Semiconductor structure and method for monitoring ion implantation state

Abstract

The invention provides a semiconductor structure and a method for monitoring an ion implantation state, the semiconductor structure comprises a substrate, and an oxide layer and a polycrystalline silicon layer which are sequentially formed on the substrate, high-dose doped ions are implanted into the polycrystalline silicon layer, covalent bonds can be formed between the doped ions and the polycrystalline silicon layer after the doped ions are implanted, and the doped ions are doped into the polycrystalline silicon layer. After the target ions are injected into the polycrystalline silicon layer, the covalent bonds between the doped ions and the polycrystalline silicon are destroyed, so that the ion injection state of the target ions can be monitored through resistance detection. Besides, the oxide layer is used as an ion barrier layer, the implanted ions cannot diffuse into the substrate, after the current ion state monitoring is completed, the oxide layer and the polycrystalline silicon layer on the substrate are removed, the oxide layer and the polycrystalline silicon layer are grown again, and high-dose doped ions are implanted into the polycrystalline silicon layer, so that the next ion implantation state monitoring can be realized, and the ion implantation efficiency is improved. Therefore, by adopting the method for monitoring the ion implantation state provided by the invention, the substrate can be reused.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a semiconductor structure and a method for monitoring ion implantation status. Background Art

[0002] Hydrogen ion / indium ion implantation is different from the implantation of other doping atoms and cannot provide sufficient carriers for the substrate. Therefore, the ion implantation status cannot be characterized by measuring the sheet resistance. However, the ion implantation machine inspection, machine recovery after shutdown, and daily monitoring of machine abnormalities all require the ability to effectively monitor the ion implantation dose / energy to prevent machine abnormalities and thus avoid affecting device performance. Summary of the invention

[0003] The object of the present invention is to provide a semiconductor structure and a method for monitoring ion implantation status to solve one or more problems in the prior art.

[0004] In order to solve the above problems, the present invention provides a semiconductor structure for monitoring the target ion implantation state, the semiconductor structure comprising:

[0005] substrate;

[0006] an oxide layer covering the substrate; and

[0007] A polysilicon layer covers the oxide layer, high-dose doping ions are implanted into the polysilicon layer, and covalent bonds are formed between the doping ions and the polysilicon layer through thermal annealing.

[0008] Optionally, in the semiconductor structure, the thickness of the polysilicon layer is 2500 to 3500 angstroms, and the thickness of the oxide layer is 1000 to 2000 angstroms.

[0009] Optionally, in the semiconductor structure, the doping ions include boron ions.

[0010] The present invention also provides a method for monitoring the state of ion implantation, comprising:

[0011] Providing a semiconductor structure as described in any of the preceding items;

[0012] implanting target ions to be monitored into the polysilicon layer; and,

[0013] The resistance of the polysilicon layer is detected, and the implantation state of the target ions is determined according to the detection result.

[0014] Optionally, in the method for monitoring the ion implantation state, the implantation conditions when implanting high-dose doping ions into the polysilicon layer include:

[0015] The implantation energy is 20-200 KeV, and the implantation dose is 2.0E14-1.0E15 ions / cm 2 , the injection angle is 3°~45°.

[0016] Optionally, in the method for monitoring the state of ion implantation, the annealing temperature during the rapid thermal annealing treatment is 1000-1150° C., and the annealing time is 20-60 seconds.

[0017] Optionally, in the method for monitoring the ion implantation state, the method for determining the implantation state of the target ions according to the detection result includes:

[0018] The detection result is compared with the known resistance value. If the difference between the detection result and the known resistance value is within a set range, it indicates that the current injection state of the target ion is stable, and the known resistance value is the resistance value of the polysilicon layer under the same injection conditions calculated before the current ion injection state monitoring is performed.

[0019] Optionally, in the method for monitoring the ion implantation state, the method for calculating the known resistance value includes:

[0020] Changing the implantation conditions of the target ions multiple times, and measuring the resistance of the semiconductor structure under each of the implantation conditions, so as to obtain a functional relationship between the resistance value and the implantation conditions; and

[0021] Under the current injection condition, the known resistance value is obtained based on the functional relationship.

[0022] Optionally, in the method for monitoring the ion implantation state, the method for calculating the known resistance value includes:

[0023] Under the same implantation condition, repeatedly performing the steps of implanting the target ions into the polysilicon layer of the semiconductor structure and detecting the resistance of the polysilicon layer;

[0024] Calculating an average value of the resistance of the polysilicon layer obtained by multiple tests; and,

[0025] The average value is taken as the known resistance value.

[0026] Optionally, in the method for monitoring the ion implantation state, after determining the implantation state of the target ions, the method further includes:

[0027] After the current ion implantation state monitoring is completed, removing the polysilicon layer and the oxide layer on the substrate; and,

[0028] When the next ion implantation state monitoring is performed, the oxide layer and the polysilicon layer are deposited on the substrate again to obtain the semiconductor structure again.

[0029] In summary, the present invention provides a semiconductor structure and a method for monitoring the state of ion implantation, wherein the semiconductor structure comprises: a substrate, and an oxide layer and a polysilicon layer sequentially formed on the substrate, wherein high-dose doping ions are implanted into the polysilicon layer, and the doping ions can form covalent bonds with the polysilicon layer after implantation, and the target ions destroy the covalent bonds between the doping ions and the polysilicon after implantation into the polysilicon layer, thereby the ion implantation state of the target ions can be monitored by resistance detection. In addition, the oxide layer is used as an ion barrier layer, and the implanted ions will not diffuse into the substrate. After the current ion state monitoring is completed, it is only necessary to remove the oxide layer and the polysilicon layer on the substrate, and re-grow the oxide layer and the polysilicon layer, and implant high-dose doping ions into the polysilicon layer, and then the ion implantation state can be used for the next ion implantation state monitoring. Therefore, by adopting the method for monitoring the ion implantation state provided by the present invention, the substrate can be reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 A schematic diagram of a semiconductor structure provided by an embodiment of the present invention;

[0031] Figure 2 A flow chart of a method for monitoring ion implantation status provided by an embodiment of the present invention;

[0032] Figure 3 A schematic diagram showing how the resistance value changes with the increase in the number of times used in an embodiment of the present invention;

[0033] Figure 4 A schematic diagram showing the change of resistance value with injection energy in an embodiment of the present invention;

[0034] Figure 5 A schematic diagram showing the change of resistance value with implantation dose in an embodiment of the present invention;

[0035] Figure 6 A schematic diagram showing the change of resistance value according to the random injection times in an embodiment of the present invention;

[0036] The descriptions of the reference numerals are as follows:

[0037] 11-substrate; 12-oxide layer; 13-polysilicon layer. DETAILED DESCRIPTION

[0038] The semiconductor structure and the method for monitoring the ion implantation state proposed by the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all in a very simplified form and are all in non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the embodiments of the present invention. In addition, the structure shown in the drawings is often a part of the actual structure. In particular, the emphasis required to be shown in each drawing is different, and sometimes different proportions are used. It should be recognized that relative terms such as "above", "below", "top", "bottom", "above" and "below" shown in the drawings can be used to describe the relationship between various elements. These relative terms are intended to cover different orientations of elements other than the orientations depicted in the drawings. For example, if the device is inverted relative to the view in the drawings, for example, an element described as "above" another element will now be below the element. It should also be understood that, unless otherwise specified or indicated, the terms "first", "second", "third" and the like in the specification are only used to distinguish between the various components, elements, steps, etc. in the specification, rather than to represent the logical relationship or sequential relationship between the various components, elements, steps, etc.

[0039] An embodiment of the present invention provides a semiconductor structure for monitoring the target ion implantation state. The target ions here may be oxygen ions, nitrogen ions, antimony ions and other non-doping ions in addition to the non-doping ions described above: hydrogen ions and indium ions.

[0040] See also Figure 1 , the semiconductor structure provided by the embodiment of the present invention includes:

[0041] Substrate 11;

[0042] an oxide layer 12, wherein the oxide layer 12 covers the substrate 11; and

[0043] A polysilicon layer 13, wherein the polysilicon layer 13 covers the oxide layer 12, high-dose doping ions are implanted into the polysilicon layer 13, and covalent bonds are formed between the doping ions and the polysilicon layer 13 through thermal annealing.

[0044] The oxide layer 12 is used as an ion implantation barrier layer. When ions are implanted into the polysilicon layer 13 , the ion implantation barrier layer can prevent the ions from further diffusing into the substrate 11 , so that the substrate 11 can be used repeatedly.

[0045] The substrate 11 can be made of an N-type or P-type wafer. The oxide layer 12 can be grown using a furnace tube process. When the oxide layer 12 is grown, the growth temperature can be about 950° C.

[0046] The polysilicon layer 13 can be grown by continuing to use the furnace tube process in the furnace tube, and the growth temperature can be about 540°C.

[0047] Preferably, the thickness of the polysilicon layer 13 is 2500 to 3500 angstroms. Within this thickness range, the influence of polysilicon growth differences on resistance can be reduced, and the monitoring accuracy can be improved. For example, when the thickness of the polysilicon layer 13 is 2500 angstroms, Figure 3 As shown in , the measured previous value error of the semiconductor structure is within 1%, and the previous value error refers to the error value of the resistance value of the polysilicon layer measured before the target ion implantation changes with the number of substrate cycles. It can be seen that before the target ion implantation, the resistance value of the polysilicon layer used for monitoring the target ion implantation state is maintained within a stable range. Figure 3 In the figure, the horizontal axis RECYCLE TIME represents the number of times the substrate is recycled, and the vertical axis RS represents the measured resistance value.

[0048] In addition, preferably, the thickness of the oxide layer 12 is 1000 to 2000 angstroms. Within this thickness range, while the diffusion of ions into the substrate 11 is well blocked, the difficulty of removing the oxide layer 12 due to excessive thickness can be avoided.

[0049] As doping ions, boron ions have the smallest relative atomic mass and the highest activation rate under the same annealing conditions. Therefore, in this embodiment, preferably, the doping ions are boron ions. After the boron ions are implanted, they are subjected to rapid thermal annealing to form B-Si bonds with silicon ions of the polysilicon layer 12. In other embodiments, other doping ions that can form covalent bonds with silicon ions may also be selected, such as oxygen, nitrogen, antimony, etc., which are not limited in this application.

[0050] Based on the semiconductor structure provided by the embodiment of the present invention, the embodiment of the present invention also provides a method for monitoring the ion implantation state, see Figure 2 The method for monitoring the ion implantation state provided by the embodiment of the present invention comprises the following steps:

[0051] S1, providing a substrate;

[0052] S2, forming an oxide layer, wherein the oxide layer covers the substrate;

[0053] S3, forming a polysilicon layer, the polysilicon layer covering the oxide layer, and implanting high-dose doping ions into the polysilicon layer, and performing thermal annealing treatment to generate covalent bonds between the doping ions and the polysilicon layer;

[0054] S4, injecting target ions to be monitored into the polysilicon layer; and

[0055] S5, detecting the resistance, and judging the injection state of the target ions according to the detection result.

[0056] The above steps S1 to S3 are steps for forming the semiconductor structure described above, so the description of each layer in steps S1 to S3 can be found in the above text and will not be repeated here. In addition, in step S3, preferably, the annealing temperature during the thermal annealing treatment is 1000 to 1150°C and the time is 20 to 60S, so that the number of covalent bonds formed between the implanted ions and the silicon ions is within a relatively stable range.

[0057] In step S4, preferably, the implantation conditions for implanting high-dose doping ions into the polysilicon layer include: an implantation energy of 20 to 200 KeV, an implantation dose of 2.0E14 to 1.0E15 ions / cm 2 , the injection angle is 3°~45°. The thickness of the polysilicon layer and the injection conditions will affect the resistance sensitivity of the semiconductor structure. When the thickness of the polysilicon layer is 2500~3500 angstroms, the injection conditions can keep the resistance sensitivity within a better range, avoiding the influence of too high or too low resistance sensitivity on the monitoring accuracy. It can be understood that the "resistance sensitivity" here represents the speed at which the resistance value changes with the injection conditions.

[0058] As an example, Figure 4 As shown in , when the thickness of the polysilicon layer is 2500 angstroms, keeping other implantation conditions unchanged, the implantation energy of indium ions is changed within the range of 20 to 200 Kev, and the resistance sensitivity is measured to be about 20Ω / Kev, as shown in Figure 5 As shown, keeping other injection conditions unchanged, the concentration of ions / cm 2 The resistance sensitivity is about 10Ω / 1% by changing the implantation dose of indium ions. It can be seen that the thickness of the polysilicon layer defined in the present application is 2500-3500 angstroms, the implantation energy of the doped ions is 20-200Kev, and the implantation dose is 2.0E14-1.0E15 ions / cm 2 , when the injection angle is 3°~45°, the resistance sensitivity can be maintained in a better range. Figure 4 In the figure, the horizontal axis ENERGY represents the injected energy. Figure 5 In the figure, the horizontal axis DOSE represents the injection dose. Figure 4 and Figure 5 In the figure, the vertical axis RS represents the measured resistance value.

[0059] It is necessary to distinguish that Figure 4 and Figure 5 In FIG. 1 , the vertical axis RS refers to the resistance value measured after the target ions are implanted. Figure 3In FIG. 1 , the vertical axis RS refers to the resistance value measured before the target ions are implanted.

[0060] In step S5, the method for judging the injection state of the target ion according to the detection result may include: comparing the detection result with a known resistance value, if the difference between the detection result and the known resistance value is within a set range, it indicates that the current injection state of the target ion is stable, wherein the known resistance value is the resistance value of the polysilicon layer 13 under the same injection conditions calculated before the current ion injection state monitoring is performed.

[0061] The setting range can be defined according to actual needs. Assuming that the known resistance value is R1 and the detection result is R2, in some application scenarios, it can be defined as: when the difference between R2 and R1 is equal to 0, it is judged that the current injection state of the target ion is stable; in other application scenarios, it can be defined as: when the difference between R2 and R1 is within the value range of (-3σ, 3σ), it is judged that the current injection state of the target ion is stable.

[0062] In an optional embodiment, the method for calculating the known resistance value includes: changing the implantation conditions of the target ions multiple times, and measuring the resistance of the semiconductor structure under each of the implantation conditions to obtain Figure 4 or Figure 5 A functional relationship showing how the resistance value shown in the figure changes with the injection condition; and, under the current injection condition, obtaining the known resistance value based on the functional relationship.

[0063] In another optional embodiment, the method for calculating the known resistance includes: under the same injection conditions, performing the steps of injecting the target ions into the polysilicon layer of the semiconductor structure and detecting the resistance of the polysilicon layer for multiple times; calculating the average value of the resistance of the polysilicon layer obtained from the multiple detections; and using the average value as the known resistance value.

[0064] It can be understood that in the above two optional embodiments, the semiconductor structure for each ion implantation and resistance detection is different. Preferably, the same substrate is repeatedly used to form the semiconductor structure to detect the resistance of the polysilicon layer. When each resistance detection is completed and the next resistance detection is performed, the polysilicon layer and the oxide layer on the substrate are removed, and the oxide layer and the polysilicon layer are deposited on the substrate again to obtain the semiconductor structure again. The reagent for removing the polysilicon layer may include nitric acid, and the reagent for removing the oxide layer may include hydrofluoric acid.

[0065] like Figure 6As shown in the example, the method for monitoring the ion implantation state provided in this embodiment has a repeatability error within 1% on the same machine, and can effectively monitor the ion implantation state, that is, effectively monitor the stability of the ion implantation process. It can be seen that the stability of the ion implantation state monitoring will not be affected when the substrate is recycled.

[0066] In summary, the semiconductor structure and the method for monitoring the ion implantation state provided by the embodiment of the present invention include: a substrate and an oxide layer and a polysilicon layer sequentially formed on the substrate, a high-dose doped ion is implanted in the polysilicon layer, and the doped ion can form a covalent bond with the polysilicon layer after implantation, and the target ion destroys the covalent bond between the doped ion and the polysilicon after implantation in the polysilicon layer, thereby, the ion implantation state of the target ion can be monitored by resistance detection. In addition, the oxide layer is used as an ion barrier layer, and the implanted ions will not diffuse into the substrate. After the current ion state monitoring is completed, it is only necessary to remove the oxide layer and the polysilicon layer on the substrate, and re-grow the oxide layer and the polysilicon layer, and implant the high-dose doped ion in the polysilicon layer, and then it can be used for the next ion implantation state monitoring. Therefore, the substrate can be reused by adopting the method for monitoring the ion implantation state provided by the present invention.

[0067] It should also be noted that, although the present invention has been disclosed as a preferred embodiment as above, the above embodiment is not intended to limit the present invention. For any technician familiar with the art, without departing from the scope of the technical solution of the present invention, the technical content disclosed above can be used to make many possible changes and modifications to the technical solution of the present invention, or modified into equivalent embodiments of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A semiconductor structure for monitoring a target ion implantation state, characterized in that: The semiconductor structure comprises: substrate; an oxide layer covering the substrate; and A polysilicon layer covers the oxide layer, high-dose doping ions are implanted into the polysilicon layer, and covalent bonds are formed between the doping ions and the polysilicon layer through thermal annealing.

2. The semiconductor structure according to claim 1, wherein: The thickness of the polysilicon layer is 2500 to 3500 angstroms, and the thickness of the oxide layer is 1000 to 2000 angstroms.

3. The semiconductor structure according to claim 1, wherein: The doping ions include boron ions.

4. A method for monitoring ion implantation status, characterized in that: Includes steps: Providing a semiconductor structure as claimed in any one of claims 1 to 3; implanting target ions to be monitored into the polysilicon layer; and, The resistance of the polysilicon layer is detected, and the implantation state of the target ions is determined according to the detection result.

5. The method for monitoring ion implantation status according to claim 4, characterized in that: The implantation conditions when high-dose doping ions are implanted into the polysilicon layer include: The implantation energy is 20-200 KeV, and the implantation dose is 2.0E14-1.0E15 ions / cm 2 , the injection angle is 3°~45°.

6. The method for monitoring ion implantation status according to claim 4, characterized in that: The annealing temperature during the rapid thermal annealing treatment is 1000-1150° C., and the annealing time is 20-60 seconds.

7. The method for monitoring ion implantation status according to claim 4, characterized in that: The method for judging the injection state of the target ion based on the detection result includes: comparing the detection result with a known resistance value; if the difference between the detection result and the known resistance value is within a set range, it indicates that the current injection state of the target ion is stable; the known resistance value is the resistance value of the polysilicon layer under the same injection conditions calculated before the current ion injection state monitoring is performed.

8. The method for monitoring ion implantation status according to claim 7, characterized in that: The method of calculating the known resistance value includes: Changing the implantation conditions of the target ions multiple times, and measuring the resistance of the semiconductor structure under each of the implantation conditions, so as to obtain a functional relationship between the resistance value and the implantation conditions; and Under the current injection condition, the known resistance value is obtained based on the functional relationship.

9. The method for monitoring ion implantation status according to claim 7, characterized in that: The method of calculating the known resistance value includes: Under the same implantation condition, the steps of implanting the target ions into the polysilicon layer of the semiconductor structure and detecting the resistance of the polysilicon layer are performed multiple times; Calculating an average value of the resistance of the polysilicon layer obtained by multiple tests; and, The average value is taken as the known resistance value.

10. The method for monitoring ion implantation status according to claim 4, characterized in that: The substrate is repeatedly used to form the semiconductor structure to detect the resistance of the polysilicon layer.

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