[0029] Since the prior art uses two semiconductor substrates to test the selectivity and thickness of the selective epitaxy process, the monitoring cost of the existing selective epitaxy process is relatively high. The invention utilizes two regions of the same semiconductor substrate to be monitored separately, thereby realizing the monitoring of the selectivity and thickness of the selective epitaxial process with one semiconductor substrate, and reducing the monitoring cost of the selective epitaxial process.
[0030] Specifically, for the selective epitaxy process monitoring method of the present invention, please refer to figure 1 As shown, the method includes:
[0031] Step S1, providing a semiconductor substrate, the semiconductor substrate is divided into a first area and a second area;
[0032] Step S2, forming a dielectric layer on the second area, the dielectric layer makes the second area have a certain color, which is different from the color of the first area;
[0033] Step S3, performing a selective epitaxial process on the semiconductor substrate with a dielectric layer formed in the second region;
[0034] Step S4, after the selective epitaxy process, observe whether the color of the second region is the same as the color before the selective epitaxy process; if the color of the second region is the same as the color of the second region before the selective epitaxy process If the same, the selectivity of the selective epitaxy process is normal, and if the color of the second region is different from the color of the second region before the selective epitaxy process, the selectivity of the selective epitaxy process is abnormal;
[0035] Step S5, after the selective epitaxy process, test the thickness of the epitaxial layer in the first region, and the thickness is the thickness of the selective epitaxy process.
[0036] The technical solutions of the present invention will be described in detail below in conjunction with specific embodiments.
[0037] First, please combine figure 2 The structure diagram of the semiconductor substrate for monitoring selective epitaxy process of the present invention is shown. A semiconductor substrate 100 is provided, and the semiconductor substrate 100 is divided into a first area 101 and a second area 102. The material of the semiconductor substrate 100 is silicon.
[0038] The first region 101 will be used to monitor the thickness of the selective epitaxy process, that is, the silicon in the first region 101 will be exposed in the chamber where the selective epitaxy process is performed. After the selective epitaxy process is performed, the second An epitaxial layer will be formed on the surface of a region 101. By testing the thickness of the epitaxial layer, it can be judged whether the thickness of the selective epitaxial process is normal. If the thickness of the epitaxial layer is normal, the thickness of the selective epitaxial process is normal; conversely, if the thickness of the epitaxial layer is abnormal, those skilled in the art need to perform related maintenance and maintenance for the selective epitaxial process until The thickness monitoring of the selective epitaxy is normal.
[0039] The second region 102 will be used to monitor the selective monitoring of the selective epitaxial process, that is, the silicon surface of the second region 102 will be covered with a dielectric layer with a certain color. After the selective epitaxial process is performed, if the color of the second area is the same as the color of the dielectric layer, it means that the selectivity of the selective epitaxial process is normal and no epitaxial layer is formed on the dielectric layer. The color of the region is different from the color of the dielectric layer, which indicates that the selectivity of the selective epitaxial process is abnormal. Those skilled in the art need to check the selective epitaxial process according to the results of the selective test of the selective epitaxial process. Perform maintenance and maintenance until the selective test result of the selective epitaxy process is normal.
[0040] As an embodiment, the first area 101 corresponds to a circular area formed by taking the center of the semiconductor substrate 100 as the center and taking 1/4 to 3/4 of the radius of the first area 101 as the radius. Part of the semiconductor substrate, the second region 102 is a region other than the first region 101 on the first semiconductor substrate 100, and the semiconductor substrate 100 is divided into the first region 101 and the second region 102. On the one hand, it is to facilitate the production of a dielectric layer on the second area 102. On the other hand, it is convenient and quicker to test the circular area due to the existing thickness testing instrument. In other embodiments, the semiconductor substrate 100 may also be divided into a first area and a second area in other ways. For example, the first area and the second area may be semicircular areas, or The first area and the second area may be two separate areas of the semiconductor substrate 100 and do not completely occupy the semiconductor substrate 100.
[0041] Then, a dielectric layer is formed on the second region 102, and the dielectric layer is used to cover the silicon of the second region 102. Since the usual color of the semiconductor substrate 100 is silver gray, when the dielectric layer is not formed in the second region 102, the colors of the first region 101 and the second region 102 are the same, and both are silver gray; After the second area 102 is covered with a dielectric layer, the color of the second area 102 is determined by the color of the dielectric layer.
[0042] In order to make the color of the second region 102 distinct from the color of the first region 101 and facilitate subsequent judgments of the color change of the second region 102, the present invention selects silicon nitride as the dielectric layer, and The thickness of the dielectric layer ranges from 800 to 1200 angstroms. Within the above-mentioned thickness range, the second region 102 appears light blue, and subsequently if an epitaxial layer is formed on the dielectric layer of the second region 102, the The color of the second area 102 will change to grayish brown, which is convenient for visual observation. In other embodiments, the dielectric layer may also be metal, but due to the reflection of the metal, the color change of the second area is not obvious, and a dedicated observation instrument may be needed to see whether the color of the second area 102 is Change.
[0043] The dielectric layer can be produced by a selective ion implantation process, a low pressure chemical vapor deposition process or an atomic layer chemical vapor deposition process.
[0044] As an embodiment, the dielectric layer is made by a selective ion implantation process, and the doped ions in the selective ion implantation process are nitrogen ions. The selective ion implantation controls the scanning radius of the ion implanted doping ions, so that the doping ions are only implanted into the second region 102. The scanning technique for controlling selective ion implantation of doped ions is a super scan technique, which can control the beam line of doped ions to scan only the second region 102. The energy range of the selective ion implantation is 1~50KeV, and the dose range is 1E14~1E16cm -2.
[0045] After the selective ion implantation, a step of annealing the semiconductor substrate 100 is also required to promote the bonding of the doped ions with the silicon of the semiconductor substrate 100 to form the semiconductor substrate 100 in the first region. Silicon nitride layer.
[0046] As another embodiment of the present invention, the dielectric layer can also be performed by using a furnace tube type low-pressure chemical vapor deposition process. The pressure range of the prior art low pressure chemical vapor deposition process is 0.01 to 1.0 Torr. The inventor’s research found that when the pressure of the low-pressure chemical vapor deposition process is greater than 0.1 Torr and less than 100 Torr, the low-pressure chemical vapor deposition process will only form a dielectric layer on the edge area of the semiconductor substrate 100, thereby forming a dielectric layer on the semiconductor substrate 100. A dielectric layer is not formed in the central area of, the central area can be used as the first area 101, and the edge area can be used as the second area 102. The greater the pressure of the low-pressure chemical vapor deposition process, the larger the area of the first region 101, and the smaller the area of the second region 102. Those skilled in the art can set the pressure of the low-pressure chemical vapor deposition process. , The areas of the first area 101 and the second area 102 are specifically set.
[0047] As yet another embodiment of the present invention, the dielectric layer can also be performed by an atomic layer deposition process in a furnace tube manner. The pressure range of the existing atomic layer deposition process is 0.01 to 1.0 Torr. Generally, the pressure of the atomic layer deposition process is 0.01 to 1.0 Torr. When the pressure range of the atomic layer deposition process is greater than 0.1 Torr and less than 100 Torr, the atomic layer deposition process will only form at the edge area of the semiconductor substrate 100 A dielectric layer, so that no dielectric layer is formed in the central area of the semiconductor substrate 100. The central area serves as the first area 102, and the edge area may serve as the second area 102. The greater the pressure of the low atomic layer deposition process, the larger the area of the first region 101, and the smaller the area of the second region 102. Those skilled in the art can set the pressure of the atomic layer deposition process, The areas of the first area 101 and the second area 102 are specifically set. The atomic layer deposition process uses NH 3 And SiH 2 Cl 2 The mixed gas is carried out.
[0048] After the selective epitaxy process, it is observed whether the color of the second region 102 is the same as the color before the selective epitaxy process. When the selective epitaxy process is not performed, the first region 101 is silicon, the first region 101 is silver gray, and the second region 102 is dark blue due to the deposition of a dielectric layer. After the selective epitaxy process is performed, an epitaxial layer will be formed on the surface of the first region 101. The material of the epitaxial layer is the same as that of silicon. Therefore, the color of the first region 101 does not change much and remains gray. For the second region 102, its color depends on whether the selectivity of the selective epitaxial process is normal. Specifically, if the selectivity of the selective epitaxial process is normal, no epitaxial layer will be formed on the surface of the second region 102, so the color of the second region 102 will not change, and it will still be dark blue; If the selectivity of the selective epitaxial process is abnormal, an epitaxial layer will be formed on the surface of the second region 102, the material of the epitaxial layer may be silicon or doped silicon, and the doped impurities of the doped silicon may be Boron, phosphorous or germanium, the epitaxial layer will change the reflection and refraction of the second region 102 to light, so that the color of the second region 102 will change, and the specific color depends on the second region 102 The material and thickness of the dielectric layer. Since the material of the dielectric layer on the second region 102 in this embodiment is silicon nitride, and its thickness ranges from 800 to 1200 angstroms, the second region appears dark blue before the selective epitaxy process. If the process selectivity is abnormal, after the selective epitaxial process, the second region 102 will appear light yellow due to the formation of the epitaxial layer. Therefore, those skilled in the art can observe the color change of the second region 102 to determine Whether the selectivity of the selective epitaxy process is normal. That is: if the color of the second region 102 is the same as the color of the second region 102 before the selective epitaxial process, the selectivity of the selective epitaxial process is normal. If the color of the second region 102 is the same as that of the selective epitaxial process The color of the previous second region 102 is different, and the selectivity of the selective epitaxial process is abnormal.
[0049] When the selectivity of the selective epitaxy process is abnormal, those skilled in the art need to inspect, maintain and maintain the equipment for performing the selective epitaxy process until the selectivity of the selective epitaxy process performed by the equipment is normal.
[0050] After the selectivity of the selective epitaxy process is normal, those skilled in the art need to test the thickness of the epitaxial layer of the first region 101, which is the thickness of the selective epitaxy process. Testing the thickness of the epitaxial layer is usually carried out with a special thickness testing instrument, and the testing method is the same as the prior art. The thickness of the epitaxial layer obtained is usually the average value of the thickness values at multiple different positions on the first region 101. If the thickness of the selective epitaxy process is abnormal, those skilled in the art need to inspect, maintain and maintain the equipment for performing the selective epitaxy process until the thickness of the selective epitaxy process performed by the equipment is normal.
[0051] It should be noted that only when the selectivity and thickness of the above-mentioned selective epitaxy process are normal at the same time, it is indicated that the selective epitaxy process meets the requirements of those skilled in the art, and the selective epitaxy process can be performed.
[0052] In summary, the present invention divides the semiconductor substrate into a first region and a second region, and a dielectric layer is formed in the second region. The dielectric layer makes the second region have a different color from the first region, thereby making selections. After the selective epitaxy process, the selectivity of the selective epitaxy process can be judged by observing the color change of the second region, and the thickness of the epitaxial layer in the first region of the selective epitaxy process of the first region is tested, This thickness is the thickness of the selective epitaxial process, so that the same semiconductor substrate is used to monitor the selectivity and thickness of the selective epitaxial process, and the monitoring cost of the selective epitaxial process is reduced;
[0053] In a preferred embodiment, the dielectric layer is a silicon nitride layer, the thickness of the dielectric layer ranges from 800 to 1200 angstroms, the dielectric layer makes the color of the second region dark blue, and the second The color of the region is significantly different from the color of the first region. After the selective epitaxy process, if the color of the second region is grayish brown, the selectivity of the selective epitaxy process is abnormal. The color changes of the two areas are quite different, which makes it easier to distinguish and judge.
[0054] Although the present invention has been disclosed as above in preferred embodiments, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.
