Method for determining conditions for formation of oxide film, method for forming oxide film, and method for producing wafer

Abstract

This method for determining conditions for the formation of an oxide film includes: an oxide film pre-formation step for forming a first oxide film on a first wafer with use of a first tray body; a correlation acquisition step for acquiring a correlation between the film thickness distribution of the oxide film and at least one constituent component among a groove part and a contact part of the tray body; a target film thickness distribution acquisition step for acquiring a target film thickness distribution of the oxide film; and a tray body configuration determination step for determining the at least one constituent component, which is capable of forming the oxide film of the target film thickness distribution, as an applied component on the basis of the film thickness distribution of the first oxide film and the correlation.

Description

Method for determining oxide film formation conditions, method for forming oxide film, and method for manufacturing wafer

[0001] The present invention relates to a method for determining conditions for forming an oxide film, a method for forming an oxide film, and a method for manufacturing a wafer.

[0002] A method for forming an oxide film on a wafer by heating a film formation tray and supplying a source gas onto the wafer mounted on the film formation tray is known (see, for example, Patent Document 1). The film formation tray described in Patent Document 1 includes a support member that supports the outer periphery of the wafer and a tray body that supports the support member. Patent Document 1 describes that reducing the contact area between the support member and the tray body makes it possible to more uniformly distribute the thickness of the oxide film on the wafer.

[0003] Re-table 2011 / 070741 publication

[0004] However, in recent years, with the demand for more uniform film thickness distribution, variations in film thickness distribution among a plurality of film deposition apparatuses have become a problem.

[0005] An object of the present invention is to provide a method for determining oxide film formation conditions, a method for forming an oxide film, and a method for manufacturing a wafer, which are capable of forming an oxide film having a desired film thickness distribution on a wafer.

[0006] The method for determining oxide film formation conditions of the present invention is a method for determining conditions for forming an oxide film on a wafer using a film formation apparatus, wherein the film formation apparatus uses a film formation tray including a support member for supporting an outer periphery of the wafer and a tray body for supporting the support member, and is configured to form the oxide film on the wafer by supplying a source gas onto the wafer while heating the film formation tray, the support member including a ring-shaped mounting portion on which the wafer is placed and legs extending downward from the mounting portion, and the tray body including a cylindrical recess for accommodating the support member and a plurality of grooves formed along the outer edge of a bottom surface of the recess. The method for determining oxide film formation conditions includes a pre-oxide film formation process for forming a first oxide film on the first wafer using a first tray body, a correlation acquisition process for acquiring a correlation between at least one constituent element of the grooves and the contact elements and a film thickness distribution of the oxide film, a target film thickness distribution acquisition process for acquiring a target film thickness distribution of the oxide film, and a tray body configuration determination process for determining, as an applicable requirement, the at least one constituent element that can form the oxide film of the target film thickness distribution based on the film thickness distribution of the first oxide film and the correlation.

[0007] In the method for determining conditions for forming an oxide film of the present invention, it is preferable that the correlation includes a first correlation between the width of at least a portion of the groove portion in the circumferential direction and the thickness of the oxide film in a region adjacent to the at least a portion in the outer periphery of the wafer.

[0008] In the method for determining conditions for forming an oxide film of the present invention, the film formation apparatus is configured to form the oxide film on the wafer supported on each film formation tray while arranging a plurality of film formation trays, each having the tray body, in the feed direction and transporting them in the feed direction, and it is preferable that the correlation includes a second correlation between the contact area of ​​the contact portion and the leg portion at a portion of the tray body on the transport width direction side perpendicular to the feed direction, and the thickness of the oxide film in a region adjacent to the portion on the transport width direction side at the outer periphery of the wafer.

[0009] In the method for determining conditions for forming an oxide film of the present invention, it is preferable that the second correlation be such that the larger the contact area at the portion on the transport width direction side, the thinner the oxide film in the region adjacent to the portion on the transport width direction side.

[0010] In the method for determining conditions for forming an oxide film of the present invention, the film formation apparatus is configured to form the oxide film on the wafer supported on each film formation tray while arranging a plurality of film formation trays, each having the tray body, in the feed direction and transporting them in the feed direction, and it is preferable that the correlation includes a third correlation between the contact area of ​​the contact portion and the leg portion at the portion of the tray body on the feed direction side and the opposite side to the feed direction, and the thickness of the oxide film in the region adjacent to the portion on the feed direction side and the opposite side at the outer periphery of the wafer.

[0011] In the method for determining conditions for forming an oxide film of the present invention, it is preferable that the third correlation be such that the larger the contact area at the portions on the feed direction side and the opposite direction side, the thicker the oxide film in the regions adjacent to the portions on the feed direction side and the opposite direction side.

[0012] The oxide film forming method of the present invention comprises a step of performing the above-mentioned oxide film formation condition determination method, and a film forming step of forming a second oxide film on a second wafer using a second tray body that satisfies the application requirements.

[0013] In the oxide film forming method of the present invention, it is preferable that the method further includes a tray body preparation step of preparing multiple types of tray bodies that differ from each other in at least one constituent element, and the film forming step selects the second tray body from the at least one constituent element corresponding to each of the multiple types of tray bodies, and forms the second oxide film using the second tray body.

[0014] The method for producing a wafer of the present invention includes the step of forming the oxide film on the second wafer by the above-described method for forming an oxide film.

[0015] 2A ; FIG. 3A is a schematic diagram showing the configuration of a film formation apparatus according to a prerequisite technique of the present invention; FIG. 4B is a plan view showing the configuration of a film formation tray according to the prerequisite technique and Experimental Examples 1 and 2; FIG. 5A is a view taken along line IIB-IIB in FIG. 2A showing the configuration of a film formation tray according to the prerequisite technique and Experimental Examples 1 and 2; FIG. 5B is a view taken along line IIC-IIC in FIG. 2A showing the configuration of a film formation tray according to the prerequisite technique and Experimental Examples 1 and 2; FIG. 6A is a plan view showing a tray main body according to Experimental Example 3; and FIG. 7A is a plan view showing a tray main body according to Experimental Example 4.. FIG. 6B is a schematic diagram of a central region constituting an evaluation region of a film thickness used in a method for investigating a correlation between structural requirements of groove portions and contact portions of a tray main body and a film thickness distribution of an oxide film.. FIG. 7C is a schematic diagram of a peripheral region constituting the evaluation region.. FIG. 8A is a schematic diagram of a transport width direction region constituting the evaluation region.. FIG. 8C is a schematic diagram of a transport direction region constituting the evaluation region.. FIG. 9 is a flowchart showing a wafer manufacturing method according to an embodiment of the present invention; and FIG. 10 is a flowchart showing an oxide film formation process according to the embodiment.

[0016] [Prerequisite Technology] First, before describing an embodiment of the present invention, the configuration of a film formation apparatus used in the embodiment will be described. FIG. 1 is a schematic diagram showing the configuration of a film formation apparatus according to the prerequisite technology of the present invention. The film formation apparatus 1 shown in FIG. 1 forms an oxide film on a wafer W. The film formation apparatus 1 includes a plurality of film formation trays 2, a circulation unit 3, and a film formation unit 4. The wafer W may be made of a material such as silicon, germanium, gallium arsenide, gallium phosphide, or indium phosphide.

[0017] The film formation tray 2 accommodates wafers W. The detailed configuration of the film formation tray 2 will be described later.

[0018] The circulation unit 3 circulates a predetermined number of film formation trays 2 within the film formation apparatus 1. The circulation unit 3 includes a first lifting / lowering unit 31, a film formation transport unit 32, a second lifting / lowering unit 33, and a return transport unit 34.

[0019] The first elevating unit 31 includes a first lift 311 on which the film formation tray 2 is placed, and a first elevating drive unit 312 that raises and lowers the first lift 311. When the first lift 311 is in the raised position, the wafer W before film formation is transferred into the film formation tray 2 by a transfer unit (not shown), and the film formation tray 2 is delivered to the film formation transport unit 32. The structure for delivering the film formation tray 2 from the first lift 311 to the film formation transport unit 32 is not particularly limited, and a well-known structure can be applied.

[0020] The film formation transport unit 32 includes a pair of transport rollers 321 and a transport belt 322 stretched over the pair of transport rollers 321. The film formation transport unit 32 rotates the transport belt 322 clockwise in FIG. 1 by rotating the transport rollers 321, thereby transporting the multiple film formation trays 2 in contact with each other to the film formation unit 4. An example of a configuration for transporting the film formation trays 2 by the transport belt 322 is a configuration in which protrusions provided on the transport belt 322 fit into fitting grooves provided on the underside of the tray body 22. The direction in which the film formation transport unit 32 transports the film formation trays 2 may be referred to as the "feed direction." Furthermore, the direction perpendicular to the feed direction and the vertical direction may be referred to as the "transport width direction."

[0021] The second lifting unit 33 includes a second lift 331 on which the film formation tray 2 is placed, and a second lifting drive unit 332 that raises and lowers the second lift 331. When the second lift 331 is in the raised position, the film formation tray 2 containing the wafers W after film formation is transferred from the transport rollers 321 to the second lift 331. When the second lift 331 is in the lowered position, the film formation tray 2 containing the wafers W after film formation is transferred to the return transport unit 34. The structure for transferring the film formation tray 2 from the transport rollers 321 to the second lift 331 and the structure for transferring the film formation tray 2 from the second lift 331 to the return transport unit 34 are not particularly limited, and well-known structures can be applied.

[0022] The return transport unit 34 transports the film formation trays 2 containing the wafers W after film formation in the direction opposite to the sending direction. The film formation trays 2 transported by the return transport unit 34 are handed over to the first lift 311 located in a lowered position. The structure for handing over the film formation trays 2 from the return transport unit 34 to the first lift 311 is not particularly limited, and a well-known structure can be applied. The direction in which the return transport unit 34 transports the film formation trays 2 is sometimes referred to as the "return direction."

[0023] When the film formation tray 2 is handed over from the return transport unit 34 to the first lift 311 at the lowered position, the first lift 311 rises to the raised position. With the first lift 311 in the raised position, the wafers W after film formation are transferred from the film formation tray 2 to a wafer storage unit (not shown) by the transfer unit. Thereafter, as described above, the wafers W before film formation are transferred into the film formation tray 2 by the transfer unit (not shown), and the film formation tray 2 is handed over to the film formation transport unit 32.

[0024] The film forming unit 4 forms an oxide film on the wafer W in the film forming tray 2 transported by the film forming transport unit 32. The film forming unit 4 includes a preheater 41, a heater 42, a raw material gas supply unit 43, a pair of shielding gas supply units 44, and a pair of exhaust units 45.

[0025] The preheater 41 and the heater 42 are disposed, for example, in a space surrounded by the conveyor belt 322. The heater 42 is disposed on the feed direction side of the preheater 41. The wafers W in the film formation tray 2 are preheated by the preheater 41 to a temperature lower than the film formation temperature, and then heated by the heater 42 to the film formation temperature.

[0026] The source gas supply unit 43 is disposed above the heater 42. The source gas supply unit 43 ejects a source gas G1 downward and supplies it onto the wafer W. An oxide film is formed by reaction on the heated wafer W. The source gas is monosilane (SiH ４ ) and oxygen (O ２ ) mixed gas, or tetraethoxysilane (TEOS, chemical formula: Si(OC ２ H ５ ) ４ ) and ozone (O ３ ) mixed gas can be exemplified.

[0027] The pair of insulating gas supply units 44 are disposed above the heater 42, on the feed and return sides of the source gas supply unit 43. Each insulating gas supply unit 44 ejects the insulating gas G2 downward to prevent the source gas G1 from leaking in the feed and return directions of the film forming unit 4. Nitrogen gas can be exemplified as the insulating gas G2.

[0028] The pair of exhaust units 45 are respectively disposed between the source gas supply unit 43 and the blocking gas supply unit 44 on the feed direction side, and between the source gas supply unit 43 and the blocking gas supply unit 44 on the return direction side. Each exhaust unit 45 exhausts the blocking gas G2 and the source gas G1 not used in film formation from the space between the source gas supply unit 43 and the film formation tray 2 to above the source gas supply unit 43.

[0029] Next, the detailed configuration of the film formation tray 2 will be described. Fig. 2A is a plan view showing the configuration of the film formation tray. Fig. 2B is a view taken along line IIB-IIB in Fig. 2A. Fig. 2C is a view taken along line IIC-IIC in Fig. 2A. As shown in Figs. 2A to 2C, the film formation tray 2 includes a support member 21 and a tray main body 22. The support member 21 and the tray main body 22 are formed of, for example, SiC.

[0030] The support member 21 supports the outer periphery of the wafer W. The support member 21 includes a mounting portion 211 and legs 212. The mounting portion 211 is formed in an annular shape. The wafer W is mounted on the mounting portion 211. The legs 212 are formed to extend cylindrically downward from the entire outer edge of the mounting portion 211.

[0031] The tray body 22 is formed in a rectangular parallelepiped shape. In the plan view shown in FIG. 2A , the side surfaces corresponding to the long sides of the rectangle of the tray body 22 constitute opposing surfaces 22A that face the adjacent film formation tray 2 when the tray body 22 is transported by the film formation transport unit 32 of the film formation apparatus 1, as shown in FIG. 1 , while the side surfaces corresponding to the short sides constitute non-opposing surfaces 22B that do not face the adjacent film formation tray 2 when the tray body 22 is transported by the film formation transport unit 32 of the film formation apparatus 1. A cylindrical recess 221 is formed in the center of the tray body 22. A plurality of arc-shaped grooves 222 are formed in the bottom surface of the recess 221 along the outer edge of the bottom surface. A portion located between a pair of adjacent grooves 222 constitutes a contact portion 223 that supports the leg portion 212 of the support member 21.

[0032] [Background to the Invention] Next, the background to the invention will be described. Experiments were conducted to investigate the correlation between the structural requirements of the grooves 222 and contact portions 223 of the tray body 22 of the film formation tray 2 described above and the thickness distribution of an oxide film on a wafer W. FIG. 3A is a plan view of a tray body according to Experimental Example 3. FIG. 3B is a plan view of a tray body according to Experimental Example 4. FIG. 4A is a schematic diagram of a central region constituting a film thickness evaluation region used in a method for investigating the correlation between the structural requirements of the grooves and contact portions of the tray body and the thickness distribution of an oxide film. FIG. 4B is a schematic diagram of a peripheral region constituting the evaluation region. FIG. 4C is a schematic diagram of a transport width direction region constituting the evaluation region. FIG. 4D is a schematic diagram of a transport direction region constituting the evaluation region.

[0033] <Method of Creating Evaluation Samples> First, four types of tray bodies 22 were prepared, each differing from the other in at least one of the constituent elements of the grooves 222 and the contact portions 223, such as the number, shape, and position. Specifically, tray bodies 23, 24, 25, and 26 were prepared as shown below in Experimental Examples 1, 2, 3, and 4. Note that the same names and symbols are used for the tray bodies 23, 24, 25, and 26 that have the same configuration as the tray body 22 of the background art described above, or that are the same as each other.

[0034] The tray body 23 of Experimental Example 1 has the configuration shown in FIGS. 2A to 2C. Six grooves 232 of the same shape are formed on the bottom surface of the recess 221 of the tray body 23. Each groove 232 is formed to have a (circumferential) length L1. As shown in Table 1 below, each groove 232 is formed to satisfy the relationship "J1:J0 = 4:1," where J1 is the width of the groove 232 and J0 is the width (thickness) of the leg portion 212 of the support member 21. The grooves 232 are formed at equal intervals so that six first contact portions 233 of the same shape are provided. The (circumferential) length of each of the first contact portions 233 thus provided is M1, as shown in Table 1.

[0035]

[0036] The tray main body 24 of Experimental Example 2 has the configuration shown in Figures 2A to 2C. Six grooves 242 of the same shape are formed on the bottom surface of the recess 221 of the tray main body 24. The length of each groove 242 is L1, which is the same as the length of the groove 232 of Experimental Example 1. As shown in Table 1, when the width of each groove 242 is J2, each groove 242 is formed to satisfy the relationship "J2:J0 = 6:1". The grooves 242 are formed at equal intervals so that the length of each first contact portion 243 is M1, which is the same as the length of the first contact portion 233 of Experimental Example 1.

[0037] The tray body 25 of Experimental Example 3 has the configuration shown in FIG. 3A . Four grooves 252 of the same shape are formed on the bottom surface of the recess 221 of the tray body 25. The length of each groove 252 is L2, which is longer than the length of the groove 232 of Experimental Example 1. The width of each groove 252 is J1, which is the same as the width of the groove 232 of Experimental Example 1. Each groove 252 is formed so that two first contact portions 233 and two second contact portions 254 are alternately arranged in the circumferential direction. When the length of each second contact portion 254 is M2, each second contact portion 254 is formed to satisfy the relationship "M2:M1 = 52:1." The length M2 of each second contact portion 254 is shorter than the sum of the length M1 of two adjacent first contact portions 233 in the tray body 23 of Experimental Example 1 and the length L1 of the groove 232 between the two adjacent first contact portions 233. Each groove 252 is formed so that the center of the length of each first contact portion 233 is located at the portion closest to the pair of non-opposing surfaces 22B in the recess 221, and the center of the length of each second contact portion 254 is located at the portion closest to the pair of opposing surfaces 22A in the recess 221. In other words, each groove 252 is formed so that one first contact portion 233 is located on each side in the conveyance width direction, and one second contact portion 254 is located on each of the feed direction side and the return direction side.

[0038] The tray body 26 of Experimental Example 4 has the configuration shown in FIG. 3B . Two grooves 262 of the same shape are formed in the bottom surface of the recess 221 of the tray body 26. The length of each groove 262 is L3, which is longer than the length of the groove 252 of Experimental Example 3. The width of each groove 262 is J1, which is the same as the width of the groove 232 of Experimental Example 1. Each groove 262 is formed so that the two second contact portions 254 are located in the same positions as the second contact portions 254 of Experimental Example 3. In other words, each groove 262 is formed so that one second contact portion 254 is located on the feed direction side and one on the return direction side.

[0039] Ten wafers W each having a diameter of 300 mm were prepared. Seven film formation trays 2 each including the tray body 23 of Experimental Example 1 and one film formation tray 2 each including the tray body 24, 25, and 26 of Experimental Examples 2, 3, and 4 were placed in the circulation section 3 of the film formation apparatus 1. An oxide film was formed on each of the four film formation trays 2 each including the tray body 23, 24, 25, and 26 of Experimental Examples 1, 2, 3, and 4. The target thickness of the oxide film was 350 nm. Hereinafter, the wafers W on which films were formed using the film formation trays 2 each including the tray body 23, 24, 25, and 26 of Experimental Examples 1, 2, 3, and 4 may be referred to as wafers W1, W2, W3, and W4 of Experimental Examples 1, 2, 3, and 4, respectively.

[0040] <Method for investigating the correlation between the structural requirements of the groove and contact portion of the tray body and the thickness distribution of the oxide film> (1. Correlation between the groove portion of the tray body and the thickness distribution of the oxide film) The thickness distribution of the oxide film was measured for each of the wafers W1 and W2 of Experimental Examples 1 and 2. Then, the average thickness of the oxide film in the central region A1 shown in FIG. 4A and the peripheral region A2 shown in FIG. 4B for each of the wafers W1 and W2 was calculated. The central region A1 is a circular region with a diameter of 60 mm centered at the center of the wafer W. The peripheral region A2 is an annular region within 30 mm from the outer edge of the wafer W. The width of the peripheral region A2 is larger than the width J2 of the groove 242 in Experimental Example 2.

[0041] Next, the first film thickness ratios for wafers W1 and W2 of Experimental Examples 1 and 2 were calculated based on the following formula (1): First film thickness ratio=Average film thickness in peripheral region / Average film thickness in central region (1) Then, the first influence evaluation value for evaluating the influence of the width of the groove portion was calculated based on the following formula (2): First influence evaluation value=First film thickness ratio for wafer W2 of Experimental Example 2 / First film thickness ratio for wafer W1 of Experimental Example 1 (2) The calculation results of formulas (1) and (2) are shown in Table 2.

[0042]

[0043] As shown in Table 2, the first impact evaluation value was a value less than 1. From this, it was confirmed that the width of the groove portion 222 and the film thickness distribution of the oxide film have a correlation such that the larger the width of the groove portion 222, the thinner the oxide film on the outer periphery of the wafer W becomes relative to the oxide film in the central portion.

[0044] The inventors speculated that the reason for this correlation is as follows: As the width of the groove 222 increases, the distance from the inner edge of the groove 222 (the edge closest to the center of the recess in a plan view) to the leg 212 of the support member 21 increases, and the amount of heat transferred from the inner edge of the groove 222 to the outer periphery of the wafer W via the leg 212 decreases. It was estimated that a decrease in the amount of heat transferred to the outer periphery of the wafer W lowers the temperature of the outer periphery, resulting in a thinner oxide film on the outer periphery. Furthermore, based on the above-described estimation results, it is believed that the smaller the width of the groove 222, the thicker the oxide film on the outer periphery of the wafer W becomes relative to the oxide film on the center. Furthermore, it is believed that by making the width of a portion of the groove 222 in the circumferential direction larger or smaller than the width of the remainder, the oxide film on a portion adjacent to the portion can be made thinner or thicker than the oxide film on a portion adjacent to the remainder. That is, it was confirmed that there is a correlation (hereinafter sometimes referred to as a “first correlation”) between the width of at least a portion of the groove 222 in the circumferential direction and the ratio of the thickness of the oxide film in the region adjacent to said at least a portion in the outer periphery to the thickness of the oxide film in the central part of the wafer W. The first correlation can also be said to be a correlation between the width of at least a portion of the groove 222 in the circumferential direction and the thickness of the oxide film in the region adjacent to said at least a portion in the outer periphery of the wafer W.

[0045] (2. Correlation between the presence or absence of contact portions in the transport width direction of the tray body and the thickness distribution of the oxide film) The thickness distribution of the oxide film was measured for each of wafers W3 and W4 in Experimental Examples 3 and 4. Then, the average thickness of the oxide film in the central region A1 and the two transport width direction regions A3 shown in Figure 4C was calculated for each wafer W3 and W4. The transport width direction regions A3 are approximately semicircular regions on both ends of the wafer W in the transport width direction. The circumferential length of the transport width direction region A3 is 60 mm, which is longer than M1, the length of the first contact portion 233 in Experimental Example 3. The radial length of the transport width direction region A3 is 30 mm.

[0046] Next, the second film thickness ratios for wafers W3 and W4 of Experimental Examples 3 and 4 were calculated based on the following formula (3). The calculation results are shown in Table 3 below. Second film thickness ratio=average film thickness in transport width direction region / average film thickness in central region (3) Then, a second influence evaluation value for evaluating the influence of the presence or absence of a contact portion in the transport width direction was calculated based on the following formula (4). Second influence evaluation value=second film thickness ratio for wafer W3 of Experimental Example 3 / second film thickness ratio for wafer W4 of Experimental Example 4 (4) The calculation results of formulas (3) and (4) are shown in Table 3.

[0047]

[0048] As shown in Table 3, the second influence evaluation value was a value less than 1. From this, it was confirmed that the presence or absence of the contact portion 223 in the transport width direction and the thickness distribution of the oxide film are correlated such that the oxide film in the region adjacent to the transport width direction portion on the outer periphery of the wafer W is thinner than the central portion when the contact portion 223 is provided in the portion on the transport width direction side of the tray body 22 compared to when the contact portion 223 is not provided. Note that, as shown in FIG. 3A , the portion on the transport width direction side of the tray body 22 on which the contact portion 223 is provided is a portion within a sector-shaped region that includes the center 221C of the recess 221, is symmetrical with respect to the reference line T1 parallel to the transport width direction, and has a central angle θ1 of 60°. Note that, in a plan view, the center 221C of the recess 221 usually overlaps with the center We of the wafer W supported by the support member 21.

[0049] The inventors speculate that the reason for this correlation is as follows: While an oxide film is being formed on a wafer W in any film formation tray 2, film formation trays 2 are present on both the feed direction side and the return direction side of the film formation tray 2 (hereinafter, the feed direction side and the return direction side may be collectively referred to as "both sides in the transport direction"), but no film formation trays 2 are present on both sides in the transport width direction. Therefore, it is considered that the temperature on both sides in the transport width direction of the tray body 22 is lower than that on both sides in the transport direction. For this reason, it is speculated that heat on both sides in the transport width direction of the placement portion 211 of the support member 21 is absorbed by the tray body 22 through the legs 212 and the contact portions 223 on both sides in the transport width direction, resulting in a lower temperature on both sides in the transport width direction of the wafer W, and a thinner oxide film on both sides in the transport width direction.

[0050] Furthermore, from the above-described estimation results, it is considered that the oxide film in the region adjacent to the portion on the outer periphery of the wafer W in the transport width direction is thicker than in the central portion when the contact portion 223 is not provided at the portion on the tray body 22 on the transport width direction side. Furthermore, when the contact portion 223 is provided at the portion on the tray body 22 on the transport width direction side, it is considered that heat on the transport width direction side of the tray body 22 is more easily dissipated when the length of the contact portion 223 is longer than when the length of the contact portion 223 is shorter. From this, it is considered that the longer the contact portion 223 and the larger the contact area between the contact portion 223 and the leg portion 212, the thinner the oxide film in the region adjacent to the portion on the outer periphery of the wafer W in the transport width direction is compared to the central portion. In other words, it was confirmed that there is a correlation (hereinafter sometimes referred to as a "second correlation") between the contact area between the contact portion 223 and the leg portion 212 at the portion on the tray body 22 on the transport width direction side and the ratio of the oxide film thickness in the region adjacent to the portion on the outer periphery of the wafer W in the transport width direction to the oxide film thickness in the central portion of the wafer W. The second correlation can also be said to be the correlation between the contact area between the contact portion 223 and the leg portion 212 at the portion on the transport width side of the tray body 22 and the thickness of the oxide film in the region adjacent to the portion on the transport width side at the outer periphery of the wafer W.

[0051] (3. Correlation between the contact area between the contact portion and the leg portion in the transport direction of the tray body and the film thickness distribution of the oxide film) The average film thickness of the oxide film in the central region A1 and the two transport direction regions A4 shown in Figure 4D was calculated for the wafers W of Experimental Examples 1 and 3. The transport direction regions A4 are approximately arc-shaped regions on both sides of the wafer W in the transport direction. The circumferential length of the transport direction region A4 is 220 mm, which is longer than the length of the arc-shaped region including the two adjacent contact portions 223 in Experimental Example 1 and the length of the single second contact portion 254 in Experimental Example 3. The width (radial length) of the transport direction region A4 is 30 mm.

[0052] Next, the third film thickness ratios for wafers W1 and W3 of Experimental Examples 1 and 3 were calculated based on the following formula (5): third film thickness ratio=average film thickness in transport direction region / average film thickness in central region (5) Then, a third influence evaluation value for evaluating the influence of the contact area between the contact portion and the leg portion in the transport direction was calculated based on the following formula (6): third influence evaluation value=third film thickness ratio for wafer W3 of Experimental Example 3 / third film thickness ratio for wafer W1 of Experimental Example 1 (6) The calculation results of formulas (5) and (6) are shown in Table 4.

[0053]

[0054] As shown in Table 4, the third impact evaluation value was a value exceeding 1. Here, the contact area between the leg 212 and one second contact portion 254 of Experimental Example 3, which is adjacent to the radially outer side of each transport direction region A4 during film formation, is larger than the sum of the contact areas between the leg 212 and two first contact portions 233 of Experimental Example 1. From this, it was confirmed that the contact area between the contact portion 223 and the leg 212 in the transport direction and the film thickness distribution of the oxide film have a correlation such that the larger the contact area of ​​the portion on the transport direction side of the tray body 22, the thicker the oxide film in the region adjacent to the portion on the transport direction side on the outer periphery of the wafer W becomes relative to the central portion. The transport direction side portion of the tray body 22 where the contact portion 223 is provided is a portion within a sector-shaped region that includes the center 221C of the recess 221, is symmetrical with respect to the reference line T2 parallel to the transport direction, and has a central angle θ2 of 90°, as shown in FIG. 3B . The transport direction region A4 is a region within the sector-shaped region shown in FIG. 3B.

[0055] The inventors speculated that the reason for this correlation is as follows. As described above, while an oxide film is being formed on a wafer W in any film formation tray 2, film formation trays exist on both sides of the film formation tray 2 in the transport direction, but film formation trays 2 do not exist on both sides of the transport width direction. Therefore, it is considered that the temperature on both sides of the tray body 22 in the transport direction is higher than that on both sides of the tray body 22 in the transport width direction. Therefore, it is considered that heat on both sides of the tray body 22 in the transport direction is transferred to the mounting portion 211 of the support member 21 via the contact portions 223 and the leg portions 212 on both sides of the transport direction. It is also considered that the amount of heat transferred to the mounting portion 211 of the support member 21 increases as the contact area between the contact portions 223 and the leg portions 212 increases. From these facts, it was estimated that the larger the contact area between the contact portions 223 and the leg portions 212, the higher the temperature on both sides of the wafer W in the transport direction, and the thicker the oxide film on both sides of the transport direction.

[0056] Furthermore, from the above-described estimation results, it is considered that the smaller the contact area between the contact portion 223 and the leg portion 212 at the portion on the transport direction side of the tray body 22, the lower the temperature at the transport direction side of the outer periphery of the wafer W, and the thinner the oxide film at the transport direction side will be compared to the central portion. Furthermore, when the contact portion 223 is not provided at the portion on the transport direction side of the tray body 22, it is considered that the heat at the transport direction side of the tray body 22 is not transferred to the mounting portion 211 of the support member 21 compared to when the contact portion 223 is provided. From this, it is considered that when the contact portion 223 is not provided at the portion on the transport direction side of the tray body 22, the oxide film at the region adjacent to the portion on the transport direction side of the outer periphery of the wafer W will be thinner compared to the central portion. That is, it was confirmed that there is a correlation (hereinafter sometimes referred to as a "third correlation") between the contact area between the contact portion 223 and the leg portion 212 at the portion on the transport direction side of the tray body 22 and the ratio of the thickness of the oxide film at the region adjacent to the portion on the transport width direction side at the outer periphery to the thickness of the oxide film at the center of the wafer W. The third correlation can also be said to be a correlation between the contact area between the contact portion 223 and the leg portion 212 at the portion on the transport direction side of the tray body 22 and the thickness of the oxide film at the region adjacent to the portion on the transport direction side at the outer periphery of the wafer W.

[0057] <Summary> The present inventors have found that the constituent elements of the groove portion 222 and the contact portion 223 of the tray body 22 included in the film formation tray 2 have the first to third correlations as described above, and the film thickness distribution of an oxide film on a wafer W. The present inventors then formed a first oxide film on a first wafer W using a first tray body 22 in a predetermined film formation apparatus 1, obtained a correlation between at least one constituent element of the groove portion 222 and the contact portion 223 and the film thickness distribution of the oxide film, obtained a target film thickness distribution of the oxide film, and determined, based on the film thickness distribution of the first oxide film and the correlation, the at least one constituent element capable of forming an oxide film with the target film thickness distribution as an applicable requirement. Then, the present inventors formed a second oxide film on a second wafer W in the predetermined film formation apparatus 1 using a second tray body 22 that satisfies the applicable requirement, thereby forming an oxide film with a desired film thickness distribution on a wafer W, and thus completed the present invention.

[0058] [Embodiment] <Oxide Film Forming Method> Next, a method for forming an oxide film according to one embodiment of the present invention will be described. Fig. 5 is a flowchart showing a wafer manufacturing method. Fig. 6 is a flowchart showing an oxide film forming step. Note that in this embodiment, as a wafer manufacturing method, a method for manufacturing an epitaxial wafer including a product wafer W as a second wafer made of silicon, an epitaxial layer provided on the front surface of the product wafer W, and a back surface oxide film (LTO film) as a second oxide film provided on the front surface of the product wafer W will be described.

[0059] As shown in FIG. 5, the wafer manufacturing method includes a pulling-up step S1, a block processing step S2, a slicing step S3, a pre-processing step S4, a double-side polishing step S5, an oxide film forming step S6, a single-side finishing step S7, a first cleaning step S8, an epitaxial layer forming step S9, and a second cleaning step S10.

[0060] In the pulling process S1, a cylindrical silicon single crystal is pulled from a silicon melt using the Czochralski method. In the block processing process S2, the outer periphery of the single crystal ingot is ground and notched according to the crystal orientation. The single crystal ingot is then cut into multiple blocks, for example, using a band saw. In the slicing process S3, the block is sliced ​​into multiple product wafers W, for example, approximately 1 mm thick, using an internal diameter cutting machine or a wire saw. In the pre-processing process S4, chamfering is performed, and rough polishing (lapping) is performed with, for example, an alumina abrasive to ensure that both surfaces of the product wafer W are parallel. Then, etching or other processes are performed as necessary, followed by planarization to remove unevenness from the surface of the product wafer W. In the double-side polishing process S5, a double-side polishing machine is used to perform a mirror finish on the pre-processed product wafer W to increase flatness.

[0061] The oxide film forming step S6 corresponds to the oxide film forming method of the present invention and includes the oxide film forming condition determining method of the present invention. In the oxide film forming step S6, a backside oxide film is formed on the backside of the product wafer W. In the single-side finishing step S7, the front side (the side on which the backside oxide film is not formed) of the product wafer W obtained in the oxide film forming step S6 is polished. By performing the polishing process in the single-side finishing step S7, scratches and damage on the front side of the product wafer W can be removed and the surface roughness of the front side can be adjusted. In the first cleaning step S8, the product wafer W obtained in the single-side finishing step S7 is cleaned, for example, with an alkaline solution. In the epitaxial layer forming step S9, an epitaxial layer is formed on the front side of the product wafer W. In the second cleaning step S10, the epitaxial wafer obtained in the epitaxial layer forming step S9 is cleaned, for example, with an alkaline solution.

[0062] Next, the oxide film forming step S6 will be described in detail. As shown in FIG. 6, the oxide film forming step S6 includes a tray body preparing step S61, a preliminary oxide film forming step S62, a correlation obtaining step S63, a target film thickness distribution obtaining step S64, a tray body configuration determining step S65, and a film forming step S66. The preliminary oxide film forming step S62, the correlation obtaining step S63, the target film thickness distribution obtaining step S64, and the tray body configuration determining step S65 constitute a method for determining oxide film formation conditions. Each of steps S61 to S66 will be described below.

[0063] In the tray body preparation process S61, the worker prepares multiple types of tray bodies 22 that differ from each other in at least one constituent element (e.g., a combination of number, shape, and position) of the groove portion 222 and the contact portion 223, such as the tray bodies 23, 24, 25, and 26 of the above-mentioned experimental examples 1 to 4.

[0064] In the preliminary oxide film formation step S62, the predetermined film formation apparatus 1 uses a first film formation tray 2 including a first tray body 22 and a support member 21 to form a test oxide film as a first oxide film on a test wafer W as a first wafer. A measuring device (not shown) measures the film thickness distribution of the test oxide film. A computer (not shown) acquires the film thickness distribution of the test oxide film, for example, based on an operator's operation of an input unit (not shown) or from the measuring device. The constituent features of the groove portion 222 and the contact portion 223 of the first tray body 22 are not particularly limited, but may be the constituent features of the tray body 22 in Experimental Example 1, for example. The first tray body 22 may be selected from the multiple types of tray bodies 22 prepared in the tray body preparation step S61, or may be a different type of tray body 22 from the tray body 22 prepared in the tray body preparation step S61.

[0065] In the correlation acquisition step S63, the computer acquires, for example, from a storage unit (not shown), a correlation between at least one of the constituent elements of the groove portion 222 and the contact portion 223 and the film thickness distribution of the oxide film. The correlation includes at least one of the first to third correlations described above. The correlation may be obtained by experiment or simulation.

[0066] In the target film thickness distribution acquisition step S64, the computer acquires the target film thickness distribution of the oxide film based on, for example, an operator's operation of the input unit.

[0067] In the tray body configuration determination step S65, the computer determines, as an applicable requirement, at least one of the configuration requirements of the groove 222 and the contact portion 223 that enable the formation of an oxide film with the target film thickness distribution, based on the film thickness distribution of the test oxide film and the correlation. For example, if the target film thickness distribution is a film thickness distribution that makes the first film thickness ratio based on the above formula (1) a predetermined value, and the first film thickness ratio of the test oxide film is greater than the predetermined value, based on the first correlation, the computer determines, as an applicable requirement for the groove 222 that enables the formation of an oxide film with the target film thickness distribution, that the width of the groove 222 be larger than that of the groove 222 of the first tray body 22. Furthermore, when the target film thickness distribution of the outer periphery is uniform and the thickness of the region of the outer periphery of the test oxide film on the transport width direction side is thicker than the other regions of the outer periphery, based on the second correlation, the contact portion 223 provided in the portion on the transport width direction side is made longer than the contact portion 223 of the first tray body 22 to increase the contact area with the leg portion 212. When the target film thickness distribution of the outer periphery is uniform and the thickness of the region of the outer periphery of the test oxide film on the transport direction side is thinner than the other regions of the outer periphery, based on the third correlation, the contact area between the contact portion 223 provided in the portion on the transport direction side and the leg portion 212 is made larger than the contact area on the first tray body 22. At least one of increasing the length of the contact portion 223 and increasing the number of contact portions 223 can be applied as a method for increasing the contact area.

[0068] In the film forming step S66, the operator selects a second tray body 22 that satisfies the application requirements from the multiple types of tray bodies 22 prepared in the tray body preparation step S61. If there is no tray body 22 that satisfies the application requirements among the multiple types of tray bodies 22, the operator selects as the second tray body 22 a tray body 22 that has configuration requirements that are closest to the application requirements. Note that selecting a tray body 22 that has configuration requirements that are closest to the application requirements corresponds to selecting a second tray body 22 that satisfies the application requirements in this invention. The specified film forming apparatus 1 forms a backside oxide film on the backside of the product wafer W using the second tray body 22 selected by the operator.

[0069] Effects of the Embodiment The oxide film forming method includes the above-described preliminary oxide film forming step S62, correlation acquisition step S63, target film thickness distribution acquisition step S64, tray body configuration determination step S65, and film forming step S66. In this manner, at least one of the constituent elements of the groove portion 222 and the contact portion 223 is determined as an applicable requirement based on the correlation between the oxide film thickness distribution and at least one of the constituent elements and the groove portion 222 and the contact portion 223, and the film thickness distribution of the test oxide film. Then, a second tray body 22 that satisfies the applicable requirement is used to form a backside oxide film on a product wafer, thereby forming an oxide film with a desired film thickness distribution on the wafer W. Furthermore, by performing the oxide film forming method and using second tray bodies 22 that correspond to the characteristics of each of the multiple film forming apparatuses 1, variation in the oxide film thickness distribution between the multiple film forming apparatuses 1 can be reduced. Furthermore, because an oxide film with a desired film thickness distribution can be formed, the yield of the wafer W can be improved, energy efficiency can be improved, production efficiency can be improved, and waste can be reduced.

[0070] The correlation acquired in the correlation acquisition step S63 includes a first correlation between the width of at least a portion of the groove 222 in the circumferential direction and the thickness of the oxide film in a region adjacent to the at least portion in the outer periphery of the wafer W. Therefore, by using the second tray body 22 in which the width of at least a portion of the groove 222 in the circumferential direction is appropriately set, an oxide film having a desired film thickness distribution can be formed.

[0071] The correlation acquired in the correlation acquisition step S63 includes a second correlation between the contact area between the contact portion 223 and the leg portion 212 at the portion on the tray body 22 on the transport width direction side and the thickness of the oxide film in the region adjacent to the portion on the transport width direction side at the outer periphery of the wafer W. Therefore, by using the second tray body 22 in which the contact area between the contact portion 223 and the leg portion 212 at the portion on the tray body 22 on the transport width direction side is appropriately set, it is possible to form an oxide film with a desired film thickness distribution.

[0072] The correlation obtained in the correlation obtaining step S63 includes a third correlation between the contact area between the contact portion 223 and the leg portion 212 at the portion on the transport direction side of the tray body 22 and the thickness of the oxide film in a region adjacent to the portion on the transport direction side of the outer periphery of the wafer W. Therefore, by using a second tray body 22 in which the contact area between the contact portion 223 and the leg portion 212 at the portion on the transport direction side of the tray body 22 is appropriately set, it is possible to form an oxide film having a desired film thickness distribution on the wafer W. In particular, if the correlation obtained in the correlation obtaining step S63 includes all of the first to third correlations, the film thickness distribution can be controlled more precisely by using a tray body 22 obtained based on the first to third correlations.

[0073] The oxide film forming method includes a tray body preparation step S61. Therefore, in the film forming step S66, an oxide film having a desired film thickness distribution can be formed simply by selecting a second tray body 22 that satisfies the application requirements from the multiple types of tray bodies 22 prepared in the tray body preparation step S61.

[0074] [Modifications] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and various improvements and design changes that do not deviate from the gist of the present invention are also included in the present invention.

[0075] For example, a part of the preliminary oxide film forming step S62, the correlation obtaining step S63, the target film thickness distribution obtaining step S64, and the tray body configuration determining step S65 may be performed by an operator. Specifically, the operator may check the film thickness distribution of the test oxide film measured by a measuring device (preliminary oxide film forming step S62), check the correlation displayed on a computer display or on a sheet medium such as paper (correlation obtaining step S63), check the target film thickness distribution of the oxide film based on product specifications, etc. (target film thickness distribution obtaining step S64), and then perform the tray body configuration determining step S65.

[0076] By attaching an attachment to the recess 221, it is possible to provide a groove portion 222 and a contact portion 223 having specified structural requirements, and by selecting one type of attachment from multiple types of attachments, a second tray body 22 that meets the applicable requirements can be created.

[0077] The tray body 22 in plan view may be a rectangle with its long sides parallel to the conveyance direction, a square, a polygon other than a rectangle, a circle, or an ellipse.

[0078] The oxide film formation condition determination method, oxide film formation method, and wafer manufacturing method of the present invention enable the formation of an oxide film having a desired film thickness distribution, thereby improving wafer W yield, improving energy efficiency, improving production efficiency, and reducing waste. The product of the present invention (epitaxial silicon wafer with an LTO film (backside oxide film)) is mainly used in logic devices. The present invention contributes to the improvement of precision in semiconductor devices and, as a fundamental technology necessary for the development and improvement of advanced industrial products, plays an important role in industrialization. The product of the present invention is used, for example, in control systems for automobiles, home appliances, medical equipment, and the like, enabling the realization of high-quality, high-reliability products.

[0079] 1...film formation apparatus, 2...film formation tray, 21...support member, 211...mounting portion, 212...leg portion, 22, 23, 24, 25, 26...tray body, 221...recess, 222, 232, 242, 252, 262...groove portion, 223...contact portion, 233, 243...first contact portion, 254...second contact portion, G1...source gas, W...wafer.

Claims

1. A method for determining conditions for forming an oxide film on a wafer using a film forming apparatus, the film forming apparatus being configured to use a film forming tray including a support member for supporting an outer periphery of the wafer and a tray body for supporting the support member, and to form the oxide film on the wafer by supplying a source gas onto the wafer while heating the film forming tray, the support member including a ring-shaped mounting portion on which the wafer is mounted, and legs extending downward from the mounting portion, the tray body including a cylindrical recess for accommodating the support member, and a plurality of grooves formed along an outer edge of a bottom surface of the recess, and configured to support the legs of the support member by contact portions located between a pair of adjacent grooves, the method for determining conditions for forming an oxide film comprising the steps of: a preliminary oxide film formation step of forming a first oxide film on the first wafer using the first tray body; a correlation acquisition step of acquiring a correlation between at least one of the constituent elements of the grooves and the contact portions, and a thickness distribution of the oxide film; A method for determining conditions for forming an oxide film, comprising: a target film thickness distribution acquisition process for acquiring a target film thickness distribution of the oxide film; and a tray body configuration determination process for determining, as an applicable requirement, at least one configuration requirement capable of forming the oxide film of the target film thickness distribution based on the film thickness distribution of the first oxide film and the correlation.

2. A method for determining conditions for forming an oxide film as described in claim 1, wherein the correlation includes a first correlation between the width of at least a portion of the groove portion in the circumferential direction and the thickness of the oxide film in a region adjacent to the at least a portion of the groove portion in the outer periphery of the wafer.

3. A method for determining conditions for forming an oxide film as described in claim 1, wherein the film forming apparatus is configured to form the oxide film on the wafer supported on each film forming tray while arranging a plurality of film forming trays, each of which has the tray body, in a feed direction and transporting the trays in the feed direction, and the correlation includes a second correlation between the contact area of ​​the contact portion and the leg portion at a portion of the tray body on the transport width direction side perpendicular to the feed direction, and the thickness of the oxide film in a region adjacent to the portion on the transport width direction side at the outer periphery of the wafer.

4. A method for determining conditions for forming an oxide film according to claim 3, wherein the second correlation is such that the larger the contact area at the portion on the transport width direction side, the thinner the oxide film in the region adjacent to the portion on the transport width direction side.

5. A method for determining conditions for forming an oxide film as described in claim 1, wherein the film forming apparatus is configured to line up a plurality of film forming trays, each of which has the tray body, in the feed direction and transport them in the feed direction while forming the oxide film on the wafer supported on each film forming tray, and the correlation includes a third correlation between the contact area of ​​the contact portion and the leg portion at the portions of the tray body on the feed direction side and the opposite direction side relative to the feed direction, and the thickness of the oxide film in a region adjacent to the portions on the feed direction side and the opposite direction side at the outer periphery of the wafer.

6. A method for determining conditions for forming an oxide film as described in claim 5, wherein the third correlation is such that the larger the contact area at the portions on the feed direction side and the opposite direction side, the thicker the oxide film in the regions adjacent to the portions on the feed direction side and the opposite direction side.

7. A method for forming an oxide film, comprising: a step of performing a method for determining conditions for forming an oxide film as described in any one of claims 1 to 6; and a film forming step of forming a second oxide film on a second wafer using a second tray body that satisfies the application requirements.

8. A method for forming an oxide film as described in claim 7, further comprising a tray body preparation step of preparing a plurality of types of tray bodies differing from each other in at least one constituent element, and the film forming step of selecting a second tray body from the at least one constituent element corresponding to each of the plurality of types of tray bodies, and forming the second oxide film using the second tray body.

9. A method for manufacturing a wafer, comprising the step of forming an oxide film on the second wafer by the method for forming an oxide film as defined in claim 7.

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