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

Abstract

The oxide film formation condition determination method includes: a pre-oxide film formation step of forming a first oxide film on a first wafer using a first tray main body; a correlation acquisition step for acquiring a correlation between the film thickness distribution of the oxide film and at least one constituent element of the groove portion and the contact portion of the tray main body; a target film thickness distribution obtaining step of obtaining the target film thickness distribution of the oxide film; and a tray main body configuration determination step for determining, as an applicable component, the at least one configuration component capable of forming the oxide film having the target film thickness distribution on the basis of the film thickness distribution of the first oxide film and the correlation.

Description

Technical Field

[0001] This invention relates to a method for determining the formation conditions of an oxide film, a method for forming an oxide film, and a method for manufacturing a wafer. Background Technology

[0002] A method is known to form an oxide film on a wafer by simultaneously heating a film-forming tray and supplying a raw material gas onto the wafer mounted on the film-forming tray (for example, see Patent Document 1).

[0003] Patent Document 1 describes a film-forming tray comprising a support member supporting the outer periphery of a wafer and a tray body supporting the support member. Patent Document 1 also describes how reducing the contact area between the support member and the tray body allows for a more uniform thickness distribution of the oxide film on the wafer.

[0004] Existing technical documents Patent documents Patent document 1: Re-Table 2011 / 070741. Summary of the Invention

[0005] The technical problem that the invention aims to solve However, in recent years, with the need for further homogenization of film thickness distribution, deviations in film thickness distribution between multiple film-forming devices have become a problem.

[0006] The purpose of this invention is to provide a method for determining oxide film formation conditions, an oxide film formation method, and a wafer manufacturing method for forming an oxide film with a desired film thickness distribution on a wafer.

[0007] Solutions for solving technical problems The method for determining oxide film formation conditions of the present invention is a method for determining the conditions for forming an oxide film on a wafer using a film-forming apparatus. In this method, the film-forming apparatus is configured to use a film-forming tray, and while heating the tray, a raw material gas is supplied to the wafer to form the oxide film. The film-forming tray includes a support member supporting the outer periphery of the wafer and a tray body supporting the support member. The support member includes an annular mounting portion for holding the wafer and a leg portion extending downward from the mounting portion. The tray body is configured to include a cylindrical recess for accommodating the support member and a cylindrical recess formed along the outer edge of the bottom surface of the recess. A method for determining the formation conditions of an oxide film includes: a pre-oxide film formation step, forming a first oxide film on a first wafer using a first tray body; a correlation acquisition step, acquiring a correlation between at least one constituent element of the trench and the contact portion and the film thickness distribution of the oxide film; a target film thickness distribution acquisition step, acquiring a target film thickness distribution of the oxide film; and a tray body composition determination step, determining at least one constituent element capable of forming the oxide film with the target film thickness distribution as an applicable element based on the film thickness distribution of the first oxide film and the correlation.

[0008] In the method for determining the formation conditions of the oxide film of the present invention, preferably, the correlation includes a first correlation between the width of at least a portion of the groove in the circumferential direction and the thickness of the oxide film in the region adjacent to the at least a portion of the outer periphery of the wafer.

[0009] In the method for determining the oxide film formation conditions of the present invention, preferably, the film forming apparatus is configured to form the oxide film on the wafer supported by each film forming tray while arranging and conveying a plurality of film forming trays, each having the tray body, along the feed direction. The correlation includes a second correlation between the contact area of ​​the contact portion of the tray body at a location on the conveying width direction side orthogonal to the feed direction and the support portion, and the thickness of the oxide film in the region of the outer periphery of the wafer adjacent to the location on the conveying width direction side.

[0010] In the method for determining the formation conditions of the oxide film of the present invention, preferably, the second correlation is as follows: 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.

[0011] In the method for determining the oxide film formation conditions of the present invention, preferably, the film forming apparatus is configured to form the oxide film on the wafer supported by each film forming tray while arranging and conveying a plurality of film forming trays, each having the tray body, along the feed direction. The correlation includes a third correlation between the contact area of ​​the contact portion and the support portion at the feed direction side and the opposite direction side of the tray body and the thickness of the oxide film in the region of the outer periphery of the wafer adjacent to the feed direction side and the opposite direction side.

[0012] In the method for determining the oxide film formation conditions of the present invention, preferably, the third correlation is as follows: the larger the contact area at the portion on the feed direction side and the opposite direction side, the thicker the oxide film in the region adjacent to the portion on the feed direction side and the opposite direction side.

[0013] The method for forming an oxide film according to the present invention comprises: a step of performing the above-described method for determining the formation conditions of an oxide film; and a film forming step of forming a second oxide film on a second wafer using a second tray body that satisfies the applicable requirements.

[0014] In the method for forming an oxide film according to the present invention, preferably, it further comprises: a tray body preparation step, in which a plurality of tray bodies with different at least one constituent element are prepared, and in the film forming step, a second tray body is selected from the at least one constituent element corresponding to each of the plurality of tray bodies, and the second tray body is used to form the second oxide film.

[0015] The wafer manufacturing method of the present invention includes a step of forming the oxide film on the second wafer by the above-described oxide film formation method. Attached Figure Description

[0016] Figure 1 This is a schematic diagram illustrating the structure of the film-forming apparatus involved in the prior art of this invention.

[0017] Figure 2A This is a top view showing the structure of the film-forming tray involved in the prerequisite technology and experimental examples 1 and 2.

[0018] Figure 2B This refers to the structure of the film-forming tray involved in the prerequisite technology and experimental examples 1 and 2. Figure 2A Sectional view of line IIB-IIB.

[0019] Figure 2C This refers to the structure of the film-forming tray involved in the prerequisite technology and experimental examples 1 and 2. Figure 2AIIC-IIC line sectional view.

[0020] Figure 3A This is a top view of the tray body involved in Experiment Example 3.

[0021] Figure 3B This is a top view of the tray body involved in Experiment Example 4.

[0022] Figure 4A This is a schematic diagram of the central region constituting the film thickness evaluation area, which is used to investigate the correlation between the constituent elements of the tray body's groove and contact portion and the film thickness distribution of the oxide film.

[0023] Figure 4B This is a schematic diagram of the outer perimeter region that constitutes the evaluation area.

[0024] Figure 4C This is a schematic diagram of the transport width direction region that constitutes the evaluation area.

[0025] Figure 4D This is a schematic diagram of the transport direction area that constitutes the evaluation area.

[0026] Figure 5 This is a flowchart illustrating a wafer manufacturing method according to an embodiment of the present invention.

[0027] Figure 6 This is a flowchart illustrating the oxide film formation process involved in the described embodiment. Detailed Implementation

[0028] [Prerequisite Technology] First, before describing the embodiments of the present invention, the structure of the film-forming apparatus used in these embodiments will be described. Figure 1 This is a schematic diagram illustrating the structure of the film-forming apparatus involved in the prior art of this invention.

[0029] Figure 1 The film deposition apparatus 1 shown forms an oxide film on a wafer W. The film deposition apparatus 1 includes multiple film deposition trays 2, a circulation section 3, and a film deposition section 4. The wafer W can be made of materials such as silicon, germanium, gallium arsenide, gallium phosphide, or indium phosphide.

[0030] The film-forming tray 2 holds the wafer W. The detailed structure of the film-forming tray 2 will be described later.

[0031] The circulation unit 3 circulates a predetermined number of film-forming trays 2 within the film-forming apparatus 1. The circulation unit 3 includes a first lifting unit 31, a film-forming conveying unit 32, a second lifting unit 33, and a return conveying unit 34.

[0032] The first lifting unit 31 includes a first lifting platform 311 for placing the film-forming tray 2 and a first lifting drive unit 312 for raising and lowering the first lifting platform 311. When the first lifting platform 311 is in the raised position, the wafer W before film formation is transferred to the film-forming tray 2 via a transfer unit (not shown), and the film-forming tray 2 is then transferred to the film-forming transport unit 32. The structure for transferring the film-forming tray 2 from the first lifting platform 311 to the film-forming transport unit 32 is not particularly limited, and known structures can be used.

[0033] The film-forming conveying unit 32 includes a pair of conveying rollers 321 and a conveyor belt 322 mounted on the pair of conveying rollers 321. The film-forming conveying unit 32, through the rotation of the conveying rollers 321, causes the conveyor belt 322 to move along... Figure 1 The film-forming trays 2 are transported to the film-forming section 4 while being rotated clockwise, so that they are in contact with each other. As a structure for transporting the film-forming trays 2 using the conveyor belt 322, an example can be shown where protrusions on the conveyor belt 322 are fitted into fitting grooves on the lower surface of the tray body 22, thereby transporting the film-forming trays 2. Furthermore, the direction in which the film-forming conveyor section 32 transports the film-forming trays 2 is sometimes referred to as the "feed direction." And, the direction orthogonal to both the feed direction and the vertical direction is sometimes referred to as the "conveyor width direction."

[0034] The second lifting unit 33 includes a second lifting platform 331 for placing the film-forming tray 2 and a second lifting drive unit 332 for raising and lowering the second lifting platform 331. When the second lifting platform 331 is in the raised position, the film-forming tray 2, containing the film-formed wafer W, is transferred from the transport roller 321 to the second lifting platform 331. When the second lifting platform 331 is in the lowered position, the film-forming tray 2, containing the film-formed wafer W, is transferred to the return transport unit 34. The structure for transferring the film-forming tray 2 from the transport roller 321 to the second lifting platform 331 and the structure for transferring the film-forming tray 2 from the second lifting platform 331 to the return transport unit 34 are not particularly limited, and known structures can be used.

[0035] The return transport unit 34 transports the film-forming tray 2, which contains the film-formed wafer W, in the opposite direction to the feed direction. The film-forming tray 2 transported by the return transport unit 34 is handed over to the first lifting platform 311, which is in the descending position. There is no particular limitation on the structure for handing over the film-forming tray 2 from the return transport unit 34 to the first lifting platform 311, and known structures can be used. In addition, the direction in which the return transport unit 34 transports the film-forming tray 2 is sometimes referred to as the "return direction".

[0036] After the first lifting platform 311 is in the descending position and receives the film-forming tray 2 from the return transport section 34, it rises to the ascending position. With the first lifting platform 311 in the ascending position, the wafer W after film formation is transferred from the film-forming tray 2 to a wafer storage section (not shown) via the transfer section. Then, as described above, the wafer W before film formation is transferred into the film-forming tray 2 via the transfer section (not shown), and the film-forming tray 2 is transferred to the film-forming transport section 32.

[0037] The film-forming section 4 forms an oxide film on the wafer W in the film-forming tray 2 conveyed by the film-forming conveying section 32. The film-forming section 4 includes a preheater 41, a heater 42, a raw material gas supply section 43, a pair of isolation gas supply sections 44, and a pair of exhaust sections 45.

[0038] The preheater 41 and heater 42 are, for example, disposed within the space surrounded by the conveyor belt 322. The heater 42 is disposed on the feed direction side relative to the preheater 41. The wafer W in the film-forming tray 2 is preheated to a temperature below the film-forming temperature by the preheater 41 and then heated to the film-forming temperature by the heater 42.

[0039] A raw material gas supply unit 43 is positioned above the heater 42. The raw material gas supply unit 43 ejects raw material gas G1 downwards and supplies it to the wafer W. An oxide film is formed by reacting on the heated wafer W. Examples of raw material gases include a mixture of monosilane (SiH4) and oxygen (O2) or a mixture of tetraethoxysilane (TEOS, chemical formula: Si(OC2H5)4) and ozone (O3).

[0040] A pair of isolation gas supply units 44 are positioned above the heater 42, on the feed direction side and return direction side relative to the raw material gas supply unit 43, respectively. Each isolation gas supply unit 44 ejects isolation gas G2 downwards to suppress leakage of the raw material gas G1 into the feed direction side and return direction side relative to the film forming unit 4. Nitrogen gas can be exemplified as the isolation gas G2.

[0041] A pair of exhaust sections 45 are respectively disposed between the raw material gas supply section 43 and the isolation gas supply section 44 on the feed direction side, and between the raw material gas supply section 43 and the isolation gas supply section 44 on the return direction side. Each exhaust section 45 discharges the isolation gas G2 and the raw material gas G1 not used for film formation from the space between the raw material gas supply section 43 and the film forming tray 2 to the top of the raw material gas supply section 43.

[0042] Next, the detailed structure of the film-forming tray 2 will be explained. Figure 2A This is a top view showing the structure of the film-forming tray. Figure 2B yes Figure 2A Sectional view of line IIB-IIB. Figure 2C yes Figure 2AIIC-IIC line sectional view.

[0043] like Figures 2A to 2C As shown, the film-forming tray 2 includes a support member 21 and a tray body 22. The support member 21 and the tray body 22 are formed, for example, from SiC.

[0044] The support member 21 supports the outer periphery of the wafer W. The support member 21 includes a mounting portion 211 and a support leg portion 212.

[0045] The mounting portion 211 is formed in a circular shape. A wafer W is mounted on the mounting portion 211. The leg portion 212 is formed to extend downward in a cylindrical shape from the entire outer edge of the mounting portion 211.

[0046] The tray body 22 is formed in a cuboid shape. Figure 2A In the top view shown, the side of the tray body 22 corresponding to the long side of the rectangle is as follows: Figure 1 As shown, when transported by the film-forming conveying section 32 of the film-forming apparatus 1, the opposing surface 22A is formed opposite to the adjacent film-forming tray 2, and the side corresponding to the short side is formed into a non-opposing surface 22B that is not opposite to the adjacent film-forming tray 2 when transported by the film-forming conveying section 32 of the film-forming apparatus 1.

[0047] A cylindrical recess 221 is formed in the center of the tray body 22. On the bottom surface of the recess 221, a plurality of arc-shaped grooves 222 are formed along the outer edge of the bottom surface.

[0048] The portion located between a pair of adjacent grooves 222 forms a contact portion 223 for supporting the leg portion 212 of the support member 21.

[0049] [Description of the Invention] Next, the process of deriving this invention will be explained.

[0050] Experiments were conducted to determine the relationship between the components of the groove 222 and the contact portion 223 of the tray body 22 of the film-forming tray 2 and the film thickness distribution of the oxide film on the wafer W.

[0051] Figure 3A This is a top view of the tray body involved in Experiment Example 3. Figure 3B This is a top view of the tray body involved in Experiment Example 4. Figure 4A This is a schematic diagram of the central region constituting the film thickness evaluation area, which is used to investigate the correlation between the constituent elements of the tray body's groove and contact portion and the film thickness distribution of the oxide film. Figure 4B This is a schematic diagram of the outer perimeter region that constitutes the evaluation area. Figure 4C This is a schematic diagram of the transport width direction area that constitutes the evaluation area. Figure 4D This is a schematic diagram of the transport direction area that constitutes the evaluation area.

[0052] <Evaluation Sample Preparation Method> First, four different tray bodies 22 were prepared, each with at least one different component (e.g., quantity, shape, and position) of the groove 222 and the contact portion 223. Specifically, tray bodies 23, 24, 25, and 26, as shown in Experimental Examples 1, 2, 3, and 4 below, were prepared. Furthermore, tray bodies 23, 24, 25, and 26 with the same structure as or identical to the tray bodies 22 described in the background art were given the same names and the same reference numerals.

[0053] The tray body 23 of Experimental Example 1 has Figures 2A to 2C The structure shown. Six grooves 232 of the same shape are formed on the bottom surface of the recess 221 of the tray body 23.

[0054] Each groove 232 is formed with a circumferential length of L1. As shown in Table 1 below, when the width of the groove 232 is set to J1 and the width (thickness) of the support leg 212 of the support member 21 is set to J0, each groove 232 is formed to satisfy the relationship "J1:J0=4:1". The grooves 232 are formed at equal intervals, so that six first contact portions 233 of the same shape are provided. As shown in Table 1, the circumferential length of each first contact portion 233 is M1.

[0055] [Table 1] .

[0056] The tray body 24 of Experimental Example 2 has Figures 2A to 2C The structure shown. Six grooves 242 of the same shape are formed on the bottom surface of the recess 221 of the tray body 24.

[0057] The length of each groove 242 is L1, which is the same as the length of the groove 232 in Experimental Example 1. As shown in Table 1, when the width of the groove 242 is set to J2, each groove 242 is formed to satisfy the relationship "J2:J0=6:1". The grooves 242 are formed at equal intervals, such that the length of each first contact portion 243 is M1, which is the same as the length of the first contact portion 233 in Experimental Example 1.

[0058] The tray body 25 of Experimental Example 3 has Figure 3A The structure shown. Four grooves 252 of the same shape are formed on the bottom surface of the recess 221 of the tray body 25.

[0059] The length of each groove 252 is L2, which is longer than the length of groove 232 in Experimental Example 1. The width of each groove 252 is J1, which is the same as the width of groove 232 in Experimental Example 1. Each groove 252 is configured such that two first contact portions 233 and two second contact portions 254 are alternately arranged in the circumferential direction. When the length of the second contact portion 254 is set to M2, each second contact portion 254 is configured to satisfy the relationship "M2:M1=52:1". The length M2 of the second contact portion 254 is less 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 portion 252 is configured such that the center of each first contact portion 233 in the longitudinal direction is located at the portion of the recess 221 closest to a pair of non-opposing surfaces 22B, and the center of each second contact portion 254 in the longitudinal direction is located at the portion of the recess 221 closest to a pair of opposing surfaces 22A. That is, each groove portion 252 is configured such that a first contact portion 233 is provided on both sides in the conveying width direction, and a second contact portion 254 is provided on both the feed direction side and the return direction side.

[0060] The tray body 26 of Experimental Example 4 has Figure 3B The structure shown. Two grooves 262 of the same shape are formed on the bottom surface of the recess 221 of the tray body 26.

[0061] The length of each groove 262 is L3 longer than the length of groove 252 in Experimental Example 3. The width of each groove 262 is J1, the same as the width of groove 232 in Experimental Example 1. Each groove 262 is configured such that two second contact portions 254 are located at the same positions as the second contact portions 254 in Experimental Example 3. That is, each groove 262 is configured such that a second contact portion 254 is provided on both the feed direction side and the return direction side.

[0062] In addition, 10 wafers W with a diameter of 300mm were prepared.

[0063] Then, seven film-forming trays 2 having the tray body 23 of Experimental Example 1, and one film-forming tray 2 each having the tray bodies 24, 25, and 26 of Experimental Examples 2, 3, and 4 respectively, are arranged in the circulation section 3 of the film-forming apparatus 1. Using one of each of the four film-forming trays 2 having the tray bodies 23, 24, 25, and 26 of Experimental Examples 1, 2, 3, and 4 respectively, an oxide film is formed on each wafer W. The target thickness of the oxide film is 350 nm. Hereinafter, the wafers W on which films are formed using the film-forming trays 2 having the tray bodies 23, 24, 25, and 26 of Experimental Examples 1, 2, 3, and 4 are referred to as wafers W1, W2, W3, and W4 of Experimental Examples 1, 2, 3, and 4 respectively.

[0064] <Methods for investigating the correlation between the constituent elements of the tray body's groove and contact portion and the oxide film thickness distribution> (1. The correlation between the groove of the tray body and the thickness distribution of the oxide film) For each of the wafers W1 and W2 in Experiments 1 and 2, the oxide film thickness distribution was measured. Then, the thickness distribution of the oxide film in each wafer W1 and W2 was calculated. Figure 4A The central area A1 shown and Figure 4B The average thickness of the oxide film in the outer peripheral region A2 is shown. The central region A1 is a circular region with a diameter of 60 mm centered on the center of wafer W. The outer peripheral region A2 is an annular region within 30 mm of the outer edge of wafer W. The width of the outer peripheral region A2 is greater than the width J2 of the groove 242 in Experimental Example 2.

[0065] Next, the first film thickness ratio in wafers W1 and W2 of Experimental Examples 1 and 2 was calculated according to the following formula (1).

[0066] First film thickness ratio = average film thickness in the outer peripheral area / average film thickness in the central area... (1) Then, the first influence evaluation value for evaluating the influence of the width of the groove was calculated according to the following formula (2).

[0067] First impact evaluation value = First film thickness ratio in wafer W2 of Experimental Example 2 / First film thickness ratio in wafer W1 of Experimental Example 1 ... (2) The calculation results of equations (1) and (2) are shown in Table 2.

[0068] [Table 2] .

[0069] As shown in Table 2, the first impact evaluation value is less than 1.

[0070] Therefore, it can be confirmed that there is the following relationship between the width of the groove 222 and the thickness distribution of the oxide film: the wider the groove 222, the thinner the oxide film on the outer periphery of the wafer W is relative to the oxide film in the center.

[0071] The inventors speculate on the reasons for this correlation as follows.

[0072] The wider the groove 222, the longer the distance from the inner edge of the groove 222 (the edge of the center side of the recess when viewed from above) to the support leg 212 of the support member 21, and the less heat is transferred from the inner edge of the groove 222 to the outer periphery of the wafer W via the support leg 212. It is presumed that if less heat is transferred to the outer periphery of the wafer W, the temperature of the outer periphery will be lower, and the oxide film of the outer periphery will be thinner.

[0073] Furthermore, based on the above-mentioned speculation, 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 is compared to the oxide film in the center.

[0074] Furthermore, it is believed that by making the width of a portion of the circumferential direction of the groove 222 greater or less than the width of the remaining portion, the oxide film of the portion adjacent to that portion can be made thinner or thicker than the oxide film of the portion adjacent to the remaining portion.

[0075] That is, it can be confirmed that there is a correlation (hereinafter, sometimes referred to as the "first correlation") between the width of at least a portion of the trench 222 in the circumferential direction and the thickness of the oxide film in the region adjacent to the at least a portion of the outer periphery of the wafer W. This thickness ratio refers to the ratio of the thickness of the oxide film in the region adjacent to the at least a portion of the outer periphery of the wafer W to the thickness of the oxide film in the central part of the wafer W. The first correlation can also be described as the correlation between the width of at least a portion of the trench 222 in the circumferential direction and the thickness of the oxide film in the region adjacent to the at least a portion of the outer periphery of the wafer W.

[0076] (2. The correlation between whether the pallet body has a contact part in the conveying width direction and the thickness distribution of the oxide film) For each of wafers W3 and W4 in Experiments 3 and 4, the oxide film thickness distribution was measured. Then, the central region A1 and [other components] in each wafer W3 and W4 were calculated. Figure 4C The average film thickness of the oxide film in the two transport width direction regions A3 shown. Transport width direction region A3 is a roughly semi-circular region on both ends of the transport width direction in the wafer W. The circumferential length of transport width direction region A3 is 60 mm, which is greater than the length M1 of the first contact portion 233 in Experimental Example 3. The radial length of transport width direction region A3 is 30 mm.

[0077] Next, the second film thickness ratio in wafers W3 and W4 of Experimental Examples 3 and 4 was calculated according to the following formula (3). The calculation results are shown in Table 3 below.

[0078] The second film thickness ratio = average film thickness in the transport width direction / average film thickness in the central region ... (3) Then, the second influence evaluation value for evaluating the influence of the presence or absence of contact in the conveying width direction was calculated according to the following formula (4).

[0079] Second impact evaluation value = Second film thickness ratio in wafer W3 of Experimental Example 3 / Second film thickness ratio in wafer W4 of Experimental Example 4 ... (4) The calculation results of equations (3) and (4) are shown in Table 3.

[0080] [Table 3] .

[0081] As shown in Table 3, the second impact evaluation value is less than 1.

[0082] Therefore, it can be confirmed that there is a correlation between the presence or absence of the contact portion 223 in the transport width direction and the film thickness distribution of the oxide film as follows: compared to the case where the contact portion 223 is not provided on the transport width side of the tray body 22, when the contact portion 223 is provided, the oxide film in the region adjacent to the transport width side portion on the outer periphery of the wafer W becomes thinner than the central portion. Furthermore, as... Figure 3A As shown, the portion of the tray body 22 with contact portion 223 on the transport width direction side refers to the portion located within the following fan-shaped area: this fan-shaped area is symmetrical about the reference line T1 containing the center 221C of the recess 221 and parallel to the transport width direction, and its central angle θ1 is 60°. Furthermore, typically, when viewed from above, the center 221C of the recess 221 overlaps with the center Wc of the wafer W supported by the support member 21.

[0083] The inventors speculate on the reasons for this correlation as follows.

[0084] It is believed that during the formation of an oxide film on a wafer W within any film-forming tray 2, the film-forming tray 2 exists on both the feed direction side and the return direction side (hereinafter, the feed direction side and the return direction side are sometimes collectively referred to as "the two sides of the transport direction"). However, the film-forming tray 2 does not exist on the two sides of the transport width direction. Therefore, the temperature on the two sides of the transport width direction in the tray body 22 is lower than the temperature on the two sides of the transport direction. Therefore, it is speculated that the heat on the two sides of the transport width direction in the mounting portion 211 of the support member 21 is dissipated by the tray body 22 via the support leg portion 212 and the contact portion 223 on the two sides of the transport width direction, resulting in a decrease in the temperature on the two sides of the transport width direction in the wafer W, thereby thinning the oxide film on the two sides of the transport width direction.

[0085] Furthermore, based on the above-described speculation, it is believed that, compared to the case where the contact portion 223 is provided on the transport width side of the tray body 22, the oxide film in the region adjacent to the transport width side of the outer periphery of the wafer W becomes thicker than that in the central portion when the contact portion 223 is not provided.

[0086] Furthermore, when the contact portion 223 is provided on the transport width side of the pallet body 22, it is believed that when the length of the contact portion 223 is longer, heat on the transport width side of the pallet body 22 is more easily dissipated compared to when the length of the contact portion 223 is shorter. Therefore, it is believed that the longer the contact portion 223 is, the larger the contact area between the contact portion 223 and the support portion 212, and the oxide film on the outer periphery of the wafer W adjacent to the transport width side becomes thinner than that on the central portion.

[0087] That is, it can be confirmed that there is a correlation (hereinafter, sometimes referred to as the "second correlation") between the contact area of ​​the contact portion 223 and the support portion 212 at the location on the transport width direction of the tray body 22 and the ratio of the following thickness: the ratio of the thickness of the oxide film in the region adjacent to the location on the transport width direction of the outer periphery of the wafer W to the thickness of the oxide film in the central part of the wafer W. The second correlation can also be described as a correlation between the contact area of ​​the contact portion 223 and the support portion 212 at the location on the transport width direction of the tray body 22 and the thickness of the oxide film in the region adjacent to the location on the transport width direction of the outer periphery of the wafer W.

[0088] (3. The relationship between the contact area between the pallet body and the support legs in the conveying direction and the thickness distribution of the oxide film) The central region A1 and in wafer W of Experimental Examples 1 and 3 were calculated. Figure 4D The average film thickness of the oxide film in the two transport direction regions A4 shown. Transport direction region A4 is a roughly arc-shaped region on both sides of the transport direction in wafer W. The circumferential length of transport direction region A4 is 220 mm, which is longer than the length of the arc-shaped region including two adjacent contact portions 223 in Experimental Example 1 and the length of a second contact portion 254 in Experimental Example 3. The width (radial length) of transport direction region A4 is 30 mm.

[0089] Next, the third film thickness ratio in wafers W1 and W3 of Experimental Examples 1 and 3 was calculated according to the following formula (5).

[0090] 3rd film thickness ratio = average film thickness in the conveying direction area / average film thickness in the central area...(5) Then, the third influence evaluation value for evaluating the influence of the contact area between the contact part and the support leg in the conveying direction was calculated according to the following formula (6).

[0091] The third impact evaluation value = the third film thickness ratio in wafer W3 of Experimental Example 3 / the third film thickness ratio in wafer W1 of Experimental Example 1 ... (6) The calculation results of equations (5) and (6) are shown in Table 4.

[0092] [Table 4] .

[0093] As shown in Table 4, the third influence evaluation value is greater than 1. Here, during film formation, the contact area between the second contact portion 254 and the support leg portion 212 of Experimental Example 3, which is adjacent to the radial outer side of each transport direction region A4, is greater than the combined contact area between the two first contact portions 233 and the support leg portion 212 of Experimental Example 1.

[0094] Therefore, it can be confirmed that there is a correlation between the contact area of ​​the contact portion 223 and the support portion 212 in the conveying direction and the thickness distribution of the oxide film as follows: the larger the contact area of ​​the portion in the conveying direction side of the tray body 22, the thicker the oxide film in the region adjacent to the portion in the conveying direction side of the outer periphery of the wafer W is compared to the central portion. Furthermore, as... Figure 3B As shown, the portion of the pallet body 22 with contact portion 223 on the conveying direction side refers to the portion located within the following sector-shaped area: this sector-shaped area is symmetrical about a reference line T2 containing the center 221C of the recess 221 and parallel to the conveying direction, and the central angle θ2 is 90°. Furthermore, the conveying direction area A4 is... Figure 3B The area within the sector shown.

[0095] The inventors speculate on the reasons for this correlation as follows.

[0096] As described above, it is assumed that during the formation of an oxide film on the wafer W within any film-forming tray 2, film-forming trays exist on both sides of the film-forming tray 2 in the transport direction, but not on both sides in the transport width direction. Therefore, the temperature on both sides of the tray body 22 in the transport direction is higher than the temperature on the side in the transport width direction. Thus, it is assumed that the 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. Furthermore, it is assumed that the heat transferred to the mounting portion 211 of the support member 21 increases as the contact area between the contact portion 223 and the leg portion 212 increases. Therefore, it is speculated that the larger the contact area between the contact portion 223 and the leg portion 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.

[0097] Furthermore, based on the above-mentioned speculation, it is believed that the smaller the contact area between the contact portion 223 and the support leg portion 212 on the transport direction side of the tray body 22, the lower the temperature on the transport direction side of the outer periphery of the wafer W, and the thinner the oxide film on the transport direction side relative to the central portion.

[0098] Furthermore, if the contact portion 223 is not provided on the transport direction side of the tray body 22, it is believed that, compared to the case where the contact portion 223 is provided, heat on the transport direction side of the tray body 22 will not be transferred to the mounting portion 211 of the support member 21. Therefore, it is believed that, compared to the case where the contact portion 223 is provided on the transport direction side of the tray body 22, the oxide film in the region adjacent to the transport direction side portion of the outer periphery of the wafer W is thinner than that in the central portion when the contact portion 223 is not provided.

[0099] That is, it can be confirmed that there is a correlation (hereinafter, sometimes referred to as the "third correlation") between the contact area of ​​the contact portion 223 and the leg 212 at the transport direction side of the tray body 22 and the ratio of the following thickness: the ratio of the thickness of the oxide film in the region adjacent to the transport width direction side of the outer periphery of the wafer W to the thickness of the oxide film in the central part of the wafer W. The third correlation can also be described as the correlation between the contact area of ​​the contact portion 223 and the leg 212 at the transport direction side of the tray body 22 and the thickness of the oxide film in the region adjacent to the transport direction side of the outer periphery of the wafer W.

[0100] <Summary> The inventors have discovered that the components of the groove portion 222 and the contact portion 223 of the tray body 22 of the film forming tray 2 have the first to third correlation relationships as described above with the film thickness distribution of the oxide film on the wafer W.

[0101] Then, the inventors obtained the following insights and completed the present invention: using a first tray body 22, a first oxide film is formed on a first wafer W by a prescribed film-forming apparatus 1; the correlation between at least one of the constituent elements of the trench portion 222 and the contact portion 223 and the film thickness distribution of the oxide film is obtained; a target film thickness distribution of the oxide film is obtained; based on the film thickness distribution of the first oxide film and the aforementioned correlation, at least one constituent element that enables the formation of an oxide film with the target film thickness distribution is determined as an applicable element; using a second tray body 22 that satisfies the applicable element, a second oxide film is formed on a second wafer W by a prescribed film-forming apparatus 1; thereby, an oxide film with a desired film thickness distribution can be formed on the wafer W.

[0102] [Implementation Method] <Methods for forming oxide films> Next, a method for forming an oxide film according to one embodiment of the present invention will be described. Figure 5 This is a flowchart illustrating the wafer manufacturing process. Figure 6 This is a flowchart illustrating the oxide film formation process.

[0103] In addition, in this embodiment, as a wafer manufacturing method, an epitaxial wafer manufacturing method will be described, which includes: a product wafer W as a second wafer made of silicon, an epitaxial layer disposed on the surface of the product wafer W, and a back oxide film (LTO film) as a second oxide film disposed on the surface of the product wafer W.

[0104] like Figure 5As shown, the wafer manufacturing method includes: pulling process S1, block processing process S2, slicing process S3, pretreatment process S4, double-sided grinding process S5, oxide film formation process S6, single-sided finishing process S7, first cleaning process S8, epitaxial layer formation process S9 and second cleaning process S10.

[0105] In the Czochralski process S1, cylindrical single-crystal silicon is pulled from molten silicon using the Czochralski method.

[0106] In the block processing step S2, the outer periphery of the single crystal ingot is ground, and notches are machined according to the crystal orientation. Then, the single crystal ingot is cut into multiple blocks, for example, by a band saw.

[0107] In the slicing process S3, an internal diameter saw or wire saw is used to slice the block into multiple product wafers W, for example, with a thickness of about 1 mm.

[0108] In the pretreatment step S4, chamfering is performed, and rough polishing (grinding) is carried out, for example, with an alumina abrasive material, to make the two sides of the product wafer W parallel. Then, after etching or other processes are performed as needed, planarization is performed to eliminate the unevenness on the surface of the product wafer W.

[0109] In the double-sided grinding process S5, a double-sided grinding device is used to perform mirror finishing on the pre-treated product wafer W to improve its flatness.

[0110] The oxide film formation step S6 corresponds to the oxide film formation method of the present invention, including the method for determining the oxide film formation conditions of the present invention. In the oxide film formation step S6, a back oxide film is formed on the back side of the product wafer W.

[0111] In the single-sided finishing process S7, the surface of the product wafer W (the side without the back oxide film) obtained in the oxide film formation process S6 is ground. By performing the grinding process in the single-sided finishing process S7, scratches and damage on the surface of the product wafer W can be removed, and the surface roughness can be adjusted.

[0112] In the first cleaning step S8, the product wafer W obtained in the single-sided finishing step S7 is cleaned with, for example, an alkaline solution.

[0113] In the epitaxial layer formation process S9, an epitaxial layer is formed on the surface of the product wafer W.

[0114] In the second cleaning step S10, the epitaxial wafer obtained in the epitaxial layer formation step S9 is cleaned with, for example, an alkaline solution.

[0115] Next, the details of oxide film formation process S6 will be explained.

[0116] like Figure 6 As shown, the oxide film formation process S6 includes: tray body preparation process S61, pre-oxide film formation process S62, correlation acquisition process S63, target film thickness distribution acquisition process S64, tray body composition determination process S65, and film formation process S66. The pre-oxide film formation process S62, correlation acquisition process S63, target film thickness distribution acquisition process S64, and tray body composition determination process S65 constitute the method for determining the formation conditions of the oxide film. The following describes each process S61 to S66.

[0117] In the pallet body preparation process S61, as with the pallet bodies 23, 24, 25, and 26 in Experimental Examples 1 to 4 above, the worker prepares a variety of pallet bodies 22 with different constituent elements (e.g., combinations of quantity, shape, and position) of at least one of the groove portion 222 and the contact portion 223.

[0118] In the pre-oxide film formation process S62, the prescribed film forming apparatus 1 uses a first film forming tray 2, which includes a first tray body 22 and a support member 21, to form a test oxide film as the first oxide film on a test wafer W, which is the first wafer. A measuring device (not shown) measures the film thickness distribution of the test oxide film. A computer (not shown) obtains the film thickness distribution of the test oxide film based on, for example, an operator's operation of an input unit (not shown) or from the measuring device.

[0119] The components of the groove 222 and the contact portion 223 in the first pallet body 22 are not particularly limited. For example, they can be the components of the pallet body 22 in Experimental Example 1 above. The first pallet body 22 can be selected from various pallet bodies 22 prepared in the pallet body preparation step S61, or it can be a different type of pallet body 22 from the pallet body preparation step S61.

[0120] In the correlation acquisition process S63, the computer, for example, acquires the correlation between at least one of the components of the slot 222 and the contact portion 223 and the film thickness distribution of the oxide film in the storage unit (not shown).

[0121] The correlation includes at least one of the correlations described in categories 1 through 3 above. This correlation can be determined experimentally or through simulation.

[0122] In the target film thickness distribution acquisition process S64, the computer acquires the target film thickness distribution of the oxide film based on, for example, the operator's operation on the input unit.

[0123] In the tray body structure determination process S65, the computer determines at least one of the components of the groove portion 222 and the contact portion 223 that can form an oxide film with the target film thickness distribution as an applicable component based on the film thickness distribution and related relationships of the tested oxide film.

[0124] For example, if the film thickness distribution based on the first film thickness ratio of the above formula (1) is the target film thickness distribution, and the first film thickness ratio in the test oxide film is greater than the specified value, then according to the first correlation, the groove 222 is determined to be an applicable requirement for forming an oxide film with the target film thickness distribution, so that the width of the groove 222 is greater than the width of the groove 222 of the first tray body 22.

[0125] Furthermore, if the target film thickness distribution of the outer periphery is a uniform film thickness distribution, and the thickness of the region on the transport width direction side of the outer periphery of the test oxide film is thicker than other regions of the outer periphery, then according to the second correlation, the contact portion 223 provided on the transport width direction side will be longer than the contact portion 223 of the first tray body 22, thereby increasing the contact area with the support leg portion 212, and this is determined to be an applicable requirement for the contact portion 223 that can form an oxide film with the target film thickness distribution.

[0126] Furthermore, if the target film thickness distribution on the outer periphery is uniform, and the thickness of the region on the transport direction side of the test oxide film on the outer periphery is thinner than other regions on the outer periphery, then according to the third correlation, the contact area between the contact portion 223 provided on the transport direction side and the support leg portion 212 is determined to be greater than the contact area in the first tray body 22, thus determining that the contact portion 223 is suitable for forming an oxide film with the target film thickness distribution. As a method to increase the contact area, at least one of lengthening the contact portion 223 and increasing the number of contact portions 223 can be applied.

[0127] In the film-forming process S66, the operator selects a second pallet body 22 that meets the applicable requirements from among the various pallet bodies 22 prepared in the pallet body preparation process S61. If no pallet body 22 among the various pallet bodies 22 meets the applicable requirements, the operator selects the pallet body 22 having the constituent elements closest to the applicable requirements as the second pallet body 22. Furthermore, selecting the pallet body 22 having the constituent elements closest to the applicable requirements is equivalent to selecting the second pallet body 22 that meets the applicable requirements of this invention.

[0128] The specified film-forming apparatus 1 uses a second tray body 22 selected by the operator to form a back oxide film on the back side of the product wafer W.

[0129] <Effects of the Implementation Method> The method for forming an oxide film includes: the above-mentioned pre-oxidized film forming step S62, the correlation acquisition step S63, the target film thickness distribution acquisition step S64, the tray body composition determination step S65, and the film forming step S66.

[0130] Thus, based on the 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, and the film thickness distribution of the tested oxide film, the at least one constituent element that enables the formation of an oxide film with a target film thickness distribution is determined as an applicable element. Using the second tray body 22 that satisfies the applicable element, a back oxide film is formed on the product wafer, thereby enabling the formation of an oxide film with a desired film thickness distribution on the wafer W.

[0131] Furthermore, by performing the oxide film formation method and using a second tray body 22 corresponding to the device characteristics of each of the multiple film-forming devices 1, the deviation in the film thickness distribution of the oxide film among the multiple film-forming devices 1 can be reduced.

[0132] Furthermore, since an oxide film with the desired film thickness distribution can be formed, the yield of wafer W can be improved, thereby achieving improvements in energy efficiency, increased production efficiency, and reduced waste.

[0133] The correlation obtained in the correlation acquisition process S63 includes a first correlation between the width of at least a portion of the trench 222 in the circumferential direction and the thickness of the oxide film in the region adjacent to said at least a portion of the outer periphery of the wafer W.

[0134] Therefore, by using a second tray body 22 in which the width of at least a portion of the groove 222 is appropriately set in the circumferential direction, an oxide film with a desired film thickness distribution can be formed.

[0135] The correlation obtained in the correlation acquisition process S63 includes a second correlation between the contact area of ​​the contact portion 223 and the support portion 212 at the part on the transport width direction side of the pallet body 22 and the thickness of the oxide film in the region of the outer periphery of the wafer W adjacent to the part on the transport width direction side.

[0136] Therefore, by using a second pallet body 22 in which the contact area between the contact portion 223 on the transport width side of the pallet body 22 and the support leg portion 212 is appropriately set, an oxide film with a desired film thickness distribution can be formed.

[0137] The correlations obtained in the correlation acquisition process S63 include: a third correlation between the contact area of ​​the contact portion 223 and the support portion 212 at the transport direction side of the pallet body 22 and the thickness of the oxide film in the region adjacent to the transport direction side portion of the outer periphery of the wafer W.

[0138] Therefore, by using a second tray body 22 whose contact area between the contact portion 223 and the support leg portion 212 at the transport direction side of the tray body 22 is appropriately set, an oxide film with a desired film thickness distribution can be formed on the wafer W.

[0139] In particular, if the correlation obtained in the correlation acquisition process S63 includes all the first to third correlations, then by using the tray body 22 obtained according to the first to third correlations, the film thickness distribution can be controlled more precisely.

[0140] The method for forming the oxide film includes a tray body preparation step S61.

[0141] Therefore, in the film forming process S66, an oxide film with the desired film thickness distribution can be formed by simply selecting only the second tray body 22 that meets the applicable requirements from the various tray bodies 22 prepared in the tray body preparation process S61.

[0142] [Variation Example] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the specific structure is not limited to these embodiments. Various modifications and design changes that do not depart from the spirit of the present invention are also included in the present invention.

[0143] For example, a portion of the pre-oxidation film formation process S62, the correlation acquisition process S63, the target film thickness distribution acquisition process S64, and the tray body composition determination process S65 can be performed by a worker. Specifically, the worker can perform: confirming the film thickness distribution of the test oxide film measured by the measuring device (pre-oxidation film formation process S62); confirming the correlation displayed on a computer display or on a sheet medium such as paper (correlation acquisition process S63); confirming the target film thickness distribution of the oxide film according to product specifications, etc. (target film thickness distribution acquisition process S64); and the tray body composition determination process S65.

[0144] By installing the attachment into the recess 221, and setting it to a structure that can be provided with a groove 222 and a contact portion 223 having specified constituent elements, a second tray body 22 that meets the applicable requirements can be manufactured by selecting one attachment from a variety of attachments.

[0145] In the top view, the pallet body 22 can be a rectangle, square, polygon other than a quadrilateral, circle or ellipse with its long side parallel to the conveying direction.

[0146] Industrial availability According to the method for determining oxide film formation conditions, the method for forming oxide film, and the method for manufacturing wafers of the present invention, oxide films with desired film thickness distributions can be formed, thereby improving the yield of wafers W, and thus achieving improvements in energy efficiency, increased production efficiency, and reduced waste. The products involved in this invention (epilithographic silicon wafers with LTO films (back oxide films)) are mainly used in logic devices. This invention contributes to the high precision of semiconductor devices, and thus plays an important role in industrialization as a fundamental technology required for the development and improvement of advanced industrial products. The products involved in this invention can be used, for example, in control systems of automobiles, home appliances, medical devices, etc., enabling the production of high-quality, high-reliability products.

[0147] Explanation of reference numerals in the attached figures 1-Film forming apparatus, 2-Film forming tray, 21-Supporting component, 211-Placing part, 212-Leg part, 22, 23, 24, 25, 26-Tray body, 221-Recess, 222, 232, 242, 252, 262-Groove, 223-Contact part, 233, 243-First contact part, 254-Second contact part, G1-Raw material gas, W-Wafer.

Claims

1. A method for determining the formation conditions of an oxide film, comprising determining the conditions for forming an oxide film on a wafer using a film-forming apparatus, wherein in the method for determining the formation conditions of the oxide film, The film-forming apparatus is configured to use a film-forming tray, supplying a raw material gas to the wafer while heating the film-forming tray, thereby forming the oxide film on the wafer. The film-forming tray includes a support member supporting the outer periphery of the wafer and a tray body supporting the support member. The support member includes an annular mounting portion for placing the wafer and a leg portion extending downward from the mounting portion. The tray body is configured to have a cylindrical recess for accommodating the support member and a plurality of grooves formed along the outer edge of the bottom surface of the recess, and the support legs of the support member are supported by contact portions located between adjacent pairs of the grooves. The method for determining the formation conditions of the oxide film includes: In the pre-oxidation film formation process, the first oxide film is formed on the first wafer using the first tray body; The correlation acquisition process obtains the correlation between at least one of the constituent elements of the groove and the contact portion and the film thickness distribution of the oxide film. The target film thickness distribution acquisition process acquires the target film thickness distribution of the oxide film; and In the process of determining the structure of the tray body, at least one of the constituent elements that can form the oxide film with the target film thickness distribution is determined as applicable elements based on the film thickness distribution of the first oxide film and the related relationship.

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

3. The method for determining the formation conditions of the oxide film according to claim 1, wherein, The film-forming apparatus is configured to form the oxide film on the wafer supported by each film-forming tray while arranging and conveying multiple film-forming trays, each having a tray body, along the feed direction. The correlation includes a second correlation between the contact area of ​​the contact portion and the support leg at the location of the tray body on the side of the conveying width direction orthogonal to the feeding direction, and the thickness of the oxide film in the region of the outer periphery of the wafer adjacent to the location on the side of the conveying width direction.

4. The method for determining the formation conditions of the oxide film according to claim 3, wherein, The second correlation is as follows: the larger the contact area at the location on the conveying width direction side, the thinner the oxide film in the region adjacent to the location on the conveying width direction side.

5. The method for determining the formation conditions of the oxide film according to claim 1, wherein, The film-forming apparatus is configured to form the oxide film on the wafer supported by each film-forming tray while arranging and conveying multiple film-forming trays, each having a tray body, along the feed direction. The correlation includes a third correlation between the contact area of ​​the contact portion and the support leg portion at the feed direction side and the opposite direction side of the tray body, and the thickness of the oxide film in the region of the outer periphery of the wafer adjacent to the feed direction side and the opposite direction side.

6. The method for determining the formation conditions of the oxide film according to claim 5, wherein, The third correlation is as follows: the larger the contact area at the location on the feed direction side and the opposite direction side, the thicker the oxide film in the region adjacent to the location on the feed direction side and the opposite direction side.

7. A method for forming an oxide film, comprising: The steps of the method for determining the formation conditions of the oxide film according to any one of claims 1 to 6; and A film-forming process in which a second oxide film is formed on a second wafer using a second tray body that meets the applicable requirements.

8. The method for forming an oxide film according to claim 7, further comprising: The pallet body preparation process involves preparing multiple pallet bodies, each with at least one different constituent component. In the film-forming process, the second tray body is selected from at least one constituent element corresponding to each of the plurality of tray bodies, and the second tray body is used to form the second oxide film.

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

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