Method for distinguishing PN inversion caused by oxygen donor effect based on crystal segment position

Abstract

The invention relates to a method for distinguishing PN inversion caused by an oxygen donor effect based on a crystal segment position, which belongs to the technical field of silicon wafer processing, and comprises the following operation steps of: 1, before statistics, confirming that a crystal segment eliminates the oxygen donor effect after high-temperature annealing, the crystal segment is a P-type product, and no material mixing occurs in the process; step 2, counting 316 crystal section bars in the range of 0-2200mm at the single crystal position, wherein 13 N-type crystal section bars appear; the number of the P type is 303; and it is judged that no N-type phenomenon occurs after 1400 mm according to the occurrence position. And 3, coding the positions of the crystal segments according to rules, and distinguishing the silicon wafers without serious oxygen donor effect, namely the silicon wafers without PN inversion. And 4, carrying out process monitoring according to the code of the crystal segment position, and observing the position of the corresponding block in the single crystal from the information of the block during use. The method has the advantages that whether the corresponding silicon wafer has the serious oxygen donor effect or not can be quickly confirmed, the silicon wafer without the serious oxygen donor effect can be selected for use, and convenience is brought to the use of an electrical monitoring process of a chip manufacturing enterprise.

Description

Technical Field

[0001] The invention relates to the technical field of silicon wafer processing, and in particular to a PN inversion method for distinguishing oxygen donor effects based on crystal segment positions. Background Art

[0002] Due to the manufacturing principle of direct-pulled single crystals, the quartz crucible used for crystal pulling reacts with Si at high temperature to produce SiO2. A small amount of oxygen enters the silicon melt, and there will inevitably be an oxygen donor effect. Due to its donor effect, it provides additional electrons to the silicon substrate, which directly affects the carrier concentration of crystalline silicon, causing the resistance of N-type silicon crystals to decrease and the resistivity of P-type silicon crystals to increase. In severe cases, the P-type silicon crystals will be converted into N-type.

[0003] Chip processing often requires the use of P-type lightly doped wafers in process monitoring. Before use, the machine will perform electrical measurements. Due to the oxygen donor effect, the P-type product will appear N-type during electrical testing, which will cause the test machine to alarm. Testers will also worry about whether there is really material mixing or abnormalities. This often causes unnecessary alarm interference on the production line and affects the processing cycle. Currently, if the test is not used, it is impossible to do a good layer classification based only on the oxygen content and resistivity of the wafer. Summary of the invention

[0004] The present invention mainly solves the deficiencies in the prior art and provides a method for distinguishing PN inversion caused by oxygen donor effect based on crystal segment position. The method has the advantages of quickly confirming whether the corresponding silicon wafer has a serious oxygen donor effect, and selecting silicon wafers without serious oxygen donor effect for use, which brings convenience to the electrical monitoring process of chip manufacturing companies.

[0005] The above technical problems of the present invention are mainly solved by the following technical solutions:

[0006] A method for distinguishing PN inversion caused by oxygen donor effect based on crystal segment position includes the following steps:

[0007] Step 1: Before statistics are collected, confirm that the crystal segment has eliminated the oxygen donor effect after high-temperature annealing, is a P-type product, and no mixing occurs during the process.

[0008] Step 2: 316 crystal segment rods between the single crystal position 0 and 2200mm were counted, and 13 N-type and 303 P-type appeared. Judging from the occurrence position, no N-type phenomenon appeared after 1400mm.

[0009] The third step: Encode the crystal segment position according to the rules to distinguish and identify silicon wafers without serious oxygen donor effect, that is, silicon wafers without PN inversion.

[0010] Step 4: Monitor the process according to the coding of the crystal segment position. When in use, the position of the corresponding block in the single crystal can be seen from the block information.

[0011] Preferably, the information naming rules of the crystal segment rod include the single product furnace number, production year, furnace number, segment head number and segment tail number.

[0012] As a preferred method, the crystal is heated to 650°C and kept at this temperature for half an hour before being rapidly cooled, so as to quickly skip 450°C and eliminate SiO4 2- Donor effect; after annealing, oxygen exists again in the form of interstitial oxygen and no longer provides electrons. The resistivity is no longer affected by it, but is determined by the concentration and distribution of the main carrier boron and returns to normal value.

[0013] Preferably, after wiping the single crystal rods clean, they are placed on a quartz plate in sequence, heated to 720°C and kept at a constant temperature for 1 to 1.5 hours, then the furnace is stopped, naturally cooled to 480°C and then rapidly cooled for 3 hours, so that the oxygen donors of the single crystal rods return to the interstitial oxygen state, eliminating the influence of the oxygen donors on the resistivity test.

[0014] As a preference, the cross-sectional resistivity of a P-type single crystal round rod is mostly high in the center and low around. Some round rod cross sections have an inverted P-type phenomenon at the center and an N-type edge. High resistance, i.e., greater than the target resistivity, and the inversion phenomenon mostly occurs at the head of the single crystal rod.

[0015] Preferably, since the segregation coefficient of oxygen is greater than 1, the oxygen in the crystal decreases linearly, resulting in a higher oxygen content in the head, which affects the resistivity, increases the nitrogen supplement, and discharges the oxygen existing in the gap form.

[0016] The present invention can achieve the following effects:

[0017] The present invention provides a method for distinguishing PN inversion caused by oxygen donor effect based on crystal segment position. Compared with the prior art, the method has the advantages of quickly confirming whether the corresponding silicon wafer has a serious oxygen donor effect, and selecting silicon wafers without serious oxygen donor effect for use, which brings convenience to the use of electrical monitoring processes of chip manufacturing companies. DETAILED DESCRIPTION

[0018] The technical solution of the invention is further specifically described below through embodiments.

[0019] Embodiment: A method for distinguishing PN inversion caused by oxygen donor effect based on crystal segment position, comprising the following steps:

[0020] Step 1: Before statistics are collected, confirm that the crystal segment has eliminated the oxygen donor effect after high-temperature annealing, is a P-type product, and no mixing occurs during the process.

[0021] Heat the crystal to 650℃ and keep it at constant temperature for half an hour, then cool it down quickly, quickly skip 450℃ to eliminate SiO4 2- Donor effect; after annealing, oxygen exists again in the form of interstitial oxygen and no longer provides electrons. The resistivity is no longer affected by it, but is determined by the concentration and distribution of the main carrier boron and returns to normal value.

[0022] After wiping the single crystal rods clean, they are placed on a quartz plate in sequence, heated to 720°C and kept at this temperature for 1 to 1.5 hours, then the furnace is stopped, cooled naturally to 480°C and then rapidly cooled for 3 hours, so that the oxygen donors of the single crystal rods return to the interstitial oxygen state, eliminating the influence of oxygen donors on the resistivity test.

[0023] Step 2: 316 crystal segment rods between the single crystal position 0 and 2200mm were counted, and 13 N-type and 303 P-type appeared. Judging from the occurrence position, no N-type phenomenon appeared after 1400mm.

[0024] The cross-sectional resistivity of P-type single crystal round rods is mostly high in the center and low around. Some round rod cross-sections have an inverted P-type phenomenon at the center and edge, that is, N-type. High resistance, that is, greater than the target resistivity, and the inversion phenomenon mostly appear at the head of the single crystal rod.

[0025] Since the segregation coefficient of oxygen is greater than 1, the oxygen in the crystal decreases linearly, resulting in a higher oxygen content in the head, which affects the resistivity, increases the nitrogen supplement, and discharges the oxygen existing in the interstitial form.

[0026] The third step: Encode the crystal segment position according to the rules to distinguish and identify silicon wafers without serious oxygen donor effect, that is, silicon wafers without PN inversion.

[0027] Step 4: Monitor the process according to the coding of the crystal segment position. When in use, the position of the corresponding block in the single crystal can be seen from the block information. The naming rules of the crystal segment rod information include the single product furnace number, production year, furnace number, segment head number and segment tail number.

[0028] In summary, this method of distinguishing PN inversion caused by oxygen donor effect based on crystal segment position has a method to quickly confirm whether the corresponding silicon wafer has a serious oxygen donor effect, and selects silicon wafers without serious oxygen donor effect for use, which brings convenience to the electrical monitoring process of chip manufacturing companies.

[0029] The above description is only a specific embodiment of the present invention, but the structural features of the present invention are not limited thereto. Any changes or modifications made by any technician in the field of the present invention are included in the patent scope of the present invention.

Claims

1. A method for distinguishing PN inversion caused by oxygen donor effect based on crystal segment position, characterized in that The steps are as follows: Step 1: Before statistics, confirm that the crystal segment eliminates the oxygen donor effect after high-temperature annealing, is a P-type product, and no mixing occurs during the process; Step 2: Count the 316 crystal segments between the single crystal position 0 and 2200mm, and there are 13 N-type and 303 P-type. Judging from the occurrence position, there is no N-type phenomenon after 1400mm. Step 3: Encode the crystal segment position according to the rules to distinguish silicon wafers without severe oxygen donor effect, that is, silicon wafers without PN inversion; Step 4: Monitor the process according to the coding of the crystal segment position. When in use, the position of the corresponding block in the single crystal can be seen from the block information.

2. The PN inversion method based on crystal segment position differentiation caused by oxygen donor effect according to claim 1, characterized in that: The information naming rules of crystal segment rods include single product furnace number, production year, furnace number, segment head number and segment tail number.

3. The PN inversion method based on crystal segment position differentiation caused by oxygen donor effect according to claim 1, characterized in that: Heat the crystal to 650℃ and keep it at constant temperature for half an hour, then cool it down quickly, quickly skip 450℃ to eliminate SiO4 2- Donor effect; after annealing, oxygen exists again in the form of interstitial oxygen and no longer provides electrons. The resistivity is no longer affected by it, but is determined by the concentration and distribution of the main carrier boron and returns to normal value.

4. The PN inversion method based on crystal segment position differentiation caused by oxygen donor effect according to claim 3, characterized in that: After wiping the single crystal rods clean, they are placed on a quartz plate in sequence, heated to 720°C and kept at this temperature for 1 to 1.5 hours, then the furnace is stopped, cooled naturally to 480°C and then rapidly cooled for 3 hours, so that the oxygen donors of the single crystal rods return to the interstitial oxygen state, eliminating the influence of oxygen donors on the resistivity test.

5. The PN inversion method based on crystal segment position differentiation caused by oxygen donor effect according to claim 1, characterized in that: The cross-sectional resistivity of P-type single crystal round rods is mostly high in the center and low around. Some round rod cross-sections have an inverted P-type phenomenon at the center and edge, that is, N-type. High resistance, that is, greater than the target resistivity, and the inversion phenomenon mostly appear at the head of the single crystal rod.

6. The PN inversion method based on crystal segment position differentiation caused by oxygen donor effect according to claim 5, characterized in that: Since the segregation coefficient of oxygen is greater than 1, the oxygen in the crystal decreases linearly, resulting in a higher oxygen content in the head, which affects the resistivity, increases the nitrogen supplement, and discharges the oxygen existing in the interstitial form.