the tungsten material layer. The tensile stress of the tungsten material layer decreases as the flow rate of the tungsten-containing gas decreases. Therefore, the tensile stress of the tungsten material layer can be reduced by adjusting the flow rate of the tungsten-containing gas, particularly when forming the tungsten bulk layer.
[0083] The flow rate of the tungsten-containing gas should be within the mass saturation range of 150 sccm-300 sccm. Within this mass saturation range, the tungsten-containing gas flow rate ensures sufficient contact with the substrate surface. When the tungsten material layer in the substrate needs to fill holes, the supersaturated tungsten-containing gas ensures uniform filling and prevents the formation of voids within the holes.
[0084] In some embodiments, the flow rate of the tungsten-containing gas is 150 sccm-300 sccm. Optionally, when forming the tungsten bulk layer, the flow rate of the tungsten-containing gas is 150 sccm-180 sccm.
[0085] Example 4
[0086] In Example 4, when the substrate undergoes a growth process on the first pedestal 101 and the second pedestal 102, the flow rate of WF6 introduced is 300 sccm, and the temperature of the first pedestal 101 and the second pedestal 102 is 300°C, forming a tungsten nucleation layer. When the substrate undergoes a growth process on the third pedestal 103, the flow rate of WF6 introduced is 150 sccm, and when the substrate undergoes a growth process on the fourth pedestal 104, the flow rate of WF6 introduced is 300 sccm; the temperature of the third pedestal 103 and the fourth pedestal 104 is 395°C, forming a tungsten bulk layer; ultimately, a tungsten material layer 7 is obtained. The remaining steps are the same as in Example 1. The tensile stress of the tungsten material layer 7 obtained in Example 4 is 1530 MPa. The difference between the compressive stress of the silicon oxide layer 5 and the tensile stress of the tungsten material layer 7 is 1200 MPa.
[0087] Example 5
[0088] In Example 5, when the substrate undergoes a growth process on the first pedestal 101 and the second pedestal 102, the flow rate of WF6 introduced is 300 sccm, and the temperature of the first pedestal 101 and the second pedestal 102 is 300°C, forming a tungsten nucleation layer. When the substrate undergoes a growth process on the third pedestal 103, the flow rate of WF6 introduced is 300 sccm, and when the substrate undergoes a growth process on the fourth pedestal 104, the flow rate of WF6 introduced is 150 sccm; the temperature of the third pedestal 103 and the fourth pedestal 104 is 395°C, forming a tungsten bulk layer; and finally, a tungsten material layer 7 is obtained. The remaining steps are the same as in Example 1. The tensile stress of the tungsten material layer 7 obtained in Example 5 is 1562 MPa. The difference between the compressive stress of the silicon oxide layer 5 and the tensile stress of the tungsten material layer 7 is 1232 MPa.
[0089] Example 6
[0090] In Example 6, when the substrate undergoes a growth process on the first pedestal 101 and the second pedestal 102, the flow rate of WF6 introduced is 300 sccm, and the temperature of the first pedestal 101 and the second pedestal 102 is 300°C, forming a tungsten nucleation layer. When the substrate undergoes a growth process on the third pedestal 103, the flow rate of WF6 introduced is 150 sccm, and when the substrate undergoes a growth process on the fourth pedestal 104, the flow rate of WF6 introduced is 150 sccm; the temperature of the third pedestal 103 and the fourth pedestal 104 is 395°C, forming a tungsten bulk layer; and finally, a tungsten material layer 7 is obtained. The remaining steps are the same as in Example 1. The tensile stress of the tungsten material layer 7 obtained in Example 6 is 1522 MPa. The difference between the compressive stress of the silicon oxide layer 5 and the tensile stress of the tungsten material layer 7 is 1192 MPa.
[0091] Comparing Examples 4, 5, and 6, it can be seen that the process conditions provided by Example 6 have the most significant improvement on the tensile stress of the tungsten material layer 7. Compared with the tensile stress of the tungsten material layer in Example 1, the tensile stress of the tungsten material layer in Example 6 is reduced by 41 MPa.
[0092] While both increasing the deposition temperature of the bulk tungsten layer and adjusting the flow rate of the tungsten-containing gas can reduce the tensile stress in the tungsten layer, the reduction is not significant. It is unknown whether the synergistic effect of process temperature and reaction gas has a significant impact on the stress in the tungsten layer. Therefore, the present invention combines these two methods for reducing the tensile stress in the tungsten layer, hoping to achieve a "1 + 1 > 2" effect.
[0093] Example 7
[0094] In Example 7, when the substrate undergoes a growth process on the first pedestal 101 and the second pedestal 102, the flow rate of WF6 introduced is 150 sccm, and the temperature of the first pedestal 101 and the second pedestal 102 is 395°C, forming a tungsten nucleation layer. When the substrate undergoes a growth process on the third pedestal 103 and the fourth pedestal 104, the flow rate of WF6 introduced is 150 sccm, and the temperature of the third pedestal 103 and the fourth pedestal 104 is 415°C, forming a tungsten bulk layer; ultimately, tungsten material layer 7 is obtained. The remaining steps are the same as in Example 1. Under these conditions, the tensile stress of tungsten material layer 7 is significantly reduced to 1360 MPa. The difference between the compressive stress of silicon oxide layer 5 and the tensile stress of tungsten material layer 7 is reduced to 1030 MPa.
[0095] The substrate C obtained in Example 7 was tested and analyzed. Figure 8 As shown in (a), under dark field defect detection, no black spots appear on substrate C, indicating that there are no defects on substrate C. Figure 8As shown in (b), substrate C is observed under a scanning electron microscope and the aluminum liner is intact. Substrate C is sliced along the direction perpendicular to its surface using a focused ion beam (FIB), and the cross section after the slice is observed using a transmission electron microscope (TEM) to observe the adhesion between the tungsten material layer and the silicon oxide layer at the corner structure of the groove structure. Figure 8 As shown in (c), there is no crack between the silicon oxide layer 5 and the tungsten material layer 7 at the edge of the substrate C at the corner of the trench structure. Figure 8 As shown in (d), there is no crack between the silicon oxide layer 5 and the tungsten material layer 7 at the center of the substrate C at the corner of the groove structure. In other words, at any position of the substrate C, the silicon oxide layer and the adhesion layer are tightly attached, and the adhesion layer and the tungsten material layer are also tightly attached. According to the method for forming a semiconductor device provided in Example 7, 25 substrates were made again, and the detachment of the aluminum liner on the substrate surface was detected by DFI. Figure 8 As shown in (e), no defects caused by aluminum liner peeling were detected in any of the 25 substrates, indicating that the method for forming a semiconductor device provided in Example 7 can completely solve the problem of aluminum liner peeling due to high stress difference.
[0096] Table 1 Stress values of Examples 1-7 and Comparative Example 1
[0097] Serial number Compressive stress in silicon oxide layer Tensile stress in the tungsten material layer Stress difference Example 1 330MPa 1563MPa 1233MPa Example 2 330MPa 1505MPa 1175MPa Example 3 330MPa 1476MPa 1146MPa Example 4 330MPa 1530MPa 1200MPa Example 5 330MPa 1562MPa 1232MPa Example 6 330MPa 1522MPa 1192MPa Example 7 330MPa 1360MPa 1030MPa Comparative Example 1 70MPa 1563MPa 1493MPa
[0098] In summary, the present invention provides a method for forming a semiconductor device that can enhance the compressive stress of the silicon oxide layer while reducing the tensile stress of the tungsten material layer. This allows the silicon oxide layer to be pulled together by the compressive stress and the tungsten material layer to be pulled together by the tensile stress. This prevents the tungsten material layer from peeling off from the underlying silicon oxide layer due to a large stress differential, protects the subsequently deposited aluminum liner, and prevents the aluminum liner from falling off the substrate. The present invention provides a solution to the problem of aluminum liner peeling defects caused by high stress in mass-produced FABs, and has significant significance for improving product quality and reducing costs.
[0099] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description is not intended to limit the present invention. After reading the above description, various modifications and substitutions of the present invention will become apparent to those skilled in the art. Therefore, the scope of protection of the present invention should be defined by the appended claims.
Claims
1. A method for forming a semiconductor device, characterized in that: include: providing a substrate; A silicon oxide layer is deposited on the substrate at a deposition rate of depositing an adhesion layer on the silicon oxide layer; depositing a tungsten material layer on the adhesion layer; An aluminum liner is deposited on the tungsten material layer.
2. The method for forming a semiconductor device according to claim 1, wherein: The tungsten material layer includes a tungsten nucleation layer deposited on the adhesion layer, and a tungsten bulk layer deposited on the tungsten nucleation layer.
3. The method for forming a semiconductor device according to claim 2, wherein: The deposition temperature of the tungsten body layer is 400° C.-430° C.
4. The method for forming a semiconductor device according to claim 2, wherein: A tungsten-containing gas is introduced into the substrate to form the tungsten material layer; the flow rate of the tungsten-containing gas is 150 sccm-300 sccm.
5. The method for forming a semiconductor device according to claim 4, wherein: When forming the tungsten bulk layer, the flow rate of the tungsten-containing gas is 150 sccm-180 sccm.
6. The method for forming a semiconductor device according to claim 1, wherein: The silicon oxide layer and the adhesion layer are tightly adhered to each other, and the adhesion layer and the tungsten material layer are tightly adhered to each other.
7. The method for forming a semiconductor device according to claim 1, wherein: The compressive stress in the silicon oxide layer is 300 MPa-350 MPa.
8. The method for forming a semiconductor device according to claim 1, wherein: The tensile stress in the tungsten material layer is 1200 MPa-1600 MPa.
9. The method for forming a semiconductor device according to claim 1, wherein: The stress difference between the silicon oxide layer and the tungsten material layer is no more than 1050 MPa.
10. The method for forming a semiconductor device according to claim 1, wherein: The substrate includes a trench structure, and the aluminum liner is deposited in the trench structure.
11. The method for forming a semiconductor device according to claim 1, wherein: The thickness of the silicon oxide layer is The thickness of the adhesion layer is The thickness of the tungsten material layer is 12. The method for forming a semiconductor device according to claim 1, wherein: The material of the adhesion layer includes tungsten nitride and / or titanium nitride.
13. The method for forming a semiconductor device according to claim 1, wherein: The semiconductor device is a back-illuminated image sensor.